E—-STIMSON HAEE

 

 

 

 

CORNELL
UNIVERSITY
LIBRARY

 

 

 

 

 

 

 
Date Due

 

3 1924 102 171 570
AMERICAN SCIENCE SERIES

—~<.—-

The principal objects of this series are to supply the lack—
in some subjects very great—of authoritative books whose
principles are, so far as practicable, illustrated by familiar
American facts, and also to supply the other lack that the ad-
vance of Science perennially creates, of text-books which at
least do not contradict the latest generalizations.

The volumes are large 12mo.

The books arranged for are as follows. They systematically
outline the field of Science, as the term is usually employed
with reference to general education. Those marked * had

been published up to Nov, 25, 1879.

I. Physics.

By ALFRED M. MAYER, Pro-
fessor in the Stevens Institute
of Technology, and ARTHUR
W. Wriaut, Professor in
Yale College.

II. Chemistry.

By SamuEL W. JOHNSON
and WILLIAM G. MIXxTER,
Professors in Yale College.

ITI, Astronomy.*

By Srmon NEWcoms, Supt.
American Nautical Almanac,
and Epwarp 8. HoLprEn,
Professor in the United States
Naval Observatory. $2.50.

IV. Geology.

By RAPHAEL PUMPELLY,
Jate Professor in Harvard
University.

V. Botany.
By C. E. Brssry, Professor

 

 

 

in the Iowa Agricultural Col-
lege and late Lecturer in the
University of California,

VI. Zoology.*

By A. 8. Packarp, Jr.,
Professor of Zoology and Ge-
ology in Brown University,
Editor of the American Nat-
uralist.

VIL. The Human Body.
By H. Newetut Marvin,

Professor in the Johns Hop-

kins University.

VIII. Psychology.

By Wi.LiaAmM JAMES, Pro-
fessor in Harvard University.

IX. Political Economy.

By Francis A. WALKER,
Professor in Yale College.
X. Government.

By Epwin L. Gopxin, Ed-
itor of the Nation.

 

HENRY HOLT & CO., PusLisHers, NEW YORK,
 

OO OG Y

FOR

STUDENTS AND GENERAL READERS

BY
A. §. PACKARD, Jr., M.D., Px.D.,

MEMBER OF THE NATIONAL ACADEMY OF SCIENCES ; PROFESSOR OF ZOOLOGY
AND GEOLOGY IN BROWN UNIVERSITY.

WITH NUMEROUS ILLUSTRATIONS.

 

NEW YORK
HENRY HOLT AND COMPANY
1879
Copyright, 1879,
BY
Henry Hout & Co.

A

Press oF Jonn A. Gray, Aat.
18 JacoB STREET,
NEW YORK.

 
PREFACE.

 

THIS book is designed to be used quite as much in the la-
boratory or with specimens in hand, as in the class-room. If
Zoology is to be studied as a mental discipline, or even if the
student desires simply to get at a genuine knowledge, at first
hand, of the structure of the leading types of animal life,
he must examine living animals, watch their movements and
habits, and finally dissect them, as well as study their mode
of growth before and after leaving the egg or the parent, as
the case may be. But the young student in a few weeks’
study in the laboratory cannot Jearn all the principles of the
science. Hence, he needs a teacher, a guide, or at least a
manual of instruction. This work is an expansion of a
course of lectures for college students, but has been pre-
pared to suit the wants of the general reader who would ob-
tain some idea of the principles of the science as generally
accepted by advanced zoologists, in order that he may under-
stand the philosophical discussions and writings relating to
modern doctrines of biology, especially the law of evolution
and the relations between animals and their surroundings.

The book has been prepared, so far as possible, on the in-
ductive method. The student is presented first with the
facts; is led to a thorough study of a few typical forms,
taught to compare these with others, and finally led to the
principles or inductions growing out of the facts. He has
not been assailed with a number of definitions or diagnoses
applicable to the entire group to which the type may belong
before he has learned something about the animals typical
iv PREFACE,

of the order or class ; but these are placed after a description
of one or a few examples of the group to which they may
belong. The simplest, most elementary forms are first no-
ticed, beginning with the Protozoa and ending with the Ver-
tebrates. In working up from the simplest forms to those
more complex, it is believed that this is the more logical and
philosophical method, and that in this way the beginner in the
science can better appreciate the gradual unfolding of the lines
of animal forms which converge toward his own species, the
flower and synthesis of organic life. Still the learner is ad-
vised to hegin his work by a study of the first part of Chap-
ter VIII., on Vertebrates, and to master, with a specimen in
hand, the description of the frog, in order that he may have
a standard of comparison, a point of departure, from which
to survey the lower forms.

Particular attention has been given to the development of
animals, as this subject has been usually neglected in such
manuals. Some original matter is introduced into the book ;
a new classification of the Crustacea is proposed, the orders
being grouped into the subclasses Meocarida and Paleocar-
ida. Most of the anatomical descriptions and drawings
have been made expressly for this book, and here the author
wishes to acknowledge the essential aid rendered by Dr. C. 8.
Minot, who has prepared the drawings and descriptions of
the fish, frog, snake, turtle, pigeon, and cat.

In compiling the book, the author has freely used the
larger works of Gegenbaur, Huxley, Peters and Carus, Claus,
Rolleston, and others, whose works are enumerated at the
end of the volume, and in many cases he has paraphrased
or even adopted the author’s language verbatim when it has
suited his purpose. Besides these general works many mon-
ographs and articles have been drawn upon.

In order to secure a greater accuracy of statement, and to
render the work more authoritative as a manual of Zoology,
PREFACE. Vv

the author has submitted the manuscript of certain chapters
to naturalists distinguished by their special knowledge of
certain groups. The manuscript of the sponges has been
read by Professor A. Hyatt ; of the worms and Mollusca, by
Dr. Charles 8. Minot; of the Echinoderms, by Mr. Walter
Faxon; of the Crustacea, by Mr. J. 8. Kingsley. Proofs of the
part relating to the fishes have been revised by Professor 'T.
Gill, whose classification as given in his ‘‘ Arrangement of
the Families of Fishes,” has been closely followed, his defin-
itions having been adopted often word for word. The man-
uscript of the Batrachians and Reptiles has been read by
Professor E. D. Cope, whose classification, given in his
““Check-List of North American Batrachia and Reptilia,”
has been adopted. Proofs of the part on birds have been
read by Dr. Elliott Coues, U.S.A., whose admirable “ Key
to the Birds of North America” has been freely used, the
author’s words having been often adopted without quotation-
marks. Dr. Coues has also revised the proofs of the pages re-
ferring to the Mammals. ‘'To the friendly aid of all these
gentlemen the author is deeply indebted.

As to the illustrations, which have been liberally provided
by the publishers, a fair proportion are original. The full-
page engravings of the anatomy of the typical Vertebrates
have been drawn expressly for this work by Dr. C. 8. Minot ;
a number have been prepared by Mr. J. 8. Kingsley ; Prof.
W. K. Brooks has kindly contributed the drawing of the
nervous system and otocyst of the clam, and a few of the
sketches are by the author.

The publishers are indebted to Prof. F. V. Hayden
for illustrations kindly loaned from the Reports of the U.S.
Geological Survey of the Territories; a few have been
loaned by Prof. S. F. Baird, U.S. Commissioner of Fish and
Fisheries, and the members of the U.S. Entomological Com-
mission ; a number have been loaned by the Peabody Acad-
vi PREFACE.

emy of Science, Salem, Mass.; by the publishers of the
American Naturalist, and by the Boston Society of Natural
History, while forty of the cuts of birds have been electro-
typed from the originals of Coues’ Key.

Measurements are usually given in the metric system ; in
such cases the approximate equivalent in inches and fractions
of an inch being added in parenthesis.

Should this manual aid in the work of education, stimu-
late students to test the statements presented in it by person-
al observations, and thus elicit some degree of the inde-
pendence and self-reliance characteristic of the original in-
vestigator, and also lead them to entertain broad views in
biology, and to sympathize with the more advanced and
more natural ideas now taught by the leading biologists
of our time, the author will feel more than repaid.

Brown UNIVERsITYy,
Providence, R. I., October 25, 1879,
CONTENTS.

+o

 

PAGE

TN DROD WCRION ererrracecic stores cs My savore cc eats wayesey seve 1
Definition) of: Zoology. recreate sce eee eis) ster 1

Mor pholor yer a tact sett aae ety ails sae va cade wees 5
Organs and their Functions...................... cece eee 8
Correlation of Organ8... ..........0. 260.5 cece eee ee.
Adaptation Of) OL an strait saree stelselete sierer-lelarelerere -'e/a6 <ioy1s 10
Analogy and) HOMO] Om year cycle eres oii eles slalele|eiariaie alee satel 12
FIMO A peond6s0 poco raseteA Red opasoaserorE nS KecdeomadS 12

IDSY CHOLOL Yin crstoncfoes See ers cise SE noe ee des Sees 12

RE Productions p.iyavpslcds scioe sess attlcemya se aoe sateen ects 13
MAUD TY Ol OS yen ciratttatsiceey oot ayeie oe eet tor stores anche aise cue) sai alee 13
Classification... .. SMCs ek ee crore etseelstsre ache oieiss cueing Tee 13

ZOOL CORTA DIY terctarpercicy)aleiecae loose iiels cis fe alanine sameeren © 16
CHAPTER I. Branch 1. PROTOZOA............ 000.0000 eee ee 17
I.* «“ 2, Porrrera (Sponges).................5 42

III. «3. CQ@LENTERATA (Hydroids, Jelly-fishes,
andseol ys) rareverereerraye pee ea IL

IV. «4, ECHINODERMATA (Crinoids, Starfish,
Sea Urchins, etc................-. 96
Vv. 5. VERMES)(WOPMIS)Meieeli. cece oon 138
VI. “6. Moxuusca (Bivalves, Snails, Cuttles)... 240
VII. «7 ARTHROPODA (Crustaceans and Insects) 285
VIII. oS SEV ERIDE BIR AUD AR meter cere) shetel ate suste aielavers's 389
IX. COMPARATIVE ANATOMY OF ORGANS..........++ 631
Organs of Digestion, the Mouth and Teeth... 631
Organs of Circulation................+...+- 635
Organs of Respiration.................+---- 637
They Nervous! Systems... 4.5.5. +- +e es eo 638

Organstof Senses an) cy) se ees e  n e 640
viil

CHAPTER X.

CONTENTS.

PAGE

DEVELOPMENT: .)o.crnnt teens eee einer 644

Metamorphosis): csicccareicctoie sem oetoroctetsrsreter ate 651
Parthenogenesis and Alternation of Genera-

tLON Gee ea rocsie ee ne Ne ree 652

Dimorphism and Polymorphism............. 654

Individuality ss ccc came envaclterie ces ere ae 656

ELS TIGily secre sleciets ole eahelotetoncterslone dtcreemettce ees 657

THE GEOGRAPHICAL DISTRIBUTION OF ANIMALS 658

Means of Dispersal...........-......25 s0- 660

Division of the Earth into Faune............ 661

Distribution of Marine Animals............. 664

Chief Zoological Faune of the Earth........ 666

. THE GEOLOGICAL SUCCESSION OF ANIMALS. .... 668

. THE ORIGIN OF SPECIES........... 0000000 ees 671

PROTECTIVE RESEMBLANCE.......--..0.0- e005 675

INSTINCT AND REASON IN ANIMAIS........ .-- 680

GELOSSAR Vinge nae nea eet Pei SEN eens ce tener 689

697
ZOOLOGY.

INTRODUCTION:

Definition of Zoology.—That science which treats of liv-
ing beings is called Biology (ios, life ; Adyos, discourse).
It is divided into Botany, which relates to plants, and Zo-
ology (C@orv, animal ; Adyos, discourse), the science treating
of animals.

It is difficult to define what an animal is as distinguished
from a plant, when we consider the simplest forms of either
kingdom, for it is impossible to draw hard and fast lines in
nature. In defining the limits between the animal and
vegetable kingdoms, our ordinary conception of what a
plant or an animal is will be of little use in dealing with
the lowest forms of either kingdom. A _ horse, fish, or
worm differs from an elm tree, a lily, or a fern in having
organs of sight, of hearing, of smell, of locomotion, and
special organs of digestion, circulation, and respiration, but
these plants also take in and absorb food, have a circulation
of sap, respire through their leaves, and some plants are me-
chanically sensitive, while others are endowed with motion
—certain low plants such as diatoms, etc., having this
power. In plants, the assimilation of food goes on all over
the organism, the transfer of the sap is not confined to any
one portion or set of organs as such. It is always easy to
distinguish one of the higher plants from one of the higher
animals. But when we descend to animals like the sea-ane-
mones and coral-polyps which were called Zoophytes from
their general resemblance to flowers, so striking is the exter-
nal similarity between the two kinds of organisms that the
2 ZOOLOGY.

early observers regarded them as ‘‘ animal flowers ;’? and in
consequence of the confused notions originally held in regard
to them the term Zoophytes has been perpetuated in works
on systematic zoology. Even at the present day the com-
pound Hydroids, such as the Sertularia, are gathered and
pressed as sea-mosses by many persons who are unobservant
of their peculiarities, and unaware of the complicated anat-
omy of the little animals filling the different leaf-like cells.
Sponges until a very late day were regarded by our leading
zoologists as plants. ‘The most accomplished naturalists,
however, find it impossible to separate by any definite lines
the lowest animals and plants. So-called plants, as Bacte-
rium, and so-called animals, as Protameda, or certain mo-
nads, which are simple specks of protoplasm, without gen-
uine organs, may be referred to either kingdom ; and, in-
deed, a number of naturalists, notably Haeckel, relegate
to a neutral kingdom (the Protista) certain low-
est plants and animals. Even the germs (zo-
ospores) of monads like Uvella (Fig. 1), and those
of other flagellate infusoria, may be mistaken
for the spores of plants ; indeed, the active fla-
eee aie gellated spores of plants were described as in-
la,a flagellate fusoria by Ehrenberg ; and there are certain so-

infusorian, or ie e 5
monad, with called flagellate infusoria so much lke low

fin ecaed plants (such as the red snow, or Protococcus),
flagella...

Greatly mag- 1n the form, deportment, mode of reproduc-
ate tion, and appearance of the spores, that even
now it is possible that certain organisms placed among them
are plants. It is only by a study of the connecting links
between these lowest organisms leading up to what are un-
doubted animals or plants that we are enabled to refer these
beings to their proper kingdom.

As a rule, plants have no special organs of digestion or
circulation, and nothing approaching to a nervous system.
Most plants absorb inorganic food, such as carbonic acid
gas, water, nitrate of ammonia, and some phosphates, silica,
etc. ; all of these substances being taken up in minute quan-
tities. Low fungi live on dead animal matter, and promote

the process of putrefaction and decay, but the food of these

 
DISTINCTIONS BETWEEN ANIMALS AND PLANTS. 3

organisms is inorganic particles. The slime-moulds called
Myxomycetes, however, envelop the plant or low animals,
much as an Ameba throws itself around some living plant
and absorbs its protoplasm ; but Myxomycetes, in their man-
ner of taking food, are an exception to other moulds. The
lowest animals swallow other living animals whole or in
pieces ; certain forms hke Ameda (Fig. 2) bore into minute
alge and absorb their pro-
toplasm ; others engulf sili-
cious-shelled plants (diatoms
and desmids) and absorb the
protoplasm filling them. No
animal swallows silica, lime,
or ammonia, or phosphates
as food. On the other hand, Fig. 2.—Ameba, a Protozoan. The right-

hand figure shows three psendopodia on the
plants manufacture or pro- right side; in the two other figures the

ary Fae pseudopodia are withdrawn in the body-
duce protein in starch, albu- mass.
men, sugar, etc., which is animal food. Plants inhale car-
bonic acid gas and exhale oxygen; animals inhale oxygen
and exhale carbonic acid ; though Draper has discovered
that, under certain circumstances, plants may exhale car-
bonic acid.

Animals move and have special organs of locumotion ;
few plants move, though some climb, and minute forms
have thread-like processes or vibratile lashes (cilia) resem-
bling the flagella of monads, and flowers open and shut, but
these motions of the higher plants are purely mechanical,
and not performed by special organs controlled by nerves.
The mode of reproduction of plants and animals, however,
is fundamentally identical, and in this respect the two king-
doms unite more closely than in any other. Plants also,
like animals, are formed of cells, the latter in the higher
forms combined into tissues.

As the lowest plants and animals are scarcely distinguish-
able, it is probable that plants and animals first appeared
contemporaneously ; and while plants are generally said
to form the basis of animal life, this is only partially true ;
a large number of fungi are dependent on decaying animal
matter; and most of the Protozoa live on animal food, as

 
4 ZOOLOGY.

do a large proportion of the higher animals. The two
kingdoms supplement each other, are mutually dependent,
and probably appeared simultaneously in the beginning of
things. It should be observed, however, that the animal
kingdom overtops the vegetable kingdom, culminating in
man.

In speaking as we have of low animals and high animals,
we are comparing very unequal quantities; the distance be-
tween monad and man is well-nigh infinite. But there isa
series or chain, sometimes broken and often with lost links,
connecting the extremes ; and as there are wide differences
in form, so there are great extremes in the organs and de-
gree of complication of function of the simple as compared
with the more complex forms. The improvised stomach of
an Ameba is not comparable with the stomach of an hydra,
nor is the stomach of the latter creature with that of a
horse ; there is a gradual perfection and elaboration gr spe-
cialization of the stomach as we ascend in the animal series.
So it is with organs of locomotion ; the pseudopods and cilia
of the Protozoans are replaced in the star-fishes and worms
by hollow tentacles or various fleshy soft appendages ; in
crabs and insects by stiff, jointed limbs, with different lev-
erage systems; and these are replaced in vertebrates by
genuine limbs supported by bones. A comparative view of
the origin and structure of organs succeeds in this book the
systematic account of the animals themselves.

We thus see that the organs of the higher animals are
merely modificutions of organs often having the same
general functions as in the lower animals; the lower or
simpler have preceded in geological history the higher or
more specialized forms, and thus we are, in ascending the
animal series, going from the simple to the complex. For
this reason the plan of this work has been to lead the stu-
dent from the simpler forms of animal life to the more
complex ; and though the vertebrate animals, such as fishes
and dogs, are more familiar and interesting to us, the seri-
ous student of zoology will feel that it is more logical and
better in the end to study the animal world in the order in
which the different forms have appeared—as we believe,
MORPHOLOGY. 5

through the orderly operations of physical and biological
laws, under the guidance of an Infinite Intelligence—a
Creator whose modes of working are revealed to us in what
we call the laws or processes of nature.

Zoology is subdivided thus :

Morphology or gross Anatomy, and minute
Anatomy (Histology).
Physiology and Psychology.

Zoology. < Reproduction and Embryology. A
Systematic Zoology or Classification.
Paleontology.

Zoogeography.

Morphology.—In order to properly understand Zoology,
one should first study Morphology—i.e., the general struc-
ture of animals. The student should first thoroughly ac-
quaint himself with the anatomy of a vertebrate animal,
such. as a frog, as compared with that of a toad or salaman-
der. The examination and comparison of the organs of
animals belonging to distinct groups, is called Comparative
Anatomy. The study of Morphology also includes the rela-
tion of the different organs to one another, and of all to the
walls of the body. Finally, we need also to study the com-
position of the tissues of the different organs ; each kind of
tissue being formed of different kinds of elements or cells.
This department of Comparative Anatomy is called Histol-
ogy (Greek, tor0s, web or tissue; Adyos, discourse). It
treats of the cell, and the combination of cells into germ-
layers, tissues, and organs.

The Cell.—The primary elements of the bodies of animals
are called cells. They are microscopic portions of proto-
plasm either with or without a wall. Protoplasm largely
consists of protein, which is a complex compound of car-
bon, hydrogen, oxygen, and nitrogen, united with a large
proportion of water. Cells are originally more or less
spherical sacs, and the protoplasm forming the cell-mass is
the dynamic part of the cell. The protoplasm of animal as
well as vegetable cells, the protoplasm of eggs and of the
cells forming the different tissues of the animal body, as
6 ' ZOOLOGY.

well as the entire Amceba or monad, is all alike, being per-
fectly homogeneous to the chemist or microscopist of our
day. Yet potentially the protoplasm of different cells exerts
widely different forces and capabilities. An egg-cell be-
comes aman, whose brain-cells are the medium of the intel-
lectual power which enables him to write the history of
his own species, and to be the historian of the forms of life
which stand below him. The cell is the morphological
unit of the organic world. With cells the biologist can
in the imagination reconstruct the vegetable and animal
worlds.

The primitive form of a cell, when without a nucleus or
nucleolus, is called a cytode ; genuine cells have a nucleus,
the latter containing anucleolus. Animals composed of but a
single cell, such as the Ameéa or an Infusorian, are said to be
unicellular, Cells grow by absorbing cell-food—i.e., by the
assimilation of matter from without, and this matter may be
in masses of considerable size when seen under the microscope.
Cells multiply by self-division. The egg-cell undergoes
division of the yolk into two, four,
eight, and afterward many cells; the
cells thus formed become arranged into
two layers or sets called germ-layers.
The outer is called the ectoderm and
the inner the endoderm. A third germ-
layer arises between them, called the

Fig. 3.—Germ of Sagitta, 7esoderm or middle germ-layer. From
foth layers formed of ma these germ-layers, or cell-layers, the
cheated cells: tissues of the body are formed, such as
muscle, bone, nerve, and glandular tissue. These tissues
form organs, hence animals (as well as plants) are called or-
ganisms, because they have certain parts formed of a partic-
ular kind of tissue set apart for the performance of a special
sort of work or physiological labor. This separation of
parts for particular or special functions is called differentia-
tion ; and the highest animals are those whose bodies are
most differentiated, while the lowest are those whose bodies
are least differentiated ; hence high animals are specialized,
and, on the other hand, Jow animals are simple. Thus dif-

 
CELLS AND TISSUES. i

ferentiation of organs involves the division of physiological
labor.

Tissues.—Of the different kinds of tissues there is, first,
epithelial tissue (Fig. 4), consisting of cells of the most prim-
itive form, and placed side by side, forming a layer. All the
organs develop originally from epitheliwm, which is the prim-
itive cell-structure and forms the tissues of the germ-layers.
Epithelial cells form the skin of animals, and also the lining
of the digestive canal. The cells of the latter may, as in
sponges, bear a general resemblance to a flagellate infuso-

 

 

Fig. 4.—Vertical section through the skin of an embryonic shark, showing at Z the
epithelial cells, forming pavement epithelium ; and at ¢, columnar epithelium.—After
Gegenbaur.

rian, as Codosiga, or they may each bear many hairs, called
cilia, which by their constant motion maintain currents of
the fluids passing over the surface of the epithelium. The
tissue forming glands is simply modified epithelium.
Connective tissue is formed by isolated rounded or elon-
gated cells with wide spaces between them filled with a ge-
latinous fluid or protoplasm, and occurs between muscles,
etc. This tissue forms in the vertebrates the ‘‘ notochord ’’
—i.e., arod supporting the bodies of vertebrate embryos.
Gelatinous tisswe is a variety of connactive tissue found in
the umbrella of jelly-fishes (Aurelia, etc.). Mibrows and
elastic tissue are also varieties of connective tissue.
Cartilaginous tissue is characterized by cells situated in a
8 ZOOLOGY.

still firmer intercellular substance ; and when the intercel-
lular substance becomes combined with salts of lime form-
ing bone, we have bony tisswe.

The blood-corpuscles originate from the mesoderm as
independent cells floating in the circulating fluid, the blood-
cells being formed contemporaneously with the walls of the
vessels enclosing the blood. In the invertebrates the blood-
cells are either strikingly like the Amedu in appearance, or
are oval, but still capable of
} changing their form. Thus blood-
corpuscles arise like other tissues,
ork Se Sirated mene Abril8 except that the blood-cells are

free.

Muscular tissue is also composed of cells, which are at
first nucleated and afterward lose their nuclei. From being
at first oval, the cells finally become elongated and unite
together to form the fibrille; these unite into bundles
forming muscular fibres, which in the vertebrates unite to
form muscles. Muscular fibrille may be simple or striated
(Fig. 5). The contractility of muscles is due to the con-
tractility of the protoplasm
originating in the cells forming
the fibrille.

Nervous tissue is made up
of nerve-cells and fibres pro-
ceeding from them; the for-
mer constituting the centres
of nervous force, and usually
massed together, forming a
ganglion or nerve-centre from
which nerve-fibres pass to the  ig.6—A ganglion in the clam, with
periphery and extremities of 2°" (e, g, k) proceeding from it.
the body, and serve as conductors of nerve-force (Fig. 6).

Organs and their Functions.—Having considered the
different kinds of cells and the tissues they form, we may
now consider the origin of organs and their functions. The
Protameba may be considered as an organless being. In
Amba (Fig. 11) we first meet with a specialized portion of
the body, set apart for the performance of a special function,

 

 
ORGANS AND THEIR FUNCTIONS. 9

Such is the nucleus ; so that Amba is a genuine organism.
Ascending to the flagellate Infusoria (Fig. 1), we have the
flagella developed as external, permanent organs of locomo-
tion. In the Hydra (Fig. 36) the tentacles are organs
whose functions are generalized. In the worms we have or-
gans arranged in pairs on each side of the body, and in gen-
eral among the higher invertebrates, especially the crusta-
ceans and insects, and markedly in the vertebrates, we have
the bilateral symmetry of the body still farther emphasized
in the nature and distribution of the appendages.

Of the internal organs of the body, the most important is
the digestive cavity, which is at first simple and primitive in
the gastrula or embryo of all many-celled animals, and as we
ascend in the animal series we witness its gradual special-
ization, the digestive tract being differentiated into dis-
tinct portions (7.e., the esophagus, stomach, and intestine),
each with separate functions and with organs of respiration,
digestion, secretion, and excretion set apart as offshoots or
outgrowths from the main alimentary tract. In like man-
ner the skeleton is at first simple and afterward is extended -
into the different organs, the various parts of the ap-
pendicular skeleton corresponding to the increased flexi-
bility and diversified leverage power ; so that limbs become
subdivided into joints, and these joints still further subdi-
vided as we go from the points of attachment to the peri-
phery or extremities, as seen in the tendency to an irrelative
repetition of joints in the limbs and feelers of crustaceans
and insects, and the digits of the lower vertebrates.

Correlation of Organs.—Cuvier established this princi-
ple, showing that there is a close relation between the forms
of the hard and soft parts of the body, together with the
functions they perform, and the habits of the animal. For
example, in a cat, sharp teeth for eating flesh, sharp curved
claws for seizing smaller animals, and great muscular activ-
ity coexist with a stomach fitted for the digestion of animal
rather than vegetable food. Soin the ox, broad grinding
teeth for triturating grass, cloven hoofs that give a broad
support in soft ground, and a several-chambered stomach
coexist with the habits and instincts of a ruminant, ‘Thus
10 ZOOLOGY.

the form of the teeth presupposes either a ruminant or carni-
vore. Hence this prime law of comparative anatomy led to
the establishment by Cuvier of the fundamental laws of
paleontology, by which the comparative anatomist is en-
abled to restore from isolated teeth or bones the probable
form of the original possessor. Of course the more perfect
the series of bones and teeth, or the more complete the re-
mains of insects or mollusks, the more perfect will be our
knowledge, and the less room will there be for error in re-
storing extinct animals.

Adaptation.—An organ with a certain normal use or
function may be adapted, in consequence of a change in the
habits of the animal, to another use than the original one.
To take an extreme case, the Anadas, or climbing fish, may
use its fins to aid it in ascending trees. On the other hand,
by disuse organs become aborted or rudimentary. The
teeth of the whalebone whale are rudimentary in the young,
and are replaced by whalebone, which is more useful to the
animal ; the eyes of the blind-fish are rudimentary, func-
. tionless. Those of certain cave-insects are entirely wanting,
being lost through disuse, owing to a change of life from
the light, outer world to totally dark caverns, and the con-
sequent disuse of their eyes. Nature is economical. Every
thing that is not of use as a rule disappears. It would bea
waste of material to nourish and care for an organ in a cave-
animal, or a parasitic insect or crustacean, which would be
of no use to the animal. On the other hand, if the leg or
tail of a newt is snipped off by some rapacious fish, it
grows out again.

Moreover, the animal organism is far more pliable than is
generally supposed. Not only is nature continually repair-
ing wounds and waste, not only is the body being contin-
ually made over again, but certain animals undergo a
change of form, either generally or in particular parts. If
the environment is unchanged, the animal remains true to
its species. The dogma of the invariability or stability of
species is a fallacy. Change the climate, moisture or dryness,
the nature of the soil ; introduce the natural enemies of the
animal or remove them ; destroy the balance of nature, in
LAW OF INHERITANCE AND TRANSMISSION. 11

other words, and the organism changes. The plants and
animals of the mummies and monuments of Egypt are prob-
ably the same as those now living in that country, because
the climate and soil have remained the same.

The assemblages of life that have successively peopled the
surface of the earth, and which are geological time-marks,
have probably become extinct because they could not adapt
themselves to more or less rapid oscillations of continents
and islands, to consequent changes of climate and the in-
coming of destructive types of life. This probably accounts
for the origin, culmination, and extinction of different
types of life. The earth has been, and still is, in a state of
unstable equilibrium. Organic life has been and is even
now, in a degree, being constantly readjusted in harmony
with these changes of the earth’s surface and climate. Thus
this adaptation of organs to their uses, of animals to their
environment, the laws controlling the origination of new
forms of life and the extinction of those which have acted
their part and are no longer of service in the economy of
nature, is part of the general course of nature, and evinces
the Infinite Wisdom and Intelligence pervading and contin-
ually operating in the universe.*

Coupled with variability is the law of inheritance and
transmission of variable parts, and the habits thus induced
by the variation of parts. It should be observed that the
portions which vary most are the peripheral parts—z.e.,
fingers and toes, tentacles and antenne, the skin and scales
and hair; it is by modifications and differences brought
about in those parts most used by animals that the multi-
tudes of specific forms have resulted. There is, as Darwin
states, a general tendency of organisms to vary ; the laws
accounting for this tendency to vary have yet to be formu-
lated ; though the attempts of Lamarck in this direction
laid the way for the discovery and application of the funda-

* That animals and plants are self-evolved, that the world has made
itself, and that all is the result of so-called physical and biological laws
operating from within outward, is as inconceivable as the medieval
dogma that animals and plants and the earth they inhabit were made
in the twinkling of an eye. See the concluding chapter on Evolution.
12 ZOOLOGY.

mental laws of evolution. On the other hand, pure Dar-
winism—viz., natural selection—accounts rather for the
preservation than the origination of the forms of life.

Analogy and Homology.— When we study the Inverte-
brates alone we see that it is often easy to trace a general
identity in form between the more important parts. We
notice that the under lip of a worm is comparable to the foot
of a mollusk, though the functions of these parts may be
quite unlike; these are therefore examples of a general
identity in structure or homology between two organs. A
closer homology implies a more apparent identity of form,
as seen in the resemblance in structure of the fore-limbs of
a whale and a seal, or the pectoral fins of fishes and the fore-
arms of man.

Analogy implies a dissimilarity of structure of two organs
with identity in use, as the wing of an insect and of a bird ;
the leg of an insect and the leg of a frog; the gill of a
worm and the gill of a fish.

Homology implies blood-relationship ; analogy repudiates
any common origin of the organs, however physiologically
alike. The most general homologies are those existing in
organs belonging to animals of different branches ; the most.
special between those of the same orders and minor groups.
Thus it is fundamentally a question of near or remote con-
sanguinity.

Physiology treats of the mode in which organs do their
work ; or, in other words, of the functions of different or-
gans. Thus the hand grasps, the fins of a fish are its swim-
ming organs ; the function of the nose is to smell, of the
liver to secrete bile, of the ovary to secrete protoplasm
which forms eggs.

Psychology is the study of the instincts and reasoning
powers of animals; how they act when certain parts are
irritated ; so that while this term is generally applied to
man alone, Comparative Psychology deals both with the
simplest automatic acts and the whole series of psychic pro-
cesses—from those exercised by the Protozoans, such as
Ameba, up to the complicated instinctive and rational acts
of man.
REPRODUCTION AND EMBRYOLOGY. 13

Reproduction.—The simplest form of reproduction is
cell-division, one cell budding or separating from another.
This mode of growth is called self-division or fission.
Where one cell separates from another, the separating part
being smaller than the original cell, or where a number of
cells separate or bud out from a many-celled animal, such as
a Hydra, the process is called gemmation. A third mode of
reproduction is sexual, the sperm-cell of the male coalescing
with the nucleus of the egg ; the commingling of the pro-
toplasm of the two nuclei resulting in a series of events
leading to the formation of a germ or embryo.

Embryology is, strictly speaking, a study of the develop:
ment of animals from the beginning of life of the egg up to
the time the animal leaves the egg or the body of the parent
—namely, up to the time when it begins to shift for itself ;
but the term embryology may also be applied to the grow-
ing animal from the egg to the adult condition. Many of
the lower animals undergo a metamorphosis, suddenly as-
suming changes in form, accompanied by changes in habits
and surroundings ; so that at different times it is, so to
speak, a different animal. For example, the caterpillar
lives on solid food, crawls on the ground, and has a worm-
like form ; it changes to a chrysalis or pupa, lying quies-
cent, taking no food; then it changes to a butterfly and
flies in the air, either taking no food or sipping the nectar
of flowers : in all these three stages it is virtually different
animals with different surroundings. Many animals besides
insects have a metamorphosis, and their young are called
larve ; thus there are larval polyps, larval star-fish, larval
worms—these larve often differing remarkably in form,
habits, and in their environment or surroundings, as com-
pared with the mature or adult forms.

Classification.—After thoroughly studying a single ani-
mal, its external form, how it acts when alive, its external
and internal anatomy after death, and the development of
other individuals of its own species, the student is then ready
to study the classification of animals.

The best method of studying classification, or Systematic
Zoology, is to make an exhaustive examination of one an-
14 ZOOLOGY.

imal, and then to study in the same thorough manner an
allied form, and, finally, to compare thetwo. For example,
take a frog and compare it with a toad, and then with a
newt, or a land salamander ; thus, by a study of the different
types of Batrachians, one may arrive at a knowledge of the
affinities of the different species of the class. The methods
of research are, then, observation and comparison. The
best and most philosophic observers are those who compare
most. Then, passing on to other animals, the student will
place in one group animals that are alike. He will find that
many agree in certain general characters common to all.
He will thus form them into classes, and those that agree in
less general characters into orders, and so on until those
agreeing in still less important characteristics may be placed
in categories or groups termed families, genera and species,
varieties and races. For example, the cat belongs to the
following groups :

Kingdom of Animals ;
Sub-kingdom, or branch, Vertebrates ;

Class, Mammalia ;

Order, Carnivora ;

Family, Felide ;

Genus, Felis ;

Species, Felis domesticus Linneus ;
Variety, Angorensis.

But these different groups are insufficient to represent the
almost endless relationships and series called the System of
Nature, which our classifications attempt to represent.
Hence we have sub-species, sub-genera, sub-families and
super-families, sub-orders and super-orders, and sub-classes
and super-classes, and the different assemblages may be
grouped into series of orders, families, etc.

The relations of the members of these different groups
may be represented in the same manner as the genealogi-
cal tree of the historian, or like a tree, with its trunk
and branches and twigs; or on a plane by a cross-section
through the tree, the different groups or ends of the
branches resembling a constellation, and embodying one’s
EIGHT BRANCHES OF THE ANIMAL KINGDOM. 15

idea of the complicated relations between animals of differ-
ent groups.

The Animal Kingdom may be divided primarily into
two series of branches ; those for the most part composed
of asingle cell, represented by a single branch, the Proto-
zoa, and those whose bodies are composed of many cells
(Metazoa), the cells arranged in three fundamental cell-
layers—viz., the ectoderm, mesoderm, and endoderm. The
series of Metazoa comprises the seven higher branches—i.e.,
the Porifera, Coelenterata, Echinodermata, Vermes, Mol-
lusca, Arthropoda, and Vertebrata. Their approximate
relationships may be provisionally expressed by the follow-
ing

TABULAR VIEW OF THE EIGHT BRANCHES OF THE ANIMAL KIN@Dom.

VIII. Vertebrata.
Fishes to Man.

VII. Arthropoda.

Crustaceans and Insects.

VI. Mollusca.
| Clams, Snails, Cuttles.

V. Vermes.
Flat and Round Worms, Polyzoa,
| Brachiopods, Annelids, Tunicates.

IV. Echinodermata.

Crinoids, Starfish, etc.

Il. Porifera.

| Hydra, Jelly-fishes.
| ae

III. Coelenterata. |
| |

METAZOA.
Many-celled animals, with 3 cell-layers,

J. Protozoa.
Single-celled animals.

It should be understood by the student that the classifi-
cation presented in this book is a provisional one, based on
our present knowledge of the structure of the leading types
16 ZOOLOGY.

of the animal kingdom, and may be regarded as rudely in-
dicating the blood-relationship or pedigree of animals. It
differs in some important respects from the classifications
given in the books ordinarily in use by American students.
It is a question whether the Tunicata should not form a
ninth branch, and stand next below the Vertebrates.

Some authors retain the four types of Cuvier, but it
should be remembered that since Cuvier’s classification was
proposed in 1812 our knowledge has been greatly extended.
The microscope has revealed an immense mass of new mi-
croscopic forms, and many facts regarding the structure and
development of the larger forms. The embranchments of
Cuvier are in all cases, except the Vertebrates, unwieldy, het-
erogeneous, and, in the light of our present knowledge, un-
natural assemblages of animals. New discoveries do away
with old systems, and the classifications adopted by differ-
ent authors represent the standpoint from which they re-
gard the system of nature. Itis not of somuch consequence
to the student to know what the system may be, as to learn
the leading facts of animal morphology and development.

Paleontology.— With a thorough knowledge of the anat-
omy of animals and their classification, the student is pre-
pared to study the remains of extinct animals, to restore so
far as possible their forms, and to classify them. With a
knowledge of the hard parts of existing animals, and of the
interaction of the tendons, ligaments, muscles, and bones,
the paleontologist can, in accordance with the law of cor-
relation of parts, refer fossils to their respective orders,
families, genera, or species.

Zoogeography, or geographical distribution, is the study
of the laws of distribution of animals over the surface of
the earth or over the bottom of the sea. The assemblage
of animals inhabiting any area is called a fauna. Thus we
have an arctic fauna, a tropical fauna, a North American
fauna, or Australian fauna. The fauna of the ocean is sub-
divided into different subordinate faune.
GERARIwE Reb,

BRANCH I.—PROTOZOA.

General Characters of Protozoans.— We can imagine no
more elementary forms of life than certain members of this
branch, whose bodies in the simplest forms are merely
masses of albumen, without any distinct permanent organs,
or portions set apart for the performance of any special
function. Yet the primary acts of animal life, such as tak-
ing food, its digestion and assimilation, and reproduction,
are carried on as effectively by these lowest as by the high-
est forms. The simplest Protozoans are like minute drops
of protoplasm or albumen, having a gliding motion, and
constantly changing their forms, throwing out temporarily
root-like projections called
pseudopodia, which serve to
gather food-particles. Fig.
7 illustrates a typical Proto-
zoan. It is the common
Ameba of standing water.
Most Protozoans are provid-
ed with a central organ or Fig. 7. —Ameeha, the nucleus not shown.
nucleus, which corresponds
to the reproductive organs of the many-celled animals.
The Protozoa are one-celled in distinction from all other
animals, from the sponges to man, which are many-celled,
though it is claimed that a few shelled forms (Rhizopods) are
composed of several indistinct cells. Thus a Protozoan cor-
responds to an egg or to any one of the cells composing the
bodies of higher animals. They may be naked, asin Proto-
mebu or Ameba, or may secrete a siliciows or calcareous
shell. The Infusoria, forming the highest class, are quite
complicated, with permanent cilia, a mouth, throat, repro-

 
18 ZOOLOGY.

ductive nucleus, and several contractile vesicles, rudely an-
ticipating the heart of higher animals. Protozoans repro-
duce by self-division and the formation of motile germs
(zoospores), and in the Infusoria of ciliated young. There
is thus a great range of forms leading from the most primi-
tive type (Protameba) to the most specialized forms, such
as the bell animalcule ( Vorticella.)

Crass I.—Monera (Moners).

General Characters of Moners.—This group comprises
the simplest forms of Protozoans, whence the name Monera
(uovnpes, simple). The lowest forms are almost identical
in appearance with the lowest plants, and they can only

 

Fig. 8.—Protomonas amyli, greatly magnified. A, when encysted; a, germs or zo-
ospores ; y, food-mass. B, germ freed from the parent-cyst. (, D, older germs. JZ,
adult encysted ; y, food ; s, projection inward of the cell-wall ; x, wall of the cyst; ¢,
germs.—After Cienkowski.

be claimed to be animals from their resemblance to higher
forms leading to Ameba, which, in turn, is connected by a
series of forms leading to undoubted animals, such as the
shelled Rhizopods (Fig. 14).

The Monera differ from the Rhizopods (Ameba, etc.) in
wanting a nucleus and contractile vesicles. Their body-
substance is homogeneous throughout, not divided into a
tenacious outer and softer inner mass, as in Ameba. They
move by the contraction of the body, and the irregular pro-
trusion of portions of the body forming either simple pro-
cesses (pseudopodia) or a network of gelatinous threads.
The food, assome diatom, desmid, or protozoan, is swallowed
MONERA. 19

whole, being surrounded and engulfed by the body, and the
protoplasmic matter is then absorbed, serving for the nour-
ishment and growth of the Moner.

The simplest form known, and supposed to be really a living
being, is Haeckel’s Protameba. It may best be described
by stating that it is like an Ameda, but without a nucleus
and vacuoles (or little cavities). It reproduces by simple
self-division, much as in Ameba (Fig. 11).

In Protomonas the body is very changeable in form, the
pseudopods often being very slender, thread-like. Fig. 8,
A represents this Moner during the formation of the young
(zoospores) in the cyst-like body, or resting-stage of the
creature ; B, one of these germs freed from the cyst and
capable of moving about by the two thread-like pseudopo-
dia; CD, the Ameba-like form which the young after-
ward assumes, and which at maturity passes into the en-
cysted or resting-stage £.

A still better idea of what a Moner is may be seen by
studying the Protomyxa aurantiaca Haeckel.

This Moner was discovered at the Canary Islands. It is
from half to one millimetre in diameter, and is a perfectly
simple mass of orange-red jelly. When hungry numerous
root-shaped threads (pseudopodia) radiate from the central
mass. Fig. 9, # represents the Protomyza after having
absorbed into its body-mass a number of shelled Infusoria.
When about to become encysted (A B) it rejects the shell
of its victims, retracts its false feet, and soon becomes fast-
ened as minute red balls to the surface of some dead shell.

The ball becomes enclosed by a thick covering (A), and
then the contents become divided into several hundred small,
round, thoroughly structureless spheres, which become germs
(B). The germs finally burst through the cyst-wall, as in
C, a, c, d, and assume various monad-like and amceboid
shapes, and finally attain, by simple additions of the proto-
plasm of its food (diatoms and infusoria), the adult form
(DH). Other Moners exist in fresh water.

We have been dealing with the simplest living forms, be-
ings showing no trace of organization, much lower and
simpler than the Amea, with its nucleus. The individual
20 ZOOLOGY.

Moner—for example, Protamwba—is simply a speck or drop
of transparent, often colorless, viscid fluid, scarcely of more
consistency than, and in all apparent physical characters
identical with, the white of ahen’s egg. And yet this drop
of protoplasm has the power of absorbing the protoplasm of
other living beings, and thus of increasing in size—t.e.,
growing ; and in taking its food makes various movements,
one or more parts of its body being more movable than

 

Fig. 9.—Protomyxa aurantiaca. A, encysted. B, cyst filled with germs. (C, germs
(a, fey issuing from the cyst. D, a oun, Protom xa swall He dis ee
£, adult after enclosing or swallowing vena Dera athe: Tae D

shelled Infusoria.—After Haeckel.

others, the faculty of motion thus being for the moment
specialized ; it has apparently the power of selecting one
kind of food in preference to another, and, finally, of repro-
ducing its kind bya process not only of simple self-division,
but also of germ-production. In short, we may say of the
Moner what Foster says of the Amceba—viz., (1) it is con-
tractile ; (2) it is trritable and automatic ; (3) itis receptive
MONERA. 21

and assimilative ; (4) it is metabolic and secretory in the
sense that the Moner digests and separates the portions
necessary for food from those which it rejects as waste ; (5)
itis respiratory, the changes involved in taking food, es-
pecially oxygen, causing the production of and excretion of
carbonic acid ; (6) it is reproductive.

It is difficult to conceive of a simpler form of life than
Protameba or Protomonas. Are the Moners animals or
plants, or do they represent a neutral division or group of
forms? It was formerly thought that Ameda was the sim-
plest possible form of life, but we shall see that that animal
is an undoubted organism, possessing a permanent organ,
the nucleus. Moreover, the Amceba intergrades with the
other Rhizopods which are undoubted animals, while the
simplest Monera have no characters which absolutely sepa-
rate them on the one hand from the plants or on the other
from the animals. Their relation to the plants is seen in
the fact that, besides the resemblance to the lowest plants,
the cyst of Protomonas is composed of cellulose, while the
granular contents of the body become colored with chlo-
rophyll.*

For these reasons, Haeckel, the discoverer of the Mfonera,
regards them as neutral beings, neither plants nor animals.
But by comparison with other Protozoa, we shall see that
the Monera only differ from the monads and Ame@ebe by the
absence of a nucleus. This may yet be found to occur in
the Monera, and from this fact we separate the group only
provisionally from the Rhizopoda. The Gregarine also pass
through a true Moner-stage. This indicates that the
Monera are allied rather to animals than plants. Another
point of difference from plants is the fact that, like the
Ameba, they engulf living plants (desmids, etc.) and ani-
mals (Infusoria), the only plants known to do this being the
singular Myzomycetes, whose position is uncertain, some
naturalists (Allman) regarding it as an animal.

It is probable that the Monera were the earliest beings to

* On the other hand, cellulose occurs in the integument of Tunicates,
and various parts of Articulates and Vertebrates, while chlorophyll
occurs in the Infusoria and Hydra.
22 ZOOLOGY

appear, and that from forms resembling them all other organ-
isms have originated. We can conceive at least of no simpler
ancestral form; and if organized beings were originally pro-
duced from the chemical elements which form protoplasm,
one would be naturally led to suppose that the earliest form
was like Protameba. It would follow from this fact that the
Monera are as low as any plants, and that animals appeared
contemporaneously with plants.

Having studied a few typical forms of Monera, we are
prepared to briefly define the group and tabulate the sub-
divisions of the class.

 

Crass I.—MONERA HAkrcKEL.

Beings consisting of transparent protoplasm, containing granules, some-
times forming a net-work, but with no nucleus* or contractile vacuole ,;
capable of automatically throwing out pseudopodia, and reproducing by
simple self-division of the body-mass into two individuals, or by division
into a number of germ-like or spore-like young, which increase in size by
absorption of the protoplasm of other organisms.

Group 1. Gymnomonera, comprising the genera Protameeba, Protogenes,
and Myxodictyum, which do not become encysted.

Group 2. Lepomonera, which become encysted and protected by a
case, as in the genera Protomonas, Protomyxa, Vampy-
rella, and Myxastrum.

Cuass II.—Ruizopopa (Root Animalcules).

General Characters of Rhizopods.—An idea of the form
and internal structure of this group can be obtained by a
study of Ameba, which may be found sliding over the sur-
face of the leaves of plants growing in pools or ponds of
fresh water. Our common Ameba has been studied by
H. J. Clark. Fig. 10 represents this animal in the three
more usual forms which it assumes. From time to time
the sides of its body project either in the form of simple
bulgings, or suddenly it throws out foot-like projections

* Should a nucleus be found hereafter to occur in the Monera, the
group should be merged into the Riizopoda, and placed next to
Ameba.
RHIZOPODA. 93

(pseudopodia) from various parts of the body, as if it
were falling apart ; then it retracts these transparent feet
and becomes perfectly smooth and rounded, resembling a
drop of slimy, mucous mat-
ter. The body-mass is di-
vided into a clear cortical and
a medullary, granular mass ;
the outer highly contractile,
the inner granular portion
acting virtually as a stock of

food. These granules, like Te Re RE areas toe ean ae ihe
the grains of chlorophyll in PEN, tows the Proud, fat, preutopodia
vegetable cells and in dia- tion of the granules.—After Clark.
toms and desmids, circulate in regular, fixed currents, the
arrows in the figure indicating the course of the circulating
food. The act of circulation is probably assisted by a con-
tractile vesicle (or
vacuole) usually
present. There is
besides a distinct
organ always pres-
ent, the nucleus (see
Fig. 11), so that the
Ameeba earns the
right to be called
an organism. Be-
sides this there is a
head-end, as distin-
guished from a
hinder portion ; this
head-end is tuber-
culated and inter-
nally free from

 

 

Fig. 11.—Ameba spherococcus. A, before division.
B, ue same in its resting stage; a, cyst or cell-wall; oranules. The Ame@-
d, body-mass; c, nucleus; b, nucleolus. @, Ameba ©
nearly divided. D, two young Ameebe, the result of ba has the power

division —After Haeckel. ie Ae :
oat of moving in partic-

ular directions, the head-end usually advancing first set
selects appropriate food, and can engulf or swallow, digest
and distribute the food thus absorbed to various portions of
24 ZOOLOGY.

its body. The Amoba reproduces its kind by simple di-
vision, as seen in Ameba spherococcus Haeckel (Fig. 11).
This species, unlike others, so far as known, becomes encysted
(B), then breaks the cell-wall and becomes free as at A.
Self-division then begins as at C, the nucleus doubling it-
self, until at Da and Db we have as the result two individ-
uals.

Order 1. Foraminifera.—Besides Ameba, several other
forms, either naked or shelled, produce, by division of an in-
ner portion of the body, numbers of ciliated young, as in
the naked Pelomyza, in certain many-chambered Fora-
minifera, and in Collosphe-
ra. An example may be
seen in the European Pelo-
myza palustris Greef (Fig.
12). This creature lives in
the mud at the bottom of
fresh-water pools, and when
first seen resembles little
dark balls of mud a milli-
metre in diameter. Instead
of one nucleus, there are
numbers of them, and nu-
merous contractile vacuoles
cortical portion; 5, diatoms enclosed in the filled with a fluid, together
body-mass. 3, amceba-like bodies originating . *
from the nuclei, which after leaving the body with spicules. The young
prcontractile vesicle:“After Greet," are at first amosba-like (B),

originating as ‘shining
bodies,’’ which have resulted from the self-division of the
nuclei. These amcba-like bodies finally assume an active,
monad-like stage C, and move about by means of a cilium
or lash.

We now come to the shelled Ameba, or genuine Foramt-
nifera. A common type is Arcella, which secretes a one-
chambered silicious shell, found in fresh water, and a
representative of the monothalamous, or one-chambered,
Foraminifera ; while the many-chambered forms are
marine, of which Globigerina bulloides (Fig. 13), found
floating on the surface of the ocean, with its pseudopodia

 

Fig. dete eOray Ee palustris. A, a, clear
FORAMINIFERA.

25

thrown out in all directions, is a type ; Rotalia veneta (Fig.

14) is another example.

The Foraminifera are nucleated. Diplophrys multiplies

by a ‘‘ process of con-

tinuous binary  fis-
sion.”’ Miliola gives
rise to small round,
sharply - defined bod-
ies, in calcareous
shells, with one turn,
but no inner walls,
and with pseudopo-
dia like those of the
adult. Microgromia so-
cialis multiplies by zo-
ospores, which are oval,
with two flagella; or,
in other cases, the

Fig. 13.—A Foraminifer.
magnified 70 diameters.—From Macallister.

 

Globigerina bulloides,

young assume an actinophrys-like form, and move about by
the aid of three or four more or less branched pointed pseudo-

 

Fig. 14.Rotalia. A Rhizopod, showing the pseudopodia.

pods (Hertwig).
In some forms,
as the fossil
Nummutites, the
chambers are
numerous and
regular, the
shells being flat
and consisting
of eight coils sit-
uated in the
same plane. A
recent species of
Foraminifer
found at Borneo
measures more
than two inches

in diameter, while a common form on the Florida reefs, de-
voured in large quantities by the Holothuria, or sea-cucum-
26 ZOOLOGY.

ber, measures about one fifth of an inch in diameter. Most
of our native species are much more minute. The Kozoon,
so-called, is supposed by some to be a Foraminifer, but
others regard it as more probably inorganic, and simply a

 

Fig. 16.—Actinospherium. a, a mor-
sel of food drawn into the cortical layer
6; ¢, central parenchymatous mass of
the body ; d, some balls of food-stuff in
the latter; e, pseudopodia of the cortical
layer.—After Gegenbaur.

 

Fig. 15.—B, Collosphera spi-
nosa, with projecting conical
points, containing little sphe-
roids, which pass into monad-
like bodies C. D, probably an

 

early stage of C. A, a young Fig. 17.—Heliophrys variabilis. A sun-
pepeuie of C. Huxleyt Miler.— animalcule, showing the pscudopods,
ter Cienkowski. nuclei, and vacuoles.—From Macallister.

mineral. Undoubted Foraminifera occur in the Silurian
formation, while large masses of carboniferous and cre-
taceous rocks are formed by their shells.

Order 2. Radiolaria.—These Rhizopods have the general
structure of Amebe, but secrete beautiful silicious shells,
RHIZOPODA. 27

of varied forms, more or less spherical, perforated for the
protrusion of the pseudopodia, with often spicules or points
radiating from the shell. They reproduce apparently by
self-division of the interior, resulting in a swarm of monad-
like young. The Heliozoa are represented by the fresh-
water Actinophrys sol, which is round, with numerous stiff
pseudopodia radiating in all directions from the body, and
by Actinospherium (Fig. 16). The true marine Radiolaria
are represented by Collosphera spinosa Cienkowski (Fig. 15).
It possesses a perforated shell beset with small spines, which
encloses a capsule with a protoplasmic wall. In the capsule-
stage (A) it often divides by fission into two halves. After-
ward the older capsule divides into a number of little round
bodies, which develop two lashes as in C.

Cuass II.—RHIZOPODA.

Unicellular organisms consisting of protoplasm, with an outer clear,
cortical, and an inner granular mass containing one or more nuclei, and
one or more contractile vacuoles ; moving by means of pseudopodia, and
either naked or secreting a one or many-chambered shell ; reproducing by
self-division, or by the production of several or many ameboid or monad-
like young.

Order 1. Foraminifera.—One-celled Rhizopods with one or many nuclei
and contractile vacuoles, secreting chambered calcareous or
horny (chitinous ?), rarely arenaceous, shells. (Amceba,
Globigerina, Nummulina.)

Order 2. Radiolaria.—Rhizopods with pointed, branched, usually anas-
tomosing and granular pseudopodia. The body contains
either numerous small heterogeneous nuclei, or a single
larger, highly differentiated vesicular nucleus. The pro-
toplasm of the body is further separated into a peripheral
non-nucleated and a central nucleated portion by a mem-
branous capsule with porous walls. Reproduction occurs
by the breaking up of the body into monad-like embryos,
with one or sometimes two locomotive lashes (flagella).
There are two divisions : (1) Heliozoa (Actinophrys, Actino-
spherium), and (2) Radiolaria (or Cytophora), having as rep-
resentatives Acanthometra, Collozotim, Spherozoiim, and
Collosphera.
28 ZOOLOGY.

Crass II].—GREGARINIDA (Gregarines).

General Characters of Gregarinida.—The largest and
best known species of this group is an inmate of the
intestinal canal of the European lobster, and was named
by KE. Van Beneden Gregarina gigantea (Fig. 18). It
is worm-like, remarkably slender, and is sixteen mil-

 

Fig. 18.—Gregarina gigantea. L, two individuals of natural size. HK, the same
much enlarged; n, nucleus. A, the same encysted. B, subdivision of the cyst. C, divi-
sion of the contents of cyst into small spheres, observed in another species. V, the
spheres enlarged. M, cyst filled with pseudonavicelle, O.—After Lieberkuhn. D—F,
moner-like young of G. gigantea. G, H, pseudofilaria stage. J, J, early nucleated
forms of Gregarina gigantea.—After Van Beneden.

limetres (over half an inch) in length, being the largest
one-celled animal known. In this organism an external,
structureless, perfectly transparent membrane with a double
contour can be distinguished. It represents the cell-wall
of the cells in the higher animals. Beneath this outer wall
is a continuous layer of contractile substance, forming a
true system of muscular fibrille comparable to that of the
Infusoria. The body-cavity of the Gregarina contains a
GREGARINIDA, 29

viscid fluid holding in suspension rounded granules, among
which the nucleus rests. This nucleus contains an inner
vesicle or nucleolus, which strangely disappears and then
reappears. Van Beneden distinguishes three kinds of mo-
tions in the Gregarine: 1. They represent a very slow
movement of translation, in a straight line, and without the
possibility of distinguishing any contraction of the walls of
the body which could be considered as the cause of the
movement. It seems impossible to account for this kind of
motion. 2. The next kind of movement consists in the
lateral displacement of every part, taking place suddenly
and often very violently, from a more or less considerable
part of its body. Then the posterior part of the body may
be often seen to throw itself out laterally by a brusque and
instantaneous movement, forming an angle with the anterior
part. 3. Owing to the contractions of the body, the gran-
ules within the body move about.

The life-history of this Gregarina is as follows : It occurs
in its normal state in lobstersin May, June, and August, but
in September becomes encysted in the walls of the rectum of its
host, the cysts (Fig. 18, A) appearing like little white grains
of the size of the head of a small pin. When thus encysted
the nucleus disappears, and the granular contents of the
cyst divide into two masses (B), like the beginning of the
segmentation of the yolk of the higher animals. The next
step is not figured by Van Beneden, and we therefore intro-
duce some figures from Lieberkuhn which show how the
granular mass breaks up into spindle-shaped bodies (called
by some authors ‘‘ pseudonavicelle,’? and by Lieberkuhn
“* psorosperms’’) with hard shells. After the disappearance
of the nucleus and vesicle, and when the encysted portion
has become a homogeneous granular mass, this mass divides
into a number of rounded balls (Fig. 18, C). These balis
consist of fine granules, which are the spindle-shaped bodies
in their first stage (Fig. 18, NW). They then become
spindle-shaped (0) and fill the cyst (Fig. 18, M7), the balls
having meanwhile disappeared. From these psorosperms
are expelled amceba-like masses of albumen (D /’), which,
as Van Beneden remarks, exactly resemble the Protam@ba
30

already described.

ZOOLOGY.

This moner-like being, without a

nucleus, is the young Gregarina.

But soon the Ameba characters arise. The moner-like
young (Fig. 18, D # F) now undergoes a further change. Its
outer portion becomes a thick layer of a brilliant, perfectly
homogeneous protoplasm, entirely free from granules, which
surrounds the central granular contents of the cytode
(Haeckel) or non-nucleated cell. This is the Amoeba stage
of the young Gregarina, the body, as in the Ameba, con-

 

Fig. 19.—Gregarina from
the alimentary canal of a
beetle, Opatrum sabulo-
sum. 1, younger state,
with a beak-like continua-
tion (a) of the head. 2,
older; a, anterior end; 6,
hinder part of the body;
c, nucleus.—After Gegen-
baur.

sisting of a clear, cortical, and granular
medullary or central portion.

The next step is the appearance of two
arm-like projections (Fig. 18, #’), com-
parable to the pseudopods of an Ameeba.
One of these arms elongates, and, sepa-
rating, forms a perfect Gregarina. Soon
afterward the other arm elongates, ab-
sorbs the moner-like mass, and also be-
comes a perfect Gregarina. This elon-
gated stage is called a Pseudofilaria (Fig.
18, G); no nucleus has yet appeared.
In the next stage (Fig. 18, H n, nucleus)
the body is shorter and broader, and the
nucleus appears, while a number of gran-
wles collect at one end, indicating a
head. After this the body shortens a
little more (J, J), and then attains the
elongated, worm-like form of the adult

Gregarina (A’). Van Beneden thus sums up the phases of

growth :

CoO Ee ON a

The Gregarine

The Moner phase.

The generating Cytode phase.

The Pseudofilaria phase.

The Protoplast (adult Gregarina).

The encysted Gregarina.

The sporogony phase (producing zoospores).

and Amosbx constitute Haeckel’s group
THE INFUSORIANS. 31

of Protoplasta. Other Gregarine are very minute, and are
parasitic in insects (Fig. 19), etc., and vary greatly in form,
some being apparently segmented, while in a few forms the
body ends anteriorly in a sort of beak armed with recurved
horny spines. We are now prepared to adopt the following
definition of the class :

 

Crass ITI.—GREGARINIDA.

Ameba-like Protozoa, more or less elongated, with a determinate cell-
wall, with a subcuticular system of muscular fibrille, with a nucleus, but no
contractile vacuole ; reproducing by encysting and subdivision of the cen-
tral mass of the body, producing shelly psorosperms, from which escape the
moner-like young, which undergo a metamorphosis into the usually worm-
shaped, parasitic adult (Gregarina).

 

Crass IV.—INFusOoRIA.

These organisms can best be understood by studying rep-
resentatives of the three orders forming the class.

Order 1. Flagellata (Monads).—A familiar example of
monads, Monas termo Ehrenberg? has been studied by
H. J. Clark. His description will suit our purpose of indi-
cating the form and habits of a typical flagellate animalcule.
It somewhat resembles our figure of Uvella in its general
shape, being pear-shaped, faint olive in color, and provided
with a vibratile locomotive lash or flagellum. In swimming,
the monad stretches out the flagellum, which vibrates with
an undulating, whirling motion, and produces a peculiar
graceful rolling motion. When the monad is fixed the fla-
gellum is used to convey food to the mouth, which lies be-
tween the base of the flagellum and beak, or ‘‘lip.’’ The
food is thrown by a sudden jerk, and with precision, directly
against the mouth. ‘‘ If acceptable for food, the flagellum
presses its base down upon the morsel, and at the same time
the lip is thrown back so as to disclose the mouth, and then
bent over the particle as it sinks into the latter. When the
lip has obtained a fair hold upon the food, the flagellum
withdraws from its incumbent position and returns to its
former rigid, watchful condition. The process of degluti-
32 ZOOLOGY.

tion is then carried on by the help of the lip alone, which
expands latterly until it

completely overlies the
particle. All this is done
quite rapidly, in a few sec-
onds, and then the food
glides quickly into the
depths of the body, and is
enveloped in a digestive
vacuole, whilst the lip as-
sumes its usual conical shape and proportions.’”’ (Clark.)
All the monads have a contractile vesicle. In Monas
termo, Clark observes that it is “‘ so large
and conspicuous that its globular form
may be readily seen, even through the
greatest diameter of the body; and con-
tracts so vigorously and abruptly, at the
rate of six times a minute, that there
seems to be a quite sensible shock over
that side of the body in which it is em-
bedded.”? The contractile vesicle is
thought to represent the heart of the
higher animals. The reproductive organ
may possibly be represented in Monas
termo by a ‘‘very conspicuous, bright,
highly refracting, colorless vil-like globule
which is enclosed in a clear vesicle’’ called
the nucleus. This and other monads live
either free or attached by a slender stalk.
As an example of the compound or aggre-
gated monads may be cited Uvella, prob-
ably glauconia of Ehrenberg. Other
forms, as Codosiga, are fixed by a stalk to
some object (Fig. 21, C. pulcherrimus
Clark). In this and allied forms the body imu
is surmounted by a collar or calyx out of Hn eecae Sena
which the flagellum projects. The Co- aay eroarete inci
dosiga has been observed by Clark to un- ae
dergo fission, two independent monads resulting, within the
space of forty minutes.

eA

 

Fig. 20.—Monads (Uvella).—After Tuttle.

   

ee 21.—A, Codosiga
pulcherrimus. B, the
THE FLAGELLATE INFUSORIA. 33

The first sign of fission is a bulging out of the collar,
which becomes still more bell-shaped. The flagellum next
disappears. Then marks of self-division appear in a nar-
row, slight furrow (Fig?47, B, e), extending from the front
half way back along the middle of the body. Meanwhile
the collar, which had become conical, expands, and, most
striking change of all, two new flagella appear. Then the
collar splits into two (Fig.-17, C’), and soon the two new Codo-
sigee become perfected, when they split asunder, and become
like the original Codosiga. Such is the usual mode of mul-
tiplication of the species in the monads.

A few monads have been observed to become encysted, and
to break up into excessively minute bodies, from which new
monads have grown. Two
individuals of the same form ,|
(Heteromita) in certain stages
fasten themselves together,
the larger absorbing the
smaller as if conjugating,
like Desmids, the compound
body resulting becoming en-
cysted ; finally the contents
of the cyst become divided _ : ee
into either large or minute fers aa eco Bee ena

: us. Greatly magnified.—After Cienkowski.
germs (zoospores) which as-
sume the parent form. The researches of Messrs. Dallinger
and Drysdale on this Heteromita have proved that while
the mature forms may be destroyed at a temperature of
61°— 80° C., the motile germs, with a diameter of soq/raa
of an inch, may be heated to 148° C., without perishing.

Noctiluca (Fig. 22) has been proved by Cienkowski to be
an enormous monad. It is a highly phosphorescent organ-
ism, so small as scarcely to be seen with the naked eye, be-
ing from } to 1 mm. (:01 to ‘04inch) in diameter. It occurs
in great numbers on the surface of the sea. It has a nearly
spherical jelly-like body, with a groove on one side from
which issues a curved filament, used in locomotion. Near
the base of this filament is the mouth, having on one side a
tooth-like projection. Connecting with the mouth is an os-

 
34  Z00LOGY.

ophagus which passes into the digestive cavity, in front of
which lies an oval nucleus. Beneath the outer skin or firm
membrane surrounding the body is a gelatinous layer, con-
taining numerous granules. A network of granular fibres
arises from the granular layer; these fibres pass into the
middle of the body to the nucleus and digestive cavity. The
young (Fig. 22, , s) result from a division or segmentation
of the entire mass of the protoplasm of the body, forming
small oval bodies with a long lash. The zoospores are like
those of other Flagellata, and for this reason and the gen-
eral structure of the adult, Noctiluca is by the best author-
ities associated with the Flagellata. Noctiluca also under-
goes conjugation, but the zoospores
appear whether conjugation has oc-
curred or not. The Noctiluca on the
coast of the United States has been
observed in abundance on the surface
of the sea in Portland harbor, by Mr.
E. Bicknell. It is phosphorescent,
but whether identical with Moctiluca
miliarts of the European seas is not
known. Leptodiscus medusoides Hert-
eer erie wig, is discoidal or medusiform in
with ifs stalk attached to a shape, the disk one and a half milli-
pate ‘i imoblike expan, metres in diameter. When disturbed
altictees uokers—From Mac: i+; darts through the water by the con-
tractions of its umbrella-shaped bedy.

It is allied to Noctiluca and was discovered at Messina.

Peridinium is the type of a third and higher division of
monads, the body being protected by a hard shell, with one
or more flagella, and a row of cilia serving as a locomotive
apparatus, and thus, together with Heteromastiz and Dys-
teria, connecting the Mlagellata with the Ciliata or true
Infusoria.

Order 2. Tentaculifera (Acinetw, Suctoria).—An Acineta
(Fig. 23) reminds us at first sight of a Radiolarian, since
the body is provided with filiform, tentacle-like processes
resembling the pseudopodia of a Radiolarian, but the ten-
tacles are in reality rather stiff, hollow, and act as suck-

 
THE CILIATE INFUSORIA,

35

ers, so that when the organism has by means of its hollow

arms or tentacles caught some
Infusorian, the arms con-
tract, draw the victim nearer
to the Acineta, and when the
sucking disk at the end of the
arms has penetrated the skin,
the contents of the body of
the Infusorian are sucked into
the food-cavity of the Acine-
ta; on the other hand, in
some Acinetz a portion of the
arms are simply prehensile.
These animals are in their
adult phase quite unlike the
Flagellata or Ciliata, but the
young are developed within
the parent and are provided
with cilia, being at first free-
swimming, and afterward
fixed by a long stalk. The
Acinete sometimes self-di-
vide, sending off from the
free end of the body a ciliated
Acinete ; they have also been
seen to conjugate.

Order 3. Ciliata (Infuso-
ria).—A common type of this
group and one easy to obtain
by the student is Parame-
cium (Fig. 24), observed in
infusions, or moving rapidly
over the bodies of larger ani-
mals which may be under the
microscope. Figure 24 rep-
resents Paramecium cauda-
tum Ehrenberg. This ani-
malcule is a mass of proto-

plasm, representing a single cell.

H

 

Fig. 24.—Paramecium caudatum. A
view from the dorsal side, magnified 340
diameters. #H, the head; 7, the tail; m,
the mouth; m to g, the throat; a, the pos-
terior opening of the digestive cavity; cv!
the anterior and cv posterior contractile
vesicles; I, II, III, the radiating canals of
cv!; n, the reproductive organ; v, the
large vibrating cilia at the edge of the ves-
tibule.— After H. J. Clark.

In the body-mass are ex-
36

ZOOLOGY.

cavated a mouth and a throat leading to a so-called stomach
or digestive cavity.

Two hollows

 

Fig. 25.—Stentor polymorphus, magnified 130
diameters, expanded and bent slightly over to-
ward the observer; the mouth m, next the eye,
and the dorsal edge in the distance. a, poste-
rior end; sh, the tube enclosing a, ¢, the cili-
ated border of the disk (s); v, the larger rigid
cilia; cv, the contractile vesicle in the extreme
distance,seen through the whole thickness of the
body; cv}, ev?, the posterior prolongation of cv,
in the distance; 7,71, the circular and radiating
branches of what, by Clark, was supposed to be
a rudimentary nervous system; n, 7}, the re-
productive system, extending from the right
side, at 2, posteriorly, but toward the eye at 7}.
—After Clark.

in the body form the con-
tractile vesicles, and an-
other cavity constitutes
the reproductive organ.
Prolongations of the body-
mass form the cilia, which
characterize the Infusoria
and give the name to the
present order, Ciliata.
Paramecium has an elon-
gated, oval body ‘* with
one end (7) flattened out
broader than the other,
and twisted about one
third way round, so that
the flattened part resem-
bles a very long figure 8.”’
In this form, as well as in
Stentor (Fig. 25), as Clark
remarks, ‘‘ we have the
mouth at the bottom of a
broad notch or incurya-
tion, and the contractile
vesicle on the opposite
side, next the convex
back, whilst the general
cavity of the body lis be-
tween these two.’’ The
arrows in the figure repre-
sent the course of the par-
ticles of indigo with which
Clark fed his specimens,
“as they are whirled
along, by the large vibrat-

ing cilia (v) of the edge of the disk, against the vestibule of

the mouth.”’
mass of rejectamenta is formed

which has appeared a short time before.

During the circuit the food is digested, a

near the protuberance, a,
This finally
THE CILIATE INFUSORIA. 30

opens, allows the rejected matter to pass out, and then
closes over, leaving no trace of an outlet. This and other
Infusoria seem, then, to have a definite digestive tract, hol-
lowed out of the parenchyma of the body.

“The system,’’ says Clark, ‘‘ which is analogous to the
blood-circulation of the higher animals, is represented in
Paramecium by two contractile vesicles (cv, cv', 1, 11, 111),
both of which have a degree of complication which, per-
haps, exceeds that of any other similar organ’’ in these ani-
mals. When fully expanded they appear round, as at cv;
but when contracted they appear, observes Clark, as ‘‘ fine
radiating streaks, and as the main portion lessens they grad-
ually broaden and swell until the former is emptied and
nearly invisible, and
they are extended
over half the length
of the body. In this
condition they might
be compared to the
arterial vessels of the
more elevated classes 7
of animals, but they #
would at the same . Fig. 26.—Process of fission in Stentor polymorphus.

c 6, a new Stentor budding out; ¢, ready to separate from
time represent the the original one; 7, the two in a contracted state.—

: 5 After Cox.
veins, since they
serve at the next moment to return the fluid to the main
reservoir again, which is effected in this very remarkable
way.’’ The contents of these vesicles is a clear fluid.

The reproductive organ in Paramecium isa small tube
(7), only seen at the reproductive period when the eggs (7)
are fully grown. Clark says that the eggs are arranged in
it ‘in a single line, one after the other, at varying dis-
tances.’ It usually lies in the midst of the body, and ex-
tends from one half to two thirds of the length of the ani-
mal. The eggs pass out from the so-called ovary through
an aperture near the mouth. Lasso-cells like those in the
jelly-fishes are said by Bitschli to exist in an infusorian
named by him Polykrikos.

In the trumpet animalcule (Fig. 25, Stentor polymor-

 
38 ZOOLOGY.

phus Ehrenberg) we have a rather more complicated form,
the infusorian attaching itself at one end by a stalk, and
building up a slight tube, into which it contracts when. dis-
turbed. The Stentor may be sometimes observed multiply-
ing by self-division, Clark observed Stentor polymorphus
undergoing the process. The first change observed was the
division of the contractile vesicle into two. The mouth of
the new Stentor was formed in the middle of the under side,

 

Fig. 27.—Epistylis flavicans Ehr., a single, many-forked colony of bell animalcules,
slightly magnified. ‘Fig. 28, one of the animalcules magnified 250 diameters. p, the
stem; d, the flat spiral of vibrating cilia at the edge of the disk; ms, the muscle; m to
s, the depth of the digestive cavity; m, the mouth; g, g}, the throat; Z, the single
vibratory lash, which projects from the depths of the throat; cv, the contractile vesi-
cle; n, the reproductive organ.—After Clark.

first appearing as a shallow pit, around which arises a semi-
circle of vibratile cilia) The mouth and throat form in the
new Stentor before any signs of division appear, but in the
course of two hours the body splits asunder, and two new in-
dividuals appear. Fig. 26 illustrates the mode of self-
division seen in Stentor polymorphus Ehrenberg, by Hon.
J. D. Cox. The process in this occupied two hours ; at the
final stage (Fig. 26, f) the connection between the two ani-
malcules parted, ‘‘and the two Stentors swam separately
THE CILIATE INFUSORIA. 39

away, both assuming the common form of the animalcule
when free- swimming, and differing from the original indi-
vidual only in being of smaller size.”’

The most complicated as well as most interesting form of
all the Infusoria is the bell-animalcule, Vereen It is
very common in pools, forming patches like white mould on
the leaves and stems of submerged plants. It may, like
Stentor, be observed under low powers of the microscope.
Their motions, as they suddenly contract and then shoot
out their bell, mounted on a long stalk, are very interesting.
The throat (esophagus) i is quite distinct, while the nucleus
is the most conspicuous organ of the body. The digestive
cavity is a large hollow in the protoplasm forming the body-
mass, in which the whole mass of food revolves ca a deter-
minate channel. Closely allied to Vorticella is Epistylis
(Figs. 27 and 28).

While most ciliate Infusoria, so far as known, multiply
by self-division, in Va aginicola the process is more like true
gemmation or budding, and is accompanied by a process of
encysting, resulting in) the production of a free-swimming
ciliated embryo, the adult Vaginicola being attached. The
Vorticella also becomes encysted, and the nucleus subdivides
until the body becomes filled with monad-like germs, the
result of the simultaneous breaking up of the nucleus. The
Vorticelle, then, pass through a flagellate or monad stage,
from which they pass into the Vorticella condition, when
they multiply by self-division and by budding, the last
generation becoming encysted.

Conjugation is a common occurrence in ciliate Infusoria,
and results in the breaking up of the nucleus of each indi-
vidual into a number of fragments, and the appearance in
each of the individuals of the nucleus and nucleolus (either
single or multiple) which characterize the species. *

* Balbiani believes that the ciliate Infusoria have eggs which are
fertilized by spermatic particles. More recently, however, Engelmann,
Biitschli, and Hertwig have denied that conjugation is of a truly sexual
character, and that the striated nucleoli of certain individual Infusoria
are spermatozoa. ‘‘ Nevertheless,’ remarks Huxley (Anatomy of In-
40 ZOOLOGY.

Crass I[V.—INFUSORIA.

Flagellate or ciliate (sometimes only ciliate in the early stages) Protozoa,
the body not changing in form, having a definite skin, and often wholly or
partly provided with cilia, usually free, sometimes stalked or attached, with
a mouth-opening and wsophagus, and rudiments of digestive, circula-
tory (two or more contractile vesicles), and reproductive organs (nucleus and
nucleolus), but with no distinctively sexual organs.

Order 1. Flagellata.—Rounded, oval, or pear-shaped organisms, usually
exceedingly minute, provided with one or two flagella, with
an oral region, into which particles of food are thrown by
the flagellum ; with a nucleus and contractile vesicles, rarely
stalked, and with a calyx; sometimes aggregated; with a row
of cilia in the highest forms serving as a locomotive appara-
tus ; reproducing by self-division or by segmentation of the
protoplasmic contents of the body, the young being minute
oval bodies, provided with a flagellum (Monas, Heteromita,
Noctiluca, Peridinium).

Order 2. Tentaculifera (Suctoria). — Naked, not ciliated, protozoans,
with long, stiff, retractile arms or tentacles, provided with a
sucker at the end, the arms hollow, conveying the food to
the digestive cavity ; originating from ciliated young ; also
by self-division throwing off ciliated forms, and undergoing
conjugation (Acineta).

Order 3. Oiliata (True Infusoria).—Body free and covered with cilia
(Paramecium, Stentor, ete.), or stalked, with the cilia con-
fined to the head end (Vaginicola and Vorticella, etc.) ; a
well-defined mouth and cesophagus ; a digestive cavity and
vent ; alarge nucleus, and two or more contractile vesicles.
Reproducing by self-division, budding or conjugating, and
producing monad-like young by self-division of the nu-
cleus ; sexuality doubtfully indicated.

The following diagram represents the relative position
ci the orders and classes of Protozoa, and in a rude way
their possible genetic relations :

vertebrated Animals, p. 662), ‘‘ it is still possible that the conjugation
of the Infusoria may bea true sexual process, and that a portion of the
divided endoplastules [striated nucleoli] of each may play the part of
the spermatic corpuscle, the conjugation of which with the nucleus of
the ovum appears, from recent researches, to constitute the essence
of the act of impregnation.”’
CLASSIFICATION OF PROTOZOA. 41

VIEW OF THE CLASSIFICATION OF THE PROTOZOA.

Ciliata.
(Paramecium.)

 

 

Tentaculata.
(Acineta.)
Flagellata.
(Monas.)
|
INFUSORIA.
Radiolaria.
(Actinophrys.)
Foraminifera.
(Rotalia.)
GREGARINIDA. | RHIZOPODA.
MoneERA.

Laboratory Work.—None of the Protozoa, except the shells of the
Foraminifera and Radiolaria, can be well preserved after death, and it
is always better to study any animal alive or freshly killed than when
preserved in any sort of fluid. Fresh-water Amabe and Monera
should be looked for on the surface of leaves and the stems of sub-
merged plants in ponds, pools, and ditches. Many fresh-water Rhizo-
pods dwell in sphagnum swamps and in damp moss or in shaded pools.
The marine forms may be gathered with a fine towing net, when the
surface of the ocean is calm. The commoner Foraminifera will be found
on shells and stones at low-water mark or in shallow water, but most
abundantly at greater depths—. e., from ten to one hundred fathoms.
On being placed in water they will, after a period of rest, send out
their pseudopodia.

To study their form and development they should be placed in a
drop of water in an animalcule or aquatic box, and kept in this way
for several days and even weeks, the box being examined daily, and
water added if necessary. The shells may be studied by grinding and
slicing into transverse and longitudinal sections. The animals of
Miliola and other forms (Rotalia, Textillaria), on being treated with
diluted chromic acid and stained with carmine, disclosed to Hertwig a
well-marked nucleus. The nucleus may also be deeply stained by
hematoxylin or carmine, and may be clearly demonstrated by acetic
acid, which tends to destroy the surrounding protoplasm. Much in-
genuity, mechanical skill, and patience is required in the study of the
Protozoa, and much yet is to be learned regarding their mode of de-
velopment and their structure,
CHAPTER UL
BRANCH II.—PORIFERA (Sponges).

General Characters of Sponges.—Although the sponges
were formerly supposed to be compound or social Ameebe,
and more recently monads, from the striking resemblance
of their epithelial cells to certain monads, and have been
generally regarded as Protozoans, later researches have
shown that they are in reality many-celled animals, and that
for a short period of their life they follow the same develop-
mental path as the higher animals. It was also discovered
that they reproduce by eggs, the latter undergoing segmen-
tation and assuming the condition of a three-layered sac,
the three layers being identical with those of the higher
branches of the animal kingdom, so that the gap between
the Protozoans and sponges is a wide one, and the latter are
more nearly allied to the Hydra, for example, than to any
one-celled animal.

One of the simplest sponges, such as Ascetta primordialis
Haeckel, is a spindle or vase-shaped cylinder, attached by its
base, with the cellular soft portion supported by a basket-
work of interlaced needles or spicules of silex or lime. The
cells are arranged in three layers, the innermost (endoderm)
being provided each with acilium. The spicules, and also
the eggs, are developed in the middle layer (mesoderm).
Moreover, the walls of the body are perforated by multitudes
of small pores (whence the name of the branch, Porifera),
through which the water percolates into the body-cavity,
carrying minute forms of life or food-particles, which are
individually thrown into each cell by the action of the single
cilium thrust out of the collar of the cell, much as in an in-
dividual monad such as Codosiga (Fig. 21). Hach cell re-
STRUCTURE OF SPONGES. 43

jects its own waste particle of food, the protoplasm having
been previously absorbed, and the waste from all the epi-
thelial cells is collectively expelled from the single excurrent
orifice (oscwlum), there being many pores or mouths, and
but a single outlet for the rejectamenta.

Such is the structure of one of the simplest sponges ; the
larger common sponges differ mainly in having a less defi-
nite form, with numerous sacs or digestive cavities or cham-
bers, and numerous excurrent orifices or oscula. It will be
seen, then, that we have in the sponge a three-layered sac,
its cavity rudely foreshadowing the gastrovascular cavity of
the Hydra, but with no genuine mouth, the pores or so-
called mouths simply allowing the sea-water laden with
sponge-food to flow in, inflowing currents being formed by
the ciliary action of the digestive cells, and the excurrent
orifice permitting its exit. ’

In the other sponges such as are figured in this chapter,
the structure is a little more complicated than in the
Ascetta. There is no general body-cavity, with a contin-
uous lining of epithelial cells, but the entire sponge-mass is
permeated by large canals ending in oscula, and there are
innumerable pores (so-called mouths) leading by branching
canals to little pockets or cavities, which are lined with the
flagellate, collared cells developed specially from the inner
cell-layer (endoderm) ; so that the animal is myriad-stom-
ached, so to speak. Moreover, the middle layer of cells is in
many sponges greatly thickened, and nearly the whole
mass, as seen in the common sponge, consists of spicules or
horny fibres, and protoplasm, through which the excurrent
and incurrent channels meander. Thread cells or lasso-
cells like those hereafter to be described in Hydra have
been detected in the sponge named Reniera.

Let us now follow out the life-history of a sponge. The
sponges are further distinguished from the Protozoa in pro-
ducing eggs and spermatic particles, the eggs being fertilized
before leaving the sponge. The egg after fertilization di-
vides in two, four, eight, sixteen, and more spheres, attain-
ing the mulberry or morula * state (Fig. 29). The result is

* The terms morula and gastrula are used in this hook simply for
44 ZOOLOGY.

the formation of atwo and afterward three-layered sac, cor-
responding to the gastrula of the higher animals. In this
state (Fig. 30) the germ breaks out of the parent sponge into
the sea. Fig. 31 represents the development of the common
little calcareous sponge (Sycon ciliatum), found between
tide-marks. A indicates the morula with the segmentation-
cavity (c), which afterward
disappears as at B. The
gastrula is represented at
C, and consists. of ciliat-
ed and non-ciliated large
round cells; the first series
ae ny gmentation of egg of sponge: formin gum sort of arch, with

a hollow in the middle,
around which a large number of very fine brown pigment
corpuscles are collected. The next change of importance is
the disappearance of the cavity, the upper or ciliated half
of the body being much reduced in size. Then the large
round cells of the hinder part are united into a compact
mass, leaving only a single row. The ciliated cells are
gradually withdrawn into the
body-cavity. Fig. 31, D, shows
this process going on. At this
period also the larva becomes ses-
sile, and now begins the formation
of the sponge-spicules, which de-
velop from the non-ciliated round
cells. Metschnikoff calls atten-
tion to the fact that at this early
stage the Sycon passes through a
phase which is persistent in the Fig. 30.—Gastrula of a sponge (Sy-
genus Sycyssa. The layer of cil- candra raphanus)—aAfter Schulze.
iated cells are gradually withdrawn into the body-cavity,
until a small opening is left surrounded with a circle of
cilia. These cilia finally disappear, a few more spicules
grow out, and meanwhile the opening disappears. In the
next stage (represented at D) a considerable body-cavity ap-

 

 

convenience to avoid circumlocution. It may be that these conditions
will be found to be essentially modified in different groups of animals.
DEVELOPMENT OF SPONGES. 45

pears which may be seen through the body-walls. At this
time the germ consists of two layers, the inner layer of cili-
ated cells (endoderm) forming a closed sac, enveloped in the
spiculiferous layer. Such are the observations of Metschni-
koff on the development of Sycon. According to the ob-
servations of Barrois, the larva or gastrula fixes itself by what
are destined to be the ectodermal cells, and which are the
round non-ciliated cells forming the posterior end (Fig. 31,
C) of the free-swimming gastrula. About this time the
mesoderm separates from the endoderm, either before or
just after the gastrula becomes stationary, according to the
group to which it belongs.

When the young sponge becomes stationary it does not
differ from the gastrula, except that it becomes more or less

 

Fig. 31.—Development of a sponge (Sycon ciliatum).—After Metschnikoff.

irregular in form. Then appear the food or digestive cavi-
ties in the endoderm, in Sycandra becoming radiating tubes
lined with ciliated, collared, monad-like cells; or in Lewcon
and Halichondria, and their allies, forming scattered pock-
ets, called ‘‘ ampullaceous sacs.”? In most sponges (except
some calcareous species) there is no general body-cavity in
the gastrula, nor in the young after the larva becomes sta-
tionary, according to Barrois. After the formation of the
ampullaceous sacs the pores open through the mesoderm
and connect the sacs and ciliated channels, as the case may
46 ZOOLOGY.

be, with the outer world. These pores may open and then
be permanently closed, new ones opening elsewhere. The
osculum bursts open by the accumulation of water between
the two layers in the same manner as the pores. Finally,
in certain sponges the horny fibres grow out from the outer
cell-layer and extend inward, surrounding the spicules, the
latter developing from the middle cell-layer.

It appears, also, that all sponge embryos form a two and
afterward three-layered sac (gastrula), in which in the sim-
plest sponges there is a primitive body-cavity and a prim-
itive mouth, while in the higher calcareous sponges and in
the silicious forms the body - cavity is only temporarily
open, being afterward filled up by the interior ciliated
cells, and thus forming a compact mass.

In the sponges, also, the larva or free-swimming young
is a three-layered sac, which is either hollow or, more com-
monly, solid, and may attach itself at the end of its free-
swimming life by one end to some fixed object. The body-
cavity may persist in the simpler forms through life, though
in most sponges there is no genuine digestive cavity, but a
large series of minute digestive sacs communicating by canals
with the large ones leading to the oscula. The more or less
regular spherical form of the young of most sponges becomes
lost as they grow ; they become irregular in form, encrust-
ing rocks, and their development retrogrades rather than
advances.

In the fresh-water Spongzlla there is a special provision for
the maintenance of the species. In autumn are formed the
so-called “‘ seed,’’ being capsules in which are enclosed eggs
which in the spring develop young sponges. This cyst or
capsule may be compared to the buds or winter eggs of the
Polyzoa or of the water-flea (Daphnia).

From the members of the next branch, the sponges differ
in the great irregularity of their form, the lack of a definite
digestive cavity and of tentacles.

Order 1. Calcispongie.—The sponges may conveniently
be divided into two orders. Those belonging to the first
secrete spicules of lime, and there are no digestive or ampul-
laceous sacs, but the minute canals are lined with ciliated cells.
SPONGES. 4Y

The calcareous sponges are few in number and are repre-
sented by a delicate little white sponge called Sycon cilia-
tum Johnston, very common on sea-weeds between tide-
marks.

Order 2. Carneospongie.—In this group the spicules
may either be fibrous and horny or silicious. The middle

 

Tig. 32.—Aginella polypoides. Fig. 33.—Hyalonema boreale,

natural size.—After Lovén.
cell-layer is very thick, the endoderm being restricted to the

numerous digestive cavities or so-called ampullaceous sacs.

The fresh-water sponge (Spongilla) occurs everywhere
on submerged sticks and stones in running or nearly stag-
nant water, usually branching. With the exception of
Spongilla and another form, Siphydora echinoides Clark,
which grows as large as one’s fist in northern ponds and
streams, all sponges are marine. One of the commonest
48 ZOOLOGY.

sponges north of New York is Chalinula oculata (Bower-
bank), which grows in long slender branches on the piles of
wharves and bridges. Allied to it is Axinella (Fig. 32, A.
polypotdes).

A representative in northern waters of the genuine sili-
cious or glass sponges is the Hyalonema (Fig. 33, H. boreaie).
At the depth of 100 fathoms in the Gulf of Maine occurs a

 

 

Fig. 34.—Pheronema Anne, half natural size, with stellate and anchor-like spicules,
much enlarged.—After Leidy.
similar species (H. longissimum Sars). Fig. 34 represents
a fine silicious sponge (Pheronema Anne Leidy) from the
West Indies. The most beautiful of all silicious sponges is
the Venus’ flower-basket (Huplectellum aspergillum), which
lives anchored in the mud at the depth of about 10 fathoms,
near the Philippine Islands.
COMMERCIAL SPONGES. 49

The Cliona bores into shells, causing them to disinte-
grate. For example, Cliona sulphurea of Verrill has been
found by him boring into various shells, such as the oyster,
mussel, and scallop ; it also spreads out on all sides, envelop-
ing and dissolving the entire shell. It has even been found
to penetrate one or two inches into hard statuary marble.

Of the marketable sponges there are six species, with nu-
merous varieties. They are available for our use from being
simply fibrous, having no silicious spicules. The Mediter-
ranean sponges are the best, being the softest; those of the
Red Sea are next in quality, while our West Indian species
are coarser and less durable. Our glove-sponge (Spongia
tubulifera Duch. and Mich.) corresponds to Spongia Adriat-
ica Schmidt, which is the Turkey cup-sponge and Levant
toilet sponge of the Mediterranean. Spongia gossypina
Duch. and Mich. the wool sponge of Florida and the Baha-
mas, corresponds to S. equina Schmidt, the horse or bath
sponge of the Mediterranean.

BRANCH II.—PORIFERA.

The sponges are many-celled animals, with three cell-layers, without a
true digestive cavity, supported usually by calcareous or silicious spicules,
the body-mass permeated by ciliated passages, or containing minute cham-
bers lined by ciliated, collared, monad-like cells. No true mouth-opening,
but usually an irregular system of inhalent pores opening into the cell-lined
chambers or passages through which the food is introduced in currents of
sea-water, the waste particles passing out of the body by a single, but more
usually, many cloacal openings (oscula). Sponges are hermaphroditic, mul-
tiplying by fertilized eggs, the germ passing through a morula and a gastrula
stage. (The characters of the Class the same as those of the Branch.)

Order 1. Calcispongie. Animal supported by a framework of calcare-
ous spicules, disposed in lines or columns at right angles to
the walls ; with cell-lined radiating canals. (Sycon.)

Order 2. Carneospongie. Mesoderm exceedingly thick; the ciliated
cells restricted to cell-lined chambers. Either no solid
framework, as in Halisarca, or usually a well-developed
fibrous or silicious framework. (Spongilla, Spongia, Hya-
Jonema, Euplectella.)
50 ZOOLOGY.

VIEW OF THE CLASSIFICATION OF THE PORIFERA.

Carneospongia.
(Spongia.)
Caleispongie.
oe
—

 

=a
PoRIFERA.

Laboratory Work.—Sponges are difficult to preserve alive in aquaria
for study. Fine microscopic sections of the living sponge may be made
with the razor or the microtome, and the tissues and eggs as well as the
young be studied, though, from their minuteness, the study of the
young is very difticult. The ciliated young of Sycon ciliatum may be
obtained in the spring and summer by picking a portion of the sponge
to pieces and tearing out small fragments with fine needles, until por-
tions are small enough to be examined under high powers of the micro-
scope. Researches on the finer structure and mode of growth of the
sponge are difficult, and require much skill and long training in his-
tological methods. The gross structure of sponges may be studied by
cross and longitudinal sections made with a razor or knife.

         

    

Sag
Rr EA

 

5
CSE,

SS
CHE i ives! i,

BRANCH III.—CCGELENTERATA (Hyproips, JELLY-
FISHES AND PoLyps).

General Characters of Ccelenterates.—In this branch,
which is represented by animals like the Hydra (Fig. 36) and
Tubularia (Fig. 35), the body consists
of three cell-layers, surrounding a
definite, single, digestive cavity, the
mouth of the cavity being surrounded
by a circle of tentacles, which are hol-
low and connect directly with the
stomach. The latter, however, is only
partly differentiated or set apart from
the body, hence the name Celenterata
(Greek, xo1A0s, hidden, and ¢vrepor,
digestive tract). From the stomach
often radiate water-vascular canals, no
blood-system yet appearing thus far in
the animal kingdom, the products of
digestion reaching the tissues from
the smaller branches of the primary
water-vascular canals. The nervous
system is either absent, or in different
grades of development, from the iso-
lated nervo-muscular cells of Hydra SA |
and the scattered nerve-cells of an Fig. 35.—A Hydroid, Tubu-
Actinia, to the continuous ganglion- ere eee stoi
ated nervous ring of the minute From Tenney’s Zoology.
jelly-fish such as Sarsia. These animals display a striking
amount of radial symmetry, the organs and body being dis-
posed in a radiate manner around a central vertical axis, in

 
52 ZOOLOGY.

part formed by the digestive tract. ‘The Coelenterata pre-
sent striking examples of self-division, gemmation, and
alternate generations, and very great extremes in degree of
complexity of structure.

The different groups have a high geological antiquity;
the species of Hydroid and coral-polyps serving as time-
marks to measure off geological periods.

Ciass I.—Hyprozoa (Hydrotids and Acalephs.)

General Characters of Hydrozoa.—An excellent idea of
the general structure of the Hydrozoa may be obtained from
a study of Hydra, the type or example of the whole class, all
the other forms being but a modification and elaboration of
this simple type. The characters of the class as a whole are
based on what is found to constitute the structure of
Hydra.

Order 1. Hydroidea.—The animal next higher in struc-
ture than the sponge is the curious Protohydra discovered
by Greef among diatoms and sea-weeds at Ostend. It is re-
garded by Greef as the marine ancestral form of the Ceelen-
terates. It is the simplest Ccelenterate yet discovered. As
the form of the fresh-water Hydra is familiar, Protohydra
may be best described as being similar to that, except that
it is entirely wanting in tentacles. It is made up of two
layers (an ectoderm and endoderm, no mesoderm having yet
been discovered), with a mouth and stomach (gastro-vascular
cavity).

A more complicated form is the fresh-water Hydra, which
is commonly found on the under side of the leaves of aquatic
plants. There are two varieties of Hydra vulgaris appar-
ently common to the fresh waters of the old and new world ;
they are Hydra viridis and fusca. The somewhat club-
shaped body consists of two layers, the inner (endoderm)
lining the general cavity of the body, which serves both as
mouth and stomach, as well as for the circulation of the
nutritive fluid, and is called the gastro-vascular cavity.
The mouth is surrounded with from five to eight tentacles,
STRUCTURE OF HYDRA. 53

which are prolongations of the body-wall, and are hollow,
communicating with the body-cavity.

Such is the general structure of the Hydra. In the
ectoderm are situated the lasso-cells or nettling organs, be-
ing minute barbed filaments coiled up in a cell-wall, which
may be thrown out so as to paralyze the animals serving as
food. While the endoderm forms a simple cell-layer, the
outer layer (ectoderm) is more complex, as just within an
external simple layer of large cells is a multitude of smaller
cells, some of them being thread or lasso-cells, while still
within are fine muscular fibrille which form a continuous
layer. The large cells first named end in fibre-like pro-
cesses, which alone possess contractility, and are thought by
Kleinenberg to be motor-nerve endings. These large cells,
from combining the functions of muscle and nerve, are
termed ‘‘nervo-muscle cells.’? The little cavities between
the large endodermal cells and the muscular layer (meso-
derm?) which lies next to the endoderm are filled with
small cells and lasso-cells, forming what Kleinenberg calls
the interstitial tissue. From this tissue are developed the
eggs and sperm-cells.

The body being but slightly differentiated or set apart
into special organs, the Hydra, like other low creatures, is
capable to a wonderful degree of reproducing itself when
artificially dissected. Trembley, in 1744, described in his
famous work how he not only cut Hydras in two, but on
slicing them across into thin rings, found that from each
ring grew out a crown of tentacles; he split them into lon-
gitudinal strips, each portion becoming eventually a well-
shaped Hydra, and finally he turned them inside out, and
in a few days the evaginated Hydra swallowed pieces of
meat, though its old stomach-lining had now become its
skin. We shall see that not only many Hydroids, Aca-
lephs, some Echinoderms, and many worms, may reproduce
lost parts and suffer artificial dissection, but that self-
division is a normal though unusual mode of reproduction
among these animals, as well as in the Protozoa, which
may also be made to reproduce by artificial division, as
Ehrenberg cut an infusorian into several pieces, each frag-
ment becoming a perfect individual,
o4 ZOOLOGY.

The process of budding is but a modification of that in-
volved in natural self-division, and it is carried on to a great
extent in Hydra, a much larger number of individuals being
produced in this way than from eggs. Our figure (36)
shows two individuals budding out from the parent Hydra ;
the smaller bud (a) is
a simple bulging out
of the body-walls, the
bud enveloping a por-
tion of the stomach,
until it becomes con-
stricted and drops off,
the tentacles mean-
while budding out
from the distal end,
and a mouth-opening
arising between them,
as at c. Budding in
the Hydra, the <Acti-
nia, and, in fact, all
the lower animals, is
simply due to an in-
crease in the growth
and multiplication of
cells at a special point
on the outside of the
body, while the asex-
ual mode of reproduc-
tion in the Aphis and
«a few other insects
results from the mul-
tiplication of cells at

 

b
Fig. 36.—Hydra fusca, with two young (a c) bud- s
ding from it; 0, the hase; s, the peste cavity; ¢, @ particular point (the

tentacles. —From Clark’s Mind in Nature. : cues
ovary) in the inside of

the body. Thus Parthenogenesis or Ayamogenesis is analo-
gous to the ordinary mode of budding. Ehrenberg first showed
that the Hydra reproduces by fertilized eggs. Kleinenberg
describes the testis, which is lodged in the ectoderm, and
which develops tailed spermatozoa like those of the higher
DEVELOPMENT OF HYDRA. 55

animals. They arise, as in other higher animals, from a
self-division of the nuclei of the testis-cells. There isa true
ovary formed in the same interstitial tissue of the ectoderm,
consisting of a group of cells, which, Kleinenberg states,
differ entirely in their mode of formation from the ovaries
(gonophores) of the marine hydroids, which are genuine
buds.

It thus seems that Hydra is monecious or hermaphro-
dite—i.e., the sexes are not distinct. The egg of Hydra
originates from the central cell of the ovary.

There is a true segmentation of the egg. The young
Hydra thus passes through a true morula stage. There
is an outer layer of prismatic cells, forming the surface of
the germ, and surrounding the inner mass of polygonal
cells. At first none of these cells are nucleated, but after-
ward nuclei appear, and it is an important fact that these
nuclei do not arise from any pre-existent egg-nucleus.

The next step is the formation of a true chitinous shell,
enveloping the germ or embryo. After this, Kleinenberg
asserts that the cells of the germ become fused together,
and that the germ is like an unsegmented egg, being a
single continuous mass of protoplasm.

The remaining history of Hydra is soon told. In this
protoplasmic germ-mass there is formed a small excentric
cavity ; this is the beginning of the body-cavity, which
finally forms aclosed sac. After several weeks the germ
bursts the hard shell and escapes into the surrounding wa-
ter, but is still surrounded by a thin inner shell. After this
a clear superficial zone appears, and a darker one beneath,
which is the first indication of the splitting of the germ into
the two, afterward three, definitive germ-lamellea, common
to all animals except the one-celled Protozoa.

The embryo soon stretches itself out, a star-shaped cleft
appearing, which forms the mouth. The tentacles next ap-
pear. The animal now bursts open the thin inner shell,
and the young Hydra appears much like its parent form. —

There is, then, no metamorphosis in the Hydra ; no cili-
ated planula, as in many other Hydroids. The adult form
is thus reached by continuous growth,
56 ZOOLOGY.

It will be seen, to anticipate somewhat, that the Hydra,
exactly as in the vertebrates, including man, arises from an
egg developed from a true ovary, which, after fertilization,
passes through a morula stage; that the germ consists at
first of two germinal layers, while from the outer layer, as
probably in the vertebrates, an intermediate or nervo-mus-
cular layer is formed, which Allman thinks is the homologue
of the middle germ-lamella of the vertebrates (mesoderm)
supposed to have originally split off from the ectoderm.

In all the other Hydroids the sexes are separate, and we
for the first time in the animal kingdom meet with two
sorts of individuals—i.e., males and females.

 

Fig. 37.—Colony of Hydractinia echinata on a shell tenanted by a hermit crab,
natural size.—From Brehm’s Thierleben.

The simplest form next to Hydra is Hydractinia, in
which the individual is differentiated into three sets of
zooids—t.e., a, hydra-like, sterile or nutritive zooids ; 4 and
c, the reproductive zooids, one male and the other female,
both being much alike externally, having below the short
rudimentary tentacles several spherical sacs, which pro-
duce either male or female medusw. These medusa-buds
(gonophores) are in structure like the free medusex of Co-
ryne. The marine Hydroids, then, are usually sexually dis-
tinct, growing by colonies, which are either male or female,
HYDROID CORALS. 5?

Hydractinia echinata (Fig. 37) forms masses (each called a
hydrophyton) encrusting shells.

In Clava the reproductive buds remain permanently at-
tached. It grows in pink masses on Fucoids, about half an
inch high, and is very common on our shores. It is repre-
sented in fresh water by Cordylophora lacustris Allman,
which lives attached to rocks and plants in Europe and this
country.

Here comes in the group of Hydroids represented by
Millepora and Stylaster, which were formerly considered to
be Anthozoan corals. By the researches of L. Agassiz in
1859, and H. M. Moseley
in 1876, Millepora, which
had been confounded
with the coral polyps,
has been proved to be a
Hydroid allied, as Agas-
siz stated, to Hydracti-
nia. Like that Hydroid,
it forms a calcareous
encrusting mass, but of
much greater extent, a
considerable proportion
of the coral in the Flori-
da reefs being formed
by the Millep OE Our Fig. 38.—Millepora nodosa. a, nutritive
American species is Mil- 700 Pept ont or
lepora alcicornis Linn.,
while our description is taken from Moseley’s account of
Millepora nodosa Esper. (Fig. 38). Its generic name is de-
rived from the numerous pores or calicles dotting its surface
and arranged in irregular circular groups, consisting of a
central calicle, or cup-like hollow, with from five to eight
smaller calicles arranged around it. The mass of the coral,
or hydrophyton, consists of fibres (or trabeculae) of lime,
forming a spongy mass, traversed in all directions by tor-
tuous canals which ‘‘ form regular branching systems with
main trunks, giving off numerous branches, from which
arise secondary branches, and from these again smaller

 
58 ZOOLOGY.

ramifications. The whole canal system is connected to-
gether by a freely anastomosing mesh-work of smaller ves-
sels, and communicates freely by numerous offsets with the
cavities of the calicles.’’ As the animals increase in num-
bers and die, the coral stock increases in size, the layer con-
taining the living animals forming a thin film only, the
bottom of the little cups or pores forming a table or plat-
form, whence the term Yudulata, originally applied to this
group, the old calicles being divided by a series of trans-
verse plates or lamin, separating them into series of cham-
bers. Moseley shows that the corallum of Millepora is dis-
tinguished from all other coralla by its systems of canals
branching in an arborescent manner, while the tabulate
structure occurs in certain Alcyonaria, Zoantharia, and in
other Hydroida; hence the group Tabulata, as previously
stated by Verrill, is an artificial one.

The animals of the Millepora are of two kinds; those in-
habiting the central cup or pore are short, thick zooids,
with a mouth and four tentacles, and only half a milli-
metre in height ; those in the smaller pores are longer and
slenderer, about one and a half millimetres in height, with
from usually five to twenty tentacles, situated at irregular in-
tervals from the base to the summit of the body. The body
cavities of the zooids end in blind saes at the bottom of the
cup, but are continuous beyond with the canals of the hy-
drophyton, the latter being defined by Allman as forming
in the Hydroids ‘‘ the common basis by which the several
zooids of the colony are kept in union with one another.’’
As we know nothing of the mode of reproduction of Mille-
pora, we must leave it for the present near Hydractinia, to
which the adult animals are nearest related. Moseley also
discovered that Stylaster, a beautiful pink coral which grows
at Tahiti, with the Millepora, is in reality a Hydroid, and
not a true coral polyp, as has always been supposed. That,
finally, Millepora isa true Hydroid is proved, Moseley thinks,
by the peculiar structure of the hydrophyton, the forms of
the zooids, the absence of all trace of mesenteries, the ap-
parent septa present in the tentacles, and by the presence
of thread-cells of the form peculiar to the Hydrozoa. The
DEVELOPMENT OF HYDROIDS. 59

living Millepora, unless handled with great care, severely

stings the hand of the collector.

We now come to Hydroids which throw off a free naked-
eyed medusa from the hydrarium (Fig.

of the disk. This is
the water-vascular sys-
tem, communicating
directly with the gas-
; A tro-vascular cavity, or
ee esiemach Hour pee
below @, and medusa-bud
(gonophore) at a. Much en- cles hang from the
Jarged.—After Agassiz. disk, and simple eye-
spots and otolithic sacs (simple ears) are usu-
ally present and situated at regular inter-
vals around the edge of the disk. Such is
the typical form of all the free-swimming
Hydroids. ‘They are said, in a few cases,
to possess a well-developed continuous ner-
vous system, consisting of a nervous ring
around the disk (Romanes). They are bi-
sexual, the ovaries or spermaries being de-
veloped on the radiating canals, the embryo
escaping into the surrounding water by rup-
turing the walls of the ovary.

The young is at first oval, ciliated all
over the surface of the body, and is called a
planula. The planula, as in Melicertum, a
genus allied to Campanularia, and a type

 

39). From the centre of these free
bell-shaped, minute jelly-fishes depends
a hollow, open sac called the manu-
brium, the cavity of which (stomach)
opens into usually four canals, which
radiate from the hollow or stomach in
the centre of the disk and communi-
cate with a canal following the margin

\\
Fig. 40.—Free Medu-
sa of Coryne.

of most marine Hydroids, at first spherical, becomes pear-
shaped, and after swimming about for a time attaches itself
to some object. It then elongates, a horny sheath (peri-
60 ZOOLOGY.

sarc) forms around it, tentacles arise around the mouth,
finally the stem branches, new Hydroids arise, until a hy-
droid community (consisting of trophosomes and gonosomes)
is formed, and in the following spring medusa-buds (gono-
phores) arise, which become free (medusoids), and thus the
reproductive cycle is completed. The developmental his-
tory of this Hydroid is a good example of what is called
‘‘ alternation of generations. ””

Budding occurs in the medusa of Sarsia prolifera, the
only example known of budding in free meduse. Mul-
tiplication by fission has been observed in the medusa of
Stomobrachium mirabile. The pendent stomach was seen
by Kélliker to divide in two, becoming doubled, which act
was followed by a vertical division of the umbrella, separat-
ing the animal into two independent halves. These again
subdivided, and Kélliker thinks this process went on still
further. Haeckel has found in cutting off a portion of the
edges of the umbrella of certain Thaumantia, that the frag-
ment in a few days became a complete medusa.

In the Tubularian Hydroids (Tubularia, Hybocodon, Co-
rymorpha, Monocaulus, etc., Fig. 41),
the mode of reproduction is peculiar.
From the medusa-buds (sporosac) is set
free an embryo (actinula), which swims
about or creeps on its tentacles, mouth
downward. It then attaches itself by a
disk-like expansion of the posterior end,
which forms a stem until the original
Tubularia form is attained.

A gigantic Monocaulus having sessile
ovisacs, measuring seven feet four inches
in height, and provided with a crown of
tentacles nine inches across from tip to
tip of the expanded, non-retractile ten-
Fig. 41.—Monocantus pen- tacles, was dredged by the Challenger

EO ieee ABDOENE: Expedition at the depth of four miles.
Allman suggests that such a deep-sea Hydroid could not, on
account of the darkness and pressure of the water at such a
great depth, produce free-swimming medusa. In Tiaropsis

 
GRAPTOLITES. 61

there is no trace of a nervous system such as exists in
Sarsia, where nerve-fibres extend around the margin and
along the radial tubes (Romanes).

In the groups of Campanularie, represented by Plumu-
laria, Sertularia, Zygodactyla, Dynamena, and Campanu-
laria, the ectoderm is protected by a horny or chitinous
sheath (perisarc) enveloping the zooids. The Hydroids re-
tract, when disturbed, into small cells (hydrothece), arranged
in opposite rows on
the stalk as in Sertu- .
laria (Fig. 42), or
singly at the ends of
the stalks, as in Cam-
panularia, while the
sheaths (gonothece)
protecting the medu-
sa-buds are distin-
guished by their
much larger size and
cup-shaped form.

The Sertularians
abound on sea-weeds,
and may be recogniz-
ed from their resem-
blance to mosses.
They are among the
most. common objects
of the seaside. The

meduse of these and Fig. 42.—Sertularia adtetina of Europe. A, natural
many other Hydroids size; B, magnified. showing the hydrarium, with the

pee collected by 4 cells.—From Macallister.
towing-net, and emptied into a jar, where they can be de-
tected by the naked eye after a little practice.
Graptolites.—More nearly allied perhaps to the Sertularian
Hydroids than any other known animals are the Graptolites
(Fig. 43), which were most abundant in the Lower Silurian
period, and lingered as late as the Clinton epoch of the Upper
Silurian. In G@raptolithus Logani the hydroid colony (hy-
drosome) is a long narrow blade, with a row of cells on one

 
62 ZOOLOGY.

side; in G. pristis the hydrosome is broader, more lanceo-
late, and the sharp, tooth-like cells are arranged on both
sides of a median stem. In Phyllograptus typus the hy-
drosome is broad and oval, leaf-like, the serrations of the
leaf marking off the cells, which are apparently supported
on acentral axis. The group also has some affinities to the
Poiyzoa, and is probably a generalized or synthetic type of
animals.

Order 2. Discophora.—We now come to meduse which
differ from the Hydromeduse in
developing directly from eggs;
in having usually no velum ; with
branching gastro-vascular canals,
and covered sense-organs. They
intergrade, however, with the
Hydroidea by the members of the
group or sub-order Trachymedu-
se, represented by the genera
Aigineta, Geryonia, etc. These
are small jelly-fishes, with often
a remarkably long proboscis
(manubrium), as in Geryonia,
and with either four single radi-
ating canals, or, in addition, as
in Geryonia, a number of smaller
canals on the edge of the disk ;
or, as in a still more complicated
form, Charybdea, the radiating
0k Oe onograntis Grodon. canals are branched, thus con-

necting this group with the true
covered-eyed Acalephs, such as Aurelia.

O. and R. Hertwig have fully confirmed Haeckel’s discoy-
ery of the nature of the nervous system in the Geryonide.
They find that the nervous system is developed in the ecto-
derm and consists of two ‘‘ ring-nerves’”’ around the edge
of the disk, formed of two filaments, one lying on the upper,
the other on the under side of the velum, immediately at its
insertion. From this double nervous ring filaments are sent
off to the ganglia near the sense-organs. This sort of a

 
DEVELOPMENT OF JELLY-FISHES. 63

nervous system is present in the Mquoride and Aginide,
but is most distinct and best developed in the Geryonide
(Glossocodon and Carmarina).

The Hertwigs have also observed in these Trachynemidx
organs of taste, consisting of groups of long stiff hairs at
the base of the tentacles. They have been observed in
Rhopalonema velatum, Aglaura nemistoma, and in Cunina,
where the hairs are shorter.

The eggs, in developing, after total segmentation (morula
state) pass into a ciliated planula state as in Aurelia, there
being at first apparently no primitive gastric cavity; the
body of the embryo or planula remains spherical, as in Gery-
onia, there being a slight metamorphosis ; or, as in Poly-
xenia and Aginopsis, where there is a decided metamor-
phosis, the spherical ciliated planula greatly lengthens out
on each side, the body becoming boomerang-shaped, each
end of the boomerang becoming an arm or tentacle. Then
it becomes a gastrula, a central cavity and mouth appear-
ing. At right angles to the two primitive arms bud out
two others, and finally others appear on the lower edge of
the umbrella, and after slight changes the adult form is as-
sumed. Cwnina is at first spherical, then, a single arm
developing, it becomes club-shaped ; finally, the full num-
ber of arms grow out, and the mature form results. It ap-
pears, then, that in the mode of development from eggs,
without passing through a hydra-like condition, and in the
structure of the body, the Zrachymeduse connect the cov-
ered-eyed meduse with the naked-eyed or Hydroidea. The
American forms live in the waters of the Carolina shores.
Cunina octonaria McCrady lives in Charleston Harbor.
Cunina has been found by Haeckel growing on the columella
of Geryonia, and McCrady has found that our native Cunina
is parasitic on Turritopsis, a hydroid medusa.

The Lucernarie, or Calycozoa, which, according to Clark,
form an order of Acalephs, are, with Huxley, regarded as
asuborder of Discophora. With essentially the structure
of the Aurelia and allies, Luwcernaria differs in having the
power of attaching itself by a sucker on the smaller end of
its body to sea-weeds, but can detach itself at will and swim
64 ZOOLOGY.

about like the Aurelia by alternate contractions and expan-
sions of the umbrella. We will now enter into a more com-
plete account of this group based on Clark’s characteriza-
tion. The disk is more or less octagonal or circular, um-
brella, funnel or arm-shaped, the end opposite the mouth
ending in a pedicel, by which it is attached temporarily to
sea-weeds. The mouth is square, and between the ectoderm
and endoderm is a jelly-like layer constituting the musculo-
gelatiniform layer (mesoderm) much as in Avrelia. This
layer extends into the tentacles and marginal anchors, as
well as into the pedicel. The cavity of the disk is divided into
four quadrant chambers, separated by as many partitions,
which extend from the mouth into the lobes nearly to the
margin between the tentacles. The latter are arranged in
eight groups or tufts just within the margin of the disk, at
eight points, which alternate with the four partitions and
the four corners of the mouth. The tentacles are hollow,
opening into the radial canals of the general cavity of the
body, and end in a globular or spheroidal expansion, sery-
ing as an organ of touch or prehension. In some forms, as
Haliclystus auricula Clark, marginal anchors are situated
at eight points, exactly opposite the four partitions and the
four corners of the mouth ; they are originally tentaculiform,
but in adult life form organs by which they adhere to or
pull themselves from place to place. The sexes are distinct,
the reproductive glands having the same position in each
sex. Nothing is absolutely known of the mode of growth
of these animals, but development is supposed to be direct.
Our common Lucernarian is Haliclystus auricula Clark.
Its umbrella-shaped disk is an inch in diameter ; including
the tentacles, an inch and a half; the pedicel half an inch
long. It ranges from Cape Cod to Greenland and south-
ward to the coast of England, and may be found on eel-
grass between tide-marks.

According to A. Meyer, the end of the stalk when cut off
produced a new disk, and even pieces cut off between them
became complete Lucernarie, evincing the extraordinary
powers of reproduction in these interesting jelly-fish.

Coming now to the true Discophora, jelly-fish, sea-
NERVOUS SYSTEM OF JELLY-FISHES. 65

nettles, sun-fish or Acalephs, of which there are about
ninety known species on the eastern coast of the United
States, we may study as the type of the suborder the
common Aurelia flavidula Péron and Lesueur of our
coast, which is closely allied to the Aurelia awrita of the
European shores. It grows to the diameter of from eight
to ten inches, becoming fully mature in August, the young
appearing late in April in Massachusetts Bay, being then
not quite an inch in diameter. The mature ones may be
easily captured from a boat or from wharves. On a super-
ficial examination, as well as by cutting the animal in halves
and making several transverse sections with a knife, the lead-
ing points in its structure may be ascertained. Its tough,
jelly-like disk is moderately convex and evenly curved, while
four thick tentacles depend from between the four large geni-
tal pouches ; the tentacles unite below, forming a square
mouth-opening, the edge of which is minutely fringed to the
end of the tentacles. On the fringed margin are eight eyes,
each covered by a lobule and situated in a peduncle, and
occupying as many slight indentations, dividing the disk
into eight slightly marked lobes. The subdivisions of the
water-vascular canals or tubes are very numerous and anas-
tomose at the margin of the disk, one of them being in
direct communication with each eye-peduncle. When in
motion the disk contracts and expands rhythmically, on the
average twelve or fifteen times a minute ; on the approach
of danger they sink below the surface.

While a distinct nervous system has not been discovered
in Aurelia, Romanes suggests that there are primitive nervo-
muscular cells, such as those shown by Kleinenberg to exist
in Hydra, and he concludes, after a series of experiments
on Aurelia aurita, that the whole contractile sheet of the
bell presents not merely the protoplasmic qualities of ex-
citability and contractility, but also the essentially nervous
quality of conducting stimuli to a distance irrespective of
the passage of a contractile wave. The later researches of
O. and R. Hertwig show that the nervous system of
Acalephe (Acraspedota or covered-eyed Meduse) is much
more primitive than in the naked-eyed or craspedote forms,
66 ZOOLOGY.

such as the meduse of the Hydroids and the Trachy-
nemide. In the European Nausithoe albida and Pelagia
noctiluca no nerve-ring is present, for this is impossible
owing to their deeply indented disks. There are instead eight

    

Fig. 44.—Gastrula of an Aure-

lia-like Medusa. a, primitive Fig. 45.—Scyphistoma of Aurelia
mouth; 2, gastro-vascular cavity; Jlavidula, at Abferent ages; magni-
¢c, ectoderm; d, endoderm.— fied.—After Agassiz. 7"
After Metschnikoff.

separate nerve-tracts which unite with the sense-organs in a
special elevation of the edge of the disk, forming so-called
sense-hearers, which alternate with the eight tentacles.
Aurelia aurita has a similar disconnected nerve system.*
Eimer confirms these discoveries, and states that the ner-
vous system in these Hydrozoa arises from the ectoderm.

  

Fig. 47. — Ephyra or
earliest free condition of
Aureia—After Agas-

Fig. 46.—Strobila of Au- siz.
relia flavidula. — After
Agassiz.

The Aurelia flavidula spawns in late summer, the females
being distinguishable by their yellowish ovaries, the male
glands being roseate, while the tentacles of the females are

* Jenaische Zeitschrift, 1877, p. 355,
DEVELOPMENT OF JELLY-FISHES. 67

shorter and thicker than in the males. The eggs pass out
of the mouth into the water along the channeled arms, and
in October the ciliated gastrula becomes pear-shaped and
attaches itself to rocks, dead shells, or sea-weeds, and then
assumes a Hydra form with often twenty-four very long
tentacles. This stage was originally described as a distinct
animal under the name of Scyphistoma. In this Scyphis-
toma stage (Fig. 45) it remains about eighteen months.
Toward the end of this period the body increases in size
and divides into aseries of cup-shaped disks. These saucer-
like disks are scalloped on the upturned edge, tentacles bud

 

Fig. 48.—Aurelia flavidula.—After Agassiz.

out, and the animal assumes the Strobila stage (Fig. 46).
Finally, the disks separate, the upper one becomes detached
and dies, but the others swim away in the Hphyra form
(Fig. 47), when about a fifth of an inch in diameter, and
toward the middle or end of summer becomes an adult
Aurelia (Fig. 48).

Though the Aurelia has lasso-cells it is not poisonous to
bathers. Not so, however, with the gigantic Cyanea arctica,
whose long tentacles are poisonous ; fishermen as well as
bathers being often annoyed by them. This giant jelly-fish
sometimes attains a diameter of from three to five feet across
68 ZOOLOGY.

the disk, though it is produced from a Scyphistoma not
more than half an inch in height. Pelagia campanella aud
a few other forms do not undergo this metamorphosis, but
grow directly from the eggs.

Various boarders or commensals—viz., temporary non-
attached parasites—live in or under the mouth-cavity or be-
tween the four tentacles of the larger Acalephs. Such is the
little Amphipod Crustacean, Hyperia, which lives within
the mouth, while small fishes, such as the butter-fish, swim
under the umbrella of the larger jelly-fishes, Cyanea, etc., for
shelter and protection. Besides small animals of various
classes, the larger jelly-fishes kill by means of their nettling
organs small cuttle-fishes and true fishes, the animals being
paralyzed by the pricks of the minute barbed darts.

Order 3, Siphonophora.—These are so-called compound
Hydroids, living in free-swimming colonies, consisting of
polymorphic individuals, or, more properly speaking, zooids
—that is, organs with a strongly marked individuality, but
all more or less dependent on each other. A Siphonophore,
such as Physalia, for example, may be compared to a so-
called colony of Hydractinia, in which there are nutritive
and reproductive zooids and medusa-buds. In Physalia
there are four kinds of zooids—i.e. (1) locomotive, and (2)
reproductive, with (3) barren medusa-buds (in which the
proboscis is wanting), which, by their contractions and
dilatations, impel the free-swimming animal through the
water ; in addition, there are (4) the feeders, a set of di-
gestive tubes which nourish the entire colony. There are
numerous genera and species (one hundred and twenty are
known), whose structure is more or less complicated and
difficult to understand without many figures and labored
descriptions. We will select as a type of the order our
Physalia Arethusa of Tilesius, or Portuguese man-of-war
(Fig. 49), which is sometimes borne by the Gulf Stream as
far north as Sable Island, Nova Scotia. Jt is excessively
poisonous to the touch, and in gathering specimens on the
shores of the Florida reefs we have unwittingly been stung
by nearly dead, stranded individuals, whose sting burns like
condensed fire and leaves a severe and lasting smart,
PORTUGUESE MAN-OF.WAR. 69

The colony or hydrosome of the Portuguese man-of-war
consists of long locomotive tentacles, which, when the ani-
mal is driven by its broad sail or float before the wind,
stretch out in large individuals from thirty to fifty feet.
These large Hydra-like zooids are arranged in small groups,
arising from a hollow stem com-
municating with the chymiferous Nn ET
cavity extending between the in-  ””  ™ ddr rn
ner and outer wall of the float. fis,
The ‘feeders’? are of two kinds, yyy
large and small, and are clustered
in branches growing from a com-
mon hollow stem, also communi-
cating with the chymiferous or
body-cavity. L. Agassiz, whose
description of this animal we are
condensing, states that he has
seen these feeders ‘‘ gorged with
food almost to bursting,’’ but has
never seen undigested food in
any of the other organs. The
medusa-buds (gonophores) arise
from a third set of very small
Hydras, but form very large clus-
ters suspended between the clus-
ters of feeders. These reproduc-
tive zooids resemble the locomo-
tive zooids, but, like the feeders,
have no tentacles. The medusa-
buds, which are male or female,
arise singly, either from the base
of the reproductive zooids or
from the stems which unite the AS 0.-7?ysala, on Fortguese
latter. These buds, asin Tubu-
laria, wither without dropping from their parent stock. It
appears, then, that the floating hydrosome of a Siphon-
ophore is like that of the fixed Hydractinia or Coryne, with
the addition of locomotive zooids and a float, ag seen in
Physatia, Velella, or the swimming-bells of Halistemma.

Me
mm

      

ail

SY Marae
mi) nes te
hae

  
70 ZOOLOGY.

The Siphonophores, as observed in Agalma, Epibulia,
Halistemma, and other forms, arise from eggs which pass
through a morula, planula, and gastrula stage. The further
development of Halistemma carum, a Siphonophore native
to the shores of New England, has been described by A.
Agassiz as follows : In the earliest stage noticed the young
looked like an oblong oil-bubble, with a simple digestive
cavity. Soon between the oil-bubble and the cavity arise a
number of medusa-buds, though without any proboscis
(manubrium), since the medusa-buds are destined to form
the ‘‘ swimming-bells,’’ which take in and reject the water,
thus forcing the entire animal onward. After these swim-
ming-bells begin to form, these kinds of Hydra-like zooids
arise. In one set the Hydra is open-mouthed, and is, in
fact, a digestive tube ; its gastro-vascular cavity connecting
with that of the stem, and thus the food taken in is circu-
lated throughout the community. These are the so-called
‘‘ feeders.’’? The second set of Hydras differ only from the
feeders in having shorter tentacles twisted like a corkscrew.
In the third and last set of Hydras the mouth is closed, and
they differ from the others in having a single tentacle in-
stead of a cluster. Their function has not yet been clearly
explained. New zooids grow out until a long chain of
them is formed, which moves gracefully through the water,
with the float uppermost.

All the Hydroids in their free state as meduse are more or
less phosphorescent, and as much or more so after death,
when their bodies become broken up, and the scattered frag-
ments light up the waves whenever the surface of the ocean
is agitated. From this cause the sea is especially phosphor-
escent in August and September, when the jelly-fishes are
dying and disintegrating. These creatures serve as food for
the whalebone whales, which swallow them by shoals.

The smaller species are abundant in the circumpolar seas,
while in the tropics the Siphonophores are especially nu-
merous, none occurring in the Arctic regions. The Hy-
droids are widely distributed, a species of Campanularia be-
ing common to the Arctic and Antarctic seas. The species
occurring on the New England coast are in many cases
DISTRIBUTION OF HYDROZOA. 71

found in Northern Europe, being circumpolar in their range.
A distinct assemblage of Sertularians, characterized by the
large number of species of Plumularia, inhabits the Florida
seas down to a depth of five hundred fathoms. Among
the Discophora the Lucernarie are arctic as well as temper-
ate forms, while Cyanea is peculiar to the Northern Hemi-
sphere. Awrelia and Pelagia are cosmopolites, while Rhaco-
pilus, Placois, and Lobocrocis are peculiar to the Southern
Hemisphere. The larger number of species are tropical and
sub-tropical. As regards their bathymetrical distribution,
while several species extend to the depth of five hundred
fathoms, Monocaulus flourishes in gigantic proportions at
the enormous depth of four miles.

The range in geological time of the Discophora extends
to the Jurassic period (middle Oolitic), large species of jelly-
fishes occurring in the Solenhofen slates. The genus Hy-
dractima first appeared in the Cretaceous period. Grapto-
lites were common in the shales of the Potsdam period, so
that if Graptolites are Acalephs, the latter are probably as
old a type as any, being contemporaneous with trilobites,
brachiopods, mollusks, worms and sponges.

 

Cuass I.—THE HYDROZOA.

Body in its simplest form a sac attached by the aboral end, composed of
three cell-layers, with a mouth and gastro-vascular cavity, and in all cases,
except Protohydra, provided with tentacles, which are hollow, forming con-
tinuations of the body-cavity. The body (hydrosome) usually differentiated
into two sorts of zootds, nutritive (polypites) and reproductive (gonosomes),
connected by a common stem or nutritive canal (cenosare), the gonosomes
producing medusa-buds (gonophores), which on being set free are called me-
duse (or medusoids) and are bisexual.* In these meduse the body is disk
or bell-shaped, the jelly-like parenchymatous substance composing the disk
constituting the mesoderm. From the gastro-vascular cavity four primary
gastro-vascular canals radiate and anastomose with a marginal circular
canal. No distinct organs of circulation, the blood being sea-water con-
taining the chyme and a few colorless blood-corpuscles. A true nervous
system rarely present, but when developed in certain medusoids, forming a

* Agassiz saw in Rhizogeton, a form allied to Hydractinia, a gonophore which had
discharged its contents, degenerating into a polypite or hydra, and its body elongating
and developing tentacles. Allman observed the same thing in Cordylophora.
492, ZOOLOGY.

thread-ring around the disk, and with ganglia near the sense-organs. In
Hydra the nervous system is represented by nervo-muscle cells ; sense-
organs usually present, represented by simple eyes and auditory vesicles
(lithocysts), the two not usually coexisting. Nettling organs (nematocysts)
usually present, and especially characteristic of the class, being most abun-
dant on the tentacles.

The sexes rarely united, usually distinct. Often a high degree of poly-
morphism in the individual hydrosome, the animal being differentiated not
only into polypites and gonosomes, but, in the free-swimming forms, into
locomotive zooids. Reproduction takes place by budding, and by fertilized
eggs developed in glands attached to or dependent from the primary ra-
diating canals. The species undergo either a slight or marked metamor-
phosis, the free gonophores being meduse (or medusoids), which produce
eggs, from which in some Discophora (such as Aurelia) arise successively
a morula, gastrula, planula, scyphistoma, strobila, and adult medusa,
representing distinct stages of growth.

Order 1. Hydroidea. — The individual either not differentiated into
zooids, as in Protohydra and Hydra, or consisting of nutri-
tive and reproductive zooids forming a compound, station-
ary, branching, moss-like body (hydrosome), the medusa-
buds remaining on the gonosomes or becoming free meduse,
with usually four simple radiating canals, a velum, manu-
brium, and naked eyes. Hydrosome either naked or as in
Sertularia, etc., protected by a horny sheath, or forming, as
in Millepora and Heliolites, a massive corallum. Suborder 1.
Tubularie (Hydra, Clava, Hydractinia, Millepora, Tubularia).
Suborder 2. Campanularie (Plumularia, Dynamena, Cam-
panularia, quorea, Zygodactyla).

Order 2. Discophora.—Meduse like those of the Hydroids, but with
the four primary radiating canals usually subdividing into
numerous branches, the eyes more or less covered by a flap ;
the velum often absent ; often four genital pouches, dis-
charging eggs into the gastro-vascular cavity ; usually of
large size, and developing either directly from eggs, or, as
in Aurelia, passing through a gastrula, scyphistoma, and
strobila stage, not being developed from a hydra-like poly-
pite. Suborder 1. Trachymedusw (AHgina, Cunina, Gery-
onia, Charybdea). Suborder 2. Zucernarie (Lucernaria).
Suborder 8. Acalephe (Pelagia, Cyanea, Aurelia, Rhizos-
toma).

Order 3. Siphonophora. —Free-swimming, polymorphic hydrosomes,
with nutritive, feeding, reproductive and locomotive zooids.
Suborder 1. Physophore (Agalma). 2. Physalie (Physalia).
3. Calycophore (Diphyes). 4. Discotdew (Velella, Porpita).
STUDY OF HYDROZOA. 43

Note.—Stephanocyphus mirabilis Allman is the type of a new order
of Hydrozoa called by Allman Thecomeduse. The animal permeates
and is parasitic in sponges. Although a Hydrozoan, it is not a
Hydroid, and cannot be referred to any of the existing orders of the
Hydrozoa. The chitinous tubes which permeate the sponge-tissue are
united toward the base of the sponge, and constitute a colony of zooids.
In many respects it is said to resemble the Campanularie.

VIEW OF THE CLASSIFICATION OF THE HypRozoa.

 

Siphonophora,
(Phyealia.)
Discophora,
(Aurelia.)
Hydroidea.
(Hydra.)
|
Hyprozoa.

Laboratory Work.—The common Hydroids, such as Coryne, Sertu-
laria, etc., may be collected from sea weeds or the piles of wharves
between tide-marks, while the meduse may be obtained by the
hand-net, or tow-net from a boat. The meduse especially abound
in eddies off points of land where different currents of the sea meet.
Towing is most effectively pursued after sunset and early in the even-
ing, when the sea is calm, and the jelly-fish swim near the surface.
They should be placed in the jars by inverting the net in the water of
the jar, and examined at once, as many will have perished by the next
morning. Jelly-fish can also be reared in roomy aquaria, in which
plenty of air is introduced by running water.

The larger meduse, such as Aurelia and Cyanea, should be sliced
in sections in order to study their gross anatomy, and portions snipped
off with scissors to be examined with the microscope. The animals of
Sertularians, Coryne, etc., can be studied alive in animalcule-boxes
and growing-cells. The coral stock of Millepora was examined by
Moseley in ground sections. ‘‘ Portions of the living coral were placed
in absolute alcohol, chromic acid, and glycerine ; portions were further
treated with osmic acid and transferred to glycerine or absolute alcohol.
Fragments of the hardened coral were afterward decalcified with
hydrochloric acid, and the residual soft structures were either mounted
entire for examination, or cut in the usual manner into fine vertical
and horizontal sections, which were then stained with carmine or
magenta. The specimens hardened in osmic acid, and decalcified after
subsequent immersion in absolute alcohol, yielded the best histological
results,”
%4 ZOOLOGY.

While the jelly-fishes should be studied alive, the larger ones can he
preserved in alcohol, after being killed by the gradual addition of
alcohol to the sea-water in which they are living. The small medusz,
as well as Noctiluca and the Ctenophores, have been preserved with suc-
cess by E. Van Beneden, by the use of a solution of osmic acid or of
picric acid. Osmic acid hardens the tissues so that fine sections can
be made, and it colors black the greasy matters, and especially myeline,
a chemical substance usually found in the nervous system, and enables
us to trace well the limits of the cells. The small jelly-fishes may be
placed in a very weak solution of osmic acid (% to 75 per cent. of
water) varying with the size of the animal, for from fifteen to twenty-
five minutes, when the animal turns brown. This brings out clearly
the gastro-vascular canals. The specimen can then be placed in strong
alcohol, without losing its form and transparence. These animals and
all other transparent animals can be well kept in a concentrated, watery
solution of picric acid. Professor Semper tells us that all soft animals,
worms as well as hydroids and polyps and mollusks, may be killed ex-
panded in chromic acid (13 per cent), or in acetic acid of variable
strength, and then preserved in alcohol.

Crass I].—THE Actinozoa (Sea-Anemones and Coral
Polyps).

General Characters of Actinozoans.—So persistent is the
form and structure of the body in these animals, that a
study of the common sea-anemone will enable the student
to readily comprehend the leading and most fundamental
characteristics of the class.

The common Actinia of our coast (Metridium marginatum)
is to be found between tide-marks on rocks under sea-weeds,
or in tidal pools, but grows most luxuriantly on the piles of
bridges. It readily lives in aquaria, where its habits may
be studied. An aquarium may be improvised by using a
preserve-jar or glass globe, covering the bottom with sand,
with a large flat stone for the attachment of the sea-ane-
mone. By placing a green sea-weed (ulva) attached to a
stone in the jar, and filling it with sea-water, the animal
may be kept alive a long time. After observing the move-
ments of the crown of tentacles as they are thrust out or
STRUCTURE OF TH# SEA-ANEMONE. 45

withdrawn, specimens may be killed expanded by the grad-
ual introduction of fresh water, or by plunging them into
picric acid. They should then be transferred to the strong-
est alcohol, and allowed to soak in it for two or three days
until the tissues become hard enough to cut well. Then
vertical and transverse sections may be made with a sharp
knife. The first fact to observe is, that an alimentary canal
is much more clearly indicated than in the Hydrozoa, there
being a distinct digestive sac, separate from the body-walls,
hanging suspended from the mouth-opening, and held in
place by six partitions or septa (mesenteries), which divide
the body-cavity into a number of chambers. The digestive
sac is not closed, but is open at the bottom of the body,
connecting directly with the chambers, so that the chyme,
or product of digestion, passes down to the floor of the
body, and then into each of the chambers; thus, by the
movements of the body in opening and closing, the chyme,
mixed with the blood, is distributed throughout the body ;
this rude mode of circulation being the only means of dis-
tribution of the nourishment contained in the circulating
fluid, there being no distinct canals, as in the Hydrozoa.
These mesenteries may be best studied in a cross-section of
the animal after being hardened. It will be found that
there are six pairs of complete or primary septa or partitions
(mesenteries) which hold the stomach in place, and a num-
ber of pairs of shorter ones of unequal length between the
complete ones. There are never less than twelve of the
secondary partitions, even in the young, and when more
numerous they occur in multiples of six (Clark). On the
free edges of these shorter mesenteries, which do not extend
out to the stomach, there is a mass of long coiled filaments,
the mesenterial filaments (craspeda, Fig. 50, cr), which con-
tain lasso-cells, situated in a peripheral layer, while the fila-
ment is hollow and contains guanin. In dissecting the
sea-anemone these mesenterial filaments are always more
or less in the way, and have to be carefully removed so as to
expose the ovaries and adjoining parts. They press out of
the mouth and the cinclides (small openings through the
%6 ZOOLOGY.

body-walls), not always present, and end of the tentacles,
and thus come in contact with animals forming their food.
The ovaries and spermaries can be distinguished by their
forming masses of closely convoluted tubes much thicker
than the mesenterial filaments, and situated on the outside
next to the free edge of each mesentery ; they are also of a
pale lilac tint in Metridium marginatum (Fig. 50, 0). They
are not easily distinguishable from each other by the naked
eye. The figure shows at the base of the body the free
edges of the mesenteries (m) of different heights, with the
spaces between them through which the chyme passes into
the body-cavity. For the com-
plete passage of the circulating
fluid the six primary mescnteries
are perforated by a large orifice
(op) more or less oval or kidney-
shaped in outline (Fig. 50). The
digestive sac is divided into two
divisions, the mouth and stomach
proper, the latter when the ani-
mal is contracted being much
shortened, and with the walls
vertically folded, as seen in the

 

ee a pecan diagrammatic CUt.

sketch o: e anatomy of an Actinia

(Metridium) wa the tentacles dis- In the tentacles are lodged the
ortionat arged. -

Bin fhe Miieseatarlers ot Betas lasso-cells or nematocysts, and

flanietS sete op, ties through the tentacles are hollow, com-
binder the authowe Qrecten eey, municating directly with a cham-

ber or space between the mesen-
teries, and are open at the end. When a passing shrimp,
small fish, or worm comes in contact with these tentacles,
the lasso-cells are thrown out, the victim is paralyzed, other
tentacles assist in dragging it into the distensible mouth,
where it is partly digested, and the process is completed in
the second or lower division of the digestive canal. The
bones, shells, or hard tegument of the animals which may
be swallowed by the Actinia are rejected from the mouth
after the soft parts are digested. Pigment-cells, which are
STRUCTURE OF THE SEA-ANEMONE. 77

supposed to be liver-cells, are said to be situated in the walls
of the stomach, and the mesenterial filaments have been sup-
posed to act as kidneys in taking up and excreting the waste
products of digestion, but this has not been proved and seems
improbable. ‘The blood, or sea-water, mixed with particles
of food (“‘ chylaqueous fluid ’’), the result of digestion, was
supposed by Williams to represent the chyle of higher ani-
mals and to contain white blood-corpuscles, but this has
been denied by Lewes (‘‘ Sea-side Studies’’) on apparent good
grounds. Bilateral or right and left symmetry is faintly in-
dicated in the young and old Actinia, as well as in some
corals, as pointed out by Clark.

While no true nervous system is known to exist in the
Actinozoa, Duncan has discovered in the base of the body a
plexus of fusiform ganglionic cells connected by nerve-fibres.
Isolated nerve-cells have been discovered by Schneider and
Rétteken near the pigment-cells or supposed eyes at the
base of the tentacles of the Actinia. In connection with
these nerve-cells are certain round refractive cells (Haimean
bodies) and other long cells, called the Rétteken bodies.
The former are thought by Professor Duncan to carry light
more deeply into the tissues than the ordinary epithelial
cells. This is also the case with the elongated Rétteken
cells and others similar to them, called daciili. All these,
when brought together in this primitive form of eye,
“concentrate and convey light with greater power, so
as to enable it to act more generally on the nervous sys-
tem probably not to enable the distinction of objects, but
to cause the light to stimulate a rudimentary nervous sys-
tem to act in a reflex manner on the muscular system, which
is highly developed.”? (Duncan.)

Nearly all the Actinozoa increase by budding, new indi-
viduals arising at the base or edge of the pedal disk of the
old ones. Clark has seen in Metridiwm marginatum as
many as twenty buds separate from the parent sea-anemone.
‘* As in Hydra they arise as simple rounded protuberances,
but in a short time six short tentacles make their appear-
ance at the free end, and a minute oblong aperture, the
78 ZOOLOGY.

mouth, is found in their midst in such a way that its two
ends have a tentacle opposite each, and the other four dis-
posed two on one side and two on the other. Within, the
organs arise at points corresponding to the position of those
outside. The semi-partitions, twelve in number, begin as
mere ridges, which extend in pairs from the anterior end of
the stomach along the oral wall toward its border.’’ Adult
Actiniz sometimes, though rarely, subdivide longitudinally,
but it is not uncommonly observed in the corals, in which
cases only the heads and stomachs divide, the general cav-
ity remaining common to the two.

The development of Actinia mesembryanthemum has been
traced by Lacaze-Duthiers. The young Actinia attains
maturity without any metamorphosis. The egg is supposed
to undergo segmentation within the ovary. In the state in
which the embryo was observed by Lacaze-Duthiers it was
oval and surrounded by a dense coat of transparent conical
spinules. Soon the two primitive germi-
nal layers (ectoderm and endoderm)
were observed. Two lobes next appear
within the body; these subdivide into
four, eight, and finally twelve primitive
lobes. This stage is represented by the
corresponding stage of the coral (Fig. 55,
B). Not until after the twelve primitive
lobes are fully formed do the tentacles

Fig. 51.-—Ciliated larva begin to make their appearance. When
Ge eenineoe imax. the first twelve tentacles have grown out,
tchoderm?’ d enicnams’ twenty-four more arise, and so on, until
After Metschnikof. With its increasing size the Actinia is
provided with the full number peculiar to each species.
Lacaze-Duthiers observed the same changes in two species
of Sagartia, and in Bunodes gemmacea. Fig. 51 represents
the ciliated gastrula of an unknown polyp allied to Kalliphobe.
While Metridiwm and Bunodes are types of the ordinary
form of Actinoids, certain forms, like Halcampa producta
Stimpson (Fig. 52), are quite long and live fixed in the
mud or sand, Allied to Halcampa is Edwardsia, which

 
CORAL POLYPS. 49

lives in deep water. Its young, however, is at an early
stage of its existence a free-swimming polyp, which was
originally described as an adult animal under the name of
Arachnactis. In Zoanthus the tegument is tough and
leathery, and the different polyps are con-
nected by stolons. Epizoanthus americanus
Verrill lives in deep water, off the coast of
New Jersey and Southern New England, in
about twenty fathoms. Certanthus, a gigantic
form, a native species of which (C. borealis
Verrill) lives at the depth of one hundred
fathoms in the Gulf of Maine deeply sunken
in the mud, where it secretes a shiny leathery
tube, is perforated at the end of the body;
the young of a corresponding European
species is also free-swimming, like the young
Edwardsia.

The coral polyps differ from the Actinoids
in secreting in the mesoderm a limestone
base, from which arise in the Zoantharian
corals stony septa serving as a support to the
animal; these septa are deposited or secreted
in the chambers, so that in the coral polyp
there are soft partitions alternating with the
limestone ones, the latter formed at the base ?
of the polyp, not completely filling the inter- damn Pea
mesenterial chambers. ae aoe

Order 1. Zoantharia.—We will now enumerate some of
the leading forms of the first order of Anthozoa, the Zoan-
tharia, to which the sea-anemones and most of the stony
corals belong. The group is called by some recent authors
Hexacoralla, the number of primary chambers and tenta-
cles being six, the latter rounded, conical, or filiform. In
the simple cup-shaped corals, as Deltocyathus and Caryo-
phyllia, the coral forms a cup or theca, the lamelle which
arise from the base terminate in as many septa, the spaces
between which are termed Jocuwli. A central pillar or col-
umn formed by the union of the septa, or arising indepen-

 
50 ZOOLOGY.

dently, is called the columella, while the small separate pillars
between the columella and the septa are termed paluli. In
the compound or tree-like corals, each young coral polyp
forms a calicle, theca, or limestone support of its own, which
unites with the other by calcification of the connecting sub-
stance of the common body. This intermediate layer is
termed cenenchyma (Huxley).

The simpler corals consist of but a single calicle contain-
ing one polyp, as in Flabellum, Deltocyathus, and Caryo-
phyllia. They live free, fixed in the mud in deep water,
and occur in water with a temperature of about 32° Fahr.
Flabellum angulare Moseley has been dredged off Nova
Scotia in 1250 fathoms.

Deltocyathus Agassizit, which is not uncommon in the
Florida channel, at depths varying from sixty to three hun-
dred and twenty-seven fathoms, has been dredged by us at the
mouth of Massachusetts Bay, in one hundred and forty fath-
oms (temperature 39° to 42° Fahr.). An allied form is
Ulocyathus arcticus Sars, said by Duncan to be the same as
Flabellum laciniatwn Edwards and Haime, a fossil of the
late tertiary, dredged by us in one hundred and fifty fath-
oms, near St. George’s Banks, Gulf of Maine.

In the family of which Oculina, the eye-coral, is a type,
the polyp stock is compound, branched, increasing by lat-
eral buds. Lophohelia prolifera Pallas (Fig. 53) occurs
in the seas of Norway, and will possibly be found to occur
on the banks off Nova Scotia and Newfoundland, since it
lives in the Florida Straits, in from 195 to 315 fathoms.

In Meandrina, or the brain-coral, Favia, Astrea and As-
trangia, we have representatives of the important group
Astreacea, in which the corallum is massive, more or less
hemispherical, and the polyp-cells or calicles are distinctly
lamello-radiate within, and generally so without. Budding
is always carried on by division of the disks, or by spon-
taneous fission. In Mussa the polyps are sometimes two
inches in breadth, as large as ordinary Actinia. Diploria
cerebriformis Edwards and Haime is a brain-coral which is
common in the West Indies and at the Bermudas, some-
CORAL POLYPS. 81

times growing to a diameter of three feet. The common
large West Indian brain-coral is Meandrina labyrinthica.
In Astrea pallida Dana, of the Feejee Islands, the polyps
are pale, the disks bluish gray, and the tentacles whitish.
The polyps of many corals are beautifully colored. Those

Ae

Se
TI

j /
A aya

— a ~) |

 

Fig. 53.—Lophohelia prolifera.—After Wyville-Thompson.

of Astrangia Dane Agassiz are white. In this coral, as
observed by Dana, the polyps stand prominently above the
calicles, as only their bases secrete coral. The tentacles
have minute warty prominences, each full of lasso-cells,
82 ZOOLOGY.

