SELECTION IN BAR-EYED RACE OF DROSOPHILA. 



373 



SELECTIONS IN THE LONG-WINGED STOCK. 



These experiments were begun on January 15 and continued 

 until the middle of June. In this case the number of flies 

 counted from the stock during selection was 91 males with an 

 average facet number of 132 and 81 females with an average 

 of 66. The first selection made was very near the mean and 

 was designated as Bai and used as part of the stock. It yielded 

 44 males and 37 females with mean facet numbers of 125 and 68 

 respectively. Jn June the eyes of 73 additional males and 97 

 additional females from the stock were counted, yielding mean 

 facet numbers of 114 and 72 respectively. Here again, as in 

 the vestigial-winged stock, there is a change in the mean facet 

 number, and in this case it also involves a decided change in the 

 ratio between male and female facet numbers. 



Little difficulty was encountered on account of sterility in this 

 stock. About 75 per cent of the matings were fertile, and 

 nearly 75 per cent of the fertile matings produced 50 offspring 

 or more. In each case all of the offspring were counted. To 

 avoid the dying out of lines a number of branches of each line 

 was run, only brothers and sisters were mated, but no attention 

 was paid to the dying out of any given branch when it did not 



