.^0^ 





Carnegie Institution of Washington, Publication No. 205 



Papkr No. 23 of the Station for Experimental Evolution 

 AT Cold Spring Harbor, New York 



From the Laboratory of Genetics, of the Bussey 

 Institution, Forest Hill, Massachusetts 



A 



f ^/ ^/ 



Copies of this Book 

 were first issued 



DEC 311914 



PRESS OF GIBSON BROTHERS, INC. 

 WASHINGTON, D. C. 



