TEXT-BOOK OF ZOOLOGY 



FOE JUNIOE STUDENTS. 



BY 



HENRY ALLEYNE NICHOLSON, 



M. D., D. Sc, Ph. D. (Gott.), F. L. S., F. G. S., 



KEGIUS PROFESSOR OF NATURAL HISTOBT IN THE UNIVERSITY OF ABERDEEN, 



FOUBTH EDITION, 

 REVISED AND ENLARGED. 



NEW YOEK •:• CINCINNATI •:• CHICAGO 



AMERICAN BOOK COMPANY. 



