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CARNEGIE INSTITUTION OF WASHINGTON 

 PUBLICATION No. 196 



PAPER No. 22 OF THE STATION FOR EXPERIMENTAL EVOLUTION AT 

 COLD SPRING HARBOR, NEW YORK. 



FROM THE LABORATORY OF GENETICS OF THE BUSSEY 

 INSTITUTION, FOREST HILLS, MASSACHUSETTS. 



PRESS OF GIBSON BROTHERS, INC. 

 WASHINGTON, D. C. 



