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“+ seh ie Sh ila a ia i

TTT
STUDEES.

ON THE

ECTOPARASITIC TREMATODES ©

OF

TAPAN
BY -
SEITARO GOTO M¥gakushi

‘Reprinted front the eee of the Collexe of Biggence, Imperial

—_

University, Tokyo 3 ‘forming Part r # Vol ‘KLT

TOKYO.
1894,

{The 27th Year, Meiji.]
39]
aot
GLy

A.\4 abe
Studies
on the
Ectopasasitic Trematodes of Japan,
BY by

‘Seitaro Got, Rigakushi,
\ no i

Science C pllege, Imperial University, Tokyo.

a Se
With Plates I-X XVII.

‘Introduction.
It was originally intended that I should publish these studies

jointly with Prof. Ijima; but as he is engaged on another work, it
has become necessary for me to take the whole responsibility upon my-
self. The species on which these studies were made were for the most
part collected by myself from various parts” of Japan during the sum-
mers of 1889, 90, 91, and "92. The present part does not include the
Gyrodactylide, the study of which I am still prosecuting ; and as this
will occupy me for some years longer, I have thought it advisable to
publish what is ready now, particularly as I have already been able to
make out the general anatomy of some of the Gyrodactylide, and can
thereforé take them into account in judging of the natural affinities
of the different species.

The specimens collected by me were usually killed with hot
saturated solution of corrosive sublimate. This reagent gives, so far as
my experience goes, the best genera] result, fixing the worms usually

in an outstretched condition and thus facilitating the process of sec-

 

; 1). The collection was made at the following localities: Hakodaté, Misaki, Tokya,
Mitsugahama (in Tyo), Ujina (the port of Hiroshima), Hagi, and Mogi (near Nagasaki).
9 8. GOTO.

=

tioning. Moreover, corrosive sublimate can be sv easily carried about,
and its saturated solution so easily made that it'is, generally speaking,
by far the best reagent for use on a collecting tour. The specimens
were preserved in 70 °/, alcohol.

For staining sections I have almost excliively used Kleinen-
berg’s solution of haematoxylin. I have tried picro-carmin and
borax-carmin, but they did not give good results, although the latter
was very excellent for staining specimens mbunted in toto. I have
also tried cochineal tincture so highly recommended by Lang for the
glandular cells of polyclads; but it gave no differential staining
whatever.

For preparation in toto, the specimens were killed under the
pressure of a cover-slip over the flame of an alcohol lamp, and were
directly immersed in 70°/, alcohol, in which they were preserved
together with other specimens. For staining I have used borax-
carmin ; the over-stain being thoroughly washed cut with acidulated
70 °/) alcohol. In most specimens, only the internal organs and the
nuclei of the mesenchyma remain stained, while the mesenchyma
itself is wholly decolourised, so that the result forms altogether a very

beautiful object under the microscope.

To Prof. Ijima and Prof. Mitsukuri are due my warmest
thanks both for supervision and for giving me suggestions and the
most friendly assistance. To Profs. Parona and Perugia of
Genoa, Prof. Monticelli of Naples, and Prof. Ramsay Wright
of Toronto, I am indebted for their courtesy in sending me their
papers on ectoparasitic Trematodes. Finally but not least my best
thanks are due to the authorities of the Imperial University for

taking charge of the publication of the paper.
STUDIES ON THE ECTOPARASITIC TREMATODES OF JAPAN. 3

A. Anatomy and Histology.
1. External Form of the Body.

Broadly speaking, the form of the body is that of the blade of a
leaf with a rounded apex; and as the leaf varies from an orbicular
to a linear or lanceolate shape, so the body of ectoparasitic Trematodes
varies in form between the same extremes. In Microcotyle the body
is generally elongated and lanceolate or fusiform, the posterior end
being rather pointed. In some species of this genus the halves
of the body are asymmetrical, one being longer than the
other, so that the axis of the body forms a curve or even a
erooked line; eg. in M. reticulata (PI. I, fig. 5) and M. seiaenae
(Pi. IL, fie. 6),

In cross-sections the body of Microcotyle presents the form of an
ellipse, of which the minor axis becomes greater and the major axis
much shorter as the section approaches the anterior end. In the pos-
terior portion of the body where the suckers are present, the cross-section
is often semicircular in outline, the diameter being the ventral side.

In Axine (Pl. VID), one side of the body is always longer than
the other, and the posterior portion of the longer side makes an angle
with the anterior part, so that this portion looks like the posterior
margin of the body, and has actually been so regarded by preced-
ing writers. But that it is really a part of the lateral margin of the
body seems to me beyond doubt both from the presence of suckers
on the other side and from the course of the principal nerves and the
excretory vessels to be described further on. In <A. abervans the
sucker-bearing portion of the longer side is perfectly straight and
makes an acute angle with the anterior part, so that one is tempted to.
regard it as the posterior border of the body ; but here too there is a

sucker on the other side. In accordance with the general asymmetry
4 8. GOTO.

of the body, the posterior end has come to be situated quite laterally,
and the general form of the body to be more or less triangular.

An interesting fact relating to the asymmetry.of the body in
Azine is that the longer side may be either the left or the right.
Thus, in A. heterocerca, out of the nine specimens which I have
examined for the purpose, three had the left side of the body shorter
while in the remaining six the right side was shorter. This fact,
though apparently insignificant, will be found to be of use at least as
a check in judging of the value of some diagnostic characters given by
previous workers.

The cross-section of the body is in Aine band-shaped ; and the
thickness of the body diminishes, while its breadth increases, as we
proceed towards the posterior part, so that in this region the cross-
section presents the shape of a narrow ribbon.

In Diclidophora (Pl. X), the cross-section presents no great devia-
tion in outline from that of Microcotyle, but the general form of the body
is greatly modified by the fact that the four pairs of suckers are hemi-
spherical, and are borne on the posterior margin of the body arranged
in a semicircle or in a horse-shoe shape. Moreover, in many species
each sucker is borne on a long pedicel (Pl. X, fig. 9), a feature
evidently which has suggested the generic name of Octodactylus to
Sir John Dalyell. The portion which bears the suckers, the
“ Haftscheibe” of German authors and which I shall call the “caudal
disc,” is in all species more or less distinctly: separated from the
anterior portion by a constriction of the body. In Diclid. tetrodonis
(Pl. X, figs. 1 & 2), however, the posterior portion of the body is con-
siderably elongated, so that the transition to the caudal disc is more
gradual.

In Heaacotyle (P]. XIII), the body is again much flattened, but

its absolute thickness is very much greater than in the other genera.
STUDIES OX THE ECTOPARASITIC TREMATODES OF JAPAN. 5

It is sharply pointed at the anterior end, very broad in the middle
portion, presents a constriction at a short distance from the posterior
end, again broadens out, and then suddenly diminishes in breadth,
so that at this part the lateral borders form the two equal sides
of a very flat isosceles triangle with its apex directed posteriad, and
have generally been designated as the posterior border. ‘There is
however a small notch at the apex.

In Octocotyle (PI. IX) and Onchocotyle (Pl. XV), the body is com-
paratively much thicker, and the cross-section presents in some parts
almost a circle. In Octocotyle, the caudal disc is not distinctly dis-
tinguishable from the rest of the body, the suckers being borne simply
on the ventro-lateral margins of the posterior portion (PI. IX, fig. 7).
In fig. 1 on Pl. IX, the caudal disc is ‘apparently set off from the
remaining portion of the body by a sudden diminution of breadth ; but
this has been caused by the specimen having been killed under the
pressure of a cover-slip, and the body proper having been abnormally
flattened in consequence. In fresh specimens or in those killed free,
there is no such distinct boundary. In Onchocotyle, on the other hand,
the caudal disc is distinctly marked off from the anterior part by a
constriction, and bears, as is well known, a subcylindrical appendage
projecting from its anterior end on the dorsal side of the body. The
end of this appendage, which bears a pair of suckers (mistaken by
Taschenberg for the terminal vesicles of the excretory system, see
p- 28) and a pair of hooks, is in my opinion to be regarded as the
posterior end of the body, with the body bent a little obliquely on itself
towards the dorsal side, so that the suckers have come to lie apparently
on the dorsal side. In proof of this view, it may be mentioned (1)
that the two surfaces of the appendage and the caudal disc are seen,
in serial sections, to be directly continuous with the dorsal and ventral
surfaces of the body ; (2) that there is a pair of hooks at the end of
6 8. GOTO.

the appendage, which is usually the case in other genera; and (3)
that according to this view the apparently dorsal side on which the
suckers are borne, is really the ventral side, a fact in harmony with all
the cases hitherto known.

In Monocotyle (Pl. XVII) again, the body is much flattened,
and its cross-section presents almost the form of a crescent whose
inner side is ventral. In general outline the body is elongated,
broad, and a little bordering on the oval. The posterior end is
quite sharply pointed. -Anteriorly the body becomes narrower,
but again somewhat broadens out in front, where at the end
there is a large, shallow notch (PI. XVII, figs. 1 & 2).
In Calicotyle (Pl. XIX), the shape of the body is that of an
ovate, heart-shaped leaf, its apex forming the anterior end,
and its basal notch bearing the posterior sucker (Pl. XIX, figs.
I, 2, & 3).

In Tristomum (Pls. XX—XXV), the body is mostly notched at
the posterior end, and its form varies from that of an orbicular to that
of an oval or ovate, heart-shaped leaf with apex more or less
truncate ; the truncated border being sometimes convex, sometimes
concave, and sometimes almost straight. In Epibdella, the body presents
the same general outline as in Tristomum, except that the posterior end,
instead of being notched, becomes gradually narrower and is directly

continued into the sucker.
2. The Investing Membrane.

In my paper on Diplozoon” I called this membrane the epidermis,
assuming in so doing that it corresponds to the true epidermis of other

animals. I have still no cause for recantation ; but as an antagonistic

 

1). This Journal, vol. IV, pt. 1, 1890.
STUDIES ON THE ECTOPARASITIC TREMATODES OF JAPAN. 7

opinion has been advanced by Brandes,” and as the genesis of the
membrane in question has not been made out embryologically, I have
thought it better to use a non-committal term, and have adopted for
this purpose the name used by Wright and Macallum,” although
it is in some respects not a very convenient one.

Three layers can be distinguished in the investing membrane of
the ectoparasitic Trematodes. These I shall call the cuticle, the sub-
cuticle, and the basement membrane. These terms, I am well aware, are
all preoccupied, and bear different significations according to different
writers ; but the coinage of new words is not very desirable and is
moreover not an easy task for one writing in a foreign language.
Words hitherto in use can, however, be used in a new sense without
any danger of occasioning confusion, when clear definitions are given.
The term ‘ subcuticle” might be somewhat objectionable, as liable
to be confounded with the ‘“‘Subcuticularschicht” of Taschenberg
and some other writers on Trematodes; but this is now so generally
recognised to be nothing more than the cortical portion of the
mesenchyma that there is, I believe, no serious danger of in-
troducing confusion of ideas by adopting, in this paper at least, the
terminology here proposed,” in place of ‘epidermal layer’ which I
used in my former paper.

The cuticle is a very thin, structureless, refractive layer which is

very distinct in fresh specimens. In sections its existence is indicated

 

1). Brandes—Zum feineren Bau der Trematoden. Zeitschr. f. wiss. Zool., Bd. 53, 1892. p.
558.
2). Wright and Macallum—Sphyranura Osleri. Journal of Morphology, vol. I, 1887. p. 1.

8). Monticelli in a paper which was received after the above had been written, calls the
investing membrane “ ectoderma,” and claims to have demonstrated in it the remnants of the
original nuclei in the form of vesicles containing deeply stained corpuscles. Granting that the
nuclei of the original epidermis may in some species remain in a comparatively unaltered state,
it seems to me that the vesicles figured by Monticelli are too numerous to be regarded as the
remnants of the nuclei of the ectoderm of the Cercaria, which are, according to the statements
8 S. GOTO.

by a fine line on the external surface of the investing membrane,
which usually stains in haematoxylin deeper than the subjacent layer ;
but its thickness is always very insignificant, and can not be measured
with any approximation to accuracy even under the magnifying
power of 300 diameters. But that it is a distinct layer of cuticular
nature is clearly proved by the fact mentioned in my former paper,
that when any fresh specimen is observed in water under the cover-
glass for a sufficient length of time, watery blisters are formed in
various parts of the investing membrane, and the cuticle is raised
from the subjacent layer. ’

Next to the cuticle comes a layer of varying thickness, form-
ing my subcuticle. In its behaviour towards staining fluids, it is
somewhat different in different’ species, the difference, however, lying
only in the different intensity of its affinity with stains. For in-
stance, in Microcotyle and Onchocotyle it is but slightly stained, while
in Tristomum and Monocotyle it takes up the stain with greater avidity.
In most species this layer is more or less granular, the ground-
substance being formed by a uniformly stained, structureless substance.
This ground substance seems, in the fresh state, to be of a semifluid.
nature in most cases, and of a greater density than water. This I infer
from the fact that when watery blisters are formed under the circum-
stances already referred to, the water seems to pass into the subcuticle
by a simple osmotic process and mix freely with its substance,—the
substance of the subcuticle being quite undistinguishable from the
water taken in. In Onchocotyle, the subcuticle appears striated in
cross-section, the striation being caused by numerous fibrillar structures

traversing it at right angles to its thickness. Besides these fibrils,

 

of Schwarze, Schauinsland, and Biehringer, very few in number (Cf. Monticelli—Studii sui
Trematodi endoparassiti: Primo contributo di osservazioni sui Distomidi. Spengel’s Zoolog.
Jahrbiicher, III. Supple., 1893.).
STUDIES ON THE ECTOPARASITIC TREMATODES OF JAPAN. 9

granules are also observable. In all the other species, the subcuticle
shows only granules, which are, however, more numerous in some
than in other species. For instance, in Microcotyle, Axine, Monocotyle,
Diclidophora, and Hezxacotyle the granules are comparatively sparse,
while in T'rristomum they are very numerous and exceedingly fine in
certain regions, ¢.g. on the ventral side of the anterior suckers.

Inward to the subcuticle comes the basement membrane. In cross-
sections it is very deeply stained, and very distinctly separable from
the subcuticle but somewhat less so from the subjacent mesenchyma.
Its thickness can not be measured with any accuracy, but it is always
thicker than the cuticle. Hallez? has shown with regard to plana-
rians, that the basement membrane is of the same nature as the dense
layer of connective tissue that surrounds the internal organs. Gene-
tically therefore it belongs to the mesenchyma rather than to the
investing membrane, and it is only in accordance with custom that
I have described it as forming one of its layers.

In Tristomum sinuatum and Trist. ovale there are numerous
papillae on the surface of the body. These are of two kinds. Those
of one kind are mostly perceivable with the naked eye. In Trist.
sinuatum: they are confined to the dorsal surface of the body, and
measure on the average about 0.028 mm. in height, the extremes
being 0.014 mm. and 0.041 mm. ; the larger ones appearing to the
naked eye as granulations. In Trist. ovale, on the other hand, they
are confined to the ventral side where they are very numerous, and
are much larger than in Trist. sinuatwm, measuring on the average
about 0.08 mm. in height, the extremes being 0.032 mm. and 0.122
mm. ‘The papillae of the other kind are all microscopic and are far

less numerous than those of the first kind. In Trist. ovale they are

 

1). Hallez—Embryogénie des Dendrocoeles d’eau douce, 1887. p. 78.
10 S. GOTO.

almost uniformly distributed on the dorsal surface, while in Trist.
sinuaium they are mostly confined to near the lateral margins of the
ventral side ; and in both species they measure on the average 0.011
mm. in height. ‘They are probably tactile organs.

In sections the papillae of the first kind (PI. XXIV, fig. 2) are
seen to be simple elevations of the investing membrane together with
the underlying mesenchyma which presents, however, a somewhat
different appearance from that of the more internal parts, and will be
described under the mesenchyma. These papillae are always traversed
lengthwise by- the terminal ramifications of the dorso-ventral muscular
fibres, one of which usually ends at the very apex. The papillae of
the second kind are distinguished not only by their minute size but
also by the total absence of muscular fibrils ; and although I have not
been able to demonstrate in them any nervous fibril I believe it will
be found out by the application of appropriate methods.

The total thickness of the investing membrane is in Microcotyle
usually a little less than 0.005 mm.; in Axine heterocerca a little less
than 0.004 mm. ; in Diclidophora 0.005 mm. ; in Hecacotyle acuta
and Octocotyle minor 0.004 mm.; in Monocotyle 0.008 mm.; and in
Onchocotyle 0.003 mm.—0.004 mm. It should however be borne in
mind that the thickness of the investing membrane varies considerably
in different parts of the body. Thus, in Tr. ovale it is 0.003 mm. on
the ventral side and 0.012 mm. in the anterior part of the dorsal
side; again in Tr. sinuatum the thickness varies from 0.003 mm. on
the dorsal side of the posterior sucker to 0.01 mm. on the dorsal side
near the anterior sucker. It is also to be noted that the thickness is
sometimes less on the dorsal than on the ventral side, eg. in
Onchocotyle.

Having described the investing membrane as it is according to

my own observations, I may now refer to some views relating to its
’

STUDIES ON THE ECTOPARASITIC TREMATODES OF JAPAN. 1l

nature. These views may be divided into two classes, viz., that which
regards the investing membrane as a true cuticle, and that which
regards it as the transformed product of the originally cellular
epidermis. Among the most recent writers on ectoparasitic Tre-
matodes, Brandes represents the first view and Braun the second.”
According to the former writer? the investing membrane is to be
regarded as a true cuticle and as the secretion product of numerous
unicellular glands scattered in groups in the cortical portion of the
mesenchyma (Ectoparenchym), the presence of which he claims to have
demonstrated in all the forms studied by him for the purpose. In
opposition to this view, Braun” brings forward the fact that in Mono-
stomum mutabile there are disseminated in the investing membrane
(‘‘ Hautschicht’”) numerous oval nuclei with sharp outline and stain-
ing weakly with picro-carmin. In absence of any direct embryolog-
ical proof it is of course useless to dogmatise on either side. But, even
laying aside the fact observed by Schwarze” that the investing
membrane of Cercaria is a transformed epidermis as not quite conclu-
sive with respect to that of the adult worm, the positive facts”
at present known, when taken together seem to me to be strongly in
favour of the view upheld by Braun. For instance, the observa-
tion of Zeller® on Polystomum, that in it the epidermal cells are not

cast off but have their nuclei merely shrivelled up, strongly points to

 

1). As stated in a previous note Monticelli is of the same opinion.

2). Brandes—l. c.

3). Braun—Ueber einige wenig bekannte resp. neue Trematoden. Verhandl. d. deutsch.
zool. Gesellsch., 1892. p. 51.

4). Schwarze—Die postembryon. Entwickl. d. Trematoden. Zeitsch. f- wiss. Zoolog., Bd.
42, 1886. p. 49.

5). Itis perhaps hardly necessary to remark here that the “matrix cells” of Wierzejski
are in reality the nuclei of the mesenchyma. Cf. Wierzejski in Zeitsch. f. wiss. Zoolog., Bd. 29,
1877. p. 552.

6). Zeller—Weiterer Beitrag z. Kenntniss d. Polystomen. Zeitsch. f. wiss. Zoolog., Bd. 27
1876. p. 262.
12 S. GOTO.

the continued existence of the original epidermis. Besides, the
differentiation of the investing membrane into the true cuticle and the
subcuticle,' and the negative fact that, although I have directed my
special attention to the point, I have utterly failed to observe those
subcuticular glands so beautifully drawn by Brandes in his figures
in the very same genera that he describes, strongly incline me to the
view that the investing membrane of the ectoparasitic Trematodes is a
transformed epidermis. I have indeed observed some cells in the
ectoparenchyma which had the appearance of a gland (Pl. XXI, fig.
4), but I have not been able to find out any duct, and believe them to
be cells.of the mesenchyma and will therefore describe them under
that head. From his statements on p. 565 (op. cit.), I gather that
Brandes regards the muscular fibres described by Poirier” in some
species of Distomum as the ducts of the subcuticular glands; but
Poirier’s figure in question is so clearly drawn that [ doubt whether
one is justified to put another interpretation on it unless he has studied
the very same species. In Brandes’ figures the muscular fibres and
the ducts of the subcuticular glands are distinguished by different co-
lours, but according to my own experience it is very doubtful whether
such difference in colour reaction exists really in nature. Moreover the
ducts of the subcuticular glands are drawn so fine in Brandes’
figures that one would be tempted to regard them also as muscular fibres
if they were coloured alike; and for my own part I do so regard them.
In this connection it may be mentioned that on examining once a
series of sections of Hexacotyle grossa which were somewhat overstained,
the terminal portions of the dorso-ventral muscular fibres were so

deeply stained that they looked just like the efferent ducts of some

 

1). Poirier—Contribution 4 V’histoire naturelle des Trématodes. Archives de Zool. expér.,
2. série., T. III, 1885.
STUDIES ON THE ECTOPARASITIC TREMATODES OF JAPAN. 13

glands ; but on comparing it with another series of sections I was
able to demonstrate clearly their muscular nature.”

3. Musculature.

The musculature of the body of the Trematodes consists, as is
well known, typically of four sets of fibres, viz., the circular, the
diagonal, the longitudinal, and the dorso-ventral. ‘There are, however,
some variations in different species and genera ; and I shall proceed
to note them in the species studied by me.

In Microcotyle, Axine, Onchocotyle, Octocotyle, Monocotyle, Calicotyle,
and Tristomum I find the musculature of the body to consist of the
typical four sets of fibres ; but the different sets or Jayers are developed
in different degrees in different species. Thus in Microcotyle, Axine,
Octocotyle, Diclidophora, Monocotyle, and Calicotyle, the circular fibres
are very fine and are directly applied to the basement membrane, so
that they appear in sagittal sections of the worms as minute dots
arranged at regular short intervals. In cross-sections of the worms
they are very difficult to demonstrate. In Tristomum, on the contrary,
the individual circular fibres are stronger and they are generally at
some distance from the basement membrane (PI. XXIJ, fig. 4; Pl.
XXII, figs. 4 and 7; Pl. XXIV, fig. 2), leaving a layer of mes-
enchyma of variable thickness between. In Onchocotyle and Heaacotyle
the circular fibres seem to be entirely wanting.

In Dielidophora an additional layer of longitudinal fibres comes
between the circular and the diagonal fibres (PI. AX, fig. 4 & PI. XI,
figs. 3 & 5). The individual fibres of this layer are separated from
one another by an intervening mass of mesenchyma ; they are usually
oval or circular in cross-section and are generally a little finer than

those of the inner longitudinal layer. ‘This layer has also been

 

1). Compare on this question the more exhaustive discussions in Monticelli’s paper (Primo
contributo etc., p. 202 et infra). :
14 S. GOTO.

observed in some turbellarians. I have been able to demonstrate it in
all the three species of Diclidophora which I have studied. The
fibres are usually arranged in a single layer ; but on the ventral side
of Diclid. tetrodonis they are, irregularly, more than one layer thick
(PI. X, fig. 4). In the pedicels of the posterior suckers of the genus
under consideration, only the circular fibres are present (Pl. XII, fig.
4); the longitudinal fibres forming in each an axial bundle which is
attached to each sucker.

The diagonal fibres that come next the circular, or in Diclidophora
next the outer layer of longitudinal fibres, are most strongly developed
in Tristomum. In Trist. ovale (P]. XXIII, fig. 7 & Pl. XXIV, fig. 2)
this layer consists of numerous fibres which are rather closely crowded
and cross each other at variable angles according to the different states
of contraction of the body. The individual fibres are somewhat
weaker than the circular fibres. In Trist. sinuatum, on the other hand,
the absolute number of fibres that constitute this layer is considerably
less than in Tr. ovale, but the individual fibres are much stronger (PI.
XXI, fig. 4), and cross each other at an acuter angle. ‘The last men-
tioned fact can not only be demonstrated by an examination of prepara-
tions in toto but is also evident from the fact that in sections of equal
thickness of the two species a shorter portion of each fibre is cut in the
one than in the other (cf. Pl. XXI, fig. 4 & Pl. XXIII, fig. 7).

In Diclidophora the individual fibres of this layer are very much
finer than the longitudinal fibres, but are comparatively numerous
(Pl. XI, figs. 3 & 6; PL X, fig. 4). In Hexacotyle, on the other hand,
the fibres are not so numerous, but each one is only a little inferior in
size to the longitudinal fibre. In Axine (PI. VIII, fig. 1) and Mono-
cotyle (PI. XVIII, figs. 2 & 5) the fibres are very fine and not very
numerous. Finally in Microcotyle the diagonal fibres are very weakly

developed and can be demonstrated only in preparations in toto.
STUDIES ON THE ECTOPARASITIC TREMATODES OF JAPAN. 15

As may be seen from the figures referred to, the layer of
diagonal fibres is generally separated both from the circular and the
longitudinal fibres by a thin intervening layer of mesenchyma.

‘The layer of inner longitudinal fibres is the most strongly
developed of all the muscular layers of the body, both as a whole and
in the strength of the individual fibres that constitute it. In Azine
and in most species of Microcotyle, the fibres of this layer are not
arranged in bundles but are almost uniformly scattered in a distinct
layer of the mesenchyma (PI. IV, figs. 6, 7, & 8; Pl. VIII, fig. 1),
and present oval or circular outlines in cross-sections. In Tristomum
(Pl. XXIII, fig. 7 & Pl. XXIV, fig. 2), Onchocotyle (Pl. XV, fig. 10
& Pl. XVI, fig. 8), and Heazacotyle (Pl. XII, fig. 5) the fibres are
united only into loose bundles ; but in nearly all the other species stud-
ied by me, the fibres of this layer are associated in compact bundles,
and present in cross-sections generally polygonal outlines, evidently
due to mutual pressure. In some species, as in Hexacotyle acuta and
Microcotyle reticulata, this inner layer of longitudinal fibres is again
divisible into two layers. In the former species the outer of the two
layers is constituted by a single layer of strong fibres at various
distances from each other (Pl. XII, fig. 5). The longitudinal fibres
of Microcotyle reticulata present some variations of arrangement, which
will be briefly noted.

In the more anterior part of the body (Pl. V, fig. 6) the fibres
are in this species distributed apparently without order, but the
outer fibres are considerably smaller than the deeper ones. In the
region of the vagina the fibres of the two layers are almost equal in
size (PI. V, fig. 5) ; but in most portions of the body the longitudinal
fibres are arranged in compact bundles, the outer fibres of which are
considerably smaller than the inner (PI. IIT, fig. 4). In this species .

the circular and diagonal fibres are but weakly developed and can not
16 8. GOTO,

be demonstrated in cross-sections ; so that the layer of longitudinal
fibres seem in such sections to be separated from the investing mem-
brane only by a layer of mesenchyma (PI. III, fig. 4). .

‘The dorso-ventral muscular fibres are developed in very different
degrees in different species, but they are, so far as I have observed,
never wanting. They are but weakly developed in Axine and in most
species of Microcotyle ; moderately in Diclidophora, Heaacotyle, Onchoco-
tyle and Monocotyle ; and very strongly in Tristomum. It is, as is
well known, the characteristic of the dorso-ventral fibres that they
ramify into a number of fine branches towards their ends, and are
inserted onto the investing membrane of the body. ‘They also traverse
some internal organs, such as the testes and the vitellarium.

In Monocotyle there are in the hindmost portion of the body
an assemblage of striped muscular fibres (PI. XVII, fig. 5); but as
these are present mainly in the posterior sucker, they will be described
in that connection.

4, The Organs of Attachment.

Under this head I include the suckers, both true and rudimen-
tary, the glands, which subserve, according to my opinion, the same
purpose, and the hooks, These, but especially the glands, are more
numerous and of more varied structure than has hitherto been thought.

Sucxers—The suckers may be classed, for the sake of description,
into the anterior and the posterior suckers, of which the latter present
more variety of structure than the former. The differences in both of
them are characteristic of the genera, and so will be treated separately
under each genus, except where another treatment is more desirable.

Microcotyle and Axine—In these two genera the anterior
and posterior suckers are of the same structure. They will therefore

be treated of together and minor differences occasionally noted.
STUDIES ON THE ECTOPARASITIC TREMATODES OF JAPAN. 17

The anterior suckers consist in both the genera of a pair of
bag-shaped bodies with thick walls, and situated one on each side
of the mouth-cavity (Pls. I, II, II, & VIII). The shape of the
sucker is very variable according to the different states of contraction
of the part of the body it belongs to, and also differs somewhat in
different species ; but when in a state of rest it is generally circular,
ellipsoidal, or egg-shaped (PI. III, fig. 8; Pl. VII, fig. 1). Its
cavity is directly continuous with that of the mouth, and in most
species of Microcotyle it is divided into two compartments by a struc-
tureless, membranous septum that usually runs obliquely to the long
axis of the body ; but the septum is also absent in some species, as in
M. reticulata. Parona and Perugia” mention “ piccolissimi e
splendenti corpicciuoli rotondi disposti a gruppi, od in una fascia” on
the free margins of the suckers ; but I have not observed such struc-
tures. ‘The wall of the sucker consists of very refractive, prismatic
fibres of a yellowish colour traversing its whole thickness, which
remain entirely unstained in haematoxylin, picro- or borax-carmin.

These fibres are closely appressed to one another—the prismatic

 

shape being apparently due to mutual pressure—and only a very thin
layer of connective tissue is left between them. This layer of connect-
ive tissue stains more or less, and in consequence, the substance of
the wall of the sucker appears in sections striated at right angles to its
surfaces. These fibres are different in appearance as well as in
colour-reaction from the muscular fibres of the body, and are perfectly
like those of the posterior suckers and of the mass of connective

tissue around the terminal portion of the vas deferens in the genera

 

1). Parona e Perugia—Res ligustice, XIV. Contribuzione per una monografia del genere
Microcotyle. p. 4. Estratto dagli Annali del Museo Civico di Storia Naturale di Genova. Ser. 2,
vol. X, 1890.
18 8. GOTO.

under consideration. In fact I consider them to’be more of an clastic
than a contractile nature ; but the reasons for so regarding them will
be stated at length further on under the head of general considerations
(vide infra, p. 144).

"The surface of the wall of the anterior sucker is covered on all
sides by a thin cuticle (PI. III, fig. 8). On the side turned towards
the mesenchyma, the fibrous connective tissue of the body forms, next
to the cuticle, a thin dense layer similar in appearance to the basement
membrane already described.

Each anterior sucker is provided with two muscular bundles, one
of which, the larger, is attached to its postero-lateral part and the
other, the smaller, to the postero-median part (PI. III, fig. 8).
Posteriorly these muscular fibres become’ mingled with the longi-
tudinal fibres of the body. ,

The physiology of suction will be considered later on (vide p.
147).

Posterior suckers—These are usually very numerous in both Azine
and Microcotyle, and in most species of the latter are symmetrically
arranged on both sides of the. caudal disc, while in the former genus
they are always asymmetrically arranged on the two sides in ac-
cordance. with the general asymmetrical form of the body already
described. ‘Their sizes differ in both the genera in different parts of
the caudal disc; the general rule being that they are largest at the
middle of the disc and diminish in size towards the ends. The pos-
terior suckers are however mostly smaller than the anterior ones.

In M. reticulata and M. sciaenae the suckers are more numerous
on the right than on the left side ; and in the latter species the eandl
disc is bent at an angle towards one side, while in the former the
right side presents only a greater curvature. This asymmetry of the

body is, as already stated, due to the fact that its one side is longer
STUDIES ON THE ECTOPARASITIC TREMATODES OF JAPAN. 19

than the other. In JV. sciaenae the suckers of the two sides do not
present any considerable difference in size”; buat in Jf. reticulata
those of the left side are much larger and fewer in number than those of
the other. Thus, in the latter species a measurement of the breadths of
the corresponding suckers of the two sides at about the middle of the
caudal disc gave for the left side 0.227 mm. and for the right 0.145 mm.

In the specimens of the two species figured on the plates the
right side is longer and bears more suckers” than the left ; but
whether this is constantly the case or not I have not had a sufficient
number of specimens to decide (of. infra de Axine).

In M. caudata, M. sebastis, M. elegans, and M. fusiformis the
caudal disc extends for some distance anteriorly from the point
where it becomes continuous with the body proper ; but in all the other
species it does not, and the suckers are arranged merely along the
lateral margins of the body.

In Amine the asymmetry which we have observed in the two
species of Microcotyle above mentioned is carried one step farther, and
one of the sides of the caudal disc makes an angle with the corres-
ponding side of the body proper (PI. VII), and appears like the
posterior border (the “appendice ptéroide” of v. Beneden). The
other side bears only a small number of suckers. In some species, as
in A. triangularis (PI. VII, fig. 7), the suckers of the two sides are
nearly of the same size; but in A. heterocerca. (PI. VII, fig. 1) they
are of very different sizes on the two sides. Thus in one specimen,

one of the largest suckers on the longer side was 0.60 mm. in breadth,

 

1). For minuter details see description of species.

2). Parona and Perugia (Res ligusticae, XIV, p, 38) believe that a similar asymmetry
occurs in DM. erythrint; but in my opinion, the supposed asymmetry in this case is
only apparent, having been caused by pressure and the twisting of the body at the point of
attachment of the caudal disc, as occurs very often when the worm.is observed under the
cover-slip. The real asymmetry could only be caused by the unequal length of the sucker-
pearing portion of the two sides, and there is none in the species in question.
20 8. GOTO.

while that of the other was only 0.095 mm. On the longer side the
largest suckers are, as.in Microcotyle, generally found in the middle
portion ; but on the shorter side the suckers gradually diminish in
size from before backwards. In A. aberrans, however, the suckers are
all of nearly equal size on the longer side. Lorenz” and others
mention the suckers only on the longer side; but in all the species
studied by me they are present on both sides (Pl. VII, figs. 1, 5,
& 7).

Now as to structure, each posterior sucker may be likened to a
flattened, rectangular bag open on the ventral side, the broader sides of
which face forwards and backwards and have a very thick wall, while
on the narrower sides the wall is very thin. This bag is supported
by a chitinous” frame consisting of five pieces, viz., four lateral pieces
in pairs and one median. Of the four lateral pieces two are imbedded
in the substance of the anterior wall and two in that of the posterior
wall, both along the lateral margins (PI. II, fig. 7). These are
curved like a hook, are somewhat triangular in cross-section, and are
entirely solid. ‘The rods of the anterior wall (a) are, at the bottom of
the sucker, directly continued on into the posterior wall (a’); and the
whole has, therefore, somewhat the form of a hook (cf. PI. III, fig. 1
& Pl. II, fig. 7). Those of the posterior wall (b) end bluntly at the

 

1). Lorenz—Ueber die Organisation der Gattungen Axine und Microcotyle. Wiener
Arbeiten von Claus. Bd. I, Hft. 3, 1878. p. 4.

2). I have used the word “chitinous” here and shall use it in describing the hooks in
accordance with the usual custom; but it should be noted that these pieces are sometimes
well stained with haematoxylin—exactly under what circumstances I have not been able to
make out; but one condition seems to be that the specimen be preserved after a certain dis-
integration of the tissues has set in—and that the hooks are soluble in a solution (35 °%,) of
caustic potash.

3). I take this opportunity to correct my statement on this head with regard to Diplozoon
Nipponicum. In my paper on this worm (i.c.) I have described the piece imbedded: in the
posterior wall and projecting towards the median piece as the process of the paired (lateral)
piece of the posterior wall, whereas it is in reality the direct continuation of the paired piece of
the anterior wall, just as in Microcotyle.
STUDIES ON THE ECTOPARASITIC TREMATODES OF JAPAN. - 9}

bottom of the suckers. ‘The median piece (c) is also imbedded in the
substance of the wall, and has the form of a regular U, one arm of
which lies in the anterior and the other in the posterior wall. The
two ends are however somewhat different in form (PI. III, fig. 1).
In the anterior wall the median piece ends with two spine-like processes
diverging from each other and almost meeting the ends of the lateral
pieces. In the posterior wall, on the contrary, these processes are
very much shorter and blunter, and the piece bears between them a
dagger-shaped, hollow, terminal piece (PI. III, fig. 1). In cross-
section, the median piece presents for the greater part of its whole
length, a rectangular outline, and is seen to be hollow. . A little above
the bottom of the sucker its cross-section presents the appearance
drawn in fig. 7 (c on the upper side), PI. IT.

In Axine the number and relative position of the chitinous pieces
are just the same as in Microcotyle (Pl. VII, fig. 2). The internal
hollow of the median piece is, however, divided in A. heterocerca into
numerous compartments by thin septa. This piece presents also a
termination in the posterior wall which is somewhat different from
that in Microcotyle and is figured in fig..2 u, Pl. VIL.

The anterior and posterior walls of the posterior sucker are very
thick and are directly continuous with.each other at the bottom of the
sucker. Their substance consists of numerous prismatic, very refract-
ive fibres closely appressed to one another and leaving a very thin,
deeply stained layer of connective tissue between. These fibres are to
all intents and purposes exactly similar to those of the anterior suckers
(PI. II, fig. 7 & Pl. VII, fig. 4). The wall is entirely surrounded
on all sides by a thin cuticular membrane. In Azine, however, the
cuticle.of the internal surface is chitinized in parallel zones running
parallel to the slit-like mouth of the sucker (PI. VII, fig. 4). The

Jateral walls of the posterior suckers are very thin and membranous.
29 8. GOTO.

The muscular fibres of the posterior suckers are attached to
the median chitinous piece of the posterior wall near the bottom
of the suckers (Pl. II, fig. 7). They are divided into a few
bundles, and are directly continuous with the longitudinal fibres
of the body.

Octocotyle, Diclidophora, and Hexacotyle—The anterior suckers
of these three genera present nothing specially different from those
of Axine and Microcotyle, and I shall therefore pass them over,
merely referring the reader to the figures (PI. IX, fig. 8; PI. X,
fig. 6; Pl: XIII, fig. 1 & 4). I shall, however, note that in
all these, there is no membranous septum, that in Diclidophora (PI.
X, fig. 6) some of the fibres of the internal bundle of muscle of one
‘side cross over to the sucker of the other side, and lastly that in
Hesacotyle the suckers are exceedingly small. ‘The posterior suckers
are, however, very different in the three genera, so that they will be
treated separately.

Posterior suckers—In Octocotyle the four pairs of. posterior suckers
are arranged merely along the ventro-lateral border of the hind-
most part of the body, so that the caudal disc is, as already mentioned,
directly continuous with the body proper. Each sucker is somewhat
bean-shaped, and is raised a little above the general surface of the
ventral side (PI. IX, figs. 1, 4, & 7). The anterior and posterior
walls are very thick, ‘and consist of prismatic fibres just as in Microco-
iyle and Axine. The.chitinous framework consists of a simple basal
piece (PI. IX, figs. 3 & 10, a) anda pair of marginal pieces (b), both
imbedded in ‘the substance of the wall. The basal piece is nearly
straight and bears at each end a short process which ‘makes a right
angle with it, and is directed towards the mouth of the sucker. The
marginal pieces are U-shaped and are imbedded in the alerts of

the anterior and posterior walls along their very margins, so that each
STUDIES ON THE ECTOPARASITIC TREMATODES OF JAPAN. 93

piece, together with the basal piece, encloses the wall like a picture in
its frame, The muscular fibres are attached to the basal piece, and
are direct continuations of the longitudinal fibres of the body. In
O. major the marginal chitinous piece is longer than in O. minor.

In Diclidophora (P1. X) the four pairs of suckers are, as already
stated, borne, in most species, each at the top of a peditel.; but in
Diclid. sessilis the stalk is very short, and in Diclid. tetrodonis entirely
wanting. But that these species are to be included in the same genus
will, I believe, be scarcely contested by any one who has studied their
anatomy. ‘The suckers are ina surface view usually circular, as in
Diclid. sessilis and Diclid. elongata, but are sometimes slightly elliptical
as in: Diclid. tetrodonis, and are arranged in a semicircle or horse-shoe
shape. ach sucker is as a whole nearly hemispherical, and its open
end is directed obliquely towards the ventral side. The wall consists
of prismatic fibres, and is divided into four equal parts by as many
chitinous rods radiating from the centre of the sucker (Pl. XII, fig.
4). The whole number of the chitinous pieces is eight for each sucker,
and are represented in their natural positions as seen from. the surface
in fig. 1, PI. XII. A T-shaped piece (a) is situated with the point of
junction of the leg and arms exactly in the centre, with the two
arms of unequal length extending some way towards the periphery of
the sucker, and. the leg extending quite to the periphery and here
dividing into two branches which diverge from each other in a diame-
trically opposite direction. The portion of this chitinous piece corres-
ponding to the leg of the T is hollow, but the remaining portions are
all entirely solid. Another hollow piece (b) extends from the centre
in an opposite direction from the leg of the T-shaped piece
towards the periphery, which it, however, does not reach. The hook-
like piece marked ¢ is paired, and bears at its angle a process which is
seen in sections to lie outside the substance of the fibrous wall (PI.
o4 S. GOTO.

XI, fig. 4, ¢'). Somewhat similar but shorter pieces (d) lie in pairs
at the peripheral end of b. A short spine-like piece (e) lies opposite
the process of the piece ¢ with its pointed end directed towards the
piece d. These last-mentioned pieces, the pieces d, and the peripheral
portions of the pieces a and ¢ are imbedded at the very margin of the
fibrous wall of the sucker (PI. XII, fig. 4).

‘In the natural position of the suckers these chitinous pieces are,
in most’ species, placed in such a way that the leg of the T-shaped
piece is directed towards the median line of the body in the anterior’
suckers, while in the posterior suckers. it is directed obliquely. forward
(Pl. X, fig. 5). In Dichid. tetrodonis, however, the same piece is
directed forwards in the posterior three pairs, but backwards in the
foremost pair. This difference of arrangement of the pieces of the
chitinous framework in the foremost pair of suckers is a curious
exception to the rule.

Each of the four quadrants into which the wall of the sucker is
divided, presents in radial sections an oval or semicircular mass, con-
sisting, as in the species already described, of prismatic fibres travers-
ing its whole thickness at right angles to its free surface (PI. XII,
fig. 4). The four quadrants are separated from each other in the centre
by an intervening mass of connective tissue, in which is imbedded the
central part of the T-shaped piece (a) already described.

The free surface of each quadrant is covered with a thick cuticle
which is locally chitinized in short staff-shaped pieces arranged in
series. ach series of these staff-shaped chitinous portions is, in a
surface view, roughly speaking somewhat semicircular (PI. XII, fig. 2),
with the open side directed towards the centre of the sucker. In fig.
1, Pl. XII, the series have been a little displaced by pressure. To-
wards the mesenchyma the wall of the sucker is bounded by a thin,

cuticular membrane. Around the outer margin of the sucker the
STUDIES ON THE ECTOPARASITIC TREMATODES OF JAPAN. 95

investing membrane of the body makes a fold filled with connective
tissue within, and forms a marginal membrane (PI. XII, fig. 4).

Strong bundles of muscular fibres are attached to each sucker.
The principal bundles are, as may be seen in fig. 4, Pl. XII, three in
number, and are attached one to the inner margin of an inner quad-
rant, another to its outer corner, and the third to the central part of the
T-shaped chitinous piece. The individual fibres that constitute these
bundles are very large. The larger part of the bundles of each sucker
are merged in a single bundle at a short distance from it, and the
bundle thus formed traverses the axis of the pedicel of the sucker,
when such is present ; but a small portion forms one or more bundles
which connect the suckers with one another. I have represented this
connection among the suckers as I have observed it in Diclid. sessilis
in fig. 5, Pl. X.

In Hexacotyle, there are four pairs of posterior suckers, and these
are arranged on each side of the median line in a line parallel with
the posterior border of the body. ‘The median pair of all is, however,
very much smaller than the others, and has been entirely overlooked by
some naturalists ; but it has exactly the same structure as the other
pairs. Each sucker is shaped like a thick but very shallow, elliptical
saucer (PI. XII, fig. 7), with its longer axis directed at a right angle
to the posterior border of the body, and is provided with three
chitinous pieces imbedded in the substance of its wall, which consists,
as in the cases already described, of prismatic, refractive fibres closely
pressed against one another. The positions of these chitinous pieces
are represented in figs. 1 & 4, Pl. XIII; and in figs. 3 & 6 each
piece has been separately drawn, so that any detailed description of
them is, I believe, unnecessary. It is to be remarked, however, that
in both the figures, a represents the piece at the anterior end of the
sucker, ¢ that at the posterior end, and b the central piece, and that
26 8. GOTO.

this last piece is imbedded in the wall of the sucker with its longer
axis coinciding with the minor axis of the sucker. The substance of
the wall is-bounded, as in other genera, both towards the mesenchyma
and the exterior by a cuticular membrane, except in the central part
where the chitinous piece is imbedded, and where this is in direct
contact with the mesenchyma. A strong bundle of muscular fibres,
which are direct continuations of the longitudinal fibres of the body,
are attached to each of the chitinous pieces of the sucker (PJ. XII,
fig. 7).

Onchocotyle—The position and structure of the suckers are
somewhat peculiar in this genus.

Anterior sucker—An anterior sucker is distinctly present, although
some writers have denied the fact, and is situated around the mouth-
cavity, and presents some resemblances of structure. to that of the
distomes. In cross-section, it is elliptical in outline, and is seen to
occupy nearly the whole of this region of the body, merely leaving a
smal] portion of mesenchyma in the lateral parts (Pl. XV, fig. 4).
The ventral half is much smaller than the dorsal half, just as in the
distomes (Pl. XV, fig. 3). The substance of the sucker consists
of connective tissue interspersed with nuclei, some of which are
surrounded by scanty masses of granular protoplasm, and of muscular
fibres, most of which are very fine, and, radially traversing the con-
nective tissue, are attached to the basement membrane which separates
the substance of the sucker from the investing membrane of the body.
Besides these radial fibres, strong muscular fibres which act as
sphincters are present in the foremost part of the dorsal half of
the sucker (Pl. XV, fig. 3, sph.)

Posterior suckers—These are eight in number arranged in four
pairs, one of which is, however, very different both in structure

and position from the others. The latter are arranged in a_horse-
STUDIES ON THE ECTOPARASITIC TREMATODES OF JAPAN. 97

shoe shape seemingly on the dorsal but morphologically on the ventral
side of the body, and are hemispherical in shape. The wall consists,
as in the preceding cases, of prismatic, refractive fibres set closely
against one another, and is bounded on all sides by a cuticular mem-
brane. This membrane is chitinously thickened into band-shaped
strips in an antero-posterior direction (Pl. XV, fig. 8). The
wall of each sucker is again divided in two, each half crescent-
shaped in cross-section, and separated from the other by an in-
tervening zone of mesenchyma, in which a single, strong, hollow,
chitinous piece of semicircular shape and provided with a hook at
one end lies imbedded (Pl. XV, figs. 8 & 9). The inner half of the
wall is smaller than the other. ‘There is no distinct marginal mem-
brane, but the investing membrane presents a fold all round at a short
distance from the mouth of the sucker (fig. 8).

In the natural position, the hooked end of the semicircular
chitinous piece is directed towards the anterior end of the body ; and a
‘strong bundle of muscular fibres is attached to the other end of the
piece. Besides this, detached fibres are also attached to the lateral
margin of the suckers.

The remaining pair of suckers, which are much smaller,: is
situated at the extremities of the bifurcations of the caudal appendage
which constitutes such a salient feature of this genus. Each sucker
has the shape of a water-melon with a constriction at the posterior
part ; and its mouth is very narrow (PI. XV, fig. 2). Its cavity is
also very narrow ; but the wall is very thick, and consists entirely of
a connective tissue interspersed with nuclei, which are more abundant
in the posterior portion of the sucker (PI. XV, figs. 1 and 2). The
fibres of the connective tissue are mainly arranged radially, and form
an irregular network. The wall is bounded towards the mesenchyma

by a thin, cuticular membrane, and its inner surface is lined by the
98 8S. GOTO.

direct continuation of the investing membrane of the body.

The pair of suckers above described has been mistaken by Tas-
chenberg” for the terminal vesicles of the excretory system (see p. 5).

Calicotyle—Anterior sucker—In this genus the anterior sucker is
developed far more imperfectly than in those hitherto described, and
is also totally different from them in structure. It is constituted by
a deep invagination of the ventral side of the body just behind the
mouth (Pl. XIX, fig. 8). From the inner surface of the investing -
membrane that lines the cavity of the sucker, numerous muscular
fibres take their origin, and diverging in various directions, become
continuous with the longitudinal fibres of the body. Besides these,
circular fibres are exceptionally developed in this part. Owing to this
local development of the musculature, the anterior sucker seems in a

surface view to be pretty well defined from the surrounding mes-
enchyma, and to form a distinct organ (Pl. XIX, figs. 1 and 4); but
sections show that this is by no means the case. Morphologically
speaking, it would be more correct, therefore, to call it a rudimentary
sucker (pseudoventose).

Posterior sucker—This is situated on the ventral side at the pos-
terior extremity of the body. Its ventral surface is marked out into
a central heptagonal and seven peripheral areas by elevations of the
ventral surface radiating from the wall of the central polygon. ‘This
central polygon does not occupy exactly the middle of the sucker, but
is situated a little more anteriorly. The hindmost area which is
the largest, occupies the median line of the body, while the others are
arranged symmetrically on either side, and decrease in size from
behind forwards (PI. XIX, figs. 1 and 3).

The musculature of the sucker consists of three sets of

fibres, which may be called the radial, the transverse or dorso-ventral,

 

1). Taschenberg—Weitere Beitriige, p. 13.
STUDIES ON THE ECTOPARASITIC TREMATODES OF JAPAN. 99

and the circular. The radial fibres must again be divided into two
groups. In one they are direct continuations of the longitudinal
fibres of the body, and on entering the sucker diverge irregularly more
or less in all directions, and are inserted, some to the elevation that
forms the wall of the central polygon, others to the periphery of
the sucker. The other group of radial fibres includes those fibres
which start from the central polygon, and passing along the radial
elevations, are inserted in the periphery of the sucker. The transverse
or dorso-ventral fibres merely traverse the thickness of the sucker, and
are inserted into the basement membrane. Like the dorso-ventral fibres
of the other parts of the body, they ramify into a number of small
branches towards their ends. The circular fibres are present only
on the dorsal side; they are arranged in circles concentric with the
circumference of the sucker, and are comparatively few. ‘lhe inter-
spaces between the muscular fibres are filled by 2 connective tissue
similar to that of the body (Pl. XIX, fig. 6).

. Monocotyle—Morphologically speaking there is no anterior
sucker in this genus, but physiologically speaking there is. The
dorso-ventral as well as the circular fibres of the body, namely, are
strongly developed at the anterior end around the mouth Chi. V Lo,
fig. 4), so that the arrangement of muscular fibres is very similar to
that which obtains in the anterior suckers of Onchocotyle and of the
distomes. ‘There is even a sort of marginal membrane on the ventral
lip (PI. XVIII, fig. 4, a). That this anterior portion acts as a sucker
is beyond doubt; for I have observed the worm execute an active leech-
like locomotion by alternately attaching and detaching the mouth and
the posterior sucker. In fact, the structure here described is a prelim-
inary step to the formation of such anterior sucker as that of
Onchocotyle and the distomes ; the only difference being that in the
latter, the sucker has been distinctly separated from the surrounding
30 8. GOTO.

mesenchyma by a compact membrane of the nature of connective
tissue.

Though closely allied to Calicotyle, the present genus presents
some peculiar feature in the structure of the posterior sucker.

Posterior sucker—This has exactly the shape of a circular saucer,
and is attached to the body by a short stalk. It is provided with a

“marginal membrane all round, which is exactly of the same nature as
that of the posterior suckers of Diclidophora ; only its connective tissue
is more compact (Pl. XVII, figs. 2, 4, and 5). A further difference is
that the membrane bears on its ventral surface numerous chitinous
projections arranged in radial series ; there being five of these chitinous
projections in each series (figs, 2,4, and 5). The internal surface of
the sucker is divided into eight equal secants by as many radiating
elevations, the positions of which are such that two of them coincide
with the median line of the body. ‘These radial elevations also bear
on their surfaces each a series of chitinous pieces which are figured in
radial section in fig. 38 (PI. XVII), and in tangential section in fig. 8.
In the latter figure it appears as if these pieces have been formed
simply by local chitinisations of the investing membrane of the body.
These so-called chitinous pieces are deeply coloured by haematoxylin,
more deeply than the investing membrane.

The muscular fibres of the sucker are very different in structure
from those hitherto described, and are all arranged, with an insigni-
ficant exception, dorso-ventrally (Pl. XVII, figs.4, 5, 7,and 12). They
are striped, and a single fibre traverses ‘the whole thickness of the
sucker. ach fibre (about 0.01 mm. thick) consists of very refractive,
narrow zones, which deeply stain in haematoxylin, alternating with
broad, non-refractive zones, which are but slightly stained with
haematoxylin and are finely but distinctly striated longitudinally.

Each of these non-refractive zones is again crossed at its middle by

a
STUDIES ON THE ECTOPARASITIC TREMATODES OF JAPAN. 31

i very narrow, secondary zone of much refractive power and well
stained in haematoxylin. ‘This zone is so narrow that it appears only
as a fine line, and its refractiveness and capacity of being stained with
haematoxylin are much inferior to those of the primary zone. I have
observed some of these fibres bifurcating towards one of their ends
(Pl. XVII, figs. 7 and 12).

The striped fibres above described are almost uniformly dis-
tributed in the secants into which the sucker is divided, as well as in
the radial elevations themselves. In the latter, the fibres lie at right
angles to their length, .and are consequently very short (Pl. XVII,
fig. 8). ‘They may also be entirely absent from them for a more or
less wide extent (PI. XVII, fig. 3). On the other hand, they are wholly
absent from those parts of the sucker which lie below the radial eleva-
tions. Here the substance of the sucker is entirely formed of connect-
ive tissue, the fibres of which unite into bundles on the ventral side
in such a way as to form a series of window-like cavities (PI. XVII,
fig. 38) ; while on the dorsal side the fibres form generally a compact
network, leaving only here and there a number of large cavities. The
centre of the sucker is wholly devoid of striped fibres, and is sharply
defined from the surrounding parts by a membrane of connective tissue
(PI. X VIL, figs. 4and 5). This central part is traversed by the terminal
portions of some of the longitudinal fibres of the body, which are here
formed into bundles and are inserted, some into the very centre of the
sucker, others more peripherally into the membrane of connective tissue
that separates the centre of the sucker from the surrounding parts.

As may be inferred from the above description, the sucker of
Monocotyle is divided both externally and internally into eight equal
secants—externally by radial elevations, and internally by correspond-
ing radiating septa formed of fibrous connective tissue and wholly

destitute of striped muscular fibres.
32 8. GOTO.

As has already been mentioned, the striped fibres are also present
in the posterior part of the body (Pl. XVII, fig. 5), and this portion
is, as in the sucker, sharply separated from the surrounding part by a
distinct membrane of connective tissue (figs. 5 and 12).

The striped muscular fibres have hitherto been observed, so far as
I know, only in the sheath of the proboscis of Tetrarhynchus» among
the Plathelminthes.

Tristomum—As is well known, the anterior suckers ave, in this
genus, situated in a pair near the anterior extremity of the body, on
both sides of the mouth or a little before it. They are more or less
circular, sometimes perfectly so and sometimes a little elliptical.
Internally the substance of the suckers is directly continuous with the
mesenchyma of the body, and the suckers are therefore to be regarded.
merely as local expansions of the body. This view is strengthened by
the fact that the muscular fibres of the suckers are the direct continua-
tions of those of the body. The dorso-ventral fibres are arranged
exactly as in the body, with the only difference that they are here more
strongly developed in accordance with their task as the chief agent
of suction (PI. XXII, fig. 5). The longitudinal and diagonal fibres,
on entering the suckers, become more or less intermingled with each
other ; but the former mostly radiate straight towards the periphery,
while the latter curve round, and are mostly arranged more or less
concentrically with the circumference of the suckers ; the terminations
of both the groups of fibres being attached to the investing membrane
on the dorsal as well as on the ventral side. The circular fibres of the
body also enter the suckers ; but they here lose their typical arrange-

ment, and become intermingled with the diagonal fibres.

 

1). Pintner—Untersuchungen ii. d. Bau des Bandwurmkoérpers. Wiener Arbeiten, Bd. 3,
2. Hft., 1880. p. 50.
STUDIES ON THE ECTOPARASITIC TREMATODES OF JAPAN. 33

In most species of this genus described in this paper, the invest-
ing membrane of the suckers is exactly similar to that of the other
parts of the body ; but in Trist. ovale the ventral (concave) surface is
raised into numerous conical papillae, at, the top of which open: the
efferent ducts of the numerous unicellular glands afterwards to be de-
scribed. Along the inner border of the suckers also there are, in this
species, numerous larger papillae crowded together (P]. XXIII, fig. 5).

Posterior sucker—The posterior sucker of Tristomum is more or less
hemispherical in form, and is very similar in structure to that of
Calicotyle. In most species, however, a short stalk may be dis-
tinguished (Pl. XX, fig.5). The ventral (concave) surface is divided,
as in Calicotyle, by radiating elevations into a central and seven
peripheral polygons that surround the former ; the hindmost of the
peripheral polygons invariably occupying the median line. In some
species (T'r. sinuatum and Tr. rotundum), the central area forms a regular
heptagon ; but in the majority of the species studied by me, its form is
that of a heptagon to one side of which an isosceles trapezoid has been
apposed by the shorter one of the two parallel sides and with the
boundary line between the two blotted out (Tr. ovale, Tr. foliaceum, Tr.
Nozawe, Tr. biparasiticum). In Tr. sinuatum the two radial sides of
the hindmost peripheral area bifurcate near their outer ends and
there form with the margin of the sucker each a small triangle (PI.
AX, fig, 1).

A marginal membrane is always present, and is thrown into
wavy folds; so that in a surface view, it seems as if it consisted of
numerous rectangular portions. Its investing membrane is very thin,
and its substance consists of a syncytium with its nuclei irregularly
scattered, and traversed by numerous fine, transverse, muscular fibres
(Pl. XXII, fig. 3).

According to my observations on T'r. sinuatum, the species to
34 S. GOTO.

which I have mainly directed my attention in this respect, the
arrangement of the muscular fibres of the posterior sucker is somewhat
different from that described by Niemic.” The fibres may be dis-
tinguished into four groups. (1) The radial fibres. These must again
be distinguished, as in Calicotyle, into two subgroups : (a) those that
are direct continuations of the longitudinal fibres of the body, and
entering the sucker, diverge irregularly in all directions, and are
inserted to the periphery of the sucker. ‘They moreover cross each
other in the stalk of the sucker; those coming from the two sides
of the body going to the opposite sides of the sucker (Pl. XX, fig. 5).
(b) Those fibres that are confined to the radiating spokes. These start
from the margins of the central polygon, and running in small bundles
along the spokes just under the investing membrane, are inserted,
likewise, in the periphery of the sucker (Pl. XX, fig. 7, rad. mus. b.).
(2) The circular fibres, i. ¢., those that run concentrically with the
circumference of the sucker. This group must also be divided into
two sub-groups. (a) Those that belong to the ventral side. These
are arranged in two sets, an outer and an inner. The fibres of the
outer set are arranged ina single layer ; while those of the inner set
are united into strong bundles, which are separated from one another by
the transverse fibres to be described presently, and from the outer set
by an intervening layer of mesenchyma (PI. XX, fig. 6, cir. mus.).
The circular fibres of the dorsal side are arranged in a single layer, and
occupy an exactly similar position to that of the outer set of the ventral
side. (3) The transverse fibres, i. ¢., those that traverse the thickness of
the sucker, and run therefore at right angles to its two surfaces.

They are, in Tr. sinuatum, very strongly developed, and, like

 

1). Niemic—Recherches morphologiques sur les ventouses dans le rgne animal. Recueil
zoolog. suisse. 'T. II, 1885. I have not been able to gain access to this paper, and am indebted
for its account to Braun’s “ Wiirmer ” in Bronn’s “ Klassen u. Ordnungen ” and to Monticelli’s
“ Saggio di una morfologia dei Trematodi.”
STUDIES ON THE ECTOPARASITIC TREMATODES OF JAPAN. 35

the dorso-ventral fibres of the body, ramify towards their ends (PI.
XX, figs. 5, 6, and 7). (4) The last group of fibres is confined to
the radial elevations, and simply traverse these from side to side, just
as the transverse fibres do the sucker (Pl. XX, figs. 5 and 6). These
fibres are absent where three elevations unite (PI. XX, fig. 4).

Epibdella—I have been able to obtain but few specimens of
this genus, and these were so badly preserved that I have not been
able to make out the minute anatomy of the various parts; but a
few points will be noted.

The anterior suckers occupy nearly the same position in the body
as in T'ristomum. They are, however, not so well developed as in that
genus, and are more of a membranous character. The two suckers
are also united with each other by a membranous anterior portion of
the body that lies between them.

The posterior sucker is either circular or elliptical in outline, and
is provided with a marginal membrane. ‘There is no division of the
ventral surface into separate areas as in Tristomum. The musculature
consists of the cireular (in two sets, dorsal and ventral), the trans-
verse, and the irregular radial fibres which are direct continuations
of the longitudinal fibres of the body ; and these various fibres are
arranged exactly like those of the same name in the posterior sucker
of Tristomum.

Sticky Guanps—Under this head I include all those glands
which are present in various parts of the body and are not intimately
connected either with the genital organs or the digestive system.
They all open on the free surface of the body, and some of them are
closely connected with the suckers.

Microcotyle and Octocotyle—In all the species of these two
genera that I have studied, except M. reticulata, there are three

groups of sticky glands in the anterior part of the body in front of the
36 8S. GOTO.

anterior suckers. One of them lies in the median line near the apex

of the body, while the other two are situated behind it in a pair, so that
the three occupy the apices of an isosceles triangle, the base of which is
perpendicular to the long axis of the body. In some species, however,
they are nearly in the same straight line (Pls. Iand II). In section,
each group is seen to consist of a limited number (5—7) of goblet-
shaped bodies with a thin wall, and filled with numerous refringent
granules of a yellowish colour, which do not stain at all in borax-
carmin and only slightly in haematoxylin. It is, however, to be
noted that their affinity for the latter dye varies according to dif-
ferent stages of secretory activity. The necks of the goblet-shaped
bodies of each group open together on the ventral side (PI. III, fig.
7). I have not been able to observe any nuclei in them; but I believe
they are to be regarded as highly modified cells, and each group, there-
fore, as an assemblage of unicellular glands. |

These glands have been observed by previous writers, but their
nature has been variously misunderstood. Wan Beneden and
Hesse,” for instance, describe them as being “ destinées 4 remplir les
fonctions de machoires.” Lorenz” on the other hand, considers them
as tactile organs. Parona and Perugia® are of the same view,
‘“‘seouendo in questo il modo di pensare del Diesing e non quello di

?

v. Beneden ed Hesse.” Now, the bodies in question are not situated
in the cavity of the mouth as v. Beneden and Hesse think, and
their glandular nature is, I believe, evident from their structure above

_ described.

