BIOLOGY 

 LIBRARY 



a 



Set up, electrotyped, printed, and copyrighted March, 1896. 

 Reprinted September, 1896. Revised, reprinted, and recopy- 

 righted August, 1898. Reprinted November, 1898. Revised, 

 reprinted, and recopyrighted August, 1900. Reprinted June, 

 1901. Revised, entirely reset, reprinted, and recopyrighted 

 May, 1903. Reprinted August, 1904. Revised, reprinted, 

 and recopyrighted May, 1906. Reprinted August, 1907, and 

 May, 1908. Revised, reprinted, and recopyrighted August, 

 1909. 



Copyright, 1909, by W. B. SAUNDERS COMPANY. 



PRINTED IN AMERICA 



PRESS OF 



W. B. SAUNDERS COMPANY 

 PHILADELPHIA 