This coral ranges as far north as Nantucket and Buzzard’s
Bay. In the mushroom corals, Fungia, the large corallum
is the secretion of a single polyp which may be a foot in
length. Large branching corals abound on the reefs of
Florida, the most abundant of which grows nearly two feet
high and branches out like the horns of a deer. Such ig
Madrepora cervicornis Lamarck.

While agamogenesis or alternation of generations is rare
among the Actinozoa, Semper has observed two species of
Fungia which he considers to reproduce in this way. The
corals ‘‘ bud out from a branched stem, and then become
detached and free, as is the habit of the genus.’’ Huxley,

 

Fig. 54.—Coral polyp (Astroides calycularis) expanded.—From Tenney’s Zoology.

from whom we take the statement, questions whether this
is a case of genuine agamogenesis.

As a good example of the mode of development of one of
the suborder Madreporaria, we will, with Lacaze-Duthiers,
study the development of Astroides calycularis Pallas.
The period of reproduction takes place between the end of
May and July, the young developing most actively at the
end of June. Unlike Actinia, which is always hermaphro-
ditic, this coral is rarely so, but the polyps of different
branches belong to different sexes.

As in the other polyps, including Actinia, the eggs and
DEVELOPMENT OF CORAL POLYPS. 83

spermatic bodies rupture the walls of their respective glands
situated on the fleshy partitions. As in Actinia, Lacaze-
Duthiers thinks the fecundation of the egg occurs before it
leaves the ovary, when also the segmentation of the yolk
must take place. Unlike the embryo Actinia, the ciliated
young of the coral, after remaining in the digestive cavity
for three or four weeks, make their way out into the world
through the tentacles. The appearance of the young, when
first observed, was like that in Fig. 55, A, being an oval,
ciliated gastrula with a small mouth and a digestive cavity.

The gastrula changes into an actinoid polyp in from
thirty to forty days in confinement, after exclusion from the
parent, but in nature in a
less time, and it probably
does not usually leave the
mother until ready to fix
itself to the bottom.

Before the embryo be-
comes fixed and the tentacles
arise, the lime destined to
form the partitions begins
to be deposited in the endo-
derm. Fig. 55, C, shows the
twelve rudimentary septa.
These after the young polyp
or “‘actinula’’ has become
stationary, finally enlarge Fig. 55.—Development of a coral polyp,

Fad Astroid+s calycularis. A, ciliated gastrula;
and become joined to the 2%. young polyp with 12 septa; C, D, young

polyp farther advanced, with 12 tentacles;
external walls of the coral ¢,thecorallum and limestone septa begin-
2 s ning to form.—After Lacaze-Duthiers.
now in course of formation
(Fig. 55, C, c), forming a groundwork or pedestal on which
the actinula rests. D represents the young polyp resting
on the limestone pedestal.

Lacaze-Duthiers found that the embryo polyp which had
been swimming about in his jars for nearly a month, sud-
denly, within the space of three or four hours after a hot
sirocco had been blowing for three days, assumed the form
of small disks (Fig. 55, B), divided, as in the Actinia, into
twelve small folds forming the bases of the partitions within.

 
84 ZOOLOGY.

The tentacles next arise, being the elongation of the
chambers between the partitions, six larger and elevated,
six smaller and depressed (Fig. 55, D). The definitive form
of the coral polyp is now assumed, and in the Astroides it
becomes a compound polypary.

There are but few facts regarding the rate of growth of
corals. Pourtales states that a specimen of Meandrina
labyrinthica, measuring a foot in diameter and four inches
thick in the most convex part, was taken from a block of
concrete at Fort Jefferson, Tortugas, which had been in the
water only twenty years. Major E. B. Hunt calculated
that the average growth of a Meandrina observed by him
at Key West was half an inch a year. From the observa-
tions and specimens collected by Mr. J. A. Whipple, as
stated by Verrill, a Madrepora found growing on the wreck
i of the Severn grew
to a height of sixteen
feet in sixty-four
years, or at the rate
of three inches a
year.

The group Rugosa
of Milne-Edwards

Fig. 56.—a, Haplophyllia paradomwa ; b. vertical sec- 1 9]
tion; c, calicle from above.—After Pourtales, and Haime contains

 

a large number of
palzozoic corals, which are mainly characterized by septa
proceeding from four primary ones, the number in all liy-
ing corals being six ; and also by “‘ the occurrence in them,
alone of all Anthozoa, of intracalicinal gemmation.”’

Pourtales has doubtfully referred to this group his Haplo-
phyllia paradoza (Fig. 56) which inhabits the Florida
Straits at a depth of over three hundred fathoms. The
nearest known fossil ally of this interesting coral is Calo-
phyllum profundum Germ., which is fossil in the Dyas for-
mation. Duncan describes Guynia annulata, another deep-
sea coral, as a recent Rugose tetrameral coral. Moseley
suggests from a study of Heliopora, together with Crypto-
hela anil other Stylasteride, that ‘‘ the marked tetrameral
arrangement of the septa in Rugosa, and the presence in
ALCYONARIAN POLYPS. 85

many forms of tabule, are certainly characters not opposed
to the alliance of these corals with the Alcyonarians,’’ and
gives other reasons of importance in favor of this view.

The group of Antipathea, represented by Antipathes ar-
borea Dana, of the Feejee Islands, produce compound
groups by budding, growing in the form of delicate shrubs.
The polyps have usually six tentacles, though in Gerardia
they have twenty-four.

Order 2. Alcyonaria.—To this group of polyps, which
have eight serrated or feathered tentacles, belong the red
coral of commerce, the sea-fans and sea-pens, in which there
are no calcareous septa, and in which the corallum has, as in
the sea-fans and sea-pens, a horny axis, while the fleshy por-
tion (ceenosare) represents the mesoderm and is filled with
calcareous spicules.

In the genera Haimea, Alcyoniwm, Tubipora, etc., the
polyps are encrusting, budding out in different ways, and
adhere to foreign bodies by the coenenchyma. Haimea is
simple, consisting of but a single polyp. In Alcyonium
the conenchym is much developed, soft, lobulated, and
branching. Our common species is A. carnewm Agassiz.
In Tubipora the polyps are compound and secrete solid
calcareous, bright red tubes, arranged side by side, like the
pipes of an organ, and supported by horizontal plates.

In the common red coral (Coralliwm rubrum) of the
Mediterranean Sea, the solid, unjointed coral-stock consists
of a crystalline basal mass, with calcareous spicules solidly
united. The bright red coral is worked into various orna-.
ments. The coral fishery is pursued on the coasts of Algiers
and Tunis, where assemble in the winter and spring from
two hundred to three hundred vessels. The coral-fishermen,
with large rude nets, break off the coral from the submerged
rocks. About half a million dollars’ worth of coral is annu-
ally gathered.

Heliopora, now proved by Mr. H. N. Moseley to be an
Alcyonarian instead of an Actinoid polyp, differs from
Corallium and Tubipora ‘‘in that the hard tissue of its
corallum shows no signs of being composed of fused spic-
ules.” This genus, together with Polytremacis and the
86 ZOOLOGY.

Silurian Heliolites, form, according to Moseley, a new
family of Alcyonarians in which the corallum consists of an
abundant tubular cosnenchym, with calicles having an
irregular number of pseudo-septa, which do not, however,
correspond with the membranous mesenteries. The polyps
are completely retractile, with the tentacles when retracted
introverted. The mouths of the sacs lining the coenenchy-
mal tubes are closed with a layer of soft tissue, but com-
municate with one another and with the calicular cavities
by asystem of transverse canals (Moseley). Heliopora ceru-
lea grows on coral reefs at the Philippine Islands and at
Singapore.

In the family of sea-fans (Gorgonide) the coral-stock is
horny or calcareous, branching tree-like, or forming a flat
network. The short calicles of the single retractile polyps
stand perpendicularly to the axis, communicating by longi-
tudinal vessels and branching canals. Gorgonia (Rhipigor-
gia) flabellum Linn. is red or yellow and abundant on the
Florida reefs. In the Arctic seas and the deeper, colder
waters of the Newfoundland Banks and St. George’s Banks,
Primnoa reseda (Pallas) and Paragorgia arborea (Linn.)
grow ; the latter being of great size, the stem as thick
through as one’s wrist, and the whole corallum over five feet
in height.

In the family of sea-pens (Pennatulide) the polyp-stock
is free, growmg in the sand or mud, usually with a horny
axis supporting the polyps, and capable of moving at the
base. In Pennatula, or the sea-pen, there are secondary
branches in which the polyps are situated ; this polyp is
phosphorescent ; one species (P. aculeata Danielsson) lives
in deep water. An Arctic form, Umbellularia groenlandica,
is a gigantic form, growing about four feet high, in from
three hundred to two thousand fathoms. The species of
Renilla are kidney-shaped, with the polyps placed on one
side. Renilla reniformis Cuvier is a rich purple species,
occurring in the sand at Charleston, 8. C. According to
Agassiz, this animal is remarkably phosphorescent, emitting
‘“a golden green light of a most wonderful softness. ”’

While coral reefs are in part composed of Alcyonarians,
FORMATION OF CORAL REEFS. 8”

Polyzoa, and certain plants called Nullipores, the Madrepo-
rarva in the main are the true reef-builders. They are con-
fined to waters in which through the coldest winter month
the temperature of the water a h | i mq

does not fall below 68° F., iy

though usually the waters are
much warmer than this, the
mean annual temperature be-
ing about 734° F. in the North
Pacific and 70° F. in the
South. Coral reefs are abun-
dant in the West Indies, but
still more so in the Central
Pacific, where there are a
much greater number of spe-
cies of corals (Dana). Along
the Brazilian coast, as far
south as Cape Frio, are coral
reefs (Hartt). In depth living
coral-reef-builders do not ex-
tend more than fifteen or
twenty fathoms below the sur-
face.

Coral reefs are divided by
Dana into outer or barrier
reefs (Fig. 57) and inner reefs.
The barrier reefs are formed
from the growth of corals ex-
posed to the open seas, while
the inner or fringing reefs
(Fig. 57) are formed in quiet
water between a barrier reef
and the island. As coral en
reefs are usually built upon o i i ur
islands which are slowly sink- i! Mh
ing, barrier reefs are simply 1) i
ancient fringing reefs formed when fa ea stood higher
above the sea, hence they are built up as rapidly as the land
sinks, and thus the top of the reef keeps at the level of

  
  

 

  
   

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MOQoPIIYL SW Wo1g—‘soor SUSU Puv JOLIE B JIM PULIST o1UvIIOA YSIH— 29 “SLT

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88 ZOOLOGY.

the sea. The reefs are often of great thickness, for, as
Dana says, ‘‘ could we raise one of these coral-bound islands
from the waves, we should find that the reefs stand upon

d
Q
a
3
a
A
a2
Z
2
9
q
So
fa
I
g
3
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°o
og
a
4
3
8
o
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8
ob
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Fig. 59.—Section of a reef.—From Brehm’s Thierleben.

 

the submarine slopes, like massy structures of artificial
masonry; some forming -a broad flat platform or shelf
ranging around the land, and others encircling it like vast
FORMATION OF CORAL REEFS. 89

ramparts, perhaps a hundred miles or more in circuit.’
Darwin has estimated that some reefs in the Pacific Ocean
are at least 2000 feet in thickness.

Thus far we have spoken of reefs surrounding mountainous
islands ; coral islands or atolls (Fig. 58) resemble such reefs,
except that they surround a lake or lagoon instead of a high
island, the coral island itself being seldom more than ten or
twelve feet above the sea, and usually supporting a growth of
cocoanut trees, while the sea may be of great depth very near
the outer edge of the atoll, which ‘‘ usually seems to stand as
if stilted up in a fathomless sea ’’ (Dana). These reefs and
atolls are formed and raised above the sea by the action of
the winds and waves, in breaking up the living corals,
comminuting it and forming with the débris of shells and
other limestone-secreting animals and plants, banks or de-
posits of coral mixed with a chalky limestone, as the base of
the reef. When it rises above the waves, cocoanuts and other
seeds are caught and washed up on the top, and gradually
the island becomes large enough to support a few human
beings. The Bermudas are the remnants of a single atoll,
and are situated farther from the equator than any other
reefs. Most barrier reefs and coral islands or atolls are
formed in an area of subsidence, where the bottom of the
ocean is gradually sinking ; this accounts for the peculiar
form and great thickness of many reefs. On the other
hand, the coral reefs of the West Indies are, generally
speaking, in an area of elevation.

A section of a coral reef is shown by Fig. 59: 2 is the point
where the shore slopes rapidly down within the lagoon
(which lies to the right), and m is where the reef suddenly
descends toward the open ocean. Between 0 ¢ and d ¢ lies
the higher part of the reef. The shore toward the lagoon
slopes away regularly from d to 2; while toward the open
ocean there is a broad horizontal terrace (a to dc) which
becomes uncovered at low water.

The theory of the formation of barrier reefs is shown by
the diagram, Fig. 60. The island, for example, the volcanic
island Coro, which is slowly sinking, at the ancient sea-level
J is surrounded by a fringing reef ff, a small rock-terrace
90 ZOOLOGY

at the former level of the sea. Where the island has sunk to
the level of the water-line II, the reef appears at the sur-
face as at b' f’,b f. There is now a fringing and a barrier
reef, with a narrow canal between them ; 0’ is a section of
the barrier reef, e’ of the canal or lagoon, and /’ of the
fringing reef. After a farther submergence to the sea-level
III, the canal e” becomes much wider. On one side (f/f)
the reef is present, on the other side it has disappeared, ow-
ing to the agency of ocean-currents. Finally, at the water-
level IV, there are two small islands surrounded by a wide
lagoon, with two reef-islets 7’”, 7'”, resting upon two sub-
marine peaks. The coral reef has now grown to great di-
mensions, and covered almost the entire original island,
and though the reef-building coral polyps cannot live below

 

Fig. 60.—Schematic section of an island with reefs.

a point fifteen or twenty fathoms below the surface, yet ow-
ing to the slow sinking of the island, they build up the
reef as rapidly as the former subsides, and in this way after
many centuries a coral reef sometimes two thousand feet
thick may be built up in mid-ocean.

Coral reefs are mainly confined to the Western and Cen-
tral Pacific and the Indian Oceans, and to the Caribbean
Sea. None occur on the west coast of North America or of
Africa, and only limited patches on the eastern coast of
South America. There were paleozoic reefs, such as the
fossil coral reef extending across the Ohio River at Louis-
ville.

 

seo
ACTINOZOA. 91

Cuass IIL.—THE ACTINOZOA.

Calenterates with a digestive sac partially free from the body-cavity open-
tng into it below and held in place by six or eight mesenteries radiating from
the digestive cavity and dividing the perivisceral space into chambers. Mouth
surrounded with a circle of tentacles, which are hollow, communicating di-
rectly with the perivisceral chambers. A slightly marked bilateral symmetry.
To the edges of the mesenteries (usually the free ones) are attached the repro-
ductive glands, both male and female, or of one sex alone ; also the craspeda,
or mesenterial filaments, which contain a large number of lasso-cells. Body
either entirely fleshy, or secreting a calcareous or horny coral-stock, and
when the species is social connected by a cenenchyme. In some forms (sea-
pens) the entire colony capable of limited locomotion. No well-marked
nervous system, but a plecus of fusiform ganglionic cells connected by nerve-
fibres in the base of Actinians. Reproduction by self division, gemmation,
or by ova, the sexes being separate or united in the same individual ; the
young undergoing a morula and gastrula condition, and then becoming
Jized.

Order 1. Zoantharia.—Mesenteries and tentacles six or in multiples of
six, coral-stock with calcareous septa. Mesenterial fila-
ments abundantly developed (Astrea, Madrepora, Actinia).

Order 2. Alcyonaria.—Mesenteries and tentacles always eight in num-
ber. Coral-stock without true septa. Mesenterial fila-
ments not usually numerous. Corallum usually horny, and
the whole colony in the Pennatulacea capable of locomo-
tion (Alcyonium, Gorgonia, Pennatula, Renilla).

View OF THE CLASSIFICATION OF THE ACTINOZOA,

Alcyonaria.
(Aleyonium.)
Zoantharia.
(Actinia.)
‘. eet

 

a
ACTINOZOA.

Laboratory Work.—Verrill has preserved Actinie completely ex-
panded by slowly adding a saturated solution of picric acid to a small
quantity of sea-water in which they had expanded. When dead they
should be transferred to a pure saturated solution of the acid, and
allowed to remain for from one to three hours, according to size, etc.
They should then be placed in alcohol, which should after a day or two
be renewed. Thus hardened they can be cut into sections. Corals
can be studied by grinding or sawing sections, and, if desirable, treated
as in the case of the corallum of the Millepores.
92 ZOOLOGY.

Cuass II].—CrenopHora (Comb-bearers).

General Characters of Ctenophores.—These beautiful an-
imals derive their name Ctenophora, or ‘‘ comb-bearers,”’
from the vertical rows of comb-like paddles (ctenophores)
situated on meridional bands of muscles which serve as lo-
comotive organs, the body not contracting and dilating as
in the true jelly-fishes. In their organization they are
more complicated than the Actinozoa, as they have a true
digestive cavity passing through the body-cavity, with two
posterior outlets (it will be remembered
that Cerianthus has one at the end of
the body). From this alimentary canal
are sent off chymiferous or water-vascu-
lar canals (Fig. 61) which correspond in
their mode of origin with the water-
tubes of the Echinoderms. As regards
the rows of paddles, each vertical row
consists of a great number of isolated,
transverse, comb-like fringes placed one
above the other, and movable, either
isolately or in regular succession or
simultaneously (Agassiz). As these rows
4 of paddles are connected for their whole

Fig. 61.—View of the length with a chymiferous tube, they
astro-vascular canals of a probably aid in respiration. These ani-

leurobrachia, from which . F
the two retractile arms mals also stand much higher in the scale
from one side, the mouth: Of life than the other Coelenterates by
fom the mouthend, being more truly bilateral, the radial
Bae SeeeRv EN symmetry so marked in the Actinia or
in the jelly-fish being in these animals less apparent, as the
parts are developed on opposite sides of a median plane.
The nervous system, as originally described by Grant, con-
sists of a ganglion situated at the aboral end (end opposite
to the mouth) of the Pleurobrachia, from which, among
other nerves, eight principal ones are distributed to the
eight rows of paddles. A nerve also proceeds to the so-
called otolitic sac (lithocyst) seated upon the ganglion.
Eimer has lately shown that the nervous system of the

 
AFFINITIES OF OTHNOPHORKS. 93

Ctenophora, as, for example, that of Beroé, agrees in general
with that of the jelly-fishes, with the difference that in the
Ctenophores the nerve-centres are not situated on the edge,
but at the pole of the body opposite the mouth. On the
other hand, the nervous system is not radiated as in the
jelly-fishes or as in the Echinoderms.

Our commonest example of this class is the Plewrobrachia
rhododacyla Agassiz. It is a beautiful animated ball of
transparent jelly moving through the water by means of
eight rows of minute paddles, throwing out from a sac on
each side of the body two long ciliated tentacles. It is
abundant in autumn; sometimes thousands may be seen
stranded on the shore at low water.

That the Ctenophores have affinities to the sea-anemones
(Actinozoa) is seen in the form and relations of the diges-
tive tract, though it differs in hanging free, not being held
in place by radiating mesenteries, and in this respect they
approach the Echinoderms. From their possessing a dis-
tinct digestive tract, the Ctenophores need not be confounded
with the jelly-fishes (Hydrozow). On the other hand, they
present some advance over the Actinozoa, and in some
respects connect the Hydrozoa and Actinozoa with the
Echinoderms. For example, the water-vascular system
arises in the Ctenophores as outgrowths from the digestive
sac, as they do in the young star-fish and sea-urchins. This
indicates that in the mode of development of both the di-
gestive tract and the water-vascular system the Ctenophores
are allied to the Echinoderms rather than to the Hydrozoa,
in which the water-vascular tubes arise as simple hollows in
the body-mass. Moreover, they are less radiated than in
the Hydrozoa or Echinoderms.

In Bolina alata Agassiz the body is plainly bilateral and
the water-vascular tubes are very distinct. In /dyia roseola
Agassiz the mouth is large, the stomach wide, and the
body is of an intense roseate hue. This beautiful species after
death, late in summer, is very phosphorescent ; all Cteno-
phores, however, even their eggs and embryos, are phospho-
rescent. In the Ctenophores the ovaries and spermaries occur
in the same individual and form blind sacs attached to the
94 ZOOLOGY.

water-vascular tubes, and are developed locally, asin Cestwm,
or along the whole length of the tubes, the sexually-differ-
ent glands being placed in Beroé and allies on opposite
sides of the tube.

When ripe the eggs pass into the perivisceral space, and
finally pass out through the openings of the body. The
eggs of Plewrobrachia escape singly ; in Bolina they are
laid in strings, while those of Idyia are deposited in a thick
slimy mass. They spawn late in the summer and in the
autumn. The young develop in the autumn, becoming
nearly mature in the following spring. Development is di-
rect, the young hatching nearly with the form of the adult,
there being no metamorphosis.

The species are widely distributed, a number being com-
mon to both sides of the Atlantic, and the same species, ap-
parently, of Plewrobrachia and Idyia occur on the east and
west coast of North America. The most widely distributed
forms are the Beroids. While the genus Mertensia is en-
tirely arctic, the larger number of species are either tropi-
cal or subtropical. The classification of the group is shown
in the following summary.

Cuass IIJ.—CTENOPHORA.

Spherical or oval, somewhat bilateral, scarcely radiated animals, with
jelly-like, transparent bodies. The digestive tract opens at the posterior
end into the perivisceral cavity ; from the canal pass off eight water-vas-
cular tubes, which are in close relation with eight vertical meridional series
of comb-like locomotive organs. Usually a pair of tentacles, which may
become withdrawn into sacs, and are provided with thickset lasso-cells on
the tentacular fringes. Nervous system consisting of an aboral ganglion,
sending off eight nervous filaments to each of the eight rows of paddles.
The sexual glands seated in the same individual. No metamorphosis,
the young when hatched resembling the adult.

Order 1. Hurystomee.—Body oval, with a large mouth and capacious
stomach. The water-vascular tubes connected with the
ctenophores, and forming numerous ramifications, commu-

nicating by means of a circular canal near the mouth
(Beroé, Idyia).
CLASSIFICATION OF CTENOPHORES. 95

Order 2. Saccate.—Body more or less spherical, with two long tenta-
cles capable of being wholly retracted in a sac (Pleuro-
brachia).

Order 3. Teniata.—Body ribbon-like, being very much compressed in
the direction of the lateral diameter (Cestum).

Order 4. Lobate.—Body lateral, compressed, bilobed (Bolina).

VIEW OF THE CLASSIFICATION OF THE CTENOPHORA.

 

 

 

Lobata.

(Bolina.)
Teniata.
(Cestum.)

Saccata.
(Pleurobrachia.)
Hurystomee.
(idyia.)
|
CTENOPHORA.

Laboratory Work.—The Ctenophore should be studied while alive.
They may be collected with a drag or tow-net from a boat when the
surface of the ocean is calm. For studying the fine anatomy and
tissues they should be treated by the same methods as the smaller jelly-
fishes.

 
CHAPTER: LVe

BRANCH IV.—ECHINODERMATA (Srar-FisH, SzEa-
URCHINS, SEA-CUCUMBERS, ETC.)

General Characters of Echinoderms.—We now come to
animals of much more complicated structure than any of
the foregoing branches, and in which the radiated arrange-
ment of the parts of the body is in most cases as marked
as the jointed or ringed structure of worms or insects ; for
not only are the body-walls of the star-fish or sea-urchin, or
even many of the Holothurians (though less plainly), di-
vided into five wedge-shaped portions (spheromeres), or pro-
duced into five arms as in the common star-fish or five-
finger, but the nervous system, the reproductive organs,
the blood and water-vascular systems, and the locomotive
appendages of the latter, are usually arranged in accordance
with the externally radiated form of the body. Still these
animals are in many cases, as in the higher sea-urchins,
plainly bilateral, while in the larval forms of all Echino-
derms whose development is known the young are not
radiated, but more or less bilateral, asin the larve of worms
and mollusks. The most trenchant character, however,
separating the Echinoderms from the Coelenterates, and ally-
ing them to the worms, is the genuine tube-like digestive
canal which lies free in the body-cavity (perivisceral cavity),
and may be several or many times the length of the body.

The student can gain a correct idea of the general struc-
ture of the Echinoderms from a careful examination of the
common star-fish (Asterias vulgaris Stimpson), which is the
most common and accessible Echinoderm to be found on the
New England shores. After placing a star-fish in some sea-
water and noticing its motions, the thrusting out of the am-
bulacral feet or suckers by which it pulls or warps its clumsy
STRUCTURE OF COMMON STAR-FISH. 97

body over the mussel-beds, or rocks, or weeds, the arms
being capable of slightly bending ; after observing the red
eye-spot at the end of each arm or ray, and the movements
of the numerous spines which are attached by a sort of ball
and socket joint to the calcareous framework of the body-
walls, and examining the movements of certain modified
spines called pedicellarie, which are pincer-like bodies situ-
ated among the spines, the student will be ready to study
the external and internal anatomy.

First, as to the calcareous framework of the star-fish.
Tn order to study this, a transverse section should be made
through an arm, and a vertical one through the body and
along the middle of a single arm, and finally the animal
should be divided into two halves, an upper and lower. It
will then be seen that the calcareous framework or so-called
skeleton consists of a great number of limestone plates or
pieces attached by a tough membrane and covered by the
skin. Between the plates are small apertures by which the
water enters the body-cavity. These plates are arranged so
as to give the greatest strength and lightness to the body.
There is also to be seen an oral (actinal) side on which the
mouth is situated, and an aboral (abactinal) side, the re-
spective limits of which areas vary greatly in the different
groups of Echinoderms. Each arm or ray is deeply chan-
nelled by the ambulacral furrow containing four rows of
suckers or ‘‘ambulacral feet,’? which are tentacle-like
protrusions of the skin growing out through orifices in
the ambulacral plates, and are a continuation of the water-
sacs or “‘ampulle’’ within. The madreporic plate is a
flattened hemispherical body situated on the disk between
two of the arms. It is perforated by canals.

We are now ready to examine the internal organs and to
study their relations to one another and to the body-walls.
The nervous system may be seen without dissection. By
closely examining the mouth a pentagonal ring is seen sur-
rounding it, each angle slightly enlarging* and sending off

* Owfsiannikoff states that the nervous ring is a flat band, con-

taining no swellings or ganglia, and not differing in structure from the
ambulacral nerves, which latter possess nerve-cells as well as fibres.
98 ZOOLOGY.

a nervous cord to the eye at the end of the ray. It may be
discovered by pressing apart the ambulacral feet along the
median line of each arm. Fine nerves are sent off to each
sucker, passing through the opening between the calcareous
plates and extending to each ampulla, thus controlling the
movements of the ambulacral feet.

 

Fig. 62.—Longitudinal section through the body and onearm of Asterias vulgaris.
m, mouth; s, stomach; 2, lobe of stomach extending into the arm; a, anus; 77, ner-
vous ring ; 7, radial nerve; vr, water-vascular ring, sending a radial vessel (v) into the
arm ; mp, madreporic plate; ¢, stone canal; 2, hemal canal ; ov, oviduct ; 0, ovary ;
am, ampulle, the ambulacral feet projecting below; 0, cceca or liver.—Drawn by
A. F. Gray, under author’s direction.

The mouth (Fig. 62, m) is capacious, opening by a short
cesophagus into a capacious stomach (Fig. 62, s) with thin
distensible walls, and sending a long lobe or sac (Fig. 62, J)
into the base of each arm ; each sac is bound down by two
retractor muscles attached to the median ridge lying be-
tween the two rows of water-sacs (ampulle, see also Fig. 63).

 

Fig. 63.—Diagram of the cross-section of an arm. A, of Asterias rubens 7B aol)
Ophiura texturata ; p, ambulacral feet ; p’, ampulle ; ¢, dermal tentacles ; 7, nervous
cords ; w, ambulacral plates ; 2m, muscles ; a, ambulacral vein ; 6, ventral plate ; ¢, lat-
eral plates; @, dorsal plate ; &, calcified portion of the integument.—After W. Lange
from Gegenbaur.

The stomach ends in a short intestine, the limits between
the two not distinctly seen. The intestine suddenly con-
tracts and ends in a minute rectum situated in an angle
between two of five fleshy ridges radiating from the centre
STRUCTURE OF COMMON STAR-FISH. 99

of the aboral disk. The anus (Fig. 62, a) is minute and
difficult to detect, being situated between the short spines,
and is evidently not used in the expulsion of fecal matter
unless the urinary secretions, if there be such, pass out of
it. Tt would seem as if the opening were rudimentary and
that the star-fish had descended from Echinoderms like the
Crinoids, in which there is a well-marked external terminal
opening of the digestive tract. Appended to the intestine
are the ‘‘cceca”’ or “‘liver”’ (Fig. 62, 0), consisting of two
long, tree-like masses formed of dense branches of from
four to six pear-shaped follicles, connecting by a short duct
with the main stem. The two main ducts unite to form a
short common opening into the intestine. The cceca are
usually dark, livid green, and secrete a bitter digestive
fluid, representing probably the bile of the higher animals.

The star-fish is bisexual, but the reproductive glands are
much alike, the sexes only being distinguishable by a micro-
scopic examination of the glands. The ovaries (Fig. 62, 0)
are long racemose bodies lying along each side of the in-
terior of the arms, and the eggs are said to pass out by a
short narrow oviduct (ov) through an opening between two
plates on each side of the base of the arms, the opening be-
ing small and difficult to detect.

The water-vascular system consists of the madreporic
body, the ‘‘ stone-canal”’ (Fig. 62, ¢), the ring or circumoral
canal (vr), and the radial vessels (v) ending in the water-
sacs (wm) and ambulacral feet. The stone-canal begins
at the outer and under side of the sieve-like madreporic
body, passing directly forward and downward in a sinuous
course to the under side of the circumoral plates. ‘The
madreporic body (md) is externally seen to be perforated by
linear apertures radiating and subdividing toward the pe-
riphery. The sea-water in part enters the body-cavity
through the fissures in the madreporic body, while most of
it enters the stone-canal, which is a slender tube scarcely
one fourth the diameter of the entire madreporic body.
The water entering the stone-canal (Fig. 62, ¢) passes di-
rectly into the water-vascular ring (Fig. 62) and- then into
the ten Polian vesicles and the five radial canals, whence
100 ZOOLOGY.

it is conveyed to each water-sac or ampulla (Fig. 62, am).
These pear-shaped water-sacs, when contracted, are supposed
to press the water into the long slender suckers or ambulacral
fect, which are distended, elongated, and by a sucker-like ar-
rangement at the end of the prehensile foot act in conjunc-
tion with the others to warp or pull the star-fish along.
Besides locomotion the ambulacral feet serve for respiration
and perception (Simroth). Hoffman shows that the feet
of the sea-urchins can be projected or thrust out without
the aid of the ampulle.

It will thus be seen that the water-vascular system in the
star-fish is in its functions partly respiratory and partly
locomotive, while it is in connection with the vascular sys-
tem, and thus partly aids in circulating the blood and
chyle.

Of the true vascular or blood system the student can ordi-
narily only discover one portion, the so-called “‘ heart ”” or
“ pulsating vessel,’’ which we may call the hemal canal (Fig.
62 h), and which runs parallel to the stone-canal from the
madreporic body to near the ring-canal.* It is nearly as
large as the stone-canal, slightly sinuous, muscular, and with
the latter is surrounded by a loose investing membrane like
a pericardium. Some observers deny the existence of a vas-
cular (sometimes called ‘‘ pseudohemal ’’) system, but it has
been recently studied by Hoffman and subsequently by Teu-
scher, who maintains that in all Echinoderms there are two
systems of blood-vessels, which belong, one to the viscera and
the other to the nervous system, forming an oral or nervous
ring and an analring. The two rings are in direct com-
munication in the star-fishes, Ophiurans and sea-urchins,
but not in the Holothurians. The radial nerves are ac-
companied by a vessel which subdivides and distributes
branches to the ambulacral feet in star-fishes, Echini, and
Holothurians. Teuscher considers that the ‘‘ heart ”’ found
in the star-fishes and Echini connecting the oesophageal (or
nerve-ring) and anal ring, is neither a gland nor a pulsating
vessel, as different authors have supposed, but perhaps only

* Simroth states that in Ophiurans (Ophiactis) the stone-canal opens
in common with the “ heart’’ into the madreporic plate.
CRINOIDS. 101

a relict of an earlier period of development. In the Ophi-
urans the oral canal opens directly into the body-cavity ;
in Hchinothriz directly connects with the outer world by
means of the interradial canals. Finally, he regards the
nervous vessel as homologous with the ventral vessel of the
worms.

Having made ourselves acquainted with the general struc-
ture of the Echinoderms as exemplified in the star-fish, we
are prepared to study the modifications of the Echinoderm
plan in the different classes.

Crass I.—Crinorpga (Stone-lilies, Encrinites, etc.)

Order 1. Brachiata.—The living representatives of those
Crinoids which lived in paleozoic and early mesozoic
times are few in number, and for the most part live in deep
water, or, as in the case of Rhizocrinus and its living allies,
at great depths. They are like Limulus and Nebalia, rem-
nants of an ancient fauna. There are but eight genera
known—viz., Holopus, Rhizocrinus, Bathycrinus, Hyocri-
nus, Pentacrinus, Comaster, Actinometra, and Antedon
(Comatula). Of the first five genera the species are attached
by a stalk to the sea-bottom, while the last three genera are
in their young state stalked, but finally become detached.
The body or calyx divides into arms bearing pinnule or sub-
branches.

The Pentacrinus lives attached to rocks from twenty to
thirty fathoms below low-water mark in the West Indies.
The stem is about a foot long, the joints pentagonal, send-
ing off at intervals whorls of unbranched cirri. ‘‘ No dis-
tinct basal piece is known, but the calyx appears to begin
with the first five radialia ’? (Huxley). Pentacrinus ca-
put-meduse Miller (Fig. 64) and P. Miillert Oersted are
West Indian species. P. Wyville-Thompsoni Jeffreys was
dredged in deep water on the coast of Portugal. In the
fossil P. subangularis the stalk was more than fifty feet long.
Bathycrinus gracilis Wyville-Thompson 1s closely allied
102 ZOOLOGY.

to Rhizocrinus, and was dredged in the Bay of Biscay at
the depth of 2435 fathoms. 8B. Aldrichianus occurred in
1850 fathoms, latitude 1° 47’ N., longitude 24° 26’ W., off
the coast of Brazil. With it and also near the Crozet
Islands occurred the interesting Hyocrinus Bethellianus
Wyville-Thompson, which bears in some points resemblance
to the paleozoic genus, Platycrinus.

 

 

Fig. 64.—a, Pentacrinus caput-meduse, half natural size; 6, calyx-disk seen from
above, natural size.—From Brehm’s Thierleben.

The most widely distributed species is the Rhizocrinus
lofotensis of Sars (Fig. 65), which is closely related to the
Bourguetticrinus of the chalk formation, and forms the
transitional type connecting the Apiocrinide with the
free-moving, unstalked Antedon. It occurs at the depth of
STRUCTURE OF ORINOLDS. 103

from one hundred to
one thousand fathoms
in the North Atlantic
and Floridan seas,
and isa characteristic
member of the abyssal,y
fauna. This crinoid®a&
consists of a jointed
stalk, a cup-shaped
body (calyx), from
the edge of which
from five to seven
(the number varies)
arms (drachia) radi-
ate, which subdivide
into a double alter-
nate series of pin-
nule. The mouth is
situated in the centre,
while the anus is situ-
ated on a conical pro-
jection on one side of
the oral disk, between
the bases of two of
the arms. R&. Raw-
sont Pourtales occurs
in from eighty to one
hundred and twenty
fathoms at Barba-
does. iH
In Holopus, ashort, 4
stout form with no “\
true stalk, but at-
tached by abroad en-
crusting base, there
are ten arms originat-
ing from five axial

joints. ‘‘ When con- Se
Fig. 65.—Rhizocrinus lofotensis Sars, twice natural
tracted the arms are size. After Wyville Thompson.

 

SSS
Se

~ toe

=oIS-,

ooo

 
104 ZOOLOGY.

rolled in a spiral and press laterally against one another so
as to enclose a hermetically closed cavity.”’ The pinnules
are formed of broad flat joints, and are “‘ rolled spirally to-
ward the ambulacral channel of the arms when contracted ”’
(Pourtales). The only species yet known is H. Rangii
D’Orbigny, from Barbadoes,

In Antedon (Comatula) the body is at first stalked, but
afterward drops off, when it represents the calyx and arms
of the ordinary Crinoids. It thus passes through a Rhizo-
crinus condition, showing that it is a higher, more recent
form. The mouth opens into a short, broad csophagus,
and a wide stomach which makes a turn and a half, ending
in the anal cone placed between the base of two of the arms.
Within the five triangular plates is a circle of tentacles.
From the space between each pair of oral plates the ambu-
lacral grooves radiate to the arms and their branches. 4H.
Ludwig maintains that Antedon possesses a true water-vas-
cular system formed on the typical Echinoderm plan;
there being a ring-canal, with radial vessels arising from it.
The tentacles of the perisome are connected with the ring-
canal, and the tentacles of the arms and pinnule are con-
nected with the radial vessel. Ludwig has also discovered
in Antedon a system of blood-vessels (‘‘ pseudo-hemal ”’
system) consisting of an oral ring-canal and five vessels
radiating from it, which send branches to the tentacles, as
in Asterias. He also detected a ‘‘ dorsal organ,’’ which
he, contrary to Perrier and P. H. Carpenter, considers to
be the central organ of the whole system of blood-vessels.
Both Ludwig and Carpenter, however, regard it as homolo-
gous with the so-called ‘‘ heart ’’ or hemal canal of Echini
and Asterias.

The nervous system consists of an oral ring with branches
extending into the arms.

The body-cavity extends into the arms, and the ovaries
for the most part lie in the cavity of the arms, as in Asterias.

The internal anatomy of Rhizocrinus has been investi-
gated by Ludwig, who finds that it agrees very closely with
that of Antedon. The water-vascular system, nervous sys-
tem, alimentary canal and its appendages, have the same
DEVELOPMENT OF CRINOIDS. 105

relations as in the unstalked Crinoids (Antedon and Actin-
ometra), only they are on a simpler plan, there being a
close similarity between Rhizocrinus and the pentacrinoid
stage of Antedon.

The ovaries of Antedon open externally on the pinnules
of the arms, while there is no special opening for the prod-
ucts of the male glands, and Thompson thinks that the
spermatic particles are ‘‘ discharged by the thinning away
and dehiscence of the integument.’’ The ripe eggs hang
for three or four days from the opening like a bunch of
grapes, and it is during this time that they are fertilized.
The following account is taken (sometimes word for word)

 

we 66.—Development of a Crinoid (Antedon). .A, morula; B, free larva, with
bands of cilia; C, young crinoid.—After Wyville-Thompson.

from Wyville-Thompson’s researches on Antedon rosaceus
(Fig. 67) of the European seas. In the first stage the egg
undergoes total segmentation (Fig. 66). A represents the
egg with four nucleated cells, an early phase of the mul-
berry or morula stage. After the process of segmentation
of the yolk is finished, the cells become fused together into
a mass of indifferent protoplasm, with no trace of organiza-
tion, but with a few fat cells in the centre. This pro-
toplasmic layer becomes converted into an oval embryo,
whose surface is uniformly ciliated. The mouth is formed
with the large cilia around it before the embryo leaves the
106 ZOOLOGY.

egg. When hatched, the larva is long, oval, and girded
with four zones of cilia, with a tuft of cilia at the end, a
mouth and anal-opening, and is about eight millimetres
long. The body-cavity is formed by an inversion of the
primitive layer which seems to correspond to the ectoderm.

Within a few hours or sometimes days, there are indica-
tions of the calcareous areolated plates forming the cup of
the future crinoid. Soon others appear forming a sort of
trellis-work of plates, and gradually build up the stalk, and
lastly appears the cribriform basal plate. Fig. 66, B, ¢, rep-
resents the young crinoid in the middle of the larva, whose
body is somewhat compressed under the covering-glass.

 

Fig. 67.—Antedon, stalked and free.—From Macallister.

Next appears a hollow sheath of parallel calcareous rods,
bound, as it were, in the centre by the calcareous plates.
This stalk (B, c) arises on one side of the digestive cavity
of the larva, and there is no connection between the body-
cavity of the larva and that of the embryo crinoid.

Two or three days after the appearance of the plates of
the crinoid, the larva begins to change its form. The
mouth and digestive cavity disappear, not being converted
into those of the crinoid. The larva sinks to the bottom,
there resting on a sea-weed or stone, to which it finally ad-
heres. The Pentacrinus form isembedded in the larval body
FOSSIL CRINOIDS. 107

(the cilia having disappeared), now constituting a layer of
protoplasm conforming to the outline of the Antedon.

Meanwhile the cup of the crinvid has been forming. It
then assumes the shape of an open bell; the mouth is
formed, and five lobes arise from the edges of the calyx.
Afterward five or more, usually fifteen tentacles, grow out,
and the young Antedon appears, as in Fig. 66,C. The
walls of the stomach then separate from the body-walls.
The animal now begins to represent the primary stalked
stage of the Crinoids, that which is the permanent stage in
Rhizocrinus, Pentacrinus, and their fossil allies. After liv-
ing attached for a while (Fig. 67), it becomes free (see right-
hand figure) and moves about over the sea-bottom.

 

Fig. 68.—A Blastoid, Pentremites, seen from the side and from above.—After Liitken.

There are two species of Antedon on the New England
coast, one (A. Sarsti) inhabiting deep water in about one
hundred fathoms, and the other (A. Hschrichtii Miller)
shallower water (twenty-five fathoms) in the Gulf of Maine.

Order 2. Blastoidea.—No forms have been discovered
later than the Carboniferous period. The group began
its existence as species of Pentremites (Fig. 68) in the
Upper Silurian, and culminated in the Carboniferous age.
It connects the Crinoids with the Cystideans ; the species
have no arms, are supported on a short, jointed stalk, and
the oral plates, when closed, as they are in a fossil state,
make the calyx look like a flower-bud. There is a mouth
and eccentric anal outlet and five radiating grooves, along
108 ZOOLOGY.

each side of which are attached a row of pinnules. Be-
sides Pentremites are the typical genera Hleacrinus and
EFleatherocrinus.

Order 3. Oystidee.—This group is likewise extinct. In
the fossil Psewdocrinus there is a short-jointed stalk, while
in Caryocystites (Fig. 69) there is no stalk and no arms, the

   
 

Fig. 69.— Caryocys-
tites, a Cystidean.—
After Liitken.

 

Fig. 71.—Agelacrinus, a Cystidean, on
the shell of a Brachiopod.—After Latken

Fig. 70.—Pseudocri-
nus, a Cystidean.—
After Liitken,

body being angulo-spherical, composed of solid plates. The
Cystideans (Figs. 69 to 71) originated in the Cambrian for-
mation, attained their maximum development in a number

of species in the Silurian, and became mostly extinct in the
Carboniferous period.

Cuass I.—CRINOIDEA.

Spherical or cup-shaped Echinoderms, without a madreporic plate, usu-
ally attached by a jointed stem, a few free in adult life, with five arms sub-
dividing into pinnule ; the ambulacral feet in the form of tentacles
arising around the mouth in the furrows of the calyx or situated on the
jointed arms. In the Blastoidea and certain Cystideans the arms are ab-
sent, but the pinnule are usually present, though absent in Caryocystites.
Circulatory, water-vascular, and sexual organs much as in other Hehino-
derms ,; the digestive canal ending in a distinct eccentric uperture.
GENERAL STRUCTURE OF STAR-FISHES. 109

Order 1. Brachiata (True Crinoids).—Calyx with large pinnulated
arms, without dorsal calical pores, mostly stalked (Encri-
nus, Pentacrinus, Apiocrinus, Rhizocrinus, Holopus, Ante-
don, Actinometra, Phanogenia).

Order 2. Blastoidea.—Armless, but with five series of pinnule, and
with a stalk (Pentremites. No living representatives).

Order 3. Cystidea.—Usually armed, with jointed pinnule, and a short
stalk, the latter sometimes absent, as in Caryocystites. (All
fossil forms, as Edriaster, Caryocystites, Sphzeronites, etc.)

Laboratory Work.—TYhe living Crinoids are great rarities, and few
students have access even to alcoholic specimens. The recent re-
searches on their internal anatomy have been made in large part by
cutting thin sections for the microscope, and staining them with car-
mine, etc., after the methods of the histologist.

Cxass II.—AsTEROIDEA (Star-jishes).

General Characters of Star-fishes.— Having already
studied the structure of the common star-fish, we are pre-
pared to understand the classification of the class. The
star-fishes have star-shaped, flattened bodies, with round or
flattened arms, a madreporic plate, and two or four rows of
ambulacral feet.

Order 1. Ophiuridea (Sand-Stars).—This division is
characterized by the body forming a flattened disk, with
cylindrical arms, the stomach not extending into the arms,
and there is no intestine or anal opening. The ambulacral
furrow is covered by the ventral shields of the tegument, so
that the ambulacral feet project from the sides of the arm.
They have no interambulacral spaces or plates. The am-
bulacral feet or tentacles do not have a sucker at the end,
but are provided with minute tubercles. They move faster
than the true star-fishes, the arms being more slender and
flexible. The madreporic body is one of the large circular
plates in the interambulacral spaces around the mouth.
The external openings for the exit of the eggs form distinct
fissures or slits, one on each side of each arm. ‘The ovaries
are situated in the body, not extending into the arms, the
110 ZOOLOGY.

eggs being expelled into the perivisceral cavity, and thence
finding their way out into the water through the interradial
slits.* The Ophiurans are bisexual, but one species being
known to be unisexual, viz., Ophiolepis squamata, accord-
ing to Metschnikoff. While most Ophiurans pass through
a metamorphosis, the young of Ophiolepis ciliata is developed
within the body of the parent, adhering by a sort of stalk
(Krohn). In Ophiopholis bellis development is direct, there
being no metamorphosis.

An Ophiuran which has accidentally lost its arms can re-
produce them by budding. Liitken has discovered that in
species of Ophiothela and Ophiactis the body divides in two
spontaneously, having three arms on one side and three on
the other, while the disk looks as if it had been cut in two
by a knife and three new arms had then grown out from
the cut side. Simroth has made farther extended researches
on self-fission in Ophiactis.

The Ophiurans in most cases undergo a decided meta-
morphosis like that of the star-fish, which will be described
at length farther on. The larva, called a pluteus, is free-
swimming, though in some species the young, in a modified
larval condition, reside in a pouch situated above the mouth
of the parent, finally escaping and swimming freely about
(A. Agassiz).

In Ophiocoma vivipara Liungman, which occurs in the
South Atlantic, the young at first live in the body of the
parent and afterward cluster on the surface of her disk.
The eggs are hatched successively, the young being found
in a regularly gradated series of stages of growth (Wyville-
Thompson). It appears probable, as in the case of the sea-
urchins, that the Ophiurans of the cooler portions of the
South Atlantic, in most cases at least, have no metamor-
phosis.

Our most common sand-star is Ophiopholis bellis Lyman
(Fig. 72), which may be found at low-water mark, and espe-
cially among the roots of Laminaria thrown up on the

* On the other hand, Ludwig denies that the eggs pass into the peri-

visceral cavity, but insists that they collect in pouches formed by an in-
troversion of the integument.
SAND-STARS AND STAR-FISHES, 111

beach. It is variable in color, but beautifully spotted with
pale and brown, its general hue being a brick-red. _Am-
phiura squamata Sars has long slender arms and is
white ; it lives below tide-marks. The basket-fish, me-
dusa’s head, or Astrophyton
Agassizti Stm., is of large
size, the disk being two in-
ches across, and the arms
subdividing into a_ great
number of tendril-like
branches. It lives from ten
to one hundred fathoms in
the Gulf of Maine.
Ophiurans are widely dis-
tributed, and live at depths guys
between low-water mark and eed anti
two thousand fathoms. Fos- Fig. 72.— Ophiopholis bellis, common Sand-
sil Ophiurans do not occur “Af Morse.
in formations older than the Upper Silurian, where they are
represented by the genera Protaster, Paleodiscus, Acroura,
and Hucladia ; genuine forms closely like those now living
appear in the muschelkalk beds of Europe (Middle Trias).
Order 2. Asteridea.—In the true star-fishes the arms are
direct prolongations of the disk, and the stomach and

 

 

Fig. 73.—Three forms of Star-fish, A, B, C, seen from above, showing the different
development of the ambulacral and interambulacral areas. The ambulacra are indi-
cated by rows of dots; 0, mouth; 7, arms; ir, interradial or interambulacral areas.
C Pteraster; B, Goniodiscus; A, Asteriscus.—After Gegenbaur.

ovaries or spermaries project into them, and there is a deep
ambulacral furrow, while the interambulacral spaces vary
much in development (Fig. 73); the feet are provided with
112 ZOOLOGY.

suckers, excepting those at the end of the arms, which are
tentacle-like. We have already described the common star-
fish of our north-eastern coast, Asterias vulgaris Stimpson
(Fig. 74). This and the allied varieties are abundant on
mussel and oyster beds, being very injurious to the latter,
which serve them as food. The star-fish projects its capa-
cious stomach, turning it inside out, between the open
valves of the oyster, and sucks in the soft parts, in this way
doing much damage to the oyster-beds of the southern coast
of New England.

 

Fig. 74.—Asterias vulgaris, natura) size.—After A. Agassiz.

The bodies of star-fishes as well as sea-urchins (Echini)
are covered with pedicellarie, which in the former are situ-
ated around the base of the spines on the upper side of the
body. They are pincer-like, consisting of but two prongs.
In the sea-urchins they are three-pronged, and scattered ir-
regularly over the surface of the body. Their use is not
really known.

The development of this species (and its ally or variety,
A. berylinus) has been studied by A. Agassiz. After pass-

ah
DEVELOPMENT OF STAR-FISHES. 113

ing through the morula and gastrula stages, the cephalula
or larval stage is reached, the mouth, digestive sac and its
posterior opening being formed, a cephalic end being dis-
tinguished from a posterior end. The larva is now bilater-
ally symmetrical. At this time two lobes arise from each
side of the mouth. These separate from their attachment
and form two distinct hollow cavities, and by the time the
larva attains the Brachiolaria stage the development of the

 

Fig. 76.—Brachiolaria
of Asterias vulgaris, en-
larged, with the star-fish

Fig. %.— Bipinnaria with the star- (7) developing at the
jt

 

fish ding from it. e@, e, d’, 9g, 9. aboral end. e, median

protuberances of the body comparable
with the ‘‘arms” of the Brachiolaria
figured in the adjoining engraving.
6, mouth; 0, vent of the larva; A, germ
of the star-fish; h, ciliated digestive
tract; 2, ambulacral rosette (germ of
the water-vessels).—After Miiller, from
Gegenbaur.

anal arm; e®, odd termi-
nal oral arm; /, brachio-
Jar arm; f!, branch of
water-tube (ww’) leading
into f” odd brachiolar
arm; f’”, surface-warts
at base of odd brachiolar
arm f/””.—After A. Agas-
siz.

body of the star-fish begins, for these two cavities subse-
quently develop into two water-tubes. On one of these cav-
ities the back of the star-fish is afterward developed, while
on the other the under side with the feet or tentacles arise.
The fully-grown larva is called a brachiolaria, as it was
originally described with this name under the impression
that it was an adult animal, as was the case with the pluw-
114 ZOOLOGY.

teus of the sand-stars, the dtpinnaria (Fig. 75) of certain
star-fishes, and the awricularia of the Holothurians.

Fig. 76 shows the star-fish developing on the aboral end
of the brachiolaria, whose body it is now beginning to ab-
sorb. ‘The brachiolaria soon shrinks, falls to the bottom,
and attaches itself by its short arms. The star-fish com-
pletely absorbs the soft body of the larva, and is conical,
disk-shaped, with a crenulated edge. In this stage it re-
mains probably two or three years before the arms lengthen
and the adult form is assumed.

In Leptychaster kerguelenensis Smith, of the South Atlan-
tic, a form allied to Lutdia or Archaster, the young develop
directly in a sort of marsupium, according to Wyville-
Thompson. Pteraster militaris was found by Sars to be
viviparous.

In Brisinga the arms number from nine to eleven, are
long, cylindrical, and, like the body, bear long spines. The
species are abyssal. 2B. endecacnemos Asbjornsen lives on
the Norwegian coast, at a depth of about 200 fathoms, and
was dredged in abundance by the Challenger Expedition in
1350 fathoms, at a station due south of St. George’s Banks,
associated with other species of star-fish (Zoroaster and As-
tropecten), and again in eighty fathoms on La Havre Bank,
off Nova Scotia. A common form living in mud in usually
from ten to thirty fathoms is Ctenodiscus crispatus Retzius,
in which the body is almost pentagonal, the arms being very
short and broad. Archaster isa genus of star-fishes occurring
at great depths, A. vexillifer Wyville-Thompson (Fig. 77),
occurring off the Shetland Islands, in from 300 to 500 fath-
oms. Luidia is called the brittle star-fish, as when brought
up from the bottom and taken out of the water it breaks up
into fragments. It has five long arms. L. clathrata is com-
mon on the sandy shores of the Carolinas, and ranges from
New Jersey to the West Indies. Astropecten articulatus
(Say) has the same range. Astrogoniwm phrygianum Parel
is a large pentagonal, bright-red star-fish, living in twenty
to fifty fathoms on rocky bottoms in the Gulf of Maine
and northward ; while Pteraster militaris Miller is an
arctic species which ranges south to Cape Cod. It is sub-
DIFFERENT FORMS OF STAR-FISHES. 115

pentagonal, with five short arms. The fine large Solaster
endeca Retzius has eleven smooth arms; it lives in deep
water. Crossaster papposus (Miller and Troschel) is com-
mon on a rocky bottom, in from twenty to eighty fathoms,
from the Gulf of Maine northward ; it is bright red, and has
thirteen to fourteen spinulated arms. Cribella sangwin-
olenta Liitken is a common species on the coast of New

 

Fig. 77.—Archaster verillifer, under side ; natural size.—After Wyville-Thompson.

England below low-water mark, and is in some respects like
Crossaster.

More closely allied to Asterias is the Pacific Coast Pyeno-
podia helianthovdes Stimpson, which ranges from Sitka to
Mendocino, Cal. It is very common in Puget Sound, under
wharves. Asterias vulgaris Stimpson represents, on the
northeastern coast, the A. rubens of Europe. Asterias
polaris (M. and T.) has six arms, and is over twelve inches
116 ZOOLOGY.

in diameter; it is very common from Labrador north-
ward.

Fossil star-fishes allied in most respects to Asterias occur
in the Lower Silurian rocks, showing the remarkable persist.
ence of this type of the order. Characteristic Lower Silu-
rian forms are Paleaster and Archasterias. In the Upper
Silurian appeared Palasterina, a genus allied to the living
Astrogoniwm, etc.

Cuass IJ].—ASTEROIDEA.

Echinoderms with a star-like or pentagonal body, with two or four rows
of ambulacral feet or tentacles on the oral side. Body covered with small,
short spines, often arranged in groups. The nervous system pentagonal,
with nerves extending into the arms ; the water-vascular and hemal systems
also radiating into the arms. Most of the species bisexual , the young usually
passing through a metamorphosis, the star-fish budding out from the water-
vascular system of the pluteus, bipinnaria or brachiolaria form, which pre-
viously passes through a morula, gastrula, and cephalula stage.

Order 1. Ophiuridea.—Arms round, starting suddenly from a round,
disk-like body. Ambulacral furrow covered by a series of
ventral plates, so that the tentacles or ambulacral feet are
thrust out laterally. The ovaries and stomach not extend-
ing into the arms; no anal-opening, no pedicellarie.
(Ophiura, Ophioglypha, Ophiolepis, Amphiura, Ophio-
coma, Astrophyton).

Order 2. Asteridea.—Body star-like, the arms being gradual extensions
of the disk, and containing the reproductive glands, di-
gestive cceca, as well as the radial nerves and radial hemal
and water-vascular canals. A deep ambulacral furrow,
containing two or four rows of ambulacral feet or tenta-
cles, those at the extremity of the arms without suckers
(Brisinga, Ctenodiscus, Luidia, Astropecten, Oreaster, As-
trogonium, Pteraster, Solaster, Crossaster, Cribrella, Pyc-
nopodia, Asterias).

Laboratory Work.—The larger star-fishes are easily dissected ; the
general relations of the integument may be perceived by making
transverse and longitudinal sections, while the viscera may be studied
by splitting the body and arms in two vertically. Thc smaller Ophiu-
rans can be hardened in alcohol, and stained sections made for
studying the intricate relations of the water-vascular, heemal, and
nervous systems,
HABITS OF SHA URCHINS. 117

Ciass IIT.—EcurnorpEa (Sea-urchins).

General Characters of Sea-Urchins.—A good idea of
the general structure of the members of this class may
be obtained by an examination of the common sea-ur-
chin, Hchinus (Fig. 78), of the eastern coast of the United

 

Fig. 78.—The common Sea-urchin, Zchinus (Strongylocentrotus) drébachiensis.
d, frame-work of mouth and teeth seen in front; c, the same seen sideways; a, 6, side
and external view of a single tooth (pyramid); all natural size.—After Morse.

States, Northern Europe, and the Arctic Seas. It is com-
mon among rocks, ranging from low-water mark to fifty or
more fathoms. It eats sea-weeds, and is also a scavenger,
feeding on dead fish, etc. We have observed great num-
bers of them assembled in large groups, feeding on fish offal,
a few fathoms below the sur-
face, in a harbor on the coast
of Labrador, where fishing-
vessels were anchored.

On placing an Echinus in
sea-water the movements of
the animal, especially its
mode of drawing itself along
by its numerous long tenta-
cles or ambulacral feet, and
how it covers itself by draw-
ing together bits of sea- _ —y
weed and gravel, may be iif, ®couth apart ota tense
observed. ment of the muscles.—From Macallister.

A habit less easily detected is that of some sea-urchins
burrowing in limestone rocks and coral reefs until the ani-
mal sinks quite far down. How the rock becomes thus
worn away, unless simply by the rotary movements of the
body, is not clearly understood.

  
118 ZOOLOGY.

In order to examine the external anatomy, the shell
should be deprived of its spines in part, meanwhile obsery-
ing the mode of attachinent of the spines, of which micro-

a scopic sections
. should be made,
ee) The solid mouth-

parts, the oral
membrane sur-
rounding the five
sharp conical teeth
or ‘‘ pyramids,”
and their mode of
attachment to the
‘‘ auricles ’’ in the
shell, should be thoroughly investigated, as well as their re-
lations to the mouth-opening and the digestive canal. The
shell is a flattened sphere, consisting of ambulacral plates,
perforated for the exit of the
feet, and a broader series of
five rows of interambulacral
plates to which the spines
are attached, and of such
form and arrangement as to
give the greatest possible
strength and lightness to the
shell (Figs. 80, 81, 82). The
outlet of the alimentary canal
is situated on the aboral

 

Fig. 80.—Schematic figures of a S¢a-urchin. A, from
the oral end; B, from one side. Ambulacra indicated
by rows of dots. 7, ambulacral; iv, interambulacral
areas; 0, mouth; a, vent.—After Gegenbaur.

 

(abactinal) or upper end of
the shell, while the madre-
poric plate is situated upon
the top or end of the shell
(as the animal moves mouth
downward), being a modifica-
tion of one of the genital

Fig. 81.—Aboral end of the shell of an
Echinus, with the upper end of the rows of
pintes: a, ambulacral area; é, interambu-
acral area; g, genital plates; ig, intergeni-
tal plates; m, one of the genital plates
forming a madreporic plate; x, anal openi ng
in the aboral area surrounded My the genil
plates. The tubercles to which the spines
are attached are only drawn on one ambula-
cral and one interambulacral area ; on the
former are also drawn the pores through
which the suckers protrude.—After Gegen-

baur.

plates (Fig. 81, m). There are
five large plates, one at each end of the interambulacral
zones meeting on the aboral end of the body ; in them are
the ovarian openings through which the eggs escape ; these
ANATOMY OF SEHA-URCHINS. 119

five plates are called the genital plates, while in each of the

five smaller plates at the end of each ambulacral series is

 

Fig. 82.—View of the calcareous net-work
from a plate of the integument of a Sea-urchin
(Cidaris). 6, section perpendicular to the hori-
zontal net-work of straight rods.—After Gegen-

ur.

an
eye-speck. The pedicel-
larie are three-pronged,
knob-like spines,  scat-

_tered over the body, es-

pecially near the mouth.
They partly serve to re-
move the fecal matter,
but their main function
is not known,

Besides the pedicel-
layie, Lovén has discov-
ered on most living
Kchini, with the excep-
tion of Cidaris, small
button-like bodies called
spheridia, situated on a
short stalk, moving on a
slightly marked tubercle.
They are supposed to be

sensorial, probably organs of taste.
The internal anatomy of the sea-urchin may be best studied

 

Fig. 83.—Shell of a Sea-urchin (Strongylocentrotus lividus). a, anus; 0¢, cesophagus;
i, intestine; s, one of the rods of the tooth-apparatus, 7, muscles of the Jaws; p, ves-
sels of the sucking feet; po, extremity of the water-vessel; ca, ocular plate; v, ovary.

by cutting the shell into fwo halves, oral and aboral. Remoy-
ing the aboral end, the digestive canal may be seen in place.
120 ZOOLOGY.

It consists of a narrow cesophagus (Fig. 83, @), more or
less pentagonal near the mouth, dilating into the stomach ;
and of a terminal intestine. The long stomach passes from
left to right around the interior of the body, then turns up
toward the aboral end, and curves back in the opposite
course, again passing around the body from right to left,
forming two series of loops partly enclosing the ovaries ; it
is held in place by a broad, thin membrane or ‘‘ mesentery.”
The reproductive and other organs are much as described
in the star-fish, there being five ovaries or spermaries, the
sexes being distinct. The nervous ring around the mouth
sends off five nerves along the ambulacra, which are accom-
panied by a water-vascular canal sending branches to the
tentacles, and a pseudo-hemal canal, there being an oral and
aboral (anal) hemal ring (their presence is denied by Hoff-
mann), as well as an oral water-vascular ring, with five Polian
vesicles (present only in the true Echini and Clypeastroids),
a stone-canal and a fusiform tube or “‘ heart ’’* next to it,
while the alimentary canal is accompanied by two hemal
vessels, one on the ‘‘ dorsal?’ and the other on the free or
ventral side, communicating with a lacunar network in its
walls.

In Echinus it is difficult to perceive any bilateral sym-
metry, the parts radiating, as in the star-fish, from the cen-
tre; but in the Spatangus and allied forms it is easy to di-
vide the animal into a right and left side, and the body is
more or less elongated, asin Powrtalesia (Fig. 87), the mouth
being situated at one end and the anus at the other.

The mode of development of the common sea-urchin
(Fig. 78) has been discovered by Mr. A. Agassiz. The earli-
est stages are much as described in the star-fish. The form
of the pluteus larva is quite remarkable, there being eight
very long slender arms supported by slender calcareous rods
projecting from the body, and, during the movements of
the animal, opening and shutting like the rods of an um-
brella. The body is provided with a sinuous row of vibra-

* Tt should be observed that the latest and best observers are at vari-
ance regarding the structure and function of the so-called Echinoderm
“heart.’”
LUULOGICAL LABORATORY, McGRAW HALL

DEVELOPMENT OF THE SEA-URCHIN. 121

tile cilia. When the larva is twenty-three days old the ru-
diments of the five tentacles of the sea-urchin appear. By
this time the pluteus-form is acquired, and also at this pe-
riod the sea-urchin growing upon the deciduous pluteus
scaffolding has concealed the shape of the digestive cavity
of the larva, and the spines are so large as to conceal the
tentacles. The body of the pluteus is gradually absorbed
by the growing sea-urchin ; the spines and suckers of the
latter increasing in size and number with age, until by the
time the larval body has disappeared the young Echinus is
more like the adult than the star-fish at the same period in

mi
rh

Ati

 

Fig. 84.—Hemiaster Philippii, with the young in two of the marsupia.—From
Wyville-Thompson’s Voyage of the Challenger.
life. Grube has found that Anochanus sinensis, supposed
to have come from the Chinese or East Indian seas, has
no metamorphosis; while Hemiaster cavernosus of Chili
was found by Philippi to carry its young in marsupia and to
develop directly. ;

Several species of sea-urchins in the cooler portions of
the South Atlantic, especially at the Falkland Islands and
Kerguelen Island, also develop directly in marsupia or brood-
hollows, without passing through a metamorphosis. In Hemv-
122 ZOOLOGY.

aster Philippit Gray (Figs. 84 and 85), from the latter island,
certain of the ambulacral plates are greatly expanded and
depressed ‘‘ so as to form four deep, thin-walled oral cups,
sinking into and encroaching upon the cavity of the test,
and forming very efficient protective marsupia.’’ The
spines are so arranged that a kind of covered passage leads
from the ovarial opening into the marsupium, and along
this passage the eggs, which are very large (a millimetre in
diameter) are passed and arranged in rows, each egg being
kept in place by two or three spines bending over it. Here
the eggs develop, and the embryos, after the calcareous

 

Fig. 85.—Marsupium of Hemiaster Philippti, containing eggs. Much magnified.—
From Wyville-Thompson’s Voyage of the Challenger.

plates once begin to develop, rapidly assume the parent form ;
when they leave the marsupium they are about two and a
half millimetreslong. In Cidaris nutriz Wyville-Thompson
the eggs are protected in a sort of tent by certain spines
near the mouth. Here the young develop without a meta-
morphosis. The allies of these forms in the Northern At-
lantic are either known or supposed to be metabolous ; and
Sir Wyville-Thompson states that no free-swimming Kchi-
noderm larve (pluteus, etc.) were seen by the Challenger
Expedition in the Southern Ocean.
PRINCIPAL FORMS OF SHA-URCHINS. 123

Taking a rapid survey of the principal forms of sea-
urchins, we may divide the class of Echinoidea into two or-
ders: the Palechinida, or older sea-urchins, in which the
shell is composed of more than twenty rows of plates ; and
the Autechinida with twenty rows of plates. *

Order 1. Palechinida.—Comprises first the suborder Me-
lonitida, in which there are more than ten rows of ambula-
cral plates, represented by Melonites of the coal formation,
and Protechinus, Palechinus, Archeocidaris, etc. In the
second suborder Hocidaria, there are ten rows of ambulacral
plates. A type of the group, Hocidaris Kaiserlingti, appears
in the Permian formation.

Order 2. Autechinida.—
To this division belong sea-
urchins with twenty rows of
plates. The first suborder is
the Desmosticha, comprising
those sea-urchins with band-
like ambulacra extending
from the mouth to the oppo-
site extremity, and of more
or less regular, flattened,
spherical form. Such are ‘
Cidaris, Echinus, Be chinom- Fig. 86.—Echinarachnius parma, com-
etra, Clypeaster, and Echi- eee Natural size.—After A.
narechnius. The Hchinus
esculentus Linn., of the Mediterranean Sea, is as large as
an infant’s head, and is used as an article of food.

In Clypeaster the body is large and the shell very solid.
C. subdepressus Agassiz is common on the Floridan coast:
An orbicular flattened type are the sand-cakes, of which the
Echinarachnius parma Gray (Fig. 86) is abundant in the
shallower portions of the North Atlantic, from low-water
mark to forty fathoms. It is replaced southward from
Nantucket to Brazil by Mellita testudinata Klein.

The last suborder, Petalosticha, is characterized by the

 

* These are terms proposed by Haeckel, who regards these divisions
as subclasses, but we think they should more properly be called orders.
124 ZOOLOGY.

leaf-like ambulacra, and the irregularly heart-shaped, often
elongated, form of the shell, an anterior and posterior end
being well defined. They for the most part live buried in
the sand or sandy mud, not moving about so actively as the
Desmosticha.

Of the family Spatangide the singular genus Pourta-
lesia (Fig. 87%, P. Jeffreysii Wyville-Thompson) deserves
notice, the species of which are bottled-shaped, with a thin,
transparent shell. The transition from such a form as this
to the Holothurians is not a very extreme one. This
genus, A. Agassiz states, is the living representative of In-
fulaster of the Cretaceous period. P. miranda A. Agassiz
was dredged in the Florida Straits, in about three hundred

 

Fig. 87.—Pourtalesia Jeffreysii, slightly enlarged.—After Wyville-Thompson.

and fifty fathoms, and by British naturalists in the Shet-
land Channel. JP. Jeffreysii was dredged in six hundred
and forty fathoms, near the Shetland Islands.

Spatangus is distinctly heart-shaped, as is Hemiaster.
An interesting deep-sea or abyssal form not uncommon in
deep soft mud, at the depth of one hundred fathoms, off the
coast of Maine and Massachusetts, and extending from Flor-
ida around to Norway, is Schizaster fragilis Agassiz.

Echinoderms range to a great depth in the ocean, and are
largely characteristic of the abyssal fauna of the globe. In
space they are widely distributed, there being but two
Echinid faune on the eastern coast of the United States,
one arctic, the other tropical. While a large number of
species characterize the arctic or circumpolar regions, the
FOSSIL ECHINODERMS. 125

larger proportion of species are tropical and subtropical.
Mr. A. Agassiz divides the Echinid fauna of the world into
four realms: the American, Atlantic, Indo-Pacific, and
Australian.

Though Crinoids were the predominant type of Echino-
derms in the paleozoic rocks, a few star-fish and Ophiurans
appeared in the Upper Silurian period, and with them were
associated one species of sea-urchin, Palechinus, though
the genus was more numerously represented in the Coal
period. Some Paleozoic forms resembled the living gen-
era Calveria and Phormosoma, and belong to the extinct
Carboniferous genera Lepidechinus and Lepidesthes ; in all
these forms, fossil and recent, the interambulacral plates
overlapped one another so as to give a certain amount of
flexibility to the shell. This feature existed in a less de-
gree in Archeocidaris. The characteristic American car-
boniferous genera are Melonites, Oligoporus, and Lepidechi-
nus. The Permian Hocidaris is nearly allied to Archeoei-
daris, so that it is a true paleozoic type (Nicholson).

In the Mesozoic epoch (Trias, Lias, and Jura) appeared a
more modern assemblage of Spatangide, and genera such as
Hemicidaris and Hypodiadema, closely allied to the Cida-
ride proper, appeared in the Trias. The Jurassic beds are
characterized by genera allied to Diadema, Echinus, Ci-
daris, and a number of species of the families Cassidulide
and Galeritide. A large number of genera survived in the
Cretaceous period, which, however, is characterized by the
marked development of the Spatangide. In the Upper
Cretaceous the earliest Clypeastride appeared, while the
Tertiary Echinid fauna is quite similar to the present one.
The striking fact in the geological history of the class is
the persistence of many of the cretaceous genera in the
abyssal or deep-sea fauna of the present time (A. Agassiz).
126 ZOOLOGY.

Cuass ITI.—ECHINOIDEA.

Spherical, heart-shaped, or disk-like Echinoderms, with a solid shell of im-
movable plates, bearing interambulacral spines ; with a mouth and anal
opening, the mouth in most of the species armed with fine teeth; am-
bulacral feet well developed. The sexes distinct. Development either direct,
or, as in most cases, by a marked metamorphosis from a pluteus larva,

Order 1. Palechinida.—Shell composed of more than twenty rows of
plates. Suborder 1. Melonitida (Melonites, Protechinus,
Palechinus, Archeocidaris). Suborder 2. Hocidaria (Eoci-
daris).

Order 2. Autechinida.—Shell composed of twenty rows of plates.
Suborder 1. Desmosticha (Cidaris, Echinus, Strongylocen-
trotus, Echinometra, Clypeaster, and Echinarachnius).
Suborder 2. Petalosticha (Echinobrissus, Anochanus, Pour-
talesia, Spatangus, and Schizaster).

Laboratory Work.—We have already given some hints as to the
mode of dissecting sea-urchins, which should be done under water in
deep pans. Great care must be taken in removing the digestive canal,
which is very delicate in itself, and usually filled with sand. In study-
ing the water-vascular and blood-vessels, careful, skilful injections with
carmine are indispensable. The spines may be studied by making thin
longitudinal and transverse sections. The test, or shell, should be de-
nuded of the spines in order to study the relations of the ambulacral,
interambulacral, and genital plates.

Cuass IV.—HoLoTHuROIDEA (Sea-cucumbers).

General Characters of Holothurians._We now come to
Echinoderms in which the body is usually long, cylin-
drical, with a tendency to become worm-like, and in cer-
tain genera, as Synapta, Chirodota, and EHupyrgus, it is
difficult both in their larval stages (Synapta) and in the
external and internal anatomy of the adults to separate
them from worms like Sipunculus ; authors have therefore
been led to the adoption of one of two views : first, either
that the worms and Echinoderms have had a common origin,
and the latter, though truly radiate, have no near affinities
(though strong analogies) with the Coelenterates, or the re-
HABITS OF HOLOTHURIANS. 127

semblance between the two branches (Echinoderms and
worms) is one simply of analogy, and involves no blood-rela-
tionship. On the other hand the radiated arrangement of
parts and the development and relations of the water-vas-
cular system ally them, through the Ctenophores, with the
Actinozoa and Hydroida, and it seems more natural to re-
gard the Echinoderms as forming a branch of animals in-
termediate between the Hydroida and the worms, there
being certain low worms with a water-vascular system.

But the student will be better
able to appreciate these general
questions after a more or less
thorough acquaintance with the
forms and structure of the pres-
ent group. For this purpose he
should first examine living sea-
cucumbers, and then carefully
dissect them. A detailed study
of the anatomy of a Pentacta or a
Holothuria, one a northern the
other a subtropical and tropical
form, and of a Synapta, found
everywhere along our coast in sand
below tide-marks, will give the
groundwork ; and this knowledge,
autoptically acquired, can then be
corrected and extended by reading
monographs or compiled state-
ments to be found in the more
authoritative general works on 3
comparative anatomy. Ripe neniag ae joni

Living Holothurians can be pro- Fm Tenney’s Zoology.
cured with the dredge or dug out of the sand between tide-
marks. They should be kept in aquaria, and their move-
ments watched as well as their mode of locomotion, and the
action of their branchie or external gills (tentacles).

The common sea-cucumber, north of Cape Cod, and ex-
tending through the Arctic regions around to Great Britain,
is Pentacta frondosa Jaeger (Fig. 88). It lives from ex-

 
128 ZOOLOGY.

treme low-water mark to a depth of fifty fathoms. It is of
a tan-brown color, from six inches to nearly a foot in
length, and in its form and the corrugations of its tough,
leathery skin resembles a cucumber in nearly all respects
except color. There are five series of ambulacral feet, each
series consisting of two irregular rows. Around the mouth
is a circle of ten much-branched tentacles or gills (homolo-
gous with the ambulacral feet).

On laying the body open by making a cut extending from
the mouth to the vent, the thick muscular walls of the body
may be observed, and the general relations of the viscera to
the body-walls, which have nothing of the radiate arrange-
ment of parts, so clearly marked in the other Echinoderms,
the ambulacra, tentacles, and longitudinal muscles alone be-
ing arranged in a radiate manner.* Unlike other Echino-
derms, the madreporic body is internal, and there is a ca-
pacious cloaca or rectum, and a large vent.

On the inside of the body-walls are numerous small cir-
cular (transverse) muscles forming slight ridges, which serve
to contract the body, and five double large longitudinal
muscles (Fig. 89, 7) lying in the ambulacral zones. The
mouth is surrounded by a muscular ring, from which arise
ten large, much-branched tentacles. The pharynx, or the
portion corresponding to ‘‘ Aristotle’s lantern,”’ of the sea-
urchin is broad and short, with five large retractor muscles
(r) originating from the ambulacral or longitudinal muscles
on the anterior third of the body. The stomach is short,
not much wider than the intestines, with well-marked trans-
verse folds within. The intestine (¢) is several times longer
than the body, with longitudinal small folds, and held in
place by a large, broad mesentery which accompanies the in-
testine through the greater part of its length. The intes-
tine terminates suddenly, in a large cloaca (c), from which

* In Hupyrgus and Lchinocucumis it is difficult to perceive any radia-
tion in the body except in the unbroken circle of tentacles, while in
Sipunculus and allied worms (Gephyrea) the tentacles form a complete
circle, and these worms have a ring-canal and an imperfect or rudi-
mentary system of vessels thought by some authors to correspond to
the water-vascular system of Echinoderms.
ANATOMY OF HOLOTHURIANS. 129

on one side arises the “‘ respiratory tree,’’ which has but one
main stem, and is only occasionally held in place by mus-
cular threads. The branches are numerous, and are smaller

 

Fig. 89.—Pentacta frondosa. t, tentacles; 2, longitudinal muscles; 7, retractor mus-
cles of the tentacular system; 7, intestine; c, cloaca; 6, respiratory tree; v7, water-
vascular ring or mng-canal, v, radial water-vascular canal; m, madreporic body; pp,
polian vesicles; am, ampulls; @, a’, pseudo-hemal contractile vessels (from Carus);
0, Ovary; ov, oviduct.—Drawn by J.S. Kingsley from a dissection made by the author.

and paler than the ovarian tubes. The water enters the
cloaca (c), passes into the respiratory tree (0), oozes out of
130 ZOOLOGY.

the ends of the branches, filling the body, whence it is taken
up by the madreporic body and carried into the water-
vascular system by the spacious duct on the left side of the
pharynx. Besides being respiratory, this organ is supposed
to be depuratory in its function. In some Holothurians
certain organs (the Cuvierian organs), supposed by Semper
to be organs of defence, as they are readily thrown out when
the animal is disturbed, are attached either to the stem of
the respiratory tree or to the cloaca. The madreporic body
(m) forms a rosette, nearly surrounding the membrane at-
tached to one side of the pyloric end of the stomach, and
leads by the madreporic canal, which is closely bound down
to the pharynx, to the ring-canal (vr). Also connected
with the ring-canal are two enormous Polian vesicles (p, 7),
which are nearly two thirds as long as the body ; by slitting
up their base with scissors they can be followed to the ring-
canal. The latter (vr) is a capacious canal surrounding the
mouth, and can be detected by laying open the oral-opening,
and then by cutting across the longitudinal muscles (as at v)
the radial vessels may be followed along the body under the
muscles. Just above the ring-canal is situated the nervous
ring (nr), and its radial nerves (7) can be traced along and
outside of the radial water-vascular canals. The ampulle
(am) are red, conical, flask-shaped, conspicuous organs, lying
irregularly, a row on each side of each longitudinal muscle.
They are filled with water from supposed lateral vessels of
the radial water-vascular canals. The single ovary is com-
posed of a large mass of long tubes, which are larger than
and tangled up with the branches of the respiratory tree.
The oviduct is attached by a membrane to the stomach, and
vpens between two of the tentacles on the edge of the
mouth.

The blood or pseudo-hemal vessels * are difficult, without
very fine dissections, to be made out. The system consists
of a plexus of vessels lying next to the ring-canal, from
which two vessels (a, a’) pass along opposite sides of the in-

* These vessels in Fig. 89 have been copied from Carus’ Icones Zo-
otomice ; in other respects the drawing represents the anatomy of
P. frondosa.
ANATOMY OF HOLOTHURIANS. 131

testine. A fluid containing nucleated cells fills both the
pseudo-hzmal and water-vascular canals.

Holothuria floridana Pourtales is a large, dark-brown
sea-cucumber, with the feet scattered irregularly over the
body, and with smaller tentacles than in Pentacta, which is
abundant just below low-water mark on the Florida reefs,
and grows to about fifteen inches in length. The aliment-
ary canal is filled with foraminifera and pieces of shells,
corals, etc.; it is about three times the length of the hody,
and ends in a much larger coecum than that of Pentacta.
There are two widely separated branches of the “ respira-
tory tree,’’ one being free, and the other, tied to the body-
walls by thread-like muscular attachments, extends to the
pharynx. The pharynx is calcareous, while in Pentacta it
- is muscular. On the madreporic body is a group of about
thirty pyriform stalked bodies, the longest, including the
stalk, about a quarter of an inch in length. Succeeding
these bodies, and situated on the madreporic canal, leading
to the ring-canal, are a large number of Polian vesicles, the
largest one an inch in length. The duct passes spirally
nearly round the csophagus, and empties into the ring-
canal by the ducts nearly a quarter of an inch apart. In
connection with the tentacles or branchiz are twenty long,
slender tentacular ampulle, not present in Pentacta and
Thyone. The ovarian tubes are very small, some enlarging
and bilobate at the end.

Closely allied in external form to Holothuria floridana,
though belonging to a different family (including Pentacta),
is Thyone briareus (Lesueur), which lives just below tidal
marks, from Long Island Sound to Florida. In this genus
the ambulacral feet are not arranged in rows, but scattered
over the surface of the body. This species is very common,
and as it is more accessible to the student than any other of
the sea-cucumbers, we give some points in its anatomy as
compared with Pentacta, with which it is more closely allied
than to Holothuria. In a specimen about eight centi-
metres (three inches) long the intestine is over two metres
(about seven feet) long, the cesophagus opening into an
oval stomach less than an inch in length. The tentacles
132 ZOOLOGY.

are capable of being very deeply retracted, and as in
Pentacta there are no tentacular ampulle. The small
madreporic body is much as in Pentacta, and connects with
a duct (madreporic canal) leading to the ring-canal. There
are three Polian vesicles, one fusiform and an inch in
length, the two others slenderer. ‘The cloaca is of mod-
erate size, as in Pentacta, and the respiratory trees divide
at once into two very bushy branches. The ovarian tubes
form a brush or round broom-like mass or tuft, about an
inch long, the tubes small, yellow, and of nearly uniform
length, the oviduct straight and bound down to the walls
of the body.

We might here mention the most aberrant type of Holo-
thurians, the Rhopalodina described by Semper, who states
that the body is flask-shaped, with the mouth and vent situ-
ated near each other on the smaller end of the body. The
mouth is surrounded by ten tentacles, and there are ten
papille around the anus. There is a spacious cloaca or
respiratory tree. ‘‘'Ten ambulacra diverge from the centre
of the enlarged aboral end of the body, and extend like so
many meridians to near the commencement of the neck of
the flask. In correspondence with each ambulacrum isa
longitudinal muscular band ; and it is an especial peculiarity
of Rhopalodina that five of these are attached to the anal
circlet, and five to the circum-cesophageal circlet’’ (Huxley).

The earlier stages of development of Holothurians, so far
as known, is like that of star-fishes. The larvawhen fully
grown is called an auricularia. It is transparent, cylindri-
cal, annulated, with four or five bands of cilia, and usually
with certain ear-like projections, from which it derives the
name originally given to this larval form. Before the auri-
cularia is fully formed the young Holothurian begins to bud
out from near the side of the larval stomach, the calcareous,
cross-like spicules appear, and the tentacles arise. The ear-
like projections disappear, the auricularia thus becoming
cylindrical. Itissoon absorbed by the growing Holothurian,
which in some genera is strikingly worm-like, and it seems
that the Holothurian is more directly developed from the
larva than in the case of the star-fish and sea-urchins, the
METAMORPHOSIS OF HOLOTHURIANS. 133

metamorphosis being less marked—i.e., growth is more
continuous, as in the Crinoids.

In Holothuria tremula and Synaptula vivipara there has
been observed a very slight metamorphosis, the young de-
veloping directly in a marsupium, as in the star-fishes and
sea-urchins. Cladodactyla crocea Lesson, of the Falkland
Islands, according to Sir Wyville-Thompson, carries its
young in a sort of nursery, being “‘ closely packed in two con-
tinuous fringes adhering to the water-feet of the dorsal am-
bulacra.’’ He also found that in Psolus ephippifer Wyville-
Thompson, which is covered with calcareous plates, there is
a dorsal group of larger tessellated plates, each supported
by a broad pedicel embedded in the skin. Under these
mushroom-like plates brood-cavities or cloister-like spaces
are left between the supporting columns, and in this archi-
tectural marsupium the embryos directly develop into sea-
cucumbers. It follows that in all free-swimming Hchino-
derm larve, there is a true metamorphosis as distinct as in
the butterfly, while in other forms in which development is
direct the embryo is sedentary and lacks the cilia and vari-
ous appendages so characteristic of the ordinary larval
Echinoderms ; thus there are different stages in the differ-
ent classes of Echinoderms between direct development or
continuous growth, and a complete metamorphosis like that
of the star-fish or sea-urchin, in which the pluteus or larva
is but a temporary scaffolding, as it were, for the building
up of the bedy of the adult.

Turning now to the classification of the Holothurians,
and beginning with the lowest, simplest, most generalized
forms (which are also remarkably worm-like), and ascend-
ing to higher or more complicated forms, we find that there
are two orders, those without feet (Apoda) and those with
ambulacral feet (Pedata).*

*It is possible that the Holothurians shouid he divided into two sub-
classes, one Diplostomidea Semper, in which the body is spherical and
the mouth and anus are close together, with ten ambulacral rows, etc.,
and the normal, cylindrical, bipolar Holothurians. Semper’s Diplostomi-
dea is based on Rhopalodina lageniformis Gray, from the Congo Coast,
and regarded hy Semper as the type of a fifth class of Echinoderms.
134

Order 1.

ZOOLOGY.

Apoda.—The simplest apodous form is the

Eupyrgus scaber Litken, in which the body shows no
external signs of longitudinal muscles, though there are
five small ones, and is covered with spine-like, soft papille

 

Fig. 90.—Chi-
rodotaleve. Half
natural size. a,
mouth, closed.

The next
Molpadide,

bearing calcareous plates. We have dredged it
frequently on the coast of Labrador in shoal-
water. It has a circle of fifteen unbranched
tentacles, and is about one centimetre long.
It also occurs in Greenland and Norwegian
waters. Myriotrochus has a transparent skin
dotted with minute white spots, which, when
magnified, appear to be wheel-like, calcareous
plates. It has a single Polian vesicle, and there
is no respiratory tree nor Cuvierian appendages
(Huxley). We have dredged this beautiful
form (M. Rinkii Steenstrup) in sand, in shoal-
water, on the coast of Labrador. A very com-
mon Labrador Holothurian is Chirodota leve
Grube (Fig. 90). It lives in shallow, sandy,
retired bays, and is whitish-gray, with five dis-
tinct muscular bands and scattered white spots,
which are calcareous, wheel-like bodies situated
in the skin.

Near Synapta, is Leptosynapta Girardii
(Verrill), our common east coast species, which
lives in sand at low tide. The body is very
long, and the animal when disturbed constricts
its body and breaks up into several pieces. The
skin contains perforated plates and anchor-like
bodies (Fig. 91). In this genus and those pre-
viously mentioned, constituting the suborder
Apneumona and family Synaptide, the sexes
are united in the same individual, and there
is no respiratory tree, while the tentacles are
simply digitated or lobulated.
suborder, Pnewmophora, forming the family
is characterized by having a respiratory tree.

In Caudina the skin is rough with calcareous pieces, the
DISTRIBUTION OF HOLOTHURIANS. 135

body ends in a long, tail-like prolongation; C. arenata
Stimpson has fifteen four-pronged tentacles; it is com-
monly thrown up on the beaches
of Massachusetts Bay. A deep-
water form, a member of the
abyssal fauna, is Molpadia tur-
gida Verrill, which we have
dredged in over one hundred
fathoms in the Gulf of Maine,
and which ranges southward to Fig. 91.— Hooks and plates of
gridacs It has head-end like ‘7@s’Gerarai—Atter Veutl-
the neck of a bottle, and the end of the body suddenly con-
tracts into a tail, with a very small anus. There are fifteen
tentacles.

Order 2. Pedata, or Holothurians with feet. The mem-
bers of the first family (Dendrochirote) have tree-like,
branching tentacles, retractor muscles, without Cuvierian
organs. It is represented by Thyone and Pentacta, while
here belong also Lophothuria Fabricit Diiben and Koren,
Psolus phantapus and P. sguamatus, in which the body is
armed with heavy calcareous plates, and the feet are confined
to a ventral creeping disk.

In the highest family, Aspidochirote, there are tentacular
ampulle ; the left respiratory tree is bound to the body-
walls, and there is a single ovary, while Cuvierian organs
are present. Holothuria is the type of the group. H. edulis
Lesson, of the Moluccas and Australia, and H. tremula
forms, when dried, the trepang sold in Chinese markets.
Our H. floridana has been dried and exported to China as
an article of food.

In their geographical distribution the Apoda are mostly
boreal and arctic. Of the Pedata, the Dendrochirote are
mostly northern or arctic, while the highest group, Aspi-
dochirote, are mainly tropical. Certain genera (Holothuria,
Thyone, Psolus, Pentacta, Chirodota, and Synapta) are almost
cosmopolitan.

A few forms attain a great depth, and certain abyssal
forms are often highly colored. One species, Synapta

 
136 ZOOLOGY.

similis, lives in brackish water, according to Claus. Sup-
posed plates of Holothurians have been found in the
Jurassic rocks.

Cuiass IV.—HOLOTHUROIDEA.

Worm-like, cylindrical Echinoderms, with a muscular body-wall usually
containing calcarecus bodies ; with a circle of branched tentacles, a terminal
opening of the intestine, madreporic plate internal, and usually a res-
piratory cecal appendage. Unisexual or bisexual, developing by a metamor-
phosis from cylindrical, auriculated, free-swimming larve; or ametabolous,
Order 1. Apoda.—No ambulacral feet. Family 1. Synaptide (Eupyrgus,

Chirodota, Synapta). Family 2. Molpadide (Caudina, Mol-
padia).

Order 2. Pedata.—Respiratory tree present, and the ambulacral feet.
Bisexual. Family 1. Dendrochirote (Thyone, Psolus, Echi-
nocucumis, Pentacta). Family 2. Aspidochirote (Stichopus,
Holothuria, Aspidochir).

TABULAR VIEW OF THE CLASSES AND ORDERS OF ECHINODERMATA,

Pedata.
(Holothuria.)

 

 

 

Apoda.
(Chirodota.)
Autechinida,
Se eninge)
HOoLOTHUROIDEA. Palechinida.
(Melonites.)
———S
ECHINOIDEA.

Asteridea.

(Asterias.)

Ophiuridea.
(Ophiura.)
Brachiata.
U——+-—_Y (Encrinus.)
ASTEROIDEA.
Cystidea.
(Spheeronites.)
Blastoidea.
(Pentremites.)
{e+ ~~
CRINOIDEA.
b |

 

ECHINODERMATA.
DISSECTION OF HOLOTHURIANS. 137

Laboratory Work.—The Holothurians are easily dissected by cutting
the body open longitudinally, and pinning the specimen down in a
dissecting-pan, with wax on the bottom for holding the pins. The
calcareous plates can be extracted from the body-walls by being placed
in a solution of potash and mounted in balsam as microscopic objects.

 

Encrinus or Stone Lily.
CHAPTER V.
BRANCH V.—VERMES (Worus).

General Characters of Worms.—Having studied the
one-celled animals, or Protozoans, and the radiated animals,
or Celenterates and Echinoderms, we pass to an assemblage
of forms which even in the simplest types are seen to have a
dorsal and ventral, a right and left side, and a head and tail
end. It israre that the form of a worm is so modified by its
habits or surroundings but that we are able to call it a worm,
though when we attempt to draw up a definition of the
branch or sub-kingdom Vermes, one which shall exclude the
worm-like Holothurians or the Mollusks, or certain low mites
and crustacea, or even the Amphioxus, we find it impossible
to lay down a set of characters which shall accurately and
concisely define them. This is due to the fact that the worms
are par excellence a generalized, synthetic type, from which
the other branches of the animal kingdom above the Protozoa
and sponges have probably originated. It will be well for
the student not to trouble himself at first about a definition
of the branch, but to study with care the leading types, and
then, in a review of the group, he will have a more or less
definite idea of the sub-kingdom, and perceive where its bor-
ders, here and there, merge into other branches, and he will
be then able to understand the grounds for the speculations
regarding the phylogeny or ancestry of the other branches,
which have all an apparent starting-point from low or simple
forms resembling such worms as we are next to describe.

As a provisional definition of a typical worm, we may say
that it is a many-celled, three-germ-layered, bilateral animal,
with a well-marked dorsal and ventral side and a head and
tail end, with the body in the higher forms divided at reg-
DICYEMA, 139

ular intervals into segments (somites or arthromeres), with
usually a definite relation of the more important viscera to
the body-walls—i.e., a digestive tract extending from the
head to the end of the body, the nervous system consisting
of a brain, or suprawsophageal ganglion, and a single or,
more commonly, double chain of ganglia, resting on the
floor of the body ; a dorsal vessel or heart is usually present
being situated above the digestive tract. True jointed
appendages are never present, and in the embryo the
blastoderm is usually without any “‘ primitive streak ’’ (the
Annulata excepted). This definition will exclude the worm-
like Actinozoa and Holothurians.

Before describing the lowest class of worms, we may call
attention to a small aberrant group called Mesozoa by H.
Van Beneden, the position ‘of which is doubtful, though the
animals composing it are probably aberrant worms.

In 1830 Krohn observed in the liquid bathing the ‘‘ spongy
bodies,’? or venous appendages, of different species of
Cephalopods certain filiform bodies, covered with vibratile
cilia, and resembling Jnfusoria. They were afterward named
Dicyema by Kolliker, who with others considered them as
intestinal worms. In 1876 Professor E. Van Beneden gave
a full account of their structure and mode of development.
He states that these organisms have no general body-cavity,
but that the body consists (1) of a large cylindrical or fusi-
form axial cell, which extends from the anterior extremity
of the body, which is slightly enlarged into a head, to the
posterior end; (2) of a single layer of flat cells forming
around the axial cell a sort of simple pavement epithe-
lium. All these cells are placed in juxtaposition like
the constituent elements of a vegetable tissue. There is
no trace of a homogeneous layer, of connective tissue, of
muscular fibre, of nervous elements, nor of intercellular
substance. There is only between the cells a homoge-
neous substance, such as is found between epithelial
cells. The axial cell is regarded as homologous with the
endoderm of the higher animals (Metazoa). Van Beneden
designates as the ectodermic layer the cells surrounding the
large, single axial cell. There exists no trace of a middle
140 ZOOLOGY.

layer of cells, nor of any organs, all the animal and vegeta.
tive functions being accomplished by the activity of the
ectodermic cells and of the single axial cell. There is no
mesodermic cell or cells. On account of these characteris-
tics, Van Beneden
regards these or-
ganisms as forming
the type of a new
branch of the ani-
mal kingdom,
which he distin-
guishes as Mesozoa.
He places the
branch, or sub-
kingdom, between
the Protozoa and
all the many-celled
animals (Metazoa),
. and includes the
ON hypothetical Gas-
Y treades of Haeckel
in the branch.
‘N While this position
OY may prove to be
the correct one, we
should prefer, while
not overlooking the
resemblance of the
Dicyemide to the
Infusoria, and even

 

Fig. 92.—a, Dicyemella Wagneri ; g, g, germigenes; 7, 5
nucleus of the axial cell ; , the sine neal eerie Dicye- the Gregarinz, to
mella, with its striated nucleus ; c, the same beginning a a
to undergo self-division ; d, final stages of self-division wait for more light
(morula); e and /, infusoriform embryo; i, germs of
the vermiform embryos of Dicyema typus ; i, gastrula ON the development

of the same; &, /, m, 0, different stages of vermiform rasiti
larvee of Dicyema typus, all highly magnified.After E. Of the parasitic

cares Platyhelminth
worms. It is not improbable, on the one hand, that the
Dicyemide, retaining their parasitic life, are retrograde
forms, which have originated from some low Cestoid or
Nematoid worm, and bear the same relation to them, the
FLAT-WORMS. 141

Cestoids especially, which have no body-cavity, as the Tar-
digrades or Linguatule do to the higher Arachnida.

Each species of Dicyema and Dicyemella (Fig. 92) com-
prises two sorts of individuals, differing externally, one (the
Nematogene) producing vermiform embryos, the other
(Rhombogene) infusoriform (but many-celled) young. The
Nematogenes produce germs which undergo total segmen-
tation, and assume a gastrula condition. After the closure
of the primitive opening, the body elongates, and the worm-
like form of the adult is finally attained, when it passes
through the body-walls of the parent.

The germs of the Rhombogenes arise endogenously in
special cells lodged in the axial cell, and called ‘ germi-
genes.”’ The germ-like cells undergo segmentation, and
then form small spheres, which become infusoriform em-
bryos. The worm-like young is destined to be developed
and live in the Cephalopod where it has been born, whilo
the infusorian-lke young probably performs the office of
disseminating the species. It is possible that in those ani-
mals, such as the Cetacea, which feed on cuttlefishes, these
worms (the Nematogenes at least) may pass into a genuine
vermian form.

Cuass J,—PLATYHELMINTHES (fVat-worms, Tape-worms,
Fluke-worms, etc.)

Order 1. Turbellaria.—In any pond of standing water
one can find on the under side of sticks or stones, small
dark flat worms. These are Planarian
worms. The common dark-brown,
almost black Planaria torva Miller
(Fig. 93) is about six or eight milli-
metres long, oblong, flat, with two

  

black eye-spots, with an oblong oval Fe. 93. . ig. 04
cae fe . ANATUA ENA TOCOLUNY
space in front of each eye. A form “ira. Dae

allied to this is a perfectly white Plana- oe
rian called Dendrocelum lacteum Oersted, which lives under
142 ZOOLOGY.

submerged stones, sticks, and leaves in ponds. The body
is partly transparent, with a dark area representing the
stomach, from which branch out at right angles a multi-
tude of ccecal canals (gastric cceca). It has two small
black eye-specks. Closely allied to this flat worm is an eye-
less form inhabiting the streams of the Mammoth and ad-
joining caves, which may be called Dendrocelum percecum
(Fig. 94).

The foregoing forms are easily obtained by the student,

who can study their habits in confinement. They all be-
‘long to the order Turbdellaria, which is characterized by the
flat, oval body, covered with cilia. The ciliary motion can
be detected, as Moseley has done, by placing a little arrow-
root meal or fine bits of paper on the back of the animal ;
these were seen to move in a forward direction on the an-
terior part of the body of Geoplana flava Moseley, a Bra-
zilian lund-planarian, and posteriorly they moved backward.

‘* Tn all regions of the dorsal surface it moved outward,
as was observed by Fritz Miller, at the same time as back-
ward or forward, and was thus rapidly thrown off at the
side of the body, the dorsal cilia apparently subserving
especially this function of the speedy removal of foreign
substances from the surface of the body ’’ (Moseley). The
structure of the flat worms may be understood by referring
to Fig. 95, which illustrates the anatomy of a common
European marine flat-worm. The digestive canal opens by
a mouth situated usually behind the middle of the body,
which leads into a chamber containing a cylindrical or
funnel-shaped proboscis, capable of being suddenly thrust
out. The digestive canal is either a short blind sac, or is
long, forked, and either simple or much branched (Fig.
95, e).

These worms have a so-called water-vascular system, con-
sisting of two lateral canals and numerous branching lat-
eral stems, with a common opening or pore in the skin be-
tween the two main stems, or there may be many pores.
The vessels are ciliated within, and are supposed to have a
respiratory or excretory function. The nervous system con-
sists of a single ganglion situated on the front end of the
PLANARIAN WORMS. 148

body (Fig. 95, 7), from which nerves pass in different
directions, but a true nerve-cord is not known with cer-
tainty to exist.* The eyes are very simple, indicated by
two or more, sometimes
thirty, dark pigment spots.
In certain forms, such as
Macrostomum, there is a ru-
dimentary ear (otocyst).
Most of the Planarians,
jand and aquatic, have organs
of defence in the form of
minute, stiff rods, either
coiled up in an irregularly
spiral manner, or short and
straight, contained in oval
cells. These bodies are shot
out in great numbers when
the animals are irritated, but
are not retractile, being pro-
jected clear from the skin.
In being neither retractile
nor barbed, they differ from
the lasso-cells of the jelly-
fishes. That, however, they
are true urticating organs
has been proved by Mr. _
Thwaites (at the suggestion 2, bisca cart) ee ee reel Grice til
of Mr. Moseley), who, on stomach ; é, branches of the stomach ; /,

ganglia ; g, testes 5 he pericule ceminales S
= sl z, male genital-canal; %, oviducts; J,
touching certain Ceylonese sperm-sac ; m, opening into the oviduct.
land-planarians with his —After Quatrefages.

tongue, felt an unpleasant tingling or scalding sensation,

accompanied by a slight swelling.

 

* Schmarda describes the nervous system of Bipalium dendrophilus
as formed of two pairs of ganglia, from the hinder of which arise two par-
allel nerve-threads, which dilate into at least nine swellings. Moseley
discovered no more than one pair of ganglia in the species of Bipalium
he examined. Blanchard has demonstrated ‘‘successive ganglionic
repetitions along the nervous-threads at the right and left sides of the
mid-line of the body of a large Planarian (Polycladus Gayt Blanch.).’’—
Clark’s ‘‘ Mind in Nature,’’ p. 258.
144 ZOOLOGY.

The Turbellaria are hermaphroditic, the ovaries and testes
with the accessory apparatus (Fig. 95) being present in the
same individual.

Little is known of the development of the flat-worms.
In a common marine Planarian, Stylochus elliptica (Girard),
which is about two centimetres long, and lives under stones
between tide-marks, north of Cape Cod, the eggs are depos-
ited in May and June, in a thin, viscid band, on stones and
sea-weeds. The eggs undergo total segmentation in four or
five days after they are laid. The larva is round, ciliated,
with a caudal flagellum. In eight or ten days after the
larva has hatched, it stops swimming about, and becomes a
‘“mummy-like body,’’ which Girard calls a ‘“‘ chrysalis.”’
In this state it floats about in the water. Its further his-
tory is unknown.

In Leptoplana (Polycelis), according to Keferstein, the
yolk undergoes total segmentation as in Stylochus; the
outer layer of cells forms a blastoderm which surrounds the
more slowly growing cells within. Keferstein describes
and figures the various stages by which the spherical cili-
ated embryo attains the form of the adult, whose devel-
opment seems to be less in the nature of a metamorphosis
than that of Stylochus.

The Planarians also in some species mul-
tiply by fission, and when cut into pieces,
according to H. J. Clark, each piece may
eventually become a well-formed Planarian.
Clark figures in his ‘‘ Mind in Nature’’ two
Planarians derived from two sections of
Dendrocelum lacteum, which became fully
developed within eleven days after the opera-
tion. Several Turbellarians are known to
undergo spontaneous fission.

Catenula lemne Duges, by transverse di-
vision, forms chain-like aggregations, and

 

: Fig. $8 Catens : f
a quaterna under-

Me eae avin, & South African species, C. quaterna, 0
—After Schmarda. Schmarda, has been found by him to have the
same habit. Fig. 96 represents two individuals (much

enlarged) in partial division, and a chain of four individ-
LAND PLANARIANS. 145

uals, natural size. The same process of strobilation has
been carefully observed by Graff in Microstomum lineare
Oersted. In the chain of four individuals (Fig. 97) I indi-
cates the division of the first order, and II those of the
second order ; at the points in the zooids marked III there
are indications of a future third subdivision, and at IV of
a fourth; so that potentially the chain con-
sists of sixteen zooids, and the division is
first indicated in the digestive tract which .
forms subdivisions with septa reaching to
the body-walls, while secondary and tertiary
mouth-germs appear in the division-sections
(m’, m”, Fig. 97).

Huxley in his Manual of the Anatomy of
Invertebrated Animals states that in some
genera of Turbellarian worms “‘a difference
is observed between the eggs produced in
summer, which have a soft vitelline mem-
brane, and those produced later. These so-
called winter ova have hard shells.

The genuine flat-worms are divided into
two suborders: Rhabdocela and Dendrocela.
In the former group there is an extensible
pharynx, and the digestive tract is not
branched. ‘The Rhabdocela are represented
by Catenula, Prostomum, Microstomum, etc.

The Dendrocela sometimes have two tenta-
cle-like continuations of the front end of the
body. The digestive canal has one anterior, two
posterior large, and many secondary branches, _ wig. 97.—strobi-
and a proboscis. Here belong the Planarians Sica RAGS
of fresh and salt water, and the Geoplanide ee Maree
or land-planarians, represented in the United
States by Rhyncodesmus sylvaticus Leidy. The only para-
sitic species of the order known are Stimpson’s Cryptoce-
lum opacum, which infests the sand-cake (Echinarachnius
parma), and Typhlocolax acuminata, which lives on a Holo-
thurian (Chirodota) ; while Semper has described Anoplo-
dium Schneideri, which lives in the intestines of Stichopus

 
146 ZOOLOGY.

variegatum and Miilleria lecanora, two East Indian Holo-
thurians.

The Planarian worms merit careful consideration, as it is
possible that the Mollusca have originated from primitive
forms resembling them.

Order 2. Trematodes.—Having studied the Planarians,
we shall be able to appreciate the characteristics of the Tre-
matode worms, which are all parasitic, and are constructed
on the dendrocelous planarian type, more or less modified
by their parasitic life, some being external, but most of
them internal parasites. They closely agree with the Tur-
bellaria in form, never being segmented. The mouth-open-
ing is usually situated near the fore-end of the body (some-
times in the centre), leading by a muscular pharynx to the
digestive canal, which is forked and endsin two ceca. Uni-
cellular glands open into the pharynx. In one genus (Am-
philina) there is no digestive canal.

The Trematodes usually possess what the Turbellarians
do not have, a sucking-disk (Fig. 98, B, s), situated a little
behind the middle of the body, by which they adhere to the
walls of the organ of the host they inhabit. The so-called
water-vascular* or excretory system forms a network of
vessels branching from two main lateral tubes, which unite
to form a contractile vesicle ending in a terminal pore, or
the main branches may end in two or more lateral pores.

The fact that there is no anal opening seems to confirm
the idea that the water-vascular system is excretory, thus
affording the only outlet for the waste products of diges-
tion. ‘There are no blood-vessels or respiratory organs, and
the surface of the body is not ciliated except in the embryo.
The nervous system is usually represented by a single gan-
glion, like that of the Turbellarians. Hye-spots are some-
times present in the young, which, with other points in their
organization, tends to show that the Trematodes have origi-
nated from Turbellaria, haying been modified by their para-

* That the so-called water-vascular system is mainly at least excretory
in its function seems proved by the fact that the fluid is watery and
contains granular concretions, thus resembling the urinary excretions
of the higher animals.
STRUCTURE OF FLURE-WORMS. 147

sitic life, and with somewhat the same relations to Turbella-
rians as Lernzan parasites have tothe normal Copepoda, or
water-fleas.

There is always one sucker which usually encircles the
mouth, the other (ventral) sucker varies in position, and
sometimes there is, as in the externally parasitic Polysto-
mide (Aspidogaster, Polystomum, etc.), a sucker on each
side of the mouth-opening. In some forms there are two
large chitinous hooks in the median line between the hinder
suckers, of which there may be several.

The reproductive glands are more or less complicated, and
are much as in the Turbellarians. The eggs are formed (as
in Cestodes, Turbellarians, and Rotifers) by two distinct
glands, a germigene and a vitellogene, the latter forming the
nutritive mass which envelops the protoplasmic germ or egg
proper, the entire mass being afterward enveloped by the
egg-shell. Frequently two or more eggs are enclosed in
one shell. The species are mostly monecious, the external
opening of the oviduct and the large intromittant organ
being contiguous.

The development of the egg begins by subdivision of the
nucleus ; the nucleolus then divides, and subsequently the
protoplasmic mass. The yolk, however, remains entirely
independent of this division, and serves as nourishment for
the other cells forming the body of the embryo. From E.
Van Beneden’s observations it appears that the eggs of the
lower flukes, as a rule, undergo total segmentation, and the
young of the Distomew are hatched in an oval ciliated
‘‘trochosphere ’’? form, without eye-specks, as in Distoma
and Amphistoma ; or, asin the Polystomee, there is no meta-
morphosis, but development is direct, the embryo passing
directly into the adult condition.

It was not known before the publication of Steenstrup’s
work in 1842 that certain worms called Cercarie were the
free larval forms of the Distomes. The Cercaria echinata,
first described by Siebold, is like a Distomum, except that
the body is prolonged into a long extensible tail. This tail,
says Steenstrup, is formed of several membranes or tubes
placed one within the other, of which the outermost is a
148 ZOOLOGY.

very transparent epidermis, under which is a tolerably thick
membrane furnished with transverse muscular fibres, while
between each pair of these transverse fibres is placed a globu-
lar vesicle which appears to be a mucous follicle or gland ;
the innermost tube is opaque and of firmer consistence ; it
contains the longitudinal muscular fibres, and is usually re-
ticulated on the surface. Through the centre of these tubes
there passes a slightly narrower canal, which becomes very
small toward the extremity of the tail. The existence of
the same layers in the body itself of the Cercaria can easily
be demonstrated ; but the transversely striated layer is here
not so much developed.

Steenstrup states that these Echinate Cercarie (Fig. 98)

DO A

u

   

Fig. 98.—Metamorphosis of a Cercaria intoa Distomum. A, parent nurse ; ¢, germs;
a, nurse. B, larva. €, encysted, pupal Cercaria, D, adult Distomum.—After
Steenstrup.

are found by thousands, and frequently by millions, in the
water in which two of the largest European fresh-water
snails, Planorbis cornea and Limneus stagnalis, have been
kept. After swimming about in the water some time, they
fix themselves by means of their suckers (B, s) to the slimy
skin of the snails, in such numbers that the latter look as if
covered with bits of wool.

The Cercaria, by contractions of its body and violent lash-
ing of the tail, forces its way into the body of its host, loses
its tail, and then resembles a mature Distoma. By turning
LIFE HISTORY OF FLUKE-WORMS. 149

about in its place and secreting a slime, a cyst is gradually
formed, with aspherical shell. This constitutes the ‘ pupa”?
state of the Cercaria. Steenstrup thinks that the Cercaria
casts athin skin. In this state the body can be seen through
the shell of the cyst, as in Fig. 98, O, where the circle of
spines embedded around the mouth is seen. The encysted
Cercari# remain in this state from July and August until
the following spring; and during the winter months, in
snails kept in warm rooms, they change into Distomas (Fig.
98, D), the mature fluke differing, however, in some im-
portant respects from the tailless larve. In nature they
remain from two to nine months in the encysted state.

** Now,’’ asks Steenstrup, ‘‘ whence come the Cercariz ?’’
Bojanus states that he saw this species swarming out from the
‘*king’s yellow worms,’’ which are about two lines long and
occur in great numbers in the interior of snails. From these
are developed the larval Distomes, and Steenstrup calls them
the ‘‘ nurses ’’ of the Cercarie and Distomes. They exactly
resemble the ‘‘ parent-nurses’’ (Fig. 98, A, and 100), and,
like them, the cavity of the body is filled with young, which
develop from egg-like balls of cells. Steenstrup was forced
to conclude that these nurses originated from the first nurses
(Fig. 98), which he therefore calls ‘‘ parent-nurses.’’ Here
the direct observations of Steenstrup
on the Cercaria echinata came to an
end, but he believed that the parent-
nurses came from eggs. The link in
the cycle of generations he supplied
from the observations of Siebold,
who saw a Cercaria-like young (Fig.
99, B) expelled from the body of the
ciliated larva of Monostomum muta-
bile. Steenstrup remarks that “‘ the 3
first form of this embryo is not un- Fig. 99—Development of
like that of the common ciliated pro- oncsionuun. Sfort a, nurses
geny of the Trematoda, as they have B, pee Biche
been known to us in many species for a long time, and it
might at first sight be taken for one of the polygastric in-
fusoria of Ehrenberg, which also move by cilia; whilst in

 
150 ZOOLOGY.

the next form which it assumes the young Monostomum
bears an undeniable resemblance to those animals which
I have termed ‘ nurses’ and ‘ parent-nurses’ in that species
of the Trematoda which is developed from the Cercaria echi-
nata.”’

Thus the cycle is completed, and the following summary
of changes undergone by the Distomes present as clear a
case of an alternation of generations as seen
in the jelly-fishes :

1. Egg.

2. Morula.

.3., Ciliated larva.

4, Redia (parent-nurse, Proscolex) produc-

5. Cercaria (nurse, Scolex).
6. Encysted Cercaria (Proglottis).
7. Distomum (Proglottis).
The Distomum echinata (Fig. 100), living
in snails which are eaten by ducks, have been
shown by St. George to develop into the adult
Distoma in the body of that bird. It is gen-
erally the case that those Distomes which pass
through an alternation of generations live in
the larval state in animals which serve as food
for higher orders. Thus the Bucephalus of
the European oyster passes in the encysted
state into a fish which serves as food for a
i larger fish, Belone vulgaris, in whose intes-
Fig. 100.—Pro- |. :
scolex or parent- tine the adult of the same worm, a species
rae OC eet of Gasterostomum, occurs. The American
raed with cerca oyster is infested by Bucephalus cuculus Mar
vaisand Beneden. crady, It infests the ovary of the oyster.
Whether it is permanently injurious to the latter is un-
known.

Fasciola hepaticum (Fig. 101), the liver-fluke, sometimes
occurring in man, is thought by Dr. Willemoes-Suhm to
begin its existence as Cercaria cystophora, parasitic on a
species of Planorbis.

It is most abundant in sheep in the spring, several hundred

 
HABITS OF FLUKE-WORMB. 151

occurring in the liver of asingle sheep. At this time it passes
into the intestine, and thence is carried out with the excre-
ment. The eggs or flukes in many cases drop
into pools, ditches, or ponds ; here the cili-
ated young (like Fig. 99) is liberated, and
soon the ciliz are absorbed, when it becomes
inert, and probably soon afterward enters
the body of a snail (Planorbis, etc.), where
it transforms into a large sac, and devel-
ops new larve in its interior. This sac-
like larva is called a ‘“‘ nurse,’’ ‘‘ sporo-
cyst,’’ or, when more highly developed, a
“‘redia.”’ The progeny of the redia is
termed a ‘‘cercaria.”? The cercarie are
restless, migrating from the bodies of their
snail-host, and have been known in a few
instances to penetrate the skin of human
beings. They are probably more usually

 

 

7 5 Fig. 101. — Fasciola
swallowed by sheep and cattle while drink- nepatica, enlarged. «,
: : : branched _intestine.—
ing or grazing, when snail-shells may be prom Gervais and Van

accidentally swallowed. From the diges- B°"°¢™

tive canal of sheep, etc., the cercaria penetrates into the
liver, where it probably loses its tail and becomes encysted,
after many weeks or even months becoming a sexually ma-
ture distome. From the liver it passes out through the
liver-ducts into the intestine, and is finally expelled, thus
completing its cycle of life (Cobbold).

Distomum lanceolatum Mehlis differs from Fasciola he-
patica in the intestine being simple and forked, while that
of the latter is much branched. It has occurred but three
times in man, but is not rare in the sheep and ox. It has
been detected in Europe in the pig, deer, rabbit, and hare.
Two immature Distomes have been found in the human
eye, and Cobbold thinks they may both be the young of
D. lanceolatum. It is described by Diesing under the name
of Distomum ophthalmobium, is half a line in length, and
occurred between the lens and its capsule, appearing as dark
spots on the surface of the lens. Distomwm crasswm Busk
and D. heterophyes Siebold haye each been only once
152 ZOOLOGY.

found in man, the former in a Lascar, the latter in an
Egyptian boy.

Bilharzia hematobia Cobbold is common in the portal
system of blood-vessels and in the veins of the mesentery,
bladder, etc., of Egyptians, and has caused an endemic dis-
ease at the Cape of Good Hope. In Egypt, out of three
hundred and sixty-three post-mortem examinations, this
worm occurred one hundred and seventeen times. It ig
bisexual, the female greatly smaller than the male, living in
a canal or passage in the male formed by the infolding of
the edges of the concave side of the body, called a gyneco-
phore. There are three other rare human flukes known:
Tetrastoma renale Delle Chiaje, Hexathyridium pinguicola
Treutler, and H. venarum Treutler, the latter occurring in
the veins (Cobbold).

The nurse of Distomuwm macrostomum Rudolphi (Fig.
102), described under the name of Leucochloridium, is
cylindrical, and strongly resembles a maggot; its strange
habitat is the tentacles of a snail (Swccinea).

Of the second suborder, Polystomee, the species have two
small anterior and one or several posterior suckers, and a
pair of eyes. They are
mostly external parasites,
like the leeches, and un-
dergo no metamorphosis.
In some forms the body
is segmented.

A type of this suborder
is <Aspidogaster concht-

 

Fig. 102.—1. Leucochloridium paradoxum, : : :
living in the tentacles of Succinea; @ Atul, cold Baer, which inhabits
grown nurse-Leucochloridium with the nurse- : : :
stock from which it has grown. Natural size. the pericardial cavity of

—After Zeller,
fresh-water mussels, and

also is an ectoparasite of fresh-water fishes. Déplozoon
consists of two Trematodes very intimately united into an
X-formed double animal. In the young stages the two ani-
mals are separate, and in this state were described under the
name of Diporpa. Diplozoon paradoxum Nordmann lives on
the gills of numerous fresh-water fishes. Polystomum has
a flat body, without suckers on the fore end, with six suck-
STRUCTURE OF TAPE-WORMS. 153

ers and two large median ventral hooks on the hinder end.
The ripe eggs are deposited in the water in winter, when
the ciliated young, with four eyes and without suckers, find
their way into the gill-cavities of tadpoles, whence, during
or after metamorphosis, they pass into the urinary bladder
of young frogs; P. integerrimum Rudolphi lives in that
of Rana temporaria (Claus’ Zoologie).

A case of budding or parthenogenesis is said to occur in
the genus (yrodactylus. This is a very small Trematode
with a large terminal disk, bearing a peripheral set of pow-
erful hooks, with two long curved median spines. The
body of the hermaphrodite worm shelters a daughter, a
granddaughter, and great-granddaughter generation. G. ele-
gans Nordmann lives on the gills of Cyprinoid and other
fresh-water fishes. Dactylogyrus lays eggs, not being par-
thenogenetic ; it has four head-flaps. D. amphibothrium
Wagener lives on the gills of the stone-perch ; D. fallax
Wagener on Cyprinus rutilus.

Order 3. Cestodes.—The common tape-worm is the type
of this order. ‘Specimens may be procured from physicians,
and a careful examination of cross-sections and ordinary
dissections will convince the student that the tape-worm has
no mouth, although a head armed with suckers or hooks.
The body is divided into an enormous number of segments
or proglottids, but there is no digestive canal, the worm
living immersed in the contents of the intestines of its host ;
its food being absorbed from the juices of its host through
the walls of the body.

The tape-worms and their allies are not known with cer-
tainty to have any trace of a nervous system. The water-
vascular system is well developed in the Cestodes, where it
seems to be excretory in its functions, as in the Trematodes.
There are usually four, sometimes only two, longitudinal
canals, which are connected in the head and in each segment
with transverse anastomosing branches, while from these main
canals a network of fine vessels branch out. Granules and
whitish chalky deposits occur in the canals, and these con-
cretions, like similar bodies in the excretory canals of Tre-
matodes, seem to have, Leuckart claims, a relation like that
154 ZOOLOGY.

of the crystals of oxalate of lime in the urinary tubes of
many insects and the concretions of phosphate of lime in
the organ of Bojanus of Lamellibranch mollusks.* The
canals terminate in a small pulsating vesicle and pore, as in
the Trematodes.

The Cestodes are hermaphroditic, and each of the body-
segments except those nearest the head contains male and
female reproductive organs. ‘The male parts consist, as in
the Trematodes, of testes, vasa deferentia, and a muscular
sac with a cirrus or intromittent organ, which may penetrate
the vagina of the same segment. The female organs consist
of an ovary (germigene), yolk-stock (vitellogene), uterus or
matrix, receptaculum seminis, and vagina, the latter opening
by a pore situated in Tenia (Fig. 107) on the side, or in
Bothriocephalus on the ventral surface of the segment.
There is a great deal of variation in the reproductive organs
of the tape-worms; a general idea of the relations of parts
may be obtained by reference to Figs. 107 and 109. The
ovary forms the most important part. It is much devel-
oped and very complicated in structure. As Gegenbaur
‘states : ‘‘ The preservation of the species is here subject to
innumerable difficulties, owing to the animal living in dif-
ferent hosts at different stages of development, and to the
wanderings which this mode of life entails ; consequently a
large number of ova have to be produced, and the cer-
tainty of fecundation insured.’? (Elements of Comparative
Anatomy, second edition, English translation.) The
male organs and products are first developed, and the
receptaculum seminis stored with spermatic cells before the
eggs fully develop in the ovary, and all these parts develop
earliest in the terminal segments of the body destined to
form the proglottides.

Development begins very probably, as in the Trematodes,

* This is Leuckart’s opinion. Sommer and Landois claim that these
bodies are scattered through the substance of the body, and do not
occur in water-vessels. Huxley endorses this view. But if these bodies
are concretions and the water-vessels are mainly excretory, as they cer-
tainly appear to be, we should judge that Leuckart’s view was the bet-
ter grounded.
DEVELOPMENT OF TAPE-WORMS.

155

through multiplication by division of the nucleus (germi-
native cell), In the eggs of Tenia bacillaris E. Van Beneden

END

UOT

io)

 

 

 

i a i i i — lottis of
Fig. 103.—Tenia solium. Nat. size, Fig. 104. Head and prog
with the head maguified. Strobila stage. T. solium.—After Beneden.
—After Beneden.

saw the nucleus subdivide ; after passing through a morula

condition the cells are arranged in two layers, and the outer
156 ZOOLOGY.

layer is thrown off (this probably corresponding to the serous
membrane of insects and crustacea); the central mass
(which is not hollow as in the gastrula of other worms, a
digestive cavity not being present in after life) forms the
embryo, and soon three pairs of hooks arise. ‘Three struc-
tureless membranes are secreted around the embryo, which
then hatches. The embryo of Bothriocephalus is provided
with a ciliated membrane, which corresponds to the first
blastodermic moult of the embryo Tenia, which, on the
other hand, is not ciliated.

The history of the human tape-worm, Tenia solium (Fig.
103) is as follows: the eggs eaten by the hog are developed
in its body into the larval tapeworm (scolex), called in this
species Cysticercus cellulose (Fig. 105; Fig. 106, head en-
larged). The head with its suckers is formed, and the
body becomes flask-shaped ; the Cysticerci then bury them-
selves in the liver or the flesh of, pork, and are transferred
living in uncooked pork to the alimentary canal of man.
The body now elongates and new joints arise behind the head
until the form of the tapeworm is attained, as in Fig. 103.

The hinder joints then become filled with eggs and break
off, becoming independent zooids comparable with the
‘* parent-nurses ”’ of the Cercarias, except that they are not
contained in the body of the Tzenia (as in the Cercaria), but
are set free. The independent joint (Figs. 104, 107) is
called a ‘‘ proglottis.’’? It escapes from the alimentary tract
of its human host, and the eggs set free, in and about
privies, are swallowed by that unclean animal, the pig, and
the cycle of generations begins anew. We thus have the
following series of changes, which may be compared with
the homologous series in the flukes :

1. Egg.

2. Morula.

3. Double-walled sac (gastrula ?).

4. Proscolex, free embryo with hooks, surrounded by a
blastodermic skin.

5. Scolex.(Cysticercus, larva). Body few-jointed.

6. Strobila (Tenia). Body many-jointed.

7. Proglottis (adult),
INJURIES CAUSED BY TAPE-WORMS. 157

The common human tape-worm, Tenia solium Linn.,
varies from ten to thirty feet in length ; there are upward
of eight hundred joints in a worm ten feet long. The head
ends in a rostellum or proboscis armed with a double crown
of hooks ; the first proglottis or sexually mature segment
begins at the 450th. While in some persons the presence
of a tape-worm is simply an annoyance, in nervous and irri-
table persons it causes restlessness, undue anxiety, and vari-
ous dyspeptic symptoms. In rare cases (over a hundred are
known) death has resulted from the presence of the Cysticer-

 

Fig. 105.—Cystt-
neu. or larval
Tape-worm.

 

Fig. 106.—Head of Tenia acanthotrias (Cysticercus)
enlarged, showing the suckers (S) and circle of hooks.

cus in the brain. ‘‘ Oysticerci may develop themselves in
almost any situation in the human body, but they occur
most frequently in the subcutaneous, areolar, and intermus-
cular connective tissue ; next, most commonly in the brain
and eye ; and, lastly, in the substance of the heart and other
viscera of the trunk ’’ (Cobbold). Among the preventive rem-
edies against tape-worms is the disuse of raw or underdone
pork, and ‘‘ measly’’ pork—.e., the flesh of swine contain-
ing the little bladder-like vesicles. Cysticerci, or larval tape-
worms, can be readily distinguished, but when thoroughly
cooked are harmless, as the temperature of boiling water is
158 ZOOLOGY.

sufficient to kill the Cysticerci. Butchers especially suffer
from tape-worms, from their habit of eating bits of raw
meat, beef and veal harboring Cysticerci, which transform
into species of Tenia nearly as injurious as Tenia solium.
As a matter of course, in the use of drugs to expel a tape-
worm, they should be pushed so as to carry off the entire
animal, as new segments grow out from near the head as
rapidly as the proglottides are detached.

The Cysticercus of another injurious tape-worm lives in
the muscles and internal organs of cattle. This is the Tenia
mediocanellata of Kichen-
meister, which is larger,
with a larger darker head,
larger suckers, and with-
out a rostrellum or hooks.
By far the most injurious
species is Tenia echinococ-
cus Siebold (Fig. 108),
more frequently causing
death than any other en-
tozoon. In its adult or
strobila state this worm
only infests the dog and
wolf, but its larva, the
hydatid of physicians, fre-
quently occurs in the hu-
man body. It is very
small, seldom exceeding
six millimetres in length,
there being but four
segments, including the
», Fig, 107—Proglottis of 7. soliuma, a, testis : head, which has a pointed
yer duct ¢ ori, of cirrus. mat yostellum, with a double
sero crown of  large-rooted
hooks ; there are four suckers present, and the last segment,
when sexually mature, is as long as the anterior ones taken
together. The hydatid (proscolex) forms large proliferous
vesicles, in which the scolices (Echinococcus heads) are de-
veloped by budding internally. About five thousand eggs

 
HYDATIDS. 159

are developed in a single segment (proglottis). The six-
hooked embryos develop, are expelled from the dog, and
find their way in drinking-water or in food into the human
intestines, whence they bore into the liver, their favorite
habitat, or are carried along the blood-vessels into some
other organ, where they develop into bladder-like bodies
called acephalocysts or hydatids. In its
earliest stages the hydatid is spherical and
surrounded by a capsule of condensed con-
nective tissue of its host. By the fourth
week the young 7. echinococcus is one half
a millimetre (one-fiftieth inch) in length, ,
and it is probably many months before the |
Echinococci heads are entirely developed.
When this stage is reached the tape-worms
become sexually mature in from seven to
nine weeks after, when the milk-white
worms may usually be found embedded in
the mucus of the duodenum and upper
part of the small intestines, with their
heads attached to the villous surface of
the intestine. The hydatids or cysts in
which the Echinococci develop are of
three kinds—viz., exogenous, endogenous,
and multilocular, and lie embedded in the
parenchym of the liver, etc., and are filled
with a clear amber-colored fluid. The
Echinococcus heads, first on the inner sur-
face of the cyst and in the interior of the
Echinococcus-head (brood-capsule), devel-
ops a second brood of scolices, contained =, i
bs = : ‘ig. 108. — Tenia
in a secondary cyst. Finally, a tertiary gchingcoccus. — After
cyst, containing tertiary or granddaughter ““""""""

scolices, arises. Sometimes the secondary hydatids will de-
velop scolices and granddaughter vesicles before the original
maternal hydatid has acquired Echinococcus heads (Cob-

bold).
The largest human tape-worm is Bothriocephalus latus

Bremser (Fig. 109).

 
160 ZOOLOGY.

This worm is extremely rare in America, but is common in
Western Switzerland and Central Europe, and in the north-
western and northern provinces of Russia, Sweden, and
Poland. It is sometimes twenty-five feet long, and nearly
an inch broad, with 4000 joints. The club-shaped head is
unarmed, and the first sexually mature segment is about

 

 

Fig. 109.—Male reproductive organs, with parts of the female of Bothriocephalus
latus. t, testicular follicles, only a part are represented ; ve, their excretory ducts;
vd, vas deferens ; ¢, cirrus ; cb, sac containing the cirrus ; w, uterus containing eggs;
ov, ovary ; gi, shell-gland ; ¢, water-vascular trunks ; v, vaginal canal.—-After Landois
and Sommer ; from Gegenbaur.
the 600th from the head. lLeuckart has suggested that
the young of this tape-worm originate in salmon and
trout.

The sheep-hydatid is the larva of Tenia cenurus (Figs.
110 and 111), the adult infesting the dog. The presence of
one or several of the hydatids in the brain of the sheep pro-
duces the ‘‘ staggers ’’ or vertigo. The vesicle varies in size
from a pea to a pigeon’s egg. It is bladder-like, filled with
a clear pale yellow albuminous secretion, with a great num-
ber of retractile papillae (D, g), which are the tape-worm heads
connected by narrow stalks to the common vesicles support-
HYDATIDS OF THE SHEEP. 161

ing the colony. This hydatid also infests cattle, the horse,
goat, various species of antelope and deer, the dromedary,
and, it is said, the rabbit. ‘‘ In the sheep the disease is rec-
ognized at first by a heavy, stupid, wandering gait, which

 

Fig. 110.—A, brain of a sheep which three weeks previous had swallowed some eggs
of 7’. cenurus, and which was killed after having shown all the symptoms of ‘‘stag-
ers.’ Bb, isolated gallery formed by the worm at the surface of the brain, the sco-
ex being found at the end of the gallery. Be, vesicle (proscolex) before the birth of
the scolex. Bd, vesicle in which the scolices will appear. (, vesicles which have
produced some scolices. D, the hydatid vesicle containing gg, the secondary vesicles.
£, scolex of 7’. cenurus, corresponding to a secondary vesicle D g, and very much
magnified and invaginated. a, point at which the head of the worm will issue out ;
6. point of junction with the hydatid vesicle ; c, hooks ; d, the suckers ; e, the neck ;
J, the wall of the hydatid cyst.—After Beneden.

is frequently succeeded by irregular, tortuous, whirling
movements of the body, accompanied with convulsions (Cob-
bold).

The simplest form in the order is Caryophylleus, in
which the body is not jointed in the adult, though it is so
162 ZOOLOGY.

in the young, and there are no suckers or hooks; while
there is but a single set of male and female reproductive
organs situated in the posterior end of the body, which can
be detached from the ante-
‘Yy rior part of the body, form-
J ] y e ing a proglottis. In fact,
ae this form is a connecting
oe 6 link between the Zrematoda
Fig. 111.—Head of 7. cenurus seen from and Cestodes. Caryophyllaus
above, with circle of hooks ; a—e, hooks; »yutabilis ‘Rudolphi lives in

all much enlarged.—After Siebold. i i is "
the intestines of Cyprinoid

fishes ; the young in a worm, Tubifex rivulorum.

Tetraryhnchus is provided with four very long slender
extensile spiny cephalic processes or beaks. The young live
encysted in bony fishes, the adults occurring in the intestines
of sharks and rays.

In Ligula the body is ribbon-shaped, not jointed, with a
series of sexual organs, and there are no suckers, and some-
times no hooks. JL. simplicissima Rud. lives in fishes and
amphibians, and attain maturity in the intestines of water-
birds, which feed on the former animals. This genus con-
nects the simpler tape-worms with Bothriocephalus and
Tenia.

 

Cuass .—PLATYHELMINTHES.

More or less flattened worms, with the body usually unsegmented ; the
head in the Cestodes often armed with hooks or suckers. A much-branched
(Turbellaria) or forked (Trematoda) digestive tract, but no general body-
cavity. (The digestive cavity ts entirely wanting in the Cestodes.) Nervous
system represented by a cephalic ganglion, which in the Cestodes is absent. A
system of vessels corresponding to the water-vascular system of Echinoderms,
but supposed to be mainly excretory in function. Monecious, rarely bi-
sexual. Ovaries differentiated into a germigene and vitellogene , often par-
thenogenetic, accompanied by strobilation in the tape-worms. When alter-
nation of generations occurs by budding, the sexual animals are united with
their nurse or a sexual form into a polymorphic colony.

Order 1, Turbellaria.—Flattened ovate worms, with a nervous gan-
glion in the head ; usually eye-specks ; body externally cili-
ated, with a much-branched digestive canal. Nettling
organs often present. Unisexual, rarely bisexual ; strobi-
THREAD-WORMS. 163

lation very rare ; a metamorphosis in the Dendrocela, the
larva being a trochosphere. Suborder 1. Rhabdocela (Mo-
nocelis, Catenula, Mesostomum). Suborder 2. Dendrocela
(Planaria, Dendrocelum, Geoplana, and Bipalium).

Order 2. Trematoda.—Usually flat, oval, rarely cylindrical, not seg-
mented, parasitic worms, with a mouth, forked intestine,
no anus ; a large sucker near the middle of the body, or
several smaller ones ; either with a metamorphosis (Dis-
tomez), the larva living in mollusks, etc., the adult in ver-
tebrates ; or with direct development (Polystomee). Sub-
order 1. Distomee (Monostomum, Amphilina, Distornum,
Amphistomum). Suborder 2. Polystomee (Aspidogaster,
Diplozoon, Polystomum, Gyrodactylus).

Order 3. Cestodes.—Parasitic, usually ribbon-like worms, without any
mouth, digestive canal, or nervous system ; with an (ex-
cretory) water-vascular system ; hermaphrodite, the joints
(proglottis) numerous and containing male and female re-
productive organs ; the eggs minute and very numerous.
The mature worm is many-jointed, the joints budding out
from near the head; in this form it is called a strobdila ,;
the terminal joints fall off, becoming independent (proglottis).
The eggs after fertilization pass through a morula and
gastrula stage, a circle of hooks and suckers developing on
the head (Caryophylleus, Tetrarhynchus, Ligula, Both-
riocephalus, Tzenia).

Laboratory Work.—The flat worms have been most successfully
studied by fine injections, especially by slicing hardened sections,
which should be stained with carmine, and mounted for the micro-
scope.

Crass II.—NeEMATELMINTHES (Round, Thread-worms).

General Characters of Thread-worms.—These worms are
either free or parasitic; examples of the former exist in
abundance under stones, etc., between tide-marks, lying
in coils; small, almost minute species occurring 1n fresh
water and in damp earth, while the parasitic species, which
are the most numerous, live free in the alimentary canal or
imbedded in the flesh of their hosts, especially fishes and
mammals, The species are remarkably persistent in form,
164 ZOOLOGY.

the specific and generic differences being very slight. They
have a mouth and digestive canal (except in Echinorhynchus),
the integument being hard, chitinous, and not segmented
(except in Desmoscolez, which approaches in this respect the
annelids), and usually smooth, except in Hehinoderes, which
is variously armed with hair-like spines. Each end of the
body is much alike, the mouth situated at the anterior end,
and the anal opening at or near the conical tip of the body.
There are two long vessels which extend from a single com-
mon pore situated on the median line of the under side of the
body, a short distance from the head ; these are supposed to
be excretory vessels. In Ascaris and Oxyuris a nervous ring
surrounds the esophagus, from which two nervous threads,
one dorsal the other ventral, pass to the end of the body, and
there are six other smaller longitudinal nerves. The gangli-
onic cells lie near the nervous ring, forming a subcesopha-
geal, supracesophageal and lateral ganglion, and there is also
a caudal ganglion. In some free-living Nematodes there are
eye-specks.

The Nematodes are usually bisexual; Pelodytes is her-
maphroditic, while the same individual of Ascaris nigrovenosa
at first produces sperm-cells and afterwards eggs. The males
differ from the females in their smaller size and the usually
curved end of the body. While most of thesc worms lay
eggs, some, as in Trichina spiralis, bring forth their young
alive.

The mode of development of these true Nematode worms
(Echinorhynchus excepted) so far as known is quite uniform,
growth being direct, without any metamorphosis. The
germ is formed in three ways: (1) usually the egg under-
goes total segmentation ; (2) others, as in Ascaris dentata
and Oxyuris ambigua, do not show any apparent trace of seg-
mentation, while (3) in Cucullanus elegans there is no yolk,
the nucleus absorbing all the vitelline matter, which is lim-
pid and transparent. The germ consists of a single series or
circle of cells bent on itself, somewhat as in Fig. 120, which
represents a little more advanced stage in Sagitta, and there
are a few cells representing the endoderm. The embryo
rapidly assumes the adult form before hatching.
THE BCHINORYNCHUS. 165

Order 1. Acanthocephali.—These are aberrant Nematode
worms (sometimes referred to a separate class), without any
mouth or digestive tract, but with an extensible spiny beak,
living by imbibition of the fluids of the alimentary canal of
their host.

The thick subcuticula is penetrated by a network of ves-
sels, whose trunks form two oval bodies of unknown use
called lemnisci, which hang down free in the body-cavity.
The sexes of Echinorhynchus are distinct. The eggs are
usually spindle-shaped. The embryo develops in the body
of the parent worm, and is surrounded by several membranes,
with a circle of hooks arranged bilaterally around the mouth.
The embryo contains an oval mass of nuclei, being the ru-

 

Fig. 112.—Echinorynchus, head retracted and in the second figure extruded ; mag-
nified. @, oval pore ; 50, protractile muscles ; ¢ c, lemnisci.—After Owen.
diments of an intestinal canal. Finally it passes into
some crustacean or insect, in whose body it becomes so far
developed, that when its host is swallowed by some vertebrate,
such as a fish, the embryo is liberated in the intestines of the
second (vertebrate) host and soon attains sexual maturity.
Nearly a hundred species are known.

Echinorhynchus gigas, the female of which is 50% centime-
tres (20 inches) in length, lives in the small intestine of the
pig. Its eggs pass out, becoming scattered on the ground,
where they are eaten by the white grub or larva of the Euro-

_pean cockchafer. The egg-membranes burst in the stomach
of the grub, and the embryos thus liberated penctrate, by
166 ZOOLOGY.

means of their spines, through the intestine into the body-
cavity of the larva, where they become encysted, and the latter
being in the beetle state devoured by the pig, finish their de-
velopment in the intestines of the latter animal. (Schneider. )
The embryos of this species also occur in the land-snails, and
those of £. claviceps have been found in fresh-water snails
(Limnea). Young Echinorhynchi occurring in the copepod
crustacean, Cyclops, become mature in a fish (Gadus lota).
Leuckart has also found that a sexless form living ina fresh-
water crustacean, Gammarus pulex, becomes developed to
sexual maturity in the perch, which feeds on the crustacean.
They attain the mature form, thongh the eggs are not ripe,
in eight or ten weeks after the eggs from which they hatch are
laid, and look lke round or oval yellowish balls from one to
one and a half millimetres in length. ‘The males mature in
about a week after the females.

The primary host of Lchinorhynchus angustatus is the
fresh-water sow-bug (Asellus). After the eggs find their
way into the intestines of the Asellus, the embryos, on hatch-
ing, pass through the walls of the hinder part of the chyle-
stomach of the Asellus into the body-cavity, by means of
the embryonal, deciduous neck apparatus; and, as in Z£,
proteus, the embryos lie between the chitinous walls of the
intestine and the muscular layer. The embryos are round-
ed, more or less spindle-shaped, with aso-called rudimentary
digestive cavity indicated by a central circle of cells, the
cells of the body-walls being situated in a parenchymatous or
protoplasmic mass (plasmodium), being thus comparable to
the blastoderm of some insects. The embryo is 0.09-0.1
millimetres long. The form of the body now becomes irreg-
ularly oval or cylindrical, being quite protean in shape, with
often a projection on one side of the end of the body. The
Echinorhynchus form then begins to appear, the metamor-
phosis being very marked. The first step is the moulting of
the embryo or larva, which loses its spines. After a few
weeks the Echinorhynchus form is attained, the body being
elongated, and with the reproductive organs developed, but
with no hook-apparatus. It is now 7 to 8 millimetres in
length, and almost as long as its host, the Asellus ; the males
 

THREAD-WORMS. 164

being smaller and shorter than the females. With the ex-
ception of the skin and lemnisci, all the parts of the adult
worm, the nervous and reproductive systems as well as the

beak, originate in the primitive
rudimentary digestive cavity,
appearing as rounded masses of
cells of like size, but differing in
structure histologically. With
the growth of the beak begins
the development of the repro-
ductive apparatus, and the hooks
are simply modified cells, with
the outer surface chitinized.

Order 2. Nematodes.—The first
suborder of this group, compos-
ing the true round worms, is re-
presented by Ascaris, Oxyuris,
Trichina, ete. The human
round worm, Ascaris lumbri-
coides Linn. (Fig. 113), is re-
markable for its large size, and
may be recognized by its milk-
white color, as well as by the
three papille around the mouth.
It inhabits the intestines, some-
times the stomach and csopha-
gus, and has been known to per-
forate the walls of the intestine.
The species of Ascaris are very
numerous, infesting mammals,
and especially fish, often occur-
ring encysted in the flesh of the
cod and other edible salt and
fresh water fish, but are as a
rule harmless. Ascaris mystax
lives in the intestines of the
cat.

 

Fig. 113.—Ascaris lumbricoides. a,
female, natural size. 6, head-end en-
larged; c, the same, front view show-
ing the mouth in the centre, sur-
rounded by three folds; d, the male,
natural size; é, the end of the body,
greatly enlarged.—After Beneden.

The common pin-worm lives in the rectum of children.
It is the Oxywris vermicularis Linn. (Figs. 114, 115). The
168 ZOOLOG ¥.

female is white and from eight to ten millimetres in length;
the male is only two or three millimetres long.

The largest known round worm is the palisade worm, or
ELustrongylus gigas Rudolphi, the female of which is a

  
 

Fig. 114.— 0x-
yuris vermicula-
vis. a, Male, nat-
ural size ; 0, the
same enlarged. —
After Beneden.

Fig. 116.— Tvichocephalus dis-
par, a, male, natural size ; 2,
enlarged; c, female, natural
size.--After Bencden.

Fig. 115.— Oxyuris
vermicularis. a, fe-
male, natural size; 0,
the same enlarged.--
After Beneden.

metre (about 39 inches) in length, and the size of a quill;
the male is one third as long. It is rare in man, and occurs
especially in the intestines, and sometimes the kidneys of
such mammals as live on fish. The mouth is surrounded
THE TRICHINA. 169

by six tubercles. Hustrongylus papillosus Diesing, accord-
ing to Wyman, lives coiled up in the brain of the anhinga,
or snake-bird of Florida. 2. dbuteonis Packard was found
living under the eyes of Buteo Swainsoni, and E. chordeilis
Packard in the brain of the night-hawk. Dochmius duoden-
alis Dubini lives in the small intestine of man.

Trichocephalus dispar Rudolphi (Fig. 116) lives in the
cacum of man, with the smaller anterior part of the body
buried in the mucous membrane.

The most formidable round worm is the Trichina spiralis
Owen (Fig. 117). The body is regularly
cylindrical, tapering gradually from the =
posterior end to the head. The end of the
body of the male is without a spiculum, but
with two conical terminal tubercles. It is
1.5 millimetres long. The female is 3 mil-
limetres in length.

Viviparous females begin about eight days
after entering the intestine of their host to
give birth to the larve, which bore through
the walls of the intestines of their host,
passing into the body-cavity, and partly in- y
to the connective tissue, and also, by means E2={beS
of the circulation, into the muscles. In oS
about fourteen days the worm coils up
spirally in a cyst (Fig. 117), which eventu- Per ee.
ally becomes calcareous and whitish. When encysted ‘im human
the flesh of the pig, infested by the encysted Mei’ Aite: Peuck-
larva, is eaten by man, the young worms ** ;
are set free in the stomach of their new host, and in three
or four days become sexually mature. The female Trichina
is capable of producing a thousand young. The original
host of the Trichina is the rat; dead rats are often de-
voured by pigs, and the use of raw or partially cooked pork
as food is the means of infection in man.

Another worm, occasionally parasitic in sailors and resi-
dents of the East Indies, is the Filaria medinensis Gmelin,
or Guinea-worm. It is remarkably long and slender, some-
times over two feet in length. The female is viviparous,

(i

 

 

 

 

 

 

 
170 ZOOLOGY.

while the male is unknown. The worm lives in the con-
nective tissue under the skin, especially of the extremities.
As the body of the female is full of young, the worm has to
be carefully and slowly extricated, so as not to be broken and
cause the embryos to be scattered under the skin of the host.
Carter regards a small worm ( Urolabes palustris) frequent in
brackish water, as the immature form of the Guinea-worm.
It is also believed that the embryos enter the bodies of water-
fleas (Cyclops, etc.), and there moult, and that consequently
they may be introduced into the body by drinking standing
water ; but this has not been proved. Other species live in the
peritoneum of the horse and apes, and an immauture species
(Filaria lentis) has been found in the lens of the human
eye. Filaria sanguinis-hominis is a worm of microscopic
size found living in the blood of the mosquito in India and
China. It is said that the eggs are swallowed in the water
drunk by man, are hatched in his intestines, and obstruct
the smaller blood-vessels, causing, it is claimed, various
forms of elephantoid disease, perhaps even leprosy. The
mosquito sucks up the parasite in the blood of leprous pa-
tients, voiding the eggs in the pools it frequents. Filaria
hematica has occurred in the blood of the foetus of a dog
whose heart was filled with them. Grains of wheat are
often infested by a minute Nematode (Tylenchus scandens
Schneider, Anguil-
lula tritici of Need-
ham, Fig. 118).
Other species live in
flowers, moist earth,
and sour decaying
substances. Anguil-
lula acett Ehren-
berg is from one to
two millimetres in
length, and lives in

 

Fig. 118.—Young Wheat-Worm, greatly magnified. _- 7
g, eectlon of a grain foe Sane aires and multi: Vluegar.
tudes of eggs, magnified ; 6, an egg containing a worm Y S
ready to hatch.—From Curtis, ater Bauer. — The genus Cheeto

soma lives free in
the sea, and has a broad swollen head beset with fine hairs.
It apparently connects the true Nematodes with Sagitta.
THE HAIR-WORMS. 171

The second suborder, Gordiacea or hair-worms, differ in
their mode of development from the true Nematode worms,
the embryo of Gordius being armed with oval spines, thus

 

Fig. 119.—Gordivs aquaticus. A, egg; B, egg undergoing segmentation of the
yolk; C, embryo (gastrula) with the primitive stomach, an infold of the outer ger-
mina} layer of cells (ectoderm); D. embryo farther advanced ; E, Jurva, with the
three circles of spines retracted within the a@sophagus; F, the same stage greatly
enlarged to show the internal organs; c, middle circle of spines, the head being
retracted ; 72, muscular layet (?) ; z beak or proboscis; é, intestine ; z, z, embryona
cells; 7, excretory tube leading from q, the secretory glands; @, esophagus ; Dv, TeC-
tum; 7, anus. . the second larva, encysted in a fish—(after Villot), H, Gordius
varius, end of body of male, much enlarged. I, Gordius aguaticus, end of body
of male, much enlarged. K, Gordius aquaticus, natural size.—(H, I, K, drawn from
nature by J. S. Kingsley.)

reminding us in this respect of Hehinorhynchi, but the em-
bryos, larvyee and adult have a well-developed alimentary
canal.
172 ZOOLOGY.

