S nor McCoMBIE-AuLD C O LLE C T I O N NEW- YORK -STATE COLLEGE orAGRICULTURE Date Due iinteoa 50 vCJ } H imM ^:-'-. ^, l9Bl? f 'J « Library Burea Cat. No. 1137 CpRNELL UNIVERSfTY LIBRARY n 19?4 oflQ R3n nfi.q r Cornell University Library The original of tliis book is in tine Cornell University Library. There are no known copyright restrictions in the United States on the use of the text. http://www.archive.org/details/cu31924089530053 ANIMAL ACTIVITIES ANIMAL ACTIVITIES A FIRST BOOK IN ZOOLOGY NATHANIEL S. FRENCH, Ph.D. Teacher of ZoSlogy in the Roxbury High School Boston, Mass. "WiiVo Klluetcatfone N£W IMPRESSION LONGMANS, GREEN, AND CO. 91 AND 93 FIFTH AVENUE, NEW YORK LONDON AND BOMBAY 190S n y^f^G Copyright, 1901, BY LONGMANS, GREEN, AND CO. First Edition, March, 1902 ; Reprinted, January, 1903. Reprinted, August, 1905. ROBERT DRUMMOND, PRINTER, NEW YORK. INTRODUCTION. The book here presented is the outgrowth of fifteen years of teaching the subject to large classes in a high school. Its aim is to interest and guide pupils in the study of living animals. Young people are usually ready to be made acquainted with their immediate neighbors in the animal world, and it is hoped that this book may be of assistance to them. In the choice and arrangement of topics the powers and interests of young students have been kept in view rather than the demands of strictly logical description and exposition. Chapter I outlines the animal kingdom in such a manner as to be useful for reference purposes. Chapter II gives directions for assisting the student in procuring his own specimens for study. Chapter III describes the activities common to all animals. With Chapter IV work on the Arthropoda begins. Animals of this group are selected for the early part of the work because living specimens can be easily collected and observed in the fall, at which time Zoology is begun in most schools. After the study of the Arthropoda, the book follows the natural order, beginning with the simplest animals and ending with the most complex. In some schools it will doubtless be better to begin with Chapter XI, and study the Arthropoda directly after the chapter on " The Earthworm ". This latter order of subjects is advised when the Zoology course begins in the winter or spring. Throughout the book adaptation to environment is constantly pointed out. Much is made of habitat in VI INTRODUCTION. connection with the manner in which an animal per- forms its Hfe-functions. The directions for laboratory work are mainly in the form of questions which must be answered irom direct observation. Comparisons and inferences are con- stantly required of the pupil. The exercises for review of note-book work enable pupils to systematize their knowledge. Useful vocabularies are frequently in- serted. For many valuable suggestions the author is in- debted to Miss Helen A. Gardner and Miss Mary E. Winn of the Girls' High School, Boston, and Prof. B. H. Van Vleck of Boston University, who read the manuscript ; and to Mr. Frank M. Whitney, principal of the Watertown, Mass., High School and Miss E. O. Patch of the Girls' High School, Boston, who ex- amined the proof-sheets. Mr. Lyman G. Smith of the Roxbury High School and Mr. Arthur E. Sanford assisted in preparing some of the drawings, and many of the illustrations have been reproduced, by per- mission, from Agassiz's "Seaside Studies " (Houghton, Mifflin, & Co.), "The- Horse" by W. H. Flower (D. Appleton & Co.), various works published by Longmans, Green, & Co., and other sources. A LIST OF BOOKS. All the books on the list given below have been found useful to pupils, and nearly all of them have been reported as ' ' interesting ' ' by many pupils who have read them. Such books may be used to advantage in the preparation of Reports. The list was first printed by a branch of the Agassiz Society connected with the Roxbury High School of Boston, Mass. Abbott, Charles Conrad: A Naturalist's Rambles about Home. Bird Land Echoes. Illustrated. Agassiz, Elizabeth and Alexander : Seaside Studies in Natural History. Illustrated. INTRODUCTION. vii Allen, Grant: Flashlights on Nature. Illustrated. Apgar, Austin C. : Birds of the United States. Illustrated. Badenoch, L. N. : Romance of the Insect World. Illustrated. Bausch, Edward : Manipulation of the Microscope. Bateman, G. C. : The Vivarium. Illustrated. Beard, James Carter : Curious Homes and their Tenants. Illustrated. Beddard, Frank E. : Elementary Practical Zoology. A Text-book of Zoogeography. BoLLES, Frank: At the North of Bearcamp Water. Brooks, W. K. : The Oyster. Illustrated. Buckley, Arabella B. : Life and her Children. Illustrated. The Winners in Life's Race. Illustrated. Burroughs, John: Birds and Bees and Sharp Eyes. Riverby. Wake Robin. Locusts and Wild Honey. Carrington, Edith : Animals' Ways and Claims. Illustrated. Chapman, Frank M. : Bird Life. Illustrated. Chatty Readings in Elementary Science (Longmans): Nature Knowledge, Books I, II, III. Illustrated. Cornish, C. J. : Animals of To-day. Illustrated. Animals at Work and Play. Illustrated. Wild Animals in Captivity. Illustrated. viii INTRODUCTION. Corey, C. B. : How to Know the Shore Birds. Illustrated. Darwin, Charles R. : What Mr. Darwin saw in his Voyage Round the World in the Ship " Beagle ". Illustrated. The Formation of Vegetable Mould. Illustrated. Davie, Oliver: Nests and Eggs of North American Birds. Illustrated. De Kay, Charles : Bird Gods. Illustrated. Dixon, Charles: Curiosities in Bird Life. DOUBLEDAY, N. B. DeG. : Birds that Hunt and are Hunted. Illustrated. Bird Neighbors. Illustrated. Duncan, P. Martin: The Transformation of Insects. Illustrated. Davenport, C. B. and G. C. : Introduction to Zoology. Illustrated. Edwards, Clarence E. : The Campfires of a Naturalist. Illustrated. Emerton, J. H. : The Structure and Habits of Spiders. Illustrated. FiGUIER, GUILLAUME LoUIS : The Ocean World. Illustrated. The Insect World. Illustrated. Flower, William Henry: The Horse. Illustrated. Forbes, Edward: A History of British Starfishes. Illustrated. French, G. H. : The Butterflies of the Eastern United States. Furneaux, W. : , The Out-door World. Illustrated. Life in Ponds and Streams. Illustrated. Graham, P. Anderson : Country Pastimes for Boys. Illustrated. Holland, W. J.: The Butterfly Book. Illustrated. INTRODUCTION. ix Jordan and Kellogg : Animal Life. Illustrated. Kearton, R.: Wild Life at Home. How to Study and Photograph it. Illustrated. KiNGSLEY, John Sterling: The Riverside Natural History, five volumes. Illus- trated. LovELL, M. S. : Edible Mollusks of Great Britain. Lubbock, Sir John : On the Origin and Metamorphosis of Insects. The Beauties of Nature and Wonders of the World. Ants, Bees, and Wasps. Illustrated. Mangin, Arthur: The Mysteries of the Ocean. Illustrated. Manton, Walter P. : Taxidermy without a Teacher. Insects, How to Catch and Prepare. Mathews, F. Schuyler: Familiar Life in Field and Forest. Illustrated. McCooK, Henry C. : The Honey Ants of the Garden of the Gods. Illustrated. Merriam, Florence A. : Birds of Field and Village. Illustrated. Birds Through an Opera Glass. Illustrated. Merriam, C. Hart: Mammals of the Adirondack Region. MiALL, Louis Compton : The Natural History of Aquatic Insects. Illustrated. Round the Year. Illustrated. MiCHELET, Jules : The Insect. Illustrated. The Bird. Illustrated. Miller, Olive Thorne: Little Brothers of the Air. Four-handed Folk. Illustrated. Bird Ways. In Nesting Time. Little Folks in Feathers and Fur. Illustrated. X INTRODUCTION. Morgan, C. L. : Animal Sketches. Illustrated. Needham, James G. : Outdoor Studies. Illustrated. Nehrling, Henry: Native Birds of Song and Beauty. Illustrated, two volumes. Oswald, Felix L. : Zoological Sketches. Illustrated. Packard, A. S. : A Guide to the Study of Insects. Illustrated. Parkhurst, H. E. : The Birds' Calendar. Illustrated. Porter, J. Hampden: Wild Beasts. Illustrated. Russ, Karl: The Speaking Parrots. Illustrated. Scudder, Samuel H. : The Life of a Butterfly. Illustrated. Butterflies: Structure, Changes, and Life-histories. Semper, Frank W. : Injurious Insects, and Use of Insecticides. Illustrated. Shaler, Nathaniel S. : Domesticated Animals. Illustrated. Simmonds, p. L. : Commercial Products of the Sea. Illustrated. Stokes, A. C. : Microscope for Beginners. Thomson, William: Great Cats I Have Known. Illustrated. Thompson, Ernest Seton : Wild Animals I Have Known. Illustrated. Torrey, Bradford: Birds in the Bush. Wallace, Alfred Russell: Darwinism. Illustrated. Weed, Clarence Moore: Life-histories of American Insects. Illustrated. INTRODUCTION. xi Wilson, Sir Daniel: Left-handedness. Wood, Theodore: The Farmers' Friends and Foes. Illustrated. Wood, Rev. J. G. : Homes Without Hands. Illustrated. Wright, Mabel Osgood : Four-footed Americans. Illustrated, Bird Craft. Illustrated. TABLE OF CONTENTS. PAGE Introduction vii CHAPTER I. Animals Classified i CHAPTER II. Material for Study 4 CHAPTER III. Activities Common to All Animals 24 CHAPTER IV. Grasshoppers and Crickets 32 CHAPTER V. Butterflies and Moths with their Protective Devices... 45 CHAPTER VI. Some Insects Classified 57 CHAPTER VII. A Chapter of Life-Histories 68 xiii XIV T/IBLE OF CONTENTS. CHAPTER VIII. PAGE Some Insect Adaptations 86 CHAPTER IX. A Spider's Activities 93 CHAPTER X. Homologies among Crustacea loi CHAPTER XI. The Activities of One-Celled Animals and Sponges 116 CHAPTER XII. The Hydra and Some Ccelenterates which Live in Colonies 128 CHAPTER XIII. The Starfish and Closely Related Animals 140 CHAPTER XIV. The Earthworm and His Work 148 CHAPTER XV. Mussels and Snails 155 CHAPTER XVI. The Structure and Activities of a Fish 169 CHAPTER XVII. Tadpoles and Frogs i^n T/IBLE OF CONTENTS. xv CHAPTER XVIII. PAGE BiRUs 197 CHAPTER XIX. Man's Near Relatives 211 CHAPTER XX. The Distribution of Animals 236 CHAPTER XXI. Animal Relationships 243 LIST OF ILLUSTRATIONS. Note. — Tke figures in brackets \\'\_followij:g- the titles re- [fer to ike list, printed betow^ of books from which the illustrations are, by permission, respectively borrowed. FIG, PAGE 1. An Insect-net 4 2. The House-cricket [i] 5 3. A Cabbage-butterfly 6 4. Spider and Web 7 5. A Water-snail 8 6. Shell of a Fresh-water Mussel [2] 8 7. An American Pondweed 9 8. The Hornwort 9 9. A Duckweed 9 10. Other Pondweeds 10 11. The Hydra [2I 10 12. Water-fleas and Cyclops 11 13. Caddis-fly Cases 1 2] 12 14. The Larva of Dragon-fly 12 15. Larva of Dyticus 12 16. Larva of Whirligig Beetle 12 17. Larva of a May-fly 12 18. Side View of Crayfish [5] 13 19. A Campanularian Hydroid Colony [6] 14 20. A Sertularian Colony [6] 15 21. A Net for Collecting at the Seaside 15 22. Sea-anemones 16 23. A Starfish [6] 17 24. A Sea-urchin 17 25. A Sea-cucumber 18 26. A Hermit-crab 18 27. A Shrimp 18 28. Tumbler with Chloroform 19 29. A Cockroach [i] 20 30. Mourning-cloak Butterfly 21 31. A Wasp's Nest [3] 22 32. Cocoon of Cecropia 22 33. Eggs of Frog Just Laid [2] 23 34. Eggs of Frog a Few Hours After Laying [2] 23 35 Apparsftus for Decomposing Water 26 36. Apparatus for Removing Okygen from Air 28 3 7. Heating a Test-tube 28 38. The Parts of a Locust 35 39. Comparison of a Grasshopper and Man 36 xvii xviu LIST OF ILLUSTRATIONS. FIG. PAGE 40. The Trachea of an Insect [2] 3^ 41. Cockroach and Cast Skin [i] 39 42. The Nervous Chain of a Cockroach [i] 4° 43. Portion of the Cornea of a Fly's Compound Eye [i] 41 44. The Hearing Organ of a Cricket [i] 4^ 45. The Stridulating Organ of a Cricket [i] 4^ 46. Antennze of Lepidoptera [4] 46 47. Eggs of Lepidoptera [4] 47 48. Some Larvae of Lepidoptera 4^ 49. Some Cocoons and Chrysalids [4] 4^ 50. A Cabbage-butterfly 49 51. Head of a Moth 50 52. The Kallima 51 53. Catocala Nupta [4] 52 54. The Milkweed-butterfly 53 55. Limenitis Ursula 53 560. Moth at Rest 55 56,5. Butterfly at Rest 55 57. Larva and Pupa of the House-fly [i] 58 58. Right Winglet of Bluebottle [i] 58 59. Balancer of Bluebottle [i] 58 60. Portion of a Fly's Foot [i] 59 61. Side View of Proboscis, partly opened [i] 59 62. Head of Bluebottle [i] 59 63. Eggs of Milkweed-butterfly 68 64. Larva of Milkweed-butterfly 69 65. Pupa of Milkweed-butterfly 69 66. Female and Male Aphis 71 67. A Microgaster Fly 75 68. The Dragon-fly f2] .' 77 69. The Imago of a Dragon-fly [2] 7^ 70. Caddis-fly, Adult and Larval Cases [2] 79 71. The Growth of a May-fly [2] 80 72. A Water-boatman 81 73. Dyticus Marginalis 81 74. Mouth of a Bug 82 75. The Egg-raft of a Mosquito [3] 82 76. The Life-history of a Mosquito 83 77. The Mouth of a Female Mosquito [2J 84 78. The Leg of a Cockroach [i] ,', 86 79. A Mole-cricket 86 80. Fore Legs of « Water-bug [2] 87 81. Legs of Dyticus [2] 87 82. Fore Leg of a Butterfly [4] 88 83. Hive-bees no 84. Fertilization of a Flower by an Insect ni 85. A Spider's Leg [2] ^4. 86. Water-spider and Nest \ ng 87. Side View of Crayfish [5] \ loi 88. Dorsal View of Crayfish [5] jq2 89. Ventral View of Crayfish [g] iq. LIST OF ILLUSTRATIONS. xix FIG. PAGE 90. Fourth Abdominal Segment of Crayfish [5] 104 91. Crayfish Appendages [5] 105 92. Longitudinal Section of Crayfish [5] 106 93. Walking Appendage of Crayfish with Gill Attached I5J 107 94. The Common Crab 108 95. Early Stages of Shore-crab 108 96. Water-flea [2] 109 97. Cyclops [2] 109 98. A Barnacle no 99. Forms of Amoebae 117 100. Amoeba Feeding [2] 118 loi . Amoeba Dividing [2] 119 102. One of the Foraminifera 120 103. The Origin of Chalk 120 104. Infusorial Earth 121 105. Infusorians 121 106. Vorticella [8] 122 107. A Paramecium [5J 123 108. Structure of a Sponge 124 109. Sponge Spicules [2] 125 1 10. Thread-cells [2] 130 111. Forms of Hydra [8] 131 1 12. Hydractinia [6] 132 113. Medusae of Campanularian Hydroid [6] 134 1 14. The Origin of a Scyphozoan Jelly-fish 135 1 15. The Structure of a Sea-anemone 136 116. A Starfish 142 117. A Brittle Starfish 144 118. The Structure of a Sea-urchin 146 119. A Sea-cucumber 146 120. An Earthworm 149 121. A Worm's Setae 150 122. Worm-casts 150 123. A Fresh-water Mussel Showing Position of Foot and Siphons. . 157 124. Fresh-water Mussel with One Valve Removed [5] 159 125. Digestive Tube of Fresh-water Mussel [5] 160 126. Cross-section of Anodon [5] 161 127. Nervous System of Anodon [5] 161 128. A Slug 163 I2g. A Snail 165 1 30. A Squid 166 13 1. Part of a Lingual Ribbon 166 132. The Circulation of Blood in a Fish 171 133. Internal Organs of Fish 172 134. Skeleton of a Fish 173 135. Tongue of a Frog 182 136. A Young Tadpole Showing External Gills [2] 182 137. Under Side of Tadpole Showing Coiled Intestine and Internal Gills [2] 183 138. Heart of Adult Frog [2] 183 139. Blood-cells of a Frog [g] 183 XX LIST OF ILLUSTRATIONS. FIG. PAGE 140. Blood-corpuscles of Man [g] 184 141. Viscera of Frog 185 142. Digestive Organs of Man [g] 186 143. Growth of Frog's Lung from Primitive Food-tube 187 144. Growth of Frog's Egg [2,} 188 145. Very Young Tadpoles [2] '. 188 146. Various Stages of Tadpole [2] 189 147. Young Frogs [2] 189 148. The Use of a Muscle 190 149. Striped Muscle-fibres [g] 191 150. Unstriped Muscle fibres [g] 192 151. A Frog's Skeleton 193 152. A Man's Skeleton. 194 153. Brain of Frog 194 154. Brain and Spinal Cord of Man 195 155. Beaks of Various Birds 199 156. The Digestive Organs of a Bird 200 157. Diagram of the Heart of a Bird [3] 201 158. The Skeleton of a Bird 202 159. A Swallow Feeding Her Young 203 160. Arm of Man, Fore Leg of Dog, Wing of Bird 204 161. A Bird's Wing 204 162. The Sternum of a Shrike 205 163. Feathers 206 164. A Bird's l«g 207 165. Feet of Birds 208 166. The Archseopteryx 209 167. Teeth of Man [g] 212 168. Teeth of Dog 212 169. Teeth of a Sheep [3] 213 170. Teeth of Hare 213 171. Skull of Cow Showing Teeth 214 172. The Human Eye 214 173. Skeletons of Man and Horse [10] 215 174. Bones of Leg and Arm of Man [11] 216 175. Vertebral Column of Man [11] 216 176. Human Skull [11] 217 177. First and Second Vertebrae of Man [9] 219 178. Skeleton of Gorilla 220 179. Diagram Showing Circulation of Blood in Man [11] 221 180. Skeleton of Bat Showing Wings 222 181. Arm and Hand of Man [11] 223 182. Skeleton of Chimpanzee Showing Hand 223 183. Fore Foot of Mole " 224 184. Fore Foot of Cat 224 185. Fore Feet of Cow ! ! ! 225 186. Fore Feet of Horse \ 225 187. Foot of Elephant " 22e 188. Feet of Bear ^ . 225 189. Sole of Foot of Man, of Dog, and of Horse [lo] 226 jgo. Finger of Man and of Horse [10] 227 LIST OF ILLUSTRATIONS. xxi PIG. PAGE 191. Feet of Ancestors of Horse 228 192. Growth of Hair [g] 229 193. Horns of Slieep, Cow, and Deer 230 194. Skull of Cow Showing the Bone of the Horn 231 195. A Manlike Ape Walking 232 196. A Chimpanzee 233 197. Feet of Ancestors of Horse 244 198. A Pterodactyl 245 1 99. The Archseopteryx 246 200. Diagram of a Sea-squirt 247 201. Amphioxus 247 202. Growth of Frog's Lung from Primitive Food-tube 248 203. Morula Stage [7] 249 204. Gastrula Stage [7] 249 205. A Genealogical Tree [7] 252 1. Our Household Insects.^/ E. A. Butler, Longmans, Green, & Co. 2. Life in Ponds and Streams ByW. Furneaux, " " " 3. The Outdoor World. . ..ffyfF. yT<;-»MKJ!:, " " " 4. Butterflies and MoTHS.^ JF. /K;-»ira«x, " " " 5. Practical Elementary Biology By John Bidgood, " " " 6. Seaside Studies in Natu- ral History. .. .By E. and A. Agassie, Houghton, Mifflin, &Co. 7. The Story OF Creation.^ ^rfif. Clodd, ILongmans, Green, & Co. 8. Animal Biology By C.L.Morgan, " " " 9. Quain's Anatomy, loth Edition " " " 10. The Horse By W.H. Flower, D. Appleton & Co. 11. Human Physiology ByW.Furneaux, Longmans, Green, &Co. ANIMAL ACTIVITIES. CHAPTER I. ANIMALS CLASSIFIED. In the course of these lessons on Animal Activities the student will be called on to observe many forms of animal life and to learn many new and perhaps strange names. In order that he may keep his bearings and feel somewhat at home from the start, the following classification of the animal kingdom is given. The student should read over this table carefully, noting especially the meaning of the names in the light of their derivation, and he should refer to it frequently. Later in the book more will be said about classification. The animal kingdom is divided by zoologists into subkingdoms. As these subkingdoms are supposed to consist of animals related through their ancestry, they are sometimes called phyla (^phylum, a tribe). Since Zoology is a rapidly growing science, authorities differ in regard to the number of divisions, or phyla, and also in regard to the names for some of the divisions. ANIM/tL ACTiyiTlES. Phylum or Sub- kingdom. I. 11. III. IV. V. VI. VII. VIII. Name of Sub- kingdom. Pro to zo'a. Po rif'e ra. cce len te- ra'ta. E CHI NO- der'ma ta. Ver'mes. Ar throp'o- DA. MOL LUS'CA. Chor da'ta. Derivation of Name, A Few Characteristics. Gr. protos^ first, and zoon^ ani- mal. Lat. porus, a pore, and _/<;?■(?, to bear Gr. koilos, hollow, and enteron, in- testine. Gr. echinoSy a hedgehog, and derma, skin. Lat. vermis, a worm. Gr. arlhron, a joint, and pous (pod), a foot. Lat. mollis, soft. Gr. chorde, a string. Familiar Examples One-celled ani- mals. They do not re- produce by eggs. Animals having many cells much alike. Food enters the body by numer- ous openings. Animals having hollow cylindri- cal bodies with only one open- ing, the mouth. Animals having very distinct ra- dial symmetry, having hard plates in the skin, and fre- quently covered by spines. Include a great variety of worm- 1 i k e animals. Some have seg- mented bodies. Animals having segmented bod- ies and jointed appendages. Soft-bodied ani- mals, often en- closed in hard shells. Almost all have back bones made up of parts called vertebras. Amoeba, Para- mecium, vor- ticella, chafc animals. All sponges. IJydras, hy. droids, jelly- fish, corals, sea- anemones Starfish, sea- urchins, sea- cucumbers, and stone, lilies. Earthworms, leeches. Grasshoppers, butterflies, spiders, cray- fish, crabs, centipedes. Clams, snails, the nautilus, and the squid. Fishes, frogs, turtles, snakes, birds, horses, and ANIMALS CLASSIFIED 3 In the following pages directions are given for the laboratory study of the activities, as well as of the structure of the animals mentioned below. A Paramecium, belonging to Protozoa. A sponge, belonging to Porifera. A hydra and a hydroid colony, belonging to Coelen- terata. A starfish and a sea-urchin, belonging to Echino- dennata. An earthworm, belonging to Vermes. A grasshopper, a butterfly, a house-fly, a potato- beetle, a spider, a centipede, and a crayfish or a lobster, belonging to Arthropoda. A mussel, a slug, and a snail, belonging to Mollusca. A fish, 2ifrog, and a bird, belonging to Chordata. Directions for a short study of some domestic animals related to man are also given. CHAPTER II. MATERIAL FOR STUDY. In order to study the activities of animals it is neces- sary (i) to have apparatus, (2) to collect many forms of animal life and provide suitable conditions for them, and (3) to prepare and preserve specimens. All work of this kind can best be done by the members of the class. It is a good plan for small groups of volunteers to assume responsibility for carrying out the directions of the several paragraphs which follow. APPARATUS AND REFERENCE BOOKS. Not much apparatus is needed. A net for collecting insects may be made by bending a piece of telegraph- wire into the shape indicated in Fig. i , fastening it to Fig. I. — An Insect-net. Drawn by A. E. Sanford. a pole, and sewing it into a bag made of mosquito- netting. For water collecting, a tin strainer attached to a wooden handle answers admirably. Fruit-jars and jelly-tumblers with tin covers make good collecting vessels. A few books should be at hand for reference. Bulletin No. 39, U. S. National Museum, can be had 4 M/ITERUL FOR STUDY. 5 by sending to the National Museum in Washington. It contains valuable directions for collecting and pre- serving animals, and no school need be without it. "The Out-door World ", Furneaux, (Longmans,) is a useful help in this work. Write your name plainly on a label affixed to the jar or other vessel in which you have placed your col- lections. Write a brief statement telling where and under what circumstances your specimens have been collected. Hand jar and statement to the teacher at the same time. LIVING MATERIAL FOR FALL USE. Grasshoppers and Crickets. Collect these insects and place them in tumblers, or similar glass vessels, covered with netting. Put earth in the bottom of each tumbler and keep it moist. Feed the insects with lettuce, or similar vegetable food. Watch the movements of male crickets while chirping. Female crickets may often be seen depositing eggs. The females may be recognized by the long, slender, egg-depositing organs at the end of the abdomen. Use these specimens with the directions in Chapter IV. Grasshoppers and crickets may be fed on bread. Wasps and Butterflies. Place wasps in tumblers in a similar manner, and feed them on sugar and water. Try, also, butterflies and moths in the same way, using larger glass vessels. If eggs are deposited, examine them carefully and watch their growth. Fig. 2. — The House- cricket. ANIMAL ACTiyiTIES. Caterpillars. Keep these singly in tumblers with fresh supplies of the plant on which they are found feeding. When many caterpillars are needed for class study a ' ' breeding-cage ' ' may be made by placing earth in the bottom of a large box, covering the box with netting, and supplying plenty of food and moisture. If panes of glass can be set in the sides of the box, so much the better. Cabbage- worms are easily ob- tained, and the butterflies can be reared from them with very little care. The cabbage - butterflies are sometimes called "whites". In observ- ing butterflies and cater- pillars use the questions in Chapter V. Flies. Allow adult bluebottle flies to deposit eggs on pieces of meat or fish in tumblers. Watch the growth of the eggs. Keep in a fairly warm place and furnish mois- ture. See further suggestions in Chapter VI. House- flies may be watched in tumblers. Feed them on sugar and watch their movements. Early in the fall house-flies will deposit their eggs on stable- manure. Spiders. All our common spiders are harmless. To collect spiders invert a tumbler over them, and im- prison the insects by covering the mouth of the tumbler with a card. The garden-spider is a good one to Fig. 3 A Cabbage-butterfly. larva; b, pupa; c, egg; d, imago. MATERIAL FOR STUtiY. observe. Provide flies and other small insects for food, and watch the web-making, the feeding, and other activities. Further questions and suggestions will be found in Chapter IX. Earthworms. Fill one or two large battery-jars with moist earth and decaying leaves and put in each jar several earthworms. Cover the jars and keep the earth well moistened. Keep all winter. Watch in connec- tion with directions in Chap- ter XIV. Turtles and Snakes. Line the bottom of a large box with sheet-lead or zinc and place panes of glass in the sides for windows. Put earth, stones, and moss, and, if convenient, a few growing ferns in the box. for turtles and snakes. Fig. 4. — Spider and Web. This makes a good home Snakes caught late in the fall will probably not eat anything through the winter, and they can be set at liberty in the spring. Turtles seldom eat in the winter, but will take flies, bits of meat, or pieces of cracker soaked in milk when hungry. ' ' The Vivarium " , an illustrated book by G. C. Bateman, will be of great assistance to pupils who are willing to care for these animals. Frogs. In a box like that described in the preceding paragraph keep several frogs. In the winter frogs do not commonly take food. Live frogs can usually be bought in the markets. Slugs. These animals are easily kept if provided with moisture and food. They eat bread or cracker as well as many kinds of vegetables. 8 ANIM/IL yiCTIVITIES. in a Snails and Mussels. Collect pond-snails and put vessel of water with sticks, dead leaves, and growing plants. Place in the bottom of the dish two or three inches of sand and introduce one or two fresh-water mussels. Watch the movements of both snails and mussels. Find out how they breathe. The plants furnish food for the snails, and the mussels thrive without feeding, living for years in an aquarium like that just de- scribed. Watch for the eggs and growing young. Use directions in Chapter XV. Aquaria. The mussels just mentioned breathe the air dissolved in the water, and, on this account, fresh air must be supplied. There are .several ways of doing this. The simplest method consists in furnishing Fig. 5.— a Water-snail {Planorbis). Fig, 6. — ^Shell of a Fresh-water Mussel (Anodori). growing plants enough in the aquarium to take up the carbon dioxide gas exhaled by the animals, and at the same time to give the water a supply of oxygen. Such plants may be easily collected while looking for snails. Water-plants are also for sale at bird stores. MATERIAL FOR STUDY. Fig. 7. — An American Pond- weed. Another method of purifying the air in water consists in forcing a stream of air through it. This is not prac- ticable in most schoolrooms. Pouring fresh water against the side of the aquarium in such a way that many bub- bles of air are caught in the descending stream is a common and easy method. Large aquaria frequently have a constant supply of running water with a regular outflow. Such aquaria are hardly neces- sary in most schools. Small rectangular glass vessels and common battery-jars answer every purpose. Of course water lost by evaporation must be re- placed. With the aquatic animals mentioned here it is a good plan to depend partly on plants to change the air in the water, but in addition to this it is better to remove the greater part of the water from time to time and to replace it by a fresh supply. An easy way to accomplish this is to have all the aquaria placed on a shelf a little higher than the faucet from which water is to be supplied. A hose can be attached to the faucet for the purpose of filling the aquaria. In order to empty the vessels, it is only necessary to unscrew the hose from the faucet while it is still filled with water, being careful to keep the end of the hose in the aquarium under water. Fig. 8.— The Horn- wort. Fig. 9. — A Duck- weed. ANIMAL ACTIVITIES. In this way the water siphons over into the sink. To prevent the passage of insects through the siphon, attach it to a tunnel having the open- ing covered with wire gauze. Hydra. Collect small sticks and dead leaves, with some mud and water, from a fresh- water pond, or from ditches used for draining swampy places. Place these in glass with growing fresh-water plants, and renew from time to Fig. io. — Other Pondweeds. Fig. II. — The Hydra (magnified). time the water lost by evaporation. Collect from several localities in separate jars, and label the jars MATERIAL FOR. STUDY. n for convenience. Watch carefully for the appearance of either brown or green hydras. They may be seen without a magnifying-glass. If only eggs are present, they may not hatch for months, ,»«*• Fig. 12. — Water-fleas and Cyclops (magnified). but sometimes adult hydras are captured attached to duckweed or other objects. Have several jars, and watch them all. Look for the appearance of buds on the sides of the hydras. Minute Crustacea (water-fleas and Cyclops) may appear in some of the jars. These are good food for hydras, and themselves furnish pleas- ing objects for study, both with and without the micro- scope. If either Crustacea or hydras appear, notice whether they prefer the light or the dark side of the jar. Add water only to replace that lost by evapora- tion. Some Water-breathing Insects. While collecting the hydras, look for objects that appear like moving sticks, or small moving rolls made of bits of leaves or pieces of sand. These are the larvae of caddis-flies. Watch them feed, and add material to the tubes which protect their delicate bodies. Keep plenty of plants about them. Larvae of other insects may be collected 12 ^NIM^L /ICTiyiTIES. at the same time and kept in aquaria. If possible collect a water-boatman. Fig. 72 shows this insect Fig. 13 Caddis-fly Cases. as it appears while swimming and while flying. A powerful aquatic insect is the large water-beetle (Dity- cus Marginalis). Fig. 1 5 shows the young and Fig. Fig. 14. — The Larva of a Dragon fly. Fig. 15. — Larva,of Dyticus. Fig. 16. — Larva of Whirligig Beetle. Fig. 17.