PREFACE TO THE SECOND EDITION 



In deference to the original plan of the author, the general form of 

 this revision of Animal Biology has not been materially changed. 



We have particularly avoided the use of text figures of laboratory 

 studies in order to direct the student's attention to his own dissections, 

 observations, and conclusions. 



The sections on the worms have been rewritten to harmonize with 

 more recent knowledge of the subject. 



About sixty new illustrations have been added, many of which have 

 been generously contributed by friends and former students and sugges- 

 tions from many outside sources have been incorporated. 



The Staff of the Department of Zoology, 

 University of Nebraska. 



February, 1940. 



vu 



