



//. 



^7 2? 



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Carnegie Institution oi Washington, Publication No. 195 



Papeb No. 21 of the Station for Experimental Evolution 

 at Cold Spring Harbor, New York 



From the Laboratory of Genetn - 

 or the Bussey Institution 



- 



U I I J i ZJ !*t 



?? 



PRESS OF GIBSON BROl HERS, INC. 

 WASHINGTON, D. C. 



