1916] Beeves: Inheritance of Extra Bristles in Drosophila 497 



Fig. 1. — Showing arrangements of extra bristles on the thorax of Drosophila 

 melanog aster. 



From the original stock, when normals were mated with normals 

 only normals were produced, but when those with five bristles were 

 mated with normals the results were as shown in table I. In all 

 matings in this paper, unless otherwise mentioned, brothers and sisters 

 were crossed. 



In table I each generation was bred in mass, obtained from the 

 normals of the previous generation, the extras being removed and 

 bred separately. 



TABLE I 

 Mass Cultures from Normals in Four Generations 









F, 







F, 







F3 







F, 





incomplete 

 hatching 



Family- 







N. 



ex. 



Per 

 cent 



N. 



ex. 



Per 

 cent 



N. 



ex. 



Per 



cent 



N. 



ex. 



Per 

 cent 



Per 



N. ex. cent 



Y, ex. X 



N. 



158 



9 



4.76 



101 



13 



11.11 



106 







.0 



105 



1 



.94 



50 .0 



X, ex. X 



N. 



19 







.00 



127 



2 



1.05 



85 



2 



2.4 



100 







.00 



85 3 3.4 



A, ex. X 



N. 



90 



1 



1.09 



75 



1 



1.32 



90 







.0 



100 



3 



3.00 



85 3 3.4 



As might be expected, a fluctuating result was obtained when nor- 

 mals were extracted from the matings between two extras, in various 

 families, and were then bred together in mass in subsequent gene- 

 rations. The results are shown in table II. 



TABLE II 



Mass Cultures of Normals Extracted from Matings Between Extras 



F. F3 F4 F5 



Per Per Per Per 



Family — N. ex. cent N. ex. cent N. ex. cent N. ex. cent 



X, ....". 101 15 14.85 101 2 1.9 95 6 5.8 



A5 38 5 12.15 105 1 .95 93 1 1.07 87 1 1.1 



Y E 40 5 6.6 93 1 1.07 27 1 *3.5 



* Incomplete hatching. 



