270 



FRANK E. LUTZ 



Wing 



Q) 





Fig. 2 Regression lines for homozygous normal flies. 



same factors cause when in a duplex or homozygous condition. 

 May it not be, then, that the greater wing development in normal 

 females is caused by their getting a double dose of certain germinal 

 elements, one dose for each X-chromosome, while the males get 

 but a single dose? The following experiments were tried in the 

 hope of getting some answer to this question. 



All the flies in the three sets of experiments were reared at the 

 same time, given an abundance of food from the same jar of fer- 

 menting banana, kept in the same sort of bottles wliich were placed 

 side by side on the table. Furthermore, the flies for each experi- 

 ment were the offspring of several score of freely interbreeding 

 parents and were reared in a number of different bottles so 

 that the chance variations of ancestral bias among the parents and 