— Larva of a May-fly. 73 shows the adult forms. The whirligig beetles seen in large numbers on the surface of fresh water have eyes adapted for seeing enemies in the air above and MATERIAL FOR STUDY. I3 in the water below at the same time. A young whirligig is shown in Fig. i6. Watch mode of breathing and of carrying air about. Observe also the manner of "feathering" the oars. Feed the beetle and larvae on bits of meat or small in- sects. Leeches. "Blood-suckers ", as the boys call them, are harmless and interesting tenants of an aquarium. Watch some of these animals, noting especially the mode of movement by means of contracting longi- tudinal and circular muscles. They feed only occa- sionally, and can be set at liberty before they suffer for food. At liberty they suck the blood from living animals. Crajrfish. These may be bought alive in the mar- FlG. l8. — Side View of Crayfish, an, antenna; r-, rostrum; cep, cephalic portion; tho, thoracic portion of cephalothorax; ab, abdomen. kets. They may be kept in shallow water in aquaria and fed on bits of fish or meat. Tadpoles. These may be caught in ponds and brooks even late in the fall. Collect several sizes and keep them in a jar or jars. They feed on vegetable matter, eating chiefly the small green plants (confervas) which grow so rapidly in stagnant water exposed to sunlight. Select a particular individual and sketch his 14 yINIMAL ACTIVITIES. actual size from time to time, dating the sketches. Make these sketches as accurate as possible. When not convenient to catch tadpoles it is easy to buy them. Fishes. Obtain alive, by using a net, either horned pout (catfish) or bream. Goldfish can be bought in case of failure to get others. Feed with fish-food, a preparation of gelatin sold by dealers in goldfish. Use plants in the aquarium, and change the water about three times a week. Use a rectangular aquarium. Shield from the direct rays of the sun. Hydroids and Jelly-fish. Unless a school is situated where it is easy to obtain an abundant supply of salt water, not many marine animals can be well kept. Before undertaking seashore work, a copy of ' ' Seaside Fig. 19 A Campanularian Hydroid Colony (Eucope diaphand). a, whole colony, one half natural size; b, single zooid magnified; c and d, stages of jelly-fish, magnified. Studies " (Agassiz) should be accessible to both teacher and pupils. There are many small marine animals resembling the hydra. Among the most abundant of these are the campanularian hydroids, colonies of hydra- like animals. The colonies are brown in color, and look like mosses or similar plants. They grow on MATERJ/tL FOR STUDY. 15 sea-weeds, on logs and sticks, and are sometimes at- tached to the shells of mussels. Find them at low tide and transfer them to a marine aquarium, made by filling ajar with salt water and introducing some marine plants collected on the rocks where the campanularians are found. Some closely related colonies are called sertularians. Hydractinia is the name given to a colony consisting of pink, salt-water hydroids found growing on the snail-shells occu- pied by hermit-crabs. Sea-anemones. These animals are hardy and may be transported for some distance in jars or pails of salt water. To obtain them, look in pools left by the tide in rocky places, or on rocky bottoms below low tide. They are sometimes found attached to the piles of wharves or bridges. They can be removed from the rocks by quickly slipping a broad, thin knife between the anemone and the rock. Their resemblance to hydras and to coral animals should be especially noted. Except as living specimens they are not of much value to beginners, as the prepared specimens are commonly too much distorted to show structure well. These animals may They As Fig. 20. — A Sertula- rian Colony. After Agassiz. ^ Fig. 2r.^A Net for Collecting at the Seaside. Starfishes and Sea-urchins. be found in the same localities as the anemones, are quite hardy and will live in salt-water aquaria, they can be collected at any time during the year, it is as well to get the living specimens when ready to study i6 ANlM/iL ACTIVITIES. Chapter XIII. Keep one animal in each battery-jar with sea-water and a few marine pknts. Sea- cucumbers. These animals are often found on beaches after a storm. They may be found on rocky bottoms in a depth of from three to six feet of water at Fig. 22. — Sea-anemones. low tide. It is easy to take them with a dip-net when once found. They are hardy and live well in aquaria. Compare with starfish and sea-urchin. Shrimps and Sand-fleas. Shrimps may be used in- stead of crayfish in studying Chapter X. They may be caught with a dip-net in shallow water at low tide. They can be kept in aquaria. Sand-fleas, sometimes called MATERIAL FOR STUDY. 17 sand-hoppers, are easily collected by overturning rocks left by the tide. Compare with shrimps. Collect also hermit-crabs. Marine Fish. Where there are conveniences for salt-water animals, a few small marine fish may be kept. No special direc- tions are necessary. Compare with other specimens of fish and use with Chapter XVI. Fig. 23. — A Starfish. After Agassiz. THE PREPARATION AND CARE OF SPECIMENS. Prepared Specimens. In addition to living animals it is always necessary to have at hand a plentiful supply i Y'v^^^ Fig. 24. — A Sea-urchin. Part of the spines have been removed. i8 ANIMAL ACTIVITIES. of prepared specimens so preserved as to be examined to the best advantage. It should be a part ol the work of the pupil to prepare at least a portion of this material. Ejilling the Specimens. Place some pieces of blot- ting-paper saturated with chloroform or ether in the Fig. 25. — A Sea-cucumber. Fig. 26. — A Hermit-crab. bottom of a jelly-tumbler provided with a tin cover (Fig. 28). In this grasshoppers, butterflies, and other small insects may be painlessly killed. It must be remembered that chloroform and ether are poisonous Fig. 27. — A Shrimp. substances, and that they must not be brought near a lighted lamp or fire, as they ignite very readily. MATERIAL FOR STUDY. 19 The cyanide bottle described in Part F of Bulletin No. 39, U. S. National Museum, can be used instead of the tumbler if desired. Animals larger than insects may be killed by chloroform or ether. Earthworms should be killed in dilute alcohol. Starfish and sea- urchins are often killed by placing them in hot, but not boiling, water. Preserving Specimens in Alcohol. Part M of Bulletin No. 39 already mentioned gives valuable directions for the preservation of specimens. Alcohol is the most important pre- „ „ ^ , , „ ., T- 1 ■ Fig. 28. —Tumbler servmg fluid. For most specimens ^jth chloroform. 50^ alcohol should be used at first. Drawn by A. E. This should be changed in a few Sanford. days to a stronger solution, about 60^. If the speci- mens are to be permanently kept they should be transferred again to joi alcohol. Strong alcohol as bought of the dealers is about 95^ pure. This should be diluted some days before the specimens are put in it, to prevent the collecting of bubbles on the surface of the animals. Parts of animals for dissecting should be hardened gradually in alcohol. Hydras, hydroids, snails, mussels, and worms are best kept in alcohol. Preserving Specimens in Formalin. This liquid as usually bought is a solution of formaldehyde in water. For most purposes it should be diluted with water to make a 2^ solution. Specimens to be used are kept in this fluid. Dried Specimens. For class use, butterflies may be kept in a tightly closed box containing naphthalin or camphor. Such specimens usually need to be preserved for a few months at most and can then be thrown away. Dragon-flies and other insects may be kept in the same box. Starfish may be dried by a slow heat after immersing for a time in hot water, not boiling, or after fjradually hardening in alcohol. Sea-urchins may be ANIMAL ACTiyiTIES. preserved in the same way, but they make better speci- mens for study, if preserved in formalin or alcohol. Shells and Bones. To remove snails from their shells put them in hot water for a few moments. The shells may then be cleaned and dried. To clean fleshy matter from a skeleton like that of the starfish use a dilute solution of caustic potash. Sometimes it is well to boil specimens in that liquid. The bones of larger animals can be cleaned enough for class use by simply boiling and removing the fleshy parts. When such specimens are to be kept for a long time more care is needed, and books containing more specific directions should be consulted. Part C of Bulletin No. 39, pre- viously mentioned, is helpful. MATERIAL FOR WINTER AND SPRING. The preceding directions are for classes which begin Zoology in the fall. When the work begins in the spring the order of work should be modi- fied somewhat, begin- ning with Protozoa and reaching the subject of Arthropoda after warm weather brings the living specimens again within easy reach. Even in winter much material can be pro- cured by the pupils for their study. Cockroaches. Cock- roaches were originally southern insects. They are now distributed Fig. 29.-A Cockroach. almost everywhere, and are fairly abundant even in cold weather. They are most easily collected at MATERIAL FOR STUDY. 21 night in warm places where there is a plentiful supply of household food. A sugar-refinery often furnishes an abundant supply of these insects. They may be kept alive as in the case of grasshoppers. With a few obvious changes in the directions and questions, the cockroach may be substituted for the grasshopper in studying Chapter III. Butterflies and Moths. Although adult forms of these insects are not abundant in cold weather, their eggs, cocoons, and chrysalids are easily obtained. In late winter or early spring pupils should collect speci- mens of the large mourning-cloak butterfly ( Vanessa Fig. 30. — Mourning-cloak Butterfly (Vanessa antiopa). antiopd), which shows the wear due to its winter sleep, and is ready to produce eggs for the summer brood. The eggs may be reared, the larvae feeding on leaves of willow or birch. On apple- and cherry-trees may be found the eggs of the tent-caterpillar moth. These eggs are glued to the stem in a mass. The large grayish-brown cocoons of the Cecropia moth are often found on pear-trees or other fruit-trees. Eggs, cocoons, and chrysalids should be brought to the schoolroom and placed under such conditions that hatching and growth may be watched. 2 2 /tNlM/IL ACTIVITIES. Other Insects. Eggs of spiders are easily found in winter. They should be kept in tumblers and watched. Nests of paper-making wasps are interesting. They often contain sleeping queens waiting for a higher tem- FlG. 31. — A Wasp's Nest. Fig. 32. — Cocoon of Cecropia. From a Photograph. perature in order to start other colonies. Insects in various stages of metamorphosis pass the winter hidden away from birds and other enemies. Locality and cir- cumstances must determine what sort of specimens pupils should search for. With the advent of spring one can obtain nearly, if not quite, all the specimens already mentioned as obtainable in the fall. MATERML FOR STUDY. 23 For Aquaria. Hydroids, hydras, and jelly-fish for the most part die off in win- ter, but sea-anemones, starfish, hermit-crabs, shrimps, and cray- fish can all be obtained through- out the year. Snails and mussels are also easily kept at all times, as are also tadpoles and frogs. In the spring the eggs of frogs and toads should be placed in aquaria and watched. Birds. Winter is the best time to begin the out- door study of birds. Familiarity with the birds which remain north throughout the winter prevents much of Fig. 33-— Eggs of Frog just Laid. Fig. 34. — Eggs of Frog a Few Hours after Laying. the confusion which so annoys the novice when he tries to observe the newcomers at the time of the spring migration. A study of crows, blue jays, and chicka- dees, during cold weather should form a part of the work for winter. English sparrows must not be despised as objects of study, and their habits, both in captivity and out of doors, should be watched. CHAPTER III. ACTIVITIES COMMON TO ALL ANIMALS. Matter. The books on physics tell us that matter is anything having extension, i.e., having length, breadth, and thickness. Living matter we call or- ganic, and matter which is not alive, and, as far as we can see, never has been alive, we call inorganic. Living Matter. Living matter dies. It always returns sooner or later to the inorganic world from which it derives the materials by means of which it keeps its living machinery active. Organisms grow, not by adding matter to the out- side, as do crystals when they increase in size, but by taking substances into the body, and there building them into matter like themselves. Before growth ceases, plants and animals reproduce. Some small portion of the body separates from the rest and begins an independent existence, repeating, very nearly, the life-history of its parents. In most cases the part which separates for the new life must join with a part of another individual before it can grow. Doubt- less pollen and ovule are familiar terms to all who will use this book. Living things, too, seem to be capable of movements which differ from the movements of inorganic things. A living tree moves with the wind just as inorganic things move, but it also has going on within it move- ments which differ entirely from any movements of which inorganic matter is capable. 24 ACTiyiTlES COMMON TO ALL ANIMALS. 25 Plants and Animals. The differences between higher animals and plants are so obvious that we need never mistake one for the other ; but, as we shall see, the differences grow less and less as we consider simpler and simpler organisms. Among the simplest living bodies the processes of life go on ; but we do not know whether to call the living things themselves plants or animals. Definitions. The science which treats of living matter is Biology. The branch of Biology treating of plants is Botany, and the branch treating of animals is Zoology. The study of the form, structure, and position of the parts of a plant or an animal is Anatomy. Minute Anatomy studied with the microscope is Histology. ' The study of the functions or uses of all parts of an organism is Physiology. Activities of our own Bodies. We may learn what the most important activities of animals are by con- sidering the chief activities of our own bodies. While our ability to move readily from place to place, and to perform the many muscular acts of daily life, is doubt- less the most noticeable sort of activity which we share with other animals, it is not the most fundamental. Back of all movement there must be a source of power. In these days, men make machines which seem almost alive. In these some sort of power which we can understand causes all the movements. Springs and weights move clocks, steam-pressure turns the wheels of factories, and electric currents move our street cars. Our Bodies Chemical Engines. Sources of power can usually be traced back to heat. The movements of a steam-engine are due to energy set free by the burning of coal. The burning of coal is a chemical activity. The heat is caused by the union of two elements, carbon and oxygen. It has been found that the movements of living things are also due very largely to chemical action. Just as coal burns or 26 ANIMAL ACTiyiTlES. oxidizes in a furnace and produces energy or power to work, so the various materials of which our bodies are made oxidize and set free the energy by which we perform the varied movements of our bodies. In a very true sense, then, our bodies may be called chemi- cal engines. Waste and Repair. The furnace which furnishes power for any kind of machinery must constantly receive new material and give out waste products. Without a constant supply of coal and air, the fire goes out and work stops. The chimney must be kept clean in order to allow the gases produced by the fire to pass out, and the ashes must be raked away as fast as they are formed, to make space for new fuel. In the same way every living animal takes into its body substances corresponding to the fuel of a furnace, and it as con- stantly gives out the waste products which would soon cause death if they should remain. In order that we may know these substances better, a few simple experi- ments may be considered. Experiment. Water. Using the apparatus shown in Fig. 35, pour water and a little sulphuric acid into the U tube, and place test-tubes filled with water over the ends of the wires. When the circuit is closed notice that bubbles of gas arise from the wires and collect in the upper part of the test-tubes. Note the fact that water is separated by a current of electricity into two invisible gases, and that, after a time, one tube contains twice as much gas as the other. The larger amount of gas is hydrogen, and Light the hydrogen, noting the Into the top of the ISO r —tT^"^ ^"^ Fig. 35. — Apparatus for Decomposing Water. Drawn by A. E. San- ford. the smaller, oxygen fact that it burns very readily ACTiyiTIES COMMON TO ALL ANIMALS. 27 tube containing oxygen thrust a glowing coal (carbon) and see that it relights. Water is composed of two gases. Hydrogen burns easily in air, and oxygen aids the burning of hydrogen, of carbon, and of other sub- stances. Elements and Compounds. Because hydrogen and oxygen cannot be further separated into other sub- stances they are called elements. Water, because it is formed by the union of two elements, is called a compound. Carbon is also an element. Experiment. The Oxidation of Magnesium. Mag- nesium is an element. To a piece of wire made of this element apply a lighted match and notice the produc- tion of heat and light. Examine the white powder produced. The oxygen from the air has united with magnesium and formed magnesium oxide. This white powder, the magnesium oxide, weighs more than the magnesium used. The process is oxidation. The oxidation of hydrogen produces hydrogen oxide, or water. The oxidation of carbon produces carbon oxide, commonly called carbon dioxide. Magnesium oxide is a solid, hydrogen oxide is a liquid, and carbon dioxide is a gas. In all cases heat and energy are produced by oxidation. Experiment. The Oxidation of Phosphorus. Phos- phorus is an element obtained from the bones of ani- mals. Caution must be used in experiments with phosphorus as it ignites so readily. Remove a piece of phosphorus from the water and allow it to dry on a piece of blotting-paper. Note the smoke arising. This is phosphorus oxide. Touch the phosphorus with a warm wire. Note the increased rapidity of the oxida- tion. The same amount of heat is produced by the oxidation of phosphorus whether the oxidation is slow or rapid. Phosphorus oxide is formed in both cases. Experiment. Nitrogen in the Air. Air is almost wholly a mixture of nitrogen and oxygen." Cover the top of a large cork with asbestos and put on it a small 28 ANIMAL ACTiyiTIES. piece of phosphorus. Float the cork on water in a soup-plate and light the phosphorus, at the same time lowering over it a jar of air, in such a manner that the mouth of the jar just dips below the surface of the water in the plate (Fig. 36). The phosphorus oxide formed dissolves quickly in the water. The water rises in the jar to replace the oxygen used up, showing that about one fifth of air is oxygen. Remove the jar from the plate and thrust into the gas a lighted match. This colorless gas forming about four fifths of the air is nitro- gen. It will not burn or aid the burning of other substances. This element is found in all animal bodies united with other elements to form Bread and meat contain compounds Fig. 36. — Apparatus for Removing Oxygen from Air. Drawn by A. E. Safiford. compounds. partly composed of nitrogen. Experiment. The Element Carbon in Starch and Sugar. Heat in the bottom of a test- tube a small amount of sugar (Fig. 37). Notice the water which col- lects on the sides of the tube. What are two elements found in sugar .' Heat slowly until no more steam escapes, break the tube and examine the residue. It is charcoal, a form of carbon. What three elements in sugar .' Repeat this experiment, using starch and wood. Graphite and diamond are other forms of carbon. Experimejit. Carbon Dioxide. Burn in a covered bottle a little charcoal attached to a wire. When it ceases to glow remove it, and shake up the gas in the .^C^ P'lG. 37. — Heating a Test-tubi-, Drawn by A. E. Sanford. ACTiyiTIES COMMON TO ALL ANIMALS. 29 bottle with lime-water. The milky appearance of the water proves that the gas, carbon dioxide, is present in the bottle. How did the gas get in the bottle .' Experiment. Carbon Dioxide in the Breath. Breathe through a glass tube into a test-tube containing a little lime-water. What does the milky appearance of the lime-water prove .'' Whence came the carbon dioxide .■' How was it produced .'' Experiment. The Oxidation of Hydrogen in our Bodies. What collects when we breathe on a cold glass .•■ Whence comes the water .'' The hydrogen enters the body with the food. How does the oxygen enter the body 1 Substances Taken into the Body and Substances Excreted. It has been found that the greater part of the substances taken into the body are compounds of hydrogen, oxygen, nitrogen, and carbon. These enter the body as food. Oxygen also enters the body in breathing. It has been found that the sub- stances regularly excreted from the body by the lungs, by the skin, and by the kidneys are carbon dioxide, water or hydrogen oxide, and a compound containing nitrogen and hydrogen, called urea. In this way the four elements which enter the body as complex com- pounds are all finally excreted as very simple com- pounds. A Summary of Activities. All animals take food of some kind. As in our bodies, so in the bodies of all other animals, the food must be chemically changed to build up tissues and furnish material for oxidation. Although all other animals do not have lungs, skin, and kidneys like ours, they nevertheless must excrete the materials which result from the oxidations and other chemical changes in the body. All animals also reproduce. All are capable of movements different from the movements of inorganic things. All, too, are able in some way to establish communication with the outside world. For this purpose we are endowed with 30 ANIM/IL ACTiyiTlES. special organs for seeing, hearing, smelling, tasting, and feeling. By these organs we discover the world about us. Many animals have not these organs of sense. Many, indeed, have no organs of any kind, yet all animals seem to possess, to some extent, the ability to discover their surroundings. If no other sense be present, something like our sense of feeling seems to be always active. We may summarize the most important activities of animals as follows: («) Taking food and oxygen. Ip) Nutrition. Ic) Excretion. {d) Reproduction. (e) Movement. {JD Discovery. Respiration combines in most animals the two im- portant functions of taking oxygen and excreting waste matter. Physiology and Anatomy. In studying animals we wish most of all to know their activities. But in order to understand these activities one must know certain facts about the structure of the animals to be studied. A sewing-machine has only one activity or function, but one must know the form and position of many parts before one knows just how the sewing is done. When we speak of the six activities mentioned we are dealing with Physiology. When we study the parts of an organism to learn their positions and shapes we are dealing with Anatomy. Evidently, then, anat- omy and physiology must be studied together in the science of Zoology. We do not study anatomy in order to become familiar with many new names, but in order to understand- the activities or uses of the parts. ACril^mES COMMON TO ALL ANIMALS. 31 VOCABULARY. A nat'o my (Gr. ana, up, and iemno, cut), the science which treats of the structure of organ- isms. Bi Ol'o gy (Gr. iios, life, and logos, a discourse), the science of living things. Bot'a ny (Gr. botania, a plant), that part of Biology which treats of plants. Cai'bOD (Lat. car bo, coal), an ele- ment found in all organic com- pounds; charcoal, graphite, and diamonds are forms of this ele. ment Car'bon di ox'ide, a heavy, color- less gas, formed by the breathing of animals and by the burning of substances containing car- bon. Ez Cie'tion (Lat. ex, out, and cer- no, separate), the act of throw- ing off waste matters from the body. Func'tion (Lat. fungor, execute), the action of any part or organ of a plant or animal. His tol'o gy (Gr. histos, a web, or tissue, and logos), the study of minute anatomy. Hy'dro gen (Gr. hydor, water, and gignomai, be bom), a colorless, gaseous element forming a part of water. In or gan'ic, not organic. Mag ne'si um (Gr. Magnesios, a district in Thessaly), a silver- white, solid, metallic element. Mat'ter (Lat materia, stuft), any- thing having extension. Ni'tro gen (Gr. nitron, nitre, and gignomai), a colorless, gaseous element composing four fifths of the air. Nu tri'tion (Lat. nutrio, feed), a series of processes by which liv- ing things maintain their life and growth by appropriating food. Or gan'ic (Gr. organon, an organ), pertaining to plants and animals. Ox i da'tion, the process of uniting chemically with oxygen. Or'gan ism, a living plant or ani- mal. Ox'y gen (Gr. oxys, sharp, and gignomai), a colorless, gaseous element, forming one fifth of the air. Phys i ol'o gy (Gr. physis, nature, and logos), the science which treats of living things. Zo ol'o gy (Gr. zoon, an animal, and logos), that part of biology which treats of animals. CHAPTER IV. GRASSHOPPERS AND CRICKETS. Directions for Work. Collect full-frrown and partly grown locusts or grasshoppers. Place some of the living insects in tumblers with fresh lettuce-leaves. Allow ventilation. Why ? Watch the insects care- fully and compare with a prepared specimen. In your note-book answer the questions below. Shape of Body. What is the shape of the body ? Are the two sides alike (bilateral symmetry) ? Is the skeleton or hard part of the body external or internal .'' The Abdomen. The chief divisions of the body arc the head, thorax, and abdomen. How many sct,rments has the abdomen .' Count the segments of the abdomen in several specimens. Is the number the same in all cases ? Do you find a row of breathing-holes (spiracles) along either side of the abdomen .' Do you find a ridge running lengthwise along the abdomen just below the spiracles ? This ridge repre- sents the softer parts of the segments. These softer portions enable the insect to move the upper and lower parts of the segments farther apart to take in air while inhaling. When they are brought together again the air is expelled. The upper hard part of each segment is called the tergum, the under part is the sternum, and the more flexible part on either side the plcurum. Can you see the movement of the abdomen made by breathing ? 32 GRyiSSHOPPERS ylSD CRICKETS. 33 Do you find the so-called ear-dnim 'UTnpanum on the first segment c f the abdomen ? The female grasshopper has organs at the end of the abdomen for placing her eggs in the ground (o\'iposi- tors). Do you find both male and female g^sshoppers ? Sketch a side view of a grasshopper's abdomen X f ■ The Thorax, \\~hat appendages are attached to the thorax ? How manj' segments in the thorax ? How many legs do \"ou find ? Are thej- jointed ? How do they differ in size ? Sketch one of the hir.c legs, indicating all the parts X 5 - How^ many wings do you see ? Are any of the wings folded ? How ? Sketch a fi^ont and a hind wii^ fully extended X 5- To what segments are the wings attached ? What can you saj^ of the grasshopjjer's jxjwers of locomotion ? How man\- times its length can a grass- hopper jump ? Do the grasshoppers j-ou have seen use their wings when they jump .' How do the wings of young grasshoppers compare with those of fiill-grown insects ? The Head. How many feelers do you find on the front of the head (antennae) ? Are they segmented ? What is their shape .' How does their length compare with the length of the bod)' ? Sketch a side view of the head showing feelers. How many eyes do you find ? Compound eyes are made up of parts called facets. Small, simple eyes are called ocelU. How many compound e}-es has the grasshopper .' How many ocelli .' Where are the eyes and ocelli situated .' Sketch a part of a com- pound eye as seen under a microscope. What is the shape of the upper lip (labrum j .' Sketch. Under this lip do j'ou find hard jaws (mandibles'j ': How many ? What color .' \\Tiat shape ? In what direction do they move .' Sketch. 34 yINlMAL ACTiyiTIES. Do you find a tongue ? Do jou find a pair of softer jaws (maxillae) behind the mandibles ? Sketch. What is the shape of the lower lip (labium) ? Do any of the mouth-parts have feelers (palpi) ? Where situated ? How many ? Does the insect bite or suck its food ? Notice the movements of its mouth-parts. Touch gently the grasshopper's feelers with a tooth- pick or stick. Touch in the same way other parts of the body. WTiere is it most sensitive to touch .' How far can a grasshopper see ? How do you determine this .■* Can the grasshopper hear ? Give a reason for your answer. Does the grasshopper have the sense of smell .' What can you now say about the grasshopper's mode of taking food ? its respiration ? locomotion .