Elementary Zoology.
by Vernon L. Kellogg.
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 (_c_) 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 cla.s.sification 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 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 cla.s.s 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 should be[1]
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 which 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 princ.i.p.al branches of the animal kingdom; it deals with[2] 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 princ.i.p.al 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. 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 seash.o.r.e 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 cla.s.sificatory 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 connection 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 cla.s.ses, 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 ill.u.s.trating 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 Mitch.e.l.l, 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 photographs of insects; to Dr. L. O. 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 Ca.s.sell & 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 a.s.sistance 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. Snodgra.s.s for reading the proofs of the directions for the laboratory exercises.
VERNON LYMAN KELLOGG.
STANFORD UNIVERSITY, May, 1901.
FOOTNOTES:
[1] 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 cla.s.sifying 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.
[2] The cla.s.sification 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.
PART I
STRUCTURE, FUNCTIONS, AND DEVELOPMENT OF ANIMALS
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 cla.s.s 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 what 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 cla.s.sified 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 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 const.i.tutes 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, const.i.tutes our knowledge of animals and is the science _zoology_.[3] Names have been given to these different groups of facts about animals. The facts about the bodily make-up or structure of animals const.i.tute that part of zoology called animal _anatomy_ or _morphology_; 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 _cla.s.sification_; 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 princ.i.p.al 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 princ.i.p.al 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. 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.
[Ill.u.s.tration: FIG. 1.--Dissection of the Garden Toad (_Bufo lentiginosus_).]
FOOTNOTE:
[3] Zoology is formed from two Greek words: _zoon_, meaning animal, and _logos_, meaning discourse.
CHAPTER II
THE GARDEN TOAD (_Bufo lentiginosus_)
LABORATORY EXERCISE
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 cla.s.s 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 ma.s.s 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 ma.s.s may be forced through the valves of the heart, thus pa.s.sing 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 princ.i.p.al 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 _papillae_ 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. Pa.s.s 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 eyeb.a.l.l.s 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.
Note far back in the mouth an opening through which food pa.s.ses. This is the _sophagus_ or _gullet_. Note just below this gullet an elevation in which is a perpendicular slit, the _glottis_. This is the upper end of the _laryngo-tracheal chamber_, and the flaps within on either side of the slit are the _vocal cords_.
Note at the posterior end of the body in the median line an opening.
This is the _a.n.a.l opening_ or _a.n.u.s_. Note the general make-up of the toad. How do its arms compare with our own? How do its fore feet (hands) differ from its hind feet? Note that the body is covered by a tough enveloping membrane, the _skin_. In the skin are many glands which by their excretion keep it soft and moist.
=Internal structure.=--TECHNICAL NOTE.--With a fine pair of scissors make a longitudinal median cut through the skin of the venter from the a.n.a.l opening to the angle of the lower jaw. Spread the cut edges apart and pin back in the dissecting-pan.
Note the complex system of _muscles_ which govern the movements of the tongue. Observe a number of pairs of muscles overlying the bones which support the arms. These are attached to the _pectoral_ or _shoulder-girdle_. Note the large sheet of muscles covering the ventral aspect of the toad. These are the _abdominal muscles_, which consist of two sets, an outer and an inner layer. Note that posteriorly the abdominal muscles are attached to a bone. This is the _pubic bone_ of the _pelvic girdle_ which supports the hind legs.
TECHNICAL NOTE.--With the scissors cut through the muscles of the body wall at the pubic bone and pa.s.s the points forward to the shoulder-girdle. Separate the bones of the shoulder-girdle and pin out the flaps of skin and muscle to right and left in the dissecting-pan (see fig. 1). Cover the dissection with clear water or weak alcohol.