GENES MODIFYING NOTCH. 



36^ 



It will be noticed in table 10 that in addition to the nliort Notch 

 there are others called intermediate and even atavistic. Tliat these 

 are for the most part due to fluctuations of the short-Notch character 

 itself is almost certain, since even in stocks bred for 20 nf'tu-'rations 

 for short Notch a similar range occurs in some bottles, but when t<'st<'<i 

 the ''atavistic" (or more generally the "interniediiitc" Notch) Rive 

 the same kinds of daughters as do their sisters, the short Notch feniales. 



Table 10. 



SECOND TEST. 



In this test the reciprocal cross was first made, viz. Star Dichirte 

 female by eosin male of short-Notch stock. The Fi male gets his X 

 chromosome from his Star Dicha?te mother. Consecjuently if it is 

 the X chromosome in the short-Notch stock tliiit carries a recessive 

 modifier for Notch (that has both the Notch-bearing X and its nonmU 

 homologous chromosome) no short-Notch daughters are exjx^cted when 

 the above Fi male is mated to a short-Notch stock female. 



The result of mating such Fi Star Dicha?te males to short-Notch 

 females is shown in table 11. Practically all of ttie Notch females are 

 atavistic or slight Notch. The result is in striking contrast to the 

 result in the first test and means, o))vi()usly, that the X chromosome 

 contains one or more modifiers that shortens the ctTects of the Notch 

 factor itself. That some of the Notch fenuiles are atavistic and some 

 slight may be expected, since separation of the two classes is difficult 

 or impossible and no emphasis can be laid on the classification as it 

 stands. 