■' its organs of sense or discovery .■' Rinnmary of Drawings, (a) Side view of abdomen X 5- (^) Sketch of one of the second and one of the third pair of legs X 5 • The parts of the leg, beginning at their union with the body, are coxa, trochanter, femur, tibia, and tarsus. Indicate these p>arts in }-our drawing. {c) Sketch of fi-ont and hind wings X 5 • (d) Side view of a grasshopper's head X S- {e) Sketch of mandible X lo. (/) Sketch of maxilla X lo. (jf) Sketch of upper lip X 20. (Ji) Section of compound ej-e (microscof)e). Internal Structure. If we wish to examine the internal structure of a grasshopper, we may prepare specimens by hardening tliem in alcohol. This changes the color and to some extent alters the size and general appearance of the organs. On this account it is well to examine a freshly killed specimen along with the alcoholic specimen for purposes of compeu-ison. GRyfSSHOPPERS AND CRICKETS. 35 For the purpose of dissection a female grasshopper should be pinned to the bottom of a dissecting-pan and covered with water. The dorsal wall of the abdomen should then be cut away with a pair of scissors, care being taken to notice the delicate tube, the heart, lying along tlie back. In the freshly killed specimens, the Fig. 3S. — The Parts of a Locust, u, head; b, eye; c, antenna; d,f, i. thorax; ab, abdomen. tracheje, or air-tubes, connecting with the spiracles on tlie outside, and ramifjang to all parts of the body, may be easily seen. At the same time a cluster of long, oval, j'ellow eggs may be seen on each side of the body, near tlie anterior part of the abdomen. From these a tube, the oviduct, leads backward to tlie o\"i- positors. Below the heart the digestive canal may be 36 ANIMAL /ICTiyiTIES. seen, consisting of the oesophagus, or gullet, a large crop, a stomach with many tubes called gastric cseca, and an intestine reaching to the anal opening. Lying along the ventral portion of the abdomen are masses of nerve-matter called ganglia, a double mass or pair of ganglia to each segment. These are connected by nerves. All the ganglia, with one exception, the supraoesophageal ganglion, or bi-ain, lie below the digestive tract. This arrangement of organs, the heart dorsal, the nervous system ventral, and the digestive tube between is characteristic of insects. It is interesting to observe Fig. 39. — Comparison of Grasshopper and Man. A, anterior; P, pos- terior; D, dorsal; V, ventral; n, nervous system; h, heart; /, food- tube. how this arrangement compares with that in the human body (Fig. 39). Taking Food. The grasshopper lives entirely on vegetable food. Although its mouth-parts appear much complicated, they are well adapted for their GRASSHOPPERS AND CRICKETS. 37 work. The palpi feel about and locate tlie juicy parts of plants, the maxilla; seize and hold them in position, while the hard mandibles tear the food into bits and pass it along to tlie digcsti\ e organs. Plants are able to build from mineral substances the materials which are useful food for the grasshopper, tlius illustrating tlie well-known fact tliat \\ithout plants animals would die. Even animals which never eat plants subsist on other animals which depend on plant-food. As far as we know animals are unable to take nitrogen unless it has been previously made into plant-tissues which are suitable for animal food. Nutrition. It is not our purpose here to describe in detail the processes of nutrition in animals having so highl\- developed a digesti\-e s\stem as we find in the grasshopper. It is enough to say that the food passes through a long tube extending from the moutli to the anal opening at tlie posterior part" of the bod}-. This tube is often called the food-tube or alimentary canal. In the grasshopper and similar insects it is enlarged in one place to form a gizzard or grind- ing stomach. In some grasshoppers this gizzard is armed \\ ith teeth. There are also two other enlcirge- ments known as tlie crop and tlie stomach. In its course through this tube tlie food is acted upon by fluids \\-hich soften it and change it chemically so that the nutritixe portion is able to soak tlirough the walls of the food-tube into the blood, which distributes it to all parts of the body, where it is used to build up tissue or to ser\e as fuel for heating tlie body. The portion of the food which is not so softened passes through the tube and is tinallv expelled from the bod\- at the anal opening. Respiration. Taking Oxygen and Excreting Waste Stibstances. Food is useless to animals without a supply of air and an outlet for carbon dioxide, water, and urea. M.m regularl\" inhales and expels air about eighteen times a minute. This process is so important 38 /(NIM/iL /tCTlVITIES. that we often speak of the " Breath of Life ". If we cover the lioles along the sides of the grasshopper's body, so that no air can enter, he dies, just as we should die if deprived of air. Throughout animal life this same necessity for air exists. The air used by the grasshopper for breathing pur- poses enters the body through little holes along the sides of its abdo- men and thorax. Eight of these openings may be easily seen on Fig. 40.— The Trachea of an Insect {magni- each side of the fi^'^)- abdomen, and two others o n each side of the thorax. These holes, or spiracles, open into air-tubes, called tracheae, which divide and subdivide in order to send branches to every part of the body, even into the wings. These tubes and their branches are surrounded by blood-vessels through which blood is constantly coursing. The oxygen of the air filters through the walls of the tracheae into the blood, and the carbon dioxide, water, and other 'waste substances in the blood pass through the same walls in the opposite direction. Such an interchange of gases through a membrane is called osmosis. Not only do these breathing-tubes carry oxygen to the blood and remove the waste products of respiration, but they also render the body very light, enabling the insect to rise easily in the air. In addition to excreting waste substances by breathing, the grasshopper pours urea into the food-tube and thence out of the body. Reproduction. But animals or plants never eat enough to make them grow or live forever. In many common plants a single cell, called an ovum, is set apart and fertilized by union with another cell to form a seed, which, under proper conditions, reproduces the plant. In the grasshopper the e.^% corresponds to the GRASSHOPPERS AND CRICKETS. 39 seed of the plant. It, too, is a single fertilized cell set apart for reproduction. The grasshopper deposits her eggs in the ground, using for this purpose the oviposi- tors at the end of her abdomen. From these eggs there hatch tiny insects much like their parents in shape, but destitute of wings. After a few days of eating, the little grasshopper becomes too large for his hard skin (exoskeleton), and proceeds to change it. The process of crawling out of the old skin is called Fig. 41 Cockroacli and Cast Skin. moulting. In this way he moults five times, after each moult appearing in every way more like the parent grasshopper. Like most other insects grasshoppers deposit an enormous number of eggs. Discovery. If one touches a stone it does not move, but if, on the other hand, one touches the feelers of a grasshopper, or moves a stick in front of its eyes, there is a movement in response to the irritation. This movement is usually entirely involuntary, like the 4° ANIMAL ACTIVITIES. movement of the eyelids when a sudden blow is threatened. Very simple and familiar illustrations of this power are common even among plants. In higher animals the response to external stimuli is often so complicated with voluntary movements that the two can hardly be distinguished, but in every animal there doubtless exists the power to respond in some way to movements of the world outside its own body. These movements may affect the animal through simple touch, or through any or all of the other senses. Every animal has at least one of the five senses. Fig. 42. — The Nervous Cliaia of a Cockroach. Sight. Although the eyes of the grasshopper are large and composed of many parts, his power of vision is doubtless far inferior to ours. Many experiments have been made on the sight of insects, and all seem to show that they can neither see far nor clearly. The compound eyes of insects, as we have seen, are made up of many hexagonal facets. Each of these facets has a tiny lens for focussing the rays of light on a nerve which transmits vibrations caused by these rays to the nerve-centres within. Hearing. The hearing of the grasshopper is prob- ably more acute than his sense of sight. Vibrations of the air set in motion the ear-drum on the first seg- ment of the abdomen, and these are conveyed to nerves which connect with nerve-centres in the thorax. The fact that grasshoppers and their relatives are able to make noises which doubtless are understood by their friends is a reason for believing that they can hear. These noises do not issue from organs of speech GRASSHOPPERS AND CRICKETS. 41 Fig. 43 Portion of the Cornea of a Fly's Compound Eye (magnified). like ours, but are more like the sounds we produce when playing on a violin. Careful observation of a male cricket will best show us a method of stridulating , as this process of insect-talk- ing is called. Watching a cricket as he stridulates, one can see that the outer wings are raised and rapid- ly moved from side to side. If, now, the wing be ex- amined with a microscope, a clear membrane remind- ing us of a drum-head will be seen on each wing, and on the under side of each outer wing will be found an enlarged roughened cross- vein which is used like the bow of a violin, being drawn across the edge of the opposite wing- cover to set in motion the membranous drum-heads. The cricket's organ of hearing is situ- ated on the tibia of the front leg. Some insects hear by means of hairs on the antennae or elsewhere which move in unison with vibrations about them. In some cases insects may be able to hear sounds entirely inaudible to human ears. Taste and Smell. The sense of taste probably resides in the palpi. That the grasshopper can smell is evident from the way in which he chooses his food, and also from the fact that certain odors seem disagreeable to him. Touch. That the grasshopper pos- sesses the sense of touch is easy to prove, and that the antennae are especially sensitive as tactile organs is equally evident. The antenna are provided with Fig. 44..— The Hearing Organ of a Cricket {magnified ). 42 /INIM/IL ACTIVITIES. hairs which seem to increase their sensibility, and they are connected with the nerve-centres within the body, as are the other organs of sense. Movements. In addition to the motion called forth by irritation of the sense-organs, the grasshopper is evidently able to move on his own account. He can walk, fly, or jump where and when he wishes. The Fig. 45 The Stridulating Organ of a Cricket. u, large vein; l>, roughened cross-vein; c, membrane. adaptation of the legs to the mode of life needs no comment. The structure of the wings, however, may be briefly considered. The wings are outgrowths of the hard exoskeleton. They are composed of a frame- work of double tubes over which is stretched a mem- brane. The inner tube of one of the veins carries air. The outer tube surrounding this is filled with blood. Thus the wing becomes an organ of respiration as well as an organ of flight. Lightness and strength are also obtained at the same time. Comparison of Grasshopper and Cricket. Crickets are easily collected. They may be studied in the same way as the grasshopper. In writing notes concerning the cricket, make use of the new descriptive words learned while studying the grasshopper. Write in your note-book only such facts as can be made out from the specimens. At the top of the page in your note-book ^rite "Grasshopper and Cricket". Draw a vertical GRASSHOPPERS AND CRICKETS. 43 line down the middle of the page. At the top of one column write " Resemblances ", and at the top of the other column write "Differences". In these spaces write all the resemblances and differences you can make out from actual observation. Notice with especial care the tibia of the front leg in order to see the ear-drum. Look on the under side of the wing-cover of the male cricket for the roughened vein used in stridulating. The pair of appendages at the end of the abdomen are called stylets. Make a drawing of a cricket as you see it. Questions, i. How do a grasshopper's activities differ from those of man .? 2. Is it an advantage in insect-life to have the nervous system on the ventral part of the body .' Why.? 3. In what respects is a segmented body an advan- tage to an animal .-" 4. At what time of year are grasshoppers most abundant ">. 5 . Whence come the grasshoppers seen in the fields in spring .' 6. Would it be wise to rid the world of grass- hoppers .'' Why .'' 7. Why does the grasshopper breathe .' What chemical changes occur in breathing .? 8. What is the color of the grasshopper's blood .■• 9. What senses has the grasshopper .■" 10. What are the differences between organic and inorganic things ? 1 1 . What are the points of similarity .' 12. What are some of the differences between plants and animals .' Topics for Reports. The Locust Scourge. Locusts as Food. How to Destroy Locusts. The Life-history of a Locust. The Cockroach. Crickets. Walking- sticks. 44 ANIMAL ACTiyiTIES. VOCABULARY. Ab do'men (derivation uncertain), the posterior part of the body in insects. An ten'na, pi. antenna (Gr. ana, up, and teino, stretch), a feeler growing from the head of an in- sect. An te'ri or (Lat. ante, before), front. Bi lat'er al (Lat. bis, twice, and latus, side), having two sides alike. Chi'tin (Gr. chiton, a tunic), the horny substance forming the exo- skeleton of insects. Cox'a (Lat. coxa, the hip), the joint of an insect's leg next the body. Dor'sal (Lat. dorsum, the back), opposed to ventral. Fac'et (a diminutive of face), apart of a compound eye. Fe'mur (Lat. femur, the thigh), the thigh. La'bi um (Lat. labium, lip), the lower lip of an insect. La'brum (Lat. labrum, lip), the upper lip of an insect. Man'di ble (Lat. mando, chew), the hard, biting jaw of an insect. Max il'la (Lat. macero, soften), the softer jaw behind the man- dibles of an insect. Mes tho'rax (Gr. mesos, middle, and thorax), the middle segment of the thorax. Me'ta mor'pho sis (Gr. met a, over or beyond, and morpho, form), the changes which take place in an animal from egg to adult. Met a tho'rax, the posterior seg- ment of the thorax. Moult (Lat. muto, change), the shedding or casting of the exo- skeleton. Nymph (Gr. nymphe, a bride), a name applied to the young of some kisects, as the grasshopper. cel'lus (Lat. dim. oioculus, eye), a small eye. vi pos'i tor (Lat. ovum, egg, and pono, place), an instrument for depositing eggs. Pal'pus, ^\. palpi IJjaX. palpo, feel), a feeler growing from one of the mouth-parts. Pleu'rum (Gr. pleuron, rib), the side of the segment of an insect. See Fig. Pos te'ri or (Lat. post, after), hind. er. Pro tho'rax (Gr. pro, before, and thorax), the first segment of the thorax. Spir'a cle (Lat. spiraculum, air- hole), a breathing-hole. Ster'num (Gr. sternon, breast), the ventral portion of the segment of an insect. Strid u la'tion(Lat. strido, creaks), a creaking noise made by in- sects. Tar'sus (Gr. tarsos, a flat surface), the foot of an insect. Ter'gum (Lat. tergum, bjick), the dorsal part of the segment of an insect. Tho'rax (Gr. thorax, the chest), the middle division of an insect's body. Tib'i a (Lat. tibia, shin-bone), the part of an insect's leg between the femur and foot. Tra'che a (Gr. tracheia, rough), one of the breathing-tubes of an insect. Tro chan'ter (Gr. trecho, run), a part of an insect's leg between the coxa and femur. Tym'pa num (Gr. tympanon, a drum), an ear-drum. Ven'trai (Lat. venter, the belly), pertaining to the belly, the part opposite the back. CHAPTER V. BUTTERFLIES AND MOTHS WITH THEIR PROTECTIVE DEVICES. Directions for Work. Watch the caterpillars which have been collected in accordance with the directions previously given. Record the changes that occur. How many segments of the caterpillar have legs ? How many of these legs are jointed ? If the jointed legs are attached only to the thorax, how many segments has the thorax ? Does the caterpillar have eyes ? antenna } palpi .■' Do you find mandibles and maxills ? Some of the caterpillars will change to chrysalids soon after collecting. In one of these chrysalids can you find head, thorax, and abdomen } Is the chrysalis capable of any movement .'' Can you find antennae, eyes, or palpi .■■ Do you find wings or legs ? Can you see parts of any organs under the skin ? Collect several common yellow butterflies, or the white cabbage-butterflies. Where do you find them .' At what time in the day do they seem to be most active .' On what plants do they feed ? How do they take their food ? Notice how they fly and how they walk. How do they hold their wings when at rest .' Secure some eggs, if possible, and watch their development. 45 46 ANIMAL ACTIVITIES. The Prepared Specimen. Examine the butterfly after it has been killed, and write the resemblances and differences for butterfly and grasshopper as in the case of grasshopper and cricket. Consider all the points noted concerning the grasshopper. Consider the stages of growth. Study with care the coiled tongue, or proboscis. Uncoil it and find out how it is used. Remove the dust from a part of the wing. Is this part of the wing now colored .' With a microscope Fig, Antennae of Lepidoptera. A, of butterflies ; B, of moths. Note note the shape of the particles of dust (scales), also how they are arranged on the wing. Measure the spread of the wings, the length and width of the anterior wings and of the posterior wings, the length of the body, and the length of the antennse. Describe the color above and below, and state the color and location of the markings you find. Notice the color of the feet, the antennae, and the eyes. Read the description of this butterfly in a good refer- ence book, and compare your own observations witt those there recorded. BUTTERFLIES AND MOTHS. 47 Write a description of a butterfly whose name is unknown to you. WVite a description of a moth. Summary of Drawings, {a) The wings as seen from above when fully extended. {b) Side view of butterfly with wings closed. {/) Side view of head — enlarged — showing proboscis and e}'e. (d) Imaginary cross-section of proboscis. {e) Larva, pupa, and imago of some butterfly not figured in the text-book. (/") The scales from a butterfly's wing as seen with a microscope. is) ^ portion of a wing, showing the arrangement of the scales. How to Tell Moths from Butterflies. Butterflies and moths are much alike. They ma}' generally be distinguished by the fact that the butterfly has knobbed antennae, holds its wings erect in repose, and flies more often in the daj-time. The moths often have feathered antennae, fold their wings horizontally over the back when at rest, and more often fly at night. Metamorphosis. The internal structure of the butterfly closely resembles that of the grasshopper, but Fig. 4.7. — Eggs of Lepidoptera. a striking difference appears in its metamorphosis, or the change it undergoes during its period of growth. The j'oung grasshopper when it emerges from the egg looks much like the adult insect; from which it diff^ers chiefly in its smaller size and in possessing smaller wings. A series of changes like that observed in the case of the grasshopper is spoken of as incom- 48 ANIMAL ACTIVITIES. plete metamorphosis. On the other hand, there emerges from the egg of the butterfly a worm-like animal totally unlike its parents, who, could they see their offspring, would doubtless disown it. This Fig. 48. — Some Larvse of Lepidoptera. larva, as we have seen, has biting mouth-parts, fit- ting it to subsist on the leaves of plants. It eats voraciously, consuming many times its weight of food during its short life, and increasing rapidly in size. It Fig. 49. — Some Cocoons and Chrysalids. moults from time to time as its skin becomes too small for its fast-growing body. During this period of its life it is usually a destructive pest. The ravages of many caterpillars are already too well known. BUTTERFLIES AND MOTHS. 49 Finally, the larva seems to have eaten enough. It brings to a close its life of unceasing feeding and pre- pares for a period of sleep. Often it spins a silken cocoon in which it rests throughout the winter ; some- times it hangs by a single thread to a rock or fence- rail, its exoskeleton making a beautiful chrysalis ornamented with spots of burnished silver, jet, and gold ; again it buries itself in the ground to await the genial warmth of returning spring. In any case it takes no food and seldom moves, but within its body changes progress, until the full-grown butterfly or moth breaks through the hard case of the pupa, stretches and dries its wings for a short time, and flies away for its brief period of aerial life. The full-grown but- terfly, or imago, no longer eats the coarse food familiar to its lar- val stage. In fact, it could not do so if it would, for its mouth is no longer fitted for biting, but is provided with a long proboscis with which it sucks honey from its favorite flowers. This series of changes is known as com- plete metamorphosis (Fig. 50). Structure of the Proboscis. The proboscis is a curious organ and well repays careful study. It is composed of two long half-tubes which are produce Fig. 50. — A Cabbage-butterfly, a larva; b, pupa; c, egg; d, imago. 5° ANIMAL ACTIVITIES. by the elongating of the maxillje of the caterpillar while it is in the pupa stage. These join by their edges to form a complete tube which the butterfly can coil or uncoil at will and in- sert in the flower on which it feeds. At the upper part of this proboscis there is a pump-like cavity provided with a valve. When this enlarges, the tip of the tube being inserted in the cup of honey, the liquid flows up the tube and fills the cavity. The cavity then contracts under the influence of the surrounding muscles. This causes a pressure which compels the valve to close and forces the honey for- ward into the stomach (Fig. 51). Depositing Eggs. At the adult period of its life, however, the butterfly is not a great eater. Its most important function, now, is reproduction, and for this purpose the female butterfly searches for the plant which will furnish suitable food for her young brood of caterpillars and deposits there her eggs, dying soon after the performance of this function. The eggs of the clover-butterfly are placed upon the under side of clover-leaves, one to each leaf. The eggs of the tent- caterpillar, so common on apple- and cherry-trees, are laid in large clusters glued to the branch of the tree by a gummy substance produced by the moth deposit- ing the eggs. In many cases the eggs of butterflies and moths show beautiful markings when studied with the aid of the microscope. Butterfly Enemies. If all the eggs of all the butter- flies and moths should be allowed to reach maturity Fig. 51. — Head of a Moth. a, upper lip; 6, mandibles; c, proboscis; d, under lip; e, antennae; /, eye. BUTTERFLIES AND MOTHS. 51 during a single season they would kill all vegetation on the earth. The number of eggs deposited is enormous, and the few which reach the caterpillar stage make great havoc with our orchards, and often with our shade-trees. The gypsy-moth alone, in spite Fig. 52. — The Kallima, natural size. Drawn by A. E. Sanford. of great efforts, still does much damage. The number and activity of caterpillar and butterfly enemies in most cases holds them in check and allows only a small number to come to maturity. Both two-winged and four-winged flies deposit their eggs on the larvae or pupae of butterflies or moths. When these eggs hatch they produce larvae which feed on the fat and muscle of their involuntary host and finally destroy its life. A living, but nearly dead, caterpillar bearing on 52 ANIMAL ACTIVITIES. its back a great number of pupa-cases of such flies is no uncommon sight (Fig. 67). Birds, too, devour im- mense numbers of insects in all stages of growth. Doubtless they would kill and eat all the insects were it not for the fact that many of them are so wonder- fully protected by their color or shape, or both. Protective Coloration. A butterfly or moth when pursued often disappears as if by magic, and only the most careful search reveals its presence. Then it is Fig. 53. — Catocala Nupta. seen that the insect has been rendered invisible, not by the helmet of Perseus, but by its resemblance to some natural object common in its vicinity. The Kallima, a large and brilliant butterfly of India, folds its wings and alights on a branch. The folding of the wings conceals every brilliant color, and the under side of the wing, which is now alone visible, resembles so accurately a leaf that a bird could find it only with great difficulty (Fig. 52). Some of our common moths, belonging to the genus Catocala, have outer wings so closely resembling the bark of birch-, poplar-, or willow-trees that when they alight on one of these trees they cannot be seen by a casual observer. Other cases of protective coloring are to be met with at every turn in the study of Zoology, and it is a part of the work of the student to find and describe them. BUTTERFLIES /tND MOTHS, i S3 Mimicry. The common milkweed-butterfly has a disagreeable odor and probably a disagreeable taste. On this account it is not a favorite food for birds. The Fig. 54. — The Milkweed-butterfly, u, dorsal view; B, ventral view. One half natural size. Drawn by A. E. Sanford. Fig. 55. — Limenitis Ursula, a, dorsal view ; b, ventral view. One half natural size. Drawn by A. E. Sanford. Limenitis Ursula, a smaller butterfly, furnishes a dainty morsel for bird palates. It would soon be exterminated were it not for the fact that it so closely resembles in color and markings the milkweed-butterfly, to which 54 ANIMAL ACTIVITIES. it is not closely related in structure or in mode of growth (Figs. 54 and 55). Such imitations of other animals less likely to suffer from enemies are common throughout the animal king- dom. In these cases, neither the mimic nor the animal mimicked is supposed to act consciously. No intelli- gence on the part of the animal itself is shown by such mimicry, for even if it intelligently wished to change its color, no butterfly could do so. The theory which is now generally believed by scientists to account for these protective devices and the thousands of others that have been observed may be briefly illustrated by considering the family history of the moth whose wings resemble birch-bark. Natural Selection. It is supposed that the earlier members of this family did not have the outer wings so marked, but that from a brood of caterpillars there hatched moths like the parent moths, yet varying to some extent on account of unknown causes. Some of these varying moths had markings on the outer wings which made them resemble in some slight degree the birch-tree on which they were accustomed to alight. It is evident that these protected moths would be less likely to be eaten than those not resembling the birch- tree ; hence they would be preserved to deposit eggs, while their less fortunate brothers and sisters would be eaten. The next brood of moths, resembling their parents as they must, would be likely to include a greater number of protected individuals, and probably some even better protected than their parents. Those best protected would be allowed to produce offspring, while the less favored would be destroyed. In this way after many generations the protective resemblance becomes more and more pronounced. This process has been called "natural selection". It is thought to explain many of the changes which have taken place in the history of both animals and plants. It is easy to see that there is really no rational selection on the BUTTERFLIES y4ND MOTHS. SS part of the animals themselves. The name was given because the process resembled somewhat the process by which bird-fanciers obtain different varieties of pigeons by "selecting " birds with peculiar markings for breeding purposes, or by which gardeners obtain new varieties of flowers by continually ' ' selecting ' ' the few having desirable peculiarities and obtaining seeds from these for the production of more and more desirable plants. In natural selection there is no bird- fancier and no gardener. On this account the process Fig. s6a.— Moth at Rest. Fig. 5 6^.— Butterfly at Rest. has been spoken of as the "survival of the fittest". In this case the " fittest " is the individual best adapted to his surroundings and best protected in every way. In these days the student of animals or plants is con- stantly on the watch for new illustrations of adaptation to surroundings on the part of living organisms. Questions, i. How do moths differ from butterflies in structure and in habits .■" 2. What are the differences between complete and incomplete metamorphosis .' 3. How much can a butterfly see .'' 4. How much can a caterpillar see .-' 5. Do either caterpillar or butterfly have a sense of smell .'' of hearing .' 6. What are some enemies of butterflies .■" 56 ANIMAL ACTIVITIES. 7. How are butterflies protected ? 8 . Does the pupa of a butterfly breathe ? 