66 



E. CARLETON MACDOWELL 



clear, although a few extra flies appeared in F]. Among 1419 

 Fi flies, 12 had one extra, 3 had two extra bristles. Sixty-five 

 pairs of normal Fi flies were mated. The total counts for their 

 children are 8421 normal, 2499 extra, which give a ratio of 3.3:1. 

 (table 5B). As in the previous crosses there is a practical 

 incomplete dominance in Fj, whatever theoretical explanation 

 may be given, and in Fo the numbers of extras are a little too 

 low, yet there can be no question that this is clear evidence of 

 the existence of a Mendelian factor that influences the number 

 of bristles. 



To test for sex linkage, five of the above crosses were made 

 with extra males and three were made with extra females. In 



TABLE 5 



Giving the results of crosses between extra bristled parents and normals from rvild 



stock (New York '12) 

 A — Extra bristled parents from the second inbred generation 



B — ^Extra bristled parents from the eighth inbred generation 