The hair-worms belong to the genera Mermis and Gordius.
In the former genus the head is beset with papille, and the
end of the body of the male is undivided, while the oviduct
of the female opens in the middle of the body. The larva
is unarmed and has no metamorphosis. Mermis acuminata
Leidy is pale brown and parasitic in the body of the cater-
pillar of the coddling moth ; another species lives in the
bodies of grasshoppers.

The true hair-worm, Gordius, has no papille on the head,
and the tail of the male is forked, while the oviduct of the
female opens at the end of the body. The following account
of the development of the common Gordius aquaticus Lion,
which is a parasite of the locust and other insects, and is
common to Europe and this country, is taken from Villot’s
“Monographie des Dragonneaux.”

The eggs (Fig. 119, A) are laid in long chains; they are
white, and excessively numerous. The yolk undergoes total
segmentation (Fig. 119, B). At the close of this period,
when the yolk is surrounded by a layer of cells, the germ
elongates at what is destined to be the head-end ; this layer
pushes in, forming a cavity, and in this stage it is called a
‘“‘oastrula” (C). By this time the embryo becomes pear-
shaped (D); then it elongates. Subsequently the internal
organs of digestion are formed, together with three sets of
stiff, spine-like appendages to the head, while the body is
divided by cross-lines into segments. The head lies retracted
within the body (£).

In hatching, it pierces the egg membrane by the aid of its
cephalic armature, and escapes into the water, where it passes
the early part of its life. Fig.119, /, represents the embryo of
Gordius aquaticus greatly magnified. It will be seen how
greatly it differs from the adult hair-worm, having in this
stage some resemblance to the Acanthocephalus by its cephalic
armature, to the Nematoidea or thread-worms by its alimen-
tary canal, and in the nature of its secretory glands to the
larvee (cercaria) of the Trematodes or fluke-worms. But the
hair-worm differs from all these worms and even Mermis, @
hair-worm much like and easily confounded with Gordius,
in having a complete metamorphosis after leaving the egg.
DEVELOPMENT OF HAIR-WORMS. 173

When in this stage it incessantly protrudes and retracts
its armed head, the spines being directed backward when the
head is out.

In the first period of larval life the worm lives encysted
in the bodies of aquatic fly larve. The vessel in which
M. Villot put his Gordius eggs also contained the larve of
Tanapus, Corethra, and Chironomus, small gnat-—like flies.
He found that each of these larvee contained numerous cysts
with larve of Gordius. He then removed the larve
from the cysts, placed them on the gnat-larva, and saw the
larval hair-worm work its way into the head of the gnat-
larva through the softer part of the integument ; during the
process the spines on the head, reversing their usual position,
enabled the worm to retain its position and penetrate farther
in. Then, finding a suitable place, it came to rest, and re-
mained immovable. Then the fluids bathing the parts co-
agulated and formed a hard, granulated sac. This sac at
first closely envelopes the body, then it becomes looser and
longer, the worm living in the anterior part, the front end
of the sac being probably never closed. In this first larval
state the worm is active.

In the second larval period the young hair-worm lives mo-
tionless and encysted in the mucous layer of the intestines
of such small fish as prey on the gnat-larve. A minnow, for
example, swallowing one of the aquatic gnat-larve, the en-
cysted larva becomes set free by the process of digestion in the
stomach of the fish; the cyst dissolving, the young hair-
worm itself becomes free in the intestine of its new host.
Immediately it begins to bore, aided by the spines around
the head, into the mucous membrane lining the inner wall
of the intestine of the fish, and there becomes encysted, the
worm itself lying motionless in its new home, with its head
retracted and the tail rolled in a spiral. The cyst is either
spherical or oval. (Fig. 119, @.)

The return to a free state and an aquatic life occurs in the
spring, five or six months after the second encystment. It
then bores through its cyst, and passes into the intestinal
cavity of the fish, and from thence is carried out with the
feeces into the water. On contact with the water great
174 ZOOLOGY.

changes take place. The numerous transverse folds in the
body disappear, and it becomes twice as long as before, its
head-armature disappears, the body becomes swollen, milky,
and pulpy. It remains immovable in the water for a vari-
able period, and then increases in size ; the integument grows
harder, and when about two inches long it turns brown and
begins to move. Most hair-worms live in ground beetles
and locusts, twining round the intestines of their host,
finally passing out of the anus. They are often seen in
fresh water pools, twisted into knots, whence their name
Gordius. They sometimes occur in horse-troughs, whence
they are supposed by the ignorant to be transformed horse-
hairs.

Order 3. Chetognathi.—This group 1s represented by a
single genus, Sagitta, which, from the singularities in its form
and structure, has by different authors been referred to the
Crustacea, the Mollusca and even the Vertebrates. Its de-
velopment and structure show that it is closely allied to the
Nematode worms. It is about two centimetres (nearly one
half inch) in length, and is found swimming at the surface
of the ocean in different parts of the world. The lateral and
caudal fin-like expansions of the skin of the end of the
body gives it a fish-like appearance. There is a well-defined
head, with several curved spines on each side of the mouth,
which serve as jaws ; besides these, at the sides of the head
are four sets of short, strong spines. In the young Sagitta
there are also a few pairs of lateral spines behind the head,
but these afterwards disappear. ‘The alimentary canal forms
a straight tube terminating in a ventral opening near the
posterior fourth of the body. The nervous system consists
of a brain from which two nerves are distributed to the eyes,
and two lateral nerves pass backward to a large ventral gan-
glion lying near the middle of the body, from which two
threads pass backwards. The sexes are united in the same
individual, the two long tubular ovaries communicating by
two long ciliated oviducts, each with a separate outlet at the
base of the tail. Behind the ovaries and anus are two cham-
bers in which the spermatic particles are developed from mass-
cs of cells floating freely in the perivisceral fluid, and escap-
THE SAGITTA. 1%

ing by a lateral duct on each side of the tail. The egg passes
through a morula and gastrula stage (Fig. 120). The prim-
itive opening (a) afterwards closes
and a new opening is made at the op-
posite pole, which is the permanent
mouth. The embryo is oval at first,
but soon elongates, and the form of the
adult is attained before the Sagitta
leaves the egg. Sagitta elegans Ver-
rill is about 16 millimetres in length,

and is common in the waters of New _ Fig. 120.—Gastrula of Sa-
gitta.—After Kowalevsky.
England.

 

Cuass II.—NEMATELMINTHES.

Round-bodied worms, with a dense integument, not jointed ; with an ali-
mentary canal (except in Hehinorhynchus); no water-vascular or respira-
tory system ,; the nervous system usually reduced to a brain and two ner-
vous threads passing along the body; with excretory organs. The head
sometimes hooked or spinulated ; and except in Echinorhynchus and Gor-
diacea no metamorphosis, the young hatching in the form of the adult.
Mostly parasitic, and usually bisexual.

Order 1. Acanthocephali.—Cylindrical, with a beak armed with hooks,
without mouth or digestive tract. (Echinorhynchus.)

Order 2. Nematodes.—Long, slender, cylindrical, with 1 mouth and
intestine ; but no metamorphosis. Suborder 1. True Ne-
matodes (Ascaris, Oxyuris, Eustrongylus, Trichocephalus,
Trichina, Filaria, Anguillula, Echinoderes). Suborder 2.
Gordiacea (Mermis, Gordius).

Order 3. Chaetognathi—Having a well-marked head, with lateral and
caudal fin-like expansions of the skin ; hermaphrodite.

(Sagitta.)

Laboratory Work.—These worms are to be mainly sought for in
the alimeatary track of fishes and mammals, while Sagitta may he
caught with the tow-net. They may be studied with good success be-
sides the ordinary mode of dissection, by cross-sections for the micro-

scope.
176 ZOOLOG Y,

Cuass III.—Rotatoria (Rotifers).

General Characters of Rotifers.—The Rotifers, or wheel-
animalcules, are abundant in standing water, in damp moss,
etc., and in the ocean, and are so transparent that their in-
ternal anatomy can be studied without dissection, while they
are so minute, being from one fortieth to three hundredths
of an inch in length (3 to $ mm.), that high powers of the
microscope are needed in
studying them. They are
of special interest from
the fact that after being

a yj. dried for months to such
s 4 degree that little if any
st eg moisture is left in the
a a body, they may be revived
ev? and become active. Pro-
cg fessor Owen has observed
ev cot the revivification of a
33 Rotifer after having been

eg} 5
kept for four years in dry

= sand.

a As an example of the
: ordinary type of Rotifer

 

we may cite Sguamella
oblonga (Fig. 121), which
is allied to Brachionus.

Fig. 121.—Squamella oblonga, magnified 200
diameters. A view from below; shell or cara-

pace (s, s1, 52); s, the anterior transverse edge
of the carapace; s!, the anterior, and s?, the
posterior corners of the carapace; s?, the border
of the oval, flat area which occupies the lower
face of the carapace; @d, the cilia-bearing velum
of the head; ¢, the fork of the tail (¢!) ; m, the
mouth ; j, jaws ; j!, muscles which move /; st,
stomach ; cv, the contractile vesicle, or heart of
the excretory system ; cv', cv?, the right, and
cv, cvs, the left excretory vessels ; eg, eg}, eg?,

The characteristic organ
of the wheel-animalcules
is the velwm (lb) or pair
of ciliated wheel-like flaps
on each side of the head,

two largely developed young.—After Clark. . .
Bee ioe which is comparable to

the velum of the larval mollusk. By means of the rotatory
movements of this velum the creature is whirled swiftly
around. The body is broad and flattened, with the walls
often dense, chitinous, sometimes shell-like, and variously
sculptured, or the animal may be long and worm-like, as in
Rotifer vulgaris (Fig. 122). The body is composed of several,
STRUCTURE OF ROTIFERS. 1v7

not over six, segments. A Rotifer may, in fact, be regarded
as an advanced trochosphere or more properly cephalula, and
comparable with the larvee or cephalule of mollusks, Poly-
zoa, Brachiopoda and the Annelids. The alimentary canal
consists of a funnel-like cavity, the mouth, which may
be central, or situated on one side of the head; it leads
to the mastaz or pharynx-like muscular sac, supporting
a complicated set of chitinous teeth within (malleus
and incus) which seize and masticate the food, which,
through the rotary action of the velum, passes
down the buccal channel or mouth-opening, and aff~_3))).
lodges within the mastax. The so-called sali- ee
vary glands are two large, clear, vesicular =
glands, which are attached to the funnel and
rest on the summit of the mastax. The latter
opens into the esophagus, ‘‘a membranous
tube, capable of great expansion and contraction,
but varying much in length and diameter in :
different genera.” Gosse also states that a cur- i
rent of water appears to be almost constantly
setting through the funnel and mastax, and sh
thence through the esophagus into thestomach ; \\Xt
the latter is quite large, and provided with so- Sc
called ‘‘ pancreatic” glands, emptying into the
anterior end. ‘There are also hepatic follicles t
and ceca, while the intestine ends in a rectum
and cloaca, the latter opening at the base of
the tail. In Wotommata, the digestive canal
ends in a blind sac, and in such male Rotifers
as are known, there is no digestive cavity, the ig. 122.0.
canal being represented by a solid thread. Oe
There are no vascular or respiratory organs, but (539 {feue
a system of long, convoluted excretory tubes,
one on each side of the body, which, as in the Trematodes
and Cestodes, unite in a common, large contractile vesicle
which opens into the end of the intestine. These tubes,
which are in places ciliated, correspond to the segmental or-
gans of Annelids; they are open at the end, the cavity of
the tubes thus communicating with the body-cavity.

 

 

 

 

 

 

 
178 ZOOLOGY.

The nervous system is very simple, consisting of a rather
large ganglion situated behind one wing of the velum, and
lying just under an eye-spot. A supposed organ of hearing,
consisting of a sac filled with calcareous matter, is attached
to the ganglion.

The sexes are distinct, and the male and female reproduc-
tive glands open into the cloaca. The sexes are, moreover,
remarkably unlike, the males being much smaller than the
females, rudimentary, sac-like in form, without any digestive
sac, and are very short-lived. Some Rotifers produce what
are called winter as well as summer eggs ; the former being,
as in some Turbellarian worms and Polyzoa, covered with a
hard shell to resist the extremes of the winter temperature.
The summer eggs develop without being fertilized, while the
winter eggs are fertilized, those of Lacinularia, however,
according to Huxley, not being impregnated.

The eggs of Brachionus are attached by a stalk to the
hinder part of the body of the female. The following
remarks apply to the mode of development of the fe-
male eggs, which are quite distinguishable from the mas-
culine ones. The eggs undergo total segmentation, and
the outer layer of cells resulting from subdivision forms
the blastoderm, and when this is developed the forma-
tion of the organs begins. The first occurrence is an in-
folding of the blastoderm (ectoderm) forming the primitive
mouth, which remains permanently open, the mouth not
opening at the opposite end as in Sagitta, but the entire de-
velopment of the germ is much as in the mollusk Calyptrea,
as Salensky often compares the earliest phases of devel-
opment of this Rotifer with those of that mollusk. The
‘‘trochal disk,” or velum, arises in certain mollusks,
as a swelling on each side of the primitive infolding.
There is soon formed at the bottom of the primitive in-
folding a new hole or infolding of the ectoderm, which is
the true mouth and pharynx, while a swelling just behind
the mouth becomes the under lip. The stomach and intes-
tine arise originally from the endoderm.

Soon after, the two wings of the velum become well
marked (Fig. 123, v), and their relation to the head is as
DEVELOPMENT OF ROVTIFERS. 179

constant as in Calyptrea. The tail (¢) becomes conical,
larger, and the termination of the intestine and anal open-
ing is formed at the base.

The internal organs are then elaborated ; first the nervous
system, consisting of but a single pair of ganglia arising
from the outer germ-layer (ectoderm). Soon after the sen-
sitive hairs arise on the wings of the velum.

Fig. 123 represents the advanced embryo, with the body di-
vided into segments, the pair of ciliated wings of the veluin
(v), and the long tail (¢). At this time the shell begins to
form, and afterwards covers the whole trunk, but not the head.

The inner organs are developed from the inner germ-layer
(endoderm), which divides into three layers, one forming the
middle part of the intestine, and the two others the glands
and ovaries. The pharyngeal jaws arise as
two small projections on the sides of the
primitive cavity. The male develops in
the same mode as the female.

Though the development of the Rotifers,
so far as known, is more like that of the
mollusks than true worms, the Rotifers
may be regarded as a generalized cephalula
form, representing the larval forms of An- _ ;
nelids and mollusks, with decided affinities, ee cei ns
when we consider their chitinous covering —Af*" Salensky-
or carapace, the fold of the intestine, and the single nervous
ganglion, to the Polyzoa, and with more remote resemblances
to the Brachiopods. They are on the whole generalized forms.
A few species are parasitic: Aldertia living internally, and
Balatro on the surface of the Nais-like worms. With the
lower Rotifers are associated a group of worm-like forms
represented by Chetonotus, Ichthydium, etc., and forming
the group Gastrotricha. They have no mastax, and the body
is only ciliated near the end. Through Dinophilus, a Tur-
bellarian worm, they are connected with the flat worms.
The genus Zchinoderes is also regarded by Claus as a low
Rotifer. It seems quite apparent from this that the Rotifers
are a type which has originated from worms resembling the
generalized Turbellarian form, and which connects the latter

 
150 ZOOLOG Y.

with the Polyzoa, Brachiopods, and possibly the Mollusca,
the latter branch being probably a modified vermian type,
and with an ancestry not unlike that of the Rotifers and
aberrant, generalized Polyzoa and Brachiopoda. ‘The classi-
fication of the Rotatoria is in an unsettled state, the group
probably consisting of three orders, viz. : the true Rotatoria,
the Hchinoderide, and Glastrotricha.

Cuass III.—ROTATORIA.

Worms with usually more or less solid segments, very unequally developed,
bearing a ciliated velum, the mouth opening into a mastax ; sexes separate,
the males much smaller, more rudimentary than the females. A small
nervous ganglion. No circulatory apparatus, but with a voluminous excre-
tory (water-vascular) organ.

(Albertia, Asplanchna, Hydatina, Brachionus, Rotifer, and the
highest form, Floscularia.)

Laboratory Work.—The Rotifers can only be studied while alive and
as transparent objects. Little is known about the American species.

Ciass IV.—Ponyzoa (Moss Animals).

The Polyzoa, though not commonly met with in fresh
water, are among the commonest objects of the seashore.
They are minute, almost microscopic creatures, social, grow-
ing in communities of cells (called poly-
zoaria or corms), forming patches on sea-
weeds and stones (Fig. 124, Membranipora
solida Pack.). Certain deep-water species
grow in coral-like forms (Fig. 125, Myrio-
zoum subgracile D’Orbigny), while the
chitinous or horny Polyzoa (Fig. 126,
Halophila borealis Pack.), are often mis-
Fig. 124—Cells of Sea- taken for sea-weeds on the one hand, and

mat, enlarged.‘ Sertularian Hydroids on the other. From
their likeness to mosses the name Bryozoa was given to the
group by Ehrenberg, a year after Thompson (1830) had
called them Polyzoa, so that the latter name has priority.

 
THE POLYZOA.

181

The simpler form of Polyzoon is a worm-like creature

enclosed in a minute, deep, horny cell,

with the alimentary

canal bent on itself and terminating in a vent situated near
the mouth, the latter surrounded, in the fresh-water forms,

 

Fig. 125.—Branching marine Polyzoon. Corm of Myriozoum subgracile,

natural size.

with a horseshoe-shaped crown, or in the marine species a
circle of slender ciliated tentacles. The animal when dis-
turbed withdraws into its tube or shell, which is often trans-

parent, allowing it to be examined
when alive. The cells are rarely
single, but a cormus, polyzoartum or
polyzoon-stock is formed by the bud-
ding of numerous cells from the one
first formed. The single polyzoon is
called a polypide, and its cell a cystid.
In Pedicellina, the simplest polyzoon,
the polypide has no cystid or cell.
The cells are, in the marine forms,
usually closed, and independent of
each other. The wall forming the
cell is called the endocyst ; it com-

 

Fig. 126.—Halophila borealis,
enlarged.

prises the ectoderm proper, with a portion (parietal layer) of
the mesoderm forming the soft lining of the cell.
182 ZOOLOGY.

The mouth is situated on a disk (lophophore, Fig. 127, B),
bearmg the tentacles, which are hollow processes of the
body-walls, communicating with the body-cavity, the blood
flowing into them, there being aérated, while they are exter-
nally ciliated. They serve both to catch food and for respir-
ation as makeshift gills. Hyatt states that the tentacles are
used not only to catch the prey, but for a multitude of other
offices. They are each capable of in-
dependent motion, and may be twisted
or turned in any direction ; bending
inwards, they take up and discard
objectionable matter, or push down
into the stomach and clear the
cesophagus of food too small to be
acted upon by the parietal muscles.
They are also employed offensively in
striking an intrusive neighbor, and
their tactile power, sensitive to the
shghtest unusual vibration in the
water, warns the polypide of the ap-
proach of danger.

The digestive canal hangs free in
the body-cavity, only attached by the
mouth and anus to the walls of the
body. It consists of a pharynx, a
large stomach, and an intestine which
Fig. 127.— Organization of 8 lies by the side of the pharynx, since

Polyzoon. A, Paludicella Eh-

renbergii. B, Plumatella fru- ¢ 3 1
eee Ptiarula beara the canal has a simple deep dorsal

oflophophore ; @, esophagus; flexure, the vent being situated on
v, stomach ; 7, Intestine; a, a :
anus ; 4, cell; x, posterior, «1, the dorsal or cardiac side, near the
anterior cord, at the insertion + 4s
of which into the body the mouth. Usually the stomach is tied
generative products are devel- : :
oped: ¢, testes ; 0, ovary; m, by a sort of ligament (funiculus) to
retractor muscles of the ante- *
rior portion of the cell; mz, a point on the body-walls, near the
Rito a maat#cter muscle— mouth. The nervous system is rep-
resented by a double ganglion form-
ing a single mass situated between the mouth and vent; it
is highly contractile and changeable in form. There is no
heart nor any circulatory apparatus. The sexes are united

in a single polypide, and form cellular masses growing on

 
STRUCTURE OF THE POLYZOA. 183

the funiculus or in the walls of the body. The body,
especially the lophophore, is retracted and pushed out
by muscles arranged in pairs on either side. As seen in
Fredericella, a fresh-water form, the alimentary canal
‘‘hangs from the lophophore, occupying the centre of
the polypide, and floating freely in the rapidly moving
blood” (Hyatt). The yellowish cesophagus, the stomach
barred with brown, and the brownish intestine are balanced
upon a fold of the intestine (the invaginated fold), which
is retained in the cell by the retentor muscles, and is sur-
rounded by a large sphincter muscle. There are two sets
of large retractor muscles, one on each side of the digestive
canal, and arising from two common bases ; each large trunk
subdivides into three branches, the retractor of the stomach,
of the lophophore, and of the anus. The crown of tenta-
cles is swayed by these muscles in every direction, or when
alarmed the polypide may withdraw by their aid into the
cell, as the finger of a glove may be inverted within the
empty palm. This may be done with great rapidity or
slowly. The process has thus been graphically described by
Hyatt: ‘‘The polypidal endocyst is first turned inwards,
folding upon itself, and prolonging the permanently invagi-
nated fold below. The tentacles, arriving at the edge of
the ceenecial orifice, are pressed into a compact bundle by
the action of their own muscles, and, together with the
lophophore, are dragged into the cell by the continued invag-
ination of the endocyst until they are wholly enclosed and
at rest within the sheath formed for them by the inverted
walls of the tube. The sphincter muscle then closes the
ceenecial orifice above, and the process of invagination is
completed.

““The polypide in its exserted state is buoyed up and sus-
tained by the pressure of the fluids within. Consequently,
when invaginated, it displaces an equal bulk of these in the
closed cencecium, and their reaction, aided by the contrac-
tion of the muscular endocyst, is sufficierit to evaginate the
whole.

«The evagination begins with the relaxation of the sphinc-
ter, which permits the ends of the tentacles to protrude.
184 ZOOLOGY.

These daintily feel about for the cause of the alarm, and, if
they fail to detect the proximity of an enemy, the whole
fascicle is cautiously pushed out, and the sentient threads
suddenly and confidently unfolded.

‘The polyzoén reasons from the sense of touch inherent
in its tentacles, and cannot be induced to expose itself above
the cencecium until thoroughly satisfied by these sensitive
feelers that no danger is to be apprehended. In fact, these
plant-like creatures, singly mere pouches with a stomach
hanging in the midst, exhibit greater nervous activity and
‘animality,’ than we find among the more highly organized
Ascidia, or shell-covered Brachiopoda.”

The eptstome is a fold of the lophophore, used to close the
mouth and thus prevent the food from escaping from the
mouth. It is tongue-like and very pliable. ‘‘ The border is
capable of a tactile motion similar to that of the human
tongue, and it takes cognizance of what passes into the
mouth by frequent and repeated jerks toward the aperture”
(Hyatt). Itis situated immediately over the ganglionic mass,
and between the anus and mouth.

The Polyzoa, as regarded by Hyatt and others, are struc-
turally nearly related to the Brachiopods, the higher forms
of which, such as Terebratula and Rhynconella, have the res-
piratory tentacles similarly placed around the disk or lopho-
phore, which is perforated at the centre by the mouth, and
from which the alimentary canal hangs, with a dorsal flexure
andanusnearthe mouth. ‘‘The extension of the lophophore
into two or three spiriform arms, the complex structure of
the tentacles and of the muscular and nervous systems, are
all more or less foreshadowed by the condition of these sys-
tems among the higher Polyzoa.” On the other hand, the
Polyzoa are closely related to the worms, the Gephyrean
worm, Phoronis, being the connecting link. The mode of
development of the Polyzoa and Brachiopoda are quite simi-
lar, as will be seen farther on, and owing to these decided sim-
larities in development and anatomy, the Polyzoa and Brachi-
opods form a natural group or series, distinct on the one
hand from the Rotatoria, and on the other from the mollusks
and worms.
DEVELOPMENT OF THE POLYZOA. 185

Certain branching marine forms are provided with organs
like birds’ heads, situated on a stalk and called avicularia, with
a movable jaw-like appendage, which keeps up an incessant
snapping. Beside the avicularia, there are, as in Scrupo-
cellaria, long bristle-like appendages to the cells, called
vibracula.

There are no organs of special sense in the Polyzoa, unless
the epistome may be regarded as an organ of sense, and the
nervous system consists of a single rounded ganglion (Frede-
ricella), or, as in Plumateila, a double ganglion, situated be-
tween the mouth and vent, from which one set of nerves are
distributed to the epistome, lophophore, tentacles, and evagi-
nable endocyst, and another set to the various parts of the ali-
mentary canal. A so-called colonial nervous system is sup-
posed to exist in the Polyzoa, as when the ccencecium in some
forms is touched all the polypides become alarmed, which
indicates that aset of nerves connect the different polypides,
though no such nerves have yet been discovered. The
fresh-water Polyzoa are not sensitive to light, nor to noises,
only to agitation of the water in which they dwell.

All the Polyzoa are hermaphrodite, the ovary and male
glands residing in the same cystid, the testis being situated
near the bottom and attached to the funiculus, while the
ovary is attached to the walls of the upper part of the cell.

Allman regards the polypide and cystid as separate indi-
viduals. The singular genus Lozxosoma is like the polypide
of an ordinary Polyzoan, but does not live in a cell (cystid).
On the other hand, we know of no cystids which are with-
out a polypide. Remembering that the cystids stand in the
same relation to the polypides as the hydroids to the meduse,
as Nitsche insists, we may regard the polypides as secondary
individuals, produced by budding from the cystids. The
large masses of cells forming the moss-animal, which is thus
a compound animal, like a coral stock, arises by budding out
from a primary cell. The budding process begins in the
endocyst, or inner of the double walls of the body of the
cystid, according to Nitsche, but according to an earlier
Swedish observer, F. A. Smitt, from certain fat bodies float-
ing in the cystid.
186 ZOOLOGY.

The Polyzoa are divided primarily into the Hntoprocta,
represented by Loxosoma alone, in which the vent is situated
within the circle of tentacles, and the Lctoprocta, in which
the vent lies outside of the lophophore—a group comprising
all the higher Polyzoa (Gymnolemata and Phylactolemata).

The development of the Polyzoa is not very complicated.
In the marine forms, as studied by Barrois, the germ passes
through a morula stage ; after which the cells are arranged
into two halves, separated by a crown of cilia; at this stage
it is called a dlastula. Atthe time of birth the ciliated germ
is a disk-shaped gastrula, with two opposite faces or ends,
separated by the crown, one (aboral) bearing in its centre
the mouth-opening. This ciliated free-swimming top-like
gastrula stage is called a trochosphere.

After swimming about as ciliated larve (trochospheres),
the shell or ectocyst develops, and the larva becoming station-
ary, the cystid forms, its calcareous shell develops, and finally
the polypide is indicated, and the primitive cell is gradually
formed.

As seen in Phalangella flabellans, the larva, after becoming
fixed to some object, consists of a white pyriform mass,
closely enveloped by an ectocyst, with numerous fat globules
between the latter and the white mass. The ectocyst swells
into a discoidal sac, with endocyst, ectocyst, and an external
zone, while the internal whitish mass transforms into the
polypide. The discoidal sac formed by the endocyst consti-
tutes simply the basal disk of the primitive cell. The future
opening of the cell appears on the upper surface of the cell.
The budding out of the secondary cells of the polyzoarium
or corm then takes place. It begins by the appearance of a
cell placed in front and below the primitive cell, and which
borders it on each side ; its secondary cell then divides into
two, each of which successively gives origin to three cells,
and we thus arrive at an Jdmonea stage; and finally the
Phalangella stage is reached, the process being a dichoto-
mous mode of budding quite analogous to that which pro-
duces the broad, flattened corm of Escharina.

The development of Membranipora pilosa, which is very
abundant on our shores, growing on sea-weeds, is of singu-
DEVELOPMENT OF THE POLYZOA. 187

lar interest. The free-swimming ciliated larva is provided
with a bivalve shell, and was originally described as a La-
mellibranch larva under the name of Cyphonautes.
Schneider discovered that it was a young Membranipora.
Barrois, who has traced its complete history, states that its
metamorphosis is fundamentally like that of the other ma-
rine Polyzoa. Flustrella hispida passes through a similar
Cyphonautes stage.

In Loxosoma young resembling the adult bud out like
polyps. Nitsche does not regard this budding process as an
alternation of generations, but states that in Polyzoa of the
family of Vesiculariide, this may occur, as in the latter
some cystids form the stem, and others (the zowcia) produce
the eggs. Most fresh-water Polyzoa reproduce by the devel-
opment of winter buds or eggs surrounded by a horny case,
and developing from the funiculus.

To recapitulate : the Polyzoa increase (a) by budding ; (0)
by normal (summer) eggs, and by producing s¢atodlasts, or
winter eggs. In reproducing from summer eggs, the young
pass successively through a morula, blastula, gastrula and
trochosphere stage before attaining maturity.

The most aberrant Polyzoan is Rhabdoplewra mirabilis Sars,
which occurs in from 100 to 300 fathoms on the coast of
Norway. It differs from other forms by the want of an en-
docyst or mantle, whence it moves up and down in its cell,
without being attached to the opening, the muscles usually
present being wanting, the cord by which it is attached to
the bottom of its long, slender tubular cell being contractile.
The lophophore is much like that of the fresh-water Poly-
zoans, consisting of two long arms, bearing two rows of
slender tentacles. The epistome is represented by a large
round disk.

The marine Polyzoa occur at great depths, and a few species
are cosmopolitan ; the type is very persistent, and occurs
in the oldest Silurian strata, the earliest forms being very
similar to their living descendants.
188 ZOOLOGY.

Cuass IV.—POLYZOA.

Animals usually forming moss-like or coral-like caleareous or chitinous
masses called corms, each cell containing a worm-like animal, with the di-
gestive tract flexed, the anus situated near the mouth. The body usually
drawn in and out of the cell by the action of retractor and adductor muscles,
The mouth surrounded by a crown of long tentacles. No heart or vascular
system. Nervous system consisting of a single or double ganglion situated
between the mouth and vent, with nerves proceeding from it. Hermaphro-
ditic ; multiplying by budding or eggs. The embryo passing through a
morula, gastrula and trochosphere stage, the corm being formed by the
budding of numerous cells from a primitive one.

Order1. Hntoprocta.—Vent within the lophophore. (Loxosoma.)

Order 2. Ectoprocta.—Vent without the lophophore. (Lepralia, Es-
chara, Idmonea, Myriozoum. )

Laboratory Work.—The Polyzoa are too small to dissect, and
must be studied while alive as transparent objects, and may be kept
in aquaria. The corms in part or whole can be mounted for the mi-
croscope as opaque objects.

Crass V.—Bracuiopopa (Lamp Shells). °

General Characters of Brachiopods.—This group is named
Brachiopoda from the feet-like arms, fringed with tentacles,
coiled up within the shell, and which correspond to the
lophophore of the Polyzoa and the crown of tentacles of the
Sabella-like worms. From the fact that the animal secretes
a true, bivalved, solid shell, though it is usually inequivalve,
z.e., the valves of different sizes, the Brachiopoda were gener-
ally, and still are by some authors, considered to be mol-
lusks, though aberrant in type. They may be regarded as a
synthetic type of worms, with some superficial molluscan
features. The shell of our common northern species, Tere-
bratulina septentrionalis, which lives attached to rocks in
from ten to fifty or more fathoms north of Cape Cod, is in
shape somewhat like an ancient Roman lamp, the upper and
larger valve being perforated at the base for the passage
through it of a peduncle by which the animal is attached
to rocks. The shell is secreted by the skin (ectoderm), and is
STRUCTURE OF BRACHIOPODS. 189

composed of carbonate (Terebratulina) or largely (Lingula,
Fig. 133) of phosphate of lime. It is really the thickened
integument of the animal, the so-called mantle being the
inner portion of the skin, containing minute tubular canals
which do not open externally.

The body of Brachiopods is divided into two parts, the
anterior or thoracic, comprising the main body-cavity in
which the arms and viscera are contained, and the caudal
portion, ze. the peduncle. The part of the body in which
the viscera lodge is rather small in proportion to the entire
animal, the interior of the shell being lined with two broad
lobes, the free edges of which are thickened and bear sete,
as seen distinctly in Lingula. The body-cavity is closed
anteriorly by a membrane which separates it from the space
in which the arms are coiled up The ‘pallial cham-
ber” is situated between the two lobes of the mantle (pai-
lium) and in front of the membrane forming the anterior
wall of the body-cavity. In the middle of this pallial
chamber the mouth opens, bounded on each side by the
base of the arms. The latter arise from a cartilaginous
base, and bear ciliated tentacles, much as in the worm Sa-
bella. In Lingula, Discina, and Rhynconella, they are de-
veloped, as stated by Morse, in a closely-wound spiral, as in
the genuine worms (Amphitrite). In Lingula the arms can
be partially unwound, while in Rhynconella they can not
only be unwound but protruded from the pallial chamber.
In many recent and fossil forms the arms are supported by
loop-like solid processes of the dorsal valve of the shell, but
when these processes are present the arms cannot be pro-
truded beyond the shell. The tentacles or cirri on the arms
are used to convey to the mouth particles of food, and they
also are respiratory in function, there being a rapid circula-
tion of blood in each tentacle, which is hollow, communi-
cating with the blood-sinus or hollow in each arm, the sinus
ending in a sac on each side of the mouth.

The digestive system consists of a mouth, csophagus,
stomach, with a liver-mass on each side, and an intestine.
Fig. 128 shows the relation of the mouth and digestive canal
to the head and arms, as seen in a longitudinal section of
190 ZOOLOGY.

the anterior part of the body of Lingula. The mouth is
bordered by two membranous, highly sensitive and movable
lips. The stomach is a simple dilatation of the alimentary
canal, into which empty the short ducts of the liver, which
is composed of
massesof coeca.
The liver origi-
nally arises as
two diverticula
or offshoots of
the stomach.
The short in-
testine ends in
a blind sac or
in a vent, and

ee a ep ie ee is, with the
Fig. 128.—Longitudinal section of the anterior portion of
Lingula. m, mouth; &, cesophagus ; s¢, stomach ; @, arm; ¢i, stomach, freely
cirri; df, brachial fold ; ch, cartilaginous base ‘of arm : 8, d d .
sinus leading to the arm; cc, cephalic collar or pallial mem- SUSpende in

brane.—-After Morse, the perivisceral
cavity by delicate membranes springing from the walls of the
body. (Fig. 129.) In those Brachiopods allied to Terebra-
tula, Terebratulina, Thecidiwm, Waldheimia, Rhynconella,
etc., the stomach ends in a blind sac, and there is no vent,
the rejectamenta escaping from the mouth. In Lingula and
Discina there is a vent which terminates anteriorly on the
right side. In Lingula
the intestine makes a
few turns, while in Dis-
cina it makes a single
turn to the right.

The nervous system
consists of two small

ce
a
‘

 

 

: Fig. 129.—Transverse section of Lingula. b,
ganglia above, and an bands suspending the intestine in the perivisce-
S é : ral cavity ; é, intestine ; s, segmental organ ; 0,
infracesophageal pair of ovaries ; i liver 5 5 Ns gills; se, setee.—After

larger ganglia, and there ™"S*

are two elongated ganglia behind the arms, from which nerves
are given off to the dorsal or anterior lobe of the mantle.
From the infracesophageal ganglia two lateral ventral cords
pass backwards, in their tract sending off delicate threads,
STRUCTURE OF BRACHIOPODS. 191

but with no ganglionic enlargements, except in Discina,
where they terminate each by a ganglion in the last two
posterior muscles. Morse has discovered the presence of

auditory capsules in Lingula.
Respiration is mainly carried on in the mantle (pallial
membrane). In ZLingwia the pallial membrane is divided
into oblique transverse sinuses, which

YRA run parallel to each other. From
ARPA \ these arise, says Morse, numerous
OO. flattened ampulle, which are highly

Fig. 190.—Ampullee of blood contractile. The blood courses in
cinnes arimgcausesmken regular order up and down these

sinuses, entering each of the ampulle
in turn. Fig. 130 represents a row of five ampulle with in-
dications of the course taken by the blood-disks. These
ampulle have not been found in Discina, though the pallial
sinuses are very prominent. The breathing process is also
carried on in the tentacles or cirri.

Intimately connected with the vascular system is a gland-
ular portion of the tubular part of the segmental organs of
the Brachiopoda, which is
supposed to represent simi-
lar parts in worms as well
as the glandular, excretory
portion of the organ of
Bojanus in mollusks, and is
supposed to be depuratory
or renal in function.

The reproductive system
of Brachiopoda consists of
ovaries, oviducts or seg-

Fig. 131.—Segmental organs of Brachio-

mental organs, Fig. 131, poe: a, Discina ; 0, Terebratulina.—After
and spermaries. The sexes ™°"S*

are probably separate in all Brachiopoda (Morse).

The ovaries are attached in Discina and Lingula to the
delicate vascular membranes of the large sinuses in the pal-
lial membranes, the vascular membranes being thrown into
conspicuous ruffs when the eggs are ripe. In Terebratulina
and Rynchonella they are not only similarly situated, but

 
192 ZOOLOGY.

hang in clusters from the genital bands in the perivisceral
cavity. The mature eggs detach themselves from the ovary
to float freely in the perivisceral cavity, whence they pass into
the flaring, ciliated mouths of the segmental organs, and are
discharged by them into the water. These segmental organs
or oviducts are tubular, trumpet-shaped, as in the true
worms (Fig. 131). In Lingula, Discina, and Terebratulina,
there is but a single pair, in Rhynconella two pairs. The
external orifices of the oviducts form simple slits, while in
Terebratulina they project from the anterior walls like
tubercles, as in the true worms (Morse). The spermaries
occur in the same situation in the perivisceral cavity as the
ovaries. As observed in Terebratulina, by Morse, in a few
hours after the eggs are discharged the embryos hatch and
become clothed with cilia. Kowalevsky observed in the egg
of Thecidium the total segmentation of the yolk (also ob-
served in Terebratulina by Morse), until a blastoderm is
formed around the central segmentation cavity, which con-
tains a few cells. The similar formation of the blastoderm
was seen in Argiope, but not the morula stage. After this
the ectoderm invaginates and a cavity is formed, opening
externally by a primitive mouth. The walls of this cavity
now consist of an inner and outer layer (the endoderm and
ectoderm). This cavity eventually becomes the digestive
cavity of the mature animal.

In Terebratulina Morse observed that the oval ciliated
germ became segmented, dividing into two and then three
rings, with a tuft of
long cilia on the an-
terior end (Fig. 182,
A). In this stage the
larva is quite active,
swimming rapidly
about in every direc-

Fig. Behe Latal “ieee of Rexetwraiminacs tion.

: Soon after, the germ
looses its cilia and becomes attached at one end as in Fig.
132, B (c, cephalic segment ; ¢h, thoracic segment; p, pe-
duncular or caudal segment). The thoracic ring now in-

 
DEVELOPMENT OF BRACHIOPODS. 193

creases much in size so as: to partially enclose the cephalic
segment, asat C. The form of the Brachiopod is then soon
attained, as seen in D, in which the head (c) is seen project-
ing from the two valves of the shell (¢h), the larger being
the ventral plate.

The hinge margin is broad and slightly rounded when
looked at from above ; a side view, however, presents a wide
and flattened area, as is shown in some species of Spirifer,
and the embryo for a long time takes the position that the
Spirifer must have assumed (Morse). Before the folds have
closed over the head, four bundles of bristles appear ; these
bristles are delicately barbed like those of larval worms.
The arms, or cirri, now bud out as two prominences, one on
each side of the mouth. Then as the embryo advances in
growth the outlines remind: one of a Leptena, an ancient
genus of Brachiopods, and in a later stage the form becomes
quite unlike any adult Brachiopod known.

The deciduous bristles are then discarded, and the perma-
nent ones make their appearance, two pairs of arms arise,
and now the shell in ‘‘its general contour recalls Siphono-
treta, placed in the family Discinide by Davidson, a genus
not occurring above the Silurian.” No eye-spots could be
seen in Terebratulina, though in the young Thecidium they
were observed by Lacaze-Duthiers. The young Terebratu-
lina differs from Discina of the same age in being sedentary,
while, as observed by Fritz Miiller, the latter ‘“‘swims freely
in the water some time after the dorsal and ventral plates,
cirri, mouth, wsophagus and stomach have made their ap-
pearance.” Discina also differs from Terebratulina in havy-
ing a long and extensible esophagus and head bearing a
crown of eight cirri or tentacles. Regarding the relations
of the Brachiopods with the Polyzoa, Morse suggests that
there is some likeness between the young Brachiopod and
the free larva of Pedicellina. Fig. 133, B, represents the
Terebratulina when in its form it recalls Megerlia or Argi-
ope. C represents a later Lingula-like stage. “It also
suggests,” says Morse, ‘‘in its movements, the nervously
acting Pedicellina. In this and the several succeeding
stages, the mouth points) directly backward (forward of
194 ZOOLOGY.

authors), or away from the perpendicular end (D), and ig
surrounded by a few ciliated cirri, which forcibly recall cer-
tain Polyzoa. The stomach and intestine form a simple
chamber, alternating in their contractions and forcing the
particles of food from one portion to the other.” Figure
133, E, shows a more advanced stage, in which a fold is
seen on each side of the stomach ; from the fold is developed
the complicated liver of the adult, as seen in EH, which
represents the animal about an eighth of an inch long. The
arms (lophophore) begin to assume the horseshoe-shaped
form of Pectinatella and other fresh-water Polyzoa. At this
stage the mouth begins to turn towards the dorsal valve, and
as the central lobes of the lophophore begin to develop, the
lateral arms are deflected asin F. In the stage G an epis-
tome is marked, and Morse noticed that the end of the

 

Fig. 133.—Later larval stages of Terebratulina.—After Morse.

intestine was heid to the mantle by an attachment, as in the
adult, reminding one of the fwnicwlws in the fresh-water
Polyzoa. In tracing the development of Argiope, Kowal-
evsky has shown that the larva is strikingly like those of the
Annelids, as well as the Tornaria stage of Balanoglossus.
While in their development the Brachiopoda recall the
larve of the true worms, they resemble the adult worms in
the general arrangement of the arms and viscera, though
they lack the highly developed nervous system of the Anne-
lids, as well as a vascular system, while the body is not
jointed. On the other hand they are closely related to the
Polyzoa, and it seems probable that the Brachiopods and
Polyzoa were derived from common low vermian ancestors,
while the true Annelids probably sprang independently
from a higher ancestry. They are also a generalized type,
DISTRIBUTION OF BRACHIOPODS. 195

having some molluscan features, such as a solid shell, though
having nothing homologous with the foot, the shell-gland
or odontophore of mollusks.

In accordance with the fact that the Brachiopods are a
generalized type of worms, the species have a high antiquity,
and the type is remarkably persistent. The Lingula of our
shores (L. pyramidata Stimpson, Fig. 134) lives buried in
the sand, where it forms tubes of sand around the peduncle,
just below low-
water mark from
Chesapeake Bay,
to Florida. It has
remarkable vital-
ity, not only with-
standing the
changes of tem-
perature and ex-
posure to death
from various oth- Fig. 134.—Lingula pyramidata making sand-tubes;

: natural size.—After Morse.

er causes, but will

bear transportation to other countries in sea-water that has
been unchanged. Living Lingule have been carried by Prof.
Morse from Japan to Boston, Mass., the water in the small
glass jar containing the specimens having been changed but
twice in four months. The living species of this cosmopol-
itan genus differ but slightly from those occurring in the
lowest fossiliferous strata. Between eighty and ninety liv-
ing species are known, most of them living, except Lingula,
which is tropical, in the temperate or arctic seas, while nearly
2000 fossil species are known. ‘The type attained its maxi-
mum in the Silurian age, and in paleeozoic times a few spe-
cies, as Atrypa reticularis, extended through an entire system
of rocks and inhabited the seas of both hemispheres.

 

 

Cuiass V.—BRACHIOPODA.

Shelled worms, with a limestone or partly chitinous, inequivalve, hinged
or unhinged shell, enclosing the worm-like animal ; with two spirally coiled
arms provided with dense ciliated cirri or tentacles, and capable of reaching
196 ZOOLOGY.

to or beyond the edge-of thegaping shells ; alimentary canal with the mouth
opening between the arms, an asophagus, stomach with a liver-mass on
each side, and a short intestine ending in a blind sac, and with the stomach
freely suspended in the perivisceral space. Nervous system consisting of a
ganglion above and beneath the esophagus, and two lateral ventral widely-
separated threads. No eyes in the adult, but present in the larve of
Argiope and Thecidium ; auditory sacs presentin Lingula. No circulatory
system, the blood impelled through the visceral interspaces and tentacular
sinuses by ciliary action alone. Respiration carried on mainly in the
mantle and also in thearms. The sexes distinct. One or two pairs of seg.
mental organs. The germ passes through a morula and gastrula stage,
becoming a segmented ciliated larva like that of the true worms, which be-
comes sessile, the shell developing from the thoracic segment of the larva and
gradually enclosing the animal.

Order 1. Testicardines.—Shell calcareous, of prismatic structure, with
hinge and teeth. Intestine ending in a blind sac. Mantle
lobes united behind. (Families Terebratulide, Spiriferide,
Rhynchonellide, Strophomenide, and Productide.)

Order 2. Ecardines.—Shell without a hinge; arms without a calcare-
ous loop and with no median lobe. Intestine either end-
ing in a blind sac or with a vent opening anteriorly on the
right side. (Families Craniide, Discinide, and Lingulide.)

Laboratory Work.—Specimens of Terebratulina can be dredged in
from ten to fifty fathoms ona rocky bottom north of Cape Cod, and the
anatomy and development of the young be studied in living examples.
Lingule can be obtained at Beaufort, N. C., and in the sandy shores
southward. While the general structure can be studied from alcoholic
specimens, the recent discoveries which have advanced our knowledge
of the Brachiopods have been made on living, active individuals. The
eggs are minute and have to be studied with high powers of the micro-
scope.

Crass VI.—Tunicata (Ascidians, Sea-squirts).

General Characters of Tunicates.—While the Tunicates
are an aberrant type of worms, with affinities on the one
hand to the larve of the lower worms, ‘.e., the Cercaria
form of the Trematodes, on the other hand they have a
startling resemblance in the tadpole-like young of many
genera to the vertebrate Amphioxus. The position given to
them between the Brachiopods and true worms not far fron
HABITS OF ASCIDIANS. 197

Balanoglossus, is a provisional one. In a diagram showing
the classification, 7.¢., the affinities of the different classes of
animals, the Tunicates may be represented as an independent
branch sent off possibly from the Trematode stem, running
parallel to the worms, near Balanoglossus, and ending a little
below the level of Amphioxus. They have certainly few
molluscan features, what do exist being superficial, and
nothing to remind us closely of the Polyzoa or Brachiopods,
and the class is here treated of because, in a serial arrange-
ment of the classes of animals, the Tunicates can best be
described at this place, rather than after the true worms, or
immediately before the vertebrates.

The Ascidians are common just below low-water mark,
either hidden in masses of mussels, attached to the rocks
under sea-weeds, or the compound species
may be found forming bright-colored masses
on the piles of wharves and bridges, while
the Botryllus grows on the leaves of cel-
grass. Jor purposes of study the larger
forms, such as Ascidia, Cynthia, and Bol-
tenia, may be dredged. On placing a good-
sized Ascidian in a vessel of fresh sea-water,
it will be found to consist of a semi-trans- :
parent or quite opaque test with two open- Fi. 135.— Molgula
ings, one lower than the other, as seen in SE et eae
Molgula, which looks, when the two orifices
are protruded, like a double-necked bottle. The anterior or
higher orifice or mouth is for the passage of currents of water
into the respiratory sac, and the posterior, usually lower,
excurrent orifice for the passage outwards of feecal matter.
The test is either delicate and semi-transparent, allowing the
intestine and ovaries and liver to be detected, or it may be
quite tough and opaque. It is rendered tough and hard by
the presence of cellulose, a substance usually occurring in
the walls of vegetable cells, but very rarely in animal tis-
sues.

Order 1. Ascidiacea.—As an example of the ordinary Twzt-
cates, we will now study the internal anatomy of Boltenia
reniformis (Fig. 136), which lives in from five to twenty-five

 
198 ZOOLOGY,

fathoms off the coast of Northern New England, but which
is sometimes thrown ashore on beaches.

On examining the test of this Ascidian, which is mounted
on a long stalk, the oral or incurrent orifice is seen at the
insertion of the stalk, and the atrial or excurrent orifice on
the same side near the opposite end. On cutting open the
thick test and throwing the flap over to the left, the deli-
cate mantle or tunic is disclosed ; it extends a short distance
into the stalk or peduncle. This thin hyaline mantle is
crossed by two scts of narrow raised muscular bands; the
transverse fibres arc arranged concentrically to the two ori-
fices, so as to close or open them, the longitudinal cnes cury-
ing outward from the left side.

Currents of sea-watcr laden with organic food pass into
the oral orifice, which is surrounded by a circle of tentacles
pointing inward, and thence into a capacious saccular bran-
chial chamber within the mantle, which contracts at the
bottom, where the @sophageal opening is situated. The
walls of this chamber, which is over an inch long in a good-
sized specimen, and gathered into fringed folds, is sieve-like
with ciliated perforations (compare Fig. 137 e), making the
walls like a lattice-work, the blood coursing through the ves-
sels passing between the meshes of the sieve-like walls.

The esophagus, which lies at the bottom of this branchial
chamber, is also situated near the intestine passing over
the anal cnd into the short stomach. The intestine is long,
passing up to the insertion of the stalk, where it is held
in place by muscular threads extending into the stalk and
attached to the mantle; it then srddenly bends back and
passes straight down to the vent, which opens opposite to
the atrial orifice ; the end of the intestine is in part revolute
and provided with a fringe of about twenty filaments. The
liver forms a broad and flat mass of a bright livid green, and
consists of three flat lobes each composed of eight or nine
lobules, with very short ducts enveloping the inner aspect of
the intestine. The ovaries are two yellowish, large and long
lobulated masses extending nearly the whole length of the
body, while the right one is a little smaller, and situated in
the fold of the intestine. The atriwm is that region of the
STRUCTURE OF APPENDICULARIA. 199

body-cavity which lies between the end of the intestine and
the atrial or excurrent orifice; into this atrial region the
feces, eggs, etc., pass on their way to and out of the atrial
orifice.

The simplest form of Tunicate is Appendicularia, which
is tadpole-shaped, bearing a general resemblance to the larva
of an ordinary Ascidian, so that it may be properly called a
larval form. The Appendicularia isa pelagic animal, usually
about a quarter of an inch in length, found floating at or
near the surface when the ocean is calm, and occurring in
all seas a few miles from land or in mid-ocean. It swims
by means of its large, long, broad, flat tail, the body being

 

Fig. 136.—Anatomy of Boltenia.—Drawn by J. 8. Kingsley from the author’s
dissections.

oval or flask-shaped. In Appendicularia flabellum, as de-
scribed by Huxley, the caudal appendage is three or four
times as long as the body. The mouth leads into a large
pharyngeal or branchial sac; a narrow cesophagus at the
bottom of this sac leads to a spacious stomach, with two
lobes, from the left one of which the intestine arises, curves
and ends midway between the mouth and insertion of the
tail. In the middle of the hemal side (that side in which
the heart is situated and bearing the atrial opening) isa
fold of the wall of the pharyngeal cavity called the endostyle.
On each side of this endostyle are two oval ciliated apertures,
200

ZOOLOGY.

corresponding to the numerous branchial ‘slits in the other

 

Fig. 137. — Struc-
ture of a compound
Ascidian, Amare-
cium. <A, branchial
sac; m, stomach ; 4,
intestine ; c, mouth ;
o’, testis ; 7 7’, effer-
ent duct of the tes-
tis; C, ovary; p’,
egg in the body-cav-
ity; p”’, eggs in the
atrium ; 7, anus; 0,
shows the site of the
heart; /, liver; e,
openings in walls of
branchial chamber.
—From Macalis er.

Ascidians, but in Appendicularia each oral
aperture leads into a funnel-shaped atrial
canal, the open end of which terminates
beside the rectum.

The heart is a large pulsatile sac situated
between the two lobes of the stomach. The
nervous system is much more fully developed
than in other Tunicates, and is constructed
on the true Vermian type, consisting first of
a ganglion situated below the mouth on the
side opposite the atrial opening and opposite
the anterior end of the endostyle. This
nerve-centre throws off nerves to the sides of
the mouth, and from it posteriorly extends a
long cord past the cesophagus to the base of
the tail, thence it extends along one side of
the axis of the tail (urochord), swelling at
regular intervals into small ganglia, from
which from two to five.small nerves radiate.
On the cephalic ganglion a round ear-vesicle
is attached. Behind the posterior turn of
the digestive canal is the testis and ovary,
the Appendicularia being hermaphrodite, as
Fol claims, though the ovary is developed
later than the testis. The Appendicularia
has no test, but secretes a fibrous envelope,
which is at first gelatinous, loosely surround-
ing the whole body, and allowing the creature
the freest motion within its cavity.

The general structure of an Ascidian may
perhaps be more readily comprehended by a
study of acompound Ascidian (Amarecium),
which grows in white or flesh-colored masses
on sea-weeds, etc. On removing an Ama-
rectum from the mass and placing it under
the microscope, its structure can be per-
ceived. The body is long and slender, as

seen in Fig. 13%. The mouth leads by the capacious bran-
STRUCTURE OF ASCIDIANS. 201

chial sac (A) to the stomach, while the intestine (B) is flexed,
directed upwards, ending at the bottom of the atrium not
far from the atrial opening. The reproductive glands are
situated behind or below the head of the intestine, the eggs
being fertilized as they pass into the atrium, and the heart
lies in the bottom of the body-cavity, being directly opposed
to the nerve-ganglion (not represented in the figure), which
lies between the two openings.

In the perfectly transparent Perophora, which grows on
the piles of wharves on the coast of Southern New England,
one individual after another buds out (as also in Olavellina)
from a common creeping stalk like a stolon. In this form
the circulation of the blood-disks in the branchial vessels and
the action of the heart can be studied by placing living ani-
mals in glasses under the microscope. The heart is a straight
tube, open at each end, and situated close to the hinder end
of the branchial sac. After beating for a number of times,
throwing the blood with its corpuscles in one direction, the
beatings or contractions are regularly reversed and the blood
forced in an opposite direction.

Renal organs are apparently represented in Phallusia by
a peculiar tissue, consisting of innumerable spherical sacs
containing a yellow concretionary matter. In Molgula and
Ascidia vitrea Van Beneden, an oval sac containing concre-
tions of uric acid lies close to the ovary.

In the forms already considered the plan of structure is
complicated, owing to the difficulty of distinguishing an
anterior or posterior, a dorsal or ventral aspect of the
animal. In Salpa and Doliolum, however, the body is more
or less barrel-shaped, the hoops of the barrel represented by
the muscular bands which, at regular intervals, surround the
body. The mouth is near the centre of the front end, the
pharyngeal sac is very large, and the digestive tract makes
less of a turn than in the ordinary Ascidians, while the
atrial opening lies directly at the posterior opening. The
heart is truly a dorsal vessel, and the nervous ganglion is ©
situated on the opposite side of the body. This relation of
the anatomical systems is most clearly shown in the genus
Doliolum, and we have here a slight approach to the sym-
202 ZOOLOGY

metrical relation of parts seen in the true worms, and which
strongly suggest the conclusion that the Tunicates are mod-
ified worms. This conclusion is strengthened by the fact
that in Appendicularia the ventral nervous cord is gangli-
onated at intervals, as in the Annelids, while the twisted
digestive tract is much as seen in Polyzoa and Brachiopods.
Furthermore, the branchial sac is strongly analogous to the
pharyngeal or gill-sac of Balanoglossus, and this structure in
the Ascidian and whale’s-tongue worm anticipates the pha-
ryngeal or gill-sac of Amphioxus and vertebrate embryos.

The simple Ascidians attain to a large size, Ascidia callosa
being about ten centimetres in diameter, quite round, and in
form and color bears a strong resemblance to a potato.
Ascidia gigas, dredged by the Challenger Expedition, is from
thirty to forty centimetres in diameter, and has a ganglion
nearly as large as a pea. A floating colony of Pyrosoma
gigas is sometimes five feet long. Cynthia pyriformis Rathke
may be called the sea-peach, from its size, form, and the rich
bloom and reddish tints of its test. It is common in deep
water from Cape Cod to Greenland and Scandinavia.

While the Ascidians as a rule do not live below a depth of
150 fathoms, the stalked Hypobythius calycodes Moseley was
dredged by the Challenger Expedition in 2900 fathoms in
the North Pacific Ocean; it is stalked, and about twenty
inches high. The aberrant Octacnemus bythius Moseley was
also dredged in 1070 fathoms near the Schouten Islands,
Tasmania.

Panceri has described the luminous organs of Pyrosoma,
which is highly phosphorescent ; the substance from which
the light is emitted is probably a fatty matter.

Ascidians multiply by budding and by eggs. Examples of
budding or germination are seen in the compound or social
Ascidians, such as Amarecium, etc., where the individuals of
the colony bud out from the primitive one just as it has left
the larval condition and has become fixed. In Didemniuwm
buds arise from masses of cells floating free within the test.
They multiply by division as soon as the digestive and repro-
ductive organs are indicated. In Botryllus the zooid which
results from the tadpole-like larva serves, according to
DEVELOPMENT OF ASCIDIANS. 203

Huxley, merely as a kind of stalk, from which new zooids
bud out, and this process, in his opinion, “leads to the still
more singular process of development in Pyrosoma, in which
the first formed embryo attains only an imperfect develop-
ment, and disappears after having given rise to four ascidio-
zooids.” In Clavellina and Perophora the original parent
Ascidian throws off branches or stolons from which develop
new individuals.

The usual mode of development in the simple and com-
pound Ascidians (forming the order Ascidiacea) is by fertil-
ized eggs. We will give the life-history of an Ascidian as
based on Kowalevsky and Kupffer’s researches on Phallusia
mammillata Cuvier, in which the embryonic stages were ob-

 

_ Fig. 138.—Embryo Ascidian. A, @, primitive opening; h, primitive digestive cav-
ity 5 ¢, segmentation-cavity or primitive body-cavity SHG; payne pee
t, epithelium forming the body-wall ; x, rudimentary notochor y
served, and Ascidia intestinalis, in which the larval and
subsequent stages were studied.

The egg consists of a yolk unprotected by a yolk-skin, but
surrounded by a layer of jelly containing yellow cells. The
yolk undergoes total segmentation. The next step is the
invagination of the ectoderm, a true gastrula state resulting.
Fig. 138, A (after Kowalevsky), represents the gastrula ; h,
the primitive digestive cavity; a, the primitive opening,
which soon closes; and c, the segmentation-cavity or primi-
tive body-cavity. After this primitive opening (@) is lost to
view, sometime before the embryo has reached the stage B,
another cavity (”) appears with an external opening. This
cavity is formed by a union of two ridges which grow out
204 ZOOLOGY.

from the upper part of the germ. This is the central ner-
yous system, and in the cavity are subsequently developed
the sense organs. We thus see, says Kowalevsky, a com-
plete analogy in the mode of origin of the nervous system of
the Ascidians to that of the vertebrates, the nervous cavity,
where the embryo is seen in section, being situated above
the digestive cavity in both types of animals.

The next important stage is the formation of the tail.
The pear-shaped germ elongates and contracts posteriorly
until of the form indicated at Fig. 138, B. At this period
appears the axial string of nucleated cells, called the chorda
dorsalis, as it is homologous with that organ in Amphioaus
and the embryo of higher vertebrates. The nervous system
consists of a mass of cells extending halfway into the tail
and directly overlying the chorda, but extending far beyond
the end of the latter as seen in the figure. The nerve-cay-
ity (B, 2) after closing up forms the nerve-vesicle, a large
cavity (Fig. 139, a), in which the supposed auditory organ
(e) and the supposed eye (a) arise ; this cavity finally closes,
and the sense-organs are indicated by certain small masses
of pigment cells in the fully grown Ascidian larva.

As the embryo matures, the first change observed in the
cord is the appearance of small, refractive bodies between
the cells. Between the neighboring cells soon appear in the
middle minute highly refractive corpuscles which increase
in size, and press the cell-contents out of the middle of the
cord. After each reproductive corpuscle grows so that the
central substance of the cell is forced out, it unites with
the others, and then arises in the middle of the simple cel-
lular cord a string of bodies of a firm gelatinous substance
which forms the support of the tail. After this coalescence
the substance develops farther and presses out the proto-
plasm of the cells entirely to the periphery. The cord when
complete consists of a firm gelatinous substance surrounded
by a cellular sheath which is formed of the remains of the
cells originally comprising the rudimentary cord. The cells
lying under the epithehal layer form a muscular sheath of
which the cord (Fig. 138, c) is the support or skeleton.

The alimentary cavity arises from the primitive cavity
DEVELOPMENT OF ASCIDIANS.

205

(Fig. 138, A, h); whether the primitive opening (Fig. 138,
A, a) is closed or not, Kowalevsky says is an interesting
question. According to analogy with many other animals

it probably closes.

The larva hatches in from
forty-eight to sixty hours af-
ter the beginning of segmen-
tation, and is then of the
form indicated by Fig. 139
(copied with some additions
and omissions from Kupffer’s
figure, being partly diagram-
matic). This anatomist dis-
covered in the larva of As-
cidia canina, which is more
transparent than Kowalev-
sky’s Phallusia larva, not
only a central nervous cord
overlying the chorda dorsalis
and extending well into the
tail, while in the body of the
larva it becomes broader,
club-shaped, and surrounds
the sensitive cavity (a), but
he also detected three pairs
of spinal nerves (s) arising at
regular intervals from the
spinal cord (h, h’) and dis-
tributed to the muscles (not
represented in the figure) of
the tail ; Kupffer calls f the
middle and g the lower brain-
ganglion. The pharynx (0),
or respiratory sac, is now
very large; it opens pos-
teriorly into the stomach and
intestine (7); # represents

 

 

Fig. 189.—Larval Ascidian. @, sense
cavity containing the eye; 5, pharynx or
respiratory sac ; c, notochord ; e, supposed
auditory organ ; 7, middle, g, lower brain-
ganglion; i, 4, spinal cord; s, s, s, three
sets of spinal nerves; i, intestine; ¢,
body-wall, consisting of epithelial cells.—
Copied with some changes from Kupffer.

one of the three appendages by which the larva fastens
itself to some object when about to change into the adult,
206 ZOOLOGY.

sessile condition ; ¢ indicates the body-wall, consisting of
epithelial cells.

We will now, from the facts afforded us by Kowalevsky,
trace the changes from the larval, free-swimming state to
the sessile adult Ascidia, which may be observed on the
New England coast in August. After the larva fastens itself
by the three processes to some object, the chorda dorsalis
breaks and bends, the cells forming the sheath surrounding
the broken axial cord. The muscular fibres degenerate into
round cells and fill the space between the chorda and the
tegument, the jelly-like substance forming a series of wrin-
kles. With the contraction and disappearance of the tail be-
gins that of the nerve-vesicle, and soon no cavity is left. The
three processes disappear ; the pharynx becomes quadrangu-
lar ; and the stomach and intestine are developed, being
bent under the intestine. A mass of cells arises on the an-
terior end beneath the digestive tract, from which originate
the heart and pericardium. In a more advanced stage, two
gill-holes appear in the pharynx, and subsequently two more
slits, and about this time the ovary and testis appear at the
bottom, beyond the bend of the alimentary canal. The free
cells in the body-cavity are transformed into blood-cells, and
indeed the greater part of those which composed the nervous
system of the larva are transformed into blood-corpuscles.
Of the embryonal nervous system there remains a very small
ganglion, no new one being formed. The adult Ascidian
form meanwhile has been attained, and the very small indi-
viduals differ for the most part only in size from those which
are full-sized and mature.

It will be seen that some highly important features, recall-
ing vertebrate characteristics, have occurred at different pe-
riods in the life of the embryo Ascidian. Kowalevsky remarks
that “the first indication of the germ, the direct passage of
the segmentation cells into the cells of the embryo; the for-
mation of the segmentation-cavity, the conversion of this
cavity into the body-cavity, and the formation of the diges-
tive cavity through invagination—these are all occurrences
which are common to many animals, and have been observed
in Amphiozus, Sagitta, Phoronis, Echinus, etc. The first
RELATION OF ASCIDIANS TO VERTEBRATES, 207

point of difference from other animals in the development
of all vertebrates is seen in the formation of the dorsal
ridges, and their closing to form a nerve-canal. This mode
of formation of the nervous system is characteristic of the
vertebrates alone, except the Ascidians. Another primary
character allying the Ascidians to the vertebrates, is the
presence of a chorda dorsalis, first seen in the adult Appen-
dicularia by J. Miller. This organ is regarded by Kowal-
evsky to be functionally, as wellas genetically, identical with
that of Amphioxus. This was a startling conclusion, and
stimulated Professor Kupffer, of Kiel, to study the embry-
ology of the Ascidians anew. He did so, and the results this
careful observer obtained led him to fully endorse the con-
clusions reached by Kowalevsky, particularly those regarding
the unexpected relations of the Ascidians to the vertebrates,
and it would appear from the facts set forth by these emi-
nent observers, as well as Metschnikoff, Ganin, Ussow, and
others, that the vertebrates have probably descended from
some type of worm resembling larval Ascidians more perhaps
than any other vermian type, though it is to be remembered
that certain tailed larval Distome appear to possess an organ
resembling a chorda dorsalis, and farther investigation on
other types of worms may lead to discoveries throwing more
light on this intricate subject of the ancestry of the verte-
brates. At any rate, it is among the lower worms, if any-
where, that we are to look for the ancestors of the Vertebrates,
as the Celenterates, Echinoderms, the Mollusks, Crustacea
and Insects, are too circumscribed and specialized groups to
afford any but characters of analogy rather than affinity.

For example, the cuttlefish, with its ‘“‘ bone,” brain-cap-
sule and highly-developed eye, is, on the whole, more remote
from the lowest vertebrate, Amphioxus, than the Appendi-
cularia or the larval Ascidian.

Certain (three) species of Molgula have been found by
Lacaze-Duthiers to have a nearly direct development, not
producing tailed young. There is a slight metamorphosis,
however, the young having five temporary, long, slender
processes. In Ascidia ampulloides the larva has a tail, no-
tochord and pigment spots, which are wanting in the young
208 ZOOLOG Y.

of several species of Molgula, but it has the five long decid-
uous appendages observed in young Molgule. Among the
compound Ascidians, Botryllus and Botrylloides have tailed
young, while in other forms there is no metamorphosis, de-
velopment being direct.

Order 2. Thaliacea.—On the whole, we may regard this
order, represented by Salpa (Fig. 140), and Doliolwm, as
comprising the more specialized forms of Tunicates. Salpa
is pelagic, one species occurring in abundance off the shores
of Southern New England, while
the others mostly live on the high
seas all over the tropical and sub-
tropical regions of the globe. Late
in the summer our Salpa spinosa
of Otto can be captured in multi-
tudes by the tow-net in Long Island
Sound.

There are in Salpa two kinds of
individuals, 7.¢., the solitary, and
aggregated or chain-Salpx. The
body of the solitary or asexual
form is more or less barrel-shaped,
with a series of circular bands of
muscles, like the hoops of a barrel,
and situated on the inner side of
the outer tunic. The test is trans-

Fig. 140,—Salpa spinosa. Anin- parent, though very thick, while
dividual from a mature chain: the outer tunic lines the cavity of

three-quarter view, enlarged. a,

atrial opening ; 6, mouth ; c, pro- 7 fs
cesses by which the members of the test as in other Tunicates. In

HetOat eons ol uieea: @ ‘he.members, of (this order the oral
gill.—After A, Agassiz, from Ver- aperture of the mantle is at one
rill’s Report. -
end of the body, and the atrial
opening at the opposite end, the minute digestive canal he-
ing but slightly curved, the body-cavity being largely occu-
pied by the pharyngeal or respiratory sac. Moreover, the dor-
sal or heemal side of the body is clearly distinguishable from
the ventral or neural side, as’ well seen in Doliolwm, where
the well-marked tubular heart lies above the digestive organs,

and is directly opposed, as in worms generally, to the nervous

 
STRUCTURE ‘OF SALPA, 209

system, which is situated ventrally between the mouth and
vent. We thus have in these Tunicates a front and hind
end of the body, a dorsal and ventral, as well as a distinct
bilateral symmetry of the body. This is seen in Appendi-
cularia as well as in Doliolum and Salpa, however much
this symmetry may be obscured in the more typical Ascidi-
ans, such as Ascidia, Molgula, Boltenia, ete.

The oral aperture leading into the respiratory sac is large,
being as wide as the body ; the respiratory sac is more com-
plicated than in other Ascidians, and more so than in Doli-
olum, where it is a wide, deep passage, the esophagus at the
hinder end, the sac itself perforated by two rows of bran-
chial slits, four or five slits in each row. In Salpa, how-
ever, the respiratory sac, as described by Brooks, is attached
to the outer tunic, around the edges of the mouth, as in
other Tunicates. There are only two branchial slits, one on
each side ; these are very large, and cover almost the whole
surface of the branchial sac, except the median dorsal and
hemal lines. On the neural side the branchial slit opens
directly into the atrium, the ciliated line where the two
tunics unite being marked by the so-called ‘‘ gill” (Brooks).
In Salpa, according to Brooks, the branchial sac, though
ciliated within, is not so directly concerned in the respiratory
act asin other Tunicates, since respiration is effected largely
by the action of the muscles, which also assist deglutition,
and are the organs of locomotion. These contract rythmi-
cally, with great regularity, and at each contraction the
water is expelled from the branchial sac through the atrial
aperture ; and when the muscles are relaxed, the elasticity
of the test distends the chamber, and a fresh supply is drawn
in through the branchial aperture, the lips of which readily
admit its passage in this direction, while a similar set of
valves allows its passage out of the atrial aperture, but pre-
vents its return.” Thus a chain of individuals move with a
uniform motion, while the solitary individuals and those
which have been set free by the breaking up of a chain, move
by jerks.

The digestive canal is small, curved on itself, the cesopha-
gus leading from the bottom of the pharyngeal or respiratory
210 ZOOLOGY.

sac into a small stomach, the intestine bending back on
itself, and the vent being near the mouth. The entire diges-
tive canal is immovable, the food being driven through the
permanently distended cavity by means of the cilia lining
its inner surface. The great posterior blood-sinus surrounds
the digestive system on all sides, the nutriment being di-
rectly absorbed from its surface and mixed with the blood.

The nervous system is, in adaptation to its locomotive life,
more specialized than in the sessile forms, and highly spe-
cialized organs of sight and hearing are present. The heart
is a short, complicated organ, lying in the sinus-system. — Its
action is often reversed ; the reversal of the beats tending
to clear the sinuses of the blood-disks overcrowding them.
In one species of Salpa Prof. Brooks states that the blood-
channels are in all cases sinuses, which are parts of the body-
cavity and have no special walls, though in species investi-
gated by other writers there are said to be true blood-vessels,
lined with epithelium.

The hermaphroditic, aggregated or chain-salpa differs from
the solitary asexual form in being less regularly barrel-
shaped, and without the two long posterior appendages of
the latter; in the proportions of the different organs, the
two forms are essentially alike.

The young chain is easily perceived in the solitary indi-
viduals in the posterior part of the body, curving around the
digestive organs. When first set free from the body of the
solitary Salpa, the chain is about half an inch long, and the
single, individual Salpe composing it are about two and a half
millimetres in length. They grow very rapidly, and soon
reach their full size, when the chains are often a foot or a
foot and a half long; the individuals composing them when
fully grown being about two centimetres in length. The
chain easily falls apart, and the individuals are capable of
living a solitary life, Huxley stating that the chain-individu-
als of the species observed by him were generally found soli-
tary ; for this reason we should regard the chain-salpe as
individuals, not zootds, being capable of leading an inde-
pendent existence, and with a structure almost identical with
that of the solitary Salpee,
DEVELOPMENT OF SALPA. 211

Brooks has studied the mode of development of the female
and male Salpa spinosa (Fig. 140). When a Salpa-chain is
discharged from the body of the asexual Salpa, each indi-
vidual of the chain contains a single egg which is fertilized

by sperm-cells of individuals belonging to some other chain,
and after passing through the mulberry stage and entering
the gastrula stage, the germ is in most intimate relation
with the body of its parent. The vase-shaped gastrula is
lodged in a brood-sac. Its body-cavity, originally formed by
invagination of the ectoderm, opens directly into the sinus-
stem of its nurse, and the blood now circulates in and out
of the primitive digestive cavity as well as around the out-
side of the embryo. But as the embryo grows and fills the
brood-sac, so that the outer surface of the gastrula becomes
intimately connected with the wall of the brood-sac, the
blood no longer bathes the outside of the embryo.

At this time the “placenta” is formed. Brooks believes
that it originates directly from the blood, ‘by the aggrega-
tion and fusion of its corpuscles,” not being derived from any
of the parts of the parent or embryo. Soon after its appear-
ance it consists of an inner chamber communicating with the
sinus of the nurse, and having no communication with any
of the cavities of the embryo ; its cavity being a part of the
original “‘ primitive stomach” of the gastrula. It finally has
two chambers, an inner and outer one, and Huxley describes*
the foetal circulation in the placenta, a deciduous organ
analogous in function, but by no means homologous in struc-
ture, with the vertebrate placenta.

When the embryo of the solitary Salpa is about four
millimetres (4, inch) long, and while still in the brood-sac of
the parent, the tube analy is to give rise to the chain ap-

~

* “ The blood-corpuscles of the parent may be readily traced enter-
ing the inner sac on one side of the partition, coursing round it, and
finally re-entering the parental circulation on the other side of the par-
tition ; while the fcetal blood-corpuscles, of a different size from those
of the parent, enter the outer sac, circulate round it at a different rate,
and leave it to enter into the general circulation of the dorsal sinus.
More obvious still does the independence of the two circulations be-
come when the circulation of either mother or fcetus is reversed.”
212 ZOOLOGY.

pears within its body. We will now briefly trace the devel-
opment of the chain-salpa, condensing Brooks’s statement.
The aforesaid tube is at first simply a cup-like protrusion of
the outer tunic into the cellulose test which now surrounds
the embryo ; the cavity of the cup is an offshoot from the
sinus-system, the blood passing in and out of it. A small
bud-like protrusion now appears upon the surface of the per-
icardium, and lengthens to form a long rod or stolon, ex-
tending across the sinus and projecting into the cavity of the
cup. At about this period a long, club-shaped mass of pro-
toplasm appears within each of the sinus-chambers of the
tube, and soon after the outer wall is constricted at regular
intervals, each segment being destined to form the outer tu-
nics of the chain-salpe, the constrictions indicating the
bodies of the latter.

By the deepening of these constrictions, each of the
sinus-chambers, which are diverticula from the body-cay-
ity of the solitary Salpa, becomes divided up to form the
body-cavities of the Salpz on one side of the chain. From
the central tube of the stolon arises a row of buds on each
side, which become the branchial and digestive organs of the
Salpee on each side of the chain ; while a similar double row,
upon the other edge, gives rise to the ganglia. The club-
shaped organs within the sinus-chambers become divided up
into single rows of eggs, one of which passes into the body-
cavity of each chain-salpa at a very early period of develop-
ment.

Thus, as Huxley states, budding occurs, not from the outer
wall alone, as in Hydroids and Polyzoa, ‘‘ but, from the first,
several components, derived from as many distinct parts of
the parental organism, are distinguishable in it, and each com-
ponent is the source of certain parts of the new being, and
of these only.” Prof. Brooks adds that while these changes
are going on the constrictions on the surface deepen, the
wall protruding from them, and each is soon seen to mark
off, on each side of the stolon, the body of a young Salpa,
which soon becomes visible to the naked eye. They do not
increase in size gradually from one end of the stolon or tube
to the other, but develop in sets of from thirty to fifty each,
GENERATIONS OF SALPA. 213

and the development of all which are embraced within a set
progresses uniformly ; there are usually three of these sets
upon the tube of an adult solitary Salpa.*

Thus the Salpa reproduces parthenogenetically as in some
Crustacea and insects, and we have here a true case of “alter-
nation of generations.” In 1819 Chamisso stated “that a
Salpa mother is not like its daughter or its own mother, but
resembles its sister, its granddaughter, and its grandmother. +

Immediately after the publication of Brooks’ researches
on Salpa spinosa, those of Salensky on Salpa democratica-
mucronata (a species said to be closely allied if not identical
with S. spinosa) appeared. According to the Russian ob-
server, as stated by Huxley, who adopts his conclusions, the
chain-salpa is a hermaphrodite, and the egg while still in
the ovarian follicle is fertilized, when the oviduct shortening
and widening forms a single uterine sac, the maternal and

* The Development of Salpa, by W. K. Brooks. Bulletin of the
Museum of Comparative Zoology, III., No. 14, Cambridge, 1876. We
have presented quite fully the author’s account of the mode of devel-
opment of the young asexual (his female) Salpa, without, however,
adopting his interpretation of the sexes of the two kinds of individuals
of Salpa ; believing his “female” Salpa to be asexual, and his “ male”
Salpa to be hermaphrodite, with an ovary and testis, as he has not ap-
parently observed the fact of the introduction of an egg into the body
of his ‘‘male” Salpa. On the contrary, it appears to be developed
originally in a true, simple ovary or “ ovarian follicle ;” the testis being
immature and the egg fertilized by sperm-cells of other hermaphro-
dites, in-and-in breeding thus being prevented.

+ This view has been endorsed by Steenstrup, Sars, Krohn, and
others, especially by Leuckart in the following words quoted by
Brooks: “It is now a settled fact that the reproductive organs are
found only in the aggregated individuals of Salpa, while the solitary
individuals, which are produced from the fertilized eggs, have, in
place of sexual organs, a bud-stolon, and reproduce in the asexual
manner exclusively, by the formation of buds. Male and female
organs are, so far as we yet know, united in the Salpz in one indi-
vidual. The Salpe are hermaphrodite.” On the other hand, Todaro,
in an elaborate memoir (1876), considers the Salpa as the synthetic
type of all the vertebrata, presenting features peculiar to each class;
even including the mammals. In his opinion it is an allantoidian ver-
tebrate, developed in a true uterus, the neck of which, after the life of
tlie embryo begins, becomes plugged with mucus,
214 ZOOLOGY.

embryonic parts of the placenta arising, respectively, from
the wall of the ovarian sac and from certain large cells (blas-
tomeres) on the adjacent (hemal) face of the embryo. Thus
the asexual development of the Salpa is like that of the germ-
masses destined to form the Cercariw developed in the body
of the Redia of the Distoma ; and is also like that of the
plant lice (Huxley). This is a reaffirmation and extension
of the original view of Chamisso.

To recapitulate, the life-history of the Salpa is as follows:
There are two kinds of individuals : a, solitary, asexual ; 0,
social, aggregated, and hermaphroditie.

(1.) The solitary, asexual Salpa produces by budding a
chain of hermaphrodite Salpe; the latter produce a fertil-
ized

(2.) Egg, which passes through a—

(38.) Morula and—

(4.) Gastrula stage, contained and growing in a placenta-
like organ, where the embryo is directly nourished by the
blood of the parent, the embryo finally becoming—

(5.) A solitary asexual Salpa.

We thus have a true alternation of generations, like the
sexless Hydroid and its sexual Medusa, the asexual Aphis
and its last brood of males and females; the asexual Redia
and the sexual Distoma ; in all these cases the offspring ()
of the asexual individual (a) is unlike the parent, but the off-
spring (c) of the second generation (8) is like (a) the grand-
parent.

Lastly, while some true worms (e.g., Balanoglossus), and the
mollusks through the cuttle-fish, present strong features an-
ticipating the vertebrate structure, the Tunicata seem more
closely allied to the vertebrates, particularly Amphiozxus, than
any other invertebrate type. ‘To sum up these resemblances :
the larval Ascidian has a notochord, a spinal nerve-cord,
and sets of spinal nerves, like those of lowly organized or em-
bryonic vertebrates, though these are morphologically on the
ventral side of the body, as in other worms; the nervous
cavity and its mode of closure in the embryo is as in the em-
bryo vertebrate ; the respiratory sac of the adult Tunicate
resembles morphologically that of the Amphiowus. Conse-
CHARACTERISTICS OF TUNICATES. 215

quently, while as a matter of fact the Tunicates, as a whole,
resemble, and as it were anticipate, the advent of a verte-
brate, like Amphioxus ; as a matter of pure hypothesis, the
Vertebrates may have descended from animals like Tunicates.
But we need not on this account dissociate the Tunicates from
the worms, remembering their resemblance to Balanoglos-
sus, and even to the Trematodes, and place them near Am-
phiozus and the Vertebrates in general. But we are obliged
to leave them at this point and pass on to the consideration
of the highly specialized worms and Mollusca, Crustacea, and
Insecta, which are circumscribed, closed types of animals
with possibly a vermian ancestry.

Cuass VI.—TUNICATA,

Body usually subspherical, or sac-like, obscurely symmetrical ; some-
times barrel-shaped, bilateral, with a dorsal and ventral symmetry, pro-
tected by a transparent or dense test, containing cellulose, lined within
by a tunic surrounding the body-cavity. Two openings in the test, one
oral, the other atrial ; mouth leading into-a capacious pharyngeal res-
piratory sac, opening posteriorly by an esophagus into a stomach, which
1s provided with a liver, intestine flewed, vent opening near the esophagus,
the feces passing into an atrium or cloacal space, and thence out of the
atrial opening. Nervous system bilateral, forming a double ganglio-
nated chain (Appendicularia), but usually reduced to a single ganglion,
situated within the tunic between the two openings ; a tubular heart, open-
ing at each end, lodged in a sinus-system, and its beatings often reversed,
the blood flowing in and out at either end. Sexes usually united ; in some
forms asexual individuals ; reproducing by eggs or budding partheno-
genetically, or by gemmation.

Order 1. Ascidiacea. — Body sac-like, subspherical, usually sessile,
sometimes stalked, simple or compound, minute individuals
growing in a common mass; the oral and atrial openings
contiguous ; often acomplete metamorphosis. (Appendicu-
laria, Botryllus, Amarcecium, Clavellina, Perophora, As-
cidia, Boltenia, Pyrosoma).

Order 2, Thaliacea.—Body barrel-shaped ; free-swimming, test thick,
hyaline ; with circular muscular bands; respiratory sac
widely open; reproducing by alternation of generations.
(Salpa, Doliolum).
216 ZOOLOGY.

Laboratory Work.—The Tunicates can well be studied only in
a living state ; or sections of hardened Salpe may be made. The
young, caught with the tow-net, should be immediately examined, as
they are very short-lived. Delicate sections of hardened eggs and
larve are made with great difficulty, but are necessary to examine in
connection with the living more or less transparent animals,

Crass VII.—NeEMERTINA (Nemertean Worms).

General Characters of Nemerteans.—The Nemertean
worms occur abundantly under stones, etc., between tide-
marks and below low-water mark ; they are of various col-
ors, dull red, dull green and yellowish, and are distinguished
by the soft, very extensile, more or less flattened, long and
slender body, which is soft and ciliated over the surface,
the skin being thick and glandular. A few forms, such as
Prorhynchus (Fig. 141), live in fresh water.

The mouth forms a small slit on the ventral surface im-
mediately behind the aperture for the exit of the proboscis.
The cesophagus leads to a large digestive tract, ending pos-
teriorly with an anus, and often with short lateral pouches
or cceca.

The nervous system is quite simple, consisting of two
ganglia in the head united by a double commissure; from
each ganglion a thread composed of nerve fibres and ganglion
cells passes back to the end of the body.

While the Nemerteans are much like the flat worms,
most of them approach the Annulata, such as the earth-
worm, in their highly complicated circulatory system, which
is composed of a series of closed contractile vessels. There
are three great longitudinal trunks, one median and two
lateral, and connecting with each other. The blood is col-
orless, with corpuscles. Another feature characteristic of
many Nemerteans is the ‘‘ proboscis,” nothing like it being
found in other worms. Along the back of the head-end is
a special muscular sheath containing the complicated probos-
cis, which is extended through a pore situated above the
mouth. The sheath contains a corpusculated fluid, and
DEVELOPMENT OF NEMERTEANS.

21%

both the sheath and proboscis lie between the commissures

of the ganglia in the front part of the head.

The ovaries and testes are situated in sacs
on each side of the digestive canal. The
sexes are distinct, with the exception of cer-
tain species of Borlasia. The breeding sea-
son is from March to April, while others
spawn all summer. The eggs are ejected
from lateral, pale, minute openings, and the
species may be either oviparous or ovovivipa-
rous. These worms when molested often
break into fragments; in such cases each
piece is capable of reproducing the entire ani-
mal and all its internal organs.

The Nemerteans present a great range of
variation in their mode of development. In
the simplest mode of growth the young is a
ciliated oval form, without any body-cavity.
In others there is a body-cavity, but the larva
is minute and ciliated, and attains the adult
form by direct growth. In still another spe-
cies (Nemertes communis) the embryo is a
ciliated gastrula, but leaves the egg in the
adult form. In others there is a complete
and most interesting metamorphosis. In
several Nemertean worms the egg undergoes
total segmentation, leaving a segmentation-
cavity. The next occurrence is the separa-
tion of a one-layered ciliated blastoderm, the
ectoderm, which invaginates, forming the
primitive digestive cavity, from which the
stomach and cesophagus are formed. The
larva (originally described under the name of
Pilidium) is now helmet-shaped, ciliated,
with a long lash (flagellum) attached to the
posterior end of the body. (Fig. 142.)

After swimming about on the surface of

the sea a while, the Nemertes begins to grow
out from near the csophagus of the Pilidium.

 

Fig. 141. — Pro
rhynchus fluviatilis,
one of the simplest
Nemertean worms.
0, mouth ; @, ceso-
phagus;i, intestine;

7, glands opening
Into the intes-
tine; o, ciliated pits;
x, style in the pro-
boscis situated
above the cesopha-
gus, which ends ina
blind sac at 7, 02,
ovary, with eggs in
different stages of
development. The
worm is externally
ciliated.—After Ge-
genbaur,

On each
218 ZOOLOGY.

side of the base of the velum (v) of the Pilidium ap-
pear two thickenings of the skin, one pair in front,
the other behind; these thickenings push inwards, and
are the germs of the anterior and posterior end of the
future worm. The anterior pair become larger than
the posterior ; the part of
the disk next to the eso-
phagus thickens; at the
same time the alimentary
canal of the Pilidium
grows smaller, and only a
narrow slit remains. The
disks now divide into two
layers, the outer much
thicker than the inner.
Soon the anterior pair of
disks unite, and the head
of the worm is soon formed,
ue when the elliptical outline
tes, with the worm Growing init, 9 veum, Of the flat worm is indi-
Seve ramaniesne of the Nemertean worm.— cated, and appears some-

what as in Fig. 142. The

yolk mass, with the alimentary canal of the Pilidium,
is taken bodily into the interior of the Nemertes, the
Pilidium-skin falls off, and the worm finally seeks the
bottom.

The free-swimming larve of other Nemerteans are very
closely similar to those of the Annelids, so
that from this fact and the nature of the
highly developed circulatory system, the
Nemerteans have been removed from the
neighborhood of the flat worms, and placed
near the Balanoglossus and Gephyrea, a8
well as the leeches.

Fig. 143. — Tetra. Order 1. Anopla.—In this group the pro-
slemina a NeTied boscis is without a style. The species of

Lineus and Meckelia are, in some cases,
very long. Meckelia ingens Leidy is 2} centimetres (an
inch) wide, and attains a length of 4 metres (154 feet). It

 

 
BALANOGLOSSUS. 219

lives under stones at or below low-water mark on the coast
of New England southwards to South Carolina.

Order 2. EHnopla.—In the members of this group the
proboscis is furnished with a style. Representatives of the
order are the species of Tetrastemma (T. serpentinum
Girard, Fig. 143) and of Nemertes. The former is a little
yellowish worm, common under stones on the coast of New
England between high and low-water mark ; it has a slightly
marked head with four dark eye-specks.

Cuass VII.—NEMERTINA.

Body ribbon-like or cylindrical, soft, extensible, ciliated externally, with
a proboscis in a sheath opening by a pore situated above the mouth. Cir-
culatory system approaching that of the Annulata. Sexual organs, duct-
less sacs; either with or without a metamorphosis.

Order 1. Anopla.—Proboscis without a style. (Lineus, Meckelia.)
Order 2. Enopla.—Proboscis with a style. (Nemertes, Malacobdella.)

Crass VIII.—EntTERopnevsta (Whale’s-tongue worms.)

General Characters of the Enteropneusta.—The re-
markable worm, Balanoglossus (Fig. 144), the type of this
class, combines characters peculiar to itself, with features
reminding us of the Nemerteans, Annelids, Tunicata, and
even the vertebrate Amphioxus, while its free-swimming
larva, before its history was known, was supposed to be a
young Echinoderm. It is therefore, like some other worms,
a synthetic or generalized type.

Balanoglossus aurantiacus (Girard, Fig. 144) is a long,
cylindrical, soft, fleshy worm, footless, without bristles, but
with a large, soft, whitish tongue-shaped proboscis in front,
arising dorsally within the edge of the collar surrounding
the mouth. At the beginning of the digestive canal is a
series of sac-like folds, of which the upper or dorsal portion
is respiratory, and separated by a constriction from the lower,
220 ZOOLOGY.

which is digestive, and leads directly to the intestine behind.
This pharyngeal respiratory portion of the digestive canal has
on each side, in each segment, a dorsal sac, the two commu-
nicating along the median line of the body. The dorsal re-
spiratory sacs bear in their walls a delicate chitinous gill-
support or arch. Between the gill-arches, forming numerous
lamelle, are a series of slits, leading on each side to open-
ings (spiracula) situated dorsally. The water passes through
the mouth into each gill-sac, and out by the spiracles. No
nervous system has yet been discovered. ‘There is a dorsal
vessel, which sends branches to the respiratory sacs, and a

 

 

Fie. 144.

 

Fig. 148.—Balanoglossus, not fully mature; magnified.

Fig. 144.—Larva (7ornaria) of Balanoglossus. a,anus; 0, branch of water-vascu-
lar system leading to the dorsal pore /d); e, eye-speck ; g, gills ; A, heart ; i, in-
testine; m, mouth; m/, muscular band from the eye to the water-vascular tube; 0,
cesophagus ; s, stomach or alimentary canal; w, lappet of stomach ; w’, anal band of
cilia ; w, water-system.—After A. Agassiz.
ventral vessel. The worm lives in sand at low-water mark
from Cape Ann to Charleston, 8. C.

The life-history of this worm is most interesting. The
young, originally described under the name of Tornaria,
was supposed to be an Echinoderm larva, though it closely
resembles the larval Gephyrea and Annelides. It is a trans-
parent, minute, ciliated, slender, somewhat bell-shaped form
(Fig. 145), with black eye-specks. When transforming to
the worm condition, a pair of gills arise on sac-like out-
growths of the oesophagus, and afterwards three additional
ANATOMY OF PHASCOLOSOMA, 221

pairs with their external slits arise, somewhat as in Ascidians.
The entire Tornaria directly transforms into the worm, the
transitional period being very short. The body lengthens,
the collar and proboscis develop, and the worm eventually is
as seen in Fig. 144; afterwards the body lengthens, the end
tapering and becoming much coiled.

Cuass VIII.—ENTEROPNEUSTA.

Footless, smooth-bodied worms ; with no bristles, a large exserted soft
fleshy proboscis ; breathing by a serics of dorsal respiratory sacs opening
into the digestive canal, and communicating externally by spiracles ; with
a metamorphosis. (Balanoglossus. )

Ciass IX.—GEpPHYREA (Star-worms).

General Characters of the Gephyreans.—The most acccs-
sible type or representative of this small but interesting group
of worms is a large, smooth, cylindrical worm from six to
ten inches long, which is common in sand or sandy mud at
low-water mark. It is the Sipunculus or Phascolosoma .
Gouldii Diesing, and from its abundance and large size, as
well as the ease with which it can be preserved in spirits, is an
excellent subject for the laboratory, serving as an example of a
very aberrant type of worm as compared with the earth-
worm, or with a Nereis. The body is as smooth as a pipe-
stem, and about that size, unarmed, with a circle of numer-
ous small, slender, simple tentacles around the mouth. On
laying open the body from the head to the extremity (Fig.
146), the body-walls are seen to be lined with fine longi-
tudinal flat muscles, with two unequal pairs of large white
retractor muscles, the anterior third of the body being
highly retractile. The intestinal part is found to float free-
ly, though anteriorly attached to the walls by a few muscu-
lar threads, in the capacious body-cavity, and is usually full
of fine mud. The esophagus is long and slender, situated
between the shorter pair of retractor muscles ; behind the
222 ZOOLOGY.

insertion of the muscles it enlarges, but there is no true
stomach ; it is about twice the length of the body, and is bent

i

 

Fig. 146.—Anatomy of Phascolosoma
Gouldii, cut open, with the flaps pinned
down. @, cesophagus ; a7, two short
muscles ; p7, two long retractor mus-
Clea; v, next to a dark line the right
side of the long cesophagus indicating
the water-vascular tube; 7, nervous
cord ; s, segmental organs ; the long,
twisted intestine returns, ending at a
Natural size.—Drawn by J. 8. Kings-
ley.

and twisted on itself, ending
dorsally in a vent marked by an
external wart, on the anterior
third of the body. Near this
point is situated a pair of large,
long, slightly twisted segmental
organs(s)the free ends of which
flare slightly. The nervous
system (7) forms an cesophageal
ring, and from it passes a well-
marked ventral single cord,
from which at short intervals
pass off small short lateral
nerves. The vascular system
is represented by a circular
vessel lying next to the ner-
vous cesophageal ring, sending
branches into, or at least in
communication with, the cavi-
ties of the tentacles, and from
the ring passing along and in-
timately connected with the di-
gestive tract, forming a ruffle-
like organ (v), ending at a point
nearly opposite the vent (qa).
Prof. Greef finds that the vas-
cular system of Hehiwrus con-
sists of two main vessels, 7. ¢.,
a dorsal and a ventral vessel ;
the former extending along the
alimentary canal, and sending
a branch to the proboscis, where
it divides into two branches,
each uniting with the ventral
vessel. The blood is pale yel-
lowish, with corpuscles. The

blood-system of the Gephyrea, then, is homologous with
DEVELOPMENT OF GEPHYREANS. 223

that of the Annulata. There is in Phascolosoma no true
ovary, but the eggs float in masses in the capacious body-
cavity, the animal being a hermaphrodite.

Phoronis is from the highly developed crown of long,
slender tentacles, and its complicated blood-system, remark-
ably like the Serpule, with which Annelids it is by some
authors associated. The alimentary tube, however, is like
that of Phascolosoma, the intestine folded and ending next
to the mouth. No nervous system has been detected. A
pulsating artery is attached to the upper side of the long
csophagus, and its branches go into the tentacles from an
esophageal ring. <‘‘ Two venous trunks open from the sin-
uses above and behind the arterial branches, and then pro-
ceed downwards, half encircling the esophagus, till they
unite in a large vessel on its neural surface.” (Dyster.)
This worm is minute, about four millimetres in length, and
lives in a tube buried in holes in rocks. It has a strong re-
semblance to a Polyzoon, but connects the Gephyrea with
the true Annelids.

In the Sipunculus-like worm Phascolosoma, and in Pho-
ronts, there is a well-marked metamorphosis, and the larve
are somewhat like those of Annelids. The larva of Phas-
colosoma is cylindrical, the head small, with a circle of cilia,
but there are no arms as in the larva of the Phoronis.

The earliest observed stage of Phoronis* is a free-swim-
ming larva, the body transparent, ciliated, with an umbrella-
like expansion on the head, covering the region of the mouth,
while the end of the body is truncated. At this stage it is a
true Cephalula, like that of Echinoderms and worms. Af-
terwards four projections arise at the end of the body, and
twelve long, arm-like projections grow out, the larval form
now being fully attained. In this condition it was de-
scribed as a mature animal under the name Actinotrocha.

When the Actinotrocha is about to transform into a Pho-
ronis the end of the intestine bends up, opening outward

*In our Outlines of Comparative Embryology this account of the
metamorphosis of Phoronis is by mistake regarded as descriptive of
Sipunculus on pp. 157, 158, under Development. The word Phoronis
on those pages should be substituted for Sipunculus.
224 ZOOLOGY.

near the mouth. The umbrella is gradually withdrawn into
the mouth, so that eventually only a crown of short tooth-
like projections surrounds the mouth. Finally the whole
umbrella is swallowed, the arms at the end of the body dis-
appearing, while the end of the intestine projects far out
from the body behind the mouth. By this time the Phoro-
nis form is clearly indicated, the body being long and slen-
der and the mouth surrounded by a crown of short tentacles,
the end of the intestine being entirely withdrawn within the
body. These changes are rapidly effected. The larva of
Echiurus is formed on the Annelid type.

In Phascolosoma cementarium (Quatrefages), the body is
much shorter than in P. Goul-
dii ; the worm lives in compara-
tively deep water (10 to 50 fath-
oms), in dead, deserted shells,
building out the aperture by a
conical tube of sand. In Sipun-
culus (Syrinx) the tentacles are
fringed or lobed. It does not
occur in American waters.

In Echiurus the intestine ends
at the end of the body, and there
is a circle of bristles at the pos-
terior end, while Bonellia differs
in having an enormous proboscis,
and only a few bristles near the
head. In Bonellia viridis Rol.
of the Mediterranean (Fig. 147),
the proboscis is deeply forked;
the intestine is very long, convo-

Fig. 147.—Bonellia viridis; the luted, and into the cloaca empty
provosse ele eeveal ines... two excretory organs. The ovary
row in the proboscis ; ,¢, digestive is a cord-like organ, which in the
canal; m, mesenterial threads (only a 5
shown on the anterior end of the di- posterior part of the body is fast-
gestive canal); g, organs of excre- . .
tion: c, cloaca; w, oviduct.—After ened to the intestine.
Tacaze-Duthiers; from Gegenbaur. = Ohtoderma nitidulum Lovén
occurs in 20-40 fathoms off the coast of Europe and
Northern New England, The body is long, cylindrical, and

 
CHARACTERISTICS OF GEPHYREANS. 225

covered with slender, firm, calcareous spines. It has no
tentacles, a straight digestive canal, the vent being terminal,
and two internal gill-sacs, with lamellate gills.

Instead of a single nervous cord, as usual in the Gephyrea,
in Chetoderma there are two separate nerve-cords, one on
each side of the body. The Gephyrea were formerly asso-
ciated with the Echinoderms, but the resemblance is only a
superficial one.

Cuass IX.—GEPHYREA.

Body long, cylindrical, smooth, or spiny, or provided with bristles, not
segmented ; usually a large proboscis, but none in Phascolosoma,; vent
either terminal or situated dorsally on the anterior end of the body. A
true blood-system homologous with that of the Annulata. Bisexual or
hermaphroditic ; young of the Annelid type, undergoing a metamorpho-
sis. (Chetoderma, Phascolosoma, Sipunculus, Bonellia, Echiurus, and
Phoronis.)

Laboratory Work.—The common star-worm, Phascolosoma, is one
of the easiest worms to dissect, as it can be readily laid open with
the scissors, and the skin pinned down on the bottom of the dissecting
trough, when the parts can be readily distinguished, its structure being
unusually simple.

Ciass X.—ANNULATA (Leeches, Harth-worms, and
Sea-worms).

General Characters of the Annulata.—This group, rep-
resented by the leeches, earth-worms, and nereids or bristled
sea-worms, tops the series of the classes of worms, and in
the highly specialized, regularly segmented bodies, with their
sense-organs and highly differentiated appendages, stand
nearer the Crustacea and Insecta than any other class of in-
vertebrate animals, their internal organization on the whole
being nearly as complicated.

Reference to the accompanying diagram (Fig. 148) will
show the general relation of the organs of an Annelid to the
body-walls, as compared with corresponding parts, when seen
in sections of Amphioxus and a fish.
226 ZOOLOGY.

The student, in familiarizing himself with the structure
and mode of growth of the leech, the common earth-worm

 

Fig. 148.—Transverse section of a worm, of Amphioxus, and a higher vertebrate
contrasted. @, skin ; 6, dermal connective layer; c, muscles; d, segmental organ ; h,

arterial, and 2, venous blood-vessel ; g, intestine ; Z, notochord.—After Haeckel,

and the Nereis, will obtain a good idea of the essential char-
acteristics of the entire class.

Order 1. Hirudinea.—In the leech (Fig. 149), Hirudo
medicinalis Linn., the type of the first and lower order, the
body is somewhat flattened and divided into numerous short,
indistinctly marked segments, not bearing any bristles or
appendages. The head is small, with no appendages, bear-
ing five pairs of simple eyes, while each end of the body ter-
minates in a sucker. The mouth is armed internally with
three pharyngeal teeth arranged in a triradial manner, so
that the wound made in the flesh of persons to whom the
leech is applied consists of three short, deep gashes radiating
from a common centre. The stomach (Fig. 150) is large,
with large lateral diverticula or lobes, while the intestine is
small. The nervous system consists of a ‘‘ brain” and ven-
tral ganglionated cord.

The vascular system is complicated, consisting of a median
dorsal and a ventral vessel, and two lateral vessels ; all these
anastomose or interbranch, and the blood which courses
through them is red, but is said to contain no corpuscles.

The segmental organs, so characteristic of the Annulata,
are well developed in the leech, consisting of about seventeen
pairs of tubes opening at one end at regular intervals on the
under side of the body, and ending in a non-ciliated coil
(Fig. 149, 7) in the leech, or in the smaller fish-leech, Clep-
sine, open into the venous sinus by ciliated, open mouths.
ANATOMY OF THE LEECH.

 

Fie. 150,

Fig. 149.—Anatomy of the medicinal leech ;
opened from below. a, h, buccal sucker ; 8, infra-
cesophageal ganglion; ¢, e, é, ventral ganglia; d, last
ganglion; 7,7,7,commissures joining the ganglia 5
9,9,9, nerves of sense and locomotion ; 7, esopha-
gus; k, k, k, k, the dilatations or cceca of the stom-
ach ; m, the last of these lobes or ceeca; p,p, intes-
tine lying, as well as the stomach, above the ner-
yous chain; g, rectum; 7,7, 7, segmental organs ;
8, pouch; x, sheath of z, coupling organ; ¢, right
epididymis; A, A, A, spermatic cords; B, B, B,
testes; D, matrix; Z, ZH, ovaries ; w, end of ovi-
duct; v, sucker.

Fig. 150.—Digestive canal of the same ; a, 0, 8,
6, b, ihe stomach and its lateral lobes or ceca; d, ¢,
the two large cceca which extend along each side
of the intestine e, e, 7, rectum.—After Gervais and
Van Beneden.

 

i
228 ZOOLOG ¥.

The lecch is hermaphroditic, while in certain allied forms
(Histriobdella, etc.) the sexes are distinct.

The eggs of leeches are laid in sacs, or, as in Clepsine, the
fish-leech, are covered with a transparent fluid substance,
which hardens and envelops the eggs. The Clepsine re-
mains over the eggs to protect them until they hatch; and
the young, after exclusion, fix themselves to the under side
of the parent, and are thus borne about until they are fully
developed and able to provide for themselves (Whitman*).
The changes in the egg of Clepsine, after fertilization, are
very complicated, and have been described by Whitman.
The egg subdivides into a bilateral mass of cells called a
blastula ; + a gastrula, and finally a “‘neurula” stage, charac-
terized by the formation of a “primitive band” like that of
insect embryos. Soon after attaining the latter stage the
embryo hatches and attaches itself to its parent. The mouth
is then formed, the nervous system{ arises from the ecto-
derm, the segments are indicated, the original number being
thirty-three, the segmental organs develop from the meso-
derm at about the time of hatching, and about six days after
the neurula leaves the egg the eyes become visible. The
innermost germ-layer (endoderm) does not arise until eight
days after hatching, and by this time the digestive tract is
perfected ; the muscular walls of the alimentary canal being
derived from the mesoderm.

*The Embryology of Clepsine. By C. O. Whitman. Quarterly
Journal of Microscopical Science. July, 1878.

+ Whitman states that a morula,as defined by Haeckel, does not
occur in the developmental history of Clepsine, and he states that when
the cleavage process of the egg has been carefully studied it has been
found to result in the production of a bilateral germ or blastula, and
not a morula, ‘‘‘A solid sphere of indifferent cells’ is, to say the
least, a very improbable form, so improbable that its existence may be
held questionable until established by positive evidence. The doubt
is all the more justifiable, as more careful investigation has in many
cases already shown that the so-called mulberry stage is not a morula,
but a blastula or even a gastrula.” (Whitman.)

¢ There is originally a pair of ganglia in each of the thirty-three
segments ; four of these are consolidated into the subassophageal gan-
glia, eight in the ganglia of the disk, and four in the terminal ganglia
of the body. (Whitman.)
EMBRYOLOGY OF LHECHES. 229

The early phases in the embryological development of the
leech (Clepsine) strongly resemble those of corresponding
stages in the vertebrates, according to a number of observers.
The origin of the germ-bands, the presence of the primitive
streak as well as the mode of cleavage, and the formation of
the gastrula* and neurula, show that, up to a comparatively
late period of embryonic life, some worms (Annulata) and
the Vertebrates travel along the same developmental path.
As observed by Whitman, the neurula of the chick, or of
the fish, belongs to the same type as that of Clepsine.
Whether the Vertebrates ever descended from the worms or
any other type of Invertebrates or not, it is a matter of fact
that there is an essential unity in organization and mode of
early development in all the Metazoa, or three-germ-layered
animals, and that the vertebrates are probably only a very
highly specialized group of animals, a branch of the same
genealogical tree from which have sprung the only less
generalized groups or branches of Mollusca, Annulata, and
Arthropoda. Certainly the division of the animal kingdom
into Vertebrates and Invertebrates, however useful, is essen-
tially artificial and misleading. Hence it follows that a
study of the Annulata, as well as other types of worms, must
prove to be fruitful in valuable results, and lead to what
may seem startling conclusions.

Order 2. Annelides.—To this order belong the earth-
worm and sea-worms. The structure of the common earth-
worm (Lumbricus terrestris Linn., Fig. 151) is essentially
like that of the leech. Externally the body is cylindrical,
many-jointed, the joints or segments much more distinct
than in the leech, and internally there are septa, or thin
muscular partitions, between them. The mouth is small,
forming an opening on the under side of the first segment.
On, or next to, the twenty-ninth to the thirty-sixth seg-
ments in Lumbricus terrestris is a flesh-colored swollen
portion called the cingulum or clitellum.

The earth-worm is able to climb perpendicularly up boards,

* Professor His admits that the bird passes through a stage compar-
able with the gastrula of other animals. (Whitman, p. 94.)
230 ZOOLOGY.

etc., as well as over the ground, by minute, short, curved
setee or bristles, which are deeply inserted in the muscular
walls of the body, and arranged in four rows along each side
of the body. The alimentary canal is straight, the stomach
has three pairs of small lateral blind sacs (cceca), and the
intestine, which is externally tubular, contains a thick inter-
nal sac-like fold called a ¢yphlosole.

The segmental organs are highly convoluted tubes, a pair
to each segment of the body, except a few near the head,
and opening internally with ciliated funnels and externally
in minute pores situated along the under side of the body.
The earth-worm is moncecious (hermaphroditic).

The oviducts open in the fourteenth segment, and the
seminal ducts (vasa deferentia) in the fifteenth. Between
the ninth and tenth, and the tenth and eleventh segments
are the four openings of the seminal receptacles (receptacula
seminis). Pairing is reciprocal (see Fig, 151), each worm
fertilizing the eggs of the other; they pair in June and July
inthe night-time. The eggs of the European Lumbricus
rubellus Grube are laid
in dung, a single egg in
a capsule; L. agricola
lays numerous egg-cap-
sules, each containing
sometimes as many as
fifty eggs, though only
three or four live to de-
velop. The development
of the earth-worm is like
that of the leech, the
germ passing through a

2 morula (blastula), gas-

Fig. 151.—Earth-worms pairing. After Curtis. ( ); 5
a, embryo (blastula) soon after segmentation of trula and neurula stage,
the yolk ; b, embryo further advanced ; 0, mouth; 1
c, embryo still older; x, primitive streak ; d, the worm, when hatch-
neurula ; 0, its mouth.—After Kowalevsky. ing, resembling the pa-
rent, except that the body is shorter and with a much less
number of segments.

While the earth-worms are in the main beneficial, from

their habit of boring in the soil of gardens and ploughed

 
ANATOMY OF NEREIS VIRENS. 231

lands, bringing the subsoil to the surface and allowing the
air to get to the roots of plants, they occasionally injure
young seedling cabbage, lettuce, beets, etc., drawing them
during the night into their holes, or uprooting them.

The next and highest type of Annulata is the common
sea-worm of our coast, Nereis virens Sars. It lives between
tide-marks in holes in the mud, and can be readily obtained.
The body, after the head, eyes, tentacles and bristle-bearing
feet have been carefully studied, can be opened along the
back by a pair of fine scissors and the dorsal and ventral red
blood-vessels with their connecting branches observed, as
well as the alimentary canal and the nervous system.

The anatomy of this worm has been described by Mr. F.
M. Turnbull. It is very voracious, thrusting out its pharynx
and seizing its prey with its two large pharyngeal teeth. It
secretes a viscid fluid lining its hole, up which it moves,
pushing itself along
by its bristles and
ligule. At night,
probably during the
breeding season,
they leave their
holes, swimming on
the surface of the
water.

The body consists
of from one hundred
to two hundred seg-
ments. The head
consists of two seg-
ments, the anterior
and buccal, the for- é ;
mer with four eyes of i Bceni (apneradonm). “ey thick cuticular
and two pairs of Yet mh Me, Porches s, which retract, the central
BP erie nT Hist aoc eo} 0up, Vale, ers pasp fo te dora eenaais
ond segment bears
four antenne (tentacular cirri). Each of the other segments
bears a pair of paddle-like appendages (rami), which may be
best studied by examining one of the middle segments which

 
232 ZOOLOGY.

has been separated from the others. or the finer structure
of the body-walls see Fig. 152.

The alimentary canal consists of a mouth, a pharynx
armed with two large teeth and much smaller ones. The
pharynx is entirely everted during the act of taking its food.
Into the cesophagus empty two large salivary glands; the
remainder of the alimentary canal is straight and tubular.
The circulatory system is very complicated ; it is closed and
the blood is red. Both the dorsal and ventral vessels are
contractile, the blood flowing forward in the dorsal vessel,
and backward in the ventral vessel. The two small vessels,
one on each side, in each segment of the body, branch off
from the ventral vessel and subdivide, each sending a branch
to the ventral ramus of the foot of the segment behind, and
another larger branch around the intestine to the dorsal ves-
sel, receiving also, on its way, a vessel from the upper ramus
of the foot of its own segment. ‘‘ Besides these principal
lateral vessels, there are five other vessels on each side
in each segment, coming from the ventral vessel. These
form a loose but regular net-work that surrounds the in-
testine and is connected with five other convoluted vessels,
which join the dorsal vessel. This net-work on the intestine
probably supplies the hepatic organ with material for its
secretion, and very likely may receive nutritive material from
the digested food.” (Turnbull.)

The blood is aérated in the finer vessels of the oar-like feet
and in those situated about the alimentary canal. The
nervous system consists of the ‘‘ brain” and ventral double
ganglionated cord.

The sexes of Nereis virens are separate; the eggs during
the breeding season fill the body-cavity, and pass out through
certain of the segmental organs, which act as oviducts, while
others, probably the more anterior ones, are excretory, like
the kidneys of vertebrates, as urea has been detected in them.
These organs are situated at the base of the lower ramus of
each foot. In some species of the Capitellide Hisig has found
that it is normal for several segmental organs to be present
in a single segment.

While the mode of development of our Nereis has not
LARVA OF ANNELIDS. 233

been studied, the eggs are probably laid in masses between
tide-marks, and the young, when hatched, swim freely on
the surface of the sea. The eggs of other worms are carried
about in lateral pouches. The germ undergoes a cleavage
phase and a gastrula stage. We have observed, in Salem
harbor, the development of Polydora (probably P. ciliatum
Clap.) which may be found in August, in all stages, on the

 

Fig. 153.—A, earliest observed stage of Polydora; B, Cephalula stage; Cand D,
later stages.—Author del.

surface of the water. When first observed (Fig. 153, A) the
body was spherical, with a short, broad intestine, and two
sets of large locomotive bristles. It then passed into the
cephalula state, the head clearly indicated and forming a
large hood. This stage is seen at B, which represents the
under side of the cephalula, the mouth being situated be-
tween the two large ciliated flaps (like the velum of larval
mollusks) of the hood; the body is now segmented, with a
third set of bristles and a band of cilia on the penultimate
segment ; afterwards as at C, dorsal view, additional rings
are present ; the eyes are distinguishable, and there are two
more sets of bristles. The new segments are, as usual in all
234 ZOOLOGY.

articulates, interpolated between the penultimate and ter.
minal segments of the body. At D, the body is many-
jointed, the tentacles well developed, the large temporary
bristles have been discarded, and the worm can be identified
as a young Polydora.

It is probable that Polydora is hatched as a trochosphere
like that of Polyzoa, Brachiopoda and certain mollusks.
The young Terebrellides Stroemiti, and of Lumbriconereis,
are at first trochospheres, 7. e., the free-swimming
germ is spherical, with a zone of cilia, two eye-
spots, and no bristles. Thus the earliest stages of
uaa) Polyzoa, Brachiopoda, Lamellibranchiata, Gastro-

\is/ poda, and even of a Cephalopod (Fig. 220), Nemer-

Fig. 154.— tina, and Annelides are almost identical. Farther
Pe aedioae along in their developmental history, the cepha-
After A. Ag- lula of the Annelides (Fig. 153, A, B, and 155),

is like that of certain Echinoderms (Fig. 155),
Geyphyrea, Polyzoa, Brachiopoda, and Mollusca. It may
here be observed that the free-swimming larvee of these types
of invertebrate animals are the young of more or less seden-

    

 

Fig. 155.—Cephalula stage of Echinoderms and Worms, lateral view. A, Holo-
thurian, B, Star-fish, C, D, of Annelides.

0, mouth ; i, stomach; a, vent ; v, preoral ciliated band, in B, C, D, independent ;
in A surrounding an oral region.—From Gegenbaur.

tary parents. In this way the species becomes widely dis-
tributed through the action of the marine currents, and too
close in-and-in breeding is prevented.

Certain Annelides sometimes multiply by self-division, the
process being called strobilation. This is commonly observed
BUDDING OF ANNELIDS. 235

in the fresh-water worm Wats, also in Syllis and Myrianida,
as well as in Filograna, Protula, etc. Autolycus, a com-
mon worm on the coast of New England, produces one gen-
eration by budding (parthenogenesis). There is, in fact, an
alternation of generations, an asexual Autolycus, giving

Fie. 156.

 

Fie. 157.

Fig. 156.—Clymenella torquata.—After Verrill. ‘ ie
Fig. 157.—Amphitrite cirrata, enlarged twice. 0}, branchia; ¢, uncini, enlarged 500

diameters.—After Verrill.
rise to a brood of males and females, the sexual and asexual
forms being so unlike each other as to have been mistaken
for different species and even genera.

In Syilis and allies certain long, slender processes of the
236 ZOOLOGY.

feet are jointed, thus anticipating the jointed appendages of
the Crustacea and Insects.

The Annelides are divided into two suborders. The first
suborder, Oligocheta, comprises Lumbricus, Nais, etc., while
the second suborder, Chetopoda, embraces Syllis, Autolycus,
Nereis, Polydora, Aphrodite, and Polynoé, which are free-
swimming, while the tubiculous worms which respire by spe-

  

Fie. 158. Fia. 159.

Fig. 158.—Cistenides Gouldii, and its tube.—After Verrill.
Fig. 159.—Huchone elegans, enlarged.—After Verrill.

cial branchie, or gills, on the head, live in tubes of sand or
in limestone shells. Those which live in sand or mud-tubes
are Cirratulus (Fig. 160), Clymene and Clymenella (Fig. 156),
which has no branchie, Amphitrite (Fig. 157), Teredrella,
Cistenides (Fig. 158), Sabella, and Huchone (Fig. 159),
while Protula, Filograna, Serpula and Spirorbis secrete
more or less coiled limestone tubes. The large solid shells
of the Serpulx assist materially in building up coral reefs,
SILURIAN WORM TRACKS. 237

especially on the coast of Brazil. The minute nautilus-like
shells of Spirorbis live attached to the fronds of sea-weeds,
especially the different kinds of Fucus.

     

 

ISG
Moen te
——

gail

Fig. 160.—Cirratulus grandis.—After Verrill.

Many sea-worms are highly phosphorescent, the light emit-
ted being intensely green. The tracks of worms like the
Nereis of to-day occur in the lower Silurian slates; their
bristles, however, were spinulose, as in the larval worms.
Thus the type, though highly specialized, has, unlike most
specialized groups, a high antiquity, the specialized Anne-
lides existing side by side with the generalized Polyzoa and
Brachiopoda. At the present time the Annelides are widely
distributed in the seas of the globe, the tropical forms being
exceedingly abundant among coral stocks and in sponges,
while the arctic seas abound with Annelid life. They also
sparingly exist at great depths, one species of a worm allied
238 ZOOLOGY.

to Clymene, having been dredged by the Challenger Expedi-
tion at the enormous depth of over three miles (about 5000
metres).

Cuass X.—ANNULATA.

Body long, bilaterally symmetrical, cylindrical, consisting of numerous
segments, either unarmed, or more usually provided with sete alone or with
sete and paddle-like appendages (rami). Head simple, with a few simple
eyes, or provided with tentacles (antenna) alone, or with tentacles and bran-
chie. Aneversible pharynx, armed with teeth, usually present. Alimentary
system straight, the tubular stomach sometimes sacculated ; vent always
situated in the last segment of the body. Nervous system well developed,
consisting of a brain and ventral ganglionated cord. Circulatory system
closed, with a dorsal and ventral and lateral vessels connected by anasto-
mosing branches in nearly each segment. A system of numerous paired
segmental organs. Sexes united or separate. Embryo passing through
a cleavage-stage (morula or blastula), gastrula, sometimes a neurula stage,
and after hatching, development is either direct or there is a marked met-
amorphosis, the larva passing through a trochosphere and cephalula
stage.

Order 1. Hirudinea.—Body unarmed, finely segmented ; with a pos-
terior sucker. (Hirudo, Nephelis.)

Order 2. Annelides.—Suborder 1. Oligocheta (Lumbricus, Nais), Sub-
order 2.—Chetopoda (Arenicola, Syllis, Autolycus, Aphro-
dite, Polynoé, Amphitrite, Terebrella, Sabella, Serpula,
Spirorbis).

TABULAR VIEW OF THE CLASSES OF WorMs (VERMES).

 

 

Platyhelminthes.
| Ai? allt |

Annulata.
Brachiopoda.
Enteropneusta. Polyzoa.
aa
Rotatoria.
Tunicata. |
| [ieccenlfate . TE ie Nematelminthes.
|

 

J
\
VERMEs.
ANNULATA. 239

Laboratory Work.—Worms should be dissected at once after be-
ing killed by ether or in alcohol, before the circulation has ceased ;
and transverse sections made to observe the relation of the appendages
to the body-walls, and of the different systems within the body-walls.
The worms should also be hardened in alcohol, and thin sections
stained with carmine be made for histological study. A portion of the
worm can be put in paraffine and sliced by hand with the razor or by
the microtome.

 

< ODE or
> ES

Amphitrite ornata.
CHAPTER@WE
BRANCH VI.—MOLLUSCA.

General Characters of Mollusks.—The characters which
separate this branch from the others, especially the Vermes
are much less trenchant than those peculiar to other groups
of the same rank, and indeed the author only retains the
Mollusks as a special branch in deference to the general
usage of zoologists, believing that the Mollusca are probably
only a highly specialized group of Vermes, where they were
originally placed by Linneus, and bearing much the same
relation to the true worms as do the Rotatoria, the Tuni-
cata, the Brachiopoda, etc. It will be seen from the fol-
lowing account of the mollusks, that they travel along, appar-
ently, the same developmental road as the genuine worms,
and then suddenly diverge, and the divergence is not an ad-
vance in a parallel direction, but if anything the road turns
back, or, to change the simile, the branch of the genea-
logical tree bends downwards. It is, and always has been,
extremely difficult to define the Mollusca, their original
bilateral symmetry being partially effaced in most of the
Gastropoda and in some Lamellibranchs, 7. ¢., in those
Gastropods with a spirally-twisted shell like the snail, or in
fixed bivalve forms like the oyster, etc. The Mollusca are
usually defined as animals with laterally symmetrical, un-
jointed bodies protected by a shell, with a foot or creeping
disk, and usually with lamellate gills, which are folds of the
mantle or body-walls. The special organs characterizing
the Mollusks are the foot and, in nearly all except Lamel-
libranchs, the odontophore; but the foot of a snail is simply
a modification of the under lip, and in reality in many forms
but a specialized ventral surface, as is that of certain non-
segmented worms, like the Planarians and Nemerteans ; while
MORPHOLOGY OF MOLLUSKS. 241

the odontophore or lingual ribbon, often absent, is appar-
ently a modification of the pharyngeal teeth of Annelides.
Mollusks in general have a heart consisting of a ventricle
and one or two auricles, and in this respect they are more
like the Vertebrates than other invertebrated animals; the
highly developed eye of the squids and their imperfect car-
tilaginous brain-box are also special characters analogous to
the eye and brain-box of Vertebrates. Still these features
are not homologous with the corresponding parts in the
Vertebrates, and we have already seen that the Twnicata,
and even the Annelides, are much more closely allied to the
Vertebrata than are the Mollusks, which should, perhaps,
be interpolated between the Brachiopods and Tunicates.
The affinities of the Mollusks are, then, decidedly with the
worms, rather than with the Vertebrates.

That the Mollusca are a highly specialized and compara-
tively modern group is shown by the fact that they began
to abound after the Brachiopods had had their day in the
Silurian seas, and had begun to decay and die out as a type;
the shelled Mollusca supplanted the shelled Vermes or Brachi-
opods. For the upper Silurian period, and those later, the
Mollusks prove useful as geological time-marks, especially in
the Cainozoic period, and so much so that Lyell based his
divisions of Tertiary time mainly on the shells which abound
in Tertiary strata.

Although morphologically the shell of a Mollusk is not
the most important feature of the animal, it is very charac-
teristic of them and of great use in distinguishing the species
of existing, but more especially of fossil, forms; still it is
liable to great variation, and mollusks of quite different
families, and even orders, sometimes have shells much alike,
so that the characters of shells, like many of those drawn
from the peripheral parts of the body, are liable oftentimes
to mislead the student. That the Mollusca are a highly
specialized group is also seen by the enormous number of
existing species, and their wide geographical and bathymet-
rical range. There are about 20,000 living and 19,000
fossil species known, and the group ranks next to the
winged insects, also a comparatively recent and highly
24% ZOOLOGY.

specialized group, in the number of species and indi-
viduals.

CLASS I.—LAMELLIBRANCHIATA (Acephala, Bivalves).

General Characters of Lamellibranchs.—This group is
represented by the oyster, clam, mussel, quohog, scallop,
ete. By a study of the common clam (Mya arenaria Linn.)
one can obtain a fair idea of the anatomy of the entire class,
as it is a homogeneous and well-circumscribed group. The
clam is entirely protected by a pair of solid limestone shells,
connected by a hinge, consisting of a large tooth (in most
bivalves there are three teeth) and ligament (Fig. 161 C 1).
The shells are equivalve, or with both valves alike, but not
equilateral, one end (the anterior) being distinguishable from
the other or posterior, the clam burrowing into the mud by
the anterior end, that containing the mouth of the mollusk.
The hinge is situated directly over the heart, and is there-
fore dorsal cr hemal. On the interior of the shells are the
two round muscular impressions made by the two adductor
muscles and the pallial impression, parallel to the edge of
the shell, made by the thickened edge of the mantle. On
carefully opening the shell, by dividing the two adductor
muscles, and laying the animal on one side in a dissecting
trough filled with water, and removing the upper valve, the
mantle or body-walls will be disclosed ; the edge is much
thickened, while within, the mantle where it covers the el-
liptical rounded body is very thin. The so-called black
head, or siphon, is divided by a partition into two tubes, the
upper, or that on the hinge or dorsal side, being excurrent,
the lower and larger being incurrent—a current of sea-water
laden with minute forms of life passing into it. Each orifice
is surrounded with a circle of short tentacles. This siphon
protrudes through a slit in the mantle-edge, and is very ex-
tensible, as seen in Fig. 161, 4; it is extended, when the
clam is undisturbed, from near the bottom of its hole to the
level of the sea-bottom. In the fresh-water mussel (Unio,
Fig. 162) the two siphonal openings are above the level of
ANATOMY OF THE OLAM. 243

the sandy bottom of the water, when the mussel is plough-

ing its way through the
sand with its tongue-
shaped foot, which is a
muscular organ attach-
ed to the visceral mass,
and is a modification
of the under lip of the
larval mollusk. In the
foot is an orifice for
the passage in and out
of water, and the spurt-
ing of water from the
clam’s hole, observed
in walking over the
flats, is the stream thus
ejected from the foot.
The inflowing currents
of water pass from the
inner end of the mus-
cular siphon below the
lenticular visceral mass
to the mouth, which is
situated at the anterior
end of the shell, oppo-
site the siphon. The
Opening is simple, un-
armed, without lips,
and often difficult to
detect. On each side
of the mouth is a pair
of flat, narrow-pointed
appendages called pal-
pi. The digestive ca-
nal passes through a
dark rounded mass,
mostly consisting of
the liver, covered ex-
ternally by the ovarian

 

 

Fig. 161.—A, Mya arenaria with its siphons ex-
tended; in its natural position in the mud _ head-
end downwards; B, transverse section of the shell,
showing the position of the spring opening the
shell; A, adductor muscle ; the ligament represent-
ed by dark mass ; C, section of Unio, showing the
position of the spring to open the shell; Z, liga-
ment ; D, ideal transverse section of Unio ; /, intes-
tine ; F, foot; V, ventricle; A, auricle; G, gills;
M, mantle ; S, shell.—After Morse.
244 ZOOLOGY.

masses. There is no pharynx armed with teeth as in the
Cephalophora and Cephalopoda, but the esophagus leads to
a tubular stomach and intestine, the latter loosely coiled sev-
eral times and then passing straight backwards along the dor-
sal side under the hinge and directly through the ventricle of
the heart, ending posteriorly opposite the excurrent division

Bae ls

Fig. 162.— Unio complanatus, partly buried in the sand, the siphonal openings
above the level of the river-bottom.—After Morse.
of the siphon. Through the visceral mass passes a curious
slender cartilaginous rod, whose use is unknown, unless it be
to support the voluminous viscera. The gills or branchie are
four large, broad, leaf-like folds of the mantle, two on a side,
hanging down and covering each side of the visceral mass
(Fig. 161, D, a). The heart (Fig. 163) is contained in a deli-
/ \ cate sac, called the pericardium, and is situ-
at ig ated immediately under the hinge ; it consists
infv “at of a ventricle and two auricles ; the former is
| ! easily recognized by the passage through it of
: ‘ the intestine (Fig. 161, D, v), usually colored
Fie. 163.—Heart dark, and by its pulsations. The two wing-
of the clam. TV; like auricles are broad, somewhat trapezoidal

ventricle; A, au- , :
iT of inform. Just behind the ventricle is the so-
Toes called “aortic bulb.” The arterial system 1s
quite complicated, as is the system of venous sinuses, which
can be best studied in carefully injected specimens. At the
base of the gills, however, is the pair of large collective
branchial veins. The kidney, or “organ of Bojanus,” is a
large dusky glandular mass (Fig. 164, 4) lying below but next
ANATOMY OF THE CLAM. 245

to the heart; one end is secretory, lamellar and glandular,
communicating with the pericardial cavity, while the other
is excretory and opens into the cavity of the body. The
nervous system can be, with care and patience, worked out
in the clam or fresh-water mussel. In the clam (Mya arena-

   

 
    

a i ay
y ro 2B 1
\ st ny : wT a
. U TU Uy “Uo er » SN
a oe OOOO 2 NS 2

: —— =
5 14

Fig. 164,—Circulatory system of Anodonta, a fresh-water mussel, after Bojanus.
1, ventricle; 2, arterial system; 14 and 15, veins which follow the border of the
mantle. The veins lead the blood in part directly towards the organ 4, which is the
kidney or ‘‘ organ of Bojanus,”’ and in part to the venous sinus of the upper surface
of this organ; 5, veins which carry back the blood from the gills, the rest going to
the sinus, 6, where arise the branchial arteries; 7, 8, the branchial veins, and 9, the
gill. —From Gervais et Van Beneden.

ria, Fig. 165) it consists of three pairs of small ganglia,
one above (the ‘‘brain”) and one below the cesophagus (the
pedal ganglia) connected by a commissure, thus forming an
cesophageal ring; and at the middle of the mantle, near the
base of the gills, is a third pair of ganglia (parieto-splanch-
nic), from which nerves are sent to the gills and to each
division of the siphon. This last pair of ganglia can be
usually found with ease, without dissection, especially after
the clam has been hardened in alcohol. The ear of the clam
is situated in the so-called foot ; it bears the name of otocyst
(Fig. 166, 7), and is connected with a nerve sent off from the
pedal ganglion. It is a little white body found by laying
open the fleshy foot through the middle. Microscopic ex-
amination shows that it is a sac lined by an epithelium, rest-
ing on a thin nervous layer supported by an external coat of
connective tissue. From the epithelium spring long hairs ;
the sac contains fluid and a large otolith. The structure of
this octocyst may be considered typical for Invertebrates,
246 ZOOLOGY.

The ovaries or testes, as the sex of the clam may be, are
bilaterally symmetrical, blended with the wall of the visce-
ral or liver-mass, and are yellowish. The genital openings

i

 

Fig. 165.—Nervous system of the clam, natural size. @, esophageal ganglion ; 0,
commissure anterior to the mouth; ¢c, pedal commissure ; @, pedal ganglia ; e, parieto-
splanchnic commissures ; f, parieto-splanchnic ganglia ; g, branchial nerves; A, J, pal-
lial nerves ; 4, siphonal nerves ; %, anai nerves ; 2, nerves to the anterior adductor.—
Drawn by W. K. Brooks.

are paired and lie near the base of the foot. Both eggs and
semen arise from the epithelium of the sexual glands. The
eggs pass out into the body-cavity, or accumulate between the
ANATOMY OF THE CLAM. 247

gills, where the embryos in

some species partially develop.

Impregnation probably takes place within the branchial

 

Fig. 166.— Pedal ganglia and oto-
cysts (ears) of the clam, magnified 10
diameters. d, pedal ganglia; e, pedal
commissures; 7, line of union of gan-
glia; g, nerve from commissure to
muscles of foot; i, auditory nerve ; i,
octocyst ; Xk, nerves from ganglia to
the pedal muscles.—Drawn by W. K.
Brooks.

chamber, the spermatozoa being
swept in with the respiratory
current, and coming in contact
with the eggs as they are dis-
charged.

An excellent general view of
the relation of parts to the
body-walls and shell may be
seen by hardening a clam, or
better a fresh-water mussel,
Unio (see Fig. 161, D) in alco-
hol, and then making trans-
verse sections. A section can
be floated off mm water and ex-
amined with a lens. The per-
fect bilateral symmetry of parts
will thus be seen.

The above description will answer for the majority of la-

 

Fig. 167.—Lima hians, flying through the water, its long numerous filaments ex-
tended.—From Brehm’s ‘“‘ Thierleben.”

mellibranchiate mollusks ; in the oyster (Ostrea) or in Ano-
248 ZOOLOGY.

mia the shell is inequilateral, one, usually the lower, being
fixed to some object, and the intestine does not pass through
the ventricle; in Arca the ventricle is double. In Lucina
and Corbis there is but one gill on each side, and in Pecten,
Spondylus and Trigonia the gills are reduced to comb-like

 

Fig. 168.—Mytilis edulis, common mussel. @, mantle; b, foot; c, byssus; d and e,
muscles retracting the foot ; 7, mouth; g, palpi; 2, visceral mass: 2, inner gill; j,
outer gill—From Brehm's ‘‘ Thierleben.”
processes. There are usually no eyes present; in the scallop
(Pecten), however, there is a row of bright shining eyes
with tentacles along the edge of the mantle, and contrary
to the habits of most bivalves, the scallop can skip over the
surface of the water by violently opening and shutting its
shell. Trigonia is also capable of leaping a short distance ;
while Lima (Fig. 167) is an active flyer or leaper. Ostrea and
Cyclas are dicecious, while many mollusks are moneecious or
hermaphroditic. The foot varies much in form, in the
mussel (Mytilus, Figs. 168, 169), Pinna, Cyclocardia (Car-
dita) (Fig. 170), and the pearl-oyster it is finger-shaped and
TYPICAL BIVALVES. 249

grooved, with a gland for secreting a bundle of threads, the
byssus, by means of which it is anchored to the bottom.

 

Fie. 169. Fie, 170.
Fig. 169.—Mytilus edulis, common mussel, with its siphons expanded, and anchored
by its byssus.—After Morse.
Fig. 170.—Cyclocardia novanglie, natural size.—After Morse.
The foot in the quohog (Fig. 171 A, Venus mercenaria),
Mulinia (171 B) and Clidiophora (Fig. 172) is large, these

 

Fig. 171 A.— Venus mercenaria, quohog, natural size, with the foot and siphons.
Fig. 171 B.—Mactra (Mulinia) lateralis, natural size.—After Verrill.

mollusks being very active in their movements. In Glyci-
meris (Fig. 173) the fringe is toothless, much as in the
oyster. In Mactra (Fig. 174) the middle tooth is large, the
250 ZOOLOGY.

corresponding cavity large and triangular. In Savicava and
Panopea (Fig. 175), the pallial line is represented by a
row of dots. In Macoma (Fig.
176) the siphons are very long.
Lithodomus, the date shell,
one of the mussels, bores into
corals, oyster shells, etc. ; the
= common Saxicava excayvates
aa sm chaiprorg trilineata, Da- Holes in mud and soft lime-
stone, as does Gastrochena,
Pholas and Petricola. Many boring Lamellibranchs are
said to be luminous.

 

 

Fig. 173.—G@lycimeris siliqua, natural size.—After Morse.

A very aberrant form of bivalve mollusk is Clavagella, in
which the shell is oblong, with flat valves, the left cemented
to the sides of a deep burrow. The tube is cylindrical,
fringed above and ending below in a disk, with a minute
central fissure, and bordered with branching tubules. In
Aspergillum, the watering-pot shell, the small bivalve shell
is cemented to the lower end of a long shelly tube, closed
below by a perforated disk like the ‘‘rose” of a watering-
pot.

The most aberrant Lamellibranch is the ship-worm, Teredo
navalis Linn. (Fig. 179). This species is now cosmopolitan,
and everywhere attacks the hulls of ships and the piles of
wharves. Itis one of the most destructive to human inter-
ests of all animals. The body is from one to two feet long,
slender, fleshy; it lives in a burrow lined with limestone,
while the shell itself is globular, and lodged at the farther
FORMATION OF PEARLS. 251

end of the tube or burrow. The mantle lobes of the ani-
mal are united, with a minute opening for the foot, which is
small, sucker-like. The heart is not pierced by the intes-

 

Fig. 174.—Mactra ovalis, natural size.—After Morse.

tine, while the siphons are very long and furnished with
two shelly styles.

Pearls are sometimes produced in bivalve shells by particles
of sand getting in between the mantle and the shell, which

   

Fig. 175.—Panopea arctica, natural size.—After Morse.

cause an irritation to the tissues of the mantle and the for-
mation of a nacreous shelly matter around the nucleus.
Excellent pearls are sometimes found in fresh-water mussels,
252 ZOOLOGY.

but the purest occur in the pearl oyster, Meleagrina marga-
ritifera (Linn.), which occurs at Madagascar, Ceylon, the
Persian Gulf, and at Panama. The largest pearl known
measures two inches long, four round, and weighs 1800
grains. All bivalves pass through a metamorphosis after
birth. The development of the
oyster is a type of that of most La-
mellibranchs.

A single oyster may lay about
2,000,000 eggs; they are yellow, and
after leaving the ovary are for the
aks Wo Macoma provima, most part retained among the gills.

In Europe tke oyster spawns from
June till September ; during their growth the eggs are en-
closed in a creamy slime, growing darker as the ‘‘spat” or
young oyster develops.

The course of development is thus: after the segmenta-
tion of the yolk (morula stage), the embryo divides into a
clear peripheral layer (ectoderm), and an opaque inner layer
containing the yolk and representing the inner germinal
layer (endoderm). A few filaments or large cilia arise on
what is to form the velum of the future head. The shell
then begins to appear at what is destined to be the posterior
end of the germ, and before the digestive cavity arises. The
digestive cavity is next formed (gastrula stage), and the anus
appears just behind the mouth, the alimentary canal being
bent at right angles. Meanwhile the shell has grown enough
to cover half the embryo, which is now in the “ Veliger”
stage, the ‘‘velum” being composed of two ciliated lobes in
front of the mouth-opening, and comparable with that of
the gastropod larve. The young oyster, as figured by Salen-
sky, is directly comparable with the Veliger of the Cardium
(Fig. 177). Soon the shell covers the entire larva, only the
ciliated velum projecting out of an anterior end from be-
tween the shells. In this stage the larval oyster leaves the
mother and swims around in the water. According to
Brooks the American oyster becomes free-swimming larva
in six hours after the egg is fertilized. At a later period it
becomes fastened to some rock. The oyster is said to be

 
EMBRYOLOGY OF CARDIUM. 253

three years in attaining its full growth, but is able to propa-
gate at the end of the first year.

The development of the cockle (Cardium pygmeum), is
better known. After passing through a morula and gastrula
stage, the embryo becomes ciliated on its upper surface and
already rotates in the shell. On one side of the oval em-
bryo is an opening or fissure, on the edges of which arise two
tubercles which eventually become the two “sails” of the
velum. The next step is the differentiation of the body
into head and hind body, é.e., an oral (cephalic) and postoral
region. Out of the middle of the head grows a single very
large cilium, the so-called flagellum (Fig. 177 A, fl; v,

yuri

 

Fig, 177.—The deere of the cockle shell (Cardium). A, the trochosphere ;
v, ciliated crown; ji, flagellum. B, Veliger stage, with the shell developing ; 2,
velum ; m, mouth ; Ui, liver lobes; ¢, stomach; i, intestine ; mt, mantle ; 7, foot;
ml, muscle ; 7, nervous ganglion.—After Lovén.

velum). The shell (B, sh) and mantle (mf; ml, muscle)
now begin to form. From the inner yolk-mass are developed
the stomach, the two liver lobes (di) on each side of the
stomach (¢), and the intestine (7). The mouth (m), which
is richly ciliated, lies behind the velum, the alimentary canal
is bent nearly at right angles, and the anus opens behind and
near the mouth. The velum (Fig. 177 B, v) really consti-
tutes the upper lip, while a tongue-like projection (B, f) be-
hind the mouth is the under lip, and is destined to form the
large unpaired “foot,” so characteristic of the mollusks.
The shell arises as a cup-shaped organ in both bivalves and
univalves, but the hinge and separate valves are indicated
very early in the Lamellibranchs. At the stage represented
254 ZOOLOGY.

by Fig. 177 B, the stomach is divided into an anterior and
posterior (pyloric) portion. The liver forms on each side of
the stomach an oval fold, and communicates by a large open-
ing with its cavity; while the intestine elongates and makes
more of a bend. The organ of hearing then arises, and be-
hind it the provisional eyes, each appearing as a vesicle with
dark pigment corpuscles arranged around a refractive body.
The nerve-ganglion (z) appears above the stomach. The
two ciliated gill-lobes now appear, and the number of lobes
increases gradually to three or four. The foot grows larger,
and the organ of Bojanus, or kidney, becomes visible. The
shell now hardens; the mouth advances, the velum is with-
drawn from the under side to the anterior end of the shell.
In this condition the Veliger remains for a long time, its long
flagellum still attached, and used in svimming even after the
foot has become a creeping organ. Latest of all appears the
heart, with the blood-vessels.

Upon throwing off the Veliger condition, the velum con-
tracts, splits up and Lovén thinks it becomes reduced to the
two pairs of palpi, which are situated on each side of the
mouth of the mature Lamellibranch. The provisional eyes
disappear, and the eyes of the adult arise on the edge of the
mantle.

In the fresh-water mussels (Unio) the developmental his-
tory is more condensed. The velum of the embryo is want-
ing or exists in a very rudimentary state. The mantle and
shell are developed very early. The
young live within the parent fastened to
each other by their byssus. The shell
(Fig. 178) differs remarkably from that of
the adult, being broader than long, trian-
gular, the apex or outer edge of the shell
Fig. 178—Young Unio, hooked, while from different points within

—After Morse. project a few large, long spines. So dif-
ferent are these young from the parent that they were sup-
posed to be parasites, and were described under the name of
Glochidium parasiticum. 'They are found in the parent
mussel during July and August.

The ship-worm (TZeredo navalis Linn. Fig. 179) after the

 
DEVELOPMENT OF THE SHIP-WORM. 255

segmentation of the yolk (Fig. 180 A) passes through a
veliger stage, the shell begins to grow, and when five days

 

Fig. 179.—The Ship-worm. ¢, siphons; p, pallets; c, collar; s, shell; 7, foot.

and a half old the germ appears as in Fig. 178, B, the shell
almost covering the larva. Soon after this the velum
becomes larger, and then decreases, the gills arise, the audi-
tory sacs develop, the foot grows, though not reaching to the
edge of the shell, and the larva can still swim about free in
the water. When of the
size of a grain of millet,
it becomes spherical, as
in Fig. 180, C, brown
and opaque. The long
and slender foot projects
far out of the shell, and
the velum assumes the
form of a swollen ring on
which is a double crown :
of cilia. The ears and fig. 180.—Development of the Ship-worm.
eyes develop more, and As;c86 wih is, Yole gues cided: Bt
thegsanimal valternately (oot wae
swims with its velum, or

walks by means of the foot. At this stage Quatre-
fages thinks it seeks the piles of wharves and floating
wood, into which it bores and completes its metamor-
phosis. On the coast of New England the ship-worm
lays eggs in May and probably through the summer.

A

 
256 ZOOLOGY.

Indeed most mollusks spawn in the summer. Species of
Keilia, Galeomma, and Montacuta are viviparous.

Some bivalves get their growth in a single year. The fresh-
water muscles live from ten to twelve years and perhaps
longer; while Zridacna gigantea probably lives from sixty
years to a century. Of about 14,000 known species of
Lamellibranchs, from 8000 to 9000 are fossil.

Cuass I.—LAMELLIBRANCHIATA.

Bilaterally symmetrical mollusks, with two valves lined by the mantle, con-
nected by a dorsal hinge and ligament; no head ; mouth unarmed, with
two pairs of labial palpi; intestine coiled in the visceral mass, usually
passing through the ventricle, and always ending at the posterior, usually
siphon-bearing, end of the body. Foot small, sometimes nearly wanting,
never used asacreeping disk. Usually two pairs of large leaf-like gills on
each side of the visceral mass. Sexes usually in separate individuals.
Embryo passing through a so-called morula, gastrula, and free-swimming
veliger condition.

Order 1. Asiphonia.—Body-wall or mantle without siphons. Shell
sometimes inequivalve. (Ostrea, Anomia, Pecten, Melea-
grina, Mytilus, Arca, Trigonia, Unio, and Anodonta.)

Order 2. Siphoniata.—Siphons present. Shell equivailve. (Chama
Tridacna, Cardium, Venus, Mactra, Tellina, Solen, Clava-
gella, Aspergillum.)

Laboratory Work.—In dissecting the clam, etc., the work should be
performed under water, in a dissecting trough. One shell should be
removed by cutting the adductor by a pointed scalpel, the mantle dis-
sected off and thrown aside, so as to expose the gills, heart, and kid-
neys. In dissecting the nervous system it is well to introduce a probe
into the mouth, and then cut down towards it from above, when the
white supracesophageal ganglia or ‘“‘brain” will be found, and the
other ganglia can thence be traced by the commissures leading from the
‘‘brain.” To find the pedal ganglia and otocyst, cut the foot vertically
in two. The heart can be readily found, and the large vein at the base
of the gills, but the arterial and venous systems can only well be
studied after making careful injections. For ordinary or even quite
fine injections, Sabatier used a mixture of lard and turpentine, some-
times adding a little suet or wax to thicken the paste, which was
colored chrome yellow, vermilion, or blue. For histological exami-
nation he used essence of turpentine, colored as before, or gelatine
SCAPHOPODA. 257%

colored by carminate or ammonia, or Prussian blue dissolved in oxalic
acid, or the precipitate of chromate of lead, or he even injected air
into the vascular cavities. The mollusk should, before injection, be
allowed to slowly die for several days, and the fluids to leave the body.
The injection should be made before decomposition has set in, otherwise
the vessels will burst. Some anatomists plunge mollusks into water
to which has been added alcohol and chlorhydric acid. After remaining
in this fluid for a day or two they can be injected. The arterial system
can best be injected by the aortic bulb, or aorta; the venous system
may be filled from the foot through the aquiferous orifice, by the
adductor muscle, or by any of the large veins. After injection the
animal should be plunged into cold water to hasten solidification and
then placed permanently in alcohol.