9. Do you know any common animals which are protected by their color ? Topics for Reports. The Silk- worm. The Gypsy- moth. The Clothes-moth. The Life-history of Cecro- pia. The Metamorphosis of Lepidoptera. How to Destroy the Most Injurious Lepidoptera. Insects as Food. VOCABULARY. A'nus (Lat. anus, a ring), the opening of the digestive canal opposite the mouth. Chrys'a lis (Or. chrysos, gold), the naked pupa of a butterfly. Cos tal (Lat. casta, a rib), the ante- rior part of a wing. Co coon' (Lat. concha, a shell), the silken covering of a pupa. Gan'gli on (Gr. ganglion, a tumor), a nerve-mass. Haus tel'late (Lat. hauslrum, a water-drawing machine), having mouth-parts fitted for sucking. I ma'go (Lat. imago, likeness), the adult insect. Lar'va (Lat. larva, a mask), the stage of metamorphosis immedi- atsjv liucceeding the egg. Wan di bu late (Lat. mando, chew), having mouth-parts fitted for biting. Ko'tum (Gr. notos, back), the dor- sal surface. Pri'ma ry wings (Lat. primus,- first), the first pair of wings. Pro bos'cis (Gr. pro, before, and bosko, feed), the sucking tongue of a butterfly. Pu pa (Lat. pupa, a doll), the stage of metamorphosis after the larva. Sec'on da ry wings (Lat. secun- dus), the second pair of wings. Vein (Lat. vena, a blood-vessel), one of the vein-like ribs of an insect's wing. Vein'ules, branches of veins. CHAPTER VI. SOME INSECTS CLASSIFIED. Tlie Bluebottle Fly. Expose a piece of fresh meat in a sunny place for a short time and these flies will collect on it. Capture some of the flies and observe them carefully. How does the fly feed .'' You can study the mode of feeding of the common house-fly by fastening a piece of sugar to a slide and placing it under a microscope in a place where flies are plentiful. What kind of food does a common house-fly prefer .' How do you know ? Devise an experiment for determining what kind of food the house-fly particularly likes. In experiment- ing with foods try sugar, honey, salt, pepper, water, and other substances. Does sight or smell seem to guide the fly to its food .■" How does a low temperature affect flies .■' How do you know } How do the flies make their buzzing .' Keep a few bluebottle flies under a tumbler with a bit of meat until eggs are deposited. Remove the flies and watch the development of the eggs. Does the fly have complete or incomplete metamorphosis .■' How many wings has the fly ? How many segments has the fly's abdomen .'' See if you can find a winglet behind the wing. Using a lens, do you find a pair of balancers behind wing and winglet ? Is one of the segments of the thorax larger than the rest ? 57 S8 ANIMAL ACTIVITIES. Do you find spiracles on either thorax or abdomen ? Do you find eyes and ocelli ? Do you find antennae ? Write resemblances and differences for fly and grass- hopper. Fig. 57. — Larva and Pupa of the House-fly. b, larva imagnified)\ c^ pupa(/«a^- nified). Fig. 58.— Right Wiiiglet o f Bluebottle {magnified). Fig. 5g. — Balancer of Bluebottle {magnified . Summary of Drawings. («) A fly as seen from above with the wings extended at right angles to the body X 5- (6) The larva and pupa of a fly X S • (c) One wing X 5- (d) A balancer much enlarged. (e) One antenna as seen with the microscope. (/) One leg and foot as seen with the microscope. SOME INSECTS CLASSIFIED. 59 Fig. 6o. — Portion of a Fly's Foot {magnified). Fig. 6i. — Side View of Proboscis, partly opened. l>. basal division; c, central division; /, labella; m, maxillary palpi. -> '0 HI 3 4-> O > T) 1- c u. t/) 11) (U -M c o c e S ■M fl) ^ tU) +3 c r: -M 3 ^ O) o C o O ^ u 11 >, ->-> XI o c )-> 3 O >. Wi o (U be ni CU ni V 3 P^ i 1 m 1 >> 1 3 2 o 6 a S i 'a s '■3 If 1"^ i .S 1 1 E 3 1 11 V a. Is 3 i bo 1 s s . •sg. s e 1 .2 ^ s tl SOME INSECTS CLASSIFIED. 63 By comparing the notes we have already made we find that the insects so far studied have bilateral symmetry , jointed bodies, and jointed appendages, as legs and antennae. They have three parts to the body; iiead, thorax, and abdomen. All have six jointed legs, and in the adult stage one or both sexes are usually provided with wings. Commonly two pairs of wings and a pair of compound eyes are present. An examination of the internal structure of insects shows a series of ganglia connected by nerves situated along the ventral portion of the body. Above this is found the digestive cavity, consisting of a tube more or less branched extending lengthwise of the body, from the mouth to the anus. Near the dorsal part of the body is found a large blood-vessel which performs the function of a heart. Breathing is carried on by means of spiracles con- nected with tracheae. Naturalists have agreed to call animals having these characteristics " Insecta ". Differences. But the class Insecta contains so many individuals that we readily see the necessity of classify- ing them in some way. The divisions of classes are called orders. If we can divide the class Insecta into orders we make our future study more systematic and more satisfactory in many ways. Such a classification must depend on differences as well as resemblances. If we should study the mouth-parts alone of the insects we have already examined, we could easily put them into two orders or subclasses, one comprising those insects which have biting mouth-parts and the other those which have sucking mouth-parts. This division is sometimes used, but for our purpose it will be better to find some differences which will give us a greater number of orders, and so greater convenience. A mode of separation based on peculiarities of the wings has been much used, and the common names for some of the orders as now most often written attempt to describe peculiarities of wing-structure. 64 /iNIMAL ACTll^ITIES. But this scheme of classification seems too artificial, that is, too much like the classification of inanimate things like tables or chairs, which may be arranged for convenience into classes according to use or shape. The course of development from egg to adult is also an important factor in classifying living things, because it is thought to show better than anything else the natural relations or affinities, or we might say the blood-relations of animals : hence in classifying insects the matter of metamorphosis must be considered. In a superficial way we might divide insects into those having complete and those having incomplete meta- morphosis, or into those having terrestrial larva; and those having aquatic larvae; but more careful study shows that these differences alone are not sufficient for a clear and systematic classification, nor do they, alone, indicate relation by descent. In fact, it has been found that with the best of effort in the matter of classification, so many intermediate forms occur that a series of individuals rather than a few orders result. Still convenience demands a classification of some kind. Taking into consideration as many differences as possible, and ignoring some of the less obvious peculiarities, we may include all insects in nine orders: Name. Typical Insect. Thysanura. Springtails. Pseudoneuroptera. Dragon-fly. Orthoptera. Grasshopper. Hemiptera. Squash-bug. Neuroptera. Caddis-fly. Coleoptera. Colorado beetle. Diptera. House-fly. Lepidoptera. Butterfly. Hymenoptera. Bee. Characteristics of the Orders. We give below the characteristics of these orders, noting chiefly the facts SOME INSECTS CLASSIFIED. 65 concerning wings, mouth-parts, and metamorphosis. There are, of course, many insects which do not fall easily into one of the orders as we have defined them, but it must be remembered that no classification of living things can be made to include all individuals. Some authors make a greater number of orders of Insecta, but the list here given is thought to conform to the best usage of writers on natural history. Thysanura. These are small wingless insects with biting mouth-parts and incomplete metamorphosis. The Pseudoneuroptera have two pairs of wings, very nearly alike in most cases. Their wings are very thin and transparent and closely veined and not capable of being folded. The rnouth-parts are fitted for biting and the metamorphosis is incomplete. The Orthoptera commonly have two pairs of wings, the under wings being folded like a fan, and protected by the outer pair. The jaws are strong and fitted for biting, and the metamorphosis is incomplete. The Hemiptera, though sometimes wingless, have more often two pairs of wings. In some hemiptera the outer wings overlap on the back, the overlapping half of each wing being thin and membranous, hence the name. The mouth-parts are fitted for sucking, being prolonged into a beak used for piercing. They have incomplete metamorphosis. The Neuroptera resemble the pseudoneuroptera in wings and mouth-parts and have complete meta- morphosis. The Coleoptera have hard outer wings called elytra which protect the inner, gauzy wings, which are folded both lengthwise and crosswise. The mouth-parts are fitted for biting and the metamorphosis is complete. The Diptera have only two wings. The mouth- parts are fitted for sucking and the metamorphosis is complete. The Lepidoptera have four wings covered with scales. The wings do not fold. The mouth is fitted 66 ANIMAL ACTIVITIES. for sucking, having a long proboscis formed of the two maxillae. The metamorphosis is complete. The Hymenoptera have four membranous wings with few cross-veins, the fore and hind wings being commonly hooked together for flight. The mouth- parts are fitted for both sucking and biting and the metamorphosis is complete. Names of Insects. Animals, like plants, are desig- nated in scientific works by two names, the first the name of the genus, and the second the name of the species. Thus, Danais archippus means that the butterfly bearing that name belongs to the genus Danais and the species archippus. We also distin- guish men by using two names. Stuyvesant, Peter, as found in a directory, means that the man in question belongs to the family Stuyvesant, and that he is the particular member of that family known as Peter. Questions. How does the grasshopper differ from all the other insects studied } How does the butterfly differ from the beetle .'' from the dragon-fly .-' from the other insects studied } How does the fly differ from the other insects .'' How does the beetle differ from the other insects } How does the squash-bug differ from the beetle } from the grasshopper. How does the wasp differ from the fly .-' from the other insects studied .' How does the dragon-fly differ from the wasp } from the butterfly } In what respects do all the insects studied resemble one another .■' Topics for Reports. House-flies. Insects in Brooks. Agricultural Ants. Insects in Ponds. Earwigs. The Cicada. Insects in Houses. Insects on Apple-trees. How to Prepare Insects for Cabinets. How to Kill Injurious Insects. Length of Life among Insects. Insect Friends. Sounds Made by Insects. SOME INSECTS CLASSIFIED. 67 VOCABULARY. Bal'an cer (Lat. ii, two, and /anx, dish), one of the poisers of a ■ dipterous insect. Col e op'te ra (Gr. koleos, sheath, and pteron, wing), beetles. Dip'te ra (Gr. di, two, and fteron), two-winged insects. El'y tron, pi. elytra (Gr. elytron, a shield), a thickened fore-wing of an insect. Ge'nus, \}\. genera (Lat. genus, a race), a group of animals or plants commonly made up of two or more species. Hal'ter, pi. halteres (Gr. halteres, jumping weights), a balancer of one of the diptera. Hem ip'te ra (Gr. hemi, half, and pteron\ an order of insects in- cluding the true bugs. Hy men op'te ra (Gr. hymen, a membrane, z.xvApteroii), an order of insects including bees and wasps. In sec'ta (Lat. prefix in, and seco, to cut), a class of Arthropoda including all true insects. Lep i dop'te ra (Gr. lepis, a scale, and pteron), an order of inse including butterflies and moti Nem- op'te ra (Gr. neuron, ner and pteron), the name of an order of insects. Or'der (Lat. ordo, order), one of the divisions into which classes of plants or animals are arranged. Or thop'te ra (Gr. ortkos, straight, ^xiA pteron), an order of insects including grasshoppers. Pseudo neur op'te ra (Gr. pseu- dos, false, and neuroptera), the name of in order of insects dif- fering from neuroptera in hav- ing incomplete metamorphosis. Spe'cies (Lat. species, outward ap- pearance), a subdivision of a genus. Thysanu'ra (Gr. ihysanos, fringe, and oura, tail), the name of an order of small insects. Wing'let, a small winglike fold behind the anterior wing in the Diptera. CHAPTER VII. A CHAPTER OF LIFE-HISTORIES. The Milkweed-butterfly. In speaking of protective coloring we have already mentioned the large and beautiful butterfly commonly known as the milkweed- butterfly. It is known to scientists as the Danais arcliippus or sometimes as the Anosia plexippus. On account of its large size, great beauty, and very general distribution, it has been much studied and its life-his- tory is well known. The female butterfly deposits her eggs one by one on the under side of milkweed-leaves. These eggs when examined with the microscope are seen to be very regu- larly carved in a beauti- ful and delicate pattern. The shape of the Gg^ is shown in Fig. 63. In a few days a little black-headed caterpil- lar, perhaps a tenth of an inch long, emerges from the egg, eats its empty shell for breakfast, and dines upon the milk- weed-leaf, on which it continues to feed for several weeks. At the end of one week, having eaten so much and grown so fast that its skin can no longer hold its body, it spins a bit of silk upon the leaf, waits until its coat splits down the back and then crawls out of the 68 Fig. 63. — Eggs of Milkweed-butterfly. a, single egg, magnified; c, eggs on leaf, one half natural size. After Riley. A CHAPTER OF LIFE-HISTORIES. 69 Fig. 64. — Larva of Milkweed- butterfly, one half natural size. After Riley. slit thus made, a larger and handsomer caterpillar. It moults in this way twice more, and at last looks like Fig. 64, having a pair of horns at each end of its body and being striped with black, white, and yellow. It will be noticed that its first three pairs of legs are jointed and furnished with claws. The other legs, ten in number, are merely fleshy prolongations of the skin, provided with suckers or hooks to aid in crawling. These are called pro-legs, to distin- guish them from the three pairs of jointed legs com- mon to all Insecta. Its mouth is provided with strong mandibles, and its digesting power is enormous. The caterpillar has now reached a length of two inches. After a little time it again becomes restless, leaves the plant on which it has so far lived, and lodges on a neighboring fence or stump. Here it spins a little silk, entangles its hind legs in the threads thus produced, and hangs head downward for a day and a night. Its skin then splits along the back and the caterpillar performs the difficult feat of crawling entirely out of its old covering without the use of legs or mandibles, for these disappear with the old skin. The little spike at the end of its tail is fastened into the web of silk, and its body sus- pended thereby for a period of rest. The skin hardens and the rich ornamentation of green, black, and gold appears. We do not wonder that it is called a chrysa- lis (Fig. 65). There is now no mouth for feeding, for the mouth-parts are undergoing a wonderful change just beneath the skin. The maxillae elongate to form a proboscis, the wings appear and Fig. 65. — Pupa of Milkweed- butterfly, one half natural size. After Riley. 70 ANIMAL ACTIVITIES. may be seen undeveloped within the chrysalis, as may also the antenna, the legs, the segments of the thorax and abdomen, and even the spiracles. At this time the young butterfly must live by using the stored-up energy developed by its enormous appetite in the larval stage. The change now going on is termed pupation. Again moulting occurs, and the imago emerges. At iirst it is soft and flabby, but the blood pumped into the baggy wings quickly distends them and they dry and harden in the sunlight. The body soon attains its full strength and the insect flies away to enjoy a life entirely different from its previous phases of existence. Now it rejoices in two pairs of large and strong wings covered with beautiful scales arranged in regular pat- terns. It sucks honey from flowers by means of its long coiled proboscis. This interesting piece of machinery has already been described. It is doubtful if this magnificent aerial creature, leisurely floating in mid-air, or bravely buffeting the winds, and sometimes sipping a bit of nectar, would recognize one of its brothers or sisters in either its gormandizing larval stage or its inactive pupal condition. Indeed, the graceful mother seems neither to recognize nor to care for the offspring crawling from the eggs she deposits from day to day. Our milkweed-butterfly lives much longer than most of her lepidoptera relatives while in the imago stage. She even migrates when autumn comes and with others of her kindred seeks a warmer climate for the winter. Some of those which do not migrate hide in sheltered crevices to emerge in the spring battered and frayed, but ready to deposit eggs for the new broods which are to people the air of the coming summer. The Cricket. The common black cHcket so often seen in the fields and about our gardens in the late summer and during the autumn is known as Gryllus abbreviatus. His pleasant chirp attracts us to an A CHAPTER OF LIFE-HISTORIES. 7 1 examination of his ways. Putting him under a tumbler over a flower-pot filled with earth, and feeding him with bits of apple or potato and sometimes a little clover, we may easily observe his movements. If we are looking at the male we must watch for the source of his cheerful music, for the males do the talking among crickets. We shall see, when the shrill sound is made, that the outer wings are raised a little and Fig. 66. — Female and Male Aphis. moved rapidly from side to side. A careful examina- tion shows on the inside of the membranous wing-cover a vein extending diagonally across the wing and fur- nished with teeth like those on the corner of a file. On the other wing-cover, near its inner margin, there is a hardened part which scrapes over the file, causing it to vibrate. The membranes of the wing re-enforce the vibration. Thus its voice comes not from its throat 72 /INIMAL ACTiyiTIES. but from its back. In this respect it resembles many other insects. If we are looking at the female cricket we are struck with the length and size of the ovipositors, which con- sist of a pair of grooved appendages which fit together to form a long tube with a sharpened point. In the autumn the cricket bores a hole in the ground with these sharp points and deposits her eggs, where they remain through the winter. In the spring the warmth of the sun causes them to hatch and the little crickets appear. Here we have something very different from the hatching of the milkweed-butterfly's egg. No caterpillar appears here, but a tiny cricket, much like its mother, but lacking wings. These little crickets moult from time to time, at each moult growing more like their parents, until about midsummer, when they attain their full size. Before winter they die. The Aphis. Plant-lice are very familiar pests, whose ravages on the leaves of rose-bushes are well known. There are many kinds of these little destroyers inhabiting as many kinds of plants. They are called Aphides, any one insect being an Aphis. A single aphis with its beak stuck into the juicy part of a leaf, from which it never moves unless forced to do so, constantly filling its stomach with sap, seems, indeed, a mere glutton, but the whole brood of aphides when watched for a summer are a wonder-working community. The laboratory for the study of these strange creatures is ready-made everywhere. Wher- ever rose-leaves grow, a lens will reveal the happenings we are about to relate. In the month of October in temperate climates the wingless female deposits her eggs about the buds of rose-bushes, so that when these develop into leaves and branches in the coming spring the young aphis may have at hand a bountiful supply of rich food. Here the egg stays until the warm sun of March or April assists in the process of hatching. A CHAPTER OF LIFE-HISTORIES. 73 There hatch from these eggs a brood of females, verj- small at first, but, after several moultings, as large as their mothers, and resembhng them in many ways. Xo males are hatched from these winter eggs. The leaf soon becomes covered with a swarm of female insects. Indeed, there are no fathers in these armies of pigmies. They produce no eggs, but proceed to fasten their beaks in a juicy spot and eat and reproduce in a most marvelous manner. From the abdomens of these strange mothers there issues day after day a numberless horde of children hke themselves. These children grow from the mother as buds grow on plants, and then break away to lead an independent life. Each tiny bud in a few days becomes a mother in the same way, and shortly, from a single egg, thousands of wingless mothers sit side b\- side, sucking sap and budding out }-oung with remarkable speed. If a man should Uve a hundred years and count at the rate of one a second, he could not begin to count in his hundred years the progeny of a single aphis for a month. Xow and then winged forms appear, and sometimes an aphis goes through something like a larval and pupal stage, while the colony keeps on increasing with incredible rapidit}' b}" the budding of generation after generation. This reproduction without males is called parthenogenesis . Toward autumn winged males are produced, and again the cycle of existence is renewed. In studying the Ufe-histor\- of the aphis one should notice the relations existing between ants smd aphides. As the aphis sucks the sweet sap from its shrub it obtains an excess of sugar; that is, in order to get all the muscle-forming food it requires it must eat more sugar than it needs. This excess of sugar is known as honey-dew, and it often covers the lea\"e3 with a stickj' film. It comes from two projections on the end of the abdomen of the aphis. This honey-dew, not 74 ANIMAL ACTiyiTIES. needed by the aphis, is rehshed by other insects, notably the ants, which may be seen stroking the pro- jections from which the honey-dew exudes and eagerly eating the sweet fluid. So much do the ants appreciate this honey-dew that they take great pains to care for their friends the aphides, in many cases herding them as men herd cows, and sometimes carrying their attentions so far as to take the winter eggs of their cows into their own houses to keep them from frost and enemies. With returning spring these eggs are taken out again and placed upon their proper food-plants to hatch in the warmth of the sun and produce another colony of aphides. The Ichneumon-fly. Teachers of Zoology fre- quently have brought to them for identification and explanation a caterpillar, having his back covered with a mass of silken cocoons. If we wait for the cocoons to hatch we may see coming from each a black four- winged insect from one eighth to one fourth of an inch in length. The female of this insect, when mature, deposits great numbers of small eggs directly under the skin of a living caterpillar. These eggs soon hatch into small grubs or maggots which live on the fat of their host, not interfering with his digestive apparatus or other vital organs. After a time the full-grown larvs bore holes through the caterpillar's skin, come out of their living prison and spin cocoons, fastening each to the caterpillar's back by a thread of silk. In these cocoons the pupa stage is passed and the adult insect gnaws his way out to begin another cycle. These insects are often called microgaster-flies. They belong to the order Hymenoptera (Fig. 6^). The Sand-wasp. Still another method of preparing fresh meat for the young has been invented by some of the wasps. These wasps catch a caterpillar, a spider, or some other insect, and sting him in such a way in the thoracic ganglia that the victim becomes A CHAPTER OF LIFE-HISTORIES. 75 paralyzed but is not killed. The wasp then drags her prey into her hole, and deposits an egg on the naotion- less but living insect, apparently knowing that death will not occur until her egg has become a larva and requires food. When the larva appears he finds his food still living, and makes it last until he is ready to assume the pupal condition. This is a remarkable insect adaptation for the preservation of food. There are many of these wasps. Some of them live in holes in the ground, which they stop up and conceal Fig. 67. — A Microgaster Fly {magnified), c, larva of a microgaster in the caterpillar of a cabbage-butterfly._ in very ingenious ways after the egg and its provender have been stored away. Others build their nests or cells of mud, enclosing the young and its food in earthen jars. A full-grown mud-wasp may be kept in confinement for a time and fed on sugar and water. Her mem- branous wings, four in number, are folded over her back when at rest, but during flight they are spread out and the fore and hind wings are fastened together in such a way by hooks and grooves tb?* they appear like a single pair. 76 /INIM/IL /ICTiyiTlES. The ovipositor differs from that organ as we have seen it in the cricket and grasshopper in having, in addition to the grooved sheath through which the eggs pass, a pair of lances which pierce the insect it wishes to paralyze or kill. The paralysis is probably caused by a bit of formic acid which is secreted by a small gland in the wasp's abdomen and injected into the body of her victim. The sting, then, in this case as in the bee and other hymenoptera, is a modified ovipositor. The care with which the wasp cleans its body and performs its toilet is worth noting. In fact, many things may be learned by watching one of these intelli- gent little workers. The Dragon-fly. To study insects which spend a part of their life in the water an aquarium is helpful and pays well for the trouble it costs. To study the young dragon-fly one should visit a pond or pool of fresh water, provided with a small net and a supply of fruit-jars. The young dragon-flies may be recognized by their flat square heads, their rudimentary wings, and their six strong legs. They frequent the bottom of the pool in which they live and their color protects them from observation, but careful watching will soon reveal their presence. One sweep of the net will sometimes bring several nymphs to the collector's jar. One must at the same time collect some aquatic plants to keep in his aquarium, and also a supply of small insects for dragon-fly food. A little mud from the pool with some submerged sticks and leaves will furnish insect-food for several days, after which a fresh supply should be provided. With a little sand in the bottom of a jar, a few growing water-plants, and a supply of dragon-fly nymphs of varying sizes, we are ready to learn something of the life-history of the mosquito-hawks, as dragon-flies are sometimes called. While collecting the young, one is likely to see the adult females dipping the tip of the abdomen beneath A CHAPTER OF LIFE-HISTORIES. 77 the surface of the water in the act of depositing eggs. These eggs soon hatch into tiny nymphs, which live in the water, and, moulting from time to time, produce the various sizes found by the collector. If we compel a few of these nymphs to go without food for a day ajad then feed them with insects, we shall be able to watch the use of the strange mask which hides the face, or perhaps we should say the mouth. This mask is really a very strange develop- ment of the so-called lower lip, the structure of which may be understood by examining one of the nymphs and comparing it with the accompanying sketches (Fig. 68). After all, it is not so much a mask as a Fig. 68.- -The Dragon-fly. A, larva; B, pupa; ing from pupa-case. C, dragon fly emerg. formidable grasping organ capable of reaching suddenly forward, seizing an unsuspecting victim, and dragging him back to the hard mandibles. 78 ANIM/IL JCTiyiTIES. Breathing of a Dragon-fly Nymph. An insect living in the water must breathe, and it is interesting to observe how insects which have chosen an aquatic life have adapted their breathing-organs to the medium in which they live. The dragon-fly larva does not trouble himself to come to the surface for air, but simply takes his oxygen from the air dissolved in the water. The spiracles which would allow water as well as air to enter the breathing-tubes are closed and covered by the hard exo-skeleton, but the tracheae or breath- Fig. 69. — The Imago of a Dragon-fly. ing-tubes, like those in the grasshopper, convey the air throughout the body. To get the air, the water is drawn in through the anal opening, where it comes in contact with some modified air-passages which have somewhat the function of gills. In these air-passages the carbon dioxide and other impurities await the opportunity to pass by osmosis to the water, while the oxygen penetrates through the membranes into the breathing- tubes. If a fine stream of bright-colored liquid be put near a nymph by means of a small pipette the currents produced by the breathing may be seen. A CHAPTER OF LIFE-HISTORIES. 