Elements of comparative zoology

Preface To The Second Edition

In preparing this edition many changes have been made; every page has been revised and some errors corrected. Several new illustrations have been added and directions for the study of other animals have been inserted. As in the first edition, greater prominence has been given to the vertebrate than to the non-vertebrate forms, since experience has shown that the work has been largely used as an introduction to or preparation for medical studies. The greatest change, however, has been in the separation of the laboratory work from the descriptive part of the text. Still, the pedagogica" advantages of the former arrangement have been maintained by numerous cross-references, while the systematic portion has a continuity which was lacking in the former edition.

In the illustrations care has been taken to figure nothing which is studied in the laboratory. Students have been known to copy drawings rather than to work the details out from the specimen.

Tufts College, Mass., June, 1904.

iii

Preface To The First Edition

The present volume is intended as an introduction to the serious study of zoology. It embraces directions for laboratory work upon a selected series of animal types and a general account of related forms. Laboratory guides are somewhat numerous, but general outlines of zoology adapted to beg'nners are few. By combining the two, it has been possible to emphasize the comparative side of the subject. A knowledge of isolated facts, no matter how extensive, is of little value in education, excepting as the powers of observation are trained in ascertaining those facts. Nature studies are truly educational only when the student is trained to correlate and classify facts. A considerable experience with students of different ages has resulted in the conviction that it is not sufficient to ask one to compare a grasshopper and a beetle, pointing out their resemblances and points of difference; leading questions must be asked. When the student has answered the questions under the headings "Comparisons' 7 in the following pages, he has a tolerably complete statement of the principal characters of the larger groups of the animal kingdom.

Several considerations have had weight in the selection of types to be studied in detail. In the first place, so far as possible, these should be such as are readily obtainable in any. locality. But there are certain important groups, all the members of which are marine. The forms of these

v vi PREFACE TO THE FIRST EDITION.

which have been used can be purchased of dealers in laboratory supplies (see Introduction) at a cost of less than sixty cents per pupil. In the second place, the number of forms studied and the extent to which details of structure are worked out must be such that the work outlined can be done by students of average ability, in the time usually allotted to such work in the ordinary course. Especial care has been taken that time shall not be wasted in working out features of no morphological importance. Counting tail-feathers or fin-rays has no place in elementary zoology.

Again, the work has been made largely macroscopic in character. Microscopes are expensive, and many institutions feel that they cannot afford to provide each student with one of these instruments. Then, too, there are enough important facts to be discovered with scalpel and hand-lens. Too many beginners have been lost among cell-theories and drowned in staining-fluids. These properly come after the elements of the study have been mastered.

In order of treatment the author has followed the sequence which he believes productive of the best results- A strictly logical course would lead from the simple to the complex, but in practice this has not been found as valuable as the order adopted here.

A number of illustrations have been prepared especially for this work. Most of the others are credited to the author from which they are taken. It may interest some to know that Figures 39 and 123 were engraved for the second part of Agassiz and Gould's "Principles of Zoology/' which was never published.

Tufts College, Mass., June 14, 1897.

Contents

PAGE

Equipment 2

Material for Dissection 4