Ciass II.—CrpHaLopHora (Whelks, Snails, etc.).

General Characters of Cephalophores.— We now come to
Mollusca with a head, distinguishable from the rest of the
body, bearing eyes and tentacles ; but the bilateral symmetry
of the body, so well marked in the Acephala, etc., is now
in part lost, the animal living in a spiral shell ; still the foot
and head are alike on both sides of the body; while the
foot forms a large creeping flat disk by which the snail glides
over the surface. Moreover, these mollusks have, besides
two pharyngeal teeth, a lingual ribbon or odontophore. In
a shelless land-snail (Onchidiwm) Semper has discovered the
existence of dorsal eyes, constructed, as he claims, on the
Vertebrate type. They are in the form of little black dots
scattered over the back of the creature, and their nerves
arise from the visceral ganglion. Familiar examples of the
Cephalophora are the sea-snails, the sea-slugs, and the
genuine air-breathing snails and slugs.

Order 1. Scaphopoda.—A very aberrant type of the class
is Dentaliwm, the tooth snail, common in the ocean from
ten to forty fathoms deep, on our coast. It lives in a long
slender tooth-like shell, open at. both ends, while the animal
has no head, eyes, or heart, and the foot is trilobed. Owing
to the presence of a lingual ribbon, we would retain it in the
present class, though it is a connecting link between this and
258 ZOOLOGY.

the preceding class, and is, by some authors, regarded as
the type of a separate class (Scaphopoda). The sexes of

 

Fig. 181.—Development of Denialium. A, morula; B, trochosphere; C, annu-
lated larva; D, larva with its rudimentary shell; z, velum ; a, shell; #, young much
farther advanced, the shell or body segmented ; @, rudimentary tentacles ; 7, sub-
cesophageal nerve-ganglia; ff’, digestive canal, and liver (/’) ; the foot protrudes
from the shell. All magnified.—After Lacaze-Duthiers.

Dentalium are distinct. The young isa trochosphere and
E afterwards becomes segmented, and the univalve
shell then appears. (Fig. 182.)

Order 2. Pteropoda.—In these winged-snails
the head is slightly indicated and the eyes are
rudimentary ; while they are easily recognized by
the large wing-like appendages (epipodium), one
on each side of the head. The shell is conical
or helix-like. The species are hermaphroditic.
Cavolina tridentata Lamarck and Styliola vitrea

u Verrill (Fig. 183) are pelagic forms, occurring on
Fig. 182.--Den- the high seas, and are occasionally taken with the

talium Indiano-

rum. Used as tow-net off the southern coast of New England.
shell money. — 7 : é . 5

After Stearns. Limacina arctica Fabr. is of the size of, and
looks like, a sweet pea, moving up and down in the water.

It is common from Labrador to the polar regions.

 
PTEROPODA. 259

A common form, occurring at the surface in harbors
north of Cape Cod, as well as many miles off shore, is Spird-
alis Gouldii Stimpson, the shell of which
resembles a conical Helix. The largest
form on the eastern coast of North
America, extending from New York to the
polar seas, is the beautiful Clione papillon-
acea of Pallas, which has a head and lin-
gual ribbon. It is rare on the coast of
New England, but abundant from Labra-
dor northward. We have observed it
rising and falling in the water between
the floe-ice on the coast of Labrador. It
is an inch long, the body fleshy, with no
shell, the wings being rather small.

The larve of the Pteropods pass through
a trochosphere stage, being, as in Cavolina, vith, —sticr Vou
spherical, with a ciliated crown. It after-
wards assumes a veliger form. Fig. 184 represents a worm-
like, segmented, Pteropod larva, the adult of which is
unknown. In other genera the larve are annulated, resem-
bling the larve of Annelides.

The Pteropods are, in some degree, a generalized type.
They have a wide geographical distribution and
a high antiquity; forms like Cavolina, viz.:
Theca, Conularia, Tentaculites, Cornulites,
etc., dating back to the paleeozoic formation ;
Theca-like forms (Pugiunculus and Hyolithes)
occurring in the primordial rocks.

Order 3. Gastropoda.—This great assemblage
of mollusks is represented by the sea-slugs,
limpets, whelks (Figs. 185-188), snails, and

Fig. 184.—Ptero- Slugs. The head is quite distinct, bearing one,
pee and sometimes, as in the land-snails, two pairs
of tentacles, with eyes either at the bases, or at the ends of
the tentacles, or, as in Trivia californica (Fig. 189), they
are situated on projections near the base of the tentacles.
All the Gastropods move or glide over the surface by the
broad creeping-disk, a modification of the foot of the clam,

 
260 ZOOLOGY.

etc. The head is alike on each side, but posteriorly the body

 

Fic. 185. Fie, 186,

 

Fig. 187. Fig. 188.

Fig. 185.-A Whelk. Buccinum cretaceum. Labrador.

Fig. 186.—A Whelk. Buccinum ciliatum.—After Morse.

Fig. 187.—Strombus pugilis. West Indies.—From Tenney’s Zoology.

Fig. 188.—Pelican’s Foot, Aporrhais occidentalis, Northern New England.—
After Morse.
ANATOMY OF THE SNAIL. 261

is, in those species inhabiting a spiral shell, asymmetrical
and wound in a spiral, the visceral mass extending into the
apex of the shell. In the Nudibranchs (Figs. 195, 197), and
the slug, the body being naked is symmetrical
on each side.

The digestive tract is doubled on itself, the
vent ending on one side of the mouth. In
some Nudibranchs the intestine has numerous
lateral offshoots, or gastro-hepatic branches,
which resemble similar structures in the Plana-
rian and Trematode worms, A heart is always
present, except in the parasitic Hntoconcha,
and sometimes, as in Chiton, Neritina, and
Haliotis, it is perforated by the intestine. In
some genera there are two auricles to the heart,
but as arule but one is present. The Gastro- 8 27 co
pods breathe by gills either free, or contained cuareed rice
in a cavity in the mantle, while in the land-
snails (Pudmonata) the air is breathed directly by a lung-like
gill in a mantle-cavity. The kidney is single. The sexes
are either distinct or united in the same individual.

An excellent idca of the structure of a typical Gastropod
may be obtained by a dissection of Natica (Lunatia) heros.
This isa large mollusk, common between tide-marks from
Labrador to Georgia. On taking it up the student will
notice the large, round, swollen, porous foot, from which
the water pours as if from the ‘‘rose” of a watering-pot.
The shell is large, composed of several whorls, with a small
flattened spire or apex. ‘The aperture is large, lunate in
shape, and can be closed by a large horny door or oper-
culum. (In some mollusks, Natica, Turbo, etc., the oper-
culum is of solid limestone, and small ones are used as “‘eye-
stones,” being inserted in the eye and moved about by the
action of the lids, thus cleansing the eye of irritant particles
of dust, etc.)

The animal should then be placed in a dish of salt water,
and its movements observed. There are but two short,
broad, flattened tendrils, situated on a flap or head-lobe
(prosoma) of the mantle or body-walls. No eyes are present

 
262 ZOOLOGY.

in this species. The mouth is situated in front of the foot
and at the base of the head-lobe, and is bounded by large puck-
ered swollen lips. Cutting down from between the tentacles,
a large buccal mass, the pharynx, is exposed. The mouth-
cavity is roofed with two broad quadrant-shaped, flat thin
teeth, with the free-edge serrated. On the floor of the
mouth lies the ‘‘tongue,” or lingual ribbon (Odontophore),
which is folded once on itself, and is a thin band composed
of three rows of teeth, those forming the two outer rows
long and much curved, those of the central row being stout
and three-toothed. The long slender esophagus is tied
down, near its middle, by the brain (supracesophageal gan-
glion); just behind and beneath which are the two large
salivary glands. The cesophagus suddenly dilates into a
large stomach-like pouch, which is much larger in this
species than in other forms allied to it. It is a sort of crop
or proventriculus (the organ of Delle Chiaje), and rarely oc-
curs in the Gastropods. On laying it open, it may be seen
to be spongy at its anterior end, and posteriorly divided by
numerous transverse partitions into small cavities. The
cesophagus beyond it is again slender, and leads to the
stomach situated on the apex of the shell, partly embedded
in the liver-mass which lies mainly beyond it. From
the stomach the intestine returns to the head, widely dilat-
ing into a large sacculated cloaca, before the free up-
turned vent, which is situated on the right side behind and
to the right of the right tentacle. The nervous system is
represented by a pair of large ganglia, forming the brain
(supracesophageal ganglia) situated just below and behind
the pharynx. The two other ganglia were not traced, but as
a rule in all Cephalophora there are three pairs of ganglia,
7. é., the brain (supracesophageal ganglia) with commissures
passing around the gullet to the pedal or infracesophageal
ganglia, thus forming the esophageal nervous ring, while the
visceral or parieto-splanchnic ganglia are placed at a varying
distance behind the head.

The heart, contained in its pericardial sac, and consisting of
a ventricle and auricle, is situated near the posterior end of
the lungs. The latter are disclosed by laying aside the man-
DEVELOPMENT OF GASTROPODS. 263

tle on the left side of the body behind the head. In a large
Lunatia it is an inch long, with a vein at the base, the gill-
lobes arranged like the teeth in a comb. A smaller, much
narrower lung lies within and parallel to it. The ovary is
situated near the stomach, the ovi-
duct ending near the vent.

The eggs are laid in capsules (Fig.
190, Purpura lapillus and two egg-
capsules) of varied form attached
to rocks or, as in Trochus and the
Nudibranchs, in masses of jelly at- a
tached to sea-weeds or stones. ie ee

As a type of the mode of devel- After Morse.
opment of Gastropods may be cited that of Oalyptrea si-
nensis, represented in our waters by Calyptrea striata Say
(Fig. 191).

 

 

Fra. 193,

Fig. 191.—Calyptrea striata, natural size.—After Morse,

Fig. 192.—Veliger of Calyptrea. f, foot; v, velum ; m, mouth; ce, ectoderm ; /ve,
mesoderm.—After Salensky.

Fig. 193.—Veliger of Culyptrea further advanced. m, mantle ; v, velum ;_f, foot;
h, larval heart ; , permanent ; &, primitive kidney ; s, crosses the shell and rests on
the yolk.—After Salensky.

According to Salensky, after segmentation of the yolk
into eight cells the first four cells or ‘spheres of segmenta-
tion” subdivide, enclosing the yolk-mass, and constituting
the ectoderm or outer germ-layer, the yolk-mass forming the
endoderm. ‘The cells of the outer germ-layer multiply and
form the blastoderm, from which the skin, mantle, and ex-
ternal organs, as well as the walls of the mouth, arise. The

*‘ primitive” mouth of the gastrula is formed by the invagi-
264 ZOOLOGY.

nation of the outer germ-layer ; the sides of the primitive
mouth form the two sails of the velum or swimming organ,
and the embryo now assumes the veliger stage (Fig. 192).
Soon the middle germ-layer (mesoderm) arises, and from
the cells composing it are developed the muscles of the foot
and head, as well as the heart itself. The mantle or body-
wall next develops, and from it the shell, which originates in
a cup-like cavity which is connected only around the edge
with the mantle, being free in the centre. The eyes and ears,
or otocysts, next appear, both organs arising as an infolding
of the outer germ-layer. Hitherto symmetrical, the alimen-
tary canal now begins to curve to the left, and the visceral
sac, or posterior part of the embryo hangs over on one side.
The nervous system is the last to be developed.

Fig. 193 represents the asymmetrical larva with the shell
enveloping a large part of the body, and the ciliated velum
(v) and foot (f) well developed. A temporary larval heart
(2) assumes quite a different position from the heart of the
adult, and the primitive, deciduous kidney (#) is situated in
quite a different place from the permanent kidney. The
further changes consist in a gradual development of the hel-
met-like shell, the disappearance of the temporary larval
structures, and the perfection of the organs of adult life, the:
gills appearing quite late.

The development of Trochus, the top-shell, exhibits more
strikingly the trochosphere and
veliger stages of molluscan life,
and most Gastropods develop
like this form. The velum
at first forms a ciliated ring
(Fig. 194, A, v) on the front end
of the trochosphere. Fig. 194,
B, represents the veliger state.

It thus appears that the tem-

 

Fig. 194.—Larval Trochus. A, tro- :
chosphere ; v, velum ; B, veligerstate; POrary larval or veliger form of

7, ‘mouth ; ; is :
Saleneky. 7? (0Ot} & shell—After the Gastropods are of vermian

origin, the organs last to be de-
veloped, 7. ¢., the foot, shell and lingual ribbon, which are the

distinctively molluscan characters, being the last to appear.
NUDIBRANCH MOLLUSKS. 265

The Nudibranch mollusks, such as the Holis and Doris and
allied forms, breathe by external gills, arranged in bunches
on the back, as seen in Fig. 195, olis (Mon-
tagua) pilata (Gould), a common species on
the coast of New England. In Doris (Fig.
196), they are confined to a circle of pinnate
gills on the hinder part of the back. They are

   

Fie. 195. Fie, 196. Fic. 197.

Fig. 195.—.olis,a Nudibranch.
Fig. 196.— Veliger of Tergipes. v, velum; s, shell ; d, foot; d, otocysts.—After

Schultze.

Fig. 197.—Doris. New England coast.
shelless, and not uncommon just below low-water mark,
laying their eggs in jelly-like masses coiled up on stones and
the surface of sea-weeds. Though the adults are shelless,
the embryos at first have a shell 3
(Fig. 196, s), indicating that
the Nudibranchs have descend-
ed from shelled Gastropods. ‘
a ig. 196 represents the veli- Fig. 198.—Physa heterostropha. Com-
ger of Tergipes lacinulata mon pond-snail.—after Morse.
Schultze, allied to Doris, with its large ciliated velum, and
protected by a deciduous shell, which finally disappears with
the velum.

The air-breathing mollusks, Pulmonata, are represented by
the pond-snails, Physa (Fig. 198) and Limneus (Figs. 199,
200), and the land-snails and slugs. Fig. 205 represents a
slug suspended by a mucous thread from a twig.

The common snail, Helix albolabris Say, is a type of the
air-breathing mollusks. Fig. 201 represents this snail of
natural size, in its shell. The opening to the lung is seen
at a, and at B is represented the heart and lung of the gar-
den slug (Limax flavus). Fig. 202 represents Helix albo-
labris with the shell removed, and the mantle thrown back,

   
266 ZOOLOGY.

showing the lung and heart (/) and the mouth (7m) as well

as the four tentacles, with an eye at the end of the two
upper tentacles. Fig. 203 shows the
brain and pedal ganglia of Helix albola-
bris. The tentacles when carefully exam-
ined may be found to contain both the
eyes (e) with the optic nerve (op) and the
olfactory nerve ‘(Fig. 206, 0). Fig. 204
represents the jaw and lingual ribbon of
Helix.

The eggs of the pond-snails are laid in
transparent capsules attached to sub-
merged leaves, etc. Those of Physa
heterostropha are laid in the early spring,
and three or four weeks later from fifty to
sixty embryos with well-formed shells may

Fig.199.—Limneus ap- be found in the capsule.
eee ent The eggs of Lymneus are laid late in
the spring in capsules containing one or two eggs, and sur-
rounded by a mass of jelly. After passing through the mo-

 

Fig. 200.—Lymnceus elodes, a common pond-snail, showing its variations.—
After Morse.

rula, gastrula, and trochosphere stages a definite veliger
stage is finally attained. 'The foot is large and bilobed, the
mantle and shell then arise, and the definite molluscan char-
acters are assumed, the shell, creeping foot, mantle-flap, eyes,
and tentacles appearing, and the snail hatching in about
twenty days after development begins.

Land-snails and slugs lay their eggs loose under damp
leaves and stones, and development is direct, the young
snail hatching in the form of the adult.
HELIX ALBOLABRIS. 267

 

Fig. 201.

 

Fie. 203.

Fig. 201.—Helia alholabris, natural size. a, orifice of lung. Also the heart and
lung of Limax flavus, magnified.

Fig. 202.—Helix albolabris, with the shell removed to show the heart (7) and the
jung; m, mouth.—This and_ Figs. 201-204 after Morse.

Fig. 203.—Nerve-centres of Helix albolabris.

Fig. 204.—Jaw (lower figure) and side and top view of teeth of lingual ribbon of

Helix albolabris.

 
268 ZOOLOGY.

The group of mollusks represented by Chiton (Fig. 207,
Chiton ruber) have been referred to the worms by Jhering,
on account of the segmented appearance
of the plated shell, and the nervous sys-
tem, which consists of two parallel
cords, connected by several commis-
sures ;* as well as from the fact that the
intestine ends at the hinder end of the
body. The young
is oval when hatch-
ed, and is a trocho-
sphere, having a
ciliated ring in the
Fig, 205.—Slug. Nat- middle of the body
mr na with a long tuft of
large cilia on the head. Afterwards
it becomes segmented, as in Fig. 208,
and is remarkably worm-like, the
limestone plates of the adult corre-
sponding to the primitive larval rings.

Certain Gastropods are useful either
as food or in the arts. In Europe
Littorina littorea, the limpet (Patella See ee on conte
vulgata), the whelk (Buccinum un- 2eTVe: % oMactory nerves.
datum), and the garden-snail (Helix
hortensis) are eaten. The sea-ear
(Haliotis) is roasted in the shell.
The animal of Cymba, Strombus gi-
gas, Turbo, Trochus, and Conus are
eaten in the tropics, while many of
the larger forms are used for fish-
bait. Pearls are sometimes found in

      
    
 

  

Fre. 208. the species of Haliotis and Turbo.
Fig. 20%7— Chiton ruber. . Senieis ae
Hie. 806.2 Segmented larva The beautiful shell of Cassis is made
of Chiton. into cameo pins, and the shell of

Strombus gigas is in the West Indies made into ornaments.

*In Fissurella and Haliotis the two nerve-cords from the pedal gan-
glia are also united by nine transverse commissures, so that here also
we have an approach to the double ganglionated cord of worms.
FOSSIL GASTROPODS. 269

Various shells, such as Marginella, Turbinella, etc., ave
strung in bracelets and armlets by savages. Cyprea moneta,
the cowry (Fig. 209), is used for money, and other shells
are worked into various shapes for wampum or aboriginal
money. Fig. 210 represents an Olivella, used by the Cal-
ifornian Indians as money. Murex and Purpura afford
the Tyrian dye.

While a few Gastropods are pelagic, living upon the high
seas, such as Janthina and the Nudibranch Glaucus, most
of the species are marine and live in all seas; the hardier,
most widely diffused species living between tide-marks, the
more delicate forms in deep water, ranging from low-water

 

Fie. 209. Fia. 210.

Fie. 209.— Cyprea moneta.—After Stearns
Fie. 210.— Olivella biplicata.—After Stearns.

mark to fifty or one hundred fathoms. The abyssal fauna
at the depth of from 500 to about 2000 fathoms has a few
characteristic mollusks.

The largest, most highly colored shells live in the tropics,
while those found in the temperate zones are less beautiful,
and the arctic species are the smallest and dullest in color.
The shells of the eastern coast of North America are
divided into several assemblages, or fauns, the West Indian
or tropical shells, in some cases, reaching as far north as
Cape Hatteras ; between this point and Cape Cod a north
temperate assemblage occurs, and north of Cape Cod the
molluscan fauna is essentially Arctic; many species being
common to the arctic and subarctic seas of the circumpolar
regions.
270 ZOOLOGY.

Marine shells in time date back to the lowest Silurian
period; such are Maclurea, Holopea, Murchisonia, Pleuro-
tomaria, etc., which occur fossil in rocks of the Potsdam
period. The Paleozoic Gastropods are few in number com-
pared with those occurring in Cretaceous and especially Ter-
tiary formations.

The earliest land-snails occurred in the Coal Period ; the
living species are exceedingly numerous, and often much re-
strictéd in range, especially in the tropics; the arctic forms
are very scarce, but four or five species occurring in Green-
land. There are over 22,000 species of Cephalophora known,
of which 7000 are fossil. There are 6500 species of Pulmo-
nata.

Subclass 4. Heteropoda.—The Heteropods form a distinct
subclass, the systematic position of which was for a long
time unsettled; but they are now classed among the Gas-
tropods, being in fact related to the Opisthobranchiata.
Their most striking peculiarity is the form of their foot,
the anterior and middle portions of which are expanded to
form a leaf-like fin, which often bears a sucker ; the pos-
terior part of the foot is much elongated, and, reaching far
backwards, appears to form a tail-like continuation of the
body. The Heteropods are more or less transparent, and
are found swimming upon the surface of the ocean, upon
their backs with their foot upwards. The shell may or may
not be developed ; when present it may be either simple or
coiled. The nervous system resembles closely that of the
true Gastropods, but is more highly developed; the brain
consists of several supracesophageal ganglia forming part of
an esophageal ring. From the brain arise the optic and
auditory nerves. The two large eyes lie in special capsules
near the feelers, and are movable by several muscles. The
otocysts are also large, and contain a large spherical otolith.
The otocysts are lined by an epithelium with bundles of
long vibratile hairs, and with a cluster of sensory cells, form-
ing a macula acustica. Organs of touch have also been
described. The sensory apparatus of the Heteropods are
highly specialized, and have been studied by Claus, Boll,
Flemming, and others. The odontophore 1s well developed ;
THE HETEROPOD MOLLUSKS. Q71

the tongue or radula has highly characteristic teeth, which
serve these rapacious animals to seize their prey. The in-
testine runs straight back from the mouth, and after mak-
ing one or two coils ends in the vent. The excretory organs
open near the anus; the contractile tube opens internally
into the pericardial cavity, and resembles in form and posi-
tion the excretory organ of the Pteropoda. The circula-
tion is imperfect, the blood passing from the wide sinuses
of the body to the ventricle of the heart. From the auricle
springs the aorta, which subdivides into several branches
that open freely into the body-cavity. The circulation can be
easily watched, owing to the transparency of the body. The
aération of the blood is effected partly through the skin,
partly through gills, except in a few species. The branchie
are either thread- or leaf-like ciliated appendages, which
may either be free or enclosed in the mantle-cavity. The
sexes are distinct. The males can be readily recognized by
the large copulatory organ, which hangs free on the right
side of the body. The sexual glands fill the posterior por-
tion of the visceral cavity, and are partly imbedded in the
liver. The oviduct is complicated by the presence of an
albumen gland and a receptaculum seminis. It opens on
the right side of the body.

The Heteropods are exclusively marine, but are found in
all quarters of the world. The number of species is small,
and there are two orders only—the Pterotracheide with a
small or no shell and free gills, and the Atlantide with a
large coiled shell and gills placed in the mantle. Péero-
trachea (Firola) coronata Forsk. is found in the Mediter-
ranean, and on account of its transparency has often been
investigated. The Heteropoda live together in large num-
bers, and feed on small animals.

The eggs are laid in cylindrical strings, which soon break
up into numerous pieces. The segmentation of the yolk is
complete but irregular. The embryo rotates within the egg
during the veliger stage, when it has two distinct sails, or
lobes of the velum, and a ciliated foot with an operculum.
In this form it leaves the egg. The velum enlarges and
forms several divisions. The otocysts, eyes, and tentacles are
272 ZOOLOGY.

then developed. The foot gradually lengthens and forms the
characteristic fin or keel. The velum is meanwhile ab-
sorbed, the operculum (Carinaria), or the operculum and
shell, are thrown off, and the larva gradually assumes the
form and organization of the adult. The close relationship
of the Heteropods and Gastropods is shown by the great
similarity of their larve. Gegenbaur even goes so far as to
include them under the Opisthobranchiata, while von Jher-
ing unites them with Chitons and some other forms under
the name of Arthrocochlide ; for the present it seems best
to retain them as a subclass.

The fossil genus Bellerophon is closely related to the
Atlantide.

Cuass [L—CEPHALOPHORA.

Mollusks with a distinct head, with tentacles, eyes and ears in the head ;
the foot forming a creeping disk , the body either naked or bilaterally sym-
metrical, or enclosed in a spiral shell, and consequently behind the head
asymmetrical. Mouth with pharyngeal teeth and a lingual ribbon (odon-
tophore). Nervous system consisting of four pairs of ganglia, the brain
well developed. The intestine usually ending near the mouth. The heart
with usually a single auricle. Breathing by a single gill, or a lung-like
gill ; a double kidney, but forming a single mass. Sexes united or sepa-
rate. Young passing through a morula, gastrula, sometimes a trocho-
sphere and usually a veliger stage; in the land-snails development
direct.

Subclass 1. Scaphopoda.—No head, several long thread-like tentacles ;
foot long, trilobed. Shell long, conical, open at each end.
A single order Solenoconche. (Dentalium, Siphonodenta-
lium.)

Subclass 2. Pteropoda —Body with two wing-like expansions (velum)
on the front part of the foot, for swimming ; body naked or
shelled. Hermaphroditic. Larva with a velum and shell.
Order 1. Thecostomata (Hyalea, Cleodora, Cavolina), Order
2. Gymnosomata. (Clione).

Subclass 3. Gastropoda.—Order 1, Prosobranchiata (Haliotis, Patella,
Trochus, Littorina, Lunatia, Paludina, Turritella, Ianthina,
Cyprea, Strombus, Cassis, Buccinum, Nassa, Purpura.)
Order 2. Opisthobranchiata. (Bulla, Aplysia, Eolis, Doris.)
Order 3. Pulmonata. (Limnzus, Planorbis, Auricnla, Helix,
Bulimus, Limax).
GENERAL CHARACTERS OF CEPHALOPODS. 273

Subclass 4. Heteropoda.—Naked or shell-bearing mollusks, with a large
prominent head, large movable eyes, and foot with a keel-
like fin, The sexes are distinct. Respiration by gills. Or-
der 1. Pterotracheide.—Pterotrachea, Carinaria, Firoloides,
Order 2. Atlantide.—Atlanta (living) ; Bellerophon (fossil),

Laboratory Work.—The Gastropods are very difficult to dissect, and
it is quite essential that the
specimen be freshly killed, and
that it has died as fully ex-
panded as possible. For this
purpose they should be al-
lowed, as Verrill suggests, to
die in stale sea-water, with
the parts expanded ; when the
animal is nearly dead, the soft
parts can be forcibly held out
by the hand while the animal
is killed by immersion in alco-
hol. Shells and other marine
animals may be obtained by
means of the dredge (Fig.
211), an iron frame with a
net, to which is attached a Fig. 211.—Dredge,
rope and weight.

 

  

Cuass III.—CrpHaropopa (Sguids and Cuttle-fishes).

General Characters of Cephalopods.—The essential
features of this class may be observed by a study of the com-
mon squid, represented by Fig. 212. The following account
is based on dissections of Loligo Pealii Lesueur (Fig.
213). A general view of the body of the entire squid,
with its arms and suckers, is given in the accompanying
illustration (Fig. 212) of Loligo pallida Verrill. The body
is fish-like, pointed behind, and with two broad fleshy fin-
like expansions at the end of the body. The head is dis-
tinct from the mantle or body, and the mouth is surrounded
by a crown of ten long stout pointed tentacles, armed on the
inner side with two rows of alternately arranged cup-shaped
suckers, each sucker being spherical, hollow, with a horny
Q74 ZOOLOGY.

rim inside. Two of the ten arms arise from the under side
of the head ; they are twice the length of the eight others,
and oval at the end. On each side of the head behind the
tentacles are the remarkably large eyes, which, though usual-
ly said to be more like the vertebrate eye than those of any
other invertebrate, are really
constructed fundamentally on
the same plan as the eye of
the snail; differing in several
important respects from that
of a Vertebrate, the resem-
blances between the two being
superficial, while the struc-
ture of the eyes of mollusks is
quite unlike that of Crusta-
ceans, insects or Vertebrates.
The mantle loosely invests
the front of the body next to
\ the head, so that the water
~| passes in around the neck in
order to bathe the gills, which
are quite free from the visce-
4\ ralmass. The mantle is beau-
tifully colored and spotted,
the change of color being due
to the change in form of the
< pigment masses or chromato-
phores, which are under the
\ influence of the peripheral
~< nerves.
The mantle is supported by
ove thind nator size ~atiervera, °™* ® horny “ pen” (Fig. 214), or
pen-shaped thin support, ex-
tending from the upper side of the anterior edge of the
mantle to the end of the body. In the Sepia of the Medi-
terranean Sea this is thick, formed of limestone, and is
called the ‘‘ cuttle-fish bone.”
The organs of digestion consist of a mouth, pharynx,
csophagus, stomach and intestine. The mouth is situated

ODD,
EOS se.

KCoy
ger

 
TS

x

(>
KK

CEA
SNe

OU

CE

Z
\
1\2

 

Fic. 213—Anatomy of common squid.—Drawn by J. 8. Kingsley, from the author’s
dissections.
276 ZOOLOGY.

between the tentacles, and is surrounded by a double fleshy
lip, the outer fold of the lip bearing short fleshy pointed lobes
opposite the spaces between the tentacles. The
pharynx is large, muscular and bulbous, contain-
ing two powerful horny teeth, shaped like a par-
rot’s beak ; the two jaws are unequal, the lower
one the smaller, moving vertically. On opening
the base of the smaller jaw, the lingual ribbon or
odontophore (Fig. 213, po) may be discovered ; it
consists of several rows of teeth, somewhat as in
those of Loligo Hartingit (Fig. 215).

The cesophagus (@) is long and slender, with two
long oval salivary ¢ glands (sg) on each side of it, just
behind the pharynx; the salivary duct leading
into the mouth-cavity. The csophagus has
several internal longitudinal folds, and passes
on one side of the large liver (7) which lies in
front of the stomach, and which is about one
third as long as the whole body, extending back-
wards.

On laying open the stomach, a series of large
semicircular transverse curved valves may be

Fig. 214.- Seen, occupying the anterior third of the stom-
vehi, dogg ach: (s), while beyond are scattered glandular

pallida, dorsal ©

tural
Bidets a masses. The pyloric end opens into an oval

  

 

Verrill. cecum (ca) with about fourteen longitudinal,
thin high ridges. There is no spiral portion attached. The
intestine (i) is straight, thick, and passes forward, ending
in a large vent (a), the edges of

which are lobulated. The ‘‘ink- ae

bag” (Fig. 213, 7) can be recog- ar ep aN a
nized as a purse-like silvery sac,

filled with a dense pigment, the “

sepia, which, like the Chinese i %15.— Part of lingual rib¥ion of
sepia, can be used for drawing, “017? 4¢7#nsits enlarged.

The duct is straight, and is intimately attached to the in-
testine, ending close to the vent, both the vent and open-
ing of the duct of the ink-bag being situated at the bot-
tom of the funnel or siphon (Fig. 213, f), which is a large
ANATOMY OF LOLIGO. Qv7

short muscular canal with a large orifice extending on
the ventral side to the base of the tentacles. Through
this siphon passes excrementitious matter as well as the ink,
and the stream of water which is foreibly ejected from the
siphon, thus propelling the squid through and sometimes
out of the water. i

The two gills (Fig. 213, 9), are large, long slender bodies, at-
tached by a thin membrane to the inner wall of the mantle,
and are quite free from the visceral mass. From the bran-
chial vein arise two rows of lamelle like the teeth of a comb.
At the base of each gill is a flatted oval body, the ‘ bran-
chial heart,” or auricle (Fig. 213, 02). The auricles are quite
separate from the large four-cornered flat ventricle (Fig.
213, h), lying in front of the stomach, and which throws off an
artery from each corner, the aorta being the largest, and
passing parallel to the cesophagus, while a large vein (vena
cava) is sent off to the gills from a circular sinus in the
head.

The nervous system is more complicated than usual in
Mollusca, and is very difficult to dissect. In Loligo Pealii the
highly concentrated nervous system is mainly contained in an
imperfect cartilaginous brain-box (cg), a slight anticipation of
the skull of the Vertebrates. The brain (supracesophageal
ganglion, Fig. 213, d) rests upon the very large optic nerves,
which dilate at the base of the eye, the latter being partially
imbedded in sockets in the brain-box. ‘The visceral (parie-
tosplanchnic) ganglion lies beneath and a little behind the
brain, supplying the nerves for the ears (otocysts), which
are enclosed in the cartilaginous brain-box, and there is a fine
canal leading from the ears to the surface of the body, so
that, as Gegenbaur states, it is possible to distinguish a mem-
branous and a cartilaginous labyrinth, analogous to the
similar parts found in the Vertebrates. The pedal ganglion
(Fig. 213, p) is paired with the visceral ganglion (Fig. 213, r),
but lies in front of it, behind and under the bulbous pha-
rynx, and from it arise ten nerves (¢), which are distributed one
to each arm, passing between the two rows of suckers. Two
smaller ganglia, the superior buccal and inferior buccal, lie
one above and one below the beginning of the cesophagus.
218 ZOOLOGY.

Besides this set of fine cephalic ganglia, there are three pairs
of ganglia belonging to the visceral or sympathetic nerve,
which arise from the visceral ganglion situated among the
viscera ; a single one (the ventricular or splanchnic ganglion)
is situated over the stomach near the origin of the aorta,
which sends a nerve to the coecum, and another accompanies
the aorta; the mate to this ganglion is situated near the
vena cava. A pair of ganglia is situated on the mantle walls
(ganglia stellata), and there are two branchial
ganglia. The kidneys (4) are irregular
branching spongy bodies, in intimate con-
nection with the central nervous system.
The sexes are distinct. The ovary (0) is
large, especially when the eggs are ripe, and
is situated in the end of the body-cavity.
The single oviduct is as in some worms,
separate from the ovary, and in this respect
the Cephalopods approach or anticipate the
Vertebrates, in which the oviduct is also
separate from the ovary. The oviduct
(ov) is a thick straight tube, with a flaring,
deeply-lobed mouth. The eggs,when ex-
truded, are enveloped in a large gelatinous
capsule (Fig. 216), which is secreted by the
large flattened nidamental gland (c) on the
floor of the body-cavity, tied down at each
end by cord-like membranes. Usually there
os Piers, ave two nidamental glands.

peat erry: The earliest phase of development of the egg
of most Cephalopods (Sepia, Loligo) is like that of birds and
reptiles, the yolk undergoing partial segmentation, the blasto-
derm being restricted to a small disk, asin Vertebrates. Even-
tually the blastoderm encloses the whole yolk, the mantle
begins to form, the eyes are at first in-pushings of the outer
germ-layer, and the mouth appears. The digestive tract
originates from a primitive invagination of the outer germ-
layer (ectoderm), as in Amphioxus, Ascidians, worms, and
some Coelenterates. About the tenth day, as observed by
Ussow, at Naples, the gills, siphon or funnel, and arms arise,

 

 
DEVELOPMENT OF CUTTLE-FISHES. 279

und a day later the rudiments of the ears, of the pharynx
and salivary glands ; while a day or two after, the ventri-
cle, auricles, the kidneys, the ink-sac, and liver develop.
Contrary to the usual rule the ganglia arise from the middle
instead of the outer germ-layer. After this the germ grad-
ually develops until it rises above the surface of the egg,
and soon the yolk is partly absorbed and is contained in a

 

Fie. 217. Fig. 218.

Fig. 217.—Embryo of Loligo Pealii. a, a’, a’, a/”, the right arms belonging to
four pairs ; c, the side of the head; e, the eye; /, the caudal fins; 2, the heart; m,
the mantle in which the color-vesicles are already developed and capable of chang-
eee colors ; 0, the internal cavity of the same ; s, siphon.—After Verrill.

ig. 218.—The same as Fig. 217, but more advanced. The lettering in Figs. 217 and
218 the same.—Both after Verrill.
large yolk sac, as in Figs. 217, 218. Finally the young cut-
tle-fish hatches in the form indicated by Fig. 219, and then
swims free upon the surface of the sea.

The development of Cephalopods in general is, then, di-
rect, 7.¢., there is no metamorphosis, the phases of meta-
morphosis seen in most other mollusks not appearing ; but
in an unknown species of cuttle-fish whose eggs were found
floating on the Atlantic, the germ, after the partial segment-
ation of the yolk, assumed a trochosphere condition (Fig. 220)
before the definitive features (Fig. 221) of the cuttle-fish
280 ZOOLOGY.

appeared. The squids or cuttle-fish are very active, some-

times leaping out of the water and falling on the decks of
large vessels. They dart rapidly back-

conn, gatsm, ward. by ejecting the water from their

em BS . \$ siphon or funnel.

el The Cephalopods are divided into

eT Lal two orders, according to the number of

their gills.

Order 1. Tetrabranchiata. — This
group, in which the gills are four in

| number, is represented by the Nautilus,
the sole living representative of a num-
ber of fossil forms, such as Orthoceras,
Gontatites and Ammonites.

Nautilus pompilius Linn. (Fig. 222),
and Nautilus wmbilicatulus are the
only survivors of about 1500 extinct

13, bat farther advanced’ Species of the order.

Order 2. Dibranchiata.— The Di-
branchiates are so called from possessing but two gills, while
the Tetrabranchiates had, as in Nautilus, numerous unarmed
tentacles ; these are now represented by ten (Decapoda). or

  
      

 

Fig. 220. Fie. 221.

Fig. 220.—Development of an unknown cuttle-fish. 2, velum; y, yolk; mé, man-
tle beginning to develop.

Fig. 221.-The same, much farther advanced. a, @, a”, arms; m, mouth ; dr, br,
gills ; 7, funnel; 2, ear ; g, optic ganglion ; mt, mantle, the dotted line ending ina
chromatophore.—After Grenacher.

eight (Octopoda) arms, provided with numerous suckers. To
the ten-armed forms belong Spirula, a diminutive cuttle, with
BELEMNITES. 281

an internal coiled shell. The shells of Spirwla Perontt La-
marck are rarely thrown ashore on Nantucket ; it lives upon

 

Fig. 222.—Pearly Nautilus, VW. pompilius. Seen in section showing
the chambers and siphuacle, Half natural size.--From Tenney’s Zo-
ology.
the high seas. The extinct Belemnites was provided with an
air-cavity (phragmocone) with a straight shell, the ‘‘ thunder-

 

Fig. 223.—Poulpe or Common Octopus of Brazilian Coast.

bolt” fossil. Allied to Loligo and Ommastrephes, are gigan-
tic cuttle-fishes which live in mid-ocean, but whose remains
282 ZOOLOGY.

have been found at sea, or cast ashore at Newfoundland and
the Danish coast; or their jaws occur in the stomach of
sperm whales, as squid of all sizes form a large proportion of
the food of sperm whales, dolphins, porpoises, and other
Cetaceans provided with teeth. The largest cuttle-fish
known is Architeuthis princeps Verrill, the body of which
must be about six and a half metres (nineteen feet) in length,

  
 

and nearly two metres
(five feet, nine inches)
in circumference. The
arms of this species are
unknown. <Architeu-
this monachus Steen-
strup has a body about
two metres (seven feet)
long, and the two long-
er arms seven metres
(twenty-four feet)
long. A still larger
individual was esti-
mated by Verrill to be
in total length about

is , fourteen metres (forty-
‘ig. 224.— Octopus Bairdii, natural size, dorsal and s
lateral view. Gulf of Maine.—After Verrill. me our feet). It is some-

times thrown ashore
on the coast of Newfoundland and Labrador, and in one in-
stance attacked two men in a boat.
The Octopus (Fig. 223) and <Argonauta represent the
eight-armed forms.
PAPER NAUTILUS. 283

Those weird, horrifying creatures, the Octopi, are very soft-
bodied, and live on shore just below or at low-water mark, or
in deeper water. They have no shell or pen. Octopus punc-
tatus Gabb expands 44 metres (14 feet) from tip to tip of the
outstretched arms. They are brought of this size into the
markets of San Francisco, where they are eaten by Italians
and Chinese. An Indian woman at Victoria, Vancouver
Island, in 1877, was seized and drowned by an Octopus, prob-
ably of this species, while bathing on the shore. Smaller spe-
cles on coral reefs sometimes seize collectors or natives, and
fastening t» them with their relentless suckered arms tire
and frighten to death the hapless victim. Octopus Bairdii
Verrill (Fig. 224) inhabits the Gulf of Maine at from fifty
to one hundred fathoms.

The Argonauta, or paper nautilus, has a beautiful, delicate
pearly shell. It lives in the Mediterranean, but in rare cases
has been thrown ashore at New Jersey and Florida. The
animal lives in the shell, but is not permanently attached to
it, the shell not being chambered, and holds on to the
sides by the greatly expanded terminations of two of its
arms, which secrete the shell. The males are very small, not
more than five centimetres (one inch) in length. During
the reproductive season the third left arm becomes larger
and different in form from the others, and becoming encysted
is finally detached from the body, and deposited by the male
within the mantle-cavity of the female, where the eggs in a
way unknown are fertilized by the spermatic bodies. The
free arm was supposed originally to be a parasitic worm, and
was described under the name of Hectocotylus.

The living species of Cephalopods have a wide geographi-
cal range, and a high antiquity, the earliest forms appearing
in the Lower Silurian Period, while the type culminated in
the Liassic, Jurassic and Cretaceous Periods.

Cuass IIIl.—CEPHALOPODA.

Mollusks with the head-lobe divided into arms, usually provided with
suckers ; eyes more highly organized than in any other invertebrates ;
284 ZOOLOGY.

nervous ganglia much concentrated and protected by an imperfect cartila-
ginous capsule ; pharynz armed with two teeth like a parrot’s beak, be-
sides an odontophore. Sexes distinct. Usually development is direct,
with no metamorphosis ; segmentation of the yolk partial, and a primi:
tive streak is present as in birds and reptiles.
Order 1. Tetrabranchiata—With four gills. (Nautilus, living : Or-
thoceras, Goniatites, Ammonites, extinct.)

Order 2. Dibranchiata.—With two gills. (Spirula, Belemnites, ex-
tinct, Sepia, Architeuthis, Loligo, Ommastrephes, Octopus
Argonauta.)

TABULAR VIEW OF THE CLASSES OF MOLLUSCA.

Cephalopoda.

| Cephalophora.

| : Lamellibranchiata.

c

ne
MOLLUSCA.

Laboratory Work.—The cuttles are not easy to dissect. A horizon-
tal section through the head will show the relations of the cartilaginous
capsule to the brain, optic nerves and eyes. The nervous ganglia can
only be traced after tedious dissection. To study the viscera freshly-
killed specimens are quite essential,
CHARTER Vil

BRANCH VII.—ARTHROPODA (CrusTACEANS AND
INSEcTs).

General Characters of Arthropods.—To this group be-
long those Articulates which have jointed appendages, i. ¢.,
antenne, jaws, maxille (or accessory jaws), palpi, and legs
arranged in pairs, the two halves of the body thus being
more markedly symmetrical than in the lower animals. The
body-walls are usually hardened by the deposition of salts,
mostly phosphate of lime, and of a peculiar organic sub-
stance, called chitine. The segments (somites or arthro-
meres) composing the body are usually limited in num-
ber—twenty in the Crustaceans and eighteen in the insects—
while each arthromere is primarily divided into an upper
(tergum), lower (sternum), and lateral portion (pleurum).
These divisions, however, cannot be traced in the head either
of Crustaceans or insects. Moreover the head is well marked,
with one or two pairs of feelers or antenne, and from
two to four pairs of biting mouth-parts or jaws, and two
compound eyes ; besides the compound eyes there are simple
eyes in the insects. The germ is three-layered, and there is
usually a well-marked metamorphosis. The Arthropoda
are nearest related to the worms, certain Annelides, with
their soft-jointed appendages (tentacles as well as lateral
cirri) and well-marked head anticipating or foreshadowing
the Arthropods. On the other hand, certain low parasitic
Arthropods, as Linguatula, have been mistaken for genuine
parasitic worms. So close are the affinities of the Vermes
and Arthropods that they were by Cuvier united as a Branch
Articulata, and while the Annelides and Arthropods may
have had a common parentage, the recent progress in our
knowledge of the worms, has led naturalists to discard the
286 ZOOLOGY.

Articulata of Cuvier as a heterogeneous assemblage of
forms embracing at least three branches of the animal king-
dom, namely, the Vermes,
Tunicata, and Arthropo-
da.

The Arthropoda are di-
vided into two well-de-
fined classes, 7. ¢., the
Crustacea with two body-
. regions, the head-thorax

Fig. 225.—Common Shrimp, Crangon. a, and abdomen (Fig. 225),
cephalo-thorax ; 0, abdomen. endl breathing through
the body-walls or by external gills; and the Insecta (Tra-
cheata), in which the arthromeres are grouped into three
body-regions, 7. ¢., a head, thorax, and abdomen ; and which
breathe by internal air-tubes (trachez).

 

Crass I.—Crustacea (Water-fleas, Shrimps, Lobsters,
and Crabs).

General Characters of Crustaceans.—The typical forms
of this class are the craw-fish, lobster, and crab, which the
student should carefully examine as standards of comparison,
from which a general knowledge of the class, which varies
greatly in form in the different orders, may be obtained.
The following account of the lobster will serve quite as well
for the craw-fish, which abounds in the rivers and streams
of the Middle and Western States.

The body of the lobster consists of segments (somites,
arthromeres), which in the abdomen are seen to form a com-
plete ring, bearing a pair of jointed appendages, which are
inserted between the sternum and tergum, the pleurum not
being well marked in the abdominal segments. The abdo-
men consists of seven segments. One of these segments
(Fig 226 D') should be separated from the others by the stu-
dent, in order to observe the mode of insertion of the legs.
Kach segment bears but a single pair of appendages, and it
a

e

SAL

 

Fig. 226,—External anatomy of the lobster.—After Kingsley.
288 ZOOLOGY.

is a general rule that in the Arthropods each segment bears
but a single pair of appendages. The abdominal feet are
called ‘‘swimmerets ;” they are narrow, slender, divided at
the end into two or three lobes or portions, and are used for
swimming, as well as in the female for carrying the eggs.
The first pair are slender in the female (Fig. 226, B 2 ) and not
divided, while in the male (Fig. 226, Bg) they are much
larger, and modified to serve as intromittent organs. The
sixth segment (Fig. 226, G@) bears broad paddle-like append-
ages, while the seventh segment, forming the end of the
body and called the “telson,” bears no appendages. It rep-
resents the tergum alone of the segment. Turning now to
the cephalo-thorax, we see that there are two pairs of an-
tennex, the smaller pair the most anterior ; a pair of mandi-
bles with a palpus, situated on each side of the mouth ;
three pairs of maxille or accessory jaws, which are flat, di-
vided into lobes, and of unequal size ; two pairs of foot-jaws
(maxillipedes), which differ from the maxille in having gills
like those in the five following pairs of legs. There are thus
thirteen pairs of cephalo-thoracic appendages, indicating that
there are thirteen corresponding segments ; these, with the
seven abdominal segments, indicate that there are twenty
segments in a typical Crustacean. By some authors the eyes
are regarded as homologues of the appendages, but in early
life they are seen to be developed on the first antennal seg-
ment, as they are in the lower Crustacea. They are simply
modified epithelial cells of the body-walls, as in the eyes of
the lower invertebrates. The ears are situated in the smaller
antenne (Fig. 226, a’). In the second or larger antenne are
situated the openings of the ducts (Fig. 226, 1) leading from
the ‘‘ green glands,” while the external openings of the ovi-
ducts are situated, each on one of the third pair of thoracic
feet.

It is impossible, except hy counting the appendages them-
selves, to ascertain with certainty the number of segments
in the cephalo-thorax, the dorsal portion of the segments be-
ing more or less obsolete, but the carapace, or shield of the
head-thorax, may be seen, after close examination, to rep-
resent the second antennal and mandibular segments,
ANATOMY OF THE LOBSTER 289

and is so developed as to cover the other cephalo-thoracic
segments, thus exemplifying, in an interesting way, Audou-
in’s law of the development of one segment or part of a
segment at the expense of adjoining parts or segments ; this
law, so universal in the Arthropods, as well as throughout
the animal kingdom, also applies to the appendages.

The same parts are to be found in the crab, but in a modi-
fied form, owing to the development or transfer of the weight
of the organization headwards ; in other words, the crab is
more cephalized than the lobster; this is seen in the small
abdomen folded under the large, broad cephalo-thorax, and
in the greater concentration headwards of the nervous sys-
tem of the crab.

To study the internal structure of the lobster, the dorsal
surface of the carapace and of each abdominal segment
should be removed ; in so doing the hypodermis or soft inner
layer of the integument is disclosed ; it is usually filled with
red pigment cells. The dorsal vessel, or heart, lies under
the hypodermis of the carapace, this being an irregular
hexagonal mass surrounded by a thin membrane (pericar-
dium) with four valvular openings for the ingress of the
venous blood. The colorless, corpusculated blood is pumped
by the heart backwards and forwards through three anterior
arteries, one median and two lateral, the median artery pass-
ing towards the head over the large stomach, and the two
lateral, or hepatic arteries, passing to the liver and stom-
ach. From the posterior angle of the heart arise two
arteries ; the upper, a large median artery (the superior ab-
dominal), passes along the back to the end of the abdomen,
sending off at intervals pairs of small arteries to the large
masses of muscles filling the abdominal cavity ; the lower is
the second or sternal artery, which connects with one extend-
ing along the floor of the body near the thoracic ganglia
of the nervous cord. ‘The arteries become, at least in the
liver, finely subdivided, forming a mass of capillaries. There
are no veins such as are present in the Vertebrates, but a series
of venous channels or sinuses, through which the blood re-
turns to the heart. There is a large vein in the middle of the
yentral side of the body.
290 ZOOLOGY.

The blood is driven by the heart through the arteries, and
a large part of it, forced into the capillaries, is collected by
the ventral venous sinus, and thence passing through the
gills, where it is oxygenated, returns to the heart.

The gills are appendages of the three pairs of maxilli-
pedes and the five pairs of feet, and are contained in a
chamber formed by the carapace ; the sea-water passing into
the cavity between the body and the free edge of the cara-
pace is afterwards scooped out through a large opening or
passage on each side of the head, by a membranous append-
age of the leg, called the “ gill-scraper” (scaphognathite).

The digestive system consists of a mouth, opening between
the mandibles, an esophagus, a large, membranous stomach,
with very large teeth for crushing the food within the large
or cardiac portion, while the posterior or pyloric end forms
a strainer through which the food presses into the long,
straight intestine, which ends in the telson. The liver is
very large, dark green, with two ducts emptying on each side
into the junction of the stomach with the intestine.

The nervous system consists of a brain situated directly
under the base of the rostrum (supracesophageal ganglion),
from which a pair of optic nerves go to the two eyes, und a
pair to each of the four antenne. The mouth-parts are
supplied with nerves from the infracesophageal ganglion,
which, with the rest of the nervous system, lies in a lower
plane than the brain. There are behind these two ganglia
eleven others; the cephalo-thoracic portion of the cord is
protected above by a framework of solid processes, which
forms, as it were, a ‘‘false-bottom” to the cephalo-thorax ;
this has to be carefully removed before the nervous cord can
be laid bare. A sympathetic nerve arises on each side of the
cesophagus and distributes branches to the stomach.

The nerves of special sense are the optic and auditory
nerves. The eyes are compound, namely, composed of many
simple eyes, each consisting of a cornea and erystailine
cone, connected behind with a long, slender connective rod,
uniting the cone with a spindle-shaped body resting on or
against an expansion of a fibre of the optic nerve, and is
ensheathed by a retina or black pigment mass (Fig. 226 s).
ANATOMY OF THE LOBSTER. 291

Though as many images may be formed in each eye as there
are distinct crystalline cones, yet, as in man with his two
eyes, the effect upon the lobster’s mind is probably that of
a single image.

The lobster’s ears are seated in the base of the smaller or
first antenne ; they may be detected by a clear, oval space
on the upper side ; on laying this open, a large capsule will
be discovered ; inside of this capsule is a projecting ridge
covered with fine hairs, each of which contains a minute
branch of the auditory nerves. The sac is filled with water,
in which are suspended grains of sand which find their way
into the capsule. A wave of sound disturbs the grains of
sand, the vibrations affect the sensitive hairs, and thus the
impression of a sound is telegraphed along the main audi-
tory nerve to the brain.

Organs of touch are the fine hairs fringing the mouth-
parts and legs. The seat of the sense of smell in the Crus-
tacea is not yet known, but it must be well developed, as
nearly all Crustacea are scavengers, living on decaying mat-
ter. Crabs also have the power of finding their way back to
their original habitat when carried off even for several miles.

The two large so-called ‘‘ green glands” situated on each
side within the head-thorax, and having an outlet at the
base of each of the larger antenne, are probably renal in
their functions, corresponding to the kidneys of the verte-
brate animals.

The ovaries and corresponding male glands, are volumi-
nous organs, the testes being white, and the ovaries, when the
lobster is about to spawn, being highly colored, usually pale
green, and the ovarian eggs are quite distinct. The lobster
spawns from March till November ; the young are hatched
with much of the form of the adult, not passing through a
metamorphosis, as in most shrimps and crabs. They swim
near the surface until about one inch long, when they re-
main at or near the bottom.

The lobster probably moults but once annually, during the
warmer part of the year, after having nearly attained its
maturity, and when about to moult, or cast its tegument, the
carapace splits from its hind edge as far as the base of the
292 ZOOLOGY.

rostrum or beak, where it is too solid to separate. The lobster
then draws its body out of the rent in the anterior part of
the carapace. ‘The claw—at this time soft, fleshy, and very
watery—is drawn out through the basal joint, without any
split in the old crust. In moulting, the stomach, with the
solid teeth in the cardiac portion, is cast off with the old in-
tegument ; why the stomach can thus be rejected is explained
by the fact that the mouth, cesophagus, and stomach are con-
tinuous in early embryonic life with the epithelium forming
the outer germ-layer, the mouth and anterior part of the
alimentary canal being the result of an invagination of the
ectoderm. The old skin is originally loosened and pushed
away from the hypodermis, or under-layer, by the growth of
temporary stiff hairs, which disappear after the skin is cast ;
the hairs, however, at least in the craw-fish, do not occur on
the line of the facetted cornea, on the eye-stalk, or on the
inner lamelle of the fold of the carapace over the gill-
opening.

The studentis now prepared to understand the descrip-
tions of the types of the different orders. The Crustacea
may be divided into two series of orders, or two subclasses,
i. e., the normal Crustacea, in large part composed of spe-
cies now living, though containing numerous paleozoic forms,
for which we would propose the term Neocarida ; and the
more generalized type of Crustacea, which abounded almost
to the exclusion of other Crustacea, except the bivalved mi-
nute forms, in the Paleozoic age of the world, and which
may be called the Paleocarida. They are represented by
the fossil Trilobites and Luryptertda, and the only surviving
member, the King-Crab (Limulus).

We will now study the orders of Meocarida, treating of
them as heretofore in the ascending order.

Order 1. Cirripedia.—The barnacles would, at a first
glance, hardly be regarded as Crustacea at all, so much
modified is the form, owing probably to their fixed, para-
sitic mode of life. Indeed they were formerly placed among
the Mollusca, until, in 1836, Thompson found that the
young barnacle was like the larva of other low Crustacea
(Copepoda). The barnacle is, as in the common sessile form

 
ANATOMY OF THE BARNACLE. 293

(Fig. 227), a shell-like animal, the shell composed of several
pieces, with a multivalve, conical movable lid, having an
opening through which several pairs of long, many-joint-
ed, hairy appendages are thrust,
thus creating a current which sets
in towards the mouth. The com-
mon barnacle (Balanus dalanoi-
des Stimpson) abounds on every
rocky shore from extreme high-
water mark to deep water, and
the student can, by putting a
group of them in sea-water, ob-
serve the opening and shutting
of the valves and the movements Fig. 227.—A barnacle. Balanus
of the appendages or “cirri.” ?” eatus, Natura size

The structure of the barnacle may best be observed in
dissecting a goose barnacle (Lepas fascicularis Ellis and
Solander, Fig. 228). This barnacle consists of a body (capit-
ulwm) and leathery peduncle. There are six pairs of jointed
feet, representing the feet of the Cyclops (Fig. 236). The
mouth, with the upper lip mandibles (B, 1), and two pairs
of maxille, will be found in the middle of the shell. A
short csophagus (according to J. 8. Kingsley, whose ac-
count we are using) leads to a pouch-like stomach and tubular
intestine. This form, like most barnacles, is hermapnroditic,
the ovary (4, 0)lying at the bottom of the shell, or in the
pedunculated forms in the base of the peduncle, while the
male gland (¢) is either close to or some distance from the
ovary. ‘There is also at the base of the shell, or in the pe-
duncle when developed, a cement-gland, the secretion of
which is for the purpose of attaching the barnacle to some
rock or weed.

While the sexes are generally united in the same indi-
vidual, in the genera bla (Fig. 229) and Scalpellum (Figs.
230, 231), besides the normal hermaphroditic form, there
are females, and also males called ‘“‘complementary males,”
which are attached parasitically both to the females and
the hermaphroditic forms, living just within the valves or
fastened to the membranes of the body. These comple-

 

 
294 ZOOLOGY,

mental males are degraded, imperfect forms, with sometimes
no mouth or digestive canal. The apparent design in nature
of their different sexual forms is to effect cross fertilization.
The eggs pass from the ovaries into the body-cavity, where

 

Fig. 228.—Anatomy of Lepas fascicularis. A. c, six pairs of legs or cirri ; f, fila-
mentary appendages ; m, mouth; s, stomach; A, openings of the liver (7) into the
stomach, which is represented as laid open; i, intestine; a, vent ; ¢, testis ; v, vasa
deferentia, one cut off ; p, male appendage ; 0, ovary ; e, adductor muscle connecting
the two bagal valves; vs, scutal valve ; vc, carinal valve ; vt, tergal valve. Enlarged
twice.

B. 1, palpus; 2, mandibles ; 8 and 4, first and second maxille.

CG. Nervous system. s, brain, sending the optic nerves to the rudimentary eye (¢),
each optic nerve having an enlargement near the eye, é. ¢., the ophthalmic ganglion (0);
between o and a are the nerves which go to the peduncle; a, nerve sent to the ad-
ductor sculorum ; @, commissure between the supra- and infracsophageal ganglia (7) ;
C, ¢, ¢, ¢, €, c, nerves to each of the six feet. Enlarged four times.—After Kingsley.

they are fertilized, and remain for some time. They pass
through a morula condition, a suppressed gastrula or two-

layered state, and hatch in a form called a Nauplius, from
the fact that the free-swimming larva of the Entomostraca
EMBRYOLOGY OF BARNACLES. 295

was at first thought to be an adult Crustacean, and described
under the name of Nauplius. The Nauplius

of the genuine barnacles (Fig. 232) has three

pairs of legs ending in long bristles, with a

single eye, and a pair of antenne, the body

ending in front in two horns, and posteriorly

in a long caudal spine. After swimming

about for a while, the Nauplius attaches it-

self to some object by its antenne, and now a pig. 999 — ora.
strange transformation results. The body is Compicmen ary
enclosed by two sets of valves, appearing as if After Darwin.
bivalved, like a Cypris (Fig. 233); the peduncle grows out,

au
eit
ae rici

sant

ul
i

Bath
iu
TTA a
a
Hcy anyaty H
iunyay
naman

 

Fig. 231. —Comple-
mentary male of Scal-
pellum regium, greatly
enlarged. — After Wy-
ville-Thompson,

 

Fig. 230.—Scalpellum regium. a, complementary
Tale; lodged within the valves, — After Wyville-
Thompson,
296

ZOOLOGY.

concealing the rudimentary antennz, and the feet grow
smaller, and eventually the barnacle-shape is attained. The

 

Fig. 282.—Nauplius of Balanus bal-
anoides, much enlarged.

 

Fig. 233.—Pupa of Lepas, much en-

larged.—After Darwin.

common barnacle (Balanus balanoides) attains its full size,
after becoming fixed, in one season, ¢. e., between the first of

April and November.

Still lower than the genu-
ine barnacles are the root-bar-
nacles or Rhizocephala, repre-
sented by Peltogaster (Fig.
234) and Saccaulina (Fig. 235),
in which the young is a more
simple Nauplius form, like
the young of the Hntomostra-
ca, while the adult is a sim-
ple sac, containing no diges-
tive organs or nerves. From
the feet of the young grow
out, after the animal becomes
sessile, long root-like fila-
ments, which ramify in the
body of the crab, to which
these animals are firmly an-
chored. We can conceive of
no lower, more degraded Crus-
tacean than these root-barna-

 

Fig. 224.— Peltogaster curvatus, en-
larged 13 times, beneath the larva or Nau-
plius of Parthenopea, enlarged about 200
times.—From Brehm’s Thierleben.

cles, the only signs of life being the powerful contractions
of the roots and an alternate expansion and contraction of
ENTOMOSTRACA. 297

the body, forcing the water into the brood-cavity, and again
expelling it through a wide orifice. These root- barnacles
recall the Trematode worms, though the
latter are much more highly organized.
fF) An allied form (Cryptophialus minutus)
undergoes the larval or Nauplius stage
in the egg, hatching in the pupa condi-
Fig. 235.—Sacculina car. tion, while another form (a species of

cini, natural size. a, base 2 . ]
Of root; B, opening for exit © Cotogaster ?) also leaves the egg in the

of cage, Prom Brebm’s pupa form.

Order 2. Entomostraca (Water-fleas).
—The type of this group is Cyclops (Fig. 236, C. quad-
ricornis, see also Fig. 237) in which the body is pear-
shaped, with a single bright eye in
the middle of the head ; two pairs
of antenne, used for swimming as
well as sense-organs ; biting mouth-
parts, and with short legs. The
sexes are distinct, the females swim-
ming about with two egg-masses
attached to the base of the ab-
domen. The young isa Nauplius,
much like that represented in Fig.
234, the mouth-organs, the legs
and abdominal segments arising
after successive moults, until the
adult form is attained. Allied to
Cyclops is Canthocamptus caver-
narum Packard (Fig. 238), an eyed
species, living in Willie’s Spring, in
Mammoth Cave.

Many Lntomostraca are parasitic,
and consequently undergo a retro-
grade development, losing the
jointed structure of the body, the
appendages being more or less , Hig. 286—Cyclont. ¢, eves 2
aborted, while the body increases Clark.
greatly in size. Such are the fish-lice, represented by the
Lernea of the cod.

 

 
298

ZOOLOGY.

In Lerneonema radiata Steenstrup and Liitken (Fig. 239),
we find the lowest term in the series of degradational forms

 

Fig.

237.—Intestine and testis (¢) of a copepod
(Plenvoma), side view. @, esophagus ; v, stomach ;

h, blind sac leading from the stomach ; a, intes:
tine; c, heart ; vd, coiled vas deferens.—Alter Claus,
from Gegenbaur..

of this order. The
mouth-parts are here
converted into five
roots, radiating from
the head; the body
is not segmented, and
ends in two long egg-
masses.

In Penella (Fig.
241) the body is cord-
like, buried in the

flesh of the sun-fish or sword-fish, etc., the females having

a long, string-like ap-
pendage. The speci-
men figured was taken
from a sword-fish off
Portland, Maine.

In Lernea branchia-
lis Linn. of the gills of
the cod, the body is
thicker, the root-like
appendages grow deep
into the flesh of its
host, like twisted and
gnarled roots, while the
shapeless sac-like body
is filled with eggs.

In Actheres, we as-
cend a step higher in
the perfection of or-
gans; the creature is
attached by a pair of
jaws which unite to
form a sucker, the an-

tenne are present, though rudimentary, while
the abdomen is faintly segmented.

Fig. 238.—Canthocamptus caver-

enlarged.

Perey

 

 

i 4

 

 

 

 

Nee eed

 

 

Fig
narum of Mammoth Cave, much Fish - Spies of

- %39.—

the Menhaden,
twice enlarged.
—After Verrill.

A. Carpentert Packard

(Fig. 240) lives on the trout in Colorado,
CLADOCERA.,

299

The highest members of the group of sucking Entomo-
straca are Caligus and Argulus, in which the body is seg-

mented, with antenne and _ free
mouth-parts and legs; the latter
genus with compound eyes. Cali-
gus curtus Miiller lives on the cod,
and Argulus alose Gould on the
alewife.

Order 3. Branchiopoda. — This
order includes such Crustacea as
im the higher forms breathe by
rather broad feet. There is a con-
siderable range of
form from the
Ostracoda, repre-
sented by Cypris,

are much as in Cy-

 

in which the feet Fig. 240.—Actheres of the trout.

 

clops, through Daphnia and Sida (Fig. 242)
which represent the Cladocera, up to the
Phyllopods. The suborder of Ostracoda
(Cypris) are bivalved, the shell often thick.
They have two eyes, two pairs of antenne,
a pair of mandibles with a jointed feeler
(palpus) and a gill, and four pairs of feet,
the second pair often carrying a small gill.
The shells of certain species allied to Cypris
abound in the lowest Silurian strata. The
species live in fresh-water pools and in the
ocean at various depths. They undergo no
metamorphosis, the youngest stage being a
shelled Nauplius.

The suborder Cladocera is represented by
fresh and salt-water species. The higher
forms are Sida and Daphnia. They are
called water-fleas from their jerky motions.
The eggs of Daphnia are borne about by

g
the sword-dsh, female, the back under the shell.

Fie 241.—Penella of the females in so-called brood-cavities on

There are two

sorts of eggs, 1. ¢., the ‘‘summer” eggs, which are laid by
300 ZOOLOGY.

asexual females, the males not appearing until the autumn,
when the females lay the fertilized ‘‘ winter” eggs, which are
surrounded by a very tough shell. Dohrn observed the de-
velopment of the embryo in the summer eggs. At first the
embryo has but three pairs of appendages, representing the
antennx and two pairs of jaws. It is thus comparable with
the Nauplius of the Copepodous Hntomostraca, and thus the

 

Fig. 242.—Sida. ¢, egg in brood-sac.

Cladocera may be said to pass through ‘a Nauplius stage in
the egg.

Afterwards more limbs grow out, until finally the embryo
is provided with the full number of adult limbs, and hatches
in the form of the mature animal, undergoing no farther
change of form.

The members of the suborder Phyllopoda are more highly
developed than any of the Crustacea mentioned, and differ
from other groups in the fact that the body is usually partly
covered by a large carapace (the mandibular segment greatly
developed), which is sometimes bent down, and opens and
shuts by an adductor muscle, so that they resemble bivalve
PHYLLOPODA. 301

Mollusca But they are especially characterized by the
broad leaf-like feet, subdivided into lobes, and adapted for
breathing as well as
for swimming. The
thorax merges insens-
ibly into the abdomen.
The number of body-
segments varies great-
ly, there being six-
teen in Limnetis, the
simplest form, and
sixty-nine in Apus,
or three times the
number present in the
lobster, the segments _ Fig. 243—Limnnetis Gouldii, much enlarged.—After
thus being irrelatively P™™°*

repeated, a sign of inferiority. There is a pair of simple
eyes consolidated into one as in Limnetis and Limnadia, or
as in Apus, there is a
pair of compound eyes,
situated in the cara-
pace, apparently on
one of the antennal
segments. In Bran-
Sa and Artemia
the compound eyes
are stalked, an antic-
Boise ee of the stalked
eye of the lobster,
etc., but the eye, it
should be noticed, is not developed from a_ separate
segment, but from one of the two antennal segments. All
the members of this order hatch in the Nauplius form, the
three pairs of appendages of the larva, representing the two
pairs of antennz and the mandibles of the adult. The spe-
cies live in pools of fresh water liable to dry up in summer ;
they lay eggs which drop to the bottom, and show great vi-
tality, withstanding the heat and dryness after the water
has evaporated ; the young hatching after the rains refill the
pools or ditches.

 

 

Fig. 244.—Limnadia Agassizii, enlarged.
302 ZOOLOGY.

This suborder presents a beautiful series of increasingly
complex forms, as we ascend from Limmnetis to Branchipus.
In Limmnetis the bivalve shell encloses the ani-
mal, and is the size of a small flattened pea.
There are from ten to twelve feet - bearing
segments. JL. Gouldit Baird (Fig. 248) is very
rare in Canada and New England. The shell
of Limnadia is thin, oval, and there are from
eighteen to twenty-six feet-bearing segments.
L. (Eulimnadia) Agassizii Packard (Figs. 244
eye and 245) inhabits pools in Southern New En-

gland. The shell of Estherta (Fig. 246, Zs-

Fig. 245.—Fore- theria Belfraget Packard) is sometimes mis-
leg of male Kuwim- taken for that of the fresh-water mollusks
ee Hees Cyclas and Pisidium. The males of the fore-
end of Pody. going genera have the first pair of feet modi-
fied to form large claspers (Fig. 245).

In Apus the abdomen projects beyond the large carapace,
and ends in two long many-jointed appendages. There are
about sixty pairs of feet, each foot
divided into several leaf-like lobes,
wherein respiration is carried on.

These Phyllopods usually swim upon
their backs, as in the species of Bran-
chipus. The females chiefly differ
from the males in the presence of an

 

zi i Fig. 246.—Shell of Estheria
orbicular egg-sac on the eleventh pair Béfragei, enlarged three

of feet, the sac being a modification of times.

two of the lobes of the feet, and containing but a few eggs.
Apus equalis Packard (Fig. 247, Fig. 249 A, represents the
larva of a European Apus) inhabits pools in the western
plains. Lepidurus differs from Apus in having the telson
spoon-shaped instead of square. L. Cowesii Packard (Fig.
248) occurs on the Rocky Mountain plateau in Utah and
Montana. It is an interesting fact in z00-geography that
there are no species of Apus and Lepidurus east of the west-
ern plains. Apus has been found by Siebold to reproduce
parthenogenetically.

The various species of Branchipus end Artemia have no
PHYLLOPOD CRUSTACEANS. 303

carapace, the mandibular segment being small and not over-
lapping the segments behind it. The second antenne are

 

Fig. 248.—Lepidurus Couesit,
side and dorsal view, natural
size.

 

Fig. 247.—Apus equalis, natural size.

large and in the male adapted for
clasping. In Thammnocephalus (Fig.
250, T. brachyurus Packard, from
Kansas) there is a singular shrub-
like projection of the front of the
head, and the abdomen is spatulate
or spoon-shaped at the end. Bran-
chinectes Coloradensts Pack. (Fig.
251) is a Rocky Mountain form. | Fig. 249.—a, Larva of Apus can-
the brine - anny, Artemia, lives Nauplius of Artemia salina of Bu:
only in brine-vats or in the salt mee

lakes of the West and of Southern Europe. Artemia gra-
cilis Verrill (Fig. 252) has thus far only been found in tubs

 
304 ZOOLOGY.

of concentrated salt water on railroad bridges in New En-
gland. Artemia fertilis Verrill abounds in Great Salt Lake.

 

 

Fig. 250.—Thamnocephalus platyurus, male, natural size. side and front view. a,
head of the female ; 5, end of the body of the female, showing the ovisac.

They may often be seen swimming about in pairs, as in
Fig. 253. This species has a Nauplius young like that of

 

Fig. 251.—Branchinectes Coloradensis Pack.

the brine-shrimp of Europe (Fig. 249 0). It is a signifi-
cant fact, bearing on the question of the origin of species,
that, according to Schmankiewitsch, Artemia may change its
TETRADECAPODS. 805

form, the change being induced by the greater or less saltness
of the water. Artemia produces young by budding (parthe-
nogenesis) as well as from eggs. e a@ 6b
A species observed near Odessa j
produced females alone in warm
weather; and only in water of ¢
medium strength were males pS ae
produced. The eggs of Arte- SPR
mia fertilis have been sent in 7
moist mud from Utah to Mu-
nich, Germany, and specimens
raised from the eggs by Siebold,
proving the great vitality of the
eggs of these Phyllopods, a fact
paralleled by the similar vitality oe
of the eggs of the king-crab.
Fig. 249 6 represents the Nau- , ee
plius of the Huropean brinc-
shrimp.

Order 4. — Tetradecapoda.—
To this order belong the sow-
bugs (Zsopoda) and the beach-
fleasen(Amgenoda) line these: Nie, M2 btne= shrimp, Arvenia

gracilis, enlarged. a, first antenna ; 6,
Crustacea there is no cephalo- second antenna or clasper; ¢, stalked

thorax, but the head is small, Sines ge ee
bearing two pairs of antenneg, and a pair of jaws, and three
pairs of maxilla. The thorax is continuous with the abdo-
men. Respiration is performed by lamellate or leaf-like
gills on the middle feet in the Amphipods, or on the hinder
= abdominal feet in
the Isopods. The
lowest Isopods are
parasitic, they
Fig. 253.—Artemia fertilis from Great Salt Lake. e, graduate into the
egg-sac ; c, male claspers. :
Amphipods, and
the higher Amphipods are connected with the shrimps (De-
capoda) through a group (probably a suborder) of synthetic
forms (Paleocaris, Acanthotelson and Gampsonyx, Fig.
254) such as are found in the coal formation of Illinois

 

  
806 ZOOLOGY.

and Europe, which may be called <Anthracarida, and
which have antenne and tails like shrimps, but the body

 

Fig. 254.—Gampsonyx fimbriatus of European coal measures, 214 times natural
size.

and limbs like Amphipods. In the Isopods the body is flat-
tened and the head rather broad.

Fig. 256 is a dorsal view of Serolis Gau-
dichaudi Audouin and Edwards, with the
two pairs of antenne and pointed sides of
each thoracic segment, dissected to show the
nervous system, the two pairs of antennal
nerves ; the optic nerves (op) sent to the
compound eyes. Fig. 257 represents a trans-
verse section of the body, showing the mode
of insertion of the legs, and the equality in
the tergal and sternal sides of the body,
Fig. 259 represents a gill. In the common
pill-bug (Porcellio) aérial respiration is per-
formed by respiratory cavities situated in
the abdomen. In 7Jylos similar cavities are
filled with a multitude of branching ceca,
serving for aérial respiration, thus antici-
pating the tracheary system of insects.
The nervous system is quite simple. (Fig.
255, Idotea, and Fig. 256, that of Serolis.)
The digestive canai is straight, consisting

Fig, 285.—Nervons of a short esophagus, a membranous stom-
ee ee. ach, and usvally a short tubular intestine ;
5. Kingsley the liver consisting of several short cceca.
In Serolis Gaudichaudt the stomach is somewhat pear-

 
EMBRYOLOGY OF ONISCUS. 307

shaped, widest behind. The intestine is on its anterior half
broader than the stomach, suddenly contracting behind.

 

Fig. 256.—Dissection of Serolis to show the nervous system.—Dissected and drawn
by J. S. Kingsley.

There is no cecal enlargement, and no “urinary” tubes.
The sexes are distinct. The young are hatched in the form
of the adult, there being no metamorphosis.

The development of the pill-bug, Oniscus murarius is
probably typical of that of most Tetradecapods and Deca-

 

Fig. 257.Transverse section of Serolis. ¢, t, tergum; s,s, sternum; em, epime-
rum ; és, episternum, at insertion of the legs.—Prepared and drawn by J. S. Kings-
ley.
pods (Bobretzky). The first change after fertilization is the
origin of the formative or primitive blastodermic cells at one
308 ZOOLOGY.

pole of the egg. This single cell subdivides, its products
forming the “‘blastodermic disk” or outer germ-layer, the
segmentation of the yolk being partial. The

\ third (innermost) and middle germ-layers next
arise (the same processes go on in certain

SS, shrimps, viz. : Crangon and Palemon). The
es intestine is formed by an in-pushing of the
& ~~ «outer germ-layer. The limbs now bud out, the
me result of the pushing out of the outer germ-
layer (ectoderm). The nervous cord arises from

the ectoderm ; the large intestine originates in

a the yolk-sac, its epithelium first
4 appearing in the liver-sac. The
heart is the last to be formed. Ex-
ternally the antenne in Oniscus
Fie 258 andalso Asellws are the first to bud
Mouth-parts of out; the remaining appendages of

Serolis. m, man-

dible ; mi’, first the head and thorax arise contem-
maxilla; ma’,

  

Fig. 259.—A

second maxilla; poraneously, and subsequently the pin §? serovis.—
mp, maxillary : ob ean by J. ‘sg
palpus.—Drawn abdominal feet. The abdomen in Qy2vyoy &: ®
y J. S. Kings- Bsley.

ley. the Isopods is curved upwards and
backwards, while in the embryo Amphipods it is bent be-
neath the body.

The development of the Amphipods or beach-fleas is
nearly identical with that of the Isopods. The eggs of cer-
tain species undergo total segmentation, while those of other
species of the same genus (Gammarus) partially segment, as
in the spiders, and in a less degree the insects.

Standing next below Cymothoa, which is of the general
Isopod shape, but which lives parasitically on the tongue
and other parts of fishes, but which from their parasitic
habits become slightly changed in form, the females espe-
cially, sometimes becoming blind, is the family of which
Bopyrus is arepresentative. ‘The females (Fig. 262) are par-
asitic under the carapace of various shrimps. In B. pandal-
icola Packard n. sp., the females are many times larger than
the males ; the ventral side of the body is partly aborted,
having been absorbed by its pressure against the carapace
of its host, which is swollen over it ; itretaing its position by
ISOPODA. 309

Fie. 261.

 

Fia. 262,

Fig. 260.—Section of the embryo pill-bug. d, intestine; 2, epithelium form-
ing the walls of the two lobes of the liver ; g, transverse section of the nervous cord ;
h, walls of the body.—After Bobretzky.

Fig, 261.—Section of more advanced embryo pill-bug. h, heart; 2p, hypoder-
mal layer or body-walls ; m, muscular wall of the intestine: ¢, epithelial lining of the
intestine; p, dividing cell-wall between the heart and intestine; 7, two lobes of the
liver; g, ganglion. the clear space being filled with the fine granular substance of the
ganglion.—After Bobretzky.

Fig. 262.—Bopyrus. A, ventral, B, dorsal side of the female; (C, lateral and D,
dorsal view ot the male ; c!, head and first thoracic segment ; ¢?, antenne—all en-
Jarged.—Packard, del,
310 ZOOLOGY.

the sharp hook-like legs around the margin of the body. The
head has no eyes nor appendages. The male (Fig. 262, 0, D)
is but slightly modified, is very minute, and is lodged partly
out of sight under the ventral plates of the female, whose
body is about five millimetres (a fifth of an inch) in length.

 

Fig. 263.—Arcturus Bafini, with its young clinging to its antenne.—After Wyville-
Thompson.

Various species of Porcellio (sow-bugs) live under stones
on land; and allied to Asellus, the water sow-bug, is the
marine Limnoria terebrans Leach, which is very injurious
to the piles of bridges, wharves, and any submerged wood.
The highest Isopods are Jdote@a, of which L. trroratus Say
(Fig. 255) is our most abundant species, being common in
eel-grass, etc., between and just below tide-marks ; and Arc-
turus (Fig. 263, A. Baffini Sabine), from the Arctic seas,
PHYLLOCARIDA. 311

The series of Amphipods begins with Oyamus ceti (Linn.),
the whale-louse, passes into Capredlu, with its linear body
and spider-like legs, to Hyperia, which lives as a mess-mate
of the jelly-fish, Cyanea, and culminates in the water-flea
(Gammarus ornatus Edwards) and sand-flea (Orchestia agilis
Smith), abundant and leaping in all directions from under
dried sea-weed at high-water mark.

Fig. 264 represents Gammarus robustus Smith, a fresh-
water form common in the western territories.

 

Fig. 264.—Gammarus robustus Smith. Utah. Enlarged.—After Smith.

Order 5. Phyllocarrda.—This name is proposed for a
group of Crustacea, the forerunner of the Decapoda and
hitherto regarded as simply a family (Nebdaliade), in which
there is an interesting combination of Copepod, Phyllopod,
and Decapod characters, with others quite peculiar to them-
selves. The type is an instance of a generalized one, and is
very ancient, having been ushered in during the earliest Si-
lurian period, when there were (for Crustacea) gigantic forms
(Dithyrocaris was over one foot in length) compared with
those living at the present day. The order connects the
Decapods with the Phyllopods and lower orders. The mod-
ern WNedalia is small, about a centimetre (.40-.50 inch) in
length, with the body compressed, four of the abdominal
segments projecting beyond the carapace, the last abdominal
segment bearing two large spines. ‘There is a large rostrum
overhanging the head ; stalked eyes, and two pairs of anten-
ne, the second pair nearly as long as the body and many-
jointed. The mandibles are succeeded by two pairs of max-
312 ZOOLOGY.

ille. Behind these mouth-parts are eight pairs of short, leaf-
like respiratory feet, which do not project beyond the edge of
the carapace. These are succeeded by four pairs of large,
long swimming feet, and there are two additional pairs of
small abdominal feet. There is no metamorphosis, develop-
ment being direct, the young hatching in the form of the
adult. Of the fossil forms, Hymenocaris was regarded by
Salter as the more generalized type. The genera Peltocaris
and Discinocaris characterize the Lower Silurian period ;
Ceratiocarts the upper ; Dictyocarts the Upper Silurian and
Lowest Devonian strata ; Dithyrocaris and Argus the Car-
boniferous period. Our northeastern and arctic species is
Nebalia bipes (Fabricius), which occurs from Maine to Green-
land.

Order 6. Stomapoda. In the small group represented by
Squilla the gills are attached to the base of the hinder ab-
dominal feet. Sguiila lives in holes below low-water mark.

Order %. Decapoda (Shrimps, Lobsters, Crabs).—A gen-
eral knowedge of the Crustacea representing this, the high-
est order of the class, may be obtained by a study of
the craw-fish and lobster. All Decapods have twenty seg-
ments in the body, a carapace covering the thorax and con-
cealing the gills, which are highly specialized and attached
to the maxillipedes and to the legs; usually a pair of stalked
eyes, two unequal pairs of antenne, the hinder pair the
larger and longer ; a pair of mandibles, often provided with
a palpus, two pairs of lobed maxille, three pairs of maxilli-
pedes, while the name of the order is derived from the fact
that there are five pairs of well-marked legs, or ten in all.
To the abdomen are appended six pairs of swimming feet.
called ‘‘swimmerets.” Another distinctive characteristic of
most, in fact all the higher Decapods, is the short, or five
or six-sided heart.

The early phases of embryological development in the De-
capods are much as in the Tetradecapods. Most Decapods
leave the egg in a larval state called the Zoéa. Certain
Zoée having originally been supposed to have been adult
Crustaceans, were described under the name Zoéa. In this
condition there are no thoracic feet, and usually at first no
DECAPODA. 313

abdominal feet; the compound eyes are large and usually
sessile, and the carapace is often armed with a long dorsal
and frontal spine. Fig. 265 represents the Zoéa, or larva of
the common shore crab (Cancer irroratus Say). After sev-

 

Fig. 265.—Zoéa of the common Crab. Cancer. Much enlarged.—After Smith.

eral moults, the thoracic legs appear, the mouth - parts
change from swimming -legs to appendages fitted for pre-
paring the food to be swallowed and digested. This stage
in the short-tailed Decapods or crabs, is called the Mega-
lops stage (Fig. 266); certain immature crabs having been
mistaken for and described as mature Crustacea, under the
name Megalops. After swimming about the surface in the
Zoéa and Megalops conditions, the body becomes more bulky,
more concentrated headwards, and the crab descends to the
bottom and hides under stones, etc.

The development of the individual crab is, in a general
sense, an epitome of the development of the order. In the
lowest Decapods, as in Cuma and Mysis, the form is some-
what like an advanced Zoéa, while the remarkable concentra-
tion of the parts headwards, seen in the crabs, is a great
314 ZOOLOGY.

step upwards. Dana’s law of cephalization, or transfer of
parts headwards, is more strikingly manifested in the Crus-
tacea than in any other animals.

Nearly «ll Decapods undergo this decided metamorphosis ;
in only a few forms, such as the craw-fish, lobster, and a few
shrimps and crabs, do the young leave the egg in the general
form of the adult, the
Zoéa stage being rap-
idly assumed and dis-
carded during em-
bryonic life. Most
Crustacea bear their
eggs about with
them ; in only a few
cases, as the Squilla
and the land-crab of
the West Indies, are
the eggs left by the
parent in holes or on

the sea-shore.

\\ The Decapoda are
4 q We divided into the
Wiig h\ Schizopoda, repre-
/, Hy a sented by ysis ;
Wii, SN the 0 :
fin my e Cumacea, repre
My bi sented by Cuma ; the
| li long-tailed Decapods,

Fig. 266.—Megalops of the Crab.—After Smith,  SUCh as the shrimps

and lobster, called
Macrura, and the genuine short-tailed Decapoda, or Bra-
chyura. Most of the species of the crabs are confined to
tropical seas and live in shallow water.

The Decapods appeared in the Coal Period, and were rep-
resented by somewhat generalized forms, such as Anthra-
palemon (Fig. 267) from the coal measures of Illinois.
Recently a genuine crab (Brachypyge carbonis) has been
described by Woodward from the carboniferous formation
of Belgium.

Crustacea, especially shrimps and crabs, are sensitive to

 

oy=
FOSSIL CRABS. 315

shocks and sounds. When alarmed, lobsters are said to
cast off their large claws, but the latter are again re-
newed. It is more probable, however, that the claws are
torn off during their contests with each other. Hensen
found that crabs and shrimps liv-
ing in water do not notice sounds
made in the air. The hairs about
the mouth are the organs of tac-
tile sense, and have been made by
Hensen to vibrate to certain sounds.
The eyes may be greatly devel-
oped in shrimps living at great
depths ; thus Thalascaris, ashrimp
living near the bottom of the At-
lantic Ocean, is remarkable for the
large size of its eyes. In the spe-
cies of Alpheus, which live in holes

in sponges, etc., theeyes are small. 5. og antnnanalannon ora:
The eyes of the blind Willemesia, cits "Naiuial size Atte eek
dredged at great depths by the
“Challenger” Expedition, are rudimentary, though in the
young the eyes are better developed. This is the case with
the young of the blind craw-fish Cambarus pellucidus (Tell-
kampf, Fig, 268) of Mammoth and other caves. The fact
that the eyes in the young are larger than in the adult indi-
cates that this species has descended from other forms living
in neighboring streams, and well endowed with the sense
of sight. The eye (Fig. 269) of the blind craw-fish differs
from that of the normal species in its smaller size, conical
form, the absence of a cornea (indicated by the dotted lines
in A), the pigment cells being white instead of black, and
by differences in the form of the brain, that of the blind
species being fuller on the sides, and wanting the conical
projection in front.

 

 

 

 

 

   

Subclass 2. Paleocarida.—This subclass is proposed for
the king-crab (Limulus), the only survivor of a large num-
ber of fossil Crustacea, which dominated the Silurian seas
and became mostly extinct in the Carboniferous period.
316 ZOOLOGY.

It comprises the order of Merostomata represented at the
present day by the king-crab, and the order Trilodbita, which
is wholly extinct. The organization of the king-crab is so

SeSy ee
a Ass OSE

Gia
_ Fig. 268.—Cambarus pellucidus, the blind craw-fish of Mammoth Cave. Natural

81Ze.

wholly unlike that of other Crustacea, when we consider
the want of antenne, the fact that the nervous system is
PALAGOCARIDA. 317

peculiar in form and also ensheathed by arteries, and the
peculiar nature of the gills of the abdominal feet, as well as
the highly developed system of blood-vessels ; that we are
obliged to place them in a subclass equivalent to all the other

A B

  

ah

Fig. 269.—A, Brain and eye of a normal Cambarus from Iowa.
B, The same of the blind craw-fish from Mammoth Cave.
¢, Cornea.—Packard, del.

Crustacea. It is possible that future research may prove that
the Paleocarida should form a distinct class of Arthropods,
equivalent on the one hand to the Crustacea and on the
other to the Jnsecta, but from the fact that they breathe like
other Crustacea by external gills, we prefer to retain them
as a subdivision of the class of Crustacea.

Order 1. Merostomata.—The only living representative of
this order is the king-crab, belonging to the genus Limulus,
represented in American waters by Limulus Polyphemus
Linn., which ranges from Casco Bay, Maine, to Florida
and the West Indies.

The body of the king-crab is very large, sometimes nearly
two feet in length ; it consists of a cephalo-thorax composed
of six segments and an abdomen with nine segments, the
ninth (telson) forming a long spine. The cephalo-thorax is
broader than long, in shape somewhat like that of Apus,
with a broad flat triangular fold on the under side. Above
are two large lunate compound eyes, near the middle of the
head, but quite remote from each other, and two small com-
pound eyes situated close together near the front edge of the
head. There are no antenne, and the six pairs of append-
318 ZOOLOGY.

ages are of uniform shape like legs, not like mandibles or
maxille, and are adapted for walking; the feet are pro-
vided with sharp teeth on the basal joint for retaining the
food. The mouth is situated between the second pair; the
first pair of legs are smaller than the others. All end in
two simple claws, except the sixth pair, which are armed
with several spatulate appendages serving to prop the crea-
ture as it burrows into the mud. The males differ from the
females in the hand and opposing thumb of the second pair
of feet. These cephalo-thoracic appendages are quite as dif-
ferent from those of other Crustacea as those of the mites
and spiders, which have a pair of mandibles and maxille,
the latter provided with a palpus. Appended to the ab-
domen are six pairs of broad swimming feet, of which the
first pair bear on the under side a set of about one hundred
respiratory leaves or plates, into which the blood is sent
from the heart, passing around the outer edge and return-
ing around the inner edge. This mode of respiration is like
that of the Isopods.

The alimentary canal consists of an cesophagus, which
rises directly over the mouth, a stomach lined with rows of
large chitinous teeth, with a large conical, stopper-like valve
projecting into the posterior end of the body ; the intestine
is straight, ending in the base of the abdominal spine. The
liver is very voluminous, ramifying throughout the cephalo-
thorax. The nervous system is quite unlike that of other
Crustacea ; the brain is situated on the floor of the body in
the same plane as the rest of the system, and sends off two
pairs of nerves—a pair to each pair of eyes.* The feet are all
supplied with nerves from a thick ring surrounding the
csophagus. The nerves to the six pairs of abdominal legs
are sent off from the ventral cord.

* The nervous system of Limulus is quite unlike that of the Scorpion,
where the brain is situated in the upper part of the head and supplies
the maxille with nerves, and is situated directly over the infraceso-
phageal ganglion; and, besides, there is no cesophageal ring as in
Limulus, only the two commissures connecting the brain with the
infracesophageal ganglion as usual in the Neocarida and Arachnida in
general.
ANATOMY OF THE KING-CRAB. 319

The heart is tubular, with eight pairs of valvular openings
for the return of the venous blood which flows into the
pericardial sac from all parts of the body ; the arterial blood

 

Fig. 270.—Nervous and part of the circulatory system of Limulus polyphemus, the
King-Crab. a, vent ; @, esophagus ; 0, brain; o, nerve to the smaller eyes; o’, nerve
to the larger eyes; 8, nerve-ring around the esophagus. All the nerves are surround-
ed by an arterial coat.—After Milne Edwards.

is sent out from the arteries branching from the front end
of the heart flowing around the upper side of the edge of the
cephalo-thorax through numerous minute vessels. Also there
are a pair of branchial arteries, and two arteries in the base of
the spine.
320 ZOOLOGY.

The arrangement of the ventral system of arteries is very
peculiar and quite characteristic of this animal. The cso-
phageal nervous ring, and in fact the entire nervous cord, is
ensheathed in a vascular coat, so that the nervous system
and its branches are bathed by arterial blood. ‘The veins
are better developed than usual ; there being in the cephalo-
thorax two large collective veins along each side of the in-
testine.

Closely connected with the two large collective veins are
two large yellowish glandular bodies each with four branches
extending up into the dorsal side of the cephalo-thorax.
They are probably renal in their nature.

Both the ovaries and testes are voluminous glands, each
opening by two papille on the under side of the first ab-
dominal feet. At the time of spawning the ovary is greatly
distended, the branches filled with green eggs.

Unlike most Crustacea, the female king-crab buries her
eggs in the sand between tide-marks, and there leaves them
at the mercy of the waves, until the young hatch. The eggs
are laid in the Northern States between the end of May and

al

 

Fig. 271. Fig. 272.
Fig. 271._Embryo of King-crab, enlarged ; am, serous membrane ; ch, chorion.
Fig. 272.--The same, more advanced,
early i in July, and the young are from a month to six weeks
in hatching.

After fertilization the yolk thakiues total segmentation,
much ag in spiders and the craw-fish. When the primitive
disk is formed the outer layer of blastodermic cells peels off
soon after the limbs begin to appear, and this constitutes
HMBRYOLOGY OF THE KING-CRAB. 321

the serous membrane (Fig. 271, wm), which is like that of
insects.

' Then the limbs bud out; the six pairs of cephalic limbs
appear at once as in Fig. 271. Soon after the two basal
pairs of abdominal leaf-like feet arise, the abdomen be-
comes separated from the front region of the body, and
the segments are indicated as in Fig. 272. A later stage
(Fig. 273) is signalized by the more highly developed dorsal
portion of the embryo, an increase in size of the abdomen,
and the appearance of nine distinct abdominalsegments. The
segments of the cephalo-thorax are now very clearly defined,
as also the division between the cephalo-thorax and abdomen,
the latter being now nearly as broad as the cephalo-thorax,
the sides of which are not spread out as in a later stage.

 

Fig. 273.—King-crab shortly before hatching ; trilobitic stage, enlarged ; side and
dorsal view.

At this stage the egg-shell has split asunder and dropped
off, while the serous membrane, acting as a vicarious egg-
shell, has increased in size to an unusual extent, several
times exceeding its original dimensions and filled with sea-
water, in which the embryo revolves.

Ata little later period the embryo throws off an embry-
onal skin (amnion), the thin pellicle floating about in the
egg. Still later in the life of the embryo the claws are de-
veloped, an additional rudimentary gill appears, and the
abdomen grows broader and larger, with the segments more
322 ZOOLOGY.

distinct ; the heart also appears, being a pale streak along
the middle of the back extending from the front edge of
the head to the base of the abdomen.

Just before hatching the head-region spreads out, the ab-
domen being a little more than half as wide as the cephalo-
thorax. The two compound eyes and the pair of ocelli on
the front edge of the head are quite distinct ; the append-
ages to the gills appear on the two anterior pairs, and the
legs are longer.

The resemblance to a Trilobite is most remarkable, as
seen in Fig. 273. It now also closely resembles the fossil
king-crabs of the Carboniferous formation (Fig. 274, Prest-
wichia rotundatus, Fig. 275, Huprodps Dane).

 

Fig. 274.—Prestwichia, natural size.— Fig. 275.—Euprodps, natural size.—
After Worthen. After Worthen.

In about six weeks from the time the eggs are laid the
embryo hatches. It now differs chiefly from the previous
stage in the abdomen being much larger, scarcely less in
size than the cephalo-thorax ; in the obliteration of the seg-
ments, except where they are faintly indicated on the car-
diac region of the abdomen, while the gills are much larger
than before. The abdominal spine is very rudimentary ; it
forms the ninth abdominal segment.

The reader may now compare with our figures of the re-
RELATIONSHIP OF LIMULUS TO TRILOBITHS. 323

cently hatched Limulus (Fig. 276), that of Barrande’s larva
of Trinucleus ornatus (Fig. 277, natural size and enlarged).
He will see at a glance that the young Trilobite, born with-
out any true thoracic segments, and with the head articu-
lated with the abdomen, closely resembles the young Limu-
lus. In Limulus no new segments are added after birth ;
in the Trilobites the numerous thoracic segments are add-
ed during successive moults. The Trilobites thus pass
through a well-marked metamorphosis, though by no means
so remarkable as that of the Decapods and the Phyllopods.

 

Fig. 277.—Larva of a Trilo-
bite, Trinucleus ornatus.—
After Barrande.

 

Fig. 276. —Larva of the King-crab.

The young king-crabs swim briskly up and down, skim-
ming about on their backs like Phyllopods, by flapping their
gills, not bending their bodies. In asucceeding moult, which
occurs between three and four weeks after hatching, the
abdomen becomes smaller in proportion to the head, and the
abdominal spine is about three times as long as broad. At
this and also in the second, or succeeding moult, which oc-
curs about four weeks after the first moult, the young king-
crab doubles in size. It is probable that specimens an inch
long are about a year old, and it must require several years
for them to attain a length of one foot.

The Limuli of the Solenhofen slates (Jurassic) scarcely
differed in appearance from those of their living descend-

ants.
Limulus, Prestwichia, Bellinurus, and Huprodps form
324 ZOOLOGY.

the representatives of the suborder Yiphosura. The second
suborder Hurypterida is represented by extinct genera Ptery-
gotus, Eurypterus and allies which appeared in the upper
Silurian Period and became extinct in the Coal Period. In
these forms the cephalothorax is small, flattened and nearly
square, while the abdomen is long, with twelve or thirteen
segments, the last one forming a spoon-shaped or acute
spine. The appendages of the cephalothorax were adapted
for walking, one pair sometimes large and chelate; the
hinder pair paddle-like. The gills were arranged like the
teeth in a rake, the flat faces being fore and aft. While the
king-crab burrows in the mud and lives on sea-worms, the
Eurypterida probably swam near the surface, and were more
predatory than the king-crabs. The Merostomata are a gen-
eralized type, with some resemblances to the Arachnida as
well as to the genuine Crustacea, representing the larval or
Zoéa form of the Decapods.

Order 2. Trilobita.—The members of this group are all
extinct. The body has a thick dense integument like that
of Limulus, and is often variously ornamented with tuber-
cles and spines. The body is divided into three longi-
tudinal lobes, the central situated over the region of the
heart as in Limulus. The body is more specialized than in
the Merostomata, being divided into a true head consisting
of six segments bearing jointed appendages, somewhat like
those of the Merostomata, with from two to twenty-six dis-
tinct thoracic segments (probably bearing short jointed limbs
not extending beyond the edge of the body, which support-
ed swimming and respiratory lobes). The abdomen consisted
of several (greatest number twenty-eight) coalesced segments,
forming a solid portion (pygidiwm), sometimes ending in a
spine, and probably bearing membranous swimming feet.
The larval trilobite was like that of a king-crab, and after a
number of moults acquired its thoracic segments, there being
a well-marked metamorphosis. The Trilobites (Paradozides,
Agnostus, etc.) appeared in the lowest Silurian strata, cul-
minated in the upper Silurian, and died out at the close of
the Coal Period.
CLASSIFICATION OF CRUSTACEA. 825

Cuass. I, CRUSTACEA.

Arthropoda breathing by gills situated on the legs, or respiring through
the body-walls. Body in the higher forms divided into two regions, a
cephalo-thorax and abdomen. Two pairs of antenne ; mandibles usu-
ally witha palpus. Heart nearly square, or in the lower forms tubular.
Often a distinct metamorphosis. Sexes distinct, except in a few cases
(certain barnacles, etc.).

Subclass 1. Neocarida.—Genuine Crustacea, with two pairs of anten-
ne; biting mouth-parts ; mostly modern types.

Order 1. Cirripedia.—Sessile often retrograded ; antennz not devel-
oped, living parasitically, the appendages of the head some-
times forming net-like organs. Young hatched in the nau-
plius state. Suborder 1.--Rhizocephala (Sacculina, Pelto-
gaster). Suborder 2.—Genuine Cirripedia (Balanus, Lepas.)

Order 2. Hntomostraca.—A cephalo-thorax developed ; mandibles and
three pairs of maxille ; five pairs of thoracic feet, no ab-
dominal feet ; without any gills. The parasitic forms more
or less modified in shape, with sucking mouth-parts ; all
the young of the nauplius form. Suborder 1. Copepoda
(Cyclops). Suborder 2. Siphonostoma (Lernea, Caligus, and
Argulus).

Order 3. Branchiopoda. Thoracic feet leaf-like ; one to three pairs of
maxille ; number of body-segments varying from a few to
sixty ; cephalo-thorax often well developed, and forming a
bivalved shell. Young usually a Nauplius. Suborder 1,
Ostracoda (Cypris). Suborder 2. Cladocera (Daphnia). Sub-
order 3. Phyllopoda (Limnadia, Apus, Branchipus, and Ar-
temia.)

Order 4. Phyllocarida.—Body compressed ; rostrum distinct from the
carapace ; thoracic feet leaf-like ; no metamorphosis. (Ne-
balia.)

Order 5.—Tetradecapoda.—No cephalo-thorax, thoracic segments dis-
tinct ; respiration often carried on by the abdominal feet.
Suborder 1. Jsopoda (Idotea, Asellus). Suborder 2. Am-
phipoda (Gammarus).

Order 6. Stomapoda.—Abdominal feet respiratory. (Squilla.)

Order 7. Decapoda.—Cephalo-thorax well marked, abdomen often bent
beneath the cephalo-thorax ; breathing by gills attached to
the maxillipedes and legs. Heart often nearly square.
Usually a well-marked metamorphosis; young called a
326 ZOOLOGY.

Zoéa. Suborder 1. Cumacea (Cuma). Suborder 2. Schiz-
opoda(Mysis). Suborder 3. Macrura (Crangon, Astacus, Ho-
marus). Suborder 4. Brachyura (Cancer).

Subclass 2. Palwocaridu.—Appendages of the cephalo-thorax in the form
of legs, rather than jaws; no antenne; brain supplying
nerves to the eyes alone; nerves to the cephalo-thoracic ap-
pendages sent off from an cesophageal ring ; nervous system
ensheathed by a ventral system of arteries ; metamorphosis
slight. Sexes distinct. '

Order 1. Merostomata.—No distinct thoracic segments and appendages.
(Limulus, Eurypterus. )

Order 2. Trilobita.—Numerous free thoracic segments and jointed ap-
pendages. (Agnostus, Paradoxides, Calymene, Trinucleus,
Asaphus ; all extinct.)

CLASSIFICATION OF THE SUBCLASSES AND ORDERS OF CRUSTACEA.

 

 

 

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Laboratory Work.—In dissecting the lobster, the shell or crust may
be removed by a stout knife ; the whole dorsal portion of the cephalo-
thorax and each segment behind, including the base of the telson,
should be removed, care being taken not to injure the brain, which lies
just under the base of the rostrum. The hypodermis, or reddish, mem-
branous, inner layer of the integument, should then be dissected away,
GENERAL CHARACTERS OF INSECTS. 327

exposing the heart, the stomach, the liver, and the large muscles of
the abdomen. The arterial system can be injected with carmine
through the heart, and the finer arteries traced into the large claws
and legs. In the crab, the entire upper side of the carapace may be
removed by the point of a knife. The smaller Crustacea, especially
the water-fleas, may be examined alive under the microscope as trans-
parent objects. In the larger forms the stomach may be laid open by
the scissors in order to study its complicated structure. The eyes of
the lobster should be hardened in alcohol and fine sections made for
the microscope. This is an operation requiring much care and expe-
rience. Experts in embryology have sliced the eggs of certain Crusta-
cea and studied their embryology with great success.

Cuass II.—Insecta (Centipedes, Mites, Spiders, Winged
Insects).

General Characters of Insects.—While in the worms
there is no grouping of the segments into regions, we have
seen that in most Crustacea there are two assemblages of
segments—1. ¢., a head-thorax and abdomen. In the insects
there is a step higher in the scale of life, a head is separated
from the rest of the body, which is divided into three
regions, the head, thorax, and hind-body (abdomen). More-
over, the insects differ from the Crustacea in breathing by
internal air-tubes which open through breathing-holes
(spiracles) in the sides of the body. The six-footed insects
also have wings, and their presence is correlated with a
differentiation or subdivision of the two hinder segments
of the thorax into numerous pieces.

The number of body-segments in winged insects is seven-
teen or eighteen—1. ¢., four in the head, three in the thorax,
and ten or eleven in the hind-body. In spiders and mites
there are usually but two segments in the head, four in the
thorax, and a varying number (not more than twelve) in
the abdomen ; in Myriopods the number of segments varies
greatly—. e., from ten to two hundred. The appendages
of the body are jointed, and perform four different func-
tions—é. e., the antenne are sensorial organs, the jaws and
maxille are for seizing and chewing or sucking food ; the
328 ZOOLOGY.

thoracic appendages are for walking, and the spinnerets
of the spider, as well as the sting or ovipositor of many
insects, are subservient in part to the continuance of the
species.

Of the winged insects there are two types : first, those in
which the jaws and maxille are free, adapted for biting, as
in the locust or grasshopper, and, second, those in which
the jaws and maxille are more or less modified to suck or
lap up liquid food, as in the butterfly, bee, and bug.

Nearly all insects undergo a metamorphosis, the young
being called a larva (caterpillar, grub, maggot) ;_ the larva
transforms into a pupa (chrysalis), and the pupa into the
adult (imago).

In order to obtain a knowledge of the structure, external
and internal, of insects, the student should make a careful
study of the anatomy of a locust or grasshopper with the aid
of the following description ; and afterward rear from the
egg a caterpillar and watch the different steps in its metamor-
phosis into a pupa and adult. The knowledge thus acquired
will be worth more to the student than a volume of descrip-
tions.

On making a superficial examination of the locust (Calop-
tenus femur-rubrum, or C. spretus), its body will be seen to
consist of an external crust, or thick, hard integument, pro-
tecting the soft parts or viscera within. This integument
is at intervals segmented or jointed, the segments more or
less like rings, which, in turn, are subdivided into pieces.
These segments are most simple and easily comprehended
in the abdomen or hind-body, which is composed of ten of
them. The body consists of seventeen of these segments,
variously modified and more or less imperfect and difficult
to make out, especially at each extremity of the body—
z.e., in the head and at the end of the abdomen. These
seventeen segments, moreover, are grouped into three re-
gions, four composing the head, three the thorax, and ten
the hind-body, or abdomen. On examining the abdomen,
it will be found that the rings are quite perfect, and that
each segment may be divided into an upper (tergal), a lateral
(pleural), and an under (sternal) portion, or arc (Fig. 278, A).
ANATOMY OF INSECTS. 329

These parts are respectively called tergite, plewrite, and
sternite, while the upper region of the body is called the

Thabrum (ca)
i S randile & zg

mt BQ 7
aq OA
Chee

Trodhar tind

 

Fig. 278,—External anatomy of Caloptenus spretus, the head and thorax disjointed.
up, uropatagium ; J, furcula : ¢, cercus.—Drawn by J. S. Kingsley.

tergum, the lateral the plewrwm, and the ventral or under
portion the sternum.
330 ZOOLOGY.

As these parts are less complicated in the abdomen, we
will first study this region of the body, and then examine the
more complex thorax and head. The abdomen is a little
over half as long as the body, the tergum extending far
down on the side and merging into the pleurum without
any suture or seam. The pleurum is indicated by the row
of spiracles, which will be noticed further on. The sternum
forms the ventral side of the abdomen, and meets the pleu-
rum on the side of the body.

In the female (Fig. 278, B), the abdomen tapers some-
what toward the end of the body, to which are appended
the two pairs of stout, hooked spines, forming the oviposi-
tor (Fig. 278, B, r, 7’). The anus is situated above the upper
and larger pair, and the external opening of the oviduct,
which is situated between the smaller and lower pair of
spines, and is bounded on the ventral side by a movable tri-
angular acute flap, the egg-guide (Fig. 278, B, eg, and Fig.
281).

The thorax, as seen in Fig. 278, consists of three seg-
ments, called the prothorax, mesothorax, and metathorax, or
fore, middle, and hind thoracic rings. They each bear a
pair of legs, and the two hinder each a pair of wings. The
upper portion (tergum) of the middle and hind segments,
owing to the presence of wings and the necessity of freedom
of movement to the muscles of flight, are divided or differ-
entiated into two pieces, the scwtwm and scutellum* (Fig.
278), the former the larger, extending across the back, and
the scutellum a smaller, central, shield-like piece. The
protergum, or what is usually in the books called the pro-
thorax, represents either the scutum or both scutum and
scutellum, the two not being differentiated.

The fore wings are long and narrow, and thicker than
the hinder, which are broad, thin, and membranous, and
most active in flight, being folded up like a fan when at
rest and tucked away out of sight under the fore wings,
which act as wing-covers.

* There are in many insects, as in many Lepidoptera and Hymenop-
tera and some Newroptera, four tergal pieces—7. ¢., preescutum, scutum,

scutellum, and postscutellum, the first and fourth pieces being usually
very small and often obsolete.
331

ANATOMY OF INSECTS.

| Metathorax ALesokhorax Prothorax

 

Fig. 279,—Male Caloptenus spretus.—Dissected and drawn by J. S. Kingsley.
332 ZOOLOGY.

Turning now to the side of the body under the insertion
of the wing (Fig. 279), we see that the side of each of the
middle and hind thoracic rings is composed of two pieces,
the anterior, episternum, resting on the sternum, with the
epimerum behind it; these pieces are vertically high and
narrow, and to them the leg is inserted by three pieces,
called respectively coxa, trochantine, and trochanter (see Fig.
279), the latter forming a true joint of the leg.

The legs consist of five well-marked joints, the femur
(thigh), ¢idia (shank), and ¢arsus (foot), the latter consist-
ing in the locust of three joints, the third bearing two large
claws with a pad between them. The hind legs, especially
the femur and tibia, are very large, adapted for hopping.

The sternum is broad and large in the middle and hind
thorax, but small and obscurely limited in the prothorax,
with a large conical projection between the legs.

The head is mainly in the adult locust composed of a sin-
gle piece called the epicranium (Figs. 279 and 280, #), which
carries the compound eyes, ocelli, or simple eyes (Fig. 280,
e), and antenne. While there are in real-
ity four primary segments in the head of
all winged insects, corresponding to the
four pairs of appendages in the head, the
posterior three segments, after early em-
bryonic life in the locust, become obsolete,
and are mainly represented by their ap-
pendages and by small portions to which the
appendages are attached. The epicranium
represents the antennal segment, and

 

Fig. 280.—Front

view of the head of C.

spretus. EH, epicrani-
um; (, clypeus; Z,
labrum; 0 0, ocelli; e,
eye; @, antenna; md,
mandible; mx,portion
of maxilla uncovered
by the labrum; p,
maxillary palpus; p/,
labial palpus.—Kings-
ley del.

280), a piece nearly twice as broad as long.

mostly corresponds to the tergum of the seg-
ment. The antenne, or feelers, are in-
serted in front of the eyes, and between
them is the anterior ocellus, or simple eye,
while the two posterior ocelli are situated
above the insertion of the antenne. In
front of the epicranium is the clypeus (Fig.
To the clypeus

is attached a loose flap, which covers the jaws when they

are at rest.

This is the upper lip or labrum (Fig. 280).
MOUTH-PARTS OF INSECTS. 333

There are three pairs of mouth-appendages : first, the true
jaws or mandibles (Fig. 278), which are single-jointed, and
are broad, short, solid, with a toothed cutting and grinding
edge, adapted for biting. The mandibles are situated on
each side of the mouth-opening. Behind the mandibles
are the maxille (Fig. 278), which are divided into three
lobes, the inner armed with teeth or spines, the middle lobe
unarmed and spatula-shaped, while the outer forms a five-
jointed feeler called the maxillary palpus. The maxille are
accessory jaws, and probably serve to hold and arrange the
food to be ground by the true jaws. The floor of the mouth
is formed by the dabiwm (Figs. 278 and 279), which in real-
ity is composed of the two second mavxille, soldered together
in the middle, the two halves being drawn separately in Fig.
278.

Within the mouth, and situated upon the labium, is the
tongue (lingua), which is a large, membranous, partly hol-
low expansion of the base of the labrum ; it is somewhat
pyriform, slightly keeled above, and covered with fine, stiff
hairs, which, when magnified, are seen to be long, rough,
chitinous spines, with one or two slight points or tubercles
on the side. These stiff hairs probably serve to retain the
food in the mouth, and are, apparently, of the same struc-
ture as the teeth in the crop. The base of the tongue is
narrow, and extends back to near the pharynx (or entrance
to the gullet), there being on the floor of the mouth, behind
the tongue, two oblique slight ridges, covered with stiff,
golden hairs, like those on the tongue.

The internal anatomy may be studied by removing the
dorsal wall of the body and also by hardening the insect
several days in alcohol and cutting it in two longitudinally
by a sharp sqalpel.

The esophagus (Fig. 281, @) is short and curved, contin-
uous with the roof of the mouth. There are several longi-
tudinal irregular folds on the inner surface. It terminates
in the centre of the head, directly under the supra-cesopha-
geal ganglion, the end being indicated by several small coni-
cal valves closing the passage, thus preventing the regurgita-
tion of the food. The two salivary glands consist each of a
334 ZOOLOGY.

bunch of follicles, emptying by a common duct into the floor
of the mouth.

The cesophagus is succeeded by the crop (ingluvies). It
dilates rapidly in the head, and again enlarges before pass-
ing out of the head, and at the point of first expansion or
enlargement there begins a circular or oblique series of folds,
armed with a single or two alternating rows of simple spine-
like teeth. Just after the crop leaves the head, the ruge or
folds become longitudinal, the teeth arranged in rows, each
row formed of groups of from three to six teeth, which
point backward so as to push the food into the stomach.
In alcoholic specimens the folds of the crop and cesophagus
are deep blood-red, while the muscular portion is flesh-col-
ored. It is in the crop that the ‘‘ molasses ’’ thrown out by
the locust originates.

The proventriculus is very small in the locust, easily over-
looked in dissection, while in the green grasshoppers it is
large and armed with sharp teeth. A transverse section of
the crop of the cricket shows that there are six large irreg-
ular teeth armed with spines and hairs (Fig. 282). It
forms a neck or constriction between the crop and true
stomach. It may be studied by laying the alimentary canal
open with a pair of fine scissors, and is then seen to be
armed with six flat folds, suddenly terminating posteriorly,
where the true stomach (chyle-stomach, ventriculus) begins.
The chyle-stomach is about one half as thick as the crop,
when the latter is distended with food, and is of nearly the
same diameter throughout, being much paler than the red-
dish crop, and of a flesh-color.

From the anterior end arise six large gastric ceca, which
are dilatations of the true chyle-stomach, and probably serve
to present a larger surface from which the chyle may escape
into the body-cavity and mix with the blood, there being in
insects no lacteal vessels or lymphatic system.

The stomach ends at the posterior edge of the fourth ab-
dominal segment in a slight constriction, at which point
(pyloric end) the urinary tubes (vasa wrinaria, Fig. 281,
ur) arise. These are arranged in ten groups of about fifteen
tubes, so that there are about one hundred and fifty long,
fine tubes in all.
335

ANATOMY OF INSECTS.

      
     

     

Bel eS
SSS

AN

   
       

SS

- =o
egg guide,

Fig. 281.—Internal anatomy of Caloptenus femur-rubrum. at, antenna and nerve leading to it from the ‘ brain” or supra-cesophageal ganglion
(sp), oc, ocelli, anterior and vertical ones, with ocellar nerves leading to them from the “‘ brain ;” ce, cesophagus ; m, mouth: /b, labium or under
lip ; if, infra-cesophageal ganglion, sending three pairs of nerves to the mandibles, maxille, and labium respectively (not clearly shown in the
engraving) ; 6m, sympathetic or vagus nerve, starting from a ganglion resting above the esophagus, and connecting with another ganglion
(sg) near the hinder end of the crop; sai, salivary glands (the termination of the salivary duct not clearly shown by the engraver); 7v, nervous
cord and ganglia; ov, ovary; wr, urinary tubes (cut off, leaving the stumps); ovt, oviduct; sb, sebaceons gland; bc, bursa copulatrix; ovi’, site of
opening of the oviduct (the left oviduct cut away); 1-10, abdominal segments. The other organs labelled in full.—Drawn from his original dis-
sections by Mr. Edward Burgess.
336 ZOOLOGY.

The intestine (ileum) lies in the fifth and sixth abdominal
segments.

Behind the intestine is the colon, which is smaller than
the intestine proper, and makes a partial twist. The colon
suddenly expands into the rectum, with six large rectal
glands on the outside, held in place by six muscular bands
attached anteriorly to the hinder end of the colon. The
rectum turns up toward its end, and the vent is situated
just below the supra-anal plate.

Having described the digestive canal of the locust, we
may state in a summary way the functions of the different
divisions of the tract. The
food after being cut up by the
jaws is acted upon while in
the crop by the salivary fluid,
i Which is alkaline, and pos-

EN) sesses the property, as in ver-
tebrates, of rapidly transform-
ing the starchy elements of
the food into soluble and as-
similable glucose. The diges-
tive action carried on in the
crop (ingluvies) then, in a veg-
etable-feeding insect like the

Fig. 282.—Transverse section of the locust, results in the conver-
ineeular Welles of Lomi lage cenrecn sion of the starchy matters
the large teeth.—After Minot. into glucose or sugar. This
process goes on very slowly. When digestion in the crop
has ended, the matters submitted to an energetic pressure
by the walls of the crop, which make peristaltic contrac-
tions, filter gradually through the short, small proventricu-
lus, directed by the furrows and chitinous projections lining
it. The apparatus of teeth does not triturate the food,
which has been sufficiently comminuted by the jaws. This
is proved by the fact, says Plateau, that the parcels of food
are of the same form and size as those in the crop, before
passing through the proventriculus. The six large lateral
pouches (ceca) emptying into the commencement of the
stomach (ventriculus) are true glands, which secrete an al-

 
DIGESTION IN INSECTS. 337

kaline fluid, probably aiding in digestion. In the stomach
(ventriculus) the portion of the food which has resisted the
action of the crop is submitted to the action of a neutral or
alkaline liquid, never acid, secreted by special local glands
or by the lining epithelium. In the ileum and colon ac-
tive absorption of the liquid portion of the food takes place,
and the intestine proper (ileum and colon) is thus the seat
of the secondary digestive phenomena. ‘The reaction of the
secretion is neutral or alkaline. The rectum is the ster-
coral reservoir. It may be empty or full of liquids, but
never contains any gas. The liquid products secreted by
the urinary tubes are here accumulated, and in certain cir-
cumstances here deposit the calculi or crystals of oxalic,
uric, or phosphatic acid. Insects, says Plateau, have no
special vessel to carry off the chyle, such as the lacteals or
lymphatics of vertebrates ; the products of digestion—viz.,
salts in solution, peptones, sugar in solution, and emulsion-
ized greasy matters—pass through the fine coatings of the
digestive canal by osmosis, and mingle outside of this canal
with the currents of blood which pass along the ventral and
lateral parts of the body.

Into the pyloric end of the stomach empty the urinary
tubes, their secretions passing into the intestine. These are
organs exclusively depuratory and urinary, relieving the
body of the waste products. The liquid which they secrete
contains urea (?), uric acid, and urates in abundance, hip-
puric acid (?), chloride of sodium, phosphates, carbonate of
lime, oxalate of lime in quantity, leucine, and coloring mat-
ters.

The nervous system of the locust, as of other insects, con-
sists of a series of nerve-centres, or so-called brains (ganglia),
which are connected by two cords (commissures), the two
cords in certain parts of the body in some insects united into
one. There are in the locust ten ganglia, two in the head,
three in the thorax, and five in the abdomen. ‘The first
ganglion is rather larger than the others, and is called the
“brain.’’? The brain rests upon the cesophagus, whence its
name, supra-cesophageal ganglion. From the brain arise the
large, short, optic nerves (Fig. 281, not lettered, but repre-
€

3, op),

which go to the compound eyes, and from the front arise

ZOOLOGY.
sented by the circle behind the brain, sp; Fig. 28

338

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From immediately in front, low down, arise

the three slender filaments which are sent to the three ocelli

(Fig. 281, oc).
NERVOUS SYSTEM OF INSECTS. 339

the antennal nerves (Fig. 281, aé). The simple brain of the
locust may be compared with the more complicated brain of
an ant, as seen in Fig. 284.

The infra-cesophageal ganglion (Fig. 283, if), as its name
implies, lies under the esophagus at the base of the head, un-

 
    

il

Fig. 284.—Right half of an ant’s-brain: uG, rales enon ues ganglion ; @, brain ;

C, central connective portions ; W, semi-circular bodies of the small-celled portion
of the brain lying next to the basal portion of the brain, from which the nerves to the
simple eyes (aw) arise; Aw, optic lobes; An, antennal lobes (the bodies appearing
like cells are rounded masses of the network of the substance of the cord ; 7, cellu-
lar cortical substance of the brain; xo, twofold body of the commissure connecting
the brain with the infra-cesophageal ganglion.—After Leydig, from Graber.

der a bridge of chitine, and directly behind the tongue. It is
connected with the supra-csophageal ganglion by two com-
missures passing up each side of the esophagus. From the
under side of the infra-esophageal ganglion arise three
pairs of nerves, which are distributed to the mandibles,
340 ZOOLOGY.

mavxille,and labium. ‘The mandibular nerves project for-
ward and arise from the anterior part of the ganglion, near
the origin of the supra-cesophageal commissures, while the
maxillary and labial nerves are directed downward into
those organs.

The sympathetic ganglia are three in number ; one situ-
ated just behind the supra-cesophageal ganglion (Fig. 278,
as), resting on the esophagus, and two others situated each
side of the crop, low down. Each of
the two posterior ganglia is supplied
by a nerve from the anterior ganglion.
Two nerves pass under the crop con-
necting the posterior ganglia, and
from each posterior ganglion a nerve
is sent backward to the end of the
proventriculus. A pair of nerves pass
under the cesophagus from each side
of the anterior sympathetic ganglion,
and another pair pass downward to a
round white body, whose nature is
unknown (Fig. 278, w).

Fig. 280 represents an enlarged
view of the brain and sympathetic

Fig. 280.—Supra-esopha. nerve of a moth. The heart isa long
geal ganglion and visceral (Of tube lying in the abdomen, dilating

sympathetic) nervous system

of the silk-worm moth (Bom- ‘ = 2
bya mori). gs, Swpra-ceso- at six places along its course, and

phageal ganglion (“brain”); ending in a conical point near the
a, antennary nerve ; 0, optic 4 ‘ ‘
nerve ; 7, azygos trunkof the end of the abdomen; it is held in
visceral nervous system ; 7”,

its roots arising from’ the place by fine muscular bands.
eupra-cesophageal ganglion ; :

6, paired nerve with its gangli- All insects breathe by means of a
i Ja ts Fo . :,
Atter Brandt, from Gegen. complicated system of air-tubes rami-
eur: fying throughout the body, the air
entering through a row of spiracles, or air-holes, or breath-
ing-holes (stigmata), in the sides of the body. There are in
locusts two pairs of thoracic and eight pairs of abdominal
spiracles. The first thoracic pair (Fig. 281) is situated on
the membrane connecting the prothorax and mesothorax,
and is covered by the hinder edge of the protergum (usually

called prothorax). The second spiracle is situated on the

 
RESPIRATORY ORGANS OF INSECTS. 341

posterior edge of the mesothorax. There are eight abdominal
spiracles, the first one situated just in front of the auditory
sac or tympanum (see Fig. 279), and the remaining seven are
small openings along the side of the abdomen, as indicated
in Fig. 286. From these spiracles air-tubes pass in a short
distance and connect on each side of the body with the spi-
racular trachea (Fig. 286,8, Fig. 287, 8) as we may call it.
The air-tubes consist of two coats, with several short spiral
threads wound around the tube (Fig. 288). These spiracu-
lar tracheze begin at the posterior spiracle, and extend for-
ward into the mesothorax, there subdividing into several
branches. Branches from them pass to the two main ven-
tral trachee (Fig. 286, v), and to the two main dorsal tra-
chee (Fig. 286, D, Fig. 287, D). The main tracheal sys-
tem in the abdomen, then, consists of six tubes, three on a
side, extending along the abdomen. The pair of ventral
trachez extend along the under side of the digestive canal ;
the dorsal trachee rest on the digestive canal. These six
tubes are connected by anastomosing traches, and, with
their numerous subdivisions and minute twigs and the sys-
tem of dilated trachex or air-sacs, an intricate network of
trachee is formed.

The system of thoracic air-tubes is quite independent of
the abdominal system, and not so easy to make out. The
tubes arising from the two thoracic stigmata are not very
well marked ; they, however, send two well-marked trachez
into the head (Fig. 286, c, Fig. 287, c), which subdivide into
the ocular dilated air-tube (Fig. 286, oc, Fig. 287, oc) and a
number of air-sacs in the front of the head.

The series of large abdominal air-sacs, of which there
are five pairs (Fig. 287, 3-7), arise independently of the main
trachee directly from branches originating from the spira-
cles, as seen in Fig. 286. They are large and easily found
by raising the integument of the back. There is a large
pair in the mesothorax (Fig. 287, 2) and two enormous sacs
in the prothorax (Fig. 287, 1), sometimes extending as far
back as the anterior edge of the mesothorax. All these sacs
are superficial, lying next to the hypodermis or inner layer
of the integument, while the smaller ones are, in many cases,
 

 

 

 

 

 
RESPIRATION IN INSECTS. 343

buried among the muscles. Besides the ordinary air-sacs,
there is in the end of the abdomen, behind the ovaries, a
plexus of six dilated air-sacs (Fig. 28%, I, II, III), which
are long, spindle-shaped, and are easily detected in dis-
secting.

There is a system of dilated trachew and about fifty air-
sacs in the head.

In the legs two traches pass down each side of the femora,
sending off at quite regular intervals numerous much-branch-
ing, transverse twigs; there is one large and a very small
trachea in the tibia, and the main one extends to the ex-
tremity of the last tarsal joint.

By holding the red-legged locust in the hand, one may
observe the mode of breathing. During this act the por-
tion of the side of the body between the spiracle and the
pleurum (Fig. 278, A) contracts and expands ; the contrac-
tion of this region causes the spiracles to open. The gen-
eral movement is caused by the sternal moving much more
decidedly than the tergal portion of the abdomen. When
the pleural portion of the abdomen is forced out, the soft
pleural membranous region under the fore and hind wings
contracts, as does the tympanum and the membranous por-
tions at the base of the hind legs. When the tergum or
dorsal portion of the abdomen falls and the pleurum con-
tracts, the spiracles open ; their opening is nearly but not
always exactly co-ordinated with the contractions of the
pleurum, but as a rule they are. There were sixty-five con-
tractions in a minute in a locust which had been held be-
tween the fingers about ten minutes. It was noticed that
when the abdomen expanded, the air-sacs in the first ab-

Fig. 286.—Showing distribution of air-tubes (trzchee) and air-sacs—side view of
the Tuody: v, Main ventral trachea (only one of the two shown); s, left stigmatal
trachea, connecting by vertical branches with D, the left main dorsal trachea; c, left
cephalic trachea ; oc, ocular dilated trachea. From the first, second, third, and fourth
spiracles arise the first four abdominal air-sacs, which are succeeded by the plexus
of three pairs of dilated trachee, I, II, III, in Fig. 287. Numerous air-sacs and
trachee are represented in the head and thorax. The two thoracic spiracles are rep-
resented, but not lettered.

Fig. 287.—D, left dorsal trachea; S, left stigmatal trachea ; I, IT, III, first, second,
and third pairs of abdominal dilated trachee, forming a plexus behind the ovaries;
1, pair of enormous thoracic air-sacs ; 2, pair of smaller air-sacs ; 3-7. abdomina:
air-sacs ; oc, ocular dilated trachea and air-sacs ; c, cephalic trachea. The relations
of the heart to the dorsal trachez are indicated.—Drawn by Emerton from dissec-
tions by the author.
344 ZOOLOGY.

dominal ring contracted. This would indicate that the
air rushes into the spiracles during the contraction of the
abdomen, and that the air-sacs are not refilled until the
spiracles are closed ; thus the air in the air-sacs is perhaps
constantly changing.

It is evident that the enormous powers of
flight possessed by the locust, especially its fac-
ulty of sailing for many hours in the air, is due
to the presence of these air-sacs, which float it
up in the atmospheric sea. Other insects with
a powerful flight, as the bees and flies, have well-
developed air-sacs, but they are less numerous.
It will be seen that, once having taken flight,
the locust can buoy itself up in the air, con-
stantly filling and refilling its internal buoys or
balloons without any muscular exertion, and
thus be borne along by favorable winds to its
ogs destination. It is evident that the process of

 

Fig. | 28 eens : :
Lowey en respiration can be best carried on in clear, sunny
trachea of Hy- weather, and that when the sun sets, or the

Creare beetle! weather is cloudy and damp, its powers of flight

ep, epithelium; : cee

cu, cuticula; 7, are lessened, owing to the diminished power of

Petter Minot Tespiration. The finer structure of the trachea
is seen in Fig. 288.

It is difficult to explain many of the actions of insects,
from the fact that it is hard for us to appreciate their men-
tal powers, instincts, and general intelligence. That they
have sufficient intellectual powers to enable them to main-
tain their existence may be regarded as an axiom. But in-
sects differ much in intelligence and also in the degree of
perfection of the organs of sense. The intelligence of in-
sects depends, of course, largely on the development of the
organs of special sense.

The sense of sight must be well developed in the locust,
there being two large, well-developed compound eyes, and
three simple ones (ocellt), situated between the former, sup-
plied with nerves of special sense.

Fig. 289 represents the eye of a moth greatly enlarged to
show the finer structure,
SHNSES OF INSECTS. 345

The antenne are, in the locust, organs of touch. The
palpi are not only organs of touch, but probably, as in some
other insects, are endowed with the sense of taste, enabling
the locust to discriminate between the different kinds of
food, and select that best adapted to suit its wants. It is
possible that the labial nerves send branches of special sense
to the tongue.

 

Fig. 289.—Longitudinal section of the facetted eye of a moth ; the eye-capsule or
sclera facetted externally (f), and sieve-like within, shows the rod-like ending of the
gpuic nerve-fibres ; k, layer of the crystalline lens; é, ig tee Dement zone; ch,
choroid composed of pigment cells ; sv, optic nerve ; ¢7, trachea lost in fine bundles
of fibrille.—After Leydig, from Graber.

The ears are well developed in the locust, and we know
that the sense of hearing must be delicate, not only from the
fact that a loud alarum with kettles and pans affects them,
but the movements of persons walking through the grass
invariably disturb them. Besides this, they produce a fid-
dling or stridulating sound by rubbing their hind legs
against their folded wing-covers, and this noise is a sexual
346 ZOOLOGY.

sound, heard and appreciated by individuals of the other
sex. Any insect which produces a sound must be supposed to
have ears to hear the sound pro-

e duced by others of its species.
In the antenne, palpi, and
abdominal appendages of dif-
ferent insects are seated mi-
nute sense organs of unknown
Fig. 290.—A, 6, sense-organ on the ab- functions, though probably

dominal appendages of a fly( Chrysopila);

¢, sense-organ on the terminal joint Of eae _ |
Oil Eonie athena either of smell or taste (Fig.
290).

The ears (or auditory sacs) of the locust are situated, one
on each side, on the basal joint of the abdomen, just be-

 

 

Fig. 291.—Ear of a locust (Caloptenus italicus) seen from the inner side. 7’, tym-
panum ; 7’, its border ; 0, u, two horn-like processes ; i, pear-shaped vesicle ; 7,
auditory nerve ; ga, terminal ganglion; st, stigma ; 7m, opening and m/ closing mus-
cle of the same; J/, tensor muscle of the tympanum-membrane.—After Graber.

hind the first abdominal spiracle (Fig. 279). The ap-
paratus consists of a tense membrane, the tympanum, sur-
rounded by ahorny ring (Fig. 291). ‘* On the internal sur-
ORGANS OF HEARING. 347

face of thismembrane are two horny processes (ow), to which
1s attached an extremely delicate vesicle (07) filled with a
transparent fluid, and representing a membranous labyrinth.
This vesicle is in connection with an auditory nerve (7)

§
\

 

Fig. 292.—A Carabus beetle in the act of walking. or running. Three legs (L!, R?,

L8), are directed forward, while the others (Z}, 2, R3), which are directed back-

ward toward the tail, have ended their activity. @6,¢cd,and ef are curves described

by the end of the tibiz and passing back to the end of the body; bh, di, and/ g are

eneves described by the same legs during their passive change of position.—After
raber.

which arises from the third thoracic ganglion, forms a gan-
glion (ga) upon the tympanum, and terminates in the im-
mediate neighborhood of the labyrinth by a collection of
3438 ZOOLOGY.

cuneiform, staff-like bodies, with very finely-pointed ex-
tremities (primitive nerve-fibres ?), which are surrounded
by loosely aggregated ganglionic globules.”’ (Siebold’s
Anatomy of the Invertebrates.)

In walking, the locust, beetle, or, in fact, any insect,
raises and puts down its six legs alternately, as may be
seen by observing the movements
of a beetle (Fig. 292). While the
structure of the limb of a ver-
tebrate and insect is not homol-
ogous, yet the mechanism or
functions of the parts are in
the main the same, as indicated
in Figs. 293 and 294.

The footprints of insects are
sometimes left in fine wet sand
on the banks of streams or by
the seaside.

In Fig. 295 the black dots
are made by the fore, the clear
circle by the middle, and the
black dashes by the hind legs
(Graber).

The wings are developed as
folds of the integument, and
strengthened by hollow rods
called ‘‘ veins ;’’ their branches

Fig. 293—Section of the fore leg of Called ‘‘ venures.’’ There are
a Stag beetle, showing the muscles. S. ; : ‘ :
sa 5 ee oe are eee
es, ee eee, en
joint, both enlarged.—After Graber. ne subcostal, median, subme-

dian, internal, and anal. They
are hollow and usually contain an air-tube, and a nerve
often accompanies the trachea in the principal veins. The
arterial blood from the heart (as seen in the cockroach by
Moseley) flows directly into the costal, subcostal, median,
and submedian veins ; here it is in part aérated, and returns
to the heart from the hinder edge of the wings through the
hinder smaller branches and the main trunks of the internal

 
FLIGHT OF INSECTS. 349

and anal veins. So that the wings of insects act as lungs
as well as organs of flight. For the latter purpose, the
principal veins are situated near the front edge of the wing,

 

Fig. 294.—Diagram of the knee-joint of a vertebrate (A) and an insect’s limb (B).
a, upper, 0, lower shank, united at A by a capsular joint, at B by a folding joint ;
d, extensor or lifting muscle ; @}, flexor or lowering muscle of the lower joint.
The dotted line indicates in A the contour of the leg.—After Graber.
called the costa, and thus the wing is strengthened when the
most strain comes during the beating of the air in flight.

The wing of an insect in making the strokes during flight
describes a figure 8 inthe air. A fly’s wing
makes 330 revolutions in a second, executing t
therefore 660 simple oscillations. |

The sexes are always distinct in insects, the
only exception being certain very low mites ae
called Tardigrada and Linguatulina, in which “9 €
both sexual glands occur in the same indi- : “)
vidual. The testes of the common red- ron. ;
legged locust form a single mass of tubular ae ( ‘
glands, resting in the upper side of the third, es
fourth, and fifth segments of the hind body. eA
Figs. 296 and 297 represent this structure in y~
other insects. The ovaries consist of two sets "O14
of about twenty long tubes, within which the |
eggs may be found in various stages of de-
velopment. The eggs pass into two main pig, 295.—Foot-

o : . : track f Necro-
tubes which unite to form the single oviduct Fiorus vespillo.

which lies on the floor of the abdomen. Rega g7e At
Above the opening of the oviduct is the sebific
gland and its duct. This gland secretes a copious supply of

a sticky fluid, which is, as in many other insects, poured

 

 

 
350 ZOOLOGY.

out as the eggs pass out of the oviduct, thus surrounding
them with a tough coat.

The external parts consist of the ovipositor (Fig. 278, B,
and Fig. 281), which is formed of two pairs of spines (rhad-
dites) adapted for boring into the earth; and of the egg-
guide (Figs. 278 and 281, eg), a triangular flap guarding the
under side of the opening of the oviduct.

   

Fig. 296.—Male sexual apparatus of a bark-beetle. aa eee ae A
st, vas deferens ; ho, testis ; b1, seminal vesicle; ag, of Acheta campestris.—After
ductus ejaculatorius.—After Graber. Gegenbaur.

There is a remarkable uniformity in the mode of develop-
ment of the winged insects. In general, after fertilization
of the egg, a few cells appear at one end of the egg ; these
multiply, forming a single layer around the egg, this layer
constituting the blastoderm. This layer thickens on one
side of the egg, forming a whitish patch called the primitive
streak or band. The blastoderm molts,
sloughing off an outer layer of cells,
a new layer forming beneath ; the skin
thus thrown off is called the serous
membrane ; the second germ-layer
(ectoderm) then arises, and a second

Fig. 298,—Section of Sphinxs Membrane (called amnion, but not
frie vol; Serena Gea homologous with that of vertebrates)
ene urea outer, peels off from the primitive band just

as the appendages are budding out, so
that the body and appendages of the embryo insect are en-
cased in the amnion as the hand and fingers are encased by
a glove. As seen in the accompanying Figs. 298-303, the

  
DEVELOPMENT OF INSECTS. 351

appendages bud out from the under side of the primitive
band, and antennz, jaws, legs, ovipositor (or sting), and the
abdominal feet of caterpillars are at
first all alike. Soon the appendages
begin to assume the form seen in
the larva, and just before the insect
hatches the last steps in the elabora-
tion of the larval form are taken.
As to the development of the in-
ternal organs, the ner-
yous system first origi-
nates ; the alimentary
canal is next formed ;

 

Fig. 299—Embryo of Sphinx : :
much more advanced. h, heart; and at about this time
g, ganglion; @, intestine; m : .
rudimentary muscular bands run- the stig mata and air-

ning to the heart ; s, stigma and s . =
beginning of a trachea (¢); d,a tubes arise as Invagina-

gland. This and Figs. 293-296

Eien Rowslevke tions of the outer germ-

layer. The development
of the salivary glands precedes that of the uri-
nary tubes, which, with the genital glands, are
originally offshoots of the primitive digestive
tract. Finally the heart is formed.

When the insect hatches, it either cuts its way
through the egg-shell by a temporary egg-cut-
ter, as in the flea, or the expansion of the
head and thorax and the convulsive movements
of the body, as in the grasshopper, burst the wig 309
shell asunder. The serous membrane is left in Primitive
the shell, but in the case of grasshoppers the eitcures
larva on hatching is still enveloped in the am- segments  in-

dicated, and

nion. This is soon cast as a thin pellicle. ws ana

The principal change from the larval to the ages. ¢, upper
adult locust or grasshopper is the acquisition of ne? ma, man-
wings. In such insects, then, as the Orthoptera Canin

and Hemiptera, in which the adults differ from ee eae
the newly hatched larva mainly in the posses- es (0 abdo-
sion of wings, metamorphosis is said to be in-

complete. In the beetle, butterfly, or bee, the metamorphosis

is complete ; the caterpillar, for example, is a biting insect,

 
352

is voracious, and leads a different life from the quiescent,
sleeping pupa or chrysalis, which takes no food; on the
other hand, the imago or butterfly has mandibles, which
are rudimentary, and incapable of biting, while the maxilla,
or ‘‘tongue,’? which were rudimentary in the caterpillar,
become now greatly developed; and the butterfly takes

 

 

Fig. 301.—Embryo of a
Water-beetle (Hydrophilus). £,
ege ; K, head ; ol, upper lip; m,
mouth ; an, antenne ;_ k,. man-
dibles; 2, kg, maxille; B,
thorax ; 5;, Do, Bq, legs ; hy-hyo,
ten pairs of rudimentary abdo-
minal legs, of which all except h,
disappear before the insect
hatches ; @, anus,—After Kowa-
levsky.

 

Fig. 302.—Profile view of embryo
Honey-bee, lettering as in Fig.
301. BM, uervous cord; 0G, brain;
D, digestive canal ; sch, the ceso-
phagus ; St, stigmatal openings of
the tracheal system; #, heart.—
After Bliitschii.

liquid food and but little of it, while its surroundings and
mode of life are entirely changed with its acquisition of
wings. Thus the butterfly leads three different lives, differ-
ing greatly in structure, externally and internally, at these
three periods, and with different environments.
METAMORPHOSIS OF INSECTS. 353

Most caterpillars moult four or five times; at each
moult the outer layer of the skin is cast off, the new
skin arising from the hypodermis, or inner layer of the in-
tegument. The skin opens on the back behind the head,
the caterpillar drawing itself out of the rent. In the
change from the caterpillar to the chrysalis, there are re-
markable transformations in the muscles, the nervous,
digestive, and circulatory system, inducing a change of
form, external and internal, characterizing the different
stages in the metamorphosis.

While the changes in form are
comparatively sudden in flies and
butterflies, the steps that lead to-
them are gradual. How gradual
they are may be seen by a study of
the metamorphosis of a bee. In
the nest of the humble or honey
bee, the young may be found in all
stages, from the egg to the pupa
gayly colored and ready to emerge
from its cell. It is difficult to
indicate where the chrysalis stage
begins and the larva stage ends,
yet the metamorphosis is more
complete—namely, the adult bee
is more unlike the larva, than in
any other insect.

Besides the normal mode of de-
velopment, certain insects, as the , Fig. 803.— Embryo of the Louse.

‘ am, serous membrane; dd, amnion;
plant-louse (Aphis), the bark-louse 4s, antenne ; vf Sorchead.—After

(Coccus), the honey-bee, the Po- aaterl

listes wasp, the currant saw-fly (Nematus), the gall-flies,
and a few others, produce young from unfertilized eggs.
Certain moths, as the silk-worm moth (Bombyx mori) and
others, have been known to lay unfertilized eggs from which
caterpillars have hatched. This anomalous mode of repro-
duction is called parthenogenesis, and fundamentally is only
a modification of the mode of producing young by budding
which is universal in plants, and is not unusual, as we have

 
354 ZOOLOGY.

seen, among the lower branches of the animal kingdom.
The object or design in nature, at least in the case of the
plant-lice and bark-lice, as well as the gall-flies, is the pro-
duction of large numbers of individuals, by which the per-
petuity of the species is maintained.

Insects are both useful and injurious to vegetation. Were
it not for certain bees and moths, orchids and many other
plants would not be fertilized ; insects also assist in the
cross-fertilization of plants. For full crops of many of our
fruits and vegetables, we are largely indebted to bees, flies,
moths, and beetles, which, conveying pollen from flower to
flower, ensure the production of abundant seeds and fruits.
Mankind, on the other hand, suffers enormous losses from
the attacks of injurious insects. Within a period of four
years, the Rocky Mountain locust, migrating eastward, in-
flicted a loss of $200,000,000 on the farmers of the West.
In the year 1864, the losses occasioned by the chinch-bug in
the corn and wheat crop of the valley of the Mississippi
amounted to upward of $100,000,000. It is estimated that
the average annual losses in the United States from insects
is about $100,000,000. On the other hand, hosts of
ichneumon flies and Tachina flies reduce the numbers and
prevent undue increase in the numbers of injurious insects.

The number of species of insects is estimated to be about
190,000. Of these there are about 25,000 species of Hyme-
noptera (bees, wasps, etc.) ; about 25,000 species of Lepi-
doptera (butterflies and moths) ; about 24,000 Diptera (two-
winged flies), and 90,000 Coleoptera (beetles) ; with about
4600 species of Arachnida (spiders, etc.), and 800 species
of Myriopoda (millepedes, centipedes, etc.)

Insects are distributed all over the surface of the earth.
Most of the species are confined to the warmer portions of
the globe, becoming fewer in the number of species as we
approach the North Polar regions. Many are inhabitants
of fresh water ; a very few inhabit the sea.

Insects, so far as the records go, first appeared in the
Devonian rocks ; these were Newroptera and Orthoptera, such
as May-flies and other forms which seem generalized in
their structure. But if highly developed flying insects, be-
PERIPATUS. 355

longing, at least the May-fly, to existing families, appeared
in the Devonian period, it is reasonable to suppose that in-
sects must have inhabited the dry land of the Silurian
period.

Insects are divided into four sub-divisions or sub-classes—
v.e., the Malacopoda, the Myriopoda, the Arachnida, and
the six-footed, winged insects, or Hexapoda. All agree in
breathing by air-tubes, and in having in most cases a tri-
regional arrangement of the segments of the body. By some
authors the three higher groups are regarded as independent
classes, but they are all modifications of a general insect
form, with similar mouth-parts, a single pair of antenna,
when these organs are present, with no palpus to the man-
dibles, and with other characters which render the class
Insecta equivalent to the class Crustacea.

Sub-class 1. Malacopoda.—This group is represented by
a single animal, the strange Peripatus of tropical coun-
tries, in which the body is cylindrical, the integument, an-
tenn, and limbs soft, not chitinized, with the head not
separate from the body, and bearing a pair of many-jointed
extensible antennz, with two pairs of rudimentary jaws
(mandibles and maxille), and from fourteen to thirty-three
pairs of feet (according to the species). This animal differs
from other Arthropods in the fact that there are two widely
separated nervous cords sent backward from the brain ;
also in the minute, numerous tracheal twigs arising from
numerous minute oval openings (rudimentary spiracles)
situated irregularly along the median line of the ventral
surface of the body. ‘The feet are soft, fleshy, and end in
two claws. Peripatus is viviparous. According to the
description and figures of Mr. Moseley, the young develop
much as in the chilopodous Myriopods (Geophilus), show-
ing that Peripatus is nearer to the Myriopods than any
other group. That it is a tracheate animal was also proved
by Mr. Moseley ; but owing to the nature of the nervous
system and the minute trachee and their numerous irregular
spiracular openings, with no chitinous edge, this form cannot
be placed among the Myriopods. On the other hand, it has
some features recalling the Linguatulina and Tardigrada,
356 ZOOLOGY.

as seen in the soft clawed feet and short wrinkled segments.
It is certainly not a worm, but, on the whole, connects the
worms with the sucking Myriopods, and suggests that the
insects may have descended from forms somewhat like Peri-
patus. Peripatus iuliformis inhabits the West Indies, and
either P. Edwardsii Blanchard, or an undescribed species
about four centimetres in length (with twenty-seven pairs
of legs), inhabits the Isthmus of Panama. The name
Malacopoda was proposed by De Blainville, who suggested
that Peripatus connected the Myriopods with the Annelids.
There is but a single genus, Peripatus.

Sub-class 2. Myriopoda.—The centipedes and millepedes
are distinguished by their cylindrical body, the abdominal
segments being numerous and similar to the thoracic seg-
ments, all provided with a pair of feet. The head is free,
with a pair of antenne, mandibles, and usually two pairs of
maxilla. The internal organization is simple, like that of
the larve of insects. Some Scolopendre are said to be
viviparous.

Order 1.  Chilognatha.—To this group belong the mille-
pedes, Julus, etc. (Figs. 304-307). The first maxille are
absent. The segments are round or flattened, and the feet
are inserted near together, the sternum being undeveloped.
In some forms (Fig. 304, Spirostrephon Copet Pack., from
Mammoth Cave) the body is hairy. They are all harmless.
The eggs are laid in large numbers an inch or two beneath
the surface of the earth. They undergo total segmentation,
and in a few days the larva (Fig. 305) hatches. At this time
it bears a resemblance to a Podura, having but three pairs
of feet, the third pair attached to the fourth thoracic seg-
ment. After a series of moults, new segments and new feet
appear, and thus these Myriopods undergo a distinct meta-
morphosis. The species feed on dead, sometimes fresh
leaves, and on fallen fruit.