79 Possibly some of the larger nymphs in the aquarium may crawl up a stick or other object and, fastening their feet firmly, await their final metamorphosis from aquatic to aerial life. At this time the exo-skeleton of the nymph splits down the back and there emerges the beautiful creature we so often see hovering over the surface of streams and ponds. The two pairs of delicately veined wings Fig. 70. — Caddis-fly, Adult and Larval Cases. are never folded like those of the grasshopper or beetle, but remain extended even while the insect alights. The lower lip has lost its mask-like appendage, the mandibles are hard and toothed, the eyes are very large, the abdomen is long and tapering, the legs are small and bunched together for security in alighting. It is now a fine creature of wonderful agility and grace. Harmless to man and larger animals, it devours mos- 8o ANIMAL ACTIVITIES. quitoes and other small insects, catching them on the wing with hawk-like flight and precision of aim. The dragon-flies belong to the pseudoneuroptera. By some they are put in a separate order, the odonata. Other Aquatic Insects. While collecting and observing the young dragon -flies one cannot help noticing the fact that many other insects spend a part Fig. 71. — The Growth of a May-fly. A, larva; B, pupa; C, imago. or the whole of their life in the water. It will be interesting to watch the young caddis-flies (Fig. 70), young may-flies (Fig. 71), the adult water-boatman swimming on his back with his legs modified to form oars (Fig. 72), the ditycus or large water-beetle carry- ing a bubble of air under his elytra and feathering his oars as he dashes through the water (Fig. 73), and the giant water-bug with powerful piercing beak and A CHAPTER OF LIFE-HISTORIES. 8] mighty fore legs for holding his victims while sucking their life-blood (Fig. 74). The Mosquito. Among aquatic insects the familiar mosquito or gnat deserves a paragraph. The female mosquito, which by the way is said to do all the biting Fig. 72. — A Water-boatman. .^, in the water; ^, while flying. and all the singing, leaves her eggs, sometimes two or three hundred in number, glued together in a sort of raft which floats upon the water (Fig. 75). In a few days the tiny larvse open the under side of the eggs 'Jh^ Fig. 73 Dyticus Marginalis. A, male; B, female. and descend into the water, where they swim rapidly about with a peculiar jerking motion. The large head is usually downward, always so while at rest near the surface of its pool. Just back of the head is a large 82 ANIM/tL /ICTtyiTlES. joint commonly called the body, and back of that the smaller joints of the abdomen. The end of the tail is double as shown in the figure. One projection is the insect's propeller, and the other its breathing-tube, which it is constantly using when at rest, opening or closing at will the tiny valve at its ex- tremity. The mosquito larva, then, breathes air directly and does not take it from the water like the young dragon- fly. Like its mother, the larva is bloodthirsty and always hungry. At the end of about two weeks, after moulting several times, the larva changes to a pupa, . bending its head under its body as seen in the figure and losing its mouth alto- gether, but retaining its power of active movement. The breathing-tube at the end of its body disappears and it now takes air by two tiny projections on its back. Finally, the pupa rises to the surface of the water and again moults, producing the adult mosquito, which uses its cast-off skin as a boat on which it floats until its wings are dry and it is ready to fly away. Should its frail boat capsize and wet its mosquito would drown. It has been found that a little kerosene spread upon the water of stagnant pools will not only kill the egg-rafts as they float about but will also destroy the perfect insects as they emerge from their pupa-case boats. The imago now breathes, like other insects, by the spiracles along the sides of its body. It has but one Fig. 74.— Mouth of a Bug. a, antennae; /, labium; m, man. dibles and maxillae; d, eye. wmgs the Fig. 75. -The Egg. raft of a Mosquito. A CHAPTER OF UFE-HtSTORlL iw''\ F;'-.. 7-1 — i ; t Lift -iii-.ir:. o: a Mosquito. 84 /tNIMAL /ICTIVITIES. pair of wings, and its mouth-parts are fitted for suck- ing. The mouth of the male mosquito is adapted for sucking honey from flowers and it leads a mild and peaceful life. The female mosquito, on the other hand, has, in addition to the proboscis for sucking blood, a number of sharp lances with which she pierces the skin of her victim. At the time of piercing she also injects an irritating fluid into the puncture (Fig. yy). The music made by the mos- quito is produced in two ways, first by the rapid movement of the wings, and second by the passage of air in and out of the spiracles. The humming thus made is thought to be heard by the male mosquito, whose ears consist of tufts of hairs on his antennse. These hairs are said to vibrate in unison with the tones made by the wings and spiracles of the female. Experiments seem to show that some varieties of mosquitoes are respon- sible for spreading both malaria and yellow fever. A comparison of the life-histories here outlined gives one a notion of the great variety of modifications of a common plan of structure to compass different objects. How these modifications have come about in the progress of insect-life is one of the most interesting problems before the student of nature's ways. The change from a caterpillar with biting mouth-parts to a butterfly with his long proboscis gives a hint of the possibilities of evolutionary growth. Questions, i . Have you observed closely the life- history of any insect .' If so, what are some of the changes you have noticed 1 Fig. 77.— The Mouth of a Female Mosquito. A CHAPTER OF LIFE-HISTORIES. 85 2. What advantages and what disadvantages must be experienced by a larva hving in water ? Topics for Reports. The Life-history of a Beetle. A Life-history I have Observed. VOCABULARY. A phis, pi. aphides (Gr. apheides, lavish), a plant-louse. Cad'dis-fly, a name given to an in- sect whose larva lives in the v^ater and builds for itself a tubular case. Gnat, a mosquito. Ich neu'mon (Gr. ichneuo, to hant), a genus of insects belonging to the hymenoptera. Mi cro gas'ter (Gr. mikr'js, small, and gaster, stomach ,, a small hymenopterous fly. Mosqui'to (Lat. musca, a fly), it well-known dipterous insect. Par then gen'e sis (Gr. parthe- nos^ a virgin, and gignomai, to be born), reproduction by means of unfertilized eggs. Pro'lee, one of the fleshy abdom- inal legs of insect larvas. Pu pa'tion (Lat. pupa, a doll), the process of imdergoing the pupal condition. CHAPTER VIII. SOME INSECT ADAPTATIONS. Structure and Habits. Fig. 78 shows the parts of the hinder leg of a cockroach, an insect whose legs are well adapted for running. Comparing this leg with the corresponding legs of a grasshopper, we find the same parts present but modified for jumping. Looking at the legs of a mole-cricket, we find again the same parts, but .in this case altered for digging. Among the large water-bugs, which live by hunting, the legs are fitted for seizing and holding prey. In some of these bugs, a portion of the leg forms a sheath into which another portion shuts like the blade of a pocket-knife when not in use (Fig. 80). Aquatic insects like the water-boat- m a n (Notonecta) and the large water- beetle (Ditycus) have legs made into powerful oars, which they are 86 Fig. 78.— Leg of a Cock- roach, a, coxa; b, trochanter; c, femur; d, tibia; e, tarsus. Fig. 79. — A Mole-cricket. SOME INSECT ADAPT/iTIONS. 87 even able to feather as they row along, yet here, as elsewhere, the plan of structure is the same as that Fig. 80. — Fore L«gs of a Water-bug. B, open; A, clpsed; C, enlarged to show sheath. seen in the cockroach and grasshopper. Some butter- flies of strong flight use their legs so little that their front legs are mere threads, yet they retain the marks Fig. 81.^ — Legs of Dyticus. A, hind legs for swimming; B, fore 1 with suckers. of the same plan we have found in the other insects examined. What is true of the legs is also true of other impor- 88 ANIMAL /ICTIVITIES. tant organs. Devices for defence, for eluding enemies, and for procuring appropriate food among insects are everywhere seen to be varied modifi- cations of the same organ or organs. In general such structures are found in any particular insect as best help it to preserve its life in the particular Fig. 82 —Fore Leg environment in which it lives. So of a Butterfly. much does the structure, tell us about the mode of life, that we are often able to infer the habits of an insect which we have never seen alive from the study of dead specimens, and even from fossil remains. Changes of Organs Because of Changes of Habit. That these variations of similar organs have arisen gradually, through changes of habit made necessary by changes in surroundings, is generally believed. At first sight the long delicate proboscis of the butter- fly, the lapping tongue of the house-fly, the beak of the aphis, the hard, biting jaws of the beetle seem very different structures, but when we watch the caterpillar of the butterfly and the grub of the beetle with mouth- parts so much alike at the start, and see that in one case the maxillae elongate into the coiled proboscis, and in the other the mouth-parts grow into the formid- able and destructive biting-organs of a carnivorous beetle, we wonder less at the divergence than at the resemblance. We see, too, how it may have been possible for organs very unlike to have arisen from similar beginnings. The great variety seen in the breathing-organs of aquatic insects furnishes another illustration of the change of organs necessitated by a change of habit. From the fact that all aquatic insects breathe air by tracheae at some period of their life it is believed that their ancestors, as well as the ancestors of insects having aquatic larvae, were originally terres- trial. Either driven by enemies or lured by more abundant food, at some distant period, these insects SOME INSECT ADAPTATIONS. 89 began an aquatic life to which they became gradually- adapted by a process similar to that by which the butterfly obtains his protective coloring. In fact the aquatic life is a protection, either from destructive enemies or from starvation. Insect Communities. In speaking of the life-history of the aphides we mentioned the fact that ants some- times keep these insects to provide them with honey- dew. It is also true that some ants capture the pupse of ants of other communities than their own and rear them as slaves. To obtain these pupae wars are often waged, hence cooperation is necessary. Cooperation leads to life in communities and life in communities makes necessary a division of labor, so that we find nurses, foragers, soldiers, queens, and drones working together in the same community, all developed from eggs which are apparently just alike. This production of seemingly different insects seems to be sometimes a matter of choice on the part of the rulers of the community, for it has been found that a worker grub, among bees, may be developed into a queen by the use of special food and the building of a royal chamber. This division of labor is best illustrated among bees, ants, and wasps. Hive-bees. In a bee community there is one female called the queen who produces all the eggs. There are a small number of males called drones. All the rest of the inmates of the hive are workers. The workers are in reality immature females. They are provided with stings which are modified ovipositors. The wax is produced within the bodies of these workers and issues from between the segments of the abdomen, whence it is taken and skilfully built into the honey- comb, with which all are familiar. The honey, when taken from the nectaries of flowers, passes into a sort of crop, or honey-bag, where it undergoes changes which alter its flavor. It is then brought to the hive and stored in the cells of the honeycomb. The young 90 MINIMAL ACTIVITIES. bees hatch from the egg as larvae, or maggots, in cells much Hke the honey-cells. In these cells they find a bountiful supply of food, known as bee-bread, which is composed of honey and pollen gathered by the workers. In these cells, too, the young bees pass through the stages of complete metam.orpho- sis. Insects and Plants. Besides the adaptations which fit insects to cooperate with one another, there are also equally wonderful adaptations of structure fitting in- sects to cooperate with plants to their mutual advantage. It is well known that plant-seeds, as well as the fertile eggs of animals, are produced only by the union of two kinds of cells, the male ele- ment being called the fertilizing cell. Among plants, pollen-cells grown on the stamens of flowers must fall upon the stigma and be conveyed thence to the ovary before seeds suitable for repro- duction can be formed. In many cases the pollen from one flower must be conveyed to the stigma of another flower before fertiliza- tion can take place. This carry- ing of pollen from flower to flower is the work of insects which visit the flowers for the purpose of getting honey. On the visit, the pollen adheres to the hairs or other parts of the insect's body, and is rubbed off" by the stigma of the next flower approached. Each flower seems to depend on a particular insect whose proboscis just fits its own honey-cup. Thus, Fig. 83. — Hive-bees, i, female; 2, male; 3, worker. SOME INSECT ADAPTATIONS. 91 red clover cannot grow without the help of bumblebees. No more can bumblebees flourish without the honey prepared by the growing clover. When this partner- FlG. 84.— Fertilization of a Flower by an Insect, a, calyx; b, curved upper lip ; c, under lip, on which the bee stands while sucking the honey; d, pistil; d', pistil at a later ."itage; e, stamen; /, stamen shedding the pollen from its anther on the back of the bee; f, bee's proboscis, with which it reaches the honey. ship between the bee and the clover began we cannot say, but there is reason to believe that passing years, with their new generations of both bees and clover, only increase the dependence of each upon the other. 92 ANIMAL ACTiyiTIES. If you examine a head of the common white clover, so abundant everywhere, you will see a part of the tiny flowers of which the head is composed standing erect and looking their best and prettiest. These are the flowers not yet visited by the bees; the dry and withered flowers hanging down near the stem have been fertilized, and each one now contains a pod in which the tiny clover-seeds are ripening. Not only do we find the proboscis of an insect fitted in structure for the plant on which it habitually feeds, but we find the plants, also, ordering their ways to conform to the habits of their insect friends. Thus, stamens grow in such a way that they must dust their pollen on the insect as he reaches the honey-cup, while stigmas reach out in their growth to occupy at maturity a position in the pathway of the pollen-laden insect. Not only do stamens and stigmas seek the insect, but the petals call their friends by color-signs and point out by brilliant lines the direction of the honey-cup, while hostile barbs and pointed hairs below the cell of nectar prevent the approach of honey-loving ants and small insects not useful to the plant. Questions. What structures would lead you to sus- pect that an insect leads an aerial life ^ an aquatic life ^ a terrestrial life .'' Knowing an insect to be capable of strong flight, what might you reasonably predict concerning this insect's legs .'' What might the mouth-parts of an insect indicate concerning its food .'' What adaptations have you noticed in insects you have observed .'' In what ways have you known insects to be espe- cially protected from enemies .-' Why do some insects commonly fly at night .? What insects have you observed at work at night .' What insect communities have you observed } Have you seen insects carrying pollen ? CHAPTER IX. A SPIDER'S ACTIVITIES. Place a living spider in a large glass jar and watch its movements for several days. Get a garden-spider if possible, and keep it well supplied with flies and other insects. How does it take its food .'' From what part of its body does its web issue ? Do all spiders make the same kind of web .■" Where have you seen spiders .'' Where have you seen the eggs of spiders .■• How do they look .'' Have you seen cast-off skins tangled in spiders' webs .'' If so does that indicate anything about the spider's mode of growth ? Can the spider smell .'' Test this point by bringing near the insect first a clean glass rod and then a rod dipped in a liquid having a strong odor. Can the spider see .'' How far from her body can she see .•■ Using an alcoholic specimen, write resemblances and differences for spider and grasshopper. How many divisions of the body .' Simple or compound eyes .-' How many .■' How many legs ? How many segments in each leg .■* Examine the feet with a microscope. At the end of the mandibles find the poison-fangs. Where are the spinnerets ? How many do you find .' 93 94 y4NIMAL ACTIVITIES. Under the abdomen near the cephalothorax find two openings to the air-sacs or rudimentary lungs. Summary of Drawings, {a) A spider seen from above X 3- (3) A front view of the mandibles X 5- (<:) A view of the top of the head showing the ocelli. {d) A hind foot much enlarged. The Spider's Activities. We have already con- sidered the activities of the grasshopper, classifying these under six heads. We have spoken of these six kinds of activities as the six functions of living things. In the spider these activities are carried on by the aid of finely adjusted machinery -A Spider's Leg. which we can only describe somewhat roughly here. Taking Food. The devices by which spiders of different kinds procure their food are well worthy of study. Nearly all spiders are aided in this work by silken threads spun from their own bodies. In the lower part of the spider's abdomen there is a bag in which is secreted a glue-like substance which issues from the spider's body at will, and hardens on exposure to the air. The wart-like projections on the lower side of the abdomen near its posterior end are pierced with many hundreds of minute holes, through each of which proceeds a microscopic thread of the glue-like fluid we have mentioned. The wart-like projections are called spinnerets. The hundreds of tiny threads from the spinnerets are grasped by the spider's claws and twisted into several strands, which, woven together, make the fibre of which webs are built. A spider's thread, then, is a rope of several strands, and each strand is com- posed of many hundred lines, yet it is so light that it floats in the air, so strong that it easily holds up many times the spider's weight, so elastic that it does not A SPIDER'S ACTIVITIES. 95 break easily, but stretches when struck heavily by large insects, and so pliable that it can be moved into any shape. No wonder, then, that the spider values so highly her magic thread, and economizes it to such an extent that she even eats the broken webs rather than have them wasted. The spider's web is used in different ways by different members of the spider family. The trap-door spider builds her cylindrical home underground, lining it with the most delicate silk, and fitting it with a hinged cover which she closes in time of danger, holding it firmly shut with her claws. The water-spider builds her dome-shaped home under water, arranging it like a diving-bell, and carry- ing to it bubbles of air from the surface (Fig. 86). Some spiders weave irregular, sprawling tangles of web to trap, their prey, while others build in accordance with a methodical pattern. One spider spins her web in such a way that it entangles in its meshes particles of warm air, thus forming a balldon with which to float in the air. The wheel-shaped web of the common garden-spider is a marvel of skill. To make it the spider first spins a thread where the wind can waft it to an anchorage on some distant twig, or other support. This line she hauls taut with her claws, and then, dropping and swinging, always holding a thread, she makes the somewhat irregular outside framework for her more accurate geometrical web. She then puts in the spokes with great care, and beginning at the middle, winds a spiral thread to the circumference, and another back to the centre. The second spiral thread is covered with little, sticky, transparent beads stand- ing side by side, ready to catch the luckless fly by wing, or leg, and hold him fast. A touch of the finger to such a thread shows the adhesive quality of the beads, and a look at them under the microscope reveals their beauty. Such a web is not a nest, or a house; it is a trap. 96 ANIMAL ACTIVITIES. Commonly the spider builds her home at one side of the trap, and, holding in one claw a thread which she Fig. 86. — Water-spider and Nest. has connected with the trap, she awaits the vibration which warns her that an insect is ready to be eaten. If the pull on the line indicates a fly, she simply goes A SPIDER'S ACTIVITIES. 97 directly to it, holds it in her mandibles, sucks the fluids from its bod}' and throws away the shell. If, however, the pulling indicates a wasp or bee the movements are of a different kind. Then the spider shows both caution and alertness. If the insect is evidently too large to attack, the spider snaps a few threads of her web and sets the captive free with as little loss of the precious web as possible. If, however, there is a chance of victor}', the spider spins more threads and winds them round and round her victim, until she has him so hopelessl}' entangled that she can safely kill and eat him at her leisure. The entrance to the spider's mouth is guarded by a pair of mandibles with sharp fangs at their tips. These tips have holes near the ends, -tthich lead by tubes to a poison-bag in the head. From these fangs the poison is squeezed into the body of the fly or other insect. Nutrition. The spider's food is alwa}'s liquid, and is pumped up into her stomach in somewhat the same wa}- as the butterfly's honey. In the stomach it receives fluids which change it chemicall}-, so that it can be used to nourish the body. Respiration. Like the insects we have studied, the spider has spiracles for breathing, but so acti\e and energetic an animal requires more oxygen than this arrangement seems able to give, and so it is provided witli rudimentary lungs or air-sacs. These sacs are situated in the anterior part of the abdomen near its junction with the cephalothorax, and open b}' two minute holes just behind, the last pair of legs. The chemistr}' of breathing is the same in all animals. Reproduction. The spider deposits her eggs in a cocoon of silk which she makes wath great care, shaping it with her bod}- as a bird shapes her nest. This cocoon, with its eggs, is fastened in a sheltered place. The }'oung spiders are hatched quite complete, like their mothers, and begin at once to spin each a 98 /INIM/IL /ICTiyiTlHS. tiny thread. They moult often, and very soon, with- out any teaching, they know how to spin IhL'ir tiny wheel-shaped webs, They cat otiier insects, as do their ciders, and often dine on one another. i''or them the struggle for existence is a fierce one, and domestic relations count for little, the mother eating not only her own children, but often making a meal of lier husband. In the spider family the mother is siiiirenie and husbands and children fare but ill. Discovery. An examination shows how larf^e is the nerve-mass concealed in the cephalothorax of the spider. Several ganglia have grown together and produced a sort of second brain, considerably lar^;er than the nerve-mass which lies above the throat. Not only is this brain large, but as it is made by the concentration of many smaller nerve-masses, or gan- glia, it represents a great concentration of power. These nerve-masses are connectetl with tJie outside of the spider's body everywhere by nerves, which carry to the central organs notice of all vibrations from witli- out. The spider then is extremely sensitive to any change in its surroundings. It sees, though not very clearly, by means of eight eyes placed on the front part of the cephalothorax; it hears, if at all, by the vibration of the hairs on its body. It tastes and smells, we have no doubt; but its keenest sense is that of touch. Movements. The s])ider is capaiiU; of (i:\N move- ments and performs these exceedingly well. Wh.at she loses by the ajjsence of wings she gains by increase of power and skill in the use of her legs, llie rnakin}^; of a web often reqiiires the most delicate movement and the greatest precision; and the spider shows this delicacy and precision to jjerfectioii. Tin- wonderful thing about the spider's automatic movements is tin: accuracy with which they are controJleii. The Lithobius. h'or purpose of comjtarison ;i Httlc time may be devoted to the many-h-'i.;|.;ed Ijrown insects which disappear so hurriedly whcji one overturns ;i A SPIDER'S ACTIVITIES. 99 board or stone, in almost any field or garden. In some localities these animals are called " earwigs ", in other places they arc known as centipedes. Another name for the mcst common species is lithobius. Speci- mens may be easily obtained by using tweezers or a piece of cloth. They may be kept in alcohol or formalin. In note-books answer these questions: What is the habitat of this animal .' Does it prefer light or darkness .'' Does it prefer moist or dry places .' Does it bite or suck its food .' In what respects does it resemble the spider .'' The grasshopper 1 How does it differ from both spider and grasshopper .' Does the number of segments correspond with the number of legs 1 The front feet have poison-claws. Do these feet have the same shape as the others .'' Drawing. A sketch of lithobius. Questions. i. How do the breath ing'-organs of a spider differ from those of the insects previously studied ? 2. Do you think the spiders breathing has any rela- tion to his activity .' 3. Have you noted any protective devices among spiders } ^ Topics for Reports. The Cochineal Insect. Aphides. Shellac. The Silk- worm. The Manufac- ture of Silk Goods. The Caddis-fly. May-flies. The Ant-lion. The Noises of Crickets, Mosquitoes, and Bees. The Habits of Honey-bees. The Carpenter- bee. Agricultural Ants. Mud-wasps. How Flies Walk on Ceilings. The Senses of a Fly (experiments). The Senses of a Spider (e.xperiments). Spider- webs. Water-spiders. Trap-door Spiders. Scorpions. Cheese-mites. Centipedes. Thousand-legs. Stings and Poisons. The Sense of Sight in Spiders. Where lOO ANIMAL ACTiyiTIES. I Have Found Spiders. Are Spiders of Any Use ? The Mosquito's Boat. My Experience in Rearing Butterflies. Lightning-bugs. Injurious Insects. Some Insect Friends. Aphides as Cows of Ants. Valuable Substances Furnished by Insects. The First Paper- makers. Do Insects Talk .■• Insects I Dislike. VOCABULARY. A e'ri al (Gr. aer, the air), inhabit- ing the air. A quat'ic (Lat. aqua, water), in- habiting the water. Ceph al tho'rax (Gr. kephale, head, and thorax), the union of head and thorax in one division of the body. Drone, a male bee. Fau'na (Lat. Fauna, the sister of Faunus, the god of agriculture), the characteristic animals of a district. Habitat (Lat. habito, to dwell), the natural abode of an ani- mal. Ma line' (Lat. mare, the sea), in- habiting the salt water. Range, the region in which an animal naturally lives. Spin ner et', one of the projections from which the spider's web issues. Suture (Lat. suo, to sew), a seam or joint. Ter res'tri al (I^at. terra, the earth), inhabiting or living on the land. CHAPTER X. HOMOLOGIES AMONG CKLSTACEA. L:v;yG cni'v"f.ih Ci:i be boujrhc in the mirker~ of liTCi cides. One or two of these shouid be kep: in An s-cuirium w-th. sei."eral inche< of \»-E.rer in a plice w:iere tlie CiA5i "Av snidv their srruccure ind cheir move- nienci :>e:ore Ar:er.:p~n^ tn^e .i2-::r3.:or\- exerc.fe on t.~e Feed the cri3.~5h "sdt^v pieces of meat or f-sh. .md To-jch t>.e ar.renn-£ with various iub, second maxilla ; £, second maxillipede. (I)) The carapace seen from above X 4- (c) Side view of thorax with carapace removed to show gills X 4- (d) An eye seen from above X 6. ((?) Large antenna x 6. (/) Small antenna X 6. {_£■) First, second, and last leg X 4. io6 ANIMAL ACTIVITIES. {h) A swimmeret from the third abdominal segment seen from behind X 6. (i) Sixth swimmeret. Homologies. In the lobster, shrimp, and crayfish, the antennae, claws, legs, and swimmerets are seen to lt.g. h Fig. 92. — Longitudinal Section of Crayfish, a, anus; d.a., dorsal artery; h.g., intestine or hind- gut; h, heart; m.g., midgut; li, liver; s, stom- ach; ki kidney; la, labrum or lip; s.a., sternal artery; n.c, nerve-chain; v.a., ventral artery. be similarly situated and to bear a strong resemblance in structure. If we should study the growth of these three animals, we should find that these appendages arise in a similar way in the process of development. Parts of animals similar in position, structure, and origin are said to be homologous. The wings of the butterfly are homologous with those of the grasshopper. The three pairs of jointed legs in the caterpillar are homol- ogous with the legs of the butterfly. When parts correspond simply in use and not in origin or structure, they are said to be analogous. Thus the- wing of a bird and the wing of a butterfly are analogous but not homologous. HOMOLOGIES AMONG CRUSTACEA. loy Serial Homology. In comparing the jointed appen- dages of the different segments of the abdomen of a lobster or crayfish with one another, we note the fact that each is com- posed of a basal joint of two seg- ments and a pair of jointed branches. One part of the basal joint is called the basipodite and the other the cox- opodite; both together are called the protopodite. The inner branch is the endopodite , and the outer branch the exopodite. In the other jointed appendages we find striking similarity to the swimmerets. They are also similar in origin ; starting as bud-like outgrowths from the rings or somites of the embryo. Indeed, each seg- ment is homologous with every other. This kind of homology is called serial homology. It is very noticeable among the Crustacea. Laboratory Exercise. Examine a sand-hopper and an asellus. How does each compare with the shrimp in regard to : {fl) The number of legs .' {b) The number and form of swimmerets .