 

1). V. Beneden et Hesse—Recherches sur les Bdellodes et les Trématodes marins, 1863. p.
113. ‘

2). Lorenz—Ueber die Organisation der Gattungen Axine u. Microcotyle. Wiener
Arbeiten, Bd. I, Hit. 3, 1878. p. 24. ;

3). Parona e Perugia—Res ligusticae, XIV.—Annali del Museo Civico di Storia Naturale
di Genova, Ser. 2, Vol. X, 1890. Estratto p. 4.
STUDIES ON THE ECIOPARASITIC TREMATODES OF JAPAN. 37

Axine, Diclidophora, & Mic. reticuiata—In these forms, there
is only one pair of sticky glands. They are situated just in front of
the mouth (PI. I, fig. 5; Pl. VIL). Their torm differs much from that
described in Microcotyle and Octocotyle and approaches more that of the
sticky gland described by me in Diplozoon Nipponicum.? They are
constituted, namely, by an invagination and transformation of the
investing membrane of the body. They are shown in section in fig.
3, Pl. II. As may be seen from it, the cavity of the invagination is
lined by a granular mass, which is a direct continuation of the
juvesting membrane. The granules are very similar in appearance
and in their reaction towards staining fiuids to those of the sticky
glands of Microcotyle. Here, moreover, there is no distinct basement
_ membrane but instead merely a dense layer of “connective tissue
gradually passing into the surrounding mesenchyma. ‘There are in
M. reticulata also some muscular fibres that come from the dorsal side
of the body and terminate in the dense layer of connective tissue just
mentioned (PI. III, fig. 3).

Calicotyle—In this genus, there are two pairs of sticky glands at
the anterior end of the body, the efferent ducts of which are com-
pletely separate one from the other, but open very close to each other
near the anterior apex of the body. Hach gland is a goblet-shaped,
hollow body situated on the external side of the pharynx, with a long
neck (the efferent duct) which proceeds towards the anterior end of
the body, where it opens. One of the pairs has a little shorter neck
than the other. ‘The goblet-shaped portion has a thick wall consisting
of a granular substance, which, in the specimen I have examined, is
stained well in borax-carmin ; but as I have been able to obtain only
a single specimen of this genus, I can not state whether it is always

so or not. The wall of the efferent duct consists of a thick membrane,

 

1). Goto—On Diplozoon Nipponicum, n. sp. This Journal, vol. IV, Pt. I, 1890. p. 166.
38 8. GOTO.

on the inner surface of which some granulations are to be observed
(Pl. XIX, figs. 1 and 4).

As to the cellular structure of this gland, which I believe is here
described for the first time in Calicotyle, there are, I think, two
alternative views to be considered. One would be to regard it as
being multicellular in its origin and to have been formed by the in-
vagination of the epidermis; the other would be to regard it as
unicellular. Against the second view it may be urged that these
glands are too large to be regarded as unicellular—incomparably larger
than the unicellular glands of similar function and position of the
Gyrodactylidae—and that the presence of the internal cavity strongly
points to the other view ; while the similarity of its wall to that of the
similar glands of Diplozoon, Axine, and Diclidophora is also in favour of
the first view.

Monocotyle—In this genus there are four pairs of sticky glands
at the anterior end of the body, and one in the posterior part. ‘The
anterior glands are of exactly the same structure as those of Microcotyle,
and are arranged at equal distances along the front part of the’
lateral border of the body, on both sides of the anterior: notch (PI.
XVII, fig. 1).

The posterior sticky glands are situated in that part of the body
which lies dorsally to the posterior sucker, and consist of numerous
small cells, each with a distinct, deeply stained nucleus and a very
finely granular or almost homogeneous cytoplasm which seems to be
destitute of an external membrane. The cells are of various sizes,
apparently owing to the different stages of secretory activity ; and the
smaller ones are more deeply stained and have more finely granular
cytoplasm than the larger ones (Pl. XVII, figs. 5 and 12). In some
parts, these cells are so closely pressed against one another that their

boundaries become indistinct, and the whole appears somewhat like a
STUDIES ON THE ECTOPARASITIC TREMATODES OF JAPAN. 39

syncytium (PI. XVII, fig. 6). They are distributed, both on the
ventral and dorsal sides (PI. XVII, fig. 5), into two groups, the
right and the left ; and the cells of each group discharge their products
into a common large duct” provided with a distinct membrane, which
opens by a minute aperture on the ventral surface of the lateral portion
of the body, at a short distance from the stalk of the sucker (PI.
XVII, fig. 12, gi’). The secretion of these granular cells is a very
granular fluid, the granules staining very deeply in haematoxylin.

Tristomum and Epibdella—As has already been observed by
Monticelli,” there are, in these genera, numerous unicellular glands
in the anterior portion of the body ; and in some species of T'ristomum
(T. sinuatum and T. biparasiticum) there is in addition a series of
groups of unicellular glands which open at regular intervals along
the lateral borders of the body.

The cells of the anterior sticky glands are more or less goblet-
shaped, with a very thin membrane, a more or less granular cyto-
plasm, a nucleus witha single nucleolus, and a long neck. The
nucleus sometimes occupies the central position, but is sometimes
quite peripheral. The cells are distributed almost uniformly, or in
groups separated from one another by dorso-ventral muscular fibres,
in the mesenchyma of the suckers and of the anterior, median portion
of the body. In some species of Tristomum (as in T. ovale) the necks
of the gland-cells open at various points on the ventral surface of the
sucker, at the tops of small, conical papillae (Pl. XXII, fig. 5), and
especially along the inner border of the sucker, where the papillae are,
as already mentioned, larger and very numerous (fig. 5). In T.

sinuatum the glands open mainly along the margin of the anterior

 

1). Its size, however, probably varies according to the quantity of its content.

2). Monticelli—Di aleuni organi di tatto nei Tristomidi: Bollet. della Soc. di Naturalisti
in Napoli, Ser. 1, Anno 5, vol. V., 1891, fas. 2.
40 8. GOTO.

sucker, on the ventral side, where the basement membrane is some-
what indistinct ; but they probably open also on the whole ventral
surface, although I can not make a positive statement to that effect,
(PI. XX, fig. 10). In Epibdella, on the other hand, the glands open
on the whole ventral surface of the anterior sucker. Here, however,
it should be remarked that in most’ cases I have not been able to
follow the neck of the gland-cells through the investing membrane of
the body to the external surface, but only up to the basement mem-
brane. In T’. ovale, on the other hand, the opening of the glands are
distinctly seen at the top of most of the conical papillae already men-
tioned. This leads me to suppose that the ducts of the glands
through the investing membrane is usually entirely collapsed, being
open only during the actual passage of the secretion. It also leads
me to suspect whether Brandes” has not mistaken these glands for
his “ subcuticular glands.”

In two species of Tristomum, viz. T. sinuatum and T. biparasiticum,
there is, as before mentioned, a series of groups of peculiar unicellular -
glands opening at intervals along the lateral margin of the body.
The series begins near the anterior end of the body, and terminates
quite near the posterior sucker (Pl. XX, fig. 1; Pl. XXV, fig. 5). In
T.. sinuatum I have counted as many as fifty-eight on one side of the
body, while in T. biparasiticum there were about sixty-two. I have
studied the histology of these glands mainly in the former species, so
that the following statements refer mainly to it alone; but the es-
sential features are the same in both species, the difference lying only
in insignificant details.

The cells that constitute these glands are of various sizes, but are
more or less polyhedral in form, owing to mutual pressure. ach cell

has a distinct wall, and in the specimens I have examined, the greater

 

1). Brandes—. c.
STUDIES ON THE ECTOPARASITIC TREMATODES OF JAPAN. 4]

part of its interior was occupied by one or more clear vacuoles. The
nucleus, which enclosed a single nucleolus, sometimes occupied a
central position, but usually lay more or less towards the periphery of
the cell ; and in most cases was surrounded by a mass of granular cyto-
plasm, which was stained in haematoxylin more deeply than the nucleus
itself. From this central mass the cytoplasm radiated, in most cases,
in the form of a few threads towards the cell-wall (PI. XXI, figs. 2
& 3). Each cell is prolonged at one of its corners into a long duct ;
and the ducts of a single group, after proceeding together for a short
distance towards the lateral border, are divided into two bundles,
which diverge from each other, and again unite just before opening
on the dorsal surface of the body, close to its lateral margin.

From the above description, the glandular nature of these cells is,
I believe, beyond doubt ; and comparing them with the cells of the
submaxillary glands” of the mammalia, there is such a similarity
between the two that it is perhaps allowable to conclude that these
unicellular glands secrete mucin and help to attach the body of the
parasite more securely to its host.

The opening of the gland above described is armed with a
chitinous piece, which is represented in surface view in fig. 3, Pl. XX,
and in section in its natural position in fig. 8, Pl. XXI for T. stnua-
tum, and in fig. 5, Pl. XXV, for T. biparasiticum. In T. rotundum
similar chitinous pieces (Pl. XXIV, fig. 7) are arranged in transverse
rows along the lateral margin of the body just as in Tr. mole”; a
single row consisting of four or five pieces in the middle portion of

the body, but of only one or two towards the ends. In this species,

 

1). Landois.—Lehrbuch der Physiologie des Menschen. 6. Aufl. p. 268-270.

2). Parona e Perugia.—Res ligusticae, VIII. Di alcuni trematodi ectoparassiti di pesci
marini. Nota preventiva. Annali del Museo Civico di Storia Naturale di Genova. Ser. 2, vol
VIL. p. 741.
492 S. GOTO.

at

however, there is no gland connected with these chitinous pieces.”

These pieces might be supposed to help the parasite in attaching itself
to the host, were it not for the fact that they are on the dorsal side of
the body, and are therefore presumably of no use in that respect ; but
I am not able to suggest any other use of them. |

If, now, we compare the structure of the glands hitherto de-
scribed, we find a close similarity of their products with one another as
well as with those of the sticky glands of Gyrodactylide. The clear,
transparent fluid that fills the vacuoles of the lateral glands of T,
sinuatum and 1’. biparasiticum. might be meutioned as exceptions ; but
we find in their efferent ducts just the same granular substance as in
the anterior glands, showing probably that the clear contents of the
cells assume the character of granules in their passage along the duct.
That the anterior glands of Gyrodactylide are sticky, and are used for
attachment can be demonstrated under the microscope; so that I
believe it is not much amiss to regard, as I do, the glands above
described as having the same function. It may also be mentioned, in
addition, that Langley? and Reid® have described granules in
the mucous glands of some ‘vertebrates, which seem to me in many
respects similar to those of the glands above described.

It is not perhaps out of place here to observe that the position of
the opening of the. posterior sticky glands of Monocotyle does not seem

 

1). Here, again, it should be observed that these so-called chitinons pieces of T. rotundum
are ‘deeply stained in borax-carmin.
2). Langley—On the Histology of the Mucous Salivary Glands, and on the Behaviour of
their Mucous Constituents. Journ. of Physiology. Vol. X, 1889. p. 433-457.
3). Reid—Mucin Granules of Myxine. Same Journ. Vol. XIV, 1893. p. 340-346.

These authors state that the granules are not stained in haematoxylin, and that cold
sublimate causes them to burst. This latter fact seems not to accord with the observations
described in the text, in which the granules are always preserved intact. Reid also states that
boiling water makes the granules break into a mass of stringy débris. Hence we should
probably infer that the granules of the glands described in the text and those of the mucous
glands of the vertebrates are not exactly of the same chemical constitution.
STUDIES ON THE ECTOPARASITIC TREMATODES OF JAPAN. 43

to accord with their supposed function. A priori, the opening
might be expected on the ventral surface of the sucker ; but as the
matter stands, I suppose the secretion of the glands flows over the
dorsal surface of the sucker on to its margin, and here helps to attach
it more firmly to the host.

The two genera Heaacotyle and Onchocotyle are destitute of any
‘sticky gland.

Hooxs”—These are usually spoken of as of a chitinous nature ;
but it should be remembered that they are soluble in a (35 °/,) solution
of caustic potash. In the natural state they are slightly yellow, and
are very refringent. When they are very slender they are wholly
solid ; but when somewhat large they are usually hollow. They lie
mostly imbedded in the mesenchyma, and only a very small portion
of the pointed end projects free on the surface of the body. Their
form, size, number, and position are very varied, but are eminently
characteristic of each species.

In Onchocotyle, Tristomum, Monocotyle, Calicotyle and Octocotyle
major there is only a single pair of hooks. In the last-mentioned
species, they are situated at the posterior end of the body between the
posterior suckers, close to the median line. ‘They have roughly the
form of a fishing hook, and have a process at about the middle of
their length, ‘to which is attached a strong bundle of muscular fibres
(Pl. IX, figs. 2 & 9 a). In the natural position the pointed end is
usually directed posteriorly, but is turned more or less in other
directions according to the different states of contraction of the muscle
attached to the hook. In QOctoc. major the hooks are hollow towards
the pointed end (Pl. IX, fig. 2) ; but in Octoc. minor they are entirely
solid (fig. 9 a).

 

1). For more minute descriptions of the hooks in different species see the systematic
portion of the present paper.
44 S. GOTO,

In Onchocotyle, the hooks are situated near the extremity of the
caudal appendage, between the pair of small suckers already described,
on the morphologically ventral side (Pl. XV, figs. 1 and 2). They
are wholly solid, and are like a fishing hook in shape ; but the basal
end is divided into two processes, one of which bears again a rounded
process (Pl. XV, fig. 5). I have not been able to demonstrate any
muscular fibres attached to the hooks.

In Tristomum, the hooks are situated at the extremities of the
posterior border of the central polygon of the posterior sucker, and are
provided each with a strong muscle formed by the direct continuations of
the longitudinal fibres of the body. They are,unlike the hooks of most
other genera, more or less straight (Pls. XX, XXIII, KK, XXYV).

In Calicotyle and Monocotyle, the hooks are situated in the
posterior radial spokes of the posterior sucker on both sides of the
median line of the body, and project free over the surface of the invest-
ing membrane at the margin of the sucker (PJ. XVII, figs. 1 and 2;
Pl. XIX, fig. 1). They are strongly recurved in both genera.

In Hezxacotyle and Octoc. minor, there are two pairs of hooks, of
which one is much smaller than the other. They are situated at the
posterior end of the body, on both sides of the median line, and
between the innermost pair of suckers in Hexacotyle. In both cases
the smaller pair of hooks lie nearer the median line (PI. IX, fig. 7;
Pl. XII, figs. 1, 2, 4, & 5).

Finally in Epibdella, there are three pairs of hooks. ‘They are
situated on the ventral side of the posterior sucker, and the three pairs
are arranged one behind the other ; the most posterior pair being close
to the margin of the sucker. Each hook is provided with a strong
bundle of muscular fibres. ;

The genera Microcotyle, Aine, and Diclidophora are, so far as I

haye observed, entirely destitute of hooks.
STUDIES ON THE ECTOPARASITIC TREMATODES OF JAPAN. 45

5. The Mesenchyma.

The mesenchyma of the Trematodes has been variously described
by different authors. ‘The tact is that it presents very different aspects
in different species and even in different parts of the same specimen.
The mesenchyma of the monogenetic Trematodes is, generally speak-
ing, of very different appearance from the typical form of the same
tissue in the Digenea, which consists of large vacuolated cells, between
which fibrous network with small nuclei is present; and varies
from a truly cellular character to that of the typical, reticulated,
fibrous connective tissue on the one hand and a true syncytium on
the other.

The general mesenchyma of the body has been distinguished by
certain writers into two parts, for which different names have been
proposed by different writers, but the terms proposed lately by
Brandes,” wz. endo- and ectoparenchyma are the simplest and
therefore the most convenient. In Axine heterocerca these two portions
are very distinctly separated from each other by a thin membrane of
compact connective tissue, and are very different in character (PI.
VIII, fig. 1). The ectoparenchyma is, in this species, again dis-
tinguishable into two layers, that in which the longitudinal fibres lie
and that in which the diagonal and the circular- fibres run. The
inner layer, ¢.¢., the one in which the longitudinal fibres run, is, in
some places, as thick as 20 4, and its connective tissue consists of very
fine, anastomosing fibres, which are but slightly stained in haema-
toxylin, and in the knots of which nuclei are here and there present.

The general course of the connective tissue fibres of this layer is at

 

1). Leuckart—Die thierischen Parasiten des Menschen. II, Aufl. I. Bd., 3. Lief., p. 13
et seq.
2). Brandes—l. c., p. 424.
46 S. GOTO.

right angles to its limiting membrane, and in some places, the fibres form
somewhat strong, compact bundles, which are more deeply stained than
the other parts. The outer layer, viz., that in which run the diagonal
and the circular muscular fibres, is generally half as thick as the inner
layer. It consists of dense, fibrous connective tissue, scantily inter-
spersed with nuclei and deeply stained by haematoxylin. This
layer is, in most parts of the body, very distinct from the inner layer,
from which it seems to be separated by a very thin membrane ; but in
some parts, the two layers are not so distinctly separated from each
other (Pl. VIII, fig. 3).

In Microcotyle reticulata, also, the external portion of the ecto-
parenchyma is clearly distinguishable from the inner ; the former con-
sisting, in fact, of a dense, diffusely stained, connective tissue, whose
fibres run parallel to the investing membrane (PI. III, fig. 4).

In all the other species I have hitherto studied, the ecto- and
endoparenchyma are not separated from each other so distinctly as in
Axine heterocerca; but in most species the two portions present
different aspects, the ectoparenchyma consisting generally of a dense,
fibrous, connective tissue which is more deeply and more diffusely
stained with haematoxylin than the endoparenchyma. There is,
however, as above stated, no distinct landmark that separates the two
from each other, and even in Axine heterocerca there is no distinct
boundary between them towards the two ends of the body.

The endoparenchyma presents, in most species, different aspects
in different parts of tne body. In Axine heterocerca (Pl. VIII, fig. 1),
the endoparenchyma is, in most parts of the body, of a cellular
nature. ‘The cells which are of very different sizes in different parts,
have usually a distinct membrane and a deeply stained nucleus
enclosing mostly a single, but sometimes two or more nucleoli.

The cell-body encloses some large vacuoles, and the protoplasm
STUDIES ON THE ECTOPARASITIC TREMATODES OF JAPAN. 47

radiates, in consequence, in the form of threads from around the
nucleus towards the cell-membrane. In some cases, however, there
are no vacuoles, and the cell-body consists simply of « slightly stained,
granular protoplasm. In still other cases (¢.q., on the right side of the
prostate glands around the vas deferens in fig. 1, Pl. VIII), the cell-
membrane is incomplete, and the boundaries of adjacent cells are
more or less obliterated. In the terminal portions of the body as
well as around the ducts of the genital organs, the endoparenchyma
consists of truly fibrous connective tissue interspered with small nuclei,
which are sometimes surrounded by a scanty mass of granular
protoplasm. Around the ducts of the genital organs I have often
observed much larger, oval or elongated nuclei surrounded also with a ~
scanty mass of granular protoplasm ; but they seem to have no special
function. The meshes of the connective tissue are filled in some parts
with slightly stained granules and:in others with a perfectly trans-
parent, clear fluid (Pl. VIII, figs. 2, 8, and 4).

In most species of Microcotyle, the greater part of the endo-
parenchyma is of a fibrous nature; but in some parts it consists of
true cells, while in others there is some tendency in it to assume the
character of a syncytium. Thus in Microcotyle truncata (Pl. III, fig.
6) and MM. caudata (Pl. III, fig. 9), the endoparenchyma consists in
the lateral part of the median portion of the body free from the
vitellarium, often of polyhedral cells each usually with a distinct
- membrane, a vacuolated cell-body, and a nucleus in the centre, from
which the protoplasm radiates in the form of fibres towards the
periphery, just.as in some mesenchyma celis of Amine already de-
scribed. In JI. caudata the vacuoles are less distinct, and the whole
cell is more granular and more deeply stained than in JL. truncata.
The nucleus usually encloses a single nucleolus, but sometimes more ;

and the boundaries of the adjacent cells are, in many cases, more or
48 8. GOTO.

less obliterated, as may be seen in the figures above referred to. In
M. reticulata, the endoparenchyma of which consists generally of a
typical, reticulated fibrous connective tissue, there are scattered here
and there, sometimes in small groups, cells of a roundish or polyhedral
outline, with a distinct membrane and a lightly stained, granular
protoplasm (PI. IIT, fig. 4, mes. c.). Besides these, vacuolated cells
whose boundaries can be recognized with difficulty are also to
be observed. In Diclidophora sessilis, I have observed in the
neighbourhood of the ovary, large vacuolated cells with a centrally
situated nucleus, from which granular protoplasmic threads radiated
towards the cell- membrane (PI. XI, fig. 7)—cells, therefore, which
are very similar to those of the mesenchyma of many distomes. In
this species there are also polyhedral cells similar to those described in
Af. truncata and M. caudata, between the lateral and the median
portion of the body (Pl. XI, fig. 5). In M. chiri (PI. IU, fig. 5), M.
elegans (Pl. V, fig. 2), M. sciaenae (PI. VI, fig. 2), Calicotyle Mitsukurit
(Pl. XIX, fig. 8), Monocotyle Ijimae (PJ. XVIII, fig. 2), Onchocotyle
spinacis (P1. XV, 10; Pl. XVI, fig. 8), and Tristomum ovale (PI.
XXIII, fig. 7),:and_in those portions of the body of M. fusiformis and
M. caudata which adjoin the genital opening, the endoparenchyma
consists of a reticulated, fibrous connective tissue with large meshes
filled with granules which are in some species faintly, but in others
well stained (PJ. V, figs. 1, 2, and 3)—the mesenchyma assuming in
the latter case more the character of a syncytium. In some species
moreover, as in Onchocotyle spinacis, the nuclei are generally surrounded
by a scanty mass of granular, well-stained protoplasm.

In Hexacotyle acuta, the greater part of the endoparenchyma
consists of cells apparently destitute of any membrane, but with well-
‘stained, granular protoplasm, and each with a distinct nucleus which

encloses one or a few nucleoli. ‘These cells are usually separated from
STUDIES ON THE ECTOPARASITIC TREMATODES OF JAPAN. 49

one another by intervening spaces which in sections appear perfectly
colourless ; but in many cases the protoplasm of adjacent cells is con-
tinuous, and no boundary can be recognised between them (PI. XIV,
fig. 2). In Hexacotyle grossa (Pl. XIV, fig. 6) and Tristomum sinuatum
(Pls. XXI and. XXII), the endoparenchyma is a true syncytium
traversed, however, by scattered connective tissue fibres. The nuclei
are very irregularly. distributed ; and in both species they are much
smaller than in others. In Hesxacotyle grossa I have observed, scattered
here and there apparently without order in the general syncytium,
cells of irregular forms, -with a homogeneous protoplasm which was
well stained by haematoxylin, but differently from the general
syncytium (PI. XIV, fig. 6, x), which was stained deep blue, while
the cells above mentioned were stained purplish red, just the colour
of acetic haematoxylin. I have occasionally observed similarly
stained cells in Onchocotyle spinacis. These cells have, so far as
I have observed, no relation with the glands hitherto described
or to be described hereafter; and the only suggestion that I
can give as to their nature is that they are perhaps worn-out: cells
undergoing disintegration, and that their colour is due to the presence
of some acids generated by decomposition. In Trristomum sinuatum, I
have often observed in the peripheral portion of the endoparenchyma
cells (already referred to in describing the investing membrane) of
a rounded outline and with a granular protoplasm. I do not know
what else they are than remnant cells of the original mesenchyma.

Around the terminal portions of the genital ducts, the mesenchyma
is specially modified in various ways. These will be treated of in con-
nection with the genital organs.

If, now, we make a general survey of the various forms of endo-
parenchyma found in the monogenetic Trematodes, we see that

even in the same species it is very different in different parts of the
50. 8. GOTO.

body, while individual variations in this respect may be almost imper-
eeptibly small. Near either end of the body the endoparenchyma
consists, in almost all species, of typical, fibrous, reticulated, connective
tissue, interspersed with nuclei (PI. II, fig. 7; Pl. IV, fig. 2; Pl.
XII, figs. 4&7; Pl. XV, fig. 8; Pl. XVI, fig. 1). In other parts
of the body we may distinguish two different tendencies in the course
of differentiation of the original mesenchyma cells. Some of these cells
appear to assume more of a vacuolated character, and these furnish the
fibres of the connective tissue ; while others come to have more and
more a granular protoplasm without any distinct membrane, and to
form finally a continuous syncytium by simple obliteration of their
boundaries. These two tendencies prevail in different degrees in
different parts of the body, and also in different species. An endo-
parenchyma of a typical, reticulated, connective tissue we have found
in Microcotyle sciaenae,. Calicotyle Mitsukurii, and in the terminal por-
tions of the body of many other species ; that of a true syncytium we
have found in Tristomum. sinuatum and Hezxacotyle grossa ; while in all
the other species the syncytial and fibrous characters are variously

intermingled.
6. The Digestive System. °

The digestive system consists of the mouth and its cavity, the
pharynx, the oesophagus, the intestine, and the glands which are
connected with them.

The mouth is a funnel-shaped opening situated, in all the species,
on the ventral side near the anterior extremity of the body. In
Microcotyle, Axine, Onchocotyle, Diclidophora, Octocotyle, and Hexacotyle,
it is close to the anterior end of the body ; while in Tristomum, Epib-
della, Monocotyle, and Calicotyle it is more distant from it. In most

species there is a tolerably ample mouth-cavity ; and in those forms
STUDIES ON THE ECTOPARASITIC TREMATODES OF JAPAN. 51

which have paired. anterior suckers within the mouth (‘‘ Mundsaug-

nipfe” of Braun), it freely communicates with the cavities of the

latter. In Microcotyle (PI. LV, figs. 1 and 2), Octocotyle, Diclidophora,

Onchocotyle, and Hexacotyle, the mouth-cavity expands more or less at

its posterior end and constitutes the prepharynz, into which the
anterior end of the pharynx protrudes. In Tristomum and Epibdella,
however, the mouth and the anterior end of the pharynx coincide so-
that in these there is no mouth-cavity (Pl. XXI, fig. 1; XXIII,

fig. 4; XXIV, fig. 12; XXV, fig. 7).

The pharynx is more or Jess ellipsoidal or almost spherical, or it
may have a constriction on each side, so that in horizontal optic
section it appears double, as in many species of Tristomum (Pl. XXIII,
fig. 1; Pl. XXIV, fig. 10; Pl. XXV, figs. 1 and 4). In Microco-
tyle, Octocatyle, Diclidophora, and Onchocotyle, it is traversed by a small,
tubular canal which puts the oesophagus in communication with
the cavity of the mouth, and is lined by a structureless membrane
of various thickness according to the species. In Monocotyle, the
cavity of the pharynx is triangular in cross-section (PI. XVIII, fig.
8) ; while in Tristomum and Epibdella, it is funnel-shaped and spacious..
Considering this internal cavity as the axis for the sake of orientation,
we may distinguish the ventral and dorsal halves of the pharynx ;
and the ventral half thus distinguished is always smaller than the other
half—resembling in this respect the oval anterior sucker of Onchocotyle
and the distomes (PI. IV, fig. 1; Pl. XV, fig. 3; Pl. XVIII, fig. 4;
Pi, MAI, fie: ly PAA, fie. as Pl AALY, fe, 12; Pl RY,
fig. 7). In nearly all species, the pharynx is an independent organ
entirely separated from the surrounding mesenchymatous tissue by a
distinct membrane of a cuticular appearance. In Tristomum, however,
this membrane is incomplete at some points at the posterior ends

of the ventral and dorsal halves, and thus affords passage to the
59 8. GOTO.

efferent ducts of the numerous glandular cells presently to be
described. The internal cavity is in some species lined with a com-
paratively thick, structureless membrane of varying thickness, staining
well with haematoxylin, as in most species of Microcotyle, Diclido-
phora (Pl. XI, fig. 1), and Monocotyle (Pl. XVIII, fig. 8); but in
others the lining membrane is. exactly similar to that which separates
the pharynx from the surrounding mesenchyma. ‘The greater part of
the substance of the pharynx consists of mesenchymatous connective
tissue essentially similar to that of the other parts of the body and
traversed by numerous muscular fibres—the muscular fibres, how-
ever, predominating sometimes to an extraordinary degree and form-
ing almost the whole, as in Monocotyle (Pl. XVIII, fig. 8) and
Microcotyle reticulata (Pl. IV, figs. 2 and 3).

The musculature of the pharynx consists typically of three sets of
fibres, viz. the internal and external circular fibres and the radial
fibres. In most species, the sets of circular fibres are arranged in a
single layer directly inside the limiting. membranes of the pharynx ;
but in some species they are more than one layer thick, as in Tristomum
sinuatum (Pl. XXI, fig. 1) and Diclidophora sessilis (Pl. XI,’ fig. 1).
Moreover in all the species of Tristomum I have studied, these two
sets of circular fibres are developed in a special degree at the anterior
end of the pharynx, and constitute a powerful sphincter (Pl. XXI,
fig, 1; Pl. XXIII, fig. 4; Pl. XXIV, fig. 12; Pl. XXV, fig. 7).
The radial fibres are but weakly developed in Microcotyle, Axine, Octo-
cotyle, and Onchocotyle ; indeed, in the last-named genus I have not
been able to demonstrate their existence with enough certainty.
In Tristomum, Monocotyle, Diclidophora, and Microcotyle reticulata, how-
ever, they are more strongly developed. Like the dorso-ventral fibres
of the body, the radial fibres divide into smaller branches towards their

ends, and are inserted into the limiting membranes of the pharynx.
STUDIES ON THE ECTOPARASITIC TREMATODES OF JAPAN. 53

Between these radial muscular fibres there are numerous nuclei,
some of which are exactly similar to those of the general mesenchyma
of the body ; but there are also others which are much larger and are
usually surrounded by a granular protoplasm (PI. XI, figs. 1 and 2).
These I believe to be remnants of cells that have produced the muscular
fibres.

The arrangement of the muscular fibres of the pharynx is in most
species as above described ; but there are numerous departures from
the rule. For instance, in Diclidophora sessilis there are longitudinal
(or meridional) fibres on the ventral side, occupying a short strip
along the median line. In Microcotyle reticulata, again, the various
sets of mucular fibres and their arrangements are so anomalous that
they require separate description. They may be conveniently dis-
tinguished into the longitudinal, the circular, and the oblique fibres.
The circular fibres must again be divided into two groups, the internal
and the external. The internal circular fibres are situated next the
lining membrane of the pharynx at a short distance from it (Pl. IV,
figs. 2 & 3, int. c. m.). : They are most strongly developed a little
behind the middle of the length of the pharynx, and diminish towards
either end. ‘They are divided into strong, compact bundles by the
radial fibres, which pass between them and are inserted into the lining
membrane of the pharynx. ‘The external circular fibres are present
along nearly the whole length of the pharynx, but are especially
developed in its posterior half, and are there more numerous than the
inner fibres, which they resemble in being divided into numerous, com-
pact bundles by the radial fibres. In the anterior half of the pharynx
they are less developed, and are divided into smaller bundles by the
oblique fibres to be presently described. In the lateral part of the
' pharynx the external circular fibres are situated about midway be-

tween the inner and the outer limiting membrane of the pharynx ;
54 8. GOTO.

but in the dorsal and ventral parts, they are situated directly inside
the external limiting membrane (Pl. IV, fig. 2). Some of the ex-
ternal circular fibres deviate more or less from their course, and passing
between the bundles of the lateral longitudinal fibres, are inserted
into the external limiting membrane. The longitudinal fibres are
divided into three groups, which may be called according to their
relative positions, the internal, the middle, and the external. The
internal longitudinal fibres are present only in the posterior third of
the pharynx, and are situated between the inner limiting membrane
and the inner circular fibres (Pl. IV, fig. 38, d). They do not form
any definite bundle, and are inserted by their ends into the inner
limiting membrane of the pharynx. The middle longitudinal fibres are
arranged in a single layer directly on the outer side of the inner
circular fibres, with which they are intimately associated throughout
their whole course (PI. IV, figs. 2 and 3, c). ‘The individual fibres of
this group are separated from one another by an intervening space,
and have a round outline in cross-section. The outer longitudinal
fibres are present only in the posterior two-thirds of the pharynx,
and are divided into four groups, crescent-shaped in cross-section,
and placed symmetrically in the lateral, dorsal, and ventral parts
(PI. IV, figs. 2 and 3, 6 and i’). The lateral groups are situated
directly inside the external limiting membrane of the pharynx; but
the dorsal and ventral groups are separated from it by the external
circular fibres already described. The constituent fibres of these
groups are formed into strong, compact bundles, which are separated
from one another by the radial fibres and also to some extent
by the external circular fibres (fig. 2). They are inserted,
posteriorly into the lining membrane at the end of the pharynx
and more anteriorly into the external limiting membrane at

various points.
STUDIES ON THE ECTOPARASITIC TREMATODES OF JAPAN. 55

There is another peculiarity in the pharynx of M. reticulata, and
that is that its anterior end is prolonged into a tube with pointed end
and with a thick wall which is differentiated into two layers unstained
by borax-carmin, the outer of which is very refractive. Both these
layers are homogeneous and without structure.

In all the species of Tristomum that I have: studied, there are
numerous papillae on the surface of the cavity of the anterior half of
the pharynx ; and in some species, as in Tr. ovale (PI. XXIII, fig. 4)
and Tr. sinuatum (Pl. XXI, fig. 1), these papillae are present also at
the anterior margin. They mark the openings of numerous unicell-
ular glands, which have been called “ Kérnerdriisen” or “ Pharyn-
gealdriisen”” by Max Braun.” I shall adopt the latter name and
call them pharyngeal glands. The glandular cells themselves are
situated, so fur as I have observed, not as Braun states, in the wall
of the pharynx, but outside it, that is, in the mesenchyma of the
median portion of the body behind the pharynx, as may be
clearly seen in fig. 5, Pl. XXI, which represents a horizontal
section of the region in question in Tr. sinuatum. ‘They are very
numerous, and vary in form from a typical goblet to a more or less
oval or polygonal shape. The goblet-shaped cells, the comparatively
large efferent ducts of which can be generally traced very distinctly to
the wall of the pharynx, have vesicular nuclei each with one or
more, faintly stained nucleoli ; both the cell-body and the efferent
duct are entirely filled with coarse granules which stain but slightly
with haematoxylin. On. the other hand, those which are oval or
more or less polygonal in form have each a rather small nucleus with
a single, deeply staining nucleolus ; and the cell-body is very finely
granular and deeply stained (PI. XXI, fig. 5). Both these and the
goblet-shaped cells seem to be entirely destitute of a membrane.

 

1). Braun— Wiirmer ” in Bronn’s Klassen u. Ordnungen. p. 450.
56 8. GOTO.

Though I have not actually observed it, a number of these efferent
ducts seem to unite into one on entering the wall of the pharynx at
its posterior part; and they finally open into its cavity at the top of
the papillae already mentioned. ‘That two or more ducts unite
together I infer from. two facts, viz. (1) that while only one duct
opens at the top of each papilla the total number of these papillae is
‘far less than that of the glandular cells, and (2) that the efferent ducts
in -the wall of the pharynx are very much larger than those of the
single cells. Sometimes also, a portion of the duct is swollen into
a reservoir which may present a vacuolated appearance (PI. XXIV,
fig. 12)." Moreover, the granules seem to disappear on entering
the ducts of the pharynx, and to. be-agglomerated into a con-
tinuous mass; for the contents of these ducts do not present any
structure, but consist of a deeply stained substance which has all the
appearance of a mucous secretory product. Braun” states that in
these glandular pharynges, such as we find in Tristomum, the pharyn-
geal cells or those large cells with a finely granular protoplasm seem.
to be absent ; but although I have found them very few, they do not
seem to be entirely absent (Pl. XXIII, fig. 4). At the same time it
should be remarked, however, that I have failed to recognise the
terminal cells of the excretory system, which are stated by Braun to
be present in the pharynx.

The cavity of the pharynx leads into the oesophagus. This is in
most species simple and tubular in form ; but in some species, as in
Axine heterocerca, Microcotyle reticulata, and Hesxacotyle, it sends out
lateral branches on both sides, the ends of which are in M. reticulata
all connected together by a longitudinal branch of the intestine (PI.
III, fig. 2). In most species of Microcotyle, and in Octocotyle, Hexaco-

tyle, and Onchocotyle it is somewhat long; but in all the other species

 

1). Braun—l. ¢. p. 450.
STUDIES ON THE ECTOPARASITIC TREMATODES OF JAPAN. 57

I have studied, it is very short or almost entirely wanting. Its
internal surface presents just the same aspect as that of the intestine,
and therefore will be described with that. In Monocotyle, Calicotyle,
and Tristomum, (and probably also in Epibdella) numerous unicellular
glands open into the oesophagus at its very beginning (Pl. XX, fig.
8: Ph SAL fe. ty Ph AX, fe 122 Pl ANY, fe. 3-2,
XXIII, fig. 4; Pl. XVIII, fig. 5; Pl. XIX, fig. 8), which have
been called the salivary glands. In Monocotyle and Calicotyle, they are
situated close around the oesophagus, and in the former also a little
behind it (Pl. XVIII, fig. 5; Pl. XTX, fig. 8). In Tristomum, how-
ever, they are situated quite in the lateral portion of the body on the
dorsal side, and are connected with the ocsophagus by long ducts (PI.
XX, fig. 8). The cells present somewhat different aspects (PI.
XX, fig. 9; Pl XVIII, fig. 5); they stain well, but in some the
eell-body is comparatively finely granular, and the oval, vesicular
nucleus encloses in its centre a single, well staining nucleolus, while
in others the cell-body is more coarsely granular and the large, round,
vesicular nucleus usually encloses a few small nucleoli besides the
large one, all of which stain more weakly than in the first class
of cells. Cells of the first class also stain more deeply than those
of the second. ‘These differences are no doubt due to the different
stages of secretory activity ; for, intermediate forms of all degrees
are also present.

In Tristomum, the oesophagus is separated from the intestine
by valve-like projections of the surrounding tissue into the cavity
of the alimentary canal in which sphincter muscular fibres are
present. (PJ. XAXI, fig. 1; Pl ARIV, fig. 12; PL XY, fic, 7;
PI. XXIII, fig. 4).

In Microcotyle, Axine, Octocotyle, Diclidophora, Hexacotyle, and
Onchocotyle, the salivary glands are absent.
5g 8. GOTO.

The oesophagus leads into the intestine. This always consists of
two branches, which proceed towards the posterior end of the
body, where they unite together. in some species, or in others
remain separate. They traverse the body midway between the
dorsal and the ventral side, and divide it lengthwise into three,
roughly equal areas, in the central one of which is placed the greater
part of the genital organs, while in the lateral areas only the vitel-
larium is generally present. The two divisions of the intestine send
out lateral branches on both sides; but those of the inner side are
generally very short, while those of the outer are long and bifurcate
repeatedly before reaching the lateral borders of the body. In some
again, as in Hexacotyle (P]. XIII), there are, besides the two main
branches of the intestine above mentioned, two others which are
situated close to the lateral borders of the body, and extend backwards
through the anterior two-thirds of the body. In this genus as well
as in Micr. reticulata, the branches of the intestine form a close
net-work not only in the lateral but also in the median portion of
the body. The relative arrangements of the main divisions of the
intestine as well as of their branches will however be best gathered .
from the accompanying plates and the description of species, so that I
may here pass them over, and proceed to the consideration of the
intestinal epithelium.

Two types of intestine. may be distinguished according to the
character of the cells that constitute its epithelium. In the first type,
the cavity of the intestine is destitute of any continuous epithelium,
but is bounded directly by a tunica propria, on the surface of which
lie cells without any membrane, which contain in their protoplasm
numerous, yellowish, dark-brown, or almost black granules of strong
refractive power. In most species, there is a distinct nucleus, and in

some, as in Onchocotyle spinacis (P]. XV, figs. 7 and 10), also a well
STUDIES ON THE ECTOPARASITIC TREMATODES OF JAPAN. 59

staining protoplasm. In the species just named, the cells are cylindri-
cal, sometimes attaining the length of about .05 mm., and are in some
parts closely crowded. But in most of the other species having the
intestine of this type, the cells are separated from one another by wide
intervals, and the protoplasm is almost entirely obscured by pig-
ment granules. In Microcotyle I have not been able to demonstrate
the existence of the nucleus, although there was a clear space in the
centre of each cell. In Onchocotyle, again, there are, besides the tall,
cylindrical cells already mentioned, smaller cells with a well staining,
finely granular protoplasm which is either entirely destitute of
pigment granules or contains fewer granules of smaller size. Some
of these cells are again very small, and have a scanty mass of
protoplasm around the nucleus, which latter remains nearly constant
in size in all the forms of cells. Intestines of the type above described
are found in Microcotyle, Axine, Octocotyle, Diclidophora, Hexacotyle,
and Onchocotyle.

The second type of intestine is similar to that of the distomes,
and is found in Tristomum, Epibdella, Monocotyle, Calicotyle, and the
Gyrodactylidae. In this type, the intestinal cavity is lined by a con-
tinuous epithelium consisting of cells which are all similar to one
another. ‘The individual cells are either cubical or cylindrical, and
have a distinct membrane except on their free borders where it seems
to be entirely wanting. ‘The nucleus is always situated close to the
tunica propria. In Monocotyle Ijimae (P]. XVIII, figs. 2 and 5), the
boundaries of the cells are, in cross-section, not to be clearly seen in
every: case ; but in a surface view they can be distinctly recognised (PI.
XVII, fig. 11). In this species, moreover, the protoplasm of the cells
stains deeply, and contains numerous, deeply staining, granules,
which are smaller than and also very different in appearance from the

pigment granules of the first type. In Tristomum, however, the
60 8. GOTO.

epithelial cells stain very slightly, are generally very clear, and are
also very much smaller than in Monocotyle.

Having now described the various parts of the digestive system, I
shall proceed to note down a few considerations on the physiology
of the accessory glands.

In the first place, as to the pharyngeal glands. As is well
known, there are in Turbellaria numerous unicellular glands in the
mesenchyma around, before, and behind the pharynx. These open
mainly on the lips of the pharynx, but according to Lang” also on
the inner and outer surfaces. They have been called the salivary
glands. According to Graff”, two sorts of these glands are to be
distinguished in Rhabdocoelida, viz., those that open into the mouth-
cavity (Pharyngealtasche), and those that open into the oesophagus
or, where such is wanting, between the pharynx and the intestine, the
latter sort alone deserving the name of “‘ echte Speicheldriisen.” Those
who have had occasion to observe any turbellarian in the living
state will have noticed how firmly it sometimes sticks to the side of
the vessel in which it is placed, by means of the pharynx and espe-
cially its lips, no doubt by virtue of the secretion of the “salivary
glands.”” Although I have not made any convincing observation on
this point, I.believe the pharyngeal glands of Tristomum serve the
same purpose, and assist in attaching the parasite securely to the host.
Again, in Distomum lanceolatum, unicellular glands with granular con-
tents open on the anterior border of the body. Their secretion is
regarded by Leuckart® as having “eine reizende Einwirkung auf
die Gewebstheile des Wirthes.” The numerous unicellular glands

that open into the ventral sucker and on both sides of the pharynx of.

 

1). Lang—Die Polycladen des Golfes von Neapel. pp. 111, 113, 115, 120.
2). Graff—Monographie der Turbellarien. Rhabdocoelida. p. 99.
3). Leuckart—Die menschlichen Parasiten. II Aufl., I Bd. II. Abtheil. p. 366-367.
STUDIES ON THE ECTOPARASITIC TREMATODES OF JAPAN. 61

the Holostomidae are regarded by Brandes” as having the same
function. As to the action of the pharyngeal glands in T'ristomum I
am not able to say anything definite ; at any rate I have not observed
any inflammation on the gill of the host, so that I believe they are to
be regarded merely as mucous glands.

Next, concerning the salivary glands. ‘These are, in my opinion,
clearly to be distinguished from the glands of the same name above
referred to in the turbellarians. In Rhabdocoelida, however, there are,
as already mentioned, two sorts of salivary glands ; and in this case
those that open between the pharynx and the intestine are perhaps
analogous to or at any rate a forerunner of the salivary glands of the
ectoparasitic Trematodes. In Distomum Westermani (Kerbert) and
Dist. palliatum (Looss), there are also true salivary glands opening
into the oesophagus. As to the function of these glands I am not in
a position to make any assertion; but some light will perhaps be
thrown on the question after we have considered the characters of the
‘intestinal epithelium.

We have already seen that the intestines may be distinguished
into two types according to the character of their epithelium. We
shall begin with the first type, viz., that in which the epithelium is
discontinuous, and in which the cells contain numerous dark-brown
or almost black granules. ‘The chief question on which I shall venture
to make a few remarks is about the nature of these pigment granules.
On this point there are, so far as I know, two views. According to
Taschenberg” these pigment granules are the food-particles taken
in by these cells from the cavity of the intestine ; and in support of

this view he cites his observation that these pigment granules are most

 

1). Brandes—Die Familie der Holostomiden. Zoolog. Jahrbiicher. Abtheil. f. Syst. Geo. u.
Biologie. Bd. 5, 1891. p. 553-561.

2). Taschenberg—Weitere Beitriige zur Kenntniss ectoparasit. mariner Trematoden, 1879.
p. 11-12.
62 8. GOTO.

abundant when the intestine contains numerous fat-globules, and
vice versa, which would not be the case were these granules emptied
into the intestinal cavity. The other view regards these granules as
zymogenic in nature. This view is probably represented by Zeller”,
who says, “ Die Zellen lésen sich mit der Zeit ab und zerfallen. Die
abgiingigen werden durch junge ersetzt, welche zwischen jenen sich
bilden. Offenbar stehen diese Zellen in ganz bestimmter Beziehung
zur Verdauung.”’ A third view is possible, according to which these
pigment granules are the indigestible remnants of the food taken in by
the cells, whether the food be in the form of granules or whether it be
entirely fluid. In my paper on Diplozoon”, I followed Taschen-
berg; but further observations and especially a careful comparison of
these pigment granules with the granules found in the epithelial cells
of Monocotyle have convinced me that the two are not of the same nature.
It is, moreover, difficult to understand by what means digestion is
carried on in those forms which have the intestine of the first type ;
for in these, salivary glands, or any other glands which may be
supposed to have a digestive function, are totally wanting. The
unicellular glands around the oesophagus described by Zeller in
Polystomum integerrimum are, I believe, analogous to the pharyngeal
glands of Tristomum ; at least they open at a similar place. Again, in
some specimens of Onchocotyle killed with hot sublimate shortly after
being detached from the host, I have often observed, in sections, the
pigment granules in question in the cavity of the intestine, sometimes
in groups and imbedded together in a weakly stained mass. In these
cases it is difficult to conceive any external force by which the intes-

tinal cells might have been torn away from the tunica propria. It is

 

1). Zeller—Weiterer Beitrag 1. Kenntn. d. Polystomen. Zeitschr. f£. wiss. Zoolog. Bd. 27
1876. p. 241.

2). This Journal, Vol. IV, Pt. I. p. 174.
STUDIES ON THE ECTOPARASITIC TREMATODES OF JAPAN. 63

therefore perhaps allowable to believe that the pigment granules are
normally thrown out into the intestine and there furnish the necessary
means for the digestion of food. On the other hand, this observation
may also be advanced in favour of the third view, according to which
the pigment granules would be finally thrown away by way of the
mouth. Zeller indeed says that the intestinal cells detach themselves
from the wall ; and in this case it is difficult to understand the total
absence of any phenomena of division among them. According to my
own observation, however, only the pigment granules seem to be
thrown out, surrounded by a scanty mass of protoplasm, while the
cells themselves in all probability remain collapsed in their former
positions, and again resume their activity after the lapse of a certain
interval. According to the second view, the smaller cells observed in
Onchocotyle with a well staining protoplasm and containing fewer
granules of smaller size are to be regarded as those which have not
yet arrived at the height of secretory activity ; while according to the
third view they are to be regarded as those in which much refuse
matter has not yet accumulated.

If digestion be regarded as taking place in the cavity of the
intestine by means of the pigment granules acting as a ferment, then its
product could pass into the tissue only by osmosis and filtration. If,
on the other hand, the pigment granules be regarded, according to the
third view, as the indigestible remnants of the food taken in by the
cells, then digestion has to be regarded as taking place intracell-
ularly ; but in this case the essential nature of the process would
remain unknown ; and it remains, moreover, to ask in what way the
digested food is passed on into the fluid which fills the mesenchyma—
a fluid which furnishes in all probability the necessary nutriment to
the various organs. I feel myself therefore obliged to leave the nature

of the pigment granules undetermined.
64 8. GOTO.

In the intestine of the second type, the epithelial cells are, as
already stated, all alike, and do not contain pigment granules. In
Tristomum and Calicotyle, they stain but slightly, and have seemed in
some cases to be more or Jess vacuolated. In Monocotyle Ijimae, on
the other hand, they contain numerous, deeply staining granules
which are to all intents and purposes exactly similar to the granules
found in the cavity of the intestine of the same worm. I therefore
believe them to be the products of (partial ?) digestion taken in by
the epithelial cells.

But by means of what is this (partial ?) digestion carried on ? It
has already been mentioned that the cells are all alike in appearance,
and none of them present any glandular appearance. In some polyclads
(Planoceridae), Lang” has described two forms of cells in the intes-
tinal epithelium : those of the first form were elongated and cylindric-
al, and usually contained large, homogeneous, refractive granules
which stained but slightly and looked like fat-globules; those of
the second form were more or less club-shaped, with the thickened end
turned towards the lumen of the intestine, and these contained, besides
an elongated nucleus, numerous granules which were very deeply
stained, and which distinguished themselves from those of the other
form of cells by their much smaller size and a regularly spherical
shape. ‘The latter cells the above named author regards as secretory
cells, and the granules as the product of secretion. In Distomum
Westermani, again, Kerbert” found, besides the ordinary intestinal
cells, “ kolbenformige Gebilde”’ similar to those of the turbellarians,
which however he holds as nothing else than ordinary epithelial cells

whose shapes have been changed by the ingestion of food. In Sphy-

 

1). Lang—i. ec. p. 141.

2). Kerbert—Beitrag zur Kenntniss der Trematoden. Archiv. f. mik. Anatomie. Bd. 19,
1881. p. 552.
STUDIES ON THE ECTOPARASITIC TREMATODES OF JAPAN. 65

ranura, Wright and Macallum” hold that the greater part of the
digestive process is effected by the fluid content of the intestine, which
they think is of an acid reaction. his they infer from their observa-
tion that the swallowed epithelial cells of the host have the form of
their nuclear chromatin preserved for a long time, which would not
be the case were the intestinal fluid of an alkaline reaction. These
writers seem to hold also that the secretion of the digestive enzyme and
the ingestion of food granules—which they concede to take place to
some limited extent—are effected by one and the same cells. Now,
remembering that even so low in the scale of lifeas in Hydra” the
cells of the endoderm are differentiated into two kinds, the secretory
and the absorptive, it would seem to many very improbable that these
two processes should be carried on in the Trematodes by one and the
same cells. Confining our attention to the ectoparasitic Trematodes,
we see that in all those forms which have the intestine of the first
type, viz., that in which the epithelium is discontinuous, and the cells
contain numerous pigment granules, the salivary glands are totally
absent ; while in those which have the intestine of the other type they
are well developed. Considering this fact in conjunction with the
view that the pigment granules of the intestinal cells of the first type
are of a zymogenic nature, the thought suggests itself whether the
pigment cells of the intestine and the salivary glands are not, in the
ectoparasitic Trematodes, vicarious in their functions ; and there seems
to be no fact, at least for the time being, that is obnoxious to this assump-
tion. In the Planocerida@ the so-called salivary glands secrete only a

sticky fluid, hence the necessity of secretory cells in the intestine. In
the Rhabdocoelida, in some of which the salivary glands are, as already

 

1). Wright and Macallum—Sphyranura Osleri. Journ. of Morphology. Vol. I, 1887 .pp. 33, 35.

2). Cf. Greenwood—On Digestion in Hydra; with Some Observations on the Structure
of the Endoderm (Journ. of Physiology, vol. IX, 1888, p. 317—344) and Nussbaum—Ueber die
Yeilbarkeit der lebendigen Materie (Arch. f. mik. Anat., Bd. 29, 1887, p. 265-366).
66 8. GOTO,

mentioned, divided into two groups, digestion is, according to
Graff,” exclusively carried on intracellularly. It is allowable, how-
ever, to suspect whether the secretory cells have not been overlooked
in some forms, especially in those in which the salivary glands form
only a single group opening on the surface of the pharynx. One
may, again, regard the “ kolbenférmige Gebilde” of Distomum Jester-
mani as secretory cells, and bring them forward in opposition to our
assumption ; since in this species the true salivary glands are present.
But if our assumption be true, there would be a time in the phylogeny
of the glands in question when both the true salivary glands and the
secretory cells of the intestine would discharge their functions side by
side. It may also be said in the way of objection to our assumption,
that food granules are observed in the intestinal cells, and that this
makes it very probable that these cells have the power of digesting
them. But it seems to me that these granules are not the product of
a simple disintegration of the swallowed food, but that they have been
produced by the action of a certain (partially ?) digestive fluid ; and
moreover it may be suspected whether these granules are not, as sug-
gested by Greenwood”, formed secondarily in the cells, and whether

they are not taken in primarily in the fluid form.

7. The Excretory System.

The excretory system is constructed on the same fundamental
plan in all the genera treated of in this paper, and presents only some
slight deviations in different genera. In all of them, there are two
main vessels on each side of the body, which are directly continuous
with each other at the posterior end. They run, roughly speaking,

on the ventral side of the intestine between it and the ventral nerve ;

 

1). Graff—Monographie, p. 96.
2). Greenwood—I. c. p. 323.
STUDIES ON THE ECTOPARASITIC TREMATODES OF JAPAN. 67

but as their course is always more or less winding, they are not seen
in cross-sections exactly between the intestine and the ventral nerve,
but are often situated more on one side, right or left, as the case may
be. One of the two main vessels, the larger one, opens to the exterior
mostly with an extremely small pore in the anterior part of the body
on the dorsal side, close to the Jateral border. This is also the case in
Onchocotyle, the paired terminal sacs described by Taschenberg”
being, as already stated, nothing else than the suckers. In Microco-
tyle, I have not been able to observe the excretory vessels in specimens
mounted in toto, and therefore have not drawn them in the figures ;
but I could always recognize the two main vessels in serial cross-
sections. In this gerfus, the excretory openings are situated nearly on
the same level with the genital opening: in WM. elegans it is 5 sections
(each=10 #), and in Of, caudata 10 sections in front of the genital
opening ; while in M. sebastis it opens on the same level with it.
Lorenz speaks of a small papilla on which the excretory vessel
opens ; but I have not observed any in my sections. In this genus,
there is no distinct terminal sac, the vessel presenting just a perceptible
enlargement before it opens to the exterior. In Diclidophora also, the
excretory openings are nearly on the same level with the common
genital opening: ec. g., in Diclid. sessilis it is about 7 sections (each =
10 #) behind it ; but in this genus there is a tolerably large, ege-
shaped terminal sac (PI. X, fig. 5), which opens directly to the exterior.
In <Axine, Onchccotyle, and Hexacotyle, the excretory openings are at
some distance in front of the common genital opening, and the two
main vessels present each only a slight enlargement before opening to the
exterior. In Monocotyle, there is a large terminal sac of an ellipsoidal
form, which communicates with the exterior by means of a short
canal proceeding from its dorso-lateral border a little before the middle

 

1). Taschenberg—Weitere Beitrige, p. 13.
68 8 GOTO.

of its lenvth, and opening to the exterior on the dorsal surface of the
body (Pl. XVII, fig. 2 & Pl. XVIII, fig. 5). In Tristomum, finally,
the larger of the two main vessels of the excretory system com-
municates, in the anterior part of the body a little behind the anterior
sucker, with a large but short vessel, which proceeds thence anteriorly
and towards the dorsal surface of the body, on which it opens a little
behind the sucker, almost midway between the lateral border of the
body and the internal ventral nerve (P]. XX, fig. 1). This terminal
excretory vessel is sometimes much swollen so as to deserve the name
of a terminal vesicle.

In Microcotyle and Onchocotyle, the two vessels run roughly parallel
to the lateral borders of the body, and remain quite distinct from each
other throughout their entire lengths, the smaller vessel proceeding past
the excretory opening towards the anterior part of the body, and there
dividing into numerous smaller vessels. This is also the case in Hexaco-
tyle ; but in this genus, the vessels, on reaching. the posterior suckers,
turn towards the median line of the body, keeping close to them, and
passing between the innermost small sucker and the next one, turn
again towards the lateral border of the body, and become continuous
with each other directly behind the outermost sucker (Pl. XIII, fig.
4). In Diclidophora, the main vessels of each side become con-
tinuous with each other at the posterior end by a cross commissure at
about the level of the second pair of suckers (Pl. X, fig. 5). In
Axine again, the main vessels of one side of the body are very much
longer, in accordance with the asymmetrical form of the body ; and
the vessels of the two sides approach very near each other at the pos-
terior extremity of the body, and are there united by a very short
transverse vessel (Pl. VII, fig. 1). The connection of the vessels of
the two sides are also effected in a similar way in Monocotyle near the

posterior extremity of the intestine. Close to the point of connection,
STUDIES ON THE ECTOPARASITIC TREMATODES OF JAPAN. 69

a vessel is given off on each side to the posterior part of the body and
the sucker (Pl. XVII, fig. 2). Finally in Tristomum, the two main
vessels are much more separated from each other than in the other
genera ; and the larger vessel runs about midway between the in-
ternal and the external ventral nerve, and becomes continuous with
the smaller vessel a short distance in front of the posterior sucker.
Anteriorly the larger vessel becomes continuous at the base of the
terminal vessel (vesicle) already described with another vessel, which
proceeds anteriorly and unites with an exactly similar vessel of the
other side just in front of the pharynx on the dorsal side of the brain.
The median vessel thus constituted proceeds for a short distance for-
wards, and then divides right and left into two branches, the rami-
fications of which supply the anterior suckers and the anterior parts
of the body proper.

From the two main excretory vessels above described, numerous
branches are given off at various points apparently without any
regularity. These branches divide again and again, and the smaller
branches anastomose variously with each other and with those coming
from the opposite side of the body. I have not been able to observe
the terminal funnels of the excretory capillaries in any of the marine
species I have hitherto studied. It should however be mentioned to
avoid misunderstanding that I have not as yet had as much op-
portunity for observing these funnels as I could wish; and consider-
ing their wide distribution among the Plathelminthes, it is scarcely to
be doubted that they would be found also in all ectoparasitic
Trematodes. In Tristomum sinuatum, however, I have observed the
excretory capillaries form a close network just inside the muscular
layer of the body. So far as I have observed, the transition from the
capillaries to the ordinary excretory vessels does not seem to be so

sudden as in those forms whose excretory systems have been so
70 8. GOTO.

minutely described by Pintner” and Fraipont.”

The wall of the excretory vessels, the larger as well as the smaller,
is constituted alike in all the species studied by me; and consists of a
structureless, refractive membrane which is, in most species, very thin,
but on which a double contour can be distinctly recognized. In. Mono-
cotyle, the wall is much thicker, as may be seen in fig. 5, PJ]. XVIII.
The membrane stains more or less with haematoxylin in most
“species, and this is especially the case in Monocotyle. The wall of the
terminal sac is exactly of the same appearance as that of the vessels.
In some sections of Tristomum sinuatum, I have observed an elongated
nucleus lying closely appressed to the wall of the excretory capillaries ;
but owing to the extreme rarity of such observations, I could not
decide whether it belonged to the wall or merely to the mesenchyma.

The calibres of the vessels are observed to vary a great deal
according to the various degrees of distention in which they are held
by the contained fluid ; and it is a necessary consequence of this that
the thickness of the membrane that constitutes the wall should vary
accordingly.

In some sections, I have observed in the cavity of the excretory
vessels a flaky substance lightly stained by haematoxylin ; but this
was rather seldom, and in most cases the cavity was wholly empty
and clear.

In my paper on Diplozoon® I have specified three alternative
ways in which the wall of the excretory vessels can be supposed to have
arisen, viz., either (1) it arose by a simple transformation of the pro-

toplasmic wall such as we find in the turbellarians, or (2) it had been

 

1). Pintner—Untersuch. ui. d. Bau des Bandwurmkorpers. Wiener Arbeiten. Bd. III, 1880.

2). Fraipont—Recherches sur l'appareil excréteur des Trématodes et des Cestofdes.
Archives d. Biologie. I’. I, 1880. p. 415.

3). Le. p. 176.
STUDIES ON THE ECTOPARASITIC TREMATODES OF JAPAN. G1

produced by a distinct external epithelium such as has-been described
by Pintner in the Cestodes, which then underwent degeneration, or
finally (3) it may be only the remnant of the walls of the original
cells whose internal part has been absorbed and which thus gave rise
to the cavity of the excretory vessel. As I have pointed out in my
paper just referred to, in the extreme case, viz., where the cells are
arranged in a single row, the last view reduces itself to the first ; and
in this case the term “intracellular” has been used by most writers on
the subject. Quite recently Haswell” has extended the application
of this term to the terminal sac of the excretory system of Temno-
cephala, so that according to this author the main canals as well as the
terminal vesicles are wholly intracellular. The ground on which
these writers regard the cavity of the excretory vessels as intracellular
has been clearly stated by one of them—the one, as far as I know,
who used the term for the first time— ; and to avoid any misinter-.
pretation I shall quote his own words. He says,” “In ziemlich
grossen Abstinden verdickt sich die Wand der grossen Caniile
einseitig und enthalt einen deutlichen, ovalen Kern. An diesen ver-
dickten Stellen inserirt sich stets je ein Biischel viel lingerer Cilien.
Die Kerne sind so weit voneinander entfernt, dass auf eine langere
Strecke je eine einzige Zelle die Wand der grossen Caniile bildet ; mit
anderen Worten, diese Caniile sind intracellular, sie stellen, durch-
bohrte Zellen dar.” From this it is I think very clear that the
excretory vessels are called intracellular only because the nuclei are
never found more than one in the same section, but separated from one
another by wide intervals. It may be doubted, however, whether this

-alone justifies the use of the term, and whether there is not another

 

1). Haswell—On the Excretory System of Temnocephala. Zool. Anz., XV. Jahrg., 1892. p.
149-151.

