Elementary zoology

Preface

It seems to the author that three kinds of work should be included in the elementary study of zoology. These three kinds are: (a) observations in the field covering the habits and behavior of animals and their relations to their physical surroundings, to plants, and to each other ; (b) work in the laboratory, consisting of the study of animal structure by dissection and the observation of live specimens in cages and aquaria ; and (V) work in the recitation- or lecture-room, where the significance and general application of the observed facts are considered and some of the elementary facts relating to the classification and distribution of animals are learned.

These three kinds of work are represented in the course of study outlined in this book. The sequence and extent of the study in laboratory and recitation-room are definitely set forth, but the references to field-work consist chiefly of suggestions to teacher and student regarding the character of the work and the opportunities for it. Not because the author would give to the field-work the least important place, — he would not, — but because of the utter impracticability of attempting to direct the field-work of students scattered widely over the United States. The differences in season and natural conditions in various parts of the country with the corresponding differences in the " seasons " and course of the life-history of the

iii iv PREFACE

animals of the various regions make it impossible to include in a book intended for general use specific directions for field-work. Further, the amount of time for field-work at the disposal of teacher and class and the opportunities afforded by the topographic character of the region in which the schools are located vary much. The initiation and direction of this must therefore always depend on the teacher. On the other hand, the work of the other two phases of study can to a large extent be made pretty uniform throughout the country. For dissection, specimens properly killed and preserved are about as good as fresh material, and by modifying the suggested sequence of work a little to suit special conditions or conveniences, the examination of live specimens in the laboratory can in most cases be accomplished.

The author believes that elementary zoological study should not be limited to the examination of the structure of several types. The student should learn by observation something of the functions of animals and something of their life-history and habits, and should be given a glimpse of the significance of his particular observations and of their general relation to animal life as a whole. The drill of the laboratory is perhaps the most valuable part of the work, but as a matter of fact the high school is trying to teach elementary zoology, an elementary knowledge of animals and their life, and dissection alone cannot give the pupil this knowledge. On the other hand, without a personal acquaintance with animals, based on careful actual observations of their life-history and habits and on the study of the structural characters of the animal body by personally made dissections, the pupil can never really appreciate and understand the life of animals. Reading and recitation alone can never give the student any real knowledge of it.

The book is divided into three parts, of which Part I

PREFACE V

should be * first undertaken. This is an introduction to an elementary knowledge of animal structure, function, and development. It consists of practical exercises in the laboratory, each followed by a recitation in w 7 hich the significance of the facts already observed is pointed out. The general principles of zoology are thus defined on a basis of observed facts.

Part II is devoted to a consideration of the principal branches of the animal kingdom ; it deals with t systematic zoology. In each branch one or more examples are chosen to serve as types. The most important structural features of these examples are studied, by dissection, in the laboratory. The directions for these dissections consist of technical instructions for dissecting, the calling attention to and naming of principal parts, together with questions and demands intended to call for independent work on the part of the .student. The directions follow the actual course of the dissection instead of being arranged according to systems of organs, and are intended for the orientation of the student and not to be in themselves expositions of the anatomy of the types. The condensation of these directions is made more feasible by the presence of anatomical plates (drawn directly from dissections). Following the account of the dissection of the type are brief notes on its life-history and habits.

* This is true if a strictly logical treatment of the subject is held to. As a matter of fact, it is often of advantage to begin with, or at least to take up from the beginning in connection with the indoor work, some field-work, such as the collecting and classifying of insects and the observation of their metamorphosis. As most schools begin work in the fall, advantage must be taken of the favorable opportunities for field-work at the beginning of the year. These opportunities are of course much less favorable in the winter.

f The classification of animals used in this book is that adopted in Parker and Haswell's " Text-book of Zoology" (2 vols., 1897, Macmillan Co.). Exception is made in the case of the worms, which are considered as a single branch, Vermes, instead of as several distinct branches.

vi PREFACE

Then follows a general account of the branch to which the example dissected belongs and brief accounts of some of the more interesting members of the branch. In these accounts technical directions are given for brief comparative examinations and for the study of the life-history and habits of some of the more accessible of these forms.

