PREFACE TO SECOND EDITION 



This revised edition of the Animal Biology incorporates numer- 

 ous changes suggested by experience and the development of the 

 science, especially in the field of genetics. Growing interest in 

 man's past has led to the introduction of a chapter on the human 

 background. 



Withal, the page and figure numbers remain unaltered in the 

 sections referred to in Professor Baitsell's Manual of Animal 

 Biology, so that book is still available for the details of the morphol- 

 ogy and physiology of selected types, as well as for laboratory 

 directions, which obviously would be out of place in the present 

 volume. 



For suggestions in regard to the new chapter I am indebted to 

 my colleagues, Professor R. S. Lull and Doctor G. E. Lewis; 

 and my thanks are due Professor J. H. McGregor of Columbia 

 University, the University of Chicago Press, William Wood and 

 Co., and the Yale University Press for permission to reproduce 

 figures from their publications. Miss E. L. Gelback has assumed 

 efficiently much of the editorial work involved in seeing the book 

 through the press. And, finally, I wish to express my appreciation 

 of the continued hearty cooperation afforded by The Macmillan 

 Company. 



L. L. Woodruff 



Yale University, 

 March, 1938. 



