364 



GENES MODIFYING NOTCH. 



cause the not-Star not-Dichsete females are practically all the selected 

 type, and the Star-Dichsete are practically all classified as atavistic; 

 yet the females of both classes contain the same Notch-bearing chromo- 

 some that must be identical, since in both it is the X chromosome of 

 the selected stock. 



In the FI generation (table 8), the parents of the flies in table 7, it was 

 found that all of the Notch females were atavistic as expected. In 

 some sets the extent to which notching was developed was greater 

 than in others. It is important for present purposes to note that 

 there is no difference in the extent of development of the character 

 Notch in the Dichaete and in the not-Dichaste (straight-winged) 

 females. This means that the wing-character Dichsete does not 

 modify the Notch character when present with it. Consequently we 

 should not expect in FI any difference between Dichsete and not- 

 Dichsete Notch females, due to the Dichsete gene. 



TABLE 8. 



SHORT NOTCH. 



Several times in the early history of the Notch stock, females 

 appeared with wings much shorter than those of the atavistic type 

 that can be obtained at any time by out-crossing selected Notch. 

 The general character of the short-Notch wing may be gathered from 

 figure 94, a. Not only is the wing shorter and broader, but the end is 

 more abruptly and fully squared off than in the typical stock or in the 

 atavistic Notch, figure 94, 6. 



Many of the females are sterile, so that the stock has nearly died 

 out several times when pairs were used, but mass-cultures of this type 

 can be kept going. Several tunes, when even shorter winged indi- 

 viduals have appeared, and I have attempted to breed from them, I 

 have found that they were sterile. The stock was first red-eyed, but 

 later eosin eye was introduced, so that the X chromosome bearing 