It will not be possible, of course, to undertake with any thoroughness the consideration of all of the branches of animals in a single year. But all are treated in the book, so that the choice of those to be studied may rest with the teacher. This choice will of necessity depend largely on the opportunities afforded by the situation of the school, as, for example, whether on the seashore or in the interior near a lake or river, or on the dry plains, and on the relation of the school-terms to the seasons of the year. The branches are arranged in the book so that the simplest animals are first considered, the slightly complex ones next, and lastly the most highly organized forms. But if in order to obtain examples for study it is necessary to take up branches irregularly, that need not prove confusing. The author would suggest that whatever other branches are studied, the insects and birds, which are readily available in all parts of the country, be certainly selected, and with this selection in view has given them special attention. Indeed some teachers may find these two branches to offer quite sufficient work in classificatory and ecological lines.

Part III is devoted to a necessarily brief consideration of certain of the more conspicuous and interesting features of animal ecology. It has in it the suggestion for much interesting field-work. The work of this part should be taken up in connection with that of Part II, as, for example, the consideration of social and communal life in connection with the insects, parasitism in connec-

PREFACE vii

tion with the worms, and also with the insects, distribution in connection with the birds, perhaps, and so on.

In appendices there are added some suggestions for the outfitting of the laboratory, and a list of the equipment each student should have. Here, also, is appended a list of a few good authoritative reference books which should be accessible to students and to which specific references are made in the course of this book. Some practical directions for the collecting and preserving of specimens are also given. (Suggestions for the obtaining of material for the various laboratory exercises outlined in the book are to be found in " technical notes " included in the directions for each exercise.) The author believes that the building up of a single school-collection in which all the pupils have a common interest and to which all contribute is to be encouraged rather than the making of separate collections by the pupils. Waste of life is checked by this, and in time, with the contributions of succeeding classes, a really good and effective collection may be built up. The "collecting interest" can be taken advantage of just as well in connection with a school-collection as with individual collections.

The plates illustrating the dissections have all been drawn originally for the book from actual dissections. Most of the other figures are original, either drawn or photographed directly from nature, or from preserved specimens. Credit is given in each case for figures not original. The drawings for all of the figures of dissections and for all original figures not otherwise accredited were made by Miss Mary H. Wellman, to whom the author expresses his obligations. The thanks of the author are due to Mr. George Otis Mitchell, San Francisco, who kindly made the photo-micrographs of insect structure from the author's slides; to Professor Mark V. Slingerland, Cornell University, for electros of his photovin PREFACE

graphs of insects; to Dr. L. 0. Howard, U. S. Entomologist, for electros of figs. 45, 52, 56, 68, 81, 82, 83, 84, 87, 90, and 92; to Professor L. L. Dyche, University of Kansas, for photographs of his mounted groups of mammals; to Mrs. Elizabeth Grinnell, Pasadena, Calif., for photographs of birds; to Mr. J. O. Snyder, Stanford University, for photographs of snakes; to Mr. Frank Chapman, editor of " Bird-lore," for electros of photographs of birds; to Mr. G. O. Shields, editor of " Recreation," for an electro of the photograph of a bird; to the American Society of Civil Engineers for electros of photographs of boring marine worms; to Cassell & Co., for electros of three photographs from nature; to Geo. A. Clark, secretary Fur Seal Commission for photographs of seals; and to the Whitaker and Ray Co., San Francisco, for electros of figs. 46, 59, 60, 61, 64, 65, 93, 94, 97, 98, 99, 100, 102, 119, and 166 to 172, published originally in Jenkins & Kellogg's ''Lessons in Nature Study.' The origin of each of these pictures is specifically indicated in connection with its use in the book.

The author's sincere thanks are also due to Mrs. David Starr Jordan and to Mr. J. C. Brown, graduate student in zoology in Stanford University, for their assistance in the correction of the MS., and in the preparation of the laboratory exercises respectively. The chapters of Part II relating to the vertebrates were read in MS. by President David Starr Jordan, whose aid and courtesy are gratefully acknowledged. Similar acknowledgments are due Professors Harold Heath and R. E. Snodgrass for reading the proofs of the directions for the laboratory exercises.

Vernon Lyman Kellogg.

Stanford University, May, 1901.

