t 



^ 



PRINCIPLES 



OF 



ANIMAL BIOLOGY 



BY 



A. FRANKLIN SHULL 



PROFESSOH OF ZOOLOGY IN THE UNIVERSITY OF MICHIGAN 



WITH THE COLLABORATION OF 



GEORGE R. LARUE 



ASSOCIATE PROFESSOR OF ZOOLOGY IN THE UNIVERSITY OF MICHIGAN 



AND 



ALEXANDER G. RUTHVEN 



PROFESSOR OF ZOOLOGY AND DIRECTOR OF THE MUSEUM OF ZOOLOGT 

 IN THE UNIVEBSITY OF MICHIGAN 



%-^'i^%^ . 



First Edition 

 Seventh Impression 



j . ] t • ^ ^' 



McGRAW-HILL BOOK COMPANY, Inc. 



NEW YORK: 370 SEVENTH AVENUE 



LONDON: 6 & 8 BOUVERIE ST.. E. C. 4 



1920 