■' {c) The number of antenna; 1 {d) The number of segments 1 (e) The divisions of the body 1 {/) The eyes 1 (^g) The carapace .' {h) The position of the gills 1 (z) The general form of the body .' Name parts of the sand-hopper which are homol- ogous with those in the shrimp. Name an organ in the sand-hopper which is anal- ogous to one in the shrimp but not homologous with it. Fig. 93. — Walking Appendage o f Crayfish with Gill, £, Attached. io8 ANIMAL ACTIVITIES. Compare the eyes in the three animals. The Importance of Homologies. We have already pointed out the fact that parts may be homologous and Fig. 94-. — The Common Crab. yet appear very unlike. Parts which arise in the same way in the processes of development may become so Fig. 95 — Early Stages of Shore-crab. variously modified that their real homologies could not be known without a study of embryology. Hence it HOMOLOGIES AMONG CRUSTACEA. 109 frequently happens that animals bearing only slight external resemblance to one another in adult life are classified together because in embryological life they show so many resem- blances. Among the ten thou- sand or more species of Crustacea, there are many strange forms which de- part from what might be called the typical crusta- cean structure. Compar- ing the common crab (Cancer irroratus) with the shrimp or crayfish, we notice the small size of the abdomen folded under the flattened carapace. In the hermit crab the abdo- men is soft and has lost part of the swimmerets, be- cause of its habit of using the shell of a snail for pro- tection, yet in the young the abdomen of this animal Fig. 96. Water-flea {Dafhnia pulex). Fig. 97. — Cyclops. A, dorsal view; B, side view. is essentially like that of the young crayfish and bears homologous parts, ANIMAL ACTIVITIES. Among the lower Crustacea there are many which show greater variations from the typical form. The Cyclops is a small lobster-like crustacean often found in drinking-water. Specimens can usually be obtained by tying a piece of muslin over the end of a faucet and allowing the water to run for a little while and then rinsing the muslin in a glass of water. The horseshoe crab is an ancient form sometimes classified with the spiders because it seems to have more homologies with them than with the common forms of Crustacea. Degeneration. The lower crustacea are called Ento- mostraca. Among these are found many forms which would not be recog- nized as allies of the crayfish and crab, but for the study of their embryology. The common barnacle (Balanus) found on all salt-water shores between high and low tide bears no re- semblance to a cray- fish, yet soon after hatching from the e.gg it is a free- swimming active crustacean, provided with organs of sense and looking much like a young shrimp. After a short time it seems to tire of its active life, and, looking about for a place of rest, it glues its head to a rock and lies feet uppermost kicking food into its mouth from the surrounding water. It builds around itself a conical shell which it opens and closes at pleasure. Thus sitting at ease and catching food as it comes, it has no use for organs of sense or locomotion and so loses these marks of higher animal life. It finally becomes a blind and stupid mass, capable of little else than the digestion of food brought to it by the Fig. 98. — A Bamacle. HOMOLOGIES AMONG CRUSTACEA. I" waves, an excellent illustration of the loss of powers by disuse. There are also many forms of fish-lice which live a parasitic life by attaching themselves to a portion of some fish and living on either the blood or food of their host. These bear very little resemblance to the cray- fish. Some have even lost the gills and breathe only by the external surface of the body. These fish-lice hatch from the egg as free-swimming larvse, bearing a striking similarity to other Crustacea at this stage of growth. The common larval form is called the nauplius. (See first stage in Fig. 95.) It has a single eye and three pairs of appendages. The higher Crus- tacea pass through this nauplius stage before hatching from the egg. From this stage, the higher forms of Crustacea which lead an active life develop more ap- pendages, and more acute sensibilities, with a corre- sponding increase of complexity in the nervous system, while the parasitic forms lose the eyes and locomotive appendages, and their whole structure degenerates into machinery for digestion and reproduction. AN EXERCISE FOR THE NOTE-BOOK. Rule a page in your note-book in the manner indi- cated on p. 112 and fill the blank spaces with such descriptive terms as you have learned in the previous lessons. Classification of the Arthropoda. We have already noted the characteristics of the class ' ' Insecta ' ' by selecting the points of resemblance among them. We readily see that the spider, the lithobius, and the cray- fish cannot be classed as Insecta without changing our present definition. We find it more convenient to include all the animals thus far studied in a larger class which naturalists have agreed to call Arthropoda. The Arthropoda are called a sub-kingdom or phylum because they constitute one of the large divisions of the ANIM/IL ACTIVITIES. Grass- hopper. Spider. Lithobius. Shrimp. Bilateral ? Are appendages jointed ? Wings, antennas, legs, and swim- merets. Divisions of body. Respiration. Locomotion. animal kingdom. Sub-kingdoms are divided into Classes, classes into Orders, orders into Families, families into Genera, genera into Species. Thus the milkweed-butterfly belongs to the sub-kingdom Ar- thropoda, the class Insecta, the order Lepidoptera, the family Nymphalidae, the genus Danais, and the species Archippus. Such an arrangement must be to some extent artificial, because animals are not run in molds like bullets or stamped with dies like coins. Never- theless, the great number of animal forms compels us to adopt some scheme of classification to prevent con- fusion. Examining our notes concerning the Arthropoda, we find that all are bilateral, all have an exoskeleton, segmented bodies, and jointed appendages. These HOMOLOGIES AMONG CRUST/ICE/I. "3 peculiarities we may call the most important character- istics of the Arthropoda. Animals not having these marks must be classified under other sub-kingdoms. In Chapter I we have classified all animals into eight sub-kingdoms. The sub-kingdom Arthropoda includes probably half of the animals of the earth, the Insecta alone having more than half a million species. Nat- uralists are not agreed yet as to the number of classes properly belonging to the Arthropoda, but usually animals like the shrimp and crayfish are called Crus- tacea, those like the lithobius Myriapoda, those like the spider Arachnida, and those like the grasshopper Insecta. The Insects have already been described. The Arachnida have eight legs, simple eyes, and a cephalothorax and abdomen. The Myriapoda have many segments with at least one pair of jointed legs for each segment. The Crustacea breathe by gills throughout life. They pass through the nauplius stage in the course of development. Further study shows other marks for identifying these classes. Many exceptional forms are found and great patience and care are necessary in order to classify accurately. Nevertheless, it is profitable prac- tice to attempt to classify animals as we see them, even if we do it somewhat roughly at first. Laboratory Exercise for Review. A variety of forms kept separately in small numbered boxes and bottles may be used. Write in the note-book: (i) The number of the specimen. (2) Its mode of locomotion. (3) Its habitat, inferred from its structure and its resemblance to forms already known, with the reason for your answer. (4) Its food and its mode of procuring it, inferred from an examination of its mouth-parts, from other points of structure, and from resemblances to forms already known, with the reason for your answer. 114 /INIMAL ACTIVITIES. (5) The class to which it belongs, with reasons for the answer. (6) In the case of Insecta, name the order to which the insect belongs, with reasons for the answer. Questions, (i) Why are the animals just studied called Crustacea .'' (2) How does their manner of breathing compare with that of Insecta .'' (3) Do lobsters breathe air .'' Explain. (4) What is meant by homology 1 By analogy } (5) What is serial homology .'' (6) Where may one iind cyclops .' (7) Why is Cyclops so named .■■ (8) How do the crabs differ from the shrimp .' (9) In what way do barnacles resemble the shrimp } (10) How does the hermit-crab differ from other crabs .'' (i i) In what cases among Crustacea does the mode of life seem to affect the shape of the body .' (12) What occurs when the limb of a crustacean is broken off .■■ What reason have you for your answer .'' (13) What is phosphorescence .■' How do you ex- plain it .'' (14) Do the Crustacea moult 1 How do you know .' (15) Do you know any animals which do not have both sides alike .'' (16) Give examples of differentiation. Topics for Reports. The Hermit-crab. Robber- crabs. Lobsters. Cyclops. Phosphorescence. Giant Crustacea. Degeneration. Uses of Crustacea. HOMOLOGIES AMONG CRUSTACEA. "S VOCABULARY. An al'o gous (Gr. ana, according to, and logos. ) Analogous organs are those having tlie same use but not necessarily the same structure or origin. Bas ip'o dite (Lat. basis, base, and Gr. pons, foot), part of a crus- tacean appendage. Car'a pace (Lat. capara, a hood), the hard covering of the cephalo- thorax in Crustacea. Ceph al i za'tion (Or. kephale, head), a tendency to aggregate nerves and organs of sense near the head. Cox op'o dite (Lat. coxa, hip, and Gr. pous), the joint of a crusta- cean appendage nearest the body. Cms ta'ce a, a class of arthropoda confimonly having a hard shell. Dec'a pod(Gr. deka, ten, and pous), an order of Crustacea having ten legs. Dif f er en ti a'tion (Lat. dis, apart, and /ero, to carry), the setting apart of tissues and organs to perform special kinds of work. Em bry ol'o gy (Gr. emliryon, an embryo, and logos), the study of embryonic life. En dop'o dite (Gr. en, in, a.n&pous), the outer branch of a, swim- meret. Ex u'vi um (Lat. exuo, to strip off), the cast-off skin of an insect or crustacean. Fang, a hollow tooth emitting poison. Fer til i za'tion (Lat./^ru, to bear), the union of male and female cells to produce living seeds or eggs. Gill, an organ for breathing the oxygen dissolved in water. Ho mol'o gous (Gr. homos, same, and logos), having the same rel- ative position and structure. I'so pod (Gr. isos, equal, anipous), an order of Crustacea having the legs of equal length. Max il'li ped (maxilla, and pous)', a foot-jaw. Os mo'sis (Gr. osmose, pushing), an interchange of gases or liquids through a slightly porous substance. Pro top'o dite (Gr. proios, first, and pous), a part of a swimmeret consisting of the basipodite and coxopodite. Ee'nal (Lat. renalis, kidney), per- taining to the kidneys. Ros'trum (Lat. rostrum, a beak), a weapon of defence on the front of the carapace of a crustacean. Sed'en ta ry (Lat. sedeo, to sit), inactive. Ses'sile (Lat. sedeo, to sit), joint- ed to the body without stems or stalks. So'mite (Gr. soma, a body), a segment of the body of one of the arthropoda. Swim mer et', a jointed appendage on the abdomen of a crustacean. Tac'tile (Lat. tango, to touch), having the sense of touch. Tel'son (Gr. telson, a boundary), the posterior somite of a crus- tacean. Tet ra dec'a pod (Gr. tetra, four, deka and pous), an order of Crustacea having fourteen legs. CHAPTER XI. THE ACTIVITIES OF ONE-CELLED ANIMALS AND SPONGES. Thus far we have been dealing with animals having more or less complicated machinery for carrying on the activities of life. We knov/ that an egg is a single cell and that as it grows it changes by increasing the num- ber of cells and by setting apart groups of these cells to perform different duties. In a single cell life is reduced to its lowest terms. In an egg we may see the process of unfolding and get greater insight into the workings of living machinery. So in studying living animals which never develop beyond the single- cell stage of existence we may gain a knowledge of animal activities not otherwise obtainable. These animals are so small that a complete study of them makes necessary the use of the compound micro- scope, but as it is not proposed to burden this course with the details of microscopic manipulation, we must content ourselves with verbal descriptions for the present. The one-celled animals are put in a sub-kingdom by themselves, called Protozoa. They are very small and for the most part inhabit the water. There are many of them, but their ways may be very well understood by studying descriptions of a few forms. The Amceba. This minute animal has been much studied and its modes of life are well known. It may be found in stagnant water in small shallow pools. It is less than a hundredth of an inch in diameter and Il6 ONE-CELLED ziNIM/tLS MND SPONGES. 117 under the microscope looks like a drop of moving jelly of irregular outline. The greater part of the Amoeba is granular in structure, being surrounded by an outer film of clearer jelly. In the midst of the cell is a nucleus, a little more opaque than the rest of the cell but made of the same substance. The jelly-like sub- stance of which the whole Amoeba is made is called Fig. 99. — Forms of Amcebae (highly magnified). 2 and 3 were drawn from the same specimen; 5, 6, 7, and 8 were drawn from another specimen; N, nucleus; P, pseudopodia. protoplasm. The same substance is found in the cells in our own bodies, as well as in the living cells of other animals and plants. Every plant and every animal begins its life as a single cell of protoplasm. Within the Amoeba's cell may be also seen a round clear spot which from time to time contracts and temporarily dis- appears. This is called the contractile vacuole. ii8 ANIMAL ACTiyiTIES. TaMng Food. Not only is the Amoeba destitute of jaws and sucking-tubes, but it even lacks a mouth. Its food consists largely of minute one-celled organisms which it swallows at any part of its body by simply flowing over and around them. Nutrition. The particles of food which have been swallowed are gradually dissolved and chemically changed so as to become a part of the protoplasm of the Amoeba's body. The shell of the plant is thrust out through the Amoeba's covering at any point when all the nutritious matter has been taken from it. Dis- solving and chemically changing the food is digestion. Making it a part of the Amoeba's protoplasm is assimi- lation. There is no stomach or intestine, but the food while digesting moves about with the granular proto- plasm in a somewhat regular way. Respiration. There are no organs for breathing, but oxygen from the surrounding water enters the living protoplasm and carbon dioxide and other impurities are given off'. Reproduction. When the Amoeba has eaten and digested food until it has grown to be too large, the nucleus shows signs of divid- ing, the Amoeba assumes a dumbbell shape and finally •■^sMjS splits into two Amoebas, ^^'^ each equally capable of Fig. ioo.— Amoeba Feeding. leading an independent ex- istence. Parent and off"- .spring are alike, if either can be called parent. This mode of reproduction by division is called Jission. Discovery. If touched the Amoeba contracts. It is then sensitive to touch, but there can be no special parts of the body fitted to receive impressions from without. It is everywhere equally sensitive. Movements. Not only does the Amceba withdraw when touched, but it seems capable of self-directed movement as well. The method of procedure consists ONE-CELLED ANIMALS AND SPONGES. 119 in projecting outward a portion of the body in the direction in which the animal wishes to move. The little swelling thus made is called a pseudopodium or false foot. Such false feet, may appear at any time on any part of the body. When this pseudopodium has extended itself sufficiently the rest of the body seems to glide into it by a sort of flowing motion. The varying position and size of the pseudopodia give it its irregular outline when seen under the microscope. The Amoeba's power of ' ' contractility ' ' is sometimes spoken of as a separate activity corresponding to the contractility noticed in the muscles in higher animals. Thus this simple bit of protoplasm performs the same functions which are common to higher animals, all the activities in this case being carried on by a single cell. As we examine other animals we find it easy to arrange a series in which each animal is only a little more specialized than the one next below it, but such a series does not include all animals. It is interesting to note that such a series bears a strong resemblance to the various stages through which an &g'g (a single cell) of one of the more specialized members of the series passes in its growth. Rhizopoda with Shells. Some of the Amoeba-like animals cover their bodies with bits of mineral matter to form shells with openings through which the pseudopodia extend to gather food and as- sist in locomotion. In many cases these shells are secreted by the animal, that is, they are formed from the protoplasm of the body as our finger- nails are formed from our blood. Sometimes the pseudopodia resemble the roots of plants and hence these Protozoa which move by pseudopodia are called Rhizopoda. Some of the Rhizopoda secrete shells of calcium car- FlG. loi. — Amoeba Divid- ing. y^NIMAL yiCTIVITIES. bonate or limestone. When these shells are perforated with many holes the animals are called Foraminifera. Fig. I02. — One of the Foraminifera. Some of these foraminifera have been found of large size and in such great numbers that their fossil remains make great deposits of limestone. Fig. 103.— The Origin of Chalk. A, chalk {magnified); B, ooze [mag- nified). Chalk. At present there live near the surface of the ocean great numbers of these shelled Rhizopods. ONE- CELLED ANIMALS AND SPONGES. 121 When they die their shells fall to the bottom and, mingling there with other similar shells, form a soft white mud which may harden to form chalk. The chalk cliffs of England were doubtless produced in this way. Tripolite. Some of the Rhizopoda have shells made of the finest possible bits of glass or silica. Deposits of these shells with similar shells of one-celled plants form tripolite, a substance used as a polishing powder. Infusoria. If hay be- placed in warm water and allowed to stand in a warm place for a few days the Fig. 104. — Infusorial Earth {magnified). Fig. 105. — Infusorians {inagnified). water will be found to be filled with many minute, one- celled, rapidly moving animals. A look at these through the microscope shows that their movements are due to the motion of hair-like projections on the body. These hair-like bodies are called cilia. One- celled animals which move by cilia are called Infusoria because some of their kind appear when infusions of hay or other vegetable matter are allowed to stand. Some of the Infusoria are fixed by a stalk, or stem, like the bell-animalcule, or vorticella, shown in the figure, and some are rapidly moving free animals like those found in infusions of hay. 122 MWMAL ACTiyiTIES. One of the Infusoria found in infusions of vegetable matter is the Paramecium, or slipper-animalcule (Fig. 107). This may be found and stud- ied very easily. Where a compound microscope is available the follow- ing exercise may be used. Laboratory Exercise. Examine in a watch-glass by using a low power of the microscope a few drops of stagnant water known to contain Infusoria. 1. Does the Paramecium have a definite shape ">. Is it bilateral .■' Is the Amoeba bilateral .' 2. Place a few drops of water containing the slipper-animalcule on a slide with a few fibres of cot- ton and examine with a higher power of the microscope. Is the body divided into parts or cells .■" 3. Do you see the movement of cilia } On what part of the body are they situated .' 4. Do you find a groove sur- rounded by cilia .' Do you find a mouth } Do you find a nucleus .'' Are there any contractile vacuoles .' 8. Feed the animal with bits of indigo. Where do the blue particles go .■" Summary of Drawings. («) A sketch of several animals as they appear when viewed with a low power of the microscope. (b) Sketch of a single animal showing as many parts as you have seen. In the Paramecium the activities of life are carried on much as they are in the Amoeba. There is, how- ever, a greater specialization of parts, especially the Fig. 106. — Vorticella {magnified). A, ex- tended; B, contract- ed; C, in fission. 5- 6. 7- ONE-CELLED ANIMALS AND SPONGES. 123 *iouth for taking food and the two kinds of cilia, one for locomotion and one for producing currents of water to drive food into the mouth. Even a single cell then may have its parts specialized for per- forming different kinds of work. Characteristics of tlie Protozoa. The Protozoa are minute animals having but a single cell of protoplasm, moving by pseudopodia, or cilia, and reproducing withouteggs. Sponges. Itis not rec- ommended that sponges be studied in the labora- tory in an elementary course, but for purposes of comparison it is neces- sary to become familiar with the most important facts concerning their structure. Sponges are composed of many cells but slightly specialized. A single sponge really seems almost as much like a colony of Protozoa as like a distinct animal. The outer layer of cells which is simply a sort of skin is called the ectoderm; the inner layer or lining of the cavities of the body is called the endoderm. Between the ectoderm and the endoderm lies the mesoglcea, in which the skeleton is produced. The flesh of the sponge taken altogether is called sarcode. The com- mon bath-sponge as we use it is only the skeleton. We may imagine that the hard parts we see have once been imbedded in fleshy matter (mesoglcea) ; that the fleshy matter was covered with a skin (ectoderm) ; and that the cavities so apparent in the skeleton were lined with another skin (endoderm). Fig. 107. — A Paramecium {highly magnified). o.g., oral groove; ///, pharynx. 124 ANIM/iL ACTIVITIES. The kind of sponge commonly called the hard-head gives a general idea of sponge-structure. The smaller holes on the outside correspond to openings in the ectoderm through which currents of water flow to the interior cavities. The large holes at the top are out- FiG. io8. — Structure of a Sponge {magnified). A. section of sponge; £, part of a digestive sac; C, one cell from a digestive sac lets for these currents. Along the passageways from these outer holes (inhalent pores) to the larger holes (oscula) there are enlargements which act like stomachs, that is, they take up the food as it passes along in the currents of water. The endoderm cells which line ONE-CELLED ANIM/ILS AND SPONGES. 125 Fig. 109. — Sponge Spicules. these cavities are provided with flagella which by their constant movement keep the water moving along from the inhalent to the exhalent openings. As the water passes along it brings within reach of t h e flagella minute animals and plants which are seized and pushed back into the cells where they are dissolved and assimilated in much the same way as the food of the Amoeba is assimilated in its cell. The breathing, too, is carried on by the indi- vidual cells as in the Amoeba. Nutriment from the endoderm cells is passed along from cell to cell to nourish the rest of the body. From this nutriment the material for building the skeleton is secreted. This skeleton is often in the shape of spicules of hard material. Spicules may be calcareous , silicious, or horny, producing these three kinds of sponges. Only the horny or keratose sponges are of any commerical use. So nearly independent are the individual cells com- posing the sponge-structure that if a few of them be separated from the original body, they go on living and divide and subdivide, making new cells and build- ing the structure of a new sponge. If a living sponge be cut into hundreds of pieces, each piece grows into an independent animal. Such an aggregate of cells may be considered as only a transition step between a Protozoon and a many-celled animal of more highly specialized struc- ture. Hence some naturalists have classed sponges as Protozoa, some make a separate sub-kingdom Porifera, while others class them with the sub-kingdom Coelen- 126 ANIMAL ACTIVITIES. terata. For our purpose it seems best to regard the Porifera as a separate sub-kingdom. Questions, i . What force propels the water through the canals in a sponge ? 2 . Write the functions of the sponge in columns as we have previously written the functions of other animals. 3. In what respects does the sponge resemble the Paramecium .' 4. How does a sponge differ from an Amoeba } 5. Where are sponges found .■■ 6. Why are sponges called animals rather than plants .'' Topics for Reports. Chalk. Tripolite. The Dis- covery of the Microscope. How to use a Microscope. Sponge-fisheries. VOCABULARY. Animalcule (Lat. dim. of ani- mal^ from animaj breath), a very small animal. As sim i la'tion (Lat. ad, to, and similiSf like), the process of making digested food into living tissue. Cal ca're ous (Lat. calx, lime), made of carbonate of calcium. Cell (Lat. cella, a small room), a bit of living protoplasm contain- ing a nucleus. Cil'i a (Lat. pi. of cilium, . How do you explain any differences .-" Are any of the spines movable } Which is the oral and which the aboral surface .' With a magnifying glass examine the aboral surface for the purpose of finding the minute pincer-like bodies called pedicellaricB. Can you find projections of the skin used in breath- ing .' Examine a dried specimen. Are all the spines of the same shape .? How many kinds of spines do you find .■• How many kinds of plates do you find } 140 THE STARFISH AND CLOSELY RELATED ANIMALS. 141 The walking, or ambulacral, surface is called the ambulacral area. How many rows of ambulacral plates in each ray ? How many rows in all ? Do the ambulacral feet pass through these plates or between them ? The regular plates situated on either side of the ambulacral areas are called inter ambulacral plates, and the surfaces they cover are called inter ambulacral areas. How many rows of interambulacral plates do you find in each ray ? How many rows in all ? How do the spines on these plates differ from those on the irregular plates of the aboral surface ? The plates on the aboral surface may be called body-plates. Can you find the single plate with its ambulacral foot at the end of each ray .-' With a partly dissected specimen, which has been prepared by hardening in alcohol, laying open the upper or aboral surface of one of the rays and removing the digestive organs, notice the ampulls or internal enlargements of the ambulacral feet. What is the use of the ampullae in locomotion .' These ampullae are connected with a tube running along the ray in the angle made by the two rows of ambulacral plates. Trace this tube, which supplies the ambulacral feet with water, up to the tube running around the mouth. Find the stone canal connecting this tube with the madreporic body. What do you think may be a use of the madreporic body t Examine portions of the skeleton of a starfish which have been decalcified by allowing them to soak in about ten per cent, nitric acid for a few days. Compare these with similar portions which have been treated with weak caustic potash until the fleshy matter has been removed. Are the plates formed inside of the fleshy skin or outside of it ? Write resemblances and differences for starfish and hydra. 142 y4NlM/4L ACTiyiTIES. Compare this starfish with the brittle starfish. Summary of Drawings, (a) Sketch of a living starfish. (3) Sketch of a portion of an ambulacral area show- ing the relative positions of the plates and the openings for the ambulacral feet. (c) Cross-section of an arm to show the relative posi- tion of feet, water-tube, plates, and spines. (d) Ambulacral feet with ampullae. {e) Sketch of a brittle starfish. Activities of the Starfish. The starfish belongs to the sub-kingdom Echinodermata, animals having hard plates in the skin. Their movements are slow and all- their activities are of a low order, yet they are more highly specialized than the Coelenterates w e have just been con- sidering. Taking Food. The mouth of the starfish is situated on the under side, hence this side is called the oral side. There are no teeth, yet the starfish lives on oysters, clams, mussels, and other hard-shelled animals. The stomach is an elastic bag which fills the central part of the body and extends into all the arms or rays, thus making the shell simply a protection for this branching, walking stomach. This stomach secretes a fluid which par- tially paralyzes its prey. If a mussel is too large to pass through the mouth, the starfish stretches a part of its stomach outside of its body, and enfolds its Fig. u6. — A Starfish. After Agassiz. THE STARFISH AND CLOSELY RELATED ANIMALS. I43 victim until the shell opens and the contents can be sucked out. Nutrition. Outside the stomach, throughout the cavities in the rays there is a glandular mass, the liver, which secretes a digestive fluid and pours it into the stomach. Here the food is digested and the nutriment absorbed. There is a very short intestine opening opposite the mouth. It is so small in diameter that the waste of the food cannot pass through it, and must therefore be ejected through the mouth. Respiration. For the most part breathing takes place at all parts of the body, but there are folds of the skin over the aboral surface which are supposed to act somewhat like gills. Reproduction. The reproductive organs, of which there are two in each ray, lie on the floor of the ray; their ducts opening in the angles between the rays. These openings are called the genital openings. After the eggs of the female and the sperms of the male have been discharged into the water, the eggs are fer- tilized by the sperms. From these fertilized eggs de- velop young starfish, which are at first bilateral, and bear no resemblance to their parents. Discovery. The only specialized sense-organs are the eye-spots at the ends of the rays. The nervous system consists of a nerve around the mouth with a branch extending into each ray and ending in the eye-- spot just mentioned. The sense of feeling is apparently dull, and the starfish seems to suffer no hardship by the deprivation of one or two of its rays, which quickly grow again when once broken off Movements. The starfish and its relatives have a method of locomotion very different from other animals. Along the oral surface of the rays are the cylindrical tube-feet, or ambulacral feet, bearing suckers at their extremities. These tubes extend through the skeleton into the body-cavity, where they enlarge into bulbs called ampulla. Each bulb connects by a small tube 144 ANIMAL ACTIVITIES. with a larger tube running lengthwise of the ray, and this in turn connects with a tube surrounding the mouth. With this oral tube the radiating tubes all unite and from this there extends the stone canal (another tube) reaching to the madreporic body on the aboral surface. The ambulacral feet have muscular walls. The madreporic body is pierced with minutt holes through which water can enter the water-system. Fig. 117.