Part I Structure, Functions, And Development Of

ANIMALS

I. -THE STUDY OF ANIMALS AND THEIR LIFE.

Our familiar knowledge of animals and their life, I. — Zoology and its divisions, 2. — A first course in Zoology, 3.

II.— THE GARDEN TOAD (Bufo Lentiginosis).

[Laboratory exercise], 5. — External structure, 5. — Internal structure, 7.

III.— THE STRUCTURE AND FUNCTIONS OF THE ANIMAL BODY.

Organs and functions, 14. — The animal body a machine, 14. — The essential functions or life-processes, 15.

IV.— THE CRAYFISH (Cambarus sp.). [Laboratory exercise], 17. — External structure, 17. — Internal structure, 21.

V.— THE MODIFICATION OF ORGANS AND FUNCTIONS.

Difference between crayfish and toad, 26. — Re-emblances between crayfish and toad, 27. — Modification of functions and structure to fit the animal to the special conditions of its life, 29. — Vertebrate and invertebrate, 30.

VI.— AMCEBA AND PARAMECIUM.

[Laboratory exercise], 31. — Amoeba, 31. — The slipper-animalcule (Paramecium sp.), 34.

ix

* CONTENTS

VII.— THE SINGLE -CELLED ANIMAL BODY; PROTOPLASM

AND THE CELL.

The single-celled animal body, 36. — The cell, 37. — Protoplasm, 39.

VIII. -CELLULAR STRUCTURE OF THE TOAD (OR FROG).

[Laboratory exercise], 40. — The blood, 40. — The skin, 40. — The liver. 41. — The muscles, 41.

IX.— THE MANY-CELLED ANIMAL BODY; DIFFERENTIATION

OF THE CELL.

The many-celled animal body, 43. — Differentiation of the cell, 43.

X.— HYDRA.

XL— THE SIMPLEST MANY-CELLED ANIMALS.

Cell-differentiation and body-organization in Hydra, 52. — Degrees in cell-differentiation and body-organization, 54.

XII.— DEVELOPMENT OF THE TOAD. [Field and laboratory exercise], 55.

XIIL— MULTIPLICATION AND DEVELOPMENT.

Multiplication, 57. — Spontaneous generation, 58. — Simplest multiplication and development, 59.— Birth and hatching, 61. — Life-history, 62.

Part II Systematic Zoology

XIV.— THE CLASSIFICATION OF ANIMALS. [Laboratory exercise and recitation], 65. — Basis and significance 01 classification, 65. — Importance of development in determining classification, 67. — Scientific names, 68. — An example of classification, 68. — Species, 69. -Genus, 70. — Family, 72. — Order, 72. — Class and branch, 73.

XV.— BRANCH PROTOZOA : THE ONE-CELLED ANIMALS. Example : The bell animalcule (Vorticella sp.) [Laboratory exercise], 75.

Other Protozoa.

Form of body, 78. — Marine Protozoa, 80,

CONTENTS xi

XVI.— BRANCH PORIFERA: THE SPONGES.

Example: The Fresh-water sponge (Spongilla sp.) [Laboratory exercise], 84.

Example: A calcareous ocean-sponge (Grantia sp.) [Laboratory exercise], 85.

Example: A commercial sponge [Laboratory exercise], 86.

Other Sponges.

Form and size, 87. — Skeleton, 88. — Structure of body, 88. — Feeding habits, 88. — Development and life-history, 89. — The sponges of commerce, 90. — Classification, 91.

XVII.— BRANCH CCELENTERATA: THE POLYPS, SEA- ANEMONES, CORALS, AND JELLYFISHES.

Polyps, sea-anemones, corals, and jellyfishes.

General form and organization of body, 93. — Structure, 94. — Skeleton, 95. — Development and life-history, 95. — Classification, 96.— The polyps, colonial jellyfishes, etc. (Hydrozoa), 97. — The large jellyfishes, etc. (Scyphozoa), 1 01. — The sea-anemones and corals (Actinozoa), 102. — The Ctenophora, 107.

XVIIL— BRANCH ECHINODERMATA : THE STARFISHES, SEA- URCHINS, SEA CITUMBERS, ETC.

Example : Starfish (Asterias sp.) [Laboratory exercise]. — External structure, 108. — Internal structure, 110. — Life-history and habits, 113.

