BIOLOGY 



LIBRARY 



G 



Copyright, 1913. by W. B. Saunders Company. 



Reprinted June, 1914- Revised, reprinted, 



and recopyrighted October, 1916 



Copyright, 1916, by W. B. Saunders Company 



Reprinted January, 1918 



PRINTED IN AMERICA 



PRESS OF 



B. SAUNDERS COMPANY 

 PHILADELPHIA 