Order 2. Pauwropoda.—The two orders of Myriopods are
connected by Pawropus, which by Lubbock is regarded as
the type of a distinct order (Pawropoda). Our only species,
Pauropus Lubbockit Pack. (Fig. 309), consists of six seg-
ments besides the head, and the young Pawropus has but
MYRIOPODS. 357

 

 

 

 

 

 

     

Fig. 305.—Larva of

Jnlus. a, third ab- Fig. 306.
dominal segment, with —Polydes-
the new limbs just mus ery-
budding out; 0, new thropygus
segments arising be- =-common
tween the penultimate Fety des-
Fig. 304.—Spiros- and the last segment.— .
trephon eae of After Newport.

Mammoth Cave.

 

  

Fig. 307.--Polydesmus cavicola, from Utah,
top and side view. a, antenna; b, a segment
and leg; c, dorsal view of two segments show-
ing ornamentation ; @, side view of two terminal
segments of the body—all magnified.

Fig. 308. — Geophilus.
Natural size.
358 ZOOLOGY.

three pairs of feet, and in this and other respects resembles
Podura. A second form, Zurypauropus, of Ryder, has six
segments, with feet wholly concealed from
above by the expanded segments.

Order 3. Chilopoda.—This group is rep-
resented by the centipede and Lithodius,
in which the body is flattened, the sternal
region being well developed. In Geophilus
(Fig. 308, G. bipuncticeps Wood) and allies
there are from thirty to two hundred seg-
ments. Our most common form is Litho-
bius Americanus Newport, found under
logs, etc. The centipede (Scolopendra
heros Girard) is very poisonous, the poison-
sac being lodged in the two large fangs or
first pair of legs. S. gigantea Linn., of
the East Indies, is nine inches long. In
Cermatia the body is short, with compound

eyes in the head and remarkably long
riobcee, Machen, slender legs. C. forceps Rafinesque, of the

lerged vis St .é2; Middle and Southern States, is said to be
and antenne and first ‘
eter deck poisonous.

 

An aberrant, generalized form is Scolo-
pendrelia, in which the head and antenne are like those of
Campodea, a Thysanurous insect ; this is therefore a con-
necting link between the Myriopods and Hexapods.

Sub-class 8. Arachnida.—The bodies of spiders and scor-
pions, etc., are divided into two
regions, a head-thorax and abdomen,
the head being closely united with
the thorax. There are no antenna,
only a pair of mandibles and a pair
of maxille, with four pairs of legs.
There are never any compound eyes.
The young are usually like the adult,
except in the mites, in which there _ Fig. 310.—Head of Pauropus
5 é a Lubbockiit. Much enlarged.
is a slight metamorphosis. In all
Arachnida there is a liver, this organ not being present in
the winged insects.

 
ANATOMY OF THE SPIDER.

359

The type of the sub-class is the spider, which is character-

 

Fig. 311—Anatomy of a spider, diagrammatic longitudinal
section through the body. qu, simple eyes and nerves leading
to them from the brain (supra-cesophageal ganglion, 0G) ;
@nq, mandibles ; ¢d_, palpus of maxilla /,; J,, first pair of legs,
6 5 , Succeeding pairs; A, head; Br, thorax ; i. hind-body
or abdomen; #z, heart or dorsal vessel ; Z, lung in front of
the opening of the oviduct G; the spinning-glands (sp) con-
nect with the spinnerets, sp W. The digestive tract is shaded,
and in the abdomen enveloped in the liver.—After Graber.

ized by the pos-
session of two
or three pairs
of spinnerets,
which are
jointed ap-
pendages ho-
mologous with
the legs. Be-
sides trachee,
spiders have a
so-called lung
(Fig. 311, L),
composed of
several leaves,
into which the
blood flows,

and is thus aérated. In Lycosa the blood flows through the
heart from the head backward. There is a great range of

structure, from the lowest
mites to the spiders, certain
mites having no heart, no
trachee, very rudimentary
mouth-parts, and no brain,
there being but a single
ganglion in the abdomen.
Order 1. Acarina.—The
mites are the simplest
Arachnida, the body being
oval in form, the head
usually small, more or less
merged with the thorax,
while the latter is not dif-
ferentiated from the abdo-
men. There is a slight
metamorphosis, the mite
when first hatched having

domesticated moose.

much enlarged.

arged.

 

 

Fig. 312.—Ixodes albipictus from a partly
The tick natura

gorged with blood, and its six-legged young,
a, beak or mandibles armed
with teeth; d, maxilla, and c, maxillary pal-
us; d,a foot with sucker and claws, en-

size,

but three pairs of legs, the fourth (and last) pair being added
360 ZOOLOGY.

after a moult. A typical mite, though above the average
size of the members of the group, is the tick (Fig. 31%),
Ixodes albipictus Pack. Closely allied to this is Ixodes bovis
Riley, the cattle-tick (Fig. 313), which buries its head in

 

Fig. 314.—Sugar-mite. Much en-

 
  

larged.
Fig. 313.—Jodes bovis. Natural size and
enlarged.
Fig. 315.--Ammothoé pycnogonoides.__ a, .
stomach with ceca (0, 0, d, 6) extending Fig. 316.--Pentastoma tentoides.
into the legs.—From Gegenbaur. Natural size.—From Verrill.

the skin, anchoring itself firmly by means of the backward-

pointing teeth of its jaws. Other examples of mites are the

cheese and sugar mites (Fig. 314, Tyroglyphus sacchari).
The sea-mites, Pycnogonide, are marine forms, without
BEAR ANIMALCULES. 361

air-tubes, with four pairs of long legs, into which ccecal
prolongations of the stomach pass, as seen in Fig. 315.

 

 

|
4
i
)
Fig. 317.— Milnesium tardigradum, i = ina scorpi }
x 120 times. 2, mouth-parts ; 0, alimen- Coa LS en, See Di Buus

tary canal ; ov, ovary.— After Doyere.

The lowest mites comprise remarkable worm-like Acarina,
called Linguatulina. The young are mite-like, the body
spherical, with boring jaws, and two
pairs of short-clawed feet. Pentas-
toma (Fig. 316) occurs in the lungs
and liver of man, and in horses and
sheep.

The Tardigrada or bear animal-
cules (Fig. 317) are a step higher
in the scale of mite life. In.these
singular beings the sexual glands
exist in the same individual.

Macrobiotus Americanus Packard
is common in sphagnum swamps. _ fig. 319.--Chelifercancroides.
Like the Rotatoria, these low mites M@snified.
are capable of revivifying after being apparently dead and
dried up.

 
362 ZOOLOGY.

Order 2. Pedipalpi.—This group embraces the scorpion
(Fig. 318), the false scorpions (Fig. 319), the whip scor-
pions, and the harvest-man (Phalangiwm). In all these
forms the abdomen is plainly segmented, the segments not
being visible in the mites or spiders. Usually the maxillary
palpi are much enlarged, and end in claws. The scorpion
is viviparous, the young being brought forth alive. The
young scorpions cling to the back of the mother. The sting
of the scorpion is lodged in the tail, which is perforated,
and contains in the bulbous enlargement an active poison.
Though producing sickness, pain, and swelling in the arm,
the sting of the scorpion is seldom fatal.

The little false-scorpions (Chelifer, Fig. 319) often occur in
books, under the bark of trees, and under stones. The whip-
scorpion is confined to warm countries. Thelyphonus gigan-
tews Lucas occurs in New Mexico and Mexico. Its abdomen
ends in a long lash-like appendage. Its bite is poisonous.
The harvest-men, or daddy-long-legs, are common in dark
places about houses. They feed on plant-lice. Our common
species is Phalangium dorsatum Say.

Order 3. Araneina.—The spiders are always recogniza-
ble by their spherical abdomen, attached by a slender pedicel
to the head-thorax. They breathe, like the scorpions, both
by lungs as well as by tracher, and the young resemble the
parent in having four pairs of feet.

The development of the spider has some peculiarities not
found in the higher insects. The egg undergoes total seg-
mentation. The germ is somewhat worm-like, as in Fig.
320, then, as in C, the primitive band forms, with head and
tail end much alike. Afterward (Fig. 321) the head ac-
celerates in development, and the appendages begin to bud
out, six pairs of abdominal limbs appearing and then totally
disappearing, except the three pairs of spinnerets, as if the
spiders were descended originally from some Myriopod-like
form. The mandibles are vertical, and end in hollow points,
through which the poison exudes, the two poison-glands
being situated in the head. The male spider is usually
much smaller than the female ; the latter lay their eggs in
silken cocoons. The tarantula (Zycosa) usually lives in
TRAP-DOOR SPIDERS. 363

holes in the ground, and sometimes conceals the opening by
covering it with a few dead leaves. Our largest spider is
Nephila plumipes of the Southern States. The common
garden spider is Hpeira vulgaris Hentz. It lives about

B A Cc

 

Fig. 220.—Development of the Spider.—A, worm-like stage ; B, primitive band ;
C, the same more advanced, with rudiments of limbs.
houses and in gardens ; its geometrical web is very regular.
The large trap-door spider (Mygale) has four lung-sacs in-
stead of two, as in the other spiders, and only two pairs of
spinnerets. Mygale Henzii Girard
inhabits the Western plains and
Utah ; Mygale avicularia Linn. of
South America is known to seize
small birds, and suck their blood.
There are probably about six or
eight hundred species of spiders
in North America; their colors
are often brilliant, and sometimes,
from the harmony in their colora-
tion with that of the flowers in
which they hide, or the leaves on
pitch ey ge ae ee the Fig. 321.—Embryo Spider, still
grasp of insectivorous birds. more advanced. This and Fig. 320

Sub-class 4. Hexapoda.—The “Yt “Mparete.
triregional division of the body is better marked in the
genuine winged insects than in the Myriopods and spiders.
They have compound as well as simple eyes; two pairs of

 
364 ZOOLOGY.

wings ; three pairs of thoracic legs ; often a pair of jointed
abdominal appendages, besides the ovipositor or sting which
morphologically represents three pairs of legs.

There are eight orders, forming two series: first, the
Heterometabola, comprising the Thysanura, Neuroptera,
Orthoptera, Hemiptera, and Coleoptera, in which the meta-
morphosis is ejther incomplete or complete; the body
shows a tendency to become flattened; the prothorax is
usually large and flattened ; the mouth-parts (except in the
Hemiptera) adapted for biting. There are a number of
wingless forms.

The second series of orders, or Metabola, comprising the
Diptera, Lepidoptera, and Hymenoptera, usually have a
cylindrical body, with the prothorax small, the mouth-parts
often adapted for sucking or lapping up liquid food ; with
a complete metamorphosis, the larva being worm-like,
cylindrical, very unlike the adult.

Order 1. Thysanura.—The spring-tails (Podura) and
bristle-tails (Zepisma) represent this group. They are
wingless, with some affinities to the Myriopods, and the
typical form Campodea (Fig. 324) is regarded as the ances-

tral form of the six-footed insects, as it is a
generalized type, and forms like it may have
been the earliest insects to appear.

In Podura, the spring-tail, and also in

Smynthurus (Smynthurus quadrisignatus
Pack., Fig. 322), the characteristic organ is
a forked abdominal appendage or “‘ spring,”
held in place by a hook ; when released the

, spring darts backward, sending the insect

Fig. 322.—Smyn- : A :
ae spring-tail, high in the air.

Our commonest Poduran is Tomocerus
plumbeus Linn. (Fig. 323), found all over the northern
hemisphere in North America and Europe. 'The snow-flea,
Achorutes nivicola Fitch is blue-black, and is often seen
leaping about on the snow in forests.

The Podurans belong to the suborder Collembola ; the
higher forms, which bear a greater resemblance to the larve
of Neuropterous insects and to the young cockroach, are
NEHUROPTERA. 365

the Cinwra, to which belong the genera Campodea (Fig.
324), Lepisma, and Machilis.

In these Thysanura there is no
spring, but the tail ends in two or
three bristles; and in Machilis,
the highest form, there are com-
pound eyes; in all there are

  

Fig. 323.—A Poduran (Zomocerus) and its scales. Much enlarged.

jointed abdominal appendages, which
structures are unique among Hexa-
podous insects. Campodea Ameri-
cana Packard isa small white slender
form, with long, many-jointed an-
tenn, and two long, slender jointed
caudal appendages. It lives under
stones, and (. Cookei Packard lives
in Mammoth Cave.

Order 2. Newropi-ra.—This group
of net-veined insects is interesting
from the fact that the existing
families are widely separate, owing
to the geological extinction of inter-
mediate links found fossil in the
Devonian and Carboniferous strata.
The mouth-parts are free, adapted
for biting ; the wings are broad, the yi, 304 — campodea. a,
hinder pair sometimes larger than mandibles ; 0, maxilla.
the front pair, and both pairs are finely net-veined. The

 
366 ZOOLOGY.

metamorphosis is either complete or incomplete. Many of
the species are aquatic. There are ten existing families,
and certain species of most of these families resemble or
anticipate the higher orders that succeeded them in time.
Thus the caddis-flies would be easily mistaken for small
moths; the Mantispa mimics Mantis, the Psocus mimics
the plant-lice, and the white ants which appeared in the
Coal Period foreshadow the genuine ants, which first ap-
peared in the Tertiary Period, wonderfully in form as well
as in the extreme differentiation of the dividual, involy-
ing a complicated colony with numerous members of the
entomological body politic.

 

Fig. 325.—Pupa of a Drag- Fig. 326.—Agrion, natural size, and a, its
on-fly (Zschna) larval gill, much enlarged.

As many of the larval Neuroptera live in the water, the
various forms of external gills are of high interest. In the
case-worms, which construct tubes of sand, bits of leaves,
etc., the gills are slender filaments permeated by air-tubes
and situated along the side of the body. In the larval and
pupal dragon-fly (Fig. 325) the water passes into the intes-
tine, where there are folds rich in minute tracheal branches.
{mn the smaller dragon-flies, such as Ayrion (Fig. 326), there
are three long, leaf-like gills, interpenetrated by air-tubes.
WHITE ANTS.

367

In the May-fly (Fig. 327) the leaf-like gills grow out from
the sides of the body. In the larval and pupal Perla
(Fig. 328), tufts of gills are situated on the under side of

 

Fig. 328.—Perla, larva.

  

Fig. 327.—May-fly and larva, the latter enlarged.

the prothorax, and in
the adult winged Pée-
ronarcys these gills
are retained. Both an
European and Brazil-
ian Caddis-fly has been
found to possess gills
in the winged condi-
tion.

The habits of the
Neuroptera are most
interesting ; the ant-
lion in the larval state
constructs a pitfall for
unwary insects. Its
metamorphosis is com-
plete, as is that of the
Aphis-lion (Fig. 329,
Chrysopa oculata Say,
adult and eggs).

As an example of
mimicry among insects
is Mantispa (Fig. 330),

which, in its raptorial fore-legs, strikingly resembles the

Orthopterous Mantis (Fig. 333).

The white ants top the Neuropterous series ; they live in
stumps and fallen trees, and in the tropics do much harm

by undermining the sills
of houses, and destroying
furniture, books, etc. The
colonies are very large and
populous. In our Termes
flavipes there are males
and females, workers and

 

Fig. 329.—Chrysopa and group of stalked
eggs.

soldiers ; the workers being small, ant-like, with small round
heads, while the soldiers have large square heads, with long
368

ZOOLOGY.

jaws ; the pups are active. Fritz Miller found in Brazil
that one species of Termes was differentiated into six
different kinds of individuals: viz., a set of winged and

 

Fig. 330.—Mantispa interrupta
Say ; and side view of the same
without wings. Natural size.—
Emerton del.

wingless females; winged and
wingless males ; workers and sol-
diers. A male always lives with a
female, and a wingless male and
female may, on the death of a
winged normal male and female,
replace them. He found a male
(king) living with thirty-one com-
plemental females. In Calotermes
there are no workers, in Anoploter-
mes no soldiers. Termes bellicosus
Smeathman, of the west coast of

Africa, builds conical hills six feet or more in height.
Order 3. Orthoptera.—The insects of this group, so called
from the straight-edged fore wings of the grasshoppers,

  

Fig. 332.—Larva of the same, but

Fig. 331.—Freshly-hatched larva of older, before the first moult. En-

Manlispa styriaca. Enlarged.

larged.—After Brauer.

locusts, crickets, etc., is characterized by their net-veined
wings and incomplete metamorphosis ; they are connected
closely with the Neuroptera by the ear-wig (forficula).
SOUNDS OF INSECTS. 369

Organs of hearing may be situated either on the fore legs,
as in the green grasshoppers, katydids, or at the base of
the abdomen, as in the locusts. Most Orthoptera have a
large ovipositor by which they burrow in the earth or into
soft wood, and deposit their eggs singly or in masses.
Mantis (Fig. 333) lays its eggs in a cocoon-like mass.

Many Orthoptera, as the crickets, green grasshoppers,
katydids, etc., and locusts, produce loud, shrill sounds,

 

iS Hig. 333.—An African Jfantis, or soothsayer, with its egg-mass.—From Monteiro’s
ngola.

which are sexual calls. They stridulate in three ways—
1.e., first, by rubbing the base of one wing-cover on the
other (crickets and green grasshoppers) ; second, by rub-
bing the inner surface of the hind legs against the outer
surface of the front wings (some locusts) ; third, by rub-
bing together the upper surface of the front edge of the
hind wings and the under surface of the wing-covers during
flight (some locusts).
370

ZOOLOGY.

Order 4, Hemiptera.—Insects of this group are called
bugs. They all (except the bird-lice and Thrips) have

 

Fig. 334. — Cor-
eus tristis, squash-
bug.

sucking mouth-parts, the mandi-
bles and first maxille are bristle-
like, and ensheathed by the labinm
or second maxille. There are no
palpi except in Thrips and the
bird-lice. The metamorphoses are
incomplete, the larva being like the
adult, except that the wings are ab-
sent. Many bugs secrete a disa-
greeable fluid from glands seated in
the metathorax. The lice are low,
wingless parasitic Hemiptera. The

 

Fig. 335.—
Thrips.

squash-bug (Fig. 384, Coreus tristis) and chinch-bug (Biis-
sus leucopterus Uhler) are types of the order.

 

Fig. 336.—Seventeen-year Locust.

a, b, pupa ; d, incisions for eggs.—After Riley.

An aberrant form is Thrips (Fig. 335, Thrips cerealium),
with long, slender white wings and free biting mouth-parts.
While most insects live but a year or two, or three at the
PLANT LICE. 371

most, the seventeen-year locust (Cicada septemdecim Linn.,
Fig. 336) lives over sixteen years as a larva, finishing its
transformations on the seventeenth ; there is also, accord-
ing to Riley, a thirteen-year variety of this species.

 

Fig. 338.—Cochineal insect,
male ; female natura} size and
enlarged.

 

Fig. 337.—Spittle insect. a, larva, enlarged ; 0,
its natural size.

The froth insect (Ptyelus lineatus, Fig. 337) abounds on
grass in early summer. The cochineal insect (Ooccus cacti)
belongs to the Coccide, or bark-lice; the dried female is
used as a dyestuff, and abounds in Central America.

The plant-louse (Fig. 339, Aphis mali Fabr.) is provided
with two tubes on the hind-body from which honey-dew

 

Fig. 339.—Apple Aphis. Natural size and enlarged.

drops, which attracts ants, wasps, etc. In summer the
plant-lice reproduce asexually, and as there may be nine or
ten generations, one virgin aphis may become the parent of
millions of children and grand-children.
372 ZOOLOGY.

Order 5. Coleoptera.—The beetles form a homogeneous
and easily circumscribed group, all having the fore-wings
thickened, not used in flight, and forming sheaths (elytra

 

Fig. 340.—Pine weevil. a, larva; 0, pupa.

or wing-covers) for the hinder pair. The mouth-parts are
free and adapted for biting. The metamorphosis is com-
plete. The young or larvee of beetles are called grubs.
Examples of beetles and their transformations are the pine

 

Fig. 341.—June Beetle and its transformations, 1, pupa; 2, larva.—After Riley.

weevil (Fig. 340, Pissodes strobi Peck.) and the June beetle
(Fig. 341, Lachnosterna fusca Frohl.). The oil beetle is
remarkable for passing through three larval stages (Fig.
OIL BEETLE. 373

342, Meloé angusticollis Say), the first larva being minute
and parasitic on bees, sucking their blood, while in the

 

Fig. 342.—Oil Beetle. a, first larva; 0, second larva; c, third larva; @, pupa.

second and third stages it feeds on the pollen mass designed
for the young bees.

 

Fig. 343.—Stylops childreni, male, dorsal and side view. Much enlarged.

The blister beetles (Lytta marginata) undergo a similar
series of transformations called a hypermetamorphosis.
374 ZOOLOGY.

The most aberrant of beetles is Stylops (Figs. 343 and 344,
S. childrent Westwood), the male of which has minute fore

 

 

Fig. 344.—Stylops childreni, female. Fig. 345.—Astraptor illuminator, larva.
a, parasitic in the abdomen of a bee ;
b, top view of the same. Much en-
larged.

 

Fig. 346.—The early stages of the common House-fly. A, dorsal and side view of
the larva; a, air-tubes; sp, spiracle. (C, the spiracle enlarged. /, head of the same
larva, enlarged ; 1, labrum (?); md, mandibles; ma, maxille; at, antenne. ZL, a
teria! spiracle much enlarged, D, puparium; sp, spiracle. All the figures much
enlarged.

wings. The female is wingless, grub-like, imperfectly de-
veloped, and is viviparous, the young issuing from her body
THE HOUSE-FLY. 375

in all directions. A few beetles are phosphorescent. Such
are the fire-flies, the cucuyo of the West Indies, the glow-
worm, and certain grubs, such as Astraptor tluminator
(Fig. 345), Melanactes, and the young of a snapping beetle.

 

Fig. 347.— Bot-fly of the ox and its larva,

We now come to the second series of orders, the Meta-
bola.

Order 6. Diptera.—The common house-fly (Fig. 346) is
a type of this division, all the members of which have but
two wings, while the tongue is especially developed for lap-
ping up liquids. The common house-
fly lives one day in the egg state, from
five days to a week as a maggot, and
from five to seven days in the pupa
state. It breeds about stables.

The Tachina-fly is beneficial to man,
from its parasitism in the bodies of
caterpillars and other injurious insects.

The bot-fly (Fig. 347, Hypoderma
Bovis DeGeer) is closely allied to the 31 %48—Sympis polis
house-fly, but the maggot is much
larger. The larval bot-fly of the horse lives in the stomach,
that of the sheep in the frontal sinus.

The Syrphus flies (Fig. 348, Syrphus politus Say) mimic
wasps ; they are most useful in devouring aphides.

 
316

ZOOLOG ¥.

  
      

?
'
A!

 
   

Se

ESSE

 

8

Fig. 349.—Metamorphosis of the Pulex irritans, or jigger, which lives in the toe of
the natives of tropical America. 1, egg; 2, embryo: 3, larva; 4, cocoon ; 5, pupa;
6, fecundated female ; 7, the same on the third day from its entrance under the skin
of its human host ; 8, the same after several days’ residence in the skin of its host ;
9, fully grown female magnified four times ; 10, head of the same still more enlarged ;
11, the female before it has entered the skin of its host ; 12, the mouth-parts, much

enlarged ; m, mandibles ; @, maxillary palpi ; uw, under-lip or labium.—After Karsten
and Guyon,

   
THE HESS8IAN-FLY. JT?

The fleas (349) are
wingless flies, allied to
winged forms intermedi-
ate between the house-
flies and crane-flies.

In the two-winged gall-
flies (Cecidomyia, etc.,
Fig. 350, C. tritici, Hes-
sian-fly) the body is small
and slender, with long
antenne. The crane-flies
(Tipula) are large flies,
standing near the head of
the order, and, like the
flea and gall-fly, the
chrysalis is enclosed in a
cocoon, there being no
puparium or pupa-case,
as in the lower flies.
Lastly, we have the mus-
quito (Figs. 351 and 352),
whose larva is aquatic,
and breathes by a process
on the end of the hody,
containing a trachea.

Order’. Lepidoptera.—
The butterflies and moths
form a well-defined group,
and are known by their
scaly bodies (Fig. 353),
the spiral maxille or
tongue, rolled up between

the two large labial palpi, °

and their usually broad
wings. As the butterfly,
the type of the order, has
been described at some
length, we will only
enumerate some of the

 

Fig. 350.—Hessian-fly. a, larva; b, pupa;
¢ inelsion in wheat stalk for larva.—After
itch.

 

Fig. 351.—A, larva; c, its respiratory tube.
B, pupa; d, respiratory tube. @, two paddles
at the end of the body.

 

Fig. 352.—Head of Mosquito enlarged. a,
antenne ; ™, mandibles ; mex, maxilla ; mp,
maxillary palpi; /g, labium.
378 ZOOLOGY.

typical forms. The lowest group are the plume-moths
(Pterophorus), in which the wings are fissured. Above

 

    

ul
ATA
Fig. 353.—Showing mode of ar-

rangement of thescales on the wings
of a Moth.

 

 

6

Fig. 355.—Grain Moth, Tinea granella. a, larva; 0, pupa, nat. size and enlarged ;
c, grain of wheat held together by a web.—After Curtis.

 

Fig. 856.—Army-worm Moth. a, male; >, female; c, eye; d, male; e, portion of
female antenna. Much magnified.—After Riley.

them stand the clothes and grain moths (Figs. 354 and 355),
which are minute moths with narrow wings.
THE COTTON-WORM. 379

The larger moths are represented by the canker-worm,
the grass army-worm (Fig. 356), and the cotton army-worm
(Fig. 357), so destructive to
vegetation; the silk- worm
moth (Lombyz mori Linn.),
of the Old World, and the
American silk-worm (Telea
Polyphemus Linn.). Certain
species of the  silk- worm
family, called basket-worms
(Giceticus), live in cases con-
structed of short or long strips

Fig. 357.—Egg, caterpillar, and moth (Fig. 358). Our native species
oF anomie wylina Say, the Cotton is Thyridopteryx ephemerefor-

mits Haworth.

The hawk-moths (Sphinx) are distinguished by their
large size and verylong tongue. The butterflies differ from
the moths in having knobbed anten-
ne, while the chrysalides are often
ornamented with golden or silvery
spots.

Order 8. Hymenoptera.—The bees
stand at the head of the insect series
in perfection and specialization of
parts, especially the organs of the
mouth, and from the fact that in the
course of the metamorphosis from
the larva to the pupa the first ab-
dominal segments become transferred
to the thorax—a striking instance of
the principle of transfer of parts
headward. In the large head, spheri-
cal thorax, and short, conical abdo-
men, the bees are opposed to the
dragon-flies and other Neuroptera,

 

 

1 1 ] Fig. 358.—Cases of African
In which the abdomen 18 long, the Baska gore: Natural size.

thorax composed of three homogene- ye
ous segments, and the mouth-parts only adapted for biting.
In the bee there is a marked differentiation of the parts of
380 ZOOLOGY.

the first and second maxille ; the tongue or fleshy prolonga-
tion of the second maxille (labiwm, see Fig. 359, g) being
very long and adapted for lapping up liquid food in the
bottom of flowers.

The Hymenoptera are represented by the saw-flies, the
gall-flies, the ichneumon-flies and the ants, the sand-wasps,
mud-wasps (Fig. 368), paper-making wasps, and bees.

The lowest family is the Uroceride, or horn-tails (Fig.
360, larva of Tremex columba Linn.), whose fleshy white

 

Fig. 359.—Side view of the front part of the head of the Humble Bee. a, clypeus
covered with hairs; 06, labrum; ¢, the fleshy epipharynx partially concealed by the
base of the mandibles (@); e, lacinia or blade of the maxilla, with their two-jointed
palpi (/) at the base ; j, the Jabium to which is appended the ligula (¢g) ; below are
the labial palpi; 4, the two basal joints ; k, compound eyes,
larve bore in trees. The adults are large, with a long, saw-
like ovipositor. In the saw-flies (Tenthredinide, Fig. 361,
the pear-slug, Selandria cerasi Peck) the larva strongly re-
sembles a caterpillar, having eight pairs of abdominal feet.

The gall-flies (Fig. 362, Cynips) are small Hymenoptera
which lay eggs in the leaves or stems of the oak, ete., which,
from the irritation set up by their presence, causes the de-
formation termed a gall.
HABITS OF ANTS. 381

5 The ichneumon-flies (Fig. 363) are very numerous in spe-
cies and individuals ; by their ovipositor, often very long
they pierce the bodies of caterpillars, inserting several or
many eggs into them ; the larve develop feeding only on
the fatty tissues of their host, but this usually causes the
death of the caterpillar before its transformation. Certain
minute species, with veinless wings (Fig. 364, Platygaster),
of the canker-worm eggs, are ege-parasites, OVipositing in
the eggs of butterflies, dragon-flies, ete.

  

Fig. 363.—An Ichneumon-fly.

Fig. oot Eee parasite of Canker-
worm. ighly magnified.

   

Fig. 360.—Horn-
tail : larvaof 7’re-
mex columba. Nat.
size.

Fig. 361.—Pear Slug,
natural size, gnawing
leaves. a, larva en--
larged ; 0, the fly.

The family of ants is remarkable for the differentiation
of the species and the consequent complexity of the colony,
the division of labor and the reasoning powers manifested
by the workers and soldiers, which, with the males and
females, constitute the ant-colony.

Certain ants enslave other species ; have herds of cattle,
the aphides ; build complicated nests or formicaries (Fig.
366), tunnel broad rivers, lay up seeds for use in the winter-
382 ZOOLOGY.

time, are patterns of industry, and exhibit a readiness in
overcoming extraordinary emergencies, which show that

 

they have sufficient reasoning powers to meet the exigencies
of their life ; their ordinary acts being instinctive—namely,

 

Fig. 366.—Diagram of an ant’s nest (Gicodoma), the chambers below containing
the ant food.—After Belt.

the results of inherited habits. ‘The leaf-cutter ants of
Central and South America (Fig. 365) are famous from
MUD-WASPS. 383

their leaf-cutting habits ; the soldiers have large triangular
heads, while the workers have much smaller rounded heads.
Fig. 367 represents a species of Heiton.

  

Fig. 367.—Eciton. Fig. 368.—Mud-dauber.

The mud-daubers (Pelopeus, Fig. 368) build their nests
against stone walls, of pellets of mud, while the sand- and
mud-wasps dig deep holes (Fig. 369, Sphea ichnewmonea

 

Fig. 369.—Sand-wasp (Sphex). Natural size.

Linn.) in gravelly walks, and have the instinct to sting
grasshoppers in one of the thoracic ganglia, thus paralyzing
the victim, in which the wasp lays her eggs; the young
384 ZOOLOGY.

hatching, feed upon the living but paralyzed grasshoppers,
the store of living food not being exhausted until the larval

Fig. 370.—Nest of Andrena. g, level
of ground; a, first-made cell, con-
taining a pupa; 0, J, larve ; ¢, pollen
mass with an egg laid on it; /, pollen
mass freshly deposited by the bee,—
Emerton del.

 

wasp is ready to stop eating
and finish its transformations.

The genuine paper-making
wasps are numerous in species;
here the workers are winged,
and only differ from the
females or queens in being
rather smaller and with unde-
veloped ovaries. The series of
genera from Odynerus, which
builds cells of mud, and in
which there are no workers,
up to those which have work-
ers and build paper cells, such
as Polistes, is quite continu-
ous. The genuine paper-
making wasps, such as Vespa,
build several tiers of cells, ar-
ranged mouth downward, and

‘enveloped by a wall of several

thicknesses of paper. In the
Vespe, the females found the
colony, and raise a brood of
workers, which early in the
summer assist the queen in
completing the nest.

The bees also present a
gradual series from those
which are solitary, living in
holes in the earth, like the
ants (Fig. 370, nest of <An-
drena vicina Smith), and form-
ing silk-lined earthen cocoons,
to those which are social, with
winged workers, slightly dif-

fering from the queens. The queen humble-bee hybernates,
and in the spring founds her colony by laying up pellets of
CLASSIFICATION OF INSECTS. 385

pollen in some subterranean mouse-nest or in a stump, and
the young hatching, gradually eat the pollen, and when it
is exhausted and they are fully fed, they spin an oval cylin-
drical cocoon ; the first brood are workers, the second males
and females. The partly hexagonal cells of the stingless
bees of the tropics (Melipona) are built by the bees, while
the hexagonal cells of the honey-bee are made by the bees
from wax secreted by minute subcutaneous glands in the
abdomen. Though the cells are hexagonal, they are not
built with mathematical exactitude, the sides not always
being of the same length and thickness.

The cells made for the young or larval drones are larger
than those of the workers, and the single queen cell is large
and irregularly slipper-shaped. Drone eggs are supposed by
Dzierzon and Siebold not to be fertilized, and that the queen
bee is the only animal which can produce either sex at will.
Certain worker-eggs have been known to transform into
queen bees. On the other hand, worker-bees may lay
drone eggs. The maximum longevity of a worker is eight
months, while some queens have been known to live five
years. The latter will often, under favorable circum-
stances, lay from 2000 to 8000 eggs a day. The first brood
of workers live about six weeks in summer, and are suc-
ceeded by a second brood.

Cuass II.—INSECTA.

A distinct head, thorax, and abdomen ; breathing by trachea ; usually
with a metamorphosis.

Sun-ciass I. Malacopoda.—Numerous simple spiracular openings with
isolated tracheal twigs ; nervous system with an incomplete
chain of minute ganglia, but the cords widely separated
(Peripatus).

Sus-ciass II. Myriopoda.—Thorax and abdomen forming a continuous
region, with from six to two hundred joints, each bearing a
pair of genuine legs.

Order 1. Ohilognatha.—Body cylindrical or flattened, with no
sternum ; a distinct metamorphcsis (Julus, Polydesmus).
386
Order

Order

ZOOLOGY.
2. Pauropoda.—Microscopic ; body of six to nine segments
besides the head (Pauropus).

3. Chilopoda.—Sternum large, body flattened (Scolopendra,
Lithobius).

Suzn-ciass III. Arachnida.—Head and thorax intimately united ; no

Order

Order

Order

antenne, and only one pair of maxille; no genuine abdo-
minal legs.

1. Acarina.—No thorax separate from the abdomen (Acarus,
Ixodes).

2. Pedipalpi.—Maxillary palpi often ending in a forceps or
claw; abdomen distinctly segmented (Scorpio, Chelifer,
Phalangium).

3. Araneina.—Abdomen rounded, bearing two or three
pairs of spinnerets, and attached by a slender pedicel to the
thorax ; no metamorphosis (Epeira, Mygale).

Sus-cuass IV. Herapoda.—Antenne always present, and two pairs of

Order

Order

Order

Order

Order

2

Order

maxille ; six thoracic legs ; a genuine metamorphosis.

1. Thysanura.—Wingless, minute, with a spring, or ab-
domen ending in a pair of caudal stylets; usually no
compound eyes; no metamorphosis (Podura, Campodea,
Lepisma).

2. Neuroptera.—Winged, net-veined, of equal size, pupa
often active ; abdomen often long and slender (Ephemera,
Libellula, Phryganea, Chrysopa, Perla, Termes).

8. Orthoptera. — Wings net-veined ; fore-wings narrow,
straight, not often used in flight ; metamorphosis incomplete;
pupa active (Forficula, Locusta, Caloptenus, Phaneroptera,
Acheta).

4. Hemiptera.—Mouth-parts forming a sucking beak ; pro-
thorax usually large; fore-wings often thickened at base ;
pupa active (Coreus, Arma, Pentatoma, Cicada, Coccus,
Aphis).

5. Coleoptera. —Fore-wings thick, ensheathing the hinder
pair, which are alone used in flight; mouth-parts frée,
adapted for biting ; metamorphosis complete (Doryphora,
Clytus, Lucanus, Harpalus, Cicindela),

6. Diptera.— Only two wings; mouth-parts adapted for
lapping and sucking ; a complete metamorphosis (Musca,
Cistrus, Syrphus, Cecidomyia, Tipula, Culex).
CLASSIFICATION OF INSECTS. 387

Order 7. Lepidoptera. — Body and wings covered with scales ;
maxille lengthened into a very long tongue; larve
(caterpillars) with abdominal legs (Tinea, Geometra, Noctua,
Bombyx, Sphinx, Papilio).

Order 8. Hymenoptera.—Wings clear, with few veins; mouth-
parts with a variety of functions, i.¢., biting, lapping
liquids, etc. In the higher families the thorax consists of
four segments, the first abdominal segment of the larva
being transferred to the thorax in the pupa and imago.
Metamorphosis complete. (Tenthredo, Cynips, Ichneumon,
Sphex, Vespa, Apis.)

TABULAR VIEW OF THE SUB-CLASSES AND ORDERS OF INSECTA.

 

 

 

 

 

 

8
eS
2 :
as
2 c
Sa
Se
gy & Sy 3S 8
SS S & s
N.8 & 8 §& :
So eS & :
S 8 2) 8) 8 eS
Sk Saas BS) aes
ys ¢ 8 8 :
S S s s 3 F S .
| Sneaks oS ae 8 Sos ¢
| Bey | ese es 3
or Ss a § Sacre esS
| x S 2 §
—_ ~-—- —VY & =
| —
Ss
= |
t | H+
HEXAPODA. ARACHNIDA. MYRIOPODA.
INSECTA.

Laboratory Work.—In dissecting Myriopods, spiders and insects, the
dorsal portion of the integument should be carefully removed with
fine scissors, leaving the hypodermis untouched ; this should then be
raised, disclosing the delicate heart or dorsal vessel. The alimentary
canal will be found passing through the middle of the body ; it should
be laid open with the scissors, or better, a hardened alcoholic specimen
can readily be cut in two longitudinally, and if the section is true, the
cesophagus and crop—for example, of a locust—can be laid open, and
388 ZOOLOGY.

the rows of teeth examined. The thoracic and abdominal portions of
the nervous system, which lies loosely on the floor of the body, can be
readily found by raising the alimentary canal ; but the brain and infra-
cesophageal ganglia can best be detected by a longitudinal section of
the head. The ovaries always lie above the intestine, and the two
oviducts unite below the nervous cord to form the common duct which
opens on the ventral side of the third segment in front of the anus,
which is situated dorsally. Insects should be dissected in a shallow
pan lined with wax or cork, and the parts floated out ; fresh specimens
are desirable. The body may also be dissected, each segment with its
appendages being separated and glued in their true sequence to a card.
By simply dissecting an insect in this way, the student will acquire a
valuable knowledge of the external structure of insects.

 

Dragon-fly (Diplax Elisa).
CHA PrerR Vil,

BRANCH VIII.—VERTEBRATA.

General Characters of Vertebrates.— The fundamental
characters of the Vertebrates are not the possession of a
segmented vertebral column, enclosing a nervous cord and a
skull, and containing a genuine brain, for these features,
though common to most Vertebrates, are wanting in the
lancelet (Amphioxus) and in a degree in the hag-fish, and
even the lamprey ; but the essential character is the division
of the body-cavity by the notochord (in the lancelet, etc.),
or by the back-bone of higher Vertebrates into two sub-
ordinate cavities, the upper (neural) containing the nervous
cord, and the lower (enteric) the digestive canal and its ap-
pendages and the heart. These are the only characters which
will apply to every known Vertebrate animal (compare p. 226
with Figs. 371, 375 and 376.)

In general, however, the Vertebrates are distinguished
from the members of the other branches by the following
characters: they are bilaterally symmetrical animals, with a
dorsal and ventral surface, a head connected by a neck with
the trunk ; with two eyes and two ears, and two nasal open-
ings, always occupying the same relative position in the head ;
an internal cartilaginous or bony, segmented skeleton, con-
sisting of vertebre, from the bodies of which are sent off
dorsal processes which unite to form a cavity for a spinal
cord, the latter sending off spinal nerves in pairs * correspond-
ing to the segmentations (vertebrae) of the spinal column.

* Except in Amphioxus, in which the spinal nerves arise right and
left alternately.
390 ZOOLOG ¥.

From the underside of the vertebre are sent off processes
articulating with the ribs, which enclose the digestive and
central circulatory organs. There is a skull formed by a con-
tinuation of the vertebral column, enclosing a genuine brain,
consisting of several pairs of ganglia. To the vertebral col-
umn are appended two pairs of limbs, supported by rays ir-
regularly repeated, or a series of bones of a definite number,

    

   
 
 

eZ 3
Udy,

   
     
 

Fig. 371.—Transverse section of a worm, of Amphioxus, and of a Vertebrate con-
trasted. a, outer or skin layer; 0, dermal connective layer; c, muscles; d, seg-
mental organ: , arterial, and 2, venous blood-vessel ; g. intestine ; ¢, notockord.—
After Haeckel.

attached to the vertebral column by a series of bones called
respectively the shoulder and pelvic girdle.

It will be observed that the fact of segmentation, so prom-

‘inent a feature in the Worms and Arthropods, survives, or at
least reappears in a marked degree in the Vertebrates, as
seen not only in the vertebral column, but in the arrangement
of the spinal nerves. It is perceived also in the arrangement
of the muscles into masses corresponding to the vertebre ;
and in the segmental organs or tubes forming the kidneys of
the sharks and rays, while segmentation is especially marked
in the disposition of the primitive vertebra of the early em-
bryos of all Vertebrates.

The digestive canal consists of a mouth with lips or jaws,
armed with teeth, a pharynx leading to the lungs ; an esoph-
agus and thyroid gland ; sometimes a crop (ingluvies), often
a fore-stomach (proventriculus) ; a stomach and intestine,
cloaca and vent. Into the beginning of the intestine pass
ducts leading from a large liver, usually provided with a gall-
bladder, a pancreas, and a spleen. The products of digestion
do not pass through the walls of the stomach and directly
enter the circulation, as in the invertebrates, but there is a
NERVOUS SYSTEM OF VERTEBRATES. 391

system of intermediate vessels called the lacteal system or
absorbents, which take up the chyle from the digestive or-
gans and convey it to the blood-vessels.

There is a true heart, with one, generally two, auricles, and
one or two ventricles with thick, muscular walls, and besides
arteries and veins, a capillary system, 7. ¢., minute vessels
connecting the ends of the smaller arteries with the smaller
veins. There are no genuine capillaries in the lower animals
exactly comparable with those of the Vertebrates.

The blood is red in all the Vertebrates except the lancelet,
and contains two sorts of corpuscles, the white. corpuscles
like the blood-corpuscles of invertebrates, and red corpuscles
not found in invertebrates, and which are said by some
authors to be derived from the white corpuscles.

While fishes and larval Amphibians breathe by gills, all land
and amphibious Vertebrates breathe the air directly by means
of cellular sacs called lungs, and connected by a trachea with
the pharynx, the trachea being situated beneath the cesopha-
gus, and the opening from the mouth into the pharynx lead-
ing into the trachea being placed below the throat or passage
to the esophagus. The air filling the cells or cavities of the
lungs passes by osmose through the walls of the cells into the
blood sent by the heart through the pulmonary artery, and
after being oxygenated it returns by the pulmonary vein to
the heart. On the other hand, carbonic acid passes from
the blood out of the lungs through the trachea.

The nervous system of Vertebrates consists of a brain and
spinal cord. The brain consists of four pairs of lobes, 1. ¢.,
the olfactory lobes, cerebral hemispheres, the optic thalami
(Thalamencephalon) and pineal gland, and the optic lobes; and
two single divisions : the cerebellum and the beginning of the
spinal cord, called the medulla oblongata. The olfactory lobes
are the most anterior, and send off the nerves of smell to the
nose. The cerebral hemispheres in the fishes and amphibians
are little larger than the adjoining lobes, but in the reptiles
become larger, until in the mammals, and especially in the
apes and man, they fill the greater part of the brain-box and
overlap the cerebellum ; the latter, in the mammals, also
exceeding all the other lobes in size, excepting the cerebrum.
392 ZOOLOG ¥.

Attached to a downward prolongation (infundibulum) of the
optic thalami is the curious pituitary body. The medulla
sends nerves to the skin and muscles, giving sensibility and
motion to the face, eyes and nose, to the larynx and sensitive
portion of the lungs; a pair also is sent to the lungs and
heart. If the spinal marrow is severed, the parts below are
paralyzed ; if the medulla is cut or broken up mammals die
at once, while the lower Vertebrata die sooner or later.
The brain in an embryo originally consists of three vesi-
cles or primitive lobes; and the correspondence between

 

Fig. 372.—Diagrammatic, longitudinal and vertical section of a Vertebrate brain.
M6, mid brain; whatlies in front of this is the fore brain, and what lies behind, the
hind brain. Z, lamina terminalis; Olf, olfactory lobes; Amp, cerebral hemi-
epheres; 7h EF, thalamencephalon ; Pn, pineal gland ; Py, pituitary body; FW, fo-
ramen of Munro; CS, corpus striatum ; 7%, optic thalamus; oo corpora quadri-
gemina; CU, cruracerebri; Cb, cerebellum ; PV, pons varolii ; 1/0, medulla oblon-
gata; J, olfactorii; Z/, optici; Z/Z, point of exit from the brain of the Motores
oculorum ; JV, of the pathetici ; VJ, of the abducentes ; V-—XVZ, origin of the other
cerebral nerves ; 1, olfactory ventricle ; 2, lateral ventricle ; 3, third ventricle; 4,
fourth ventricle.—After Huxley.

the three primitive lobes, called respectively the force, mid,
and hind brain, may be seen by the following table :

TABULAR VIEW OF THE SUBDIVISIONS OF THE VERTEBRATE BRAIN,

Olfactory lobes or ganglia, with their ventricles (rhinen-
cephalon).

Cerebrum or cerebral lobes or hemispheres (with the
two lateral or first and second ventricles, forming
the prosencephalon or prothalami).

Optic thalami, with the third ventricle and conarium
above and hypophysis below (Thalamencephalon ;

L pineal gland).

Fore brain. 1
NERVOUS SYSTEM OF VERTEBRATES. 393

Optic lobes, corpora bigemina or quadrigemina (mesen-
cephalon).

Crura cerebri.

Optic ventricle or Iter a tertio ad quartum ventriculum.

Mid brain.

CerebelJum (with its ventricle and the pons varolii, form-
Hind brain. J ing the metencephalon).
| Modula oblongata and fourth ventricle,

The accompanying sketches represent the typical nervous
system of an amphibian, which also resembles that of many
fishes, and even the lower Reptilia.

The spinal cord (Fig. 374) usually
extends through the whole length of
the spinal canal, except in the toads
and frogs, birds and many mammals,
where it stops short of the end of its
canal. In those Vertebrates with
limbs, the cord enlarges where the
nerves which supply them are sent off ;
these are the cervical or thoracic, and
lumbar enlargements, especially large
in turtles and birds. The white and
gray substance of the brain continues
in the cord.

As the most essential characteristic
of Vertebrates is the internal skeleton
(endoskeleton) we will enter more into
detail in describing it, and afterwards

notice the external skeleton (exo-

Fig. 373 —Brain and spinal
skeleton). cori of the frog. A, Fail

7 above, B, from below. 4a, ol-
In the embryos of higher Vertebrates footy Auhoe nb cerebral

and in the adult lancelet, hag-fish and hemispheres; c, optic lobes;
d, cerebellum in the form of a

lamprey, the vertebral column is rep- lamella bridging over the
: : fourth ventricle (s) ; m, apna
resented by a rod-like axis (notochord cord ; t, terminal cord.—After
é F ; egenbaur.
or chorda dorsalis) which is composed
of indifferent, or only partly organized cells, the substance
of the chord resembling cartilage. These chordal cells secrete

a membrane called the chordal sheath. Thenotochord is not

 

 

 
394 ZOOLOGY.

segmented. In all Vertebrates above the lamprey, the verte-
bral column grows around the notochord, which finally

 

Fig. 374.—Transverse section through the spinal cord of a calf. a, anterior, 6,
posterior longitudinal fissure ; c, central canal; d, anterior, e, posterior cornua; J,
substantia gelatinosa; g, anterior column of the white substance ; /, lateral, z, pos-
terior column ; &, transverse commissures. —After Gegenbaur.

Fig. 375.—Section through the vertebral column of Ammocetes (lamprey). Ch, no-
tochord; cs, chordal sheath ; m, spinal chord ; a, aorta; v, veins.

Fig. 376.—Section through the spinal column of a young salmon. Ch, notochord ;
cs, chordal sheath; m, spinal chord; X, superior, X’, inferior arch (rudimentary) ; a,
aorta; v, veins.—After Gegenbaur.

forms the central portion of the bodies of the vertebre, and
in the higher Vertebrates is wholly effaced ; the centra or
LIMBS OF VERTEBRATES. 395

bodies of each vertebra of a lizard, bird or mammal being
solid bone. Figs. 375 and 376 represent the relations of the
notochord in an adult lamprey and a young fish.
The vertebra of a bony fish

or higher vertebrate consists fa
of a body, with a dorsal or we r

: ‘ : - yy)
neural spine; a pair of oblique ,-@ 4
processes (zygapophyses)arching / ;” NC Nee iN
over and enclosing the spinal = | eo )
cord; and ¢ransverse processes, \.\, j

 

. . /
bending downwards, to which te
the ribs are articulated ; certain —— Ya
of the thoracic ribs uniting Nate 4
with the s¢ernwm or breast-bone ; NS

i Fig. 377.—Diagram of a Vertebra
(Figs. 377 and 378.) with its body (5), rib (7), breast-bone
6); 1, neural spine; 2, 3, fore and

Vertebree like those of fishes, Poh oblique processes ; 4, transverse
which are hollow or concave at Pr°s*®
each end, are said to be amphicelous ; those hollow in front
and convex behind procelous, as in most toads and frogs
and crocodiles, and most existing
lizards, and those convex in front
and concave behind opisthocelous,
as in the garpike, some Amphib-
ians (the salamanders and cer-
tain toads, Pipa and Bombinator).

Wepre ironies vertebra of Vertebrates never have more
buzzard (Buteo vulgaris). c, centrum than two pairs of limbs, an an-
or body; s, superior spinous pro- ‘ ; ‘
cess; tr, transverse process; %0, terior and hinder pair ; the pecto-
rib; a, tuberculum of the rib ; 3, ca- .
piahnmatthairib- Aten Ceaen: ral pair of fins of fishes represent
panr the fore limbs of Amphibians and
higher Vertebrates, and the arms of man; the two ventral
fins represent the hind legs of higher Vertebrates, and the
legs of man. Each pair of limbs is connected by ligaments
and muscles to a girdle or set of bones, called respectively
the shoulder girdle and pelvic girdle, each girdle being con-
nected by muscles to the vertebral column. The shoulder
girdle consists of a clavicle (or collar-bone), scapula (or
shoulder-blade), and coracoid bone, usually a process of the
scapula. ‘These bones differ greatly in the different classes,

 
396 ZOOLOGY.

and are reduced to cartilaginous pieces in sharks. The pelvic
girdle, or pelvis, consists of three bones, 7.e., one dorsal, the
tlium, and two ventral, the anterior of which is called pubis,
and the posterior ischiwm.

The limbs each consist of a single long bone, succeeded by
two long bones, followed by two transverse rows of short
wrist or ankle bones, and five series of long finger or toe
bones, called phalanges. For example, in the fore limb of
most Vertebrates, as in the arm of man, to the shoulder gir-
dle, 7.e., at the point of junction of the three bones com-
posing it, is articulated the humerus ; this is succeeded by

 

Fig 380.

Fig. 379.—Sternum and shoulder girdle of Frog (Rana
temporaria). p, body of the sternum ; sc, scapula; sc’,
supra-scapula ; co, coracoid bone, fused in the middle line
with its fellow of the opposite side (s) ; c/, clavicle ; e, epis-
ternum. The extreme shaded double portion below pis the
xiphisternum, The cartilaginous parts are shaded.—After
Gegenbaur.

Fig. 380.—Fore-leg of a seal. S, scapula; H, humerus;
O, olecranon or tip of elbow; &, radius; U, ulna; Po.
pollex, or thumb.

Fig. 381.—Pelvis or pelvic bones on one side of amar-u_ «
pial (Kangaroo). 62, ilium; a, situated on the pubic bone
(pubis) indicates the acetabulum or concavity for the ariic-
ulation of the head of the femur; 63, ischium, consolidated with the pubis. The
three bones thus consolidated form the os innominatum ; m, marsupial bones ar-
ticulated to the pubic bones.—After Owen.

 

the wlna and radius, the wrist-bones or carpals, and the fin-
ger-bones or phalanges, the single row of phalanges forming
a digit (finger or toe). To the point of union (acetabulum,
Fig. 381, a) of the three pelvic bones is articulated the fe-
mur, cr thigh; this is succeeded by the tibia and fibula
(shank-bones), the tarsal and metatarsal bones (ankle-bones),
and the phalanges or bones forming the digits (toes).

Figs. 383-385 represent the simplest form of the posterior
limbs in the higher Vertebrates, that of the bird showing an
COMPOSITION OF THE SKULL. 397

extreme modification in form. At first all limbs arise as
little pads, in which the skeletons subsequently develop, and
in early life the limbs of all Vertebrates above the fishes are
much alike, the mod-
ifications taking place
shortly before birth. Ac-
cording to Gegenbaur
and others, the limbs of
Vertebrates have been
probably derived from
the pectoral and ventral
fins of fishes in which
the fin-rays are irrela-
tively repeated. *

In the fins of fishes
there is a simple system
of leverage ; in the limbs
of higher air-breathing Fig. 382.—a, skull; 4, portclie c, sacrum,
Vertebrates, formed by and e, its continuation (urostyle) ; f, suprascap-

ula; g, humerus; #, fore-arm bones; 2, wrist

alki ¢ m- bones (carpals and metacarpals) ; d, ilium; m,
walking orm land, Ley thigh (femur) ; 2, leg bone (ulna) : 0, elongated

pound system of lever titel or plalanyes.—atver Owen. > "4"
age (Wyman).

The head of all Vertebrates above the lancelet is supported
by a more or less perfect cartilaginous or bone framework,
the skull (cranium), or brain-box (Fig. 386). It is a contin-
uation of the vertebral column, and protects the brain,
besides forming the support of the jaws, tongue-bone
(hyoid bone), and branchial arches. The series of lateral
(visceral or branchial) arches varies, but there may be nine;
the most anterior (if it be counted as the first one, Fig.
387, a, b,c) is formed by the labial cartilages (¢rabecule
cranit) ; next comes the mandibular arch (0, 2), which is suc-
ceeded by the hyoid arch (II.) and the six branchial arches.
In the embryos of all Vertebrates these visceral arches are

      

SS

* A modified form of this theory is advocated by Balfour and J. K.
Thatcher, who attempt to show that the limbs with their girdles were
derived from a series of similar simple parallel ravs, and that they
were originally a specialization of the continuous lateral folds or fins of
embryo fishes, and probably homologous with the lateral folds of the
adult lancelet (Amphioxus).
398 ZOOLOGY.

well marked; of the slits or openings between them, the
first is destined to form the mouth, the next pair of slits

    

Was
Fie. 384. Fig. 385.

Fig. 383.—Hind leg of a larval Salamander. The dotted lines are drawn through
the rays to which the different pieces belong. Fe, femur: 7, tibia; F, fibula; 4, ¢,
c, f, tarsal bones; 7, os intermedium ; ¢, tibiale; /, fibulare; c, centrale ; 1-5, the
five Sraale. The first row of phalanges are called metatarsals (in the haud, meta-
carpals).

Fig. 384.—Bones of the foot of a Reptile (lizard) A, and an embryo bird, B. /f, fe-
mur; ¢, tibia; m, fibula; ¢s, upper, ¢, lower pieces of the tarsus ; m, metatarsus ;
i-V, metatarsalia of the toes.

Fig. 385.—Leg of the Buzzard (Buteo vulgaris). a, femur; 8, tibia; 0, fibula; ¢,
tarso-metatarsus ; c’, the same piece isolated, and seen from in front; dd’, ad” a”
the four digits or toes.—After Gegenbaur. 2G Lie ene

in the Amphibia and higher Vertebrates forms the ear-pass-
age, while the other slits may remain open in fishes, form-
COMPOSITION OF THE SKULL. 399

ing gill-slits or spiracles, but are closed in the higher Verte-
brates. As a rule, the skull is symmetrical, exceptions being
found in the flounders and the bones about the nose of cer-

 

Fig. 386.—Skull of the Lion. 2, occipital condyle ; %, Parietal bone and sagittal
crest ; 8, paroccipital ; 277, squamosal bone ; 27, zygomatic arch; 26, malar bone ;
11, frontal bone ; 12, post-orbital process ; 15, nasal bone; 21, maxillary bone ; 22,
premaxillary bone ; 32, mandible ; 3, occipital crest ; c, canine teeth ; p?, second pre-
molar ; m/, molar tooth.—After Owen.

tain whales and porpoises. The base of the skull is perfo-
rated for the exit of the nerves proceeding from the base of
the brain, and the hinder bone (occiput) is perforated ( fora-
men magnum) for
the passage of the
spinal cord from the
medulla oblongata.
It is probable that
there is a general
parellelism between
the head of Insects
and _ Vertebrates,
i.e., that while the Fig. 387.—Skull and visceral skeleton of a Selachian
4 _ (diagram). occ, occipital region; da, wall of the laby-
head of insects, for rinth; eth, ethmoidal region ; n, nasal pit; q, first, d, ¢,
F second labial cartilage ; 0, superior, n, inferior portion
example, consists Of of the mandibular arch 7. ; Z/., hyoid arch; Z/Z.- VIII.
* (1-6), branchial arches.—After Gegenbaur.

a certain number of
segments, homologous with those of the rest of the body,
and with mouth-parts homologous with the limbs; that the
skull is also segmented, and an expansion and continuation
of the vertebral column. Gegenbaur even maintains that
the various arches of the head are homologous with the limbs.

 
400 ZOOLOGY.

On the other hand, while the brain of insects is a single
pair of ganglia like those of the rest of the body, the differ-
ent ganglia forming the brain of Vertebrates are concen-
trated in the head alone; still the different pairs of nerves
sent off from the base of the brain are homologous with
the spinal nerves, sent off at intervals corresponding to each
vertebra.

There are two theories of the composition of the skull.
That of Oken, Goethe, and of Owen, who believed that the
skulls of the bony fishes and mammals were composed of
three or four segments. It should be noticed that these
views are based on an examination of highly specialized ver-
tebrates. From a study, however, of the more generalized
types of fishes (such as the sharks), and the embryos of ver-
tebrates belonging to different groups, the old vertebrate
theory of the skull has been discarded, and the view of Ge-
genbaur, confirmed by Salensky, is probably nearly the cor-
rect one. As stated by Gegenbaur :

1. The skull is comparable to a portion of the vertebral
column, which contains at least as many vertebral segments
as there are branchial arches. This view is borne out by the
following facts :

a. The notochord, which forms the foundation of the
vertebral column, passes through the cranium in the
same way as it passes through the vertebral column.

b. All the nerves which pass out of the base of the
skull (or that portion traversed by the notochord)
are homologous with the spinal nerves.

c. The difference between the skull and vertebral col-
umn consist of secondary adaptations to certain con-
ditions, which are external tothe skull, and were
partly due to the development of a brain.

2. The skull may be divided into two regions, a vertebral
portion and an anterior everfebral portion, lying beyond
the end of the notochord.

3. The number of vertebrae which enter into the forma-
tion of the skull are nine at least (according to Salensky, in

the sturgeon, seven) ; the exact number is immaterial.
TEETH OF VERTEBRATES. 401

In the lancelet there is no skull, or even the rudiments of
one (unless the semi-cartilaginous supports of the tentacles
be regarded as such), hence the Vertebrates are divided into
the skulless or acraniate (Acrania, represented by the lance-
let alone) and the skulled or craniate (Craniota), the latter
series comprising all forms from the hag-fish to man. In
the Craniota the skulls may be, according to Gegenbaur, di-
vided into two groups. In the hag and lamprey the noto-
chord is continued into the base of a small cartilaginous
capsule, enclosing the brain, and which represents the skull
of higher Vertebrates (Craniota). This capsule behind is
continuous with the spinal column.

With the skull of the second form two jaws are developed,
hence all the vertebrates above the hag and lamprey form a
serles (Gnathostomata) opposed to the former, or Cyclos-
tomata.

In the Gnathostomata there is a gradual modification and
perfection of the skull. In the sharks it may be quite sim-
ple and cartilaginous ; in the bony fishes it is highly special-
ized, consisting of a large number of separate bones. In
the Amphibians we first meet with askull consisting of few
bones, easily comparable with those of mammals; in the
reptiles and birds the ear-bones are external, forming the
large quadrate-bone by which the lower jaw is articulated to
the skull. A progress is seen in the mammals where the
quadrate-bone becomes internal—one of the ear-bones (the
incus). Nowalso, the brain becoming much larger, evincing
amuch higher grade of intellect, the skull is greatly en-
larged to accommodate the great increase in size of the
cerebrum and cerebellum, the perceptive and reasoning fac-
ulties predominating over those regions of the brain and
skull devoted to perceiving, grasping, and masticating the
food.

Though not properly forming part of the skeleton or de-
veloped with it, we may here consider the teeth.

The teeth of Vertebrates are formed from the modified
epidermis and cutis, or dermis; the former secretes the
enamel and the latter is changed into the pulp or dentine.
The simplest form of tooth is conical. In the jawless hag
there are no teeth in the lips, but a single median tooth on
402 ZOOLOGY.

the palate and two rows of comb-like teeth on the tongue.
In the lamprey the edges of the circular mouth are provided
with circular rows of conical horny teeth. The teeth of
higher Vertebrates are derived from the cells of the mucous
membrane of the mouth, which is formed of connective tis-
sue as well as epithelium. The teeth of fishes are developed
not only in one or several rows in the lip, but may also arm
the bony projections into the mouth-cavity of the palate,
vyomer and parasphenoid bones and the hyoid and bran-
chial arches. In the Amphibia teeth survive on the palatine
and vomerine bones, more rarely on the parasphenoid ; among
the reptiles, the snakes and lizards alone have teeth on the
palatine and pterygoid bones, while in the crocodiles and in
mammals the teeth are confined to the maxillary bones. In
the geckos, snakes and the crocodiles, as well as the mam-
mals, the teeth are inserted in sockets (alveoli) of the jaw.
(Gegenbaur. )

In certain extinct birds (Odontornithes) there were teeth
in the jaws, though all existing birds are toothless. It is
said that rudimentary
teeth were found by
Geoffroy St. Hilaire in
the jaws of a parrot.
Blanchard afterwards
found the germs of
teeth there, though
they never come
through. In the Mam-
mals the teeth are dif-
Fig. 383.—Teeth of the Tasmanian devil. The ferentiated into inci-

incisors are situated in front of the large conical :
canine teeth. 2,3, premolars; m, 1-4, four molar SOYS, Canines, premo-

teeth.—After Owen. lars and molars (Fig.
383). In descriptive anatomy the teeth are for convenience
expressed by a formula, the number of teeth of the upper
jaws being placed like the numerator of a fraction, and those
of the lower jaw like the denominator, the initials of the
names of the teeth being placed before the figures, thus
=? pt a eee

d

 

 

> ay

‘i i 2)
the dental f la of man is J cereals ‘
e dental formula of m pao aes

es aleom
SCALES, HAIRS, AND FEATHERS. 403

In the fishes, Amphibians and reptiles, the worn-out teeth
are replaced by a succession of new ones ; in mammals (ex-
cept cetaceans, where there is no change) there is but a single
change, the first (milk) teeth being replaced by a second set
of permanent teeth. The teeth of the lower Vertebrates
are shed while swallowing the food. In the boa (Python)
the teeth thus shed are found scattered along the intestinal
canal and are discharged with the remnants of the food
(Wyman).

The dermal or evoskeleton consists of the scales of fishes,
reptiles and certain mammals, such as the armadillo, the

 

Fig. 384.—Vertical section through the skin of an embryonic shark. (, corium or
dermis ; ¢,c, ¢, layers of the corium ; d, uppermost layer ; p, papilla; Z, epidermis;
é, its layer of columnar cells; 0, enamel layer.—After Gegenbaur.
feathers of birds and the hairs of mammals. Most scales
arise from dermal papille (Fig. 384, »), and are covered over
by a layer of enamel (Fig. 384, 0) developed from the epider-
mis; so that the scales of sharks and rays, for example,
arise from both the dermis and epidermis.

A hair or feather is a modification of a scale; the papilla
is sunken in a pit of the dermis, the conical cap of epi-
dermis arising from it ultimately forming the hair or feather.
The plates of turtles, the scales of snakes and lizards, and
the claws of birds are epidermal. In the horns of mammals,
as of the rhinoceros, and the hoofs of the horse, the epi-
dermal substance is penetrated by numerous long dermal

papillee.
404 ZOOLOGY.

The head of the sturgeon, garpike, and of other ganoid
fishes, is protected by solid dermal bones, and the shells of
turtles are dermal structures.

The color of the skin of Vertebrates is due to pigment-
granules situated either in the epidermis or dermis, and in
the chameleon they
are contained in special
sacs (chromatophores)
which are under the
control of the nervous
system.

The muscular system
of Vertebrates arises
from the middle germ-

: layer (mesoderm), and
Fig. 385.—Placoid scale of dog-fish (vertical sec- .
tion Taagnified). a, enamel 3 dog 6, dentine of the in the germ the muscles

spine on the scale. —-After Owen. in part arise from the
primary segments indicated by the protovertebre, while in
the adults of fishes and certain salamanders, the muscular
system is distinctly segmented, corresponding to the seg-
mentation of the ver-
tebral column, the
four lateral trunk-
muscles being divided
into a number of seg-
ments by tendinous
bands, which corre-
spond in number to
the vertebrae (Gegen-
baur).

The eye in Verte-
brates in its develop-
mentalhistory belongs
to a different type of
structure from that of
any invertebrates, un Fig. 386. —Cyloid scale of roach, magnified, seen in
less it be the larva] 8¢ction, 4, and from the surface, B.—After Owen.
Ascidians, for in both types the eye is said by Gegenbaur not
to be directly developed from the ectoderm, but from the

 

 
EYES AND EARS OF VERTEBRATES. 405

anterior portion of the central nervous system. The differ-
ence between the highly-developed eye of a cuttle-fish and
a bony fish, for example, consists in the fact that the rods
and cones (similar to those of the invertebrate eye) forming
a layer (the bacillar layer) behind the retina, are in the ver-
tebrate eye turned away from, while in the invertebrates they
are directed toward the opening of the eye.

The ear of Vertebrates is at first a primitive otocyst, or
ear-vesicle, which is gradually cut off and enclosed, forming
a cavity of the skull. As we rise towards the mammals, the
ear becomes more and more developed until the inner,
middle, and outer ear is formed ; the Eustachian tube being a
modification of the first branchial cleft, forming the spiracle
in the sharks (Sedachiz) and Ganoids.

In the lancelet a head is scarcely more set apart from the
rest of the body than in many invertebrates. In the fishes
and Amphibians the head is not separated by a neck from
the trunk ; in reptiles the neck begins to mark off a head
from the thorax, while in the birds and mammals the head
is clearly demarked, the degrees of cephalization and trans-
fer headward of those features subordinate to the intellec-
tual wants of the animal becoming more striking as we
ascend through the mammalian series to the apes, and finally
man.

The development of Vertebrates can scarcely be epitomized
in a few lines. The mode of growth of Amphioxus is a
general expression for that of all Vertebrates, for all develop
from fertilized eggs, which undergo total or partial segmen-
tation of the yolk, become three-layered sacs and assume the
peculiar vertebrate characters, the development of the mam-
mals differing from that of the other classes only in compar-
atively unimportant features.

The Vertebrates are divided into two series or sub-branches:
the Acrania and Craniota ; the former type is represented
by but a single genus, order’and class, the lancelet or Am-
phiozus. The sub-branch Craniotais divided into six class-
es, the Marsipobranchs, fishes, amphibians, reptilia, birds
and mammals,
406 ZOOLOGY.

Crass 1. Leprocarpir (Lancelet).

The lancelet is the only type of this class. From its
worm-like form it was regarded as a worm by some authors,
and as a mollusk (‘‘Limax”) by

Corea
o-- 8 -
BES ae Pallas. The body is four or five cen-
G5 8S x timetres in length, slender, com-
moo oo & é
ie zy pressed, pointed at each end, hence
ao . .
PESEE the generic name (Amphioxus, appt
a GS8 5 2 >
Sages both, ous, sharp), the head-end be-
ee s3* ing thi ed. The muscu-
Eae8— ing thin, compressed.
oom 8 lar segments are distinct to the
Bees
SEE Ce naked eye. From the mouth to the
BUSES vent is a deep ventral furrow, and
es85° P ?
BG gee a slight fin extends along the back
gee
g Eos g and ventrally as far front as the vent.
Be Bee The lancelet, A. lanceolatus (Pal-
© - . * <
5 207 las), lives in sand just below low-
SSR water mark, ranging on our coast from
mo
fog the mouth of Chesapeake Bay to
or . .
ear Florida ; it also occurs on the South
Ba . .
298 American coast, and in the European
od 2 . .
228 seas and the East Indies, the species
eee being nearly cosmopolitan.
"2 BE As this is the lowest Vertebrate, its
°
goE structure and mode of development
oQ .
ESF merit careful study.
8 The mouth is oval, surrounded

with a circle of ciliated tentacles
supported by semi-cartilaginous pro-
cesses arising from a circumoral ring.
The mouth leads directly into a large
broad pharynx or ‘branchial sac”
(Fig. 387, d), protected at the en-
trance by a number of minute cili-
ated lobes.

: The walls of this sac are perforated
by long ciliated slits, comparable with those of the bran-

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DEVELOPMENT OF THE LANCELET. 407

chial sacs of Ascidians and of Balanoglossus. The water
which enters the mouth passes out through these slits when
it oxygenates the blood, and-enters the general body-cavity,
thence passing out of the body through the abdominal pore
(Fig. 387, c). The pharynx leads to the stomach (e), with
; which is connected the liver or cecum (f). There is a
pulsatile vessel or tubular heart, beginning at the free end
of the liver, and extending along the underside of the phar-
ynx, sending branches to the sac and the two anterior branches
to the dorsal aorta. ‘‘On the dorsal side of the pharynx the
blood is poured by the two anterior trunks, and by the
branchial veins which carry away the aérated blood from
the branchial bars, into a great longitudinal trunk or dorsal
aorta, by which it is distributed throughout the body.”
(Huxley.) There are also vessels distributed to the liver,
and returning vessels, representing or foreshadowing the
portal and hepatic veins. The blood-corpuscles are white
and nucleated.

The vertebral column is represented by a notochord which
extends to the end of the head far in front of the nervous
cord ; and also by a series of small semi-cartilaginous bodies
above the nervous system, and which are thought to repre-
sent either neural spines or fin-rays. The nervous cord les
over the notochord ; it does not enlarge in the head to form
the brain, but sends off a few nerves to the periphery, with
nerves to the four minute eye-spots. There are no kidneys
like those of the higher Vertebrates, but glandular bodies
which may serve as such. The reproductive glands are
square masses attached in a row on each side of the walls of
the body-cavity. The eggs may pass out of the mouth or
through the pore. Kowalevsky found the eggs issuing in
May from the mouth of the female, and fertilized by sper-
matic particles likewise issuing from the mouth of the male.
The eggs are very small, 0-105 millimetres in diameter. The
eggs undergo total segmentation, leaving a segmentation-
cavity which becomes the body-cavity.

The blastoderm now invaginates and the embryo swims
about as a ciliated gastrula. The body is oval, and the germ
does not differ much in appearance from a worm, starfish,
408 ZOOLOGY.

or ascidian in the same stage of growth. No vertebrate
features are yet developed.

Soon the lively ciliated gastrula elongates, the alimentary
tube arises from the primitive gastrula-cavity, while the edges
of the flattened side of the body grow up as ridges which
afterwards, as in all vertebrate embryos, grow over and en-
close the spinal cord. When the germ is twenty-four hours
old it assumes the form of a ciliated flattened cylinder, and
now resembles an Ascidian embryo (Fig. 138, 2), there
being a nerve-cavity, with an external opening, which after-
wards closes. The notochord appears at this time.

In the next stage observed the adult characters had ap-
peared, the mouth is formed, the first pair of gill-openings
are seen, eleven additional pairs appearing. It thus appears
that while the lancelet at one time in its life presents Ascidian
features, yet as Balfour states ‘all the modes of develop-
ment found in the higher Vertebrates are to be looked upon
as modifications of that of Amphioxus.”

A second form of this group, from Moreton Bay, North-
ern Australia, has been described by Peters under the name
of Epigonichthys cultellus. It differs from Amphioxus in
the presence of a high dorsal fin, in the want of a distinct
caudal and anal fin, with some differences in the structure
of the mouth and oral tentacles. It is from thirteen to
twenty-three millimetres in length.

Crass I.—LEPTOCARDII.

Comprising the lowest Vertebrate known ; body lancet-shaped, with no
skeleton ; notochord persistent, no brain ; no cranium ; no paired fins ;
blood colorless ; a metamorphosis ; gastrula ciliated, free-swimming.

A single order (Pharyngobranchi), family (Amphioxini), and genus
(Amphioxus), each with the characters of the class.

Laboratory Work.—The structure of the lancelet can only be imper-
fectly made out by a triplet lens and higher powers ; but by sections
stained with carmine the anatomy can be well studied. Brooks has
found the young in the later free-swimming stages on the surface of
the ocean near Fortress Monroe.
GENERAL CHARACTERS OF MARSIPOBRANCHS. 409

Crass Il. Marsrpoprancuit (Lampreys, or Cyclostomi).

General Characters of the Cyclostomatous Vertebrates.
—In the hag-fish and lamprey, representatives of the jaw-
less Vertebrates, the body is long and slender, cylindrical,
the skin smooth, scaleless, with only a median dorsal and
ventral fin (or in Myzxine only a small lower median fin) ;
the mouth is circular, and in the lampreys armed with nu-
merous conical teeth. There is no bony skeleton; the
spinal column is represented simply by a thick rod (dorsal
cord, notochord) surrounded by a sheath. The skull is car-
tilaginous, not movable on the vertebral column; is very
imperfectly developed, having no jaws, the hyo-mandibu-
lar bones and the hyoid arch existing in a very rudimentary
state. The few teeth present in the hag-fish are confined to
the palate and tongue ; those of the lamprey are numerous,
conical and developed on the cartilages supporting the lips.

The nervous system is much as in the fishes, the brain
with its olfactory, cerebral lobes, thalami, optic lobes, and
medulla being well developed, the cerebellum apparently not
being differentiated from the medulla. The digestive canal
is straight, with no genuine stomach, but the liver is much
as in higher Vertebrates. The respiratory organs are
very peculiar, being purse-like cavities (whence the name
Marsipobranchit), in the lamprey being seven in number on
each side of the pharynx, opening externally by small aper-
tures ; internally they connect with a long cavity lying under
the esophagus, and opening anteriorly into the mouth. The
heart is like that of fishes, as are the kidneys. The eyes
are minute, sunken in the head and under the skin in the
hag (Myzxine), but larger in the lamprey.

Another extraordinary feature in the class is the single
nasal aperture, as opposed to the two occurring in all
higher Vertebrates. The aperture leads to a sac, which
in the Myxine communicates with the mouth (pharynx), but
in the lamprey forms a cul-de-sac.

The ovaries and male glands (the sexes being distinct) are
unpaired plates suspended from the back-bone, and have no
410 ZOOLOGY.

ducts, the eggs breaking through the walls of the ovary, fall-
ing into the abdominal cavity and passing out of the abdom-
inal pore. The eges of Myxine are very large in proportion
to the fish, enclosed in a horny shell, with a filament at each
end by which it may adhere to objects.

The hag-fish is about afoot long and an inch thick, with
the head small, a median palatine tooth, and two comb-like
rows of teeth on the tongue. There is a single gill-opening
a long ways behind the head; there are large mucous or
slime-glands on the side of the body, for these fishes are
very slimy. The hag lives at considerable depths in the sea ;
we have dredged one at 114 fathoms in soft deep mud off
Cape Ann. It is often parasitic, attaching itself to the bod-
ies of fish, and has been found to have made its way into the
body-cavity of sturgeons and haddock.

The lamprey lives both in fresh and salt water. The eggs
of the common lamprey, Petromyzon marinus (Linn.), are
laid in early spring, the fish following the shad up the rivers,
and spawning in fresh water, seeking the sea in autumn ;
small individuals, from five to seven inches long, have been
seen by Dr. Abbott attached to the bellies of shad, sucking
the eggs out of the oviducts.

The lamprey when six inches long is quite unlike the adult,
being blind, the eyes being concealed by the skin ; it is tooth-
less, and has other peculiarities. It is so strangely unlike the
adult that it was described as a different genus (Ammocetes).
P. nigricans Lesueur is smaller, and occurs in the lakes of
New York and eastward, while P. niger Rafinesque is still
smaller, and lives in the Western States.

Cuass II. MARSIPOBRANCHI.

Worm-like Vertebrates, without paired fins ; notochord persistent ; a
single nasal sac, siz or ten pairs of purse-like gill-sacs, no jaw-bones.

Order 1. Hyperotetra.—Nasal duct leading into the mouth. (Myxine.)

Order 2. Hyperoartia.—Nasal duct a blind sac, not connecting with
the mouth. (Petromyzon.)
GENERAL CHARACTERS OF FISHES. 411

Laboratory Work.—The anatomy of these animals is exceedingly in-
teresting ; the respiratory sacs and nasal duct can be exposed by a lon-
gitudinal section of the head ; the relations of the notochord can be
best seen by transverse sections ; the heart and vessels should be in-
jected. Preparations of the brain should be made, and with care the
skull prepared.

Cuass III. Pisces (Sharks, Rays, Sturgeons, Garpikes, and
bony fishes).

General Characters of Fishes.—We now come to Verte-
brates which have genuine jaw-bones and paired fins, and
which, in short, are affiliated to the Batrachians, and through
them with the reptiles, birds, and mammals. All the fishes
agree in having a true skull, to which is attached a movable
lower jaw. The brain is well developed, with its lobes for
the most part, at least, equivalent to or homologous with
those of the reptiles, birds, and mammals, though the cere-
bral hemispheres are small, and in most fishes of nearly the
same size as the optic lobes; the cerebellum is also generally

Jin.

GQ

Dorsal

       

Anal. Ventral. Pectoral.
Fig. 388.— The Mud-Minnow.

of moderate size. The head forms part of the trunk, there
being no neck (except in the Hippocampide), and the body
is usually compressed and adapted in shape for rapid motion
in the water.

Paired fins are always primitively developed, though the
posterior or ventral fins, at least, are in many cases wanting
through the atrophy of parts developed in embryonic life.
The pectoral and ventral fins (Fig. 388), which represent the
fore and hind legs of higher Vertebrates, are attached to the
body or trunk by a shoulder and pelvic girdle. The shoulder
412 ZOOLOGY.

girdle is either lyre-shaped or forked, like a bird’s wish-bone,
curved forward, and with each side connected below; the
fishes in this respect differing from the Batrachians (Gill).
The shoulder girdle is usually closely connected by a series
of intervening bones with the skull, and makes its first ap-
pearance opposite the interval between the second and third
vertebree.

The skull and skeleton may be either cartilaginous or bony,
and the bones of the head and skeleton very numerous. In
some sharks there are 365 vertebre ; in some bony fishes 200,
while in the Plectognathi (fishes like the sun-fishes and Ba-
listes) there may be no more than fifteen; thus in some
fishes there may be about one thousand separate bones. No
fishes have a well-defined sternum or breast-bone, this bone
appearing for the first time in the Batrachians. The verte-
bre are almost always biconcave ; this is the simplest, most
primitive form of vertebra: ; it forms a weak articulation,
admitting, as Marsh states, of free, but limited motion.

All fishes breathe by gills, which are supported generally
on four or five cartilaginous or bony supports or arches. The
gills are never purse-shaped, as in the lampreys, and are
mostly situated within the head, in front of the scapular arch.

The mouth is generally armed with teeth varying greatly
in number and form, and in the bony fishes especially, not
only the jaws, but any bony projections, such as the palatine,
pterygoid and vomerine bones, as well as the tongue and pha-
ryngeal bones may be armed with teeth, so that the food is
retained in the mouth and more or less torn and crushed be-
fore being swallowed.

Fish have no salivary glands. The tongue moves only as
a part of the hyoid apparatus upon which it is attached.
After being crushed and torn in the mouth the food passes
through a short throat or cesophagus into the stomach. The
intestine is generally provided at the anterior end with
several or numerous cecal appendages which are especially
abundant in the cod. The gut is twisted once or twice be-
fore reaching the vent, but is usually much shorter than in
the air-breathing Vertebrates, while the vent is placed much
nearer the mouth than in the tailed Amphibians, thus sepa-
STRUCTURE OF FISHES. 413

rating the trunk into a thoracic and caudal portion. To
make up for the short intestine, its absorbing surface is
greatly increased in all except the bony fishes by a peculiar
fold called the ‘‘spiral valve.” The rectum always opens in
front of the urinary and genital outlets; except when the
latter communicates directly with the rectum, thus forming
acloaca. All fishes have a well-developed liver, usually a gall-
bladder, with several gall-ducts ; and in general a yellowish
pancreas.

The heart consists of a ventricle and auricle, the latter
branchial with a venous sinus (stnws venosus) ; while to the
ventricle is added an arterial bulb, which subdivides into five
pairs of arteries, one for each gill-arch. The Dipnoi ap-
proach the Amphibians in the possession of a second auricle
as well as of genuine lungs, 7.e., cellular air-sacs. The lungs
are fundamentally comparable with the air-bladder or swim-
ming bladder. It is generally situated below the back-bone,
and is developed originally as an offshoot of the cesophagus.
It is either free, not connected with the digestive tract, or its
original attachment may be retained in the form of the
“pneumatic duct,” which, when persistent, opens into the
esophagus. In the sharksit is either absent or exists in a
rudimentary state.

The kidneys are two voluminous, dark-red lobulated or-
gans, lying close together next to the back-bone, behind, 7. e.,
above the air-bladder, and occupying nearly the whole length
of the abdominal cavity. The efferent ducts (ureters) either
pass along in front of or by the side of the kidney, and some-
times unite to form a single sac, the outlet of which is situ-
ated either behind or below the generative orifice. It has
been found that the minute structure of the kidneys of em-
bryo sharks resembles somewhat the segmental organs of
worms, the original kidney being composed of bundles of
ciliated funnels, like those of worms, combined, however,
with Malpighian bodies and renal lobules which do not exist
in worms, while all these parts have a common duct, the
ureter, which also does not exist in worms, being character-
istic of Vertebrates.

In the fishes the sexes are, with a very few exceptions, dis-
414 ZOOLOGY.

tinct. The ovaries are large bodies, either discharging the
egos directly, as in the eel, salmon, and trout, into the body-
cavity, thence passing along a fold of the peritoneum out of
a minute opening situated directly behind the vent, or, as in
most bony fishes, there is a duct leading from each ovary to
the common outlet. In the sharks and skates (Elasmo-
branchs) the ovary is single, and the oviducts unite behind
to serve as a uterus in such sharks as are viviparous ; or the
same parts secrete a shell in the egg-laying sharks (Seylliwm)
and skates.

The reproductive glands of most fishes are, except in the
breeding season, so much alike, that it is difficult to distin-
guish them except by a microscopic examination. In the
breeding season the ovaries of the cod, perch, and smelt are
very large and yellowish, while the testes are small and white.
Fishes, like some Amphibians and many invertebrates, may
be able to perform the reproductive functions before they are
fully mature ; in fact, some fishes continue to grow as long
as they live.

The fishes are not a homogeneous or “closed,” 7. ¢., well-
circumscribed, type, as the birds and mammals, for the form
of the body is liable to great variation, the differences be-
tween the subdivisions or orders, families and genera being
much greater than in birds and mammals.

The class is divided into three subclasses, viz. : the Hlas-
mobranchit (sharks and rays), the Ganotdea (sturgeons, gar-
pikes, ete.), and the Zeleostei, or bony fishes. The classifi-
cation we adopt is that of Professor Gill.

Subclass 1. Elasmobranchii (Selachians, or Sharks and
Rays).—These are the most generalized as well as among the
oldest of all fishes. In some respects they stand above the bony
fishes, with some features anticipating the Amphibians, while
in their cartilaginous skeleton, their numerous gill-openings,
and their general appearance they are scarcely higher than the
embryos of the bony fishes. It would seem as if a shark were
an embryo fish, which had been hurried by nature into exist-
ence with some parts more perfect than others, in order to
serve in the Upper Silurian and Devonian times as destructive
SHARKS AND RAYS. 415

agents to the types of invertebrate life which then became
extinct, partly through their means. These and ganoid fishes
having thus accomplished their work were replaced in the
later ages by more highly elaborated and specialized forms,
a.e., the bony fishes. Sharks and skates are engines of de-
struction, having been since their early appearance in the
Upper Silurian age the terror of the seas. Their entire
structure is such as to enable them to seize, crush, tear, and
rapidly digest large invertebrates, and the larger marine
members of their own class. Hence their own forms are
gigantic, soft, not protected by scales or armor, as they have
in the adult form few enemies. Hence they do not need a
high degree of intelligence, nor special means of defence or
protection, though from their activity the circulatory system
is highly developed.

In the general form the sharks are long and somewhat cylin-
drical, with the head rather large, often pointed, sometimes,
in in the hammer-headed shark, extraordinarily broad, with a
capacious mouth, situated in the under-side of the head.
The body tapers behind, and the caudal portion is unequally
lobed, the upper lobe being much longer than the lower,
upturned and supported by a continuation of the vertebral
column, while the tail-fins of bony fishes are equally lobed
and consequently called homocercal; those of sharks are
unequally lobed, and are therefore said to be heterocercal. In
this respect they resemble an early stage in the development
of bony fishes, such as the trout or herring. Sharks, like
bony fishes, have two pectoral and generally two ventral
fins ; these two pairs of fins corresponding to or homologous
with the limbs of air-breathing Vertebrates, and besides this
there is one or usually two dorsal fins, and an anal fin, the
latter situated behind the vent.

The skin is either smooth or covered with minute placoid
scales (see Fig. 385); the integument of such species as
are provided with these fine scales forming shagreen. While
the spinal column is in the sharks usually cartilaginous, and
easily cut with a knife, there are different grades of devel-
opment from certain forms, as the Chimera, to a well-marked
416 ZOOLOGY.

column or series of biconcave vertebra, with the cartilage in
part replaced by bone, forming radiating leaves or plates ;
while in the rays or skates the anterior part of the column
is bony.

The ribs are small, sometimes rudimentary. The skull is
rudimentary, without membrane-bones, embryonic in char-
acter, forming a simple cartilaginous brain-box, without pre-
maxillary or maxillary bones, the constitution of the jaws be-
ing quite unlike that of the bony fishes, the jaws being formed
of elements, 7. e., “‘ cartilaginous representatives of the pri-
mary palatoquadrate arch and of Meckel’s cartilage.” (Hux-
ley.)

There are no opercular bones such as cover the gill-open-
ings in bony fishes, their place being taken by cartilaginous
filaments.

The mouth is armed in most sharks with numerous sharp,
flattened, conical teeth, arranged in transverse rows and
pointing backwards; they are never fixed in sockets, but
imbedded in the mucous membrane of the upper and under
jaws. In the Heterodontide, represented by Cestracion or
Port Jackson shark, the teeth are much blunter than in
other living sharks, the middle and hinder teeth having
broad, flattened crowns, forming a pavement of rounded
teeth. The Devonian sharks were in most cases like the
Cestracion in this respect. In the Carboniferous age, sharks
with teeth more like those of modern forms came into ex-
istence ; and they must have been of a more active nature,
the sharp teeth directed backward indicating the rapacity of
these monsters, which darting after and seizing their prey
were enabled to retain it by the backward-pointed teeth ;
while the more sluggish Devonian Cestracions kept near the
bottom and devoured the shelled mollusks, etc., possibly Or-
thoceratites, Nautili, and Trilobites, which became nearly
extinct about the time the type of pavement-toothed sharks
culminated.

The teeth of the skates or rays have obtuse points. In
Myliobatis the teeth ave flatted and united to form a solid
pavement, so that the mouths of these large rays are fur-
DEVELOPMENT OF SHARKS AND RAYS. 417

nished with an upper and nether millstone for crushing and
comminuting the thick, solid shells of mollusks. The mouth
in both sharks and rays is always situated on the underside
of the head, all being ground-feeders. Such sharks as rise
to the surface for food seize it by turning over before closing
their jaws on the luckless victim.

The throat or cesophagus is wide ; the stomach a capacious
sac, and the intestine short, separated from the stomach by
a pyloric valve. The spiral valve of the intestine is a fold
projecting into the cavity of the gut, the fixed edge forming
a spiral line around the inner wall of the intestine.

The heart consists of a ventricle and auricle, with an
aortic bulb which pulsates as regularly as the heart ; and the
blood must be sent forward with great force, as the very mus-
cular bulb is provided within with three rows of semi-lunar
valves.

The gills are pouch-like, generally five, rarely six or seven,
in number, the external openings or gill-slits being usually
of moderate size, but sometimes long and large, as in the
basking shark. While the clefts or slits open on the side of
the neck in sharks, in the skates they are placed beneath the
neck.

A spiracle or opening leads, in some sharks, from the up-
per side of the head into the mouth. According to Wyman
this is the remnant of the first visceral cleft of the embryo.

The brain is like that of fishes in general, the olfactory
lobes being large and long in the skates. The optic nerves
unite, as in higher Vertebrates, forming a common stem or
chiasma, before diverging to the eyes.

The eyes of some sharks have a third lid or nictitating
membrane analogous to that of birds. The ear, except in
Chimera, has the labyrinth completely surrounded by carti-
lage. There are two testes, and usually two ovaries, but in
the dog-fishes and the nictitating sharks there is but a single
ovary. The oviducts are true ‘‘ Fallopian tubes,” expanding
posteriorly into uterine chambers, which unite and open
into the cloaca. (Huxley.)

The sharks and skates are not prolific; having but few
418 ZOOLOGY.

enemies they do not lose much ground in the struggle for
life. The oviparous forms such as the dog-fishes, skates,
and Chimera, lay large eggs enclosed in tough, leathery,
purse-shaped cases. The other Elasmobranchiates are vivip-
arous, bringing forth their young alive. In Musteluws and
Carcharias a rudimentary “placenta” analogous to that of
Mammals is developed from the yolk. ‘The following ac-
count of the development of the dog-fish (Mustelus), which
is condensed from Balfour, may be found to be applicable to
sharks in general :

The blastoderm or germinal disk is a large round spot
darker than the rest of the yolk, bordered by a dark line
(really a shallow groove). Segmentation occurs much as de-
scribed in the bony fishes, reptiles, and birds. The upper
germ-layer (epiblast) arises much as in the bony fishes, the
Batrachians and birds, while the two inner germ-layers are
not clearly indicated until a considerably later stage. The
segmentation-cavity is formed nearly as in the bony fishes.
There is no invagination of the outer germ-layer to form the
primitive digestive cavity, as in Amphioxus, the lamprey,
sturgeons, and Batrachians, but the Selachians agree with
the bony fishes, the reptiles, and birds, in having the alimen-
tary canal formed by an infolding of the innermost germ-
layer, the digestive track remaining in communication with
the yolk for the greater part of embryonic life by an
umbilical canal. This mode of origin of the digestive cav-
ity, Balfour regards as secondary and adaptive, no “‘ gas-
trula” (Heckel) being formed as in Amphioxus, etc. The
embryo now rises up as a distinct body from the blastoderm,
just as in other Vertebrates, and there is a medullary groove
along the middle line, and by the time this has appeared the
middle and inner germ-layers are clearly indicated. After
this development continues in much the same manner as in
the chick.

At this time the embryo dog-fish externally resembles the
trout; the chief difference is an internal one, the outer
germ-layer not being divided into a nervous and epidermal
sublayer as in the bony fishes.
DEVELOPMENT OF SHARKS AND RAYS. 419

The next external change is the division of the tail-end
into two caudal lobes. The notochord arises as a rod-like
thickening of the third germ-layer, from which it afterwards
entirely separates, so that the germ, if cut transversely,
would appear somewhat as in the embryo bird.

The primitive vertebra next arise, and about this time the
throat becomes a closed tube. The head is now formed by
a singular flattening-out of the germ, like a spatula, while
the medullary groove is at first entirely absent. The brain
then forms, with its three divisions, into a fore, middle, and
hind brain. Soon about twenty primitive vertebre arise,
and by this time the embryo is very similar, in external
form, to any other vertebrate embryo, and finally hatches in
the form of the adult.

The skate was found by Wyman to be at first long and
narrow, the dorsal and anal fins extending to the end of the
tail, as in the eel. Soon after it becomes shark-shaped, and
finally assumes the skate form. Thus skates pass through
a shark-stage, and this accords with the position in nature
of skates, since they are, as a whole, a more specialized as
well as more modern group than the sharks. Wyman found
that there are in the skate at first seven branchial fissures,
the most anterior of which is converted into the spiracle,
which is the homologue of the Eustachian tube and the
outer ear-canal; the seventh is wholly closed up, no trace re-
maining, while the five others remain permanently open.

The Elasmobranchs are subdivided into two orders (re-
garded by Gill as super-orders, the Plagiostomi, represented
by the sharks and rays, and the Holocephali, the type of
which is Chimera.

Order 1. Plagiostomt.—In the sharks and skates the teeth
are very numerous; the gill-slits are uncovered. ‘The rays
or skates differ from the sharks in their broad, flat bodies,
with the gill-slits opening below; the great breadth of the
body is due to the enlargement of the pectoral fins which
are connected by cartilages to the skull ; there is likewise no
median articular facet upon the occiput or base of the
skull, for the first vertebra.

The most common of our Selachians is the mackerel shark
420 ZOOLOGY.

or Iswrus punctatus (Fig. 389). The head is conical, with
the nostrils under the base, and the lobes of the tail are
nearly equal. It is from four to eight feet in length, and is
often taken in fish-nets, being a surface-swimmer. In the
thresher shark (Alopectas vulpes Cuvier), the upper lobe of
the tail is nearly as long as the body of the shark itself. It
grows twelve or fifteen feet in length, and lives on the high
seas of the Atlantic.

Nearly twice the size of the thresher is the great basking
shark, Selache (Cetorhinus) maxima Cuvier, of the North
Atlantic, which becomes nine to thirteen metres (thirty or
forty feet) in length. It has very large gill-slits, and is by
no means as ferocious as most sharks, since it lives on small

 

Fig. 389.—Mackerel Shark.—From Tenney’s ‘‘ Zoology.”

fishes, and in part, probably, on small floating animals, strain-
ing them into its throat through a series of rays or fringes of
an elastic, hard substance, but brittle when bent too much,
and arranged like a comb along the gill-openings, the teeth
being very small.

Among the smaller sharks is the dog-fish (Squalus Ameri-
canus Storer), distinguished by the sharp spine in front of
each of the two dorsal fins. It is caught in great numbers
for the oil which is extracted from its liver. The dog-shark
(Mustelus canis Dekay), which is a little larger than the
dog-fish, becoming over a metre (four feet) long, brings forth
its young alive. In the European Mustelus levis Risso a
so-called placenta is developed, while it is wanting in the
Mustelus vulgaris of Miller and Henle.
SHARKS AND RAYS. 421

Among the more aberrant sharks is the hammer-headed
Sphyrna zygena (Linn.), which grows to the length of twelve
feet, and is one of the most rapacious and formidable of the
order.

Of the rays and skates, the saw-fish approximates most
to the sharks. Its snout is prolonged into a long, flat
bony blade, armed on each side with
large teeth. Pristis antiquorum
Latham (Fig. 390), the common saw-
fish, inhabits the Mediterranean Sea
and the Gulf of Mexico ; it is vivipa-
rous (Caton.) Pristis Perroteli lives
in the Senegal River, while Carcharias
gangeticus is found sixty leagues from
the sea.

The genuine skates or rays have the
body broad and flat, rhomboidal (ow-
ing to the great extension of the
thick pectoral fins). Portions of the
ventral fins in the males are so elon-
gated and modified as to form inter-
mittent and clasping organs. They
swim close to the bottom, feeding upon
shell-fish, crabs, etc., crushing them
with their powerful flattened teeth.
The spiracle is especially developed in
the rays, while, as observed by Gar-
man, in the majority of the sharks
which swim in midwater or near the
surface, the water enters the mouth
and passes freely out of the gill-open-
ings, but in the rays, which remain at er anaes
the bottom, the purer sea-water enters rent Bslow. Stowe ‘te
the spiracle from above to pass out of fea ies aan
the gill-slits.

The smallest and most common skate of our northeast-
ern Atlantic coast is Raja erinacea Mitchell. It is one half
of a metre (twenty inches) in length, and the males are
smaller than the females. The largest species is the barn-
door skate, Raja levis Mitchell, which is over a metre (forty-

 
422 ZOOLOGY.

two inches) long. Raja eglanteria Lacepéde (Fig. 391)
ranges from Cape Cod to the Caribbean Sea. The smaller
figures in Fig. 391 represent respectively the mouth and
gill-slits, and the jaws of Myliobalis fremenvillit Lesueur.
In the torpedo the body is somewhat oval and rounded.
Fig. 392 represents Torpedo marmoratus, of the Mediter-
ranean Sea.
Our native species, found mostly in winter, especially
on the low sandy
shores of Cape Cod,
is Zorpedo occiden-
talis Storer. Its bat-
teries and nerves are
substantially as in
the European  spe-
cies. The electrical
organs are construct-
ed on the principle
of a Voltaic pile,
consisting of two
series or layers of
hexagonal cells, the
space between the
numerous fine trans-
verse plates in the
cells filled with a
trembling jelly-like
mass, each cell
representing, so to
Fig. 391.—Raja eglanteria, male. Mouth and gill- speak, a Leyden jar,
slits, jaws and teeth of Myliobatie fremenvillit 2. There are about 470
cells in each battery, each provided with nerves sent off from
the fifth and eighth pairs of nerves. The dorsal side of
the apparatus is positively electrical, the ventral side nega-
tively so. The electrical current passes from the dorsal to
the ventral side. When the electrical ray is disturbed by the
touch of any object, the impression is conveyed by the sen-
sory nerves to the brain, exciting there an act of the will
which is conveyed along the electric nerves to the batteries,

 
THE ELECTRICAL RAY. 423

producing a shock. The benumbing power is lost by fre-
quent exercise, being regained by rest; it is also increased
by energetic circulation and respiration. As in muscular

fh Nik as Ti
Eee Pea <*(
ea eee
NB iy onl
yi A B AIS ‘ 4 4 \ f
Wi Ss Ne} Wee +
“eh AG SINGS ///\ a
WS

ly Nh rm
Mga

i

RES

a
|

a ee
\ v i

 

Fig. 392.— To pedo marmvratus. a, brain; 6, medulla oblongata ; c, spinal cord ;
d and b’, electric portion of the trigeminate or fifth pair of nerves ; ee’, electric portion
of the pneumogastric or eighth pair of nerves; /, recurrent nerve ; g, left electric
organ entire ; g’, right electric organ dissected to show the distribution of the nerves ;
A, the last of the branchial chambers ; i, mucus-secreting tubes.—From Gervais and
Van Beneden.

exertion the electrical power is increased by the action of
strychnine (Owen).

Marey has more recently made interesting experiments on
the torpedo, examining the discharge of this fish with the
424 ZOOLOGY.

telephone. Slight excitations provoked a short croaking
sound. Hach of the small discharges was composed of a
dozen fluxes and pulsations, lasting about one fifteenth of a
second. The sound got from a prolonged discharge, how-
ever, continued three to four seconds, and consisted of a sort
of groan, with tonality of about m7 (165 vibrations), agree-
ing pretty closely with the result of graphic experiments.

Marey has also studied the resemblance of the electrical
apparatus of the electrical ray or torpedo and a muscle.
Both are subject to will, provided with nerves of centrifugal
action, have a very similar chemical composition, and re-
semble each other in some points of structure. A muscle in
contraction and in tetanus executes a number of successive
small movements or shocks, and a like complexity has been
proved by M. Marey in the discharge of the torpedo.

The sting-rays (Zrygon) have no caudal fin, but the spinal
column is greatly elongated, very slender, and armed with a
long, erect spine or ‘‘sting.” Some live in fresh water ;
several species of sting-rays (Potamotrygon) inhabit the large
rivers of Brazil and Surinam, as the Amazon, Tapajos, Ma-
deira, and Araguay, digging holes in the sand, in which they
lie flat and await their prey. In this connection it may be
said that Raia fluviatilis of India has been taken near Ram-
pur, nearly 1000 miles above tide-reach.

Myliobatis has the teeth forming a solid plate or pavement.
The devil-fish (Cephalopterus diabolus Mitchell) of the coast
of South Carolina and Florida is the largest of our rays, be-
ing eighteen feet across from tip to tip of its pectoral fins,
and ten feet in length, weighing several tons. It sometimes
seizes the anchors of small vessels by means of the curved
processes of its head and swims rapidly out to sea, carrying
the craft along with it.

Order 2. Holocephali.—This small but interesting group
is represented by Chimera of the north Atlantic, and Cal-
lorhynchus of the antarctic seas. In these fishes the four
gill-openings are covered by an opercular membrane ; thus
approaching the true bony fishes, and there are but four teeth
in the upper and two in the lower jaw. The brain of Chi-
mera is said by Wilder to combine characters of those of
GANOID FISHES. 425

Selachians, Ganoids, and Batrachians. Chimera plumbea
Gill lives in deep water off the coast of New England.

Subclass 2. Ganoidei (Garpikes, Lung - Fishes).—The
term Ganoid was applied to these fishes from the form of
the scales, which in most of the species are angular, square,
or rhomboidal and covered with enamel, as seen in the com-
mon garpike. In others, however, as in the Amia and Dip-
noans, the scales are rounded or cycloid. These fish, i.e.,
both the genuine Ganoids and Dipnoi, were the character-
istic fishes of the Devonian age, which has consequently been
called the Age of Fishes, there being no bony fishes (Teleos-
tet) at that time. The forms were much larger than at
present, far more numerous in species, genera, and families,
and they, with the sharks, were the rulers of the sea.

At the present day the type is nearly extinct, being repre-
sented by such isolated forms as the sturgeon, the paddle-
fish, the lung-fish (Dipnot), the garpikes, and the American
mud-fish (Amita). Like most of the paleozoic types of life,
the Ganoids were both generalized forms and also combined
the characters of classes of animals not then in existence; in
other words they were synthetic or comprehensive types.
Thus in forms like Amia, the Teleostean fishes were antici-
pated ; in the Dipnoi, with their external gills and lungs,
not only the Amphibians, but even the reptiles were indica-
ted in their hearts with two auricles, just asthe Trilobites and
Merostomata, as indicated by the structure of the living
king-crab, combined with the structure of Crustaceans, fea-
tures which became in a degree reproduced in the terrestrial
scorpions and spiders which subsequently appeared. Owing
to this intermixture of ancient and modern characteristics,
this reaching up and out of the piscine type of life over into
the amphibian and reptilian boundaries, the classification,
i.é., actual position in nature of the Ganoids, becomes very
difficult, and the views of naturalists regarding their system-
atic position are very discordant. If, as insisted on by Guill,
we recognize the fact that the Ganoids are an older, more
generalized, and therefore more elementary group, and the
osseous fishes a newer, more highly specialized group, and
426 ZOOLOGY.

that there is a natural series of forms leading from the stur-
geon, which is nearest the Elasmobranchs, up through the
Dipnoans to the true Ganoids, and that the latter, through
Ama, leads to the bony fishes, we shall have a clue to the
intricate relations existing between them and the other sub-
classes of fishes. *

The Ganoids of the present day are well nigh confined to
fresh water, the sturgeons alone living in the sea as well as
ascending rivers; though the Devonian and carboniferous
forms occur as marine fossils.

In synthetic forms, like the Ganoids, it is difficult to find
absolute characters separating them from the Elasmobranchs
on the one hand and the Teleosts on the other. The diag-
nostic characters are the following: the skeleton is either
wholly cartilaginous, or partly or wholly bony; the skin is
either smooth, or with cycloid, or usually with ganoid scales ;
the gills are free ; the gill-opening is covered with an oper-
cular bone ; the first fin-rays generally sharp ; the air-blad-
der with a pneumatic duct ; the embryos sometimes with ex-
ternal gills.

The spinal column is usually cartilaginous; in the Dip-
noans, the sturgeons, the paddle-fish and allies, the notochord,
with its sheath, is persistent ; while in Polypterws and Amia
the spinal column is completely bony, the vertebre being
amphicelous, 1. e.,biconcave ; while in the garpike (Lepidos-
tews) the vertebra are convex in front and concave behind.
The cartilaginous skull is covered by broad, thin membrane-
bones, as seen in the sturgeon. The tail is heterocercal, the
lobes being, in Amia, nearly equal.

The brain is as in the Elasmobranchs, the optic nerves
wuting in a chiasma. The heart and aortic bulb are as in the
Elasmobranchs, and all but Lepidosteus have a well-devel-
oped spiral valve in the intestine, the valve being rudimentary

* Although strongly inclined to regard the Dipnoans from their am-
phibian and reptilian characters as types of a subclass, Dipnoi, yet in
defrrence to the principles stated by Gill, which we had previously fol-
lowed independently in the classification of the neocaridan and paleo-
caridan Crustacea, we here adopt the classification of Prof. Gill.
DEVELOPMENT OF THE STURGEON. 4

in the garpikes. The oviducts communicate with the ure-
ters as in the sharks and amphibians. The different modifi-
cations of Ganoid structure may be observed in the examples
of the different orders.

Many of the Ganoids of the Upper Silurian and Devonian
rocks belonged to the groups Cephalaspide and Placoder-
mata. In the Cephalaspids, represented by the singular
Cephalaspis Lyellit of Agassiz, the broad head was covered
by a single semi-circular plate, with large orbits above, the
mouth being below. The pectoral fins were rayless folds of
the skin ; the body behind the head was covered with rhom-
boidal scales, and provided with adorsal fin. The Péteraspis
had a head-shield composed of seven pieces. Among the
Placoderms, Pterichthys had a plated head half as long as
the body, the tail short and scaled. These fishes, the earliest
known Vertebrates, were bottom-feeders. Nothing is known
as to the nature of their jaws or teeth.

Order 1. Chondroganoidei.—In these Ganoids the dorsal
chord is not ossified ; the skull is cartilaginous, covered with
membrane-bones ; they were either toothless or with small
teeth. The skin is naked as in the paddle-fish, or protected
as in the sturgeons with very large, bony, solid plates. The
sturgeons have the snout long and pointed, with the mouth
underneath, and toothless. Acipenser sturio Linn. is the
common sea-sturgeon of our coast, ascending rivers. The
shovel-nosed sturgeon, Scaphirhynchops platyrhynchus has a
spade-like snout. It inhabits the waters of the Mississippi
Valley. Salensky has studied the embryology of the Russian
sturgeon. The freshly-laid eggs are two millimetres in di-
ameter, the yolk undergoes nearly total segmentation, thus
connecting most Vertebrates in which the eggs only partially
segment, with the Amphioxus, lampreys, and amphibia, in
which segmentation is total. The skeleton is developed
much as in the Elasmobranchs. The sheath of the noto-
chord develops in three weeks after hatching. At the
end of the third week the upper and lower vertebral arches
appear, arising as in other fishes. The skull is indicated in
two or three weeks after hatching.
428 ZOOLOGY.

The singular spoon-bill, Polyodon foliwm Lacepéde, is five
feet long ; it is smooth-skinned and has a snout one-third as
long as the body, and spatulate, with thin edges. It has a
very wide mouth with minute teeth, and lives on small
Crustacea. It abounds in the Mississippi, and its larger
tributaries.

Order 2. Dipnot.—The lung fishes are so called from the
fact that often being in pools and streams liable to dry up,
they breathe air directly, having true lungs, like those of
Amphibians, as well as gills. From the nature of their brain
and heart, the Dipnoans are quite different from all other
fishes, anticipating in nature the coming of Amphibians,
while on the other hand the notochord and sheath is persist-
ent, and as they were characteristic and more numerous in
Devonian times, they may be said to be a prematurative
type.

The body of the Dipnoans is somewhat eel-shaped, though
not very long in proportion to its thickness, and is covered
with cycloid scales. The pectoral and ventral fins are long,
narrow, and pointed, and there is a long caudal fin which is
protocercal, a term propose. by Wyman to designate the form
of the caudal fin of embryo sharks. In fact, the tail of the
young garpike, as of embryo Teleosts or bony fishes, is at
first protocercal, afterwards being heterocercal in adult
Ganoids, such as the garpike, and in the embryo and
early free stage of most bony fishes; the tail in the latter
becoming finally homocercal or equal-lobed. Thus the
tail of the Dipnoans may be said to be embryonic, 7.¢.,
protocercal.

The spinal column is represented by a simple notochord and
sheath ; within the latter the basal ends of the bony neural
arches and ribs, and near the tail the lower (hemal) arches
are imbedded. The skull is cartilaginous. The extremity of
the lower jaws supports large tooth-like plates (dentary plates)
which shut in between the few palatine teeth ; in Ceratodus
these plates are single, and in all Dipnoans these single den-
tary plates are very characteristic of the group. The narrow
pectoral and ventral fins are supported by a single, median,
LUNG FISHES. 429

many-jointed cartilaginous rod, to which is attached fine fin-
rays, supporting the thin edge of the fin.

The spiral valve and cloaca are present in the intestinal
tract. In the brain the cerebral hemispheres are larger
than the olfactory lobes, and there 1s an optic chiasma ; the
heart has besides the right large auricle, a left smaller one
which receives the blood from the lungs, and a single ven-
tricle, as in Amphibians and most reptiles; they have true
nostrils. The lungs are like those of Amphibians, and in
addition they possess both
internal and external gills
(Hig. 393), the latter nearly
aborted in the adult.

The genus Ceratodus was
originally named by Agassiz, Mis, 38. 52stera gis of « young Po
from teeth found in Jurassic
and Triassic strata in Europe. Living specimens were found
by Mr. Krefft in Queensland, Australia, and called Ceratodus
Fosteri Krefft (Fig. 394). This fish is rather more elemen-
tary in form than Lepidosiren, the body being stouter, and
the large scales of the body, with the fin-like paddles and
distinctly rayed vertical fins, cause it to resemble more closely
ordinary bony fishes than Lepidosiren (Gtnther). Moreover

 

 

Fig. 394.—Ceratodus, or Australian Lung-Fish. (The tail in nature ends in a point.)
—After Giinther ; from Nicholson.

the lung is single, and not used so much as the two perfect
lungs of Lepidosiren. It attains a length of six feet. It
can breathe by either gills or lungs alone. When, Gtinther
thinks, the fish is compelled to live during droughts in thick
muddy water charged with gases which are the product of
decomposing organic matter, it is obliged to use its lungs.
The gills are more like those of ordinary bony fishes than
those of Lepidosiren. It lives on the dead leaves of aquatic
grasses, etc. The local English name is ‘“ flat-head,” the
430 ZOOLOGY.

native name being “barramundi.” Nothing is known of its
breeding habits or mode of development. The eggs when
ready to be laid are 2.5 millimetres in diameter. The lower
part of the oviduct is much asin Menopoma. Fossil teeth
of Ceratodus occur in the Jurassic beds of Wyoming, and two
species have been found in still older beds in Illinois, regarded
by Cope as either Upper Carboniferous or Permian. Thus,

 

Fig. 395.—-Protopterus annectens, a Lung-fish of Africa. One third natural size.

as remarked by Gtinther, we have in Ceratodus a genus
which has survived from the Triassic period.

The lung-fish are distinguished by two well-formed lungs,
and the narrow ribbon-like fins. In Lepidosiren paradoxa
Fitzinger, there are five gill-arches, with four slits, and the
body is rather longer, more eel-like, with a blunter snout
than in Protopterus. It grows to one metre in al and

ss Ws NESS
GLEE, ITITT mi
WME: Lm TIT SST ex

GG

BY Deo

  
 
 

 

 

ane

Fig. 396.—Skeleton of Protopterus annectens, showing the protocercal tail and the
simple rod-like limbs, the pelvic and shoulder girdles, and the nature of the jaws.
ch, notochord ; 7, bones representing the heemal arches attached to the notochordal
sheath 3 hs, heemal spines ; én, éh, rays of the caudal fin.—After Owen.

inhabits the rivers of Brazil. This is represented in Africa
by the closely allied Protopterus annectens Owen (Figs. 395
and 396 skeleton), which has six gill-arches, with three
pairs of external gills in the young. It is 40-70 centimetres
in length. It lives on leaves in the White Nile, Quilimani,
Niger, Gambia, and their tributaries. It buries itself in the
mud a foot deep. Giinther states that numerous examples
POLYPTERUS.

431

of Lepidosiren ‘have been kept in captivity, but none have

shown a tendency to leave the water.”

The modern Dipnot represent the Devonian fishes Holop-

tychius, Dipterus, and Phaneropleuron,
and the American Dinichthys Torrelli
of the Devonian rocks of Ohio, which
is said by Newberry to have been about
five metres (from fifteen to eighteen
feet) in length, and a metre in thickness,
being inferior only in size to the Astero-
lepis, a Placoderm of the old red sand-
stone of Great Britain.

Order 3. Branchioganoidet.—Here be-
longs the Polypterus of the Nile and
Senegal. In these Ganoids the tail is

either protocercal or heterocercal; the #

scales are cycloid or rhomboid. The
dorsal fin is long, subdivided into divis-
ions, each with a separate ray and spine.
Polypterus bichir Geoffroy (Fig. 397)
has a protocercal tail. The young has
external gills (Fig. 393). It inhabits the
river Nile, P. senegalus the Senegal.
Calamoichthys differs in having no ven-
tral fins and in its elongated form. It
inhabits the rivers of Old Calabar. Al-
lied to these living forms are the De-
vonian Osteolepis, Celacanthus, and Ho-
loptychius.

Order 4. Hyoganoidet.—This group is
represented by the garpike and Amia or
mud-fish of the United States, which
is an annectant form connecting the
Ganoids with the Teleosts. In these

 

i ‘ Fig. 397.—Polypterus bi-
fishes the spinal column is-bony, the ¢é.—From Cuvier.

tail partially heterocercal.

In Lepidosteus (Fig. 398, L. osseus Agassiz) the body is
long, the jaws long and armed with sharp tceth, the vertebrae
are opisthocelous, and the scales are large and rhomboidal,
432 ZOOLOGY.

while the air-bladder is cellular, lung-like. Fossil species oc-
cur with those of Ama in the tertiary rocks of the West.
Lepidosteus osseus Agassiz, the bony gar, with a long, slender
snout, is sometimes five feet long; L. platystomus Rafin.
has a short nose, while the alligator gar, L. spatula Lacé-
péde, has a short and wide snout, and grows to a larger size
(nearly three metres) than the other species, and inhabits
the Mississippi Valley. The garpikes are carnivorous, very
rapacious, and are said to destroy large numbers of food-
fishes. They usually remain near the surface of the water,
emitting bubbles of air and apparently taking in a fresh
supply. Wilder has observed Ama inhaling air, and re-
marks that ‘‘so far as the experiments go, it seems probable
that, with both Amia and Lepidosteus, there occurs an inha-
lation as well as exhalation of air at pretty regular intervals,
the whole process resembling that of the Menobranchus and
other salamanders, and the tadpoles, which, as the gills

 

Fig. 398.—Garpike. From Tenney’s Zoology.

shrink and the lungs increase, come more frequently to the
surface for air.” Both of these fishes are very tenacious of
life and withstand removal from water much better than
bony fishes and sturgeons, on account of the lung-like nature
of their air-bladder. Wilder shows that there is a series of
forms, mostly Ganoids, from the Amia and Lepidosteus in
which the pneumatic duct enters the throat on the dorsal
side, up to Lepidosiren in which it enters the throat on the
ventral side, like the air-tube or trachea of Amphibians and
higher Vertebrates.

The breeding habits and external changes in form of the
garpikes have been described by Mr. A. Agassiz. The gars,
which are nocturnal in their habits, appear on the shores of
Lake Ontario at Ogdensburg in immense numbers between
MUD FISH. 433

the middle of May and the 8th of June, remaining at other
times of the year in deep water.

The young begin to hatch about the end of May. At
first the embryo gar possesses an unusually large yolk-sac,
while the notochord is very large; otherwise posteriorly it
resembles the young of bony fishes. It differs, however, in
its large mouth, which is surmounted with a hoof-shaped
depression edged with a row of projecting suckers, by which
it attaches itself, hanging immovable, to stones; the eye and
brain is smaller than in bony fishes. The tail is at first
protocercal, beginning on the second day to become hetero-
cercal. On the third day the gill-covers form rectangular
flaps, and the first traces of the pectoral fins appear, while
the snout becomes longer. By the fifth day the traces of
the dorsal, caudal, and anal fins appear. When a little over
three weeks old it assumes a more fish-like form ; the suck-
ing disk has nearly disappeared, the lower jaw greatly length-
ened, and the gill-covers extend to the base of the pectoral
fins. When between two and three weeks old the young
gar-fish is 20 millimetres (inch) long. The young rise to the
surface to swallow air, as in the adult. Soon after this it is
of the form first discovered and figured by Wilder. The
gar-fish, according to Agassiz, bears some resemblance to
the sturgeon in certain stages of growth, and in the forma-
tion of the pectoral fins from a lateral fold, as well as by the
mode of growth of the gill-openings and the gill-arches, while
it closely resembles the young of bony fishes in the develop-
ment of the posterior part of the body, by the mode of origin
of unpaired fins from the embryonic fin-fold, and by the
mode of formation of the fin-rays, and of the ventral
fins.

The mud-fish, Ama calva Linn., is like an ordinary bony
fish in form, with rounded scales; the caudal fin ‘‘ masked
heterocercal,” the snout is short and rounded, and the air-
bladder is large and cellular. It attains a length of two
thirds of a metre, and occurs in the Mississippi Valley and
as far east as New York. A fossil form closely allied to
Amia dates back to the Cretaceous Age, and the genus
Caturus is a Liassic and Oolitic genus.
434 ZOOLOGY.

Subclass 3. Teleostei (Pony fishes).—We now come to a
type of fishes which, within very recent geological times as
well as during the present period, has become differentiated
or broken up into thousands of species, corresponding to
the complexity of their physical environment as compared
with the simple features of the physical geography of De-
vonian and Carboniferous land-masses. Like most of the
larger groups of animals, as the Decapod Crustacea, and
especially the insects, as well as the mollusks, the bony
fishes have attained an astonishing amount of specialization,
as if the tree of icthyic life, taking root in the Silurian Age,
and sending out but a few branches in later Paleeozoic times,
had suddenly, in the Cretaceous and Tertiary Ages, thrown
out a multitude of fine branches and twigs intertwining and
spreading out in a way most baffling to the systematist.

The essential, diagnostic characters of the bony fishes, 7.¢.,
such as separate them from the Elasmobranchs and Ganoids,
are as follows: The skeleton is bony, the vertebree being sep-
arate ; the outer elements of the scapular arch are simple, the
inner elements for the most part bony and usually three or
two in number ; the pectoral fins are without any bone rep-
resenting the humerus, and are connected with the scapular
arch by several (generally four) narrow bones (Gill). The
optic nerves cross one another. The gills are free, usually
four on each side, and with several opercular bones. The
heart is without a cone, but with an arterial bulb, and with
but two valves at the origin of the aorta. The intestine is
destitute of a spiral valve.

The student should dissect a typical Teleost, such as a
fresh-water or sea perch, with the aid of the following ac-
count of its anatomy. The drawing and account here given
of the anatomy of the sea-perch have been prepared by Dr.
C. Sedgwick Minot. The common sea-perch or cunner
(Tautogolabrus adspersus Gill, Fig. 399) resembles the fresh-
water perch very closely in its anatomy, the most note-
worthy difference being the absence of the ceca at the
pyloric end of the stomach in the marine species; with this
exception the following description applies almost equally
well to the fresh-water perch, so that this account will be
ANATOMY OF THE CUNNER. 435

available tor western students who have not access to speci-
mens of the cunner.

The perch has the general form of a flattened spindle, for
it-tapers down at either end and is compressed laterally.
There is no neck marked off externally, and the head ap-
pears as the direct continuation of the body, but separated
from it by a fissure on either side; this is the opening of
the gills, which extends from above downwards and curves
forward, nearly meeting its fellow on the median line of the
under jaw ; upon opening the gill-slit the pectinate or comb-
like gills or branchiz are seen within. ‘There are four sets
of branchial filaments, each set attached to a separate de-
scending arch, in front of each of which isa slit leading into
the cavity of the mouth ; but there is no slit behind the
last gill. The branchie are protected externally by the gill-
cover or operculum, which is attached in front, but is free
behind, where it forms the front edge of the gill-slit ; it is
composed of four distinct parts: 1. The preoperculum
nearest the eye, and with its lowest corner almost a right
angle; its posterior and vertical edge is furnished with
numerous minute projecting spines. 2. Appended to the
underside of the margin thus armed is the operculum. 3.
Below the preoperculum is the interoperculum, which par-
tially covers up 4, the suboperculum. Tach of these parts
has a separate bony support ; all four bones are developed
only in the Teleosts; in sturgeons, for example, there is
only an operculum, to which in other Ganoids other parts
are added; in Selachians the whole apparatus remains
undeveloped.

The mouth is placed in front; the upper lip is capable of
independent motion, being supported by the premaxillary
bones, which are but loosely attached to the cranium, though
in many other fishes the union is closer. The eyes are large
and lidless ; just in front of each eye is an opening of the
size of a pin’s head ; these openings lead into the nasal sacs,
of which there are two, but both are without communica-
tion with the mouth ; in higher vertebrates, from the Dip-
noi upwards and in Myxine, there is such a communication.
In the Marsipobranchii there is but a single median nasal sac.
436 ZOOLOGY.

The ear has no external opening, being completely encased
in bone. Nearly parallel with the line of the back extends
a continuous row of yellow spots marking the lateral line
(Fig. 399, Z), along which are found the pore-like open-
ings of the so-called muciparous glands.

All fish have fins of two kinds—unpaired and paired ; the
latter, four in number, correspond to the limbs of other Ver-
tebrates. The unpaired fins are first developed on a contin-
uous median flap of integument, which extends along the
back, around the tail, and on the underside as far forward as
the anus ; cartilaginous or bony rays are developed in it as a
support. In the adult fish the fold is generally discontinu-
ous, being usually separated into three distinct fins—dorsal,
caudal, and anal ; the dorsal fin is frequently, the anal fin
sometimes subdivided. The fin-rays are (1) either simple
pointed rods, or (2) jointed and branching. All the rays of
the caudal fin, and the posterior rays of the dorsal and anal
fins, are branching. In some Malacopterygians all the rays
are branching ; in many, however, the first ray is simple in
the dorsal and anal fins, while fishes like the perch and cun-
ner are distinguished by having several or many of the an-
terior rays of the dorsal and anal fins simple and pointed.
In the cunner half the rays of the dorsal and the first two of
the anal fin are simple.

The pectoral fins are attached to the side of the body and
are large and rounded. The ventral fins le further back
near the median ventral line ; they are smaller than the pec-
torals. The position of the ventrals varies in different fish,
and is much used in classification. The anus lies immedi-
ately in front of the anal fin.

The body is covered by scales, which overlap one another
from before backward ; their free edges are rounded and
smooth, hence they are called cycloid. These scales, as in
all Teleosts, are ossifications of the underlying cutis, and are
covered by the epidermis ; they were formerly wrongly sup-
posed to be epidermal structures.

To dissect a perch the side-wall of the mouth must be re-
moved, then the gill-cover ; study the arrangement of the
gills). Next make an incision along the median ventral line
ANAYOMY OF THE CUNNER. 437

from the level of the pectoral fins to just before the anus, and
following the upper edge of the body-cavity upward and for-
ward cut away the body-wall, taking care not to injure the
large swimming-bladder above, nor the heart in front. Now
open the pericardial cavity, which lies ventrally immedi-
ately behind the gills (see Fig. 399, H¢#). Cut away the mus-
cular masses around the back of the head ; expose the cavity
of the brain, and remove the loose cellular tissue around the
nervous centres. If the gills of one side are excised and the
intestine drawn out, the dissection will appear very much as
in Fig. 399.

The cavity of the mouth widens rapidly and continues as
the branchial chamber or pharynx (4), whence we can pass a
probe outward through any of the gill-slits. There is a single
row of sharp-pointed teeth in front on both the under and
upper jaws; in the pharynx above and below there are
rounded teeth. At the side of the pharynx are the four gill-
slits and the four arches ; the inner surface of the anterior
three arches is smooth, while the arch behind the fourth slit
is much modified in shape and is armed with tubercles
and teeth. The entrance of each slit is guarded in front
and behind by a row of projecting tubercles appended to the
arches. On the outside of each arch, except the fourth, is
a double row of filaments, richly supplied with blood-vessels
which, shining through, give a brilliant red color to the
gills; on the fourth arch there is but a single row. At the
upper and posterior corner of the pharynx is the small open-
ing of the short esophagus. The branchial chamber has an
upward extension on the sides of which lie the pseudobran-
chiz (Ps), accessory respiratory organs not connected with
the gills proper, and receiving their blood-supply from distinct
arteries. There are no salivary glands.

The esophagus dilates almost immediately to form the
stomach (partly concealed in the figure by the liver, Zz),
which seems hardly more than a dilatation of the intestine
(dn). This last isof nearly uniform size throughout, and after
making three or four coils terminates at the anus, immedi-
ately in front of the urinary and genital apertures. When
in situ, the terminal portion of the intestine or the rectwm
438 ZOOLOGY.

extends straight along the median ventral line. The liver
(Zi) forms an elongated light-brown mass resting upon the
stomach. The elongated gall-bladder lies between the
liver and stomach, somewhat imbedded in the substance of
he former. There is no pancreas, though it is present in
some fishes. The spleen (Sp) lies between the stomach and
intestine, in the mesentery; it is dark reddish-brown in
color.

The air-bladder (S) is a single large sac, placed in the dor-
sal part of the body-cavity. Its glistening walls are com-
posed mainly of tough fibrous tissue. The pneumatic duct,
by which the bladder communicates with the esophagus in
many fishes, is wanting in the perch as in nearly all other
Teleosts. The air-bladder normally contains only gases. It
conceals most of the kidneys, which extend the whole length
of the body-cavity on either side of the middle line, as two
long strips of a deep though dull red. They project beyond
the air-bladder in front (A7) and behind (A7’). Their an-
terior ends are somewhat separated from one another by the
intervening pharynx. The ureters open into a urinary
bladder (42) behind the anus.

The ovary is single and varies greatly in size according to
the season. In the male the sexual glands are double. Each
testis (7) is an elongated, whitish, lobulated organ, placed im-
mediately below the swimming-bladder, and continues pos-
teriorly with the spermiduct, which opens immediately be-
hind the anus.

The heart (7) lies in the triangular pericardial cavity ; it
consists of two portions, the dark-colored venous chamber,
or auricle, above, and the lighter-colored arterial chamber, or
ventricle, below. The auricle receives from above two large
veins, one from either side ; these veins are called the ducti
Cuvieri. Each Cuvierian duct, as can be seen in the figure,
ascends beside the cesophagus, and there receives a large jug-
ular vein from in front, and a large cardinal vein from be-
hind. Furthermore, a large vein, the sole representative of
the vena cava of higher Vertebrates, passes from the liver,
near its anterior end, through the pericardium, and empties
into the Cuvierian ducts near their common auricular orifice.
ANATOMY OF THE CUNNER. 439

The walls of the auricle are comparatively thin ; the auriculo-
ventricular orifice is provided with valves, which prevent
the blood flowing back into the auricle. The walls of the
ventricle are thick and very muscular; from the upper end
of the ventricle close to the base of the auricle springs the
bulbus arteriosus, a muscular cylinder, which, running hori-
zontally forward, passes out through the pericardium, and is
continued as the less muscular aorta (A) underneath the
branchial arches along the median line ; the aorta gives off
branches on both sides, one to each arch to supply the bran-
chiz ; the vessels after ramifying are gathered together, to
again form a single trunk, which passes backward immedi-

 

Fig. 399.—Anatomy of the Cunner, male. Z, lateralline ; Hz, heart ; G, pharynx ; Ps,
pseudobranchia ; Sp, spleen ; S, air-bladder; Ai, Ki’, kidneys ; b/, bladder ; 7, tes-
tis; A, aorta; B, brain ; Jn, intestine ; Zi, liver 3 G, gills.—Drawn by C. 8. Minot.
ately underneath the spinal column ; it is called the descend-
ing aorta.

The body and pericardial cavities are called serous, because
their lining membranes are always moist with serum, a watery
fluid, very much like blood-plasma. The lining of the body-
cavity is named the peritoneum, and forms a continuous cov-
ering around the viscera. It is important to observe that the
various organs simply project into the body-cavity and do
not lie really inside of it. In fishes we find the disposition of
the parts to correspond more closely with the fundamental
type of Vertebrate structure than it does in higher forms, in
which further modifications have supervened. The pharynx
still has its distinctive character ; the pericardium lies at the
440 ZOOLOGY.

base of the neck, instead of in the thorax as in the higher Ver-
tebrates. The heart still preserves its primitive division ; on
the other hand, the swimming-bladder is a special adaptation
of the piscian type, while the frequent absence of the pan-
creas is a peculiarity of fishes the meaning of which is not
yet understood.

The brain (BL) does not occupy the whole of the cranial
cavity, but is imbedded in a large accumulation of cellular
tissue. In order to study the brain satisfactorily, it should
be exposed from above, laying bare at the same time the optie
nerves and muscles as in Fig. 400. Most anteriorly are two
lobes (7), the cerebral hemispheres, and immediately behind
them two larger lobes (Q), the corpora bi- or quadri-gemina
(optic lobes, not optic thalami) ; further back follows a single
median lobe (C0), the cerebellum, somewhat conical in shape
and resting upon the medulla oblongata (M), from which
spring various nerves, and which, tapering backward, is con-
tinued as the spinal cord. In front arise the very large and
conspicuous optic nerves (Op), the right nerve passing
obliquely to the left eye, the left nerve to the right eye
running under the right nerve, but forming no chiasma;
each optic nerve is a plaited membrane, folded somewhat
like a fan when shut up, an arrangement occurring only
among fishes. In a side-view of the brain (Fig. 400), the
curious disposition of the optic nerves can be clearly seen ;
it further shows the various forms of the lobes of the brain,
and the large inferior lobes (L) below the corpora quadri-
gemina; these lobes are very remarkable and difficult to
homologize.

The eyes lie in two sockets, separated by an interorbital
septum (Fig. 400, 8). The eyeball has the form of an ob-
late spheroid, and is moved, as in all Vertebrates, by four
rectt and two obliqui muscles. The recti spring from around
the exit of the optic nerve from the brain-case, and thence
diverge to be inserted into different parts of the eyeball ;
above is the rectus superior (Rs) ; towards the interorbital
septum (8) rectus internus (Rt), opposed to the last is the
rectus externus (Re), and below is the rectus inferior, not
shown in the figure. In Teleosts both oblique muscles, the
ANATOMY OF THE CUNNER. 44]

superior (Os) and inferior (Ot), arise from the front of the
orbit near the interorbital septum. The disposition of the

 

Fig. 400.— Anatomy of the brain of the Cunner, dorsal and side view.—Drawn by

Cc. S. Minot.

recti is very constant, but the obliqui vary considerably in

their origin in different Vertebrates.

If a perch be cut through transversely, so that the section

passes through the fore-part of the
air-bladder, and the anterior portion
then looked at from behind, a very
instructive view will be obtained, as
in Fig. 401. The best sections can be
made by first freezing the fish. The
vertebral column (V) appears a little
above the middle ; overlying it is the
neural canal with the spinal cord ; im-
mediately below it is the descending or
dorsal aorta (Ao), on either side of
which follow the kidneys (’), resting
directly upon the air-bladder (Bi).
Lowermost is the body-cavity, with
the stomach (S’), and intestine (Zn),
surrounded by the liver, which has
been almost entirely removed. The

 

Fig. 401.—Transverse section
through the middle of the body
of a Cunner.—Drawn by C. 8.
Minot.

rest of the section is occupied by muscles, which, it will thus
be seen, make up the main bulk of the body. (Minot.)
442 ZOOLOGY.

The so-called ‘* mucous canal” or lateral line of fishes and
Amphibians is sensory. It consists of small masses of
nerve-epithelium, arranged in linear series along the sides of
the head and body, having hair-cells continuous with nerves.
They are called ‘‘nerve-buttons” or ‘‘ nerve-heaps.” Accord-
ing to Schultze, their office appears to be to appreciate mass-
movements of the water, and more particularly vibrations,
which have longer periods than those appreciated by the ear
(Dercum). In the blind-fish of the Mammoth Cave a row
of sense-papille is situated on the front of the head, sup-
plied with nerve-fibres sent from the fifth pair of nerves
(Wyman).

The angler (Lophius piscatorius) has long been known to
possess hinged teeth, capable of being bent inward toward
the mouth, but by virtue of the elasticity of the hinge at
once resuming the upright position when pressure is removed
from them. Anabdbleps and Pecilia have also movable teeth.
The hake, a voracious predatory fish, and in a less degree
other Gadide@, are possessed of hinged teeth.

The nature of respiration is intimately connected with the
production of sounds by fishes. Recent researches by Jobert
on certain unusual modes of breathing in fishes are of special
interest. He has examined certain fishes of the Amazons,
a.e., species of Callichthys, Doras, Erithrinus, Hypostomus
and Sudis gigas or ‘‘ pirarucu” of the natives, the latter being
allied to the herring. In the Callichthys the intestine is trans-
formed into a respiratory organ. When the water dries up
it emigrates to other pools or streams, creeping by means
of its pectoral fins. This fish can live twenty-four hours
out of the water with impunity.

In the gigantic pirarucu, the swimming-bladder is a long
sac, and the upper part does not look like that organ, being
spongy, areolar, reddish-brown, friable, and intimately
pressed to the dorsal and lateral walls of the body ; its color
recalls that of the lungs of a bird, and functionally it re-
sembles the latter.

Among accessory breathing organs are the lamellate cavity
of the Anabas, and the sac-like appendages which are in con-
nection with the gill-cavity, and extend under the muscles
MUSICAL FISH. 443

of the body of Amphipnous cuchia, Gymnarchus and Sacco-
branchus singio.

The noises produced by certain fishes are due primarily to
the action of the pneumatic duct and swimming-bladder,
while different kinds of noises are made accidentally or in-
voluntarily by the lips or the pharyngeal or intermaxillary
bones, as in the tench, carp and a large number of other
fishes. Over fifty species of fish are known by Dufosse to
produce sounds of some sort, and Abbot has increased the
number in this country. The swimming-bladders of Trigla
and Zews have a diaphragm and muscles for opening and
closing it, by which a murmuring sound is made. The

 

Fig. 402.—Gizzard Shad.

loudest sounds are made by Pogonias chromis, the drum-
fish. In some Cyprinine, Siluroids and eels the sound is
made by forcing the air from the swimming-bladder into the
esophagus. In the sea-horse (Hippocampus), the sounds
are made by the vibrations of certain small voluntary
muscles.

Dr. C. C. Abbot has in this country discovered that the mud
sun-fish (Acantharchus pomotis) utters a deep grunting sound;
the gizzard shad (Dorosoma cepedianum, Fig. 402) makes “an
audible whirring sound ;” the chub-sucker or mullet (Zrimy-
zon oblongum) ‘‘utters a single prolonged note accompanied
by a discharge of air-bubbles ;” the cat-fish (Amiwrus Lyne)
444 ZOOLOGY.

produces ‘‘a gentle humming sound ;” eels utter a more dis-
tinctly musical sound than any other of those observed by
Abbot, who states that ‘‘it is a single note, frequently re-
peated, and has a slightly metallic resonance.” It should
also be noticed that the organs of hearing in many musical
fishes are said to be unusually well developed, hence these
sounds are probably love-notes; and Abbot notices the fact
that these fishes are dull-colored during the reproductive sea-
son, as well as at other times, while voiceless fishes, such as
the perch, common sun-fish, chub, roach, etc., are highly
colored during the breeding season, and thus the sexes are
mutually attracted in the one case by music, and in the other
by bright colors. Finally the sounds of fishes may be said
to be homologous with those of reptiles, birds and mammals,
the air-bladder being homologous with the lungs of the
higher Vertebrates, while the pneumatic duct is comparable
with the trachea of birds and mammals.

In swimming, the propelling motion is mainly exerted by
the tail, the movements of which are somewhat like those of
an oar in sculling. The spines of the tail-fin are movable,
and are capable of being brought into such a position that
the fin will meet with less resistance from the water while
the tail is bent, then straightened, and it is when being
straightened that the fish is propelled. The movements of
the pectorals and ventrals are to steady the fish and to ele-
vate and depress it, while the dorsal and anal fins steady
the body and keep it upright, like a dorsal and ventral keel.

Among viviparous bony fishes are certain Cyprinodonts
(as Anableps and Pecilia), the eel-like Zources, and the
blind-fish of the Mammoth Cave. A small family of Cali-
fornian marine fishes, in form resembling the sun-fish (Pomo-
tis) are called by Agassiz Hmbiotocide, from the fact that
they bring forth their young alive. 2mbiotoca Jacksoni
Agassiz, which is twenty-seven and a half centimetres (104
inches) long, has been known to produce nineteen young,
each about seven and a half centimetres (3 inches) long.

During their reproductive season, many bony fishes, such
as the stickleback, salmon, and pike, are more highly colored
than at other times, the males being especially brilliant in
DEVELOPMENT OF FISH. 445

their hues, while other secondary sexual characters are devel-
oped. The female deposits her eggs either in masses at the
surface of the water, as the goose-fish, or at the bottom
on gravel or sand as do most other fishes, the male passing
over them and depositing his “‘ milt” or spermatic particles.
The egg has a thin transparent shell, and the yolk is small,
covered with a thick layer of the ‘‘ white.”

The eggs after fertilization undergo partial segmentation,
the primitive streak, notochord, nervous cord, and brain de-
velop as in the chick, but that the embryo is to become a
fish issoon determined by the absence of an amnion and allan-
tois, and by the fact that the germ lies free over the yolk
like a band.

In the pike the heart Rogie to beat about the seventh day,
and by this time the alimentary canal is marked out. The
primitive kidneys are developed above the liver. The air-
bladder arises as an offshoot opposite the liver from the ali-
mentary canal, and the gall-bladder is also originally a
diverticulum of the intestine. The urinary bladder in the
fish is supposed to be the homologue of the allantois of the
higher Vertebrates. The nrinoipal external chan ge is the
appearance of the usually large pectoral fins.

The embryo pike hatches in about twelve days after devel-
opment begins, and swims about with the large yolk-bag
attached, and it is some seven or eight days before the young
fish takes food, living meanwhile on the yolk mass. The
perch hatches in twelve days after the egg is fertilized, and
swims about for eight or ten days before the yolk is absorbed.
The gills evadually develop with the absorption of the yolk.

The tail in most bony fishes is at first protocercal, then
becoming heterocercal as in the adult sharks, but subse-
quently, after the fish has swam about for a while and in-
creased in size, it becomes homocercal or symmetrical. The
scales are the last to be developed.

In the large size of the pectoral fins, the position of the
mouth, which is situated far back under the head, the hetero-
cercal tail, the cartilaginous skeleton and uncovered gill-
slits, the embryo salmon, pike, perch, etc., manifest transi-
tory characters which are permanent in sharks.
446 ZOOLOGY.

The bony fishes date back to the Jurassic period, but did
not become numerous until the Cretaceous and especially the
Tertiary Period. The Green River beds of Wyoming abound
in their remains.

The Teleosts are divided into eight orders, in an ascending
series as follows : Opisthomi, Apodes, Nematognathi, Scypho-
phori, Teleocephali, Pediculati, Lophobranchii and Plectog-
nathi.

Order 1. Opisthomi.—The fishes of this group are char-
acterized by the separation of the shoulder-girdle from the
head. The ventral fins are either abdominal or wanting.
The typical genus is Notocanthus, in which the body is elon-
gated, with a proboscis-like snout.

Order 2. Apodes.—In this group, algo, the scapular arch

 

Fig. 403.—Commion Eel, Anguilla acutirostris.

is free from the skull, while the maxillary bones are rudi-
mentary. The branchial apertures are unusually small, and
there are no ventral fins, while the body is very long, cylin-
drical, snake-like. The order is represented among many
other forms by the common eel (Anguilla), the conger-eel,
and the Murena of the Mediterranean Sea. The conger-eel
(Conger oceanicus Gill) ranges from Newfoundland to the
West Indies. Gill, as well as Giinther and others, regards a
long transparent ribbon-like fish, described under the name
of Leptocephalus as the young of the conger-eel.

The common eel, Anguilla acutirostris (Fig. 403), occurs
on both sides of the Atlantic, on the North American coast
as far south as Cape Hatteras, and in inland rivers and lakes.
The sexes do not differ externally, and internally only
BREEDING HABITS OF THE EEL. 444

as regards the form cf the reproductive glands. The
ovaries form two ribbon-like masses extending from the
liver to just beyond the vent and attached by one edge
to the walls of the body, with the free edge hanging
downwards. When in spawn the ovary is very thick,
white, and the eggs can be seen with the naked eye,
being nearly one half millimetre in diameter. When ripe
they break through the wall of the gland and drop into
the body-cavity, there being no oviduct, and pass out of the
genital opening situated directly behind the vent. The male
glands occupy the same position as the ovaries of the female,
but are smaller, narrower, and distinctly lobulated. Out of
about six hundred specimens of eels, only four males have
yet been found in this country. These had testes like those
described by Syrski in the Italian eel (4. vulgaris), while Pack-

 

Fig. 404.—A Siluroid Fish, Avius. Young with the yolk not absorbed.

ard detected the mother cells, and Mr. Kingsley observed mov-
ing active spermatozoa. It is probable that the eel descends
rivers in October and November, spawning in the autumn and
early winter at the mouth of rivers, and in harbors and es-
tuaries in shallow water. By the end of the spring the
young eels are two or three inches long, and then ascend
rivers and streams. They grow about an inch a month, and
the females do not spawn at least before the second year, 7. ¢.,
when about twenty inches long. Mr. Mather estimates that
the ovary of an eel weighing six pounds when in spawn con-
tains upwards of 9,000,000 eggs.

Order 3. Nematognatht.—This group is represented in
North American waters by the catfish and horned pout.
The name of the order (from vaya, vnparos, thread, and
448 ZOOLOGY.

yvaGos, jaw) is in allusion to the filaments or barbels grow-
ing out from the jaws, and which are characteristic of the
members of the group. The upper jaw is formed by the
intermaxillary bones only, while
the supra-maxillary bones form
the bases of the large barbels.
The suboperculum is always ab-
sent, as is also the symplectic;
the supra-occipital and parietal
bones are co-ossified. The skin is
either naked or with bony plates.
The air-bladder connects by a
duct with the roof of the cesoph-
agus. While a few forms are
marine, most of the Siluroid
fishes are inhabitants of the riv-
ers of tropical countries, a large
number being characteristic of
the rivers of Brazil. All the
North American species belong to
the family Silwride, of which
the common representatives are
the horned pout and western
catfish. In these forms the skin
is naked. The horned pout,

Amiurus atrarius Gill, ranges

Og eT apedo, a Siaroid Ssh, trom New England to Maryland
seen from beneath, with its egg-cap- 5 y
lee AmNnd Oy Diente and the Great Lakes. It breeds in
New England in holes in gravel during the midsummer. The
Great Lake catfish, Amiurus nigricans Lesueur, is abundant
in the Great Lakes, and is about a metre (2-4 feet) in length.
The blind catfish, Gronias nigrilabris Cope, inhabits a sub-
terrancan stream tributary to Conestoga River in Eastern
Pennsylvania.

Among the exotic South American Siluroids are Arius
(Fig. 404) and Aspredo (Fig. 405) of Guiana. In Arius and
some of its allies in South America the eggs are carried by
the males in their mouth, from five to twenty being thus

 
EGYPTIAN ELECTRICAL FISH 449

borne about until the young hatch. They are probably
caught up after exclusion and fertilization. Some of these
eggs are half an inch in diameter. Dr. Day states that the
same habits occur in certain Indian species of Ariws and
Osteogeniosus. A species of Arius was found by Stein-
dachner, at Panama, to carry its eggs in a fold of the skin of
its belly ; afterwards the males bear them about in their
mouth.

The females of Aspredo have on the ventral surface
horny, stalked capsules, which contain eggs from one to two
millimetres in diameter ; the capsules disappear as soon as
the young hatch.

Malapterurus electricus Lacépéde, of the Nile, is electri-
cal, the electric cells forming a layer directly beneath the
skin and enveloping the whole body, except the head and
fins. The cells are minute, lozenge-shaped, about one and
a half millimetres in diameter. They are supplied by a
nerve from the spinal cord. The shock is comparatively
feeble, but suffices for defence, “‘ the fish being protected by
its electrifying coat, as is the hedgehog by its spines.”
(Owen. )

Order 4. Scyphophori.—Vhis order, first named and
characterized by Cope, derives its appellation from the
Greek oxtvqos, a bowl, and pépw, to bear, in allu-
sion to a peculiarity of the pterygoid bone, which is en-
larged, funnel-shaped, and excavated by a bowl-like cham-
ber which expands laterally and is covered by a lid-like bone.
The brain has a peculiar plicated organ over the cerebellum ;
the air-bladder is simple, communicating by a duct with the
intestinal canal. The order comprises two families, the
members of which inhabit the rivers of Africa; they are the
Mormyride, represented by a number of genera and species,
and the Gymnarchide, of which Gymnarchus niloticus is
the only known species.

Order 5. Teleocephali.icThese are our common types of
fishes, and are, whether we consider their individual struc-
ture or the number of specific forms, the most highly de-
veloped, t. e., specialized, of the class. The name is derived
from réAezos, perfect, and xepadn, head, in allusion to the
450 ZOOLOGY.

high degree of elaboration and diversity in the bones of the
head. The skeleton is usually completely ossified. The
bones of the skull and of the jaws are fully developed. The
lower jaw is attached to the skull by a suspensorium of sey-
eral well-marked bones, including a symplectic, while the
hyoid and gill arches are well developed, as is the scapular
arch. The brain has small olfactory lobes and a small cere-
bellum. The scales are generally present, and either cte-
noid (.e., rough-edged) or cycloid (é.e., rounded but smooth
on the edge). The common examples are the carp, herring,
trout and salmon, pike, perch, cod, and flounder.