Example : Sea-urchin (Strongylocentrus sp.) [Laboratory exercise]. ■ — External structure, 113.

Other Starfishes, Sea-urchins, Sea-cucumbers, etc.

Shape and organization of body, 116. — Structure and organs, 117. — Development and life-history, 119. — Classification, 120. — Starfishes (Asteroidea), 121. — Brittle stars (Ophiuroidea), 122. — Sea-urchins (Echinoidea), 123. — Sea-cucumbers (Holothuroidea), 124. — Feather-stars (Crinoidea), 125.

XIX.— BRANCH VERMES: THE WORMS.

Example: The Earthworm Lumbricus sp.) [Laboratory exercise].

External structure, 127. — Internal structure, 129. — Life-history and habits,

133- Other Worms.

Classification, 135. — Earthworms and leeches (Oligochaeh-e . 136. — Flat worms (Platyhelminthes). 137. — Round worms (Nemathelminthes), 140. — Wheel-animalcules (Rotifera), 142.

xii CONTENTS

XX.— BRANCH ARTHROPODA : THE CRUSTACEANS, CEN- TIPEDS, INSECTS, AND SPIDERS.

Class Crustacea: Crayfishes, crabs, lobsters, etc.

Example; The crayfish (Cambarus sp.). Structure, 146. — Life-history and habits, 146.

Other Crustaceans.

Body form and structure, 147. — Water-fleas (Cyclops), 148. — Wood-lice (Isopoda), 150. — Lobsters, shrimps, and crabs (Decapoda), 151. — Barnacles,

XXL— BRANCH ARTHROPODA (CONTINUED).

Class Insecta : The Insects.

Example : The red-legged locust (Melanoplus femur-rubrum), [Laboratory exereise]. External structure, 157. —Life-history and habits, 161.

Example: The water- scavenger beetle (Hyerophilus sp.) [Laboratory exercise]. External structure, 163. — Internal structure, 166. — Life-history and habits, 169.

Example : The monarch butterfly (Anosia plexippus) [Laboratory exercise]. External structure, 171. — Life-history and habits, 175.

Example : Larva of monarch butterfly [Laboratory exercise] . Structure, 177.

Other Insects.

Body form and structure. 181. — Development and life-history, 188. — - Classification, 191. — Locusts, cockroaches, crickets, etc. (Orthoptera), 192. — The dragon-flies and May-flies (Odonata and Ephemerida), 194. — The sucking-bugs (Hemiptera), 197. — The flies (Diptera), 201. — The butterflies and moths (Lepidoptera), 205. — The beetles (Coleoptera), 206. — The ichneumon flies, ants, wasps, and bees (Hymenoptera), 212.

Class Myriapoda : The centipeds and millipeds.

Class Arachnida : The scorpions, spiders, mites, and tics.

XXII.— BRANCH MOLLUSCA : THE MOLLUSCS.

Example : The fresh-water mussel (Unio sp.) [Laboratory exercise]. Structure, 239. — Life-history and habits, 243.

Other Molluscs.

Body form and structure, 245. — Development, 246. — Classification, 246. — Clams, scallops, and oysters (Pelecypoda), 246. — Snails, slugs, nudibranchs, and " sea-shells " (Gastropoda), 252.— Squids, cuttlefishes, and octopi (Cephalopoda), 255.

CONTENTS xin

XXIII.— BRANCH CHORDATA: THE ASCIDIANS, VERTE- BRATES, ETC.

Structure of the vertebrates, 259. — Classification of the Chordata, 260. — The ascidians, 261.

XXIV.— BRANCH CHORDATA (CONTINUED).

Class Pisces : The Fishes.

Example : The golden sun fish Eupomotis gibbosus) [Laboratory exercise]. External structure, 263. — Internal structure. 265. — Life-history and habits, 270.

Other Fishes.

Body form and structure, 271. — Development and life-history, 276. — Classification, 277. — The lancelets (Leptocardii), 277. — The lampreys and hag fishes (Cyclostomata), 278. — The true fishes (Pisces), 279. — The sharks, skates, etc. (Elasmobranchiij. 279. — The bony fishes (Teleostomi), 281. — Habits and adaptations, 285. —Food-fishes and fish-hatcheries, 288.