— a Brittle Starfish. When the starfish wishes to advance, some of the am- bulacral feet are elongated in the direction of progres- sion by squeezing the ampullae and forcing the water into the feet. When the feet are fully extended the sucker at the end of each foot fastens itself to the rock, or other support near, and the longitudinal muscles of the tube contract, shortening the ambulacral foot and pulling the starfish to the rock. THE STARFISH AND CLOSELY RELATED ANIMALS. US The Sea-urchin. If possible get a living sea-urchin and watch its movements in a pail of salt water, or better, in a s^lt- water aquarium. What is the shape of the body ? Do you find oral and aboral surfaces ? What is the shape of the spines ? How do they move ? Do you find the ambulacral feet ? Examine the mouth and notice the manner of feed- ing. Hold the living animal in the hand and observe its mode of locomotion. Place it upside down in the water and watch it. Does it have bilateral symmetry or any kind of sym- metry .■• Examine the test or shell which has been freed from spines. How can you tell the ambulacral from the inter- ambulacral plates .'' How many rows of each kind of plates do you find .' What is the shape of these plates .■' Look at broken pieces of tests. Do you find a single plate or tentacle at the end of each ambulacral area, as in the starfish (ocular plates) } At the ends of the interambulacral areas do you find the genital openings 1 How many do you find 1 The small plates, in the circle surrounded by the genital plates, correspond to what plates in the starfish .' Do you find the madreporic body 1 What changes would have to occur in the body of the starfish to give it the form of the sea-urchin .-" What parts of the sea-urchin are homologous with parts of the starfish .-' Examine the teeth. How many teeth do you find } Write resemblances and differences for starfish and sea-urchin. Compare a sea-cucumber with a sea-urchin. 146 ANIM/tL ACTiyiTIES. Summary of Drawings. («) A living sea-urchin, natural size. {b) A single spine showing mode of attachment to the shell. (c) Several ambulacral and interambulacral plates. {d) External form of a sea-cucumber. Pig. 118. — The Structure of a Sea-urchin. teeth. A, interior of shell ; B, Activities of the Sea-urchin. The activities of the sea-urchin resemble those of the starfish. One pecul- iarity deserves mention. The mouth of the sea-urchin is provided with a complicated arrangement of teeth, five in number, uniting at a point. This whole apparatus is called Aristotle's lantern in honor of the philosopher who first de- scribed it. With these teeth and possibly by the aid of oral secre- tions the sea-urchin is enabled to burrow into solid rock. Other Echinoderms. Sea- cucumbers of many kinds, the worm-like Synapta with i t s anchor-shaped plates, the great variety of starfishes, sand-dol- lars, Crinoids both fossil and present, with other less common forms all bear a striking resemblance to the two forms studied. Fig. 119. — A Sea-cucum- ber. THE STARFISH AND CLOSELY RELATED ANIMALS. U? Characteristics of Echinodermata. This sub-king- dom enjoys the distinction of being the most exclusive division of the animal kingdom. These animals secrete bony plates in the skin ; they have marked radiate structure, almost alw^ays being divided into five radiat- ing parts. With the radiate structure we may also trace a bilateral condition. (In the case of the starfish this condition may be seen by drawing a line through the madreporic body and the opposite ray.) The water-system with its ambulacral feet is peculiar to this sub-kingdom. All are marine. Topics for Reports. The Burrowing of Sea-urchins. Sea-cucumber as Food. Radiate Structure. Where I Have Seen Echinoderms. The Senses in a Starfish. Young Starfishes. Basket-fish. Stone-lilies. VOCABULARY Abo'ral (Lat. ai, from, and as, mouth), the surface opposite the mouth. Am bu la'cral (Lat. ambulo, to walk about), a word applied to the walking areas of Echino- derms. Am puria, pi. ampullce (Lat. ampulla, a flask), the enlarged end of one of the tube-feet of an Echinoderm. De cal'ci fy (Lat. de, from, and calx, lime), to remove the calca- reous matter. Gen'i tal o pen ings, the openings for the passage of eggs and sperm in starfishes and sea-urchins. Mad re por'ic body, a hard plate pierced with holes through which water filters into the tube- feet of a starfish or sea-urchin. O'ral (Lat. os, the mouth), pertain- ing to the mouth. Ped i eel la'ri a (Lat. pediculus, a small foot or stalk), a minute pincer-like organ on the skin of an Echinoderm. Sa'di ate (Lat. radius, a ray), having the parts regularly ar- ranged around a centre. CHAPTER XIV. THE EARTHWORM AND HIS "WORK. The earthworm or angleworm belongs to the sub- kingdom Vermes. It also belongs to the class Annu- lata, which includes the most highly organized and most intelligent animals belonging to this sub-kingdom. In studying it we must note how it differs from any or all of the Arthropoda, and discover if possible why naturalists have not classified it with this sub-kingdom. The earthworm may be easily observed alive by placing several individuals in a glass jar with loam and dead leaves, and occasionally feeding them with bits of meat or vegetables. Is the body bilateral } Can you distinguish a head ">. a head end 1 a neck ? a dorsal and ventral surface .'' Is the body anywhere flattened .' Are there any divisions in the body like those in the Arthropoda } Are there any jointed appendages .■' Do you find any eyes 1 Is the worm sensitive to touch .■• to light } to strong odors .'' to irritating fluids } While the worm is feeding can you see any teeth 1 Do you see something which looks like a proboscis "i Do you see the red blood-vessel near the dorsal sur- face .'' Earthworms tanned by the use of chromic acid make good specimens for class use. They may be prepared as follows: Place the worms in dilute alcohol for three or four days and then transfer them to strong alcohol, 148 THE EARTHIVORM AND HIS IVORK. 149 Fig. 120. — An Earthworm. where they may remain for several weeks. Then put them in a one per cent, solution of chromic acid for five or six days. Remove them from this solu- tion, wash them thor- oughly in water and place them in a dish with turpentine, al- lowing them to re- main there for a few days longer. They may then be dried, when they are ready for use. The worms should be spread out in flat- bottomed dishes during the processes of tanning. With specimens thus prepared or simply hardened in alcohol, the class should write the answers to the fol- lowing questions: Do the worms all have the same number of seg- ments .'' Do you find several rings together which seem to be enlarged .'' This is the clitellum or reproductive girdle. How many segments from the clitellum to the head end } Is the body of the angleworm smooth } Does it appear more rough when the finger is moved in any special direction .' The roughness is caused by bristles or setm. Do they all point in the same direction } How many rows of setas along the body t How many setae on a single segment .'' Does the worm have an internal skeleton .'' Does a thin cuticle separate easily from the body of a worm which has been soaking in water for a time } Can you make out the shape of the segment in front of the mouth .'' Summary of Drawings, {a) The whole worm, nat- ural size. {b) The segments near the head X 6. ISO ANIMAL ACTIVITIES. IMII 121. — A Worm's Setae. (c) A cross-section of one segment to show the setae X 6. Taking Food. The earthworm has neither hard mouth -parts for biting food nor a tube for sucking. Its mouth is simply a hole bounded by fleshy lips. The segment in front of the mouth forms a sort of proboscis or elongated upper lip which is used to push the food Fig. 121. — a Worm's into the mouth. The food con- sists of fallen leaves or any organic matter found in or around its bur- row. Decaying vegetable matter forms the greater part of its food, and if it cannot get decayed leaves it can pour out of the mouth a fluid which makes the leaf decay and blacken at once. Since the worm gets much of its food beneath the surface of the earth, it builds a burrow for its home. Such a burrow is a plain hole usually slanting from the surface down to a depth of four or five feet, always extending below the frost of winter. At the bottom of this hole is a small round room carefully lined with stones or seeds. In making this burrow the worm not only eats the vegetable matter Fig. 122. — ^Worm-casts. in the ground but swallows the earth as fast as he excavates it, thus mixing his food with loam. Nutrition. The worm has no teeth and no jaws ; so his food passes down the gullet or oesophagus to an enlargement of the alimentary canal called the crop. THE EARTH IVORM AND HIS IVORK. 151 Next it goes on to the gizzard, which is filled with little stones to make a mill for grinding the food. After being ground, the food passes into the intestine, where the nutritious matters are taken into the blood and carried to the tissues of the body, while the part which cannot be digested is cast out at the end of the body, usually near the opening of the worm's burrow. The blood which carries the nutritious matter to the parts where it is needed is of a reddish color, but the color is in the liquid part of the blood and not in the corpus- cles, as is the case in our own bodies. Respiration. An examination of the earthworm's body reveals neither spiracles nor gills. In fact it has no breathing organ, but takes oxygen from the air at all parts of its skin and sends out or excretes carbon dioxide and other impurities at the same time. The blood-vessels are so near the surface that the necessary interchange of gases can easily take place as long as the worm's skin is moist. Worms cannot live long in the sunlight or in dry sand because they cannot breathe under such conditions. Reproduction. On the under side of the fourteenth and fifteenth segments in a common species are to be found some small openings which lead to the ovaries or egg-producing organs. Several segments in front of these, there are tiny holes in the grooves between the segments. These open into receptacles containing the male cells or sperms. When the time for depositing eggs arrives certain glands of the clitellum become very active and pour out on the surface of the body a fluid which hardens into a tough membrane, making a girdle around the body, the reproductive girdle. A jelly-like liquid remains between the girdle and the body while it is gradually pushed forward. When the girdle passes the openings to the ovaries the eggs are discharged into it, and when it passes the segments from nine to eleven the sperms pass into the fluid with the eggs. The '5* /INIM/tL /iCTIl/'mES. girdle then passes over tlie lu-ad and cluscs at holli ends, forming' a capsule containinf^i- the repi'ddiictivc cells. Here fertilization takes place, and the e^^j^rs hatch finally into little worms which rapidly grow hy the addition of new segments. Discovery. We find no eyes, ears, or olher organs of sense on examining the earthworm, )'et wv. know that he has to some slight extent a sense of smell, Inr he enjoys the smell of onions, cabbages, and other dainty articles of earthworm diet. I'ossibly, too, he can hear a little, for he is disturbed by sounds wliicli shake the earth near his burrow, though tilleily dis- regarding the loudest noises made in the air .above him. Although without eyes he can tell daylight from d.irk- ness; the power of doing this is said to reside in the first few segments of his body in which his brain is found. He is probably somewhat sensitive to light in all segments of his body. His sense of touch is keenest of all and, indeed, his whole body seems to lie ;i sort of feeler. Movements. The earthworm doubtless controls his own movements to a considerable extent. He even shows signs of intelligence, though of a very low order. The most brilliant thing the eartliwr)rm does is to ])lug up the opening of his burrow to hide it from his enemies. For this purpose he selects his material with some care. Leaves, bits of paper, twigs, wool, and sometimes stones are used by the worm to make this plug, or door, to his hole. He seizes with his lips the substances to be used and fits them neatly to the mouth of the burrow. When he uses ;i leaf he drags it in by tin,' part best suited by its shape to fit the place intended for it. Mr. Darwin nrjticed that sometimes ;i worm would let go a leaf and then try a new way of jjulling it into his hole. The; worm also moves up and down his burow at will, and if necessary he tan travel sotnc distance from THE EARTH IVORM AND HIS IVORK. I53 home, crawling over very difficult roads and even scaling perpendicular walls. The controlling mechan- ism for these movements lies in a small brain situated above the oesophagus and hence sometimes called the supraoesophageal ganglion, and in a series of ganglia lying under the alimentary canal, a pair in each seg- ment. These ganglia are connected with each other and with the brain by nerves, and branches ramify from them to all parts of the body. This arrangement of nerve-masses along the ventral portion of the body is decidedly advantageous to a crawling animal, giving him constant information concerning the ground over which he travels. Locomotion in the earthworm is accomplished by the use of three sets of muscles under the control of his nervous system. One set of muscular fibres runs lengthwise of the body, another surrounds each ring, and a third layer sends its fibres diagonally across the segments. When an earthworm wishes to go forward he fixes his setae in the ground in such a way that his body cannot move backward, but will easily move for- ward. If, now, his body is already extended its full length, he contracts his longitudinal muscles, thus shortening his body and making it much thicker. He then contracts the circular muscles surrounding the segments, elongating the body and making it much smaller in circumference. Since the setae prevent the body from going backward, it must move forward. The setae are curved near the end to make them more useful in holding the body in place. The diagonal muscles are used in moving the body from side to side. The Usefulness of the Earthworm. In spite of his apparent insignificance the earthworm is the farmer's loyal friend. He is a ploughman of ancient lineage and his work is most efficient. He brings to the sur- face fresh subsoil to replace the exhausted layer which the farmer has been cultivating. He grinds up organic matter and leaves it finely powdered in his castings for 154 ANIMAL ACTIVITIES. the use of plants. He renders the earth porous for the better spread of moisture and the more rapid pushing of plant-roots. He buries rocks far beneath the soil and covers old fields with fresh loam. All pupils should read Mr. Darwin's book entitled "The Forma- tion of Vegetable Mould." The Earthworm's Relatives. Along with the earthworm are classified many animals which outwardly bear no resemblance to him. It sometimes seems as if naturalists reserved the sub-kingdom Vermes as a sort of waste-box in which to place all creatures not easily classified elsewhere. The strange ways of the Vermes must be studied by the help of other books. CHAPTER XV. MUSSELS AND SNAILS. The Fresh-water Mussel (Anodon or Unio). These mussels may be easily obtained on the sandy bottoms of fresh-water ponds or streams. A few should be placed in an aquarium which has a few inches of sand on the bottom. They do well without feeding. Little- neck clams make good individual specimens for the work here outlined. Boil the clams to harden them. Notice the color and shape of the shell. How many parts has it ? Do you see any markings on the outside ? What do these seem to indicate ^ Does the shell seem to be covered ? Compare it with a dried shell. Is the entire surface covered .'' How do you explain your observation .'' The bared projection is called the umbo. How are the two parts of the shell held together .■" Is the hinge you find at the dorsal or ventral margin of the valves .■' How can you tell .'' In what direction does the animal move } How fast .■■ Is the umbo nearer the anterior or the posterior end .'' How can you tell .'' Find the right and left valves. Observe the foot. How is it used .' Is it at the anterior or posterior end of the body .' At the end opposite the foot find the fringed open- ings. When the shell is open and the animal is feed- ing comfortably, color the water directly in front of these openings with a little indigo or cochineal solution 155 IS6 MNIMAL ACTIVITIES. introduced by a pipette. What do you learn from this concerning the manner of feeding ? What happens when you touch the animal on its shell and at different places on its fleshy parts when it is feeding quietly ? Examine a mussel or clam which has been boiled, or hardened in alcohol. Press the valves together and quickly release them. Why do they fly open again .-" When the mussel was alive what held the valves together .? Explain the manner of opening and closing the shell. Place the mussel on its side in a dish of water so that the dorsal portion is away from you. Is the anterior portion of the mussel near your right hand, or your left hand } Carefully remove the upper valve without disturbing the soft parts beneath. Have you removed the right or left valve .'' The membrane lining the interior of the shell is the mantle which secretes the material of which the shell is formed. Does this mantle line the entire shell } Is it of equal thickness in all parts .'' How many muscles held the valves together .■• On a dry shell do you find the marks which show where the muscles were attached } Do you find the muscles themselves .' Determine which is the posterior adductor muscle and which is the anterior adductor muscle. Find the mark which the mantle makes where it adheres to the inside of the shell. Call it the pallial line. Do you find any other markings on the inside of the shell .' Compare mantle outside of pallial line with that above. What is the relation of mantle to shell .' Raise the mantle and notice the striated leaf-like gills. How many do you find } Look for the labial palps near the anterior portion MUSSELS AND SNAILS. 157 of the gills. How many do you find ? The mouth is between the palps. Examine the ventral and dorsal passages of the siphon. Are they connected } Into what cavity does each lead } See if you can find the heart near the dorsal margin. Have you found that the mussel has a head .? What organs of sense have you found .'' Examine mussel-shells which have been burned for some liours in a hot fire. Compare with them some Fig. 123. — ^A Fresh-water Mussel (A/wdon) Showing Position of Foot and Siphons. shells which have been immersed in weak acid for several days. Examine, also, oyster-shells which have been prepared in the same way. Describe the structure of a shell. On the dorsal margins of the valves of a shell find IS8 ANIMAL /ICTiyiTIES. the hinge-teeth if there are any. How many teeth do you find on each shell ? Compare the shell of the common salt-water clam {My a Arenarid) with that of the mussel {(Jnio). How do the teeth and hinge-ligament differ ? How do the markings on the inside of the shell differ ? What differences in the structure of the animals do these markings indicate ? In the same manner compare the shell of oysters, pectens, and other bivalves. Write a description of a shell you have not previously seen and compare your description with that given in Woodward's MoUusca or a similar book. Summary of Drawings. («) Sketch of a living mussel showing foot and siphons. {b) Cross-section of valves showing action of hinge. {c) Inside of shell showing all muscular impressions and the pallial line. {d) Sketch of mussel in its shell. {e) Cross-section of the body of the mussel near the umbo. (/") Shells of several bivalves. Activities of the Clam or Mussel. Feeding. We have already noticed currents of water flowing in and out of the siphon at the posterior end of the body. The water enters by the ventral opening and goes out by the dorsal opening. The dorsal and ventral passages are separated, and this separation continues through the body of the clam, dividing it into two chambers, the dorsal or cloacal chamber and the branchial or gill- chamber. In many marine clams the mantle-edges unite again below the branchial siphon, but in the fresh-water clam they are free along the ventral border. As water enters the lower siphon it brings with it food and oxygen into the branchial chamber. In this chamber hang the two pairs of ridged leaf-like gills bearing cilia which by their movements keep the cur- rents of water in motion. These cilia also select from MUSSELS AND SNAILS. 159 the water the minute animals and plants which nourish the clam. These bits of food are collected along the ridges on the gills and thence passed to their ventral edges, on each of which there is a groove leading to the mouth. Along this groove the food passes, whipped on by the cilia, until it enters the mouth, which is a.ai Fig. 124. — Fresh-water Mussel with One Valve Removed, fi, peri- cardium; p. a,, posterior adductor muscle; a. a., interior adductor muscle; a, anus; e.s,, exhalent siphon; i.s., inhalent siphon; /.m., cut edge of mantle; o.g., outer gill; v.g., inner gill;/, foot; /.p., labial palps. situated between the labial palps at the anterior end of the body. To understand what becomes of the water that brings in the food we must remember that each gill is a fold of membrane pierced with tiny holes. In order to pass from the branchial chamber to the cloacal chamber the water must pass through these holes. A cross-section of a gill has a V shape, and the water goes through the sides of the V into the opening above and thence passes out of the cloacal chamber by the upper siphon. i6o y4NlMAL ACTIVITIES. Nutrition. In the clam the various processes con- cerned in nutrition are more distinctly separated than in any of the other sub-kingdoms below the Arthrop- oda. When the food enters the mouth it passes down the throat to the stomach. The dark portion of the body surrounding this alimentary canal is the liver, which secretes digestive fluids and pours them on the food. The intestine beyond the stomach passes directly Fig. 125. — Digestive Tube of Fresh-water Mussel (AnodonK m, mouth; /, liver; s, stomach; i and t\ intestine; «, anus; /, pericardium; k, kidney; s.c, chamber above gills; g, gullet. through the heart and opens into the cloacal chamber in the current of water which passes out of the upper siphon. The digested food is taken up by the blood and carried to all parts of the body by the circulating system. The most important organ of this circulating system is the heart, which is situated just below the hinge. It has a ventricle and two auricles. In its course, part of the blood is purified by the gills MUSSELS AND SNAILS. i6i and passes from these organs to the auricles. Part of the blood also flows through the renal organs, which take from the blood (excrete) the nitrogenous waste matters and empty them into the outgoing current of water. The ventricle forces the blood, constantly coming to the auricles, away from the heart all over the body. As in other animals, the separate cells take from the circulating liquid the substances necessary to produce Fig. 126. — Cross-section of Anodon. «, intestine; z'.^'., heart; i.g. and o.g., gills; /, foot; mJ., mantle. Fig. 127. — Nervous System of Ano- don. c.^., ganglia near the mouth; P-^-, ganglia of the foot; e.g., ganglia of the posterior adductor. more cells like themselves or to manufacture intercel- lular structures. The . cells of the mantle secrete carbonate of lime, which forms in layers on the inside of the shell and along its edges, thus increasing both its thickness and its size. If the mantle be irritated by the introduction of minute particles of foreign matter or by disease the secretion of carbonate of lime at a defi- nite point is hastened and a pearl is formed. Respiration. As the water passes through the gills it flows over and around many blood-vessels, through i62 Ah'lMAL ACTIVITIES. whose walls the interchange of gases common in all breathing takes place. Reproduction. The eggs of the fresh-water mussel pass from the ovaries to the cavity of the outer gill, where they hatch. The number of young is enor- mous. They remain for a time within these gills and then pass out to grow or to be destroyed, as the case may be. Discovery. The senses of the mussel are not acute and there are no special organs of sense. Touch is more acute in the foot and at the margins of the mantles, as might be expected, these being almost the only exposed parts. There is a so-called ear-sac in the foot, but it is not probable that the mussel can hear. The nervous system consists of three pairs of ganglia connected by nerves. One pair form a sort of brain {the supraoesophageal ganglia), one pair lie directly under the posterior adductor muscle [the visceral ganglia), and the third pair are imbedded in the tissue where the foot joins the body (^pedal ganglia). Motion, The opening and closing of the shell at will is brought about by the action of an elastic hinge- ligament and a pair of adductor muscles. When the muscles contract the shell is closed ; when they relax the hinge-ligament acts like a door-spring and forces the valves apart. The foot is protracted partly by muscular activity and partly by increasing its size by pumping its vascular vessels full of blood. When left lying on its side in the aquarium the animal rises to an erect position by sinking its foot into the sand. It plows its way through the mud or sand by muscular contractions of this foot. The Garden-slug. Obtain some garden-slugs, or, better still, some of the larger slugs found in damp cellars or green-houses. Keep them in a box with plenty of moisture and feed them with cabbage-leaves and bread. Watch the mode of locomotion. Allow the animal to crawl on a piece of glass and watch the MUSSELS AND SNAILS. 163 movements of the foot. Examine the trail of mucus left as the animal advances. Do you find the place from which this mucus comes.' Do you find a head .? a neck .'' What organs of sense do you find .'' Describe their position. How does the slug feed } Has it a shell 1 a mantle' On which side of the body is the breathing orifice .' How often does the slug breathe .' How often do you breathe .' Is there any relation between rapidity of breathing and rapidity of movement .' Do you call the slug's body warm or cold .■' Fig. 128 A Slug. Does the rate of breathing have anything to do with the snail's temperature .' Write resemblances and differences for slug and fresh- water mussel. Sketch the slug as you see him. Pond-snails. These animals are found in almost all ponds, crawling on dead leaves or aquatic plants. They may be easily kept in a jar of water for class- study. Get some pond-snails and keep them in a jar of fresh water. Watch all their movements. Write resemblances and differences for snail and slug. Note all points mentioned in regard to slug and mussel. i64 ANIMAL ACTIVITIES. Can a snail leave its shell and return ? ■ Can it close its shell ? Examine different kinds of snails for this charac- teristic. Do all the snails you have seen breathe in the same way ? Can a snail swim ? Can it walk on the surface of the water ? Is the snail bilateral ? Compare a land-snail with a water-snail. Study several shells and notice the sutures, the apex, the spire, the whorls, the lines of growth, the aperture, and the lip. Compare these parts in snail- shells of different kinds. Notice all other differences and tabulate your obser- vations. The columella is the axis of the spire. The piece which closes the snail's shell is the operculum. Hold the shell with the apex upward. Is the aper- ture toward the right [dextral) or the left {sinistral) of the columella 1 Is the aperture notched or entire ? Describe a shell from observation of the specimen and compare your description with that found in a' standard work. Summary of Drawings, {a) A pond-snail as it appears while crawling X 3- (^b) A shell of litorina or similar shell. (c) A shell of purpura or a similar shell. (d) A shell of a limpet. {e) Right valve of an oyster. (f) Various shells showing different structures. Snail and Mussel. A comparison of the snail and mussel shows on the part of the snail a distinct advance in the collecting of organs of sense at the anterior por- tion of the body and the growth of a head there. The possession of a head with a brain and active sense- organs is apparently associated with the matter of food- supply and feeding. So long as a soft-bodied animal MUSSELS AND SNAILS. 