Turning now to some of the more characteristic members
of the order, we first notice one of the lowest Teleosts, the
electrical eel (Gymnotus electricus Linn.) of South Amer-
ica, which is two metres in length, and is characterized by
its greatly developed electrical batteries. These are four in
number, situated two on each side of the body, and together
form nearly the whole lower half of the trunk. The plates
of the cells are vertical instead of horizontal, as in the tor-
pedo, while the entire batteries or cells are horizontal, in-
stead of vertical, as in the electrical ray. The nerves sent
to the batteries of the eel are supplied by the ventral
branches of about two hundred pairs of spinal nerves.

Succeeding these and allied forms are the herrings (Clu-
pede), represented by the common English herring, Olupea
harengus Linn., which inhabits both sides of the North
Atlantic, extending on the American side from the polar
regions to Cape Cod; the alewife, Pomolobus pseudoharengus
Gill, which ranges from Newfoundland to Florida ; the shad,
Alosa sapidissima Storer, which has the same geographical
distribution as the alewife; and the menhaden or pogy,
Brevoortia tyrannus Goode, which extends from the coast
of Maine to Cape Hatteras. These, with the cod, hake,
haddock, salmon, and a few other species, comprise our
most valuable marine food-fishes. The fisheries of the
United States yield about $9,000,000 annually, whilst those
of Great Britain amount to about $8,000,000, and those of
Norway about $14,000,000.

The herring is a deep-water fish which visits the coast in
HABITS OF THE HERRING AND SHAD. 451

spring in immense schools, in which the females are three
times as numerous as the males, to spawn, selecting shoal
water from three to four fathoms deep in bays, where the
eggs hatch. At this season, and early in the summer, hun-
dreds of millions are caught, especially on the Canadian,
Newfoundland, and Labrador coasts. The English white-
bait is the young of the herring. The herring is caught in
deep nets with meshes large enough to capture individuals
of ordinary size, the nets having a finer mesh than those
used for the mackerel fishery.

The alewife and shad are said to be anadromous, from
their habit early in spring of visiting the coast and ascend-
ing rivers in vast numbers to spawn. The eggs are of mod-
erate size ; the ovaries are said to contain about 25,000, and

 

Fig. 411.—The Herring, Clupea harengus, one third natural size.—From the Ameri-
ean Naturalist.

at times as many as 100,000 or 150,000 eggs. They are dis-
charged near the surface, sinking slowly to the bottom.
The time between impregnation and hatching varies from
about three to six days, according to the temperature. The
shad eats little or nothing in fresh water, being then engaged
in the act of reproduction. In the sea they live on small
Crustaceans, such as Mysis, etc. The menhaden is now put
up as a substitute for sardines, and is of great value as fish-
bait, especially in the mackerel fishery, and for its oil.

The family Salmonide comprise the salmon, trout, and
whitefish, with a number of species and varieties. The
species of the genus Salmo have not more than eleven rays
to the anal fin, while the salmon of the west coast, guinnat,
452 ZOOLOGY.

has fifteen or sixteen anal rays. The Salmo salar Linn,
sometimes weighs eighty pounds. It is common to Europe
as well as Northeastern America. In the autumn the salmon
ascends rivers to spawn, penetrating as near the source as
possible. During the breeding season the males differ de-
cidedly from the females, in the long, slender, hooked snout,
the body being thin and high-colored. ‘The eggs are very
large, exceeding a pea in size, and are laid in shallow holes
made in the gravel of streams. The extreme young are
banded and called parr; when about a year old, and of a
bright silvery color, before descending the rivers to the sea,
it is called a smolt; after its return from the sea into fresh
water it goes by the name of grilse; and finally, after re-
turning a second time from the sea, it assumes its name of
sulmon. The trout, Salmo (Salvelinus) fontinalis Gill and

 

Fig. 412.—The Smelt—-Osmerus mordax—one half natural size.--From the Amer-
ican Naturalist.

Jordan, also breeds in the autumn and early winter; it is
not anadromous, living permanently in streams and ponds.

An allied family embraces the smelts, Osmerus eper-
lanus Linn., and O. mordax Mitchill, which live on both
sides of the Atlantic, and range from Nova Scotia to Vir-
ginia. The capelin, Mallotus villosus Cuvier, is valuable
as bait in the cod fishery. It spawns in the summer. The
males are distinguished by a prominent lateral ridge along
the sides of the body and are more numerous than the
females.

Belonging to the same suborder or group of families
as the Salmonide is the family Galaxiide, represented by
Galavias and Neochanna (Fig. 413), in the latter of which
the ventral fins are absent.
BLIND FISH. 453

The carps (Cyprinus), shiners and minnows abound every-
where in the Northern States in ponds and weedy streams. The
breeding habits of the dace (Rhinichthys atronasus Mitchill)
have been observed by Dr. Gregg. The females spawn over
“nests” or shallow depressions two feet in diameter in run-
ning brooks about a foot deep; the male passes over the
eggs fertilizing them; then the pair bring small pebbles
which are dropped over the eggs, until layer after layer alter-

 

Fig. 413.—Neochanna.—From Liitken.

nately of eggs and pebbles are deposited, when a heap is
formed, the young hatching out and remaining among the
pebbles until old euough to venture out into the stream.
The dace is closely allied to the chub (Semotilus rhotheus
Cope, Fig. 415). Succeeding them are the suckers (family
Catostomide) of which Catostomus teres Lesueur is an ex-
ample.

The blind fish of the Mammoth and other caves, and of

 

Fig. 414.—Mud-Minnow.—From Abbot.

adjoining wells connecting with subterranean streams, are
remarkable for the rudimentary state of the eyes, and con-
sequently of color. There are several species, the most
common and largest being Amblyopsis speleus De Kay ; this
species is viviparous. Representing the family Umbrid@ is
the mud-minnow (Melanura limi Kirt., Fig. 414).

The flying-fish represent another family. Their pectoral
fins are very broad and large. They dart from the water
454 ZOOLOGY.

with great speed without reference to the course of the wind
and waves. They make no regular flying motions with their
pectoral and ventral fins, but spread them out quietly,
though very rapid vibrations can be seen in the outstretched
pectoral fins. They usually fly farther against the wind than
with it, or if their track and the direction of the wind form
an angle. Most flying-fish which fly against or with the
wind continue in their whole course of flight in the same di-
rection in which they come out of the water. Winds which
blow from one side on to the original track of the fish bend
their course inward. All fish which are at a distance from
the vessel hover in their whole course in the air near the sur-
face of the water. If in strong winds they fly against the

 

Fig. 415.—The Large Chub, Semotilus rhotheus, one fifth natural size.—From Abbot.

course of the waves, then they fly a little higher ; sometimes
they cut with the tail into the crest of the waves. Only
such flying-fish rise to a considerable height (at the highest,
by chance, five metres above the surface of the sea) whose
course in the air becomes obstructed bya vessel. In the
daytime flying-fish seldom fall on the deck of the ship, but
mostly in the night; never in a calm, but only when the
wind blows. (Moebius.)

Following the flying-fish is the family represented by the
silver gar or bill-fish (Belone longirostrus Mitchill, Fig. 416).

The sucker (£cheneis remora Linn.) occurs along the
whole coast of the United States, and is found all over the
HABITS OF THE PERCH, ETC. 455

tropical and subtropical seas. It is provided with a broad
oval sucker on the upper side of the head, by which it ad-
heres to other fish or even to ships, and may thus be trans-
ported long distances. Another noticeable member of the
order is the blue-fish (Pomatomus saltatrix Linn., Fig. 417),
so valuable as a food-fish.

Ts

 

Fig, 416.—The Bill-fish, Belone longirostrus.—From the American Naturalist.

The dolphin (Coryphena) is sometimes found upon our
coast, but it is essentially a pelagic fish, occurring only out
of sight of land upon the high seas. The pilot-fish is also
a pelagic form.

The percoid fishes are represented by the perch (Perca flu-
viatilis Linn.), which spawns in winter, making slight hol-
lows in the gravel in shoal places in ponds ; their movements

 

Fig. 417.—The Blue-fish, Pomatomus saltatriw, one sixth natural size.—From the
American Naturalist.

can be watched through the ice. On the other hand, the
sun-fish or bream (Zupomotis aureus G. and J.) spawns in
the summer time, making a nest, which they scoop out of
the river bottom. The banded sun-fish (Mesogonistius che-
todon Gill) occasionally scoops out a little basin in the sand,
in which it deposits its eggs late in thespring. The spotted
456 ZOOLOGY.

sun-tish (Lnneacanthus obesus Gill, Fig. 418) lives in muddy
streams, burying itself in the mud in winter. Of similar
mud-loving habits is the mud-minnow (Melanura limi
Agassiz), which spawns in the spring. The pirate perch
(Aphredoderus sayanus De Kay) occupies the nest of com-

 

Fig. 418.—The Spotted Sun-fish, Hnneacanthus obesus.—After Abbot.

mon sun-fish, and with the female guards it and afterwards
the young till they are nearly a centimetre (two-fifths inch)
in length, when they are left by their parents. (Abbot.)

The darters, Htheostomide, belong near the perches, and
comprise the smallest of fishes. They inhabit the streams
of the Mississippi Valley. A common example is the sand-
darter (Pleurolepis pellucidus Agassiz, Fig. 419).

 

Fig. 419.—Sand-Darter.— After Jordan.

The male stickleback ((asterosteus) makes an elaborate
nest of leaves, etc., suspended in mid-water, within which it
remains watching the eggs and young.

One of the most valuable food-fishes is the mackerel
(Scomber scombrus Linn., Fig. 420), whose range is from
HABITS OF THE MACKEREL. 457

Greenland to Cape Hatteras. It remains in deep water dur-
ing the late autumn and winter, approaching the coast in
May and June for the purpose of spawning, its annual
appearance being very regular. The number of eggs de-
posited in one season by each female is said to be from five
to six hundred thousand. After spawning they move north-
ward, following the coast until they are checked by the
coolness of the water, when they return, and in November
seek the deep water again. When spawning they do not
take the hook ; they are then lean ; but at the time of their
departure from the coast they are fat and plump. (Blake.)
The eggs of the mackerel as well as of the cod are so light
as to rise to the surface, where they develop. Allied to the
mackerel, though of great size, are the horse-mackerel and
the sword-fish, whose upper jaw is greatly prolonged.

 

Fig. 420.—The Mackerel, Scomber scombrus, one quarter natural size —After Blake.

The singular Anabas of the Hast Indies is the representa-
tive of a small group of fishes called Labyrinthici or laby-
rinth-fishes, in allusion to a cavity on the upper side of the
branchial cavity on the first gill-arches, containing a laby-
rinthine organ, which consists of thin plates, developed
from the upper pharyngeal bones, enabling the fish to live
for a long time out of water. <Anabas scandens Cuvier, of
the fresh waters of India, will travel over dry land from one
pond to another, and is even said to climb trees by means
of the spines in its fins.

Near the head of the order stands the cunner (Tauéogola-
brus adspersus Gill), whose anatomy is represented by Figs.
404-406 Passing over the tautog, the voracious wolf-fish
(Anarrhichas), the blennies (Blennide), in which the body
458 ZOOLOGY.

is long and narrow, and the viviparous eel-pout (Zoarces), the
cottoids or sculpins, and a number of allied forms, we come
to the hake (Merlucius bilinearis Gill), the haddock (Melano-
grammus eglefinus Gill, Fig. 421), and cod (Gadus morrhua

 

Fig. 421.—The Haddock, Melanogrammus ceglefinus.—From the American Nat-
uralist.

Linn., Fig. 422), all of which extend northwards from Cape
Hatteras, the cod abounding on both sides of the Atlantic,
being a circumpolar fish. The cod does not, as formerly
supposed, migrate along the coast, but seeks the cool tempe-
rature to which it is adapted by gradually passing in the

 

Fig. 422.—The Cod-fish, Gadus morrhua.—From the American Naturalist.

early summer from shallow to deep water, and returning as
the season grows colder. It visits the shallow water of Mas-
sachusetts Bay to spawn about the first of November, and
towards the last of the month deposits its eggs. About
ASYMMETRY OF THE FLOUNDER. 459

eight or nine million of eggs are annually deposited by each
female. (Blake.) The eggs laid by the cod rise to the sur-
face of the water, on which they float. The young fish
hatch on the New England coast in twenty days after they
areextruded. Several millions of cod were artificially hatched
at Gloucester, Mass., in the winter of 1878-9, by the United
States Fish Commission; it has thus been demonstrated
that this fish can be artificially propagated.

The cod is the most important of all the food-fishes,
whether we consider the number taken and the amount of
capital involved in the cod-fishery. It abounds most on
the Grand Banks of Newfoundland. The breeding habits
of the haddock, hake and pollock are probably like those of
the cod.

Fierasfer is a small eel-like fish, with a long, thin tail. It
is typical of a peculiar family, and is noteworthy from being
a “commensal” or boarder in the digestive canal of Holo-
thurians, etc. #. acus Briinn. lives in Holuthurians, and
another species in a star-fish (Cwlcita). The Brotulide are
fishes allied to the cod, but constituting a distinct family.
Most of them are salt-water species, but allied forms (Luci-
fuga subterraneus and Stygicola dentata) live in subterra-
nean waters in Cuba.

At the head of Teleocephali stand the flounders, halibut
and soles, which are an extremely modified type of the order.
In these fishes the body is very unsymmetrical, the fish vir-
tually swimming on one side, the eyes being on the upper
side of the head. The upper side is colored dark, due as in
other fishes to pigment-cells ; the lower side is colorless, the
pigment-cells being undeveloped. When first hatched the
body of the flounder is symmetrical, and in form is some-
what cylindrical, like the young of other fishes, swimming
vertically as they do, and with pigment-cells on the under-
side of the body. Steenstrup first showed by a series of
museum specimens that the flounder was not born with the
eyes on the same side of the head, but that one eye gradually
passed from the blind to the colored side. Mr. A. Agassiz
has studied the process, and finds that the transfer of the eye
from the blind side to the colored side occurs very early in
460 ZOOLOGY.

life, while all the facial bones of the skull are still cartilagi-
nous, long before they become hard and ossified, 7.¢., when
the flounder (Plagusia) is twenty-five millimetres (one inch)
long. ‘‘The transfer of the eye from the right side to the
left. takes place by means of a movement of translation, ac-
companied and supplemented by a movement of rotation
over the frontal bone.” Young flounders, when less than
two inches in length, are remarkably active compared with
the adults, darting rapidly through the water after their
food, which consists principally of larval, surface-swimming
crustaceans, etc. (A. Agassiz.) The common flounder from
Nova Scotia to Cape Hatteras is Pseudopleuronectes Ameri-
canus of Gill.

 

Fig. 423.—Goose-fish, one tenth natural size.—From Tenney's Zoology.

Order 6. Pediculati.—The type of this order is the goose-
fish. The name was given to the group from the long
slender bones supporting the pectoral fins. The gill-open-
ings are small and placed in axils of the pectoral fins. Lo-
phius piscatorius Linn., the goose-fish or angler (Fig. 423),
has an enormous mouth, and swallows fishes nearly as large
as itself. The head and fore-part of the body is very large ;
the skin is naked, scaleless. Its eggs are laid in broad,
ribbon-like, thin gelatinous masses, two metres long and
half a metre wide, which float on the surface of the
ocean.

Order 7. Lophobranchiti. —The tufted-gilled fish—such the
name of the order indicates—have a fibro-cartilaginous skele-
THE PIPE FISH. 461

ton; a single opercular bone, while the snout and lower
jaw are prolonged into a tube, with the mouth at the
end. The chief peculiarity, however, is the gills, which are
developed in the form of a row of tufted lobes on each side
of the branchial arches. The scales are large, forming an-
gular plates arranged in longitudinal rows (Gill). In Sole-
nostoma of the Indian Ocean the female carries the eggs in
« pouch formed by the union of the ventral fins with the
integument of the breast.

The male of the pipe-fish (Syngnathus peckianus Storer)
receives from the female the eggs, and carries them in a
small pouch under
his tail, which is
open beneath
through its whole
length. This sin-
gular mode of mas-
culine gestation is
still farther per-
fected in the sea-
horse (Hippocam-
pus hudsonius De
Kay, Fig. 424),
which lives off-
shore from Cape
Cod to Cape Hat-
teras). The pouch
is situated on the
breast. The male, by simple mechanical pressure of its
tail, or by rubbing against some fixed object, as a shell,
forces the fry, to the number of about a thousand, out of its
brood-pouch, the young at this time measuring about twelve
millimetres (5-6 lines) in length. In the young the head is
at first rounded, the snout being short and blunt (Lockwood).

Order 8. Plectognathi.—This group, represented by a few
singular forms, such as the trunk-fish, file-fish, puffers, and
sun-fish, is characterized by the union of the bones of the
upper and especially the lower jaws. There are few verte-
bree, the scales are often modified to form spines, and the

   

Fig. 424,—Sea-horse, male, with the young issuing
from the brood-pouch.—After Lockwood.

 

 
462 ZOOLOGY.

ventral fins are usually absent. They are inhabitants of warm
waters. The trunk-fish or box-fish, Lactophrys trigonus
Poey, is a West Indian fish ; one specimen has appeared at
Holmes’ Hole, Mass. The porcupine-fish (Chilichthys
turgidus Gill) and smooth puffer (Tetrodon levigatus Gill)
and the spring box-fish (Chilomycterus geometricus Kaup)

 

 

Fig. 425.—Sun-fish, Mola rotunda, one eighteenth natural size.—After Putnam.

range from Cape Cod to Florida. The sun-fish (Mola ro-
tunda Cuvier, Fig. 425) is, like the others of the order, a
surface-swimmer. It is sometimes a metre or more in
length, weighing five hundred pounds or more. Allied
forms are Orthagoriscus oblongus (Fig. 426) and the globe-
CLASSIFICATION OF FISHES. 463

fish, Molacanthus Pallasii (Fig. 42%), which occur in the
North Atlantic.

 

Secret)
Fig. 427.—Mola-
canthus  Pallasii,
3 half grown, natural
Fig. 426.— Orthagoriscus oblongus, young, natural size.— After Put-
size.—After Harting. nam.

 

CLASS III.—PISCES.

Aquatic Vertebrates with a movable lower jaw, a cartilaginous or
osseous skeleton, with paired and unpaired fins supported by fin rays ;
no sternum; usually covered with scales; breathing by gills. Heart
with a single ventricle and auricle. Mostly oviparous.

Subclass 1. Hlasmobranchit.— Skeleton cartilaginous ; skull without
membrane bones, five to seven pairs of gill-sacs and gill-
openings; no opercular bones; tail heterocercal; scales
placoid ; heart with a pulsating aortic bulb; optic nerves
forming a chiasma; intestine with a spiral valve; both
oviparous and viviparous.

Order 1. Plagiostomi (Selache, Lamna, Raia).
Order 2. Holocephali (Chimera).

Subclass 11. Ganoidei—Skeleton cartilaginous or ossified ; skull with
plate-like membrane bones; one pair of gill-openings cov-
ered by opercular bones; skin usually with cycloid or gan-
oid scales; air-bladder with a pneumatic duct ; embryos or
young sometimes with external gills ; chiasma of the optic
nerves ; intestine with a spiral valve ; development, so far
as known, much as in the sharks, and in some respects like
the bony fishes; the living forms oviparous.

Order 1. Chondroganoidet (Acipenser).
Order 2. Dipnot (Ceratodus, Lepidosiren).
464 ZOOLOGY.

Order 3. Branchioganoidet (Polypterus),
Order 4. Hyoganoidet (Lepidosteus, Amia).

Subclass II. Teleostei.—Skeleton bony; skull composed of numerous
bones ; optic nerves crossing each other ; usually four pairs
of gills, with several opercular bones; heart without a cone,
but with an arterial bulb; intestine generally without a
spiral valve ; mostly oviparous.

Order 1. Opisthomi (Notacanthus).

Order 2. Apodes (Anguilla).

Order 3. Nematognathi (Amiurus).

Order 4. Scyphophori (Mormyrus).

Order 5. Teleocephali (Salmo, Perca, Gadus).
Order 6. Pediculati (Lophius).

Order 7. Lophobranchtt (Hippocampus).
Order 8. Plectognathi (Tetrodon, Mola).

Laboratory Work.—Fishes should usually be dissected, except when
large, under the water; small specimens can be pinned down to the
bottom of cork- or wax-lined dissecting pans, and the more delicate
parts worked out with fine scissors and knives. The brain and spinal
cord can be dissected with ease, provided care be taken, with scalpel
and scissors, as the bones covering them can be cut away by means of
stout scissors and bone-pliers and fine surgical saws. Lozigitudinal
sections will bring out the relations of the brain and beginnings of the
nerves, and transverse sections of the tail may be made to show the
disposition of the muscles. The skeleton may be prepared whole by
removing the flesh carefully from alcoholic or partly macerated speci-
mens. Disarticulated skeletons for study can be made by parboiling
the fish and then separating the bones from the flesh. To study the
circulation, careful injections should be made by the use of an inject-
ing syringe, with wax, plaster of Paris, or vermilion as the injecting
medium.

Crass IV.—Batracuia (Salamanders, Toads, and Frogs).

General Characters of Batrachians.—We have had an-
ticipations of the Batrachians or Amphibia in the Ganoids,
especially the Dipnoan fishes, which it will be remembered
approach the members of the present class in the lung-like
nature of the air-bladder and in the presence of external
ANATOMY OF BATRACHIANS. 465

gills in the young, as well as in the form of the skull, there
being many bony parts in the skull which resemble similar
parts in Batrachia. Indeed so close in some characters is the
approximation of the fishes to the Batrachians, that the two
classes have been placed in a series called Ichthyopsida. The
Batrachians, however, differ essentially from the fishes in hav-
ing the bones of the skull few, directly comparable with
those of reptiles, birds, and mammals, and in being jointed
to the vertebral column by two articular surfaces called con-
dyles, the first vertebra, or atlas, having two corresponding
articulating hollows. The limbs have the same number of
subdivisions, with distinct leverage systems, as the higher
Vertebrates, the bones composing them being closely homol-
ogous. ‘True ribs now appear. Some have persistent exter-
nal gills, and all have well-developed lungs. So that for the
first time we have the coexistence of true limbs and lungs
in animals which are air-breathing and move about freely on
land, though from passing a part of their adult life in or
about fresh water they are said to be amphibious. The skin
is usually scaleless. The circulation is incompletely double,
there being sometimes two auricles. Like fishes, they are
cold-blooded. They are mostly oviparous, a few are vivipa-
rous, and nearly all undergo a metamorphosis.

To enter more into detail: The vertebre of Batrachians
are in the living Profews and allies, and in the blind-worms
(Apoda) biconcave ; in the salamanders and in the Surinam
toad (Pipa) and Bombinator they are concave behind, but
in the toads and frogs generally they are for the most part
concave in front, but vary in different parts of the spinal
column, some of the same individuals being biconvex and
others biconcave. While the vertebre are numerous in the
tailed forms, in the tailless toads and frogs there are but
eleven, two in the coccyx, one in the sacrum, the remaining
eight forming the rest of the column. In the frog, when
the tail disappears, a long, spine-like piece (Fig. 428, e) called
the wrostyle is developed from the rudiments of a few verte-
bre. In the extinct Archegosaurus the bodies of the verte-
bree are but little ossified ; in Trimerorhachis they are rep-
resented by the bony rings of three segments, while in allied
466 ZOOLOGY.

Labyrinthodonts such as Rhiachitomus, the vertebre are
ossified, but the centra consist of three pieces. In Cricotus
there are two kinds of bodies, centra and intercentra. The
ribs are rudimentary, except in the blind-worms (Cecilia).

The skull is usually broad and flattened ; it differs from
that of fishes in having no bones representing the operculum,
suboperculum, interoperculum, or branchiostegal bones ; but
a membrane bone probably homologous with the preopercu-
lum is said to exist. (Cope.) The maxillary and premaxil-
lary bones are always present, usually armed with teeth ; no
Batrachian possesses a complete basioccipital, supraocci-
pital, basisphenoid, ali-
sphenoid, or presphe-
noid cartilage bone;
while ‘the frog’s skull
is characterized by the
development of a very
singular cartilage bone,
called by Cuvier the ‘os-
en ceinture,’ or girdle-
bone.” (Huxley.)

The embryonic carti-
lage persists in the low-
er jaw in adult Batra-
J chians as in fishes, and
igh Skelton of arog. 4 ako 2. bony parts are developed
(urostyle); f, suprascapula ; g, humerus; /, fore’ in connection with it
arm bones ; #, wrist bones (carpals and meta- 2 i
carpals); d, ilium; m, thigh (femur) , n, leg which essentially corre-
bone (ulna): 0, elongated first pair of ankle-
bones (tarsals) ; p,¢, foot bones or phalanges. spond to those of fishes.
—After Owen.

(Gegenbaur. )

The suspensorium is immovably joined to the skull, and
with it is connected the hyoidean arch. The branchial
arches in the tailed forms persist in varying numbers, i. ¢.,
from two to four, but are dropped in the toads and frogs. The
skulls of certain Labyrinthodonts are roofed in by broad,
flat bones, so that they bear a strong resemblance to certain
Ganoids represented by the garpike, while Gegenbaur states
that there are many bony parts in the skull of the Batra-
chians which resemble those in the Dipnoan fishes. The ex-

      
ANATOMY OF BATRACHIANS. 467
tinct Archegosawrus had in its larval life branchial arches,
and in fact so close are the affinities of some Amphibians to
the Ganoids that it is probable that both types have had a com-
mon origin ; while on the other hand the bones of certain
extinct scaly Labyrinthodonts have been regarded by some
authors as reptiles ; for example, the Carboniferous Mustodon-
saurus was described as a reptile, but has been referred to
the Amphibians by modern writers.

The sternum or breast-bone (Fig. 429, s) first appears in
the Batrachians. The shoulder-girdle is in great part carti-
laginous. In the toads and
frogs (Anwra) the fore limbs,
the radius, and ulna, and in
the hind limbs the tibia and
fibula, grow together; there
are four toes in the fore feet,
and five toes in the hind feet.

 

In the Stren the hind legs are
wanting ; in the congo-snakes
(Amphiuma) the limbs are
either two or three-toed.

The teeth of modern Ba-

Fig. 429.—Sternum and shoulder-girdle
of Frog (Rana temporaria). p, body of
the sternum ; sc, scapula ; sc’, supra-scap-
ula; co, coracoid-bone, fused in the mid-
dle line with its fellow of the opposite
side (s); cl, clavicle; e, episternum. The
extreme shaded double portion below p
is the xiphistenum. The cartilaginous

F . parts are shaded.—After Gegenbaur.
trachians are conical or lobate,

and microscopically are simple, while those of the extinct
forms are mostly complicated by the labyrinthine infolding
of the walls, as seen in microscopic sections; the teeth of
many Ganoids have a similar, though much simpler struc-
ture. They are usually of the same size, and may be ar-
ranged on projecting portions of different bones of the mouth,
i.e., the premaxillary, maxillary, mandibular, vomerine, pal-
atine, and pterygoid bones, as in fishes. In tadpoles and
in Siren the jaw-bones are encased in horny beaks like those
of turtles and birds. In many Labyrinthodonts two tusks
were developed on the palate. The nasal canal is much as
in the Dipnoan fish, the internal opening being situated in
the Perennibranchiates just within the soft margin of the
mouth. In the salamanders and frogs it is bordered with
firmer parts of the jaw. The labyrinth of the ear is large,
and the tympanum or drum of the ear is external, Am-
468 ZOOLOGY.

phibians having a middle ear in addition to the internal ear
of fishes. In toads and frogs the tongue is quite free and
capable of being protruded, except in Pipa and Dactyle-
thra, where it is entirely wanting. In other forms the
tongue is much as in fishes, not being capable of extension
from the mouth. As in
fishes, there are no salivary
glands. The gills of Am-
phibians consist of two or
three pairs of branched,
fleshy appendages, which
grow out from as many
arches. While in the toad
and frog the gills are small
and remain but for a short
time, in the Jarval salaman-
ders, especially the axolotl
(Fig. 480), the gills are still
longer retained, while in
the mud-puppy (Nectwras)
they persist throughout life.

The digestive canal is us-
ually simple, straight, there
being no enlargement form-
ing a stomach; in other
species, both tailless and
tailed, the canal dilates into
a stomach, which in the

, f toad lies across the body-
ai A Apolo Jawvel Selemander, cavity. In tadpoles, which
and lungs (PA). F valmenary aries: Jive on decaying vegetable
from wien te vasiniar arches (2) Oriel: matter, the digestive tract
cays ¥., descending prea. Prom Gervais as very long and closely cous

ed (Fig. 431).

The lungs are long, slender sacs, much like those of the
Dipnoan Lepidosiren, which extend backwards into the ab-
domen, as in the lizards and snakes, no diaphragm existing
to confine them in a thoracic cavity. The larynx exists in
a very rudimentary state, though the vocal powers of the

 
ANATOMY OF BATRACHIANS. 469

toads and frogs are so highly developed. The trachea is
short.

The heart has two auricles, the right one the larger, and a
single ventricle ; but in Protews the auricles connect with
each other, and in the salamanders there is a hole in the par-
tition separating the auricles. There are also indications of

   

Fig. 431.—Mouth and digestive
canal of a Tadpole. A, mouth; 0,
intestine coiled on itself ; ¢, liver ;
d, hepatic duct; e, pancreas; /,
rudimentary hind legs ; g, rectum.
—After Gervais and Van Beneden.

a partition in the ventricle. Fig.
432 represents the circulatory or- =

‘ Ee Fig. 432.—Tadpole of a Frog. 1,

gans of a tadpole, after the gills yens'cavay 2, lett auricle; 3 pul

have become absorbed, and before Mouary vein and its origin in the

: fa i PSAs) ads 7 9, VE

the aortic arches are reduced in ‘ticle; 6, arterial bulb ; 7, branchial

artery and its internal branches; 8,

number. branchial veins ; 9, aorta; 10, pul-

aa 5 monary artery and its subdivisions

The nervous system is much _ inthe iungs.—After Gervais and Van

as in fishes; but the optic lobes °°

are rather smaller, as the eyes are smaller. The kidneys are
in many respects like those of fishes, especially sharks, as
is the internal reproductive system. The ovaries are greatly
enlarged during the breeding season. The sperm is usually
passed to the kidney, and thence through the ureters out of
the cloaca. The oviducts and ureters have a common outlet
470 ZOOLOGY.

into the cloaca. In the salamanders the end of the oviduct
serves as a uterus. There are also fat-bodies (Fig. 433) at-
tached to the anterior end of the reproductive glands of the
toads and frogs, the use of which is unknown. For a gene-
ral idea of the structure of Amphibians the student should
dissect a frog or toad in connection with the following de-
scription and accompanying illustration (Fig. 433), prepared
by Dr. C. 8S. Minot.

The frog is one of the types of Vertebrates most valuable
to the student, being readily obtained and easily dissected.
The accompanying figure represents the anatomy of the
spotted or leopard frog, Rana halecina, male.

The skin is smooth, having neither scales, feathers, nor
hairs, and contains numerous microscopic glands, of which
there are said to be two kinds—one having an acid, the other
an alkaline secretion (L. Hermann). It is pigmented on
the dorsal surface, but whitish underneath. The head is
broad, triangular, with two large nasal openings in front,
large and prominent eyes, two tympanic membranes formed
by a part of the integument stretched across a hard ring,
and an enormous mouth. The neck is short and not con-
stricted. The body tapers slightly posteriorly, and has the
opening of the cloaca upon the posterior end of its back.
Each limb consists of the three divisions: in the front leg,
brachium, antebrachium, and manus with four digits, of
which the fourth is very much thickened in the male ; the
sexes may be distinguished by this mark. In the hind leg
the three divisions are the femur, crus, and pes, with five
long digits, between which the membranous web is stretched.
If the web is examined in a living frog with a microscope,
the circulation of the blood in the capillaries can be studied.
The current of corpuscles and plasma is constant, and in a
given vessel passes only in one direction ; by following the
stream backwards and forwards it will be found to issue
from larger vessels, the arteries, and to enter into other and
different vessels, the veins. The pigment corpuscles can
also be seen in the web; they are branching bodies, capable
of drawing in or expanding their processes, and they can be
made to contract by an electrical shock from an induction
apparatus.
ANATOMY OF THE COMMON FROG. 471

Slit open the skin along the median ventral line the
whole length of the animal, turn the skin back, and then
cut through the muscular walls of the abdomen, being care-
ful not to injure the underlying organs. The viscera will
then be exposed : the coiled intestine, the large liver, and in
the female the sexual organs at either side; finally, pos-
teriorly, the thin-walled bladder, B. The next step is to
seize the posterior end of the sternum with a pair of for-
ceps, lift it up, cut the fibres which run from its under sur-
face, and cut with a pair of strong scissors along both sides
of the sternum and around its anterior end, so as to remove
itentirely. Underneath the sternum lies a thin-walled bag,
the pericardium, enclosing the heart. On either side are
the lungs.

To complete the preparation dissect out the intestine, by
cutting through the mesentery ; follow it to the stomach,
which must be separated from the cesophagus and drawn
aside together with the intestine, while the liver must be
turned over to the right of the animal. The pericardium
must be cut through and removed without injury to the
heart; finally, the skin must be removed from the hind
legs. If the dissection is of a male, it will then appear very
much as in the figure.

The heart is conical in shape ; its apex points backwards,
and is formed by a single chamber, the ventricle, with thick
muscular walls, from which springs on the ventral surface a
little to the right the ¢rwnecus arteriosus (Ao), which runs
forward and divides into the two aortic arches. The base of
the heart contains two chambers, the right and left auricles,
the separation of which is not marked externally. A large
vein (V) passes from the liver to the back of the heart, and
there empties into a thin-walled sac, the sinus venosus,
which also receives on either side a vein from above, the
vene cave superiores. The vein from the liver receives also
the genital and renal veins, and is then called the vena cava
inferior. As the heart continues to beat for many hours
after a frog has been killed, if a fresh specimen is taken for
dissection the rythmically alternating dilatations and con-
tractions may be observed. The order of contraction is,
472 ZOOLOG Y.

Ist, the sinws venosus ; 2d, both auricles; 3d, the ventricle ;
4th, the truncus.

In front of and below the heart may be seen the trachea,
easily recognized by the hard rings of cartilage, and having
the larynx just in front of the aortic arches and giving off
two branches posteriorly, the bronchi, which run directly to
the lungs. The trachea overlies the esophagus, which ter-
minates in the stomach (S¢). On either side of the trachea
lies a thyroid gland (th).

The liver (Lz) is a large brown mass, composed of two
lobes, of which the left is the larger, and subdivided into
two. Between the two lobes lies a small greenish sac, the
gall-bladder (0). The liver receives a large vein (pv) from
the kidneys ; this is the portal vein, which distributes to the
liver the blood which has already once passed through the
capillaries of the other abdominal viscera. The hepatic vein
takes the blood from the liver directly to the heart.

The stomach (S¢), when in situ, lies on the left side of the
abdominal cavity, its esophageal end being the largest ; it
leads directly into the intestine, which is of uniform width
throughout, but terminates in the dilated rectum (22), which
in its turn opens into the cloaca. To the ventral surface of
the cloaca is appended the bladder (B). Imbedded in the
mesentery near the commencement of the intestine is a pale
compact mass, the pancreas, not represented in the figure,
and a little farther from the stomach a small round dark
body, the spleen (Sp).

The kidneys (47%) are two elongated deep red bodies, upon
which lie a number of yellow spots, the adrenal glands.
The renal ducts arise from the outer and anterior portion of
the kidneys and then run backwards as two white convoluted
canals (vd), at first very narrow, then widening, and end-
ing with a dilatation immediately before they open into the
cloaca. These ducts serve at once as wreters and vasa defer-
entia. In front of the kidneys le a pair of oval yellow
bodies, the testes (Ze). The female has both ureter and
oviduct. The ovary varies greatly in size and appearance
according to its condition. The oviduct is a very long con-
voluted tube running from the pericardium backwards to
ANATOMY OF THE COMMON FROG. £73

the cloaca, where it opens just in front of the ureter. At
the season of reproduction the oviduct is found very much
distended with ova. Its anterior end has a ciliated opening
into the body-cavity. In the neighborhood of the sexual
glands lies the fat-body (/).

The lungs (dw) are two large sacs with very elastic walls,
richly supplied with blood-vessels. These vessels spring
from the pulmonary artery. From each division of the
truncus arteriosus are given off four branches (Fig. 433, I).
The first is the pulmonary aorta (Pa), which also gives off
a large cutaneous branch; the second, the true aortic arch
(Ao), which, curving backwards, unites with its fellow just
in front of the kidneys and below the spinal column, to form
the descending aorta; the third (er), the carotid artery, run-
ning to the head, and bearing at its origin the singular caro-
tid gland (cg) ; the fourth, the lingual artery. The blood
is returned from the lungs by two veins, which empty into
the left auricle.

The space of the lower jaw is covered over by a thin trans-
verse muscle (My), the mylohyoid. On either side behind
the posterior edge of this muscle lies a croaking bag or air-
sac (S). In the mouth are to be observed, Ist, the mus-
cular tongue, attached by its anterior end to the lower jaw,
and forked posteriorly ; 2d, the openings of the nasal cavi-
ties; 3d, the recessus Hustachii, lying further back, and
leading into the tympanic cavity ; 4th, the opening of the
cesophagus ; and 5th, the slit-like epiglottis.

The muscles are best dissected in alcoholic specimens.
The muscles of the hind limbs are as follows : On the ven-
tral surface, the cut ends of the recti abdominis (r. ad.) ;
on the ventral surface, 1, of the thigh, outwardly musculus
vastus internus (mvi), the adductor longus (a), the sar-
torius (ms), adductor magnus (a), rectus internus minor
(rt”) ; the rectus internus major (ri'); a small part of the
adductor brevis cav be seen close to the pubis between the
adductor magnus and the rectus internus major ; underneath
the rectus internus major lies the long and the semitendino-
sus with two heads; 2, of the leg (crus) gastrocnemius (7),
and between that muscle and the bone the éibialés posticus :
A474. ZOOLOGY.

 

Fig. 433.—Anatomy of the common Frog.
ANATOMY OF THE COMMON FROG. 475

in front is the tibialis anticus (ta). On the dorsal surface
of the thigh (Fig. 433, III) the gluteus (gl), the pyriformis
(p), the rectus anticus femorus (ra), the vastus externus
(ve), the biceps (6), the semimembranosus (sm), lying deep
between the biceps and semimembranosus are seen the
femoral vessels and sciatic nerve ; the rectus anticus, vastus
internus and externus are known collectively as the ¢riceps
femoris ; in the leg the gastrocnemius (g) and peroneus (p).

The sympathetic nerves can be seen as two cords, one on
either side of the vertebral column. ‘The spinal nerves can
be seen as white threads on the dorsal surface of the body-
cavity. The brain may be dissected out by opening the
skull from above; its parts and its connection with the
spinal cord are sufficiently illustrated by reference to Fig.
368. The seventh, eighth, and ninth spinal nerves unite to
form the very large sciatic trunk ; the intercommunications
of these nerves form the lumbar plexus; while the second
and third spinal nerves form the brachial plexus from which
arises the brachial nerve. (C. 8. Minot.)

Certain glands in the skin of some Batrachians secrete a
corrosive, or as in the European Salamandra maculosa, a nar-
cotic poison, which is poisonous to small animals. The
toads secrete in the parotid glands a bad-smelling fluid,
which applied to tender skins produces erysipelas. Lacerda
states that the poison of the Brazilian Bufo ictericus is a
milky humor from the glands on the sides of the neck. The
action of the poison is Jess fatal to small animals than that
of the European toad ; it gives a slight acid reaction and is
not soluble in alcohol, while that of the European toad is.

Like fishes, the Batrachians assume high colors during
the breeding season. The males of the newts at this time

 

Fig. 433.—Anatomy of common Frog. My, mylohyoid; s7, sternoradials; th,
thyroid ; dz, lungs ; f, fat-body ; Te, testis ; St, stomach; Sp, spleen ; , rectum ;
a, adductor longus; mv, vastus internus; ms, sartorius, 7%, rectus internus
major ; ¢a, tibialis anticus ; g, gastrocnemius ; ri’, rectus internus minor; @, ad-
ductor magnus ; 7a), rectus abdominalis ; 8, bladder ; vd, vas deferens ; 0, gall-
bladder; Az, kidney ; pv, portal vein ; Ii, liver; V, vena cava inferior ; Ao, aorta ;
S, vocal sac, or croaking-bag. ae : 3 oT

II. Origin of the arterial trunks. 1, arteria ingualis ; cg, carotid gland, which is
merely a rete mirabile ; cr, carotid artery ; Ao, aortic arch: Pa, pulmonary artery. :

TIL. Dorsal view of muscles of hind leg. gi, gluteus ; 7a, rectus anterior ; p, pyri-
formis ; ve, vastus externus; $7, semi-membranosus ; 0, biceps ; 7, gastrocnemius ;
per, peroneus.—Drawn by Cc. S. Minot.
AQ6 ZOOLOGY.

acquire the dorsal crest and a broader tail-fin, while in some
species prehensile claws are temporarily developed on the fore
legs of the male. The males of the Anura (toads and frogs)
are musical, the females being comparatively silent ; the vocal
organs of the male are more developed than in the females, and
in the edible frog (Rana esculenta) large sacs for producing
a greater volume of sound stand out on each side of the head
of the males. Among the few viviparous Batrachians known
is an Alpine European Salamandra (S. atra) which brings
forth its young alive.

It is common to find tadpoles in the winter in ponds,
which have been retarded in their metamorphosis, and by
artificial means this retardation may be greatly increased.
For example, Wyman is said to have kept tadpoles of the
bull-frog for seven years in a cellar.

Unlike the higher Vertebrates the segmentation of the egg
in the Amphibia is total, the process beginning usually about
three hours after impregnation in the frog, and lasting twen-
ty-four hours. The primitive streak, the notochord and
nervous system then arise as in other craniated Vertebrates.
After the appearance of the branchial arches, the gills begin
to bud out from them, finally forming the larger gills of the
tadpole. Unlike young fishes, the yolk is entirely absorbed
before the tadpole leaves the egg. In warm climates the
tadpoles hatch in four or five days after the eggs are laid.
When hatched the tadpole is not so well developed as in most
young fishes. The digestive canal at first is simple and
straight. Afterwards it becomes remarkably long and coiled
in a close spiral. The mouth is small (Fig. 481, A), with no
tongue and only horny toothless jaws. The vertebrae of the
tadpole are biconcave as in fishes, afterwards becoming con-
verted into cup-and-ball joints.

The accompanying figures represent the external changes
of the toad from the time it is hatched until the form of the
adult is attained. The tadpoles of our American toad are
smaller and blacker in all stages of growth than those of the
frog. The tadpole is at first without any limbs (Fig. 434 A),
and with two pairs of gills; soon the hinder pair bud out.
After this stage (B) isreached, the body begins to diminish in
METAMORPHOSIS OF BATRACHIANS. 4G?

size. The next important change is the growth of the front
legs and the partial disappearance of the tail (C’), while very
small toads (D und #), during midsummer, may be found on
the edges of the pools in which some of the nearly tailless tad-
poles may be seen swimming about. It is three years before
the Amphibia are capable of breeding. In the newts (Z?i-
ton) the gills are in three pairs, larger and more complex
than in the frog ; the fore limbs are the first to grow out,
and the gills persist long after the hind limbs are developed.
In the newts we have the larval state of the toads and frogs
persistent ; thus the successive steps in the development of
the individual frog is an epitome of the evolution of the
typical forms of the class to which it belongs.

= ,
4p

 

Fig. 484.—Metamorphosis of the Toad.—After Owen ; from Tenney’s Zoology.

In certain Batrachians as the Alpine salamander, the Su-
rinam toad (Pipa) and the Hylodes of Guadaloupe in the
West Indies, the metamorphosis is suppressed, development
being direct; though the young have gills, they do not lead
an aquatic life. In the axolotl there isa premature devel-
opment of the reproductive organs, the larve as well as the
adults laying fertile eggs.

The Batrachians are inhabitants of the warmer and tem-
perate zones. Frogs extend into the arctic circle. The
Amblystoma mavortium breeds at an altitude of about 8000
feet in the Rocky Mountains. Rana septentrionalis Baird
extends to Okak, Northern Labrador, where the climate is as
extreme as that of Southern Greenland ; frogs have also been
478 ZOOLOGY.

observed at the Yukon River in lat. 60° N., but the climate
there is milder than that of Labrador. The common toad
and a salamander (Plethodon glutinosa Baird ?) extend to
Southern Labrador.

Nearly 700 species of existing Batrachians are known, 101
of which are North American, and about 100 fossil forms
have been described.

There are five orders of Batrachians, Professor Cope’s
classification being adopted in this work. Those Batrachians
with persistent gills are sometimes called Perennibranchiates.

Order 1. Trachystomata.—The sirens have a long eel-like
body, with persistent gills; there is no pelvis or hind limbs,
and the weak, small fore legs are four or three-toed. The
great siren, Stren lacertina Linn., is sometimes a metre in
length, and has four toes in the fore leg ; it lives in swamps
and bayous from North Carolina and Southern Illinois to
the Gulf of Mexico. A small siren with three toes and
small gills is Psewdobranchus striatus Le Conte. It occurs
in Georgia.

Order 2. Protetda.—This group is represented by the
Proteus of Austrian caves and the mud-puppy (Necturus)
of the United States. These Batrachians have bushy gills,
with gill-openings and well-developed teeth. In Proteus,
which is blind, there are three toes in the fore feet and two
in the hinder pair. In the mud-puppy, WMectwrus (formerly
Menobranchus) lateralis Baird, each foot is four-toed. The
head and body are broad and flat, brown with darker spots.
It has small eyes and is about half a metre (from 8 inches to
2 feet) in length. It inhabits the Mississippi Valley, extend-
ing eastward into the lakes of Central New York. The
Proteus as well as the mud-puppy lay eggs.

Order 3. Urodela.—The tailed Batrachians or Salaman-
ders have no persistent gills, these organs being larval or
transitory ; the body is still long and fish-like, the tail some-
times with a caudal fin-like expansion as in the newts, but is
usually rounded, and the four legs are always present. With
only one or two viviparous exceptions, most of them lay eggs
in the water. The eggs of Triton are laid singly on sub-
merged leaves ; those of Notophthalmus viridescens are laid
SALAMANDERS. 4N9

singly on leaves of Myriophyllum, which adhere to the glu-
tinous egg, concealing it. (Cope.) Those of Desmognathus
are laid connected by a tough thread on land. (Baird.) The
common land salamander, or Plethodon erythronotum
Baird, lays its eggs in summer in packets under damp
stones, leaves, etc. ; the young are born with gills, as is the
case with the viviparous Salamandra atra of the.Alps. The
possession of gills by land salamanders, which have no use
for them, and which consequently drop off in a few days,
leads us justly to infer that the land salamanders are the de-
scendants of those which had aquatic larve.

The lowest form of this order is the aquatic Congo-snake
or Amphiuma means Linn., in which the body is large, very
long, round and slender, with small rudimentary two-toed
limbs ; there are no gills, though spiracles survive. It lives
in swamps and sluggish streams of the Southern States.

A step higher in the Urodelous scale is the Menopoma, which
is still aquatic, with persistent gills, but the body and feet
are as in the true salamanders. The Menopoma Alleghani-
ense Harlan, called the hellbender or big water lizard, is
about half a metre (14-2 feet) in length, and inhabits the
Mississippi Valley. Allied to the Amphiuma is the gigantic
Japanese salamander, Cryptobranchus Japonicus Van der
Hoeven, which is a metre in length. Allied in size to this
form was the great fossil salamander of the German Tertiary
formation, Andrias Scheuchzeri, the homo diluvii testis of
Scheuchzer, thought by this author to be a fossil man.

In the true salamanders the body is still tailed, the eyes are
rather large ; there are no spiracles ; they breathe exclusively
by their lungs, except what respiration is carried on by the
skin.

The genus Amblystoma comprises our largest salamanders ;
they are terrestrial when adult, living in damp places and
feeding on insects. The larve retain their gills to a period
when they are as large or even larger than the parent. The
most interesting of all the salamanders is the Amdlystoma
mavortium, whose larva is called the axolotl, and was origi-
nally described as a perennibranchiate amphibian under the
name of Siredon lichenoides Baird. This larva is larger than
480 ZOOLOGY.

the adult, terrestrial form, sometimes being about a third of
a metre (12 inches) in length, the adult being twenty centim-
etres (8 inches) long, forming an example of what occurs
in the Amphibians and also certain insects, of the excess in
size and bulk of the larva over the more condensed adult
form. This law is also strikingly observed in the Psewdes
(Fig. 437). This fact of prematuritive, accelerated, vegetative
development of the larva over the adult is an epitome of what
has happened in the life of this and other classes of animals.
The fossil, earliest
representatives of the
Amphibians, as we
shall see farther on,
were enormous, mon-
strous, larval, prem-
ature forms com-
pared with their de-

 

Fig. 485.—Siredon or larval Salamander.—From
Tenney’s Zoology. scendants. The same

law holds good in certain groups of the crustacean (trilobites)
insects, fishes, reptiles and mammals.

The axolotl or siredon abounds in the lakes of the Rocky
Mountain plateau from Montana to Mexico, from an altitude
of 4000 to 8000 or 9000 feet ; the Mexican axolotl being of
a different species, though closely allied to that of Colorado,
Utah and Wyoming. The Mexicans use the animal as food.
Late in the summer the siredons at Como Lake, Wyoming,
where we have observed them, transform in large numbers
into the adult stage, leaving the water and hiding under
sticks, etc., on land. Still larger numbers remain in the
lake, and breed there, as I have received the eggs from Mr.
William Carlin, of Como. Thousands of the fully-grown
siredons are washed ashore in the spring when the ice melts.
They do not appear at the surface of the lake until the last
of June, and disappear out of sight early in September.
They are laid in masses, and are two millimetres in diameter.
Mr. F. F. Hubbell has observed in Como Lake, July 23d,
young siredons four to six centimetres (14-24 inches) in
length, and September 3d specimens eight centimetres (3
inches) long. In Utah, Mr. J. L. Barfoot raised in 1875
HABITS OF THE AXOLOTL. 481

several adults from the larva, and I have been told that sire-
dons in the mountains among the miners’ camps near Salt
Lake City leave the water and transform. It thus appears
that inthe elevated plateaus* as well as at the sea-coast, some
siredons transform while others do not. Mexican siredons
have for a number of years been bred from eggs in the
aquaria of Europe, laying eggs the second year.

The change from the larva to the adult consists, as we have
observed, in the absorption of the gills, which disappear in
about four days ; meanwhile the tail-fins begin to be absorbed,
the costal grooves become marked, the head grows smaller,
the eyes larger, more protuberant, and the third day after
the gills begin to be absorbed the creature becomes dark,
spotted, and very active and restless, leaving the water. Their
metamorphosis may be greatly retarded and possibly wholly
checked by keeping them in deep water. The internal
changes in the bones of the head and in the teeth are very
marked, according to Dumeril.

Experiments made in Europe show that the legs and tail
of the axolotl, as of other larval salamanders, may be repro-
duced. We cut off a leg of an axolotl the first of November ;
it was fully reproduced, though of smaller size than the
others, a month later. The tail, according to Mr. L. A.
Lee, if partly removed, will grow out again as perfect as ever,
vertebra and all.

The Tritons or water-newts, represented by our common,
pretty spotted newt, Diemyctylus viridescens Rafinesque, are
also known in Europe to become sexually mature in the larval
state when the gills are still present, as has been observed by
three different naturalists. The female larva of Lissotriton
punctatus has been known to lay eggs.

Order 4. Gymnophiona.—The blind snake with its several
allies is the representative of this small but interesting order.

* It has been stated by De Saussure, Cope, Marsh, and more recently
by Weismann, that the siredon does not change in its native elevated
home. No naturalist has seen the Mexican siredon transform into an
Amblystoma, but as it does so in abundance in Wyoming and Utah,
it probably transforms in Mexico, for the Mexican species is very
nearly allied to A. mavortiwm.
482 ZOOLOGY.

The body is snake-like, being long and cylindrical; there
are no feet and no tail, the vent being situated at the blunt
end of the body. The skin is smooth externally, with scales
embedded in it, but with scale-like transverse wrinkles. The
eyes are minute, covered by the skin. The species inhabit
the tropics of South America, Java, Ceylon, and live like
earthworms in holes in the damp earth, feeding on insect
larve. They are large, growing several feet in length.
Cecilia lumbricoides Daudin inhabits South America. Ce-
cilia compressicauda of Surinam is viviparous, the young
being born in water and possessing external gills which are
leaf-shaped sacs resting against the sides of the body ; when
the animal leaves the water they are absorbed, leaving a scar.
(Peters.) Siphonops Mexicana Dumeril and Bibron, is a
Mexican form.

Order 5. Stegocephala.—Here belong an order of extinct
Batrachians, with three suborders, Labyrinthodontia, Grano-
cephala, and Microsauria (Cope). In these forms the skulls
were either somewhat like those of the frogs, or the crania
were roofed in by solid flat bones, similar to those of ganoid
fishes. The vertebree were biconcave. The limbs of the
Labyrinthodonts were like those of the tailed Batrachians, of
small size and weak, compared with the great size of the
body. Von Meyer states that Archegosaurus possessed
branchial arches when young, and that probably other Laby-
rinthodonts resembled it in this respect. It had paddles
instead of feet, the head had an armor of plates, and the
body was covered with overlapping ganoid scales. It had
teeth like those of ganoid fishes; it had a notochord, the
bodies of the vertebre being neither bony nor cartilaginous.
Owen regards it as combining the characters of the perenni-
branchiate Amphibians and the Ganoid fishes. It was a
little over a metre (33 feet) in length. It is a representative
of the suborder Ganocephala.

While the older text-books in the restorations of Laby-
rinthodon represented it as like a toad, with large legs and
tailess, it is now known that some of the gigantic prede-
cessors of the salamanders and tritons had long tails, while
others had long, cylindrical, snake-like bodies. Unlike exist-
LABYRINTHODONT BATRACHIANS. 483

ing Batrachians, their fossil ancestors had an armor of large
breast-plates, with smaller scales on the under and hinder
part of the body.

But the largest forms were the true Labyrinthodonts repre-
sented in the Carboniferous rocks of this country by Baphetes,
and in Europe by Anthracosaurus, Zygosaurus, and in the
Permian beds of Texas by Eryops. Labyrinthodonts also
abounded in the Triassic Period, and forms like the Euro-
pean Labyrinthodon or Mastodontosaurus must have been
colossal in size. Footprints occur in the Subcarboniferous
rocks of this country which indicate forms still larger than
any yet discovered in the Old World. A large number
(thirty-four species, referable to seventeen genera) of medium-
sized Labyrinthodonts have been described from the coal
measures of Ohio by Cope which were characterized by
their long, limbless, snake-like bodies and pointed heads,
forming a still more decided approach to the Ganoids. This
was the lowest group of Stegocephala, called Microsauria by
Dawson.

Thus we have in these Labyrinthodonts synthetic or an-
nectant forms, which connect the fishes with the Am-
phibians, and on the other hand point to the incoming of
the reptiles. They were thus prematuritive, larval forms,
which in certain characters anticipated the coming of a
higher type of Vertebrate. The reptiles were ushered
in during the Permian Period, the rocks of this age imme-
diately overlying the coal measures, though it should be
stated that there are obscure traces of reptiles in the Carbon-
iferous rocks. It is not improbable that evidence will be
found to substantiate the impression that the reptiles,
together with but independently of the Amphibians,
branched off from the Ganoid fishes, or from extinct forms
related to them. :

Order 6. Anura.—The toads and frogs represent this
order, which comprises tailless Batrachians, with the four
limbs present, the toes being very long (due to the great
length of the calcaneus and astragalus), while the body is
short and broad, the skin soft and smooth, scaleless, though

small plates are sometimes embedded in it. The lower jaw is
484 ZOOLOGY.

usually toothless. The larve are called tadpoles, and repre-
sent the permanent, adult form of the perennibranchiate
Urodela.

Among the lower frogs or arciferous Anura of Cope, é.e.,
those with the acromial and corocoid bones divergent and
connected by distinct cartilage plates, are certain forms,
as Alytes, Pelobates, and Pelodytes, whose breeding habits
are peculiar and interesting. The eggs of Pelodytes are
deposited in small clusters in the water, those of Pelo-
bates in a thick loop. The male of the European Alytes
obstetricans winds a string of eggs which it takes from
the female, and goes into the water, where it remains
until the young (which have no gills) are hatched. The
American Scaphiopus, or spade-footed toad, is not known to
have this obstetrical habit. This singular toad appears sud-
denly and in great numbers. It remains but a day or
two in the water, where it lays its eggs in bunches from
one to three inches in diameter. The tadpoles hatch
in about six days after the eggs are laid; their growth is
rapid, the young toads leaving the water in two or three
weeks. The croaking of this toad is harsh, peculiar, and
need not be confounded with that of any other species.
(Putnam.) As the spade-footed toads are rarely seen, it is
possible that they burrow in the soil, like the European
Alytes. Another peculiarity in the reproductive habits of
Alytes, Pelobates, Cultripes, and Pelodytes is that they
spawn at two seasons instead of one, and that their larve,
like Pseudes (Fig. 487), attain a greater size than those of
other frogs before completing their metamorphosis. (Cope.)

Among the tree-toads, Polypedates of tropical Western
Africa, contrary to the usual habits of frogs, deposits its eggs
in a mass of jelly attached to the leaves of trees which bor-
der the shore overhanging a pond. On the arrival of the
rainy season, the eggs become washed into the pond below,
where the male frog fertilizes them. Our common piping
tree-toad (Hyla Pickeringii Le Conte), about the middle of
April, in the neighborhood of Boston, attaches her eggs
simply to aquatic plants. The young are hatched in about
twelve days.
SUPPRESSHD METAMORPHOSIS. 485

As an example of a suppressed metamorphosis, due ap-
parently to a radical difference in the physical environment
of the animal, may be cited the case of a tree-toad in the
island of Guadaloupe. There are no marshes on this island,
consequently in a species of Hylodes the development of
the young is direct; they hatch from the eggs which are
laid under moist leaves, without tails, and are otherwise, ex-
cept in size, like the adults. On the other hand, a tree-toad
of the island of Martinique (Hylodes Martinicensis, Fig.
436) has tadpoles, which it carries on its back. The female
of Nototrema marsupiatwm Dumeril and Bibron, of the
Andes, has a marsupium or sac on its back in which the
young are carried. The Notodelphys
of South America has similar habits ;
for example, the female Opisthodel-
phys (Notodelphys) ovifera has a dor-
sal sac a centimetre deep in which
the eggs are carried. In the young
of this and of Gastrotheca also of
Central America, Peters found traces
of external gills. The Pipa, or Suri-
nam toad (Pipa Americana Laurent),
which has no tongue, neither teeth in Z
the upper jaw, has similar breeding pig. 43¢.-The Martinique
habits. In this interesting toad the 7teetoad carrying the young
young, according to Prof. Wyman,
are provided with small gills, which, however, are of no
use to them, as the tadpoles do not enter the water, but are
carried about in cavities on the back. The eggs are placed
by the male on the back of the female, where they are
fertilized. The female then enters the water; the skin
thickens, rises up around each egg and forms a marsupial
sac or cell. The young pass through their metamorphosis
in the sacs, having tails and rudimentary gills ; these are
absorbed before they leave their cells, the limbs develop,
and the young pass out in the form of the adult.

The toad (Bufo lentiginosus Shaw) is exceedingly useful ag
a destroyer of noxious insects. It is nocturnal in its habits ;
is harmless, and can be taken up with impunity, though it

 
486 ZOOLOGY.

YZ

A#
Sy FPL
yu S

SD wy 3
Dy pe

<< SS VS

 

Fig. 437.—The Paradoxical Frog. 1, 2, larva, nearly of natural size; 3,4, Pseudes
minuta, natural size. —1, 2, after Pizarro ; 3, 4, after Garman.—From the American
Naturalist.
CLASSIFICATION OF BATRACHIANS. 487

gives out an irritant acrid fluid from the skin, which may
poison the eyelids. In New England toads begin to make
their peculiar low trilling notes from the middle to the 20th
of April; from the latter date until the first of June they
lay their eggs in long double strings, and the tadpoles (Fig.
434) are usually hatched i in about ten days after the eggs are
deposited. (Putnam.)

The paradoxical frog of South America (Pseudes para-
doxa Wager, Fig. 437, 1, 2, the larva) is remarkable from the
fact that the larva is larger than the adult. 38 and 4 repre-
sent another species of Pseudes (P. minuta).

The highest genus of the Anwra is Rana, of which there
are numerous species, our American forms being the bull-
frog (Rana pipiens Linn.), the Rana palustris Le Conte, or
pickerel-frog, and the marsh-frog (Rana halecina Kalm).
They lay their eggs in masses in ‘the water in April, May,
and the early part ot June, according to the latitude.

While most frogs are eaten by birds, and in such cases are
preserved from extinction by their nocturnal habits and their
protective resemblance to the herbage and the bark and leaves
of trees, Thomas Belt records the case of a little Nicaraguan
frog which is very abundant in damp woods, and ‘‘ hops
about in the daytime, dressed in a bright livery of red and
blue.” Its immunity from destruction is due to the fact
that ducks and fowl could not be induced to eat it, owing to
its unpleasant taste, the same reason inducing birds to reject
certain bright-colored caterpillars, which are distasteful to
them.

Cuass IV.—BATRACHIA.

Amphibious Vertebrates, with gills in certain adult aquatic forms, all
breathing air by lungs ; the skin of existing species naked; with true
limbs like those of higher Vertebrates ; skull with two occipital condyles ;
heart with two auricles and one ventricle. Mostly oviparous ; a distinct
metamorphosis.

Order 1. Trachystomata.—Body long, eel-like, with persistent gills ;
no pelvic bones or hind limbs; no maxillary bone. (Siren.)
488 ZOOLOGY.

Order 2. Proteida.—Body flattened, with persistent gills, and gill-
openings; a maxillary bone. (Proteus, Necturus.)

Order 8. Urodela.—No persistent gills, body with a tail ; no gill-open-
ings except in Menopoma and Amphiuma. (Salamandra.)

Order 4. Gymnophiona.—Body snake-like, no feet; no tail ; young with
gill-openings, but no gills. (Cccilia.)

Order 5. Stegocephala.—Extinct forms; the temples with a bony roof;
often large; either snake-like, without limbs, or with pad-
dle-like limbs, or with four legs; teeth with or without
labyrinthine structure. (Archegosaurus, Labyrinthodon.)

Order 6. Anura.—Body short, tailless, with four limbs ; toes very long ;
leapers ; larve tailed. (Bufo, Rana.)

Laboratory Work,—The student should carefully follow, with a speci-
men in hand, the description of the structure of the frog, aided by the
figure; then should make a skeleton of the same species. These
studies should then be followed by a close comparison with the struc-
ture of a mud-puppy and of a salamander—the osteology and anat-
omy of the softer parts receiving equal attention. The breeding hab-
its of the Batrachians may be studied by confining them in jars or
aquaria. The embryology can best be studied by hardened stained
sections of the eggs.

Cuiass V.—Reprinia (Lizards, Snakes, Turtles, and
Crocodiles).

General Characters of Reptiles.—In the members of the
present class we have a still farther elaboration of a type of
structure which first appears in the Batrachians, with the
addition of features, which on the other hand are wrought
out ina more detailed manner in the birds, so much so that
while the fishes and Batrachians form one series (Icthyop-
sida), a study of different fossil reptiles, especially the bird-
like reptiles (Dinosaurs and Pterosaurs), which clearly con-
nect the birds with the reptiles, shows that the two latter
groups should be united into a series called Sawropsida.
Thus no one class of Vertebrates stands alone by itself ; every
year fresh researches by paleontologists, and the re-examina-
tions of living Vertebrates, especially as to their embryonic
history, proves that no single class, not even a type so well
REPTILES. 489

circumscribed as the modern birds, is without links forming
genetic bonds allying them all together. In fact, the different
classes of Vertebrates, as well as of other branches of the
animal kingdom, form an ascending series, from the more
generalized, though not always simple forms (numerous
groups comprising synthetic types), to those which are more
specialized, 7.e., in which separate organs or groups of or-
gans are elaborated and worked out in great detail. This is
the tendency all through nature, and were Cuvier himself
now living, and were he to examine the facts revealed since
his death, he would, as many others in advanced life have
done, cast aside the limited, analytical notions of the past,
based as they were on fragmentary evidence, and adopt
the more philosophical principles of classification, based on
sciences that were in embryo thirty or forty years since.
These reflections have great force in the study of a class like
the reptiles where there are a larger number (five) of extinct,
than of living (four) orders, and where the fossil types were
of a more general, almost embryonic type, and consequently
gigantic and ill-shapen, showing a tendency to extremes or
prematurity in development rather than to an equality in and
maturity of the whole organization compared with their de-
scendants. A high degree of specialization of type tends
nearly always in living beings, plants as well as animals, to a
condensation and higher grade of form. These animals also
have given a name to the Age of Reptiles, the middle or
Mesozoic age of the world, when they were the dominant type
of life.

The essential characters of reptiles are the following: As
regards the skeleton, the bodies of the vertebre vary in being
either biconcave, concave in front, concave behind, or flat
at each end ; the cup-and-ball vertebre are most common,
forming a strong and flexible joint well fitted for general
motion. The ribs are well developed, the sternum is rhom-
boidal; there are usually, if not always, more than three
toes. The body is covered with scales ; the blood is cold, the
heart has in the crocodiles, the highest order, four chambers ;
two or more aortic branches persist, and certain membranes,
called an amnion and allantois, envelop the embryo.
490 ZOOLOGY.

The vertebral column is now more distinctly marked off
than in the Batrachians ; a cervical and lumbar region being
indicated in most reptiles except the snakes and turtles. Well-
marked ribs exist in nearly all the vertebre of the trunk,
except in the turtles, where the so-called ribs are possibly,
vel B

 

Fig. 438.—Skull of a Tur-
tle seen from behind, 1,
basi-occipital ; 2, exoccipi-
tal; 3, supraoccipital; 5, basi-
sphenoid ; 15, prootic (pe-
trosal) ; 17, quadrate.—After
Gegenbaur.

according to Gegenbaur, modified
transverse processes.

The skull of reptiles is much
more like that of birds than of
Amphibians. There is a single
occipital condyle, and the lower
jaw is articulated by the quad-
rate-bone to the base of the skull.
The primitive skull, or that part
immediately enclosing the brain,
has an incomplete roof, but still
is more bony than in Batrachi-
ans; while owing to the great
size of the bones developed orig- vo
inally in and from the palato- Fig. 439.—Bones of the foot of a
quadrate cartilage, but a small] Reptile (lizard) A, and an embryo

bird, B. f,femur ; ¢, tibia ; p, fibula;
part of the true skull is to be %, upper, d, lower pieces of the tar-
é sus ; 7, metatarsus ; J- V, metatarsa-
seen. The parts forming the lia of the toes.
hyoid suspensorium in fishes (hyomandibular and symplectic
bones) are, as in the Batrachians, entirely separate from the
skull.
While the limbs are, as a rule, absent in the snakes, the

fore legs always wanting, in a few forms, as the pythons, |

 

 
STRUCTURE OF REPTILES. 491

boas, and Tortrices, the pelvis exists in a rudimentary state,
and attached to it is a pair of rudimentary hind legs ending
in claws ; in all other existing reptiles the limbs are directly
comparable with those of birds and mammals, the bones of
the legs being best developed in the Chelonians (turtles),
which have nine carpal bones and five fingers in each foot.
Certain extinct saurians had paddle-like limbs, others bird-
like limbs, and still others approached the crocodilian type,
in which the carpal bones and phalanges become reduced in
number. In the hind limbs an intermedium (in birds only
present in the embryo) is united with the ¢idiale bone to
form an astragalus or heel-bone.

The scales of reptiles are very characteristic, though scales
existed on the underside of the body of most Stegocephalous
Batrachia. The scales of lizards and snakes are developed
from the cutis. The large horny plates of Chelonians are
greatly developed and unite above with the “ribs” to form
the shell or carapace, while nine large plates below form
the plastron.

The teeth are simple, conical, and while in the lizards
and snakes they may exist on the palatine and pterygoid
bones, in the crocodiles, where they are implanted in sockets
of the jaw-bones, they are, as in the mammals, confined to
the maxillary bones. They are reproduced as fast as they
are shed. The Chelonians have no teeth, the jaws being, as
in birds, enclosed in a stout horny case, developed from the
epidermis. There is a middle and internal ear much as in
birds. The New Zealand lizard, Hatteria, is the only reptile
which has the beginning of a spiral turn indicated in its
cochlea, which in other reptiles is, as in birds, merely a
flask-shaped cavity. (Rolleston.) The eyes of reptiles ap-
proach those of birds, and in both there is an upper and a
lower movable eyelid besides a nictitating membrane.

True nostrils exist in reptiles for the first time among
Vertebrates.

The tongue is either not extended out of the mouth, and
is broad, as in turtles and crocodiles and some lizards, or as
in most lizards and all snakes it is long, slender, forked, and
can be darted rapidly out of the mouth.
492 ZOOLOGY.

True lips now, as in birds, border the jaw-bones, while
salivary glands for the first time in the Vertebrates appear
in the Chelonians and lizards ; besides these there are smaller
glands in the lips of lizards and snakes, the poison-glands
of the rattlesnake, viper, etc., being modifications of these
labial glands.

While the cwsophagus is wide and the stomach usually
quite simple, in the crocodiles there is a muscular gizzard
approaching that of birds, and there is a special pyloric por-
tion in the crocodiles like that of grallatorial and swimming
birds. The liver and pancreas have, as in birds, two or more
excretory ducts, and a gall-bladder is always present. <A
large fat-body (Fig. 440, /) is present on each side of the
body.

The lungs, trachea, and larynx of reptiles are much
simpler than in birds; in the long slender-ringed trachea
there is an approach to that of birds, but the lungs are
modelled on the Amphibian type; the larynx, especially in
the Chelonians and crocodiles, is much more perfect than in
the Amphibians.

The organs of circulation show a decided advance in situ-
ation over the Batrachians. The heart (Fig. 440) recedes
farther back into the thorax. Of the two auricles the right
and larger one receives the systemic and the left the pul-
monary veins. In all but the crocodile the ventricle has
a partition, the right half containing venous and the left
arterial blood, while in the crocodiles there are two ven-
tricles, so that the heart is four-chambered. In the lizards
two aortic branches (a right and a left) survive. In the
crocodiles a vessel which gives off the right aortic arch and
the carotids arises from the left ventricle, while a left aortic
arch and the pulmonary arteries arise from the right ven-
tricle. In the reptiles as in birds there are two superior as
well as one inferior vena cava. In reptiles as in lower Ver-
tebrates there are no true lymphatic glands; an organ re-
sembling them is present in reptiles (Fig. 440, th), forming a
small swelling situated behind the angle of the lower jaw.

While the brain is still simple, though it fills the cavity of
the skull, the different lobes being subequal in size, the cere-
ANATOMY OF THE LIZARD. 493

 

Fig. 440.—Anatomy of a lizard, Sceleporus undulatus. t, trachea $ ¢, carotid artery;
th, thyroid gland ; h, ventricle of the heart—above are the two auricles; Ju, lung;
7, liver turned out; s, stomach ; i, intestine ; a, vent —above it the cloaca is laid
open to disclose the openings (0 0) of the kidneys (4); above are the two openings of
the oviducts; m, oviduct; 0, ovary ; v, vena cava; jf, fat-body.—Drawn by A. F.
Gray from dissections made by the author.
494 ZOOLOGY.

bellum is small, especially in the serpents. In the croco-
diles the brain most approaches that of birds, the cerebellum
being larger than usual in the middle, and in this respect
somewhat approaching the birds. Corpora striata (which
are thickenings of the outer walls of the cerebral hemispheres)
and the anterior commissure of the cerebral hemispheres are
present for the first time in the vertebrate series,

The kidneys (Fig. 440, &) are lobulated, varying in form
and position, and usually situated near the cloaca, the ureters
being short and opening into the cloaca. The reproductive
organs are generally like those of the Batrachians. The
ovaries lie on each side of the vertebral column, and vary in
size with the season, being largest during the time of repro-
duction. The oviducts (Fig. 440, 2) are voluminous coiled
canals, which in most reptiles open into the cloaca; in the
turtles, however, opening into the neck of the so-called
urinary bladder. After the egg passes into the oviduct it
is enveloped by the ‘‘ white” or albumen, which is secreted
in the anterior part of the oviduct, while the thick-walled
terminal part secretes the shell.

The external differences between the sexes is more marked
than in the Amphibians. According to Darwin, the sexes of
the Chelonians and snakes differ very slightly ; male rattle-
snakes are said to be more yellow; in the East Indian Dip-
sas cynodon the male is bright green, while the female is
bronze-colored. Male lizards are usually larger, while male
snakes are always smaller than those of the opposite sex.
Various appendages, such as crests, warts, horns, etc., when
present in both sexes, are most developed in the males,
while the colors and markings are brighter in the latter sex,

The moulting of the skin is effected by its being pushed off
by the upward growth of fine, temporary cuticular hairs.
On certain parts of the body, as on the underside of the
capsular skin and scales of the eyes, these hairs do not de-
velop. After the skin is loosened, it dries and is readily
shuffled off.

The eggs of turtles, like those of birds, are very large,
the yolk mass being greatly developed. The lizards, snakes,
and crocodiles lay their eggs in sand or light soil, while those
DEVELOPMENT OF REPTILES. 495

of the iguana are laid in the hollows of trees. Certain
snakes, as the vipers, are viviparous. In many snakes and
lizards the development of the embryo goes on in the egg
before it leaves the oviduct ; such species are said to be ovo-
viviparous, the young being born living. The Hutenia
sirtalis, or common striped snake, brings forth its young
alive, and is probably ovoviviparous rather than viviparous.
The early phases of the development of the reptiles, in-
cluding the origin of the amnion and allantois, is much as
in the chick. In the turtle, by the time that the heart has
become three-chambered, the vertebre have reached the
root of the tail, the eyes have become entirely enclosed in
complete orbits, and the allantois begins to grow. The
nostrils may now be recognized as two simple indentations
at the end of the head, and at first are not in communica-
tion with the mouth, but soon a shallow furrow leads to it.
The shield begins to develop by a budding out laterally of
the musculo-cutaneous layer along the sides of the body,
and by the growth of narrow ribs extending to the edge of
the shield. In the oviparous snakes (¢.9., Natrix torquata)
the embryo partially develops before the egg is laid, while
the young hatches in two months after the egg is deposited.
By this time the amnion is perfected, the head is distinct,
and shows the eyeball and ear-sac ; also the maxillary and
mandibular processes. The allantois is about as large as the
head. The long trunk of the serpent grows in a series of
decreasing spirals, and when five or six are formed, the rudi-
ments of the liver and the primordial kidneys are discern-
ible. At the latter third of embryonic life the right lung
appears as a mere appendage to the beginning of the left.
The reptiles are essentially tropical and subtropical ani-
mals ; they are scarce in north temperate countries, though
in North America snakes extend north farther than lizards ;
in Europe snakes cease at 60° north latitude, and at 6000
feet elevation in the Alps; lizards in Europe sometimes ex-
tend farther north than snakes, and ascend to an elevation
of 10,000 feet in the Alps. Reptiles are usually wanting in
oceanic islands which possess no indigenous mammals, though
lizards are sometimes found on islands where there are
496 ZOOLOGY.

neither mammals nor snakes. The reptiles in cool climates
hibernate, while those of the tropics have a summer-sleep in
the dry season, becoming active when the rainy season begins.

There are about three thousand species of living reptiles
known, of which three hundred and fifty-eight are North
American ; between three and four hundred fossil forms
have been described. The reptiles are divided into nine
orders, of which five are extinct.

Order 1. Ophidia. The snakes, of which there are over
one hundred and thirty species in America north of Mexico,
have a remarkably long cylindrical body, the tail very long
and slender ; they are footless, with no shoulder girdle, and
are covered with scales, which are all shed simultaneously.
These scales:are epidermal growths, and while usually they
overlap, in a few cases (Acrochordus, etc.) they are tubercu-
lar, and do not overlap. The eyes are not protected by true
lids, but the-latter are thin, covering the eye permanently,
thus accounting for the fixed, stony stare of snakes. The
number of vertebre (which are hollow in front and convex
behind), may in the boa amount to more than four hundred.
Each vertebra, except the first (the atlas) is provided with
ribs, and the processes with articular facets, which interlock-
ing give great strength and flexibility to the spinal column.
The hyoid bone is very slightly developed, though the
tongue is long, forked, can be rapidly darted out, and with-
drawn into a sheath ; the quadrate bones connecting the
lower jaw with the skull are movable. The bones of the
brain-case are firmly united together, while those of the jaws
and palate are more or less freely movable to allow the snake
(the boa especially) to distend its throat immensely and
swallow comparatively large animals, though ordinary snakes
will swallow large toads and frogs and other snakes but
slightly smaller than themselves. In order to retain the
prey and prevent its slipping out of the mouth, the recurved
short conical teeth are developed on the maxillary, palatine,
pterygoid, and mandibular bones, and occasionally on the
premaxillaries ; they are not set in sockets, and consequently
are not used to crush or tear food.

The peculiar gliding motion of snakes is effected by the
ANATOMY OF THE SNAKE. 497

movements of the large ventral scales, which are successively
advanced, the hinder edges of the scales resting on the
ground and forming fulcra; resting on these the body is
then drawn or pushed rapidly forwards.

The brain of serpents is small, much as in the lizards, the
cerebellum being especially small and flat, while the cerebral
hemispheres together form a mass broader than long.

The more characteristic features of the internal anatomy
of snakes is a want of symmetry in the paired organs, as seen
in the absence of a second functional lung, and second pul-
monary artery, one of the lungs being minute, rudimentary,
while the other is very long and large; the trachea is also
very long, while the right ovary is larger than the left and
placed in front of it. The other visceraare so arranged as to
pack well in the long narrow body-cavity.

The student should dissect a snake with the aid of the ac-
companying figure of the common striped snake (Hutenia
sirtalis Baird).

A few snakes are viviparous, as the vipers ; others are ovo-
viviparous. In the oviparous Natrix torquata of Kurope,
the embryo partly develops before the egg is laid, while the
young hatches in two months after the egg is deposited. At this
time the amnion is fully formed, the head is distinct, as well
as the eyeball, and ear sac. The long body grows in a series
of decreasing spirals, and when five or six are formed, the
rudiments of the liver and of the primordial kidneys may be
detected, while at the latter third of embryonic life, the
right lung appears as a mere appendage to the beginning of
the left. The embryo, at the time of hatching, is provided
with a temporary horny tooth on the snout to cut through
the egg shell.

Most snakes conform in coloration to the nature of the
soil or places they frequent ; some being, as in the rattlesnake
of the western plains, of the color of the soil in which they
burrow ; the little green snake is of the color of the grass
through which it glides; other are dull gray or dusky, har-
monizing with the color of the trunks of trees on which
they rest. The poisonous Hlaps of the Central American
forest is gaily and conspicuously colored ; indeed it can af-
ford to be brightly colored, as no birds dare to attack it.
498

ZOOLOGY.

 

Hy, hyoidean apparatus ; TY,
trachea ; th, thyroid ; Oe, cesophagus ; 7’, thymus ; Il, heart ; Br, bronchus ; L,
lung ; A, air-sac; Li, liver ; Ov, ovary 5 Sp, spleen; Pa. pancreas ; Od, oviduct;
Cl, cloaca ; R, rectum + Od’, right oviduct cut off; u, ureter; A, kidney ; V, vena
porte ; Z, intestine.—Drawn by C. 8. Minot.

Fig. 441.—Anatomy of the common striped Snake.
POISONOUS SNAKES. 499

The Salenoglyph poisonous snakes may always be recog-
nized by their broad, flattened heads, and usually short thick
bodies. The poison gland of the rattlesnake (Fig. 442, a) is
a modified salivary gland. The two fangs are modifications
of maxillary teeth, each of which has been, so to speak,
pressed flat, with the edges bent towards each other, and
soldered together, so as to form a hollow cylinder open at
both ends, the poison duct leading into the basal opening.
When the fangs strike into the flesh, the muscles closing
the jaws press upon the poison gland, forcing the poison
into the wound. The poison-fangs are largest in the most
deadly species, as
the viper ( Vipera),
the puff adder
(Clotho), the rat-
tlesnake, and fer-
de-lance (Trigono-
cephalus), but are
small in the asps
or hooded snakes
(Naja). The bite
of the rattlesnake
is intensely painful;
it is best cured by Fie. 442.—Head of the rattlesnake : aa, poison gland

5 and its excretory duct: e, anterior temporal muscle; /,
sucking, freely lan- posterior temporal muscle; g, digastricus ; h, external

C pterygoid muscle ; i, middle temporal muscle ; g, arti-
cling, and by cauter- culo-maxillary ligament which joins the aponeurotic

oat capsule of the poison gland; 7, the cervical angular
izing the wound, muscle ; ¢, vertebro-mandibular muscle 3 uw, costo- man-

and drinking large dibular muscle.—After Duvernoy.

quantities (at least a pint) of whiskey or brandy, sufficient
' ordinarily to produce insensibility. Deaths from the bite of
rattlesnakes are not common, while in India it is estimated
that several thousand people annually die from the bite of
the cobra—10,000 dying each year from the bite of snakes
and the attacks of wild beasts. The “‘rattle” of the rattle-
snake is a horny appendage formed of buttonlike compart-
ments ; the sound made by the rattle, which has been com-
pared by some to the stridulation of a Carolina locust, or of
the Cicada, is an alarm note, warning the intruder ; the rat-
tle is sprung before the snake strikes. Allied to this snake

 
500 ZOOLOGY.

is the copperhead (Ancistrodon contortriz Linn.) and the
black mocassin (Ancistrodon piscivorus Linn.). In the water
snakes the tails are laterally compressed, while the poison-
fangs are small. These snakes are not much over a metre in
length, and live far from land in the East Indian seas.

The poisonous snakes stand lowest in the series; they are
succeeded by the striped snake, milk adder, and by the boas,
which attain a length of five metres; while the anaconda
grows eight metres long.

In time snakes reach back to the Eocene Tertiary period,
when a great sea-snake (Zitanophis), represented by several
species, one six metres in length, haunted the coast of New
Jersey, while in the western lake-deposits of the same age,
forms allied to the existing boa-constrictor were not un-
common. The snakes, then, appear to be a modern type
compared with the lizards, turtles, and crocodiles.

Order 2. Pythonomorpha.—This group includes a num-
ber of colossal serpent-like forms, with paddle-like feet, which
are regarded by Cope as the types of a distinct order, char-
acterized by a complex suspensorium, by the absence of a
sternum and sacrum, by the rootless teeth, recurved parie-
tal bones, etc.

They were fifty and sixty feet in length, and Mosasaurus
maximus Cope, from New Jersey was still more colossal.
They combined characters of the snakes, lizards, and plesio-
saurs, and correspond in a degree to the descriptions of the
mythical sea-serpent.

The resemblance to the Ophidians is still farther strength-
ened by the late discovery by Professor F. H. Snow, that one
of the forms (Liodon) was covered above by small imbricated
scales, like those of the snakes, rather than large ones, like
those of reptiles. The more abundant type is the Mosa-
saurus of the Cretaceous seas, which was a huge sea-serpent
originally referred by Cuvier and Owen to the neighborhood
of the lace-lizards (Varanide) ; Cope describes it as a long
slender reptile, with a pair of powerful paddles in front, a
moderately long neck, and flat pointed head, with a long
forked tongue. The very long tail was flat and deep, like
that of a great eel, forming a powerful propeller. The
ORDER OF LIZARDS. 501

arches of the vertebral column interlocked more extensively
than in other reptiles except the snakes. hey swam rapidly
through the water by rapid undulations of their bodies aided
by the paddles. The skull was not so strong, though as
light as that of the serpents. ‘‘ While the jaws were longer, the
gape was not so extensive as in serpents of the higher groups,
for the os quadratum, the suspensor of the lower jaw, though
equally movable and fastened to widely spread supports, was
much shorter than in them. But there was a remarkable
arrangement to obviate any inconvenience arising from these
points. While the branches of the under jaw had no natural
connection, and possessed independent motion, as in all ser-
pents, they had the additional peculiarity, not known else-
where among Vertebrates (except with snakes), of a movable
articulation a little behind the middle of each. Its direction
being oblique, the flexure was outwards and a little down-
wards, greatly expanding the width of the space between
them, and allowing their tips to close a little. A loose flexi-
ble pouch-like throat could then receive the entire prey
swallowed between the branches of the jaw ; the necessity of
holding it long in the teeth, or of passing it between the
short quadrate bones could not exist. Of course the glottis
and tongue would be forwards.” The order became extinct
before the Tertiary Period.

Order 3. Lacertilia. —The existing lizards or Sauwrians are
the survivors or descendants of a multitude of forms, many
colossal in size, which characterized the Permian and Meso-
zoic periods; while the extinct forms of reptiles were in
many cases synthetic types, with affinities to fishes, Am-
phibians, and even birds. The group as now existing is well
circumscribed.

Most lizards have cylindrical bodies, usually covered with
small overlapping scales, with a long, slender tail, and general-
ly two pairs of feet, the toes long and slender, and ending in
claws. They run with great rapidity, and are active, agile
creatures, adorned with bright metallic colors, in some cases
green or brown, simulating the tints of the vegetation or
soil on which they live ; some are capable of changing their
color at will, as in the chameleon and Anolis; this is due to
502 ZOOLOGY.

the fact that the pigment cells or chromatophores are under
the influence of the voluntary nerves.

While the scales of the body are developed, as a rule, from
the epidermis, in the scink there are dermal scales (scutes),
and such dermal plates in the head may unite with the bones
of the skull. In most lizards, all except the Geckos, the
vertebre are procelous, t.e., with a ball-and-socket joint,
the vertebree being rounded in front, and concave behind.
In the Geckos the vertebral column is fish-like, the notochord
persisting except in the centre of each vertebra, which is bi-
concave. In many lizards (Lacerta, Iguana and the Geckos),
the middle of each caudal vertebra has a thin cartilaginous
partition, and it is at this point that the tails of these liz-
ards break off so easily when seized. In such cases the tail
is renewed, but is more stumpy. The tail of the specimen
of Sceloporus (Fig. 440) which we dissected is much shorter
than in the normal animal, and must have grown out after
having been lost.

The throat is often distensible by the hyoid apparatus ;
but the bones of the jaws are firm, the bones united in front.
Both jaws are provided with teeth, while some have them
developed on the palatine and pterygoid bones. The teeth
are usually simple, sharp, conical, as in most lizards, includ-
ing the Monitor, or they are flattened, blade-like, with ser-
rated edges, as in the Iguana, or as in Cyclodus they are
broad, adapted for crushing the food. Most lizards prey on
insects ; some live on plants. New teeth are usually devel-
oped at the bases of the old ones. They are attached to the
surface of its jaws; in certain extinct forms (Thecodonts)
they are lodged in sockets. (Huxley.) The eyelids are
well developed except in the Geckos, in which the lids are
modified somewhat, as in the snakes, to form a transparent
skin over the cornea of the eyes. The tongue is free and
long, sometimes forked ; in the iguana it ends in a horny
point.

While the limbs are usually present, one or the other pair
may in rare cases (in Psewdopus the fore feet are wanting ; in
Chirotes the hind feet are absent) be absent, or as in Am-
phisbena and its allies the feet are entirely wanting, though
HORNED TOADS. 503

the shoulder-girdle invariably remains, the pelvic-girdle in
such cases disappearing; the pelvis being complete, how-
ever, when the hind limbs are present. The feet are five-
toed. The internal anatomy of lizards has already been de-
scribed and illustrated on p. 493. In the snake-like lizards
(Anguis) the left lung is the smaller, and in Acontias
and Typhline it is almost wanting. A urinary bladder,
wanting in the snakes, is present in lizards.

The lizard lays eggs in the sand or soil; those of the iguana
are deposited in the hollows of trees. Certain lizards are
viviparous.

There are between seven hundred and eight hundred species
of existing lizards, most of which inhabit tropical or subtrop-
ical countries : ; eighty-two species of lizards inhabit America
north of Mexico. The earliest lizards date back to the Kim-
meridge or middle division of the Jurassic rocks.

Reviewing some of the more interesting lizards in the as-
cending order, we may, passing over the snake-like, limbless
Amphisbena, and the limbless glass snake (Opheosaurus),
first consider the chameleon of the Mediterranean shores, in
which the eyes are movable with a circular eyelid, and with
the five toes in two opposable groups adapted for grasping
twigs of trees. It is remarkable for its power of changing
its colors. The tongue of the chameleon (Fig. 448) is
capable of extending five or six inches, and is covered with
a sticky secretion for the capture of insects, as the crea-
ture itself is very sluggish. The chameleon of our country
is the Anolis of the Southern States, and is a long smooth-
bodied lizard, which can change its color from a bright pea-
green to a deep bronze-brown.

The horned toads (Phrynosoma) are characteristic of the
dry western plains ; the body is broad, flattened, and armed
with spines ; its coloration depends on that of the soil it in-
habits. It will stand long fasts. When Phrynosoma Dou-
glassit of the Northwestern Territories and States is about to
moult, small dry vesicles appear on the back and sides, run-
ning along the horizontal rows of pyramidal scales forming
the margin of the abdomen. In a day or two the vesicles
break and desquamation begins, which continues for eight or
504 ZOOLOGY.

ten days, the skin finally separating from the spines of the
head and the claws. (Hoffman.)

Our most common lizard in the Middle and Southern
States is Sceloporus undulatus Harlan (Fig. 440). It is
common, running up trees. The iguanas are very large liz-
ards inhabiting the West Indies and Central America ; the
head is protected by numerous small shields, with a dorsal row
of bristling spines. They are about three feet long, live in
the lower branches of trees, and are said to be excellent eat-
ing. <A still larger form, closely resembling the iguanas, is
the sea-lizard (Amblyrhynchus) of the Galapagos Islands,
where it lives in the rocks by the shore, feeding on seaweeds.
These large creatures are among the largest of existing liz-

      
 
  
   

  
  
  
  
 
 

 

es

Y aA

es as

BON OES
HK

<
ot
LZ

  

Fig. 443.—Tongue of Chameleon. Natural size.—After Rymer Jones.

ards, being eighty-five centimetres (over 3 feet) in length.
Closely allied to the iguanas were a number of extinct sau-
rians of colossal size which flourished in the Jura-Triag and
Chalk Periods.

The largest lizard in Mexico is the Heloderma horridum
of Wiegmann. It grows to the length of one metre (over
three feet). It is allied to the iguanas, but the body is
heavily tuberculated. Heloderma suspectwm Cope, inhab-
its southern Utah, Arizona, and New Mexico. The largest
of the existing lizards are the monitors, or species of Vara-
nus, of tropical rivers, which nearly rival the crocodiles in
size, being five or six feet in length.

Order 4. Chelonia.—Although the tortoises and turtles
are a well circumscribed group, with no aberrant or connect-
ANATOMY OF THE TURTLE. 505

ing forms, yet they have some affinities with the Batrachia.
They are distinguished from the other reptiles by the shell,
the upper part forming the carapace, and the lower the
plastron ; these two parts unite to form a case or box within

 

Fig. 444.—Skeleton of European Tortoise, with the plastron or under shell removed.
—After Owen.

which the turtle can retract its head and limbs and tail.
Owing to the presence of the carapace, the dorsal vertebra
are immovable, and the ribs do not move upon the vertebre.

The bones of the ventral shield or plastron are usually
506 ZOOLOGY.

nine in number. The jaws are toothless, being, as in birds,
encased in horny beaks; there are rarely fleshy lips; the
tongue is spoon-shaped and immovable. The heart consists
of two auricles and a ventricle. The brain has larger cere-
bral lobes than in the lizards. The eyes have a third lid, or
nictitating membrane. The student can best obtain an
idea of the organization of the turtles by studying the skel-
eton and dissecting a turtle with the aid of the accompany-
ing description and figure of the common turtle.*

The common swamp-turtle (Chryemys picta) is a good type
of the Chelonia. The animal is enclosed in a hard shell,
made up of an arched dorsal portion, and a flat ventral por-

 

 

Fig. 445.—Shell of Chrysemys picta.—Drawn by C. 8. Minot.

tion, the two connected laterally, but widely separated an-
teriorly to give exit to the head and fore limbs, and pos-
teriorly for the tail and hind limbs. These parts can all be
withdrawn within the protecting shell, by being doubled or
folded back upon themselves. The soft parts of the skin are
covered with scales, formed by overlapping folds. The limbs
are stout; upon the anterior feet there are five, upon the
posterior four claws. On the under surface of the short
tapering tail near its base is the wide opening of the cloaca.
The ventral plastron consists of twelve symmetrical pieces,
six on each side, Fig. 445. The first and last pair are tri-
angular, the others are four-sided ; the fourth pair is the

* This ‘description has been prepared and the illustrations drawn by
Dr. C. 8. Minot.
ANATOMY OF THE TURTLE. 507

largest. The dorsal carapace is composed of thirty-eight
plates, twenty-five marginal, of which the most anterior lies
in the middle line; there are five median and two lateral
rows of four plates each.

To dissect a turtle, saw through the lateral pieces of the

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igs
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Fig. 446.—Anatomy of the Turtle, Chrysemys picta.—Drawn by C. S. Minot.

shell which unite the plastron and carapace, then remove
the ventral piece, carefully freeing it from the underlying
organs.

Fig. 446 represents a female, with the intestines and di-
gestive glands partially freed and turned aside, while the
shoulder-blade, oviduct, and ovary of the left side and the

  

    
    
  
 
508 ZOOLOGY.

right lung have been entirely removed. The middle line of
the neck is occupied by the trachea, which overlies the much
wider csophagus, which again rests upon two very large
cylindrical muscles, the powerful retractors of the head.
The muscles () extend backwards along the vertebral
column, behind the heart and through the abdomen. The
trachea branches just in front of the heart, to send a
bronchus to each lung. The left bronchus can be seen in
the figure, passing between the pulmonary artery () in
front, and the pulmonary vein behind ; the three tubes run
closely parallel forming the so-called root of the lung.
Each lung (Zu) is a large elastic sack with numerous air-
cells. The size of the lung depends upon its degree of ex-
pansion; when entirely collapsed it is quite small, but it may
easily be blown up through the trachea. The heart (#?) is
much broader than in the frog or bird. We shall recur to
its structure presently.

Below the trachea lies the much larger esophagus, a cyl-
indrical tube with muscular walls. The cesophagus termi-
nates in the stomach (’), which, together with the remaining
digestive organs and the spleen, is drawn aside in the figure.
The long and coiled intestine can be followed to the point
where it passes under the oviducts (ovd) and the bladder
(Ll) to terminate in the cloaca, the external opening of
which is represented at C7. The main mass of the elongated,
gray, and mottled liver lies upon the intestine, being turned
so as to show its raphe (m), by which it is suspended from the
peritoneum, the portal vein (v), and the retort-lke gall-
bladder (G) ; the gall duct passes through the body of the
pancreas (Pan), an elongated whitish mass resting upon the
first coil of the intestine, the so-called duodenum. Alongside
the pancreas is the much smaller dark oval spleen (Sp).

The specimen figured is a female killed during the period
of reproduction. The genital organs are therefore enor-
mously developed. The long and prominent oviducts con-
tained eggs already provided with a shell. The right
oviduct is seen drawn out and suspended by a mesentery, a
thin and transparent membrane with numerous blood yes-
sels. The lower end of the oviduct is seen through the
ANATOMY OF THE TURTLE. 509

mesentery, and contains three oval eggs, one of which is
lettered Hg. The oviduct can be followed to its anterior
end which is much pigmented and has a terminal opening.
The cut-end of the left oviduct (ovd) shows the folds of the
lining mucous membrane.

The ovary (0) is likewise suspended by a thin membrane,
the mesovarium, and is equally developed on both sides in a
complete specimen. It is easily recognized by the numerous
bulging yellow spheres, of all sizes, which are the egg-yolks
in various stages of development.

The heart of the turtle (Fig. 447) will repay careful dis-
section. A small round body lies just in front of it; this is
usually considered the equivalent of the thyroid gland,
through its real nature is still un-
certain. The heart itself (Fig. 447)
consists of two auricles and one
ventricle (ven), with an imper-
fect internal septum. It receives
the veins upon its dorsal surface,
and gives off the arterlal trunks
from its ventral side. The two
auricles are equal in size ; together
they a little more than equal the
ventricle. The arterial vessels arise
together a little to the right, and
are most conveniently described as
three in number: Ist. The right
aorta (R Ao) arising on the left ; to)
2d. The left aorta on the right | Fig. 447—Ventral surface of

; the heart of the Turtle, Chryse-
(L Ao) ; the two cross near their mys picta. Dissected and drawn
origin and curve upwards and back- >” © & Minot
wards, to reunite posteriorly just in front of the retractor
muscles, their union forming the single median descending
aorta ; 3d. The pulmonary aorta (pa), which soon divides
into a branch for each lung. The left aorta gives off a
branch (d) which persists as a mere cord, the remnant of the
ductus arteriosus, which originally united the aorta with the
pulmonary artery. The right aorta gives off an innominate
branch, that soon divides, Sant from each division springs

   
510 ZOOLOGY.

the carotis cor, and subclavian artery of the same side. The
veins are two in number, as they enter the heart: Ist. The
pulmonary veins (pv) unite to form a very short trunk
emptying into the left auricle; while (2d) the two vene
cave superiores unite with the cava inferior (V) to empty
through the sinws venosus into the right auricle.

The kidneys lie at the posterior end of the body against
the vertebral column. In the figure they are concealed by
the bladder and oviducts. (Minot.)

There are about forty species of Chelonians in America
north of Mexico. The lower forms of turtles are the marine
species. Such is the great sea-turtle (Sphargis coriacea
Gray) of the Atlantic and Mediterranean, which is the
largest of all existing turtles, and is sometimes eight feet
long, weighing from eight hundred to twelve hundred pounds.
Next to this species is the loggerhead turtle (Thalassochelys
caouana Fitzinger), which is sometimes seen asleep in mid-
ocean. Still another is the hawk-bill or tortoise-shell turtle
(Eretmochelys imbricata Fitz.), the plates of whose shell is
an article of commerce. The green-turtle of the West
Indies weighs from two hundred to three hundred pounds,
and is used for making delicious soups and steaks ; being
caught at night when laying its eggs on sandy shores. All
the foregoing species have large, flat, broad flippers or fin-like
limbs, while in the pond and river turtles the feet are webbed,
and the toes distinct. A very ferocious species is the common
soft-shelled turtle (Aspidonectes spinifer Lesueur), whose
shell is covered with a thick leathery skin. It is carnivorous,
voracious, living in shallow muddy water, throwing itself
forward upon small animals forming its prey. The snap-
ping-turtle (Chelydra serpentina Schweigger) sometimes
becomes five feet long ; its ferocity is well known ; the flesh
makes an excellent soup.

The terrapins belong to the genus Pseuwdemys ; the pretty
painted turtle (Chrysemys picta Agassiz) is common in the
Eastern States, while the Nanemys guttatus (Agassiz), or
spotted tortoise, is black, spotted with orange. In the land
tortoises the feet are short and stumpy. The Testudo Indica
of India is three feet in length. The great land tortoises of
THE ICHTHYOSAURS. 511

the Galapagos Islands, the Mascarine Islands (Mauritius and
Rodriguez), and also of the Aldabra Islands, lying northwest
of Madagascar, are in some cases colossal in size, the shells
being nearly two metres (six feet) in length. The fierce Mas-
carine species were contemporaries of the dodo and solitaire,
and are now extinct. The bones of extinct similar species
have been found in Malta and in one of the West Indian
islands. The land tortoises are long-lived and often reach a
great age. Certain tortoises of the Tertiary Period, as the
Colossochelys of the Himalayas had a shell twelve feet long
and six feet high. The turtles extend back in geological
time to the Jurassic, a species of Compsemys being char-
acteristic of the Upper Jurassic beds of the Rocky Moun-
tains. (Marsh.)

The eggs of turtles, as those of birds, are of large size ;
they are buried in June in the sand and left to be hatched
by the warmth of the sun. It is probable that turtles do not
lay eggs until eleven to thirteen years of age. The develop-
ment of turtles is much as in the chick. By the time the
heart becomes three-chambered, the vertebrae develop as far
as the root of the tail, and the eyes are completely enclosed
in their orbits. The shield begins to develop as lateral folds
along the sides of the body, the narrow ribs extending to the
edge of the shield. In the lower forms of turtles (the
Ohelonioide), the paddle-like feet are formed by the bones of
the toe becoming very long, while the web is hardened by
the development of densely packed scales, so that the foot is
nearly as rigid as the blade of an oar.

Order 5. Rhynchocephalia.—The only living representa-
tive of this order is the Sphenodon or Hatteria of New Zea-
land; a lizard-like form of simpler structure, however, than
the lizards in general. This rare creature somewhat re-
sembles an iguana in appearance, having a dorsal row of
spines. It is nearly a metre (32 inches) in length. In this
group the vertebre are biconcave ; the quadrate bone is im-
movable, and there are other important characters based on
a study of the living and fossil forms, the latter represented
by the Triassic Rhynchosaurus and Hyperodapedon.

Order 6. Ichthyopterygia.—This order is entirely extinct.
512 ZOOLOGY.

The Ichthyosaurs were colossal reptiles from two to thirteen
metres (six to forty feet) in length, swimming 1n the ocean by
four paddle-like limbs consisting of six rows of digital bones ;

   
 

Nie aN

 

Fig. 448.—Skull of Zchthyosaurus ; lateral view. Pmx, premaxillary bone ; Mx,
maxillary; WV, nasal; Fr, frontal; Prf, prefrontal; Pof, postfrontal ; Pu, parietal ;
ZL, lachrymal; M, malar; Qj, quadratojugal ; Q, quadrate ; Pob, postorbital ; Sq,
squamosal; PD, dentary; Ang, angular; Art, articular; 8. Ar, subarticular ; Pler,
pterygoid.—After Cope.
the head was very large, the neck very short, and the orbits
were enormous; the vertebra were remarkably short and bi-
concave. They were carniv-
orous, and powerful swim-
mers, and common in the Ju-
rassic seas of Europe; one
form existed in the Jurassic
times in Wyoming.

Order %. Theromorpha.—
This order is divided into the
Pelycosauria and Anomo-
dontia. The beaked Saurians
were somewhat lizard-like, but
Fig. 449.—Posterior view of the skull of were synthetic types, combin-

Ichthyosaurus ; lettering as in Fig. 443, .
with following additions; Bo, Tasioed: ing the characters of the Ich-

pital; Ho, Exoccipital ; Sup. 0, supra-
occipital ; Opo, opisthotic ; Stap. supra- thyosaurs, the turtles, the
stapedial or hyomandibular.—A fter Cope. fee : .

; Sphenodon, with those of liz-
ards, Dinosaurians, and crocodiles. The skull was short,
and in Dicynodon the jaws in front had the nipping, horny
beak of a turtle, while from behind in the upper jaw pro-
truded two long, curved, canine teeth. Dicynodon tigriceps

Owen, had a skull about half a metre’ (20 inches) long,

3
ea
3 BS
VU

Pof.

 

 
THE PLESIOSA URS. 513

Another form was still more like the turtles, the jaws being
toothless and enclosed in a nipping, horny beak. In Lys-
trosaurus (Fig. 450) the head was blunt, the jaws armed in
front with stout teeth, and behind with canine teeth; and
these animals, anticipating in their dentition the lions and
tigers, were called by Owen Theriodonts (beast-toothed).
These forms lived during the Permian and Triassic times.
Order 8. Sauropterygia.—The Plesiosaurus is the type

 

 

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4
|
Le
te

Fig. 450.—Skull of Lystrosaurus frontosus from Cape Colony. Profile. Lettering
as in Fig. 443 and 444, with the following additions: Ztvom, ethmovomerine ; Sph,
sphenoid ; pro, Prootic; Pter, Pterygoid ; Col, Columella: Hetp, Ectopterygoid ;
Subart, subarticular bone.—From Cope.

of this extinct order. The Plesiosaurs were somewhat like
the Ichthyosaurs, swimming by paddle-like feet, but the neck
was very long, and the head rather small. The largest true
Plesiosaur was about nine metres in length. They abounded
during the Jurassic and Cretaceous period. During the lat-
ter period off the coast of New Jersey and in the seas of
Kansas flourished huge Plesiosaurian reptiles, such as Hlas-
mosaurus, Which had an enormous compressed tail. The
514 ZOOLOGY.

vertebre of FH. platyurus Cope, of the New Jersey marl-
beds, had vertebra nearly as large as those of an elephant,
while the creature was whale-like in bulk, the neck long and
flexible, the paddles short. The skull was light, with a
long, narrow, very flat muzzle It must have been the ter-
ror of those times; it was about fifteen metres (45 feet)
in length. (Cope.)

Order 9. Crocodilia.—The crocodile, caiman, gavial, and
alligator are the types of this well-known group. They pre-
sent a decided step in advance of other reptiles, the heart
approaching that of birds, in having the ventricle completely
divided by a septum into two chambers ; the venous and arte-
rial blood mimgle outside of the heart, not in it, as in the
foregoing living orders. The brain is also more like that of
birds, the cerebellum being broader than in the other rep-
tiles. The nostrils are
capable of closing, so
that crocodiles and
alligators draw their
prey under the water
and hold them there
until they are drown-
ed; but they are

Fig. 451.—Head of the Florida Crocodile—after Obliged to drag them
ey ashore in order to eat
them. The skin is covered with bony, epidermal scales. The
conical teeth are lodged in sockets in the jaws. The vertebra
are concave in front and convex behind, or the reverse ; the
quadrate bone is immovable. The feet are partly webbed.
The crocodiles and gavials appeared during the Jurassic pe-
riod, but the early forms were marine and like gavials, the
head being long and narrow in front, with biconcave verte-
bre. They lay from twenty to thirty cylindrical eggs in the
sand on river banks. The crocodiles are distributed through-
out the tropics, even Australia; the gavials are mostly con-
fined to India and Malaysia, and also Australia. The group
is represented in the Southern States by the alligator (A.
Mississippiensis Daudin). It is nearly two metres (10-12
feet) long; while the Florida crocodile (C. acutws Cuvier,

 
DINOSAURIAN REPTILES. 515

Fig. 451) in which the jaws are much narrower, is over two
and a half metres (14 feet) long. It inhabits the rivers of
Florida where it is very rare, and also the West Indies and
South America. The cayman of Guiana belongs to a dis-
tinct genus, Caiman, and is characteristic of the rivers of
tropical South America.

Order 10. Dinosauria.—We now come to reptiles which
have more decided affinities as regards their skeleton (the
only parts preserved to us) to the birds, especially the os-
triches, than any reptiles yet mentioned ; while the Dino-
saurs were genuine reptiles, in the pelvis and hind limbs,
including the feet, they approached the birds. This is seen
especially in the ischium, which is long, slender, and inclined
backwards as in birds. In the hind limbs the resemblance
to birds is seen ; among other points, in the ascending pro-
cess of the astragalus, in the position of the farther (distal)
end of the fibula, and in their having only three functional
toes. The fore limbs were shorter and smaller than the
hind extremities, sometimes remarkably so. Moreover, the
limb-bones, vertebre, and their processes were sometimes
hollow; the sacrum consisted of four or five consolidated
vertebre, in this respect anticipating the birds and mam-
mals. They walked with a free step, like quadrupeds,
instead of crawling like reptiles; some walked on the hind
legs alone, making a three-toed footprint, occasionally
putting down the forefoot, like the kangaroo. The lar-
gest Dinosaurs were the Jgwanodon, which was from ten
to sixteen metres (30-50 feet) in length, and the Cama-
rasaurus (Atlantosaurus) which was about twenty-seven
metres (80 feet) in length. The Cetiosawrus had a length of
from twenty to twenty-three metres (60-70 feet). The Ha-
drosaurus stood on its ponderous hind legs, with a stature of
over eight metres (25 feet). These were bulky, inoffensive,
herbivorous monsters, able to rise up on their hind feet and
browse on the tops of trees; their undue increase was
prevented by carnivorous forms like Lelaps, which was an
active, possibly warm-blooded Dinosaur, with light, hollow
bones, large claws, and serrate, conical teeth. It stood six
metres (18 feet) high, and could leap a distance of ten

metres through the air. (Cope.)
516 ZOOLOGY.

Still nearer the birds was the Compsognathus; it was
only two thirds of a meter (2 feet) long, with a light head,
toothed jaws, and a very long, slender neck ; the hind limbs
were very large and disposed as in birds, the femur being
shorter than the tibia; moreover, the fore legs were very
small. ‘It is impossible,” says Huxley, ‘‘to look at the
conformation of this strange reptile and to doubt that it
hopped or walked, in an erect or semi-erect position, after
the manner of a bird, to which its long neck, slight head,
and small anterior imbs must have given it an extraordi-
nary resemblance.” The so-called bird tracks of the Triassic
rocks of the valley of the Connecticut were all reptilian
footprints, and without doubt made by Dinosaurs with the
above-mentioned affinities to the birds. These bird-like,
colossal lizards appeared in the Jura-Trias Period, and be-
came extinct in late Cretaceous times.

Order 11. Ornithosauria.—The name of this order, rep-
resented by the Pterodactyles, would lead one to infer that the
group was still more bird-like than the Dinosaurs, and See-
ley has shown that they have as many and important points
of similarity to that class as the preceding group. They are
a sort of reptilian bats, forming links between reptiles and
flying birds, as the Dinosaurs connect with the ostriches,
and it is in the hand and foot, which in birds are the most
characteristically ornithic, that they resemble the ornithic
type. They also approach birds in their long heads and
necks, the jaws with or without teeth, the short tail, in the
skull which is more rounded and bird-like than in other
reptiles, with large orbits, as also in the form of the brain ;
while the jaws were probably, in part at least, encased in
horny beaks. The shoulder girdle was bird-like, and the
sternum was keeled, but the pelvis and limbs were like
those of lizards, while the fore-feet were much larger than
the hinder ones, and the ulnar finger was enormously
long and probably supported a broad membrane, connecting
the fore and hind limbs, as in bats; moreover, the limb
bones were hollow, and air-cells were present, so that
these winged lizards could fly like birds or bats. The jaws
of the Pterosaurs were completely toothed; those of the
CLASSIFICATION OF REPTILES. 517

Rhamphorhynchus had teeth in the back of the jaw, the
ends of the jaws being toothless and probably encased in
horny beaks, while in Pteranodon the jaws were toothless.
They were of different size, some expanding only as much
as a sparrow, others with a spread of about nine metres (27
feet). They were contemporaries of the Dinosaurs, several
forms, discovered by Marsh, occurring in the Cretaceous
beds of Kansas.

Cuass V. REPTILIA.

Air-breathing Vertebrates, with limbs usually ending in clas ; limbs
sometimes absent, rarely paddle-shaped ; body scaled ; ribs well developed ;
heart in the highest forms four-chambered ; cold blooded ; an incomplete
double circulation ; ovipurous ; eggs large; embryo with an amnion and
allantois ; no metamorphosis.

Order 1. Ophidia.—Body long, cylindrical, usually limbless; no shoul-
der girdle. (Eutznia.)

Order 2. Pythonomorpha.—Extinct, snake-like, limbs paddle-shaped.
(Mosasaurus. )

Order 3. Lacertilia.—Body with a long tail; usually four limbs; mouth
not dilatable, the bones of the jaw being firm. (Sceleporus.)

Order 4. Chelonia.—Body enclosed in a thick shell, within which the
head and limbs can be withdrawn. (Testudo.)

Order 5. Rhynchocephalia.—Lizard-like ; vertebre bi-concave, species
mostly extinct. (Sphenodon.) \ :

Order 6. Ichthyopterygia.—Head large, orbits large; limbs paddle-
shaped; extinct forms. (Ichthyosaurus.)

Order 7. Theromorpha.—Mammal-like saurians with solid pelvis and
shoulder-girdle, and with canines, or toothless and beaked.
(Dicynodon.)

Order 8. Sauropterygia.—Extinct colossal saurians, with long necks,
head of moderate size. (Elasmosaurus.)

Order 9. Crocodilia.—Thick-scaled; heart four-chambered. (Croco-
dilus.)

Order 10. Dinosauria.—Colossal extinct saurians, capable of rising
and resting on the hind legs, and making three-toed tracks,
(Hadrosaurus.)

Order 11. Pterosauria.—Extinct flying saurians, with the fore limbs
large and a very long ulnar finger; toothed or toothless.
(Pterodactylus.)
518 ZOOLOGY.

Cuass VI. Aves (Birds),

General Characters of Birds.—We have met in the rep-
tiles, especially in the fossil forms, many characters indicat-
ing that birds are by no means so specialized or so well
circumscribed a group as was formerly supposed. Such a
relationship between the two classes has recently been still
further exhibited by Meyer’s discovery of Archeopteryx litho-
graphica of the Solenhofen slates of the Jurassic beds of
Germany, and by Marsh’s discovery of birds with teeth and
biconcave vertebre in the Cretaceous rocks of North Ameri-
ca. On account, therefore, of the close relations between
birds and reptiles, Huxley has placed these two classes in a
series called Sauropsida, which may be opposed to the Jch-
thyopsida (Fishes and Batrachians) on the one hand, and
the Mammalia on the other, by the following characters :—

Sauropsida.—There are no mammary glands. There is
an amnion and an allantois; the species are oviparous or
ovoviviparous, with reproductive organs and digestive canal
opening into a common cloaca, and Wolffian bodies replaced
functionally by permanent kidneys. There is no corpus
callosum, nor complete diaphragm. Respiration is effected
by lungs, never by gills. The heart is two or three cham-
bered, and there are usually two or three aortic arches; in
birds but one ; there are red oval nucleated blood corpuscles.
The bodies of the vertebre are ossified, but without terminal
epiphyses. There is a single convex, occipital condyle, in
connection with an ossified basi-occipital. The ramus of
the mandible consists of several pieces, the articular one of
which is connected with the skull by a quadrate bone. The
ankle-joint is between the proximal and distal divisions of
the tarsus. The skin usually developes scales or feathers.

These important characters, derived from Huxley (as are
many of those given beyond for the class Aves), may remind
the student of the actual affinities between birds and rep-
tiles. The former are distinguished from other Sawropsida
by the following peculiarities :—

Aves.—The body is covered with feathers, a kind of der-
mal outgrowth found in no other animals. The fore limbs
STRUCTURE OF BIRDS. 519

form wings, serviceable in nearly all cases for flight. There
are never more than three digits in the hand, two of them
usually much reduced, and none of them bearing claws
(with rare exceptions); nor more than two separate carpal
bones in adult recent birds ; nor any separate interclavicle ;
the clavicles are normally complete, and coalesce to form a
“merry - thought.” The sternum is large, and usually
keeled (the only exception among recent forms being the
struthious birds); it ossifies from two to five or more centres,
and the ribs are attached to its sides. The skull articulates
with the spinal column by a single median convex condyle,
developed in connection with a large ossified basi-occipital.
The lower jaw consists of several pieces, articulated by a
quadrate bone to the skull, and in all recent birds both jaws
are toothless and encased in a horny beak. The bodies of
at least some of the vertebra of recent birds have sub-cyclin-
drical, articular faces ; when these faces are spheroidal, they
are opisthocelian, but some fossil forms are amphiccelian.
The proper sacral vertebrae have no expanded ribs abutting
against the ilia. The ilia are greatly prolonged forwards ;
the acetabulum is aring, not a cup; the ischia and pubes
are prolonged backwards ; there is no ischial symphysis ;
there may be a prepubis; a process of the astragalus early
anchyloses with the tibia. The incomplete fibula does not
reach the ankle-joint; there are not more than four digits,
the normal numbers of phalanges of which are 2, 3, 4, 5.
The 1st metatarsal is incomplete above; the 2d, 3d and 4th
anchylose together, and with the distal tarsal bone unite to
form a tarso-metatarsus. The heart iscompletely four-cham-
bered ; there is but one aortic arch (the right), and but one
pulmonic ‘trunk from the right ventricle ; the blood is red
and hot. The large lungs are not free in the cavity of the
thorax, but fixed and moulded to the walls of that cavity ;
and in all recent birds the larger air-passages of the lungs
terminate in air-sacs. More or fewer of the bones are
usually hollow, and permeable to air from the lungs. There
isat most a rudimentary diaphragm. The eggs are very large,
in consequence of a copious supply of albuminous substance,
in the form of yolk and white, and are enclosed in a hard
520 ZOOLOGY.

 

Fig. 452.—Topography of a bird. 1, forehead (frons); 2, lore; 3, circumocular
region ; 4, crown (vertex) ; 5, eye; 6, hind head (occiput) ; 7, nape (nucha) ; 8, hind
neck (cervix); 9, side of neck; 10, interscapular region ; 11, dorswm or back proper,
including 10; 12, noteum, or upper part of body proper, including 10.11 and 13;
13, ramp (wropygium); 14, upper tail coverts; 15, tail; 16, under tail coverts ; 17,
tarsus ; 18, abdomen ; 19, hind toe (halla) 3 20, gastreum, including 18 and 24; 21,
outer oF fourth toe ; 22. middle or third toe ; 23, side of the body ; 24, breast (pectus);
25, primaries ; 26, secondaries ; 27, tertiaries, Nos. 25, 26, 27 are all remiges; 28,
primary coverts ; 29, alla, or bastard wing ; 30. greater coverts ; 31, median coverts ;
32, lesser coverts ; 33, the “‘ throat,” including 34, 87 and 38; 34, jagudum, or lower
throat ; 35, auriculars ; 36, malar region ; 37, gu/a@ or middle throat; 38, mentum or
chin ; 39, angle of commissure, or corner of mouth; 40, ramus of under man-
dible ; 41, side of under mandible ; 42, gonys; 43, apex, or tip of bill ; 44, tomia. or
cutting edges of the bill; 45, evdmen, or ridge of upper mandible, corresponding to

onys ; 46, side of upper mandible ; 47, nostril; 48, passes across the bill a little in
ront of its face.—From Coues’s Key.
STRUCTURE OF BIRDS. 521

calcareous shell ; there is an amnion and allantois, and no
metamorphosis after hatching.

The external form of birds is very persistent ; the different
parts of the body have been named in terms of continual use
in descriptive ornithology. Hence, without entering into
details, we reproduce from Coues’s ‘‘ Key” his figure of the
topography of a bird.

The student, after a careful study of the external form,
should prepare a skeleton of the common fowl, or examine one
already at hand, and observe those characters pecular to birds.
The skull is formed of bones consolidated into a more roomy
brain-box than in any reptiles, unless it be the Pterosanrians.
In the parrots the beak of the upper jaw is articulated (Fig.
453, 2) to the skull, so that the movement of the beak on the
skull is unusually free. The
quadrate bone (Fig. 453, e) is
usually movable on the skull;
and in the parrots when the
mouth opens the upper jaw rises,
since when the mandible is low-
ered, the maxillo -jugal rod ie tass Mal cd Pirate eee:
or bar (Fig. 453, l) pushes the maxillary bone ensheathed in horn ;

A 15, nasal bones ;_ v, mandible, the
premaxilla (22) upwards and end sheathed with horn; 7, malo-
s Enis squamosal zygomatic style or max-
forwards. This is a constant fea- illo-jugal bar ; g, post-frontal bone ;
ture in recent birds, the degree thaniee the aruodnfion oe ine ok
of motion which this peculiar bremasvlary hone; ¢ quadrase bone:
mechanism allows being variable. Ower-

The form of a bird’s vertebre is peculiar to the class ; the
articulation of the body (centrum) in all the vertebre in
front of the sacrum being saddle-shaped. ‘‘In Strigops
and a few other land birds; in the penguins, the terns, and
some other aquatic birds, one or more vertebre in the dor-
sal region are without the saddle-shaped articulation, and
are either opisthoccelian, or imperfectly biconcave.” (Marsh. )
In the fossil Ichthyornis, which had a powerful flight, the
vertebre are bi-concave, as in fishes, and Amphibians, and
a few reptiles ; but the third cervical shows an approach to
the saddle -vertebre of all other birds. The saddle form
renders the articulation strong and free, and especially
adapted to motion in a vertical plane. (Marsh.)

 
522 ZOOLOGY.

While the sternum of the cassowaries and other struthious
birds (Ratite) is smooth, approaching that of reptiles, that
of the higher living birds is keeled or carinate (Fig. 454,
ers); hence these birds are called Cari-
nate ; to this keel and neighboring parts
the muscles which raise and lower the wings
are attached.

The fore limbs of birds (Fig. 455) are
greatly modified to form the framework of
the wings. In spreading and closing the
wings, the bones of the forearm slide along
each other in a peculiar manner. (Coues.)
The ulna is usually thicker and longer than
the radius, and there are only two carpal
bones, one radial, the other ulnar, in adult
recent birds. The hand in the Apteryx and

Fig. 454.—Sternmm cassowaries has but one complete digit,
of the Guinea Hen, Cero : aes
eeen from in front; while in other birds there are three digits,
ers, crest; c, coracoid :
bone.—After Gegen- Which probably correspond to the first,
aad second, and third fingers of the human
hand. The wings are attached to a strong shoulder-girdle,
which consists of the two collar bones, uniting to form the
wish-bone, and of acoracoid bone and scapula.

 

A dq.
A ‘

    
  

t
er B 8 qr D
Fig. 455.- -Right wing bones of a young Chicken. A, shoulder; B, elbow; C, wrist
or carpus; D, tip of third finger; @, humerus; 0, ulna; ¢, radius; d, scapholunar
bone ; e, cuneiform bone; f, g, epiphyses of metacarpal bones /. k, respectively ; h,
metacarpal and its digit ¢.—From Coues’s Key.

The pelvis of birds is remarkable for the long slender back-
wardly projecting ischium and pubic bones; there is generally
STRUCTURE OF BIRDS. 523
no bony union of the two pubic bones, nor do the ischia
unite with the sacrum or each other, except in Rhea. In the
ostrich, the pubic bones are solidly united. The hind limbs
(Fig. 456) are two, three, or four toed, the ostrich having
but two digits ; in most four-toed birds, one toe (the hallux)
is directed backwards, while in the parrots and trogons,
etc., there are two toes in front and two toes behind, and
in the swifts and certain other forms all
four toes are turned forwards. The bones of
the skeleton are dense and hard; both the
long bones and the bones of the skull are
commonly hollow, containing air; the air-sacs,
in connection with the lungs, communicating
with the hollows of the bone. In some birds
which fly well, only the skull-bones have air-
cells, while in the ostrich which is unable to
fly, the bones have even a greater number of
cavities than the gull. The body during
flight is thus greatly lightened, and the bird
can sustain itself in the air for many hours in
succession.

With all these characters, the most re-
markable and diagnostic external feature is
the presence of feathers; no reptile on the
one hand, or mammal on the other, is clothed
with feathers, though the scales on the legs

 

and feet of birds are like those of reptiles,
and it should be borne in mind that feathers
are fundamentally modified scales or hairs.
The ordinary feathers are called penne or
contour feathers ; as they determine by their
arrangement the outline of the body. They

Fig. 456.—-Hind
limb of a Hawk,
Buteo vulgaris. a,
femur; 0, tibia; 0’,
fibula; c, tarso-met-
atarsus; ¢’, the same
piece isolated, and
seen from in front ;
dad’, a/’d’”, the four
toes.—After Gegen-

G E F b . baur.
are, like hairs, developed in sacs in the skin ;

the quill is hollow, partly imbedded in the derm ; this merges
into the shaft, leaving the outgrowths on each side called bards,
which send off secondary processes called darbules. These
tertiary processes (called barbules and hooklets) are com-
monly serrated, and end in little hooks by which the bar-
bulés interlock. Down is formed of feathers with soft,
524 ZOOLOGY.

free barbs, called plumules. Over the tail-bone (coccyx) are
usually sebaceous glands, which secrete an oil, used by the
P bird in oiling and dress-
ing or ‘‘preening” its
feathers. In some birds,
\ especially in the males of
( ) the gallinaceous fowls, as
} the cock and turkey, the
te head and neck are orna-
us!

 
   
 

 

mented with naked folds
Fig. 457.—Brain of the Hen. A, from above, of the skin called peony
B, from helow; a, olfactory bulbs; 0, cere- and ‘* wattles.”
bral hemispheres; ¢, optic lobes; d, cerebel- ness
lum; d/, its lateral parts; e¢,medulla—after The brain is much larger
SEA eee than in the reptiles, the
cerebral hemispheres heing greatly increased in size, while
the cerebellum is transversely furrowed, and is so large as to
cover the whole of the me-
dulla. The alimentary tract
consists of an cesophagus as
long as the neck; it dilates
in the domestic fowl and other
seed-eating birds, as well as
in the raptorial birds, into a
lateral sac called the crop (in-
gluvies). The stomach is di-
vided into two parts, the first,
the proventriculus, which is
glandular, secreting a digest-
ive fluid; and the second,
which corresponds to the pylo-
ric end of the stomach in the
mammals, is round, with mus-
cular walls, especially develop-
ed in seed-eating birds, and
valled the “gizzard.” In the — Fig. 458—Thymus (‘2) and thyroid (0)
ve a e : glands of a young hawk, Buteo vulgaris
fowl the gizzard is lined with or Europe ; ¢7, trachea.—After Gegen-
a firm horny layer, by which °*""
the food is crushed and comminuted, thus taking the place
of teeth. The intestine (including the large and small intes-

 

 
ANATOMY OF THE PIGEON. 525

tine) is long and ends in a cloaca, which receives the ends
of the urmary canals and oviducts. Attention should be
given to the trachea ; its bronchial branches, the larynx and
the syrinz or lower larynx, which may be developed either
at the end of the trachea, or at the junction of the trachea
and bronchi, or in the bronchi alone. The thymus gland
(Fig. 458, th) is very large and long, while the thyroid (¢) is
a small, oval mass situated at the beginning of the bronchi.

The following account and drawings of the anatomy of
the pigeon have been prepared from original dissections by
Dr. C. 8. Minot. As pigeons are one of the most readily
obtainable and convenient types of birds, the following
description of the anatomy of a male is given as illustrative
of the class, those peculiarities being especially noticed by
which birds are distinguished from reptiles and mammals.

Before dissecting a bird, it must be carefully plucked ;
this operation is much facilitated by dipping the animal in
boiling water for a few minutes. The limbs and muscles of
one, best of the left, side are to be removed ; the powerful
pectoral muscles cut off close to their attachment to the
keel of the breast-bone, and the ribs then cut away, care
being taken to avoid injuring any of the internal organs,
most of which will now be displayed in situ nearly as shown
in Fig. 459, which represents a dissection carried somewhat
further.

The skin (Fig. 459, #, from the neck) is characterized by
the presence of numerous ridges which cross one another,
so as to enclose quadrilateral spaces ; at the intersections
of the ridges are small pits in which the feathers are in-
serted.

The digestive canal begins in the horny bill with three
openings, one the large gape or mouth, and two oblique
elongated nasal clefts (7), through which respiration is or-
dinarily alone effected. It then extends backward under-
neath the base of the skull, where it splits into the cesopha-
gus and trachea, two large tubes which run down the front
of the neck, the cesophagus on the right and the trachea
on the left. Just below the head the trachea lies, in its
normal position, in front of the esophagus, though in most
526 ZOOLOGY.

adult birds both tubes follow a symmetrical course, but ex-
hibit a mock or secondary symmetry with regard to each
other. The origin of the two canals is embraced by the
hyoidean apparatus, one of the horns (cornwa) of which ap-
pears at Hy; the apparatus is too complicated to be de-
scribed here; it closely resembles that of reptiles, and is
functionally connected with the rapid thrusting out of the
tongue. In some birds, as, for example, the woodpeckers
and humming-birds, the horns are so developed as to curve
round the back of the cranium on to the top of the skull.
(Fig. 474).

The trachea (7%) is composed of cartilaginous rings with
intervening membranes, and an external sheath of connect-
ive tissue, which has been removed at 7r. It extends into
the thorax, and is of nearly uniform diameter throughout,
except at its lower extremity, where, as shown in Fig. 459,
D, it forms an enlargement, the syrinx or vocal chamber
(Z), found only in birds, but wanting in the ostrich, etc.
(Ratite), storks, and certain birds of prey. The trachea
terminates immediately behind the syrinx in two smaller
branches, the bronchi (&), each of which passes into the
lung (Zw) of the same side. The cartilaginous rings of
the bronchi are incomplete, the walls being partly formed
by an elastic membrane. The rings of the trachea are pe-
culiarly modified in the syrinx, which is furnished with ex-
ternal muscles and internal membranous expansions, serving
to produce the voice ; the muscles are the sterno-tracheal,
furculo- or claviculo-tracheal, and the proper muscles of the
syrinx. A true larynx is present in the upper part of the
trachea, but is unessential to the formation of the voice.
The trachea presents flexuosities in various birds, usually
more marked in the male than in the female ; in swans there
is a great band which extends into the hollow breast-bone,
but the object of this disposition is unknown.

The lungs (Fig. 459, Zw) are two large sacs, placed dor-
sally in the anterior part of the body-cavity, but not suspend-
ed freely in a short thoracic sac nor enclosed in a pleura, as
in mammals; they are composed of reddish spongy tissues,
and are attached between the ribs by connective tissue.
ANATOMY OF THE PIGEON. 527

Each lung has upon its outer and dorsal surface five trans-
verse depressions, corresponding to as many ribs. The
bronchi and pulmonary blood-vessels enter together the
anterior third of the lungs, and follow one another in their
ramifications, but the bronchus traverses the lungs, giving
off numerous branches, and opens into the abdominal air-
sac, while upon the surface of the lungs there are small
openings communicating with the remaining air-sacs.
These structures the student had best tear through and
altogether neglect in his first dissection. The air-sacs are
thin-walled bags, nine in number: three near the clavicle,
four in the thorax, and two in the abdomen ; their ramifi-
cations extend even into the bones, most of which are ac-
cordingly found to be hollow. This striking organization
is one of the most characteristic peculiarities of birds, and
serves to lighten the body by filling large spaces with warm
air, besides fulfilling certain other less obvious functions.
In many chameleons and some Geckos the lungs have di-
verticula or offshoots, which foreshadow the air-sacs of
birds.

The alimentary canal consists of seven parts: the es-
ophagus, crop, glandular and muscular stomachs, large and
small intestines, and cloaca. The cesophagus extends about
three fifths of the way down the right side of the neck, and
is approximately of the same diameter as the trachea, with
regard to which, as before mentioned, it lics symmetrically.
It opens into the crop (Cr), a thin-walled sac, which fills
the triangular space between the base of the neck and the
keel of the sternum, and forms a large part of the curved
outline of the breast. In the specimen figured, the left half
of the crop has been removed to show the irregular folds
upon the inner surface, the deep lateral pouch and the
three posterior longitudinal folds of one side, which serve
to guide the food onward to the stomach. As shown in
Fig. 459, D, the crop (Cr) ends just to the right of and
above the trachea, in a dorsally-placed, narrow tube, that
reaches to the origin of the bronchi, and there gradually ex-
pands into the glandular stomach, which cannot, however,
be seen in a general dissection, while the heart, lungs, and
528 ZOOLOGY.

liver are still im situ. The muscular stomach or gizzard
(St) of the main figure is represented very large, being
distended with food; it is sometimes found much con-
tracted ; it is not sharply separated from the glandular
stomach, the two being in reality only the greatly modified
anterior and posterior divisions of the same dilatation. The
opening of the glandular stomach and the origin of the
small intestine are near together upon the anterior border
of the gizzard. The walls of this last organ are remarkable
for the enormous development of the muscular layers,
especially in the graminivorous birds, under which pigeons
are to be included ; the muscles radiate on each side from
a central tendinous space. The small intestine has nu-
merous coils, in the first of which lies the pancreas (Pan),
very much asin mammals. The large intestine (A) is rel-
atively short ; its commencement is marked by two small
diverticula, distinctive of birds.* These appendages are
well developed in some species, as, for instance, the Galli-
naceew, while in the bustard they have been described as
three feet long. Gegenbaur considers the cesophagus, crop,
and stomach to be derived from the fore-gut, the small in-
testine from the mid-gut, and the large intestine from the
hind-gut of the embryo. The cloaca (C7) is the short and
widened termination of the alimentary canal, and further
receives four ducts, the two ureters (Ur), and in the male
the two vasa deferentia (Vd), in the female the two ovi-
ducts.

The digestive canal has two glandular appendages, the
pancreas (Pan) and the liver (Zz); the former, as in
birds generally, is quite large, whitish, and sends out a pro-
longation, which extends to the spleen ; it has two ducts.
The liver (Zi) is very voluminous, dark reddish brown in
color, and forms two lobes, which rest upon the apex of the
heart and the gizzard, and conceal the glandular stomach.
There is no gall-bladder, a somewhat unusual feature among
birds, but there are two bile-ducts, the larger and shorter

* Some snakes have a single diverticulum, as is said to be the case
with herons.
ANATOMY OF THE PIGEON. 529

opening into the upper part, while the longer duct, after
uniting with that of the pancreas, opens into the lower part
of the duodenum.

The length of the neck in birds is never less than the
height at which the body is carried from the ground ; the
number of vertebrae entering into its formation varies from
9 to 24 (swan); in the pigeon there are twelve, accompanied
by a corresponding number of spinal nerves, the branches of
which may be observed immediately underneath the skin.
The main mass of the neck is composed of the vertebral col-
umn and muscles, the trachea and esophagus. On either
side of the base of the neck, in close proximity to the trachea
and carotid artery, is a small oval white body, the thyroid
gland (77), at first developed as an evagination of the fore-
gut, but afterward becoming a closed and ductless sac,
which is found in the majority of vertebrates, but the use of
which to the organism is entirely unknown. Above the thy-
roid lie the carotid artery and jugular vein, the main vas-
cular trunks of the head and neck. The right jugular vein
is usually the largest. Along the side of the neck, above
the trachea on the left and the cesophagus on the right, lies
the elongated thymus gland (7m), drawn somewhat dia-
grammatically ; this gland forms part of the lymphatic sys-
tem, and in minute structure resembles the spleen.

The heart (H7¢) lies immediately below the lungs and
against the sternum, with its apex between the two lobes of
the liver pointing obliquely downward and backward ; it
is enclosed in a thin membranous bag, the pericardium,
which is filled with serous fluid and attached to the rvots of
the main vascular trunks. To study the heart, it must be
excised, taking the greatest care to leave as much as possible
of the vessels, especially the large veins behind, in connec-
tion with it. Viewed from behind (Fig. 459, C), the heart
is seen to be composed of four chambers, the two anterior
ones, the auricles, being the smaller. The left auricle receives
upon its dorsal side the opening of the united pulmonary
veins (Pv), one from each lung ; the right auricle is larger
than the left, and receives in its upper portion the right vena
cava superior (Vsd); in its lower portion the left vena
530 ZOOLOGY.

cava superior (Vs), just above which opens the vena cava
inferior (Vi). The two larger and posterior chambers, the
ventricles, form the apex of the heart, and give off the
arterial trunks. Of the ventricles, the left (Ven. s) is the
largest, has the thickest walls, and alone extends to the apex
of the heart ; it gives off the aorta, a short trunk which
divides into a right and left branch, from which spring the
carotid arteries for the head and neck, and which continue
as the subclavian or auxiliary arteries 4 and A’ for the
wings. From the base of the right branch A arises the
large aorta (Ao), which turns around the bronchus of the
same side, and runs to the front and right of the vertebral
column through the abdomen, forming the descending aorta
which gives off arteries to the intercostal and lumbar regions
and to the viscera, and terminates in acrwral branch to each
leg. The right ventricle (Ven. d) has much thinner walls
than the left; from it arises the pulmonary aorta (Pa)
which soon branches to each side.

Birds are distinguished from reptiles by having a four-
chambered heart and a single permanent aortic trunk ;
from mammals by the persistence of the right instead of
the left aortic arch to form the aorta. Each auricle com-
municates with the ventricle of the same side; the con-
necting orifices are furnished with valves. The right
auriculo-ventricular valve is muscular in all birds, while
the left is membranous.

The uro-genital organs lie dorsally in the hinder part of
the body-cavity. The dark reddish brown kidneys (47%)
consist, as in most birds, each of three lobes, the posterior
being the largest ; they lie immediately behind the lungs.
The ureters (Ur) are slightly curved, whitish tubes, which
pass back from the kidneys and open into the dorsal side of
the cloaca. The testicles (7) are two large oval whitish
bodies, each situated immediately behind the lung and be-
low the kidney of the same side. The vasa deferentia (Vd)
arise from the anterior and inner surfaces of the testicles,
have a flexuous course, and, after forming terminal enlarge-
ments, open separately into the cloaca, in front of the
ANATOMY OF THE PIGEON. 531

ureters. In neither sex in birds are the genital ducts pro-
vided with accessory glands.

As usual among birds, the head is approximately top-
shaped. The eyes are very large and much exposed, as be-
comes evident upon dissecting off the skin as in the figure.
The external ear isa mere circular opening, entirely covered
during life by the feathers. The side of the cranium may
be removed soas to expose the brain, with the large smooth
cerebral hemispheres (C’), the convoluted cerebellum (C2),
and the much smaller medulla (J/d). To study the brain
satisfactorily, it must be removed from its case. A view of
it from the side is given in Fig. 459, A, and a view from
above in the same figure at B. The medulla oblongata
(M1) appears as hardly more than the enlarged upper end
of the spinal cord ; upon its dorsal surface there is a trian-
gular depression IV, the fourth ventricle, which is par-
tially concealed by the cerebellwm (Cb), a large mass mark-
ed by transverse ridges and imperfectly divided into three
lobes, thus exhibiting, both in its size and its complication
of structure, a great advance over the reptiles. The corpora
quadrigemina or bigemina* (Q) project as two large lobes far
out on the sides and down the base of the brain ; their posi-
tion and great size are characteristic for the whole class.
The optic thalami, which intervene between the bigemina
and the hemispheres, are relatively small ; they enclose the
third ventricle and have a funnel-shaped downward exten-
sion, to which the pituitary body is attached, as to a stalk.
The cerebral hemispheres (He) form more than half of the
whole brain ; their surfaces are entirely without convolu-
tions, but each hemisphere has a small projection, the olfac-
tory lobe (Ql), upon its anterior and inferior extremity.
The cavities of the hemispheres or the lateral ventricles are
very large and extend also into the olfactory lobes. The
greatly thickened inferior walls of the hemispheres are
termed the corpora striata. Birds differ from mammals in
having only a rudimentary fornix and no corpus callosum.
The description of the cranial nerves is purposely omitted.

* Also called the optic lobes, middle brain, and mesencephalon.
5382 ZOOLOGY.

Between the liver and the glandular stomach lies the
small, somewhat elongated, reddish brown spleen.

In birds, as in most vertebrates, several spinal nerves unite
to form a brachial plexus, part of which is shown at B, and
which supplies the wings. Posteriorly, there is also formed
a plexus, the lumbar, for the legs.

The muscles of the limbs are much modified in accordance
with the peculiar locomotion of birds. In connection with
the power of flight, the sternum has a very large keel, to
which are attached the pectoral muscles. The pectoralis
major (Pe) is the most external ; it arises from the outer
half of the keel and is inserted into the humerus, and effects
the downward stroke of the wing. The second pectoral
(pectoralis tertius of some authors and the homologue of
the comparatively insignificant subclavius of human anat-
omy) arises from the inner portion of the keel, runs forward
and outward, and, tapering off, passes through a groove be-
tween the coracoid and sternum, as over a pulley, to be in-
serted into the humerus. The wing is raised by its action.
In the ostrich, etc. (Ratite), the breast-bone has no keel,
and the disposition of the muscles of the rudimentary wings
therefore differs greatly from that here described. (Muinot.)

The ovary may be distinguished hy the large incipient eggs
forming the greater part of the mass. The right ovary is
usually undeveloped, but when partly formed, as in some
’ hawks, the eggs do not mature.

The *‘ white’’ is deposited around the true egg in the upper
part of the oviduct, while the shell is secreted from glands
emptying into the lower part of the duct. The eggs of
birds are enormous in proportion to those of other verte-
brate animals, except the lizards. The egg of the Zpyornis,
an extinct bird of Madagascar, is about a third of a metre
(1384 inches) in length, and as the egg is in reality a cell,
this is the largest cell known. The development of the
chick is better known than that of any other animal. It
travels the same developmental path as other vertebrates in
which an amnion and allantois are formed. About the sixth
day of embryonic life the bird-characters begin to appear,
the wings begin to differ from the legs, the crop and giz-
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ANAVOMY OF THE PIGEON.

 

 

 
384 ZOOLOGY.

zard are indicated, and the beak begins to develop. By the
ninth or tenth day the feathers originate in sacs in the
skin, these sacs by the eleventh day appearing to the naked
eye as feathers ; the nails and scales of the legs and toes are
marked out on the thirteenth day, and by this time the
cartilaginous skeleton is completed, though the deposition
of lime (ossification) begins on the eighth or ninth day by
small deposits of bone in the shoulder-blade and limb-bones ;
centres of ossification appearing in the head by the thir-
teenth day.

“* After the sixth day, muscular movements of the embryo
probably begin, but they are slight until the fourteenth day,
when the embryo chick changes its position, lying length-
ways in the egg, with its beak touching the chorion and
shell membrane, where they form the inner wall of the
rapidly increasing air-chamber at the broad end. On the
twentieth day or thereabouts, the beak is thrust through
these membranes, and the bird begins to breathe the air
contained in the chamber. Thereupon the pulmonary cir-
culation becomes functionally active, and at the same time
blood ceases to flow through the umbilical arteries. The
allantois shrivels up, the umbilicus becomes completely
closed, and the chick, piercing the shell at the broad end
of the egg with repeated blows of its beak, casts off the
dried remains of allantois, amnion, and chorion, and steps
out into the world.’’? (Foster and Balfour.)

Some young birds have, as in turtles and snakes, a tem-
porary horny knob on the upper jaw, used to crack the
shell before hatching. In birds which lay small eggs, with
a comparatively small yolk, the young are brooded in nests
and fed by the parent ; but in the hen and other gallina-
ceous birds, in the wading birds and many swimmers, as
ducks, where the yolk is more abundant, the young main-
tain themselves directly on hatching.

Following the business of reproduction is the process of
moulting the old and weather-beaten feathers. This is often
a critical period in a bird’s life, judging by the occasional
mortality among domesticated and pet birds. The annual
noulting begins at the close of the breeding season, though
SONGS OF BIRDS. 535

some birds moult twice and thrice. The quill-feathers (rem-
iges) are usually shed in pairs, but in the ducks (Anatide)
they are shed at once, so that these birds do not at this
time go on the wing, while the males put off the highly-
colored plumage of the days of their courtship, and as-
sume for several weeks a dull attire. In the ptarmigan
both sexes not only moult after the breeding season is
over into a gray suit, and then don a white winter suit,
but also wear a third dress in the spring. In the northern
hemisphere the males of many birds put on in spring
bright, gay colors. Other parts are also shed ; for example,
the thin, horny crests on the beak of a western pelican (Peli-
canus erythrorhynchus), after the breeding season, are shed
like the horns from the head of deer. Even the whole
covering of the beak and other horny parts, like those
about the eyes of the puffin, may also be regularly shed.
The variations in the frequency, duration, and completeness
of the process are endless.

As a rule, male birds are larger and have brighter col-
ors, with larger and more showy combs and wattles than
the females, as seen in the domestic cock and hen; and the
ornamentation is largely confined to the head and the tail,
as seen especially in male humming-birds. Mr. Darwin has
adduced a multitude of examples in his Descent of Man,
Vol. 2. Sometimes, however, both sexes are equally orna-
mented, and in rare cases the female is more highly colored
than the male; she is sometimes also larger, as in most birds
of prey. There is little doubt that the bright colors of male
birds render them more conspicuous and to be more readily
chosen by the females as mates, for in birds, as in higher
animals, the female may show a preference for or antipathy
against certain males. Indeed, as Darwin remarks, when-
ever the sexes of birds differ in beauty, in the power of sing-
ing, or in producing what he calls ‘‘ instrumental music,”’
it is almost invariably the male which excels the female.

The songs of birds are doubtless in part sexual calls or
love-notes, though birds also sing for pleasure. The notes of
birds express their emotions of joy or alarm, and in some
cases at least the notes of birds seem to convey intelligence
536 ZOOLOGY.

of the discovery of food to their young or their mates. They
have an ear for music ; some species, as the mocking-bird,
will imitate the notes of other birds. The songs of birds
can be set to music. Mr. X. Clark has published in the
American Naturalist (Vol. 13, p. 21) the songs of a number
of our birds. The singular antics, dances, mid-air evolu-
tions, struts, and posturings of different birds, are without
doubt the visible signs of emotions which in other birds find
vent in vocal music.

The nesting habits of birds are varied. Many birds, as
the gulls, auks, etc., drop their eggs on bare ground or rocks ;
as extremes in the series are the elaborate nests of the
tailor-bird, and the hanging nest of the Baltimore oriole,
while the woodpecker excavates holes in dead trees. Asa
rule, birds build their nests concealed from sight ; in tropi-
cal forests they hang them, in some cases, out of reach of pred-
atory monkeys and reptiles. Birds may change their nesting
habits sufficiently to prove that they have enough reasoning
powers to meet the exigencies of their life. Parasitic birds,
like the cuckoo and cow-birds, lay their eggs by stealth in
the nests of other birds.

The duties of incubation are, as a rule, performed b J the
female, but in most Passerine birds and certain species of
other groups, the males divide the work with the females,
and in the ostrich and other Fatit@ the labor is wholly per-
formed by the males.

There are probably from 7000 to 8000 species of living
birds; Gray’s ‘‘ Handlist ’’ enumerates 11,162, but many
of these are not good species. Of the whole number, about
700 distinct species or well-marked geographical races in-
habit North America north of Mexico. The geographical
distribution of birds is somewhat complicated by their mi-
grations. While the larger number of species are tropical,
arctic birds are abundant, though most of them are aquatic.
In the United States there are three centres of distribution :
(1) the Atlantic States and Mississippi Valley; (2) the
Rocky Mountain plateau, and (3) the Pacific coast. The
migrations of birds will be treated of near the close of this
volume,
FOSSIL BIRDS. 537

While in former times existing birds were divided into a
large number of ‘‘ orders,’’ these are now known to be sub-
divisions of sub-classes or orders—t.e., sub-orders (the latter
category is adopted in this book), and probably in many cases
should be honored only with the rank of families. The
discovery of the Archeopteryx and of birds with teeth and
biconcave vertebra has essentially modified prevailing views
as to the classification of birds.