2). Lang—Die Polycladen des Golfeg von Neapel. p. 163-166., This writer also applies the
term “intracellular” to the vas efferens of some polyclads.
72 8. GOTO.

way of interpretation. Pintner’ has described a well developed
epithelium on the main vessels of the excretory system. Hence I
think it is more in accordance with the procedure elsewhere general,
to regard the excretory vessels not as intracellular but as bounded by
a true epithelium, which however, consists of only a small number of
cells, so that the single cells have been greatly flattened and have
assumed the form of a tube by the union of its opposite margins. In
this case, the cavity of the vessel would be as truly outside the cell as
any other intercellular spaces. It is true indeed, that according to
Schwarze” the terminal excretory vessels of the distomes are formed
by the absorption of the axial part of an originally solid string of cells.
But even taking this statement as it stands—and without suspecting
whether it may not be formed by a simple rearrangement of the cells as
is stated by Looss” to be the case in the genital ducts,—it is not neces-
sary to suppose that exactly the same process takes place in the smaller
' vessels as in the terminal vesicle; and therefore the view is perfectly
allowable that where the cells are arranged only in a single row, each
one assumes, to speak on supposition, a crescent shape at first and
then closes into a tube by the union of the opposite margins. Such
tubes, open and placed end to end would form a vessel such as is
found in the turbellarians. There is another objection to the word
‘intracellular’; and that is the presence of cilia on the internal
surface of the wall of the vessels. So far as our experience goes, there
is no case in which cilia are found growing within the cells, but only

on the external surface.

 

1). Pintner—Untersuch. ti. d. Bau des Bandwurmkérpers. Wiener Arbeiten. Bd. 3, 1880.
p..21, ;

2). Schwarze—Die postembryon. Entwickl. der Trematoden. Zeitschr. f. wiss. Zool. Bd.
42, 1886. p. 58.

3). Looss—Ist der Laurer’sche Kanal der Trematoden eine Vagina? Centralbl. f.
Bakteriol. u. Parasitenk. Bd. XITI, 1893. p. 809 (Nr. 25).
STUDIES ON THE ECTOPARASITIC TREMATODES OF JAPAN, 73

The foregoing discussion may have seemed needlessly long to
some readers; but it has appeared necessary to me, as one writer
must have been misled by the term “intracellular,” and thus been
prevented from seeing the real significance of the structure he was
studying. I refer to Otto Biirger. According to this writer”
“die Kanitle des N, ephridialapparates der Nemertinen sind mit einem’
Flimmerepithel ausgestattet und enden mit hohlen blinden Kolbchen,
die gleichfulls ein einschichtiges vielzelliges Epithel auskleidet. In
jedem Kélbchen, angeheftet am blinden verdickten Ende, schwingt
eine Wimperflamme in das Lumen des Kélbchens hinein.” And after
referring to the works of Lang and Pintner he proceeds,” “ Man
ersicht aus dem Angefiihrten, dass ein genaueres Studinm der Nephri-
dien der Nemertinen nicht dazu fiihren kann, sie als typischen
Exkretionsapparat der Plathelminthen hinzustellen. . Sehr schwer

wiegt meines Erachtens der Mangel einer Schlusszelle. Sie wird bei
den: Nemertinen ersetzt durch den Wimperkolben......... Ich hezweifle

nicht dass beiderlei Nephridien genetisch grundverschiedene Bildungen
STDC sco Die Eutwicklung der intracelluliiren Nephridienkaniile hatte
jenen eigenthiimlichen Endapparat in Gestalt der Trichterzelle in
Gefolge, eben so (oder besser gesagt aus demselben Grunde) wie mit
der Entwicklung der Nephridienkaniile der Nemertinen, die von
Anfang an epithelial umgrenzte Hohlriume darstellen werden, die
Entwicklung der Wimperkolben—es folgt das Eine aus dem Anderen
—Hand in Hand gehen wird.” It is somewhat surprising how near
the mark the writer comes but seems to miss just on the point of
hitting it. And from the above quotations, it will be clear that the
word “intracellulitr’”’ has had a not inconsiderable part in the matter.
The writer also lays weight on the difference of the epithelium

 

1). Biirger—Die Enden des exkretorischen Apparates bei den Nemertinen. Zeitschr. f.
wiss. Zool. Bd. 53, 1892. p. 330 et seq.
2). le. p. 881 et infra.
74 S. GOTO.

described by Pintner, which is situated outside the cuticular mem-
brane. But to me it seems that the mere presence of a cuticle is
morphologically a quite unimportant matter, so that the ‘“ Aussen-
epithel” of Pintner is as truly an epithelium as that of the ex-
cretory canals of the Nemertinei, just as the cells that produce the
chitinous wall of the trachea of insects are as truly of an epithelial
nature as any others that do not secrete chitin. Then as to the dif-
ference of the terminal “Kolben” of the Nemertinei from the
terminal excretory cells of other flat-worms, it seems to me that this
is also of quite a secondary significance ; that an organ consists of a
single cell does not afford, it seems to me, any more reason against its
homology with a multicellular organ than the fact that an organ
consists of five cells is any ground against its being homologous with
another consisting of six cells. If, on the other. hand, we do not take
into account the number of cells, there is a striking similarity between
the terminal excretory organs of the Nemertinei and other Plathel-
minthes. I therefore believe that the excretory systems of the
Plathelminthes, the Nemertinei inclusive, have all been derived from
the same primitive form, in other words, that they are homophylous.

To recapitulate the above discussion, it is my opinion that the
term “ intracellular” is quite inappropriate to the excretory system
of the Trematodes and the Turbellaria, as it gives occasion to much
misapprehension and prevents the true understanding of the exact
state of the matter. It is also my opinion that the excretory systems
of the Nemertinei and the other Plathelminthes are phylogenetically
of the same origin, the number of cells that compose the various
purts of the system being of quite secondary importance in discussing

its phylogeny.”

 

1). Whitman, from a totally different point of view, comes to the same conclusion. He says,
“The nephrostome is a nephrostome all the same whether it consists of one ‘cell, two cells,
STUDIES ON THE ECTOPARASITIC TREMATODES OF JAPAN. 7

Or

8. The Nervous System.

The brain is situated in the anterior part of the body. In Tri-
stomum, Calicotyle, Epibdella, and Monocotyle, it is in front of the
pharynx ; in Microcotyle, Octocotyle, Diclidophoia, Hexacotyle, and Axine,
it is behind, while in Onchocotyle it is just over, the same organ. It is
always situated on the dorsal side of the body, and is a somewhat cylin-
drical nervous mass crossing the median line. From it: is given off
both forwards and backwards a certain number of nerves. In all the
species that I have examined, two pairs of nerves proceed posteriorly
from the two lateral ends of the brain, which may be distinguished as
the external” and the internal lateral nerves. The internal lateral nerves
are by far larger than the external, and proceed in most species along
the main trunks of the intestine towards the posterior end of the body.
In Tristomum, it is about midway between the lateral border of the body
and the median line, and runs almost parallel to the former. In this
genus the two lateral nerves of each side unite with each other on enter-
ing the posterior sucker, and the single nerve thus formed immediately
divides into a certain number of smaller branches, which supply the
various parts of the sucker. Thus, a nerve is given off towards the
anterior part, which runs concentrically with the circumference of the
sucker, and after giving off at intervals some lateral branches, unites

at last with its fellow of the opposite side; so that this nerve

 

or many cells. Its form and function are independent of the number of component cells.
Cells multiply, but the organ remains the same throughout” (“The Inadequacy of the Cell-
theory of Development” in Journal of Morphology, vol. VIII, 1893, p. 645); thus extending
the homology not only to the Nemertinei but also to the annelids. Monticelli, on the other
hand, in his “ Primo contributo di osservazioni sui Distomidi,” which I received-after the above
had been written down, homologises the terminal funnel of Plathelminthes with the head-
kidney of amelids (cf. J. c. p. 45 et infra). Schuberg is reported to have arrived at a similar
conclusion concerning the nature of the wall of the excretory capillaries.

1). In my paper on Diplozoon I have called this pair the ventro-lateral nerves, but the
terms above mentioned are better as being of wider application.
76 8. GOTO.

describes a circle which is incomplete only at the hinder part. A
second nerve is given off towards the hinder part of the sucker ;
this gives off at a short distance from its origin a small branch, and
after this, it takes a somewhat similar course in the hinder part to
that pursued by the first nerve in the anterior, but remains through-
out separate from its fellow of the opposite side. A third nerve is
given off towards the lateral part of the sucker; but this soon
proceeds forwards, and runs almost concentrically with the first
nerve, but outside it near the margin of the sucker. This nerve
could be followed only for a comparatively short distance. These
three nerves all take their origin at the same point, and are repre-
sented in fig. 1, Pl. XX.

In Diclidophora (Pl. X, fig. 5) and Monocotyle (PI. XVII, fig. 1),
the external lateral nerve could be traced along the ventro-lateral border
of the body almost up to the point of union with the internal lateral
nerve ; but in all the other genera that have come under my observa-
tion I could follow it only for a comparatively short distance ; and
in these it became gradually so small and its tissue so imperfectly dif-
fentiated from the surrounding mesenchyma that I could not be sure
whether I had the section of the nerve before me or not. The internal
lateral nerves, on the contrary, could always be distinctly followed up
to the region of the suckers ; and in Onchocotyle, they become con-
tinuous with each other and form a loop at about the level of the
second pair of suckers, on the ventral side of the intestine (PI. XV,
fig. 2).

In Tristomum, a pair of dorsal nerves has been described by some
writers, and I have myself observed it in Onchocotyle ; but in all the
other genera, I could not demonstrate it with any satisfaction to
myself,

The four posterior nerves are united with each other at regular
 

 

STUDIES ON THE ECTOPARASITIC TREMATODES OF JAPAN. a 0G

intervals by numerous commissures, which all lie in the same straight
line (Pl. XXI, fig. 1). Ata short distance from the brain, a branch
is given off from the internal lateral nerve towards the median line ;
this curves inwards and supplies the pharynx. Besides the regular
commissural nerves Lang” has described others which take more
or less irregular courses. I have observed similar nerves ; but
they seem to be of quite irregular occurrence, and to run in various
directions, but more or less parallel to the diagonals of the rectangles
formed by the lateral nerves and their commissures. I have re-
presented such a nerve in the anterior part of the body in fig. 1, Pl.
XX. Again, in Tristomum in the posterior part of the body, just
before the suckers, the commissures of the two internal lateral nerves
give off branches which anastomose variously with one another as
well as with the neighbouring commissures, and form a network in
this region (PI. XX, fig. 1). The commissural nerves are con-
tinued towards the lateral parts of the body and there divide into
numerous branches. In the posterior part of the body there are,
besides the direct continuations of the commissural nerves, others
which branch off from these and proceed towards the lateral part of
the body ; so that the transverse nerves in the lateral parts are more
numerous than the regular commissures.

In Azine (PI. VII, fig. 1), the internal lateral nerve of one side is
much longer than its fellow of the other side, and gives off a large
nerve at about the middle of the seemingly posterior border of the
body, which then proceeds along it close to the suckers in a dia-
metrically opposite direction from the main nerve. This branch is to
be regarded as a special development of one of the commissural nerves

which are no doubt present in this genus also. The nervous system also

 

1). Lang—Untersuch. «. vergleich. Anatomie u. Histologie des Nervensystems der Plathel-
minthen. If. Mitheil. w. d. zoolog. Station zu Neapel, Bd. 2, 1881. p. 35.
tS 2 8. GOTO.

is moulded in accordance with the general asymmetry of the body:

From the front of brain two pairs of nerves are given off (PI.
XX, fig. 1), the inner of which proceeds towards the corners of the
anterior border, its branches supplying mainly that part of the body
which lies between the anterior suckers. The outer pair is connected
with the posterior nerves by a commissure, which arises at the common
base of the two posterior nerves, and curving a little outwards, unites
with the external anterior nerve at a short distance from its origin.
The external pair mainly supplies the anterior suckers.

The above-description of the commissures and the anterior nerves
is based mainly upon observations on Tristomum. In the other
genera, also, the commissures are present and can under favourable cir-
cumstances be demonstrated in sections ; but I have not had enough
opportunity to examine fresh specimens, and therefore have not been
able to obtain a general view of the arrangement of the commissures
and their relations to the main nerves.

I shall now proceed to the histology of the nervous, system, and
shall begin with the brain.

In cross-sections of the body, the brain is seen to be a band-
shaped body arching over the alimentary canal (oesophagus, pharynx,
or mouth-cavity, as the case may be), and in many species is entire-
ly free from cells. The greater part of its substance consists of
connective. tissue, and, being consequently slightly stained, is
very conspicuous in cross-sections. In some species, however, it
contains besides the reticulated connective tissue a finely granular
substance which stains more deeply than the former, but after all
only weakly, as in Microcotyle fusiformis (Pl. IV, fig. 6) and’ Di-
clidophora sessilis (P]. XI, figs. 1 and 2). In most species of Microcotyle,
there are numerous, well staining, rounded nuclei containing one or a

few nucleoli crowded around the brain (Pl. IV, fig. 6), while no
STUDIES ON THE ECTOPARASITIC TREMATODES OF JAPAN. 79

obviously ganglionic cells can not be observed ; but in Microcotyle
sebastis there are two pairs of large polygonal cells in the ventro-
lateral portion of a cross-section passing through the anterior part of
the brain, which are provided with very large, vesicular nuclei with a
distinct membrane and containing each a single, large nucleolus and
numerous, weakly stained granules (probably chromatin). The proto-
plasm is finely granular and has no external membrane, so that the
cell-body becomes gradually fainter towards the periphery (PI. IV,
5). In Asine heterocerea (PJ. VII, fig. 2) also, there are some
cells of this kind of various sizes in the same region of the body.
In Diclidophora sessilis (Pl. XI, figs. 1 & 2) the brain itself is entirely
free from cells of all sorts; but at the root of the posterior nerves,
there are numerous cells of polygonal form with finely granular,
well-staining protoplasm, and with a nucleus containing one or more
nucleoli. ‘These are undoubtedly nerve cells. Besides these, how-
ever, there are in this species two pairs of gigantic cells in that part
of the body which corresponds to where the large cells already
mentioned are found in Microcotyle sebastis. They are polygonal in
form, and the large vesicular nucleus, which contains, besides a single
large nucleolus, numerous small granules, is surrounded by a very
finely granular, well-staining protoplasm which is totally destitute of an
external membrane. Sometimes the protoplasm has seemed to be
drawn out into a faint process, and fibres to be given out from the peri-
phery of the nucleus (Pl. XI, fig. 1, left side). I have described similar
cells in similar positions in Diplozoon”; and I have no doubt that they
as well as those of Microcotyle and Axine are ganglionic cells.

In Tristomum, there are numerous ganglionic cells within the

brain as well as in the main nerves. The greater number of them are

 

1). Le. p. 171, and fig. 25.
80 . 8. GOTO.

bipolar cells, but there are also among them multipolar cells (P]. XXIV,
fig. 5); and unlike what is seen in the other genera, the fibres proceed-
ing from them can be very distinctly followed for a ,considerable
distance. These fibres are direct continuations of the protoplasm of
the cells, are destitute of any sheath, and run in the long direction of
the brain, i. ¢., at right angles to the long axis of the body. They
stain quite deeply near the nucleus, but become fainter and fainter
as we follow them away from the nucleus, until they finally, in their
affinity for stains, become scarcely distinguishable from the fluid which
fills the meshes of the connective tissue. _

In the brain are imbedded the eyes, when such are present.
Among the genera I have studied, these are present only in Tristomum,
Epibdella, and Monocotyle, and are arranged in two pairs. In all the
three genera just mentioned, their relative positions are such that an
isosceles trapezoid is formed by connecting them. In Tristomum and
Epibdella, the shorter of the two parallel sides of the trapezoid is
situated anteriorly, while in Monocotyle the reverse is the case. I have
carefully studied these eyes only in Tristomum ovale ; and my results
are somewhat different from those arrived at by Lang.” This
writer enumerates four elements of which a single eye is formed, viz.,
(1) the pigment, (2) the lens, (3) the retina, and (4) the ocular
muscle. According to my observation the last is no other than the
dorso-ventral muscles of the body which traverse the brain close to
the eyes, and it therefore seems to me morphologically more correct
to call them by that name, although physiologically they take great
part in the movements of the eyes, which are merely passive, the
worm having no power to direct its eyes in any special direction.
In the anterior eye (PI. XXIV, fig. 3) the lens is an ellipsoidal,

 

1). Le. p.4l.
STUDIES ON THE ECTOPARASITIC TREMATODES OF JAPAN. 81

homogeneous body capped on the dorsal side by a mass of black pig-
ment granules. Immediately beside it there is a tolerably large
ganglionic cell, the processes of which pass on to both the dorsal
and ventral sides of the lens. In the posterior eye the. place of the
lens is taken by a large multipolar ganglionic cell also capped by a
mass of pigment granules. The nucleus of this cell is very large and
spherical in form ; it stains more deeply than the protoplasm, and
no definite structure can be observed within it except some faintly
staining granules (PI. XXIV, fig. 4).

In the above description I have adopted the name commonly
used and have called the structures described eyes. Morphologically
speaking they are certainly degenerated eyes ; and have probably been
derived from some such eyes as are found in the Turbellaria ; but I do
not think that they are functional. In the first place, the pigment
granules are situated on the dorsal side and thus prevent the light
from reaching the lens, since the dorsal side is the only direction from
which light can come. In the second place, there is not always a
distinct retina. In Tristomum molae, the species studied by Lang,

the retina is said to be present ; but in T'rist. ovale there is none, since
“the ganglionic cells in the immediate vicinity of the lens already
mentioned are not in such a position as to receive the light that has
passed through the lens. Jf these “eyes” are really still useful to
the animal, they may possibly be a temperature sense organ ; and for
this purpose their structure seems to answer well. For, the black
pigment granules would easily absorb the dark heat-rays and cause
some molecular change in the lens which they cap. This Jens shows
no cellular structure in the anterior eye, but in the posterior eye it is
a veritable ganglionic cell, as has already been described. The tem-
perature sense organ may be of use to the animal in warning it from

wandering too near the extremities of the body of the host, where it
82 S. GOTO.

would be in danger of being swept away. But on this head nothing
definite can be asserted. On the other hand, the. comparatively
perfect structure of the eye in Tr. molae may be due to the habit of
this species. or, according to Lang” and Monticelli” this
worm is met with very commonly on the surface of the body of
Orthagoriscus mola, and is thus constantly exposed to light, which is
not the case in T'r. ovale.

In cross-sections the brain as well as the nerves show the re-
ticulated appearance s6 universally described by students of the flat-
worms. In the brain of Tristomum, the meshes are completely
filled with nervous fibres, direct continuations of the processes
of ganglionic cells (Pl. XXIII, fig. 4; Pl. XXIV, fig. 12; PL.
XXV, fig. 7; Pl. XX, fig. 1); but in the nerves the fibres often do
not quite fill up the meshes, but leave a clear space between them-
selves and the walls of the meshes. In Tristomum, as has already been
mentioned, the fibres show less and less an affinity for stains as we
recede from the nucleus, and finally they can scarcely be distinguished
from the fluid that fills the meshes of the connective tissue ; so that
in this case the meshes of the nerves are seen in cross-section to be
merely filled with a very weakly staining, slightly granular substance
(Pl. XX, fig. 10). In Dielidophora the nervous fibres are very
slender, and in cross-sections are seen merely as minute dots (PI. XI,
fig. 1); while in nearly all other species the nervous fibres are very
difficult to make out in cross-sections. The nerve itself, however, can
be followed with certainty for the greater part of its course, but becomes
indistinct in the posterior part of the body where, as already stated, the

mesenchyma consists almost exclusively of reticulated connective tissue.

 

1). Lang—l. ¢. p. 29.

2). Monticelli—Intorno ad alcuni elminti del Museo Zoologico della R. Universit’ di
Palermo. Naturalista Siciliano, An. XII, 1893. Estratto p. 5.
STUDIES ON THE ECTOPARASITIC TREMATODES OF JAPAN. 83

Doubt has been expressed by some writers whether the meshes
of the nerves represent themselves the cross-sections of nervous fibres,
or whether they are formed by the connective tissue with the fibres
running within them. Poirier”, for instance, on the ground of his
observations on Distomum decides for the former view, and seems to
believe the same to be the case also in the Turbellaria ; but it will be,
I believe, clear from my descriptions above that considerable variations
must be allowed for in this respect, and that the results obtained from a
single species or genus can not be applied 71 toto to others.

About the sense-organs on the surface of the body I have not
been able to make any minute observation, and will only refer the

reader to the interesting paper of Monticelli” already mentioned.
9. The Reproductive System.

Since the general view of the reproductive organs can easily be
obtained from the plates accompanying this paper, I shall at once

proceed to the description of the constituent parts.

(a) The Male Organs.

Trstes—In all the species described in this paper there are more
than one testis, and these are as a whole situated in the posterior
part of the body behind the ovary. The only- exceptions in this
respect that [ have observed are in Diclidophora sessilis (Pl. X, fig. 5),
Tristomum ovale (Pl. XXIII, fig. 1), and the genus Octocotyle (Pl. IX,
fies. 1 & 7). In the first of the species just mentioned, there are

numerous testes, and these are situated not only in the posterior part

 

1). Poirier—Contribution a Vhistoire nvturelle des Trématodes. Arch. d. Zool. expér. et
générale. T. III, 1885. p. 603.

2). Monticelli—Di alcuni organi di tatto nei Tristomidi. Estratto dal Boll. della Soc.
di Naturalisti in Napoli. Ser. 1, vol. 5, 1891, fasc. 2.
84 S. GOTO.

of the body but also in the anterior part, extending forwards almost
as far as the brain; in the second species also, the numerous testes
extend forwards almost up to the anterior suckers on both sides of
the ovary ; while in both species of Octocotyle described in this paper
the anterior testes are arranged in a single row on the left side of
the ovary, while the posterior ones are arranged in two irregular
rows. In some other species also, as in Onchocotyle and most species
of Tristomum, the foremost testes more or less overlap or surround
the ovary ; but in the majority of species the testes are situated wholly
behind the ovary. In most species again, they occupy the median
portion of the body between the main trunks of the intestine, but in
some species of Tristomum (Tr. ovale and Tr. Nozawae) they stretch
more or less into the lateral part outside the intestinal trunks (PI.
XXIII, fig. 1; Pl. XXV, fig. 1). In Epibdella there is only a
single pair of testes of an irregularly ellipsoidal shape; while in
Monocotyle the testes are three in number, of which two are situated
anteriorly and in a pair, and the remaining one posteriorly, with its
‘anterior end more or less wedged in between the former. In all the
other species the testes are very numerous, and are either rounded or
more or less polygonal in form according as they are more or. less
pressed against one another. Sometimes also they are lobed, as in
Tristomum ovale (PI. XXII, fig. 1).

In most species the area occupied by the testes is entirely free
from all other organs, and the testes are situated midway between the
dorsal and the ventral side of the body. In Tristomum ovale, however,
the vitellarium, which in other species is confined to the lateral parts
of the body, extends into the central portion ; and the testes are here
situated quite on the ventral side, immediately inside the muscular
layer, leaving the whole dorsal side for the vitellarium (PI. XXIII,
fig. 7).
STUDIES ON THE ECTOPARASITIC TREMATODES OF JAPAN. 85

Each testis is separated from its neighbours by a more or less thin
layer of mesenchyma, which in this region assumes the character of
reticulated, fibrous connective tissue (Pl. V, fig. 7; Pl. XI, fig. 3;
Pl. XXIII, fig. 7; Pl. XXIV, fig. 2); and is usually destitute of
any distinct epithelium. The testes are also traversed by the dorso-
ventral muscular fibres ; but the greater part of these pass between
them through the mesenchymatous septa just mentioned. The con-
tents of the testes consist of sperm cells in various stages of develop-
ment, scattered without any regularity. In some species, as in
Diclidophora sessilis (Pl. XI, fig. 5), I have often observed cells with
large nucleus arranged in a single layer on the wall of the testis ;
but these seemed not to form a permanent epithelium. For, they
were only loosely apposed to the mesenchyma, and in many testes,
especially in those in which the greater part of the sperm cells had
finished their development, they were wholly absent. A general view
of the contents of the testes may be obtained from fig. 7, Pl. V, figs. 3
& 5,.P]. XI, fie. 7, Pl ALU and. fic. 2, Pl: XALV. ‘The most
conspicuous elements besides the already developed spermatozoa are the
groups of large nuclei containing a certain number (how many I have
not been able to make out with satisfaction) of chromatin granules, the
interspaces of which stain uniformly but far more weakly with
haematoxylin, and the cells of large dimensions usually more or less
of a spherical form, with a single, long thread of chromatin forming an
irregular skein, or with numerous, more or less lozenge-shaped pieces
of chromatin. The large nuclei just mentioned were usually sur-
rounded by such a scanty layer of protoplasm as almost to look naked.
Besides these there are also groups of much smaller nuclei imbedded
together in a uniform mass of very finely granular protoplasm, which
sometimes showed traces of separation corresponding to each nucleus.

The various elements above characterised are obviously stages in
| 8. GOTO.

the development of spermatozoa from the mother-cells ; and a glance
at them will convince one that spermatogenesis must be effected in
this group in a manner quite different from what we are wont to see
in others. I have endeavoured to trace the various stages of sper-
matogenesis, and although I have not come out perfectly clear in every
point of detail, still I believe I can communicate the result as being in
the main correct. I have represented the various stages in fig. 3, PI.
VI, as found in Microcotyle caudata. The various zones that have
been described by recent writers in the genital glands can not be
distinguished in the testes of the ectoparasitic Trematodes ; on the
contrary, the sperm mother-cells as well as the spermatozoa in various
stages of development are, as already stated, mingled pell-mell. The
youngest stage is probably that of the small nuclei already referred to
as forming a group, each having a finely granular cytoplasm of its own
(PL VI, fig. 8, «) and containing a small number (4 or 5) of
chromatin granules. These nuclei grow larger and larger, and the
chromatin granules increase in number and also more or less in size ;
the cytoplasm, however, seems to remain almost constant, and in the
stages represented in b and ¢ it forms an inconspicuous thin layer
around each nucleus. The individual nuclei become more ‘and more
detached from one another; but I have sometimes observed them in
these stages still kept together by a common mass of protoplasm (d).
The nuclei still grow and grow, and the chromatin granules increase
considerably in number (¢) ; and although I have not been able to
observe the intermediate stage, these granules must come either to
form a reticulum and then a single thread, or passing over the re-
ticulum stage form directly the single thread. The stage which I take
to be the next is represented in f. Here the chromatin forms a single
thread coiled so as to form numerous loops, and, so far as I have

observed, having no end ; the nuclear membrane has also disappeared
STUDIES ON THE ECTOPARASITIC TREMATODES OF JAPAN. ST

and the thread lies in a very finely granular, weakly staining substance.
Then this thread splits into numerous shorter pieces (y), which
gradually separate more and more from: each other, and_ finally
occupy the periphery of the common mass in which they lie imbedded
(h, 7). At this stage each piece of chromatin has assumed a lozenge
shape, and become intersected by small clear spaces, effecting a
partial division of it into several parts. It contracts more and
more and finally becomes a veritable nucleus (k) having a contain-
ing membrane with a few granules of chromatin (chromosomes)
inside. The newly formed nuclei then repeat the very same
changes above described, but how many times it is impossible to tell.
The small lozenge-shaped chromatin pieces finally formed then begin
to lengthen from one end (m), this time apparently without becoming
a veritable nucleus such as is represented ink. The tail continues to
lengthen more and more until only a small portion of the chromatin
remains as the head, so that the ripe spermatozoon has the form of a
long pin, formed head and tail throughout of chromatin (7) ; and all
the spermatozoa derived from a single mother-cell of the last gene-
ration form a bundle, with the head imbedded in a common mass
of finely granular protoplasm. It may be, however, that the proto-
plasm forms an exceedingly thin layer around the head as well as
the tail. The spermatozoa seem finally to free themselves from the
mass of protoplasm ; for [ have sometimes observed similar masses
floating in the cavity of the testes (0). In/ I have figured a stage
which does not seem to come in well in the above series, and which
I have observed only rarely. It may perhaps represent a stage im-
mediately prior to the one represented in k and of exceedingly
short duration. In it the small nuclei have each a cytoplasm of its
own of prismatic shape, and are arranged on the surface of « central,

spherical mass of protoplasm, which is wholly destitute of a nucleus.
88 S$. GOTO.

The above account of spermatogenesis has been based on observa-
tions of Microcotyle caudata; but the process is essentially the same in
all the genera treated of in this paper. It will be seen that it differs
in many respects from the statements of other writers” on the same
subject ; but the various stages observed seem to me to be capable of
orderly arrangement only in the way indicated above. The process of
spermatogenesis above described also differs considerably from that
which takes place in Diplozoon (Pl. VI, fig. +). In this the sperm
mother-cell first divides by ordinary mitosis, then effects what has
been termed reduction-division ; and each daughter-cell thus formed
developes into a spermatozoon, in which the chromosomes can still be
distinctly seen. Finally the mode of division above described is so
different from ordinary mitosis that I am not able to say what
relation it bears to that. This and other obscure points indicated
above I must leave to future investigations.

Vas DEFERENS—In Tristomum the vasa efferentia that proceed
from the testes can in most cases be traced out ; but this is possible
only when they are made visible by being filled with spermatozoa,
which stain very deeply with most colouring fluids. The vasa
efferentia unite with one another and finally form a pair of large
vasa efferentia, which again unite with each other in the median
line of the body and form a single vas deferens. ‘This is at first of
small calibre, but becomes gradually larger and larger as it proceeds
forwards on the left side of the ovary, and after undergoing numerous
smaller windings, forms just in front of the ovary, a large loop, the
closed end of which is directed towards the right side of the body, and
in most species also more or less forwards (Pl. XX, fig. 1; Pl. XIII,

 

1). Kerbert—Beitrag zur Kenntniss der Trematoden. Archiv f. mik. Anatomie, Bd. XIX,
1881. p. 559 et infra. Also Monticelli — (According to Braun’s report in Centralblatt f.
Bakteriologie u. Parasitenkunde, XTIT. Bd., 1893, p. 180).
STUDIES ON THE ECTOPARASITIC TREMATODES OF JAPAN. 89

fiz. 8; Pl. XXIV, figs. 6, 9,&10; Pl. XXV, figs. 1, 3, 5, 8, & 9).
It then proceeds either staight forwards or else a little to the left,
making all the while numerous small but close convolutions ; and
then turning more or less towards the right on the dorsal side of the
penis, enters the latter close to its base. Here it forms a swelling,
the resicula seminalis, and then again contracting to a very small canal
and traversing the penis parallel to its central cavity, opens finally
into this at some distance from its apex, in some species on the top of
a papilla (Pl. XXII, fig. 4).”

St.-Remy” distinguishes in Tristomum three portions of the
vas deferens, viz., (1) the single “‘canal séminal,” (2) the “ vésicule
éjaculatrice” situated in the penis and receiving at one of its ends the
narrow termination of the seminal canal and continued at the other
into the (3) ‘canal éjaculateur,” with which it communicates by a
very short, narrow canal. It does not, however, seem to me necessary
to distinguish these parts. As I have mentioned above, there are
numerous constrictions in the course of the vas deferens; but these
are quite irregular, and can not, in my opinion, be taken as marking
off distinct portions of the vas deferens from each other. It
is, however, convenient to designate that portion of the vas deferens
which lies within the penis the ductus ejaculatorius, although it should
be remembered that in many species this is not the only portion that
is concerned in ejecting the sperm fluid. In Tristomum and Epibdella,
this portion is provided with circular muscular fibres (PI. XXII, fig.
45 Pl ARV, ne. 7).

In Epibdella a short vas efferens proceeds from each testis ; but

soon unites with its fellow and forms a single vas deferens. This

 

1). For minuter details see the description of species.

2). G. St.-Remy—Contribution 4 l'étude de l'appareil génital chez les Tristomiens. Archives
de Biologie, T. XIT, 1892. p. 5 et infra.
90 S. GOTO.

then runs forwards on the left side of the ovary, then towards the right,
then again forwards, undergoing more or less windings on the way,
and then towards the dorsal side of the penis, which it enters near its
base and, traversing it longitudinally, finally opens into its cavity
near or at its apex, just as in Tristomum (PI. XXVI, figs. 1, 3, 4,
& 6). During its course the vas deferens undergoes numerous con-
strictions and enlargements.

In Microcotyle, Axine, Diclidophora, Octocotyle, Hesxacotyle, Calico-
tyle, Monocotyle, and Onchocotyle I have not been able to observe the
vasa efferentia. In these genera, the irregular cavities of the mes-
enchyma between the testes probably serve as such. The single vas
deferens, however, can in all these genera be followed with certainty
up to the testes. In Calicotyle the vas deferens proceeds forwards on
the left side of the median portion of the body to near the pharynx, and
then turns backwards and towards the right and continues its course
into the penis. In most of the other genera above mentioned, the vas
deferens takes its origin from the testes more on one side of the body,
right or left according as the case may be, and undergoing numerous
windings on its course forward, opens finally into the genital atrium.
When the uterus and the vas deferens come to lie in the same sagittal
plane, the latter is always situated on the dorsal side, and opens into
the genital atrium also more dorsally than the former. In Azine
and Microcotyle the vas deferens proceeds forwards on the ventral
side of the ovary (Pls. I, II, & VI).

The wall of the vas deferens consists in most species of a
structureless, refractive membrane of varying thickness according to
the species, and wholly destitute of nuclei; but in some species there
is a more or less distinct protoplasmic layer separated from the
mesenchyma by a basement membrane, and exhibiting at irregular

distances, rounded or oval, well-stained nuclei, usually containing
STUDIES ON THE ECTOPARASITIC TREMATODES OF JAPAN. 9]

each a single nucleolus, as in Microcotyle chiri (PI. V, fig. 4),
M. sciaene (Pl. VI, fig. 2), and Onchocotyle spinacis (Pl. AVI,
fig. 8). It seems to me therefore clear that the structureless membrane
of the vas deferens of most species is to be regarded as the transform-
ed product of the originally cellular epithelium ; and this becomes the
more probable when we see that nuclei are present in some parts of
the uterus but are wholly absent from others, as will be described later
on. In those species in which the wall of the vas deferens consists
only of a structureless membrane there is often a coarsely granular
layer on the inner surface of the wall, which will be described pre-
sently in treating of the prostate gland. In most species the
vas deferens is wholly destitute of any musculature ; but in some, as
in Microcotyle sciaene (Pl. VI, fig. 2) and Hewacotyle (Pl. XII, fig. 5),
it is provided with a single layer of circular fibres.

In Monocotyle there is a peculiar organ around the vas deferens at
a short distance from where this opens outwards (Pl. XVII, fig. 1
& Pl. XVIII, fig. 3, bud. e.). It is spherical in shape, is hollow,
and is traversed by the vas deferens. The wall of this organ is very
thick, and consists of connective tissue fibres which are all arranged
radially ; it is bounded both internally and externally by a structure-
less membrane ; but the external membrane is incomplete for a short

space on the dorsal side, and here the substance of the wall is directly

 

continuous with the surrounding mesenchyma,—the one passing
gradually into the other—thus showing that both are of the same
nature. On the surface of the internal limiting membrane there is a
thin granular layer ; and just externally to the same membrane there
is a layer of circular muscular fibres (P]. XVIII, fig. 3, bul. ¢.). The
only use that I can attribute to this organ is to eject the sperm,
and I shall therefore call it bulbus ejaculatorius. Around it there

is a circular canal, the plane of which coincides with that of
92 8. GOTO.

the body (Pl. XVIII, fig. 3, x), and the wall of which consists of a
thin refractive membrane, which bears at some points flattened nuclei.
I have not observed any connection of this canal with the excretory
vessel, and am at a loss to say what purpose it may serve.

In Calicotyle also there is a bulbus ejaculatorius. It is situated on
the terminal portion of the vas deferens close to the penis, and is a
somewhat dumb-bell shaped organ consisting of a compact connective
tissue entirely separated from the surrounding mesenchyma by a
membrane. ‘I'he terminal rounded portions of the organ are hollow,
and these hollows seem to communicate with the vas deferens by a
very narrow canal, although on this point I am not able to make a
positive statement owing to the scantiness of material (Pl. XIX,
fig. 10).. Considering, however, the close affinity of this genus to
Monocotyle, 1 think I am justified in calling the organ in question the
bulbus cjaculatorius.

An ejaculatory organ similar to that of Monocotyle has been de-
scribed by St.-Remy” in Microbothrium.

Prexis—In many species the terminal portion of the vas deferens
is surrounded by a mass of connective tissue which presents a very
different appearance from the general mesenchyma of the body, and is
sometimes separated from it by a distinct membrane. ‘This portion
deserves, in my opinion, the name of penis, but it is clearly to
be distinguished from the structure in connection with the genital
atrium hereafter to be described. In many species two portions can
again be distinguished in the penis, viz., a more distal, chitinous por-
tion anda more proximal portion consisting of ordinary connective
tissue or of a modification of it. The latter portion I shall call the

connective-tissue penis and the former the chitinous penis.

 

1). G. St.-Remy—Etude de l’appareil génital, etc., p. 31.
STUDIES ON THE ECTOPARASITIC TREMATODES OF JAPAN. 93

The form and character of the penis are characteristic of the
genera, and will therefore be treated separately for each.

Diclidophora—In this genus the penis is an ellipsoidal body
situated right at the end of the vas deferens and bored by it through
the centre. It bears a certain number (the number varies in dif-
ferent species) of chitinous hooks, together constituting the chitinous
penis (Pl. X, figs. 2 & 3; Pl. XI, fig. 4). The substance of the
penis consists of prismatic fibres arranged at right angles to its
central cavity, t.¢., the vas deferens. These fibres are exactly like
those which have been described in the suckers of Microcotyle and
some other genera, both in their general appearance and in their
reaction towards stains, and are separated from the surrounding mes-
enchyma by a distinct, structureless membrane. ‘The chitinous hooks
are arranged at regular intervals on the external face of the penis
around the opening of the vas deferens, and although the proportions
of the different parts vary in different species, they are constituted
alike in all the species of the genus described in this paper. Lach
hook may be regarded as consisting of two portions, the basal and the
distal. ‘The distal portion consists of a slender, chitinous thread, and
may be described as forming a loop, the free ends of which have fused
together (Pl. X, figs. 7 & 10). This sits by the round end of the
loop on the basal portion in such a way as to form an angle with
it. The basal portion is hour-glass shaped when looked at from the
front and is imbedded in the superficial part of the substance of
the penis-bulb by its triangular end (PI. X, figs. 7 & 10, b). In
profile the basal portion looks somewhat triangular (PJ. XI, fig. 4).

Octocotyle—In this genus the connective-tissue penis consists of
a median saucer-shaped body with two lateral bean-shaped bodies
mounted on its edge (PI. IX, figs. 5, 12, & 13). The median
body is perforated through its centre by the vas deferens, and
94 S$. GOTO.

on its external, concave face bears a number of recurved, chitinous
spines, which together constitute the chitinous penis. Hach of these
hooks consists of a mound-shaped basal portion and a hollow, spinous
distal portion. ‘The substance of the penis bulbs has the same his-
tological structure as that in Diclidophora.

Calicotyle—In this genus the connective-tissue penis is a some-
what kidney-shaped body formed of fibrous tissue containing nuclei,
separated however, from the surrounding mesenchyma by a distinct
membrane, except at one place where the fibres of the surrounding
mesenchyma are seen to be directly continuous with those of the penis
(PI. XIX, fig. 11), The. penis has one end smaller than the other,
and in its natural state, is placed so that its smaller end occupies
a more dorsa] position in the body than the other (P]. XIX, figs. 7
& 11). Its smaller end is directly continued into the chitinous penis,
which is an exceedingly long, hollow tube with obliquely cut end,
and is twice bent on itself in such a way that the middle portion
crosses the middle of the distal portion (P]. XIX, fig. 10). As
just side, its base is directly applied to the outer end of the con-
nective-tissue penis (PJ. XIX, fig. 11); and it lies in a tubular
cavity just large enough to receive it, the direct continuation of the
genital atrium.

Monocotyle—The connective-tissue penis is in this genus a
somewhat pear-shaped organ attached to the body by its smaller end
at the bottom of the genital atrium (PI. XVITI, fig. 3), and is perfo-
rated by a canal. ‘The substance of the penis consists of fibres which
are of similar general appearance to those of the suckers of Micro-
cotyle and some other genera, but are finer and stain better with
hematoxylin. They are arranged perpendicularly to the surface of
the penis, and at its base are seen to be directly continued into the

mesenchyma of the body, which, however, ‘consists in this region of a
STUDIES ON THE ECTOPARASITIC TREMATODES OF JAPAN. 95

finely fibrous, compact connective tissue (Pl. XVII, fig. 3). The
chitinous penis is similar to that of Calicotyle, but is shorter and more
slender (Pl. XVII, figs. 1 & 2; PI. XVIII, figs. 3 & 7), and is
somewhat spiral. Its base is directly applied to the termination
of the vas deferens, and lies enclosed in the tubular cavity of the
penis with only its terminal part projecting into the genital atrium
under the usual circumstances.

Tristomum and Epibdella—tIn these genera the chitinous penis
is entirely wanting, and in both, the penis is nearly alike in structure as
well as in position relative to the other parts of the genital organs.
Unlike all the genera hitherto described, the common genital
pore, or ii some species the separate male and female openings. are
situated quite in the lateral part of the body, a little behind the left
anterior sucker. The penis is an elongated, hollow, subconical body
projecting for the greater part of its whole length into the genital
atrium. ‘The basal portion of the penis is separated from the surround-
ing mesenchyma by a thin, dense layer of connective tissue which vivid-
ly takes up the stain. This layer is, however, absent for a certain
extent at the very base of the penis, so that here the substance of the
penis is directly continuous with the general mesenchyma of the body
(PI. XXII, fig. 2). The cavity of the penis is tubular for the greater
part of its length, but at its base it is enlarged spherically and receives
the openings of the prostate glands.

The substance of the penis is somewhat different in histological
structure in different species; but generally it consists of a loose,
reticulated, fibrous connective tissue (Pl. XXII, fig. 4; Pl. XXIV, fig.
1). In those species the mesenchyma of which is more or less of a
syncytial nature, as Trist. sinwatwm, the meshes of the connective tissue
are filled with a granular substance; but the fibrous element seems

always to preponderate in the penis (Pl. NNIT, fig. 4). ‘Towards the
96 8. GOTO.

internal and external surfaces of the penis, the connective tissue is re-
placed by a granular, or a uniformly staining, homogeneous, substance.
In Tristomum ovale I have observed in the substance of the penis
numerous, small, spherical, vesicular bodies which stain deeply with
hematoxylin (PJ. XXIV, fig. 1), and which are quite different from the
nuclei of the mesenchyma, but may be their remnants. In the species
just’ mentioned and in Trist. liparasiticum the internal surface of the
tubular cavity of the penis is raised into numerous subconical or
mound-like elevations closely crowded together and pressed against one
another (Pl. XXIV, fig. 1); in Trist. foliaceum also there are similar
papilla, but they are much smaller. These papillae consist of a
coarsely granular substance which stain deeply with hematoxylin.
Internally this granular substance passes gradually into the fibrous
connective tissue.

The penis is provided with a musculature of its own, which con-
sists of four sets of fibres, viz., the internal and the external circular fibres,
the longitudinal, and the retractor fibres. Of these the external circular
fibres are by far the most strongly developed. In Trist. ovale
(Pl. XXIV, fig. 1) they form’a layer about 104 in thickness just inside
the external membrane of the penis, but separated from it by a small
interval. Next these come the longitudinal fibres which do not
form bundles, the individual fibres being separated from one another
by greater or less intervals. They are direct continuations of some
of the longitudinal muscular fibres of ‘the body, and are attached at
the apex of the penis to its external limiting membrane. The
internal circular fibres are situated just inside the internal limiting
membrane of the penis, or in those cases where the internal surface of
the penis is raised into papilla, just at the base of these, and are, so
far as I have observed, arranged in a single row. The individual

fibres are also smaller than the external circular fibres. The retractor
STUDIES ON THE ECTOPARASITIC TREMATODES OF JAPAN. 97

muscle consists of a few fibres, which are attached to the base of the
penis a little towards one side.

It is perhaps hardly necessary to remark that the relative thick-
ness of the different layers of muscular fibres just described varies
according to the species.

Under the usual circumstances the penis lies completely in the
genital atrium; but it is sometimes seen projecting from the opening
of the atrium, which is then thereby forcibly enlarged (PI. XXIII,
fig. 8).

Onchocotyle—In this genus the penis is very different from those
hitherto described, at least in its relation to other parts of the genital
ducts. It does not, namely, project into a genital atrium—this is
indeed entirely wanting in this genus—or into a homologous cavity,
but is constituted simply by a mass of peculiar connective tissue around
the terminal portion of the vas deferens, which therefore, consistently
with our nomenclature, is to be called the ductus ejaculatorius
(Pl. XVI, fig. 7). This mass of connective tissue is, roughly speaking,
conical in shape, and is separated from the surrounding mesenchyma
by «a thin layer of well staining, dense, fibrous connective tissue,
just as in Tristomwn. But unlike what is seen in that species the sub-
stance of the penis consists of a strongly refringent, somewhat yel-
lowish, structureless substance which does not stain with haematoxylin,
but which is traversed by more or less well staining, reticulated fibres.
It contains 2 small number of nuclei which are perfectly like those of
the surrounding mesenchyma, and are sometimes surrounded by a
granular protoplasm (Pl. XV, fig. 10; Pl. XVI, fig. 7). ‘The ductus
ejaculatorius makes numerous windings in the penis, and finally opens
into the uterus just before this opens to the exterior.

A xine, Hexacotyle, and Microcotyle reticulata—Strictly speak-

ing there is no separate organ that can be called penis in these forms ;
98 S. GOTO.

but the mesenchyma around the terminal portion of the vas deferens
has assumed a character more or less different from that of the other
parts ; and although it is not so distinctly separated from the remaining
portion as in Onchocotyle, it still forms doubtless the morphological
equivalent of the penis. Physiologically, too, this portion seems to
deserve the name, since in Hezxacotyle (P]. XII, fig. 6) numerous
muscular fibres take rise from the papilla on the top of which the vas
deferens opens, and taking mostly a direction backwards are inserted
into the dorsal wall of the body. These constitute doubtless the
retractor muscle. In Axine (PI. VII, fig. 5; Pl. VILL, fig. 3) I have
not been able to demonstrate the presence of any retractor ; but the ter-
minal portion of the vas deferens is surrounded by a mass of connective
tissue which is very similar to that of the penis of Onchocotyle with the
only difference that the meshes are closer and the fibres finer, and
which remains wholly unstained by borax-carmin. An exactly similar
tissue is present in Microcotyle reticulata (Pl. V, fig. 6), a species
which approaches in many respects the genus Azine. Had a mem-
brane been developed around this peculiar mass of connective tissue
nobody would hesitate to call it the penis; but as it is, we can not
give it a distinct boundary. Physiologically, however, there is little
doubt that this tissue acts as a true penis; for in Microcotyle reticulata
and Azine aberrans the internal surface of this part of the vas deferens
is armed with numerous chitinous spines (PI. V, fig. 6; Pl. VIL,
fig. 6 a). In the former species each spine consists of a hemispherical,
basal portion and a spinous, distal portion, and is perfectly straight ;
in the latter species the spines are simple and are slightly curved. It
is difficult to conceive the use of these spines unless the portion that
bears them can be evaginated.

The chitinous copulatory organ of Microcotyle is somewhat dif-

ferent from those hitherto described, and will be treated of in connec-
STUDIES ON THE ECTOPARASITIC TREMATODES OF JAPAN. 99

tion with the genital atrium. In Hexacotyle the homologue of the
connective-tissue penis of such genera as T'ristomum, Epibdella, and
Monocotyle is present in the form of a conical papilla at the top of
which opens the vas deferens, as will be explained under ‘General
Considerations.’

GLANDULA PROSTATICA—So far as I know, the prostate gland has
hitherto been described only in Yristomum among the ectoparasitic
‘Trematodes ; but according to my observations it is present in all the
genera described in this paper. Only in Octocotyle I have not been
able to demonstrate it owing to scantiness of the material and its bad
preservation. Even early in the course of my present studies my
attention was drawn to cells of a peculiar appearance around the vas
deferens, which were very unlike those of the mesenchyma ; but their
nature long remained to me a problem. In Azine (PI. VIII, fig. 1)
and Microcotyle (P). III, fig. 10; Pl. V, fig. 6) they always occupy
the median portion of the body, and in some species this portion is al-
most wholly occupied by these cells to the exclusion of all others (PI.
III, fig. 10). They are of a rounded or more frequently of a polygo-
nal outline, with a finely granular, deeply staining protoplasm destitute
of any distinct external membrane. In Microcotyle the nucleus is
usually very large and contains one or more nucleoli; but in Azine it
is smaller (PI. VIII, fig. 1). In AMonocotyle also, peculiar cells can
always be observed in the mesenchyma around the vas deferens
(Pl. XVII, fig. 2, pros. gl.) which always form a group very con-
spicuous in sections. The individual cells are in this case provided
with 2 membrane of its own, and are more or less vacuolated, the
granular protoplasm forming simply a thin layer just inside the cell-
membrane, or radiating in threads from the nucleus towards the peri-
phery, or sometimes distributed uniformly but thinly through the cell-
body. The form of the cells is either polygonal or globular, and the
100 8. GOTO.

nucleus which mostly occupies a central position is very small and
contains a single or a few small nucleoli. In this genus as well as in
Axine and Microcotyle the cells in question are mostly present around
the terminal half of the vas deferens and are entirely absent near the
testes. As I have said above, these cells remained to me an enigma
for a long time ; judging from their appearance I was tempted to at-
tribute to them a secretory function. Fortunately, however, the study
of Hexacotyle in the latter part of my studies solved for me the
enigma. In some sections of Hexacotyle acuta, one of which I have re-
produced in fig. 5, Pl. XII, I could distinctly trace the efferent ducts
of numerous cells around the vas deferens having a coarsely granular
protoplasm. ‘These cells seemed to be destitute of any membrane,
were of an irregularly polygonal shape, and their nuclei contained
each a single or sometimes a few nucleoli. They are therefore very
similar to the cells already described in MMuicrocotyle, except in the
coarseness of their protoplasmic granules. Not only could the efferent
ducts be distinctly traced up to the thick membrane of the vas deferens,
but a granular substance exactly similar in appearance to the contents
of the cells above described (except in staining more deeply) could be
observed on the inner surface of the membrane, forming numerous
prismatic columns. Each of these columns has doubtless been formed
by the secretion of a single cell, which is therefore the prostate gland.
After this observation every one would admit that the peculiar cells
around the vas deferens in Axine, Microcotyie, and Monocotyle are of the
same nature, since they occupy similar positions and closely resemble
one another in their appearance as well as in their reaction towards
staining fluids. I have not been able to observe the efferent ducts in
the genera just mentioned ; but this is, I believe, owing to the fact that
the glandular cells were in the state of rest when the animal was killed.
At least in the case of the shell-glands afterwards to be described, the
STUDIES ON THE ECTOPARASITIC TREMATODES OF JAPAN. 101

efferent ducts can not be observed when the cells are not in an
active state. I believe Lorenz’ had the prostate glands before him
when he speaks of cells around the uterus, which had a granular
protoplasm.

In Dielidophora the prostate glands are more scattered than in
the genera hitherto treated of, and are especially abundant around
the terminal portion of the vas deferens. In this genus also, the
cells are wholly destitute of external membrane, the protoplasm is
finely granular, and the nuclei, which are more or less vesicular in ap-
pearance, vary much in size. The larger ones are more or less oval,
and contain a large nucleolus enclosing a vacuole, and a few smaller
nucleoli. After secretion the cells seem to shrink to a very small size,
and in these shrunken cells the efferent ducts are very distinct (PI.
XI, fig. 4). The interior of the vas deferens is filled with numerous
coarse granules, evidently the secretion of the prostate glands. This
secretion seems to form at first a single drop for each cell and then to
break up into numerous, smaller granules (Pl. XI, fig. 4). In On-
chocotyle the prostate glands are present not only around the vas
deferens, but also on the more ventral side of the body (Pl. XVI,
fig. 8). The cells are very similar to those of Hexacotyle.

In Epibdella the prostate gland is an egg-shaped, or elongated
cylindrical, hollow body, lying just behind the penis and communi-
cating with its cavity either directly or by means of a short canal
(PI. XXVI; figs. 1, 3,4, & 6). In Epib. ovata (fig. 6) the wall is
composed of a coarsely granular, well staining substance, and has a
distinct basement membrane which separates it from the mesenchyma.
In a specimen of Epib. Ishikawae which I examined, the cavity

contained a well staining, homogeneous coagulum which looked very

 

1). Lorenz—Ueber die Organisation der Gattungen Axine u. Microcotyle. Wiener Arbei-
ten, Bd. 1, 1877, p. 8. ;
102 8. GOTO.

much like the albuminous substance contained in the egg-capsules of
the earthworm and other animals when coagulated ; and the wall was
completely shrunken, apparently owing to the great secretory activity
which produced the coagulum. I have not, however, been able to
study the minute structure of the gland in this genus owing to
scantiness of the material and its imperfect preservation ; and I must
therefore content myself with the above meagre account. What von
Linstow” calls the “ Samenblase” in Phylline Hendorfii and P. J. v.
Beneden” the “ vésicule séminale”’ situated outside the penis in E.
Hippoglossi, is undoubtedly the prostate gland. I also think that
what St.—Rem y” calls the ‘‘vésicule prostatique accessoire” is nothing
else than a portion of the prostate gland which seems, in Phyllonella
solee according to that writer’s account, to consist of numerous
lobes.

In Tristomum ihe prostate gland is much developed and has been
already observed by my predecessors. It consists of numerous unicell-
ular glands with exceedingly long necks, which in some species, ¢. 4.,
Trist. foliaceum, are arranged distinctly in two separate groups
(PI. XXV, fig. 9). The cells themselves are scattered without any
order through the mesenchyma of the median and lateral portions of
the body around the foremost part of the vas deferens (PI. XXII,
fig. 1). They present somewhat different aspects according to the dif-
ferent states of their secretory activity. They are either polygonal or
spherical, but are of very different sizes; the smaller ones stain
deeply and their protoplasm is finely granular, while the larger ones
have a more coarsely granular and more weakly staining protoplasin.

The nucleus is always very distinct; it is vesicular, and contains

 

1). Von Linstow—Beitrag zur Anatomie von Phylline Hendorffii. Archiv f. mik. Ana-
tomie, Bd. 33, 1889, p. 171.

2). P. J. v. Beneden—Mémoire sur les vers intestinaux. p. 29 & Pl. III, fig. 1.
3). St.-Remy—Etude de l’appareil génital chez les Tristomiens, p. 17.
STUDIES ON THE ECTOPARASITIC TREMATODES OF JAPAN. 103

one or several nucleoli. The efferent ducts are exceedingly long and
variously cross each other in their course. When the cells are active
these ducts are filled with a weakly staining, granular substance
exactly like in appearance to that of the cells themselves. In this
case their wall is very distinctly visible, but in the intervals of
secretion it seems to collapse entirely, and the ducts are then no
more visible.

In the genus under consideration the prostate glands enter the
penis at its base a little towards one side (PI. XXII, fig. 2), and open
into its cavity. Just before entering the penis, the ducts are often
filled to such a degree as to be partially stopped up, and at this point
often present in consequense a ruggedly swollen appearance (PI. NAV,
fig. 8).

In Epibdella I have observed 2 pair of peculiar egg-shaped organs
on either side of the median line just behind the testes (P]. XXV, figs.
4&6, 2). In sections they are seen to be a mass of polygonal cells,
each of which contains a nucleus with a nucleolus, and has a coarsely
granular, slightly staining cytoplasm (Pl. XXVI, fig. 8), the whole
mass being provided with a distinct limiting membrane. Judging
from their appearance and reaction towards staining fluids I should
consider them as glands, but I have not been able to find out any

duct or any connection with the neighbouring organs.

(b). The Female Organs.

Ovary—The ovary is always single and is simply a cavity in the
mesenchyma filled with germ-cells. Unlike what is seen in the
testes, however, the cavity is usually bounded by a thin membrane of
connective tissue, closely applied to which are sometimes observed
oval or flattened nuclei (PI. IV, fig. 8); but these are in my

opinion to be regarded as the nuclei of the mesenchyma, and not as
104 S. GOTO.

the remnants of the original epithelium of the ovary. When the
ovary is more or less elongated the zones of formation and growth can
be very clearly distinguished ; the maturation of the ovum taking
place probably after its enclosure in the egg-shell. In Mierocotyle and
in most species of Azine (Pls. I, II, & VII) the ovary is more or less
S-shaped when looked at from the dorsal side of the body ; in some
species the lower half of the S is drawn out almost straight, while in
some others this portion is coiled spirally on itself (PI. II, fig. 6).
The formative zone is situated at the posterior end of the ovary, and
looks in sections as a continuous mass of homogeneous protoplasm in
which numerous nuclei lie imbedded. These are provided with a
distinct membrane and contain numerous granules of chromatin. As
we proceed away from this into the growing zone the protoplasm
becomes more and more distinctly separated around each nucleus,
or, in other words, the ova gradually acquire their independ-
ence; the nuclei become larger and larger, the chromatin granules
become more and more undefined, and a distinct nucleolus makes its ap-
pearance in each nucleus; until finally in the terminal part of the
ovary, 7. ¢., in that part where the oviduct takes its rise, each
ovum is provided with a large, clear, thin-wallel, vesicular nucleus
containing, besides numerous, faint, minute granules of chroma-
tin, a single large nucleolus, which takes up all stains with extreme
avidity and encloses a single Jarge or several smaller vacuoles
(PL IN figs, 8 a 0; PL VIL fe. By Pl LX, fie. 62 Pl X, fio. 8s
Fi. AV, fig. G5 Vl. AVL, fie. 63-0) XX, fe 13). In age
aberrans (Pl. VI, fig. 5) and in Octocotyle (Pl. IX) the ovary is an
elongated, cylindrical body which is bent on itself at its middle,
so that its ends come to be apposed to each other, and which
is placed with its long axis parallel to that of the body. In
Calicotyle (Pl. XIX, fig. 1) too it is a very long, slender body bent on
STUDIES ON THE ECTOPARASITIC TREMATODES OF JAPAN. 105

itself at the middle, so as to form a loop across the length of the
body ; but in this genus the proximal end of the ovary, i. ¢., the zone
of formation, is enlarged into a globular shape, while the remaining
portion is throughout of an almost uniform thickness so that Wierze-
jski? was led to call this portion the oviduct (Hileiter). But that
it corresponds in reality to the zone of growth is very clear from
a comparative study of the ovary in different genera. What
seems to be very peculiar is that the closed end of the loop which
the ovary forms in this genus encircles the intestine (PI. XIX,
fig. 1). This is also the case in Monocotyle; but in this genus the
formative zone passes gradually into the zone of growth, and the whole
ovary makes an additional large winding or two (Pl. XVII, fig. 1).
In Diclidophora the form of the ovary varies much in different
species. The simplest form is found in Diclid. elongata, in which a
long cylindrical ovary is twice bent on itself so that each half is horse-
shoe shaped (PI. X, fig. 9). In Diclid. sessilis also, each half of the ovary
is bent on itself so‘that the whole looks somewhat like the lefter W;
but the four arms of the W are closely applied to each other, and the
terminal portion, i. ¢., that which gives rise to the oviduct is very
much larger than the other three, and contains a cavity filled with
a sparsely fibrous connective tissue (PI. X, fig. 5). In Diclid.
tetrodonis, again, the somewhat comma-shaped ovary makes a spiral
winding to one side at its middle, so that the whole looks some-
what like the embryo of the chick in profile, with its large heart
protruding from its ventral side at a short distance from the head
(Pl. X, fig. 1); the head of the embryo answering to the oviduct
end of the ovary and the tail end to the formative zone. In Onchoco-

tyle the zone of formation occupies about one-fifth of the whole length

 

1). Wierzejski—Zur Kenntniss des Baues von Calicotyle Kroyeri. Zeitschr. f. wiss.
Zoolog., Bd. 29, 1877. p. 557.
106 8. GOTO.

of the ovary, is of an irregular shape, and occupies a position
anterior to the rest of the ovary (PI. XV, fig. 1, or). The
remaining part is twice bent on itself at equal distances apart so
that it may be considered as consisting of four portions united end to
end, ‘The ovidut portion is very much larger than the other three
portions.

In Hexacotyle the ovary makes numerous, exceedingly complex
windings which can not be described with any degree of clearness, and
the reader is therefore referred to figs. 1 & 7 of PJ. XIV. In Heaaco-
tyle acuta I have not been able to obtain a general view of the whole
ovary, and fig. 1 on the plate just referred to has been composed from
a series of sections, controlled as much as was practicable by examina-
tions of the specimens mounted 7n toto. The general form of the
ovary is that of a long cylinder bent on itself at its middle portion,
each half of which makes numerous convolutions.

In Fpibdella the ovary is a simple, spherical body, in which
the zones of formation and growth can not be distinctly separated
from each other, but the younger ova are found towards the
periphery, while the riper ones are situated in the central part. In
some species of Tristomum also the ovary is simply an irregularly
globular body ; but in most species it consists of a certain number of
more or less distinct lobes, which are incompletely separated from one
another by an intervening layer of connective tissue, all however freely
communicating with one another at the centre of the ovary. As in
Epibdella the unripe ova occupy the periphery, while the riper ones are
situated more in the central part.

The ovarian ova are in all the species totally destitute of any
external membrane.