XXV.— BRANCH CHORDATA (CONTINUED).

Class Batrachia : The Batrachians.

Body form and organization. 292.— Structure, 293. — Life-history and habits, 295. — Classification, 297. — Mud-puppies, salamanders, etc. (Urodela), 297. — Frogs and toads (Anura), 299. — CceciHans (Gymnophiona), 302.

XXVI. —BRANCH CHORDATA (CONTINUED).

Class Reptilia: The snakes, lizards, turtles, crocodiles, etc.

Example : The garter snake (Thamnophis sp.) [Laboratory exercise]. Structure, 303. — Life -history and habits, 308.

Other Reptiles.

Body form and organization, 310. — Structure, 311, — Life-history and habits, 312. — Classification, 313. — Tortoises and turtles (Chelonia), 314. — Snakes and lizards (Squamata), 317. — Crocodiles and alligators ^Crocodilia), 325.

XXVII.— BRANCH CHORDATA (CONTINUED).

Class Aves : The Birds.

Example: The English Sparrow iPasser domesticus) [Laboratory exercise]. External structure. 327. — Internal structure [Laboratory exercise], 329. — Life history and habits, 335.

Other Birds.

Body form and structure, 336. — Development and life-history, 339. — Classification. 340. — The ostriches, cassowaries, etc. (Ratitae), 341. — The xiv CONTENTS

loons, grebes, auks, etc. (Pygopodes), 343. — The gulls, terns, petrels, and albatrosses (Longipennes), 345. — The cormorants, pelicans, etc. (Steganopodes), 346. — The ducks, geese, and swans (Anseres), 347. — The ibises, herons, and bitterns (Herodiones), 347. — The cranes, rails, and coots (Paludicolse), 348. — The snipes, sand-pipers, plovers, etc. (Limicolae), 349. — The grouse, quail, pheasants, turkeys, etc. (Gallinse), 358. — The doves and pigeons (Columbse), 351. — The eagles, hawks, owls, and vultures (Raptores), 351. — The parrots (Psittaci), 353. — The cookoos and kingfishers (Coccyges), 354. — The woodpeckers (Pici), 354.— The whippoorwills, chimney-swifts, and humming-birds (Macrochires), 356. — The perchers (Passeres), 357. — Determining and studying the birds of a locality, 359. — Bills and feet, 362. — Flight and songs, 364. — Nestling and care of the young, 366. — Local distribution and migration, 367. — Feeding habits, economics, and protection of birds, 370.

XXVIIL— BRANCH CHORDATA (CONTINUED).

Class Mammalia : The Mammals.

Example : The Mouse (Mus musculus) [Laboratory exercise]. Structure, 373. — Life-history and habits, 379.

Other Mammals.

Body form and structure, 381. — Development and life-history, 387. — Habits, instincts, and reason, 387. — Classification, 388. — The opossums (Marsupialia), 389. — The rodents or gnawers (Glires), 390. — The shrews and moles (Insectivora), 391. — The bats (Chiroptera), 391. — The dolphins, porpoises, and whales (Cete), 393.— The hoofed mammals (Ungulata), 394. — The carnivores (Ferae), 396. — The man-like mammals (Primates), 398.

Part III Animal Ecology

XXIX.— THE STRUGGLE FOR EXISTENCE, ADAPTATION, AND SPECIES-FORMING.

The multiplication and crowding of animals, 404. — The struggle for existence, 406. — Variation and natural selection, 406. — Adaptation and adjustment to surroundings, 407.— Species forming, 408. — Artificial selection, 409.

XXX.— SOCIAL AND COMMUNAL LIFE, COMMENSALISM, AND

PARASITISM.

Social life and gregariousness, 410.— Communal life, 411,— Commensalism 413. — Parasitism, 415.

CONTENTS xv

XXXL— COLOR AND PROTECTIVE RESEMBLANCES.

Use of color, 424. — General, variable, and special protective resemblance, 426. — Warning colors, terrifying appearances, and mimicry, 430. — Alluring coloration, 433.