165 can have all the food he wishes brought to him by currents of water there is no use for head, or eyes, or sensitive feelers. On the other hand, an animal which must forage for his food can do it more advantageously if he learns to walk head foremost. In order to make great progress in this way he must have some means of discovering obstacles in his pathway. Hence the necessity of feelers and eyes. In the struggle for food among animals the headward growth and specialization is a great advantage. Active exercise in earning a living in competition with other animals which desire the same food not only Fig. 129 A Snail. sharpens the wits but actually increases the physical development of those organs on whose activity intelli- gence depends, just as vigorous muscular exercise develops the parts trained. Mussels and snails belong to the sub-kingdom Mol- lusca. The mussels, clams, oysters, and similar bivalves are members of the class Pelecypoda. These animals are sometimes called Lamellibranchiata be- cause they have four leaf-like gills, and sometimes Acephala because they have no heads. Univalves like the snails and the limpets, and slugs which have no shells, are classed as Gastropoda. 1 66 /1NIM/4L ACTiyiTlES. Fig. 130. — A Squid, its pen. P, Another important class of moUusks is the Cephalop- oda. The squid belongs to this class, as do the octopus, the argonaut, and the pearly nautilus. Characteristics of MoUusca. The name Mollusca is given on account of the fact that the bodies of these animals, ex- cepting the shell, have no hard parts. In Mollusca the body- is typically bilateral. There is a mantle present which in most cases secretes a shell which is as much a part of the animal as is the mantle itself. These shells increase in size as the animal grows, and . so exhibit lines of growth. A fleshy foot is also present. The nervous system consists of three pairs of ganglia connected by nerves. Eyes are present in many forms and in the higher cephalopods they closely re- semble the eyes of Vertebrates. In all but the Pelecypoda the mouth is provided with a lingual ribbon, which is a sort of rasp in the mouth by which in many cases thick shells may be bored entirely through. Questions. How do the sense- organs of moUusks' which forage for food compare with those of sedentary mollusks } What protective devices do you observe among mollusks .■" How can one compel an oyster to produce a pearl .'' Topics for Reports. Tyrian Dyes. Eye-stones. The Octopus and Squid. The Chambered Nautilus. 9f^^f^^ Tv"irvi>|, Fig. 131 Part of a Lingual Rib- bon {magnified). MUSSELS /tND SNAILS. 167 The Argonaut. Some Fabulous Monsters of the Sea. Oyster Farming. Pearl Fisheries. Famous Pearls. The Ship-worm. Wampum and Suckanhock. The Scallop. VOCABULARY. A.d duc'tor (Lat. ad, to, and litico, Ic.id), a word applied to the muscles which hold together the shells of bivalves. An'odon {Gr. ii, priv., and-tJt/i^/w, a tooth), a genus of fresh-water mussels having no hinge-teeth. Bi'valve (I.at. ii, two, and valva, a leaf of a door), having two shells which open and shut. Bran'chi a (Gr. iranchia, gills, pi. of branchion, a fin), gills. Bys'sus (Gr. byssos, a kind of flax), a bunch of tough threads by means of which some bivalves attach themselves to rocks. Car niv'o reus (Lat. caro, flesh, and voro, to devour), flesh-eat- ing. Col u mel'la (Lat. dim. of colu- men, a column), the upright pil- lar in the axis of a univalve shell. Dex'tral (Lat. dexter, right), right-handed, Epider'mis (Gr. epi, upon, and derma, skin), the outer skin of an animal. Her biv'o rous (Lat. herba, grass, and voro, to devour), vegetable- eating. Hinge Lig'a ment (Lat. ligo, to bind), an elastic substance forc- ing open bivalve shells when the muscles relax. Lin'gual Rib'bon (Lat. lingua, tongue), a rasp-like organ used in boring holes through shells. Mantle (Lat. manus, hand, and tela, a web), the soft outer cover- ing of the body of a muUusk, commonly just under the shell. Na'cre, mother of pearl. (E soph'a gus (Gr. oiso, will bear and phagein, to eat), the tube leading from the mouth to the stomach. per'cu lum (Lat. operailum, a lid), the lid closing the aperture of a snail's shell. Pal'lialLine {^■i.i. pallium, a man- tle), the mark on the inside of a mollusk-shell made by the man- tle. Se'tae (Lat. pi. of seta, a bristle), bristles. Sin'is tral (Lat. sinister, left), left- handed. Si'phon (Gr. siphon, a siphon), a tube for passing water through the gill-cavity of a moUusk. Su'pra oe soph a ge'al (Lat. supra, above, and cesophagits), an ad- jective applied to the ganglion aVjove the throat. TJtnbiricus (Lat. umbilicus, navel), an opening near the cen- tre of the base of some spiral shells, XJm'bO (Lat. umbo, the boss of a shield), a prominence near the hinge of a bivalve shell. Un'io (Lat. unus, one), a genus of fresh-water mussels. Whorl, one turn of the spire of a univalve shell. 1 68 /tNIMAL /tCTiyiTIES. c a o •a 1 I i in i I i < cd i Skeleton, plates, rings, or spicules. Internal or ex- ternal. 1 c 1 1 O CHAPTER XVI. THE STRUCTURE AND ACTIVITIES OF A FISH. Goldfish or other small fish fi-om streams or ponds are easily kept in aquaria. With a few living fish placed where pupils can observe them, and a smelt or perch from the market as an individual specimen for study on each bench, the following ques- tions may be answered : Shape and Covering. Is the fish bilateral ? Esti- mate length, thickness, and depth. What is the shape of the body ? Do you find a head .'' a neck } D.O you find scales } Do they cover the entire animal } Are the scales joined edge to edge {tesselated') or do they overlap {imbricated^- Remove some of the skin. What is the appearance of the muscle below } Notice the line extending along the side of the fish from head to tail {lateral line). Do the scales cover- ing this line differ from those found elsewhere on the body } The Fins. How many fins do you find .■' How many are dorsal .■' How many ventral .'' How many are paired .'' Which fins correspond to the limbs on our own bodies } The paired fins nearest the head of the perch are , called the pectoral fins, those somewhat farther back nearer the anal opening are called the pelvic fins. The large fin along the back is the dorsal fin. The unpaired 169 '7° MIMML ^CriyiTlES, fin .ildMf^^ the median vciUial line is (lio fi>/(i/ nr vciili al fin, 'i'lic I'm .il the end of the tail Im tlw utiiilitl I'lii. Sl<('tcli a fisli with fins extended. indii ale lli<' names of the fins. or wliat UHe are tlie hunes in tlie (ins (fin-ia)'sj? Does the fish swim by nsin^ its iins, or its tail, oi holl) ? The Head. What iir^;;ins of sense do yon lind ? 'J'lie ears are internal. Arc the eyes movable ? Do they have lids ? How does the eye of the fish resenilile the eye ol man ? ol the f;rasslH)|)])cr ? ilow does it iliCfcr fi-oni lliesi' ? iJo the nostrils open into the mouth ? Use a toolli- pick for a probe. Arc the noslrils ol nse in hieatliini; i" Of what use are they ? J)(>es the mouth open vertieally, or lafrraljy ? Where arc the tcetli situated ? What is their shape ? Whal about tlic shape and jiosition of llif totifoie ? Gills and Heart. What movemcnls dors ihe nsli make while breathinf,' ? Raise the ^'ill-cover of the specimen on thf lieni h. low many f;ill» do yon find? Ilow many (;ill-el<'lts )r sjjaces between the f^dll.s ? The bony siip|)orts of the (^ills arc (ailed liraiuliidl ardiL's. The sfWt delicate red brani lies from these arches are the ^^ill-filnincnls. In these the blood is purified. What is the color of the blood ol a fish ? ('an you sec the branchial arches hy lookinj; into the mouth of a fish ? Remove the skin ;ind mns( iilar walls from that por- tion of the ventral cavity dirc'ttly behind the jolls, riiis c,xj)oscs the heart. Can yon >:cf the ';wcllin(;s indicating the two f avitics of the heart, the run nic and the Tfiit/'irir 7 The vcntri» h: ha-, the form ol ;r lii- anf^nlar pyramid. The auricle is thin- walled ;iiid Idled with venous blr)r;d, hence it looks like a ( lot ol blood attached to the ventricle, 'I he lar(;c tilor,d-ve -.-.f j from the heart to the gills i» the ventral aorta. Ii-, THE STRUCTURE y4ND /iCTiyiTlES OF A FISH. 171 enlargement near the heart is called the 2xiers2\ bulb. The blood-vessels bringing blood to the heart are called veins. Do you find the ventral aorta, the arterial bulb, and a large vein 'i Make a sketch to show their position. Sketch a single gill from a cod, or other large fish. Indicate the parts observed. Trace the course of the blood- vessels in an injected specimen. Internal Structure. With a sharp knife make a cross-section of the body of a fish a little in front of the anal opening. Sketch the appearance of the section, shov/ing the location of the vertebral column or back-bone, the spinal nerve within the neural cavity, the visceral cavity, and the muscles surrounding all. Do you find any large blood-vessels ? Place the fish on its side in the bottom of a pan containing water enough to cover Fig. 132. — The Circulation of Blood in a Fish. A, aortic bulb; H. heart; B, arteries supplying gills; V, veins; b. veins conveying aErated blood from the '^illstothe dorsal aorta; Z, vessels of liver; v4', kidney. it. With sci.ssors re move the portion covering one side of the digestive 172 ANIM/IL JCTiyiTIES. cavity, being careful not to disturb the organs within. Do you find the body-cavity ? Pass a probe down the mouth until you are able to make out the stomach, the oesophagus, extending from the mouth to the stomach, and the intestine, extending from the stomach to the anal opening. This is the alimentary canal. Is the intestine coiled or straight .'' Sketch this alimentary canal. Do you find a membrane holding the stomach and intestine in place .■■ This is the mesentery. Do you see blood-vessels in the mesentery .■• In the front of the body-cavity do you see the large, Fig. 133 — Internal Organs of Fish, a, oesophagus; bed, stomach; /, duct of swimming-bladder; k, swimming-bladder; h, ovary. brownish liver ">. Can you find a gall-bladder, green or yellow in color, attached to the liver .? In the body-cavity can you see the reproductive or- gans } Usually these are smooth and whitish in the male and yellow and granular in the female. Directly under the back-bone do you find the air- bladder .? This organ is homologous with the lungs of higher vertebrates. Do you also find a large blood- vessel above the air-bladder f Brain and Nerves. Use the head of a large fish obtained from the market. With great care remove the upper part of the skull. Commonly it is better to use preparations previously dissected by the teacher. These may be kept in formalin, or alcohol. The THE STRUCTURE AND ACTIVITIES OF A FISH. i73 largest pair of globular masses are the optic lobes. In front of these we find the cerebral lobes, corresponding to the cerebrum or front brain in man. Behind the optic lobes the cerebellum is situated. Sketch the brain showing all these parts, showing also the olfactory nerves extending to the nostrils, the optic nerves lead- ing to the eyes, the auditory nerves leading to the ear-sac with its "ear-stone," and the spinal nerve extending along the back. The Bones of a Fish. Skeletons or parts of skele- tons can be easily prepared for laboratory use by soak- ing in hot water. Heads and backbones of large fish can be obtained without cost at the markets in most places. Fig. 134.— Skeleton of a Fish. With the skeleton of a fish notice the visceral cavity and the neural cavity. What is the relation of these cavities 1 Notice the brain-cavity. Where was the brain con- nected with the spinal cord .' Do you find openings for nerves extending to ears, eyes, and nostrils } Do you see how the skull is joined to the vertebral column .'' 174 ANIMAL ACTII^ITIES. How is the lower jaw suspended from the skull ? Separate the back-bone, or vertebral column, into parts (vertebrae). Are the vertebra; near the tail like those near the head ? Study particularly one of the vertebrae near the tail. The main part of a vertebra is the centrum. Is the centrum entirely solid .'' What is its shape in a longitudinal section after removing all soft parts 1 Sketch front and side view of a vertebra, and a longitudinal section. Do you find the cavity for the spinal cord } Call this cavity the neural cavity, and the processes at- tached to the centrum and enclosing the neural cavity, the neural arch, and the spine above it the neural spine. Is this spine dorsal or ventral } Does it point towards the anterior or the posterior part of the body .'' Do you find the cavity for the passage of the large blood-vessel .' Call this the haemal arch, and the spine attached to it the haemal spine. This arch protects the dorsal aorta. Are there any ribs present .' Using one of the vertebrae above the visceral cavity, find how it differs from a vertebra near the tail. Summary of Drawings, {a) Side view of fish with fins extended. {b) Side view of head of a fish showing as many parts as possible. {c) Gill of a fish showing parts. Heart of fish with arteries and veins. ( o CHAPTER XVII. TADPOLES AND FROGS. In the study of the frog, aquaria are indispensable. The expense, however, need not be large. In one aquarium tadpoles should be placed together with a few aquatic plants. The minute green plants which grow on the sides of the aquarium will furnish food enough. The adult frogs can be kept in a box with glass sides with only a small amount of water in the bottom and a netting to cover the top. In warm weather frogs feed on insects; in winter they go without food. The Tadpole. Is it bilateral .' Is the skin naked or scaly .' Do you see a lateral line .'' In what ways does it resemble a fish .'' How does the tail of a tadpole differ from the tail of a fish .' In any of the tadpoles can you see the beginnings of limbs .'' Which limbs appear first ? In a young tadpole how do the gills appear .' Can you see the gills in an older tadpole ? Do tad- poles come to the surface of the water to breathe ? Can you find in a specimen which has been hardened in alcohol a gill-cavity ? Can you find an opening into this cavity .'' Are the jaws hard or soft .' Watch the tadpoles feeding on the sides of the aquarium, or Jar. How does the size of the mouth compare with that in the adult .' 179 i8o ANIM/1L ACTiyiTlES. In a specimen which has been hardened in alcohol do you find vertebrae ? Do you find a notochord ? Do you find muscles like those in the fish ? Notice the spirally coiled intestine. Hold the tail of a living tadpole under a compound microscope and observe the movement of the blood. Notice the corpuscles. Summary of Drawings, {a) Side view of tadpole. {b) Dorsal view of a young tadpole to show gills. (c) Sketch to show blood-vessels as seen under the microscope. The Frog Alive. How does the frog resemble the fish .'' the tadpole .-" Do you find scales, hair, claws, or nails 1 Do you find tail or fihs .'' How about legs } What is the frog's mode of locomotion on land ? in water .■' How many divisions have the hind limbs 1 the fore limbs 1 How do they compare with the limbs of the human body .-' Do the joints move in the same way as ours .'' Do you find arm, forearm, and wrist .'' How many fingers } How many toes } Are fingers or toes webbed .■" Do you find a thumb } How does the frog take its food .'' How does the tongue act 1 What movements are made in breathing .' Are there any gills .■' How long can a frog live under water .'' Does the frog have the same senses and the same organs of sense as man } Do you find ears .'' eyelids .' Do you find a mem- brane covering the eye (nictitating membrane) .' Frog Hardened in Alcohol. Look in the mouth. Do you find any teeth .-" How many } Where are they .? What is the shape of the tongue .' Do the nostrils connect with the mouth .' Does the ear-cavity connect with the mouth ? T/1DPOLES AND FROGS. i8i (Eustachian tube.) Cut open the membrane covering the ear and use a probe. Using a prepared specimen showing the internal organs, do you find the peritoneum .'' the mesentery .'' the stomach ' the intestine ? the liver .-' the heart .'' Do you find the lungs ? Is there a diaphragm separating the heart and lungs from the stomach, liver, and intestine .-' Dorsal to the viscera in a freshly prepared specimen look for nerves branching out from the spinal cord. Do you find nerve-masses (ganglia) on these nerves on each side of the spinal column ? Are these ganglia connected by a nerve running lengthwise .' Call this the sympathetic system of nerves. In a prepared specimen notice the brain and spinal cord. Sketch the brain in outline. How does this sketch compare with the sketch you have made of the brain of the fish .' In what ways does a frog resemble a fish ? How does the frog differ from the fish ? Summary of Drawings, (a) Outline of organs seen in the visceral cavity. (<5) Sketch of ganglia of sympathetic system with connecting nerves. (c) Outline sketch of brain of frog. Activities. Both the structure and the activities of the frog interest us because they are so much like those of man himself. The frog has been much studied because of the remarkable changes in structure and habits which the animal undergoes after leaving the egg- Taking Food. The frog lives on insects, worms, and other small animals. As a rule frogs eat only dur- ing the summer months, remaining torpid without food in winter. The tongue of the frog is peculiarly adapted for catching insects. It is fastened to the lower jaw by its front end, and turns a somersault when shot out at a fly. The hinder end is covered with a sticky l82 ANIM/IL ACTIVITIES. saliva which holds the fly a prisoner until the jaws close over him. The ease and quickness with which an insect disappears are always a surprise to the observer. When feeding on large animals the frog seizes his prey with jaws and front legs, and hurriedly crowd- ing his luckless victim into his mouth, swallows him alive. Teeth are present on the upper jaw and on the palate or roof of the mouth. Taking Oxygen. When the young frog emerges from the egg it takes air from the water by means of external gills. Into these the blood is pumped directly from the heart, as in fishes. Here the oxygen passes into the blood for purification, and thence is conveyed to all parts of the body. In a few days these external gills disappear, and other gills grow under the opercular membrane. This Fig. 135. — Tongue of a Frog. Fig. 136. — A Young Tadpole Showing External Gills. membrane is joined to the body-wall except on the left side, where an opening for the passage of water remains. The young frog now breathes like a fish. The TADPOLES AND FROGS. 183 heart, too, like that of a fish, has only two chambers, an auricle and a ventricle. After a time lungs develop, and the tadpole, while still using his gills to some extent, finds it necessary to come to the surface of the water occasionally for air. Finally the gills disappear and the frog breathes only Fig. 137. — Under Side of Tadpole Showing Coiled Intestine and Internal Gills. by lungs. While these changes are going on, the heart develops another auricle on the left side for the reception of the purified blood from the lungs. The right auricle receives the impure blood returning from the circuit of the body. Not only does the frog, at different times, breathe in the three ways just mentioned, but at all times it ^V^ Fig. 138.— Heart of Adult Frog. a, auricles ; v, ven- tricle. Fig. 139. — Blood-cells of a Frog, a, red cor- puscle; 6, colorless cor- puscle. breathes by the entire surface of the body, the skin being especially rich in blood-vessels. 1 84 ANIMAL ACTIVITIES. The adult frog pumps the air into the lungs by the movements of the muscles of the throat and lower part of the mouth-cavity. When the mouth-cavity enlarges, air rushes in through the nostrils. When the cavity contracts, valves close the openings to the nostrils and the air is forced down into the lungs. The frog has Fig. 14.0. — Blood-corpuscles of Man. s, r', r'', red corpuscles ; p and g, white corpuscles; c, crystals. neither ribs nor diaphragm — organs of great importance in our own breathing. The oxygen, once taken by the blood, is carried by the red corpuscles, or blood-cells, to all parts of the body, where in the capillaries it is given up to burn, or oxidize, tissues and food substances in order to produce heat and energy. Nutrition. Food passes from the mouth to the stomach, where it is acted on by fluids like those in our own bodies. It then passes to the intestines, where the bile secreted by the large liver and the pancreatic T/tDPOLES AND FROGS. i8S juice from the pancreas are poured upon it. Here further changes take place and the digested food is absorbed and taken to the blood-vessels. The un- digested portions of the food pass along the intestine to the cloaca, which is the common receptacle for use- FlG. 141. — Viscera of Frog. .S/w./k., small intestine; Z./., large intes- tine; Ur.Bl., bladder; pe.ca., pericardial cavity; V, ventricle; T.A,, large artery; Ao, aorta; /, pulmonary artery; Pn, pancreas. less substances from the food-tube, and the kidneys and eggs or sperm-cells from the reproductive organs. Thence the useless matter and the reproductive cells pass from the body. When the tadpole first comes from the egg, the food- tube quickly grows into the long coiled tube shown in Fig. 137 and this in turn gives place to the tube as we have seen it in the adult frog. It is interesting to note that the lungs, liver, and pancreas are outgrowths from the side of the food-tube, 1 86 ANIMAL ACTll^ITIES. produced by a pushing out of the walls of the tube itself (Fig. 143). Excretion. Carbon dioxide and water are taken by the blood-corpuscles to the breathing organs and to the skin, where they are thrown out of the body. Urea and GATE (pylorus). 12 INCH PIPEI DUODEN STOMACH Fig. 142. — Digestive Organs of Man. water are taken from the blood by the kidneys and passed along to the urinary bladder and thence out ol the body. Reproduction and Metamorphosis. The female frog deposits her eggs in the water in spring in large jelly-hke masses. As soon as hatched the young tad- TADPOLES AND FROGS. 187 poles cling in clusters to plants, or other objects; life being sustained by the food-yolk within the body. After a few days, a mouth with horny jaws develops and the animals begin to feed. The tadpole now eats plants, being especially fond of the green confervae so common on the sides of aquaria. Growth is now rapid, and in a few months the legs appear and the tail is absorbed. Fig. 143. — Growth of Frog's Lung from Primitive Food-tube. Movements. The most important organs of motion are the muscles. A muscle causes movement by shortening itself, and thus bringing nearer together its two ends with whatever is attached to them. In gen- eral, muscles are attached to bones. How muscle and bone together produce movement may be well under- stood by studying Fig. 148 in connection with the movements of the human arm. ANIM/fL /tCTiyiTIES. Fig. 144. — Growth of Frog's Egg. A muscle shortens because the cells of protoplasm of which it is composed all have the power of contrac- tility. The cells all contract in one direction, making the whole muscle shorter and thicker. These contractions are under the control of the nerves. A number of muscle-cells make one of the fibrillse. Several of these fibrillar wrapped in a sheath form a fibre. The fibres are wrapped in bundles, and these bundles are covered by a thin layer of tough connective tissue. The sheaths or coverings of muscles, bundles, and fibres unite to form tendons by which the muscles are attached to the bones (Figs. 149 and 150). Muscles under the control of the will, like those in the leg of a frog or of a man, show peculiar cross-mark- ings. Muscles not under the control of the will, like those of the intestine or stomach, are commonly unstriped. The bony skeleton of the frog, on which the muscles act to cause the movements of the body, has an axis of nine movable bones, the vertebrse. Behind these a long bone, the urostyle, reaches to the hips, and in front is at- tached the head with its broad skull and large jaws. On the base of the skull are two rounded prominences called condyles, which fit into corresponding de- pressions on the atlas-bone, the first bone of the vertebral axis (Fig. 151). The fore limbs are attached to the axial skeleton by muscles and ligaments. A shoulder, or pectoral girdle, consisting of several bones is present. The hinder Fig. 145 Very Young Tadpoles. TADPOLES AND FROGS. 189 limbs are attached to the axial skeleton through the pelvic girdle. The bones of the arm consist of the humerus, or forearm, the radio-ulna, corresponding to \iy Fig. 146. — Various Stages of Tadpole. the two bones, the radius and ulna in man, the carpal or wrist-bones, the metacarpal or hand-bones, and the fingers or phalanges. In the leg are the femur or thigh-bone, the shin-bone corresponding to the tibia Fig. 147.— Young Frogs. and fibula in man, the tarsal bones, two of which are much longer than the others, the metatarsal or ankle- bones and the //^a/a^^^^i' (Fig. 152). Controlling the organs of motion and extending into 1 9° ANIMAL ACTiyiTIES. every muscle for that purpose is the nervous system. This consists of a brain connected with the spinal cord, and a series of ganglia with nerve connections in the visceral cavity. From these centres nerves run to all parts of the body. The division between brain and spinal cord is not so sharp as in man. The brain itself has the same parts as the brain of man, but these parts do not have the same shape or relative size (Figs. 1 5 3 and 1 54) . Fig. 148.— The Use of a Muscle. Notice how large the olfactory and optic lobes appear in the frog. In man- they are small and do not show in the figure. In man, too, the cerebrum or forebrain has grown so large that it occupies almost the whole of the brain-cavity. These facts of structure would seem to indicate that sight and smell are of more im- portance to the frog than memory or reason. Discovery. It is the duty of the nervous system to keep in touch with the outer world, in order that the movements made may be useful to the animal. TADPOLES AND FROGS. 191 Sight. The optic lobes just mentioned are con- nected with a pair of eyes very much like our own. Each eye is really a camera obscura with its lens and darkened walls. The image of an external object is thrown on the retina, which corresponds to the ground glass of a camera and is composed of nervous tissue forming the end of the optic nerve. The frog sees well, B ■i^" Fig. 149.— Striped Muscle-fibres. A, a fibre much magnified; B, a fibre breaking up into fibrillee. as is evidenced by the precision with which he strikes a fly with his tongue. Hearing. On either side of the head is a dark cir- cular spot which indicates the position of the ear. This ear is wholly internal. Under the skin is a membrane, or ear-drum, and under that a cavity, the middle ear. This cavity connects with the mouth by the eustachian tube as in man. Back of this cavity is another, the inner ear, containing the nerves which conduct sound vibrations to the brain. Smell. In the nasal cavities fibres of the olfactory nerve are spread out to receive the sensations of smell. 192 /tNlMAL ACTiyiTlES. Taste. Special organs of taste are found on the tongue and on the membrane hning the mouth. Touch. The skin is well supplied with nerves, and there are special tactile areas. Classification. The frog belongs to the division of Vertebrata known as Amphibia or Batrachia. They receive their name Amphibia from the fact that the young live in water breathing by gills, while the adult forms breathe air. As might be ex- pected, there are exceptions to this general rule. The Amphibia are destitute of scales, the skin being perfectly naked, and in most cases provided with peculiar glands. They have no claws. The Amphibia differ from the fishes in having a connection between the mouth and nostrils, and also between mouth and ear. The heart in the adult has three chambers, a ventricle and two auricles. In the larva the heart is two-chambered. All live in fresh water. To this class belong the toads, frogs, and sala- manders. Reptiles. Questions similar to those used concerning the frog may be answered about turtles and snakes. Living turtles and snakes are easy to obtain and fairly easy to keep alive. A large box with glass sides covered with wire netting makes a good vi- varium. Sand and gravel and a dish of water should be kept in the bottom of this box. A little moss provides a carpet. The class Reptilia resembles in many ways the ■a .5* m C I d TADPOLES AND FROGS. 193 Amphibia. The class includes many animals resem- bling toads and salamanders, besides the well-known turtles, snakes, crocodiles, and alligators. Among Reptiles the body is more or less completely covered Fig. 151. — A Frog's Skeleton. by scales, and when there are any toes these are armed with claws. The heart is three-chambered, as in the case of Amphibians, except in alligators. The young do not breathe by gills as in Amphibia. The eggs are 194 ANIM/1L ACTIVITIES. commonly large and when deposited for hatching out- side of the body are covered with a limy shell. A Fig. 153. — Brain of Frog.