GENES MODIFYING NOTCH. 



iiO.J 



Notch has as its mate in the female an X chrom^jsome l)e^irinK oosin. 

 Such a female crossed to an eosin brother gives 1 red -eyed Notch 9 : I 



Fig. 94. 



eosin 9 : 1 eosin cf , and the expected number of cross-overs. The 

 stock was kept running by breeding in every generation a number of 

 short-Notch females to some of their eosin brothers, the eosin sisters 

 being rejected. No special effort was made to pick out the shortest 

 of the Notch females. The general run of the stock may be gathered 

 from table 9 for the fourth, fifth, and sixth generations. For some time 



I thought that short Notch might be an allelomorph of Notch — a 

 difficult point to settle if it were, because there are no males of either 

 class to bring the two allelomorphs together, and no other way of getting 

 them into the same individual. But if the shortness of this tyix* is due 

 to a modifying gene it should be carried by the not-Notch males a.^ well 

 as by the female, and its presence could be demonstrated by crossing. 



