PREFACE 



This book has been written to be read by students of 

 eighteen to twenty years of age. With this in mind the 

 .chapters have been made short, and an attempt has been 

 made to enliven the text by interpolating a considerable 

 number of illustrations that lean more toward natural 

 history than anatomy. 



The purpose of the book is to give a general survey of 

 the important points relating to the chief groups of animals. 

 The first four chapters deal largely with generalities and 

 may well follow chapters which come later if such an ar- 

 rangement is more expedient for any particular course. 

 An important place is given to insects because they afford 

 the most available material for collecting, classification, 

 and dissection students can acquire a variety of first-hand 

 knowledge from them as from no other group of animals. 



The writer is convinced that students of biology get the 

 best training in scientific methods of thought from practical 

 work, and that it should constitute the chief part of any 

 course; also that a text-book should not repeat what is 

 observed in laboratory or field, but supplement and general- 

 ize upon such information. The book ought, therefore, 

 to contain more of natural history and general biological 

 theory than anatomy. Some chapters in the present work 

 (e.g., X) are perhaps , without much unity or apparent 

 purpose, and are intended primarily to serve for reference 

 in connection with laboratory or field studies. 



Anyone who teaches is stimulated by association with 

 great teachers men of originality who are scientific, yet 

 human, and who are ever willing to help or encourage 

 students. Though this book intends to be original, the 

 writer is fully aware that he has consciously and uncon- 

 sciously used the ideas of others. Foremost among those 