Ovinpuct—As I have stated elsewhere,” I designate by this

 

_1). Centralblatt f. Bakteriol. u. Parasitenkunde, Bd. XIV, 1893. p. 798.
STUDIES ON THE ECTOPARASITIC TREMATODES OF JAPAN. 107

name that portion of the female efferent duct that lies between the
ovary and the ootyp, the beginning of the latter being always distinctly
marked by numerous unicellular shell-glands. Its course and _ its
relation to other genital ducts are very different in different species,
and will be described afterwards for each species in the systematic
part, but some of its common features must be noted down here. It
lies, namely, in all the species dorsal to the unpaired yolk-duct, and
communicates with it as well as with the canalis genito-intestinalis when
such is present. In Microcotyle, Axine, Onchocotyle. Diclidophora, and
Culicotyle it bears the receptaculum seminis. In the first two genera
just mentioned this organ is formed simply either by a lateral evagina-
tion, or by the swelling of a portion, of the oviduct ; and seems to be
actually present only when it is filled with sperm mass, and to
shrink together when there is no sperm to fill it. so that then it
seems as if entirely wanting. In Diclidophora the receptaculum
seminis is exceedingly large, and is very conspicuous, especially in
Dielid. sessilis (Pl. X. fig. 5). In this species it is a very large
sac situated on the median line of the body just behind the ovary,
and consists of numerous lobes. These lobes are mostly situated
on the dorsal side of the body, and are separated from each other
by a thin layer of connective tissue. They all converge towards the
oviduct as a centre. and communicate with it just where it makes
a short forward bend to meet the unpaired yolk-duct (Pl. X. fig. 5 ;
Pl. XI, fig. 5). In cross-section the cavities of the lobes are seen to
be destitute of any distinct lining membrane. In all the specimens
I have examined, they were always completely filled with sperm-mass.
In Dicelid. elongata the seminal receptacle is also large, but is consider-
ably smaller than in Diclid. sessilis, and is simply globular in shape
(Pi, X, fig. 9). In Dicelid. tetrodonis I have not observed any seminal

receptacle, but this was, believe, owing to the absence of any sperm
108 8. GOTO.

mass at the time. I think this the more probable, as the only specimen
I have examined had numerous eggs in its uterus, in the formation of
which all the sperm mass that may have been present in the seminal
receptacle would have been used up (PI. X, fig. 1).

ha Onchocotyle spinacis the seminal receptacle is a tolerably large,
ellipsoidal sac situated just in front of the ovary, and is provided
with a long stalk, by means of which it communicates with the
oviduct at the point where the latter receives the unpaired yolk-duct
and the genito-intestinal canal (PI. XV, figs. 1 & 2). It therefore
presents some difference from that of Oncho. appendiculata, in which
it is, according to Taschenberg, merely a local enlargement of the
oviduct.

Close to the ovary the wall of the oviduct consists of a thin
structureless membrane ; but as we approach the ootyp there is a thin
layer of homogeneous or very finely granular substance probably of a
protoplasmic nature, which stains pretty well with haematoxylin,
so that the membrane just referred to above is in reality a true base-
ment membrane with probably a very thin protoplasmic layer on its
inner surface. I have nowhere been able to observe any nucleus in
the wall of the oviduct; but that it originally consisted of a true
epithelium seems to me beyond doubt, from the presence of the
protoplasmic layer already mentioned, aud from the fact that nuclei
are present in other parts of the female efferent duct. In Diclidophora
the oviduct presents at short intervals circular thickenings of its wall
exactly similar to those which will be described afterwards in the
genito-intestinal canal.

Ootrp—The ootyp is a spindle-shaped portion of the female
efferent duct situated between the oviduct and the uterus, where the
ovum and the yolk-cells become enclosed together in the egg-shell.

In many species it is always distinctly set off from the other parts of
STUDIES ON THE ECLOPARASITIC TREMATODES OF JAPAY. 109

the female duct by its constant form; but in Microcotyle, Aine,
Octocotyle, Diclidophora, Hexacotyle, and Onchocotyle, it can not be dis-
tinguished superficially from the other parts unless during the period
of reproductive activity. It is, however, usually well characterised by
the fact of its receiving the openings of numerous unicellular shell-
glands either throughout its whole extent, as in .1aine, Microcotyle, ~
Octocotyle, Diclidophora, Onchocotyle, and Hexacotyle; or, «us in
Tristomum, Epibdella, Calicotyle, and Monocotyle, only at the beginning
of the ootyp. In most genera of the first group the shell-glands are
situated only around the ootyp; but in most species of Microcotyle
they are present not only around the ootyp but also at some distance
behind it (PI. IV, fig. 4), so that those that are far removed
from the ootyp come to be provided with long efferent ducts, which
then open close to each other at the very beginning of the ootyp.
When the glands are active these efferent ducts are filled with a
granular substance, evidently the product of secretion, which stains
deeply with haematoxylin (PI. IV, fig. 4). It is undoubtedly these
ducts which Lorenz” has described as the “ Quaste.” In Jeroco-
tyle the shell-glands form, moreover, a compact mass around the
ootyp, which looks usually triangular in cross-section (PI. IV, fig. 8),
owing to the pressure of the neighbouring organs. In other case,
where the glands are free from any pressure, they are arranged almost
uniformly on all sides of the ootyp, as in Axine, Hexacotyle, Octocotyle,
and Dicélidophora.

In Onchocotyle the shell-glands are divided into four groups
owing to the intervention of other organs (PI. XVI, fig. 3). There
are two groups on the dorsal side and two on the ventral side of the

body, the groups on the same side being separated from each other in

 

1). Lorenz—Ueber die Organisation der Gatt. Axine u. Microcotyle. Wiener Arbeiten,
Bd. 1, 1878. p. 17 & 27.
110 8. GOTO.

the median line. ‘The cells, especially of the ventral groups, are far
removed from the ootyp; and they are therefore provided with long
efferent ducts, which open into the ootyp after making more or
less windings on the way (Pl. XVI, fig. 4). In T'ristomum also, the
shell-glands are far removed from the ootyp, and open by means of
long ducts into its very beginning (Pl. XXII, fig. 3). In some
species of this genus (¢. g. Trist. sinuatum) the wall of the ootyp sends
out a few small, tubular evaginations, into which the shell-glands open
(PL. XXII, fig. 6). In Monocotyle too, these glands are provided with
long stalks, and open only at the beginning of the ootyp.

_ As to the shell-glands themselves, they are in most species of an
irregular polygonal form. ‘The nucleus is more or less vesicular and
contains one or a few nucleoli ; the protoplasm is usually granular,
stains well, and is wholly destitute of any external membrane. The
glands, however, often appear like small naked nuclei, owing to the
shrinkage of their protoplasm. ‘This condition is evidently owing to
exhaustion, and corresponds to the period of complete rest. In Mono-
cotyle the shell-glands are ellipsoidal or spherical, and are, as already
stated, provided with long stalks (PI. XVIII, fig. 1). The nucleus,
which contains in this case usually a single nucleolus, occupies a more
or less eccentric position, and the cytoplasm is finely granular and
stains weakly. The ducts are on the other hand often filled with a more
deeply staining, and more coarsely granular substance ; the cytoplasm
and the contents of the duct being sometimes separated by a sharp
line (PI. XVIIL, fig. 1). I do not know what interpretation to put on
this phenomenon, except to regard these goblet-shaped cells as having
arrived at the culminating point of their secretory activity and to have
almost entirely emptied themselves of the product of secretion, leaving
only the protoplasm in the body of the cell—in other words, I regard

the deeply staining contents of the duct as the product of secretion, and
STUDTES ON THE ECTOPARASITIC TREMATODES OF JAPAN. 111

suppose the cells to shrink soon after discharging their contents. In
these goblet-shaped cells just mentioned I could observe a distinct
cell-membrane. In the immediate neighbourhood of these cells there
are in Monocotyle numerous large cells of an irregular shape, each with
a rather smal] nucleus which contains a single nucleolus, and with
a coarsely granular, well-staining protoplasm destitute of an external
membrane. Judging from their similarity to the shell-glands of
other genera and from the fewness of the goblet-shaped cells above
mentioned in the genus under ‘question, I think they are shell-glands
which are still in the interval in secretory activity.

As stated above, the ootyp is characterised by the fact that it
receives the openings of the shell-glands. Tt is, moreover, separated
from the oviduct by a constriction, which is usually very distinct—
“une sorte de pylore” as P. J. v. Beneden” calls it. Anteriorly
it is in most species directly continued into the uterus without
undergoing any constriction ; but in many species of T'ristomum (T.
sinuatum, T. ovale, T'. biparasiticwn, and T. foliacewm) its anterior
extremity protrudes into the hinder end of the uterus, just in the
same way as the neck of the uterus projects into the vagina in the
mammalia ; so that in this genus the uterus and the ootyp may be
said to be separated from each other by a valve, which allows a body
to pass from the Jatter into the former but not in the contrary direc-
tion (Pl. XXII, fig. 3). In Monocotyle the ootyp opens directly into
the genital atrium, the uterus being totally wanting in this genus. In
Axine, Microcotyle, Octocotyle, Diclidophora, and Hexacotyle the wall of
the ootyp is not specially different from that of the oviduct; 7. ¢., it con-
sists of a thin, homogeneous, protoplasmic layer resting on a basement
membrane ; but in some species there is an assemblage of oval nuclei

at the entrance of the oviduct (PI. IV, fig. 4). In some cases there

 

1). P. J. v. Beneden—Mémoire sur les vers intestinaux. p. 43.
112 S. GOTO.

was also a rather thick layer of granular substance on its wall (PI. LV,
fig. 8), which I believe to be the secretion of the shell-glands. In
Onchocotyle the ootyp presents in cross-section a very peculiar ap-
pearance. Its cavity looks stellate, caused by the fict that the
cells that constitute its epithelium have assumed a_ laterally
flattened conical form and are arranged in close series in parallel
longitudinal lines, so that the wall is, so to speak, furnished with
pilasters projecting into the cavity of the ootyp (PI. AVI, fig. 4).
That these pilasters are composed of cells is clear from the fact that
here and there in cross-sections nuclei are observed near the outermost
end of the sections of the pilasters ; the comparative fewness of the
nuclei being accounted for by supposing that the cells have been much
elongated parallel to the length of the ootyp. The individual cells
are completely fused with each other, and no boundary line can be
observed ; the furrows between the pilasters, however, probably mark
the boundaries between the longitudinal series of cells. The wall of
the ootyp is separated from the mesenchyma by a distinct basement
membrane ; but there is no membrane on its inner surface (PI. XVI,
fig. 4). In Tristomum the wall of the ootyp consists of a sort of
syncytium in which nuclei are sparsely dispersed, and which is
separated from the mesenchyma by a basement membrane. The
syncytium itself stains well, is very finely granular, and has no
membrane on its: free surface (Pl. XXII, fig. 3). The nuclei seems
sometimes to be very regularly distributed : for instance, in Tristomum
sinuatum I have observed in a median longitudinal section of the
ootyp four nuclei arranged in pairs in the central portion and two
others also arranged in a pair near the oviduct end (PI. XXII,
fig. 3) ; they were all vesicular, stained rather weakly, and contained
each a single, deeply staining nucleolus. In Calicotyle and Monocotyle

the wall of the ootyp consists of a true epithelium resting on a basement
STUDIES ON THE ECTOPARASITIC TREMATODES OF JAPAN. 113

membrane and consisting of tall, prismatic cells, each with a small
nucleus near the base (Pl. XVIII, fig. 2; Pl. XIX, fig. 7). These
nuclei are spherical and vesicular, but stains well, and each contains a
single dot-like nucleolus. In Calicotyle the boundaries of the cells are
distinct ; but in Monocotyle they become indistinct towards the free
surface of the cells. ‘The protoplasm of the cell is finely granular and
stains a beautiful purplish blue with Kleinenberg’s haematoxylin.
In the specimens of Monocotyle examined by me the free borders of the
cells remained almost totally unstained and presented a somewhat
stringy appearance, as if a layer had been artificially formed by the
sticking together cf closely ageregated fine cilia (PI. XVIII, fig. 2).
St.-Remy” considers what I have regarded as the epithelium of the
ootyp as of the nature of a connective tissue and calls it “cuticle” ;
and in support. of his view he mentions the fact that although the wall
of the ootyp shows a certain tendency towards its external side (/. e.
the side turned towards the mesenchyma) to break up into irregular
prisms, the lines of separation do not correspond with the distribution
of the nuclei. From his statements elsewhere I gather that the author
does not mean by “une, certaine tendance a se dissocier en prismes
irréguliers”’ that he has actually tried to separate these prisms by
maceration or other means, but I believe he is here speaking
of the lines which J have regarded as cell-boundaries. If so, it is to
be observed that even in the case of a true epithelium the boundaries
do not always seem in cross-sections to correspond exactly with the
distribution of the nuclei, as actually for example, in the intestine of
Monocotyle and Calicotyle. St.-Remy* admits that “il est vrai-
semble que dans le jeune Age, il y avait 14 des cellules ;” but he thinks

“que cette fragmentation ne correspond pas a leurs limites.” It is

 

1). St.-Remy—l. c. pp. 10, 26, 33.
2). Le. p. 26.
114 8. GOTO.

after all not clear to me what the author means when he speaks of a
“cuticle” containing nuclei and of a layer of finely granular, or, as he
says, homogeneous substance lining a cavity as being of a connective
tissue uature. Comparative considerations seem to me to compel us to
regard the wall of the ootyp of Monocotyle and Calicotyle as consisting
of a true epithelium ; only in the case of Tristomum the cell-boundaries
have completely, and in that of Onchocotyle partly, disappeared.

In Tristomum the mesenchyma around the ootyp presents an
appearance very different from that of the rest. Where’ the
general mesenchyma consists of a fibrous connective tissue, the
reticulum is always much looser around the ootyp than in the other
parts. In Trist. sinuatum in which, «s already described, the mesen-
chyma consists of a syncytium, the part around the ootyp contains
numerous cavities separated from each other by a thin layer
of the syncytium (PI. NXT, fig. 4). This loose portion of the
mesenchyma is, in all the species, surrounded by a layer of muscular
fibres, which are of two sorts, those which run parallel to the length
of the ootyp and those that run in a dorso-ventral direction. The
latter fibres are no other than the dorso-ventral fibres of the body.
The two sets of fibres are also present around the uterus, and therefore
the farther course of the horizontal fibres will be again treated of
under that head. They evidently serve by their contraction to drive
out the egg from the ootyp.

Returning to the ootyp of Monocotyle and Calicotyle and consider-
ing the appearance and reaction towards colouring fluids of the cells
that constitute its wall, one is, I think, strongly tempted to sus-
pect their glandular nature. But as the shell-glands are present out-
side the ootyp, I can not conceive any purpose they might serve
in case of their being really glands. They are probably a simple lining

epithelium, of which, however, the character has undergone a certain
STUDIES ON THE ECTOPARASITIC TREMA'TODES OF JAPAN. tis

change, perhaps better fitting it to bear the abrasion to which it is
necessarily exposed during the formation of the egg-shell.

Urerus—With this name I designate that portion of the female
efferent duct which is continued forwards from the ootyp and opens
to the exterior or into the genital atrium when such is present. In
Aonocotyle it is, as already mentioned, wholly wanting, the ootyp
opening in this genus directly into the genital atrium. In Calicotyle
it is very short and is lined by the continuation of the epithelium of
the ootyp (PI. XIX, fig. 7) ; the cell-boundaries, however, can not be
observed satisfactorily. In Hpibdella too the uterus is exceedingly short;
in fact it may be said to be wanting in FL. [shikawae.- On the other
hand, in Axine, Microcotyle, Hexacotyle, Octocotyle, and Diclidophora the
uterus is very long, and its wall consists of a membrane which is in
most cases very thin, but sometimes very thick and refringent, as in
Microcotyle reticulata and Aaine heterocerca (PI. V, fig. 5; Pl VII,
fig. 1). In Octocotyle, Hexacotyle, Onchocotyle, and in all the species of Ji
crocotyle except M. sciaene (Pl. VI, fig. 2), the inner surface of the uterine
wall is covered with cilia ; but in all the other species treated of in this
paper it is entirely naked (Pl. V, figs. 1, 2, 3, 4, & 5; Pl. VI, fig. 1;
PJ. LX, fig. 12; Pl. ATV, fig. 3). In Axine heterocerca and Dielidophora
sessilis the uterus is provided with a double layer of muscular fibres
consisting of the inner longitudinal and the outer circular fibres
(Pl. VIL, fig. 1; Ph XI, fig. 4). In Hewxacotyle, on the other hand,
only the circular fibres are present.

The uterine wall of Onchocotyle presents some peculiar aspects and
deserves a separate description. Close to the ootyp the wall of the
uterus presents an aspect closely similar to that of the ootyp (PI. XVI,
fig. 5); only the pilasters are lower and spindle-shaped in cross-
section, and some of them are seen to contain nuclei, which are mostly

oval and contain each a single nucleolus. Those that do not contain
116 S. GOTO.

nuclei, 7. ¢., those whose nuclei have not met the section, are seen to
contain one or several vacuoles in their protoplasm (Pl. XVI, fig. 5).
The top of each pilaster is seen in section to bear numerous cilia. As
we recede from the ootyp, the pilasters become more and more flattened,
the cilia become longer, and the nuclei finally disappear altogether ;
but the pilasters are still separated by a shallow furrow, (Pl. XVI,
fig. 6). As we recede still farther from the ootyp the pilasters
finally disappear entirely, 7. ¢., the protoplasmic remnants of the original
epithelium have almost wholly disappeared, and the inner surface of
the uterine wall is covered uniformly with long, stout cilia (PI. XV,
fig. 10; Pl. XVI,fig. 8). In this genus there is no genital atrium,
and the uterus consequently opens directly to the exterior by means of
a small pore (PI. AVI, fig. 7).

Monticelli” thinks that in Onchocotyle the terminal portion of
the uterus is specialised into an “ ovidotto esterno”’; but I think the
enlarged portion figured by Taschenberg is due to the eggs that
are contained therein. So far as I have observed there is in the Mono-
genea no specialised portion corresponding to Monticelli’s ‘“ovidotto
esterno.”

In most species of T'ristomum the posterior end of the uterus is, as
already stated, enlarged into the shape of a funnel with its mouth
directed towards the ootyp, the front attenuated end of which
projects into it. It is usually of uniform size throughout: the
rest of its extent; ‘but in Trist. sinuatun I have observed it
undergo another enlargement and then to be reduced to a narrow canal
of uniform calibre (P]. XXII, fig. 2), The wall is in all cases formed
throughout of a thin, structureless membrane. In Trist. ovale and
Trist. rotundum the uterus opens directly to the exterior, close beside
the male genital opening (Pl. XXIII, fig. 8; Pl. XXIV, fig. 6) ; but

 

1). Monticelli—Primo contributo etc. p. 118.
’

STUDIES ON THE EC'TOPARASITIC 'TREMA'TODES OF JAPAN. 117

in all the other species it opens into the genital atrium at various dis-
tances from its external opening (Pl. XXI, fig. 8; Pl. XXII, fig. 2;
Pl. XXV, figs. 3, 8, and 9).

As already mentioned above, there are in this genus two sets of
muscular fibres in the loose connective tissue around the uterus, which
are exactly similar to, and one of which is the direct continuation of,
those around the ootyp. The dorso-ventral fibres are present only a-
round the lower part of the uterus; but the horizontal fibres are con-
tinued to the margin of the body, where they become continuous with
the diagonal fibres of the body (Pl. XXII, fig. 4).

VireLLariuM—This is a very extensive organ situated mostly
in the lateral portions of the body and extending through the
greater part, or in some species throughout the whole length,
of the body (Tristomum, Epibdella). In accordance with its position
in the body, it consists of two parts, a right and a left half,
which remain in many species entirely distinct throughout their
whole extent; but in other species they pass into each other
at both ends. Again, in most species, the vitellarium seems
to be closely connected with the intestine in its arrangement, be-
ginning and ending with the main intestinal trunks. In Iicrocotyle
this relation is especially conspicuous. As already mentioned, the
two trunks of the intestine are in some species of this genus of unequal
lengths ; and then the halves of the vitellarium also show a cor-
responding asymmetry, as in M. elegans (PI. I, fig. 4) and MM. sciaence
(PI. TI, fig. 6). There are, however, also species in which the vitel-
larium and the intestinal trunks do not show any correspondence of
lengths, as Mf. caudata and M. sebastis (PI. I, figs. 1 & 2). Again, in
many species in which lateral branches of the intestinal trunks are
given off towards the median line, these are accompanied by the vitel-

larium, which then surrounds them on all sides. In Axine, Microcotyle,
118 8. GOTO.

Octovotyle, Diclidophora, Onchocotyle, Monocotyle, and Calicotyle the
front attenuated portion of the body is entirely free from the vitel-
larium; the hinder caudal portion is also mostly free from it ; but to
many species this statement Hoes not apply. In Diclidophora tetrodonis
which has a very elongated body, the vitellarium is wholly absent from
the whole slender posterior portion. Ih many species of T'ristomum
the vitellarium occupies not only the whole lateral portions of the body
but extends also into the median portion (T. ovale, T. Nozawae). In
Microcotyle, Octocotyle, Diclidophora, Monocotyle, Calicotyle, Epibdella,
and in most species of J'ristomum the vitellarium ix present on the
dorsal and ventral sides of the body alike; but in Azine the veutral
side is mostly free from it (PI. VII. fig. 1), and in Trist. ovale the
dorsal side of the median portion of the body is entirely occupied by
the vitellarium, which thus leaves only the ventral side for the testes
(Pl. XAT, fig. 7). In VY. Nozawue too the vitellariuam occupies in
the median portion of the body a position nearer the dorsum than the
testes; but in this species the vitelline lobes are more sparsely distributed
in this region.

The vitellarium consists of numerous lobes, which are in most
species more or less rounded, but are tubular in Cadicotyle, so that in
this genus the vitellarium cousists of a system of tubes filled with yolk-
cells. In Monocotyle, Onchocotyle, Tristomam, Octocotyle, and in most
species of Microcotyle and Diclidophora these lobes are very closely ag-
gregated, and leave only avery thin layer of mesenchyma between
them, so that they are very difficult to distinguish from each other in
sections { Pl. IV", fig. 7; Pl, XI, fig. 33 Pi. XVIG, fig. 5); but in all
the other species the lobes are separated from each other by a more or
less thick layer of the intervening mesenchyma. For instance, in
Heaacotyle each lobe is surrounded on all sides by the mesenchyma,

which thus completely separates it from its neighbours (PI. XI, fig. 8;
STUDIES ON THE ECTOPARASITIC TREMATODES OF JAPAN. 119

PI. XIV, figs. 2 & 6); while in Calicotyle and Microcotyle reticulata the
vitelline lobes are distinctly but less completely separated from each
other (PI. III, fig. 4; Pl. NIN, fig. 9). In Tristomum (Pl. XXT,
fig. 7) and Calicotyle (Pl. NXT, fig. 9) LT have observed a thin but
distinct membrane surrounding the lobes; but in most other genera
they seemed to be contained in mere cavities of the mesenchyma
destitute of any lining membrane.

The yolk-cells contained in the lobes present different aspects ac-
cording to the stages of development. ‘The ripe cells are of
very different size? in different genera; but present nearly the same
aspect in all. While in the vitellarium, they are of various forms ac-
cording to the pressure of ‘the neighbouring cells; but when freed they
invariably assume the form of a regular sphere. Each cell is provided
with a distinct, refractive membrane (of tolerable thickness in Mono-
cotyle Ijimae, P\. XVIII, fig. 5), and contains numerous, yellow, re-
fringent granules. The vesicular nucleus usually occupies a central
position, generally stains well, and contains a single nucleolus ; it
sometimes loses its affinity for stains, but alwavs subsists to the very
last. The protoplasm seems mostly to have entirely disappeared in
the ripe cells; but sometimes it remains as a slightly staining network
hetween the yolk-granules (P]. NNT, fig. 7). Besides the ripe yolk-
cells above described, there are, especially in the peripheral part of the
vitelline lobes, intensely staining cells of a much smaller size, closely
pressed against one another, and with a homogeneous or, in the larger

ones, 2 finely granular protoplasm. ‘The nucleus is clear and vesicular,

 

1). Lappend here in the form of a foot-note the results of the measurements of yolk-cells
in different species. The figures give the diameter, and are in most cases the average of a
number of measurements (not less than five): Aine heterocerca, 0.03 mm.; Microcotyle caudata,
0.035 mm.; WM. reticulata, 0.015 mm.; Diclidophora tetrodonis, 0.022 mm.; Diclid. sessilis, 0.028
mn. ; Onchocotyle spinacis, 0.032 min.; Monocotyle Ijimae, 0.0184 mm.; Epibdella orata, 0.021
mm.; Tristomum rotundum, 0.015 mm.; Tr. foliaceum, 0.019 mm.; 7'r. orale, 0.016 mm.; 7'r.
sinuatum, 0.018 mm. ;
120 8. GOTO,

and contains a single small nucleolus. It appears in some cases to be
more weakly stained than the protoplasm; but this is, I believe, owing
to the entire absence of any granules from the nuclear fluid, which,
in consequence, appears very clear and transparent. However,
the nucleus itself stains equally or often ‘a. little more deeply
than the protoplasm. As these yolk-cells grow and become larger, the
protoplasm becomes more and more coarsely granular and _ stains less,
until at last the whole protoplasm is replaced by the yolk-granules
already described. In some cases I have observed cells one half of
which contained only yolk-granules, while the other half had still
a coarsely granular protoplasm (PI. IV, fig. 7). Lorenz” had
perhaps the young yolk-cells above described before him when he men-
tions the occurrence, directly inside the muscular layer of the body, of
small cells (0.006 mm.) having a strong affinity for carmin, and the
central parts of which remain clear and contain each a dot-like body.
Considering that the yolk-cells are drained off in considerable numbers
during the period of reproductive activity, one would very naturally
expect to meet with the phenomena of division among the young
yolk-cells, and it appears to me somewhat remarkable that I have never
been able to observe in them any division either direct or mitotic.
York-pucts—In most genera the primary yolk-ducts that pro-
“ceed from the lobes could not be observed; but in T'ristomum T could
often observe them in sections (Pl. XXI, fig. 7). They have a very
small calibre, and are provided with a thin but distinct, membranous
wall. In other species I have often observed yolk-cells passing out
from the lobes, but the ducts seemed to close together as soon as the

cells had passed along,

any longer. In Tristomum again, the secondary and tertiary ducts

so that their presence could not be recognised

were ustully filled with yolk-cells, and could be easily recognised in

 

1). Lorenz—i. ¢. p. 5.
STUDIES ON THE ECTOPARASITIC TREMATODES OF JAPAN. 121

surface views. The numerous ducts that proceed from each half
of the vitellarium at Jast unite with one another and form a single
large duct, the paired yolk-duct. Thes2 are in most species sym-
metrically disposed with respect to the median line of the body,
but in Hezxacotyle that of the right side is situated much more
in front of the left (PI. XIV, figs. 1 & 7). In Dielidophora a
similar asymmetry is also observable, but is not so striking (PI. X,
figs. 1, 5, & 9); and in this genus the relative positions of the ducts of
the two sides of the body are the reverse of what is found in
Heaacotyle, the duct of the left side being situated anterior to
its fellow of the opposite side. During the summer season the
pared yolk-ducts are almost always filled with yolk-cells, and
are consequently very conspicuous, being sometimes perceptible
with. the naked eye through the transparent tissue of the worm.
In Axine heterocerca, Microcotyle, Hexacotyle, and Onchocotyle they
run for the greater part of their lengths parallel to the long axis of
the body, just on the inner side of the intestinal trunks; but in Cali-
catyle, Monocotyle, Tristomum, Epibdella, and Diclidophora the ducts of
both sides are situated on the same straight line, which is directed at
aright angle to the long axis of the body. In zine aberrans and in
Octocotyle the paired ducts unite with each other in the medi:n line of
the body immediately after leaving the vitellarium, and form the
single yolk-duct (PI. VII, fig. 5). In Tristomum, Calicotyle, and Mono-
cotyle the paired yolk-duct of each side is again formed by the union
of two smaller ducts which come respectively from the anterior and
posterior part of the vitellarium; sometimes, however, it is formed
by the simultaneous union of numerous ducts, as in T'rist. ovale

(PI. XXITI, fig. 1). In Microcotyle truncata the paired yolk-ducts appear

to unite with each other at the very beginning and then to separate again

into two ducts similar to those of the other species (PI. II. fig. 1);
192 8. GOTO.

this, however, I conaeive to be due not to the actual union of the yolk-
ducts, but to the circumstance that the paired portion of the vagina is
exceedingly short. The paired ducts of the two sides finally unite
with each other, in most species in the median line of the body; but in
Diclidophora sessilis the point of union is displaced a little towards the
right side. In all the species the paired yolk-ducts form by their
union an enlargement, which during the period of reproductive activity
is usually swollen to a considerable size by the great quantity of
yolk-cells which it contains, and has received the name of ritedline
reservoir. In most genera this portion passes without any marked con-
striction into the contiguous parts; but in Hpibdella and Tristomum it is
usually spherical in form and is distinctly set off from the other parts.
In Onchocotyle and Hexacotyle also, it passes without any distinct demar-
cation into the anterior part of the yolk-ducts, but is distinctly
set off from the unpaired yolk-ducts to which it gives rise (PI. XV,
fig. 1). The vitelline reservoir must not be regarded as a permanent
organ, being observable only when it is filled with yolk-cells.

From the yolk-reservoir proceeds the unpaired yolk-duct. This
is usually much smaller than the terminal portions of the paired ducts,
and is therefore distinctly marked off from the reservoir. In most
species it either takes its rise on the ventral side of the reservoir or
proceeds from it directly backwards, and after a course of various
length according to the species finally opens into the oviduct. In
Hezacotyle, however, it proceeds laterally from the reservoir and unites
with the oviduct. In Calicotyle the unpaired yolk-duct is exceedingly
short, and in Monocotyle it is entirely wanting, the paired ducts open-
ing in this genus separately into the oviduct from either side.

Where the various genital ducts come to lie in the same
sagittal plane, the yolk-duct is generally situated ventrally to them,

but in Calicotyle, in which it opens into the seminal receptacle,
STUDIES ON ''THE ECTOPARASITIC TREMATODES OF JAPAN. 123

it occupies a position dorsal to the vagina.

The wall of the larger yolk-ducts, like that of the primary ones,
consists of a thin structureless membrane wholly destitute of nuclei.

Vacins—The vagina is very generally present in the iono-
genetic Trematodes ; so far as I have observed it is wanting only in
Oetocotyle and Diclidophora. Dieckhoff” indeed describes it in
Octobothrium lanceolatum ; but from his general description of this
species and especially from the structure of the posterior suckers and
of the genital organs as described by the same writer, I doubt whether
this species is to be included in either of the two above mentioned
genera as I shall define them in the systematic part of the present
paper. The vagina is paired either throughout its whole extent, or
in only its proximal part, or again it may be truly unpaired; in
most species it opens by its proximal end into the yolk-duct. In
Monocotyle, however, it opens directly into the oviduct at the same
level, and side by side, with the paired yolk-ducts, so that in this
genus three separate ducts come to open at the sume point into the
oviduct. In Calicotyle, again, the paired vaginal canals” unite with
each other in the median line of the body, and form a short unpaired
duct which then opens into the receptaculum seminis (which is in this
species nothing else than an enlarged portion of the oviduct) at a very
short distance from the opening of the unpaired yolk-duct.

Having thus given a general orientation I shall now proceed to
describe the vagina in different species.

As I have already stated elsewhere,” a truly paired vagina is
present in Calicotyle and Onchocotyle. In the latter genus the vaginal

openings lie on the ventral side of the body near the median line only

 

1). Dieckhoff—Beitrige zur Kenntniss der ectoparasitischen Trematoden. Archiv f.
Naturgeschichte, 57. Jahrg., 1. Bd., 1891. p. 264. /

2). By “ vaginal canal” I mean the canal into which the vaginal opening leads.

3). Centralblatt fir Bakteriol. u. Parasitenkunde, Bd. XIV, 1893. p. 798.
124 8. GOTO.

a few sections (each= 0.01 mm.) behind, and on either side of, the
genital pore (Pl. XV, fig. 1). The opening is ‘wholly naked, and
leads into a long canal, the vaginal canal, which proceeds just on
the inner side of, and parallel to, the intestinal trunk, and finally
opens into the fore end of the paired yolk-ducts. The vaginal
canals are at first nearly of a uniform: calibre, but very gradually
become larger as they approach the yolk-ducts. In Calicotyle the
vaginal openings lie nearly midway between the median line and the
lateral margins of the body, nearly on the same level with the middle
of the uterus. The vaginal canals, the terminal halves of which have
a smaller calibre than the others, proceed at right angles to the long
axis of the body towards the median line, where they unite with each
other, and form a single duct, which then opens into the seminal
receptacle from the antero-dorsal side (PI. XIX, fig. 1).

In all the species of Microcotyle and Azine I have examined, the
vaginal opening is single, and is situated in the median line on the
dorsal side of the body. In most species of Microcotyle the vagina is
wholly naked, but in Mic. reticuluta (PI. V, fig. 5) and in Azine
heterocercu and A. aberrans (PI. VII, figs. 5 & 6; Pl. VILL, fig. 4) its
cavity is armed with numerous, conical, chitinous spines, which are seen
in sections to be formed by simple elevations and transformation of the
direct continuation of the investing membrane of the body (PI. V,
fig. 5; Pl. VIII, fig. 4). Moreover in all these species the mesen-
chyma around the vagina is modified into a very compact connective
tissue consisting of closely reticulated fibres, the interspaces of which are
filled with an exceedingly refractive substance, which remains wholly
unstained either with borax-carmin or haematoxylin (PI. V, fig. 5 ;
Pl. VII, fig. 5; Pl. VIII, fig. 4). Again, in most species of Micro-
cotyle the vaginal opening leads into a single median canal of different

length according to the species, which usually proceeds straight back-
STUDIES ON THE ECY'OPARASITIC TREMATODES OF JAPAN. 125

wards, but sometimes makes more or less windings (PI. II, fig. 5).
In M. fusiformis (Pl. I, fig. 3) the vagina is but slightly enlarged,
but in DM. truncata it assumes the shape of a goblet with its short neck
directed towards the front end of the body (PI. IJ, fig. 1). In the
latter species it communicates by an exceedingly short, paired canal
with either of the paired yolk-ducts; while in most other species the
single vaginal canal proceeds backward for a greater or less distance
along the median line of the body, and then divides right and left
into two branches, the paired vaginal canals, which finally open each
into the paired yolk-duct of the corresponding side, just as in Oncho-
cotyle. In Mf. sciaenae the vagina immediately divides into two canals,
which, after proceeding backwards for a short distance, unite with
each other in the median line of the body between the vas deferens on
the dorsal and the uterus on the ventral side, then again separate from
each other, and proceed backwards for a short distance, and finally
open into the paired yolk-ducts (PI. I, fig. 6). In laine heterocerca
also, the vagina divides immediately into the paired canals; but in
this species these remain separate throughout their whole lengths, and
proceeding backwards just on the inner’ side of the main trunks of the
intestine, finally become continuous with the yolk-ducts” (Pl. VII,
fig. 1). There is in this species another opening a little behind the
vagina (Pl. VIII, fig. 3, 2), which leads into «a blind cavity, the
internal surface of which is armed with low, conical spines like those
of the vagina; but although I have directed special attention to the
point I have not been able to ohserve any connection with the genital
organs, and am perfectly at a loss what function to attribute to it.
In Aine aberrans the vaginal canal is single throughout its extent,

and opens into the fore end of the unpaired yolk-ducts. In Avxine

 

1). The boundary between the vaginal canal and the yolk-duct is marked in the figure
with an asterisk. ;
126 8. GOTO.

triangularis I have not been able to observe the vagina, since I had
only a single specimen of this species ; but its presence is scarcely to
be doubted.

In Hexactyle also, the vagina opens to the exterior on the dorsal
side of the body in the median line, a short distance behind the com-
mon genital pore on the ventral side (Pl. XIII, figs. 1 & 4; Pl. XII,
fig. 6); and its internal surface is armed with numerous chitinous,
conical’ teeth similar to those of Aine (Pl. XII, fig. 6; Pl. XIV,
fig. 3). The connective tissue around it presents a very different aspect
from that of the remaining parts of the body, and is exceedingly com-
pact and refractive. It is somewhat yellowish in the fresh state, and
remains totally unstained with carmin or haematoxylin. In fact it is
of the same nature as the tissue that surrounds the vagina in Axine
and the terminal portion of the vas deferens in Microtyle reticulata and
Onchocotyle ; but it is far more compact, so that it appears as if it were
somewhat chitinous. In the genus under consideration the vagina is
surrounded by numerous, circular muscular fibres; moreover from the
chitinous cuticle that lines its cavity numerous muscular fibres take
rise and radiating in all directions and ramifying each into a
number of fibres, are at last inserted into the investing membrane
of the body (PI. XIV, fig. 3). These muscular fibres are evidently
the retractores vaginae. ‘The vagina soon divides into two canals, the
canales vaginales, which, as in the cases already described, proceed on
the inner side of, and parallel to, the trunks of the intestine, and open
into the paired yolk-ducts. In accordance with the asymmetry in
this genus of ‘the yolk-ducts of the two sides, already mentioned, the
vaginal canal of the left side is longer than that of the right (Pl. XIII,
fies. 1 & 4; PI. XIV, figs. 1 & 7).

From the above description the paired origin of the vagina in

Microcotyle, Axine, and Hexacotyle is, I believe, beyond question.
STUDIES ON THE ECTOPARASITIC TREMATODES OF JAPAN. 127

In Aonocotyle, Tristomum, and Epibdella the vagina is present
only on the left side of the body, and opens to the exterior on
the ventral surface. In Monocotyle the vaginal opening is situated
close to the left trunk of the intestine, about midway between the
porus genitalis communis and the anterior end of the ovary, and is sur-
rounded by a compact tissue exactly similar to that described in [Texaco-
tle; but there are no muscular fibres (PI. XVII, fig. 1). It leads
into a short canal which soon opens into a large spherical cavity, the
receptaculum seminis; from the other end of this a canal proceeds
backwards, and opens into the oviduct at the point where the
latter receives the paired yolk-ducts. In Tristomum the vaginal open-
ing is situated a short distance behind the opening of the genital atrium,
in some species more towards the lateral margin, but in others nearer
the middle line. In most species the opening is surrounded more or
less with the compact tissue so often mentioned in other genera ; but
this is in most species very inconspicuous. ‘The vaginal canal makes
in this genus numerous complicated windings in its course ;
and at various distances from the external opening according to
the species it is swollen to a considerable size and is filled with
sperm mass—forming the receptaculum seminis. Beyond this the
vaginal canal contracts into a very fine canal, which then opens in all
the species I have observed into the yolk reservoir (Pl. XXI, fig. 8;
Pl. XXII, fig. 5; Pl. XXIII, fig. 8; Pl. AAV, figs. 3, 8, & 8), and
not into the oviduct as is stated by Monticelli” to be the case in
Trist. uncinatum.

From the above it is evident that the seminal receptacle in

Tristomum and Monocotyle is nothing else than a part of the vaginal

 

1). Monticelli—Tristomum uncinatum, n. sp. Boll. d. Soc. di. Nat. in Napoli. An. III, fase.
II, 1889.

i
128 S. GOTO.

canal swollen by the sperm mass which it contains ; and is therefore
subject to considerable variations in size.

In Epibdella the position of the external opening of the vagina
ix very similar to that in Tristomum: in E. Ishikawae it is only a short
distance behind the common genital pore, but in J. orata it is situated
about midway between the posterior end of the pharynx and the
anterior end of the ovary, a little internally to the left intestinal
trunk, and is surrounded by the compact, refractive tissue already men-
tioned in describing other genera ’(P]. XX VII, figs. 1, 8,4,& 6). In F.
Ishikawae the vaginal canal makes numerous windings in its course,
and finally opens into the yolk-reservoir ; but in J. ovata it is nearly
straight, and after a short course opens into the yolk-reservoir as in
the other species. In this genus I have not observed any receptaculum
seminis, but this may possibly be owing to the absence of any sperm
mass at the particular time or in the particular specimens [ have
examined. Von Linstow” does not mention any vagina in Phyl-
line Hendorffi, bat what he describes as the receptaculum seminis is
probably nothing else than the proximal end of the vaginal canal, com-
parable to the seminal receptacle of Tristomum. In Phyllonella soleae
also, the vagina has not been described; hut to judge from the figure of
the worm given by Cunningham,” I believe it is present likewise
in this species. ‘The convoluted dark tube drawn by that writer on the
left side (right side of figure) of the yolk-reservoir in fact represents,
in my opinion, the proximal portion of the vaginal canal.

The wall of the vaginal canal consists in most species of a thin,
refractive membrane similar to that of the larger yolk-ducts ; and

T have never observed any nuclei in it. In Calicotyle, however, the

 

1). V. Linstow—Beitrag zur Anatomie von Phylline Hendorffii. Archiy f. mik. Anatomie.
Bd. 33, 1889, p. 173.

2). J.T. Cunningham—A Treatise on the Common Sole, 1890. p. 93.
STUDIES ON THE ECTOPARASITIC TREMATODES OF JAPAN. 129

membranous wall is exceedingly thick, and its internal surface is
uniformly covered with stout cilia, The terminal half of the vaginal
canal is, in this genus, surrounded by numerous unicellular glands, the
vaginal glands. Since I had only a single specimen of the worm and
was therefore compelled to pass and repass it through absolute alcohol,
clove oil, and turpentine in order to cut it into serial sections after a
detailed examination in toto, 1 am not able to state anything definite
as to the histological character of these glands ; but each gland is a
goblet-shaped cell with a short neck and with a vesicular nucleus
near its larger end, which usually encloses a single, small nucleolus
(Pl. XIX, figs. 1 & 12). These glandular cells are in most places
arranged in a single layer around the vaginal canal, but are in other
places also arranged in two layers. Wierzejski” states that in C.
Kroyeri the vaginal canal is muscular, but in the species I have
observed its wall is simply membranous. In Onchocotyle also the in-
ternal surface of the vaginal canal is covered with cilia, which are, how-
ever, finer and shorter than those of Calicatyle (Pl. XV, fig. 10). I have
besides observed in the former species that in the hinder portion
there is often on the inner surface of the vaginal canal a thin layer of
granular substance very similar to that observed in the vas deferens. [
have therefore been led to suspect whether the irregular polygonal or
goblet-shaped cells drawn in fig. 8, Pl. XVI, on the ventral side of the
vaginal canal and which were at first regarded by me as the prostate
glands be not in reality the vaginal glands ; but hitherto I have not
been able to find out any ducts. In all the other species I have not
observed any glandular cells around the vagina.

In many specimens collected during the summer season the
vagina was found filled with spermatozoa. I have observed this in,

Microcotyle, Axine, and Tristomum; and since, as I have said in my

 

1). Wierzejski—l. c. p. 558.
130 8. GOTO.

paper on Diplozoon, the yolk-cells are during this season almost con-
tinuously poured down the yolk-ducts, the spermatozoa in the vagina
can not but have come from another individual. Often indeed the
yolk-ducts were also filled entirely with spermatozoa instead of with
yolk-cells. Therefore there can scarcely be any doubt that the vagina
really serves as such in these forms, and the same is in all probability.
true of other species.

CANALIS GENITO-INTESTINALIS—I have proposed” to substitute
this name for the cne already in vogue, canalis ritello-intestmalis, on
the ground that in many, indeed in most, species it has no direct
connection with the yolk-duct. This name, which was first used
by the editor of the “ American Naturalist’’,? is of wider applica-
tion and will cover all those cases which may be brought to light
by future investigations, provided only that the canal connects the in-
testine with any one part of the genital system. The genito-intestinal
canal was first observed in its true relation by Ijima® and although
the connection with the intestine was denied or questioned by some
writers his observation was afterwards confirmed and extended by
Dieckhoff,” R. Wright and Macallum® and by the present
writer,” and in this paper further cases will be brought forward.

Among the genera described in this paper this canal is absent in

Tristomum, Epibdella, Monocotyle, and Calicotyle, but is present in all

 

1). Goto—Der Laurer’sche Kanal und die Scheide. Centralblatt f. Bakteriol. u. Parasiten-
kunde, Bd. XTV, 1893. p. 793.

2). Vol. XXV, 1891. p. 665.

3). Ijima—Ueber den Zusainmenhang des Eileiters mit dem Verdauungscanal bei gewissen
Polystomeen. Zool. Anzeig., VII, 1834. p. 635. :

4). Dieckhoff—l. c.
5). BR. Wright and Macallum—Sphyranura Osleri. Journal of Morphology, Vol. 1, 1887.

6). Goto—This Journal, Vol. IV, 1890. p. 185.
» On the Connecting Canal between the Oviduct and the Intestine in some
Monogen. Trematodes. Zoolog. Anzeig., XIV, 1891. p. 103.
STUDIES ON THE ECTOPARASITIC TREMATODES OF JAPAN. 131

the others. In Microcotyle and Azxine it arises from the -oviduct
opposite, or ata short distance from, the point where this receives
the unpaired yolk-duct, in some species more towards the ovary and
in others more away from it; it then proceeds toward the right
of the body and also more or less forwards, and finally opens
into the right trunk of the intestine. In Diclidophora (Pl. X,
figs. 1, 5, & 9) it does nearly the same, but its origin is always
at a short distance towards the ovary from the point of union
of the unpaired yolk-duct with the oviduct. In Octocotyle the
genito-intestinal canal opens into the oviduct side by side with
the unpaired yolk-duct, proceeds on the right side far towards
the anterior part of the body, and finally opens into the right
intestinal trunk nearly on the same level with the point of union
of the paired yolk-ducts (PI. IX, figs. 1,7, &11). In all the
genera hitherto mentioned the canal is almost straight or makes
only a slight winding or two. In Onchocotyle it arises trom:
the oviduct at the point where this bends backwards towards
the ootyp and where from one side the neck of the seminal
receptacle and from the other the median yolk-duct opens into
the oviduct. It then proceeds for some distance towards the right
side of the body, then bends backwards, making a few additional
windings on the way, and opens at last into the intestinal trunk
of the right side. It is, as I have stated elsewhere, the Laurer’s
canal of Taschenberg,” which he represents as being on the
left side of the body and as opening to the exterior on the ventral
surface. But I have carefully followed it in serial sections and could
distinctly perceive its opening into the intestine; while as to its
position in the body, one must not rely on the posterior suckers for

orientation, in this case ; for, as I have already stated, these are situat-

 

1). Taschenberg— Weitere Beitriige, p. 22.
132 8. GOTO.

ed on the side turned towards the dorsum, so that when the observer
looks at the worm with the suckers turned towards him he has before
him the dorsal side of the body, whereas in other species the ventral
side would under the same circumstance be turned towards him. I
therefore believe that Taschenberg was misled in his orientation by
the abnormal position of the suckers, and this is the more probable
because he seems to have had but little recourse to serial sections.

In Hexacotyle grossa the origin of the genito-intestinal canal from
the oviduct is also near the opening of the yolk-duct a little towards
the ovary. Proceeding a very short distance forwards it undergoes
a rather sudden and somewhat club-shaped enlargement which, since
it contains sperm mass in its interior, may well be called recepta-
culum seminis. From its opposite end arises a much convoluted small
canal, which proceeds forwards and towards the right side of the
body, and finally opens into the intestine (P]. XIV, fig. 7). In Heaa-
cotyle acuta the genito-intestinal canal opens into the oviduct side by
side with the unpaired yolk-duct, and, in most specimens, was soon
enlarged into the receptaculum seminis, so that the latter was connected
with the oviduct by an exceedingly short canal. The general form of
the seminal receptacle in this species is similar to that of the other
species, but its outline is in most cases irregularly wavy, and the
whole organ usually assumes such a position that its long axis is
directed obliquely to the long axis of the body. The anterior end of
the seminal receptacle gives rise to a small canal of variable length,
which, proceeding a little forwards when the receptacle is small or a
little backwards when it is large, and making some convolutions on
the way, finally opens into the intestine (PI. XIV, fig. 4). In both
species of Hexacotyle the seminal receptacle is situated on the ventral
side of the ovary.

From the above description it will be evident that the receptaculum
STUDIES ON THE ECTOPARASITIC TREMATODES OF JAPAN. 133

seminis of Hexacotyle is nothing but a part of the genito-intestinal
canal, just as in Tristomum it is a part of the vaginal canal. ‘The small-
ness of the seminal receptacle and the greater length of the canal pro-
ceeding from it towards the intestine observed in Hezacotyle grossa as
compared with H. acuta is perhaps due to the fact that the sperm mass
was comparatively small in the specimens of the former examined;
for in H. acuta I have observed the seminal receptacle to vary con-
siderably in size, and the small canal to vary in length; the size of the
receptacle and the length of the canal being complementary, the
receptacle being formed inferentially, at the expense of the canal.
The fact already mentioned that in H. acuta the small canal proceeds
from the seminal receptacle sometimes in one direction and some-
times in the other also points to the same interdependence; the
cramming of the receptacle with sperm mass and its consequent
lengthening causing displacement of the genito-intestinal canal.

The wall of the canalis genito-intestinalis is formed of a thin,
structureless membrane, whose inner surface is uniformly covered with
fine cilia, the motion of which is distinctly observable in living speci-
mens under the microscope. It is wholly destitute of nuclei. In
Microcotyle and Axine the wall is thickened circularly at short intervals
just like the wall of the Laurer’s canal in some species of Distomum
described by Poirier;” only the thickenings are here much smaller
and nearer one another. In oblique or longitudinal sections of the
canal these thickenings look somewhat like septa, but that they.are
not really such is very clear on attentive observation. In a surface
view these thickenings appear like circular muscular fibres.

As to the opening of the canal into the intestine, it is to be noted

that it is exceedingly small and in most cases never appears in more

 

1). Poirier—l. c., p. 577.
134 S. GOTO.

than two consecutive sections (each=0.01 mm). Dieckhoff? has
described in Polystomum integerrimum a sort of valvular mechanism at
the opening of the canal; I have not myself observed the canal
running any distance into the intestine, but have found it always to

ov, and to

contract to an exceedingly small size just before opening,

communicate with the intestine by a minute pore which will be at once
closed by pressure from within the intestine.

The homology of the genito-intestinal canal will be discussed later
on under ‘ General Considerations.’

ATRIUM GENITALE—I shall adopt this name for the cavity into
which, in many genera, the vas deferens and the uterus, or else the
former alone, open, whether this cavity be large and open to
the exterior by a small pore, or merely a shallow invagination of the
general surface of the body. ‘This cavity has been more generally
known as the genital cloaca; but since the vas deferens only in some
cases opens into it I prefer the above name for it. It is very generally
present not only in the Monogenea but also in the distomes; and in
some cases what has been described as the penis or “ Cirrusbeutel”’
(tasca del pene, poche de cirrhe) is to be culled more correctly the
genital atrium, as will become clear as we proceed.

Among the species that I have hitherto examined the genital
atrium is absent only in Onchocotyle spinacis, in which the vas deferens
opens, as already stated, directly into the terminal part of the uterus
(PI. XVI, fig. 7). This part might perhaps be considered by some as
the genital atrium; but as may be seen from the figure just referred to,
its internal surface is covered up to its very opening with stout cilia
exactly similar to those of the part of the uterus posterior to it ; and
this fact should prove beyond doubt that the genital atrium is

totally wanting in this species. Moreover it seems to me that the

 

1). Dieckhoff—i. c. p. 248.
STUDIES ON THE ECTOPARASITIC TREMATODES OF JAPAN. 135

genital atrium should be regarded as the invagination of a portion of
the surface of the body. We have as yet no adequate embryological
proof? on this point ; but the fact that the investing membrane of
the body isin many cases directly continued, at least for a certain
distance, into the atrium, and the many gradations in form of
this chamber from that of a mere pit to that of a deep and spacious

cavity seem to me to Jend very.strong support to this view—a view
oa

 

which has recently found expression from another side”

The genital atrium is most developed and presents the most
varied formsin Jficrocotyle. In this genus it is a deep cave-like cavity,
into which the vas deferens and the uterus open, and communicates
with the exterior by means of a minute opening, the porus genitalis com-
munis. Its inner surface is lined by a thin but deeply staining mem-
brane which in sections is seen to be formed by the direct continuation
and gradual thinning of the investing membrane of the body (Pls. V,
& VI), and is covered in all the species with hollow, chitinous spines.
In M. elegans (P1. V, fig. 2.) it is a somewhat reniform cavity, with
the part corresponding to the hilus directed obliquely forwards and
towards the ventral side, into which the uterus opens close to the ex-
ternal pore, while the vas deferens opens more on the dorsal side almost

opposite the hilus. The conical spines which are mainly confined to

 

1). The results obtained by Voeltzkow in Aspidogaster conchicola (Wiirzburger Arbei-
ten, Bd. 8, 1888, p. 279) do not seem to me to decide the question. According to this naturalist
the “ Penisschlauch’’ and the “ Vulva” arise “als solider, von der Haut am Anfang des
Halses, schief nach hinten und oben aufsteigender...... Zapfen an.” Referring to the figure it
seems to me that the solid mass of cells which becomes afterwards the “ Penisschlanch ” and
the “ Vulva” is not of an ectodermal origin but mesodermal ; for the true ectoderm is already
in this stage transformed into a membrane. If I may put my own interpretation on the figure
of another, the solid mass of cells above referred to is probably differentiated into the peculiar
connective tissue that constitutes the penis; and in this case the lining of the “‘ Penisschlanch”
would alone be derived from the ectoderm.

2). Monticelli—Primo contributo di osservazioni sui Distomidi (Studii sui Trematodi endo-
parassiti), p. 86. Spengel’s Zool. Jahrbiicher, III. Suppl., 1893.
136 8. GOTO.

the anterior half of the atrium are comparatively short. I have observ-
ed only a few spines on the posterior face of the atrium between the
uterus and the vas deferens; and these were mostly a little longer than
those of the anterior and dorsal sides. In M. fusiformis (Pl. V, fig. 1)
the genital atrium is considerably elongated in the dorso-ventral direc-
tion of the body and may be distinguished into two portions, a :
ventral, larger portion communicating with the exterior and a
dorsal, narrower portion. The larger, ventral portion receives close to
its opening the uterus and at its dorsal end the vas deferens. The
narrower, dorsal portion merely extends dorsad towards the oesophagus
and there ends blindly, receiving no duct. ‘The spines which are
generally just perceptibly shorter than those of M. elegans are mostly
confined to the anterior face of the atrium but are also present on the
posterior face for a very short distance continuous with the anterior face.
The wall of the atrium is raised a little around the vas deferens, making
it open on a blunt papilla (P1.V, fig. 1). In M. caudata (PI. V, fig. 3)
again, the genital atrium may be distinguished into two portions, a
ventral which in this case is narrower, and a dorsal portion which
is triangular in sagittal section and whose surface is covered with
Jong, slightly recurved spines. The ventral portion receives, as in other
species, the uterus near its external opening ; and at its postero-dorsal
corner it communicates with a cup-shaped accessory cavity, into which
the vas deferens opens at the top of a comparatively large, teat-shaped
papilla, In Af. sebastis (Pl. VI, fig. 1) the main cavity of the genital
atrium proceeds obliquely forwards from its external opening, and
ends with a short bifurcation, so that it is somewhat Y-shaped. The
spines are long and slightly recurved, and are present along the
whole anterior and dorsal surfaces of the atrium; but these are divided
into two groups separated from each other by a short space, in which

the spines are totally absent. As in the preceding species the vas
STUDIES ON THE ECTOPARASITIC TREMATODES OF JAPAN. 137

deferens opens at the top of a papilla, which however is of the
shape of a truncated cone in this case, and projects into a cup-shaped

accessory cavity of the genital atrium. In some specimens I have
observed a layer of coarsely granular substance covering the in-

ternal surface of the vas deferens as well as the surface of the
truncate papilla, and of the cavity into which it projects; this is, in
my opinion, the secretory product of the prostate glands. In
M. chiri (Pl. V, fig. 4) the genital atrium is very narrow and is
elongated in the dorso-ventral direction of the body, and the uterus
and vas deferens open into it close to each other. Its internal surface
is lined by an exceedingly thin membrane, and the spines, which are
very similar to those already described as being present in the terminal
part of the vas deferens in Jl. reticulata, are in this species attached to
the internal face of a cup-shaped organ at the dorsal end of the atrium,
which will be described afterwards. In WM. sciaene, again, the
genital atrium is an elongated cavity directed obliquely in an
antero-posterior direction and opening outwards by means of a very
small pore (Pl. VI, fig. 2). The chitinous spines are of two forms,
the shorter and the longer, arranged in two circular sets around
-the middle portion of the atrium; the shorter ones, which are hook-
shaped, being imbedded for the greater part of their lengths in the
substance of the wall of the cylindrical organ afterwards to be describ-
ed, with only their hooked ends projecting into the atrium. The
spines of the other set are much longer, and are slightly curved twice
in opposite directions; only their terminal parts project into the atrium,
and they are provided with a special set of muscular fibres, probably to
be regarded as belonging to the sets of dorso-ventral fibres which take
their origin from them and which, proceeding backwards and towards
the dorsum are inserted into the investing membrane on the dorsal side

of the body (Pl. VI, fig. 2). The uterus opens into the atrium near
138 8. GOTO..

its external pore, while the vas deferens opens between the two sets
of chitinous armature just described.

Owing to scantiness of specimens I have not been able to
make sagittal sections of Jf. truncata and M. reticulata ; but comparing
the preparations in toto of these species with those of others, the pre-
sence of the genital atrium can hardly be doubted, and the general
disposition of its parts is, I believe, similar to that found-in other
species. In M. truncata the chitinous armature of the atrium consists
of twenty long, hollow rods, slightly curved twice in opposite direc-
tions (PI. II, fig. 2). ‘They are elliptical in cross-section (fig. 2, ¢),
and although on a surface view they appeared of unequul lengths, as
represented in the figure, I believe this is owing to the fact that some
were looked at more obliquely than others. They are arranged in a
circle, but the series is broken in the median line on the dorsal side.

The genital atrium of M. reticulata and Axine aberrans are very
similar to each other, the internal surface being in both the species
covered with spines, and the mesenchyma around the atrium being
transformed into the refractive connective tissue so often mentioned
already. The form of the spines are, however, different in the two
species, those of A. aberrans being simply conical and slightly curved,
while those of M. reticulata are exactly similar to those that are present
in the terminal portion of its vas deferens, and consists, as already
described, of a hemispherical basal and a straight, spinous, distal
portion (PI. V, fig. 6). In Axine heterocerca the genital atrium is an
irregular, tolerably spacious cavity, and is surrounded by a refractive,
fibrous connective tissue somewhat similar to that just mentioned
in M. reticulata. Unlike that, however, it stains but slightly
(PI. VIII, fig. 3), and in fact its occurrence here appears to me
as a step towards the formation from the usual form of the mes-

enchyma of such refractive tissue as has been described above in
STUDIES ON THE ECTOPARASITIC TREMATODES OF JAPAN. 139

many species of Microcotyle. Of Axine triangularis. (Pl. VII, fig. 7) I
have had only a single specimen, and therefore could not make sagittal
sections of it; but judging from analogy and from a comparison of pre-
parations of it in toto with those of others, I believe the genital atrium
of this species to be very nearly similar to that of M. chiri already
described (PI. V, fig. 4). There is a hemispherical organ on the
dorsal side of the atrium exactly similar in form to that of M. chiri,
and the internal surface of which is covered with slightly recurved,
conical spines (PJ. VII, figs. 7 & 8). I have not been able to see
distinctly the opening of the vas deferens; but I believe it lies as
in M. chirt, and not therefore in the hemispherical organ—again
relying in so doing on analogy.

In Octocotyle the genital atrium is somewhat vase-shaped, with a
short narrow neck which opens to the exterior. It receives at one of its
sides the uterus, and the chitinous spines of the penis project from the
base of its cavity (PI. LX, fig. 12). In Diclidophora, on the other hand,
the genital atrium has a wide opening to the exterior, almost of an equal
diameter with the atrium itself (PI. XI, fig. 4). Tt sends out backwards
a tubular prolongation which becomes continuous with the uterus, the
boundary line between the two being in this case especially hard to deter-
mine. On the dorsal side, the main cavity of the atrium communi-
cates by means of a minute pore with asomewhat cone-shaped side-cavity,
into which the chitinous hooks of the penis project (PI. XI, fig. 4). In
Hexacotyle the genital atrium communicates with the exterior by
means of a short, tubular canal formed by the thickening of the lips of
its external opening (PJ. XII, fig. 6). As a whole it is a tolerably
spacious cavity; but all its central part is occupied by a large conical
popilla—the homologue of the penis—on the top of which opens the vas
deferens. In this genus the direct continuation of the external invest-

ing membrane of the body into the genital atrium can ke observed
140 S. GOTO.

very distinctly (PJ. XII, fig. 6); and on the posterior surface of the
penis the membrane seems to be changed to a certain extent into a
chitinous nature; for here it remains wholly unstained with haema-
toxylin and has all the optical properties of a chitinous substance. In
Calicotyle (PI. XIX, fig. 7) the atrium genitale is reduced to a very
small cavity communicating with the exterior by a comparatively
large pore, and the greater part of it forms merely a sheath for the ex-
ceedingly long, chitinous penis already described. In Monocotyle it is
more spacious and opens to the exterior by a somewhat small pore;
but the greater part of its cavity is almost completely taken up by the
penis (PI. XVIII, fig. 3). Theexternal membrane of the body is also
in this case clearly seen to be continued into the genital atrium; here,
however, it becomes very much thinner and compact, and loses its
granular character.

In all the species hitherto considered the genital atrium receives
both the vas deferens and the uterus, so that it may without any
impropriety be called the genital cloaca; but this is not the case in
some species of the next genus as will presently be seen.

In Tristomum as well as in Epibdella the genital atrium is
an elongated, more or less tubular cavity with a very small
external opening. Into it the penis projects; and in most species
the uterus opens into it, but in some species, as in JT. rotundum
and T. ovale, this opens independently to the exterior, so that the
cavity can not be called the genital cloaca. In Epibdella ovata it is for
the greater part of its length tubular, but is enlarged towards its ends
to make room for the penis (Pl. XXVI, fig. 6). The uterus opens
into it between the tubular and the enlarged portion. In E. Ishikawae
the whole atrium is more or less tubular in accordance with the
greater length of the penis; and the uterus opens on the top of a low,
conical papilla, a short distance behind the middle of the length of
STUDIES ON THE ECTOPARASITIC TREMATODES OF JAPAN. 141

the atrium; so that here the atrium is locally enlarged and sends out
a lateral evagination on one side (P]. XXVI, fig. 3). In both the
species of Epibdella above mentioned the genital atrium extends up to
the very base of the penis, so that this projects wholly into it. In
Tristomum, on the other hand, the basal portion of the penis lies imbed-
ded in the mesenchyma, so that the genital atrium forms a sheath only
for the terminal portion of the penis. Its form is very varied
in different species; but always consists of a more or less tubular distal
portion of various length and a more enlarged proximal portion
forming the sheath for the penis. The internal surface is lined by a
thin membrane, which is the direct continuation of the external mem-
brane of the body on one side and of the investing membrane of the
penis on the other. Where the uterus opens into the genital atrium,
its opening lies at various distances from the external atrial pore
in different species, being in some situated close to it, while in others
it is far removed towards the bottom of the atrium (PI. XXI, fig. 8;
Pl. XXII, figs. 2 & 4; PL XXIII, fig. 8; Pl. XXV, figs. 3,
8, & 9).

The genital atrium of Tristomum and Epiblella is wholly destitute
of. any chitinous armature.