Order 1. Saurure.—The oldest bird, geologically speak-
ing, is the Archwopteryx (Fig. 460) of the Jurassic slates of
Solenhofen, Germany. This was a bird about the size of a
crow, the tail being 22 cent. (8-9 inches) long, but longer

 

Fig. 460.—Restoration of Archewopteryx macrura,—After Owen, from Nicholson.

than the body, supported by many movable vertebra and
covered with feathers in distichous series, not in the shape
of a fan. The jaw-bones were long, and probably contain-
ed teeth. In this respect and in the long tail the creature
served as a connecting link between the reptiles, such as
the bird-like Compsognathus and the existing birds. The
hind legs and wings have the ordinary bird structure,
though the metacarpal bones were not co-ossified ; the foot
consisted of four digits.

Order 2. Odontornithes.—Still another connecting link
between the reptiles and birds has been discovered by Marsh
538 ZOOLOGY.

in the upper Cretaceous beds of this country. The remains
of Ichthyornis indicate an aquatic bird about the size of a
pigeon. The reptilian affinities are seen in the vertebre,
which, unlike those of all other birds, are biconcave, and in
the long, slender jaws, with stout, conical teeth held in
sockets, as in the crocodiles. On the other hand, the wings
were well developed, and the legs were of the ordinary bird
type, the metacarpal bones being co-ossified, while the ster-
num was keeled. In asecond member of the group (Hes-
perornis) the teeth were in grooves, the vertebra as in recent
birds, the sternum without a keel, and the wings were rudi-
mentary (Marsh).

Order 3. Ratite.—This order, represented by the kiwi-
kiwi, the moa, cassowary, and ostrich, is characterized by
the smooth unkeeled sternum and the short tail ; the wings
are rudimentary and the hind legs strong, these birds (except
Apteryz) being runners, and either of large or, as in the
extinct forms, of colossal size.

The simplest form is the ‘‘ kiwi-kiwi,’’? or Apteryx of
New Zealand (Fig. 461), of which there are three or four
species. It is of the size of a hen, witha long slender beak,
the nostrils situated at the end of the upper jaw, while the
body is covered with long hairy feathers. The female lays
only a single large egg, which weighs one quarter as much as
the bird itself, in a hole in theground. It is a night bird,
hiding by day under trees.

The giant, ostrich-like, extinct birds of New Zealand,
called moa, and represented by several species, chiefly of
the genera Dinornis and Palapteryx (Fig. 461), were sup-
posed to have been contemporaries of the Maoris or natives
of New Zealand. While a fourth toe (hallux) is present in
the Apteryz, the moa-bird has only three toes.

The largest of the moas, Dinornis gigantews of Owen,
stood nearly three metres (94 feet) in height, the tibia or
shin-bone alone measuring nearly a metre (2 feet 10 inches)
in length. These moa birds belong to three genera: Dt-
nornis with ten, Palapteryx with three, and Aptornis with
a single species.

Allied to the moa was a still larger bird, the Apyornis
CURSORIAL BIRDS. 539

maximus, of Madagascar, supposed by some to be the roc
of the Arabian N ights’ Tales. Of this colossal bird, remains
of the skull, some vertebra, and a tibia 64 cent. long, have
been found. The single egg discovered is of the capacity of
one hundred and fifty hens’ eggs.

To this order belong the three-toed cassowaries of the
East Indies and Australia, and the emeu of Australia ; both

 

Fig. 461.—Moa, Palapteryx, with three Kiwi-kiwi birds.—After Hochstetter, from
Tenney’s Zoology.

of these birds are about 2 metres (5-7 feet) high. The
South American ostrich (Rhea Americana) with three toes to
each foot, is a smaller bird, standing 1-3 metres high, run-
ning in small herds on the pampas. The two-toed ostrich
(Struthio camelus Linn.), of the deserts of Africa and
Arabia, now reared for the feathers of its wings and tail, so
540 ZOOLOGY.

valuable as articles of commerce, is the largest bird now liv-
ing, being 2-2-7 metres (6-8 feet) high. It can outrun a
horse, and lives in flocks. It lays about thirty large white
eggs in a nest in the sand; they are covered in the day-
time by the hen or left exposed to the sun, while at night
the male sits over and guards them. In Cape Colony, os-
trich-culture has become an important business ; in 1865

 

 

Fig. 462.—Great Auk.—From Coues’ Key.

there were only eighty individuals on the ostrich farms ; in
1875 there were 32,247 ostriches, either free or in parks
where Lucerne grass is cultivated as food for these useful
birds. The South American ostrich is in Patagonia hunted
for its feathers. During the Eocene Tertiary period a gi-
gantic ostrich-like bird (Diatryma Cope), twice as large as
DIVING BIRDS. 541

an ostrich, lived in Texas and New Mexico, part of a leg-
bone having been found on the San Juan River.

Order 4. Carinate.—All other living birds belong to this
group; they are remarkably homogeneous in form and
structure, and the subdivisions may be regarded as sub-
orders. They are characterized by the keeled breast-bone
or sternum—the wings, as a rule, being well developed.

The diving birds (Pygopodes) are eminent as swimmers,
and comprise the penguins, auks, puffins, grebes, and loons.
The penguins are confined to the antarctic regions. They
are large birds, and form a characteristic element in a Pata-
gonian landscape. The bones are solid, not light and hol-
low, as in other birds; the wings are small, paddle-like,
with scale-like feathers ; on shore they have an awkward
gait. They lay but a single egg, and some species do not
lay their egg on the rocks, but bear it about in a pouch-
like abdominal fold. The penguins, however, differ so
much from the other divers that they are now often ranked
as a separate group of this grade, called Sphenisct.

The guillemots and auks are cliaracteristic arctic birds
ranging from Labrador northward, and have great powers
of flight. The gare fowl, or great
auk (Alcea impennis, Fig. 462), is
nearly or quite extinct, being un-
til lately confined to one or two
inaccessible islets near Iceland,
where it has been extinct since
1844, and to Labrador, though
formerly it ranged from Cape
Cod northward, a few survivors
having lived on the Funks, an
islet on the eastern coast of New-
foundland, within perhaps thirty
years.

The loons are well known for Fig. 463.—Roseate Tern.—From

p : : : Coues’ Key.
their large size and quickness in
diving. They are migratory, laying two or three eggs in
rushes near the water’s edge.

The petrels, gulls, and terns (Fig. 463, roseate tern) rep-

 
042 ZOOLOGY.

resent the group of long-winged swimmers (Longipennes).
They have long, slender, compressed bills, long, sharp wings,
immense powers of flight, and lay their eggs in rude nests
on rocks or upon the ground. The most notable member
of the group is the albatross (Diomedea exulans) of the South-
ern hemisphere. Its wings expand more than three metres
(nearly ten feet). It lays a single egg 12 cm. long, and
spends most of its life on the ocean far away from land.
The sooty albatross (D. fuliginosa Lawrence, Fig. 464), is
occasionally seen on our coast.

 

FE Pal EE 7

Fig. 464.—Sooty Albatross.—From Coues’ Key.

These birds are succeeded in the ascending series by the
tropic-bird, frigate or man-of-war bird, the darter or snake-
bird, the cormorants, pelicans, and gannets (Steganopodes),
in which all four toes are fully webbed, the web reaching te
the tips of the toes. The body, especially in the pelicans and
gannets, is buoyed up more than in other birds by a large
number of much subdivided air-cells under the subcutane-
ous areolar tissue of the body.

The pelican is remarkable for the large, loose pouch on
the under jaw, capable of holding several quarts, or several
SWIMMING BIRDS. 543

hundred small fishes. In the Hast Indies, pelicans are
tamed and used by the natives in fishing, as isthe cormorant
in China, while in early times it was in England.

The ducks and geese (Lamellirostres) have usually broad
bills furnished with lamellate, teeth-like projections. The
feet are palmated, adapted for swimming rapidly. In the
mergansers the bill is narrow and more strongly toothed.
The eider duck (Somateria mollissima) breeds from Labra-
dor around northward to Scotland, plucks its down from its
breast, building with it a large loose warm nest under low
bushes on the sea-coast, where it lays three or four pale

 

Fig. 465.—Summer Duck.—From Coues’ Key.

dull green eggs. The canvas-back (Fuligula vallisneria)
feeds, as its specific name implies, on the wild celery ( Vai-
lisneria) on the middle Atlantic coast in winter, whence it
derives its delicious flavor. The summer duck (Atiz sponsa,
Fig. 465) breeds in trees. The original source of our do-
mestic duck is the mallard, or Anas boschas. It is known
to cross with various other species. Upward of fifty kinds
of hybrid ducks are recorded, some of which have proved
to be fertile (Coues). The black duck (Anas obscura) is
abundant on the shores of Northeastern America, and is fre-
544 ZOOLOGY.

quently brought into the market. The wild goose (Branta

 

Fig. 466.— Carolina Rail. — From
Coues’ Key.

Canadensis) breeds in the North-
ern United States and in British
America. While it usually breeds
on the shores of rivers, it has
been known in Colorado and
Montana to nest in trees. Allied
to it is the barnacle goose of
Europe (Branta leucopsis), which
very rarely occurs in this coun-
try. The swans are characterized
by their long necks, the trachea

or wind-pipe being remarkably long, especially in the trum-
peter swan, where it enters a cavity in the breast-bone,

makes a turn and enters the lungs,
after forming a large coil.

To this group, or next to it, also
belong the flamingoes, the American
flamingo (Phenicopterus ruber) occur-
ring on the Florida and Gulf coast.
Its feathers are scarlet, its bill yellow,
large and thick, while the legs and
neck are of great length. It connects
the swimming with the wading birds.
The foregoing group forms a division
called the Natatores or swimming
birds. We now come to the Gralla-
tores or wading birds, which have long,
naked legs, and therefore long necks,
with usually remarkably long bills.
They are divided into cranes, rails, etc.
(Alectorides), the herons and their
allies (Herodiones), and the shore-birds,
snipes and plovers, or Limicole.

The cranes, together with rails (Por-
suna Carolina, Fig. 466) sometimes
have lobate feet, the toes are often
long, and in some forms, such as the

 

Fig. 467.—The ‘ Giant” of
Mauritius.—After Schlegel.

coots and gallinules, there is an approach to the ducks.
WADING BIRDS.

045

Allied to the gallinules is the ‘‘ giant’? or Gallinula (Le-
guatia) gigantea of Schlegel (Fig. 467), which formerly lived
in the Mascarene Islands, having been observed as late as

1694,

  

Fig. 468.—Long-billed Curlew.—From
Coues’ Key.

It stood two metres (over six feet) high.

 

With it was
associated a large blue galli-
nule—Porphyrio (Notornis ?)
cerulescens Selys—which was
last seen on the Isle Bourbon
between 1669 and 1672. It
was incapable of flight, but
ran with exceeding swiftness.

The cranes are of great
stature, the legs and neck very
long, with the head sometimes
curiously tufted. With the

true herons are associated the night herons and the bitterns
of the United States, the boat-billed heron of Central Am-
erica, and the odd Baleniceps rex of Africa, which has an

enormous head and broad, large bill.

The herons are suc-

ceeded by the singular spoon-bills represented by the rose-

ate spoon-bill, and which, with
the wood Ibis and other species
of this group, adorn the swamps
and bayous of the South Atlan-
tic and Gulf States.

The shore-birds, or the cur-
lews (NMumenius longirostris,
Fig. 468), plover, sandpipes,
peeps, snipes (Gallinago Wul-
sonit, Fig. 469), woodcock, and
stilt (Himantopus nigricollis,
Fig. 470), are long-legged, long-
billed birds, going in flocks by
the seashore or river-banks,
sometimes living inland on low

 

Fig. 469.—American Snipe.—From
Coues’ Key.

plains ; they are not, generally speaking, nest-builders, the
eggs being laid in rude nests or hollows in the ground.
They feed on worms, insects, and snails, either picking
them up from the surface or boring for them in the mud or
546

ZOOLOGY.

sand, or forcing the vermian food out of their holes by

Fig. 470.—Stilt.—_From Coues’ Key.

 

stamping on the ground.
Connecting in some degree
the waders and gallinaceous
fow] are the bustards of the
Old World, certain strange
exotic birds, especially the
horned screamers represented
by a very rare bird, the Pala-
medea cornuta Linn., which
has sharp horns on the wings.
The form of the gallina-
ceous birds, formerly called
Rasores, from their peculiar
habit of scratching the ground
for food, is readily recalled
by a simple enumeration of
the partridge, Oreortyx (0.

pictus, Fig. 471), quail (Ortyx), ptarmigan (Lagopus, Fig.
472), pinnated grouse or prairie hen (Cupidonia cupido),

sage-cock, Canada grouse
or spruce partridge (Te-
trao), and wild turkey
(Meleagris), as well as the
exotic forms, the pheasant
of the Old World, the use-
ful hen or barn-yard fowl,
which is a descendant of
Gallus Bankiva Tem-
minck, of India. These are
alliedto the argus-pheasant
and the peacock, the latter
rivalling the humming-
birds in its gorgeous plum-
age. The guinea-hen is
an African bird. To this
group belongs the curious
mound-bird (Megapodius),

of Australia and New Guinea.

 

Fig. 471.—Plumed Partridge.—From Coues’

Key.

It heaps up a large mass of
GALLINACHOUS BIRDS. 547

rubbish, forming a hot-bed, in which its eggs are left to
hatch. The megapods, together with the American guans
and curassows (Cracide), form a sort of passage from the
gallinaceous to the columbine birds. One of the most puz-
zling forms for the systematic ornithologist to deal with is
the hoasin of Guiana (Opisthocomus cristatus Iliger). In
this bird the keel of the breast-bone is
cut away in front, the wish-bone unites
with the coracoid bones, and also with
the manubrium of the breast-bone, a
thing of rare occurrence (Coues).

In the tinamous of Central and South
America the tail-feathers are, in some
cases, entirely wanting, and the breast-
bone and skull-bones have some anom-
alous features. Most all gallinaceous
birds have plump
bodies, with short
beaks and small
rounded wings, not
being good fliers.
In some of their
cranial characters
they are so peculiar
that Huxley makes
them one of his
primary divisions
of Carinate.

We now come to
birds of a higher

 
 
 
 
 
  
  
    

ES

P , Fig. 472.—White-tailed Ptarmigan (Lagopus leucurus),
type, in which the in (upper figure) summer and (lower figure) winter

plumage.—From Hayden’s Survey.
knee and part of

the thigh are free from the body, the leg being usually
feathered down to the tibio-tarsal joint ; the toes are usually
on the same level, being fitted for grasping or perching.
The doves are rapid fliers, but a notable exception is seen
in their extinct ally the Dodo (Didus ineptus Linn.) of
Mauritius, which became extinct on the island of Mauritius
in the seventeenth century, while the solitaire, Didus (Pe-
548 ZOOLOGY.

zophaps) solitarius Schlegel, inhabited the island of Ro-
driguez, having been exterminated about the same date
(1681). These were clumsy, defenceless birds, incapable of
flight, and were destroyed by the domestic animals which
accompanied the Portuguese voyagers to the Mascarene
Islands. The doves and their allies now commonly form a
group, called Columbe.

The birds of prey (Raptores), comprising the vultures,
buzzards, falcons, hawks, eagles, and nocturnal owls, have
a hooked and cered beak—i.e., with a waxy, dense mem-
brane situated at the base of the upper mandible. The
claws are large and sharp. The raptorial birds live either on
birds and mammals, or fish, reptiles, batrachians, and insects.
Of the vultures, the most notable for size is the condor of
the Andes (Sarcorhampus gryphus), which has great powers
of flight, its wings expanding nearly three metres (nine
feet).

The carrion crow and turkey buzzard (Cathartes atratus
and C. aura Nig. ) are useful as scavengers, especially the
former, which is partly domesticated in southern cities and
towns ; they nest on the ground or in stumps, and are more
or less ‘social. The bald-headed eagle (Haliaétus leucocepha-
lus) is dark-brown when young, ‘and before shedding its
youthful plumage is larger than the white-headed adult, It
nests on inaccessible rocky points ; is the sworn enemy of
the fish-hawk, and, like it, fond of fish, often wresting its
living food from the talons of the hawk. This species is the
emblem of our country. The osprey or fish-hawk (Pandion
haliaétus) is two-thirds of a metre long, nests in tall trees,
and is migratory. Among the hawks, the most notable are
the falcons or hunting hawks, used during the Middle Ages
in hunting the hare, etc.; in nature they chase their prey
and kill it immediately, devouring it, and rejecting the
bones and hair of the partly digested food in a ball from the
mouth.

The owl is a bird of the night ; its flight is noiseless, ow-
ing to its soft plumage, the feathers having no after-shaft.
Tt has large eyes and a hooked bill, giving the bird of Mi-
nerva an air of consummate wisdom. Owls capture living
BIRDS OF PREY. 549

mice and other small nocturnal animals, ejecting from the
mouth a ball of the indigestible portions of their meal.
The little burrowing owl of the western plains (Spheotyto
cunicularia, var. hypogea) consorts with the prairie dogs and
rattlesnakes, nesting in the holes when deserted. Their
rusty, dull hues assimilate them with the color of the soil
they inhabit. Our largest owl is the great gray owl (Syr-
nium cinereun) ; it isnearly # metre (24 feet) in length, and

 

Fig. 473.—Carolina Parroquet.—From Coues’ Key.

is an inhabitant of Arctic America. A visitor in winter
from the Arctic regions is the snowy owl (Myctea nivea),
which is nearly 3 m., or two feet long. The great horned
owl (Bubo Virginianus) is about the same size as the snowy
owl, but has two conspicuous ear-tufts, adding to its height
and its general impressiveness as a bird of more than ordi-
nary sagacity.

Of more intelligence and gifted with the power of speech
550 ZOOLOGY.

are the parrots (Psittaci). The tongue is large, soft, and
remarkably mobile, as the muscles at the base are more dis-
tinctly developed than in other birds, and the lower larynx
is complicated with three pairs of muscles; hence these
birds are wonderful mimickers of the human voice, imi-
tating the laughter or crying of babies, and repeating brief
sentences, while some sing. In proportion to their capacity
for talking, parrots command a very
high market price. Their toes are in
pairs, the bill is cered and very stout,
adapted for cracking hard nuts. The
wish-bone is sometimes rudimentary,
and the sternum entire, not notched.
Parrots are monogamous, like the hawks,
and nest in rocks or hollow trees. Our
only parrot is the Carolina parroquet
(Conurus Carolinensis Kuhl, Fig. 473),
which is common in Florida. It for-
merly extended to the Great Lakes and
to New York, but is nearly exterminated.
About three hundred and fifty species
are scattered through tropical countries,
Australia and South America being
especially favored by these gorgeous
birds. The ground parrot of New Zea-
land does not fly, all the others being
Fig. 474 —Skull of Ge- good fliers.

cinus viridis L., showing G 4 a

the asymmetrical position The Picarte, «a somewhat miscella-

of the horns (cornua lin- : Stas
gue) and De ee er eons group of birds, comprising the

yoneh intingerdof the Woodpeckers, the cuckoos, and allies,
cavity covered by theme and the swifts and humming-birds, con-
: nect the preceding groups with the Pas-
serine or singing birds. From the latter the Picarie com-
monly differ in the form of the sternum, in the less
developed vocal apparatus, there being no more than three
pairs of separate muscles, so that the birds are not musical ;
as well as in the nature of the toes and wing and tail
feathers.
The woodpeckers usually have pointed, stiff tail-feathers,

 
PERCHING BIRDS. 551

and the bill is straight and strong. The tongue is long,
flat, horny, and barbed at the end, and can be usually darted
out with great force, so that the bird can make holes in the
bark of trees and draw out the larvee of insects boring under
the bark ; in this way these birds render us signal service.
The tongue, as in all vertebrates, is supported by the hyoid
apparatus, especially by two cartilaginous appendages to the
hyoid bone, called ‘‘ the horns.’? These in the woodpeckers,
when fully developed, are curved into wide arches, each
horn making a loop down the neck, and thence bending
upward, sliding around the
skull, and even down on the
forehead. Through a peculiar
muscular arrangement of the
sheaths in which the horns slide,
they can be retracted down on
the occiput, and work as springs
on the base of the tongue, forc-
ing it out with great velocity.
Lindahl] has noticed in some
European woodpeckers an asym-
metric arrangement of the horns
as Indicated in Fig. 474.

The second group, the Cuculi,
comprise the hoopoes, horn-bills,
kingfishers, toucans, and cuck-
oos. These are succeeded by
the Cypseli, embracing the hum- ,28;
ming-birds, goatsuckers, swifts,
nighthawk (Chordeiles Virginianus, Fig. 475), and whip-
poorwill, which have long pointed wings, great powers
of flight, small weak feet, and, in the humming-birds,
long slender bills. The latter are peculiar to America,
being chiefly confined to South and Central America, only
one species (Trochilus colubris Linn.) extending into the
Eastern United States, though a dozen or more species oc-
cur in the Western United States, and very many in Mexico.

The highest group of birds, those which sing, are the
Pusseres or perchers. In these birds the feet are adapted for

 

4%5, — Nighthawk. — From
Coues’ Key.
552 ZOOLOGY.

grasping, one toe projecting backward, while the bill is horny,
usually sharp—conical, according to Coues. Various as are
the shape of the wings, they agree in having the great row
of coverts not longer than half the secondaries ; the pri-
maries either nine or ten in number, and the secondaries
more than six. The tail, extremely variable in shape, has
twelve rectrices (with certain anomalous exceptions). There
is but one common carotid artery, and the sternum is very
uniform in shape. Their high physical irritability is co-
ordinate with the rapidity of their respiration and circula-
tion; they consume the most oxygen and live the fastest
of all birds (Coues).

There are two groups of
Passerine birds, differing in
the structure of the lower
larynx ; in the first (Clama-
tores) the vocal organs are
more or less rudimentary,
the species not being singers,
while in the second and
higher division (Oscines) the
lower larynx is so developed
that most of the species ex-
cel as singers. In the sing-
ing birds the vocal apparatus
(syrinz), or lower larynx, is
situated next to the lungs at
the end of the windpipe, with a muscular apparatus formed
of five or six pairs of muscles, whose action varies the
tension of the vocal cords and narrows or widens the
glottides, which are elastic folds of the mucous membrane.
A fold of the tympanal membrane of the syrinx, called the
membrana semilunaris, projects inward.

Representatives of the Clamatores are the Acadian fly-
catcher, the wood pewee, the pewee or pheebe-bird, and the
kingbird (Fig. 476). The last, sometimes called the bee-
martin, Coues tells us, destroys a thousand noxious insects
for every bee it eats. The lyre-bird (Fig. 477) is also a
member of this group.

 

Fig. 476.—Kingbird.—From Coues’ Key.
SINGING BIRDS. 553

This bird, with tail feathers so strikingly developed (Fig.
77), is so peculiar among higher Passeres that it has been
proposed tv separate it, with certain probable allies, from
all the rest.
The Oscines are represented by a host of species. These
birds stand at the head of their class ; and as they are mostly

 

Fig. 477. —The Lyre-bird of Australia (Menura superba).

of small size, it may be said of them that they excel in qual-
ity, not quantity ; most of them sing, being highly wrought,
exquisite winged gems. Among the most notable are the
jays, including the magpie of the Rocky Mountains (Fig.
554 ZOOLOGY.

478), the crow, and blackbird, so useful a bird, notwith-
standing its mischievous propensities; the oriole, whose

   

        
   
    

Lees

SN

SS

SS

I
We

  

AN

 

Fig. 479.—Butcher-bird.—From Cones’ Key.

hanging nest, brilliant colors, and lively song render it one
of our most interesting birds; while the reed-bird of the
SINGING BIRDS. 555

South or bobolink, as it is called in the North, wakes up the
meadows with his lively notes. The finches with their
conical beaks are succeeded, in the ascending series, by the
English sparrow, a bird useful in the cities in destroying
canker-worms, but a nuisance in
the country. Our song-sparrow
(Melospiza fasciata) is widely
distributed, and everywhere
commends itself by its pleasant
notes. Quite opposed in its
habits is the butcher-bird or
shrike (Fig. 479), a quarrelsome,
rapacious bird, which feeds on
insects or small mammals, often
impaling them on thorns or sharp
twigs, and leaving them there. The group of vireos or
greenlets (Fig. 480) are peculiar to America ; their bills are
hooked, with a notch at base ; they are warblers. The wax-
wing (Ampelis cedrorum, Fig. 481) is the type of an allied
family. The swallows and
martins are interesting from
the change made in the nest-
ing habits of the more com-
mon species which rear their
young in artificial nests or
in barns, or under the eaves
of buildings.

Another group character-
istic of North America is
the warblers, Dendreca (D.
virens, Fig. 482) being the
representative genus. On
the other hand, the larks
are an Old World assemblage __ Fig. 481.—Carolina Waxwing —From

f : Coues’ Key.
of birds, but few species
occurring in this country, while the wrens (Fig. 483) are
mostly restricted to America.

The smallest bird in the United States, except the hum-
ming-bird, is the gold-crested kinglet (Regulus satrapa

 

Fig. 480.—Warbling Vireo.—From
Coues’ Key.

 
556 ZOOLOGY.

Lichtenstein), which is less than 9 cm. (3% inches) in length.
Lastly come the bluebird, the melodious thrushes, and the

 

Fig. 482.—Black-throated Green Warbler.—From Coues’ Key.

 

Fig. 488.—Winter Wren.—From Coues’ Key.

mocking-bird, while at the head of the class in this country
stands the robin (Turdus migratorius Linn.).
CLASSIFICATION OF BIRDS. 557

Cuass VI.—AVES.

Feathered Vertebrates ; jaws encased in horny beaks in existing forms ;
the fore-limbs forming wings; warm-blooded ; heart four-chambered ;
lungs with accessory air-sacs ; the bones dense, hollow ; oviparous ; eggs
very large, covered by a calcareous shell.

Order 1. Saurure.—Tail as long as the body ; metacarpals not co-ossi-
fied ; with feathers, scales, and teeth. (Archeopteryx.*)

Order 2. Odontornithes.—Vertebrie biconcave, or as usual ; jaws slen-
der, with teeth implanted in sockets or in grooves; meta-
carpals co-ossified ; sternum keeled or unkeeled ; wings well
developed. (Ichthyornis.)

Order 3. Ratite.—Sternum smooth ; wings rudimentary. (Struthio.)
Order 4. Carinate.—Sternum keeled ; wings well developed. (Turdus.)

Laboratory Work.—The student should prepare a skeleton of a hen or
any other bird, and compare it, and especially the skull and limbs, with >
those of a reptileand a mammal. In dissecting a pigeon or fowl, at-
tention should be given to those points previously indicated in which
birds diverge from reptiles on the one hand and mammals on the other.

Crass VIT.—Mammarra (Mammals).

General Characters of Mammals.—In the mammals, which
begin with the duck-bill, a creature in some respects re-
minding us of the birds, and end with man, we observe,
as compared with birds, an increased complexity of struc-
ture ; and in the nature of the work done by the different
organs, we may see a constant tendency to a development
of parts headward, so that the head becomes large in pro-
portion to the body, the brain increases in size, and the fore-
limbs finally become hands, ministering to the intellectual
wants of the animal. Also, as we ascend the series, the body,
from being horizontal, with limbs adapted for walking on all
fours, becomes finally in the apes semi-erect, in man wholly so.

The greatest step in advance over the reptiles and birds

* Vogt believes that this is a bird-like reptile ; a second, more per-
fectly preserved specimen having lately been found at Solenhofen.—
Nature, Sept. 4th, 1879.
558 ZOOLOG ¥.

is in the nature of the limbs, the structure of the head, the
organs of special sense, together with the increased com-
plexity of the teeth, and the size and complicated structure
of the brain, particularly of the cerebrum and cerebellum.
The more important (diagnostic) features of the mammals
are the articulation of the lower jaw directly to the skull,
the quadrate bone becoming one of the ear-bones (the mal-
leus) ; there are two occipital condyles ; the teeth are differ-
entiated into incisors, canines, premolars, and molars; the
body is covered with hair. The body-cavity is divided into
two compartments (thorax and abdomen) by a large muscle,
the diaphragm, so that the lungs are separated from the ab-
dominal viscera. From the four-chambered heart the
single aorta is reflected over the left bronchus ; the blood is
warm, with non-nucleated corpuscles ; the circulation is com-
plete, the blood being entirely received by the right auricle
and transmitted by the right ventricle to the lungs for aéra-
tion, whence it is afterward returned by the left ventricle
through the system. The brain is much larger than in
birds, the cerebral hemispheres forming the bulk of the
brain, and gradually, in different members of the ascending
series, overarching and finally concealing from above the
cerebellum. The cerebral hemispheres are more or less
connected (and in nearly inverse ratio) by an anterior com-
missure and a superior transverse commissure (corpus callo-
sum), the latter more or less roofing in the lateral ventricles
(Gill). Mammals are viviparous, the embryo developing
from a minute egg, and the young after birth are fed by
the mother with milk secreted in the mamme or mammary
glands ; hence the name of the class, Mammailia.
Returning to the skeleton, which we may examine more
in detail: the skull, as a brain-box, is much larger than in
the reptiles and birds. The brain-cavity of Coryphodon
and other extinct Tertiary mammals was exceedingly small,
scarcely larger in proportion than in reptiles, and there is a
progressive increase in size of the cavity of the skull in the
more specialized descendants of this early Tertiary type, as
seen in that of the horse, when compared with its Eocene
progenitors. There is also a decided increase in the brain-
STRUCTURE OF MAMMALS. 559

box of the monkey as compared with that of the lemur, and
of apes as compared with monkeys, while in man the brain
capacity is twice that of the highest apes.

The different regions of the vertebral column are better
defined than in the birds and reptiles; this is seen in the
cervical vertebre, the number of which is usually seven.
The exceptions to this rule are few, there being six in one
sloth (Cholepus), eight or nine in another sloth (Bradypus),
and six in the American manatee. Behind the cervical is
the dorsal region, consisting of from ten to twenty-four,
usually thirteen, vertebre, and the lumbar region, which is
composed of from two to nine, usually six or seven, vertebra,
and is marked off by the absence of movable ribs. The

 

Fig. 484.—Skull of the Lion.—After Owen.

shoulder-girdle is not solidly united to the dorsal vertebree,
but loosely attached by muscles and tendons. The pelvis
—1t.e., that portion called the ilium—connects with a single,
sometimes two, rarely three, vertebre of the sacral region,
and the union of these vertebra with one or more caudal
vertebre forms an assemblage of consolidated vertebre, called
the os sacrum, which in the sloths, or Edentates, comprises
eight or nine vertebra. The number of caudal vertebra
in the monkeys may amount to thirty, in the long-tailed
manis (Fig. 501) to forty, while in other mammals there may
be less than this number, there being four retained by man
and the larger apes, while in some bats there are only
three.
560 ZOOLOGY.

But it is in the limbs, and especially the feet, of mammals
that the skeleton varies most, and always in accordance with
the different habits of the creature. The limbs of mammals
differ from those of the lower vertebrates in the fact stated
by Gegenbaur, that the planes in which the angles of the
limbs of either side are set are parallel to the vertical me-
dian plane of the body, thus giving greater independence to
the limbs, which now become supports for the body, since
they raise it from the ground. Beside this, the angles be-
tween the equivalent portions in each limb do not agree
with each other, as in the rep-
tiles, but point in an opposite
direction in the case of the fore
and hind limbs respectively
(Gegenbaur). As we ascend in
the mammalian series, the limbs,
particularly the fore-limbs, are
variously modified. The limbs
of whales are paddle-like, though
the bones of the hmbs are homo-
logous with those of other mam-
mals. The feet of the seal are
webbed, forming flippers ; it can-
not support itself on its limhs,
but the fore-feet have consider-
able motion of the radius on the
ulna. In the dog the fore-limbs
have but little motion of the
cig ee of the Thumbless radius on the ulna, but the cats

(Felide) have more of this rotary
motion, enabling them to grasp with the fore-foot. This
rotary motion of the fore-arm, involving the modification
of the fore-foot into a hand, is seen in the thumbless mon-
keys (Fig. 485), and in those provided with a thumb, in the
gorilla, and especially in man. The extreme of specializa-
tion of all four limbs is seen in the horse, which has but
one digit, and walks on its single toe-nail. In the bat, the
ulna and radius are fused together as one bone, and the
last three fingers are greatly lengthened. The liberation of

 
HAIR AND HORNS OF MAMMALS. 561

the limb from the body becomes more marked as we ap-
proach man. In the seal, only the wrist protrudes from
the skin, the limb of the otter slightly more; the horse’s
leg does not protrude beyond the elbow, that of the monkey
projects two thirds of its length, while in man the limbs
become wholly free from the trunk (Wyman).

The hairs originate in minute sacs which extend from the
epidermis into the cutis ; from the bottom of this inpushing
of the epidermis grows up the shaft of the hair, which is

 

Fig. 486.—Diagram of the development of the nipple ; vertical section. a, periphery
of the glandular area (}); gl, glands. A, form of the gland in Echidna; B, its form
in most mammals; C, its form in some ungulates, as the cow, mare, etc.—After
Gegenbaur.
surrounded at the base by the cellular wall of the hair-sac
forming the root-sheaths. The spines of the porcupine, the
scales of the Manis, of the armadillo, of the tail of the rat,
are modlified hairs, all developing in the same manner.

Many mammals, especially the ruminants, as the deer, ox,
rhinoceros, etc., are armed with horns. There are two
kinds, those with a bony core surrounded with a horny
epidermal case as in the deer ; while in others, as the ante-
lopes, sheep, goats, and oxen, the horns are hollow; hence
562 ZOOLOGY.

they are sometimes called Cavicorns. In most horned
mammals, the horns are persistent; in the deer they are
dropped annually ; in the prong-horned antelope (Fig. 487)
the horns are also shed annually.

The mammary glands are modifications of the tegument-
ary glands which are found in all vertebrates except fishes.
In the duckbill and spiny ant-eater (Hchidna), these glands
retain their simple elementary nature. In all others nip-
ples are developed (Fig. 486). They correspond in general
to the number of young in a litter.

The dentition needs careful study in connection with the

  

Fig. 487. — Hollow
horn of the Prong

horned Antelope. Fig. 489.—Skull of a Porcupine.—After Owen.

fossil remains of matnmals, as the different orders are char-
acterized in great part by the differences in the form and
number of the teeth, which are intimately correlated with
the structure of the digestive organs and the nature of the
limbs ; thus while vertebre are useful in identifying or re-
storing fossil reptiles, the teeth are especially serviceable in
classifying fossil mammals. Some existing forms are en-
tirely toothless, as the duckbill, where the teeth are repre-
sented by horny plates, and the ant-eater (Fig. 488). While
the sloths have no incisors, these are present and very
large in the rodents, but the canines are absent (Fig. 489).
THE HAR OF MAMMALS. 563

In the elephant the upper canines form the tusks, the cor-
responding teeth of the lower jaw being absent. In many
teeth, as those of the deer (Fig. 490), the
crown of the molars is. quite convex, with .
crescent-shaped enamel areas. The canines
are large and sabre-shaped in the cat fam-
ily, while in the pigs, especially the baby-
roussa of Malaysia, the upper pair curve
upward and backward to the forehead.
The premolars and molars have two or Hig. 490—crown of
three roots or fangs ; in none of the lower {6 (Pom or e orery
vertebrates do the teeth have more than g™¢scents.— After
one root.

The organs of sense are much developed, especially the
ear. The quadrate bone of the reptiles and birds, which is

 

 

Fig. 491.—Diagram of the labyrinth of the ear in 7, the fish, JZ, the bird, and 777, a
mammal. J, utriculus; S, sacculus; US, utriculus and sacculus; Cr, canalis reuniens ;
R, recessus labyrinthi; UC, commencement of the cochlea, (, Z, lagena; A, cecal
sac at the apex; (, cecal sac of the vestibulum of the cochlear canal.—After Wal-
deyer, from Gegenbaur.

large, external, and suspends the lower jaw to the skull, now
becomes minute, internal, and forms one of the internal

bones (malleus) of the ear. The labyrinth of the ear,
largest in fishes, is smallest in mammals. The cochlea
564 ZOOLOGY.

(Fig. 491, C’) is greatly developed in the mammalia, while
the external ear now appears. This is a prolongation of
the edges of the first branchial cleft of the embryo. There
is, however, no external ear in the Monotremes (duckbill).
It is also absent in whales, the Sirenians or sea-cows, in
most seals, and is very small in the eared seals (O¢aria).
The eye of mammals is not essentially different from that of
the lower vertebrates.

The general anatomy of the soft parts of a mammal may
be studied by dissecting a cat, with the aid of the following
description and drawings prepared by Dr. C. 8. Minot :

Fig. 492 illustrates the general anatomy of the cat ; the
skin and right half of the body-wall have been removed.
The body-cayity is divided into an anterior and posterior
division by a transverse arched partition, the diaphragm (D),
composed of a thicker peripheral muscular portion and a
thinner central tendinous part. Through the latter pass
the great blood-vessels and the wsophagus. The anterior
chamber is the thorax or pleural cavity, and contains
the respiratory organs and heart. To show these, the
right lung has been removed. The heart (H?) was en-
closed in the thin-walled pericardial sac, which has been
cut away. The great systemic veins enter from behind—
i.e., dorsally ; from below the vena cava inferior V, passing
up through the diaphragm and uniting opposite the heart
with the large vein, cava superior, from above, the two
emptying into the right auricle. The cesophagus (0e)
overlies the trachea (77). The aorta arises from the heart,
and, curving upward and backward, runs to the left of
both trachea and cesophagus, as indicated by the dotted
lines, and continues its backward course (40) just in
front of the vertebral column into the abdomen. The
trachea gives off a bronchus to each lung (Zu). The lungs
are sacculated elastic organs, with no main central cavity.
They are separated dorsally by a thin median vertical mem-
brane (Mf), the mediastinum, the equivalent of the mesen-
tery in the abdomen. Lying on the side of the vertebral
column can be seen part of one of the two chains of sym-
pathetic nervous ganglia (8).
ANATOMY OF THE CAT. 565

The abdominal cavity contains the principal reproduc-
tive, excretory, and digestive organs. The cesophagus ter-
minates in the stomach almost immediately below the dia-
phragm. ‘The stomach (S¢) occupies a transverse position,
its larger (cardiac) end, which receives the esophagus, lying
on the left, the smaller (pyloric) end on the right. The
pylorus is furnished with a sphincter muscle, a ring of
fibres, which can completely close the orifice by their con-
traction. The stomach is followed by the long, coiled
small intestine (Jz). The posterior portion of the intestine
is somewhat dilated, and is called the colon, which passes
into the wide terminal rectum (R). The whole abdominal
portion of the intestinal canal is suspended from the me-
dian dorsal line by a thin membrane, the mesentery, which
forms several folds, the most striking of which is the omen-
tum or grand epiploon (Om.). This fold, when in situ,
hangs down from the stomach like an apron, covering over
the intestines ventrally. Upon opening the walls of the
abdomen, it is the first structure met with. It usually con-
tains a great deal of fat. Its principal function is supposed
to be to prevent the loss of heat. The omentum is present in
all maminals, but is least developed in Cetaceans, being most
prominent in Carnivora and ruminants. Connected with
the intestine are two glands, the liver (Zi) and pancreas
(Pan). The liver is large and lies directly underneath
the diaphragm. One part of it has been cut across and
left in sitw to show the oblong gall-bladder (G). The
pancreas is very much elongated and lies upon the upper
part of the intestine, the so-called duodenum. The spleen
(Sp) is closely connected with the stomach, and is of an
elongated shape, as in the majority of the Mammalia mono-
delphia.

The kidneys (A) are large and oval, and lie on either
side of the vertebral column; the aorta passes between
them, giving off a renal branch to each gland. A delicate
ureter passes from each kidney obliquely across the rectum
to the large flask-shaped bladder (B). A wrethra, not
shown in the figure, arises from the bladder posteriorly and
566 ZOOLOGY.

opens in the female immediately below the anus, but in the
male enters the penis.

The ovary (Ov) is small and is placed near the open end
of the oviduct or Fallopian tube, which can be seen in the
figure extending alongside the rectum above the bladder.
The two oviduets unite posteriorly to form the uterus.

Upon the head are to be noticed, first, the ear (La) ;
second, the eye; third, the tactile hairs (2), which form
the so-called whiskers ; fourth, the thyroid gland (772).

By carrying the dissection further, the student will be able
to examine the tongue with its papille ; the epiglottis at
the back of the mouth in front of the trachea ; the larynx,
a peculiarly modified portion of the trachea in the neck,
with two elastic bands stretched across its interior ; the
bands or vocal cords may be set in vibration by a blast of
air from the lungs. The heart may also be dissected fur-
ther to find the origin of the pulmonary vessels, and to
make out the four divisions or chambers. In making this
dissection, a description of the human heart will be found a
sufficient guide. (Minot.)

The eggs of mammals are exceedingly minute, partly owing
to the small quantity of yolk in them ; the eggs of the few
which have been examined are about a quarter of a milli-
metre (;4;—;4, inch) in diameter. In the duckbill the egg
is large and with more yolk, like those of birds, being about
five millimetres in diameter. Mammals are divided into
non-placentals and placentals, according as the embryos are
surrounded or not with a placenta or ‘‘ after-birth.’’ This
organ is a development of the allantois, serving as a means
chiefly of nutrition, being filled with blood-vessels leading
from the walls of the womb of the parent, and also acting
as an organ of respiration, and to carry off the effete pro-
ducts by means of the maternal circulation.

Mammals may be born helpless and only partly developed,
as in the Marsupials ; or capable of locomotion and sucking
milk, as in the calf or colt; or helpless for many months,
as in human infants. The changes in the form of the body
after birth are much less, on the whole, than in the birds.

The sexes differ externally in size and ornamentation.
567

ANATOMY OF THE CAT.

 

Fig. 492.—Cat. D, diaphragm; Ht, heart; V, vena cava inferior; Oc,

St, stomach; Jn, intestines; 7, rectum; Om, omentum; Zi, li
Ov, ovary; Ea, ear; h, whiskers; Th, thyroid gland; S, sympa

  

Pan, p
nerve!

    

agus; 7’, trachea; Ao, aorta; Lu, lung; M, mediasti
as; G, gall-bladder; Sp, spleen; K, kidneys; B, t
, psoas muscle.—Drawn by Dr. C. 8. Minot.

  
568 ZOOLOGY.

Darwin calls attention to the fact thatin mammals the male
wins the female rather by the law of battle than by the dis-
play of high colors and attractive ornaments. During the
breeding season, desperate contests take place between the
rival males ; even the males of the timid hare will at such
times fight until the weaker is killed ; so moles, squirrels,
horses, male seals and male sperm-whales, whose heads are
larger than in the female, and beavers, will fight desperately.
It is a rule that the males of such animals as are provided
with tusks or horns always fight for the possession of the
female. It is so with bulls, deer, elephants, boars, and rams ;
at the same time these are organs of defence by which the
males protect their family, flock, or herd. On the other
hand, in the female rhinoceros, some antelopes, the reindeer,
as opposed to the other deer, some sheep and goats, etc., the
horns are nearly as well developed as in the opposite sex.
The modes of attack are various: the ram charges and
butts with the base of his horus, the domestic bull gores
and tosses any troublesome enemy, while the Italian buffalo
‘*is said never to use his horns; he gives a tremendous blow
with his convex forehead, and then tramples on his fallen
enemy with his knees.’? Darwin also says that male quad-
rupeds with tusks use them in a variety of ways; thus the
boar “strikes laterally and upward, the musk-deer with
serious effect downward,’’ while the walrus can strike either
upward, downward, or sideways with equal dexterity.

The males are usually larger when there is any difference
in size ; this is seen in the eared seals, especially Callorhinus
ursinus, in the ox, Indian buffalo, and the American bison,
as well as the lion. The mane of the latter adds to its ap-
pearance of greater weight and bulk, and Darwin says that
the lion’s mane “‘ forms a good defence against the one
danger to which he is liable—namely, the attacks of rival
lions.”’ As regards distinctions in color, male ruminants
are most liable to exhibit them. In the Derbyan eland the
body is redder, the neck much blacker, and the white band
separating these colors broader than in the females. In the
Cape eland the male is slightly darker than the female. In
the Indian black-buck the male is very dark, almost black,
VOCAL ORGANS OF MAMMALS. 569

while the female is fawn-colored : male antelopes are blacker
than the female. The Banteng bull is almost black, while
the cow is of a bright dun. Among the lemurs the male of
Lemur macaco is coal-black, while the female is reddish yel-
low. The sexes of monkeys differ much in coloration. Cer-
tain male seals, bats, rats, and squirrels have brighter colors
than in the opposite sex. On the other hand, the female
Khesus monkey is adorned with a brilliant red naked ring
around the tail ; this is wanting in the male, which, how-
ever, is larger, with larger canines, more bushy whiskers
and eyebrows ; and Darwin states that in monkeys the males
usually differ from the females in “‘ the development of the
beard, whiskers, and mane.”’

The vocal organs of mammals are, in general, constructed
on the same type. The larynx is formed by a modification
of the uppermost ring of the trachea, called the ericoid car-
tilage, to the anterior and dorsal edges of which two arytenoid
cartilages are attached, while a V-shaped thyroid cartilage,
open behind, is attached to its side. The vocal cords, which
are modified folds of the mucous membrane lining the
trachea, are stretched between the arytenoid and thyroid
cartilages, the slit between them being called the glotéis,
which is covered by the epigiottis. Thus, in mammals the
organs of voice are situated almost solely at the upper end
of the trachea. In the whales the vocal chords are not de-
veloped. The male gorilla, which has an exceedingly loud
voice, as well as the adult male orang and the gibbon, is
provided with a laryngeal sac. In the howling monkey
(Mycetes) of Brazil, the hyoid apparatus and larynx are re-
markably modified, the body of the former being changed
into a large bony drum or air-sac communicating with the
larynx. The vocal organs are a third larger in the males
than in the females. ‘‘ The males begin the dreadful con-
cert, in which the females, with their less powerful voices,
sometimes join, and which is often continued during many
hours’? (Darwin). They apparently howl, as birds sing,
for the simple pleasure of the thing. Apparently, the most
musical mammal, man excepted, is a gibbon (Hylobates
agilis), which can sing ‘‘ a complete and correct octave of
570 ZOOLOGY.

musical notes’? (Martin ex Darwin). While quadrupeds
use their voices as alarm calls, most of the sounds are pro-
duced by the males, especially during the breeding season.

Animals are mutually attracted or are individually pro-
tected from the attacks of other species by odors. The
scent-bags or odoriferous glands secreting a fluid differing
in consistency in different animals, are situated near the
base of the tail, as in the skunk, polecat, musk-deer, civet-
cat and allies, or they may be developed in the side of the
face, as in the male elephant, as well as sheep and goats.
The odor is either of musk or some form of it. The shrew-
mice, by reason of their odoriferous glands, are disliked and
consequently not hunted by birds. Universal deference is
paid to the skunk ; few dogs, and only those which are in-
experienced or peculiarly gifted, attacking them. The
males more usually emit a stronger odor than those of the
opposite sex.

Some mammals have a summer and a winter pelage. The
hare, at the beginning of winter, doffs its summer coat for a
suit of white. The hybernation, or winter-sleep, is a re-
markable feature in the life of quadrupeds living in the
north temperate zone, such as the bear, dormouse, and bats.
During this period the temperature of their body falls,
respiration and circulation are lowered in the one case or
nearly ceases in the other, and life is sustained by the ab-
sorption of fat, which accumulates on the under side of the
neck in the so-called hybernation-glands.

There are about 3500 species of mammals described, of
which 2100 are living; of these 310 inhabit America north
of Mexico. Mammals live all over the earth’s surface, but
mostly in the tropical region, those of the arctic zones having
been derived from the south since the end of the Tertiary
period. The range in space of certain species is very great—
for example, the cougar, panther, or puma ranges from Brit-
ish to South America (Chili). The mammalian fauna of the
Tertiary deposits of the west was far more abundant than now,
the remains of over five hundred species having been already
discovered by Leidy, Cope, and Marsh in the few spots ex-
amined. The earlier (Hocene) mammals were generalized
ORIGIN OF DOMESTIC MAMMALS, 571

forms, combining in a remarkable degree characters more
elaborated, and in great detail, in different orders of living
mammals, especially the Ungulates. For example, from the
Hocene Coryphodon, a generalized ungulate animal, have
probably been derived the ruminants, the tapirs, hog, hip-
popotamus-like forms, the rhinoceros, and, finally, the
horse. This inference is based on the fact that the bones
and teeth of Coryphodon present characters which are no
longer combined in any one species of mammals, but which
are found worked out in detail in the members of the differ-
ent orders referred to.

Moreover, the early Tertiary mammals had brains ee
smaller than in any existing forms, and with only one ex-
ception, without convolutions—showing that the develop-
ment of the size of the brain and its convolutions, and con-
sequently of the intellect, has kept pace with the successive
stages in the specialization shown in existing forms, and
which agree with the increasing complexity of the Ameri-
can Continent and the subdivision of the western part of
the continent into distinct basins, with separate mountain
systems and river-valleys. The result of all this apparent
waste of generalized forms, and the survival of the few
favored types now existing, has been the preservation of
animals which have been domesticated by man, such.as the
dog, pig, horse, ox, camel, elephant, and of others useful as
food or as intelligent servants ministering to his every-day
wants.

The earliest mammals were small insectivorous or gnaw-
ing marsupials, none larger than a cat, and first appearing
in Jurassic strata.

The Mammalia are divided into three sub-classes—viz., the
Ornithodelphia (duckbill and Echidna), the Didelphia or
marsupials, and the Monodelphia, comprising all the higher
mammals.

Sub-class 1. Ornithodelphia.—The duckbill and spiny ant-
eater (Fig. 493, Hchidna hystriz) are the only representatives
of the sub-class, of which there is but a single order, called
Monotremes, and are distinguished by the following char-
acters. The oviducts, vasa deferentia and ureters, open into
572 ZOOLOGY.

the cloaca, as in birds. The sternum is provided with a pecu-
liar T-shaped bone, and there are important features in the

 

  

Fig. 493.—Spiny Ant-eater (Hehidna hystriz).—From Brehm’s Thierleben.

  
 
 
  
 
 

fv toe, MA
\ yy Wy Ai f

fs sha
\ Ligy | hy

ff ies
ay za 2 thy i
4 72,

 

brain separating them from the members of the higher sub-
classes, There are several characters allying them to the
DUCKBILL AND ECHIDNA. 573

birds and reptiles, and besides those mentioned one of the
most obvious is the long, toothless jaws (there are eight
horny teeth in the duckbill), which are long and narrow in
the Lchidna, or broad and flat in the duckbill (Ornithor-
hynchus paradoxus Blumenbach), where it is covered by a
leathery integument ; the external ear is wanting.

A PPOSTe RAND.

at

        
      
   

  

   

Aly

   

      

Fig. 494.—Skeleton of Hchidna hystrix._From Brehm’s Thierleben,

In the aquatic duckbill the feet are webbed, with claws
of moderate size. It is covered with a soft fur, and is about
half a metre (17-22 inches) long. Its
habits are like those of a muskrat, fre-
quenting rivers and pools in Australia
and Van Dieman’s Land, sleeping and
breeding in holes extending from un-
der the water up above its level into
the banks, and with an outlet on shore.
It lives on mollusks, worms, and
water-insects. Young duckbills, five
cm. long, have been found in their
nests.

The spiny ant-eater (Figs. 493 and
494) is represented by three species,
the Echidna hystrix Cuvier, of Aus-
tralia, #. Lawesit Ramsay, from Port
Moresby, New Guinea, also by a re- .
cently discovered form inhabiting the | Fig. sine eee
elevated portions of Northern New marsupial bones. ie
Guinea, and called by Gervais Acanthoglossus Bruijnti. In
these singular animals the bill is long and slender, tooth-

J
=)
574 ZOOLOGY.

less, while the palate is armed with rows of strong, sharp
spines ; the tongue is long and slender, like that of the ant-
eater, while the body is armed with quills like those of a
porcupine ; the claws are very large and strong, adapted for
tearing open ant-hills. All the species are from one third
to one half of a metre (12-19 inches) in length.

 

Fig. 496.—Skeleton of the Kangaroo.—From Brehm’s Thierleben.

Sub-class 2. Marsupialia.—These are singular forms, rep-
resented by the opossum in this country, and the kangaroo,
with a number of other forms, in Australia. They differ
from all other mammals in having a pouch (marsupium) for
the reception of the young immediately upon birth, where
MARSUPIALS. 575

they are attached to the nipples at the bottom of the pouch.
This large pouch (absent in some opossums and in the
Dasyurid@) is supported by two long slender bones attached
to the front edge of the pelvis and projecting forward (Fig.
495 m and Fig. 496).

In Thylacinus, the Tasmanian wolf, these bones are car-
tilaginous. In the opossum, the kangaroo, and probably
most marsupials, the young remains in the pouch attached
to the nipple, which fills the mouth. ‘‘ To this it remains at-
tached for a considerable period, the milk being forced down
its throat by the contraction of the cremaster muscle. The
danger of suffocation is avoided by the elongated and coni-
cal form of the upper extremity of the larynx, which is em-
braced by the soft palate, as in the Cetacea, and thus respi-
ration goes on freely,
while the milk passes,
on each side of the
laryngeal cone, into
the esophagus”
(Huxley). In the car-
nivorous forms the
brain is low in struc-
ture, the olfactory
lobes being very large,

completely exposed,
s Fig. 497.-Teeth of the Tasmanian devil. The
while the cerebral incisors are situated in front of the large conical

hemispheres are small Ge te Rese premolars ; m, 1-4, four molar
and quite smooth.

The dentition of marsupials is characteristic, none having
three incisor teeth upon each side, above and below, and
none but the wombat (Phascolomys), with an equal num-
ber of incisors in each jaw, there being usually more in the
upper than in the under jaw.

The lowest marsupial is the Tasmanian wolf (Thylacinus),
which is rather smaller than the wolf. The Tasmanian devil
(Dasyurus ursinus Geoffroy, Fig. 497) is a vicious, trouble-
some creature, about the size of a badger. The opossums
inhabit North and South America. They have a long tail
and a plantigrade step—i.e., they walk on the sole of the
whole foot. The Virginian opossum (Didelphys Vir-

 
576 ZOOLOGY.

giniana Shaw) lives chiefly in trees. Lawson says that
‘““the female doubtless breeds her young at her teats, for I
have seen them stick fast thereto when they have been no

Hil ni i" ,
i i i

 

Fig. 498.—The Kangaroo (Macropus).—From Brehm’s Thierleben.

 
 

II | I
Hn
{| i
' |

\| \ i

{|
3

i T

 
 
 
 

bigger than a small rasberry and seemingly inanimate. She
has a paunch, or false belly, wherein she carries her young
after they are from those teats, till they can shift for
EDENTATE MAMMALS. 577

themselves. Their food is roots, poultry, or wild fruits.
They have no hair on their tails, but a sort of a scale or
hard crust, as the beavers have. If a cat has nine lives,
this creature surely has nineteen ; for if you break every
bone in their skin and mash their skull, leaving them for
dead, you may come an hour after and they will be gone
quite away, or perhaps you may meet them creeping away.”
(“‘ Perfect Description of Virginia,’ 1649.)

There are squirrel-like flying marsupials (Petawrus),
marsupial rats, marsupial bears, and marsupial ant-eaters
(Myrmecobius), but the most characteristic Australian ani-
mals are the different kinds of kangaroo (Macropus thetidis,
Fig. 498).

The largest species, W. gigantews Shaw, is 1-8 metres, or
nearly six feet long. Kangaroos go in herds, and move by
a succession of long leaps.

All marsupials are stupid, low in intelligence, and, in the
insectivorous and carnivorous forms, of vicious temper.
With the exception of the opossums, all are confined to Aus-
tralia, New Zealand, and New Guinea.

Sub-class 3. Monodelphia.—While in the marsupials the
termination of the oviduct is double, in the present group
it is always single, whence the name Monodelphia. The
members of the group are also called placental Mammalia,
because the young at birth are of considerable size and
nearly perfect in development, being nourished until born
by a highly vascular mass or thick membrane ( placenta)
supplied with arteries and veins, developed originally from
the allantois, which is a temporary embryonic membrane.
The brain, as a rule, presents an advance over that of any
of the preceding mammals, the corpus callosum being better
developed, while the anterior commissures are all reduced.
There are no marsupial bones, though in some Carnivora
certain small cartilages appear to represent them.

There are twelve orders, as follows :

Order 1. Bruta or Hdentata.—These creatures, repre-
sented by the sloths, ant-eaters, pangolins, and armadillos,
stand next above the non-placentals or marsupials, as the
brain is but little better developed, the hemispheres in some
578 ZOOLOGY.

forms being nearly smooth, while, in point of their general
structure and intelligence, they stand at the foot of the sub-
class. The teeth may be entirely undeveloped, as in the
common ant-eater, but when developed they are not encased

Fig. 499.—Skeleton of the Ai, or Three-toed Sloth.—After Owen

 

inenamel. In most Edentates the incisors are absent, but
the lateral one may exist in the armadillo (Dasypus). The
feet are formed for grasping or digging, and end in large
straight or curved claws. They are either hairy or pro-
SLOTHS AND THEIR ALLIES. 579

tected, as in the pangolins (Fig. 501) and armadillos (Fig.
002), with large thick scales. ‘They feed on insects and de-
cayed animal matter, or on leaves. They are of moderate
size, though certain extinct forms were colossal in stature.
The leaf-eating forms, viz., the sloths, differ from the
other Bruta in the very long and slender limbs, the hinder
pair the shorter. There are five teeth above and four below,
which become sharp with use, like chisels ; the stomach is
said to be remarkably complex. In disposition these crea-
tures are types of sluggishness; they live in trees, being
absolutely helpless on the ground, not being capable of
walking on the bottom of the foot.
Waterton says that, in climbing, the
ai (Bradypus tridactylus, Figs. 499 and
500) uses its legs alternately ; that its
hair ‘‘is thick and coarse at the ex- &
tremity and gradually tapers to the ‘
root, where it becomes fine as a spider’s
web. His fur has so much the hue of
the moss which grows on the branches
of the trees, that it is very difficult to
make him out when he is at rest.’
None of the Edentates now occur in
the United States, but formerly colos-
sal, sloth-like forms, with some resem- )
blance to the ant-eaters, ranged over | Fig, 500.— Ai, or Threo-
the Southern and Middle States as far tude.— After Wood, from
north as Pennsylvania, their bones oc- Bae we
curring in caves. Such was the Meyatherium, a gigantic,
sloth-like creature, which extended from Pennsylvania to
the pampas of South America, and whose skeleton is over
five metres (18 feet) long. With it was associated the Meg-
alonyz, first described by Thomas Jefferson ; it was as large
as a bison, as was the Mylodon. ‘These animals walked on
the soles of the feet, could rise on their hind legs and partly
support themselves by their thick tails, pulling down large .
trees and feeding upon the leaves and smaller branches.
In the ant-eaters the jaws are toothless, but very long, and
the tongue is of great length and very extensile ; the sub-

  
580 ZOOLOGY.

maxillary glands are very large, so that the viscid salivary
fluid is very abundant. They burrow into ant-holes, thrust-
ing the tongue among the ants, which stick in multitudes to
the viscid, writhing rod, and are withdrawn into the mouth.
The pyloric end of the stomach is gizzard-like. The ant-
eaters (Myrmecophaga) inhabit South America.

The pangolins, or species of Manis, are mail-clad ant-
eaters, the body and long tail being covered with large
overlapping scales. When molested they roll up the body.
In walking the hind feet rest on the soles, while the fore-
feet are supported by the upper side of the long bent
claws.

 

 

Fig. 501.—Pangolin (Manis longicaudata) robbing white ant-nests —After Monteiro.

The long-tailed pangolin of the West Coast of Africa (Fig.
501) tears open with its long claws the nests of the white
ants. It is nearly 3 metre (28-30 inches) in length.

The armadillos (Fig. 502) are small mammals covered with
a carapace, consisting of from three to thirteen transverse
rows of movable scales ; by rolling into a ball, these singu-
lar creatures become thoroughly protected from their ene-
mies. Dasypus novem-cinctus Linn. is much like the Peba
armadillo, and extends from South America to Texas. The
strange extinct armadillo-like Glyptodon of South Amer-
ica, which was over two metres (8 feet) long, was covered
THE ARMADILLO, 581

by a heavy, solid coat-of-mail consisting of polygonal plates
soldered together immovably.

The three following orders have by most authors been
placed near the Primates (monkeys, etc.), but Owen, from

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the characters afforded by the brain, has shown that they be-
long at or near the bottom of the scale. Gill has shown
that not only by the brain, but by other characters corre-
lated with the low development of the brain, the Rodents,
582 ZOOLOGY.

Insectivora, and bats should be associated with the Edentates
in Bonaparte’s division (or, as Gill terms it, super-order)
of Ineducabilia (which corresponds to Owen’s sub-class
Lissencephaia). In these four orders, then, the cerebrum is
small, smooth, with none or few convolutions ; in front
it does not cover the olfactory lobes, and behind leaves
the cerebellum wholly or partly uncovered.

On the other hand, in the super-order Hducabilia, com-
prising the following orders : Cetacea, Sirenia, Proboscidia,
Hyracoidea, Toxodontia, Ungulata, Fere, and Primates,
the brain has a relatively large cerebrum, behind overlap-
ping much, or all, of the cerebellum, and in front much, or
all, of the olfactory lobes (Gill). The cerebrum is also con-
voluted ; the convolutions increasing in number and com-
plexity, until we reach the apes and man, and accompanied
by increasing intelligence and capability for mental im-
provement. Other important characters are mentioned by
Owen and by Gill in support of this arrangement.

In the smooth small cerebrum, as well as in other re-
spects, the Zneducabilia are related, together with the mar-
supials and duckbill, to the birds and reptiles. In the
cloaca, the convoluted trachea, the long, slender, beak-like,
toothless jaws and the gizzard of the ant-eaters, the quills
of the porcupine and hedge-hog, the proventriculus or crop
of the dormouse and beaver, in the growing together of the
three chief metatarsals of the jerboa, asin birds, in the keeled
sternum and wings of the bats, there are points of resem-
blances to birds. Owen, whom we have quoted, also adds
the aptitude of the bats, insectivores and certain rodents
“to fall, like reptiles, into a state of torpidity, associated
with a corresponding faculty of the heart to circulate car-
bonized or black blood.”’

However, there are points in which these orders are re-
lated to the lemurs and monkeys.

Order 2. Glires. (Rodentia.)—The rats, squirrels, por-
cupine, and beaver are common examples of this extensive
group. They differ from other orders in the large incisors,

the dental formula of which is normally 2 (4 in Leporide

and Lagomyide), and in the absence of canine teeth. The
ORDER OF RODENTS. 583

condyles of the lower jaw are longitudinal, not received in spe-
cial glenoid sockets, but gliding freely backwards and forwards
in longitudinal furrows. The feet are adapted for walking
and climbing or burrowing, the claws being well developed.
A peculiarity in the incisors is that they grow out as fast as
they are worn down ; this is due to the fact that the pulp is
persistent ; the enamel in front causes them to wear away

 

Fig. 503.—American Flying Squirrel (Sctwropterus Volans).

behind so that they are chisel-shaped. The species are pro-
lific, live mostly on vegetable food, and are of small size;
the muskrat, beaver, and capybara being the largest mem-
bers of the group. The flying squirrels (Fig. 503) take
short flights by means of the expansion of the skin between
the fore and hind legs. The Norway lemmings are notice-
able for their remarkable migrations from the elevated
584 ZOOLOGY.

plateaus of Scandinavia down and into the sea; the object
and origin of which are inexplicable, and are not indicative
of much intelligence. From this and their nest-building
habits, rodents are, as a rule, not unlike birds ; and Owen, for
these reasons, ascribes to them a low degree of intelligence.
Granting that this is the case, an exception to this rule is
seen in the social beavers, which evince a high, exceptional
degree of intelligence. Beavers build a dam in a running
stream so as to create an artificial pond as a refuge when at-
tacked, as well as a subaquatic entrance to their lodges and to
their burrows in the banks of the streams they inhabit. Bea-
ver dams are built at first by a single pair or family, and are
added to from year to year, and afterwards maintained for
centuries by constant repairs. They are built of sticks and
mud, usually curve up stream, with a sloping water-face.
Beavers lay up stores of wood for winter use in the autumn ;
they can gnaw through trees eighteen inches in diameter; they
work mostly at night. They often construct artificial canals
for the transportation of the sticks of wood to their lodges.
This, in the opinion of Mr. Morgan “is the highest act of
intelligence performed by beavers.” When ponds do not
reach hard-wood trees or ground in which they can burrow
for safety, they will build canals with dams, and so excavate
them that they will hold the surface drainage. Morgan
describes one canal about 161 metres (523 feet) long which
“served to bring the occupants of the pond into easy con-
nection, by water, with the trees that supplied them with
food, as well as to relieve them from the tedious, and per-
haps impossible, task of moving their cuttings five hundred
feet over uneven ground, unassisted by any descent.” Bea-
vers, In swimming, use their tail as a scull, and the hind
feet being webbed, its propelling power while swimming is
very great. They carry small stones and earth with their
paws, holding them under the throat, and walking on their
hind feet. They use the tail in moving stones, working it
under so as to ‘ give it a throw forward.” Beavers are very
social, working together and stormg up wood in common.
““A beaver family consists of a male and female, and their
offspring of the first and second years, or more properly,
HABITS OF THE BEAVER. 585

under two years old. The females bring forth their young

from two to five at a time, in the month of May, and nurse
them for a few weeks,

after which the latter
takes to bank.” They
attain their full growth
at two years and six
months, and live from
twelve to fifteen years. *

Allied to the beaver,

 

Fig. 504.—Sewellel or Showt’l. Much reduced.

but forming the type. —From ere Naturalist.
of a distinct family, is the singular sewellel or showt’l

ue Cea
a }

a E

 

SON ST SRS
Fig. 505.—Alpine Hare of the Rocky Mountains.—After Hayden

(Haplodon rufus Coues, Fig. 504) of the mountains of west-
ern Oregon and Washington Territory. It is nearly as large

* The American Beaver and his Works. By Lewis H. Morgan. 1868.
586 ZOOLOGY.

as a muskrat, is nocturnal in its habits and, therefore, rarely
seen, and burrows in the earth, feeding on roots.

The lowest in intelligence are, perhaps, the hares, rep-
resented by the common varying hare (Lepus <America-
nus Erxleben, Fig. 505), of which an interesting variety,
L. Bairdii, lives on the Alpine summits of the Rocky Moun-

 

Fig. 506.—The Spalax or Blind Rat.—After Owen.

tains. The largest of all existing rodents is the Capy-
bara of South America, which looks like a pig. This is
succeeded by the porcupine, which either lives in trees or
burrows in the earth, while the more intelligent, active
forms are the beaver, muskrat, the European blind rat
(Spalax, Fig. 506) the rats and mice, squirrels, and lastly
the marmots. The domes-
tic mouse and the two rats,
the brown or Norway rat
(Mus decumanus Pallas),
the black rat (Mus rattus
Linn.), and the common
Lei N : house mouse (Afws muscu-
Fig. 507.—Jumping Mouse (Zapus hud- lus Linn.), are cosmopoli-
sonius).—From Tenney’s Zoology. tan animals. The jumping
c Jumping
mouse (Fig. 507) has remarkably long hind legs and short
fore legs. Peculiar to the western plains is the prairie-dog,
(Cynomys ludovicianus) which represents the marmots of
the Old World ; it is semi-social and takes in perforce as
boarders the owl and rattlesnake, which devour its young.

  
MOLES AND SHREWS. 587

Order 3. Insectivora—In the moles the incisors, the
canines, and molars are well developed, and the molars have
the crown surmounted by conical projections called cusps.
The fore feet are plantigrade, with large claws, and the en-

tire limb is short, thick, mus-
cular, and fossorial,7.¢., adapted
for burrowing in the soil (Fig.
508). The shrews comprise
the smallest mammals. Nearly
all are nocturnal, burrowing
under the surface, and never
seen by day; consequently,
their eyes are small, and most-
ly hid under the fur; while the
ears are small and concealed by
the hair.

The shrews are mouse-like,
having feet of the normal form,
and a long nose. In our com-

 

Fig. 508.—Bones of fore leg of a
Mole. 52, the cubital scapula; 53,
humerus; 54, ulna; 55, radius.—Af-
ter Owen.

mon shrew (Sorex platyrhinus Wagner, Fig. 509), the nose
is long, and the tail shorter than the head and body.

The genuine moles are the characteristic forms of the
order ; the most peculiar being the star-nosed mole, Condy-

   

HLLNICHOLS.SC.

Fig. 509.-Common Shrew.—After Coues.

lura cristata Linn., which occurs from the Atlantic to the
Pacific Ocean, while the common mole (Fig 510) is abundant

in the Eastern United States.

A flying form with a superficial resemblance to the bat, and
088 ZOOLOGY.

with the same habit of sleeping, head downward, holding on
by its hind feet, is the Galeopithecus of the East Indies.
This singular creature has been placed among the lemurs
by some authors. G. volans Pallas inhabits Java, Sumatra,
Borneo, and Siam.

DE =

Fig. 510.—Common Mole (Scalops aquaticus Linn.).—After Coues.

 

Order 4. Chiroptera.—The bats form a well-circumscribed
group of mammals, very distinct from any other, especially
in the greatly modified fore-limbs, the radius and ulna being
united, and the second to the fifth metacarpal bones and
phalanges being very long and slender, supporting a thin,
leathery membrane or skin, extending to the hind legs, and
wholly or partly enclosing the tail ; the hind toes being, how-
ever, free, as when at rest or in the vegetarians when feeding,
bats hang head downwards, holding on by their claws. The
sternum is slightly keeled for the attachment of the mus-
cles of flight. The mammary glands are pectoral. In other
respects, especially the dentition, the bats resemble the
Insectivora. The form of the teeth differs from the ordi-
nary insectivorous bats in those which live on fruit. The
vegetable-eating or fruit-eating bats have a superficial resem-
blance to the flying lemurs ; and because their mamme are
pectoral, have been placed next to the Primates.
HABITS OF BATS. 589

Bats live in caves and in the hollow of trees by day ; all
hibernate in the same situations, going into winter quarters
in the autumn, and reappearing in the warm twilight of
spring. Though the eyes are small, and the sight, so far as

  

mS Ao - ==

    

.

; as | p |

7 o_-

Fig. 511.—Skeleton of a fruit bat (Pteropsus).—After Owen.

we know, deficient in keenness, they show wonderful skill
in avoiding objects during their rapid flight. The ears are
very large, and in the vampires the nose is adorned with
590 ZOOLOGY.

sensitive, leaf-like growths of complicated form. The vam-
pires are known to enter houses, and suck the blood from

R ~ Aa

 

Fig. 512.—Skull of adult sperm whale seen from above and from the side. 00,
basioccipital bone ; ¢0, exoccipital ; so, supraoccipital ; p, parietal ; s, squamosal ; 7,
frontal ; pl, palatine; j, jugal ; sh, stylohyoid ; bh, basihyoid ; th, thyrohyoid.—After

ower.

the extremities of sleeping persons, who awaken to find their
feet covered with blood.
CETACEANS. 591

The largest bats are the fruit bats or flying foxes (Ptero-
pus) of the East Indies ; one species of which expands one
and a half metres (nearly five feet) from tip to tip of the
wings. Our commonest species is
the little brown bat, Vespertilio
subulatus of Say ; nearly as com-
mon is the red bat, Atalapha no-
veboracensis Coues.

Order 5. Cete (Cetacea).—We
now come to the Hducadilia, in
which the brain is more highly de-
veloped, and begin with two very
aberrant orders, the whales and
Sirenians, in which the body is
fish-like, though the tail is hori-
zontal ; the pelvis and hind limbs
are wanting, either wholly, or mi-
nute rudiments may be present ;
and they are aquatic, occasionally
leaping out of the water, but usu-
ally only showing the dorsal fin or
nose when at the surface to breathe.

The whales and porpoises have
a large, broad brain, with numer-
ous and complicated deep convolu-
tions.

In the skull (Figs. 512, 513) the
aperture for the spinal cord ( fora-
men magnum) is entirely posterior
in situation and directed some-
what upward. The lower jaw is
straight, with no ascending ramus,
the narrow condyles being situated
at the end of the jaw, at the point pig 513.—skull of the sperm
indicated by the angle of the ramus Whels, longitudinal section show.

ing the relative size and form of
1 7 \ ra the cranial cavity. m, maxilla;
in other mammals. The teeth are Pe eae oe
conical, with a single root, but are
sometimes wanting. There is no neck; the cervical verte-

bre are sometimes confluent, forming a single mass. The

  
 
592 ZOOLOG ¥.

limbs form a pair of paddle-like appendages just behind and
under the head, which are supported by short, flattened
limb-bones, the carpals and phalanges often separated by car-
tilage ; the second digit being composed of more than three
phalanges. There are two mamme situated near the anus.
The external nostrils are either single or double, and are sit-
uated on the top of the head ; they are modified to form the
spiracles or ‘‘ blow-holes ;” certain folds of the skin prevent
the water from entering the air-passages. The vapor blown
from the holes does not consist of water, but of the mucus
from the nostrils, and the moisture in the breath. The
blow-holes vary in form in different kinds of whales. The
“spout” or stream of vapor issues in a single short
stream from the extreme end of the snout, and curls over
in front of the head; that of the fin-back whale forms
a single column of vapor about ten feet high ; the right
humpback and sulphur-bottom whales each ‘“‘blow” in a
double stream which is directed backward toward the tail.

Whales are rarely over fifty feet long; the sperm-whale
has been known to reach a little over twenty-three metres
(76 feet) in length, but Professor Flower questions whether
the sperm-whale frequently, if ever, when measured in a
straight line, exceeds a length of sixty feet. The largest of
all whales, as of all existing animals, is the fin-back or ror-
qual (Balenoptera boops), which sometimes measures thirty-
four metres in length. The smallest Cetacea are the por-
poises.

In the Mysticete or whalebone whales, the teeth, present in
the embryo, become reabsorbed into the gums before birth and
are replaced by plates of whalebone (Fig. 514), three hun-
dred of which may be present on each side of the mouth.
The inner edges of these plates have projecting fibres, form-
ing arude strainer ; these whales feed on small pelagic jelly-
fish, molluscs and crustacea, by taking in a mouthful of
water, and then pressing the tongue against the roof of the
mouth, expelling the water through the openings between
the plates, the fibres acting as a strainer. Three thousand
five hundred pounds of whalebone have been obtained from
a single bow-head or Greenland whale (Balena mysticetus).
THE SPERM WHALE. 593

The cachelot or sperm-whale (Fig. 515) has an enormous
head, and is without the power of smell. Above the nasal,
frontal, and maxillary bones are cavities filled with a fatty
fluid called spermaceti, used in the manufacture of candles,
ointments, and cosmetics, such as cold cream. A large sperm-

 

Fig. 514.—Head and tongue of whale, Balena (the latter (a) drawn much too
large) ; d, whalebone plates.
whale will yield 2500 kilograms of this substance. Another
valuable substance is amdergris, a morbid product, the result
of injury to the intestine by the beaks of cuttle-fishes, upon
which animals the toothed whales largely prey. It isa kind
of bezoar or gall-stone, fatty, aromatic, burning with a clear
flame. It is composed of benzoic acid, united with chlorine,
of a balsamic substance, and ambrain. It is used in making
perfumes.

 

Fig. 515.—Outline of the cachelot, showing how the plubber is removed : 8, the
situation of the ‘case’; c, the junk; d, the bunch of the neck ; h, the hump ; é, the
ridge; k, the small; 7, the tail or flukes; between the oblique dotted lines are the
spiral strips or blanket pieces.—After Beale, from Gill.

But the chief use of whales is the oil extracted from the
fat enveloping the body, called blubber by whalers. The
most valuable of the whales is the Greenland whale, as it
contains the most oil, individuals having been known to
yield nearly three hundred barrels.
594 ZOOLOGY.

The whale-fishery first sprang up in the twelfth century
in the Bay of Biscay. In the New England colonies whales
were pursued in boats from the shore. In 1854 the fishery
culminated ; since then it has decreased. It is principally
rarried on by Americans, New Bedford being now the lead-
ing port from which whalers are sent out to the Arctic

 

Fig. 516.—Kogia Floweri.—After Grayson, from Gill.

regions and Behring’s Straits, one hundred and ten vessels
having been sent out in 1876 from this port.

Closely allied to Physeter macrocephalus Lacépéde, are
the pigmy whales, represented on the Californian coast by
Kogia Flowert Gill (Fig. 516), which is nearly three metres

 

Fig. 517.—Skull of Callignathus simus, seen from the side and from below.—
After Owen.

(nine feet) in length, with a conical head. In Callignathus
simus Owen (Fig. 517) the skull is short and broad; it is
found on the coast of Madras, India.

The narwhale (Aonodon monoceros Linn.) is distinguished
by the long, spirally-twisted, horn-like tusk of the male,
formed of the left upper incisor, which becomes nearly three
SIRHNIANS Oh SHA-COWS. 595

metres long, the female having no visible teeth ; there being
two rudimentary incisors which never appear through the
gum. It ranges from Hudson's Straits to the Arctic seas,
having formerly been seen along the coast of Labrador. To
the family of dolphins and porpoises belong the white whale
or Delphinapterus leucas Pallas, which ranges from the Gulf
of St. Lawrence northward ; the grampus (Grampus griseus
Cuvier) ; the blackfish, of which there are.two species, one
Globicephalus melas Trail, ranging north of New York, and
one G@. brachypterus Cope, to the southward, and the por-
poises, of which the most common on our coast is Phocena
brachycium Cope; the rarer is P. lineata Cope. On the
coast of Labrador, as well as northward, occurs the thrasher
whale or killer (Orca gladiator Gray) which has large
teeth, and a high dorsal fin ; it attacks whales, gouging out
the flesh from their sides. Certain fossil whales were pigmies
in size; while the Zeuglodon of the Alabama Eocene Ter-
tiary beds, was an enormous serpent-like whale, which must
have measured over seventy feet in length.

Order 6. Sirenia.— In the few species of sea-cows represent-
ing this order, the lower jaw is more as in other mammals,
having well developed ascending rami and normal transverse
condyles and coronoid processes. The teeth are well developed,
both incisors and molars, the latter with flattened or ridged
crowns, adapted for the trituration of vegetable food. A
neck is indicated; the two nostrils are situated at the
upper part of the snout, and the lips are beset with stiff
bristles, while the mamme are pectoral. The fore limbs are
of moderate length, with five well-developed digits, but still
fin-like and bent at the elbow. The brain is narrow com-
pared with that of cetaceans, and the heart is deeply fissured
between the ventricles. The manatees of America and the
dugong of Australia and India (Fig. 518) live in the mouths of
large rivers, feeding on seaweeds, aquatic plants, or the grass
along the shore. The Florida manatee (Manatus Ameri-
canus Desmarest) grows to a length of from two to nearly
three metres. It ranges from Florida to the Amazons, where
it is called Vacca marina ; it ascends the river as far as Pehas,
Peru, and is killed and eaten, its flesh resembling beef.
596 ZOOLOGY.

Steller’s manatee (Rhytina Steller’) was in the last century
found in abundance on the shores of Behring’s Island on the
coast of _Kamtchatka; twenty-seven years afterwards (in
1768) it was totally exterminated by the sailors, and only a
few imperfect bones exist at St. Petersburg. ‘This is the

Boe

Fig. 518.—The Dugong.—From Brehm’s Thierleben.

i
|

‘
hi

largest Sirenian known ; it was over six metres in length.
It differed remarkably from the other forms, in having no
teeth, but was provided with a very large, horny, palatine
plate, and a corresponding one covering the enlarged point
of union, or symphysis, of the lower jaws. In the Tertiary

 
THE PROBOSCIDIANS. 597

Period a fossil Sirenian (Halitheriwm) inhabited the shores
of western Europe.

In the structure of the skull, their dentition and their her-
bivorous habits the Sirenians in a degree connect the Ceta-
ceans with the Ungulates.

Order %. Proboscidia.—Only two representatives of this
group are now in existence, the Asiatic and African elephant,
a number of other forms having become extinct. The group
is well circumscribed, when we consider the living species,
but in the early (Eocene) Tertiary Period there existed forms
which indicate that the Proboscidians and Ungulates had a
common origin. In
the elephants the up-
per incisors are enor-
mously developed,
while there are none
in the lower jaw.
There are no canine
teeth, while the few
molars are large, trans-
versely ridged. In the
elephants the ridges
are numerous, the
spaces between them
filled with cement.
The young mastodon
has cement on the up-
ae surface of the Fig. 519.—Skull of young elephant ; 22, premax-
tooth ; the ridges af-  itlary bone containing the root of the tusk, k; 15,
terwards become free 25, molar, zigomatic arch? 4, lower jaws c- upper

. jaw ; m, molar tooth ; 21, maxilla ; 11, frontal; g,
and covered with Squamosal.—After Owen.
enamel. <A peculiari-
ty in the elephant’s skull is its large size, the brain cavity
being very small in proportion to the bulk of the skull itself.
To give lightness to what would be otherwise an insupportable
weight, the cranial bones contain numerous large air-cells
(Fig. 520). Another remarkable feature,from which the group
takes its name, is the trunk or proboscis, a long, thick, fleshy,
flexible snout, growing from the front edge of the nasal

 
598 ZOOLOGY.

bones (Fig. 520, a). The trunk ends in a finger-like, highly
sensitive point, below which are situated the nostrils. The
brain has a large cerebrum, with numerous convolutions, but
more of the cerebellum is exposed than in any of the succeed-
ing orders ; in this respect and in the large incisors the Pro-
boscidians approach the Rodentia.

In the nature of the limbs, especially from the fact that
elephants walk on their toes, a relation to the Ungulates is
indicated. They are
five-toed, but the dig-
its are represented ex-
ternally only by the
five broad, shallow
hoofs, the foot being
supported by thick,
broad pads. The legs

   
 

HTN)
y wll )

  
 
 

     

are almost wholly free
Y M1] from the body. The
I, > igs placenta is zonary

and deciduate. The
skin is naked in the
existing elephants,
but the extinct mam-
moth was covered
sparsely with hairs.
Elephants live in
herds, browsing on
the leaves of trees
Fig. 520.—Section of an elephant’s skull, showing

the small size of the brain cavity as compared to the and herbs. They at-

whole skull, and the numerous large air cells. 2, * oO Pony
posterior nostrils; 13, cavity of the nose ; a, front tain a height of from
opening of the bony nostrils, to the edge of which +thyee to four metres

the trunk is attached.—After Owen.

(10-12 feet). The
Asiatic elephant has a concave forehead and small ears, while
the African species has a full, rounded forehead and large
ears, with four hoofs on the fore feet and three on the hind
feet, the Asiatic elephant having one more hoof on each foot.
The fossil mammoth (Zlephas primigenius Blumenbach),
which was contemporaneous with early man, was not much
larger than the existing species. Its tusks, however, were of
MAMMOTH AND MASTODON. 599

great size, some being five metres long. It formerly ranged
in herds over northern Europe and Asia, as well as America,
bones occurring under swamps in the Northern and Middle
United States. A carcass frozen in the ice, with the hair
still on, was discovered near the mouth of the Lena River in
Siberia. A pigmy, extinct Maltese elephant of the late Ter-
tiary Period was only 1.7 metres in height.

The Mastodon was characterized by having incisors in both
jaws of some of the species. The mastodon had molars with

 

Fig. 521.—Dinotherium. —From a restoration by Brandt.

conical cusps, and was 33-4 metres (12-13 feet) in height.
The mastodon (Mastodon giganteum Cuvier) was an earlier
type than the elephant, and formerly inhabited the North
American continent.

In the Dinotheriwm of the Middle Tertiary (Fig. 521) there
were only two incisors, and they grew out from the under
jaw. It was elephantine in its form, according to Brandt.

Order 8. Hyracoidea.—With some affinities to the Ro-
dentia, and a decided resemblance in some particulars to
600 ZOOLOG ¥.

the rhinoceros among the Ungulates, the members of this
small order are in general characterized by having long,
curved incisors ; and by feet provided with pads as in Ro-
dents and Carnivora, the toes being encased in hoofs (four in
front and three behind). The Hyraa, a little gregarious
animal living in holes among rocks, of which there are two
or three species known, one South African, and another in
the Holy Land and Arabia, thought to be the coney referred
to in the Bible, is the only genus.

Order 9. Toxodontia.—Of this group, of which no spe-
cies are now living, the types are Tozxodon and Nesodon.
They are placed by many authors among the odd-toed Ungu-
lates, not far from the tapirs. Their incisors were ¢ or ¢.
Toxodon in its skull bore some resemblance to the Sirenians,
and in the teeth were in certain respects like the Edentates.
The species lived in South America during the early Tertiary
Period.

Order 10. Ungulata.—The larger proportion of mammals
belong to this interesting order, which comprises nearly all
those species of mammals useful to man, such as the ox,
camel, pig, deer, and horse. They are, in general, charac-
terized by walking, so to speak, on their toes, each toe being
at the end encased in a horny hoof ; not more than four toes
being completely developed on a foot. The teeth are usually
well developed, with six incisors in each jaw, but these are
often, especially in the upper jaw less in number or entirely
absent, as in the sheep, deer, and ox. The collar-bone is
absent. The brain still remains small compared with the
bulk of the skull, and the intestinal canal is of unusual
length compared with that of animals of the previous orders.

The Ungulates have been divided by Owen into two sub-
orders, according to the odd number of toes (Perisso-
dactyla) or even number (Artiodactyla). In the Perisso-
dactyles there may be three toes on each foot, as in the rhi-
noceros, or one, as in the horse ; while in the Artiodactyles
there may be four toes (Hippopotamus), or two, as in the
giraffe, or two functional and two rudimental, as in the ox
and deer, 7. e., most Ruminants. The more generalized ex-
isting form of Ungulates is the tapir; the most specialized
ORDER OF UNGULATES. 601

type is the horse, with its single toe on each limb. A large
number of extinct Tertiary Ungulates in the Western States
and Territories, and the Tertiary basins of Paris and Lon-
don, more or less allied to the tapir, especially Coryphodon,
Anoplotherium, Paleotherium, ete., were generalized or
ancestral forms, from which the modern, more specialized
types have probably been evolved, and a study of these fossil
Ungulates shows that there was then (7. ¢., in Eocene times)
an essential unity of organization in all Ungulates, including
the Ruminants; the breaking up of the Ungulate stem into
special groups, along favored lines or paths of development,
having resulted in a gradual improvement and_ elabora-
tion of particular parts, which rendered them more fitted
for their present life, and more intelligent in meeting and
overcoming the emergencies their more complex surround-
ings subjected them to. Thus in the Eocene Ungulates,
such as Coryphodon, the cerebrum was small, without convo-
lutions, indicating a slight degree of intelligence compared
with the modern Ungulates, while the gradual differentiation
of the horse, with its single toe and hoof, from its tapir-like
ancestors, is a marked example of the intelligent, beneficent
selection of favored, useful types which has gone on from the
earliest geological times.

All this specialization of type involved the destruction of
great numbers of forms unfitted to withstand changes in
their surroundings, or not sufficiently intelligent or wary to
avoid the attacks of carnivorous forms, and thus the present
number of Ungulates is much exceeded by the fossil forms.

Perissodactyles. The odd-toed Ungulates, on the whole,
stand lower than the even-toed forms. They all have at
least twenty-two dorsal and lumbar vertebra, and a simple
stomach, with a large, sacculated cecum. The tapirs are
the more elemental, generalized forms. Fossil tapirs occur
in the older Tertiary beds of the West. The snout is
almost proboscis-like, and the legs are moderately long, with
four toes in front, three toes behind. The tapirs inhabit the
tropics of the New World and Sumatra. They are succeeded
by the rhinoceros, represented in this country by a number
of extinct Tertiary allies, the living species being restricted
602 ZOOLOGY.

to Africa and the East Indies. The skinis remarkably thick
and dense, while these animals have either one or two long
median horns growing from the skin of the nose. A rhinoc-
eros contemporary with early European man formerly inhab-
ited England, France, and Germany, and extended into Si-
beria.

A number of fossil forms lead up to the family compris-
ing the horse, ass, zebra, and quagga, etc., in which there
is a single toe, being the third on each limb. Their den-
tion is—

6 ,1-1 ,4-4 ,,3-3
1 e CS Ca M 323°

The genealogy or series of ancestral extinct Ungulates
leading from tapir-like forms to the modern horse has been
worked out partly by Huxley, and especially by Marsh, who
has with Leidy discovered a large series of remains in the Ter-
tiary beds of central and western United States, America being
the original home of the horse. The earliest member of the
series directly leading up to the horse was Hohippus, an older
eocene form, about as large as a fox, which had four well-
developed toes and the rudiments of a fifth on each fore-foot,
and three toes behind. In later eocene beds appeared an
animal (Orohippus) of similar size, but with only four toes in
front and three behind. In newer beds, 7. e., lower miocene,
are found the remains of Mesohippus, which was as large as
a sheep and had three toes and the splint of another in each
fore-foot, with but three toes behind. In later miocene beds
another form (Anchitherium or Miohippus) had the same
number of toes, but with the “‘ splint bone of the outer or fifth
digit reduced to a short remnant.” The splint bones, then,
represent two of the digits of several-toed animals. The suc-
ceeding forms were still more horse-like. ‘‘In the Pliocene
above, a three-toed horse (Hipparion or Protohippus), about
as large as a donkey, was abundant, and still higher up a near
ally of the modern horse, with only a single toe on each foot
(Pliohippus) makes his appearance. A true Zqwus, as large
as the existing horse, appears just above this horizon, and
the series is complete.” (Marsh.) Fossil horses extended
over portions of North and South America, but became ex-
tinct before the present Indians appeared,
THE HORSE AND ITS VARIETIES. 603

The horse (Zquws caballus Linn.) is the most useful of all
domestic animals, and next to shipsa prime means of the
diffusion of civilization. By artificial selection a great num-

s,WYyoIg Wo, —‘snuvjododdiyy oy} Jo uojafoyS— eee "SNA

+
Lu

“maqaratty

 

ber of varieties, races, and strains have been produced,
adapted for the performance of different kinds of work. The
horse only exists in a domesticated state. Sanson states that
604 ZOOLOGY.

the horse in the Orient has five, and in the west (Africa) six
lumbar vertebra ; in Arabia both forms occur ; in the horse
with but five lumbar vertebre the shape of the skull is also
different. The Hemippus, the tarpau and muzir of Tartary,
as well as the white, shaggy horse of the elevated plains of
Pamir in central Asia which is often regarded as the original
stock, may be a race which has returned to a wild state, since
partly wild horses occur in Syria, on the Don, and live
in great herds on the llanos and pampas of South America.
There are two primitive races of horses, the Oriental and
Western. To the first belong three types : the Arabian, with

 

Fig. 523.—Stomach of a ruminant (sheep), showing the four compartments ; a, @so-
phagus ; 0, paunch ; c, honeycomb or reticulum ; d, liber psalterium or manyplies ; e,
true digestive stomach ; 7, beginning of the intestine.—After Owen.

the Berber, Andalusian, Neapolitan; and in England the
blood horse; the Nizaischan type of the Deccan, India, to
which belong the Persian, Turkestan, Turkish horses, and
the Tartarian. The western races comprise the Frieseland,
to which belong the Brabant, Holstein, Mecklenburg, and
the English farm-horse, and among others the Percheron
horse, of France. Ponies are dwarf horses produced in cool,
mountanous areas, such as the Shetland Islands. The wild
ass (Zquwus onager Brisson) ranges from the Indus to Meso-
potamia. Hqguus hemionus Pallas, the Dschiggetai or Kiang,
goes in herds in central Asia and Mongolia. The hinny and
EVEN-TOED UN@GULATES. 605

mule are infertile hybrids of the horse and ass (Zguus
asinus Linn.).

Artiodactyles.—The even-toed Ungulates comprise the
peccary, pig, hippopotamus, and the Ruminants represented
by the deer, sheep, ox, and camel. The pig and peccary are the
descendants of a number of extinct earlier forms which flour-
ished in the Tertiary Period; the pig, as Marsh observes,
having held its own with characteristic pertinacity. The
Hippopotamus (Fig. 522) has a large head, with large canines,
a clumsy body, and short, three-toed legs. Hippopotamus
amphibius Linn., ranges from the Upper Nile to the Cape of
Good Hope, and westward to Senegambia. It is nearly
3% metres (11 feet) in length.

Ruminantia.—The remaining Artiodactyles are called
Ruminants, from the fact that they chew their cud. The
molars are provided with two double crescent-shaped folds
(compare Fig. 490). The stomach (Fig. 523) is divided into
at least three, usually four compartments, i.e., the paunch,
the reticulum or honeycomb, so named from the polygonal
cells on its interior, the psalteriwm or manyplies, and lastly
the rennet or true stomach. When a sheep, cow, or any
other Ruminant feeds, it thrusts out its long tongue, seizes
a bunch of grass, and bites it off by pressing the incisors
of the lower jaw against the toothless gum of the opposing
part of the upper jaw ; the mouthful of grass is then swal-
lowed, mixed with much saliva. When its appetite is satis-
fied it seeks a retired spot away from its carnivorous ene-
mies, if not a domesticated animal, and after lying down,
suddenly regurgitates a ball of grass, the cud,* which it slow-
ly grinds up between its molar teeth into a pulp. The
cropped grass passes into the honeycomb and paunch; the
manyplies serves as a strainer for the pulp, which in the
fourth stomach is digested by the gastric juice.

Among a number of fossil forms leading up to the exist-

* The regurgitation of the cud is probably due to a sudden and sim-
ultaneous contraction of the diaphragm and of the abdominal muscles,
which compresses the contents of the rumen and reticulum, and
drives the sodden fodder against the cardiac aperture of the stomach,
which opens and the cud is propelled into the mouth. (Huxley.)
606

ZOOLOGY.

 

Fig. 524.—Restoration of buck, doe, and young Sivatherium.—After Hawkins.
EVEN-TOED UNGULATES. 607

 

Fig. 525.—Skeleton of Sivatherium restored.—After Hawkins,

 

y.—From Caton.

Fig. 526.—Virginian Dee
608 ZOOLOGY.

ing deer and antelopes is the Sivatherium (Fig. 524, 525)
of the Tertiary beds of the Himalaya Mountains, which had
two pairs of horns, and were gigantic creatures. nearly as

ee

alan

\ "

VAN

PEN \\V elec hh
N yy aX wh = aa)

 

Fig. 527.—Elk or Wapati.—From Caton’s Antelope and Deer of America.

bulky as an elephant, and of the singular form approxi-
mately indicated by the accompanying illustrations, having
affinities to the antelopes and the giraffe.

The deer family (Cervide) is represented in the United
THE SHEEP AND ITS VARIETIES. 609

States by the common Virginian deer (Cariacus Virginianus
Gray, Fig. 526), the elk or wapiti (Cervus Canadensis Erxle-
ben, Fig. 527), and the caribou (Rangifer caribow Audubon
and Bachman), which is probably a variety of the European
reindeer (2. tarandus Sundevall). In these beautiful, grace-
ful forms the solid antlers are cast off annually ; with the
exception of the reindeer the females or does have no antlers.

The prong-horn antelope (Antilocapra Americana Ord,

 

Fig. 528.—Head of young Prong-horn Antelope.—After Hays.

Fig. 528) so characteristic of the western plains, also drops
its horns in the autumn, though they are hollow (Fig. 529)
and with a persistent core asin the ox and ‘goat. It crops
grass, not, like the deer, eating leaves of trees and shrubs ;
“in fleetness it excels all other quadrupeds of our conti-
nent,” though it is short winded, and does not run a great
distance (Caton). In its hollow horns, and the presence of a
gall bladder, which is absent in the Cervide, the prong-horn

~
610 ZOOLOGY.

connects the deer family with the Bovide, represented by
the sheep, goat, antelope, gazelle, and ox.

The domestic sheep (Ovies aries Linn.) is not a natural
species, but an association of races whose specific origin is
obscure. Some authors regard the turf sheep of the stone
age of Europe as the ancestor of the domestic sheep, as forms
like it are now living in the Shetland Isles and in Wales.
It was of small size, with slender limbs, and erect, short
horns. This sheep was supplanted by a curved, large-horned
form, the modern domestic sheep. This latter form is pos-
sibly the descendant of the Ovis argali Pallas, of Asia, which
in North America is represented by the Ovis montana Cuvier,
the Rocky Mountain sheep or big-horn (Fig. 530), still com-
mon on the less accessible summits along the upper Missouri
and Yellowstone Rivers, as well as the mountains of Wy-
oming and Montana.

In the same, though
higher and more inac-
cessible situations lives
the rare mountain
goat, Aploceros monta-
nus Richardson, whose
horns are jet black and
polished, slender and
conical, like those of
the Swiss chamois. It
is found sparingly in

Fig. 529.—Horns at different ages of the Prong- Bee higher SHULENS Bs
horn Antelope, showing the hollow structure.— the Rocky Mountains

and the Cascade range ;
an individual has within a few years been shot on Mount
Shasta, California. Passing by the gazelles and true an-
telopes we come to another characteristic American an-
imal, the musk sheep (Ovibos moschatus Blainville,
Fig. 531), now confined to the arctic regions. A closely
allied species, Ovibos priscus of Riitimeyer, formerly during
the post-glacial period existed in England, France, and Ger-
many. Closely allied to the musk sheep is a fossil form
(Boitheriwm of Leidy) which is regarded by Riitimeyer and

   
THE BISON. 611

others as a musk sheep (Ovibos priscus Rutimeyer). If this
is the case the musk sheep, or a species closely allied to it,
formerly extended to the Middle States at or near the close
of the glacial period.

We now come to the bison and ox. The American bison

 

Fig. 530.—Rocky Mountain Sheep or Big-Horn.—From Brehm’s Thierleben.

(Bison Americanus Gmelin) formerly ranged from Virginia
and Lake Champlain to Florida, and westward from the
northern limit of trees to the Rocky Mountains and eastern
Mexico. It is nowin danger of extermination, being mainly
restricted to a few herds on the plains. It is closely
612 ZOOLOGY.

‘allied to the European bison, (Bison Huropeus Owen), the
“‘auroch,” now preserved in the forests of Bialowicza, and
living wild in Caucasus. Bos primigenius Bojanus, which

Fig. 631.—Musk Sheep.—From Brehm’s Thierleben.

 

in the time of Cxsar lived in Germany and England bear-
ing the name ‘urus,” is the “ur” of the Niebelungen
song. From it has descended the half-wild cattle in certain
THE OX AND ITS VARIETIES. 613

English parks, also certain large domestic races, such as the
Holstein and Friesland breeds. From another fossil species
(Bos longifrons Owen) arose the so-called brown cattle of
Switzerland, and the ‘‘runts” of the Scottish Highlands.
Still other domestic races are traced back to another fossil

‘daMQO 1eIJV—'MOD OT}SeUI0g JO WoJa[aHS— "seg SLL

 

quaternary species, Bos frontosus Nilsson. Our present
races of domestic cattle, however, do not represent a genuine
species, but a number of races which have descended from
several fossil species ; the name Bos tawrus (Fig. 532) is
simply, then, a conventional name (Carus’ Zoologie). The
bison is known to breed with cattle in the Western States,
614 ZOOLOGY.

though whether the hybrids thus produced are fertile or not
is unknown. ;

The ox is succeeded by the giraffe, with its long neck,
which makes it the tallest of all quadrupeds. ;

The last family of Ungulates, the Camelide, comprises the
camels of the Old World, and the llama and vicuna of South
America. In former (Tertiary) times a Hama-like animal
inhabited the Pacific coast to Oregon. In the camels the
upper lateral incisors are present ; the stomach is less
distinctly divided into four chambers, the third stomach, as
such, is wanting, though the second stomach has the deep
cells, which suggested the fable that the camel stores up a

supply of water in its stomach for its march over deserts.
5) ll qa

   

Fig. 533.—Skull of Lion.

The toes have very large, thick pads, while the hoofs are
reduced to nail-like proportions.

Order 11. Carnivora (Fere).—The bear, cat, tiger, and
' lion recall the leading forms of this order. The skull is
massive, though the head is small or of moderate size; the
teeth are all well developed, especially the canines ; the mo-
lars usually have two or three roots, and the feet have large
claws. The stomach is simple. The cerebral hemispheres
of the lower carnivores have usually but three distinct con-
volutions, while the latter are much more numerous and
complicated, the brain itself being broader, in the aquatic
forms (Pinnipedia). The group is divided into two sub-
orders, 7.e. the Pinnipedia or seals, and the land species (Fis-
sipedia). In the former group the feet are webbed, the toes
BEARS AND THEIR ALLIES. 615

being connected ; the wrist and foot only projecting beyond
the skin of the body, and there are no external ears, or only
small ones.

The walrus (Fig. 534), the seals, and the eared seals or
sea-lions (Otariide)
are the types of the
aquatic Carnivores ;
the sea-lions can walk
on all fours, and in
certain peculiarities of
the skull they’ resem-
ble the bears.

Of the terrestrial,
normal Carnivora, the
raccoon, coati, Cerco-
leptes, and bear, to-
gether with a number
of extinct forms, are
the more generalized
or lower types. They
are plantigrade, and
while standing at the
base of the carnivorous
series, have some fea-
tures suggesting and
anticipating those of
the lemurs, and mon-
keys. The raccoon,
Procyon lotor (Linn.),
abounds throughout
the United States. Al-
lied to it is the coati
(Nasua) of Central
America, a creature
about the size of, and
with the general hab-
its of the raccoon, being an exceedingly knowing and mis-
chievous animal. A number of extinct Hocene mammals
are also allied to a small plantigrade, long- tailed carnivore,
Cercoleptes, which resembles the Primates in its two cutting

‘TOQeIOIGL §,Wyaig WoLg—'snsye MA oq} JO UOJaTOYS—FeEQ “SLT

 
616 ZOOLOGY.

pre-molars and three true molars; while the rami of the
mandible are codssified; for these reasons it was placed
by F. Cuvier between the orders Carnivora and Primates
(Cope). Itis allied to the raccoon, is called the kincajou,
and lives in northern South America.

The bears have a thick, clumsy body, with a rudimentary
tail, and the teeth are broad and tuberculated, so that they
can live indifferently on fish, insects, or berries. Our North
American species are the polar bear (Ursus maritimus
Linn.) and Ursus arctos Linn., with its varieties of brown,

  
 
  
     

   

Wie. Se
yer
MMtyy ”
yn Wilt tana

 
     

coe
Sl Ore

NS
a
a

\
\\

\
NY

 

Uf (OX ti:pit

Fig. 535.—Skeleton of the Polar Bear, showing the plantigrade feet. 51, scapula;
53, humerus; /4, radius; 55, ulna; 62, ilium; 63, ischium; 65, femur; 66, tibia; 67,
fibula ; cl, calcareum ; C, cervical vertebree.—After Owen.

cinnamon and grizzly bears; and the true black bear, Ursus
Americanus Pallas.

The bears are succeeded by the Maustelide, or the otter,
skunk, badger, wolverene, weasel, mink, ermine, etc., nearly
all of which are valuable for their furs.

The dog family (Canide) is represented by the fox, wolf,
and dog. The gray fox (Urocyon Virginianus Erxleben) the
common red fox ( Vulpes vulgaris Fleming), with its varie-
ties, the cross, silver, and black fox, as well as the wolf
(Canis lupus Linn.), are valuable for their furs. The wolf
is mostly gray northward, becoming ‘“‘southward more and
THE SPECIES OF DOGS AND CATS. 617

more blackish and reddish, till in Florida black wolves pre-
dominate, and in Texas red ones.” (Jordan’s Manual of
Vertebrates.) The prairie wolf or coyoté (Canis latrans
Say), is characteristic of the Western plains and Pacific coast.
The Indian dogs breed with the coyoté, and the offspring is
fertile. (Coues.) This fact appears to support the theory
that the domestic dog (with its conventional name Canis
familiaris Linn.) is a descendant of the wolf. On the other
hand, Fitzinger in his ‘‘ Researches on the Origin of the
Dog,” states that fourteen kinds of dogs can be distinguished
in the Roman and Greek records ; of these he considers five
to be principal types or species, five others climatic varieties,
the remainder being either breeds artificially produced or
hybrids. As regards the Egyptian dogs, seven kinds may be
distinguished, besides the jackall, three of them being dis-
tinct species. He believes that wolves, jackalls, foxes, etc.,
are species quite distinct from the domestic dog; they
may have interbred with the latter, and thus influenced cer-
tain breeds ; but they are not the parents of the domestic
dog. He concludes that there are seven species among our
dogs :—C. domesticus, extrarius or spaniel and Newfound-
land dogs, vertagus or badger dog, sagazx or hound, molossus
or bulldog, leporariws or greyhound, and the naked dog,
C. caribeus. Among half-wild dogs is the dingo or hunt-
ing-dog of Australia, which goes in packs.

The Viverra and Genetta or civet cats, and the hyenas
lead to the cat family, which stands at the head of the Car-
nivora. The panther, leopard, tiger, and lion belong to the
genus Felis. The Felis concolor Linn., cougar or puma,
ranges over both continents; it is 1-1-3 metres in length.
The domestic cat, Felis domestica Linn., was first domes-
ticated in Egypt, the Greeks and Romans not possessing
it; the cat and common marten were in use as domesticated
animals side by side; and at the same time in Italy, nine
hundred years before the crusades. It appears that the do-
mestic cat of the ancients was Mustela foina (Rolleston).

Of the lynxes there are two species in North America,
Lynx rufus Rafinesque, the American wildcat, and the
Canada lynx, Lynx Canadensis Rafinesque, the latter being
much the larger species,
618 ZOOLOGY.

Order XII. Primates.—The last and highest order of
mammals contains a series beginning with creatures resem-
bling squirrels and bats, 7. ¢., the lemurs, and comprising
monkeys, apes, and ending with man. In all the Primates,
the legs are exserted almost or quite free from the trunk,
with the great toe of the hind foot usually enlarged and op-
posable to the others ; nails, except in the marmosets, replace
claws ; the teeth are usually of the following formula :

ae 1-1 p3= 3 3-3
veyaree siesrp scree Acre

with one pe cue teeth are always present ; ee pre-.

 

—3
molars are usually 2 a 2 but in the American monkeys © 35

The hemispheres of the brain may in the lower forms be
quite smooth, but in all there is a well-developed ‘‘ calcarine
furrow,” giving rise to a “‘ hippocampus minor” within the
posterior cornu of the ventricle, by which the posterior lobe °
of the cerebrum is traversed (Flower). The collar-bones
(clavicles) are for the first time in the series well developed.
The placenta is also different in shape from that of other
mammals, being round, disk or cake-like.

The Primates are divided into two sub-orders, 2. ¢., the
Prosimie and Anthropoidea. The former group embraces
the lemurs, which vary in size from that of a rabbit to a
large monkey. They are covered, the face as well as the rest
of the body, with a dense fur; walk on all-fours, usually
have long tails, though the lori is tailless, while the fore
limbs are shorter than the hind limbs. The skull is small,
flattened, and narrow in front; the brain-cavity small in
proportion to the rest of the skull, ¢.¢., the face compared
with the monkeys. The cerebral hemispheres are small and
flattened, the frontal lobes narrow and pointed, and behind
they only slightly cover the cerebellum.

By some authors the lemurs are separated from the Pri-
mates, the Insectivora and Cheiroptera being placed between
the Prosimie and the other Primates. They have characters
in which they resemble Jnsectivora, Rodentia, and Carnivora,
but the weight of organization, or the sum of their charac-
ters, ally them nearest to the monkeys. They are therefore
essentially a generalized or ancestral type. Recent discov-
THE PRIMATES. 619

eries have led to the hypothesis, that from still older, more
generalized types, four lines of development, respectively
culminating in the typical Carnivores, Cetaceans, lemurs, and
monkeys, have taken their origin. That the lemurs, though
now restricted to Madagascar, eastern Asia, and South
Africa, were preceded by still more generalized types on the
American Continent, is indicated by the discovery of fossil
bones in the Eocene beds of the Rocky Mountains, referred
by Marsh and Cope to the Primates; Marsh stating that
the principal parts of the skeleton are ‘much as in some of
the lemurs.”

Allied to the true lemurs is a very puzzling creature, the
aye-aye or Chiromys, of Madagascar, whose dentition differs
from that of all other Primates, and resembles that of the
Rodents ; the thamb also is not truly opposable, and all the
hind digits, except the great toes, have claw-like nails. The
Gaiago, of West Africa, somewhat recalls the Insectivora,
while ‘“‘in the more active and flexible-bodied Lemuride,
the trunk-vertebre resemble in proportions, connections, and
direction of neural spines those of the agile Carnivora.”
(Owen.)

The genuine Primates or suborder Anthropoidea are, in
brief, characterized by the large, convoluted cerebral hemi-
spheres which nearly, or in the higher apes and man, conceal
the cerebrum when seen from above.* The ears are rounded,
with a distinct lobule, and the two mamme are pectoral.
These Anthropoidea are divided into two subdivisions, the
first comprising the monkeys and apes, and the second, man.
In the first group (Simic), the body is prone, the animal
walking on all-fours, only the orang and gorilla walking
partly erect; the great toe is rather short, thumb-like, and
opposable to the fingers, while the body is very hairy. The
monkeys of the New World have a wide septum to the nose,
and are hence called Platyrhine ; they also have long tails.

The little, squirrel-like, gregarious marmosets are the small-
est of the monkeys and nearest allied to the lemurs. They
walk on all-fours, the anterior extremities being like the

*In the low Hapale and Cebus, however, the cerebrum projects
backward as far or even farther than in man (Gill).
620 ZOOLOGY.

hind feet, and resting on the same plane, serving as a paw ;
the teeth are sharply tubercled, and the nails, except those of
the great toe, are claw-like. The cerebral hemispheres are
nearly smooth, though relatively large. Jacchus and Midas
are the typical genera, inhabiting South America. While
the marmosets (Midid@) have but thirty-two teeth, in the
true platyrrhine monkeys there are thirty-six teeth ; there
being an additional molar on each side of each jaw, and the
thumb is slightly opposable to the fingers (though a true
thumb is wanting in the spider monkeys). The New World
monkeys also have long prehensile tails, so useful in climb-
ing as to be sometimes called a fifth hand, as seen in the
spider monkeys (Aféeles), in which the tail underneath is
naked and very sensitive. The skull varies greatly in the dif-
ferent genera, as does the brain, which in Chrysothriz, etc.,
is nearly smooth, while in Cebus the hemispheres are nearly
as much convoluted as in the catarrhine apes. (Huxley.)

The monkeys of the Old World intergrade with the apes,
and are thus more specialized or highly developed than
those of the New World. The septum of the nose is narrow,
hence they are said to be catarrhine or thin-nosed, while the
tail is short and not prehensile.

The catarrhine monkeys (Cercopithecide) walk on all-
fours ; the body being horizontal or prone ; they have thirty-
two teeth, as in man, though the canines are large and
sharp; the thumb is well developed, and they are truly
quadrumanous; the skull has a comparatively large facial
angle, and the hemispheres of the brain are well furrowed.
They have highly-colored, naked callosities over the ischiatic
bones, and cheek-pouches for the temporary reception of
the food. Of the baboons, with their dog-like muzzles and
short tails, the mandrills are the most noticeable, with their
white beards, scarlet lips, and blue cheeks; they are less
arboreal than the macaques of Asia, running about over
rocks on all-fours. The common monkeys of menageries
are the macaques (Macacus) of India. All the foregoing
catarrhine monkeys have a simple stomach, as in man, but
in the sacred monkey of India (Semnopithecus) and the
African thumbless Colobus, the stomach is more complex,
and there are no cheek pouches.
THE MONKEYS AND APES. 621

The apes live in trees, only occasionally walking on the
ground ; their posture is semi-erect ; they are tailless, the
fore legs are much longer than the hind legs, and used as

arms, the radius being ca-
pable of complete prona-
tion and supination. In
the form of the skull, of
the brain with its convolu-
tions, and in the teeth,
there is a still nearer ap-
proach to man.

There are three typical
forms or genera of apes,
1.e., the gibbon (Hylobates,
Fig. 536); the orang (J/i-
metes pithecus) and chim-
panzee (M. niger, Fig.
537), and the gorilla. The
gibbons are nearest to the
monkeys; they are little
less than a metre (3 feet)
in height, and are very
slender, with very long
arms, so that they are rapid,
agile climbers, also run-
ning over the ground with
ease and rapidity; when
standing erect the fingers
touch the ground; only
the thumbs and great toes
have true nails, in all the
higher apes the nails of all
the digits being flattened ;
the spinal column is nearly
straight; they have four-
teen pairs of ribs and
eighteen dorso-lumbar ver-

 

Fig. 536.—Skeleton of Siamang Ape, a gib-
bon.—After Owen. Pee

tebre, there being in the other apes usually seventeen, as in
man. The siamang lives in the forest of Sumatra; others
inhabit Java, Borneo, Cambogia, etc.
622 ZOOLOGY.

The orang-outang is 1-38 metres (44-5 feet) high ; it has
twelve pairs of ribs, the same number as im man ; the arms
are very long, reaching the ground, so that in walking they
rest on their knuckles, swinging the body through their long
arms as if walking on crutches; their posture is only par-
tially erect. The forehead is less strongly marked than in

/

Wii j/7,

 

Fig. 537.—The Chimpanzee, variety Tshego.—From Brehin’s Thierleben.

the other apes, showing better the shape of the skull. The
volume of the brain, both of the orang and chimpanzee is
about twenty-six or twenty-seven cubic inches. The follow-
ing table will show, according to Wyman, the relative
capacity of the skull in the different apes as compared with
man :
CHIMPANZEE AND GORILLA. 623

The ayes age pepe of the Caucasian skull is 92 cubic inches.

ce Australian ‘“ %5 oe
‘ec ce 6c Gorilla Be 29 to near 35
cubic inches.
‘« “ «© Chimpanzee ‘“ 26 rf
PG 6c ““ Orang So 2 ao

According to Wyman, the range of variation in different
races of men, as seen in seventeen skulls, is from 92 to 75
cubic inches ; in the gorilla from 34 to 25 cubic inches, nine
skulls having been measured. There is but a single species
of orang, which is restricted to Sumatra and Borneo. It is
said to be very intelligent, to possess a voice so loud as to be
heard one or two miles, and to build a nest to sleep in.

The chimpanzee and gorilla are only found on the west
coast of Africa. The chimpanzee (Mimetes niger Geoffroy
with its variety Tschego, Fig. 537) inhabits the coast from
Sierra Leone to Congo. It is about 14 metres (5 feet) in
height. It can stand or run erect, but it usually leans for-
ward, resting on its knuckles ; the arms span about half as
much again as the creature’s height. Both the chimpanzee
and gorilla have fourteen pairs of ribs. The chimpanzee lives
on fruit, is an active climber, and nests in trees, changing its
rude quarters according to circumstances. Rev. Dr. Savage
states that ‘they generally build not far above the ground.
Branches or twigs are bent, or partly broken, and crossed,
and the whole supported by the body of a limb or a crotch.
Sometimes a nest will be found near the end of a strong
leafy branch twenty or thirty feet from the ground.”

The gorilla, like the chimpanzee, goes in bands, but the
company is smaller, and led by a single adult male. They
make similar nests, which, however, in the case of both apes,
afford no shelter, and are only occupied at night. The
gorilla sometimes reaches the height of about 1} metres (53
feet) and weighs about 200 pounds. Its ordinary attitude is
like that of fii chimpanzee ; there is a web between the first
joints of all the fingers and three of the toes, and both hands
and feet are broader, while the body is much more robust
than in the other apes, being very broad across the shoulders.
The span of the arms is to the height as three to two, or a
little over eight feet. The skull is thick, and the strength
624 ZOOLOGY.

and ferocity of the creature is evinced by the thick supra-
orbital ridges and the high sagittal and lambdoidal crests on
the top of the skull; the face is wide and long, the nose
broad and flat, the lips and chin prominent. The gorilla
walks like the chimpanzee, though it stoops less. It is very
ferocious, bold, never running when approached or attacked
by man. It lives on a range of mountains in the interior of
Guinea, its habitat, so far as known, extending from a little
north of the Gaboon River to the Congo.

Thus, to recapitulate, while the gibbons are most remote
from man, the orangs approach him nearest in the number
of the ribs, the form of the cerebral hemispheres, and other
less obvious characters ; the chimpanzee is nearest related to
him in the form of the skull, the dentition and the propor-
tions of the arms, while the gorilla resembles him more in
the proportions of the leg to the body, of the foot to the
hand, in the size of the heel, the curvature of the spine, the
form of the pelvis and the absolute capacity of the skull
(Huxley). Anatomists have and do differ as to whether the
chimpanzee or the gorilla is nearest to man.

Whether man (Homo sapiens Linn.), when considered
simply as an animal, is the representative of a distinct sub-
class, order, suborder or family, is and may never be settled ;
though the tendency among zoologists is to leave him among
the Primates, where he was placed by Linneus. When we
consider the slight absolute anatomical differences separating
man from the apes, and take into account the great variations
in form between the different genera of apes, and still more
in the monkeys, it seems best, throwing out, as we have to
do ina purely zoological classification, the intellectual and
moral faculties of man, to adopt the view that man is
the representative of a group of Primates.* The absolute
differences of man from the apes consist in the greater num-
ber and irregularity of the convolutions of the cerebral hemi-

* Geoffroy St. Hilaire placed man in a kingdom by himself ; Owen
assigned him to a subclass ; by others he is generally regarded as a
representative of an order Bimana, as opposed to the order Quadru-
mana, or monkeys and apes; while from recent comparative studies
man is considered as belonging either to a separate suborder or a fam-
ily.
DIFFERENCES OF MAN FROM THE APES 625

spheres, which are also much larger compared with the cere-
bellum, and completely cover the latter; the entire brain
being at least double the size proportionately of that of the
gorilla ;* it is also stated that two muscles exist in man
which have not yet been found in any ape, the extensor primi
tnternodit pollicis and the peroneus tertius, belonging to the
thumb and foot respectively (Huxley).+ There are also points
in the origin of certain muscles which are peculiar to man, but
Huxley adds that all the apparently distinctive peculiarities
of the muscles of the apes are to be met with, occasionally,
as varieties in man. On the other hand, the relative differ-
ences of the skulls of the gorilla and man are, as Huxley
states, ‘‘immense.” In man the cranial box overhangs the
orbits ; in the gorilla the forehead is hollowed out. The
hinder portion of the brain is also much more developed in
man than in the apes, and in the hinder part of the hemi-
spheres the convolutions are more numerous than in the
chimpanzee, this part in monkeys losing its convolutions
altogether (Wyman). Man stands erect; his arms span a
distance equal to his height; the spinal column has four
curves; the skin of the hands and feet of man is highly
sensitive, compared with that of the apes. Finally, as Cuvier
stated, the grand distinctive zoological character separating
man from the other animals is the possession of the power of
speech.

Sometimes in man the coccyx has one or two more joints
than the normal number, but the apes have no tail; though
the human embyro, like other young animals, has a tail,

* «Tt must not be overlooked, however, that there is a very striking
difference in absolute mass and weight between the lowest human
brain and that of the highest ape—a difference which is all the more
remarkable when we recollect that a full-grown gorilla is probably
pretty nearly twice as heavy as a Bosjes man, or as many an European
woman. It may be doubted whether a healthy human brain ever
weighed less than thirty-one or two ounces, or that the heaviest gorilla
brain has exceeded twenty ounces.” In another place Huxley states
that “an average European child of four year’s old has a brain twice
as large as that of an adult gorilla.”—Man’s Place in Nature.

+ Dr. Chapman has found in the arm of a gorilla a distinct extensor
primi internodit pollicis muscle, but no trace of the flexor longus polli-
cis.— American Naturalist, June, 1879, p. 395.
626 ZOOLOGY.

and, as Wyman has observed, it is not impossible that it
might sometimes continue to exist after birth. The black
and Australian races are slightly nearer the apes than civil-
ized peoples. In apes, as in the lower mammals, the pelvis
1s higher than wide ; when there is a degradation in the hu-
man pelvis it tends to become higher than wide, as seen in
the pelvis of the Hottentots. In civilized man the legs are
one half the height of the body, but in the South African,
Hottentot, and Bushmen the legs are a little less than half
the height, and the thigh bone is flattened from side to side,
as in the gorilla. The waist is broader in the African than
in the European ; the os calcts is not longer in negroes than
in the white man, the larger heel of the former being simply
due to an expansion of the
soft parts.

The form of the skull va-
ries greatly in the different
races, and even in individ-
uals of the same race of
vy. mankind. This is seen in
spi ‘» the difference of the facial

Fig. 588._Skull of a Negro, showing its a7gle. This is obtained by
Bree = nen Sey: drawing a line from the
occipital condyle along the floor of the nostrils, and inter-
secting it by a second, touching the most prominent parts
of the forehead and upper jaw; the angle they make is
an index of the cranial capacity, and of the degree of in-
telligence of the individual. The facial angle in the reptiles
is very slight, as it is in the birds ; in the dog it is 20°, in the
gorilla 40°, in the Australian 85°, in the civilized Caucasian
it averages 95°, while the Greek sculptors adopted an ideal
angle of 100°. (Owen.*) When the lower part of the face
protrudes, as in the negro, the face is said to be prognathous
(Fig. 538) ; where the facial angle is high, and the face
straight, as in the more intellectual forms, the cranium is

 

* Pagenstecher states that the facial angle in the Caucasian Euro-
pean is 80°-85°, and even over 90°; in the Mongolians 75°-80° ; in
negroes 70°-75°; in the tribe of Makoias in South Africa 64°; in the
tribe of Tikki-Tikki, or Akka negroes, the dwarfs described by
Schweinfurth, only 60°.—Allgemeine Zoologie, i., p. 250.
THE VARIETIES OF MAN. 627

said to be orthognathous. ‘Those skulls which are high and
narrow, t.é., with the longer diameter to the shorter, as 100
to 65, are said to be dolichocephalic, while those with the
diameters as 100 to 85 are called brachycephalic, but these dis-
tinctions have been found to be quite arbitrary.

The classification of the human races is in as an unsatis-
factory state as that of the domestic animals. Naturalists
are now agreed that there is but one species of man. Blu-
menbach, from the shape of the skull and the color of the
skin, divided mankind into three varieties, the white or Cau-
casian, the brown or Mongolian, and the black or Ethiopian,
considering the American variety as connecting the Caucasian
and Mongolian, and the Malayan as intermediate between
the Caucasian and Ethiopian. Hamilton Smith divided
man into three varieties, Caucasian, Mongolian, and Tropi-
cal; Latham, also, into three, Japetide, Mongolide, and
Atlantide ; and Pickering into white, brown, and black
varieties, with intermediate races. Huxley divides the dif-
ferent races into two primary groups, the Ulotricht, with
crisp or woolly hair, and the Letotricht with smooth hair.

The average height of Englishmen is 5-8-5-10 feet; in
the universities more. In America, the average height of
medical and military men is 5-93 feet. The Patagonian men
are nearly six feet high on an average; the women 5-10 feet;
the Bushman and Esquimaux 4-7, the latter being the small-
est people on the earth. The smallest dwarfs in Europe
were 33 and 28 inches in height respectively ; while Pat-
rick Cotter, the Irish giant, was 8 feet 7 inches tall.

It is claimed by some naturalists that man has descended
from some generalized type of animal which gave rise to
several series of forms culminating in the monkeys, apes,
and man respectively, and by others that he is a direct
descendant of forms like the chimpanzee or gorilla; but
it is probable that from the want of sufficient data,
the question as to the origin of man can never be def-
initely settled: Setting hypothesis aside, in ascending
the mammalian series, we have seen in the forms lead-
ing from the extinct Eocene generalized types of Hd-
ucabilia to the Carnivora and Primates, a tendency to
an extreme specialization of those parts ministering to the
628 ZOOLOGY.

intellectual behests of the creature. On the other hand, in
all general points, man’s limbs are those of the primitive
type so common in the Eocene Period. As Cope remarks :
“He is plantigrade, has five toes, separate carpals and tar-.
sals; a short heel, rather flat astragalus, and neither hoofs
nor claws, but something between the two. The bones of
the fore arm and leg are not so unequal as in the higher
types ; and remain entirely distinct from each other, and the
ankle joint is not so perfect as in many of them. In his
teeth his character is thoroughly primitive. He possesses, in
fact, the original quadrituberculate molar with but little
modification. His structural superiority consists solely in
the complexity and size of his brain.”

Whether man in common with other animals is the result
of divinely ordered processes of biological laws, appearing at
the head of a long series of forms, and, as probably many
other animals have, with comparative suddenness, being at
the outset in all essential respects man, though a savage, and
not with a long pedigree of morphologically impossible Dar-
Winian ‘‘ missing links,”—whether he thus originated, or by
an independent creative act, the result is a being concerning
whom the fact that he is physically an animal, is after all the
least important characteristic of the nature of him who is
the historian of his own and other species; who is capable
of studying and in a degree comprehending the universe in
which he lives, and who whatever his physical origin may
have been, has intellectual, moral, and spiritual capabilities
which render his nature susceptible of endless improvement,
endowing him with immortality and all that it involves.

Cuass VII.—MammMaL.ta.

Body covered with hair ; young nourished with milk secreted in mam-
me ; lower jaw articulating directly with the skull, the quadrate bone be-
coming one of the ear-bones (malleus) ; a diaphragm dividing the body-
cavity into thoracic and abdominal portions ; heart with the aorta reflect-
ed over the left bronchus ; blood-corpuscles non-nucleated ; brain large,
especially the cerebral hemispheres ; viviparous ; uterine gestation.
Subclass I. Ornithodelphia.—Order Monotremata.—Urinary and gen-

ital outlets opening into the cloaca. (Echidna, Ornitho-
rhynchus.)
CLASSIFICATION OF MAMMALS. 629

Subclass II. Didelphia.—Order Marsupialia—Mammals with a mar-
supium and bones supporting it. (Macropus, Didelphys.)

Subclase III. Monodephia.—Placental mammals.

Super-order I. Ineducabilia.—Brain with a relatively small,
smooth cerebrum,

Order 1. Bruta.—Incisors absent; sometimes toothless.
(Bradypus.)

Order 2. Gires.—Rodents, incisors large. (Sciurus.)

Order 3. Insectivora.—Fore limbs often peculiarly adapted
for burrowing ; molars with conical cusps. (Scalops.)

Order 4. Chiroptera.—Fore limbs adapted for flight. (Ves-
pertilio.)

Super-order IT, Hducabilia.—Brain with a relatively large, con-
voluted cerebrum.

Order 5. Cete.—Cetaceans; fish-like in form, no hind
limbs. (Balzena.)

Order 6. Sirenia.—Fish-like in form, but with ascending
rami to the lower jaw; teeth ruminant-like. (Mana-
tus.)

Order 7. Proboscidea.—Snout prolonged into a proboscis.
(Elephas.)

Order 8. Hyracoidea.—Long curved incisors; feet with
pads; toes encased in hoofs. (Hyrax.)

Order 9. Toxodontiw.—Extinct forms, with well developed
incisors. (Toxodon.)

Order 10. Ungulata.—Ungulates ; toes encased in hoofs.
(Equus, Bos.)

Order 11. Carnivora.—Teeth pointed; claws large. (Felis,
Canis.)

Order 12. Primates.—Brain with cerebrum nearly or quite
covering the cerebellum ; nails usually present; body
quadrupedal, quadrumanous, or erect and bimanous.
(Cebus, Gorilla, Homo.)

Laboratory Work.—All the craniate vertebrates may be dissected in
the same general manner, either under water in pans, or, if large, upon
the dissecting table. The necessary tools are a scalpel, forceps, scis-
sors, and tenaculum or hook for suspending the specimens or portions
630 ZOOLOG ¥.

of large subjects for better facility in dissecting. A small sharp-
pointed narrow-bladed scalpel, besides a large one, curved, as well as
sharp-pointed scissors are useful, with a German silver blow-pipe
for temporarily distending vessels; and also a blunt-pointed copper
wire or probe made for surgeon’s use, will be necessary. All these in-
struments, put up in a compact box, can be purchased at the surgical
instrument maker’s, as well as syringes for injecting the circulatory
organs and vascular parts of the viscera.

TABULAR VIEW OF THE SEVEN CLASSES OF VERTEBRATES.

— VII. Mammatra.—Mammals.

(ea AVEs.—Birds.
-——V. Reptitia.—Snakes, lizards, etc.

=a BaTracuia.—Salamanders, frogs, etc.

TL, Pisces — Fishes

TI. MARSIPOBRANCHII.—Lampreys.

 

 

SuB-BRANCH II].—CRANIOTA

Sup-Brancu I.—ACRANIA, I, Leprocarpr (Lancelet).
CHAPTER IX.
COMPARATIVE ANATOMY OF ORGANS.

Havine studied the morphology of animals in a system-
atic way, it will be well for the student to make a brief re-
view of those facts stated in the foregoing chapters bearing
on the origin and successive degrees of complication of the
most important organs.

Organs of Digestion—The Mouth and Teeth.—The most
important organs in the animal system are these relating to
digestion, as an animal may respire solely through its body-
walls, or do without a circulatory or nervous system, but
must eat in order to live and grow. The opening by which
the food is taken into the alimentary canal is called the
mouth, whether reference is made to the ‘‘mouth’’ of a
hydra or of a vertebrate ; although the structure of the edges
may differ radically, still in all Metazoa the mouth is due to
an inpushing of the ectoderm, however differently the
edge of the mouth may be supported and elaborated. The
edges of the mouth are usually called the lips, but true lips
for the first time appear in the Mammalia. The trituration
or mastication of the food is accomplished among the in-
vertebrates in a variety of ways, and by organs not always
truly homologous.

Hard bodies serving as teeth occur for the first time in the
animal series in the sea-urchins, where a definite set of cal-
careous dental processes or teeth (Figs. 78 and 79), with solid
supports and a complicated muscular apparatus, serves for
the comminution of the food, which consists of decaying an-
imals and sea-weeds. In those Echinoderms which do not
have asolid framework of teeth, the food consists of minute
forms of life, protozoans and higher soft-bodied animals,
632 ZOOLOGY.

or the free-moving young of higher animals, which are
carried into the mouth in currents of water or swallowed
bodily with sand or mud.

Among the worms true organs of mastication for the first
time appear in the Rotatoria (Fig. 122), where the food, such
as infusoria, etc., is crushed and is partly comminuted by
the well-marked horny or chitinous pieces attached to the
mastax. In most other low worms the mouth is unarmed.
In the leeches there are three, usually in the annelids two,
denticulated or serrate, chitinous flattened bodies situated
in the extensible pharynx of these worms, and suited for
seizing and crushing their prey.

In the higher mollusks, such as the snails (Cephalophora)
and cuttles, besides broad thin pharyngeal teeth, compara-
ble with those mentioned as existing in the worms, is the lin-
gual ribbon already described (p. 276, Fig. 215), and admira-
bly adapted for sawing or slicing sea-weeds and cutting
and boring into hard shells, acting somewhat like a lapi-
dary’s wheel ; this organ, however, is limited in its action,
and in the cuttles the jaws, which are like a parrot’s beak,
do the work of tearing and biting the animals serving as
food, which are seized and held in place by the suckered
arms.

In the crustaceans and insects we have an approach to
true jaws, but here they work laterally, not up and down or
vertically, as in the vertebrate jaws ; the mandibles of these
animals are modified feet, and the teeth on their edges are
simply irregularities or sharp processes adapting the mandi-
bles for tearing and comminuting the food. It is generally
stated that the numerous teeth lining the crop of crustacea
and insects (Fig. 282) serve to further comminute the food
after being partially crushed by the mandibles, but it is now
supposed that these numerous points act collectively as a
strainer to keep the larger particles of food from passing
into the chyle-stomach.

The king-crab burrows in the mud for worms (Nereids,
etc.) ; these may be found almost entire in the intestine,
having only been torn here and there and partly crushed by
the spines of the base of the foot-jaws, which thus serve the
COMPARATIVE ANATOMY OF ORGANS. 633

purpose effected by the serrated edges of the mandibles of
the genuine Crustacea and insects.

Among vertebrates, the lancelet is no better off than the
majority of the Celenterates and worms, having no solid
parts for mastication ; and we have seen that the jaws and
teeth of the hag-fish and even the lamprey eel form a very
different apparatus from the jaws and its skeleton in the
higher vertebrates ; and that, even in the latter, the bony
elements differ essentially in form in the different classes,
though originating in the same manner in embryonic life.
In the birds we have seen that the mandible and maxilla are
encased in horny plates, that true teeth are remarkably ex-
ceptionable, the gizzard being, however, provided with two
hard grinding surfaces ; on the other hand, mammals with-
out teeth are exceptionable.

The teeth of fishes are developed, not only in the jaws,
but on the different bones projecting from the sides and
roof of the mouth, and extend into the throat. In many
cases, in the bony fishes, these sharp recurved teeth serve to
prevent the prey, such as smaller fish, from slipping out of
the mouth. On the other hand, the upper and lower sides
of the mouth of certain rays (Myliobatis) are like the solid
pavement of a street, and act as an upper and nether mill-
stone to crush solid shells.

In the toothless ant-eaters the food consists of insects,
which are swallowed without being crushed in the mouth ;
true teeth in the duckbill are wanting, their place being
taken by the horny processes of the jaws, while in Steller’s
manatee the toothless jaws are provided with horny solid
plates for crushing the leaves of aquatic succulent plants.
Examples of the most highly differentiated teeth in verte-
brates are seen in those animals, like the bear, whose food is
omnivorous, consisting of flesh, insects, and berries, where
the crown of the molars are tuberculate; while the canines are
adapted for holding the prey firmly as well as for tearing the
flesh, and the incisors, for both cutting and tearing the food.

The simplest form of a genuine digestive or enteric canal
is to be found in the Hydra, and in a more advanced stage
in the marine Hydroids. For the technical name of the
634 ZOOLOGY.

digestive tract we may adopt Haeckel’s term enteron. In
the jelly-fishes the stomach opens into four or more water-
vascular canals or passages, by which the food, when par-
tially digested and mixed with sea-water, thus forming a
rude sort of blood, supplies the tissues with nourishment.
In the sea-anemones and coral polyps, the digestive cavity is
still more specialized, and its walls are partly separated from
the walls of the body, though at the posterior end the
stomach opens directly into the body-cavity. In the Echi-
noderms and worms do we find for the first time a genuine
digestive tube, lying in the perivisceral space (which, with
Haeckel, we may call the celwm), and opening externally
for the rejection of waste matter.

In the worms the digestive canal now becomes separated
into a mouth, an csophagus, with salivary glands opening
into the mouth, and there is a division of the digestive tract
into three regions—i.e., fure (esophagus), middle (chyle-
stomach), and hind (intestine) enteron. In the mollusks
and higher worms there is a well-marked sac-like stomach
and an intestine,with a liver, present in certain worms (in
the ascidians and mollusks), opening into the beginning of
the intestine. All these divisions of the digestive tract ex-
ist still more clearly in the crustacea and most insects. In
the latter, six or more excretory tubes (Malpighian vessels)
discharge their contents into the intestines, and in the “‘ res-
piratory tree ’’ of the Holothurian and the excretory vessels
of certain worms we have organs with probably similar uses.

In the vertebrates, from the lancelet to man, the alimen-
tary canal has, without exception, the three divisions of ces-
ophagus, stomach, and intestine, with a liver. In this branch
the lungs are either, as in the lancelet, modified parts of
the first division of the digestive tract or originally sac-like
dilatations of the digestive tract. The intestine is also
subdivided in the mammals into the small and large intestine
and rectum, a cecum being situated at the limits between
the small and large intestine. We thus observe a gradual
advance in the degree of specialization of the digestive or-
gans corresponding to the degree of complication of the an-
imal.
COMPARATIVE ANATOMY OF ORGANS. 635

Organs of Circulation.—Intimately associated with the
digestive canal are the vessels in which the products of di-
gestion mix with the blood and supply nourishment for the
tissues, or, in other words, for the growth of the body. In
the Infusoria the evident use of the contractile vesicles is to
aid in the diffusion of the partly digested food of these mi-
croscopic forms. In the Hydra the food-stuff is directly
taken up by the cells lining the ceelum, while the imper-
fectly formed blood also finds access to the hollows of the
tentacles. ‘The mode in which the cells lining the canals
in the sponge take up, by means of the large cilia, micro-
scopic particles of food, directly absorbing them in their
substance, is an interesting example of the mode of nourish-
ment of cellular tissues of the lower animals.

The sea-anemone presents a step in advance in organs of
circulation ; here the partly digested food escapes through
the open end of the stomach into the perivisceral chambers
formed by the numerous septa, the contractions of the body
churning the blood, consisting of sea-water and the particles
of digested food, and a few blood-corpuscles, hither and
thither, and forcing it into every interstice of the body,
even into the tentacles, so that the tissues are everywhere
supplied with food.

The water-vascular system of the Ceelenterates presents an
additional step in degree of complexity; but it is not until
we reach the Echinoderms on the one hand, and such
worms as the Nemertes and allies on the other, where defi-
nite tubes or canals, the larger ones contractile, and in the
latter type at least formed from the mesoderm, serve to
convey a true blood to the various parts of the body, that
we have a definite blood system. In the Echinoderms a
true hemal or vascular system may co-exist with the water-
vascular system. In the annelids, such as the Nereis, one
of the blood-vessels may be modified to form a pulsating
tube or ‘‘ heart,’’ by which the blood is directly forced out-
ward to the periphery of the body through vessels which may,
by courtesy, be called arteries, while the blood returns to
the ‘‘ heart ’’ by so-called veins.

The mollusks have a circulatory system which presents a
636 ZOOLOGY.

nearer approach to the vertebrate heart and its vessels than
even the crustaceans and insects, for the ventricle and one or
two auricles, with the complicated arterial and venous sys-
tem of vessels of the clam, snail, and cuttle-fish, truly fore-
shadow the genuine heart and systemic and pulmonary cir-
culation of the vertebrates. The mollusks, and king-crab,
and the lobster present some approach to the capillaries of
vertebrates. The circulation in certain worms, from Ne-
mertes upward, may be said to be closed, the vessels being
continuous ; but they are not so in insects, where true veins
are not to be found, the blood returning to the heart in
channels or Jacwne in the spaces between the muscles and
viscera.

We have seen that in vertebrates the ‘‘ aortic heart ’’ of
the lancelet or Amphiowus is simply a pulsating tube, and
there are portions of other vessels which are pulsatile, so
that there is, in some worms, a system of ‘‘ hearts.’’ A gen-
uine heart, consisting of an auricle and a ventricle only, first
appears in the lamprey. This condition of things survives
in fishes, with the exception of those forms, such as the lung-
fish (Dipnoans), whose heart anticipates in structure that of
the amphibians and reptiles, in which a second auricle ap-
pears. Again, certain reptiles, such as the crocodiles, antici-
pate the birds and mammals in having two ventricles—1.e.,
a four-chambered heart. It should be borne in mind that
in early life the heart of all skulled vertebrates (Craniota)
is a simple tube, and as Gegenbaur states, ‘‘ as it gradually
gets longer than the space set apart for it, it is arranged in
an 8-shaped loop, and so takes on the form which the heart
has later on.’’? Owing to this change of form, it is divided
into two parts, the auricle and ventricle.

A striking feature first encountered in the craniate ver-
tebrates is the presence of a set of vessels conveying the
nutrient fluid or chyle which filters through the walls of
the digestive canal to the blood-vessels ; these are the lym-
phatics. In the lancelet, as well as in the invertebrate ani-
mals, such vessels do not occur, but the chyle oozes through
the stomach-walls and directly mixes with the blood.
COMPARATIVE ANATOMY OF ORGANS. 637

Organs of Respiration.—Always in intimate relation with
the circulatory system are the means of respiration. The
process may be carried on all over the body in the simple
animals, such as Protozoa or sponges, or, as in Celenterates,
it may be carried on in the water-vascular tubes of those
animals, while in the so-called ‘‘ respiratory tree”? of Echin-
oderms it may go on in company with the performance of
other functions by the same vessels. Respiration, however,
is inclined to be more active in such finely subdivided parts
of the body as the tentacles of polyps, of worms, or any
filamentous subdivisions of any of the invertebrates ; these
parts, usually called gills, though only the gills of fishes are
traly such, present in the aggregate a broad respiratory sur-
face. Into the hollows of these filamentous processes,
which are usually extensions of the body-walls, blood is
driven through vessels, and the oxygen in the water bathing
the gills filters through the integument, and immediately
gains access to and mixes with the blood.

The gills of the lower animals appear at first sight as if
distributed over the body in a wanton manner, appearing
in some species on the head, in others along the sides of the
body, or in others on the tail alone ; but in fact they always
arise in such situations as are best adapted to the mode of
life of the creature.

The gills of many of the lower animals afford an admira-
ble instance of the economy of nature. The tentacles of
polyps, polyzoans, brachiopods, and many true worms serve
also, as delicate tactile organs, for grasping and conveying
food to the mouth, and often for locomotion. The suckers
or ‘‘feet’’ of star-fish or sea-urchins also without doubt
perform the office of gills, for the luxuriously branched,
beautifully-colored tentacles of the sea-cucumber are simply
modifications of the ambulacral feet. One of the readiest
ways of judging of the mental condition, so to speak, of a
worm, such as Sabella or Terebrella or of a polyzoon or a
brachiopod, is to watch the movements of their beautiful
delicate gills, which are thrust in or out, waved back and
forth, slowly or suddenly, according to the degree of tran-
quillity or disquietude of their possessors.
638 ZOOLOGY.

In the mollusks, especially the snails and cuttle-fish, the
gills are in close relations with the heart, so that in the ecut-
tle-fish the auricles are called ‘‘ branchial hearts.’? The
gills of crustaceans (Fig. 259) are attached either to the
thoracic legs or are modified abdominal feet, being broad,
thin, leaf-like processes, into which the blood is forced by
the contractions of the tubular heart. Respiration in the
insects goes on all over the interior of the body, the tracheal
tubes distributing the air so that the blood becomes oxyge-
nated in every part of the body, including the ends of all the
appendages. The gills of aquatic insects are in all cases fila-
mentous or leaf-like expansions of the skin permeated by
trachee (Fig. 326) ; they are, therefore, not strictly homolo-
gous with the gills of crustaceans or of worms.

The gills of fishes are so situated as to be constantly
bathed by fresh water ; in the amphibians and lung-fishes,
lungs, which are outgrowths of the enteric canal, replace the
air-sacs of the fishes, the air being now swallowed by the
mouth and gaining access by a special duct, the larynx, to
highly specialized organs of respiration, the lungs, which
are situated in the thoracic cavity near the heart.

The Nervous System.—We have seen that animals of com-
paratively complicated structure perform their work in the
animal economy without any nervous system whatever. It
has been only recently discovered that in a few jelly-fish is
there, for the first time in the animal series, a consecutive
nervous system, with definite nerve-centres or ganglia. In
most Acalephs none has been found, so that the majority
of Ccelenterates perform their complicated movements,
swimming about for food, taking it in, digesting it, and re-
producing their kind, without the aid of what seems, when
we study vertebrates alone, as the most important and
fundamental system of organs in the body.

The Protozoa, sponges, and most Celenterates depend, for
the power of motion, on the contractility of the protoplasm
of the body, whether or not separated into muscular tissue.
In the Hydra for the first time appear the traces of a ner-
vous tissue in the so-called nervo-muscular cells, one por-
COMPARATIVE ANATOMY OF ORGANS. 639

tion of a cell being muscular, the other nervous in its func-
tions.

A more definite nervous organization is the disconnected
bodies and rod-like nerve-cells, and other nervous bodies
found near the eye-spots, and the nerve-cells and fibres at
the base of the sea-anemone ; but, as has been stated, a gen-
uine nervous system for the first time appears in certain
naked-eyed jelly-fishes, in which it is circular, sharing the
radiated disposition of parts in these animals. The Echin-
oderms have a well-developed nervous system, consisting of
a ring (without, however, definite ganglia, though masses of
ganglionic cells are situated in the larger nerves), surround-
ing the esophagus, and sending a nerve into each arm ; or in
the Holothurians situated under the longitudinal musclés
radiating from that muscle closing the mouth.

In all other invertebrate animals, from the worms and
mollusca to the crustaceans and insects, the nervous system
is fundamentally built upon the same plan. There is a pair
of ganglia above the cesophagus called the “ brain ;”’ on the
under side is usually asecond pair ; the four, with the nerves
or commissures connecting them, forming a ring. This ar-
rangement of ganglia, often called the ‘‘ esophageal ring,”
constitutes, with the slender nerve-threads leading away from
them, the nervous system of the lower worms, in many of
which, however, as also in the Polyzoa and Brachiopoda,
the subeesophageal ganglia are wanting. Now to the
csophageal ring with its two pairs of ganglia add a third
pair of visceral ganglia, and we have the nervous system
of the clam and many mollusks. In the higher ringed
worms, the Annulata, and in the Crustacea and Insects, a
chain of ganglia, or brains, which is ventral, lying on the
floor of the celum or body-cayvity, completes the highest
form of nerve-centre found in the invertebrate animals,
unless we except the mass of ganglia, partly enclosed in an
imperfect cartilaginous capsule of the Cephalopods, which
hints at the brain and skull of Vertebrates. The nervous
cord of the Appendicularia, an Ascidian, is constructed on
the same plan as in the Annulata, but the mode of origin and
apparently dorsal position of the nervous system of the
640 ZOOLOGY.

tailed larval Ascidian presents features which apparently
anticipate the state of things existing among the lower ver-
tebrates, such as the lancelet.

In the last-named animal the nervous cord has a dorsal
position—z.e., rests above the alimentary canal; but as yet
no brain appears, only a very slight enlargement of the an-
terior end of the nervous cord from which a few nervous
threads are distributed to minute sense-organs in the head.
In all the craniate Vertebrates, from the lamprey upward,
the brain is a series of close-set ganglia, having a definite
site, enclosed by a skull or brain-box, and with definite re-
lations to the sense-organs. Attention has already been
given in a general way, in the foregoing pages, to the increcas-
ing complexity of the brain, especially to the relative size
and markings of the cerebral hemispheres and cerebellum,
as we rise from the fish to man.

