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Carnegie Institution of Washington, Publication Xo. 195 



Paper No. 21 of the Station for Experimental Evolution 

 AT Cold Spring Harbor, New York 



From the Laboratory of Genetics 

 of the Bussey Institution 



■' t ?'$ Book 

 issued 



^E8 181914 



PRESS OF GIBSON BROTH KRS. INC. 

 WASHINGTON, D. C. 