In most species of Axine and Microcotyle the conical spines that
arm the genital atrium are distinctly seen to be formed by the eleva-
tion and transformation of the lining membrane (PI. V, fig. 8; Pl. VI,
fig. 1; also in figs. 1 & 2, Pl. V, though not clearly shown in the
figures). These spines are, as already stated, hollow, and the internal
cavity is filled in most species with a deeply staining, homogeneous
substance which is directly continuous with the basement membrane
and is indistinguishable from it by. optical characters. In M. chiri
(PLY, dig: 4), M. reticulata (PI. V, fig. 6), and M. sciaenae (PI. VI,
fig. 2) the cavity in the spines is reduced to very small dimensions
142 8. GOTO.

appearing only as a dark line in optic sections, and is closed towards
the base of the spines. In these species the spines either merely
rest on the lining membrane or are imbedded in the connective tissue.
In IL chirt the spines rest on the internal surface of the hemispherical
organ already referred to, and lie mostly imbedded in the mesenchy-
ma, with only their tips projecting into the genital atrium.

Let us now turn our attention to the mass of connective tissue of
peculiar appearance so often referred to already, which is present in
many species around the genital atrium, and which extends in some
species for a certain distance around the vas deferens.

In Microcotyle caudata (Pl. V, fig. 3) and M. fusiformis (Pl. V,
fig. 1) the mesenchyma on the antero-dorsal side of the genital atrium
presents an unusual appearance, and consists of compact, fibrous con-
nective tissue wholly destitute of nuclei, although these are very nu-
merous around it in M. caudata. In M. fusiformis this mass of connect-
ive tissue is of spherical form, and seems but little different from the
tissue around, the difference lying mainly in its greater compactness;
but in M. caudata its meshes are filled with a refractive, granular
substance, somewhat yellowish in the fresh state and more decidedly
yellow after treatment with borax-carmin. The granulation diminishes
towards the genital atrium, close to which it becomes exceedingly
fine. In M. elegans (PI. V, fig. 2) and M. -sebasts (Pl. VI, fig. 1)
there is a kidney-shaped mass of connective tissue wholly destitute
of nuclei, and very refractive—the refraction. being caused by
a perfectly homogeneous substance filling the meshes of the con-
nective tissue, the fibres of which are directly continuous with
those of the surrounding mesenchyma. In WM. elegans there are some
coarse granulations close to the genital atrium at the place correspond-
ing to the hilus of the kidney. In this species-the kidney-shaped

mass just described is pretty distinctly separated from the surrounding
STUDIES ON THE ECTOPARASITIC TREMATODES OF JAPAN. 143

tissue; while in M. sebastis the transition is more gradual. , Moreover,
in the latter species there are numerous large, vesicular nuclei close
around the mass, each of which is surrounded by a sparse quantity of
finely granular protoplasm gradually fading away towards the periphery,
just asin M. caudata. In M. chiri (Pl. V, fig. 4) and M. sciaenae (Pl. VI,
fe

g. 2) there is at the dorsal end of the genital atrium a cup-shaped or

bag-shaped organ, the wall of which is completely set off from the
surrounding tissue by a membrane, and is composed of refractive,
prismatic fibres exactly similar in optic properties to the fibres that
have been described in the suckers of Axine, Microcotyle, Octocotyle, and
some other genera. In M. chit this organ is, as already mentioned,
hemispherical in shape, and is separated from the cavity of the genital
atrium by a layer of connective tissue ‘ moreover, the external limiting
membrane of the organ reveals, on careful examination, on its outer
side a transition of its substance into’ the fibrous connective tissue
around. In MM. sciaenae it is cylindrical in shape, and appears
U-shaped in longitudinal sections, and forms the wall of the
posterior part of the genital atrium. [or reasons already stated
I am not able to make any definite statement on this head
concerning Jf. truncata and MM. reticulata ; but the latter species
seems to resemble closely M. sebastis in this respect ; while in the
former species the compact, refractive mass of connective tissue is
more elongated in form. In Avine the compact connective tissue
already described around the terminal portion of the vas deferens is
continued on around the genital atrium.

A genital atrium similar to those above described in most species
of Microcotyle seems, to judge from the figures and description of
Leuckart,” to be present also in Distomum heterophyes. As in this

endoparasite, so in Microcotyle I believe the genital atrium can be

 

1). Leuckart—Die Parasiten des Menschen. To. Aufl, p. 401 et infra.
lit 8. GOTO.

evaginated, and the spines serve to assist the act of copulation.

After what have been said above I believe it is hardly necessary
to point out that the description of the “Cirrus” by Lorenz” in
Axine belones seems to me not to correspond to the actual relation of
things. I also venture to believe that what has been described by the
same writer as the male genital opening in Microcotyle mormyri is in
reality the opening of the genital atrium, and the assumed female pore
to be the opening of the uterus not to the exterior but into the genital
atrium.

The spines that are present on the internal surface of the genital
atrium in Microcotyle and Axine I shall call atrial spines to distinguish
them from the penis spines or hooks of Octocotyle and Diclidophora
and from the tubular chitinous penis of Calicotyle and Monocotyle.

10. General Considerations and Comparison of Results.

I shall now add, partly by way of recapitulation, some general
considerations; and in the first place I shall discuss—

1. The Nature of those prismatic, refractiwe Fibres which constitute the
Wall of the Suckers of Axine, Microcotyle, Octocotyle, Diclidophora, Hexa-
cotyle and Onchocotyle. ‘These fibres have been spoken of by most writers
simply as muscular fibres; the only exception being, so faras I know,
Wright and Macallum, who say,” “Instead of the substance of
the sucker being formed of muscular fibres disposed in three directions,
and capable of modifying the shape of the cavity, as in the distomes,
it is not possessed of contractility in Sphyranura (and probably in
Polystomum), and is formed of prismatic fibres, rather of a supportive
than of a muscular character, arranged perpendicularly between the

concave and convex limiting membranes of the sucker.’ My observa-

 

1). Lorenz—l. c. pp. 14 & 25.
2). Wright & Macallum—l. c. p. 12.
STUDIES ON THE ECTOPARASITIC TREMATODES OF JAPAN. 145

tions have led me to the same conclusion. I have indeed no positive
proof of the non-contractile nature of these fibres; but the indirect
evidence which I shall here advance seems to me, when duly con-
sidered, too strong to be resisted. :
In the first place, the fibres under question are different from the
ordinary muscular fibres of the body and from those of the suckers of
the Tristomidae and the Monocotylidae, as well as from those of the
anterior sucker of Onchocotyle, both in optical characters and in
reaction towards staining fluids. ‘Thus, these fibres are in the fresh
state slightly yellowish in colour and are less refractive than the mus-
cular fibres; and while the latter stain with hematoxylin usually well,
though not deeply, the former remain in most cases totally unstained.
There are indeed cases, as in Hesacotyle, in which the fibres of the
suckers stain slightly; but they then always stain more weakly
than the muscular fibres. They seem also to have a greater affinity
for colouring substances when the worm has been preserved some time
after its death, and therefore presumably after some post mortem change
has set in, as well as in those specimens which have been kept in
alcohol for a long time”. But in nearly all cases the differences in the
two respects above specified—refrangibility and reaction towards
colouring fluids—are enough to impress one with the idea that the
fibres under question must be very different in their nature from the
muscular fibres that are found in other parts of the body. For instance,
a glance at fig. 4, Pl. XII, which, represents as exactly as I could make
it, a portion of the longitudinal section of a sucker cf Diclidophora,
will convince one of the difference at least in optical characters between
the fibres that constitute the wall of the sucker and the muscular fibres
that are attached to it. But in the second place we can trace all the

various stages between these fibres and the ordinary connective tissue

 

1). In the latter case all the tissues stain more diffusely than when new.
146 8. GOTO.

that constitute the mesenchyma of the body. In doing this, however,
it will be necessary for us to widen our field of view and take into
account the mass of peculiar connective tissue already described around
the genital atrium of Microcotyle. Let us compare the suckers, both
anterior and posterior, of Microcotyle, Axine, or any other of the genera
mentioned at the beginning of this chapter, with the hemispherical or
elongated sac-like organs which form the wall of the posterior or dorsal
part of the genital atrium in Microcotyle sciaene and M. chiri, and we
shall at once recognise that both are composed of fibres of the same nature
—so exactly alike are they both in optical characters and in their reac-
tion towards staining fluids. Now any one who cared to peruse the
descriptions I have given above of this mass of peculiar connective
tissue in different species of Microcotyle, and took the trouble of com-
paring the figures of it given in Pls. V & VI would at once see that it
is in reality a specially differentiated portion of the general mesenchyma
of the body. In Microcotyle fusiformis (Pl. V, fig. 1) and M. caudata
(Pl. V, fig. 3) it is clearly seen to be nothing but a part of the
mesenchyma, which has, however, assumed a somewhat different
character from the surrounding portion; in M. elegans (PI. V, fig. 2)
and M. sebastis (Pl. VI, fig. 1) it is more clearly distinguishable
from the surrounding part, but its origin is still unmistakable;
and finally in M. chit (Pl. V, fig. 4) and M. sciaene (PI. VI,
fig. 2) a limiting membrane has been developed around it and has
distinctly separated it from the surrounding tissue. In Mf. chin,
however, the outer membrane is, as already mentioned, not so distinct
from the surrounding mesenchyma as in M. sciaene and in the
suckers of other species, but reveals a perceptible transition into it; the
fibres of the mesenchyma passing into, and forming, the membrane.
In this connection it should also be borne in mind that the wall of the

small suckers at the apex of the caudal appendage in Onchocotyle is
STUDIES ON THE ECTOPARASITIC TREMATODES OF JAPAN. 147

formed of a connective tissue whose fibres are arranged mainly at right
angles to the outer and inner limiting membranes. We have, there-
fore, an. almost complete series. of stages from the ordinary fibrous,
reticulated connective tissue, to the compact substance consisting of re-
fractive, prismatic fibres, which constitutes the wall of the suckers of
Axine, Microcotyle, Octocotyle, Diclidophora, Heaxacotyle, and Onchocotyle,
(the anterior sucker excepted in the last genus) and the hemispherical
or cylindrical organ around the genital atrium of some species of them.
The prismatic fibres seem to be formed by a transformation of the
granular substance usually present in the meshes of the connective
tissue, while the connective tissue fibres themselves appear to remain
mostly unchanged and are seen well stained in sections.

As I have said above, we have no positive proof that the prismatic
fibres in question are non-contractile; but! their genesis as above ex-
plained seems to me to exclude the view which regards them as of
muscular nature.

If now the fibres that constitute the wall of the suckers of the
genera above mentioned are non-contractile, the question arises how is
the suctorial action to beexplained. Lorenz” indeed has denied such
an action to the posterior organs of attachment of Microcotyle and Axine,
and has called them simply ‘“‘ Haftorgane”; but that they are true suckers
is beyond doubt; for I have observed living specimens of Microcotyle
attach themselves to a glass slide by means of the posterior suckers. I
have also observed them execute a leech-like locomotion by alternately
attaching and detaching the anterior and posterior ends of the body;
and I can not see how the worm can attach itself to a glass slide un-
less the action of these posterior organs of attachment be suctorial.
The anterior suckers must also be able to exercise suction; for in

Microcotyle there is no other organ at the anterior end of the body, by

 

1). Lorenz—l. c., p. 6.
148 8. GOTO.

means of which the worm can attach itself to foreign bodies sufficiently
firmly as to drag. its body after it. We are therefore compelled to
admit the suctorial action of both the anterior and the posterior suckers,
This action I shall now proceed to explain.

The so-called chitinous rods and pieces that compose the sup-
porting frame-work of the suckers are, as I have already stated, not
formed by true chitin, but are soluble in caustic potash, and in some
species stain more or less, and do not seem to be rigid. On the contrary,
I believe they are easily flexible but elastic, so that when distorted
by external force they constantly tend to resume their original form.
In fact, if a living worm he observed under the microscope the suckers
are seen to constantly change their form; and this seems to be im-
possible if the so-called chitinous-frame-work be perfectly rigid. I also
believe that the prismatic fibres which compose the wall of the suckers
are likewise elastic; this seems to be very probable from their great
(doubly?) refractive power and from their other optical characters.
The image, then, I form of the suckers from the physiological
point of view is that of a bag (hemispherical or rectangular) with
athick, elastic wall which constantly tends to be flattend out, but
which is kept in proper shape by an external force, that of the
muscular fibres that are attached to the bottom of the suckers. If
these muscular fibres relax, the wall of the sucker becomes flattened
out. by virtue of its elasticity and applied to its substratum, the
body-surface of the host; if now the muscular fibres contract, the
sucker assumes the form of a bag, and thus a vacuum tends to
form within, giving rise to a suctorial action. In favour of this
view it may be mentioned in addition that in many sections of the
suckers the prismatic fibres are seen to be much pressed against one
another at the inner side of the suckers near the point where the wall
is folded on itself—the part where the fibres must necessarily be
STUDIES ON THE ECTOPARASITIC TREMATODES OF JAPAN. 149

exposed to strong mutual pressure (Pl. ITI, fig. 8; Pl. XV, fig, 8;
Pl. IX, fig. 8). In this process the portions of the investing
membrane of the inner surface of the suckers, which have in some
species been clritinously changed, would materially assist the elasticity
of the wall.

The bulbous penis of Octocotyle, Diclidophora, and Calicotyle are
evidently composed of fibres the same in nature as those of the suckers’
of the first-named two genera, and therefore in my opinion not
muscular,

If, again, my view as to the origin of the genital atrium be
true, that it is formed by the invagination of the surface of the
body, it unifies in an unexpected manner the relation of the suckers
of the genera so often mentioned above to the hemispherical or
cylindrical organs about the genital atrium’in some species of JMi-
crocotyle, in being composed of exactly the same substance, for since,
according to it both kinds of organs fall under the same category
of local modifications for special purposes of the mesenchyma near
the external surface of the body, they therefore consist of the same
substance.

2. Penis—After what I have said about the penis in different
species and genera I believe that the relation of its different forms
can be made out more satisfactorily than has hitherto been done.

The penis seems to have its most complicated structure in
Tristomum and Epibdella. It is here, as already described, a hol-
low club-shaped organ projecting by its distal portion into the
genital atrium with which its internal cavity is directly continuous,
and is provided with muscular fibres of its own arranged in two
ways, viz., circularly and longitudinally. In my opinion, it is
to be regarded as formed by an elevation of the wall of the

genital atrium around the opening of the vas deferens and a simul-
150 8. GOTO.

taneous displacement of the latter from the base of the penis
towards its top; so that the cavity of the penis is morphologic-
aly speaking as much the external surface of the body as
the genital atrium, and the prostate glands are therefore to be
regarded as a special modification of the dermal glands,—a view.
clearly in accordance with some facts observed in Temnocephala.”
The tissue of the large papilla projecting into the genital atrium
at the top of which the vas deferens opens in Hexacotyle ix not
bounded off from the surrounding mesenchyma; but that it is
the homologue of the penis will, I believe, scarcely be contested
by any one. In Monocotyle (Pl. XVIII, fig. 3), on the other
hand, the connective tissue that forms the substance of the penis
has undergone some transformation, having become fibrous with
the fibres arranged at right angles to the internal and ex-
ternal limiting membranes of the penis. It is, however, not yet
distinctly separated from the surrounding mesenchyma by a mem-
brane. The penis encloses, in this genus, a tubular, chitinous
organ—the chitinous penis—which is attached to it at the bottom of
its cavity, and into which the vas deferens opens. ‘This chitinous
penis is regarded by St.-Remy” as the transformed terminal portion
of the vas deferens. It seems to me, however, to be more in accordance
with facts to regard it ax the prolonged portion of the inner limiting
membrane of the penis, which has then undergone a chitinous trans-
formation ; and as this limiting membrane is morphologically no
other than a portion of the lining membrane of the genital atrium,
which is again but the invaginated portion of the investing

membrane of the body, the chitinous penis is, in my opinion, to

 

1). Hasweil—On Temmocephala, an Aberrant Monogenetic Trematode. Quart. Journ. of
Mic. 8:., vol. 28, 1838. p. 283.

2). St-Remy—l. c. p. 24.
STUDIES ON THE ECTOPARASITIC TREMATODES OF JAPAN. 151

be regarded as a chitinixed portion of the investing mem-
brane. This view will, as will be seen afterwards, unify the origin
of the chitinous hooks and rods that are found in various parts
of the body.

The connective-tissue and chitinous penis of Monocotyle seem to
me to afford a starting point for another type of copulatory organs,
that of the penis of Diclidophora and Calicotyle. In the latter genus
(Pl. XIX, fig. 11) the bulbous penis, or as it may be called the bulbus
copulatorius», is a kidney-shaped mass of fibrous connective tissue
around the terminal portion of the vas deferens, before it is con-
tinued into the tubular chitinous penis. The latter is essentially
similar to that of Monocotyle, and is enclosed in the genital atrium
which has here been reduced to a mere sheath for the chitinous penis.
The bulbus copulatorius may be regarded as a further differentia-
tion in a different direction of such penis as that of Monocotyle, in
consequence of which it has been almost completely separated from the
surrounding tissue. The only difference is that in Monocotyle it pro-
jects into the genital atrium, while in Calicotyle it does not, and is
therefore traversed by the vas deferens. The connective-tissue penis of
Diclidophora (Pl. XI, fig. 4) is essentially similar in structure—histo-
logical details and the shape not considered—to that of Calico-
tyle. The chitinous penis is, however, replaced by the hooks already
described. These are also, in my opinion, formed by the local transforma-
tion of the lining membrane of the genital atrium, and are therefore
homologous in a broad sense to the chitinous penis of Calicotyle and
Monocotyle. Unlike, however, what occurs in these genera the lining
membrane has in Diclidophora not been raised and prolonged into a
tubular form and the whole then changed into a chitinous substance,

but it has been raised at some particular points into the particular

 

1). Braun—Wirmer. p. 475.
152 &. GOTO.

shape of the hooks already described, and the raised part chitinised.”
It should, however, be observed that the process of absorption has pro-
bably played as much part in the formation cf the hooks as that of
chitinisation.

The penis in Octocotyle is essentially similar to that in Diclidophora,
but its hooks are more like the atrial spines of Microcotyle. In Oncho-
cotyle the penis is nothing else than a mass of elastic connective tissue
around the terminal portion of the vas deferens, which is separated
from the surrounding mesenchyma by a membrane, and is therefore
essentially similar to that of Diclidophora. ‘The hooks are, however,
totally absent.

The atrial spines of Microcotyle are, as already described, formed
by local, conical elevations and chitinous transformation of the lining
membrane of the genital atrium, and are therefore homologous in a
broad sense with the chitinous penis and penis hooks of other genera
as well as with the hooks which are present in many genera in the
posterior sucker or in the posterior part of the body, and with the
Iccal chitinous areas of the lining membrane of the suckers (PI. VI,
fig. 4; Pl. XII, fig. 4). I also believe that the chitinous frame-work
of the suckers of many genera is homologous with the structures just
mentioned, 7. ¢., that it is a product of the local transformation of
the investing membrane of the body.

The homologue of the penis of Monocotyle and Hexacotyle and
therefore of Tristomum can also be traced in Microcotyle. It has already
been stated that in some species of this genus, as MM. fusiformis (Pl. V,
fig. 1), M. caudata (fig. 3), and M. sebastis (PI. VI, fig. 1), the vas
deferens opens at the top of a conical papilla projecting into the genital

atrium. ‘This papilla is, in my opinion, the homologue of the penis.

 

1). Here I have for convenience used « false expréssion. In point of fact the process
of raising and that of chitinisation probably proceeed simultaneously.
STUDIES ON THE ECTOPARASITIC TREMATODES OF JAPAN. 153

A penis similar to that of Tristomum occurs according to Poirier,”
among the Digenea, in Distomum clavatum, D. verrucosum, D. insigne
and D. Megnint. In these forms, however, it has a much simpler
structure than in T'ristonum; and it should moreover be remarked that
in the two last-mentioned species it is also traversed by the uterus
and that in D. verrucosum it does not prominently project into the
genital atrium, and somewhat approaches in form that of Onchocotyle in
having its tissue distinctly separated from the surrounding mesenchyma.

It will be observed that in my descriptions I have nowhere used
a term corresponding to “ Cirrusbeutel (poche de cirrhe, tasca del pene)”
so often met with in the literature on the Trematodes and the Cestodes.
This I-have done with an express purpose. The term “Cirrusbeutel”
and those that correspond to it have been used to designate various
structures by different writers. Leuckart” uses it for “ein keulen-
oder birnférmiges Organ von ansehnlicher Grésse und wesentlich
muskuléser Beschaffenheit,...der das Endstiick des Samenleiters,
den sog. Ductus excretorius, in sich einschliesst.” Poirier® on the
other hand uses it in D. insigne and D. Megnini, in which a distinct
penis is present, for an ovoid sac around the terminal portion of the
vas deferens, which has a distinct wall and contains the prostate glands
together with a comparatively small quantity of connective tissue;
while Monticelli? seems to use it for the penis itself, reserving the
word penis for that terminal portion of the vas deferens (7. e. the ductus
ejaculatorius) which is evaginated during copulation. In view of these
various significations of the term, and considering that the so-called

“Cirrusbeutel” is not a hollow organ, but simply a mass of specially

 

1). Poirier—l. ¢.

2). Leuckart—Parasiten. II. Aufl., 1 Bd. p. 43.

8). Poirier—t. c. pp. 551 & 553; Pl. XXXII, fig. 1 & Pl. XXXIV, fig. 1.
4). Monticelli—Studii, p. 80 et infra. .
154 S. GOTO.

modified tissue around the terminal part of the vas deferens, which has
been set off from the surrounding mesenchyma by a membrane or a
layer of muscular fibres, I have thought it advisable to abandon its use
altogether and to adopt the terminology used in this paper. The term
“cirrus”? has been used by many writers for the spines either of the
penis or of the genital atrium.

3. The prostate gland (= Kérnerdriise of Lang and Graff,
Penisdriise of Ijima) has been described in other members of the
Plathelminthes, and I believe’ I have succeeded in demonstrating it
in the monogenetic Trematodes generally.

4, Homology of the canalis genito-intestinalis—I shall now proceed
to discuss the homology of this problematic canal and endeavour to
throw some light on the question ; and in doing this I shall be led to
consider also the homology of the vagina and the uterus of the
Cestodes as well as the vagina of the ectoparasitic Trematodes and the
Laurer’s canal of the Digenea. Before, however, expounding my own
opinion, it will not be out of place here to bring together the views of
preceding writers.

The genito-intestinal canal of the Monogenea was discovered in
its right connection by Ijima” (Polystomum, Axine, Octobothrium).
To the question, which of the two canals, the vagina or the genito-
intestinal canal, is the homologue of the Laurer’s canal” his answer
is not decisive either way. He says, “Was nun den Zusammen-
hang der Scheide mit dem Oviduct anbelangt, so findet er entweder
direkt (Calicotyle, Pseudocotyle, Axine) oder indirekt durch den Dot-
tergang statt. In ersterer Hinsicht finde ich keine wesentliche Ab-
weichung von den meisten von uns bekannt gewordenen Fiillen des
Laurer’schen Kanals. In zweiter Hinsicht erinnere ich an das Oeffnen

 

1). Ijima—Ueber den Zusammenhang d. Hileiters mit d. Verdauungskanal bei gewissen
Polystomeen. Zool. Anz., Jahrg. VII, 1884, p. 635.
2). The use of this name I shall confine to the Digenea.
STUDIES ON THE ECTOPARASITIC TREMATODES OF JAPAN. 155

des Laurer’schen Canals in den Dottergang bei Distomum hepaticum.”
Leuckart” regards the genito-intestinal canal as homologous
with the Laurer’s canal and applies this name to the former. He says,
“Die Scheide von Polystomum integerrimum erscheint hiernach als ein
Gebilde, welches, da es neben dem Laurer’schen Kanale existirt, dem-

selben nicht homolog sein kann,” He is of the opinion that the
supposed (by Lorenz) opening of the genito-intestinal canal into the
vitellarium can no more be regarded as an objection against his view
than that the unpaired condition of the vagina in certain monogenetic
Trematodes can be advanced as an objection against its homology
with the paired vagina of Polystomum. ‘“ Jedenfalls,” he warns us in
conclusion, “ist das, was man bei den Trematoden als Scheide
bezeichnet, nicht ohne Weiteres iiberall als dasselbe Gebilde in An-
spruch zu nehmen und als Laurer’scher Kanal zu _bezeichnen.”
Leuckart is inclined to regard the Laurer’s canal as being homo-
logous with the vagina of the Cestodes.

- Wright and Macallum” after describing the canal in Sphy-
ranura, say, ‘‘ How such an economical method of disposing of sur-
plus yolk can have been arrived at, whether by the modification of a
Laurer’s canal or otherwise, we are unable to say.”

Monticelli®: “ Lasciando induscussa la questione, se serve 0 no
il canale di Laurer come organo di accompiamento, ........ giudicando
ora la cose dal punto di vista puramente morfologico, io credo, come
del resto parmi pienamente giustificabile, che il canale di Laurer dei
digenetici per la sua posizione e il suo decorso, per i suoi rapporti con
Yovidotto interno e con gli organi femminile in generale e per la

presenza di uno slargamento vesicolare, paragonabile al ricettacolo

 

1). Leuckart—Parasiten, II. Aufi., 1. Bd, 1886, p. 58-59.
2). Wright and Macalluam—Sphyranura Osleri. Journ. of Morphology, VoL I, 1897, p. 42.
3). Monticelli—Saggio, 1888, pp. 58-59.
156 8. GOTO.

seminale interno dei monogenetici, rappresenti morfologicamente
parlando Ja vagina dei digenetici, come gia Blumberg aveva pensato
.....-Ln favore di queste interpretazione, va ancora considerato che nei
digenitici non vié altra parte ‘dell’ apparachio genitale che possa
riguardarsi come una vagina.” I am afraid the language used by the
writer is somewhat confusing ; but his view is unmistakable, as may
be seen from another passage, in which after speaking of the genito-
intestinal canal, he says, “ Ad ogni modo si é tuttora in presenza di
fatti che vogliono essere ancora meglio investigati, ma non parmi che
questi abbiano, nello stato attuale delle nostro conoscenze, valore tale
da impedire di stabilire una omologia del canale di Laurer dei digene-
ticl con la vagina dei monogenetici, d’ altra parte la presenza del
canale cosidetto escrezione nei Polystomidae..., come nei Microcotyli-
dee potrebbe benissimo riguardarsi come un adattamento speciale in
queste subfamiglie.”

In his recently published work,” which I received while I was
writing this paper, he has further expounded the same view. In it
he speaks of the Laurer’s canal throughout as vagina, and regards it
as homologous with the vagina of the monogenetic Trematodes. He
says, “ Ho conservato il nome di vagina, enon quello di canale di
Laurer, perché le mie nuove ricerche ed i miei nuovi studii compara-
tivi mi confermano nelle conclusioni alle quali io ero pervenuto nel
mio saggio, che essa, morfologicamente rappresenta, nei Distomi ed in
tutti gli endoparassiti, la vagina dei monogenetici ; cosicché i due
organi devono riguardarsi omologhi: e cid, sia per i rapporti che esso
canale degli endoparassiti contrae con Jl’ovidotto che ripetono le
istesse condizioni che si verificano in quelli (infatti, come nei mono-

genetici Ja vagina pud apprirsi, o nell’ovidotto, o nel ricettacolo semi-

 

1). Monticelli—Primo contributo etc. (Studii sui Trematodi endopar.). Zoolog. Jahr-
bitcher, IIT. Suppl., 1898. p. 98 et infra.
STUDIES ON THE ECTOPARASITIC TREMATODES OF JAPAN. 157

nale, o, insieme a questo, nell’ovidotto, oppure nel ricettacolo vitellino),
sia per la sua posizione e per il suo decorso.”” And further on he
adds, ‘‘ Mi importa qui assai di far notare che nessuna omologia esiste fra
al canale vitello-intestinale...... e la vagina degli endoparassiti: esso é
tutt’altra formazione e niente impedisce che possa coesistere con la vagina, e
considerarsi ed essere un adattamento speciale in alcuni monogenetici.”

Pintner” is of the same opinion as Monticelli. He holds the
Laurer’s canal as homologous with the vagina of the Cestodes. But
it seems to me that he infers the homology of these canals from their
analogy, and I fear he has not on the other hand taken the genito-
intestinal canal sufficiently into consideration.

Braun” also regards the Laurer’s canal as the homologue of the
vagina of the Monogenea. After observing that in those cases where
the vaginal opening is situated ventrally or on the lateral margin of
the body, it lies asymmetrically with regard to the median line of the
body, he says, “ Demnach diirften wir die doppelten Vaginen als
ursprunglich ansehen, aus denen durch Atrophie der einen, und zwar
der rechten, das Verhalten von Onchocotyle etc. hervorgegangen ist ;
diese unpaare Vagina riickt dann seitlich mit ihrer iusseren Miindung
und schon bei Azine sieht dieselbe dorsal, wie Lorenz berichtet, so
das von da bis zu dem Verhalten von Octobothrium nur ein relativ
kleiner Schritt ist ; an letztere Gattung wiirden sich in diesem Punkte
die Digenea anschliessen ; trotz der verschiedenen Verbindungsstellen
halte ich demnach diese Kaniale fur homologe Bildungen.” It should
be remarked that the writer regards the genito-intestinal canal of

Onchocotyle as the vagina—an error which is quite natural, as the true

 

1). Pintner—Neue Beitrige zur Kenntniss des Bandwurmkérpers. Wiener Arbeiten,
T. 9, 1890.

2). Braun—“Wiirmer” in Bronn’s “Klassen und Ordnungen des Thierreichs,” 1890.
pp. 489—490.
158 S. GOTO.

vagina of this genus has been made known for the first time ‘by
these studies.
Hatschek” in his “Lehrbuch” has the following passage :
“ Bei Polystomum findet sich nebst dem primiren weiblichen Aus-
fiihrungsgang...... und dem Laurer’schen Gange noch ein paariger,
rechts und links miindender weiblicher Begattungsgang ; auch bei
Calicotyle und .anderen ist letzterer beobachtet.” It is unmistakable
that in this passage the writer designates the genito-intestinal canal as
the Laurer’s canal.
Brandes” in criticising the view of Pintner, says, “ Dass
der Laurer’sche Kanal morphologisch der Vagina der Cestoden und
ectoparasitischen Trematoden entspricht, ihr also homolog ist, hat
bisher meines Wissens noch Niemand ‘bezweifelt...... ”; and further
on he adds, ‘“ Der Laurer’sche Kanal der entoparasitischen Trematoden
ist der Vagina der ectopar. Trematoden und der Cestoden homolog,
aber nicht analog, die Vagina der letzteren ist der Uterusmiindung
der ersteren analog, aber nicht homolog.” Iam afraid the writer is
going too far when he infers from the silence of most authors on the
homology of the vagina of the Cestodes that they have no doubt of
its homology with the Laurer’s canal of the Digenea. In his work on
the Holostomidae published the previous year, the same writer ‘seems
to have expressed a somewhat different view ; for, after stating the
ground of his disbelief in the supposed function of the Laurer’s canal
as a passage for the surplus product of the vitellarium, he says,”
“ Auf jeden Fall, meine ich, darf man annehmen, dass bei dem

Bediirfnisse eines Abflussrohres fiir iiberschussiges Material sich die

 

1). Hatschek—Lehrbuch der Zoologie, 3. Lieferung, 1891, p. 343-344.

2). Brandes—Zur Frage des Begattungsaktes bei den entopar. Trematoden. Centralbl. f.
Bakter. u. Parasitk,, Bd. 9, 1891, p. 265 et infra.

3). The italic is mine.
STUDIES ON 'HE ECTOPARASITIC TREMATODES OF JAPAN. 159

Vagina der Cestoden in besserer Weise den neuen Verhiltnissen
angepasst haben wiirde.”

Dieckhoff,” who directed his attention specially to the canalis
genito-intestinalis, is of the same opinion as Braun, under whose direc-
tion his studies were made. After describing the canal in different
species studied by him he says, “Ijima glaubte eine Nebeneinander-
stellung desselben mit dem Laurer’schen Kanal der Digenea nicht von
der Hand weisen zu diirfen. Da aber auch bei Thieren mit unpararer,
dorsal miindender Vagina, wie z. B. bei Octobothrium lanceolatum und
Diplozoon paradozum, ein in den Darm fiihrender Kanal existirt, und
da auch tiberhaupt die Ableitung des Laurer’schen Kanales aus den
paarigen Vaginen, wie mir scheint, geniigend dargethan ist, so ist
dieser Gedanke wohl nicht annehmbar”; and a little further on he
adds, “ Vorliufig muss man in dem Canalis vitello-intestinalis eine
Bildung sui generis sehen, deren genetische Beziehungen ganz
fraglich sind.”

Quite recently Looss” has advanced a view which presents
considerable differences from those of the preceding writers. He
considers the question from a purely morphological point of view and
comes to the conclusion that the uterus of the Trematodes is homo-
logous with the vagina of the Cestodes, the uterus of the latter with
the Laurer’s canal of the Digenea and with the canalis genito-intes-
tinalis of the Monogenea. The vagina of the latter he regards as a
structure sue generis.

I have already in a preliminary paper” discussed briefly the

 

1). Dieckhoff—Z. c.

2). Looss—Ist der Laurer’sche Kanal der Trematoden eine Vagina? Centralbl. f.
Bakter. u. Parasitk., Bd. 13, 1893. p. 808 et infra.

8). Der. Laurer’sche Kanal und die Scheide. Centralbl. f. Bakter. u. Parasitenkunde,
Bd. 14, 1893. p. 797.
160 S$. GOTO.

differences of my view from that of the last mentioned writer, and I
shall now proceed to explain it more at length.

Let us in the first place consider the vagina of the Monogenea.
So far as I ‘know this organ is truly paired only in Onchocotyle,
Calicotyle, Polystomum, and Sphyranura. In the first two genera its
external opening is situated on the ventral side of the body, while in
the other two genera it is situated on the lateral margins. In Calico-
tyle it opens into the oviduct, but in all the other three genera it be-
comes continuous with the yolk-duct. In Microcotyle, Amine, and
Hexacotyle the vaginal opening is situated on the dorsal side in the
median line of the body (or sometimes on the lateral margin as in
Axine belones according to Lorenz); but that the vagina in these
forms has been derived from a truly paired one seems to me beyond
doubt. Thus, in Axine heterocerca the vagina immediately divides
right and left into two canals, which proceeds backwards, keeping
symmetry with respect to the median line of the body ; in Microcotyle
reticulata, M. chiri, M. truncata, and in Hexacotyle the vagina remains a
single duct for a certain distance in the median line of the body, but then
divides into two canals; in M. fusiformis, M. caudata, and some other
species of the same genus the vagina remains single for a longer dis-
tance ; in Microcotyle sciaenae the paired vaginal canals unite with and
separate from each other twice during their course; while finally in Axine
aberrans the vagina remains single throughout its whole extent, and
opens into the fore end of the unpaired yolk-duct. Lorenz” in one
place figures the vagina in Axine belones as opening directly into
the oviduct, but in another figure (fig. 2) “he represents it as
opening into the yolk-duct. Considering his figures alone I

should trust the former figure as showing more details; but

 

1). lc.—Taf. L. fig. 4.
STUDIES ON THE ECTOPARASITIC TREMATODES OF JAPAN. 161

unfortunately it is not in accordance with my observations. on
a closely allied species (Axine aberrans), in which the vagina
opens, as stated above, into the yolk-duct. If now we eliminate
the case of Azine belones as requiring further examination, we have
in the above mentioned forms a perfect series of vagine from a truly
paired to as truly an unpaired condition—Onchocotyle and Calicotyle
standing at one end of the series and Axine aberrans standing at the
other. In Monocotyle, Tristomum, and Epibdella the external opening
of the vagina is single and is situated on one side of the body. In
Monocotyle it opens into the oviduct from the ventral side; while in
Tristomum and Epibdella it opens into the yolk-reservoir more to the left
or.right. The latter fact has been regarded by Braun as indicating
the formation of the vagina in these species by the simple atrophy of
one of the originally paired vagine ; but the relation of things above
mentioned in Monocotyle, considered together with the evidently close
systematic relationship of this genus with Calicotyle, seems to me to
point strongly to the view that its unpaired vagina has been formed
by the union and subsequent displacement towards one side, of the
originally paired vaginee, and not as Braun supposes by the atrophy
of one of them. That the vagina in Octobothrium lanceolatum—a form
the single vagina of which Braun regards as due to the atrophy of
one of the originally paired vaginee—has been formed by the union of
the originally paired vagine seems to me evident from its exact
similarity to Azine aberrans both in the position of its external open-
ing as well as in its relation with the yolk-ducts as described by
Dieckhoff; and in Tristomum and Epibdella the displacement of the
external opening of the vagina towards one side of the body may have
entailed a similar displacement of its internal opening. I therefore go
one step farther and regard the unpaired vagina—whether its opening

be situated on the ventral or on the dorsal side, or whether it be in the
162 8, GOTO.

median line of the body or otherwise—as formed by the union of the
originally paired vagine, such as we now meet with in Calicotyle and
Onchocotyle. Asa further support to this view it may be mentioned
that in .Dactylogyrus and Tetraonchus the unpaired vagina, which is
present only on one side of the body, opens according to my own
observation, into the oviduct in the median line of the body at the
same level. as the paired yolk-ducts, just as in Monocotyle. This view
appears to me to be more in accordance with the actual state of things
than the other, in favour of which hardly a single positive fact can, as
it seems to me, be brought forward.

Let us now turn our attention to that problematic organ, the
canalis genito-intestinalis. This canal is less widely distributed among
the .ectoparasitic Trematodes than the vagina: of the genera I have
hitherto studied it is present only in Diplozoon, Microcotyle, Axine,
Octocotyle, -Diclidophora, Onchocotyle, and Hexacotyle. According to
my own observations it seems to be wholly wanting also in the
Gyrodactylidae.» It always opens at one end into the oviduct near
where the latter receives the unpaired yolk-duct —in fact the genito-
intestinal canal and the yolk-duct sometimes open opposite, or side by
side with, each other; but usually the two openings are more or
less separated from each other; and in this case that of the genito-
intestinal canal is situated in some species nearer and in others farther
from:the ovary than that of the yolk-duct. The wall of the genito-
intestinal canal presents nothing special except that in some species it
presents circular thickenings at stated intervals.

As a preliminary step to the discussion of the homology of the

 

1). I beg to remark here that in my paper on Diplozoon (p. 183) I alluded to the vagina of
Dactylogyrus as being similar to the genito-intestinal canal. I then suspected that these
canals might be homologous with each other; but on further reflection such a view seems
to me untenable.
STUDIES ON THE ECTOPARASITIC TREMATODES OF JAPAN. 163

canalis genito-intestinalis we must consider that of the vagina of the
Cestodes.

Until quite recently the vagina of the Cestodes appears to have
been generally regarded as homologous with the Laurer’s canal
of the distomes; but a careful examination of this view convinces
me that hardly a single positive proof can be cited in its favour,
and that it is grounded on a mistaken estimate of the analogy
(as opposed to homology) that has been supposed to exist between
the two organs. Looss” has however recently shown that the
vagina of the Cestodes is to be regarded as the homologue of the
uterus of the Trematodes. On my part I entirely agree with him on
this point, and will briefly recapitulate the reasons that led me to this
conclusion, even before I had read Looss’ paper.

If we cast a glance on the genital organs of the Plathelminthes
(the Nemertinei excepted), we find that in all the three classes two
ducts open to the exterior, 7. ¢., to the morphologically external surface
of the body, near each other. One of them is the vas deferens ; the
other is in Turbellaria the efferent duct of the ovary, while in the
Cestodes and Trematodes it is called respectively the vagina and
the uterus; but in these classes it is likewise the direct con-
tinuation of the oviduct. In Caryophylleus tuba, indeed, the uterus
opens, according to Monticelli”, side by side with the vagina,
and in C. mutabilis, according to Will”, it unites with the vagina, so
that in this genus the uterus and not the vagina corresponds in the
position of its external opening to the uterus of the Trematodes. But
the uterine opening seems to be very unstable in its position in the

Cestodes ; for in Amphilina it is near the anterior end of the body,

 

1). Looss.—l, ¢.

2). Monticelli—Appunti sui Cestodaria. p. 5.

3). Heinrich Will—Anatomie von Caryophylleus mutabilis. Zeitschr. f. wiss. Zool.
Bd. 56, 1893. Taf. II. fig. 17
164 8. GOTO.

while in the Bothriocephalide it is on the ventral or the dorsal side ac-
cording to the species. In contrast therewith the vaginal. opening
of the Cestodes is very constant in its position and is situated close
to that of the vas deferens. The vagina of the Cestodes
and the uterus of the Trematodes I therefore regard
as homologous structures, having as they do their
external openings always near that of the vas deferens,
and both being the direct continuation of the oviduct.

Which now of the two ducts, the vagina or the genito-intestinal
canal, of the ectoparasitic Trematodes.is the homologue of the Laurer’s
canal of the Digenea?

In the first place, the position of the genito-intestinal canal
corresponds very well with that of the Laurer’s canal—and be it
remarked that I confine the latter term to the Digenea: both arise
from the oviduct between its origin and the ootyp, near or opposite
the opening of the yolk-duct. The striking difference is that one
opens to the exterior while the other communicates with the intestine;
but this is in my opinion of quite a secondary importance, and
can not be regarded as a serious reason against the homology of
the two canals, any more than the absence of any external opening of
the uterus in Tenia can be regarded as against its being homo-
logous with the uterus of Bothriocephalus. In the second place the
Laurer’s canal is admitted by most writers” to present an abortive
character, and in many species of the Digenea it is totally wanting ;
and the same seems to me to hold true of the genito-intestinal canal of
the Monogenea. Thus it has no definite function; for the explanation
of Ijima seems to me, as it hag seemed to others, to be rather forced,

and as Prof. Ijima himself now admits it to be in conversation; then,

 

1). Looss, Monticelli, Brandes, etc.
STUDIES ON THE ECTOPARASITIC TREMATODES OF JAPAN. 165

its wall presents in some species circular thickenings just as in some dis-
tomes ; and in many genera it is totally absent. Considering these cor-
respondences of the two canals I believe them to be homologous
structures—the Laurer’s canal and. the genito-intestinal
canal. As already mentioned in the historical portion, some writers
maintain that the Laurer’s canal is homologous with the vagina of
the Monogenea ; but several considerations speak against this view.
Thus, the vagina of the monogenetic Trematodes opens in the majority
of species into the yolk-duct, and where it opens directly into the
oviduct it does so side by side with the yolk-ducts; while the Laurer’s
canal mostly takes its origin directly from the oviduct. In Distomum
hepaticum, indeed, the Laurer’s canal was supposed to open into the
yolk-duct, but Leuckart” and Poirier” have distinctly proved that
it opens not into the yolk-duct but into the oviduct, side by side with
the unpaired yolk-duct. So far as I know, there only remains in this
respect the case of Dist. cylindraceum, in which, according to Monticelli,”
the Laurer’s canal opens into the yolk-reservoir. Now the difference
in this respect between the two canals under consideration will be
found by any one who will take the trouble to examine the actual state
of things in each particular case to be very much more considerable
than can be expressed by a single general statement (c/. e.g. the
various figures); and the single case above mentioned (which it is,
however, very desirable to examine more closely) can not be regarded
as a serious objection against my view. ‘Then, the Laurer’s canal.
may, according to Monticelli®, be regarded as “ una continuazione
e dipendenza dell’ovidotto,” since its wall has the same structure as

that of the latter. ‘This, however, can not be maintained with any

 

1). Leuckart—Die menschl. Parasiten. II. Aufl. pp. 53, 321, 238.
2). Poirier—i. c. Pl. XXX., fig. 4.

3). Monticelli—Primo contributo etc. p. 106.

4). l..¢ p. 106.
166 8. GOTO.

degree of plausibility for the vagina of the Monogenea, as will be
apparent from the descriptions already given and a comparison of my
figures ; while, on the other hand, it holds very well for the genito-
intestinal canal, the wall of which is, as already mentioned, charac-
terised in some species by having circular thickenings exactly similar
to those of the oviduct ; and Dieckhoff” has even expressed the
view that the canal may perhaps be a rudimentary (abortive?) oviduct.
Add to these the considerations that the vagine of the Monogenea are
clearly seen to have been originally paired, while on the other hand
we have no trace of the paired condition of the Laurer’s canal and of
the genito-intestinal canal; that the latter was regarded as, and
called by some writers, the Laurer’s canal so long as they believed it
to open to the exterior (Taschenberg in Onchocotyle) or to be in
direct continuation with the vas deferens of the other individual
(Zeller in Diplozoon); and finally that the yenito-intestinal canal, like
the Laurer’s, “ puo apprirsi, o nell’ovidotto, o nel ricettacolo seminale
(as in Hexacotyle) o, insieme a questo, nell’ovidotto,” the evidences
in favour of my view—that the genito-intestinal and the
Laurer’s canal are homologous with each other—seem to
me to be very strong, much stronger than the evidences that can be
brought forward in favour of the other view, which appears far from
being “ irrefutable.”

I have said above that we have no evidence of the fact that the
genito-intestinal canal was originally paired. There are, however,
some statements that require consideration in this respect. According
to Zeller® the genito-intestinal canal is, in Polystomum integerrimum,

situated indifferently on the left or on the right side of the body,

 

1). Dieckhoff—/. c. p. 248.

2). Zeller—Weiterer Beitrag zur Kenntniss der Polystomen. JZeitschr. f. wiss. Zool.,
Bd. 27, 1876. p. 245.
STUDIES ON THE ECTOPARASITIC TREMATODES OF JAPAN. 167

always, however, opposite the side at which the ovary is situated. In
Polystomum ocellatum, again, the canal is described and figured by
Dieckhoff” as lying on the left side ; and in Sphyranura Osleri it is
figured by Wright and Macallum” as lying likewise on the left
side. On the contrary, in all the species I have examined, the canal
is situated, as already mentioned, on the right side of the body ; and
this led me to ask Prof. Ijima whether he had not observed such a
position of the cana]. He very kindly examined the serial sections of
two individuals of Polystomum ocellatum which he had at hand, and he
has informed me that the canal is situated on the right side in both.
This perhaps shows the necessity of a reéxamination of the statements
to the contrary. effect; but.as this is at present impossible for me to
do, I shall only remark that they do not oblige us to regard the genito-
intestinal canal as having been originally paired, any more than the
varied position of the common genital pore in Tenia compels us
to infer its having been paired originally.

It will be remembered that one ot the reasons that have led
Monticelli to assert the homology of the Laurer’s canal with the
vagina of the Monogenea is that “ nei digenetici non vi é altra parte
dell’apparechio genitale che possa reguardarsi come una vagina.”
But if instead of starting with the assumption that a morphological
equivalent of the vagina of the Monogenea must exist in the
Digenea, he had put the question simply as we have done, he
would have been led not to make the positive statement we have
quoted, denying all homology of the genito-intestinal canal with
the Laurer’s.

In my paper on Diplozoon® I expressed the opinion that the recep-

 

1). Dieckhoff—I. c. p. 250.
2). Lee
8). Goto—l. c. p. 184.
168 8. GOTO.

taculum vitelli described by Voeltzkow™” in Aspidogaster conchicola is
homologous with the genito-intestinal canal, and this seems to me to
be more probable now that I have shown the homology of the genito-
intestinal canal with the Laurer’s. For, according to Voeltzkow the
receptaculum vitelli arises in Aspidogaster as a solid string. of cells,
which reaches the ectoderm on the dorsal side and there spreads out in
the form of a funnel. It is therefore exceedingly probable that. the canal
originally opened to the exterior on the dorsal surface of the body, just
as the Laurer’s canal now does in the distomes. Hence I regard it as
homologous with the Laurer’s and therefore with the genito-intestinal

canal,

It still remains to inquire whether the Cestodes have any organ
homologous with the Laurer’s canal or with the vagina of the Mono-
genea. My answer is that they all possess a homologue of the latter,
and some (Amphilina) also one of the former.

Let us begin our comparison with the unsegmented forms of the
tapeworm, which have recently been erected by Monticelli”, under
the name of Cestodaria, into a separate class of the same grade as that
of the ‘Trematodes or the Cestodes. Thanks to the investigations
of that zoologist the anatomical relations of the genital organs of
these forms have been clearly exposed. In Amphilina there are two
vaginee, one posterior and opening outwards near the posterior
end of the body near the external opening of the vas deferens, the
other anterior and ending blindly after preceeding for a certain dis-
tance forwards from the beginning of the oviduct. Now, everybody

will allow that the posterior vagina of this worm corresponds mor-

 

1). Voeltzkow—Aspidogaster conchicola. Wiirzburger Arbeiten. Bd. 8, 1888. p. 263
& 279.

2). Monticelli—Appunti sui Cestodaria. Estratto dal vol. V, ser. 2, No. 6, degli Atti della
R. Accademia delle Scienze fis. e mat. di Napoli, 1892. :
STUDIES ON THE ECTOPARASITIC TREMATODES OF JAPAN. 169

phologically to the vagina of other tapeworms and is homologous
with it. What then is the blind vagina? My answer is that it is the
homologue of the genito-intestinal canal of the Monogenea and there-
fore of the Laurer’s canal. What has struck me as a remarkable
coincidence is that all these organs bear a decidedly abortive character.
That the Laurer’s and the genito-intestinal canal appear to be in the
process of gradual disappearance has been already explained, and will,
I think, be admitted by most persons; and the blind vagina of
Amphilina appears to me as unmistakably abortive—the very fact
of its being blind and its total absence in the nearly related form
Caryophylleus speaking strongly for this view. Then, it bears at its
beginning a receptaculum seminis just like Laurer’s canal in most of the
distomes or the genito-intestinal canal in some Monogenea ( Hexacotyle).
Again, if, as I have explained above, the receptaculum vitelli of Aspido-
gaster is homologous with the Laurer’s canal, we have another simi-
larity between it and the accessory vagina of Amphilina, in their both
ending blindly. Lastly, the relation of this vagina to the oviduct is
exactly the same as that of the Laurer’s or of the genito-intestinal canal
to the oviduct in the Trematodes. I therefore believe them all homolo-
gous with one another. ‘The blind ending of the canal in Amphilina
may have been brought about by a simple abortion of its terminal por-
tion, as in Aspidogaster, or by a total disappearance of the alimentary
canal, with which it had been connected as it now is in many species
of Monogenea.

I am now going to propound the opinion which may seem to
many exceedingly heterodox, that the uterus of the Cestodes is
homologous with the vagina of the monogenetic Trematodes. But to
make my arguments properly appreciated it is necessary to explain
my conception of the relations of the various genital ducts in the

Cestodes. In these the uterus has, I believe, usually been regarded as
170 8. GOTO.

the direct continuation of the oviduct, and the vagina as an accessory
duct. From a physiological point of view this.conception is quite
correct—the ovum in fact passes from the ovary into the uterus.
But, as I have already explained above, this mode of conception seems
to me morphologically not correct. I regard the vagina as the direct
continuation of the oviduct, and both the yolk-duct and the uterus as
accessory ducts opening into the former.’ And in accordance with
this view I regard that portion of the genital duct in Tenia and
Caryophylleus (Pl. XXVII, figs. 5 & 6) which lies between the
beginning of the vagina and the beginning of the uterus asthe yolk-
duct. It may be objected that the position of the shell-glands, which
are in other forms always situated around a portion of the oviduct, is
against such a view. But the shell-glands being evidently a special
physiological provision, I believe that their position must not be regard-
ed as constant; in fact, they do vary considerably in position even
among the monogenetic Trematodes; and if they can be displaced in
one direction there seems to me to be no reason why they. can not be dis-
placed in another, provided only that there be a physiological necessity
for it or an advantage gained thereby. I therefore believe that in
Tenia the shell-glands have shifted position from the initial portion of
the vagina (or its homologue, as in the Trematodes) towards the
uterus, in consequence of the changed functions of these two canals
(i.e. their respective homologues) in the Trematodes and the Cestodes—
assuming for the time being that the monogenetic Trematodes present
a more primitive state of things. This granted, let us compare the
uterus of the Cestodes with the vagina of the monogenetic Trematodes.

The.most striking difference between these two structures is that

one of them is clearly seen to have been originally paired, while the

 

1). Cf. Monticelli’s “Appunti “etc.” and Will’s “Caryophylleus mutabilis ” (Pl. Il,
fig. 17). 3 . =
STUDIES ON THE ECTOPARASITIC TREMATODES OF JAPAN. 171

other presents no trace of such a condition. ‘This difference, how-
ever, appears to me to be not so fundamental as to effectually bar
the homology of the two ducts, since both the Cestodes and the mono-
genetic Trematodes must have undergone numerous modifications in
different directions since they have diverged from a common stock,
This difference, then, being eliminated as of secondary importance,
and the blind ending of the uterus in Tenia being assumed to be also
a secondary modification scarcely requiring further exposition here,
there is a remarkable coincidence between the vagina of the Monogenea
on the one hand and the uterus of the Cestodes on the other, in their
relation with the other genital ducts. Thus, both unite with the
yolk-duct at one end and open outwards at the other. It is indeed
true that in Bothriocephalus latus the uterine pore is situated on the
ventral side; but the homologous pore is also on the same side in
many species of ectoparasitic Trematodes, as Tristomum, Monocotyle, etc.;
and in many species of Bothriocephalus the opening is on the dorsal.
side, as may be seen from the figures published by Matz” in his
paper on Bothriocephalus. After all, the position of the external
openings is, as Looss has justly remarked, of quite secondary
importance, and as already mentioned varies considerably in different
members of the same group. In Bothriocephalus the uterus can not
exactly be said to open into the yolk-duct; on the contrary, the uterus,
the oviduct, and the yolk-duct meet at one point ; but a similar case
occurs in Monocotyle among the monogenetic Trematodes. I there-
fore -believe that the uterus of the Cestodes is homologous
with the vagina of the Trematodes.

The view above explained seems to me to possess at least one

advantage over others, which is that it leaves no residual pheno-

 

1).. Matz—Beitriige zur Kenntniss der Rothriocephalen. Archiv f. Naturgeschichte,
Jahrg. 58,1. Bd. : 7s
172 8. GOTO.

menon. For, according to the view of Monticelli and Pintner,
the genito-intestinal canal is “ un adattamento speciale” in the Mono-
genea, while according to that of Looss the vagine of the same are
“ Bildungen sui generis’’—7. ¢., in logical language residual pheno-
mena. And as to the genito-intestinal canal being a special adapta-
tion in certain members of the Monogenea, it is exceedingly difficult
to see how and from what necessity such a canal could have been
specially developed in a limited number of forms, while totally want-
ing in othérs. Whereas, if we regard the canal as in process of
abortion, we meet with no difficulty, and the various facts appear to
me capable of being brought into harmony with each other. Accord-
ing to my view, then, the Trematodes and the Cestodes are to be
derived phylogenetically from a form which—adopting the termino-
logy applicable at present only to the Monogenea—possessed the
paired vagine, the uterus, and another duct, the homologue of the
canalis genito-intestinalis. In saying this, however, it should be observ-
ed that I by no means assert these organs to have had in the suppos-
ed ancestral form the same function as they have now in either of its

descendants.
As an addendum to the above discussion I beg to make just one

short remark on the vagina of Diplozoon. In my paper on Dipl.
Nipponicum, I have described the vas deferens of one individual as
standing in direct connection with the yolk-duct of the other. In
doing so I stated merely what I could directly observe ; for in my
sections I could not distinguish the vagina from the vas deferens. It
is true that the terminal portion of what I then considered the vas
deferens was exceedingly small, but this portion was not set off by
any demarcation from the proximal portion. I fully admit, how-
ever, the justness of Pintner’s” criticism on this point. I have

1). Pintner—Nochmals iiber den Begattungsakt der parasitischen Plathelminthen. Cen-
tralbt. f. Bakter. u. Parasitenk., Bd. 9, 1891, No. 22.

 
STUDIES ON THE ECTOPARASITIC TREMATODES OF JAPAN. 173

indeed virtually admitted the presence of the vagina in Diplozoon in
my comparison ? of it with Microcotyle, a genus which seems to me
to be closely allied in many respects to the former ; but I did not
then sufficiently so consider the theoretical aspect of the question as
to clearly express myself on the point.

5. The Protrusion of the Penis—Although I have not had much
opportunity to observe it, there can.scarcely be any doubt that the true
penis as well as the chitinous armature of the genital atrium (of
Microcotyle) can be protruded. In those forms which have the tubular
chitinous penis this is probably the sole part which is protruded and
introduced into the vagina of the other individual. On the other
hand, in Tristomum and Epibdella, or more generally in those forms
which have a well-developed conical or club-shaped connective-tissue
penis it is this which is protruded ; but in this case it is not certain
whether it is actually introduced into the vagina of the other
individual. It has been a mistake on the part of some writers to draw
conclusions as to the inability of the penis to protrude from the small-
ness of the opening of the genital atrium or the shortness of the penis,
and, again, as to its incapability of being intreduced into the vagina on
account of its great size. It should be remembered that the body in the
Trematodes is exceedingly soft and capable of both extension and con-
traction, as may be seen from Pintner’s observation on the copula-
tion of the tapeworm, and mine on the protrusion of the penis in
Tristomum ovale. As already mentioned, in Tristomum some of the
diagonal fibres of the body are specially developed around the penis,
and no doubt assist in its protrusion ; but in most of the species studied
by me there are no protractors; and in these cases the general

musculature of the body is, I think, entirely responsible for the protru-

 

1). Le. p. 187.
174 S. GOTO.

sion. If all the sets of muscular fibres of the body contract at the
same time, the investing membrane must be subjected to pressure from
within, great enough to evaginate the genital atrium and protrude the
penis.

6. Remarks on the Terminology of the Genital Organs—In conse-
quence of the complicated relation of the genital organs of the
Trematodes the same word has, on the one hand, been often used in
different. senses by different writers, and on the other hand, cor-
responding organs have been designated by different names. It may
therefore not be quite out of place here to compare, without aim-
ing at exhaustiveness, the terms which have been used"; confin-
ing our attention mainly to the ectoparasitic Trematodes. In his
““Saggio”” Monticelli used the term “ ovidotto interno” for that
portion of the female efferent duct which lies between the ovary and
the ootyp ; the latter he called “utero” ; while the remaining por-
tion, i. ¢., the portion lying between the ootyp and the external
opening, he called “ ovidotto esterno.’’ In his recently published
‘“* Primo’ contributo,”’ however, he uses these terms in other senses.

Leaving the “ ovidotto interno”

‘with the same sense, he now ap-
plies the term ‘‘utero” to that portion which lies beyond the shell-
glands and which “conserva lo stesso calibro,” and ‘ ovidotto
esterno” for “‘ sua porzione terminale, dove si allarga ad imbuto molto
allungata.” The term “ootypo ” he uses in the sense given it in the
present paper.
Wright and Macallum in their paper on Sphyranura apply

the term “uterus” to the ootyp, and use the latter term for that

 

1), The descriptions of Vogt in his paper, “ Ueber die Fortpflanzungsorgane einiger
ectoparasitischer mariner Trematoden” (Zeitsch. f. wiss. Zool., Bd. 30, Suppl. 1878, p. 306-340)
are unfortunately so imcomplete and obscure that I could not make mitich use of them. His
terminology will not therefore be considered here, lest I should misinterpret his observations.
STUDIES ON THE ECTOPARASITIC TREMATODES OF JAPAN. 175

enlarged portion of the female duct which is found in Sphyranura at
the junction of the oviduct with the unpaired yolk-duct and the
genito-intestinal canal. Those portions of the “ oviduct” which lie
between the ovary and their “ ootyp” and between this and their
“uterus” they call respectively the ‘“ovarian’’ and the “ uterine’
portion. The portion corresponding to what has been called the
uterus in this paper is wanting in Sphyranura.

Taschenberg” uses the term “ Uterus” for the ootyp and
holds any special name for that portion of the female duct which lies
beyond it “ fiir véllig iiberfliissig.”

Braun”. in his “ Wiirmer ”’ uses the term.“ ootyp”’ in the sense
it has in this paper. “ Keimleiter”’ or ‘ Germiduct” he calls that
portion of the female duct which extends from the ovary “ bis der-
selbe (the duct) mit den Dottergingen in Verbindung tritt.” And
at page 490 he says, ‘‘ Was jenseits des Ootyps bis zur weiblichen
Geschlechtséffnung liegt, bezeichne ich als Uterus” ; so that according
to his terminology strictly taken, no name is left for that portion of
the female duct which lies between the opening of the yolk-duct and
the ootyp. Perhaps he means to call this portion ‘‘ Keimdottergang,”
a term used, as he himself tells us, by Stieda.

tis perhaps hardly necessary to remind the reader that in this
paper the term “oviduct” is used for that portion of the female efferent
duct which lies between the ovary and the “ ootyp”’; the latter for that
portion which is distinguished by the presence of shell-glands around
it; “uterus” for that portion which lies beyond the ootyp. In my
paper on Diplozoon I called “uterus’’ all that portion which lies

between the genital opening and the ootyp inclusive, and distinguish-

 

ed the latter as “uterus proper.” But I find the term “ ootyp”

1). Taschenberg—Weitere Beitriige. p. 37 et infra.
2). Braun—l. c., p. 483 & 490.
176 S. GOTO.

now so often used by German and other continental writers, and
also by some English-writing authors, that I believe myself justified
in adopting it too—and in the sense in which it has been used
by P. J. v. Beneden” and just now defined in this paragraph.

In conclusion I wish to make a short remark on the terms
“vagina” and ‘“ Laurer’s canal” as applied to. the Monogenea. The
former possesses, etymologically speaking, only a physiological signi-
fication, and it is very unfortunate that Monticelli has attached to
it a morphological meaning, and has called the Laurer’s canal vagina,
although, according to his own opinion, not this canal but the
“ovidotto esterno”’ functions as such; so that if we should adopt
consistently Monticelli’s terminology we should be led to some
such awkward expressions as “the vagina of the endoparasitic ‘Tre-

797

matodes.is not a true vagina but the ‘ ovidotto esterno. “¢ Laurer’s
canal” now so familiar to helminthologists ought, in my opinion,
to be retained, as its homology is still under discussion. It is, on
the other hand, not advisable to apply the name to the vagina of
the. Monogenea, as has been done by some writers. For, in the first
place, we have for this group such a good name as “ vagina,” and in
the second place—and this is a very serious objection—the homology
of the two canals is far from being yet made out. It is therefore
to be hoped in the cause of science that we shall use non-commital
terms, and simply speak of the “ vagina” of the Monogenea, and the

“ Laurer’s canal ”’ of the Digenea.