XXXII. —THE DISTRIBUTION OF ANIMALS.

Geographical distribution, 435. — Laws of distribution, 437. — Modes of migration and distribution, 437. — Barriers to distribution, 438. — Faunae and zoogeographic areas, 440. — Habitat and species, 441. — Species-extinguishing and species-forming, 442.

APPENDICES

EQUIPMENT AND METHODS

APPENDIX I.— EQUIPMENT AND NOTES OF PUPILS.

Equipment of pupils, 447. — Laboratory drawings and notes, 447. — Field observations and notes, 448.

APPENDIX II.— LABORATORY EQUIPMENT AND METHODS.

Equipment of laboratory, 450. — Collecting and preparing material for use in the laboratory, 451. — Obtaining marine animals, microscopic preparations, etc., 453. — Reference-books, 454.

APPENDIX III.— REARING ANIMALS AND MAKING COLLEC- TIONS.

Live cages and aquaria, 457. — Making collections. 461. — Collecting and preserving insects, 463. — Collecting and preserving birds, 466. — Collecting and preserving mammals, 470. — Collecting and preserving other animals, 472.

CHAPTER I THE STUDY OF ANIMALS AND THEIR LIFE Our familiar knowledge of animals and their life

We are familiarly acquainted with dogs and cats ; less familiarly probably with toads and crayfishes, and we have little more than a bare knowledge of the existence of such animals as seals and starfishes and reindeer. But what real knowledge of dogs and toads does our familiar acquaintanceship with them give ? Certain habits of the dog are known to us: it eats, and eats certain kinds of food ; it runs about ; it responds to our calls or even to the mere sight of us ; it evidently feels pain when struck, and shows fear when threatened. Another class of attributes of the dog includes those things that we know of its bodily make-up: its possession of a head with eyes and ears, nose and mouth; its four legs with toes and claws; its covering of hair. We know, too, that it was born alive as a very small helpless puppy which lived for a while on food furnished by the mother, and that it has grown and developed from this young state to a fully grown, fully developed dog. We know also that our dog is a certain kind of dog, a spaniel, perhaps, while our neighbor's dog is of another kind, a greyhound, it may be. We know accordingly that there are different kinds of tame dogs, and we may know that wolves are so much like dogs that they might indeed be called wild dogs, or dogs called a kind of tame wolf. But how little we really know about the dog's body and its life is apparent at a moment's thought. We see only the outside of the dog, but w r hat an intricate complex of parts really composes this animal ! We see it eat and breathe and run ; of what is done with the food and air inside its body, and of the series of muscle contractions and mechanical processes which cause its running, we have but the slightest conception. We see that the pup gets larger, that is, grows; that it changes gradually in appearance, that is, develops; but of the real processes and changes that take place in growth and development how little we know ! We know that there are other kinds of dogs; that wolves and foxes are relatives of the dog; and we have heard that cats and tigers are relatives also, although more distant ones. We know, too, that all the backboned animals, some of them very unlike dogs, are believed to be related to each other, but of the thousands of these animals and of their relationships our knowledge is scanty. Finally, of the relations of the dog, and of other animals, to the outside world, and of the wonderful manner in which the dog's make-up and behavior fit it to live in its place in the world under the conditions that surround it, we have probably least knowledge of all.

Zoology and its divisions. — What things we do know about the dog, however, and about its relatives, and what things others know, can be classified into several groups, namely, things or facts about what the dog does, or its behavior, things about the make-up of its body, things about its growth and development, things about the kind of dog it is and the kinds of relatives it has, and

THE STUDY OF ANIMALS AND THEIR LIFE 3

things about its relations to the outer world, and its special fitness for life.

All that is known of these different kinds of facts about the dog constitutes our knowledge of the dog and its life. All that is known by scientific men and others of these different kinds of facts about all the 500,000 or more kinds of living animals, constitutes our knowledge of animals and is the science zoology * Names have been given to these different groups of facts about animals. The facts about the bodily make-up or structure of animals constitute that part of zoology called animal anatomy or morpliology; the facts about the things animals do, or the functions of animals, compose animal physiology; the facts about the development of animals from young to adult condition are the facts of animal development; the knowledge of the different kinds of animals and their relationships to each other is called systematic zoology or animal classification; and finally the knowledge of the relations of animals to their external surroundings, including the inorganic world, plants and other animals, is called animal ecology.

