PREFACE 



Ix the following pages an attempt is made to present the 

 animal world as a living unit, showing the interrelationships 

 of the various divisions, and the relations of the whole to the 

 plant world, to physical conditions, and to man. Such a treat- 

 ment is complementary to the usual one in which the various 

 animal t>-pes are taken up in sequence and separately dis- 

 cussed. 



The ascertained facts concerning the various forms of animal 

 life mentioned in the succeeding chapters are so very widely 

 scattered through such a vast number of publications that it 

 has not been possible to give references to the original sources 

 consulted in the preparation of this book; indeed, an adequate 

 bibliography would occupy more space than the entire text. 

 Few people, perhaps, realize that the mere recitation of the 

 names of the insects already known to us at the rate of four 

 a minute for eight hours every day would require about ten 

 months, and nearly three months additional would be required 

 to name the remaining forms of animal life. Yet the name 

 of an animal alone is nothing more than a key to its relation- 

 ships and the clue by means of which we are enabled to search 

 out in our libraries the information in regard to it. 



It is unfortunately quite impossible to give a complete list 

 of all those numerous friends who have been so kind as to 

 make suggestions of various sorts in regard to the treatment 

 of different animal types, and to check up for me statements 

 made concerning animals with which I have only a slight 

 personal acquaintance. 



I am under special obligations to Dr. John C. Merriam, 

 Dr. Walter K. Fisher, Dr. Asa C. Chandler, Dr. John M. 

 Aldrich, Dr. James A. Hyslop and Dr. Adam Boving, who were 

 so good as to read almost the entire manuscript; to Dr. Henry 

 B. Bigelow, who reviewed the section dealing with the biology 