B. Biological Notes.

Hazitat—The particular habitat of each species will be stated
in the systematic part of this paper ; but some general facts must be

noted down here. By far the greater number of ectoparasitic Tre-

 

1). P.J.v. Beneden—l. ¢. p. 15.
STUDIES ON THE ECTOPARASITIC TREMATODES OF JAPAN, 177

matodes live attached to the gill of the fish ; but many live in the
mouth-cavity or on the general surface of the body. For instance,
Tristomum Nozawae, the specimens of which I owe to my friend Mr.
S. Nozawa of the Fisheries Bureau of the Hokkaidd Ché, was found,
according to my friend’s statement, attached to the fins of Thynnus.
sibi. Monocotyle Ijimae I have found parasitic in the mouth-cavity.
of Trygon pastinaca, and Diclidophora sessilis and Diclid. elongata res-
pectively in that of Cherops Japonicus and Pagrus tumifrons. It is
stated by Monticelli ) that some species of Octocotylidae are parasitic
on Cymothoa ; I have once found a single specimen of Diclidophora
elongata attached to the caudal segment of a Cymothoa, and according
to Prof. Ijima’s statement in manuscript Diclidophora smaris
was also found attached to a Cymothoa. But as Prof. Ijima
remarks, these facts alone cannot be taken as proving that these
Trematodes are true parasites of the Cymcthoa; for all the other
specimens of Diclidophora elongata which I have collected from the
same host were found attached directly to the wall of the mouth-
cavity, and therefore the single specimen that was attached to the
Cymothoa must be regarded as accidental. It is, however, quite other-
wise with Tristomum biparasiticum. In the first place, every one of the
specimens of this species that I have collected was attached to the
carapace of a copepod, probably of the genus Parapetalus, parasitic on
the gill of Thynnus albacora ; and in the. second place, a very curious
relation exists between the Trematode and the copepod. I have
namely found the egg of the former attached to the ventral side of an
abdominal segment of the copepod. In most specimens two eggs were
attached to one individual in like positions on the two sides, but in
some I have found only one. The egg I have reproduced in fig. 4a,

Pl. XXV; and as may be seen from the figure, the chitinous shell

 

1). Monticelli—Saggio, p. 18.
178 8. GOTO.

eonsists of numerous concentric layers and is provided at one end

with a hollow filament, by. means of which the egg is attached to the

host. In view of these facts, it can scarcely be doubted that we have

here a case which can not well be brought under the’ category of '
either commensalism or parasitism ; for the Trematode seems to

derive its food, like other species, from the gill of the fish, deriving

only some advantage by attaching itself and its eggs to the body of

the copepod. It. is not, however, clear to me what advantage the

parasite derives by attaching its eggs to the copepod.

Another interesting fact may be here mentioned. It is this, that
Tristomum sinuatum and Tristomum ovale, which inhabit the same host
(Histiophorus sp.), keep strictly separate from each other, and appear
never to wander one into the habitat of the other. T'. ovale, namely,
is found in the mouth-cavity—on its wall or on the branchial arches
—while T. sinuatum is confined to the inner surface of the branchial
plates—the branchial filaments of the same series coalescing in the above
mentioned fish with each other and forming a single plate. I have never
found any specimen of T. ovale attached to the gill ; nor have I any of
T. sinuatum on the outer surface of the gill plate. Perhaps this depends
on the nature of food of the two species, 7’. sinuatum living on blood,
while 7’. ovale seems to live on the slime of the mouth-cavity ; but
then it is not easy to see why T. sinuatum never wanders out to the
outer surface of the gill-plate.

‘Locomotion—The locomotory movements of some ectoparasitic
Trematcdes have been described by Haswell” and Monticelli” ;
and I have observed similar movements in Tristomum sinuatum,

Monocotyle Ijimae, and some species of Microcotyle. When on one

 

1). Haswell—On Temnocephala, an Aberrant Monogenetic Trematode. Quart. Journ. of
Mic. Sc., vol. XXVIII, 1888. p. 282 et infra. :

2). Monticelli—Saggio. pp. 19-20.
STUDIES ON THE ECTOPARASITIC TREMATODES OF JAPAN. 179

occasion I kept a few specimens of Mf. caudata just taken from a very
fresh fish, on a glass slide ‘covered with sea-water, these executed
what Haswell calls “looping” movements (spannende Bewegung)
like those of the leech. The worm, namely, first attached its anterior
end to the slide, apparently by means of the anterior suckers, and
dragging after it the hinder part of its body, attached the caudal disc
close up to the anterior end by means of the posterior suckers, the
body in the meanwhile being folded on itself on the ventral side so
as to form a loop ; the worm then let go the anterior end and stretch-
ing its body, again attached it to the slide, detaching at the same time
the posterior suckers, which were then again brought close up to the
anterior end, and soon. ‘The looping movement is slow in Microco-
tyle, but in Monocotyle it is very rapid and energetic and is just like
that of an excited leech. ‘The worms moved quite rapidly while on
the host, but when I transferred them to a watch-glass filled with sea-
water, they at once began wandering about so quickly that each
looping movement could only just be distinguished, and now and then
they groped about with the anterior extremity of their body, thus show-
ing apparently signs of surprise. ‘The posterior sucker of this worm,
containing as it does the striped muscular fibres already described,
adheres very strongly to external objects—not only to the surface of the
mouth-cavity but also to a smooth surface such as that of the watch-
glass. Tristomum sinuatum executes locomotion quite rapidly but
still much more slowly than Monocotyle. The comparatively small
posterior sucker of this worm is capable of adhering very tightly to
the surface of the gill. When the worm advances its anterior suckers
to attach them to the substratum, it stretches out its body to such an
extent that it becomes much elongated and its breadth is reduced to
about one-third its length. Besides the looping movement which all

the three species above mentioned are able to execute, I have also
180 S. GOTO.

observed in Monocotyle and Tristomum those twisting movements
mentioned by Haswell and Monticelli. These worms, namely,
are capable of moving their bodies in lateral directions while keeping
the posterior sucker attached to a fixed substratum. This is due to
the crossing of the muscular fibres that enter the sucker from the
body and form the irregular radial fibres of the sucker already describ-
ed—those coming from the right side of the body going to the left
side of the sucker and those from the left going to the right. In this
connection it may be mentioned that in many specimens of T’. sinua-
tum which were killed with hot sublimate or heat alone, the posterior
suckers were seen to have been more or less rotated from their normal
position—a fact due to.the unequal contractions of the irregular radial
fibres of the suckers.

In all the three species above mentioned the anterior suckers
are chiefly used for attaching the anterior end of the body in
locomotion. In Monocotyle indeed there is, properly speaking, no
anterior sucker ; but the special development of the dorso-ventral
fibres already described serves in its stead. In Microcotyle the
anterior end is seen, when it is being attached to a hard substratum
such as a glass slide, to become much broadened out. ‘This seems
to be brought about by a partial evagination of the mouth-cavity,
by which the suckers are brought in direct contact with the
external object. In Tristomum, on the other hand, the mouth, 7.c., in
this case the anterior end of. the pharynx, was often seen to be not in
close contact with the substratum, while the suckers were closely
applied to it.

Foop—The majority of the species described in this paper live
on the slime of the host ; but some are also able to extract its blood.
For instance, I have observed many specimens of Tristomum sinuatum

whose alimentary canal was gorged with blood, and they in conse-
STUDIES ON THE ECTOPARASITIC TREMATODES OF JAPAN. 181

quence looked much redder than they really were—this species
possessing a light flesh-red colour of its own.

CoLouratTion—Most of the monogenetic Trematodes that I have
studied may be described as having a colourless and transparent body;
but since the internal organs are more or less visible from the exterior
the body appears coloured. The only real exceptions in this respect
that I have observed are Tristomum sinuatum and T. rotundum, which
possess, as just mentioned, a light flesh-red colour of their own; but
in which tissue of the worm this colour is lodged I have not been able
to make out ; possibly it may be in the investing membrane. The
specimens of Hexacotyle acuta that I have myself collected had all a
dusky colour like that of the gill of its host, but those that were
collected by my friend Mr. Nozawa were perfectly colourless except
where the vitellarium was seen through, which is in this species more
or less dusky coloured. I therefore believe that the generally dusky
colour of my specimens was due to a greater development of the
vitellarium.

The only internal organs that possess any colour of their own are
the vitellarium and the pigment cells of the intestine already describ-
ed. In fresh specimens the former looks dark and granular by
incident light, and slightly yellowish by transmitted light ; while
the pigment cells of the intestine look dark brown or perfectly black
by both incident and transmitted light. ‘The body of most ecto-
parasitic Trematodes being thus transparent and allowing the substra-
tum to be seen through—for the vitellarium is in fresh specimens
not conspicuously dark, and the intestinal pigment-cells are not close
enough to each other to constitute a single visible object—they are some-
what difficult to detect at first sight. This, however, must not be
regarded as a case of protective colouration ; for in the first place, the

nature of the habitat already protects the parasites from being at-
189 8. GOTO.

tacked by their enemies, and in the second place, they are but very
imperfectly exposed to light, and thus the conditions of their exist-
ence prevents any effective play of natural selection.

Ingury To tae Host—On this head I am only able to add
an observation or two to that of v. Baer on Nitzschia elongata men-
tioned by Braun.” It has already been said that Tristomum sinuatum,
like Diplozoon Nipponicum, can extract blood from the gill of the
host, and thus may cause some injury to it. In one case I observed
that a specimen of Diclidophora elongata had caused an abnormal
excrescence to form around its caudal disc, which, together with the
posterior part of the body proper, was thus completely immersed

in the excrescence and hidden from view.

C. Systematic.

In this part of my paper I shall confine myself to the cha-
racterisation and description of the genera and species studied by
myself, leaving their systematic classification to those who may have
occasion to study personally a larger number of forms and especially to
reéxamine the species previously described. Owing to incompleteness
in the literature I could gain access to, I have not been able to make the
historical notices as exhaustive as I could wish ; they are, however,
published with the hope of lightening, in ever so slight a degree, the
labours of future workers in this field. For the reason above stated I
have also been compelled to satisfy myself in many places with second
hand quotations and references. In such cases the authorities are
invariably mentioned.

Before proceeding to the systematic descriptions of the different

genera and species, I wish to remark once for all with special em-

 

1). Braun—Wiirmer. p. 512.
STUDIES ON THE ECTOPARASITIC TREMATODES OF JAPAN. 183

phasis, on the usefulness for systematic purposes of the examination
of the hooks which are often present near the posterior end of the
body. Drawings of them made from glycerine-gelatine preparations
as mentioned at the beginning of the present paper would be of in-
valuable service in the identification of species. Indeed, different
species of the same genus can be distinguished and identified with a
good degree of certainty by proper examination of these hooks alone.
When one has a new species before him and yet has not time enough
to make a sufficiently minute study of it, he would do well to add
to its more prominent characteristics a sketch of the hooks from a
glycerine-gelatine preparation, care being taken to bring them to
such a position as to enable him to get a good view of the characteris-
tic form—a job which can usually be effected with ease by repeatedly
melting the imbedding medium and giving proper shifts and pressure

to the cover-glass.

I. Mricrocotyrr, P. J. v. Beneden et Hesse.

This genus was first erected in 1863 by P. J. van Beneden and Hesse with
the following diagnosis’): “Une partie du corps est séparée en arricre par un
étranglement et porte, des deux cédtés du corps, un trés-grand nombre de petites
ventouses 4 crochets. Les eufs sont munis d’un filament aux deux péles.” These
writers have described five species, viz., Af. labracis from the gill of Labrax lupus,
M. canthari from the gill of Cantharus griseus, M. donavani from the gill of Labrus
donavani, MM. erythrini from the gill of Pagellus erythrinus, and M. chrysophrii from the
gill of Chrysophris vulgaris.

In 1878 V og t® described a new species, AM. mugilis, from the gill of Mugil cephalus.
According to- this writer this genus should be united with <A.xine, since “die
innere Organisation ist durchaus dieselbe, nur ist bei Axine orphii... der Vorder-

theil des Kérpers weit melir in die Linge gezogen und schmal, wiilirend zugleich das

 

1). P. J. v. Beneden et Hesse—Recherches sur les Bdellodes et les Trématodes marins.
p. 112.

2). Vogt—Ueber die Fortpflanzungsorgane einig. ectopar. marin. Trematoden. Zeit-
schr, f. wiss. Zoolog., Bd. 30, Suppl., 1878.
184 8. GOTO.
Hinterende mit den Saugniipfen nosh etwas schiefer zur Achse des Kérpers steht als
bei den typischen Microcotylen.” In the same year Lorenz” described another
species, Af. mormyri, from the gill of Pagellus mormyrus, and shed much light on its
anatomy and histology. ,

Parona and Per ugia® have recently (1889 & 1890) described four additional
species, viz., Mf. sargi from the gill of Sargus Rondeletit, 8. annularis, and S. vulgaris,
M. alcedinis from the gill of Smaris alcedo and Muna vulgaris, M. trachini from the
gill of Trachinus radiatus, and 3M. salpae from the gill of Bow salpa. Thesé writers
have also minutely redescribed all the preéxisting species and added a valuable con-
tribution to our knowledge of the general anatomy of the genus. Finally in 1891
Sonsino®» described a new species:from the gill of Umbrina cirrhosa, and named it
AM. Paneerii.

It has already been mentioned above that according to Vogt this genus should
not be separated from Axine. Lorenz, on fhe other hand, decidedly maintains its
separation as a distinct genus. The distinctive characteristics are according to him
(1) that Mficrocotyle is perfectly symmetrical in external form, the symmetry showing
itself especially in the form of the caudal disc, (2) that in Microcotyle the penis is
absent and that the vas deferens and uterus open outwards by distinct apertures,
while in 4.zine both have a common opening, (8) that in Microcotyle the vagina is .
situated on the dorsal median line, while in Avine it is situated on the lateral margin,
and (4) that in Microcotyle a large number of eggs are found in the uterus at the
same time, while in Azine only one egg is found at a time. Parona and
Perugia, who studied nearly all the species hitherto known, say, “ Differenze
salienti fra Aaine e Microcotyle stanno nell’avere il primo vagina laterale ed armata
ed il secondo mediana; e nel portare un’unica serie di ventose caudali l’ 4rine e due
il Microcotyle.”

According to my own observations every one of the distinctions mentioned by
the preceding writers falls away. (1) As already stated, Jf. reticulata and II. sciaene

have a decidedly asymmetrical form, while in some other species a slighter degree of

 

1). Lorenz—Ueber die Organis. d. Gattung. Axine u. Microcotyle. Wiener Arbeiten.,
Bd. I, Hit. 3, 1878.

2). Parona e Perugia—Res ligustice, XIV. Contribuzione per una monografia del genere
Microcotyle. Estratto dagli Annali del Museo Civico di Storia Naturale di Genova, ser. 2,
vol. X, 1890.

8). Sonsino—Di un nuovo Microcotyle raccolto dall’ Umbrina cirrhosa. Proc. verb. d. Soc.
Tosc. di Scienze Natur., 1891. Cited on the authority of St.-Remy.
STUDIES ON THE ECTOPARASITIC TREMATODES OF JAPAN. 185

asymmetry presents itself in some internal organs, as in the different lengths of the
two branches of the intestine. (2) In all the species of Microcotyle what Lorenz
calls “Penis” is distinctly present 1) as also the genital cloaca; and his observa-
tion as to the separate opening’ of the male and female ducts is, as Parona and
Perugia have pointed out, erroneous. (8) In the species of Avxine which I have
studied, and which are described below, the vagina is situated, as in Microcotyle, on the
dorsal median line. (4) Ihave observed some specimens of dine heterocerca dis-
charge, while kept in sea-water in a watch-glass, a large number of eggs from the
uterus, which was afterwards found to be much enlarged in consequence. (5) In all
the three species of Aaine I have studied, two series of suckers are distinctly present,
although one of the series is much reduced in number. Thus we find no absolute
difference between the two genera, the difference lying ouly in the degree in which
the asymmetry is manifested in each. Still the general form of the two genera
presents quite a perceptible difference, so that we may keep them distinct for con-
venience’ sake. A sharp distinction between two such nearly allied genera can not
be expected.

‘In view of the facts above summarised, the diagnoses given by the preceding
writers are no longer quite satisfactory ; I therefore venture to modify them as

follows :

Body elongated, mostly symmetrical, with the an-
terior end rounded and the posterior end usually pointed.
With a pair of suckers in the mouth-cavity. The caudal
disc, which is in most species separated from the body
proper by lateral constrictions, usually bears a large
number of minute suckers. Genital cloaca present ;
genital opening on the ventral median line; vaginal
opening single, situated in the median line on the dorsal
side. No chitinous hooks at the posterior end of the

body.

 

1). Cf. Parona and Perugia—Res ligusticae, XIV. p. 8.
186 8. GOTO.

1. Microcotyle caudata, n. sp.
(Pl. I, fig. 1; Pl. II, fig. 7; Pl. ITD, figs. 7, 8, 9, 10;
Pl, IV, figs. 7 & 8; Pl. V, fig. 3; Pl. VI, fig. 3.)

Body” elongated, about 3.2 mm. in length, symmetrical. An-.
terior sucker with a membranous septum. Common genital opening on
the same level as the beginning of the intestinal trunks ; atrial spines
conical and slightly curved, the longest measuring 0.01 mm. Ovary
situated at about the middle of the whole length of the body, with the
oviduct end on the right side, thence extending towards the left,
presenting a convex border in front. On being folded on itself on
reaching the left intestinal trunk, it turns again towards the right, and
on reaching its oviduct end takes a backward direction and ends at the
anterior end of the testes by being folded once on itself. The single,
median vagina is situated about six times as fur forwards from the
anterior end of the ovary as it is behind the genital opening ; it leads
into a single, median canal, which, after proceeding backwards half
way towards the anterior end of the ovary, divides right and left
into two canals. These, the paired vaginal canals, after proceeding
backwards for a short distance, become continuous with the paired
yoli-ducts. The genito-intestinal canal takes its rise from the oviduct
exactly opposite the unpaired yolk-duct, and after proceeding for a
short distance backwards and towards the left side of the body,
suddenly turns towards the right, and finally opens into the in-
testinal trunk of the right side. The vitellaria of the two sides
are very distinct in front; but posteriorly the. boundary between
the two can not usually be distinguished. The paired yolk-ducts begin
at about the end of the anterior third of the whole length of

 

1). In this as in the following species, the curvatures of the body, when there are any, are
not taken into account. I would point out also that the length of the body varies considerably
according to the different state of contraction, and that therefore much weight should not be
laid on it in the identification of species. >
STUDIES ON THE ECTOPARASITIC TREMATODES OF JAPAN. 187

the body, and unite in the median line at the Jevel of the hinder end
of the anterior third of the ovary. ‘The testes occupy a little Jess than
one quarter of the whole length of the body and are situated behind the
ovary ; they are large and are about 23 in number. The two main
trunks of the intestine send out lateral branches both inwards and out-
wards ; the left trunk is longer than its fellow, and extends beyond
the vitellarium into the caudal disc, while the right trunk ends with
the vitellarium. The caudal disc is about } the length of the whole
body, and is narrow. Posterior suckers about 25 on each side;
breadth 0.045-0.08 mm.

Habitat—Gill of Sebastes sp. sp. (Jap. Mebaru and Kin-mebaru).

Locality—Mitsugahama (Prov. Tyo).

Date—August 1889.

2. Microcotyle sebastis, n. sp.
(PI. I, figs. 2 & 3; Pl. IIT, fig. 1; Pl. IV, figs. 1, 4, & 5.)

Body about 5.5 mm. long, slender, symmetrical. Anterior sucker
with a septum. Common genital opening a little in front of the point
of bifurcation of the alimentary canal ; atrial spines conical, slightly
curved, the longest about 0.017 mm. Ovary long, situated at about
‘the middle of the entire length of the body ; the anterior portion is A-
shaped and the posterior portion somewhat S-shaped with its left
anterior end continuous with, and folded on, the leg of the “\; the
hindmost terminal portion being folded many times on itself. Vaginal
opening single, median, and dorsal, situated about thrice as far in front
of the anterior end of the ovary as it is behind the common
genital opening. The vaginal canal continues single for about half
way towards the anterior end of the ovary, then divides, and the
two ducts thus formed, after traversing about one-third their way

towards the ovary, become continuous with the paired yolk-ducts.
188 S. GOTO.

These unite with each other at the level of the front end of the
posterior S-shaped portion of the ovary, and the single yolk-duct opens
into the oviduct at a little distance from the beginning of the ootyp.
The genito-intestinal canal opens into the oviduct about midway between
the origin of the latter and the beginning of the ootyp. The vitellaria
of the two sides are entirely distinct both in front and behind ;
they end anteriorly near the point of bifurcation of the alimentary
canal, and posteriorly with the body proper, not extending into the
caudal disc, but leaving the posterior portion of the intestinal trunks
naked. Testes occupying a little less than one-fifth the whole length
of the body, posterior to the ovary ; of rather small size, about 40
in number. The two trunks of the intestine sending out only a few
short branches towards the median side ; the left leg longer than the
right, and both extending for a certain distance into the caudal disc.
This occupies about 4 the whole length of the body. Posterior suckers
about 29 on each side; breadth 0.068-0.128 mm.

Habitat—Gill.of Sebastes sp. sp. (Jap. Ma-zoi and Nagara-zoi).

Locality—Hakodaté.

Date—August 1890.

3. Microcotyle elegans, n. sp.
(PL. I, fig. 4; Pl. V, fig. 2.)

Body about 4 mm. long, slender, symmetrical. Anterior sucker
with a septum. Common genital opening a little in front of
the beginning of the intestinal trunks; atrial spines conical, about
0.005 mm. in length; a few spines being also present on the posterior
wall. Ovary in the anterior half of the body, its hinder end being
nearly at the middle of the whole length. Its anterior half is inter-
mediate in form between the corresponding portions of M. caulata and
M. sebastis; the posterior half is S-shaped, and the terminal portion is
STUDIES ON THE ECTOPARASITIC TREMATODES OF JAPAN. 189

folded many times on itself. Vaginal opening single, median, and
dorsal, situated four times as far in front of the anterior end of the
ovary as it is behind the common genital pore. The vaginal canal
continues single for a little more than half its whole course towards
the ovary, then divides, and the two canals after traversing one-fourth
their way towards the ovary become continuous with the paired yolk-
ducts. These unite at the level of the anterior end of the S-shaped
portion of the ovary, and the single yolk-duct thus formed opens into
the oviduct about midway between the beginning of the ootyp
and the point where the former receives the genito-intestenal canal.
This opens into the oviduct about half-way between the origin of the
oviduct and the beginning of the ootyp. The vitellaria of the
two sides are entirely distinct both in front and behind; ending
anteriorly at some distance from the point of bifurcation of the
alimentary canal, and reaching posteriorly the terminations of the
intestinal trunks, of which the left extends beyond the right. Testes
occupying a little less than one quarter of the whole length of the
body; of large size, about 27 in number. The trunks of the intestine
sending out numerous short branches on the inner side; the left
trunk longer than its fellow; both extending into the caudal disc,
and entirely surrounded by the vitellarium. Caudal disc a little
longer than 4 the entire length of the body ; posterior suckers about
50 on each side; breadth 0,040-0.068 mm.

Habitat—Gill of Scombrops chilodipteroides (Jap. Mutsu).

Locality—Misaki.

Date—December 1889.

4, Microcotyle reticulata, n. sp.
(Pl. I, fig. 5; Pl. ILL, figs. 2, 8, & 4; Pl. IV, figs. 2 & 8; Pl. V, figs. 5 & 6.)

Body 6-10 mm., or more, long, elongated, and slightly asymme-
190 8. GOTO.

trical. Anterior sucker without any septum. With only a single pair of
sticky glands near the anterior end of the body. Common genital opening
just behind the posterior end of the oesophagus ; atrial spines straight
and conical, about 0.016 mm. in length, composed of two parts, the
basa], hemispherical portion and the distal, spinous portion mounted
on the former. Ovary slender, situated at about the middle of
the whole length of the body; roughly speaking, S-shaped, and
making numerous minor windings, especially in its anterior half.
Vaginal opening single, median, and dorsal, armed with low conical
teeth, and situated at a short distance behind the common genital
opening. The single vaginal canal divides into two at a point
which is as far behind the external opening of the vagina as this is
behind the genital opening; and the two vaginal canals after proceeding
backwards for a short distance, become continuous with the paired
yolk-ducts at the point marked with an « in fig. 5, Pl. I. The paired
yolk-ducts unite at about the anterior end of the ootyp, and the single
yolk-duct opens into the oviduct just where this is continued into the
ootyp. The genito-intestinal canal opens into the oviduct about twice
as far from the origin of the latter as from the beginning of the ootyp.
The vitellaria of the two sides are distinct in front ; the lobes are
small and scattered, and are situated mainly on the dorsal side of the
intestine. Testes occupying a little less than one-half the whole median
portion of that part of the body which lies behind the posterior
end of the ovary; of small size and very numerous. The terminal
portion of the vas deferens (PI. V, fig. 6) is armed with conical spines
just like those of the genital atrium. The branches of the intes-
tine form a complicated net-work (PI. ILI, fig. 2). Caudal dise con-
tinuous with the rest of the body. Posterior suckers occupying somewhat
more than one-third the entire length of the body; more numerous

and smaller in size on the right than on the left side, there being about
STUDIES ON THE ECTOPARASITIC TREMATODES OF JAPAN. 191

42 on the right and only 23 on the left side; breadth 0.075-0.227 mm.
Habitat—Gill of Stromateus argenteus (Jap. Mana-gatsuwo).

Locality—Mitsugahama.
Date—August 1889.

5. Mierocotyle truncata, n. sp.
(PL II, figs. 1 & 2; Pl. Ti, fig. 6; Pl. V, fig. 7.)

Body about 3.3 mm. long, slender, pointed anteriorly, and ending
posteriorly with a truncate, triangular caudal disc. Common genital
opening on the same level with the point of bifurcation of the alimentary
canal; genital atrium armed with twenty rods about 0.13 mm. in length,”
arranged in a circle which is incomplete on the dorsal side. The
S-shaped ovary is situated in the front half of the body, the hinder
end lying at the middle of the whole length of the body. Its anterior
third is large, but its posterior two-thirds are slender, and it pre-
sents a slight enlargement at the posterior end which is in close
contact with the foremost testes. The single, median, dorsal vaginal
opening is situated a little more anteriorly than midway between the
common genital opening and the front end of the ovary. Vaginal
canal goblet-shaped, the mouth of the goblet corresponding to the ex-
ternal vaginal opening, and the bottom communicating with the paired
yolk-ducts. These, proceeding backwards, unite with each other at
about the level of the front end of the ootyp, and open into the
oviduct midway between the origin of the oviduct and the beginning
of the ootyp. The genito-intestinal canal opens into the oviduct just
opposite the yolk-duct. The vitellaria of the two sides are quite dis-
tinct both in front and behind, reaching in the former region up

to the very point of bifurcation of the alimentary canal. Here also the

 

1). The apparent difference of length in fig. 2, Pl. II, is, as stated in the anatomical
part, probably due to the fact that the ventral ones are looked at not quite perpendicularly to
their long axes.
199 8. GOTO.

lobes of the two sides are closely applied to each other so as to
appear almost continuous. » Testes occupying two-fifths of the entire
length of the body, posterior to the ovary; of moderate size
and numerous. The vas deferens presents a sudden expansion at
the level of the beginning of the paired yolk-ducts and remains
large up to its opening into the genital atrium. ‘The trunks of the
intestine send but a few short branches towards the median line ;
and both end behind on the same level. Caudal dise very short.
Posterior suckers 10 on each side; breadth 0.055-0.072 mm.

Habitat—Gill of Pristipoma Japonicum (Jap. Isaki).

Locality—Mitsugahama.

Date—August 1889.

6. Microcotyle fusiformis, n. sp.
(Pl. I, fig. 3; Pl. IV, fig. 6; Pl. V, fig. 1.)

Body about 2 mm. long, symmetrical, fusiform in outline. An-
terior sucker with a septum. Common genital opening a little anterior
to midway between the hinder end of the pharynx and that of
the oesophagus; atrial spines small, conical, about 0.007 mm. in length.
The ovary when viewed from the ventral side has nearly the shape of
an interrogation-point; the front half large, and the hinder half
slender. J'aginal opening single, median, and dorsal, situated behind
the common genital opening two-fifths the whole distance between
this and the front end of the ovary. The vaginal canal con-
tinues single until within the last fifth of the above distance, then
bifurcates; and the two canals thus formed immediately become con-
tinuous with the paired yolk-ducts. These unite at a short distance
in front of the level of the origin of the oviduct, and open into it
just opposite the genito-intestinal canal at a short distance from the

beginning of the ootyp. ‘The vitellaria of the two sides are distinct
STUDIES ON THE ECTOPARASITIC TREMATODES OF JAPAN. 193

in front, but apparently continuous behind. Testes occupying a
comparatively small area about one-sixth the whole length of the
body, posterior to the ovary; of moderate size and comparatively
few in number (about 15). No lateral branches on the median side
of the intestinal trunks; the left trunk longer than the right. Caudal
disc continuous with the rest of the body, and the suckers occupying
nearly one-half the whole lateral borders of the body; suckers 30-33
or more on each side; breadth 0.046-0.065 mm.
Habitat—Gill of Centronotus rubulosus (Jap. Gimpo).

Locality—Mitsugahama,
Date—August 1889.

7. Microcotyle chiri, n. sp.
(PL IT, figs. 4 & 5; Pl. III, fig. 5; Pl. V, fig. 4.)

Body about 4.2 mm. long, symmetrical, slender in the anterior
portion where the vitellarium is absent, but the remaining portion
much broader, rounded at both ends. Common genital opening
situated a little in front of the hinder end of the oesophagus; genital
atrium with a hemispherical, cup-shaped organ on the dorsal side, the
inner surface of which is covered with spines similar in shape to those
of M. reticulata, and about 0.015 mm. long. The front half of the
ovary follows in its course nearly the three sides of an isosceles triangle
whose apex is directed backwards ; and the posterior half is many
times folded on itself into a close, irregular spiral. Vaginal opening
single, median, and dorsal, nearly half as far behind the common
genital opening as it is before the front end of the ovary. The
vaginal canal divides into two at a point which is about half as far
from the vaginal opening as from the anterior end of the ovary, and
the two canals, after traversing only a short distance, become continu-

ous with the paired yolk-ducts. These unite a little in front of the
194 8. GOTO.

anterior end of the ootyp, and the single yolk-duct thus formed opens into
the oviduct about midway between the beginning of the ootyp and the
opening of the genito-intestinal canal. The latter opens into the oviduct
at the beginning of the last third of the whole course of the ovi-
duct. The vitellaria of the two sides are quite distinct in front as well as
behind, though the lobes of the opposite sides come close to each other.
Testes occupying a narrow region between the two trunks of the intes-
tine, posterior to the ovary; rather small in size; about 25 in number.
No lateral branches on the median side of the intestine; the two intes-
tinal trunks of equal length, and nearly reaching the posterior end of
the body. Caudal disc continuous with the rest of the body ; suckers
occupying the posterior half of the lateral border of the body; about
30 on each side; breadth 0.090-0.140 mm.

Habitat—Gill of Chirus hexagrammus (Jap. Ainamé).

Locality—Hakodaté.

Date—August 1890.

8. Microcotyle sciaenae, un. sp.

(Pl. TI, figs. 6 & 6 a; Pl. VI, fig. 2.)
Body about 4 mm. long, slender, asymmetrical, rounded at
the anterior end and pointed posteriorly. Anterior sucker with a
septum. Common genital opening on the same level as the beginning.
of the intestinal trunks ; genital atrium armed with two sets of chitin-
ous rods arranged in circles (Pl. VI, fig. 2,.a & b). The longer
ones (a) are about 0.11 mm. long, each presenting two curvatures in
opposite directions, and are situated just in front of the opening
of the vas deferens. Only a small, terminal portion of these rods
projects into the cavity of the atrium, the remaining portion lying im-
bedded in the mesenchyma. The other shorter ones (b) have the

form of a hook and are about 0.02 mm. in length. ‘These are arrang-
STUDIES ON THE ECTOPARASITIC TREMATODES OF JAPAN. 195

ed at the mouth of the cylindrical sac before spoken of, the curved
portion projecting into the caviy of the atrium and the remaining
portion lying in the wall of the sac and the surrounding mesenchyma.
Ovary consisting of a A-shaped anterior portion and a posterior but
slightly slenderer portion which is turned spirally twice in the same
direction and once folded on itself in the opposite direction at the
hinder end. Vaginal opening a little less than twice as distant from
the front end of the ovary as it is behind the genital opening. ‘The
vaginal canal immediatly divides into two; and the two canals thus
formed proceed a little way backwards, and turning to the ventral
side of the vas deferens unite on the dorsal side of the uterus, then
again separate from each other and become continuous with the paired
yolk-ducts. ‘These begin in front of the anterior end of the ovary at
the distance of two-fifths the whole distance between the ovary and the
common genital opening, and unite with each other at the end of the
foremost third of the antero-posterior extension of the ovary. The
single duct thus formed opens into the oviduct about midway between
the beginning of the ootyp and the opening of the genito-intestinal canal.
The latter opens into the oviduct at the end of the anterior two-thirds
of the course of the oviduct. The vitellaria of the two sides are entire-
ly distinct both in front and behind, extending into the caudal
portion and surrounding the two intestinal trunks. Testes occupying
about two-fifths the whole length of the body proper, posterior to the
ovary ; large; about 27 in number. No branches on the median
side of the intestine, the two trunks of which extend far into the caudal
disc and are in this region wholly destitute of lateral branches ; the
right trunk describing a larger curve in consequence of the general
asymmetry of the body. The caudal disc is bent at an angle to the
body proper and is only a little shorter than it. Posterior suckers about
75 on the right and 60 on the left side; breadth 0.048-9.110 mm.
196 S. GOTO.

Habitat—Gill of Sciaena sina (Jap. Ishimochi or Guchi).
Locality—Mogi (near Nagasaki).
Date—July 1889.

II. Axine, Abildgaard.

This genus was erected by Abildgaard towards the close of the last century.
He described in 1794 a species, 4. belones, from the gill of sou belones. In 1836 -

Diesing divided it into two species, Heteracanthus pedatus and H. sagittatus; but
in his “Systema helminthum” he again united them into a single species.) In
1861 P. J. v. Beneden®) again described the same species and made some observa-
tions on the genital opening and the spines with which it is armed. He also
observed the similarity of the suckers to those of Diplozoon. In 1863 the same
writer in conjunction with Hesse) described two species, A. orphii from the gilt
of Esov belone and A. triglae from the gill of Trigla hirundo. The former, is, how-
ever, granted by later writers to be identical with 4. belones, already described by
v. Beneden. Finally in 1878 Lorenz‘) published a very detailed accounl
of the anatomy and histology of A. belones.

In accordance with the facts mentioned in the anatomical part of the present
paper I give the generic diagnosis as follows :

Body elongated, anteriorly slender, but broad pos-
teriorly. In consequence of an unequal development of
the two sides of the caudal disc the body is asymmetrical,
and the posterior end occupies a lateral position. The
longer side of the caudal disc bears numerous suckers, is
either convex or straight, and is bent at an angle to the
lateral border of the body proper; the other side bears only
asmall number of suckers or(?) noneatall. Nochitinous

hooks at the posterior end of the body. With a single,

 

1). Diesing—Systema helminthum, vol. I, p. 425.

2). P.J.v. Beneden—Mémoire sur les vers intestinaux, p. 53.

3). P.J. v. Beneden et Hesse—Recherches sur les Bdellodes et les Trématodes marins.
p. 116-117.

4). Lorenz—Untersuch. ii. d. Organisation d. Gattung. Axine u. Microcotyle. Wiener
Arbeiten, Bd. I, Hft. 8, pp. 3-20.
STUDIES ON THE ECTOPARASITIC TREMATODES OF JAPAN. 197

dorsal, median or a lateral vaginal opening. With a pair

of egg-shaped or spherical suckers in the mouth-cavity.

I. Axine heterocerca, n. sp.
(PI. VIL, figs. 1, 2,8, 4; Pl. VILL)

g, with a form roughly like that

3)

Body flat, about 10 mm. lon
of the blade of a Turkish sword, with a convex border behind.
Common genital opening situated a little behind the termination of the
oesophagus. Ovary at the posterior end of the middle third of the
body, comparatively small, long, following in its general course the
three sides of a triangle, the apex of which is directed towards the
front end of the body, and making numerous smaller windings; its
exact form is as represented in fig. 1, Pl. VII, and fig. 5, Pl. VIII.
Oviduct arising from the ovary on the right side of the body, and bear-
ing a small seminal receptacle close to its origin, proceeds backwards and
towards the left, and is continued into the ootyp in the median line of
the body. The uterus proceeds from the ootyp straight forwards and
opens into the genital atrium. Vaginal opening single, dorsal, median,
situated as far behind the common genital opening as this is behind
the pharynx. The vaginal canals are paired from the beginning, and
proceeding backwards on the inner side of the intestinal trunk are
continued into the paired yolk-ducts at the point marked with + in
fig. 1, Pl. VII. With a second dorsal opening behind the vaginal
opening, which ends blindly. The vitellaria of the two sides are whol-
ly separate in front; but their boundary behind can not be dis-
tinguished ; extending from the level of the vaginal opening to near
the posterior extremity of the body. Paired yolk-ducts arising from
the vitellarium on each side at the level marked with « in fig. 1, Pl. VII,
and proceeding backwards as the direct continuations of the vaginal

canals, unite with each other in the median line of the body, on the
198 8. GOTO.

ventral side of the uterus. The single yolk-duct thus formed then
proceeds almost straight backwards and opens into the oviduct
where this is continued into the ootyp. Genito-intestinal canal arising
from the oviduct at the middle of its course, and proceeding forwards
and towards the right, opens into the intestine. Testes occupying a
little less than two-thirds of the whole median portion of the body
lying posterior to the ovary, of moderate size, tolerably numerous.
Vas deferens describing numerous convolutions on its way towards the
genital atrium. Oe¢sophagus sending out numerous lateral branches.
Intestinal trunks with numerous branches both on the inner and outer
sides; those of the former, however, mostly very short. With about
30 suckers on one side and only 9 on the other; the largest of these,
lying at about the middle of the longer side, measuring 0.600 mm. in
breadth, and the smallest 0.065 mm.

Habitat—Gill of Seriola quinqueradiata (Jap. Buri or Hamachi).

Locality—Hiroshima (Ujina Port), Mitsugahama, and Misaki.

Date—August 1889 (H. & Mits.); December 1890 (Mis.).

2. Asxine aberrans, n. sp.
(PI. VII, figs. 5 & 6.)

Boily about 5 mum. long, flat, lanceolate, curved on one side, and
with a straight, posterior border making acute angles with the lateral
borders. Common genital opening situated about § the whole length
_ of the body from the anterior end. Genital atrium armed with conical
spines. Ovary situated at the hinder end of the front half of the
body, nearly cylindrical, bent on itself in the form of the letter U, and
with the open end directed forwards. ‘The oviduct arises from the
ovary a little on the right side of the median line; and after proceeding
for a short distance forwards, suddenly bends backwards, and after pro-

ceeding in the same direction, suddenly bends forwards and is continu-
STUDIES ON THE ECTOPARASITIC TREMATODES OF JAPAN. 199

ed into the ootyp. It bears a small, globular receptaculum seminis at a
short distance from where it bends backwards towards the ootyp.
The uterus proceeds from the ootyp almost straight forwards toward
the genital atrium. J’aginal opening single, dorsal, median, situated
about as far behind the common genital opening as this is from the
anterior end of the body; it leads into a single vayinal canal, which
proceeds straight backwards on the dorsal side of the vas deferens and
opens into the yolk-duct just where the paired yolk-ducts unite with
each other. ‘The vaginal canal is armed with conical spines near its
external opening. J?tellarium of each side distinct only at the anterior
end, extending from between the vaginal and the common genital
opening to near the posterior border of the body. Paired yolk-ducts
arising about midway between the common genital opening and the
front end of the ovary, and soon uniting with each other in the
median line on the ventral side of the uterus. Unpaired yolk-duct
proceeding almost straight backwards and opening into the oviduct
just where this bends backwards towards the ootyp. Genito-intestinal
canal arising from the oviduct side by side with the unpaired yolk-duct
and proceeding forwards and towards the right finally opens into the
intestine. Testes of moderate size, tolerably numerous, occupying a
little less than 3 the whole median portion of the body. Genital
atrium as well as the terminal portion of the vas deferens armed with
conical spines. Suckers of but slightly unequal size, measuring
0.040-0.058 mm. in breadth; about 25 on one side and only one on
the other.”

Habitat—Gill of Belone schismatorhynchus (Jap. Datsu).

Locality—Hagi.

Date—July 1889.

1). In reality there may be more. My specimens were, as already stated, collected some
time after the death of the worms, and consequently some of the suckers may have been torn
away.

 
900 8. GOTO.

3. Aine triangularis, n. sp.
(Pl. VIL, figs. 7 & 8.)

Body about 1.5 mm. long, flat, broad, and triangular, with an
almost straight posterior border. Common genital opening close
behind the termination of the oesophagus. Ovary at about the an-
terior end of the last third of the whole body ; form like that of
an interrogation-point when looked at from the ventral side. Oviduct
arising a little on the right side of the median line ; and thence pro-
ceeding backwards is swollen into a receptaculum seminis, which is
wound spirally once on itself. Beyond the seminal receptacle the
oviduct again proceeds backwards, and after receiving the genito-
intestinal canal, bends towards the Jeft, and at the same time proceed-
ing posteriorly, is continued into the ootyp on the median line of the
body just in front of the testes. From the ootyp the uterus proceeds
along the median line towards the genital atrium. Vitellariwm of each
side distinct both in front and behind, extending from the level of
the common genital opening to near the posterior extremity of the
body. Paired yolk-ducts arising a short distance in front of the anterior
end of the ovary and soon uniting with each other on the median
line. The unpacred yolk-duct proceeds backwards along the median line
and bending towards the right at the level of the ootyp opens into the
oviduct at a short distance from where the latter receives the genito-
intestinal canal. Testes rather small, only about 12 in number.
Genital atrium with a circular, cup-shaped organ like that of Microcotyle
chiri, the diameter of which is about 0.035 mm., and the internal
surface of which is covered with conical spines. Ocesophagus exceedingly
short. Intestinal trunks sending out numerous bifurcating branches on
the outer side, but only shallow evaginations on the inner. Suckers
about 36 on one side and only 6 on the other ; breadth 0.04-0.06 mm.
STUDIES ON THE ECTOPARASITIC TREMATODES OF JAPAN. 901

Habitat—Gill of Anthias Schlegelii (Jap. Akasagi).
Locality—Misaki.
Date—December 1889.

II!. Ocrocotytr, Diesing.

This and the following genus Diclidephora have been combined by most
writers under the name of Octobothrium. The latter name is dueto F. 8.
Leuckart» whose original diagnosis runs: ‘Corpus elongato, depresso, plano ;
apertura oris antica, infera, simplice; in utroque partis corporis posticae latere
acetabula suctoria quator.” He, howeyer, included in it at least two groups of
forms which are, in my opinion, to be separated from each other and placed
in distinct genera. So far as I have been able to make out with a somewhat
scanty access to the literature of the subject, especially the older, Diesing is the
first writer who has made this distinction and erected two genera, which respectively
include those forms which are, in my opinion, to be brought under at least two
distinct genera. One of these lias been named by him Octocotyle, the diagnosis
of which he gives as follows?): ‘ Corpus elongatum depressum. Caput corpore con-
tinuum. Os terminale. Acetabula in postico corporis margine uncinis duobus sub-
basilaribus interjectis utrinque quator, prominula orbicularia inermia (?) et duo
parellela infra os sita. Apertura genitalis feminea elliptica uncinulorum corona
simplici cincta. Penis............... Porus excretorius.............4. Piscium marinorum
ectoparasita.” The other of lis genera is Diclidophora, the original diagnosis») of
which ran: “Corpus subovale v. sublanceolatum depressum. Caput corpore con-
tinuum. Os subterminale. Acetabula in margine caudali octo, solitaria, valvulis
4 membranaceis asserculatis, in cardine transverso mobilibus, longe pedicellatis.

Apertura genitalis.............. -Porus excretorius...........00. Piscium marinorum ecto-

 

1). F.S. Leuckart—Versuch einer naturgemiissen Eintheilung der Helminthem nebst
dem Entwurf einer Verwandtschafts- und Stufenfolge der Thiere tiberhaupt. Heidelberg,
1827. I make the above quotation on the authority of Braun (Wiirmer, p. 534).

2). Diesing—Systema helminthum, vol. I, 1850. pp. 417 & 421.

3). This was slightly improved in his “ Revision der Myzhelminthen ” (p. 383) as follows :
“Corpus subovale v. sublanceolatum depressum. Caput collo continuum, subtus acetabulis
duobus juxtapositis. Os subterminale. Plectana octo pedicellata in postico corporis margine,
202 8. GOTO.

parasita.” Although in these diagnoses tlhe only point of difference of some generic
importance observed by the author seems to have been the pediculate condition of
the posterior suckers of the one in contradistinction to those of the other, yet most
of the spesies known to Diesing and placed by him respectively in the two genera
are precisely those which, though I have not been able to study them personally,
still judging from the descriptions of others, I should bring just under those two
genera in which they are respectively included by him. Thus there can be no doubt
on the one hand that O. scombri (Kuhn), one of the two species described by
Diesing, is to be included in this genus as I have characterised it below. On the
other hand, Diclidophora Merlangi (Kuhn) is, to judge from its (incomplete) descrip-
tions given by Dieckhoff," in all probability to be included under Diclidophora
as defined below, while as to D. palmata ( Leuck.) there can be no doubt, from the
general form of its body, of its belonging to the same genus. As to Octocotyle lun-
ceolata (IF. S. Leuck.) there is no doubt from its descriptions given by Dieckhoff»
that it is to be brought under another genus, the most salient point of difference
being the presence of a dorsal vagina. I have, however, adopted Diesing’s
nomenclature, as he seems to be the first who has recognised the difference of the
two genera under question. P. J.v. Beneden and Hesse also have noticed this
difference and included them under two genera, Octocotyle and Pterocotyle ; the latter
being co-extensive with our Diclidophora, as may be seen from the following diag-
nosis given by the authors: ‘‘Huit ventouses portées sur de longs pédoncules
unis 4 la base terminent le corps en arriere. Le ver est réguliérement effilé en
avant, large vers Je milieu et rétréci vers J’origine des ventouses. La bouche est
flanquée de deux ventouses et une couronne de crochets entoure l’orifice des organes
sexuels.” Like Diesing these authors regarded the unimportant pedicels of the
posterior suckers as of generic value ; but their idea is capable of a surer foundation,
as may be seen from the diagnoses of the two genera given below.

The name Oetostoma was proposed by Kulin in 1829; but like most writers

 

singulum quadrivalve, valvulis semicircularibus, »nembranaceis, limbo corneo cinctis, asser-
culatis, in cardine transverso mobilibus. Androgyna ; apertura genitalis mascula............ feminea
antrorsum sita, uncinulorum corona simplici cincta. Porus excretorius............ Tractus in-
testinalis bicruris, coecus.—Ovipara, ovulis utraque extremitate appendice filiforme crasso.—
Piscium marinoruin ectoparasita.” ‘The penis is evidently mistaken for the female genital
opening.

1). Dieckhoff—l. v. p. 265.

2). Dieckhoff—l. c. p. 235.
STUDIES ON THE ECTOPARASITIC TREMATODES OF JAPAN. 903

he included in it the forms which I hold to require separation into two genera.

The genus QOctocotyle I propose to characterise as follows:

30dy lanceolate, usually thick”; anterior end obtuse-
ly triangular, posterior end rounded. With a single
pair of ellipsoidal anterior suckers inside the mouth,
and with four pairs of posterior, somewhat bean-shaped
suckers on the ventral side at the posterior end of the
body. With one or two pairs of hooks between the last
pair of posterior suckers. Without a vagina. With a
penis consisting of a median, cup-shaped body with a
thick wall, which is perforated by the vas deferens,
and an accessory, bean-shaped body attached to it
on each side; all three bearing hooks on their inner

surface.

1, Octocotyle major, n. sp.
(PI. IX, figs. 1-6.)

Body lanceolate and thick”, about 4 mm. long, the anterior part
free from the vitellarium very short; posterior suckers small, being
about® 0.045 mm.x0.038 mm., and arranged close to the lateral
margin of the body. With only one pair of large hooks between the
hindmost pair of suckers. The hook with a process at the middle
of its length, its distal half enclosing a narrow cavity within (PI. IX,
fig. 2), and its proximal portion striated lengthwise; the latter
appearance being due to the presence of longitudinal furrows on its sur-

face; length of the hook 0.1 mm., the curvature not taken into account.

 

1). The term “ depressum ” I find to be wholly inappropriate to the species observed by me.
2). In the figure the body seems flatter and broader than it is in reality, owing to the
pressure of the cover-glass to which the specimen was subjected when killed.

8). The length of the posterior sucker has been measured parallel to the arms of the
U-shaped chitinous piece, and its breadth at right angles to the same.
204 S. GOTO.

Ocsophagus rather short ; the main trunks of the intestine wholly dis-
tinct from each other ; sending out lateral branches both outwards
and inwards, those of the inner side, however, being a little shorter
than those of the outer ; the trunks terminating a little in front of the
foremost pair of posterior suckers. Common genital opening at the
hinder end of the anterior portion of the body free from the vitel-
larium ; penis spines short, recurved, arranged in five pairs ; each spine
consisting of a slender, spinous portion and a basal, lens-shaped
portion. Diameter of the central bulb of the penis about 0.035 mm.;
length of the lateral bulb 0.027 mm. Ovary long, U-shaped, with the
open end directed forwards and the two arms of the U closely apposed
to each other; the oviduct end occupying the median line of the
body and the other end situated more to the right. Oviduct after
procceding from its origin a short distance forwards turns backwards
and a little towards the left, and is continued into the ootyp, which is
situated just in front of the ovary a little on the left side. From the
ootyp the uterus proceeds straight forwards. Genito-intestinal canal
arising from the oviduct just before the ootyp, and thence proceeding
forwards and slightly towards the right, opens into the intestine at
the same level as the paired yolk-ducts. The vitellaria of the two
sides are quite distinct behind but less so in front. The paired
yolk-ducts are very short and unite with each other on the median line,
about half as far from the anterior end of the ovary as from that of
the body. The unpaired yolk-duct proceeds straight backwards, and
opens into the oviduct side by side with the genito-intestinal canal
but nearer the ootyp. Testes comparatively few in number, small ;
the anterior ones arranged in a single row on the left side of
the ovary; the whole testes extending from a little behind the
front end of the ovary to about midway between its hinder

end and the termination of the intestinal trunks. Vas deferens
STUDIES ON THE ECTOPARASITIC TREMATODES OF JAPAN. 905

proceeding forwards from the foremost testis dorsally to the uterus.
Habitat—Gill of Scomber colias (Jap. Saba).
Locality—Misaki.
Date—December 1889.

2. Octocotyle minor, n. sp.
(Pl. IX, figs. 7-13.)

Body lanceolate, thick, about 2 mm. long, narrow anteriorly but
broader posteriorly ; the anterior portion free from the vitellarium
long, separated from the hinder part by a slight constriction, and
becoming gradually narrower towards the front end. Posterior suckers
smal], a little broader than long (being 0.03 mm.x0.037 mm.),
arranged in a straight line parallel to the median line of the body ;
the hindmost pair being close to the margin of the body and the
anterior ones more removed from it. With two pairs of hooks at the
posterior end of the body between the hindmost pair of suckers ;
the outer pair stouter, about 0.037 mm. long (curvature not reck-
oned), wholly solid, and with a process near the proximal end ; inner
pair filiform and curved, about 0.02 mm. (curvature reckoned). Oeso-
phagus longer than in O. major ; main trunks of the intestine completely
separate from each other and reaching the foremost pair of
posterior suckers ; each sending out lateral branches both outwards
and inwards, the inward branches, however, being very short. Com-
mon genital opening midway between the pharynx and the posterior
end of the oesophagus. Penis spines long, arranged in six
pairs, the foremost and longest ones being curved almost semi-
circularly ; each hook consisting of a long, slender, spinous, distal
portion and a lens-shaped, basal portion attached to the penis

bulb ; diameter” of the central penis bulb about 0.05 mm., length

 

1). Too much specific value must not, however, be placed on these figures; for in another
206 8. GOTO.
of the accessory bulb 0.032 mm. Ovary long, U-shaped, with the
open end directed forwards, and with the two arms of the U closely
apposed to each other ; the end containing the young ova once more
bent on itself; the larger arm situated on the left side of the smaller,
and occupying nearly the median line of the body. JVitellaria of
the two sides nearly distinct both in front and behind. Relative
disposition of the genital ducts same asin O. major. Testes more
numerous than in O. major ; the anterior ones extending as far an-
teriorly as the front end of the ovary, and arranged ina single row
on its left side ; the posterior ones extending about two-thirds the
distance between the posterior end of the ovary and the foremost
pair of suckers.

Habitat—Gill of Scomber colias (Jap. Saba).

Locality—Hagi and Misaki.

Date—August 1889 (Hagi), Dec. 1889 (Mis.).

I believe there is no doubt that the species above described are
new, although they inhabit the same host as O. scombri (Kuhn). I
at first suspected that the two species might have been confounded
with each other and described as a single species by European
writers, the contradictory statements of v. Beneden and Hesse” on
the one hand and St.-Remy on the other as to the number of the
penis spines of O. scombri seeming in some degree to favour such a view.
But the hooks at the posterior end of the body of both the species

here described are entirely different in form from those of O. scombri,

 

individual, that represented by fig. 12, I found the diameter of the central bulb to be only
0.035 mm.

1). P. J. v. Beneden and Hesse state them as being ten in number (Recherches sur les
Bdellodes et les ‘I'rématodes marins, p. $7), while aceording to St.-Remy they are twelve
(Synopsis des Trématodes monogénéses, p. 32).
STUDIES ON THE ECTOPARASITIC TREMATODES OF JAPAN. 207

as may be seen from a comparison of my figures of the former with

those of the latter given by Parona and Perugia.”

IV. Dicripornora, Diesing (1850).

Body flat and of various forms, but generally speak-
ing leaf-shaped; with a pair of spherical anterior suckers
in the mouth-cavity and with four pairs of hemispheric-
al (inasurface view circular) or slightly semi-ellipsoid-
al suckers arranged in a semicircle or horse-shoe shape
at the posterior end of the body; each sucker often provid-
ed with a more or less long pedicel, and having a
chitinous, supporting frame-work, the general structure
of which is represented in fig. 1, Pl. XII. Intestinal
trunks of both sides usually uniting with each other at
the posterior end of the body, and besides connected with
each other by numerous commissural branches. Penis
spherical, perforated by the vas deferens, with a certain
number of hooks of the general shape drawn in figs. 7 &

10, Pl. X,andarrangedinacircle. Without vagina.

1. Diclidophora smaris (Ijima, Ms).”
(Wood-cut 1.)
Synonym: Octobothrium smaris, Tjima.

Bo:ly 64-8 mm. long, separable into three parts, a slender, nar-

oD)

row, anterior portion, a broad, oval, leaf-shaped, middle portion, and a

 

1). Parona e Perugia—Res ligusticae, VIII. Dialcuni trematodi ectoparassiti di pesci
marini. Annali d. Museo Civico d. Storia Naturale di Genova. Ser. 2, vol. VII, p. 742.

2). This is the species which has been supposed by Dieckhoff to be identical with Octo-
bothrium Merlangi (1. ¢. p. 250).
v. def.

ink

ovd.

S. GOTO.

 

"pen.

ut.

 

 

 

 

 

 

 

 

yk. duct.

 

OV.

vit.

tes.

Wood-cut 1.—Diclidophora smaris, Ijima. Reproduced

after a Drawing by Prof. Ijima.

small caudal disc bearing
on its margin the toler-
ably long pedicels of the
circular posterior suck-
ers. The anterior portion
which is, roughly speak-
ing, a little less than
one-third the total length
of the body, is 0.25-
0.30 mm. broad in the
middle part, and in some
specimens a circular fold-
ing of the surface of the
body was present just in
front of the pharynx.
The middle portion mea-
sures, where it is broad-
est, viz., a little behind
the ovary, 2.25 mm.
The caudal disc is at
its anterior end about
1.00 mm. wide. The
first pair of sucker-
pedicels lies in a straight
line at right angles to
the long axis of the
body, and the rounded
angles between each two
successive pedicels are
equal to one another; the

pedicels are cylindrical.
STUDIES ON THE ECTOPARASITIC TREMATODES OF JAPAN. 909

Oesophagus short ; anterior portion of the intestinal trunk destitute
of lateral branches, but the remaining portion sending out numer-
ous lateral branches both inwards and outwards; those of the
inner side posterior to the ovary uniting with those of the opposite
side and forming commissures. From the point of union of the two
intestinal trunks a single median trunk proceeds backwards ; this,
however, is very short and soon breaks up into a few secondary
branches. Common genital opening situated about 4 mm. behind
the mouth ; penis with six hooks of the usual shape in this genus.
Ovary situated in the median line, about the middle of the whole
length of the body, long, bent on itself by its middle, and the whole
curved, the long axis of the ovary roughly coinciding with that
of the body. Oviduct arising from the anterior end of the ovary on
the right side of the body, thence proceeding backwards and, curving
inwards toward the median line, is continued into the ootyp, which
is situated in the median line of the body just in front of the posterior
end of the ovary. From the ootyp the wterus proceeds straight
forwards. ,Genito-intestinal canal rather short, opening into the
oviduct half as far from the beginning of the oviduct as from the
ootyp, thence proceeding towards the right, and finally opening
into the intestine. Vitellaria of the two sides distinct in front
but continuous behind. LPaired yolk-ducts of the two sides
symmetrically disposed at right angles to the long axis of the
body, and uniting with each other in the median line. Unpaired
yolk-duct opening into the oviduct about halt as far from the ootyp
as from the opening of the genito-intestinal canal into the ovi-
duct. Testes numerous, all situated behind the ovary; vas de-
ferens running dorsal to the uterus and usually making some

convolutions.
210 8. GOTO.

Habitat—Mouth-cavity of Smaris rulgaris (on the caudal segment
of a Cymothoa). ?

Locality—Gulf of Naples. Collected by Dr. Max y. Brunn.

Date—Not recorded.

2, Diclidophora elongata, n. sp.
(Pl. X, figs. 9-10; Pl. XI, fig. 8; Pl. XII, figs. 1-2.)

Body lanceolate, anteriorly rather pointed, about 8 mm. long, the
pedicel of the hindmost pair of suckers inclusive, divisible only
into two parts, the body proper and the caudal disc, the latter being
only about one-sixth the total length, and bearing on its margin the
long pedicels of the circular posterior suckers; pedicels making
equal angles with each other, and each containing in its proximal
half a branch of the intestine and a portion of the vitellarium sur-
rounding the former. Ocsophagus very short. The two intestinal
trunks sending out not very long lateral branches outwards, and con-
nected with each other by cross-commissures, which unite with each
other by means of secondary commissures ; the trunks continued into
each other at the posterior end of the body, thus forming here a
loop. From the loop are sent out at regular intervals eight, somewhat
long lateral branches, each of which penetrates into the pedicel of the
sucker as above mentioned. Common genital opening close behind the
termination of the oesophagus. Penis with eight hooks. Ovary
occupying the posterior end of the middle third of the body, long,
cylindrical, bent on itself once at its middle and the whole again
bent on itself at its middle, so that the ovary has the form of a
double V one placed within the other ; with the angle of the V

 

1). On this head Prof. Ijima remarks; “Ich glaube jedoch, dass sie nicht als Parasit
jenes Schmarotzer-Krebses, sondern vielmehr als derjenige des den letzteren beherbergenden
Fisches anzusehen ist” (MS).
STUDIES ON THE ECTOPARASITIC TREMATODES OF JAPAN. 211

=

directed towards the left side of the body, and the whole lying more
to the left than to the right of the median line. Oviduct arising from
the front end of the larger half of the ovary, thence proceeding for
a short distance forwards and towards the left, and then bending on
‘itself and retracing its course, proceeds backwards, and approaching
the posterior end of the body bends towards the right, and is con-
tinued into the ootyp, which is therefore situated on the right side
of the body at a short distance from the trunk of the intestine. Ovi-
duct bearing a tolerably large, round receptaculum seminis at its
foremost end where it bends on itself. From the ootyp the wéerus
at first proceeds forwards and towards the left side of the body, and
reaching the angle of the smaller (inner) half of the ovary, bends
slightly towards the right, and then proceeds straight forwards.
Vitellaria of the two sides distinct in front but continuous be-
hind. Paired yolk-ducts slightly asymmetrical, that of the left side
being situated a little anterior to its fellow; the ducts directed
obliquely across the long axis of the body, and uniting with each
other on the same level as the front end of the smaller half of the
ovary. The unpaired yolk-duct thence proceeds backwards and slightly
towards the left, and reaching the angle of the V-shaped ovary, bends
on itself and proceeds towards the right side, and finally opens into
the oviduct.  Genito-intestinal canal arising from the oviduct a
little anterior to the opening of the unpaired yolk-duct, proceeds
forwards, and towards the right opens into the intestine. Testes
numerous, rather small, extending from a little behind the ootyp
to the level of the pedicels of the foremost pair of suckers.

Habitat—Mouth-cavity of Pagrus twmifrons (Jap. Tai). Some-
times on the Cymothoa parasitic in the mouth-cavity.

Locality—Mogi (near Nagasaki) and Hakodaté.

Date—July 1889 (Mogi) and August 1890 (Hako.).
212 8. GOTO.

This species is evidently closely allied to Octobothrium palmatum,
F, S. Leuck.