Organs of Sense.—While all animals, perhaps without
exception, unless it be the root-barnacles, and a few other
parasitic forms, have the sense of touch, which, in the lower
Protozoa is so slight as to be compared with the contractility
common to all living protoplasmic matter, whether existing
in cellular tissue or one-celled, independent animals ; not all
of the lower animals have, however, definite sense-organs.

The Eye.—The most important of these are undoubtedly
eyes, as they are the most commonly met with. The sim-
plest form of eyes are perhaps those of the sea-anemone, in
which there are, besides pigment cells forming a colored
mass, refractive bodies which may break up the rays of light
impinging on the pigment spot, so that these creatures may
be able to distinguish light from darkness. The next step
in advance is where a pigment mass covers a series of refract-
ive cells called ‘‘ crystalline rods’? or “‘ crystalline cones,”
which are situated at the end of a nerve proceeding from
the ‘‘ brain.’ Such simple eyes as these, often called ‘‘ eye-
spots,’? may be observed in the flat worms, and they form
the temporary eyes of many larval worms, Echinoderms
and mollusks. In some nemertean worms, such as certain
species of Polia and Nemertes, true eyes appear, but in the
ringed worm, Neophanta celox, Greef describes a remarka-
COMPARATIVE ANATOMY OF ORGANS. 641

bly perfect eye, consisting of a projecting spherical lens
covered by the skin, behind which is a vitreous body, a
layer of pigment separating a layer of rods from the exter-
nal part of the retina, outside of which is the expansion of
the optic nerve. Eyes are also situated on the end of the
body in some worms, and in a worm called Polyophthalmus
each segment of the body bears a pair of eyes.

The eyes of mollusks are, as a rule, highly organized, un-
til in the cuttle-fish the eye becomes nearly as highly de-
veloped as in fishes, but still the eye of the cuttle-fish is not
homologous with that of Vertebrates, since in the former
the crystalline rods are turned toward the opening of the
eye, while in Vertebrates they are turned away from the
opening of the eye, so that, as Huxley as well as Gegen-
baur show, the resemblance between the eye of the Ce-
phalopods and of the Vertebrates is a superficial one.

While, as we have seen, the eyes of the worms and the
mollusks are situated arbitrarily, by no means invariably
placed in the head, in the Crustaceans the eyes assume in
general a definite position in the head, except in a schizo-
pod crustacean (Huphausia), where there are eye-like organs
on the thorax and abdomen. In insects there are both sim-
ple and compound eyes occupying definitely the upper and
front part of the head.

The eyes of the lancelet are not homologous with those
of the higher Vertebrates, being only minute pigment spots
comparable with those of the worms. In the skulled Ver-
tebrates the eyes are of a definite number, and in all the
types occupy a definite position in the head.

The Ear.—The simplest kind of auditory organ is to be
found in jelly-fishes, where an organ of hearing first occurs.
In these animals, situated on the edge of the disk, are minute
vesicles containing one or more concretionary bodies or
crystals. Reasoning by exclusion, these are supposed to rep-
resent the ear-vesicles or otocysts of worms and mollusks ;
and the concretions or crystals, the otoliths of the same kind
of animals.

The otocysts or simple eyes of worms and mollusks are
minute and usually difficult to find, especially the auditory
642 ZOOLOGY.

nerve leading from them to the nerve-centres. In the
clam it is to be looked for in the so-called foot. In the
snails the auditory vesicles are placed in the head close to
the brain, as also in cuttle-fish. The ears of Crustacea are
sacs formed by inpushings of the integument filled with fluid,
into which hairs project, and which contain grains of sand
which have worked in from the outside, or concretions of
lime. These are situated in the shrimps and crabs at the
base of the inner antenne, but in certain other lower Crusta-
cea, as in Mysis, they are placed at the base of the lobes
of the tail. In the insects the ear is a sac covered by a
tympanum, with a ganglionic cell within, leading by a
slender nerve-fibre to a nerve-centre, and in these animals
the distribution of ears is very arbitrary. In the locust they
are situated at the base of the abdomen (Fig. 279) ; in the
green grasshoppers or katydids and the crickets in the fore
tibie ; and it is probable that in the butterflies the antenne
are organs of hearing.

The vertebrate ears are two in number and occupy a dis-
tinct, permanent position in the skull, however much modi-
fied the middle and outer ear become.

Organs of Smell.—The sense of smell is obscurely indi-
cated by special organs in the invertebrate animals, nasal
organs as such being characteristic of the skulled Vertebrates.
Whether organs of smell exist in any worms or not is un-
known ; there are certain pits in some worms which may
possibly be adapted for detecting odors. In some insects at
least the organs of smell are without doubt well developed ;
the antenne of the burying beetles are large and knob-like,
and evidently adapted for the detection of carrion. It is
possible that certain organs situated at the base of the wings
of the flies and on the caudal appendages of the cockroach
and certain flies (Fig. 290) are of use in detecting odors.
CHAPTER X.

DEVELOPMENT AND METAMORPHOSES OF ANI-
MALS.

Embryology.—The development of the individual is often
an epitome of the classification of the order or class to which
it belongs, as well as of the development or appearance in
geological history of the different members of the order or
class to which the individual belongs. The changes under-
gone by the animal within the egg are often so sudden and
marked that the separate chapters of its history as an em-
bryo can be read side by side with the history of the succes-
sion of the different genera and families of its type in past
ages. Moreover, it is now generally supposed by naturalists
that these critical periods in the development of the individ-
ual have a constant relation to external causes which have
acted on the ancestors of the animal, and hence that these
changes are the result of influences and changes in the sur-
roundings of the forms which have preceded. So much in-
terest, therefore, attaches to the subject of the early develop-
ment of animals, that much prominence has in the foregoing
pages been given to the matter.

We may now briefly review the more striking phenomena
of development in the invertebrate animals, and close with a
summary of the mode of development of Vertebrates.

The eggs of all animals consist of three portions, the egg
proper, consisting of a mass of protoplasm enveloped by
the yolk or food-stuff, the nucleus or germinative vesicle,
and the nucleolus or germinative spot.

Before the egg is ready for fertilization it undergoes a
- special process of maturation, involving the following series
644 ZOOLOGY.

of events: 1. Transportation of the germinal vesicle to the
surface of the egg; 2. An absorption of the membrane of
the nucleus or germinative vesicle and a change in the ger-
minative spot ; 3. The portion of the nucleus surviving as-
sumes a spindle-shape, this portion being largely formed
from the nucleolus ; 4. One end of the spindle enters into a
protoplasmic prominence at the surface of the egg ; 5. The
spindle divides into two halves, one remaining in the egg,
the other in the prominence, the latter separating from the
egg and forming the polar cell ; 6. A second polar cell forms
in the same manner as the first, part of the spindle still re-
maining in the egg; 7. The part of the spindle remaining
in the egg, after the formation of the second polar cell, is
converted into a nucleus, the female pronuclews, and finally,
just before fertilization, the female pronucleus takes its po-
sition at the centre of the egg.

 

Fig. 539.—Development of the sperm-cells of a blind worm (Epicrium glutinosum).
a, testis-cell; 6, the same, more numerous; ¢, @, €, becoming more numerous and
finally forming spermatozoa (f). Highly magnified.—After Minot.

After this, the first step in the development of many-celled
animals is the fusion of the protoplasm of the female pronu-
cleus with that of the sperm-cell ; for this end the latter is
exceedingly minute and provided with a vibratile cilium or
‘tail,’ so that it may force its way in toward the centre
of the egg. These sperm-cells are developed in the testis
of the male. On close examination with very high powers of
the microscope, certain cells, called ‘‘ mother cells,’’ may be
found developed in fine tubules forming the gland ; these are
known to possess several nuclei, which are destined to be-
come spermatozoa (Fig. 539, a and 0) ; these multiply until
they become very numerous, elongated, and packed side by
DEVELOPMENT OF ANIMALS. 645

side in bundles (e) ; from each one a cilium or “tail” grows
out, when they are set free from the mother-cell. In this
tailed form they are very active, and effect the fertilization
of the egg of an animal of the same species. This is due to
contact of one spermatozoon with the female pronucleus situ-
ated in the egg. Immediately after the spermatozoon has
penetrated into the egg, its ‘‘head’”’ is converted into a
nucleus, called the male pronucleus ; after this, radiating
strie make their appearance around its surface ; then the
male pronucleus travels toward the female pronucleus, and
finally the male and female pronuclei fuse together and form
the first ‘“‘ segmentation nucleus.”’

This nucleus subdivides, and the result is a mass of cells
resembling a mulberry, and hence called the morula. The
outer circle of the.cells of the morula may hereafter form
what is called the blastoderm ; after a while it pushes in at
one point, and the portion thus forced is called the inner
germ-layer (endoderm) and the outer is called the ectoderm
or outer germ-layer, and in this condition the germ is called
a gastrula. Subsequently, a third layer develops from the
others—just how is not certainly known—and after this the
different tissues become developed.

All animals, from sponges to man, become first two- and
afterward three-layered sacs ; so that all animals above the
Protozoa not only, as a rule, originate from eggs, but may be
said to travel, up to a certain point, the same developmental
path. From this point the members of different types of
life diverge. How different are the modes of development
of animals has been set forth in the different life-histories
related in the foregoing pages of this book.* But the laws
of growth are as stable and uniform—certain causes pro-
ducing certain results—as the laws of the motions of the
heavenly bodies.

When the workings of these laws of development are in-
terfered with by sudden accidents, by too scanty nourish-
ment, and by the transmission of the effects of such acci-

* For a fuller, more consecutive, though still fragmentary account,
the reader is referred to the author’s ‘‘ Outlines of Comparative Em-
bryology, or Life Histories of Animals, including Man.”
646 ZOOLOGY.

dents or abnormal products from parents who have been
affected by them, the results are usually abnormal, more or
less distorted forms, with greater or less defects ; and here
again have been observed laws governing the production of
abnormalities, the study of these being called teratology.

We may study the mode of development of the domestic
fowl or hen as the best known example to illustrate the
changes undergone by an embryo vertebrate, for this pur-
pose condensing the statements of Foster and Balfour in
their ‘‘ Elements of Embryology.”’

 

Fig. 540.—Blastodermic disk and germ of a rabbit about one day old, seen from the
back. a, edge of the head-end of the amnion; 6, fore-brain; c, teer expansion of
the same, or primitive eye-vesicle; d, middle, e, hind brain. There are eight protover-
tebrz, between which is situated the spinal cord. Enlarged ten times.—After Bischoff.

First Day.—After fertilization of the egg, segmentation of
the egg occurs, but instead of being total, forming a morula
or mulberry mass, it is, as in all birds and in the majority of
fishes and reptiles (except the lancelet and lamprey eel), par-
tial, or confined to the periphery of the yolk, resulting in
the formation of a blastoderm, the oval more apparent por-
tion being called the ‘‘ blastodermic disk,’’ which is the be-
ginning of the embryo. In six or eight hours after fertili-
zation the three germ-layers appear. From the outer germ-
DEVELOPMENT OF ANIMALS. 647

layer are destined to arise the skin and wall of the body
with the nervous system; from the second (mesoderm, in
the embryo called the mesoblast) are formed the heart and
the vascular system, as well as the stomach and intestines.

The middle layer now thickens, causing the mark known
as the “‘ primitive streak,’’ along the middle of which runs
the “‘ primitive groove.’’ The notochord now appears and
the primitive vertebra (protovertebre, Fig. 540). The am-
nion arises as a membrane, splitting off from the outer germ-
layer of the embryo, and finally forms a cavity which is
filled with a fluid. About this time the allantois arises as
an offshoot of the alimentary canal, budding out at the
hinder end of the embryo, and finally curving over the em-
bryo, serving as a foetal respiratory membrane.

Second Day.—The three portions or vesicles of the brain
now appear (Fig. 540), as well as the alimentary tract and
heart, both arising in the head-fold or enlargement (Fig. 540,
a to c), and soon the blood-vessels arise as channels in which
blood-corpuscles appear, originating as ameba-like cells
separating from the cellular mass of the mesoderm. Dur-
ing the second day also the eyes and ears begin their devel-
opment, being at first simply folds or inpushings of the
outer germ-layer.

Third Day.—This is one of the most eventful days, as im-
portant steps in the elaboration of the different organs are
taken ; the different parts of the brain, of the alimentary
tract and its appendages being sketched out, and the rudi-
ments of the lungs, the liver, pancreas, nose, and different
parts of the eye and ear appearing. On the fourth day the
wings and legs grow out, appearing first as flattened buds.
The notochord, which is indicated by the second day, by the
sixth begins to diminish in size, disappearing by the time
the chick is hatched, while by the twelfth day the deposition
of bone in the bodies of the vertebree commences. Between
the eightieth and one hundredth hour the internal differences
in the sexes appear, the testes beginning to arise on the
sixth day.

fifth Day.—The limbs have by this time developed so as
to show the knee- and elbow-joints, as well as the cartilages

 
648 ZOOLOG ¥.

 

Fig. 541.—Five schematic figures showing the development of the foetal egg-mem-
branes, where in all except the last the embryo is represented as if seen in longitudinal
section. 1. Diagram of egg with zona pellucida, blastoderm (a, 7), germinal disk, and)
embryo. 2. Egg with the first traces of the yolk-sac (d) and amnion (Xs, ss, and am.
3. Egg with the amnion uniting and forming a sac; the allantois (a/) budding out.
4, Egg with the villi of the serous membrane (sz); the allantois larger; embryo with
mouth and anal opening. 5. Egg in which the vascular layer of the allantois lies close
to the serous layer and has grown into the villi of the same, constituting the true
chorion (ch). Yolk-sac much smaller, about to be drawn into the cavity of the amnion,
DEVELOPMENT OF ANIMALS. 649

which precede the formation of the bones of the digits and
limbs. The primitive skull also arises from the mesoderm.

Until the sixth day it would be impossible to say whether
the embryo was that of a bird, reptile, or mammal, but now
the characters peculiar to birds appear. The wings and legs
manifest their bird-like characters, the crop and intestinal
coeca are indicated, ‘‘ the stomach takes the form of a giz-
zard, and the nose begins to develop into a beak, while the
incipient bones of the skull arrange themselves after the
avian type. . . . From the eleventh day onward, the embryo
successively puts on characters which are not only avian,
but even distinctive of the genus, species, and variety ”’
(Balfour). By the ninth or tenth day the feathers originate
in sacs in the skin, while the nails and scales begin to ap-
pear on the thirteenth day, and at this time the various
muscles of the body can be distinguished. Development is
thus seen to be from the general to the special, from the
simple to the complex ; the trunk is first indicated ; while
the peripheral parts—i.e., the extremities, the digits, the
skin, feathers or scales, or hair, whatever be the type of
Vertebrate—are the last to be elaborated ; in other words,
the characters of the branch, class, and orders are the first
to be evolved, those of the family, genus, and species the
last.

The development of the rabbit, guinea-pig, or any mam-
mal, including even man, follows much the same order as
in the chick, there being, however, a well-marked morula ;
the differences are due to the fact that the embryo mammal

d, yolk-skin ; d’, villi of the yolk-skin ; sh, serous membrane; sz, villi of the serous
membrane ; ch, chorion (vascular layer of the allantois); chz, true villi of the chorion
(arising from the projections of the chorion and the sac of the serous membrane);
am, amnion ; ks, head-fold of the amnion ; ss, tail-fold of the amnion; ah, cavity of
the amnion ; as, sheath cf the amnion for the navel-string ; a, the first beginning of
the embryo arising from a thickening of the outer layer of the blastoderm a’; m,
thickening forming the germ in the middle layer of the blastoderm (m/), which at first
only reached as far as the germinal disk, and afterward forms the vascular layer of
the yolk-sac (df) which connects with the intestino-muscular layer (darmfaserblatt);
st, sinus terminalis ; dd, intestino-glandular layer (darmdrusenblatt) arising out of a
part of i, the inner layer of the blastoderm (afterward the epithelium of the yolk-
sac); kh, cavity of the blastoderm, which afterward becomes (ds) the cavity of the
yolk-sac ; dg, passage way of the yolk; al, allantois ; e, embryo; 7, original space
between the amnion and chorion, filled with albuminous fluid ; 2, anterior body-wall
in the region of the heart ; Ah, cavity of the heart without the heart itself. In Figs.
2 and 3, the amnion is, for the sake of clearness, represented as situated too far away
from the embryo ; so also the cavity of the heart is drawn too small and the embryo
too large, since, except in Fig. 5, they are only drawn diagrammatically.—From Kol-
liker’s ‘‘ Entwickelungsgeschichte des Menschen und der hoheren Thiere.”’
650 ZOOLOGY.

develops in a specialized portion of the oviducts, the uterus
or womb, and that the growing germ until birth is supplied
not with yolk as food, but by the nourishment in the ma-
ternal blood. In fact, while the eggs of reptiles and birds
are enormous, it was not known with certainty until 1827
that mammals developed from eggs. The eggs of these an-
imals are very minute, owing in part to the minute amount
of yolk they contain ; that of man being less than a quarter
of a millimetre (+4, inch) in diameter.

The mammalian embryo, nourished as it is through the
maternal circulation, needs additional temporary organs,
which the bird does not possess ; these are the chorion (Fig.
541, ch), a vascular layer of the allantois, which sends off
villi or processes extending into the walls of the womb.
Besides this, in the higher or placental mammals, the pla-
centa or after-birth is formed, which serves as an organ of
respiration as well as to supply the embryo or foetus with
nourishment, and to carry off its effete products by means
of the maternal circulation.

It is comparatively late in embryonic life that the mam-
malian features appear; in the dog it is twenty-five days
before it can be told whether the embryo is a mammal or
not.

All mammals may be said to pass through a morula and
gastrula stage. In the next stage when the nervous chord
and notochord arise, the mammalian germ is on the same
footing with an Ascidian larva. In a succeeding stage,
when the protovertebre appear, an Amphioxus stage is
reached ; when a brain is formed, the level of the fishes is
reached ; after the limbs bud out the young mammals may
be said to assume the condition common to the embryos of
all Amphibian and higher Vertebrates. When the allantois
begins to appear the amphibian feature (the want of an
allantois) is dropped. When the chorion and placenta arise
the avian characters are surpassed and the mammalian feat-
ures assumed. Thus the development of the individual
mammal is an epitome of that of the branch or type to
which it belongs, and the successive steps in the degree of
specialization of the individual mammal are also paralleled
METAMORPHOSES OF ANIMALS. 651

by the gvological succession of the representatives of the
different classes, as without much doubt lancelets (or at least
acranliate, boneless forms) were the first Vertebrates to ap-
pear, and we know that fishes appeared before Amphibians,
that their type culminated before the reptiles held full
sway in Mesozoic times, and that birds, after them mam-
mals, and, last of all, man appeared, who crowns the series
of vertebrate forms.

Metamorphosis.—While many animals are hatched like
the chick with the form of the parent, others pass through
a series of changes of form called metamorphoses ; these
changes of form adapt the animal to changes in its sur-
roundings, involving alterations in its mode of life—slight if
the change of body-form is slight, thorough-going and radi-
cal if its body becomes profoundly modified. As an exam-
ple of a complete metamorphosis may be cited the life-his-
tories of the jelly-fishes, the star-fish, sea-urchins, sea-cu-
cumbers, the marine-worms, the mollusks, the crustaceans,
insects, and the salamanders and toads and frogs, already de-
scribed in the foregoing pages. If the student will read and
compare these different accounts, and then consider the
striking differences between the complicated histories of cer-
tain species, compared with the direct mode of growth of
other species of the same order or family, or even of the
same genus, the inquiry will arise, What is the purpose or
use of such a series of changes? If he look carefully into
the embryological changes of those species which are born
or hatched with the form of the adult, he will see that their
embryological history is, in point of fact, a condensed suin-
mary of the changes undergone after hatching by their co-
species, which, to gain the same adult form, have been sub-
jected by nature to a series of complicated, and, at first
sight, superfluous changes of form and environment.

Most shrimps and crabs undergo a complicated metamor-
phosis ; in the different changes of forms they lead different
lives, and are subjected to different surroundings, the larve,
for the most part, being free-swimming and living near the
surface of the water, while the parents are stationary. The
barnacle, when very young, swims near the surface of the
652 ZOOLOGY.

sea, afterward, as a pupa, becoming fixed to a rock ; the
young oyster-spat swims freely about, finally becoming fixed
to the bottom. ‘This change of life and of form undoubted-
ly tends to prevent the extinction of the species, since, if at
a given moment the parents were swept out of existence,
the young living in a different station would continue to
represent the species. This law is seen to hold good among
insects, where many species are represented in- the winter-
time by the egg alone, others by the caterpillars, others by the
chrysalis, while still others hybernate as imagines. Again,
in the marine species, the free-swimming young are borne
about by ocean and tidal currents, and in this way what in
adult life are the most sedentary forms become widely dis-
tributed from coast to coast and sea to sea. On the other
hand, the larval forms of fixed marine animals serve as food
for fishes, especially young fishes and numerous inverte-
brates, while their stationary parents afford subsistence for
still other forms of life ; thus were it not for the metamor-
phoses of animals, many species would become extinct
sooner than they do, while the great overplus of larval
forms gives to many other species of animals a hold on ex-
istence.

Metamorphosis among the invertebrate animals, espe-
cially, is perhaps the rule and not the exception. Where ani-
mals develop directly, as in certain insects, crustaceans, cer-
tain salamanders, toads and frogs, this is due to some
change in the environment; in the case of Amphibians,
perhaps the want of water, or some other cause, there always
being an adaptation in the case of the direct mode of de-
velopment to the surroundings of the animal and the require-
ments of its existence.

Parthenogenesis, and Alternation of Generations.—
Having traced the normal process of development of ani-
mals, we may turn to certain unusual or abnormal modes of
production. Asan example of what is known as “ alternation
of generations,’’ may be cited the mode of development of the
jelly-fish, such as the naked-eyed meduse (Melicertum and
Campanularta), which at one time of life develop by budding,
at another by eggs ; of the trematode worms, the adult forms
ALTERNATION OF GENERATIONS. 633

of which lay eggs, while the redia or proscolez of the same
worm produces cercarie by internal budding. Here also
may be cited the cases of strobilation of the Aurelia, the
tape-worm, the Nais, Syllis, and Autolycus, among Anne-
lids. Thusamong Celenterates and worms, as well as some
Crustacea, a large number of individuals are produced,
not from eggs, but by budding.

Similar occurrences take place among insects, as the
Aphis or plant-louse, in which a virgin Aphis may bring
forth in one season nine or ten generations of Aphides, so
that one Aphis may become the parent of millions of
young. These young directly develop from eggs or buds
which are never fertilized, hence the term parthenogenesis,
or virgin-reproduction, sometimes called agamogenesis (or
birth without marriage). The bark-lice as well as the
Aphides develop in this manner during the warm wea-
ther ; but at the approach of cold both male and female
Aphides and Coccidsz appear, the females laying fertilized
eggs, the first spring brood thus being produced in the
normal, usual manner.

Still more like the production of young in the redia of
the Trematode worms is the case of the larva of a small gall-
gnat (Miastor), which during the colder part of the year from
autumn to spring produces a series of successive generations
of larve like itself, until in June the last brood develops
into sexually mature flies, which lay fertilized eggs.

While the larval Miaster produces young like itself, the
pupa of another fly, Chironomus, also lays unfertilized eggs.

A number of moths, including the silk-worm moth, are
known to lay unfertilized eggs which produce caterpillars.
Among the Hymenoptera, the currant saw-fly, certain gall-
flies, several species of ants, wasps (Polistes), and the honey-
bee, are known to produce fertile young from unfertilized
eggs; in the case of the ants and bees, the workers lay egys
which result in the production of males, while the fertilized
eggs laid by the female ant or queen bee produce females
or workers.

Taking all these cases together, parthenogenesis is seen to
be due to budding, or cell-division, or multiplication. Now,
654 ZOOLOGY.

it will be remembered that the egg develops into an animal
by cell-division, so that fundamentally parthenogenesis is
due to cell-division, the fundamental mode of growth ;
hence, normal growth and parthenogenesis are but extremes
of a single series. In this connection, it will be remembered
that all the Protozoa reproduce by simple cell-division,
that among them the sexes are not differentiated, that they
do not reproduce by fertilized eggs ; hence, so to speak,
among Protozoa parthenogenesis is the normal mode of re-
production ; and when it exists in higher animals it may
possibly be a survival of the usual protozoan means of
stocking the world with unicellular organisms, with which
we know the waters teem. And this leads us to the teleol-
ogy or explanation of the cause why parthenogenesis has sur-
vived here and there in the world of lower organizations ;
it is plainly, when we look at the millions of Aphides, of
bark-lice, the hundreds of thousands inmates of ant-hills
and bee-hives, for the purpose of bringing immediately
into existence great numbers of individuals, thus ensuring
the success in life of certain species exposed to great vicis-
situdes in the struggle for existence. That this unusual
mode of reproduction is all-important for the maintenance
of the existence of most of the parasitic worms, is abundantly
proved when we consider the strange events which make up
the sum total of a fluke or tape-worm’s biography. With-
out this faculty of the comparatively sudden production of
large numbers of young by other than the slow, limited
process of ovulation, the species would be stricken off the
roll of animal life.

Dimorphism and Polymorphism.—Involving the produc-
tion of young among many-celled animals (Metazow) by what.
is fundamentally a budding process, we have two sorts of
individuals. When the organism is high or specialized
enough to lay eggs which must be fertilized, we have a
differentiation of the animal into two sexes, male and fe-
male. Reproduction by budding involves the differentia-
tion of the animal form into three kinds of individuals—
t.@., males, females, and asexual individuals, among insects
often called workers or neuters. These have usually, as in
DIMORPHISM. 655

ants and bees, a distinct form so as to be readily recog-
nized at first sight. Among the Celenterates and worms
the forms reproducing by parthenogenesis are usually larval
or immature, as if they were prematurely hurried into ex-
istence, and their reproductive organs had been elaborated
in advance of other systems of organs, for the hasty, sud-
den production, so to speak, of large numbers of individu-
als like themselves.

In insects, as we have stated elsewhere,* dimorphism is
intimately connected with agamic reproduction. Thus the
summer wingless, asexual Aphis and the perfect winged
autumnal Aphis may be called dimorphic forms. The per-
fect female may assume two forms, so much so as to be mis-
taken for two distinct species. Thus, an oak gall-fly (Cy-
nips quercus-spongifica) occurs in male and female broods in
the spring, while the autumnal brood of females were de-
scribed originally as a separate species under the name C.
aciculata. Walsh considered the two sets of females as di-
morphic forms, and that Cynips aciculata lays eggs which
produce C. quercus spongifica. Among butterflies, dimor-
phism occurs. Papilio memnon has two kinds of females,
one being tailless, like the tailless male, while Papilio Pam-
mon is polymorphic, there being three kinds of females be-
sides the male.

There are also four forms of Papilio Ajax, the three
others being originally described as distinct species under
the name of P. Marcellus, P. Telamonides, and P. Walshii.
Our Papilio glaucus is now known to be a dark, dimorphic,
climatic form of the common Papilio Turnus. There are
dimorphic males among certain beetles, as in the Golofa
hastata Dejean, of Mexico, in which one set of males are
large and have a very large erect horn on the prothorax,
and in the other the body is much smaller, with a very
short conical horn.

Temperature is also associated with the production of
polymorphic forms in the temperate regions of the earth,
as seen in certain butterflies, southern forms being varieties

* Quide to the Study of Insects, sixth edition, p. 52.
656 ZOOLOGY.

of northern forms, and alpine “‘ species ’’ proving to be va-
rieties or seasonal forms of lowland species. For example,
Weismann states that the European butterflies, Lycaon amyn-
tas and polysperchon, are respectively summer and spring
broods. <Anthocharis Simplonica is an alpine winter form of
Anthocharis Belia, as is Pieris bryonie of Pieris napi. In
this country, as Edwards has shown, two of the polymorphic
forms of Papilio Ajax—i.e., Walshii and Telamonides—come
from winter chrysalids, and P. marcellus from a second
brood of summer chrysalids. It thus appears that poly-
morphism is intimately connected with the origin of species.
Perhaps the most remarkable case of polymorphism is to be
seen in the white ants (Zermites), where in one genus there
are two sorts of workers, two sorts of soldiers, and two kinds
of males and females, making eight sorts of individuals ; in
the other genera there are six. Among true ants there are,
besides the ordinary males, females, and workers, large-
headed workers. In the honey-ant (Myrmecocystus Mexi-
canus), besides the usual workers, there are those with
enormous abdomens filled with honey. Other insects, es-
pecially certain grasshoppers, are dimorphic. Certain par-
asitic Nematode worms are dimorphic; and among the
Celenterates, especially the Hydroids, there is a strong ten-
dency to polymorphism.

Individuality.—Perfect individuality among animals is
the rule, each individual being capable of maintaining an
independent existence ; but we have seen that there are many
of the lower animals in which it is difficult to determine
whether the different members of a colony are really in-
dividuals or simply individualized organs.

The student, in referring back to the account of the Por-
tuguese man-of-war, will find it difficult to say whether the
four kinds of members of the floating colony are organs or
individuals, and he will probably agree with the view that
it is best to provisionally call them zooids or individualized
organs ; for the feeders, the reproductive zooids, the digest-
ive zooids, and the swimming float, or the swimming bells
of the other Siphonophores, are highly specialized organs,
and only differ from true individuals in lacking the power
w

INDIVIDUALITY AND HYBRIDITY. 657%

of free motion and of maintaining an independent existence.
So with many other Coelenterates and with the tapeworm,
whose proglottides or segments are finally capable of sepa-
rate existence. Among the higher invertebrates, even the
different members of a colony of white or true ants lack a
certain amount of individuality, the workers performing
labors upon which the maintenance of the very existence of
the colony depends, so that there are different grades of in-
dividuality, from examples like the Hydractinia and the
Siphonophores up to those insects which live socially ; and
we see that the most perfect individuality exists in those
animals which can most efficiently provide for their own
sustenance and for the continuance of their species.

Hybridity.—It is rare that two species, even of the same
genus, can produce offspring ; when such cases occur, the
result is called a hybrid. For example, the mule is a hybrid,
being bred from a female horse and an ass; but the mule
is not fertile, and hybrids are very rarely fertile. The In-
dian dog and coyote are said by Coues to interbreed, and
on the Upper Missouri we have seen dogs which had every
appearance of being such hybrids. Dogs also cross with the
fox (Darwin). The American bison is known to breed with
the domestic cattle—whether the offspring is fertile re-
mains to be seen.

Darwin states that he knows of no thoroughly well-au-
thenticated cases of perfectly fertile hybrid animals, though
“he adds, ‘‘I have reason to believe that the hybrids from
Cervulus vaginalis and Reevesii and from Phasianus col-
chicus with P. torquatus are perfectly fertile.’’ The hare
and rabbit are supposed to have fertile offspring ; the hy-
brids of the common and Chinese geese (Anser cygnoides)
have interbred. The crossed offspring from the Indian
humped and common cattle interbreed. Among insects
different moths hybridize, but it is not known whether the
offspring are fertile, unless such be the case with the com-
mon black and Italian bees, which are supposed to be dis-
tinct species.
GHAP GER

THE GEOGRAPHICAL DISTRIBUTION OF ANI-
MALS.

THE assemblage of animal life peopling any one locality
or area is called its fauna, as the plants of a place consti-
tute its flora. Where the physical geography—i.e., the con-
tour of the surface, the plains, valleys, and hills—is of iden-
tical character and the climate the same, the fauna is much
the same, but when these characteristics of soil and climate
change, as in passing from lowlands to highlands, or from
south to north, the assemblage of animals will be found
to change in a corresponding ratio. And as there are no
definite limits to any large area of the earth’s surface, the
physical features of one area merging insensibly, as a rule,
into adjoining districts, so adjoining faune merge into one
another, and a certain proportion of the species may range
through two or more faunal areas.

There are in nature causes tending to restrain animals
within their faunal limits, and others tending to diffuse
them, or to cause them to migrate from their specific cen-
tres or centres of creation—namely, the point where the in-
dividuals of a species are most abundant, and where, ac-
cordingly, they are supposed to have originated.

Barriers to the Spread of Animals from their Specific
Centres.—Among the most important are the oceans and
their basins. The animals of the opposite sides of the Pa-
cific Ocean are entirely unlike, no species being common to
the two sides; while, of the immense numbers of animals
peopling the coast of Brazil and the opposite coast of Af-
rica, only two or three are known to be identical. Differ-
ence in climate is also a great barrier, the animals of the
GHOGRAPHICAL DISTRIBUTION. 659

tropics, as a whole, being unlike those of the temperate
zones ; while arctic and antarctic animals have features in
common. Mountains serve as most important barriers, re-
straining animals within their limits; thus the basins be-
tween or surrounded by continuous ranges of mountains
harbor faune differing from those on the opposite sides of
the mountains. For example, the majority of the animals
of the Great Basin between the Rocky Mountains and the
Sierra Nevada differ from those of the Pacific slope or the
prairie lands lying east of the Rocky Mountains, as the
meteorological and geological features are different. The
Cordilleras of South America form a barrier to the diffusion
westward of Brazilian animals. Still this fact is not to be
taken too literally, as the mountains are divided by valleys
and rivers, which afford means of communication and an
interchange of specific forms; thus certain species of ani-
mals of the Rocky Mountain plateau occur on each side of
the range, as do those in the Alleghany district of the At-
lantic coast. In the West Indian and especially the Hawa-
lian Islands, where the species of land snails are very numer-
ous, certain forms are restricted to the deep narrow valleys,
being confined to very restricted areas. So also the cold
Alpine summits of the White Mountains of New Hamp-
shire, of the Rocky Mountains, of the Alps and Scandina-
vian mountains harbor a few species either peculiar to those
extremely limited tracts or found northward in the Arctic
regions.

Deserts may act much as inland seas to separate the ani-
mals of the adjoining more fertile tracts, and they afford
dwelling-places for. animals which are incapable of living
elsewhere. Desert faune have a general facies the world
over, though the original elements out of which the faune
have been made up may radically differ.

The distribution of plants also has much to do with that
of those animals which are dependent on them for food ;
aga rule, the distribution of both plants and animals de-
pends on the same physical causes.

Large rivers sometimes act as barriers, but more often,
perhaps, aid in the diffusion of the smaller forms, such as
660 ZOOLOGY.

insects, mollusks, and crustaceans. Different systems of riv-
ers have distinct sets of fluviatile animals ; for example, the
fishes of the Ohio and Upper Mississippi and its tributaries
differ from those of the Hudson River and the New England
rivers, and the latter from those draining the Southern At-
lantic States. The fresh-water mussels, so abundant and
characteristic of the waters of the Mississippi and its tribu-
taries are confined to the region lying west of the Allegha-
nies and east of the Great Plains. The fishes and mollusks
of the rivers of the Pacific slope differ from those of the
scanty waters of the Great Basin.

Means of Dispersal.—_The most general are the alterna-
tions of winter and summer, leading birds and mammals to
migrate great distances to and from their breeding-places.
Ocean-currents are most important factors in the dispersal
of many marine and some land animals. By means of such
great currents as the Gulf Stream, tropical animals are borne
to temperate and even subarctic regions ; and, on the other
hand, arctic and temperate animals are borne southward,
and thus marine faune interdigitate and merge insensibly
into one another. By this agency also new coral islands
are peopled from the mainland, and peninsulas are colo-
nized from adjoining continents or islands; for example,
the southern extremity of Florida has been visited by trop-
ical plants and animals borne by currents and winds from
the West Indies, thus lending a purely tropical aspect to
the southern part, a semi-tropical fauna occupying the mid-
dle and northern part of the State.

Trade winds play an important part in scattering insects,
and especially the minute forms of life ; whirlwinds and
tornadoes catch up larger forms and transport them from
stream to stream, pond to pond, and from lowlands to
highlands, and even to Alpine summits, where may some-
times be found, under loose stones, multitudes of insects
which have been borne up from below by strong gales or
ascending currents of air.

The direction of the migrations of the Rocky Mountain
locust seems to be mainly Gipcndent on the direction of pre-

vailing winds. Insects as well as birds are blown off-shore
GHOGRAPHICAL DISTRIBUTION. 661

sometimes for hundreds of miles, and in this apparently
haphazard way islands are, in part at least, supplied with
their quota of animal life.

Great rivers, like the Missouri, Mississippi, and the Ama-
zons, afford means of transportation from one part of a con-
tinent to another, from the interior to the seaboard, of
which many fishes, insects, and especially fluviatile mollusks,
avail themselves. Artificial means of crossing broad rivers
are offered, to insects especially, by country-roads and bridges
and railroad bridges, of which the potato-beetle and the
cabbage-butterfly have fully availed themselves. The Colo-
rado beetle has advanced steadily eastward, suddenly ap-
pearing in isolated points in New England, having appar-
ently been transported by through grain-cars from Chicago,
and has been carried to Europe in vessels. The European
cabbage-butterfly introduced into Quebec spread southward
into Maine along the Grand Trunk Railroad, into New
York along the railroads from Montreal to New York, and
then along the railroads to Washington.

Geological changes, such as the rise and submergence of
the edges of continents, and also the incoming and wane of
the glacial period, were still more general and fundamental
means of the dispersal and rearrangement of faune.

Division of the Earth into Faune.—When we go from
Maine to California we shall find that the faunistic features
of the country radically change three times. Leaving the
moist, temperate, forest-clad Atlantic region with its char-
acteristic animals, and entering on the broad, treeless, dry,
elevated plateau of the Rocky Mountains, we shall notice
that the Atlantic fauna has been replaced almost wholly by
anew and strange assemblage ; and when we descend the
Pacific slope of the Sierra Nevada, there will be found to
be a second replacement, though much less marked than
the first. Again, when we pass from Labrador to the Isthmus
of Panama, we shall find several distinct faune, from an
arctic one to a purely tropical one. If we pause at Wash-
ington and analyze the fauna of that point, we shall see
that it is made up mainly of animals common to the Middle
Atlantic States, with an infusion of northern and southern
662 ZOOLOGY.

forms. Indeed, at almost any point in temperate North
America the fauna is found to consist of three elements—
i.e., mainly a temperate, with a certain percentage of boreal
or subarctic and of southern or semi-tropical forms ; and if
the point be situated near some lofty range of mountains, a
fourth element—i.e., a purely arctic or alpine feature—is
superadded. The earth’s surface may then be mapped out
into general and special divisions. First, a tropical, tem-
perate, and arctic or circumpolar fauna or realm, and, sec-
ondly, each continent may form asmaller subdivision or spe-
cific centre—i.e., the Europeo-Asiatic, the African, the Aus-
tralian, and the South and North American regions, for
each of these continental divisions have been peopled with
animals which have been from the earliest geological times
the original possessors of the soil, though they may have
adopted members of each other’s faune.

Confining ourselves to the North American Continent,
let us examine the distribution of life on its surface. We
shall have to throw out the arctic regions, which belong
with the arctic regions of Europe and Asia, to a distinct
circumpolar fauna or realm, and then map out the rest of
the continent into five provinces—.e., the Canadian, the
Alleghanian, the Central or Rocky Mountains, the Pacific
or Californian, and the Mexican ; all of these provinces are
bounded by natural geological limits and differ in tempera-
ture and moisture. While the cougar, or Felis concolor, is
common to each one of them, and the bison and black bear
range throughout the Canadian, Alleghanian, and Central
provinces, there are a certain percentage of animals which
are confined to each province ; and on closer examination,
each province, especially on the Atlantic and Pacific coasts,
will be found capable of minuter subdivision into more lo-
cal faune or faunule.

It will also be found that the animals, especially the
insects, of the Atlantic province have certain elements
reminding us of Northeastern Asia, while on the Pacific
slope—t.e., the Californian province, a few insects, shells,
and crustacea, as well as the birds, remind us of European

types, which are wholly wanting east of the Rocky Moun-
tains.
GHOGRAPHICAL DISTRIBUTION. 663

On inquiring into the origin of the North American
fauna, in the light of the geological history of the conti-
nent, we shall find, first, that immediately preceding the
glacial period, Arctic America was peopled by a flora and
fauna of which the larger proportion of the animals of the
continent north of latitude 30° are probably the descend-
ants ; and, second, that a number of species migrated north-
ward from the South American Continent. Now, when
the glacial period came in, the semi-tropical and warm tem-
perate animals of the northern two-thirds of the continent
were mostly swept out of existence ; a scanty arctic fauna
took their place ; as the ice melted and retreated to its pres-
ent limits, the present assemblage of temperate animals,
mostly modified descendants of those originally driven south,
migrated back again and colonized the region laid compara-
tively bare by the ice and cold of the glacial period. This
is an illustration of the sweeping extinctions, recolonizations,
and extended migrations of animals on our continent in
former times, by which the existing relations of faune have
been brought about. Parallel events have occurred on the
Europeo-Asiatic Continent, and thus geological extinctions
and widespread migrations and recolonizations have taken
place ; and it is only in this way that the existing relations
in the geographical distribution of animals as well as plants
can be accounted for.

It should also be observed that in the beginning of
things the continents were built up from north to south—
such has been at least the history of the North and South
American and the Europeo-Asiatic and African Conti-
nents ; and thus it would appear that north of the equator,
at least, animals slowly migrated southward, keeping pace,
as it were, with the growth and southward extension of the
grand land masses which appeared above the sea in the Pa-
leozoic Ages. Hence, scanty as is the arctic and temperate
regions of the earth at the present time, in former ages these
regions were as prolific in life as the tropics now are, the
latter regions, now so vast, having all through the Tertiary
and Quaternary ages been undisturbed by great geological
revolutions, and meanwhile been colonized by emigrants
driven down by the incoming cold of the glacial period.
664 ZOOLOGY.

It appears, then, that each continent has had from the
first its distinct assemblage of life, and thus opposing con-
tinents, such as South America and Africa, have fundament-
ally different faunz, because they have had a separate geo-
logical history. Though the climate, moisture, and extent
of forests of Brazil and the West Coast of Africa may, for
example, be nearly identical, the animals are of a different
type. At the present day, Australian trees may be trans-
planted to California, and flourish there, and camels from
the Orient may breed in Southern California, because at the
present day the climate and soil are so much alike in the two
countries.

Distribution of Marine Animals.—Nearly all that has
been said thus far applies to land animals. Marine species
are assorted into faunse which are nearly as well marked as
terrestrial assemblages of species. The barriers restraining
them within their faunal limits are the temperature of the
water, this being modified more or less by the ocean-cur-
rents, the nature of the shore, whether rocky or muddy or
sandy, and the nature of the sea-bottom, whether also
rocky, muddy, orsandy. Many marine animals live attached
to rocks and stationary pebbles, others are found only in
coarse or in fine sand, while the muddy bottoms of harbors,
bays, and gulfs, or the soft, deep ooze of the ocean-depths
harbor a different assemblage of mud-loving species. The
temperature of the water is the most important agency now
in operation in the limitation of marine animals. Thus
there is a tropical, north and south temperate, an arctic
and probably an antarctic zone, and these are, along the
shores of the different continents, subdivided into distinct
faune. For example, along the coast of Eastern North
America, the arctic or circumpolar fauna extends from the
polar regions to Labrador and Newfoundland ; a second,
the Acadian, to Cape Cod; between Cape Cod and Cape
Hatteras another assemblage (the Virginian) is found ; from
Cape Hatteras to Southern Florida a fourth, and the Flor-
idan peninsula belongs to the tropical regions. Along these
different areas the water is of different temperatures. We
also find a large proportion of circumpolar animals in the
GHOGRAPHICAL DISTRIBUTION. 665

Acadian fauna and a few in the Virginian fauna, as the
Labrador or polar current passes down along the coast,
bathing the New England coast north of Cape Cod, and
even extending under the warm surface- water as far as New
Jersey. On the other hand, the great volume of heated
tropical water forming the Gulf Stream issuing from the
Straits of Florida makes its influence most sensibly felt as
far as Cape Hatteras, and in a diminished degree to Cape
Cod, and even southern shells, etc., are found as outliers of
more southern faune near Portland, Me., and Nova Scotia.

As we descend from the shore into deep water, the tem-
perature becomes lower and lower the deeper we go, until
we come toa stratum or zone of water about 32°-36° Fahr.,
where circumpolar or arctic life alone abounds. Wherever
deep abysses off the coast or at the bottom of bays or gulfs
occur, the water is found to be colder than elsewhere ; just
as when we ascend a mountain the air becomes colder, un-
til at the Alpine summits we find an arctic temperature
and fauna ; thus, in the sea, increase of depth is paralleled
by increase of height on land.

Usually, off the coast of the United States, north of New
York, there is a distinct zone of life between high and low
water, asecond extending to the depth of about fifty fathoms,
anda third to one hundred fathoms or over. Ata depth of
from one or two hundred fathoms in the Northern Atlantic,
and from five hundred to one thousand fathoms in the sub-
tropical and tropical seas, down to the deepest parts of the
ocean, now known in a few points to be about five miles in
depth, the water is about 32° Fahr. and the animal life is
polar in its nature. The water of the ocean all over the
globe, as shown by the results of the ‘‘ Challenger’? and
other expeditions for the exploration of the sea at great
depths, everywhere below a depth of one thousand fathoms,
is of an arctic temperature, overlaid by the heated water of
the tropics. The abysses or deeper parts of the ocean-bed
support a nearly uniform assemblage of life, which may be
called the deep-sea or abyssal fauna. The animals largely
consist of Echinoderms, notably Crinoids, with Coelenterates,
mollusks, worms, and Crustacea, and it is an interesting fact
666 ZOOLOGY.

that a few of the Echinoderms belong to genera which flour-
ished in the Cretaceous Period ; so that in a sense the abys-
sal fauna may be said to be an extension in time of the
Cretaceous fauna ; the physical features of the deeper parts
of the sea having remained nearly the same, while the
shallower parts have risen and fallen so as to undergo great
changes, and have wrought corresponding changes in the life
along the shores of the continents.

The following tabular view of the chief zoological faunas
of the earth, proposed by Mr. J. A. Allen, is based on a
study of the mammals, but will primarily apply to most
land animals. The arctic realm is most distinctly charac-
terized by the distribution of marine invertebrates, when it
becomes of primary value :

I. Arctic realm, undivided.

Il. North Temperate realm, with two regions, viz. :

1. American region, with four provinces, viz.:

a. Boreal.
6. Eastern.
c. Middle.
d. Western,

2. Europeo-Asiatic region, also with four provinces, viz. :

a. European.

b. Siberian.

c. Mediterranean.
ad. Manchurian.

III. American Tropical realm, with three regions, viz. :

1. Antillean.
2. Central American.
3. Brazilian.

IV. Indo-African realm, with two regions, viz. :

1. African region, with three provinces, viz. :

a. Eastern.
b. Western.
c. Southern.
GHOGRAPHIUAL DISTRIBUTI ON. 667

2. Indian region, with two provinces, viz. :

a. Continental.
6. Insular,

V. South American Temperate realm, with two provinces, viz. :

a. Andean.
b. Pampean.

VI. Australian realm, with three regions, viz. :

1. Australian, with two provinces, viz.:

a. Australian.
b. Papuan,

2. Polynesian.
3. New Zealand.

VII. Lemurian realm, undivided.

VIII. Antarctic or South Circumpolar, undivided,

Migrations of Animals.—Intimately connected with zoogeog-
raphy are the migrations of animals, especially birds. Nearly all the
birds of the United States which breed in the central and northern
portions pass southward in the autumn, and winter in the Southern
States or in Central America and the West Indies. Most of the birds
which breed in Northern and Central Europe fly at the approach of
cold weather into Southern Europe or across the Mediterranean into
Northern Africa. The causes of this regular periodical migration are
probably due, primarily, to the changes of the seasons and to the want
of food in the colder portion of the year, and, secondarily, to the
breeding habits of birds.

The periodical migrations of fishes from deep to shoal water are
connected with their breeding habits, the marine fish being in most
cases compelled to spawn in rivers or in shoal-water. The mi gratory
movements of fishes along the coast are probably connected with the
presence or absence of their accustomed food.

The partial, occasional migrations of locusts depend on the undue
increase in the numbers of the insects, and the consequent lack of
food, while the direction of the swarms is largely dependent on the
general course and force of the winds.
CHAPTER XII.
THE GEOLOGICAL SUCCESSION OF ANIMALS.

THE different systems of rocks, from the Silurian to the
Quaternary or present age, contain the fossil remains of ani-
mals, which show that in the beginning the animals were,
as a whole, unlike those now living, the later types becom-
ing more and more like those now constituting the earth’s
fauna. The oldest set of animals, the Paleozoic, comprised
species of nearly all the branches of invertebrates, with a
few fishes. A large proportion of these animals belonged
either to simple or to what are called generalized types,
though some were as specialized as any invertebrates now
living. Progress upward has involved the disappearance of
most of the generalized types, and their replacement by more
or less highly specialized types. Thus the earliest corals were
mostly of the Rugose type, which were succeeded by the
more complicated recent forms ; the Brachiopods or shelled
worms were replaced by mollusks ; the generalized trilobites
gave way to the genuine specialized shrimps and crabs ; the
existing generalized king-crab, with its affinities to spiders,
has survived a number of still more generalized or synthetic
allies. The generalized sharks and ganoids abounded at a
time when there were no bony fishes like the cod and her-
ring. Nearly nine thousand species of bony fishes have
appeared since the extinction of the earlier types of cartila-
ginous and mail-clad fishes. The highly specialized horse
was preceded by a number of more generalized species and
genera, the oldest of which approached the tapir, one of the
most generalized of mammals. The succession of forms
leading up to the horse is paralleled by the succession of
GHOLOGICAL SUCCESSION OF ANIMALS. 669

sea-urchins and of ammonites, the older being of simpler,
more generalized forms, and the later with a greater
specialization or elaboration of the different, especially ex-
ternal, hard parts of the hody.

When we ascend to the Amphibians, the reptiles and the
mammals, we shall find that there has been an elaboration
or working out into great detail, of the parts most used by
the animal, this differentiation being more and more marked
as we approach the present time; and this has been in ac-
cord with the building up of the continental masses, and
the differentiation or specialization of the surface of the
different continents into plains, plateaus, highlands, and
mountain ranges, with their different climatic features,
and the dividing up of the waters into mediterranean
seas, friths, fiords, rivers, and lakes. Thus the extinction
of successive faune all over the globe has been followed by
the appearance of new sets of animals, each assemblage be-
ing adapted to the new and improved condition of things.

Having seen that the earlier forms of life were of a sim-
pler form, though often combining the features of diverse
classes and orders of animals which appeared afterward, so
that Agassiz called them, in some cases, prophetic types,
combining as they did characters which have been trans-
mitted to two or more later groups, and these specially elab-
orated, so that such generalized or prophetic types serve as
points of departure from which several series of forms have
arisen—having traced the law or principle underlying the
geological succession of animals, we may inquire whether
this has been paralleled by the development of any one of
the members of a group. That this is the case has been
proved by Hyatt, who shows that the development of the
individual Ammonite is paralleled by that of the geological
succession of the members of the order to which it belongs.
Stalked Crinoids were the style in Paleozoic ages, while free
Crinoids are more abundant at the present day ; and we
have seen that in the individual development of the existing
Antedon, the young is stalked at first, afterward becoming
free. The young, bony fish has at first a cartilaginous
skeleton and a heterocercal tail, these being characteristics
670 ZOOLOGY.

of early fishes. The earlier Batrachians were tailed, the
tailless toads and frogs in general appearing last, as the
tadpole precedes the frog condition.

Extinction of Species.—The laws governing the extinction
of animals are obscure, but we know that geological extinc-
tions must have been due to natural causes, since the earth
has at different periods evidently undergone great changes,
sufficient to account for the death of such species as were
unable to withstand the oscillations and changes of climate.
In Paleozoic times existed multitudes of animals which, judg-
ing by their descendants of later times, belonged to old-fash-
ioned, obsolete, useless types. They cumbered the ground,
and were destroyed by the beneficent action of unerring natu-
ral laws promoting the decay and extinction of antiquated
forms, and the recreation, by the laws of transmission with
modification, of new, improved types, useful in their day and
generation as stepping-stones to a still higher, more improved
stock. That the extinction was due to causes acting pri-
marily from without, and secondarily from within by trans-
mission force, seems demonstrated when we take into ac-
count the destruction of life which we know took place
during and at the close of the Glacial Period, when the
earth was swept with glaciers, and afterward garnished
with the vegetation and fresh life of the post-glacial times,
and made ready for the abode of man. Thus the death of
species by the action of laws that we can comprehend in-
volves the recreation of new and improved animal forms by
laws that we can at least in part, if not fully, understand.
CHAPTER XIII.
THE ORIGIN OF SPECIES.

THE extinction of species was in some cases gradual, in
others sudden, so in all probability as different assemblages
of life became slowly extinct new forms as slowly originated
from them by genetic descent and took their places. While
here and there certain species, under favorable circumstances,
suddenly appeared, if we could have been there to look on,
it would perhaps have been as difficult to have observed the
process as it is at the present day to observe the changes
going on in the relation of existing faune. We know,
however, that changes are going on in the world of life about
us, that the balance of nature is being disturbed.

The nature of the evidence tending to prove that species
have originated through the agency of physical and biologi-
cal laws is mainly circumstantial, there being comparatively
few facts in demonstration of the theory, the direct act of
transformation of one species into another under the eye of
scientific experts having never been observed.

Reasoning @ priori, we assume that organisms, both
plant and animal, have been created by development from
pre-existent forms because it agrees with the general course
of nature. All the events in geology, as in physics and as-
tronomy, being due to the operation of natural laws, it is
reasonably supposed that the production of all the species
of plants and animals from original simple forms, like the
Monera or bacteria, have been the result of the action of
natural law. The study of the early forms of life found in
the Paleozoic strata ; the laws of the succession of types ; the
correlation existing between the development of the indi-
672 ZOOLOGY.

vidual and of the members of the class to which it belongs ;
the parallelism between the formation and differentiation
of the land-masses of the globe and the successive extinc-
tions and creations of plants and animals—all these facts,
notwithstanding the imperfections of the geological record,
and the fact that many of the older forms of animals were
nearly as much specialized as those now living ; tend strongly
to prove that, on the whole, the world as it now exists has
been the result of progressive development, one form com-
ing genetically from another ; the animal and plant worlds
constituting two systems of blood relations, rather than sets
of independent creations.

When to more special studies of those species which live
in extraordinary environments, such as cave-animals, para-
sitic animals, brine-inhabiting animals, Alpine forms and
certain deep-sea species, we add the study of rudimentary
organs in adult animals, of temporary, deciduous organs in
young or larval animals ; when we compare the metamor-
phoses of some species congeneric with others which undergo
no transformations ; when we study the delicate balance in
nature as observed in the geographical distribution of ani-
mals ; the harmony in nature between species and their en-
vironment ; protective coloration and resemblance in form,
the relations between carnivorous and herbivorous creatures,
the struggle for existence between animals, we are forced
to acknowledge that the operations of nature, as a whole,
tend, on the one hand, to the origination of new forms
and the preservation of those which are useful, or, in other
words, arein harmony with their surroundings ; and, on the
other hand, to the destruction of those which are incapaci-
tated by changes in their environment for existence in what
has been and now is a constantly changing, progressive
world.

Again, reasoning by induction, as an actual fact we know
that species vary ; that hardly any two experts agree exactly
as to the limitation of species ;* that varieties tend to break

* As one of many examples, we may cite the fact that fifty-nine nom-
inal species of the squirrels have been described as inhabiting tropical
America, but lately the number has been reduced to twelve.
THE ORIGIN OF SPECIES. 673

up into races, and that no two individuals of a race are ex-
actly alike. Where the climate and soil remain the same,
the species tends to remain fixed and stable ; remove the
stability in the environment, or subject the individuals of a
species to changes of soil and temperature, and expose it
more than usual to the attacks of its natural enemies, it
then begins to undergo achange. This is seen in those in-
dividuals of a species which live on the borders of lowlands
and highlands, of deserts and fertile tracts, of salt and
brackish water, of shallow and deep water, and of polar and
temperate zones, or to the influence of alternating cold and
warm weather. When, as in some cases, climatic or other
agencies suddenly change, we may have species and even
genera suddenly appearing, as is known to be the case in
the change of one genus to another of brine shrimps when
the water changes from brackish to a brine, as worked out
by Schmankevitch in Russia.

The struggle for existence resulting in the survival of the
fittest is a fact now generally observed. The cod may de-
posit several millions of eggs, but of this immense number
only one or a few pair of adults survive ; there are probably
no more codfish now than two centuries since—indeed, not
as many; the eggs are devoured by different animals, the
young fish, as soon as hatched, form the food of larger fish,
half-grown cod serve to supply the wants of larger animals,
until finally the survivors may be to the original number of
eggs as one to a million. The queen bee may, during her
whole life, lay more than a million of eggs, the queen
white ant may lay eighty thousand eggs a day, an Aphis
may be the mother of a hundred young, those hundred may
each produce their centesimal offspring until the result in one
season, at the end of the tenth generation, amounts to a
quintillion of plant-lice ; but most of these insects serve as
food for other species, many die of disease and cold, until
at the end of the season only one or several pairs survive to
lay a few eggs, which represent the species in the winter-time.

Lastly, the variation in domestic animals, the result of
the subjection of the species to influences not felt in what
we call a state of nature, is an indication that animals not
674 ZOOLOGY.

exposed to human interference may vary when subjected to
changes in their environment. Also the fact that man can, by
careful selection, breed races of horses adapted for draught,
speed, or the road ; races of cows for different qualities of
milk ; beeves for meat ; races of sheep for pre-eminence in
the quality of their wool or mutton, or races of doves or
poultry for beauty, usefulness, or other qualities ; the fact
that gentleness, and generally good mental qualities, can be
made to replace viciousness in horses, cattle, dogs—all these
and many other facts, in the art of breeding animals known
to fanciers, indicate that nature has, through the past ages,
by the operation of natural laws, evolved races and species
of animals which have followed constantly improving lines
of development, the outcome of which are creatures the best
fitted to withstand the struggle for existence, the most use-
ful in the scheme of nature, and the most in harmony with
the world about them. Progress, on the whole, therefore,
has been beneficent, the best proof of which is the last
product of evolution, man, the paragon of creation.
Clie een.
PROTECTIVE RESEMBLANCE.

CLOSELY related to the foregoing subjects is the protective
resemblance or ‘‘ mimicry’’ of natural objects by which spe-
cies of animals are preserved from extinction. Animals may
‘*mimic”’ or imitate, or be assimilated in shape or in color
to natural objects, as stones, lichens, dry bushes, the bark
of trees, or portions of leaves, or entire leaves, fresh or
dried, and their stems, or so closely imitate other animals
which enjoy an immunity from attack as to escape notice
or attacks from their enemies, and thus prolong their own
lives and that of their species.

The animal is, as a rule, unconscious that it is thus pro-
tected ; though there are examples, as in the case of the
trap-door and other spiders, which cover their holes in such
a way to avoid notice that it would appear as if they were
semi-conscious or aware of what they were doing.

In the first place, we know that animals may be deceived,
as is proved by the various subterfuges employed by hunters
in tolling or deceiving the larger quadrupeds, the use of
decoy-ducks, by which water-fowl are often thoroughly de-
ceived and brought within reach of the gun.

The disguises worn by animals, the exquisite adaptation
of the colors of their fur or feathers to their surroundings,
are part of the general harmony existing throughout nature.
Desert animals are rusty or light-colored ; birds and insects
and lizards, as well as frogs and tree-toads, which live among
trees, are green; those which live among the trunks and
larger branches of trees assimilate in color to the color of
the bark. The cougar, which clings to the trunk of some
676 ZOOLOGY.

tree, prepared to spring upon the deer passing underneath,
is protected from observation by its brown neutral color,
while the bars and lines of the tiger are said to resemble the
lights and shades of the jungle grass in which it les in wait
for its prey. The prairie-dog, the deer, buffalo and ante-
lope on the Western plains, are concealed by their resem-
blance in color to the soil, or to the bushes on its surface.
Among insects, the grasshoppers nearly always harmonize
in color with the general hue of the fields in which they
abound ; insects on light-colored sandy beaches are often
pale, as if bleached out by the sun’srays. Alpine and arctic
butterflies and moths, which have limited powers of flight,
when nestling on lichen-covered rocks, are difficult to detect.

 
  

 
    

SST YH Wi
OA

K Yip
mgs
e

Fig. 542.—A Katydid-like form resembling a leaf.

Certain orthopterous insects resemble leaves; such are
certain katydids (Fig. 542), and especially the famous leaf-
insect, Phylliwm siccifolium Linn. (Fig. 548), which strik-
ingly resembles a green leaf. The stick-insects (Fig. 544)
also would be easily mistaken for the twigs of trees or stalks
of leaves, one species (Fig. 544) representing a moss-grown
twig. The under sides of the wings of our native Grapta
butterflies have the color of dead leaves, so that when they
are at rest they resemble a withered dry leaf. The most
perfect resemblance to a leaf with its stem is the Kallima
butterfly when setting at rest with its wings folded over its
PROTECTIVE RESEMBLANCE. 677

back. The caterpillars of the geometrid moths often won-
derfully mimic the stems of the plants they feed upon, in
color and markings, even to the
warts and tubercles on their skin.

As an example of possibly con-
scious mimicry or effort at conceal-
ing their nest from the search of
their enemies, may be cited the trap-
door spider observed by Moggridge
in Southern Enrope. This spider
digs its hole among moss and small
ferns, and after the trap-door is

made the top is covered with growing

ia, Halt camel Pty ferns, etc., transplanted by the spider,

and the deception is so perfect that

Mr. Moggridge found it difficult to detect the position of
the closed trap, even when holding it in his hand.

Mimicry of other insects is of
very frequent occurrence, certain
flies resembling bees in appearance
and the sounds or buzzing they
make; the Syrphus flies closely
imitate wasps. Fig. 545 illustrates
acase observed by Belt in Nicara-
gua, where a wasp (Priocnemis) is
mimicked by a hemipterous insect
(Spiniger luteocoriis Walker, the
left-hand figure) in every part,
even to its vibrating, brown, semi-
transparent wings and its wasp-like
motions. Here the bug is evidently
protected by its resemblance to the
wasp, for whose ferocity and sharp
sting all unarmed insects have
great respect. ;

Some butterflies are distasteful Fig. 544,--Stick insect.
to birds, and there are other but-
terflies which have no bad taste, but closely resemble in
color such species as are passed over by birds. Thus,

 

 
678 ZOOLOGY.

Danais archippus, 1 common large butterfly, is not eaten
by birds on account of its pungent odor, which is disagree-
able to them. Another butterfly, Limenitis disippus, a
smaller but similarly colored butterfly, which is inodorous,
is supposed to be mistaken by the birds for the Danais, and
thus escapes destruction.

Belt says that in Central America stinging ants are not
only closely copied in form and movements by spiders, but
by species of Hemiptera and Coleoptera ; as stinging ants
are not usually eaten by birds, this disguise is thought to
protect the various forms which imitate them.

Many highly-colored caterpillars, which live exposed on
the leaves of plants, are not eaten by birds, owing to their
bad taste. This and other bright-colored insects may be said

 

Fig. 545—Wasp mimicked by a bug.—After Belt,

to bang out danger-signals to warn off hungry birds. Mr.
Belt, in his ‘‘ Naturalist in Nicaragua,’’ suggests that the
skunk is an example of this kind. ‘‘ Its white tail, laid
back on its black body, makes it very conspicuous in the
dusk when it roams about, so that it is not likely to be
pounced upon by any of the Carnivora mistaking it for other
night-roaming animals.’’ He also cites the case of a very
poisonous, beautifully banded coral snake (laps), which is
‘marked as conspicuously as any noxious caterpillar with
bright bands of black, yellow, and red.’? This author also
found that while the frogs in Nicaragua are dull or green-
colored, feeding at night, and all preyed upon by snakes
und birds, one little species of frog, dressed in a bright liv-
PROTECTIVE RESEMBLANCE. 679

ery of red and blue, hops about in the day-time, and, as he
proved by experiment, is thoroughly distasteful to fowls
and ducks.

We have seen that many animals resemble externally those
above them in the scale of life ; in the synthetic or general-
ized types from which the more specialized forms have prob-
ably originated, there are characters which cause them to
resemble more recent, new-fashioned types. It is possible
that in many cases the older types, doomed as they were to
destruction, have had their existence prolonged by their
protective resemblance to modern types.

For example, the Newroptera as a group are geologically
of high antiquity ; owing to geological extinction, but few
species, compared with those of other orders, have survived ;
and those which are now living often resemble members of
higher, more recent orders. The inference is, then, that
the mimickers have survived by reason of their resemblance
to the more abundant forms which appeared, as the more
old-fashioned types were waning or dying out.

Certain Brazilian species of the lepidopterous family,
Zygenide and Bombycide, mimic in form and coloration
certain butterflies, especially the Heliconide, which abound
in Brazil. The former groups are evidently the older geo-
logically, as there are wide gaps between the genera; and
the indications are that these butterfly-like moths have
likewise, from their resemblance to the more abundant Heli-
conide, been preserved. It thus appears that protective
mimicry may be an important factor in the preservation of
species.
CAP DERG AWve
INSTINCT AND REASON IN ANIMALS.

WE have seen that animals have organs of sense, of per-
ception, in many cases nearly as highly developed as in man,
and that in the mammalia the eyes, ears, organs of smell
and touch differ but slightly from those of our own species ;
also that the brain and nervous system of the higher mam-
mals closely approximate to those of man. We know that
all animals are endowed with sufficient intelligence to meet
the ordinary exigencies of life, and that some insects, birds,
and mammals are able, on occasion, to meet extraordinary
emergencies—in other words, to rise with the occasion.
These occurrences indicate that what usually goes by the
name of ‘“‘instinct’’ is more or less pliable, unstable ;
that animals are in a limited degree free agents, with powers
of choice. Moreover, those naturalists who observe most
closely and patiently the habits of animals do not hesitate
to state their belief that animals, and some more than
others, possess reasoning powers which differ in degree
rather than in kind from the purely intellectual acts of
man.

As a matter of not infrequent observation, animals exer-
cise the power of choice, they select this or that kind of
food, prefer this or that kind of odor, and have their likes
and dislikes to certain persons, and all this aside from mere
physical stimulation of the senses. Moreover, animals are
subject to the passions, they show anger, even when not
hungry or under the domination of the reproductive in-
stincts ; their sounds express dissatisfaction or contentment.
Indeed, many facts could be stated showing that animals
INSTINCT AND REASON. 681

not only have feelings, intelligence, and volition, but are
possibly, in a very slight degree, self-conscious. The fact
that animals exercise discrimination in the selection of
food, in the choice of a flower or object of one color in
preference to another, in perceiving likeness or unlikeness in
two objects, indicates that they can exercise the power of
intelligent discrimination, as has been said by Mr. G. H.
Lewes :* ‘‘ When there is no alternative open to an action
it is impulsive ; when there is, or originally was, an alter-
native, the action is instinctive ; where there are alterna-
tives which may still determine the action, and the choice
is free, we call the action intelligent.’

Indeed, animals have the principle of similarity strongly
developed. It is the bond that holds together the social or-
ganizations of such insects as live in colonies, and such fish,
birds, or mammals as go in schools, flocks, or herds. Were
it not for this mental quality some species would tend to
die out.

Animals possess memory, which consists in storing up in
the mind the results of external impressions, so that they
are enabled to perceive the points of resemblance or differ-
ence between two objects, after having been out of sight of
them for a greater or less length of time: Bain defines
memory, acquisition or retention, as ‘“‘ being the power of
continuing in the mind impressions that are no longer stim-
ulated by the same agent, and of recalling them afterward
by purely mental forces.’

With the aid of memory, birds make their migrations,
bees and ants find their way back to their nests. As we
have elsewhere said, ‘‘ No automaton could find its way
back to a point from which it had once started, however
well the machine had been originally wound up. Nor does
the common notion of an inflexible instinct meet the case.
Memory is often due to a repetition of certain experiences,
and experiences lay the foundation for instinctive acts ; it
is the sum of these inherited experiences which make up
the total which passes under the name of instinct.’’+

* Article on Instinct in Nature, April 10th, 1873.
+ Half Hours with Insects, p. 374.
682 ZOOLOGY.

It would appear, then, that animals have in some slight
degree what we call mind, with its threefold divisions of the
sensibilities, intellect, and will, When we study animals in
a state of domestication, especially the dog or horse, we
know that they are capable of some degree of education,
and that they transmit the new traits or habits which they
have been taught to their offspring ; so that what in the
parents were newly acquired habits become in the descend-
ants instinctive acts. We are thus led to suppose that the
terse definition of instinct by Murphy, that it is “‘ the sum
of inherited habits,’’ is in accordance with observed facts.
Indeed, if animals have sufficient intelligence to meet the
extraordinary emergencies of their lives, their daily, so-
called instinctive acts, requiring a minimum expenditure of
mental energy, may have originated in previous genera-
tions, and this suggests that the instincts of the present
generation may be the sum total of the inherited mental ex-
periences of former generations.

Descartes believed that animals are automata. Lamarck
expressed the opinion that instincts were due to certain in-
herent inclinations arising from habits impressed upon the
organs of the animals concerned in producing them.

Darwin does not attempt any definition of instinct ; but
he suggests that ‘‘ several distinct mental actions are com-
monly embraced by this term,’’ and adds that “‘a little
dose, as Pierre Huber expresses it, of judgment or reason
often comes into play, even in animals low in the scale of
nature.’? He indicates the points of resemblance between
instincts and habits, shows that habitual action may become
inherited, especially in animals under domestication ; and
since habitual action does sometimes become inherited, he
thinks it follows that ‘‘ the resemblance between what origi-
nally was a habit and an instinct becomes so close as not to
be distinguished.’? He concludes that, by natural selection,
slight modifications of instinct which are in any way useful
accumulate, and thus animals have slowly and gradu-
ally, “‘ as small consequences of one general law,’’ acquired,
through successive generations, their power of acting in-
INSTINCT AND REASON. 683

stinctively, and that they were not suddenly or specially
endowed with instincts.

Rey. J. J. Murphy, in his work entitled ‘‘ Habit and In-
telligence,’’ seems to regard instinct as the sum of inherited
habits, remarking that ‘‘ reason differs from instinct only
in being conscious. Instinct is unconscious reason, and
reason is conscious instinct.’’ This seems equivalent to
saying that most of the instincts of the present generation
of animals is unconscious automatism, but that in the begin-
ning, in the ancestors of the present races, instincts were
more plastic than now, such traits as were useful to the or-
ganism being preserved and crystallized, as it were, into the
instinctive acts of their lives. This does not exclude the
idea that animals, while in most respects automata, occa-
sionally perform acts which transcend instinct ; that they
are still modified by circumstances, especially those species
which in any way come in contact with man ; are still in a de-
gree free agents, and have unconsciously learned, by success
or failure, to adapt themselves to new surroundings. This
view is strengthened by the fact that there is a marked de-
gree of individuality among animals. Some individuals of
the same species are much more intelligent than others,
they act as leaders in different operations. Among dogs,
horses, and other domestic animals, those of dull intellect
are led or excelled by those of greater intelligence, and this
indicates that they are not simply automata, but are also in
a degree, or within their own sphere, free agents.
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——

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London, 1828.

* Works used in the preparation of this volume, with the titles of others indispen-
sable to the student.
686 ZOOLOGY.

Manual of Entomology. By H. Burmeister. London, 1836.

Guide to the Study of Insects. By A.S. Packard, Jr. Sixth edition.
New York, 1878.

Invertebrate Animals of Vineyard Sound. By A. E. Verrill. (Re-
port U. 8. Commissioner of Fish and Fisheries.) Washington, 1873.

Invertebrata of Massachusetts. By A. A. Gould. Edited by W. G.
Binney. Boston, 1870.

First Book of Zoology. By E. §. Morse. Second edition. New
York, 1875.

Manual of the Mollusca. By 8. P. Woodward. Second edition.
London, 1868.

Corals and Coral Islands. By J. D. Dana. New York, 1872.

Introduction to the Osteology of Mammalia. By W. H. Flower.
London, 1870.

Advanced Text-Book of Zoology. By H. A. Nicholson. New
York, 1878.

Elementary Biology. By T. H. Huxley and H. N. Martin. New
York, 1876.

With the works and monographs of Dana, Wyman, Leidy, L. and A.
Agassiz, H. J. Clark, Cope, Gill, Hyatt, Verrill, Scudder, Binney,
Allen, Coues, Smith, Baird, Ridgway, Brewer, Dall, Cooper, Wilder,
Riley, Uhler, Edwards, Grote, Le Conte, Hagen, Scammon, Stimpson,
Jordan, Morse, Thomas, Gould, Bland, Prime, Tryon, Gabb, Packard,
and others, and the standard works of Linnzeus, Cuvier, Von Baer,
Leuckart, Gegenbaur, Haeckel, St. Hilaire, Huxley, Mivart, Allman,
Hincks, Shuckard, Westwood, P. J. and E. Van Beneden, Brandt,
Ratzburg, Burmeister, Oscar Schmidt, Metschnikoff, Kowalevsky,
Kupffer, and many others.

The student should also consult the following serials : American Jour-
nal of Science and Arts, New Haven, Conn. ; The American Naturalist,
Philadelphia ; Nature, London ; Quarterly Journal of Microscopical
Science, London; Archiv fiir Naturgeschichte, Berlin; Annals and
Magazine of Natural History, London ; Annales des Sciences Naturelles,
Zoologie, Paris ; Siebold und Kélliker’s Zeitschrift, Canadian Ento-
mologist, London, Canada ; Psyche, Cambridge.

Descriptions of North American animals and essays on their anatomy,
physiology, and development are to be found in the Transactions and
Proceedings of the following scientific societies: American Academy
of Arts and Sciences, Boston ; American Philosophical Society, Phila-
delphia ; Academy of Natural Sciences, Philadelphia ; Boston Society
of Natural History ; Smithsonian Institution ; American Entomologi-
cal Society, Philadelphia; Museum of Comparative Zoology, Cam-
bridge, Mass. ; Essex Institute ; Peabody Academy of Science, Salem;
Academy of Sciences, San Francisco, Cal. ; and other societies in Port-
land, Me. ; Buffalo, N. Y.; Davenport, Iowa; St. Louis, Mo., and
Charleston, 8. C.
BIBLIOGRAPHY. 687

HISTOLOGY.

Handbook of Human and Comparative Histology. By S. Stricker.
New York, 1872.

And the monographs or essays of Leidy, Clark, and C. S. Minot.

PHYSIOLOGY.

Treatise on Human Physiology. By J. C. Dalton. Philadelphia,
1861.

Elementary Lessons in Physiology. By T. H. Huxley. Fourth
edition. London, 1870.

Text-Book of Physiology. ByM. Foster. London, 1877.

EMBRYOLOGY,

Entwicklungsgeschichte der Thiere. Von Baer. Konizsberg,
1828.

Entwicklungsgeschichte des Menschen. Von A. Kolliker.
zig, 1861.

Elements of Embryology. By M. Foster and F. M. Balfour. Lon-
don, 1874.

With the monographs of Wolff, Harvey, Barry, Coste, Pouchet,
Von Baer, Remak, Bischoff, L. and A. Agassiz, Weismann, Metsch-
nikoff, Huxley, Balfour, Parker, and others.

Leip-

ZOOGEOGRAPHY.

The Geographical Distribution of Animals. By A. R. Wallace.
2 vols. New York, 1876.

With the essays of Agassiz, Baird, Allen, Verrill, Ridgway, Gill,
Packard, and others.

EVOLUTION AND RELATION OF ANIMALS TO THEIR ENVIRONMENT.

Philosophie Zoologique. a J.B. de Lamarck. 8vo, 2 vols. 1809.

On the Origin of Species. By Charles Darwin. New York, 1871.

The Origin of Genera. By E. D. Cope. Philadelphia, 1861.

Contributions to the Theory of Natural Selection. By A. R. Wal-
lace. New York, 1870.

On the Origin of Species. By T. H. Huxley. New York, 1863.

With the essays of Cope, Hyatt, Wagner, Weismann, Haeckel,
Kupffer, Palmén, Lubbock, and others.

NATURAL HISTORY OF MAN.

De Generis Humani Varietate Nativa. Von J. F. Blumenbach.
Editio 3. Gottingen, 1795.
683 ZOOLOGY.

Researches into the Physical History of Mankind. By J. C. Prich-
ard. London, 18651.

Types of Mankind. By J. C. Nott and G. R. Gliddon. Philadel-
phia, 1854.

Natural History of the Varieties of Man. By R. G. Latham. Lon-
don, 1850.

Races of Man. By Charles Pickering. London, 1863.

Evidence as to Man’s Place in Nature. By T. H. Huxley. New
York, 1863.

Prehistoric Times. By Sir John Lubbock. London, 1872.

Natural History of the Human Species. By H. Smith. Edinburgh,
1852.

With the works and essays of Reizius, Wilson, Mortillet, Broca,
Lartet, Von Baer, St. Hilaire, $8. Van der Kolk, Vrolik, Schaaffhausen,
Ritimeyer, Busk, Morgan, Wyman, Squire, Davis, Schmerling, Wag
ner, Vogt, Rolle, and others.
GLO

8

SARY.

 

ABDOMEN. In mammals the part
of the trunk below or behind the
thorax ; in insects the third re-
gion of the body, or hind body.

ABERRANT. Departing from the
regular or normal type.

ABORAL. Opposite the oral or)
mouth-region.

ACUMINATE. Ending in a pro-
longed point.

AtveoLtus. <A _ hollow cavity

forming the socket in the jaw
of vertebrates for the teeth.
AMBULACROM (Lat. from ambu-
lare, to walk, a garden-walk).
The perforated space or area in

the shell of the sea-urchin or the
arm of astar-fish, through which |

the foot-tubes or ambulacral
feet are protruded.

AMETABOLIC (Gr. a, without ;
métabole, change). Referring to
insects and other animals which
do not undergo a metamorpho-
sis.

AmorPHous (Gr. a, privitive ;
morphe, form). Without a defi-
nite figure ; shapeless ; especially
applicable to sponges.

AMPHICaLOUS (Gr. amphi ; koilos,
hollow). Applied to vertebrie
which are doubly concave, or
hollow at. both ends.

Anasromosine. Inosculating or

running into each other like
veins.

AncHyLosis. The growing to-
gether of two bones so as to pre-
vent motion between them.

ANNULATE. Whenaleg or antenna
is surrounded by narrow rings
of a different color.

APLACENTAL. Referring to those
mammals in which the embryos
are destitute of a placenta.

Apopous. Footless.

APpTERousS (Gr. a, without ; pteron,
wing). Destitute of wings.

AQquIFERous (Lat. aqua, water ;
fero, I carry). Applied to the
water-carrying or water-vascular
system of the sponges, etc.

AREOLATE. Furnished with small
areas ; like a net-work.

ARISTATE. Furnished with a hair.

ARTHROPODA (Gr. a, without ;
arthros, a joint; pous, podos,
foot). Those Articulata with
jointed feet.

ARTICULATA (Lat. articulus, di-
minutive of artus, a joint).
Cuvier’s subkingdom of worms,
crustacea and insects.

ARTIODACTYLA (Gr. artios, even ;
daktulos, finger or toe). Those
Ungulates with an even number
of toes, as the ox.

AsExuAL. Applied to animals,

|
|

 
690

especially insects, in which the
ovaries or reproductive organs
are imperfectly developed ; and
which produce eggs or young by
budding.

AURELIA. Old term for the pupa
of an insect.

AURICLE (Lat. auricula, a little
ear). One of the cavities of the
heart of mollusks and verte-
brates.

Azyeos (a, without; zugon, a
yoke, apair). Anorgan, suchas
a nerve or artery, situated in the
middle line of a bilaterally sym-
metrical animal, which has
therefore no fellow.

BLASTODERM (blastos, a bud or
sprout ; derma, skin). The outer
layer of the germ-cells of the

embryo.

Birip. Divided into two parts ;
forked.

Brancuia. A gill or respiratory

organ of aquatic animals.
Buccau. Relating to the mouth
or cheeks,
Buuuate. Blistered.

CADUCIBRANCHIATE (Lat. caducus,
falling off ; Gr. bragchia, gills).
Applied to those Batrachia in
which the gills become absorbed
before adult life.

CALCARATED. Armed with spurs.

Catyx. A little cup; often ap-
plied to the body of a Crinoid.

CapiTate. Ending in a head or
knob.
CuHELA. The terminal portion of

a limb with a movable lateral
part, like the claw of a crab ; as
m the chelate maxilla of the
scorpion.

Cutasma (Gr. chiasma, a crossing.)

 

ZOOLOGY.

The commissure of the optic
nerves in most vertebrates.

Curtin (Gr. chiton, a tunic). The
horny covering of insects, etc.

CuyLeE (Gr. chulos, juice). The
milky fluid resulting from the
action of the digestive fluids on
the food or chyme.

CHyME (Gr. chumos, juice). The
acid, partly fluid or partly di-
gested food, produced by the ac-
tion of the gastric juice on the
food.

Cruium (pl. cilia). Microscopic
filaments attached to cells, usu-
ally within the body, and mov-
ing usually rhythmically,

Cacau. Ending blindly or in a
cul-de-sac,

Cacum. A blindsac; usually ap-
plied to one or more append-
ages of the digestive canal.

Ca@nencuyMa (Gr. kotinos, com-
mon ; chwmos, chyme or juice).
Applied in polyps to the coral
mass containing the chymiferous
or nutritive canals connecting the
different polyps.

CommissuRE. The nerves con-
necting two ganglia.

ConcoLorovus. Of the same color
as another part.

ConpyLE (Gr. kondulos, a
knuckle). The articular sur-
face of a bone, especially of the
occiput.

CorticaL. Relating to the cortex

or inner skin; external as op-
posed to medullary.

CostaL (Lat. costa, a rib).
ing to the ribs.

CRIBRIFORM (Lat.cribrum, a sieve ;
forma, form). With perfora-
tions like those of a sieve.

Crop. A partial dilatation of the
gullet or cesophagus, the inglu-

Relat-
GLOSSARY.

vies ; in many insects the fore
stomach or proventriculus.

CuTicLE. The outermost layer of
the integument.

DeENTATE. Furnished with teeth.

DweE.puta (Gr. dis, two, or dou-
ble ; delphus, womb). The sub-
class of Marsupials.

DIFFERENTIATION. The special-
ization or setting apart of special
organs for special work, as the
specialization of the hand of man
from the fore-fvot of other mam-
mals ; also applied to the special
development during embryonic
life of parts adapted for peculiar
or special functions.

DrwiwiaTe. Half round.

Diccious (Gr. dis, two; ovkos,
house). With distinct sexes.

Drerera (Gr. dis, two; pteron,
wing). Two-winged flies; an
order of insects.

DIVERTICULUM. An _ offshoot
from a vessel or from the
alimentary canal.

Ecpysis (Gr. ekdusis, casting off).
The process of casting the skin ;
moulting.

EcHINODERMATA (Gr. echinos, a
hedgehog or urchin ; hence ap-
plied to the sea-urchin; and
derma, skin). The fourth sub-
kingdom of animals.

ELASMOBRANCHII (Gr.
strap; bragchia, gill).
sharks and rays.

Enytra (Gr. elutron, a sheath).
The fore-wings of beetles, serv-
ing to cover or sheathe the hind
wings.

Eprstoma. That part of the face
of flies situated between the
front and the labrum.

elasma, a
The

 

691

EquiuaTeRAL. Having the sides
equal, as in Brachiopod shells.
EquivaLve. Applied to shells like

the clams and most Lamelli-
branchs, which are composed
of two equal pieces or valves.
ExserTED. Protruded , opposed
to enclosed.
Exvuvium. Cast-off skin.

Fissiparous (lat. fissus, cleft ;
pario, to bring forth). Applied
to a form of asexual generation
where the parent splits into two
parts, each part becoming a new
individual.

GEMMIPAROUS (gemma, bud;
pario, to bring forth). Applied
to a form of asexual generation
where new individuals arise as
buds from the body of the
parent.

GuaBRous. Smooth ; opposed to
hairy ; downy, villous.

Guavucovs. Bluish green or gray.

Hamat (Gr. haima, blood).
Connected with the blood-ves-
sels or heart.

Hauteres (Gr. hailteres, poisers).

Balancers; the rudimentary
hind wings of Diptera.
HavstTeLuaTe. Furnished with a

proboscis so as to take food by
suction.

Hemiptera (Gr. hemi, half: pteron,
wing). Anorder of insects with
the fore-wings partly opaque,
hence called hemelytra.

HERMAPHRODITE (Gr. Hermes,
Mercury ; Aphrodite, Venus).
Any animal having the organs of
both sexes, usually the ovary
and testes, combined in the same
individual.
692

Hexapopous. Provided with six
feet.

HYMENOPTERA (Gr. humen, by-
men, or membrane; pteron,
Wing). Anorder of insects with
two pairs of membranous wings.

Hyorp (Gr. Y, eédos, resemblance).
A bone in man named from re-
sembling the letter U ; its form
being different in other verte-
brates: aiso called os lingua,
from its supporting the tongue.

Imaco. The final or fourth,
winged and adult state of insects.

INEQUILATERAL Having the two
ends unequal, as in the clam,
quohog, and most Lamelli-
branch shells.

INEQUIVALVE. With one valve
differing in size or shape from
the other, as in the oyster or
Brachiopod shells.

Irroratep. Freckled ; sprinkled
with atoms.

LAMELLIBRANCHIATA (Lat. la-
mella, a leaf or sheet ; branchia,
gill), A class of mollusks with
large leaf-like gills.

Larva (Lat. larva, a mask).
The second stage of the insect, a
caterpillar, grub, or maggot.

Lumpar (Lat. lwmbus, a loin).
Connected with the loins.

Monecrous (Gr. monos, single ;
otkos, house). With the sexual
glands, etc., united in the same
individual.

NeEmarocyst (Gr. nema, a thread ;
kustis, abladder). The nettling,
stinging organs or thread-cells
or lasso-cells of the jelly-fishes
and polyps, etc.

 

ZOOLOGY.

NEUROPTERA (Gr. neuron, a cord ;
pteron, wing). The order of
net-veined insects.

NipaMENTAL. Referring
nest, or egg-sac.

Notocnorp (Gr. noton, back ;
chorde, a string), or chorda
dorsalis. The primitive support
of the body of vertebrate embry-
as, larval ascidians, and the back-
bone of the lancelet and lam-

preys.

to a

OBTECTED. Covered ; concealed.

ODONTOPHORE (Gr. odous, a tooth ;
phero, I carry). The so-called
tongue or lingual ribbon of the
higher mollusks.

Cisopwacus (Gr. oisos, a reed;
phagein, to eat). The gullet.

OPERCULUM (Lat. operio, to cover).
In fishes one or more bones
covering the gills ; in Gastropod
Mollusks a horny plate or solid
limestone mass closing the orifice
of shells.

OPpisTuocasLous (Gr. opisthen, be-
hind ; kovlos, hollow). Those
vertebrates with bodies hollow
behind and convex in front.

ORAL. Related to the mouth.

ORNITHODELPHIA (Gr. ornis, bird ;
delphus, womb). The sub-class
of mammals and order Monotre-
mata,

ORTHOPTERA (Gr. orthos, straight ;
pleron, wing). The order of
insects with straight narrow fore-
wings, as the grasshoppers.

OsrRacoDa (Gr. ostracodes,shelled).
A group of shelled crustacea.

OroLiTHs (Gr. ous, ear; lithos,
stone). Small bones suspended
in the internal ear of fishes, or
concretions in the auditory sacs
of invertebrates.
GLOSSARY.

Oviparous (Lat. ovowm, an egg ;
pario, I bring forth). Applied
to animals bringing forth eggs
instead of living, active young.

OviposiTor (Lat. ovum, an egg ;
pono, I place). An organ in in-
sects homologous with the sting,
by which eggs are deposited in
solid substances.

Ovisac. A sac or bag-like mem-
brane attached to the parent,
and containing eggs.

Ovo-viviparous (Lat. ovwm, an
egg ; vivus, alive ; pario, I bring
forth). Applied to such animals
as retain their eggs in the body
until they are hatched.

Pauutum (Lat. acloak). The man-
tle or body-wall of mollusks,
which secretes the shell; adj.
pallial.

PARENCHYMA (Gr. paregchuma,
from para, en, chuo, something
poured in besides). Applied to
the proper substance of viscera,
excluding connective tissue,
blood-vessels, and other accesso-
ry parts.

Pexacic. Living on the high
seas, away from the coast ; in
mid-ocean.

PERISOME (Gr. perz, around ; soma,
body). In Crinoids the oral re-
gion of the cup or body.

PERRENNIBRANCHIATA (Lat. per-
ennis, perennial ; branchia, gill).
Those Batrachia which retain
their gills throughout life.

PERISSODACTYLA (Gr. perissos, un-

, even ; daktulos, finger). Those
Ungulates with an uneven num-
ber of toes, as the horse.

PERITONEUM (Gr. pert, around ;

teino, I stretch). The membrane |

 

693

lining the abdominal walls and
covering the enclosed viscera.

PERIVISCERAL (Gr. pert, around ;
Lat. viscera, the internal organs,
especially of the abdominal cav-
ity). The body-cavity contain-
ing the alimentary canal with
its outgrowths.

Picrovs. Pitchy; the color of
pitch ; shining reddish black.
Pinose. Clothed with pile, or

dense short down.

Puiexus (Lat. a knot). Applied
to a knot-like mass of nerves
or blood-vessels.

PotypmE or Po.LypitE. The
separate animals of a Hydro-
zoon.

Preorau. In front of the mouth.

Process. <A_ projection; used
chiefly in osteology.

Proce@1ovus (Gr. pro, front ; koilos,
hollow). Those vertebra con-
cave or hollow in front.

PRroTOPLASM (Gr. protos, first ;
plasma, from plasso, I mould).
The albuminous, elementary
matter forming cells and the
body-substance of Protozoa.

Proxmat. (Lat. provimus, next).
The fixed end of a limb, bone or
appendage; that nearest the
body , opposed to distal, the
farther end.

Pseupopopia (Gr. pseudes, false ;
odes, feet). The temporary pro-
cesses sent out from the bodies
of Protozoa.

Preropopa (Gr. pteron, wing ;
podes, feet). A class of pelagic

mollusks.

PUBESCENT. Coated with very
fine hairs.

PuncturED. Marked with nu-

merous small impressed dots.
Pupa (Lat. a doll). The third or
694
usually quiescent, chrysalis
stage of insects.

Ratirz (Lat. ratis, a raft), A
division of birds with a keelless,
raft or punt-like sternum.

Ruizopopa (Gr. rza, root ; pous,
podos, foot). The root-footed
Protozoa.

Rotrrera (Lat. rota, a wheel;
ero, [ bear). An order of crus-
tacea with a pair of ciliated vela
in motion, resembling wheels.

SarcopE (Gr. sarz, flesh; odos,
way). Equivalent and earlier
term for protoplasm.

scaBrous. Rough like a file,
with small raised dots.

SEracrous (Lat. seta, a bristle).
Bristle-like.

SPIRACLE (Lat. spi7o, to breathe).
The lateral breathing pores of
insects.

SriemMaTa (Gr. stigma, a mark). A
synonym of spiracle.

StToton (Lat. stolo, a shoot spring-
ing from the root of a plant).
Applied to the root-like creeping
growths of polyps and other Cee-
lenterates.

STREPSIPTERA (Gr. strephis,a twist;
pteron, wing). A group of beetles,
whose minute front wings appear
as if twisted.

STROBILA (Gr. strodvlos, a fir cone}.
The chain of zooids of a larvai
medusa ; the chain of proglot-
tides of a tape-worm.

Suture. A seam or impressed
line between the bones of the
skull or parts of the crust of an
Arthropod.

Sympuysis (Gr. swmphusis, a grow-
ing together). The uuion of
two bones.

 

ZOOLOGY.

TELson (Gr. telson, from telos, end).
The rudimentary terminal seg-
ment of the abdomen of Arthro-
pods.

TENERAL. A state of the Neurop-
terous imago after exclusion
from the pupa, in which it has
not fully completed its coloring,
clothing, etc.

TENTACULUM (Lat. tento, I touch).
A feeler or tentacle.

TERGUM (Lat. back). The dorsal
region of Arthropods.

Test (Lat. testa, a shell). The
thickened integument of Tuni
cata.

Testacrtous. Dull red; brick
color.

THorax (Gr. thorux, a breast-
plate). The chest in verte-

brates ; the middle body in in-

sects and some crustacea.
Tuysanoura (Gr. thusanoi, fringes ;

oura, tail). The lowest order of

insects.

ToMENTOSE. Covered with fine
matted hairs.

TRABECULZ (cranii), dim. of

trabs, a beam. Applied to the
longitudinal cartilaginous bars of
the fore-part of the head of ver-
tebrate embryos.

TRACHEA (Gr. tracheia, the rough
windpipe). The respiratory
tube in vertebrates; the air-
tube of Tracheate insects.

TREMATODA (Gr. trema, a pore

or hole). An order of
worms.

TRUNCATED. Cut squarely off ;
docked.

TUBERCULOSE. Covered with tu-
bercles.

TunicaTa (Lat. tundea, a cloak).
The class of worms called As-
cidians.
GLOSSARY.

Umeo (Lat. the boss of a shield).
The beak of a Lamellibranchiate
shell.

Uneutata (Lat. wngula, a hoof).
The order of hoofed mammals.
URODELA (Gr.owra, tail ; delos,visi-
ble). The tailed Batrachians.

VACUOLE (Lat. vacuus, empty).
The little cavities in the bodies
of Protozoa.

VENTRAL. Applied to the under
side of the abdomen, or of the
body of invertebrates.

VENTRICLE (Lat.  ventriculus,
diminutive of venter, belly). One
of the cavities of the heart.

VERRICULATE. With thick - set
tufts of parallel hairs.

VERRUCOSE. Covered with wart-
like prominences.

VERTEBRA (Lat. verto, I turn).

 

695

One of the bones of the spinal
column or backbone.
VERTICILLATE. Placed in whirls.
VESICLE (Lat. vesica, a bladder).
A little sac, bladder, or cyst.
ViscErA (Lat. viscws). The inter-
nal organs of the body.
Viviparous (Lat. vs, alive ; and
pario, L bring forth). Applied to
animals which bring forth their
young alive.

Zobrp (Gr. zodn, animal; eidos,
form). The highly specialized
organs of such animals as the
Hydroids, and other compound
forms which have a marked in-
dividuality, and which might be
mistaken for genuine individu-
als.

ZooPuytsE (Gr. zodn, animal ; phu-
ton, plant). Applied to the
plant-like polyps, sertularians,
and sponges.
INDEX.

ACANTHARCHUS POMOTIS, 443
Acanthocephali, 165, 175
Acanthoglossus Bruijnii, 573
Acarina, 359, 386
Achorutes nivicola, 564
Acineta, 34
Acipenser sturio, 427
development of, 427
Acrania, 401, 405
Actheres Carpenteri, 298
Actinia, 74, 78
Actinophrys sol, 27
Actinospherium, 26 ‘
Actinozoa, 74, 91
budding of, 77

Adaptation of animals to their’sur-

roundings, 10
Adder, puff, 499
Aigineta, 62
AXolis pilata, 265
ZHpyornis, 588
Agamogenesis, 54
Agelacrinus, 108
Ai, 579
Aix sponsa, 543
Albatross, 542
Albertia, 179
Alca impennis, 541
Alcyonaria, 85, 91
Alectorides, 544
Aletia, 379
Alewife, 450, 451
Alligator Mississippiensis, 514
Alopecias vulpes, 420
Alosa sapidissima, 450
Alpheus, 315

 

Alytes obstetricans, 484
Amarecium, 200
Ambergris, 593
Amblyopsis spelzus, 453
Amblyrhynchus, 504
Amblystoma mavortium, 479
Amia calva, 433
Amiurus lynx, 443
Ammocetes, 410
Ammonites, 280
Ameeba, 8, 17, 22
Ampelis cedrorum, 553
Amphibia, 464
Amphioxus, structure of, 406
development of, 407
Amphipoda, 305
Amphisbena, 502, 503
Amphitrite cirrata, 236
ornata, 239
Ampulle of Echinoderms, 97
Anabas scandens, 457
Anadromous fishes, 451
Analogy, 12
Anas boschas, 543
obscura, 543
Anchitherium, 602
Ancistrodon contortrix, 500
piscivorus, 500
Andrena, 384
Andrias Scheuchzeri, 479
Anemone, sea, 74
Angle, facial, 626
Angler, 442, 460
Anguilla acutirostris, 446.
Anguillula aceti, 170
tritici, 170
698

Animalcule, bear, 361
Auimalcules, bell, 39
infusorian, 31
root, 22
trumpet, 35
Animal kingdom, classification of,
15
Animals, development of, 643
distinguished from plauts, 1
high and low, 6
Annelides, 229, 238
Annulata, characters of, 225
classification of, 238
Anochanus sinensis, 121
Anodonta, 245
Anolis, 503
Anomodontia, 512
Anopla, 218
Anoplodium Schneideri, 145
Ant, 381
Ant-eater, spiny, 573
Ant, white, 367
Antedon rosaceus, 103
Antelope, prong horn, 609
Anthracarida, 306
Anthrapalemon, 314
Anthropoidea, 618, 619
Antilocapra Americana, 609
Antipathes arborea, 85
Anura, 483, 488
Apes, 621
Aphis, 371, 653
lion, 367
Apis mellifica, 385
Aploceros montanus, 610
Apodes, 446
Appendicularia, 199
Apteryx, 538
Aptornis, 538
Apus equalis, 302
Arachnactis,79
Arachnida, characters of, 358, 386
development of, 362
Araneina, 862, 3886
Arcella, 24
Archwopteryx macrura, 53

 

INDEX.

Archaster, 114

Archegosaurus, 482

Architeuthis monachus, 282
princeps, 282

Arciferous Anura, 484

Arcturus Baffini, 310

Argonauta, 283

Argulus alos, 299

Armadillo, 580

Army worm, 879

Artemia fertilis, 304
gracilis, 303

Arthromere, 286

Arthropoda, characters of, 285

Artiodactyla, 600, 605

Ascaris dentata, 164
lumbricoides, 167
inystax, 167
nigrovenosa, 164

Ascetta primordialis, 42

Ascidia callosa, 202
gigas, 202

Ascidiacea, 197, 215

Ascidians, 196

Asellus, 308, 310

Asexual generation, 633

Asiphonia, 256

Asp, 499

Aspergillum, 250

Aspidogaster conchicola, 152

Aspidonectes spinifer, 510

Aspredo, 449

Asterias vulgaris, 96, 112, 115

Asteridea, 111, 116

Asteroidea, 109, 116

Astreea pallida, 81

Astrangia, 80

Astrangia Dane, 81

Astrogonium, 114

Astroides, development of, 82

Astropecten, 114

Astrophyton Agassizii, 111

Atalapha noveboracensis, 591

Ateles, 560, 620

Atlantosaurus, 515

Atoll, 89
INDEX. 699
Atrium, 198 Bear, 615
Auk, great, 541 Beaver, 584

Aurelia aurita, 63
flavidula, 65

Auricularia, 132

Auroch, 612

Autechinida, 123, 126

Autolycus, 235

Automata, animals as, 682

Aves, anatomy of, 518, 525
characters of, 518, 557
development of, 532
feathers of, 523
moulting of, 5384
nesting habits of, 53
sexual colors of, 585
skeleton of, 518, 519, 521
songs of, 535
topography of, 520

Axinella polypoides, 48

Axolot], 479

Aye-aye, 619

BaBoon, 620
Balena mysticetus, 592
Bualeeniceps rex, 545
Baleenoptera boops, 592
Balanoglossus aurantiacus, 219
Balanus balanoides, 293
Balatro, 179
Baphetes, 483
Barnacle, 292
anatomy of, 293
Barramundi fish, 480
Bathycrinus, 101
Bats, 588
Batrachia, breeding habits of, 484
characters of, 464, 487
development of, 476
gills of, 468
poison of, 475
reproduction of lost parts of,
481
skeleton of, 465
teeth of, 467
viviparous, 479

 

Bee, 379, 385
Beetles, 872
oil, 372
Belone longirostrus, 454
Bilateral symmetry of Ctenopbora,
92, 93
Echinoderms, 96, 120
Bilharzia hematobia, 152
Bill fish, 454
Bimana, 624
Bipalium dendrophilus, 148
Bipinnaria, 113
Birds, diving, 541
of prey, 548
perching, 551
raptorial, 548
swimming, 543
(Also see Aves.)
Bison, 611
Bladder, swimming, of fishes, 442
Blastoidea, 107, 109
Blind fish, 442, 444, 453
shrimps, 815
Blissus leucopterus, 370
Blister beetles, 373
Blood, circulation of, 685
Blood corpuscles, 8
Blue-fish, 455
Boa-constrictor, 496
Bolina alata, 92, 93
Boltenia reniformis, anatomy of,
197
Bonellia viridis, 224
Bootherium, 610
Bopyrus pandalicola, 308
Bos longifrons, 612
primigenius, 612
taurus, 613
Bot fly, 375
Bothriocephalus Jatus, 159
Box-fish, 462
Brachiata, 101, 109
Brachiolaria, 113
Brachionus, development of, 178
700

Brachiopoda, development of, 192
structure of, 188, 192, 195
Brachypyge carbonis, 314
Bradypus tridactylus, 579
Brain coral, 80
Branchinectes Coloradensis, 303
Branchioganoidei, 431
Branchiopoda, 299, 825
Branchipus, 303
Branta Canadensis, 544
leucopsis, 544
Bream, 455
Brisinga, 114
Bristle-tails, 364
Bruta, 577, 629
Bryozoa, 180
Bubo Virginianus, 549
Buccinum undatum, 268
Bucephalus cuculus, 150
Budding in Ascidians, 202, 212
Hydroids, 54
Infusoria, 37
Medusa, 60
Polyps, 77, 82
Starfish, 110
Bufo ictericus, 475
lentiginosus, 485
Bugs, 370
Bustard, 546
Butcher bird, 555
Butterfly, 377
Buzzard, turkey, 548

CACHELOT, 593

Caddis fly, 367

Caiman, 515

Cayman, 515

Calamoichthys, 431

Calcispongie, 46, 49

Caligus curtus, 299

Callignathus simus, 594

Callorhynchus, 424

Caloptenus spretus, 328
femur-rubrum, 328

Calyptreea sinensis, 263
striata, 263

 

INDEX.

Camarasaurus, 515

Cambarus pellucidus, 315

Camel, 614

Camelus, 614

Campanulariz, 61

Campodea, 364
Americana, 365
Cookei, 365

Cancer irroratus, 313

Canis caribeeus, 617
domesticus, 617
extrarius, 617
familiaris, 616
latrans, 617
leporarius, 617
molossus, 617
sagax, 617
vertagus, 617

Canthocamptus cavernarum, 297

Capelin, 452

Capybara, 586

Carcharias gangeticus, 421 -

Cardium pygmzum, development

of, 258

Cariacus Virginianus, 609

Caribou, 609

Carinate, 541, 557

Carneospongee, 47, 49

Carnivora, 614, 629

Carp, 453

Caryocystites, 108

Caryophylleus, 161, 162

Cassowaries, 539

Catarrhine, 620

Cat, anatomy of, 564
civet, 617
domestic, 617

Cat-fish, 443

Catenula lemne, 144
‘quaterna, 144

Cathartes atratus, 548
aura, 548

Cattle tick, 360

Caudina arenata, 134

Cavolina tridentata, 258

Cebus, 620
INDEX. 701

Cecidomyia, 377
Cells, 5
Centipede, 358
Cephalaspis Lyellii, 427
Cephalization, 289, 314, 405
Cephalophora, characters of, 257
classification of, 272
Cephalopoda, characters of, 272
classification of, 283
develepment of, 27
Cephalopterus diabolus, 424
Cephalula, 177
of worms, 283, 234
Ceratodus Fosteri, 429
Cercaria cystophora, 150
echinata, 150
Cercaria, history of, 147
Cercoleptes, 615
Cercopithecide, 620
Cerianthus borealis, 79
Cermatia forceps, 358
Cervus Canadensis, 609
Cestodes, structure of, 153, 163
Cestracion, 416
Cetacea, 591, 629
Cete, 591, 629
Cetiosaurus, 515
Chetoderma nitidulum, 224
Chetognathi, 174, 175
Chetopoda, 236
Chetosoma, 170
Chalinula oculata, 48
Chameleon, 503
Charybdea, 62
Cheiromys, 619
Chelifer, 362
Chelonia, anatomy of, 505
characters of, 504, 517
Chelydra serpentina, 510
Chick, development of, 646
Chilichthys turgidus, 462
Chilognatha, 356, 385
Chilomycterus geometricus, 462
Chilopoda, 358, 386
Chimera, 425
plumbea, 425

 

Chimpanzee, 622
Chinch-bug, 370

Chirodota leve, 124
Chiroptera, 588, 629
Chirotes, 502

Chiton, nervous system of, 268
Chiton ruber, 268
Chondroganoidei, 427
Chorda dorsalis of Ascidians, 206
Chordeiles Virginianus, 551
Chrysemys picta, anatomy of, 506
Chrysothrix, 620

Chub, 453

Chub sucker, 443

Chyle of polyps, 77

Chyme of polyps, 75

Cicada, seventeen-year, 371
Cidaris nutrix, 122

Ciliary motion, 142

Ciliata, 35, 40

Cinclides, 75

Cinura, 365

Cirratulus grandis, 23
Cirripedia, 292, 325
Ciatenides Gouldii, 236
Cladocera, 299 :
Cladodactyla crocea, 133
Clam, anatomy of, 242
Clamatores, 552
Classification, 13

Clepsine, embryology of, 228
Clidiophora trilineata, 250
Climbing fish, 457

Cliona sulphurea, 49

Clione papillonacea, 259
Clupea harengus, 450
Clymenella torquata, 236
Clypeaster, 123

Coati, 615

Cochineal insect, 371

Cod, 458

Codosiga pulcherrimus, 32
Ceecilia, 482

Coelenterata, 51

Coenosarc of coral polyps, 85
Coleoptera, 372, 886
702 INDEX.

Collembola, 864
Collosphcera spinosa, 27
Colobus, 621
Coloration, protective, 675
of snakes, 497
Colossochelys, 511
Commensals, 68, 459
Comparative anatomy, 631
Complementary males, 293
Compsemys, 511
Compsognathus, 516
Condor, 548
Condylura cristata, 587
Conger oceanicus. 446
young of, 446
Conjugation in Infusoria, 39
Conurus Carolinensis, 550
Copperhead snake, 500
Corals, deep sea, 84:
development of, 83
fishery, 85
polyps, 74
rate of growth of, 84
reefs, formation of, 86, 88
tabulate, 58
Corallium rubrum, 85
Cordylophora lacustris, 57
Coreus tristis, 370
Cormus, 181
Coryne mirabilis, 59
Coryphena, 455
Coryphodon, 571, 601
Cotton worm, 379
Cowry money, 269
Crane fly, 3877
Cranes, 544
Craniota, 401, 405
Craspeda of polyps, 75
Craw-fish, 315
Cribella sanguinolenta, 115
Crinoidea, 101, 108
development of, 105
Crocodilia, 514, 517
Crocodilus acutus, 514
Crossaster papposus, 115

 

 

Crow, carrion, 548

Crustacea, classification of , 292,325
structure of, 286

Cryptobranchus Japonicus, 479

Cryptocelum opacum, 145

Cryptophialus minutus, 297

Ctenophora, bilateral symmetry

of, 92

characters of, 92, 94
classification of, 95
digestive cavity of, 92, 93
nervous system of, 92
water-vascular system of, 92

Cuculi, 551

Cuma, 313

Cumacea, 314

Cunina octonaria, 63

Cunner, anatomy of, 434

Curlew, 545

Cuttle-fish, 27.
gigantic, 281

Cyamus ceti, 311

Cyanea arctica, 67

Cyclocardia novangliz, 249

Cyclops quadricornis, 297

Cyclostomata, 401

Cyclostomi, 409

Cymothoa, 308

Cynthia pyriformis, 202

Cyphonautes, 187

Cypreea moneta, 269

Cyprinus, 458

Cypris, 299

Cysticercus cellulose, 156

Cystid, 181

Cystideze, 108, 109

Cytode, 6

Dacz, 453

Dactylogyrus amphibothrium, 153
fallax, 153

Daphnia, 299

Darter, 456

Dasypus novem-cinctus, 580

Date shell, 250
INDEX. 703

Decapoda, 312, 825
Cephalopoda, 280
Deer, 608
Deltocyathus Agassizii, 80
Dendroceela, 145
Dendroccelum lacteum, 141, 144
perceecum, 112
Dendreeca virens, 555
Dentalium, 257
Desmosticha, 126
Devil-fish, 424
Diatryma, 540
Dibranchiata, 289, 284
Dicyema, 139
Dicyemella, 140
Dicynodon, 512
tigriceps, 512
Didelphia, 571, 628
Didelphys Virginiana, 575
Didus ineptus, 547
Diemyctylus viridescens, 481
Differentiation, 6 .
Digestion, organs of, 631
Digestive canal, 9
Dimorphism, 604
Dingo, 617
Dinichthys Torrelli, 431
Dinornis giganteus, 538
Dinosauria, 515, 517
Dinotherium, 599
Diomedea exulans, 542
fuliginosa, 542
Diploria cerebriformis, 80
Diplozoon paradoxum, 152
Dipnoi, 425, 425, 428
Diptera, 375, 386
Discina, 193
Discophora, 62, 72
Dispersal of animals, 660
Distomum crassum, 151
development of, 147
heterophyes, 151
Janceolatum, 151
macrostomum, 152
ophthalmobium, 151
Distribution, geographical, 658

 

Dodo, 547

Dog-fish, 420
shark, 420

Dog, varieties of, 617

Doliolum, 201, 208

Dolphin, 455

Doris, 265

Dorosoma cepedianum, 443

Dove, 547

Druin-fish, 443

Duck, black, 543
canvas-back, 543
eider, 543
summer, 543

Dugong, 596

EAGue, bald-headed, 548
Ear, 641
of clam, 245
of crustacea, 291
Ears of mammals, 563
Earwig, 368
Earthworm, anatomy of, 229
embryology of, 230
Ecardines, 196
Echeneis remora, 454
Echidna hystrix, 573
Echinarachnius parma, 123
Echinococcus, 159
Echinoderes, 179
Echinodermata, blood system of,
100, 130
characters of, 96
direct development of, 114,
121, 133
“heart ” of, 100, 104
metamorphoses of, 106, 112,
120
nervous system of, 97, 104
skeleton of, 97, 118
viviparous, 110, 121, 122
water-vascular system of, 99,
130
Echinoidea, 117, 126
Echinorhynchus angustatus, 166
claviceps, 166
704

Echinorhynchus gigas, 165
Echinus, 117
esculentus, 123
Echiurus, 224
Eciton, 383
Ectoderm, 6
Ectoprocta, 188
Educabilia, 582, 591
Edentata, 577, 629
Edible Holothurians, 135
sea-urchin, 123
Edwardsia, 78
Kei, breeding habits of, 446
conger, 446
sound produced by, 444
Kel-pout, 458
Eggs, winter, of Crustacea, 300
Planarians, 145
Polyzoa, 187
Rotatoria, 178
Elasmobranchii, characters of, 414,
463
development of, 418
eyes of, 417
teeth of, 416
Elaps, 497, 678
Elasmosaurus platyurus, 513
Electrical eel, 450
fish of the Nile, 449
ray, 422
Elephant, 597
Elephas, 597
prinigenius, 598
Elk, 608
Elytra, 872
Embryology, 18, 643
Encrinites, 101
Encrinus liliformis, 137
Endocyst, 181
Endoderm, 6
Endostyle, 199
Enneacanthus obesus, 456
Enopla, 219
Enteropneusta, development of, 220
structure of, 219, 221
Entomostraca, 297, 325

 

INDEX.

Entoprocta, 188
Eohippus, 602
Epeira vulgaris, 363
Ephemera, 367
Epigonichthys cultellus, 408
Epipodium of mollusks, 258
Epistome of Polyzoa, 184
Epistylis, 39
Epithelium, 7
Epizoanthus Americanus, 79
Equus asinus, 605

caballus, races of, 603

hemionus, 604

onager, 604
Erimyzon oblongum, 443
Eretmochelys imbricata, 510
Escharina, 186
Estheria Belfragei, 302
Enchone elegans, 236
Euplectellum aspergillum, 48
Eupomotis aureus, 455.
Euproédps Dane, 322
Eupyrgus, 128
Eurypauropus, 358
Kurystomee, 94
Eustrongylus buteonis, 169

chordeilis, 169

gigas, 168

papillosus, 169
Evolution, 11
Existence, struggle for, 673
Eye, 640

dorsal, of Mollusca, 257

of blind craw-fish, 315

of Crustacea, 290

of mollusks, 274

FASCIOLA HEPATICUM, 150
Fauna, 661
chief zoological, 666
Favia, 80
Feathers, 523
Felis concolor, 617
domestica, 617
Fere. 614
Fer-de-lance, 499
INDEX.

Fertilization of ege, 644
~Fierasfer, 459

Filaria hematica, 170
lentis, 170
medinensis, 169
sancuinis-hominis, 170

Fishes, see Pisces.

Fishes, anatomy of, 434
bony, 484
characters of, 411
climbing, 457
development of, 445
Elasmobranch, 414
fins of, 411, 428
ganoid, 425
lateral line of, 442
mucous canal of, 442
respiration of, 442
sounds produced by, 442
spiracle of, 417
teeth of, 416, 442
viviparous, 418, 444

Fish-hawk, 548

Fish-lice, 297

Fission in Planarians, 144

Flabellum angulare, 80

Flagellata, 31, 40

Flamingo, 544

Flea, 377
sand, 311, 376
snow, 3864
water, 299

Flounder, 459

Fluke-worms, 147

Fly, bot, 375
house, 374, 375

Flying-fish, 453

Foraminifera, 24, 27

Forficula, 368

Fossil jelly-fishes, 71
sea-urchins, 125
star-fishes, 116

Frog, 487
anatomy of, 470

Fuligula vallisneria, 543

Fungia, 82

 

xd
oO
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GADUS MORRHDA, 458
Galago, 619
Galeopithecus volans, 588
Gall-flies, two-winged, 377
Gall-fly, hymenopterous, 380
Gallinago Wilsonii, 545
Gallinula, 544, 545
Gammarus robustus, 311
Gampsonyx, 3806
Ganglion, 8
Ganocephala, 482
Ganoidei, characters of, 425, 463
development of, 482
Gare fow], 541
Gar-pike, 481
development of, 432
Gasterosteus, 456
Gastreades, 140
Gastropoda, 259, 272
Gastrotheca, 485
Gastrotricha, 179
Gastrula, 43
Gavial, 514
Generations, alternation of, 652
in Ascidians, 210
in corals, 82
in Trematodes, 147
in worms, 2353
Geographical distribution, 658
Geological succession, 668
Geophilus bipuncticeps, 858
Geoplana flava, 142
Gephyrea, development of, 223
structure of, 221, 225
Gerardia, 85
Germigene, 141, 147
Geryonia, 62
Giant bird, 545
Gibbon, 621
Gills, 637
Gizzard-shad, 443
Gland, green, of lobster, 291
Glass-snake, Opheosaurus, 503
Glires, 582, 629
Globe-fish, 463
Globicephalus brachypterus, 595
106

Globicephalus melas, 595

Globigerina bulloides, 24

Glycimeris siliqua, 250

Gly ptodon, 580

Gnathostomata, 401

Gonotheca, 61

Goose, barnacle, 544
wild, 544

Goose-fish, 460

Gordiacea, 171

Gordius aquaticus, 172

Gorgonia flabellum, 86

Gorgonide, 86

Gorilla, 623

Grallatores, 544

Grampus griseus, 595

Graptolites, 61, 71

Grasshopper, anatomy of, 828

Gregarina gigantea, 28

Gregarinida, 28, 31

Grilse, 452

Guanin, 75

Guillemot, 541

Guinea-hen, 546

Guynia annulata, 84

Gymnarchus niloticus, 449

Gymnolemata, 186

Gymnomonera, 22

Gymnophiona, 481, 488

Gymnotus electricus, 450

Gynzecophore of trematode worms

152
Gyrodactylus elegans, 153

Haprosaurus, 515
Hag-fish, 409

Haimea, 85

Hair, 561

Hair-worms, 171

Hake, 458

Halcampa producta, 78
Haliaétus leucocephalus, 548
Halicore, 596
Halistemma carum, 70
Halophila borealis, 180
Halyclystus auricula, 64

 

INDEX.

Haplodon rufus, 585

Haplophyllia paradoxa, 84

Hare, varying, 586

Harmony between animals and

their surroundings, 670

Harvest men, 362

Hatteria, 511

Hearing, organs of, in mollusks,

270

Heliopora ccerulea, 80

Heliozoa, 27

Helix albolabris, anatomy of, 265

Hell-bender, 479

Heloderma horridum, 504
suspectum, 504

Hemiaster cavernosus, 121
Philippii, 121

Hemippus, 604

Hemiptera, 370, 386

Herring, 450

Hesperornis, 538

Hessian fly, 377

Heterometabola, 364

Heteromita, 33

Heterodontidez, 416

Heteropoda, 270, 273

Hexapoda, 363, 386

Hexathyridium pinguicola, 152
venarum, 152

Himantopus nigricollis, 545

Hipparion, 602

Hippocampus, 443

Hippocampus minor, 618

Hippopotamus, 600

Hirudinea, development of, 229
structure of, 226, 233

Hoasin, 547

Holocephali, characters of, 424

Holopus, 104

Holothuria edulis, 135
Floridana, anatomy of, 131

Holothuroidea, 126, 136

Homology, 12

Homo sapiens, 624

Horned toad, 503

Horn-tail, 880
INDEX.

Horse, genealogy of, 602
races of, 604
House-fly, 374
Humming-bird, 551
Hyalonema boreale, 48
longissimum, 48
Hybrid ducks, 548
Hybridity, 657
Hydatids, 158
Hydra, anatomy of, 52
development of, 56
vulgaris, 52
Hydractinia echinata, 56
Hydroidea, 52, 72
Hydrozoa, 52, 71
classification of, 73
nervous system of, 62, 65
organs of taste in, 63
Hyla Pickeringii, 484
Hylobates, 622
Hylodes Martinicensis, 485
Hymenoptera, 379, 387
Hyocrinus, 102
Hyoganoidei, 431
Hyperia, 68, 311
Hyperoartia, 410
Hyperotetra, 410
Hypobythius calycodes, 202
Hypodermis, 289
Hyracoidea, 599, 629
Hyrax, 599

IBia, 293

Ichneumon fly, 381

Ichthyopterygia, 511, 517

Ichthyornis, 538

Ichthyosaur, 512

Idotz#a, nervous system ox, 306,
310

Idyia roseola, 93

Iguana, 504

Iguanodon, 515

Individuality, 656

Ineducabilia, 582

Infusoria, 31, 40

Inheritance, law of, 11

 

707

Insectivora, 587, 629

Insects, anatomy of, 328
brain of, 339
characters of, 827
classification of, 3885
digesticn in, 336
ears of, 345
eye of, 345
embryology of, 349
locomotion in, 347
metamorphosis of, 328
parthenogenesis in, 353
polymorphism in, 368
respiration of, 343
senses of, 346
useful, 854

Instinct, nature of, 680

Tsopoda, 305

Isurus punctatus, 420

Ixodes albipictus, 359
bovis, 360

JACCHUS, 620
Jaws, 631
Jelly-fish, 62
Julus, 356

KANGAROO, 575, 577
Katydid, 676
Killer-whale, 595
King-bird, 552
King-crab, 317
Kinglet, 555
Kiwi-kiwi, 538
Kogia Floweri, 594

LABYRINTHICI, 457
Labyrinthodon, 482, 488
Labyrinthodontia, 482
Lacertilia, 501, 517
Lachnosterna fusca, 372
Lactophrys trigonus, 462
Lelaps, 515
Lagopus leucurus, 546, 547
Lamellibranchiata, 242
classification of, 256
708

Lampreys, 409
Lamp shells, 188
Lancelet, 406
Larva of Echinoderms,
110, 112, 120
Hydrozoa, 83
Insects, 828
Worms, 232
Lasso-cells in Aurelia, 67
Hydra, 53
Infusoria, 37
Polyps, 76, 81
Sponges, 43
Worms, 148
Lateral line of fishes, 442
Leaf insect, 677
Leech, 226
Lemnisci, 165
Lemur, 618
Lepas fascicularis, 293
Lepidoptera, 377, 387
Lepidosiren paradoxa, 430
Lepidosteus, development of, 432
osseus, 431
platystomus, 432
spatula, 432
Lepidurus Couesii, 302
Lepomonera, 22
Leptocardii, 406, 408
Leptocephalus, 446
Leptodiscus medusoides, 34
Leptoplana, 144
Leptosynapta Girardii, 134
Leptychaster, 114
Lepus Americanus, 586
Bairdii, 586
Lernza branchialis, 297
Lerneonema radiata, 298
Leucochloridium, 152
Lice, plant, 371
Ligula simplicissima, 162
Limacina arctica, 258
Limax flavus, 265
Limicole, 544
Limnadia Agassizii, 302

Limnetis Gouldii, 301, 302

96, 105,

 

INDEX.

Limnoria terebrans, 310
Limpet, 263
Limulus, anatomy of, 317
development of, 320
Polyphemus, 317
Lineus, 218
Lingual ribbon of mollusks, 276,
682
Linguatulina, 361
Lingula, 189, 190, 191
pyramidata, 195
Liodon, 500
Lissotriton punctatus, 481
Lithobius Americanus, 358
Lithodomus, 250
Littorina littcrea, 268
Liver fluke, 150
Lizards, sea, 504
structure of, 501
Lobatee, 95
Lobster, anatomy of, 286
Locust, anatomy of, 3828
Loggerhead turtle, 510
Loligo pallida, 273
Pealii, anatomy of, 273
Loon, 541
Lophius piscatorius, 460
Lophobranchii, 460
Lophohelia prolifera, 80
Lophophore, 182
Loxosoma, 185, 187
Lucernaria, 63
Lucifuga subterraneus, 459
Luidia, 114
Lumbricus agricola, 230
rubellus, 230
terrestris, 229
Lunatia heros, anatomy of, 261
Lung-fish, 428
Lymnezus appressus, 266
elodes, 266
Lymphatics, 636
Lynx Canadensis, 617
rufus, 617
Lyre-bird, 552
Lystrosaurus, 513
_ INDEX.

Lytta marginata, 373

Macacwus, 620
Machilis, 365
Mackerel, 456
Macrobiotus Americanus, 3861
Macropus thetidis, 577
Mactra lateralis, 249
ovalis, 251
Madrepora cervicornis, 82
Meandrina, 80,81, 84
Magpie, 554
Malacopoda, 355, 385
Malapterurus electricus, 449
Male fishes, obstetrical habits of,
449, 461
Mallotus villosus, 452
Mammalia, anatomy of, 564
characters of, 557, 628
development of, 566
ears of, 563
hair of, 561
horns of, 561
limbs of, 560
music of, 569
sexual differences of, 566
skeleton of, 558
teeth of, 562
Mammals, development of, 649
Mammoth, 598
Man, embryology of, 650
origin of, 627
relation to apes, 624
‘skull, 626
varieties of, 627
Manatus, 59%
Mandrill, 62
Manis, 580
Mantis, 369
Manubrium, 70
Marine animals, distribution of,
664
Marmoset, 619
Marsupialia, 574
Marsipobranchii,
409, 410

characters of,

 

709

Mastodon giganteum, 599
May fly, 367
Meckelia ingens, 218
Medusa, 59
Megalops, 313
Megapodius, 546
Megatherium, 579
Melanogrammus eglefinus, 458
Melipona, 385
Mellita testudinata, 123
Meloé angusticollis, 373
Melospiza, 555
Membranipora pilosa, 186
solida, 180
Memory of animals, 681
Menhaden, 450
Menobranchus, 478
Menopoma Alleghaniensis, 479
Merostomata, 317, 326
Mesenteries of polyps, 75
Mesoderm, 6
Mesogonistius chzetodon, 455
Mesohippus, 602
Mesozoa, 139
Metabola, 364
Metamorphosis, 651
cf Batrachia, 476
suppressed, 477, 485
of crustacea, 313
of echinoderms, 105, 110, 112
Metridium marginatum, 74
Miastor, 653
Microsauria, 482, 483
Microstomum lineare, strobilation
in, 145
Midas, 620
Migrations of animals, 667
Millepedes, 356
Millepora alcicornis, 57
nodosa, 57
Milnesium tardigradum, 361
Mimicry, protective, 675
Mimetes niger, 622
pithecus, 621
Mind, in animals, 682
Miohippus, C02
710

Mites, 359
Moa, 588
Moccasin snake, 500
Molacanthus Pallasii, 463
Mola rotunda, 462
Mole, 587
Molgula, 197
Mollusca, development of, 253, 263
structure of, 240
Molluscs, edible, 268
Monads, 31
Monas termo, 31
Monera, 18, 20
Money, shells used as, 269
Monitor, 504
Monkey, 619
Monocaulus, 60
Monodelphia, 571, 577, 629
Monodon monoceros, 594
Monograptus, 62
Monostomum, development of, 149
Monotremes, 571
Morphology, 5
Morula, 43
Mosasaurus maximus, 500
Mosquito, 377
Moths, 378
Mound bird, 546
Mouse, 586
Mucous canal of fishes, 442
Mud dauber, 383
Mud fish, 482
puppy, 478
sun fish, 443
Mullet, 448
Mus, 586
Musca domestica, 875
Musical fishes, 443
Music of mammals, 569
Mussa, 80
Mussel, edible, 248
development of, 254
Mustela foina, 617
Mustelus canis, 420
levis, 420
vulgaris, 420

 

INDEX.

Muzir, 604

Mya arenaria, 242

Mygale avicularia, 363
Hentzii, 363

Myliobatis, 416, 424
fremenvillii, 422

Mylodon, 579

Myriopoda, 356, 885

Myriotrochus Rinkii, 134

Myriozoum subgracile, 180

Mysis, 313

Mysticete, 592

Mytilus edulis, 248

Myxine, 409

Naga, 499
Nanemys guttatus, 510
Narwhale, 594
Nasua, 615
Natatores, 544
Natica heros, anatomy of, 261
Natrix torquata, 495
Nauplius, 294
Nautilus pompilius, 280
Nebalia, 311
bipes, 312
Necturus lateralis, 478
Nematelminthes, development of,
164
structure of, 163, 175
Nematodes, 167, 175
Nematogene, 141
Nemertian worms, 216
Nemertina, development of, 217
structure of, 216, 219
Neocarida, 292, 325
Neochanna, 452
Nephila plumipes, 363
Nereis virens, anatomy of, 231
Nervous system, 638

| Nervous system of ctenophores, 92

hydrozoa, 62, 65
Nests of birds, 536
Neuroptera, 365, 386
Neurula stage of leeches, 228
worms, 230
INDEX. T11

Nighthawk, 551

Noctiluca miliaris, 33

Noises produced by fishes, 442, 443
Notacanthus, 446

Notochord of ascidians, 206
Notommata, 177

Nototrema marsupiatum, 485
Nudibranch molluses, 265
Numerius longirostris, 545
Nummulites, 25

Nurse of trematode worms, 149
Nyctea nivea, 549

OctULina, 80
Octacnemus bythius, 202
Octopod cephalopoda, 280
Octopus Bairdii, 282
punctatus, 283
Odontophore, 276
Odontornithes, 587, 557
(&icodoma, 382
Oligochaeta, 236
Onchidium, 257
Oniscus murarius, 807
Operculum of gastropoda, 261
Ophidia, 496, 517
Ophiocoma vivipara, 110
Ophiopholis bellis, 110
Ophiuridea, 109, 116
Opisthodelphys ovifera, 485
Opisthomi, 446
Opossum, 575
Orang, 622
Orca gladiator, 595
Oreortyx pictus, 546
Organisms, 6, 23
Organs,comparative anatomy of,631
of circulation, 635
of digestion, 631
of respiration, 637
of sense, 640
of smell, 642
nature of, 4, 6, 8, 9
Origin of species, 671
Ornithodelphia, 571, 628
Ornithosauria, 516

 

Orohippus, 602
Orthagoriscus oblongus, 462
Orthoptera, 368, 386
Oscines, 552, 553
Oscula of sponges, 43
Osmerus eperlanus, 452
mordax, 452
Osprey, 548
Ostracoda, 299
Ostrich, 539
Otocyst, 270, 641
cf clam, 245
of worms, 143
Ova, winter, of planarians, 145
of polyzoa, 187
of Rotatoria, 178
Ovibos moschatus, 610
priscus, 610
Ovis argali, 610
aries, 610
montana, 610
Owl, 548
Ox, 612
Oxyuris vermicularis, 167
Oyster, pearl, 252

PADDLE FISH, 427

Paleocarida, 292, 315, 336

Paleontology, 16

Palamedea cornuta, 546

Palapteryx, 538

Palechinida, 123, 126

Palisade worm, 168

Paludicella, 182

Pandion haliaétus, 548

Pangolin, 580

Panopea arctica, 250

Paragorgia arborea, 86

Paramecium caudatum, 35

Parr, 452

Parroquet, 550

Parrot, 550

Parthenogenesis, 54, 652
in ascidians, 213

Partridge, 546

Passeres, 551
712

Patella vulgata, 268
Pauropoda, 356, 386
Pauropus Lubbockii, 356
Pearl oyster, 252
shell, 252
Pedicellaria, 97
Pediculati, 460
Pedipalpi, 362, 386
Pelagic molluscs, 258, 269
Pelecanus erythrorhynchus, 535
Pelican, 542
Pelobates, 484
Pelodytes (a genus of frogs), 484
(a genus of thread worms),
164
Pelomyxa palustris, 24
Pelopeus, 383
Peltogaster, 296, 297
Pelycosauria, 512
Penella, 298
Penguin, 541
Pennatula aculeata, 86
Pentacrinus, 101
Pentacta frondosa, anatomy of, 127
Pentastoma, 361
Pentremites, 107
Perca fluviatilis, 455
Perch, 455
sea, anatomy of, 434
Peridinium, 34
Peripatus, anatomy of, 355
Perisarc, 61
Perissodactyla, 600
Perla, 367
Perophora, 201
Petalosticha, 123, 126
Petromyzon marinus, 410
niger, 410
nigricans, 410
Pezophaps solitarius, 547
Phalangella flabellans, 186
Phalangium, 862
Pharyngobranchii, 408
Phascolosoma cemeatarium, 224
Gouldii, 222
Pheronema Anne, 48

 

INDEX.

Phocena brachycium, 595
lineata, 595
Pheenicopterus ruber, 544
Phoronis, 223
Phosphorescent annelides, 237
ascidians, 202
Hydrozoa, 70
insects, 375
Protozoa, 33
worms, 237
Phrynosoma Douglassii, 503
Phylactolemata, 186
Phyilocarida, 311, 325
Phyllopoda,. 300
Physa heterostropha, 265
Physalia arethusa, 68
Physeter macrocephalus, 594
Physiology, 12
Picarie, 550
Pigeon, anatomy of, 525
Pilidium, 217
Pill bug, 306, 307
Pipa Americana, 485
Pipe fish, 461
Pirarucu, 442
Pisces, characters of, 411, 463
development of, 413, 432, 445
Pissodes strobi, 3872
Plagiostomi, 419
Plagusia, 460
Planarian worms, 141
land, 145
lasso- cells of, 143
nervous system of, 143
parasitic, 145
Planaria torva, 141
Plant lice, 371
Planula, 59
Platygaster, 381
Platyhelminthes, 141, 162
Platyrhine, 619
Plectognathi, 461
Pliohippus, 602
Plesiosaurus, 513
Plethodon erythronotum, 479
Pleurobrachia rhododactyla, 93
INDEX. 713

Pleurolepis pellucidus, 456
Pleuroma, 298
Pleurum of insects, 329
Plumatella, 182
Pneumophora, 134
Podura, 864
Pogonias chromis, 443
Pogy, 450
Poisonous batrachians, 475
jelly fish, 67
siphonophores, 68
snakes, 497, 499
Polycelis, 144
Polycladus Gayi, 143
Polydora, development of, 233
Polykrikos, 37
Polymorphism, 654
in insects, 368
Polyodon folium, 428
Polypedates, 484
Polypide, 181
Polyps, coral, 74
Polypterus bichir, 481
Senegalus, 431
Polystomee, 152
Polystomum integerrimum, 153
Polyzoa, development of, 185
structure of, 180, 188
Polyzoarium, 181
Pomatomus saltatrix, 455
Pomolobus pseudoharengus, 450
Pomotis, 455
Porcellio, 806, 310
Porcupine fish, 462
Porifera, 42, 49
Porphyrio ccerulescens, 545
Porpoise, 595
Porsana Carolina, 544
Portuguese man-of-war, 69
Potamotrygon, 424
Pourtalesia, 124
Prestwichia rotundatus, 322
Primates, 618, 629
Primnoa reseda, 86
Pristis antiquorum, 421
Perrotcli, 421

 

Proboscidea, 597, 629
Procyon lotor, 615
Proglottis of tape worms, 156
trematode worms, 150
Prorhynchus, 216
Proscolex of tape worms, 156
trematode worms, 150
Prosimiz, 618
Protameeba, 19
Protaster, 111
Protective resemblance, 487, 675
Proteida, 478, 488
Proteus, 478
Protista, 2
Protohippus, 602
Protomonas amyli, 19
Protomyxa, 19
Protomyxa aurantiaca, 19
Protoplasm, 5
Protoplasta, 31
Protopterus annectens, 430
Protozoa, 17, 41
contractile vesicles of, 32
Pseudes paradoxa, 487
Pseudobranchus striatus, 478
Pseudocrinus, 108
Pseudofilaria, young of gregarina,
30
Pseudemys, 510
Pseudopleuronectes Americanus,
460
Pseudopodia, 23
Pseudopus, 502
Psolus ephippifer, 133
Psychology, 12
Ptarmigan, 546
Pteranodon, 517
Pteraster, 114
Pterodactyle, 516
Pteropoda, 258, 272
Pterosauria, 516, 517
Pterotrachea coronata, 271
Ptyelus lineatus, 371
Puffer fish, 462
Pulex irritans, 376
Pulmonata, 265
714

Pupa of insects, 328

of the barnacle, 296
Purpura lapillus, 263
Pycnogonide, 360
Pycnopodia, 115
Pygidium, 324
Pyrosoma gigas, 202
Pythonomorpha, 500, 517

QuoHoe, 249

Raccoon, 615
Radiolaria, 26, 27
Rail, 544
Raja eglanteria, 422
erinacea, 421
fluviatilis, 424
levis, 421
Rana, 487
halecina, 470
Rangifer caribou, 609
tarandus, 609
Raptores, 548
Rasores, 546
Rat, black, 586
blind, 586
Ratite, 538, 557
Rattlesnake, 499
Ray, 421
sting, 424
Reasoning power of animals, 380
Redia of trematodes, 150, 151
Reefs, coral, formation of, 87
Reindeer, 609
Renilla reniformis, 86
Reproduction, 13, 643
Reproduction of lost parts in Hy-
drozoa, 53
planarians, 144
Reproduction of lost parts in Ba-
trachia, 481
Reptilia, characters of, 488, 517
development of, 495
skeleton of, 489
sexual differences of, 494
teeth of, 491, 499

 

INDEX.

Reptilia, viviparous, 495, 497

Resemblance, protective, 487, 575

Respiration, organs of, 637

Rhabdoceela, 145

Rhabdopleura mirabilis, 187

Ramphorynchus, 517

Rhea Americana, 539

Rhinichthys atronasus, 453

Rhizocrinus lofotensis, 102

Rhizopoda, 22, 27

Rhombogene, 141

Rhopalodina, 132

Rhynchocephalia, 511, 517

Rhyncodesmus sylvaticus, 145

Rhytina Stelleri, 596

Robin, 556

Rodentia, 582, 629

Root barnacle, 296

Rotalia, 25 4

Rotatoria, development of, 178
structure of, 176, 180

Rotifera, 176

Rotifer vulgaris, 176

Rugose corals, 84

Ruminantia, 605

SaccatTa, 95

Sacculina, 296

Sagitta, 174

Salamander, 479

Salenoglyph snakes, 499

Salmo fontinalis, 452
quinnat, 451
salar, 452

Salmon, 451

Salpa, development of, 211, 214
structure of, 201, 208
spinosa, 211

Sarcorhamphus gryphus, 548

Sauropterygia, 518, 517

Sauropsida, 518

Saurure, 537, 557

Saw fish, 421

Saw fly, 380

Saxicava, 250

Scalpellum, 293
INDEX.

Scaphiopus, 484
Scaphirhynchops platyrhynchus,
427
Scaphopoda, 257, 272
Sceleporus undulatus, anatomy of,
493, 504
Schizaster fragilis, 124
Schizopoda, 314
Scolex of tape worms, 156
trematode worms, 150
Scolopendra gigantea, 358
heros, 358
Scolopendrella, 358
Scomber scombrus, 453
Scy phophori, 449
Seal, 614
Sea-anemone, 74
Sea-cow, 595
Sea-cucumber, anatomy of, 123
apodous, 133
pedate, 1383, 135
Sea-fan corals, 86
Sea-horse, 443
Sea-lion, 614
Sea-pen, 86
Sea-squirts, 196
Sea-worms, 231
Selache maxima, 420
Selachians, 414
Semotilus rhotheus, 453
Semnopithecus, 621
Sense, organs of, 640
Serolis Gaudichaudi, 306
Sertularia, 61
. Sewellel, 585
Sexual coloration in fishes, 444
Shad, 450, 451
gizzard, 443
Shagreen, 415
Shark, basking, 420
hammer-headed, 421
mackerel, 419
Port Jackson, 416
thresber, 420
Sharks, 414
Sheep, varieties of, 609

 

715

Sheep, musk, 610
Sheep hydatid, 160
Shells, fossil, 270
Ship worm, 250, 244
Showt’l, 585
Shrew, 587
Shrike, 555
Shrimp, 312, 314
Sida, 299
Simiz, 619
Siphoniata, 256
Siphonophora, 68, 72
Siphonops, 482
Siphydora echinoides, 47
Sipunculus, 221, 224
Siredon, 479
Sirenia, 595, 629
Siren Jacertina, 478
Sivatherium, 605
Skates, 421
development of, 419
Skull, brachycephalic, 627
dolicocephalic, 627
Slug, 265
Smelt, 452
Smolt, 452
Smynthurus, 364
Snail, 265
Snake, hooded, 499
striped, anatomy of, 498
Snakes, 496
protective coloration of, 497
viviparous, 497
Snipe, 545
Snow-flea, 364
Solaster endeca, 115
Solitaire, 547
Somateria mollissima, 543
Somite, 286
Sorex platyrhinus, 587
Sounds produced by insects, 369
Sounds, fishes’, 442
Spalax, 586
Sparrow, 555
Spatangus, 124
Specialization, 6
716

Species, origin of, 672
variation of, 10, 672, 673
Spermaceti, 593

Spermatozoa, formation of, 644

Spherodorum 231
Sphargis coriacea, 510
Sphenodon, 511
Spheotyto cunicularia, 549
Sphex ichneumonea, 883
Sphinx, 379
Spiders, 362
Spirialis Gouldii, 259
Spirula Peronii, 281
Sphyrna zygeena, 421
Spirorbis, 237
Spirostrephon Copei, 856
Sponges, 42
useful, 49
Spongia adriatica, 49
equina, 49
gossypina, 49
tubulifera, 49
Spongilla, 47
Spoonbill fish, 428
Sporocyst of Nematodes, 151
Spring-tails, 364
Squalus Americanus, 420
Squamella oblonga, 176
Squid, anatomy of, 273
Squilla, 312
Squirrels, flying, 583
Star fish, 96, 109, 111
anatomy of, 96
Star worm, 221
Statoblast, 187
Stegocephala, 482, 488
Steller’s manatee, 596
Stentor polymorphus, 36
Sternum of insects, 829
Stick insect, 677
Stickleback, 456
Stilt, 546
Sting rays, 424
Stomapoda, 312, 325
Stone lilies, 101
Strobila of Hydrozoa, 66

 

INDEX.

Strobila of planarians, 144
tape worms, 156
Strobilation in worms, 144, 145,
234
Struggle for existence, 673
Struthio camelus, 539
Sturgeon, embryology of, 427
Sturgeon, 427
shovel-nosed, 427 °
Stygicola dentata, 459
Stylaster, 58
Styliola vitrea, 258
Stylochus elliptica, 144
Stylops, 373, 3874
Sucker, 458, 454
Suctoria, 40
Sun fish, fresh water, 455
banded, 455
spotted, 456
salt water, 462
Swimming, in fishes, 444
Sycandra, 44
Sycon ciliatum, 45
Syllis, 285
Symmetry, bilateral, in cteno-
phores, 92, 93
echinoderms, 120
Synapta, 134, 135
Syngnathus peckianus, 461
Synthetic types, 483, 679
Syrinx, 526, 552
Syrnium cinereum, 549
Syrphus, 3875

TABULATE CORALS, 58

Tachina, 875

Tenia acanthotrias, 157
bacillaris, 155
coenurus, 160, 161
echinococcus, 158
mediocanellata, 158
solium, 155, 157

Teniata, 95

Tape worms, development of, 154
structure of, 153

Tardigrades, 361
INDEX.

Tarpau, 604
Tasmanian devil, 575
wolf, 575
Taste, organs of, in Hydrozoa, 63
insects, 346
polyps, 77
Tautogolabrus adspersus, auatomy
of, 484
Teeth, 631
rudimentary, 402
of sea-urching, 118
Teleocephali, 449
Teleostei, characters of, 434, 464
anatomy of, 434
Tentaculifera, 34, 40
Teratology, 646
Terebratulina septentrionalis, 188
development of, 192
Terebrella, 236
Teredo navalis, 250
Tergipes lacinulata, 265
‘Tergum of insects, 329
Termes bellicosus, 368
flavipes, 367
Terrapin, 510
‘Yesticardines, 196
Testudo Indica, 510
Tetrabranchiata, 280, 284
Tetradecapoda, 805, 825
Tetrao, 546
Tetrarhynchus, 162
Tetrastemma serpentinum, 219
‘Tetrastoma renale, 152
Tetrodon levigatus, 462
Thalascaris, 315
Thalassochelys caouana, 510
Thaliacea, 208, 215
Thamnocephalus brachyurus, 303
Theca of corals, 79
Thelyphonus giganteus, 362
Theriodonts, 513
Theromorpha, 512, 517
Thrasher whale, 595
Thrips, 370
Thylacinus, 575
Thyone briareus, anatomy of, 131

 

717

Thysanura, 364, 386
Tick, 859
Tinamous, 547
Tipula, 377
Tissues, 6, 7
Tissue, bony, 8
cartilaginous, 7
connective, 7
elastic, 7
epithelial, 7
fibrous, 7
gelatinous, 7
muscular, 8
nervous, 8
Titanophis, 500
Toad, 485
horned, 503
metamorphosis of, 477
poison of, 475
spade-footed, 484
Tomocerus plumbeus, 364
Tooth shell, 257
Torpedo marmoratus, 422
occidentalis, 422
Tortoise, 510
Touch, organs of, in crustacea, 291
molluscs, 270
Toxodontia, 600, 629
Trachymeduse, 62
Trachystomata, 478, 487
Transmission, law of, 11
Trematodes, structure of, 146, 163
development of, 147
pupa of, 149
Trichina spiralis, 169
Trichocephalus dispar, 169
Trigla, 448
Trigonocephalus, 499
Trilobita, young, 323
Trinucleus, young of, 823
Triton, 478
Trivia californica, 259
Trochilus colubris, 551
Trochosphere, 259
of polyzoa, 186
of worms, 147
718

Trochus, development of, 264
Trout, 452
Trunk fish, 462
Trygon, 424
Tubularia, 60
Tubipora, 85
Tunicata, development of, 208, 211
structure of, 196, 215
Turbellaria, 142, 162
Turdus migratorius, 556
‘Turkey, wild, 546
Turtle, green, 510
hawkbill, 510
loggerhead, 510
sea, 510
snapping, 5i
soft-shell, 510
swamp, anatomy of, 506
tortoise shell, 510
Tylenchus scandens, 170
Tylos, 806
Typhlocolax acuminata, 145
Tyroglyphus sacchari, 360

ULOCYATHUS ARCTICUS, 80

Umbellularia greenlandica, 83

Ungulata, 600, 629

Unio complanatus, 244

Urchins, sea, 117

Urodela, 478, 484, 488

Urolabes palustris, 170

Ursus americanus, 616
arctos, 616
maritimus, 616

Urus, 612

Uvella, 82

Varanus, 504

 

Variation of species, 672
Veliger stage of molluscs, 252, 259, |
263, 266
Velum of rotifers, 176, 178
Venus mercenaria, 249
Vermes, characters of, 138
classification of, 238

 

Vertebra, 395

INDEX.

Vertebrata, characters of, 389
classification of, 630
brain of, 392
ear of, 405
eye of, 404
hair of, 4038
limbs of, 396
notochord of, 893
scales of, 403
skeleton of, 395
skull of, 397
teeth of, 401
Vertebrates, relations of ascidians
to, 207, 214
molluscs to, 241
wornis to, 214, 219, 229
Vespertilio subulatus, 591
Vinegar worm, 170
Viper, 499
Vipera, 499
Vitellogene, 147
Viviparous fishes, 444
reptiles, 495
sea-urchins, 121, 122
starfish, 110, 114
Vorticella, 39
Vulture, 548

Watrus, 614
Wapati, 608
Wasp, 380
Water bear, 361
Water flea, 299
Watering-pot shell, 250
Wax wing, 535
Whale, 591
fishery, 594
sperm, 593
bone, 592
white, 595
Whale’s tongue worm, 219
Whelk, 268
White ant, 367
Worms, 13
flat, 141
fluke, 146
INDEX. 719

Worms, nemertean, 216 Wren, 555
parasitic, 145, 146

XIPHOSURA, 324
phosphorescent, 237

round, 163 ZEUGLODON, 595
strobilation in, 144, 145 Zoantharia, 79, 91
tape, 153 Zoanthus, 79

thread, 163 Zoéa, 313

trematode, 146 Zoégeography, 16, 658

Worm, whale’s tongue, 219 Zodids, 202. 210
OUTLINES OF COMPARATIVE EMBRYOLOGY ;

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GUIDE TO THE STUDY OF INSECTS,

AND A TREATISE ON THOSE INJURIOUS AND BENEFICIAL TO CROPS.
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Sixth edition. $5.

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HENRY HOLT & CO., PupnisHeRs, NEW YORK.
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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