vi PREFACE 



to be able to recite the various ingenious hypotheses 

 of the ancestry of echinoderms. Our conviction is, we 

 feel sure, the common conviction of college teachers of 

 zoology, who have often occasion to deplore the ignorance 

 that their students show about common animals. It is 

 the conviction of many other thoughtful men also who 

 have recognized that an interest in nature is a powerful 

 agent in making men more moral, more capable of appre- 

 ciating the world they live in, and of finding satisfaction 

 in living. 



The aim of the book is indicated by its title. It is not 

 a treatise on the modern science of zoology. It is a guide 

 to the study of animals, which it is hoped may introduce 

 many students to the sciences of comparative anatomy, 

 comparative embryology, cytology, general physiology, 

 variation and inheritance, and the others that are grouped 

 under "zoology." This book is like a " Synoptic Room ' 

 in the vestibule of a vast museum, containing the most 

 essential things for those who can go in but a little way, 

 but also fundamental for those who can penetrate farther. 



The illustrations of this book have received especial at- 

 tention. An attempt has been made to give a lifelike figure 

 of a representative of almost every family mentioned in the 

 text. For courteous permission to reproduce the copied 

 figures we are deeply indebted to many publishers and 

 authors. We have to thank the authorities of the Field 

 Columbian Museum for original photographs, Figs. 301, 

 302, and 305. Mr. H. W. Menke, of the same institution, 

 kindly gave us permission to use his interesting photo- 

 graphs of live rattlesnakes, Figs. 261, 262. To Mr. V. H. 

 Lowe, Entomologist of the New York State Agricultural 

 Station at Geneva, N.Y., we are indebted for the photo- 