3. Diclidophora sessilis, n. sp.
(PI. X, figs. 5-8; Pl. XI, figs. 1-7; Pl. XII, figs. 3-4.)

Boly about 5mm. long, elongated-oval, generally broad but
narrower in front, anterior end obtuse, divisible into the body
proper and the caudal disc, which are separated from each other by a
sharp constriction. Body proper leaf-shaped, occupying a little less
than three-fourths of the total length ; caudal disc small, bearing the
circular sucker on its margin. Suckers sub-sessile, arranged in a
semicircle close to each other. Oesophagus exceedingly short. The
two intestinal trunks sending out lateral branches outwards, connected
with each other by anastomosing commissures, and uniting with
each other at the level of the first pair of posterior suckers; from
this intestinal loop backwards are given off numerous branches
which reach the base of the suckers. Common genital opening close
behind the termination of the oesophagus. Penis with six hooks.
Ovary occupying the middle of the body, long, twice folded on itself
in the form of a W ; the last arm of the W, which gives rise to the
oviduct, is hollow, very much larger than the others, and is situated:
furthest to the left. Oviduct arising from the large end of the ovary,
proceeds at first for a short distance towards the right, then bends,
and after proceeding backwards for some distance bends forwards and
towards the left, then again bends towards the left, and reaching the
right angle of the W-shaped ovary, is continued into the ootyp.
Oviduct bearing an exceedingly large seminal receptacle consisting of
numerous lobes at the point where it bends forwards to unite with
the yolk-duct. From the ootyp the uterus proceeds at first forwards
and towards the right, and reaching the median line of the body, pro-
STUDIES ON THE ECTOPARASITIC TREMATODES OF JAPAN. 915

ceeds straight forwards towards the common genital opening. Paired
yolk-ducts slightly asymmetrical, making an angle with the long
axis of the body, and uniting with each other on the same
level as the fore end of the ovary. The unpaired yolk-duct
thence proceeds backwards and towards the left, and unites with
the oviduct in the median line of the body, just where the oviduct
bends to the left towards the ootyp. Genito-intestinal canal tolerably
long, and arising from the oviduct side b y side with the receptaculum
seminis, proceeds slightly forwards and towards the right, and finally
opens into the intestine. Testes exceedingly numerous, tolerably
large, extending from a little behind the common genital opening to
the level of the first pair of posterior suckers, and occupying the
whole region enclosed by the two intestinal trunks, 7. ¢, three-
fifths of the total breadth of the body. Vas deferens as usual on the
dorsal side of the uterus.

Habitat—Mouth-cavity of Chocrops Japonicus (Jap. Kobu-dai or
Kan-dai). Young specimens also on the gill.

Locality—Mitsugahama (Prov. Iyo).

Date—August 1889.

4, Dielidophora tetrodonis, n. sp.
(Pl. X, figs. 1-4.)

Body long and slender, spathulate, 5-15 mm. long, divisible into
three portions, an anterior, fusiform portion a little over half the entire
length of the body, a middle, slender, stalk-like portion half as long
as the former, and the caudal disc a little less than half the stalk-like
portion and bearing the suckers along its margin on the ventral side ;
the three portions, however, gradually passing into each other with-
out any sharp demarcation. Suckers sessile, elliptical, arranged in a

deep horse-shoe shape, the open end of which is directed forwards ;
214 8. GOTO.

the four suckers of each side equidistant from each other, and those
belonging to the last pair separated from each other slightly more than
those of the same side are from each other. Ocesophagus almost wanting.
The two intestinal trunks sending lateral branches outwards, and
connected with each other by sparsely anastomosing commissures only in
the anterior, fusiform portion of the body ; in the stalk-like portion the
two trunks also send out short lateral branches but run paralled to each
other and remain wholly separate up to their terminations between the
last pair of suckers. Common genital opening close behind the begin-
ning of the intestine. Penis with ten hooks. Ovary comparatively
sinall, occupying the median part of the body in the anterior half of
the last third of the fusiform portion ; when viewed from the ventral
side somewhat like two commas placed obliquely one above the other,
with the upper one more to the right. Oviduct arising from the en-
larged head of the anterior half of the ovary and thence proceeding
backwards and slightly towards the right as far as the posterior end
of the ovary, bends slightly towards the left, keeping its backward
course, and reaching the front end of the testes in the median line,
suddenly bends forwards and is continued into the ootyp. Vitellaria
of the two sides distinct both in front and behind ; absent from the
stalk-like portion. Paired yolk-ducts symmetrical, uniting with each
other at about the hinder end of the foremost third of the whole
body, dorsally to the uterus. The unpaired yolk-duct thence proceeds
backwards and slightly towards the right, and reaching the level of the
middle of the ovary, turns slightly towards the left, and reaching the
level of the front end of the testes, bends rather sharply towards the
right, and opens into the oviduct a short distance in front of the point
where the latter bends forwards to meet the ootyp. From this the
uterus proceeds forwards, and its anterior part sometimes contains

numerous eggs, in consequence of which it is greatly enlarged and
STUDIES ON THE ECTOPARASITIC TREMATODES OF JAPAN. 915

swollen, giving rise to an elevated patch on the ventral side of the
body. Genito-intestinal canal arising from the oviduct a little nearer its
origin than the opening of the unpaired yolk-duct, proceeds forwards
and a little towards the right, and finally opens into the intestine.
Testes small, comparatively few in number, together forming a
triangular patch behind the ovary, between the two trunks of the
intestine ; not extending into the stalk-like portion.

Habitat—Gill of Tetrodon sp. sp. (Jap. Kogomé-fugu and Koyosé-
fugu).

Locality—Hagi.

Date—August 1889.

Although this species presents conspicuous differences from the
two foregoing species, there is no doubt that it is to be included in
the same genus, both from the form of the penis and its hooks and the
form of the sucker and its chitinous framework, as well as from some
other less significant points of similarity. As to the chitinous
frame-work of the suckers, it is to be remembered that, as already
mentioned in the anatomical part, that of the first pair presents
such a change in the relative position of the component pieces as
to have to be regarded as having undergone a rotation of 180° on its
own axis, the piece directed forwards in the other suckers being
turned backwards in this. In fact this species represents an aberrant

member of the genus.

VY. Hexacotyir, Blainville.

This genus was founded in 1828 by Blainville, and contains at present only

a single species, which was first met with by De la Roche” on the gill of Scomber

 

1). Dela Roche—Sur deux animaux vivants sur les branchies des poissons. Nouv. Bull.
d. sciences d. 1. soc. Philom., 1811., No. 44., 270-273. I cite this on the authority of Dujardin,
Diesing, and Braun.
216 8. GOTO.
thynnus and described by him under the name of Polystoma thynni. Later it
was described under the name of Polystoma duplicata by Rudolphi” in his
“Entozoorum synopsis.” The diagnosis?» given by Blainville is as fol-
lows: “Corps ovale, déprimé, continu ou non articule, composé de deux parties ;
une antcrieure, bien plus petite, subcylindrique, ridée; autre postcrieure, beaucoup
plus grande, ovale, alongée, deprimée et bordée inferieurement par trois paires de
ventouses, armées 4 Vinterieur de deux petits crochets opposes. Tcte petite, peu
distincte, portant la bouche & son extremité. Anus dorsal 4 la jonction du cou et du
corps. Orifice des organes de la génération au meme endroit en dessous.” The
“anus” above referred to is probably the opening of the vagina, which is very con-
spicuous on a surface view. In his “ Histoire naturelle des Helminthes” Dujardin*)
gives the following diagnosis of the species, for which he adopts the name given it by
Rudolphi: “Corps grisitre, mou et lisse, long de 12 4 16 mm., large de 3.4 mm., et
elliptique au milieu, rétréci en avant, élargi en arricre, ou se trouvent les six
ventouses rangées transversalement, avec deux papilles intermediaires ;—bouchic
terminale ;—ventouses bivalves, soutenues par plusieurs pieces cornées qui, en
se rapprochant les font paraitre divisces (duplicata),” a description differing only
in a few points from that of Blainville, but in many respects more incomplete.
Diesing*) in his “Systema helminthum” erected for the species a new genus
Plagiopeltis, with the following diagnosis: ‘Corpus elongatum depressum. Caput
corpori continuum. Os.........Acetabula ventralia octo in corporis parte dilatata mar-
ginalia, serie simplici disposita, elliptica planiuscula, marginata, singula acetabulum
transverse ellipticum margine involutum, centrali minus, includentia. Genitalia
externa......... Porus excretorius......... Piscium marinorum ectoparasita.” A new
addition to our knowledge of the genus contained in the above is the correct ascer-

tainment of the number of posterior suckers (eight), the innermost pair of which is

 

1). Rudolphi—Entozoorum synopsis, 1819. pp. 125 & 438. Cited on the authority of
Dujardin, Diesing, and Braun.

2). Blainville—Dictionnaire des sciences naturelles. 'T. 57, 1828. p.570. Pl. XXVII, fig. 1.
Cited on Braun’s authority.

3). Dujardin—Histoire naturelle des helminthes, 1845. p. 318. j

4). Diesing—Systema helminthum, p.416. The diagnosis given in his “Revision der
Myzhelminthen ” (p. 363) seems to me scarcely an improvement.
STUDIES ON THE ECTOPARASITIC TREMATODES OF JAPAN. O17

much smaller than the others. Taschenberg,!) on the other hand, in a paper
published in 1879, repeated the incorrect statements of the earlier writers as to the
number of suckers. In 1890, however, Diesing’s statement on this point was
almost simultaneously confirmed by Montice11i® on the one hand and Parona
and Perugia) on the other. So far as I know our knowledge of this genus

has after all been very incomplete. The generic diagnosis I give is as follows:
Body flattened, elongated, broad in the middle
portion, slender and subcylindrical in front, acutely
pointed at the anterior end, broad and expanded be-
hind; posterior margin forming two sides of an isosceles
triangle, with a notch atthe apex. With a pair of ex-
ceedingly small, spheroidal anterior suckers within the
mouth. Posterior suckers elliptical; in four pairs close
to the posterior margin, with their major axes directed at
right angles to the margin; each with three chitinous
supporting pieces arranged in a lineon the major axis of
the sucker; the innermost pair of suckers very much
smallerthantheothers. With two pairs of hooks between
the innermost pair of suckers. With a single, dorsal,
median vagina. Common genital opening ventral and

median.

1. Hesxacotyle acuta, n. sp.
(PJ. XII, figs. 5-7; Pl. XIII, figs. 1-3; Pl. XIV, figs. 1-5.)
Body 11mm. or more in length, divisible into three portions

separated from each other by two broad constrictions, an anterior slender

 

1). Taschenberg—Zur Systematik der monogen. Trematoden. Zeitschr. f. d. gesamm.
Naturwissensch., 52. Bd., 1879. p. 232-265. Cited on Braun’s authority.

2). Monticelli—Note elmintologiche. Boll. d. Soc. d. Natur. in Napoli. Ann. IV, 1890,
fasc. II. p. 195. Cited on Braun’s authority.

3). Parona e Perugia—Intorno ad alcune Polystomeae e considerazione sulla sistem. di
questa famiglia. Atti del. Soc. Ligust. d. Scienz. Natur. e Geogr. Vol. I, fase. III, 1890.
Estratto, p. 15, foot-note.
918 8. GOTO.

portion which ends with a mucronate apex, a middle portion oc-
cupying about half the whole length of the body, and a posterior,
broad portion mostly free from the vitellarium and carrying the
suckers near its posterior margin. ‘The innermost small pair of
suckers situated in a line with the posterior halves of the others.
Chitinous pieces of the suckers as represented in fig. 3, Pl. XIII.
Inner pair of hooks solid, very much smaller than the outer, with
strongly recurved, pointed end and bent almost at aright angle at
the middle of their length, 0.03 mm. long if its middle bending be
straightened out. Outer pair solid, strongly recurved at the end, with
a large process a little distally from the middle of its length, 0.09 mm.
long (curvature not taken into account); their forms as represented
in fig. 2, Pl. AIL. Ocsophagus single only for a short distanee
posterior to the small pharynx, and sending out numerous lateral,
anastomosing branches during the remainder of its length. Two.
pairs of main intestinal trunks may be distinguished, the inner
of which corresponds to those of other species and reaches the
hinder end of the body; the outer on the other hand extends
only for about two-thirds of the whole length of the body from
a short distance behind the front end of the body close to the
lateral margins. All the four trunks are connected with each other
by numerous, closely anastomosing branches. Common genital opening
near the hinder end of the anterior, slender portion of the body, just
behind the beginning of the inner pair of intestinal trunks. Ovary
median, at about the middle of the whole length of the body ; its
windings very complicated, as represented in fig. 1, Pl. XIV. Oviduct
arising from the posterior right end of the ovary, thence proceeding
backwards and towards the left side, and almost reaching the median
line of the body suddenly turns dorsad and towards the right, and

continuing its course for a short distance, again turns dorsad, anteriad,
s

STUDIES ON THE ECTOPARASITIC TREMATODES OF JAPAN. 219

and towards the left, and is continued into the ootyp, which is some-
what long in this species, and lies near the dorsal side of the body with
its length placed at right angles to the long axis of the body. The
uterus proceeds from the left end of the ootyp forwards and slightly
towards the right, and after reaching the median line of the body
some distance in front of the ovary, proceeds straight forwards to the

common genital opening. Vitellarium extending from the level of the

_vaginal opening to that of the posterior end of the testes. Paztred yolk-

ducts asymmetrically disposed on the two sides. That of the right side
arises more in front than the other, a short distance in front of the
origin of the oviduct ; it at first proceeds perpendicularly to the long
axis of the body towards the median line, where it suddenly changes its
course and turns posteriorly and proceeding backwards with a few wind-
ings unites with its fellow of the other side just behind the ootyp.
The yolk-duct of the left side on the other hand arises from the vitel-
larium wholly behind the ovary, and proceeding straight towards
the median line of the body, there bends at right angles to its previous
course and unites with its fellow coming from the front. The
unpaired yolk-duct is short, and proceeds from the point of union of the
paired yolk-ducts towards the right side, and opens into the oviduct
at about the middle of its whole length. Grenito-intestinal canal arising
from the oviduct side by side with, and just in front of, the unpaired
yolk-duct ; the canal at first very small, but soon swollen into a
voluminous receptaculum seminis, from the front end of which it
again continues, and proceeding towards the right with a few
convolutions, at last opens into the inner trunk of the intestine.
Vagina dorsal, a little behind the genital opening, armed with conical
teeth, and surrounded on both sides with a compact, refractive mass
of connective tissue, in consequence of which the opening is often seen

to have a swollen lip in specimens killed with hot sublimate ; vaginal
290 8. GOTO.

canal at first single, but soon divides right and left into two canals,
which then proceed backwards on the inner side of the inner intestinal
trunks, and become continuous each with the paired yolk-duct of the
same side. Testes tolerably numerous, of moderate size, situated
between the inner pair of intestinal trunks behind the ovary, and
extending to the constriction which divides the middle from the
posterior portion of the body.

Hatbitat—Gill of Thynnus sibi (Jap. Shibi).

Locality—Hagi and Osatsubé (Hokkaidd, where it was collected
by my friend, Mr. Nozawa).

Date—August 1889 (Hagi).

2, Hexacotyle grossa, n. sp.
(Pl. XIII, figs. 4-6; Pl. XIV, 6-7.)

Body flattened, elongated, thick, about 18 mm. long, divisible
into three portions as in the preceding species, but the anterior slender
portion with lateral swellings at a short distance from its front end
and passing more gradually into the middle, broad portion, and with
the hindmost portion shorter than in H. acuta. The innermost
small pair of suckers situated in a line with the posterior borders of the
other suckers. Chitinous pieces of the suckers as represented in fig. 6,
P]. XIU. Inner pair of hooks very much smaller than the outer, solid,
with strongly recurved ends, bent at a right angle at the middle of its
whole length, 0.04 mm. long if the middle bending be straightened
out; outer pair entirely hollow, with a rather thin wail, with
strongly recurved, pointed end, and with a large process at the
middle of its length, 0.126 mm. long (curvature not reckoned);
their forms as represented in fig. 5, Pl. ATII. Ocsophagus and intestine
disposed as in H. acuta, the only difference worth noting being that

the inner pair of intestinal trunks converge at a short distance in
STUDIES ON THE ECTOPARASITIC TREMATODES OF JAPAN. 991

front of the suckers, and unite in the median line just in front of the
innermost of the larger pair of suckers. Common genital opening a little
in front of the anterior end of the median pair of intestinal trunks.
Ovary in the median line, at about the middle of the whole length of
the body, long, bent on itself like a loop, with numerous secondary con-
volutions, and with the open end of the loop directed backwards. The
oviduct arises from the end of the right arm of the loop, thence proceeds
backwards and towards the right, and after receiving the genito-intes-
tinal canal turns backwards, and then making one or two convolu-
tions, turns dorsad, and is continued into the ootyp, which is tolerably
long, and lies with its length directed obliquely in an antero-
posterior direction. Uterus taking a course as in H. acuta. Genito-
intestinal canal arising from about the middle of the whole course of
the oviduct, enlarged into a voluminous receptaculum seminis, from the
anterior end of which the small convoluted canal proceeds forwards
and towards the right, and finally opens into the inner trunk of the
intestine. Vtellarium extending from the level of the vaginal opening
to a short distance behind the posterior end of the testes. Pazred yolk-
ducts asymmetrically disposed with respect to each other ; that of the
right side arising from the vitellarium on the same level with the
opening of the genito-intestinal canal into the intestine. The
arrangement of the paired yolk-ducts with respect to each
other and to the unpaired yolk-ducts as in H. acuta. The
unpaired yolk-duct opening into the oviduct side by side with
the genito-intestinal canal, but not so closely as in H. acuta.
Vaginal opening dorsal, a short distance behind the common
genital opening; the single vaginal canal soon dividing into
two, which are disposed as in H. acuta and become continuous
each with the paired yolk-duct of the same side. Testes numerous,

of moderate size, posterior to the ovary, and ending a little in
999 §. GOTO.

front of the constriction which divides the middle from the posterior
portion of the body.
Habitat—Gill of Thynnus sp. [Jap. Mebachi-maguro).
Locality—Misaki.
Date—August 1891.

Although we have no adequate description of Hexacotyle thynni,
de la Roche, tie only species of the genus hitherto described, I believe
there is scarcely any doubt that the two species here described are new.
Thus, in the first place, the general form of the body of both the species
differs from that of H. thynni as figured by St.-Remy” and Dies-
ing”; and in the second place, according to the statement and figure
of the former writer, the larger pair of hooks is situated in front of

the other, which is not the case in either of the species here described.

VI. Owncuocorytr, Diesing.

This genus is due to Diesing who erected it in his “Systema helminthum”
(1850) for an ectoparasite found for the first time (1829) by Kuln® on the gill of
Squalus catulus and described by him under the name of Polystoma appendiculatum. The
same species was afterwards redescribed more at length by Nordmann®*), Thaer5)»
P.J.v. Beneden®, and Taschenberg”. In 1853 P.J.v. Beneden?)

added a new species (O. borealis) ; in 1878 two more new species (O. abbreviata and

 

1). St.-Remy—Synopsis. Pl. X, fig. 22.

2). This I cite on the authority of Braun, in whose “ Wiirmer” the figure is reproduced
(Pl. XII, fig. 8).

3). Kuhn—Description d’un nouveau genre de j’ordre des douves etc. Mém.d. mus. d’hist.
nat. T. XVIII, 1829. Also in Annal. d. scien. d’observ., IT, 1829. Both cited on the com-
bined authority of Diesing, Dujardin, and Braun.

4). Nordmann—Mikrographische Beitriige, p. 80.

5). Thaer—De Polystomo appendiculato, 1851. Also “Ueber Polystomum appendicula-
tum” in Miiller’s Archiv f. Anat. Phys, Jahrg. 1850. The latter is cited on Braun’s authority.

6). P. J. v. Beneden—Mémoire sur les vers intestinaux. 1861. p. 54.

7). Taschenherg—Weitere Beitriige.

8). P.J.v. Beneden—Espéce nouvelle de genre Onchocotyle vivant sur les branchies du
Scymnus glacialis. Bull. d. Acad. roy. d. Belg., t. XX, 1853. p. 59. Cited on the authority of
P. J. v. Beneden and Braun.
STUDIES ON THE ECTOPARASITIC TREMATODES OF JAPAN. 993

O. emarginata) were described by Olsson; and finally in 1890 a fourth species
(O. Prenanti) was added to the genus by St.-Remy”. Besides these there is
according to Diesing®) another species not yet described but mentioned by Wage-
ner ina note toa paper of his published in “Naturk. Verliand. Harlem, XIII,”
as living on the gill of Scymnus ainosi. This species is not mentioned either by
Braun or St.-Remy, and I am not sure whether it will prove to be identical
with some one of the species already described, or to belong to quite another genus.

The original diagnosis of Diesing is as follows; “ Corpus lineari-lanceolatum
depressum, utringue angustatum. Caput corpore continuum. Os subterminale.
Acetabula sex disco elliptico extremitati caudali supra adnato, biseriatim immersa,
hemisphaerica, margine uncino simplici inferna adnato apice libero armata.
Aperturae genitales............ Porus excretorius in apice caudali.—Piscium marinorum
ectoparasita.” This was improved in his “ Revision”) as follows: ‘Corpus
lineare-lanceolatum depressum, appendiculo caudali postico. Caput corpore con-
tinuum. Os subterminale. Acetabula sex, lamellae ellipticae, extremitati corporis
posticae subtus adnatae, biseriatim immersa, hemisphaerica, margine uncino simplici
inferne adnato, apice libero, armata. Androgyna; aperturae genitales postpositae
ventrales antrorsum sitae, medianae; penis vaginatus ante aperturam femineam
situs. Pori excretorii duo in appendice caudali, terminales.—Tractus intestinalis
bicruris, coecus.—Ovipara ovulis utraque extremitate appendiculo filiformi in-
structis.—Piscium marinorum ectoparasita’’—a diagnosis which has been repeated
in its essential points by subsequent writers, but which requires some modifications
in accordance with the facts already mentioned in the anatomical part of the
present paper. It has moreover been stated that in some species the caudal append-
age does not bear any hooks near its extremity. This statement sounds somewhat
anomalous to me; but as Iam not able to reéxamine thie species in question, I shall
leave the statement as it stands, and give the generic diagnosis as follows:

Body elongated, very thick, narrow towards both

ends; anterior end blunt, and with a sub-ellipsoidal sucker

 

1). Olsson—Bidrag til Scandinaviens helminthfauna. Kgl. svenska vetensk. Acad. Handl.
N. F. XIV, 1878. p. 35. Cited on the authority of Braun and St.- Remy.

2). St.-Remy—Sur une espéce nouvelle de Polystomien du genre Onchocotyle Dies. Rev.
biol. d. Nord de la France. III. ann., 1899. p. 41. Cited on the combined authority of Braun
and St.-Remy.

3). Diesing—Revision der Myzhelminthen, 1858, p. 371.

4). Diesing—Revision, p. 370. The italics are mine.
224 8. GOTO.

around the mouth-cavity; with three pairs of circular or
elliptical suckers at the posterior end, each with a semi-
circular chitinous supporting piece with one of the ends
provided with a claw. With a subcylindrical caudal
appendage, which bears at its extremity a pair of small
suckers destitute of any chitinous framework; often with
a pair of hooks between these suckers. With a paired
vaginal opening on the ventral side of the body. Porus

genitalis ventral and median.

1. Onchocotyle spinacis, n. sp.
(Pls. XV & XVI)

Body long-lanceolate, elliptical in cross-section, about 8 or
9mm. long, with the anterior end roundly truncate. Mouth
subterminal, ventral, with a large sucker around it like that of
the distomes. The three pairs of large, slightly elliptical posterior
suckers are arranged in a typical horse-shoe shape, with their mouths
turned dorsad (but lying on the morphologically ventral side), each
with a long semicircular chitinous piece with a narrow axial cavity
throughout its length and with one of its ends pointed and curved in
the form ofa claw. ‘These chitinous pieces lie in the suckers with
their lengths parallel to the longer axes of the suckers. Caudal
appendage sabcylindrical, with a bifid extremity which carries a pair
of small ellipsoidal suckers with their mouths opening at the top of
either bifid end ; with a pair of hooks 0.04 mm. long (curvature not
reckoned) and of the form represented in fig. 5, Pl. XV, between the
suckers ; directed obliquely forwards towards the left side of the body.
Ocsophagus of moderate length. Intestinal trunks simple, uniting with
each other at the level of the first pair of posterior suckers, and at this

point giving out two simple branches, one of which is continued
STUDIES ON THE ECTOPARASITIC TREMATODES OF JAPAN. 993

backwards between the suckers, and the other enters the caudal
appendage and ends a little before reaching the level of the small
suckers at the extremity. Genital opening on the same level with the
posterior end of the oesophagus, without any chitinous armature.
Ovary long, with numerous windings (PI. XV, fig. 1), situated near
the hinder end of the anterior half of the body; of small size in
relation to the whole body. The oviduet proceeds from its origin for
a certain distance forwards with a few windings, and then sharply
turns backwards and towards the right, and after proceeding posteriorly
for a short distance, again turns sharply forwards and is continued
into the ootyp. ‘This is tolerably long and lies with its long
axis nearly coinciding with that of the body. From its front end
the uterus proceeds straight forwards toward the genital opening.
Vitellarium extending from a little behind the anterior end of the in-
testinal trunks to the point of their union at the level of the first
pair of posterior suckers; separate in front but continuous behind.
Paired yolk-ducts perfectly symmetrical on the two sides, arising from
the vitellarium at about the level of the front end of the last
third of the anterior half of the whole body ; proceeding at first
somewhat forwards and towards the median line, then bend-
ing backwards, and uniting with each other in it to form a sort of
vitelline reservoir. From this a small unpaired yolk-duct proceeds
backwards and opens into the oviduct at the point where this
turns sharply backwards towards the ootyp. The genito-intestinal
canal, arising from the oviduct side by side with the unpaired yolk-
duct, proceeds at first towards the right, then turns backwards
and finally opens into the intestine. Receptaculum seminis situated on
the right side of the median line just in front of the ovary, large,
oval, with a long neck which opens into the oviduct side by side

with the genito-intestinal canal. Testes numerous, of moderate size ;
296 8. GOTO.

the anterior ones overlapping the posterior portion of the ovary ;
ending behind at a distance from the first pair of posterior
suckers equal to about the length of the caudal appendage.
Hobitat—Gill of Spinaz sp. (Jap. Tsubakurozamé).
Locality—Odawara.
Date—February 1891. '

VII. Caxicotyir, Diesing.

This genus was erected in 1850 by Diesing for a worm found by Kroyer on
the surface of the body of Raja radiata near the anus and afterwards described and
studied more minutely by Diesing” himself, Hoek, and Wierzejski*®; and up
to the present date it has contained only a single species, Culicotyle Kroyeri, Diesing.
Its original diagnosis*) as given by its founder is as follows: ‘ Corpus planum late
obovatum. Caput corpore continuum. Os subterminale transverse ellipticum.
Tractus intestinalis bifureatus (?). Acetabulum basilare ventrale, urceiforme
septangulare intus dissepimentis septem a centro radiantibus. Aperturae genitales
infra os, approximatae. AMNUS..........0068 Piscium marinorum ectoparasita.” This
was emended in his “Revision” as follows: ‘Corpus planum late obovatum.
Caput corpore continuum. Os subterminale transverse ellipticum. Acetabulum
unum subbasilare ventrale, urceiforme, septangulare, intus dissepimentis septem e
centro radiantibus, quinque inermibus uncino valido vaginato retractili armatis.
Androgyna ; aperturae genitalium infra os oblique juxtapositae approximatae. Porus
@XCLeLOVIUS.........00000 Tractus intestinalis bicruris, coecus.—Ovipara.—Piscium mari-
norum endo- et ectoparasita.” The last remark was probably occasioned by the
fact that Caltcotyle Nroyeri was found by H6k in the anus as well as in the rectum.
Subsequent diagnoses of the genus have been based on that of Diesing, which

is no doubt in the main correct, but which I believe I can improve as follows :

3ody flat, ovate, with a median notch at the pos-

 

1). Diesing—Vierzehn Arten von Bdelliden. Denkschr. d. k. Acad. d. Wiss. Wien., Bd.
14, 1858. p. 63-80. Cited on Braun’s authority.

2). Hoek—Om Calicotyle Kroyeri. Oefversigt “af. k. vet. Akad. Pérhandl, 1856. Cited
on the combined authority of Braun and Wierzejski.

3). Wierzejski—Zur Kenntniss des Biues von Calicotyle Kroyeri. Zzitsch. £. wiss. Zool.,
Bad. 59, 1877. p. 551.

4). Diesing—Syst. helm. p. 431 & 631.
STUDIES ON THE ECTOPARASITIC TREMATODES OF JAPAN. 997

teriorend, at the apex of which is attacheda large, cir-
cular, saucer-shaped sucker, the cavity of which is
divided by means of elevated, radial spokes intoa central
heptagonal area and seven quadrangular, peripheral areas,
the most posterior of which is larger than the others and
occupies the median line of the body, while the rest is
symmetrically disposed on the two sides. With a pair
of hooks imbedded in the radial spokes that bound the
hindmost peripheral area. Mouth subterminal and
ventral, with a rudimentary sucker just behind it.
With a paired vaginal opening on the ventral side of the
body. Common genital opening median and ventral.

With a tubular, chitinous penis.

1. Calicotyle Mitsukurit”, n. sp.
(Pl. XIX.)

Body very flat, ovate, about 8mm. long and 5mm. broad. Pos-
terior sucker sessile, large, having a diameter equal to about one-third
the whole length of the body; with seven, small notches at the
periphery corresponding to each radial spoke ; central area of the
sucker situated a little in front of the true centre of the sucker ;
the sucker projecting beyond the posterior end of the body proper
by about one-third of its diameter. Hooks very stout, hollow in
its distal portion equal to about one-fourth its whole Jength; strongly
recurved at the end; of the form represented in fig. 5, PI. XIX ;
0.56 mm. long (curvature not reckoned). Anterior end of the body
rounded ; with two pairs of hollow, goblet-shaped sticky glands opening

by their long necks at the anterior end om each side of the median

 

1). Dedicated to Kakichi Mitsukuri, Ph. D., Rigakuhakushi, Professor of Zodlogy
in the College of Science; Imperial University, Tokyo.
928 S. GOTO.

=

line. Mouth at a short distance from the front end of the body,
slit-like, with its length at right angles to the long axis of the body.
The anterior rudimentary sucker very conspicuous in surface view.
Pharynx ellipsoidal, with the internal tubular cavity coinciding with
the smaller axis. Oesophagus almost wanting. The two intestinal
trunks unbranched, distinct behind, running almost parallel to the
lateral margins cf the body, but each making a slight inward winding
at the level of the ovary (at about the end of the anterior third of
the whole body), and approaching towards each other at the posterior
end just in front of the sucker. Common genital opening ventral
and median, a little behind the middle of the anterior half of the
body proper. Chitinous penis exceedingly long and twice bent on
itself ; with an obliquely cut extremity ; about 0.59 mm. long. Ovary
situated at the hinder end of the anterior third of the whole
body, long, doubled on itself so as to form a loop with its open end
directed towards the left side of the body, looping the right intestinal
trunk, and with numerous smaller convolutions. Oviduct very short,
with a portion of it expanded into a small receptaculum seminis. Ootyp
of a rhombic form in longitudinal section. Uterus very short. Vitel-
larium confined to the lateral portion of the body outside the intestinal
trunks ; consisting of numerous, branching tubules ; and extending
from the level of the pharynx to that of the posterior sucker. The
numerous tubules of the anterior and the posterior parts of the vitella-
rium of each side unite among themselves into a single duct, which
traverses the length of the intestinal trunk, and just outside this, and
uniting with its fellow coming from the opposite direction at the level
of the anterior third of the body proper, forms the paired yolk-
duct. This then runs straight towards the median line of the body,
unites with its fellow of the opposite side, and forms the unpaired yolk-

duct, which is exceedingly short and immediately opens into the
STUDIES ON THE ECTOPARASITIC TREMATODES OF JAPAN. 999

seminal receptacle. Vaginal openings in the lateral region of the body;
about half as distant from the outer border of the intestinal trunk as
from the lateral margin of the body; in a plane a little in front of
that of the paired yolk-ducts. The rayinal canals proceed thence a
little backwards and towards the median line, where they unite and
form a single short duct, which then opens into the seminal receptacle
side by side with the unpaired yolk-duct. Testes situated behind
the ovary, numerous, closely packed, occupying nearly the whole
mesial region of the body posterior to the ovary, and enclosed by the
intestinal trunks.

Habitat—Cloaca of Rhina sp.? (Jap. Katasashi-zamé).

Locality—Mitsugahama.

Date—August 1889.

That the species above described is new can, I think, be hardly
doubted, as it presents many differences from C. Kroyeri. To men-
tion only one, the hooks of the present species are much longer than
those of C. Kroyeri, the Jatter being, according to my own measure-
ment, only 0.30 mm. long ; and their forms are also different, as may
be seen by comparing fig. 5 with fig. 14, Pl. XIX, the latter of
which has been drawn from a specimen of C. Kroyert brought back

from Europe by Prof. Ijima and kindly Jent me by him.

VIII. Moyocoryre, Taschenberg.

This genus is due to Taschenberg who erected it in 1878 for an ectoparasite
found by him on the gill of Alyliobates aquila in Naples, and named by him df. mylio-
batis, which has remained, up to the present date, the only species of the genus. The
somewhat imperfect description by Taschenberg™ is as follows: “ Der Kérper

ist langgestreckt, von vorn nach hinten etwas erweitert, und triigt am hintern Ende

 

1). Taszhenberg—Helminthologisches. Zeitschr. f. d. gesamm. Naturwiss., Bd. 51, 1878.
p. 562. Cited on the combined authority of Braun on the one hand and Parona and Perugia
on the other.
230 8. GOTO.

einen ziemlich grossen sitzenden Saugnapf. Derselbe besitzt acht Speichen, von
denen die eine in der Lingsachse des Thieres gelegen ist, wilrend jederseits drei
vom Centrum nach der Peripherie lin ausstrallen. Da wo die beiden letzten den
Rand des Saugnapfes erreichen, sind zwei grosse, starke Chitinhaken eingefiigt, die
in der Querachise desselben gelegen sind. Die Mundiffuung am vordern Korperende
ist selar weit und dient gleiclfalls zum Ansaugen. Die Liinge des Thieres betrigt
5 mm. bei einer Breite von 2mm. Der Saugnapf hilt 1.6mm. in Durchmesser. Die
Farbe ist weisslich.” Later in 1890 Parona and Perugia” published a short
anatomical description of the same species, confining themselves, however, from
want of material, to the consideration of the sucker as well as some parts of the
genital organs. Many of their statements, however, seem to me so ancmalous and
are in many important respects so at variance with the results of my own studies
as set forth in the anatomical part of the present paper that I have thought it
advisable to base myself only on my own observations in forming the diagnosis of
the genus, which I believe I can best embody in what follows :

Body elongated, flattened; with a large circular, sub-
sessile, sub-basilar, posterior sucker, the internal surface
of which is divided by means of eight radial spokes meet-
ing at the centre into as many equal secants. The pos-
terior radial spokes lying on each side of the median line
carry each a large hook. Mouth large, subterminal,
ventral, destitute of any sucker. With three testes.
Common genital opening ventraland median. Vaginal

opening ventral and lateral. With two pairs of eye-spots.

1. Monocotyle Ijimae”, n. sp.
(Pls. XVII & XVIIZ.)

Body about 3 mm. long, elongated, flattened, but not very broad;

posteriorly pointed ; gradually becoming narrower in front and

 

1). Parona e Perugia—Di alcuni trematodi ectoparassiti di pesci adriatici. Annali del
Mus. Civ. di Storia Naturale di Genova. Ser. 2, vol. IX, 1890. Estratto pp. 5-8.

2). Dedicated to Isao Ijima, Ph. D., Rigakushi, Rigakuhakushi, Professor of Zodlogy
in the College of Science, Imperial University, Toky3.
STUDIES ON THE ECTOPARASITIC TREMATODES OF JAPAN. 931

ending with a slight lateral expansion. Anterior end with a large,
not very deep notch. With four pairs of sticky glands on each side of
the notch. Sucker circular, sub-basilar, with a short stalk, with a
diameter equal to about one-third the length of the body proper,
provided with a marginal membrane ; every two of the radial spokes
lie in a line, and one of these pairs coincides with the median line of
the body. The marginal membrane as well as the radial spokes car-
rying numerous minute chitinous bodies on their free surface. At the
centre of the sucker where the radial spokes all meet together is left
asmall cup-shaped hollow area. Hooks large, strongly recurved at the
end, and with a sort of conspicuous barb; 0.12mm. long (curvature
not taken into account). Mouth large, at a short distance from the
anterior end of the body, with a capacious funnel-shaped cavity. No
anterior sucker, but with the dorso-ventral musculature around the
mouth specially developed and serving asa sucker. Pharynx typical-
ly egg-shaped, large. Ocsophagus exceedingly short. Intestinal trunks
simple, tubular, describing a few windings, and ending just
behind the anterior end of the sucker, in the median line, close
to each other but separate. Common genital opening about as far
behind the posterior end of the pharynx as the total length of the
latter ; with a tubular chétinous penis making a single spiral wind-
ing, about 0.18 mm. long. Ovary situated a little in front of the
middle of the whole body, long, large, and globular at its proximal
end (i.e. the formative zone) but slender towards its distal end, twice
forming a loop, and the more distal loop embracing the intestinal
trunk of the right side. The oviduct proceeds from its origin at first
forwards and towards the left, and after receiving the yolk-ducts and
the vaginal canal, it sharply turns back towards the right, keeping
its forward course, and is continued into the ootyp. This with its

thick wall is very large and conspicuous, and opens directly into the
232 8. GOTO.

genital atrium. Vaginal opening on the left side of the body, a little
behind the common genital opening and on the same plane with the
anterior end of the ootyp, surrounded with a mass of compact connect-
ive tissue ; vaginal canal short and leading into a spacious, globular
receptaculum seminis, from which a short canal proceeds backwards and
opens into the oviduct side by side with the yolk-duct.  Fitellurium
mainly confined to the lateral areas of the body outside the intestinal
trunks, extending from about the plane of the front end of the
pharynx to that of the termination of the intestinal trunks. The
vitellarium of each side gives rise to two yolk-ducts which, coming
one from the anterior and the other from the posterior part, unite
just inside the intestinal trunks and give rise to the paired yolk-duct.
This thon proceeds straight towards the median line and opens into
the oviduct at the point above specified, side by side with its fellow
of the opposite side. Testes posterior to the ovary, large, three
in number; one being situated behind in the median line and
globular in form; the other two just in front of this and closely
appressed, to each other as well as to the posterior testis, so that the
boundary separating the three has the form of A. Vas deferens arising
from the anterior testis of the left side, proceeding forwards just inside
the left intestinal trunk to about midway between the common genital
opening and the hinder end of the pharynx, then turning back-
wards on the right side, and making one or two convolutions,
reaches the front end of the ootyp. Here it again turns forwards
and passing through the bulbus cjaculatorius, opens finally at the base
of the tubular chitinous penis.

Habitat—Mouth-cavity of Trygon pastinaca (Jap. Aka-ei).

Locality—Hiroshima (Ujina Port).

Date—August 1889.
STUDIES ON THE ECTOPARASITIC TREMATODES OF JAPAN. 988

IX. Eprepenua, Blainville.

An excellent summary of the history of this genus up to 1861 is found in P. J.
v. Beneden’s “ Memoire sur les vers intestinaux” (pp. 18-21), and I have nothing
to add to it. It has been already pointed out by Braun” that Diesing’s genus”
Benedenia is based without any sufficient ground on Epibdella sciaenae, P. J. v. Bene-
den. In 1889 a new species E. Hendorffii (—Phylline Hendorfii, Linstow )) was
described, so that the genus contains at present three species, viz., the one just men-
tioned from the surface of the abdomen of Coryphaena hippurus, E-. hippoglossi, O. Fr.
Miiller from the bedy surface of Pleuronectes hippoglossus, and FE. gece, P. J. vy.
Beneden from the body surface of Seivena aquila.

P. J. v. Beneden® gives the following diagnosis of the genus: “Corps de
forme ovale, mince et aplati; tte pourvue de deux ventouses, une grande ventouse
en arriére armée de crochets et couverte en dedans de papilles régulicrement dis-
posées, avec le bord frangi; les orifices sexuels situés sur le bord A droit prés de la
ventouse buccale; deux vésicules pulsatiles, s’ouvrant en avant, 4 quelque distance
du bord. Ils vivent sur la peau des poissons ”—a diagnosis which has been repro-
duced in essence by subsequent writers. I believe I can improve it as follows :

Body flat, thin, more or less oval; with a pair of el-
liptical or circular suckers at the anterior end of the
body on either side of the mouth, and with a circular or
elliptical sucker at the posterior end. The posterior
sucker destitute of any septa, and with three pairs of
hooks near its posterior border. Mouth subterminal.
Common genital opening ventral, on the left side of
the body, just behind one of the anterior suckers, and
near the margin of the body. Vaginal opening ventral,

on the same side as the common genital opening, and

 

1). Braun—Wiirmer. p. 518.

2). Diesing—Revision d. Myzhelminthen, p. 363. Nachtriige u. Verbeper. z. Rev. d:
Myzhelm., p. 19.

3). Linstow—Beitrag z. Anat. v. Phylline Hendorffii. Archiv f. mik. Anat. Bd. 33, 1889.
pp. 153-180.

4). P. J. v. Beneden—Mémoire ete. p. 18.
934 8. GOTO,

behind it at various distances. With conico-cylin-
drical or club-shaped penis. Testes two. With two
pairs of eye-spots.

1. Epibdella Ishikawae, n. sp.
(Pl. XXVI, figs. 1-3.)

Boily elongated-oval, flat, about 4 mm. in length. Anterior suckers
nearly circular, connected together by a thin, membranous continuation
of the anterior end of the body. Posterior sucker circular, with a
marginal membrane; with three pairs of flattened hooks of the
form represented in fig. 2, Pl. XXYVI, in its posterior half.
Mouth small, a little in front of the plane of the posterior end of
the anterior suckers. Ocsophagus- wanting. Intestinal trunks with
lateral branches, separate behind, ending at the plane of the front end
of the posterior sucker. Common genital pore close to the left lateral
margin of the body, at the plane of the mouth, just outside the
anterior sucker; leading into a deep genital atrium, in which
lies the long, conico-cylindrical penis. Ovary comparatively small,
globular, situated in the median line, a little in front of the middle
of the body proper. Oviduct arising from the ventral side of the
anterior end of the ovary, thence proceeding forwards with a few
slight windings and continued into the ootyp a little behind
the posterior end of the penis. ‘The ootyp is rhombic in horizontal
section, and opens into the genital atrium by means of an exceedingly
short neck. J7tellarium extending from the level of the front end
of the pharynx to about the anterior end of the posterior sucker; that
of the two sides intermingling with each other behind the testes.

Paired yolk-duct of each side formed by the union of two ducts coming

 

1). Dedicated to Chiyomatsu Ishikawa, Ph. D., Rigakushi, Rigakuhakushi, Profes-
sor of Zodlogy in the College of Agriculture, Imperial University, Tokyo.
STUDIES ON THE ECTOPARASITIC TREMATODES OF JAPAN. 935

respectively from the anterior and posterior portions; proceeding towards
the median line, and uniting with its fellow of the opposite side
at the front end of the ovary a little to the left of the median
line. Unpatred yolk-duct very short, proceeding from the point of
union of the paired yolk-ducts straight to the oviduct. Vaginal
opening a short distance behind the common genital opening,
nearly on the same longitudinal line; vaginal canal long, mak-
ing numerous convolutions and opening into the yolk-duct at
the point of union of the paired ducts of the two sides. Testes
large, two in number, paired, irregularly ellipsoidal, situated just
behind the ovary. A single short vas efferens arising from each
testis, immediately uniting with the other and forming the vas
deferens. This proceeds forwards with numerous complicated convolu-
tions as represented in fig. 38, Pl. X XVI, and finally entering the
penis at its base and traversing nearly its whole length. finally opens
near its apex. Prostate gland very large, vesicular, elongated, just
behind the penis.

Habitat—Gill of Lethrinus sp.? (Jap. Kuchibi-dai).

Locality—Hagi.

Date—August 1889.

2. Epibdella ovata, n. sp.
(PI. XXVI, figs. 4-8.)

Body squarish-oval, a little broader in the posterior part, flat,
about 2 mm. long. Anterior suckers elliptical, connected with each
other by a thin membrane. Posterior sucker elliptical, with its long-
er axis at a right angle to the long axis of the body, with a
marginal membrane, with a pair of notches on its anterior and
posterior margins, due to the insertion of muscular fibres at these

points; with three pairs of hooks of the form represented in fig. 5,
936 S. GOTO.

Pl. XXVI. Mouth small, at the plane of the hinder end of the
anterior suckers. Ovsophajus wanting. Intestinal trunks with nu-
merous lateral branches, terminating at the front end of the posterior
sucker, widely separated from each other. Common genital opening near
the left lateral margin of the body, a little in front of the hinder
end of the anterior sucker; leading into a deep genital atrium, in
which lies the club-shaped penis with its smaller end directed out-
wards. Ovary spherical, comparatively small, in the median line,
at the end of the anterior third of the whole body. The oviduct
arises at the anterior end of the ovary on the ventral side, and thence
proceeds at first forwards, then turns backwards, and then again
proceeds forwards, undergoing more or less convolutions on the way,
and is finally continued into the ootyp, which opens into the genital
atrium by means of a short duct, the uterus (cf. fig. 6, Pl. XXVI).
Vitellarium extending from the level of the front end of the pharynx
to the front end of the posterior sucker; the lobes of the two sides
intermingled with each other behind the testes. Paired yolk-ducts
directed transversely to the long axis of the body, that of the right
side longer than its fellow of the opposite side; the two therefore unit-
ing with each other on the left side of the ovary and there forming a
capacious, globular yolh-reservoir, from which a short unpaired yolk-duct
leads into the oviduct. Vaginal opening on the left side of the body,
about midway between the common genital opening and the front
end of the testes, surrounded by a mass of compact connective tissue.
Testes large, ellipsoidal, paired, just behind the ovary. A single vas
efferens arising from each testis, and uniting just in front of the testis
of the left side. The vas deferens thence proceeds forwards with nu-
merous complicated convolutions as represented in fig. 6, Pl. XXVI,
and traversing the whole length of the penis finally opens at its apex.
With a pair of small globular bodies behind the testes. Prostate gland
STUDIES ON THE ECTOPARASITIC TREMATODES OF JAPAN. 937

conspicuous, egg-shaped, hollow, with a thick wall, and communicat-
ing with the penis by means of a short, slender duct.
Habitat—Gill of Anthias Schlegelii (Jap. Akasagi).
Lovality—Misaki.
Date—August 1891.

X. Tristomumu, Cuvier.

This genus was created by Cuvier! in 1817 for a worm found on the gill of
various species of fish and named by him T. coccinewm, a species which was afterwards
examined and described more minutely by Taschenberg. Previous to Cuvier’s
erection of the genus, however, a worm of the same genus had been described (1786)
by La Martinicere”, the Z, maculatum of Rudolphi. In 1836 a second species
was described by Diesing and was named by him 7. papillosum, a species which
was afterwards made the object of a more minute study by Kéllicker®» and
Taschenberg; in 1847 two new species (T. squali and T. miokee) were described
by Blanchard); in 1878 TZ. pelamydis was described by Taschenberg® and
was afterwards redescribed somewhat more at length by Parona and Perugia”,

and more clearly distinguished from the other species; in 1889 a seventh species,

 

1). Cuvier—Réegne aninial, 1817, t. IV, p. 42. From the quotation in Braun’s “ Wiirmer”
(p. 528) it appears that Cuvier at first mistook the anterior end for the posterior, but in
a later edition the mistake is corrected (cf. Régne animal, t. III, Paris, 1830. p. 265).

2). Martiniére—Journ. d. physique, 1787, p. 207. Also in “ Voyage de Lapérouse,” 1798,
t. IV, p. 79. Cited on the combined authority of Dujardin, Diesing, and St.-Remy.

3). Kollicker—Ueber Tristomum papillosum Dies. Berichte von d. kénigl. zoot. Anstalt
z. Wirzburg, II. Ber. f. d. Schuljahr 1847/48. 1849. pp. 21-27. Cited on Braun’s authority.
4). Taschenberg—Beitriige z. Kenntniss mar. ectopar. Trematoden, 1879.

5). Blanchard—Recherches sur l’organisation des vers. Annales d. sciences natur., 3. ser.,
VIII, 1847. Cited on the combined authority of Braun and St.-Remy.

6). Taschenberg—Helminthologisches. Zeitsch. f. d. gesuamm. Naturwiss., 1878. p. 562-577
Cited on the combined authority of Braun and St.-Remy.

7). Parona e Perugia—Di alcuni trematodi ectoparassiti di pesci adriatici. Op. cit.,
ser. 2, vol. IX, 1890. Estratto p. 3-5.
938 8. GOTO.

=

T. uncinatum, was described by Monticelli”; and finally in 1891 three species
were added to the genus, two (T. interreptum and T. Levinseni’) by Monticelli?) and
one (T. histiophori) by Jeffrey Bell).

The emended generic diagnosis of Diesing*) is as follows: “Corpus suborbicu-
lare v. oblongum, planum v. depressum. Caput discretum, acetabulis duobus margin-
alibus v. juxtapositis subcircularibus. Os inter acetabula subterminale. Acetabulum
corporis radiatum ventrale inferum, sessile, disciforme explanatum, intus septemradi-
atum, disco centrali minore. Androgyna; aperturae genitales approximatae,
feminea infra os, mascula in sinistro corporis latere, pene filiformi. Porus ex-
cretorius......... Tractus intestinalis bicruris, coecus. Ovipara.—Piscium marinorum
ectoparasita.” Following closely Braun and St.-Remy I give the generic diag-
nosis as follows :

Body circular to elongated-oval, much flattened; with
two circular or elliptical anterior suckers at the anterior
end of the body on either side of the subterminal mouth,
and a single circular sessile sucker at the posterior
extremity. Posterior sucker provided with a mar-
ginal membrane, with its internal surface divided by
means of a certain number of radial septa and the bars
connecting them, into a central polygonal area and
a certain number of peripheral areas; generally car-
rying hooks (mostly one pair), Uterus opening into
the genital atrium or independently of it directly to the
exterior. Genital opening or openings ventral, on the
left side of the body near the anterior sucker. With a

vagina opening ventrally on the left side of the body,

 

1). Monticelli—Tristomum uncinatum, n. sp. Boll. d. Soc. d. Nat. in Napoli. An. LII, fase.
II. 1889. pp. 117-119. With one plate.

2). Monticelli—Di alcuni organi di tatto nei Tristomidi: Contributo al. Stud. d. Trem.
monog., parte I. Boll. d. Soc. d. Nat. in Napoli. Ser. L, ann. 5., vol. 5, 1891. p. 122,
Notes III & IV.

3). Jeffrey Bell—Description of a New Species of Tristomum from Histiophorus breviros-
tris. Annals & Mag. of Nat. Hist., vol. VII, 6th. ser., 1891. pp. 534-535.

4). Diesing—Revision d. Myzhelminthen, p. 365.
STUDIES ON THE ECTOPARASITIC TREMATODES OF JAPAN 939

more or less behind the common genital opening or the

male and female openings. |

1. Tristomum sinuatum, n. sp.
(Pls. XX, XNI, XXII)

Body ovato-oval, about 8 mm. long by 7 mm. broad, anterior
border concave, with a deep, acute notch at the posterior end, with
numerous uniformly scattered, small papillae on the dorsal side,
ventrally smooth; lateral margins sinuate and with a minute crown-
shaped chitinous body” at the top of each wave (PI. XX, fig. 3).
Anterior suckers elliptical, of moderate size, attached to the body at the
apices of deep indentations that divide the anterior from the lateral
margins of the body. Posterior sucker circular, small, only about twice
as large as the anterior sucker, at the apex of the posterior notch,
much in front of the posterior end of the body; central area forming a
regular heptagon with one of its sides perpendicular to the long axis
of the body, with an isosceles-trapezoidal peripheral area corresponding
to each of its sides; the two equal sides of the hindmost peripheral
area bifurcating towards their outer ends and thus giving rise toa
small accessory, triangular area on each side. Hooks present in a
single pair, stout, solid, slightly curved, and with free end curved
like the claw of a cat (Pl. XX, fig. 2), 0.195 mm. long, situated
at the ends of the posterior border of the central heptagon. Mouth
small, at the plane of the beginning of the hindmost third
of the anterior suckers. Pharynx simple, short, cylindrical.
Oesophagus exceedingly short. Intestinal trunks continuous behind,
describing some distance in front of the posterior sucker an are

with its convexity turned forwards ; with numerous repeatedly bifur-

 

1). In one specimen I have counted fifty-eight of these bodies on each side.
240 8. GOTO.

cating Jateral branches on the outer side and a smaller number (about
four or five) of less repeatedly dividing branches on the inner.
The foremost inner branches of both sides form a pair, and pro-
ceed at first backwards and towards the median line and then again
diverge, thus making the figure of two bows with their backs turn-
ed towards each other ; the branches of the two sides being, however,
often of unequal lengths. Common genital opening close behind the
anterior sucker of the left side. Penis club-shaped, of moderate length.
Ovary much lobed, in the median line, at the beginning of the middle
third of the body. Oviduct arising from the ventral side of the an-
terior end of the ovary, proceeding forwards and towards the left dorsal-
ly to the yolk-duct, continued into the ootyp ahout midway between
the hinder end of the penis and the front end of the vitelline reservoir.
Uterus of moderate length, following the same general course as the
oviduct, opening into the genital atrium at a short distance from the
external opening of the latter. J7tellaritum almost wholly confined to
the lateral and posterior regions of the body, but also following the
intestinal branches into the median region ; with a large yolk-duct just
inside the intestinal trunk on each side ; this yolk-duct, by its union
with a similar duct coming from the anterior part at the plane of the
front end of the ovary, gives rise to the paired yolk-duct, which unit-
ing with its fellow of the opposite side at the front end of the ovary
on the left side of the median line, forms here a large yolk-reservoir.
From this the unpaired yolk-duct proceeds dorsad, anteriad, and towards
the right, and opens into the oviduct. Vaginal opening a short dis-
tance behind the common genital opening, a little farther from the
median line ; the much convoluted vaginal canal lies for the most part
just outside the vas deferens, is swollen into a comparatively small
receptaculum seminis near its external pore, and finally opens into the

yolk-reservoir. Testes small, very numerous, confined to the median
STUDIES ON THE ECTOPARASITIC TREMATODES OF JAPAN. 941

region between the intestinal trunks, mostly behind the ovary,
but extending also forwards on both sides about midway up the
ovary. Numerous vasa efferentis uniting in the median line and
forming a single vas deferens, which, with numerous convolutions,
proceeds forwards, keeping itself close on the left side of the
ovary, and reaching the front end of the latter here forms a long
loop with its closed end directed forwards and towards the right ;
after this the vas deferens proceeds, still with complicated con-
volutions, for a short distance forwards, then bends towards the right;
and entering the penis at its base, finally opens into its cavity on
the top of a papilla, at a short distance from its apex ; its calibre
generally decreasing all along after the large loop at the front end
of the ovary.

This species has a light flesh-red colour of its own, which does
not wholly disappear in alcoholic specimens.

Habitat—Inner side of the gill-plates of Histiophorus sp. (Jap.
Kajiki).

Locality—Misaki.

Date—August 1891.

2. Tristomum ovale, n. sp.
(Pl. XXIII; Pl. XXIV, figs. 1-5.)

Body oval, about 13mm. long by 12 mm. broad or larger,
sometimes approaching more nearly a circle, with numerous, uniform-
ly scattered conspicuous papillae on the ventral surface, dorsally smooth.
Anterior border convex, separated from the lateral borders by a deep,
large notch on each side, at the apex of which is attached the anterior
sucker of either side; posterior end with a large obtuse notch. Lateral
margins entire, destitute of chitinous bodies. Anterior suckers of moderate

size, nearly circular, with numerous papillae on their inner margins.
242 8. GOTO,

Posterior sucker circular, large, with a diameter equal to half the
length of the body proper ; projecting beyond the body by about one-
third of its diameter, with a marginal membrane; central area a
nine-sided polygon formed by bringing the shorter of the two parallel
sides of an isosceles trapezoid on one side of a regular heptagon and
by obliterating the boundary (7. ¢., central heptagon open behind),
and with the added trapezoid projecting backwards ; peripheral
areas seven in number, the four anterior of equal size, with the
form of an isosceles trapezoid, the next two on either side of a
different form from the others, but similar to each other, with
the form of an isosceles trapezoid with one of its corners cut off
obliquely ; and the hindmost area which occupies the median- line
again with the form of an isosceles trapezoid, but much smaller than
the others. Hooks in one pair, solid, flattened, with a form like that
of the butcher’s knife (P]. XXIII, fig. 2), longitudinally furrowed,
with a deep notch at the proximal end, large, being 0.91 mm., imbed-
ded in the non-parallel sides of the isosceles-trapezoidal portion of the
central area. Mouth at some distance from the front end of the body,
between the anterior suckers, a little anterior to the plane of their
hinder ends. Pharynx double, i. ¢., divided by a deep constriction
into an anterior, larger portion and a posterior, smaller portion, so that
the whole has somewhat the form of the numeral 8. Ocsophaqus very
short. Jntestinal trunks continuous with each other posteriorly a
little behind the anterior end of the posterior sucker, enclosing a
rather small, rectangular area; each with a small number (5)
of literal, repeatedly bifurcating branches on the outer side,
and only «about three shorter branches on the inner. Denis
exceedingly large and long, cylindrical, often projecting beyond
the opening of the genital atrium. Ovary sub-globular, much

lobed, in the median line, at the hinder end of the anterior
STUDIES ON THE ECTOPARASITIC TREMATODES OF JAPAN. 943

half of the body proper. Oviduct arising from the ventral side of the
ovary; thence proceeding forwards and towards the left it is continued
into the ootyp at about the plane of the hinder end of the penis.
Uterus of moderate length, running parallel to the penis, and opening
to the exterior just behind the opening of the genital atrium.
Vitellarium occupying neary all those portions of the body left vacant
by the other internal organs, extending from the anterior nearly to
the posterior end of the body, and also occupying the whole dorsal side
of the median region enclosed by the intestinal trunks. Pazred yolk-
ducts formed by the union of two large ducts coming from the anterior
and posterior regions of the vitellarium on each side of the body, or by
the union of a larger number of smaller ducts ; proceeding at right
angles to the long axis of the body, and forming by their union a large
yolk-reservoir at the front end of the ovary just on the left side of
the median line. Unpaired yolk-duct short, proceeding dorsally from
the yolk-reservoir and opening into the oviduct. Vaginal opening a
little behind that of the uterus, nearer the median line ; vaginal canal
proceeding backwards and inwards at first with a slight winding
or two, but reaching the plane of the yolk-reservoir it makes some
complicated convolutions and after being enlarged into a seminal recep-
tacle, finally opens into the yolk-reservoir. Testes rather small, very
numerous, of an irregular shape and more or less lobed, not confined
to the median region of the body but extending on both sides a
little less than two-thirds the distance between the lateral margins of
the body and the intestinal trunks, and in the latter regions reaching
from the hinder end of the anterior suckers to the front end of
the posterior sucker; the whole area occupied by the testes thus
assuming somewhat the form of a cross-section of a biconcave lens.
Vas deferens formed by the union of a certain number of vasa efferentia

at the posterior, left corner of the ovary, thence proceeding forwards
244 S$. GOTO.

on the left side of the ovary, and reaching the plane of the anterior end
of the latter, it bends towards the right and forms a large loop with
secondary windings lying horizontally just in front of the ovary,
with its closed end directed towards the right ; after this the vas
deferens makes numerous, complicated convolutions, and proceeds
forwards and towards the left, keeping itself just inside the vaginal
canal ; a little in front of the ootyp it bends towards the right and
enters the penis at some distance from its base, and finally opens into
its cavity on the top of a small papilla at some distance from its apex ;
diminishing in calibre generally all the way after forming the large
loop just in front of the ovary.

Habitat —Mouth-cavity of Histiophorus orientalis (Jap. Basho-
kajiki), Histiophorus sp. (Jap. Kajiki), and another undetermined
species perhaps of the genus Cybium (Jap. Oki-ma-zawara).

Locality —Misaki.

Date—August 1891 and ’92.

This species may possibly prove identical with T. histiophori of
Jeffrey Bell, specimens of which had been collected in Madras by
F,. Day from Histiophorus brevirostris ; but from the meagreness of the
description I am not able to determine whether it is really so or not.
For the sake of comparison I here subjoin the whole description” and
the measurements of the worm recorded : “ With a close resemblance
to T. coccineum, it is distinguished by the absence of parallel rows of
chitinous corpuscles and by the fact that the posterior sucker projects
by about one-third of its diameter beyond the margin of the body.”
Measurements of three specimens are stated to have been respective-

ly 15 mm.x12 mm., 14 mm.x11.5 mm., and 10.5 mm.x10 mm.

 

1). Jeffrey Bell—Description of a New Species of Tristomum from Histiophorus brevirostris.
Annals and Magazine of Nat. Hist., vol. VII, 6th ser. 1891. pp. 534-535.
STUDIES ON THE ECTOPARASITIC TREMATODES OF JAPAN. 945

3. Tristomum rotundum, n. sp.
(Pl. XXIV, figs. 6-9.)

Body oval in the state of perfect rest, with the antero-posterior
axis shorter, about 11.5 mm. by 13 mm., but sometimes a little longer
antero-posteriorly ; smooth both dorsally and ventrally ; with the
anterior border concave, and separated from either lateral margin by a
deep, not very wide notch; with only a shallow concavity on the
posterior border. Lateral margins entire, with numerous transverse
rows of chitinous bodies somewhat similar in form to those of
T. mole” ; each row consisting of four or five bodies in the middle
part but diminishing in number towards both ends, beginning
just a little behind the anterior suckers and entirely absent for
a certain stretch on the concavity at the posterior end of the body,
on both sides of which each row contains only a single chitinous
body. Anterior suckers elliptical, of moderate size, attached to the
body at the apices of the notches that divide the lateral from the
anterior border of the body. Posterior sucker circular, with its
hinder end scarcely reaching the posterior border of the body, of
moderate size, with a diameter equal to about one-third the length of
the body proper ; with an elevated, central, regularly heptagonal area
and seven peripheral areas of the form of an isosceles trapezoid ; the
latter all of equal size and the hindmost one occupying the median
line of the body. Hooks in one pair, solid, imbedded at the ends
of the posterior side of the central heptagon, thickened and pointed
at both ends, but with the free end sharper, of the form represented in
fig. 8, Pl. XXIV, 9.16 mm. in length. Jouth small, between the

anterior suckers, at the plane of the beginning of the posterior third of

 

1). Parona e Perugia—Res ligusticae, VIII. Di aleuni trematodi ectopar. d. pesci marini:
Nota preventiva. Op. cit., ser. 2, vol. VII, 1888. p. 741.
246 8. GOTO.

their lengths. Pharynx simple but slightly constricted in the middle,
short, cylindrical. Oessphagus very short. Intestinal trunks continuous
posteriorly a little in front of the posterior sucker, enclosing a
kidney-shaped area ; the posterior commissural limb very slightly
curved, with its convexity directed forwards; each intestinal trunk
with numerous, repeatedly bifurcating branches on the outer side,
but sending only a few branches on the inner, two of which
are longer than the others and send out secondary branches.
The foremost of these approaches its fellow of the opposite side
in the median line of the body and forms with it the figure of
two bows with their backs turned against each other, as in 7’. sinu-
atum. Penis tolerably long, club-shaped. Ovary in the hinder part
of the anterior half of the body proper, roundish, longer transverse-
ly than antero-posteriorly, deeply lobed. Oviduct arising at the front
end of the ovary in the median line, and thence proceeding at first
towards the left and then more forwards, it is continued into the
ootyp. Uterus tolerably long, opening to the exterior just behind
the opening of the genital atrium, on the same plane with
the hinder end of the anterior sucker. Vitellarium mostly con-
fined to the lateral regions of the body, but also extending into the
anterior, median lobe of the body, and wholly absent from the median
region except around the intestinal branches. Paired yolk-ducts
formed by the union of two large yolk-ducts as in the other species ;
uniting with each other and forming a yolk-reservowr at the front
end of the ovary a little on the left side of the median line. Unpaired
yolk-duct very short, connecting the yolk-reservoir with the oviduct.
Vaginal opening some distance behind the uterine opening and more
removed from the median line ; vaginal canal proceeding backwards
and towards the median line with numerous close convolu-

tions, forming a capacious, elongated flask-shaped receptaculum seminis
STUDIES ON THE ECTOPARASITIC TREMATODES OF JAPAN. DAT

about midway on its whole course, and finally opening into the yolk-
reservoir. ‘Testes small, numerous, confined to the median region
enclosed by the intestinal trunks, mostly behind the ovary. Jas
deferens taking the usual course up to the anterior end of the ovary ;
the loop which it forms at this level is placed perfectly transversely
to the length of the body, with the closed end directed as usual
towards the right; after this the vas deferens proceeds forwards,
making numerous convolutions on the way, and reaching the
front end of the ootyp turns backwards, and enters the penis at a
short distance from its base, and describing some convolutions
within it finally opens into its cavity about midway its whole
length ; the calibre of the vas deferens being very small in the latter
part of its course.

