^ (1,0 



Carnegie Institution of Washington. Publication No. 179. 



Papers Nos. 18 and 19 of the Station for Experimental Evolution at Cold Spring 



Harbor, New York. 



2 ^f 7 / 



Copies of this Bool* 

 were first issued 



SEP 13 1913 



PRESS OF GIBSON BROTHERS 

 WASHINGTON, D. C. 