Any study of animals and their life, that is, of zoology, may include all or any of these parts of zoology. Most zoologists do, indeed, devote their principal attention to some one group of facts about animals and are accordingly spoken of as anatomists, or physiologists, systematists, and so on. But such a specialization of study should be made only after the zoologist has acquired a knowledge of the principal or fundamental facts in all the other branches of zoology.

A first course in zoology. — The first " course," then, in the study of animals should include the fundamental facts in all these branches or parts of zoology. That is what the course outlined in this book tries to cover.

* Zoology is formed, from two Greek words: zoon, meaning animal, and logos, meaning discourse.

But no text-book of zoology can really give the student the knowledge he seeks. He must find out most of it for himself; a text-book, based on the experiences of others, is chiefly valuable for telling him how to work most effectively to get this knowledge for himself. And the best students always find out things which are not in books. Especially can the beginning student find out things not known before, "new to science," as we say, about the behavior and habits of animals, and their relations to their surroundings. The life-history of comparatively few kinds of animals is exactly known; the instincts and habits of comparatively few have been studied in any detail. The kinds of food demanded, the feeding habits, nest-building, care of the young, cunning concealment of nest and self, time of egg-laying or of producing young, duration of the immature stages and the habits and behavior of the young animals — a host, indeed, of observations on the actual life of animals, remain to be made by the "field naturalist.' Any beginning student can be a "field naturalist" and can find out new things about animals, that is, can add to the science of zoology.

CHAPTER II THE GARDEN TOAD {Bufp lentiginosus)

Technical Note. — Although this description is written for the toad it will fit for the dissection of the frog. It will be found, after casting aside a few ungrounded prejudices, that the toad is the better for class dissection. Toads are best collected about dusk, when they can be picked up in almost any garden in town or in the country. During the spring many can be found in the ponds where they are breeding. To kill the toad place it in an air-tight vessel with a piece of cotton or cloth saturated in chloroform or ether. When the toad is dead, wash off the specimen and put in a dissecting pan for study. Several specimens should be placed in a nitric acid solution for a day or so (for directions for preparing, see p. 12) to be used later for the study of the nervous system. Also several specimens should be injected for the better study of the circulatory system. With an injecting mass made as directed on p. 451 introduce through a small canula into the ventricle of the heart. This will inject the arterial system, and with increased pressure the injecting mass may be forced through the valves of the heart, thus passing into the auricles and throughout the venous system. After injecting use the specimen fresh or after it has been preserved in 4% formalin.

External structure. — Note that the body of the toad is divided into several principal regions or parts, as is the human body, namely, a head, upper limbs, trunk, and lower limbs. As you look at the toad note the similarity of the parts on one side to those of the other, as right leg corresponding to left leg, right eye to left eye, etc. This arrangement of the body in similar halves among animals is known as bilateral symmetry. As a rule animals which show bilateral symmetry move in a definite direction. The part that moves forward is the anterior end, while the opposite extremity is the posterior end. In most animals we note two other views or aspects ; that which is called the "back' and with most animals is, under ordinary conditions, uppermost is the dorsum or dorsal aspect, while that which lies below is the venter or ventral aspect. When referring to a view from one side we speak of it as a right or left lateral aspect. These terms hold good for most of the animals that we shall study.

Note at the anterior end of the toad a wide transverse slit, the mouth. What other openings are on the anterior end ? Note the two large eyes, the organs of sight. Just back of each eye note an elliptical, smooth membrane. This is the tympanum of the outer ear, and through this membrane the vibrations produced by sound-waves are transferred to the inner ear, which receives sensations and transmits them to the brain. Open the mouth by drawing down the lower jaw. Note just within the angle of the lower jaw the tongue. How is it attached to the wall of the mouth ? On the tongue are a great many fine papillce in which is located the sense of taste. It has now been seen that most of the special senses of the toad have their seat in the head. Pass a straw or bristle into one of the nostrils. Where does it come out ? These internal openings to the nose are the inner nares. Note in the roof of the mouth just posterior to each of the eyeballs an opening. These are the internal openings to the wide Eustachian tubes, which lead to the mouth from the chamber of the ear behind the tympanum.