Like T. sinuatum this species has a light flesh-red colour of
its own.

Habitat—Gill of Xiphias gladius (Jap. Mekajiki).

Locality—Misaki.

Date—August 1891.

This species is evidently very closely related to 7’. coceineum, with
which I have at first suspected it to be identical. And even now I
find myself unable to give up this suspicion, although there are some
small but positive differences between the two species if Taschen-
berg’s figures” are perfectly accurate. In the first place the form of
the hooks is different, being in 7’. coccineum simply obliquely hollowed
out at the two ends; and in the second place the transverse rows of
minute chitinous bodies on the lateral margins of the body are in
T. rotundum wholly absent on the concavity at the posterior end of

the body, whereas in T. coccincum the rows of both sides are, accord-

 

1). Taschenberg—Beitriige etc.
248 S. GOTO.

ing to Taschenberg, wholly continuous with each other along the

posterior border of the body.

4. Tristomum foliaceum, n. sp.
(Pl. XXIV, figs. 10-12; Pl. XXYV, fig. 9.)

Body elongated, slightly ovate, about 6 mm. by 3 mm.;
with the anterior border brace-shaped (--); lateral margins entire,
destitute of any chitinous corpuscle, and divided from the median,
anterior lobe of the body only by a slight constriction, where the
anterior suckers are attached ; with a not very deep notch at the
posterior end. Aundterior suckers circular, of moderate size in com-
parison to the body. Posterior sucker slightly elliptical, with the
major axis directed antero-posteriorly, projecting beyond the body by
about one-third of its length ; provided with a marginal membrane ;
with a diameter equal to the breadth of the body just behind the
anterior suckers ; its internal surface divided into areas just as in
T. ovale. Hooks in one pair, in position as they are in T. ovale,
hollow, spinous, with a deep notch at the proximal end, of the form
represented in fig. 11, Pl. XXIV, about 0.175 mm. long on the
average. In the specimen examined by me the hooks were of unequal
lengths on the two sides, that of one side being 0.164 mm. and that
of the other 0.186 mm., thus giving the average above recorded.
Mouth of moderate size, at the plane of the hinder end of the
anterior suckers. Pharynx divided by a constriction into two unequal
portions as in TJ’. ovale. Oe8sophagus very short. Intestinal trunks
continuous with each other behind, a little in front of the posterior
sucker, with numerous dendritic branches on the outer side, and with
a few shorter branches on the inner; enclosing a not very ex-
tensive area in the middle portion of the body similar in form to

that of the latter. Common genital opening a little on the left side of
STUDIES ON THE ECTOPARASITIC TREMATODES OF JAPAN. DAO

the pharynx, at about the plane of the middle of the whole length of
the latter. Dents short and thick. Ovary at the hinder end of the an-
terior third of the body proper, ovoid, being longer from right to
left, not lobed. Oriduct arising at the front end of the ovary in the
median line, thence proceeding forwards with a slight winding or two,
and continued into the cotyp. Uterus not very long, opening into
the genital atrium near its bottom. itellar‘um mainly confined to the
lateral regions and the anterior lobe of the body, and only accompany-
ing the intestinal branches into the median region. Paired yolk-duets,
yolk-reservoir, and unpaired yolk-duct as in the preceding species. Testes
small, globular, numerous, confined to the median region between the
intestinal trunks. Vaginal opening a little behind the common genital
opening ; rayinal canal proceeding as usual backwards and towards the
median line, and after forming a capacious, globular receptaculum
semis, opening finally into the yolk-reservoir.

Habitat—Gill of an undetermined species of fish the Japanese
name of which is Hazara.

Locality—Misaki.

Date—August 1891.

5. Tristomum Nozawae,” n. sp.
(Pl. XXV, figs. 1-3.)

Body elongated-ovate, about 12 mm. long by 7 mm. broad, with
the truncate anterior border perfectly straight, with the anterior
lobe of the body separated from the lateral borders only by a
shallow constriction ; lateral margin entire, destitute of any chitin-

ous corpuscle ; with a large notch at the posterior end of the body

 

1). Dedicated to Shunjiro Nozawa, Nogakushi, Naturalist to the Fisheries Bureau
of the Hokkaid6 Cho, to whom as well as to Kazutaka Ité Esar., the then Director of the
Fisheries Bureau, are due my best thanks for giving me numerous facilities for collection
during my stay in Hakodaté. :
250 8. GOTO.

proper. Anterior suckers of moderate size, nearly circular. Posterror
sucker slightly elliptical, with its major axis coinciding with the
median line of the body ; with a diameter equal to the breadth of the
body at the plane of the mouth ; with its internal surface divided into
areas like those of T’. ovale and T. foliaceum. Hooks in one pair, in a
position similar to that in the two species just mentioned, long,
slender, slightly curved, with a narrow cavity in the interior, 0.18 mm.
long. Mouth small, a little in front of the plane of the hinder end of
the anterior sucker. DPharynx elongated, with a constriction at the
middle of its length as in T. ovale and T. folicaceum. Oesophagus
very short. Intestinal trunks continuous behind just in front of the
posterior sucker, enclosing an area of a similar form to that of the
body, but with the posterior commissural limb straight ; with nume-
rous, dendritic branches on the outer side and with a few short,
simple branches on the inner. Common genital opening a little behind
the anterior sucker of the left side. Penis short and small, club-
shaped. Ovary in the hinder part of the anterior half of the body
proper, irregularly globular, not lobed. Oviduct arising from the front
end of the ovary, thence proceeding forwards with a slight winding or
two, and soon continued into the ootyp. Uterus of moderate length,
opening into the genital atrium at a short distance from its external
pore. Vitellarium present not only in the lateral regions and the anterior
lobe of the body but also on the whole dorsal side of the posterior two-
thirds of the median region enclosed by the intestinal trunks; but in the
latter region. the lobes are more sparsely distributed than in the
former. Paired yolk-ducts formed as usual by the union of large ducts
coming from the anterior and the posterior part. Yolk-reservoir and
unpaired yolk-duct as usual. Vaginal opening a little behind the common
genital opening but nearer the median line ; vaginal canal proceeding,

as usual, backwards and inwards with numerous convolutions, forming
STUDIES ON THE ECTOPARASITIC TREMATODES OF JAPAN. 951

a capacious ovoidal receptaculum seminis at about two-thirds of its whole
course, and finally opening into the yolk-reservoir. Testes numerous,
globular, present not only in the median region posterior to the ovary,
but extending on both sides a little way into the lateral regions of the
body. Vas deferens formed as usual, proceeding at first forwards on the
left side of the ovary ; forming, also as usual, a large loop at the
front end of the ovary, and after describing numerous, complicated
convolutions it enters the penis, inside which it expands and forms
a sort of vesicula seminalis, and finally opens into the cavity of the
penis at a short distance from its apex.

The body of this species is so transparent that even in alcoholic
specimens the internal organs, even the smallest vasa efferentia, can be
seen through, and their relations ascertained without staining and
mounting.

Habitat—Fin of Thynnus sibi (Jap. Shibi).

Locality—Osatsube (Hokkaidd); collected by Mr. Nozawa in
whose honour it is named.

Date—Not recorded.

6. Tristomum biparasiticum, n. sp.
(Pl. XXV, figs. 4-8.)

Body elongated-oval, about 6 mm. long by 3 mm. broad, with
a sudden diminution of breadth in the anterior part a little behind
the anterior suckers ; with the anterior border slightly convex ; with
a notch at the posterior end of the body ; lateral margins entire, with
a series (of about sixty-two) of chitinous corpuscles like those of Trist.
sinuatum, one of which is represented in fig. 5, PI. AAV; the series
beginning a little behind the anterior suckers at the point where
the body undergoes a sudden increase of breadth, and terminating a

little before reaching the posterior sucker. Anterior suckers nearly
6. GOTO,

©

circular. Losterivr sucker slightly elliptical, with its longer axis dirceted
antero-posteriorly and with a diameter equal to about one-fifth the
length of the body proper ; with a marginal membrane and with its
internal surface divided into areas like those of T. Nozawae, 7’. ovale,
and 7’. foliaceum. Hooks in one pair, in the position of those in the
species just mentioned, solid, straight, bifurcating at the proximal end,
with a pointed, free end and with a harb-like process near it (fig. 6, PI.
XXV); 0.111 mm. long. (In the specimen on which I made the
measurement, the hooks of the two sides were of uncqual length, that
of one side being 0.122 mm. and that of the other 0.100 mm., thus
giving the average above recorded.) Mouth small, at the same plane
with the hinder end of the anterior suckers, Dharyna divided by a
constriction into two unequal parts. Ocsophagus very short.  Jnles-
tinal trunks continuous with each other some distance in front of the
posterior sucker, enclosing an elongated, oval area a little Jess than half
as long as the whole body ; sending out numerous (about ten), dendri-
tic branches on the outer side and about as many shorter branches on
the inner. Common genital openiny a little behind the anterior sucker
of the left side, about midway between the lateral) margin of the body
and the pharynx. Denis of moderate length, club-shaped. Ovary at
the hinder end of the anterior third of the body, of a similar
form to that of T. foliaceum. Oviduct arising at the front end of
the ovary in the median line, and thence proceeding forwards and
towards the left it 1s continued into the ootyp at the level of the base
of the penis. Uterus short, opening into the genital atrium about mid-
way between its external pore and the base of the penis.  Vitellarinn
confined to the Jateral regions and the anterior lobe of the body, only
accompanying the intestinal branches into the median region. aires
yolk-ducts, yolk-reservoir, and unpaired yolk-duct as in T. foliaccum.

Vaginal opening about us much behind the common genital opening as
STUDIES ON THE ECTOPARASITIC [TREMATODES OF JAPAN. 953

“

this is behind the anterior sucker, but a little nearer the median line;
vaginal canal swollen at the beginning, then becoming very fine, and
taking the usual course and describing some convolutions, opens at
last into the yolk-reservoir after it has formed an elongated, oval,
capacious receptaculum seminis just in front of the reservoir. ‘T'estes nu-
merous, irregularly polygonal, confined to the median region between
the intestinal trunks, mostly behind the ovary.

Habitat—Carapace of a copepod, probably of the genus Parapetalus,
parasitic on the gill of Thynnus albacora (Jap. Sdda-gatsuwo),.

Locality—Misaki.

Date—August 1891.

Tokyo, March 12, 1894.
8. GOTO.

bo
Or
He

Analytical Key to the Species described.

Body symmetrical except in a few cases.
1 With a pair of spheroidal suckers within the mouth,
and with numerous, small, flattened suckers on both
sides of the caudal disc; body sometimes asym-
metrical ok, cee eee tee eee tee eee) ee MICROCOTYLE. p. 185.
*1 Body symmetrical, about 3.2 mm. long; caudal
disc distinctly separated from the body proper,
about } the total length of the body ; with about
25 suckers on each side; genital atrium armed
with slightly curved, conical spines... ... ...M. caudata. p. 186.
*2 Body symmetrical, slender, about 5.5 mm.
long; caudal disc distinctly set off from the
body proper, about 4 the total length of the
body; suckers about 29 on each side; genital
atrium armed with slightly curved, conical
spines generally longer than those of
MM. caudata ... 0 ce. cee vee cee eee eee) ML. sebastis. p. 187.
*8 Body symmetrical, slender, about 4 mm. long ;
caudal disc distinctly set off from the body
proper, a little longer than 4 the whole length
of the body; suckers about 50 on each side;
genital atrium armed with conical spines about
0.005 mm.long... ... ... .. ...M. elegans. p. 188.
“4 Body slightly asymmetrical, elongated, thick,
6-10mm. long; caudal disc not distinctly separat-
ed from the body proper, somewhat longer
than } the total length of the body; suckers
about 42 on one side and 23 on the other ;

intestinal branches forming a complicated
STUDIES ON THE ECTOPARASITIC TREMATODES OF JAPAN, 955

network; genital atrium armed with straight

spines consisting of a hemispherical, basal por-

tion and a straight, spinous, distal portion...M. reticulata. p. 189.
*5 Body symmetrical, slender, about 8.8 mm.

long ; caudal disc not distinctly separated from

the body proper, very short, isosceles-trape-

zoidal, with about 10 suckers on eacli side ;

genital atrium armed with 20 long, chitinous

rods arranged ina circle ... ... ... ... ...M. truncata. p. 191.
*6 Body symmetrical, fusiform, about 2 mm. long ;

candal dise not separated by a constriction from

the body proper, nearly } the total length of

the body, with about 30 or more suckers on

each side; genital atrium armed with short,
conical spines ... 20.0.6. see eee eee «eM. fusiformis. p. 192.

*7 Body symmetrical, anterior portion slender but
the remaining portion broader, about 4.2 mm.
long; caudal disc not separated from the body
proper by a constriction,? with about 380
suckers on each side; genital atrium with a
cup-shaped organ, the internal surface of which
is covered with straight, conical spines con-
sisting of a hemispherical, basal and a spinous,
distal portion 10.0 66.0 ce eee eee eee) eM. chiri. p. 193.
*8 Body prominently asymmetrical, slender, about
4 mm. long; caudal disc slender and pointed at
the end, making an angle with the body proper,
with about 75 suckers on one side and 60 on
the other; genital atrium with a bell-shaped
organ, and armed with two sets of slender,
chitinous rods, one of which is look-shaped
and short, and the other slightly curved and
long uk eee nee nee tee tee nee eee) we ML sciaenae. p. 194.
1? Body always symmetrical; with a pair of spheroidal

suckers within the mouth, and with four pairs of
8. GOTO.

ho
Or
a

small, bean-shaped, sessile suckers arranged in
straight lines on each side on the ventral surface of
the hindmost portion of the body; penis consisting
of three bulbs armed with long, hollow spines; with
chitinous looks at the posterior end of the body ...OCTOCOTYLE. p. 203.
*1 Body thick, about 4 mm. long; with a single
pair of hooks at the posterior end of the body ;
penis spines in 5 pairs... ... ... «4. 0. major. p. 208.
*2 Body thick, about 2 mm. long; witl: two pairs
of hooks at the posterior end of the body, the
inner pair being filiform; penis spines in 6
PALS: aie ae een ape ee es nee ate on -Qi minors p. 205,
}8 Body always symmetrical; with a pair of spheroidal
suckers within the mouth, and with four pairs of
hemispherical suckers arranged in a semicircle or a
liorse-shoe shape at the posterior end of the body,
mostly provided with pedicels; penis spherical and
with a certain number of hooks; without any hook
at the posterior end of the body... ... ... ... ...DICLIDOPHORA. p. 207.
“1 Body elongated, 64-8 mm. long, in form
like that of the leaf of a rose with a narrow
anterior portion; with the four pairs of
hemispherical posterior suckers, arranged in a
semicircle at the top of long pedicels; penis
with 6G hooks ...  ...  .. ee wee eee) D. smaris. p. 207.
*2 Body elongated, not so broad as in the preced-
ing, about 8 mm. long; posterior suckers
hemispherical, with long pedicels and arranged
in a semicircle; penis with 8 hooks ... ...D. elongata. p. 210.
*3 Body elongated-oval, about 5 mm. long;
posterior suckers liemispherica], sub-sessile,
arranged in a semicircle ; penis with 6 hooks...D. sessilis. p. 212.
*4 Body long and slender, spatulate, 5-15 mm.
long, with a long, slender posterior portion ;

posterior suckers sessile, semi-ellipsoidal,
STUDIES ON THE ECTOPARASITIC TREMATODES OF JAPAN. 957

arranged in a horse-slioe shape; penis with
10 hooks 00.0... wk cee eee tee vee) wD. tetrodonis. p. 218.

t# Body always symmetrical; with a pair of exceedingly
small spheroidal suckers within the mouth, and with
four pairs of semi-ellipsoidal suckers at the posterior
end of the body, the innermost pair of which is
considerably smaller than the others ; with two pairs
of hooks between the innermost pair of posterior

suckers... 02. ee cee eee tee tee eee ee) HEXACOTYLE. p. 217.
*1 Body acutely pointed in front, broad in the
middle portion as well as at the posterior end,
about 11 mm. long; with the outer pair of

hooks at the posterior end solid, about 0.09
mm. long ; vagina armed with chitinous teeth.H. acuta. p. 217.
*2 Body with a lateral swelling on each side close
to the front end, with the anterior portion
slender, broad in the middle part as well as at
the posterior end, about 18 mm. long; with tle
outer pair of hooks hollow and about 0.125 mm.
long; vagina armed with chitinous teeth ...H. grossa. p. 220.
1° Body always symmetrical, elongated and slender ;
with an ellipsoidal sucker around the mouth-cavity ;
with three pairs of hemispherical suckers at the
posterior end of the body, each with a semicircular
chitinous rod with a claw at one end; with a sub-
cylindrical appendage projecting from between the
foremost pair of suckers. ... 0... «6. ss. see + ONCHOCOTYLE. p. 228.
“1 Posterior suckers arranged in a_horse-shioe
shape; appendage bifid at the extremity, with
a pair of small suckers at the bifid end, and a
pair of hooks between them ... ... ... ...0. spinacis. p. 224.
+® Body always symmetrical, flat, heart-shaped; with
a rudimentary sucker around the mouth; with
a circular posterior sucker, the internal surface of

which is divided into a subcentral and seven peri-
258 8. GOTO.

pheval areas; with a pair of hooks in the sides of the
-hindmost peripheral area ... ... 0... ... «1 «..CALICOTYLE. p. 226,
*1 Body very flat, ovate, about 8 mm. by 5 mm.;
posterior sucker sessile, with a diameter equal
to about } the total length of the body; with
two pairs of sac-like sticky glands opening by
means of long necks at the anterior end of the
body; tubular chitinous penis very long and
twice bent on itself; hooks about 0.56 mm.
lo ay Ake ee ee ee ee, Ge ow a, Miter ps, 297,
+’? Body always symmetrical, without any anterior
sucker, but with a large, circular posterior sucker,
the internal surface of which is divided by eight
radial spokes into as many equal secants ; two of the
posterior radial spokes on either side of the median
line each with a strong hook; with two pairs of
ocular spots in front of the pharynx... ... ... ...MONOCOTYLE. p. 280.
“1 Body elongated, flattened, about 3 mm. long;
mouth sub-terminal, large ; sucker sub-basilar ;
hooks strongly recurved at the end but straight
in the remaining portion, and with a barb-like
process near the recurved end; about 0.12 mm.
Tongs: ee: sea eee aes weet aes ... «MM. Tjimae. p. 280.
t® Body flat, oval, ovate, or circular; with a pair of
saucer-shaped anterior suckers on either side of the
mouth, and a circular sucker at the posterior end of
the body.
*“1Tnternal surface of the posterior sucker not
divided into areas, and with three pairs of
hooks ; anterior suckers connected together by
a@ membrane... 26. wee ee eee eee) os KPIBDELLA. p. 233.
§1 Body elongated-oval, flat, about 4 mm.
long; anterior suckers nearly circular ;
posterior sucker circular ... ... ... ...H. Ishikawae. p. 234.

§?Body squarish-oval, flat, about 2 mm.
STUDIES ON THE ECTOPARASITIC TREMATODES OF JAPAN. 959

long; anterior suckers elliptical ; posterior
sucker with a pair of notches on its anterior
and posterior borders ... ... ... -..H. ovata. p. 235.
*2 Internal surface of the posterior sucker divided
into a central and seven peripheral areas... ... TRISTOMUM. p. 2388.
§ Body broadly ovate, about 8 mm. by 7
mm.; anterior border concave, lateral
margin finely sinuate, with about 58
chitinous corpuscles; posterior sucker
smal], not reaching the posterior end of
the body proper, with the central area
regularly leptagonal and with a small
triangular accessory area on each: side of
the hindmost peripheral area ... ... ...T. sinuatum. p. 289.
§°Body broadly oval, about 18 mm. by 12
mm. or Jarger; anterior border convex;
lateral margin entire, without any
chitinous corpuscle; posterior sucker
large, with a diameter equal to about 4
the length of the body proper and pro-
jecting beyond it by one-third of its
diameter, with the central area 9-sided...T. ovale. p. 241.
§§ Body oval, about 11.5 mm. by 13 mm.,
with the breadth greater than the length ;
anterior border concave; lateral margin
entire, with numerous transverse series
of chitinous corpuscles, each series con-
sisting at most of five corpuscles ; posterior
sucker small, barely reaching the posterior
end of the body proper; with the central
area regularly heptagonal and raised a
little above the peripheral areas... ...T. rotundum. p. 245.
§4 Body elongated and slightly ovate, about
6 mm. by 8 mm.; anterior border

a~~x-shaped; lateral margin entire and
260 8, GOTO.

destitute of chitinous corpuscles ; posterior
sucker tolerably large, slightly elliptical,
with the central area 9-sided, projecting
beyond the body proper by 4 of its length.T. foliaceum. p. 248.
§> Body elongated-ovate, about 12 mm. by 7
mm.; anterior border truncate; lateral
margin entire, without any chitinous
corpuscle ; posterior sucker slightly ellipti-
cal, tolerably large, with the central area
D-sided ... sk cae nee vee eee ee D'. Nozawae, p. 249.
§* Body elongated-oval, about 6 mm. by
3 mm.; anterior border slightly convex ;
lateral margin entire and with a series of
about 62 chitinous corpuscles; posterior
sucker slightly elliptical, of moderate size,
with the central area 9-sided .... ... ...T. biparasiticum. p. 251.
Body always asymmetrical.
. With a pair of spheroidal or egg-shaped suckers
within the mouth and with an unequal number of
gencrally small, flattened suckers on either side of
the posterior part of the body; destitute of any hook
at the posterior end of the body... ... ... ... ..AXINE. p. 196.
*1 Body with the form somewhat like that of
the blade of the Turkish sword, flat, about 10
mm. long, with one side of the caudal disc
making an obtuse angle with the correspond-
ing side of the body proper; with about 80
suckers on one side and 9 on the other ... ...A. leterocerca. p. 197.
*2 Body curved towards one side, elongated, flat,
about 5 mm. long; with one side of the caudal
dise making an acute angle with the corres-
ponding side of the body proper; caudal dise
with about 25 suckers on one side and only one
(or perhaps two or three?) on the other ...A. aberrans. p. 198:

*3 Body triangular, flat, short and broad, about
STUDIES ON THE ECTOPARASITIC TREMATODES OF JAPAN. 261

1.5 mm. long; with one side of the caudal
dise making with the corresponding side of the
body a less acute angle than in A aberruns ;
caudal dise with about 36 suckers on one side
and only 6 on the other; genital atrium with
a cup-shaped organ, the internal surface of

which is covered with straight conical spines...A. triangularis. p. 200.
262

10.

11.

12.

13.

14.
15.

8S. GOTO.

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The asterisk marks those to which I have not been able to gain access.

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Braun, M.—Wiirmer. Bronn’s Klassen und Ordnungen des Thierreichs, Bd.

Braun, M.—Ueber einige wenig bekannte resp. neue Trematoden. Verliand-
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Cunningham, J. T.—A Treatise on tle Common Sole. 1890.

Cuvier, G.—Regne animal, t. IV, p. 42. 1817.
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#34.

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Fraipont, J.—Recherches sur lappareil excreteur des Trematodes. Archives
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Goto, S.—On the Connecting Canal between the Oviduct and the Intestine in
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Goto, 8.—Der Laurer’sche Kanal und die Scheide. Centralbl. f. Bakteriol.
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Graff, L. v—Monographie der Turbellarien : Rhabdocoelida. 1882.
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Kéllicker, A.—Ueber Tristomum papillosum Dies. Bericlite von d. kinigl.
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39.

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*41,

42.

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45,

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47.
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#49,

*50.

1.

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8. GOTO.

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53.

59.

60.

61.

62.

63.

64.

65.

66.

67.

STUDIES ON THE ECTOPARASITIC TREMATODES OF JAPAN. 965

Monticelli, Fr. Sav.—Intornoad alcuni elminti del Museo Zoologico della
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266

*68.

*69,
“70.

73.

73a.

75.
"76,

“77.

79.

80.

81.

82.

83.

8t.

8. GOTO,

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‘

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87.

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wiss. Zoologie, Bd. XXVII. 1876.
268 S. GOTO.

ConrtTENTS.

IntRopuction

Anatomy anp Histouocy ... re
External Form of the Boly...
Investing Membrane
Musculature .. ea
Organs of Attacliment ...

Suckers ..

Of pcan and Axine saa ER
Of Octocotyle, Diclidophora, and ee
Of Onchocotyle

Of Calicotyle...

Of Monocotyle

Of Tristomum

Of Epibdella ...

Sticky Glands

Of Microcotyle and Bes ae
Of Axine, Diclidophora, and Mic. reticulata

Of Calicotyle... 0.0.0... one
Of Monocotyle i
Of Tristomum and Epibdella

Hooks
Mesenchyma...
Digestive System ...
Excretory System...
Nervous System ...
Reproductive System ...

Male Organs...

Testes

Vas deferens ..

16.
22.
26.
28.
29.
32.
36.
35.
35.

37.
38.
39.
43.
45.
50.
66.
15.
83.
83.
83.
88.
STUDIES ON THE ECTOPARASITIC TREMATODES OF JAPAN. 969

PAG

Penis... .. ile. eet? tah ania, Bieta, few, Ephesus eaten Sate AU:

Of Diclidophom dis Bike teen Ge hie Aitin th Bie atin Ss Bs

OE Octocotyless wae one aha Sak Sek was ae ea cur ase O85

OF Calicotylese«.: sae see oeae- dae Gee cee Gas Bea vee ane D4.

Of Monocotyle ... a GO Sek Roh au Aden Gem ohm, (OR

Of Tristomum and Bpibdella SUSo aay Cimiinh “ude Gite alee bere CODY

Of Onchocotyle: ssn age. aay sen ack: wee em ces eee ee “OT:

Of Axine, Hexacotyle, and Mic. reticulata... ...0 0... ... 97.
GlanidtilaprostatiGa: 28) ie Gees eee awe Me Sen eee Rea aes DO:

. BemaleOreans: sex ean cae sue aka eee ea Bee ae ee ics. “ey Os
ONETY gic + att tay Ri. eA Hine: ew ge aie, Geen aden Shee Gee DOSE
OVidWebisses sek. caer Shap Hage nebo Gh aks, Ue da Sew es: OGY

QOotyp ose sce Ges sess Rew Gee ces Gu ae ee ae em are LOB:
UGGTUS: ae Bais ey ee ee ee QA ee ave ek Hed ade, ote TE
Wate ise aaa, Gadi cemies paws- haw Gee Bae een a Ga. eee LEE
Volkeauicts: gee. sen core eee “hea eee ake Rat ee ae ae cen HZ,
VaGinaave, Che. Eke cit Gs ctiteo Gian. aes SUA Gabo eiale. Hae cee TBS
Canalis Genito-intestinalis ... 0... 0 ce. cee ee eee cee vee eee 180.
Miptorey Gem: csi ate. tte bw Re ae Wael dow ud, ohn new BE,
General Consideration and Comparison of Results... ... 0 ... we TEL
Prismatic Fibres of the Wall of the Suckers of Axine, ‘eae ete. ... 144.
Penis... ...... Bish “AGS, Raecwekh, Fae. “eho Wake ie Geis cae Soe lg,
Prostate Glaiidy. as!) leas! gee. es eee aS dees eh a ide, eee tet
Homology of Canalis Genito-intestinalis ... 0... 0... ee ee DOE.
Proteusion of the Penis sss. ase sae en see aes cee aay eee eee 1TB:
Remarks on the Terminology of the Genital Organs www ww. ww TEL
BIOHOGTCALNOPES: iss ues ely ase dhe ae. Bide aie ee ae er ee ae, DEG,
Habitatives: sw ses. aes Gee ake Sen le Gus ae Gis eee ede cha LG,
JUGCOMOUIONY pits wees GAR Tide tein attgs aie aan Belo eds ait thee ean EBs
POG! iene SAS Cae cuss, Tees adel See Ge Sakis eet Sec Vass ESO:
Colouration sax. sees ase See wee cee Gee Gee. eee oe ces oes, TOL,
Tnynry toe lost: agg. ke St ey ewe ee ee ek ote TB
SYSTEMATICAS: eiev seat, Wake Gell awele GES. Ae ee ei cee, ene tke CBR ae, LODE
Ti -MiGrocotyle: wiv eves gee ace ee Hue cee Mee Ge “eee wae eke dee 188,
1, Miscaudati: case doy chm cake a GR Gee ead po OR See Sie, DOE
270

Mt.

TI.

IV.

VI.

VIL.

VIII.

IX.

8. GOTO.

2. M. sebastis
3. M. elegans...

4. M. reticulata

5. M. truacata

6. M. fusiformis ...
7. M. chiri

8. M. sciaenae
Axine

1. A. heterocerca ...
2. A. aberrans

8. A. triangularis...
Octocotyle

1. O. major ...

2. O. minor ...
Diclidophora ...

1. D. smaris...

2. D. elongata

8. D. sessilis...

4. D. tetrodonis ...

. Hexacotyle ...

1. H. acuta .

2. H. grossa...
Onchocotyle ...

1. O. spinacis
Calicotyle

1. C. Mitsukurii ...
Monocotyle ...

1. M. Tjimae...
Epibdella

1. E. Ishikawae ...
2. E. ovata ...

. Tristomum

1. T. sinuatum
2. T. ovale
8. T. rotundum

Pack

. 187.
. 188.
. 189.
. 191.
.-. 192,
. 193.
. 194,
. 196.
. 197.
. 198.
» 200.
. 201.
. 208.
. 205.
.. 207.
. 207.
. 210.
. 212.
. 218.
. 215.
. 217.
. 220.
. 222.
. 224,
» 226.
we. 227.
. 229.
. 230.
. 283.
. 234,
. 2385.
. 237,
. 239.
. 241.
. 245.
STUDIES ON THE ECTOPARASITIC TREMATODES OF JAPAN. 971

PAGER

4. SD AGUACEMIM hie, eek ck he deme HGR og: HR ae, ee EBs
BT Nozawae sev ae ce. Gee ee aes 4 Ge ae Ave gee oen 24)
C.D. bipavasitietimi ses age “eee Ge ae a ee ER ee ee
AwnatyticaL Key ro tHe Sprcres DescRIBED ... 20.0 c. cee eee ee eee ee 254,

IGTTERATORES CITED? Gis. gax eee- Bees es aes. Se we es ese aa (gs eee BOD)
1
“I

Ww

ant. such.
UP ide seins
bul. ej...
can. ge. int.
chit. mee
cir. mus.
diag. mus.
duce. ej. ...
d.v. mus.
C8. OP. ave
ev. C. Mees
€0, SUC. oe
eu. Ves. 2.
Gen. OP. vee
ant. ae
WE Cs eas
tit. Cm.

do mus. ...

MeS. C. as
MES. 1. wee
mus. sae
nere,

HEU. Ce ase

oesoph. ...

oot. aes
OES, sacaxs see
ovd, ma
pen. tte
pe. oa.

8S. GOTO

Explanation of Plates.

Abbreviations common to all the figures.

anterior sucker.

. brain.

. bulbus ejaculatorius.

. canalis genito-intestinalis.

. chitinous piece or framework of the sucker.
. circular muscle.

. diagonal muscle.

... ductus ejaculatorius.

.. dorso-ventral muscle.

. excretory opening.

. external circular muscle.
. terminal excretory sac.
. excretory vessel.

. genital opening.

. intestine.

. intestinal cell,

. internal circular muscle.
. longitudinal muscle.

. mesenchyma cell.

.. mesenchyma nucleus.

.. muscle.

. nerve.
. herve-cell.

. oesophagus.

-+. Ootyp.

ovary.

.. oviduct.

. penis.

... chitinous penis.
STUDIES ON THE ECTOPARASITIC TREMATODES OF JAPAN. 273

PUD Fee Sipe shee ele. Salle Sasa Meee PMARYUR:

phar. gi. bie bee ee tee eae eee Pharyngeal gland.

phar gl. cc see cee vee eee ees Cuet or opening of the pharyngeal gland.
pos. such, se see ee vee vee eee posterior sucker.

pros. gl. cee see eee tee eee) eee prostate gland.

pros gl. eee cae nee eee eee Cut of the prostate gland.
prephar. ics ave oe ae ee ees PLEpharynx,

rad. MUS. eevee vee vee eee eee Vadial muscle.

VCC SCMisee cee vee eee ee eee aes FECeptaculum seminis.

SUL Gls ie Ade Gg eee neyo ae See BANVREY Bland:

SAU. QU cee ee eee ee eee eee) ee Cuet of the salivary gland.
She Gls use Sex ea aes eee ae) vee Bhellegland,

sphin, ce. see cee eee nee eee) es Sphincter muscle.

Stich. glicc. ce cee nee ee eee ee Stielty gland.

OSs? Kage. ey ciwe owabo ark aigh otek TESHIS.

ities aaa. eet aes: Wek. aay aia was. TbELUS:

Vif. cee cee cee nee eee vee eee VS deferens.

UUs. deiee “Basi, Cees: See Sek. Sey See MARINO:

VAG. CUR, ee eevee eee eee) wee Vaginal canal.

Pithege. Meg Pag aes Se see age. ee Witellariuim:

les 20s — sits ae axe deal aise gas len YON cell,

yk. duct. div ey kee wes ace ee Yolk-duct,

Yle. VCS. cee vee nee nee tee ee ees Yolk-reservoir.
PLATE I.
‘pls [VSIOP OT]} TOA, POMOTA ‘VEVINOILAM ATALOOOUOTTYL “g
‘Opls [VSAIOP Ol[} WOT POMOTA ‘SNVDATH TIALOOOMSTTY “PF
“OP VUUITUS
oy IIA eaqF poT[H] uommeds vw wiory ‘pury-ooay Sopyord Ul aKVS THY, “8
‘apIs [VSIOP OT[} TOTJ POMDTA ‘SILSVAAS TIALOOOMOITY “G
‘Opls [BSAOP OT} WOTJ pOMOTA ‘VEVGNVO ATALOOONOITYT ‘TL
“par stoyons Iortosod ory} Jo oposngYT ‘AoppoA wtoyshs SNOATON
‘st A[[eor
qt ULIT) AOpvorq OPI] BV poytasordot ATyUoUbosuod st Apoq or] PUv dtys-19A09

@ jo ornssoad or} Tapun polly suotmoeds Troy UAVAP MOOG EATT] F PUL “G ‘T “SSL

] 2eld
uedur gAWo, Opemxiog

ee /9p 4oq0nY

 

t
lOO
\
‘

is SAN wells
A aah

(re cai
<—

                     

a

ei
pos sod

yosiop
——

a

         

syous vod

—_~

     

 

 

 

 

ys sod
a
way \\
rl a i oe
, PUL AE
Abs ad
| 1 ws oy)
unas iad | ol?
onp ya ‘
7
‘AO
syonp yf poanp yh
Wa
f
’
papa yop a
ilo onl »ydosao |
a) apy dou ;
., 3
yon yu a . syd "7 yds a
4 yoy yas yp vyous yu i \
au? nl r fe ee yous yup
p ig ¥ 1 sapyd }
i , aw a oe
DPN ID V wpb i ueon } 2 sy, y .

DEPP Tr

 

 

 

1 ofd THA TOA) fog a8 top seeps arenes =
PLATE II.
‘go0rd Uvrpertt otf} ‘9 £ [TVA AorLeysod atT} Jo por snouryIo “q £ [TVA Torteysod
oY} UL ToTeNUTMOD syt (/ f [TVA TOTAIOYTE oT[} JO por snouts ‘y “UTvIp
G0G X ‘WOT}O9S UT sIoYONS Ior1aysod ot]} Jo eu ‘VEVANVO ATALOOONOITY

*sToxONS

Ot} MOTS 0} {OPIS [VIJWAA OT]} TOA, POAOIA OSIP [UpNtQ ‘“ANVS AH,
"OYLUTTTGNS JOU TILA. 9OAF por[H] woud

-toods @ MOI, “Opls [VSIOP OT]} WOT, POAMOIA “AVNAVIOS MIALOOONOIIY
“Apo oT} JO WILOF [VANZVU OTT} AMOTTS OF | OFVUITTGNS yor]

YA VIZ poppy weutioeds v tot ‘ASIA oOVJANS [VSIOp VUT “ANVS THT,
‘diys-1aA00 v Jo aansserd ory} Tapun poT[Ty

uotttoeds B MIOTY “apts [VSIOp oly} Worf poAOTA ‘INIHO PIALOOOMOITY
‘dijs-taa00 v Jo onsserd at} Teptmn peT[HyT weturoeds

@ TOI  ‘“opls [vstop ett} TOA} POMOTA “SINMOTISNT ATALOOOUOI]
‘pULT-V91f TABIP ‘9 Yq  “WOTOES-SSO.10

ur ourds o[8uis v & { pagraseat A[su01s stot outds opsuts v “¢ f WOTVeATp
[eayWas-Ostop BUT pedeld Ano18 aporpa oy} v ‘scurds [vy “INVS THY,
“diys-1aA00 v Jo ornssard ot[} Aeptmn poT[Ty wou

-1oads B WOT, “Opts [VsIop ot]} WOIF POMOTA ‘VEVONOUL TIXLOOOMOT]Y

‘Il 78ld

‘Pp cc

*g “
vedas) yor opemyas

yop soqony

 

yoo

yop a

«dow

sydosa0 4
\

empyd pee,

D
A qu
we
or

a, ue *
0" 9
IDWS “WE
[P-JAWyA JOR *1f09 99 *INaP

 

        

‘ppa

             

   

‘dou \ eee

\
vydosvo is ‘doi

‘ \ eydosao
yas TUP ‘od sapyd
gee : : wea yu
as T 2 “
ee *
af a §

LENO Tf
SMO PSA Te

ya
;
sya)
aw
oie
at ee
y tease
w Ws
tas oad \ Bax

 
     

                

yous sod

 

Fas

-ydose?

“LW

apy aia

4 yous

 

 

“DYPIUNL] “fr

 

 
PLATE III.
Fig.

Cu

10.

Plate Ill.

MicrocorTyue SEBASTIS.

Chitinous framework of the posterior sucker. x 204 diam.

MicrocoTyLeE RETICULATA.

Semi-diagrammatic representation of the intestine.

A small ventral portion of a cross-section of the body near its anterior
end; to show the sticky glands. a, foremost end of the mouthi-cavity.
x 805 diam.

A small ventral portion of a cross-section of the lateral part of the body.
x 805 diam.

MiIcROcoryLe CHIRI.

A small ventral portion of a median sagittal section of tle body some

distance in front of the ovary. x 805 diam.

MiIcrRoOcOTYLE TRUNCATA,

A small portion of the mesenchyma lying just inwards to the intestinal
trunk. x 305 diam.

MiIcROCOTYLE CAUDATA,

A small portion of the cross-section of the body through the front end
of the anterior sucker ; to show the sticky glands. x 460 diam.

Anterior end of the body; to show the muscular fibres attached to the
suckers.

A small portion of the mesenchyma lying just inwards to the intestinal
trunk. x 805 diam.

Median portion of the cross-section of the body a little in front of its
middle. x 305 diam.
Missing Page
PLATE, Ivy.
Fig.

Plate IV.

Microcotyze sesBastis. Median sagittal section of the pharynx.
x 805 diam.

Microcotyie reticuLata. Median portion of a cross-section of the
body through about the middle of the pharynx. x 204 diam.

Tue same. Horizontal (optic) section of the pharynx, showing the
muscles ; from a small individual. x 305 diam.

MicrocotyLe segastrs. Longitudinal section of the ootyp, showing
the shell-glands. x 805 diam.

Tue same. One-half of the cross-section of the body just through the
anterior end of the brain ; to show the nerve cells (). x 805 diam.
MricrocotyiLxe Fusirormis. A cross-section of the body at the level
of the origin of the posterior nerves. x 805 diam.

MicrocotyxLe caupata. Lateral portion of a cross-section of the
body. x 3805 diam.

Tue same. Median portion of a cross-section of the body through. the
region of the ovary. The yolk-duct was filled with yolk-cells, but these are
not drawn in thefigure. x 805 diam.

Tue same. A portion of the section of the ovary near the oviduct end.

x 805 diam.
Missing Page
PLATE, V.
Plate V.

Fig. 1—4 represent median sagittal sections.

ds

or eg po

MricrocoTyLe FUSIFORMIS. x 805 diam.

Microcotyie ELEGANS. xX 805 diam.

Microcotyue caupata. %x806 diam.

Microcoryie cairi. x 204 diam.

Microcotyie reticuuata. Median portion of tlie cross-section of
the body through the vaginal opening. x 204 diam.

Tue same. Median portion of a cross-section of the body through the
terminal portion of the vas deferens (6th section from the common genital
opening, each—0.01 mm.). x 204 diam.

Microcoryie truncata. A small portion of a horizontal section

of the testes. x 805 diam.
dour. Sc, Co/!. Vol. Vill PI. V.

 

     

M.elegans.

M. fusiformis.

 

br

 

Mchiri.

 

M.caudata.

3
3
S
=
x
=

 

ut.

Mreticulata.

 

 

duclar del.

T.ARAL SC.
PLATE VI.
Plate VI.

MicrocoryLe segastrs, Median sagittal section through the region
of the genital atrium. x 305 diam.

Microcotyze scraENnAr. Median sagittal section through the region
of the genital atrium. x 305 diam.

MrcrocoTyLe caupata. Successive stages of spermatogenesis. x 305
diam. For detailed description see p. 86 of the text.

Diptozoon Nrpponicus. Successive stages of spermatogenesis. x 427
diam. In a@ and b only the nucleus is represented ; and in ¢ and d the tail

is cut short. For detailed description see p. 88 of the text.
Jour, Sc. Coll. Vol. VIL Pl. YI,

 

 

 

M. sctaenae.

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Fig.

ot

Plate VII.

AXINE HETEROCERCA.

The whole worm viewed from the dorsal side ; from a specimen killed under
aslight pressure. «, dorsal opening of unknown nature (cf. fig. 4, Pl. VITI) ;
%, point of junction of the yolk-duct and the vaginal canal.

I, Chitinous framework of the posterior sucker. x73 diam. IJ, terminal
portion of the posterior arm of the median u-shaped piece. Free-hand.
Ovarian ova near the oviduct end. x 805 diam.

Section of the posterior sucker parallel to the median piece of the chitinous

framework. x 204 diam.

AXINE ABERRANS.

The whole worm viewed from the dorsal side.
a, chitinous armature of. the terminal portion of the vas deferens. x 305

diam. 0b, the same of the vagina. x 305 diam.

AXINE TRIANGULARIS.

The whole worm viewed from the ventral side..
a, cup-shaped organ of the genital atrium. x 204 diam. 2, spine of the

same. x460 diam.
Jour. Sc, Coll, Vol. Vill. Pl. VIL.

 

 

 

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PLATE VIII.
Fig.

Plate VIII.

AXINE HETEROCERCA.

A portion of the cross-section of the body some distance behind the common

genital opening. x 204 diam.

A small portion of the cross-section of the body through the anterior part
of the brain. x204 diam. a, nerve cells.

Median sagittal section of the body through the region of the common
genital opening. x 204 diam.

Median sagittal section through the vagina. x204 diam. 2, an opening
of unknown nature.

Ovary and the genital ducts adjoining it. x50 diam.
Missing Page
PLATE, 1x.
Fig.

10.

11.
12.

13.

Plate IX.

OcTocoTyYLE MAJOR.

The whole worm viewed from the ventral side. From a specimen killed
under the pressure of a cover-slip, and therefore much broader than it
really is.

Hooks at the posterior end of the body, with muscular fibres attached.
x 204 diam.

Chitinous framework of the posterior sucker viewed from one side. x 805
diam. ‘The piece b is paired.

One of the posterior suckers viewed entire in profile. x 3805 diam.

Penis viewed in its natural position from the ventral side. x 805 diam.
For clearness’ sake the spines are drawn fewer tlian they really are.

Ovarian ova near the oviduct end. x 805 diam.

OcTOCOTYLE MINOR.

The whole worm viewed from the ventral side. From a specimen killed
free with hot sublimate. The nervous system is shaded with parallel
lines.

Anterior end of the body. x805 diam. To show the attacliment of
muscular fibres to the anterior suckers.

Hooks at the posterior end of the body. «, outer pair; x 305 diam. 4,
inner pair; x 427 diam.

Chitinous framework of the posterior sucker viewed from one side. x 305
diam. The piece 6 is paired.

Female genital ducts viewed from the ventral side. Free-hand.

Median sagittal section through the region of the genital atrium. x 3805
diam.

Penis viewed in its natural position from the ventral side. x 805 diam.

The spines are represented one less than they really are.
Jour. Se. Goll, Vol. Vill. Pl. IX.

   
 

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PLATE. X,
xt

10.

Plate X.

DicLIpOPHORA TETRODONIS.

The whole worm viewed from the ventral side. The uterus is greatly
distended by the numerous eggs which it contains.

Surface view of the whole worm, from the ventral side. x5 diam.
Anterior part of the body in profile.

Cross-section through the slender stalk-like portion of the body. x73

diam.

DIcLIDOPHORA SESSILIS.

The whole worm viewed from the ventral side. Nervous system, chiti-
nous framework of the suckers, and egg-shells yellow ; excretory system
indigo-blue ; muscle of the posterior suckers red.

Anterior end of the body; to show the muscular fibres attached to the
anterior suckers. x73 diam.

u, hook of the penis a little in profile. 6, basal portion of the same
viewed from the front. Both x 805 diam.

Ovarian ova near the oviduct end. x 805 diam.

DiIcLIDOPHORA ELONGATA.

The whole worm viewed from the ventral side. Nervous system yellow.
a, look of the penis a little in profile. b, basal portion of the same

viewed from the front. Both x 805 diam.
Jour. Sc. Coll. Vol. Vill. PI. X.

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PLATE XI.
Fig.

ot

Plate XI.

DiciiDOPHORA SESSILIS.

Cross-section of the body through the posterior part of the pharynx; to
show a pair of gigantic ganglionic cells (nerv. ¢.). x 204 diam.

A portion of a cross-section of the body two sections (each = 0.01 mm.)
behind the one represented in fig. 1; to show the ganglionic cells (nerv. ¢.)
at the root of the posterior nerves. x 204 diam.

A small ventral portion of the right side of a cross-section of the body.
x 805 diam.

An almost median sagittal section of the body through the region of the
common genital opening. x 204 diam.

Median portion of a cross-section of the body through the receptaculum
seminis at the level where it communicates with the oviduct. x 204 diam.
Diagonal muscular fibres, together with a few longitudinal fibres ; drawn
from a specimen in toto. x 805 diam.

Mesencliyma cells adjoining the oviduct end of the ovary. x 305 diam.

Drawn from a specimen in toto.

DicLiDOPHORA ELONGATA.

Three lobes of the vitellarium. x 3805 diam.
Missing Page
 
PLATE XII.
Fig.

Plate XII.

DicLipOPHORA ELONGATA.

Chitinous frame-work of the posterior sucker in surface view. x about 78
diam. The semicircular series of chitinous, rod-shaped pieces are repre-
sented only in one quadrant.

One of the semicircular series of chitinous, rod-shaped pieces represented in

the preceding figure. x 204 diam.

DicLIDOPHORA SESSILIS.

Optic cross-section of the prismatic fibres of the posterior sucker; x 805
diam.
Section of a posterior sucker parallel to the length of its pedicel. x 204

diam.

HEXACOTYLE ACUTA.

Median part of a cross-section of the body, to show the prostate glands
Ventral side below. x 204 diam.

Median sagittal section through the region of the genital opening. x73
diam. The vas deferens opens into the genital atrium in the next section.
Section of the hinder extremity of the body at a right angle to the posterior

border, to show the structure of the sucker. x73 diam.

HEXACOTYLE GROSSA.

One of the intestinal trunks near its hinder end, in a surface view. x73

diam.
Jour. Sc. Coll. Vol. Vil Pl. Xil

 

 

 
PLATE XIII.
Fic. 1.

Fig. 4.

» Oo.

Plate XIII.

HexacoTYLE ACUTA.

The whole worm viewed from the ventral side. From a specimen killed
under a slight pressure. c

Hooks at the posterior extremity of the body. x 204 diam.

Chitinous pieces of the posterior sucker. x204 diam. a, that at the

anterior end; b, that at the middle ; ¢, that at the posterior end.

HEXACOTYLE GROSSA.

The whole worm viewed from the ventral side. Nerve yellow; excretory
vessel indigo-blue.
Hooks at the posterior extremity of the body. x 204 diam.

Chitinous pieces of the posterior sucker. a, b, ¢ as in fig. 8.
Missing Page
PLATE XIV.
Fig.

oO

Fig.

Dm

Plate XIV.

HEXACOTYLE ACUTA.

Central part of the genital organs, viewed from the ventral side. x about
50 diam.

A small portion of the mesencliyma, from the lateral part of the body.
x 204 diam.

Section through the vagina. x 204 diam.

Same as fig. 1; showing the ducts.

Terminal part of the genital ducts, viewed from the ventral side. x50

diam.

HEXacOTYLE GROSSA.

A small portion of the mesenchyma, from the lateral part of the body.
x 204 diam.

Central part of the genital organs, viewed from the ventral side. x73
diam.
Missing Page
PLATE XV.
ie aN as

10.

Plate XV.

ONCHOCOTYLE SPINACIS.

The whole worm viewed from the dorsal side; from a specimen killed free
with hot sublimate. With the main excretory vessels.

The same in outline, with the nervous system.

Median sagittal section through tle anterior end of the body. x 204
diam.

Cross-section of the anterior sucker through the beginning of the pos-
terior one-third of its length. x 204 diam.

One of the hooks at the extremity of the caudal appendage. x 805 diam.
Ovarian ova near the oviduct end. x 204 diam.

Cross-section of the intestine. x 204 diam.

Cross-section of one of the posterior suckers. x73 diam. chit’, space
left by the breaking away of the chitinous supporting rod.

Chitinous supporting rod of the posterior sucker. x 204 diam.

Median portion of a cross-section of the body (22nd section behind the

genital opening). x 204 diam.
Missing Page
PLATE XVI.
NF oT BF © bp

Plate XVI.

ONCHOCOTYLE SPINACIS.

Cross-section through one of the bifurcated ends of the caudal appendage,
to show the structure of the small sucker. x 204 diam.

Sagittal section through the same. x 204 diam. <

Cross-section of the body through the region of the ootyp. x73 diam.

A portion of the section represented in fig. 3. x 204 diam.

Cross-section of the uterus near the ootyp. x 204 diam.

Cross-section of the uterus more removed from the ootyp. x 204 diam.
Median sagittal section through tlie region of the genital opening. x 204
diam. Only the ventral side is represented in detail.

Median portion of a cross-section of the body not much removed from the

genital opening. x 20+ diam.
Jour, Se. Coll, Vol, Vill, Pl XVI

 

 

 

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PLATE XxX Vil.
ig. 1.

10.
11.
12,

Plate XVII.

MonocoTyLeE Is1MAeE.

The whole worm viewed from the ventral side; from a specimen killed
under the pressure of a cover-slip. The body is therefore represented a
little broader than it really is. With the nervous system shaded with
parallel lines.

The same with the excretory system.

A portion of the radial section of the posterior sucker along one of the
radial spokes. x 305 diam.

Cross-section of the body and sucker through the stalk of the latter.
x 78 diam.

Median sagittal section of the same. x73 diam.

A small portion of the part marked yi. in fig. 5, to show the sticky glands.
x 805 diam.

Striated muscular fibres of the sucker. x 305 diam.

Cross-section of one of the radial spokes of the posterior sucker. x 805
diam.

A small portion of a horizontal optic section of the sucker. x 3805 diam.
The white irregular patches represent the optic sections of the muscular
fibres.

One of the hooks of the sucker. x 805 diam.

A small portion of the intestinal epithelium in surface view. x 805. diam.
A portion of the cross-section of the body through the stalk of the sucker.
x 204 diam. To show the sticky glands (yl.) and their common efferent
duct (gl’.).
Missing Page
PLATE XVIII.
oo

ord

Plate XVIII.

Monocoryue Igimaeg.

A portion of the cross-section of the body through the level at which the
oviduct is continued into the ootyp. x 305 diam.

Median portion of a cross-section of the body through the ootyp. x 204
diam.

A portion of the median sagittal section of the body through the region of
the common genital opening. x204 diam. a, a circular vessel which

surrounds the bulbus ejaculatorius.

An almost median sagittal section of the anterior part of the body. x73
diam. a, ventral lip.

Cross-section of the body through the beginning of the intestinal trunks
x 204 diam.

Section of the ovary near the oviduct end. x 305 diam.

Chitinous penis. x 805 diam.

Cross-section of the pharynx. x 204 diam.
Missing Page
PLATE, XTX,
”

Fig.

ee SS WR «Se bor

10.

11.

12.
13.

14,

Plate XIX.

Cazicotyte Mitsuxvurit.

The whole worm viewed from the ventral side.

The same viewed from the dorsal side. x about 5 diam.

The same viewed from the ventral side. x about 5 diam.

Foremost portion of the body, viewed from the ventral side. x 29 diam.
Hook of the same very nearly in profile. x78 diam.

Saggital median section of the posterior sucker. x29 diam.

Sagittal median section of the body through the region of the ootyp. x73
diam.

Sagittal median section of the foremost portion of the body ; composed
from four sections. x78 diam.

A small portion of the mesenchyma with vitellarium ; from a sagittal section.
x 805 diam.

Terminal portion of the male genital duct viewed from the ventral side.
x 204 diam.

An almost median sagittal section of the penis bulb with the basal part of
the chitinous penis. x 805 diam. The two large cells drawn below are
probably the prostate glands.

Cross-section of the glandular portion of the vaginal canal. x 305 diam,

Ovarian ova from the oviduct portion of the ovary. x 805 diam.

CaLicotyLe Kroyer.

Hook in profile. x 204 diam. Drawn for the sake of comparison.
Jour. Sc. Coll. Yor. Vill. PI. XIX,

 

       

       

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Fig.

10.

Plate XX.

TRISTOMUM SINUATUM.

The whole worm viewed from the ventral side. The vitellarium is re-
presented only on one side, and the nervous and excretory systems on the
other. Nervous system shaded with parallel lines; excretory system
shaded darkest.

One of the looks of the posterior sucker. x 204 diam.

Chitinous corpuscle at the opening of the Jateral gland. x 204 diam.
Three elevations of the posterior sucker at the point of their junction,
in a surface view. x 204 diam.

Cross-section of the posterior sucker through its stalk. x29 diam.

A small portion of the radial section of the posterior sucker transversely
to the long axis of the body. x 204 diam. :

A small portion of the tangential section of the posterior sucker. x73
diam.

A portion of the cross-section of the body at the level of the oesophagus, to
show the salivary glands. x78 diam.

Two cells of the salivary gland. x 427 diam.

A portion of the cross-section of the anterior sucker of the right side and of

the adjoining part of the body. x 204 diam.
Missing Page
PLATE XXII.
Plate XXI.

TRISTOMUM SINUATUM.

Median sagittal section of the anterior part of the body. x73 diam.
A small lateral portion of a horizontal section of the body; to show the
marginal sticky glands and their ducts. x 204 diam.

A small lateral portion of a cross-section of the body; to show the open-
ing of the marginal sticky glands. x 204 diam.

A small ventral portion of a cross-section of the body. x 204 diam.

A portion of a horizontal section of the body just behind the pharynx.
x 204 diam.

Cross-section of the oviduct at the point of its junction with the ootyp; to
show the opening of the shell-glands. x 204 diam.

Beginning of the yolk-duct. x 427 diam.

Principal part of the female genital organs viewed as a transparent object
from the ventral side. x44 diam.
Missing Page
PLATE XXII.
Plate XXII.

TRISTOMUM SINUATUM.

A small portion of a horizontal section of the body near the terminal portion
of the vas deferens. x204 diam. To show the prostate glands.

A small portion of a horizontal section of the body near the genital open-
ing. x50 diam.

Horizontal section through the ootyp and the adjoining parts. x 204
diam.

Submedian section of the penis; from a horizontal section of the body.
x 204 diam.

A small ventral portion of a cross-section of the body through the yolk-
reservoir. x 204 diam.

A section through the right, hinder eye-spot and the adjoining parts of the
brain. x 427 diam.
Missing Page
PLATE XXIII.
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Plate XXIII.

TRISTOMUM OVALE.

The whole worm viewed from the ventral side. The testes are represented
only on one side.

One of the hooks of the posterior sucker. x70 diam.

Tangential section of the marginal membrane of tle posterior sucker.
x 204 diam.

Median sagittal section through the region of the pharynx. x50 diam.
Cross-section through the region of the left anterior sucker. x50 diam.
Cross-section through the anterior part of the pharynx. x50 diam.

A small portion of the ventral side of a cross-section of the body. x 204
diam. The contents of the testes are only partially drawn.

Central portion of the genital organs viewed as a transparent object from

the ventral side. x29 diam.
Missing Page
PLATE XXIV.
Fig.

”

”

_

10.

11.
12.

Plate XXIV.

TRISTOMUM OVALE,

A small portion of the wall of the penis in longitudinal section. x 204
diam.

A small ventral portion of a cross-section of the body. x204. The
reference lines for 1. mus. and diay. mus. should reacli more inward, the
latter to the oblique lines next the cir. mus., and the former to the nume-
rous closely crowded dots next the foregoing.

Cross-section of the left anterior eye and its vicinity. x 427 diam.
Cross-section of the left posterior eye. x 427 diam.

Two nerve-cells from the brain. x 427 diam.

TRISTOMUM ROTUNDUM,

The whole worm viewed from the ventral side. On the right side the
testes are shown only in outline, and the vitellarium is wholly omitted.
Three chitinous corpuscles from the margin of the body. x 204 diam.
One of the hooks of the posterior sucker. x 204 diam.

Central part of the genital organs viewed from the ventral side. x29

diam.

TRISTOMUM FOLIACEUM.,

The whole worm viewed from the ventral side. The vitellarium is not
shown on the right side.

Hooks of the posterior sucker. x 204 diam.

Median sagittal section of the anterior part of the body. x78 diam.
Jour. Sc Coll. Vol. VII. PI. XXIV.

   
 
  
 

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PLATE XXV.
Fig.

a

Plate XXV.

Tristomum Nozawae.

The whole worm viewed from the ventral side ; the vitellarium is represented
only on one side.

One of the hooks of the posterior sucker; a small portion was broken off
during preparation. x 204 diam.

Central portion of the reproductive organs viewed ‘as a transparent object

from the ventral side. x75 diam.

TRISTOMUM BIPARASITICUM.

The whole worn viewed from the ventral side ; the vitellarium is represented

only on one side.

. An egg-shell. x 50 diam.

One of the chitinous corpuscles of the lateral margins of the body. x 204
diam.

Hooks of the posterior sucker, from the same pair. x 204 diam.

Median sagittal section of the body through the region of the pharynx.
x 78 diam.

Central portion of the genital organs viewed as a transparent object from

the ventral side. x50 diam.

TRISTOMUM FOLIACEUM.

Central portion of the genital organs viewed as a transparent object from
the ventral side. x78 diam. A part of the vas deferens has been
omitted to make place for the prostate glands.
Missing Page
PLATE XXVI.
Plate XXVI.

EpisppELua ISHIKAWAE:

The whole worm viewed from the ventral side; from a specimen killed free.
The nervous system is shaded with parallel lines.

Hooks of the posterior sucker. x 204 diam.

The genital organs, vitellarium exclusive, viewed from the dorsal side.

x 50 diam.

EPIBDELLA OVATA.

The whole worm viewed from the ventral side; from a specimen killed free.
x 50 diam.

Hooks of the posterior sucker. x 204 diam.

The genital organs, vitellarium exclusive, viewed from the dorsal side.
x about 78 diam. 2, an organ of problematic nature.

Cross-section of the penis. x204 diam. The cavity of the penis lies
above due. ej.

Section through one of the organs of problematic nature shown in fig. 6,

with some of the histological elements in its vicinity. x 204 diam.
Jour. Se. Coll, Vol. Vill. PI. XVI.

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PLATE XXVII.
Fig. 1.
2.

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”

Plate XXVII.

Diagrams intended to show the homology of the genital ducts in the Trematodes

and the Cestodes. Homologous ducts are coloured alike.

Microcoryug; dorsal view.

Distomum; dorsal view. Based on the figures of Leuckart and
Ijima.

Dacty.Logyrus; dorsal view.

Ampuriina; ventral view. Based on the figure and description of
Monticelli.

CarnyvorpHYLLaEus; ventral view. After Monticelli.

Taxznra; ventral view. After L euckart.

BoruRiocePHauus; ventral view. After Leuckart.
Jour. Sc. Coll. Vol Wi. PI. XXVI,

    

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