ZOOLOGY 



A TEXT-BOOK FOR 

 UNIVERSITIES, COLLEGES 

 AND NORMAL SCHOOLS 



BY 



THOMAS WALTON GALLOWAY, Ph. D., Litt. D. 



FORMERLY PROFESSOR OF ZOOLOGY, BELOlf~c"OLLEGE, BELOIT, WISCONSIN; ANI> OF BIOLOGY IN THE 



JAMES MILLIKIN UNIVERSITY, DECATUR, ILLINOIS: ASSOCIATE DIRECTOR EDUCATIONAL 



ACTIVITIES, AMERICAN SOCIAL HYGIENE ASSOCIATION, NEW YORK 



CO-REVISER 



PAUL S. WELCH, Ph. D. 



ASSOCIATE PROFESSOR OF ZOOLOGY, UNIVERSITY OF MICHIGAN, ANN ARBOR, MICHIGAN 



FOURTH EDITION, REVISED 

 WITH ZS5 ILLUSTRATIONS 



PHILADELPHIA 



P. BLAKISTON'S SON'& CO. 



1012 WALNUT STREET 



