58 



SEX-LINKED INHERITANCE IN DROSOPHILA. 



back-crossed to vermilion fused males, a linkage value of 27 units. 

 Two lo-day broods were reared from each female. The data given in 

 table 38 show that the percentage of crossing-over does not change as 

 the flies get older. The locus of fused on the basis of all of the data is 

 at S9-S- 



Table 37. — Pi vermilion 9 9 X fused cfcf . 

 X Fl vermilion cf cf . 



Fl wild-type 9 9 



Table 38. 



-Pi wild 9 9 X vermilion fused d'd'. Pi wild-type 9 

 X Pi wild-type cT cf . 



FORKED. 



On November 19, 191 2, there appeared in a stock of a double 

 recessive eye-color, vermilion maroon, a few males which showed a 

 novel form of the large bristles (macrochaetae) upon the head and 

 thorax. In this mutation (text-fig. e) the first of several which affect 

 the shape and distribution of the bristles, the macrochaetae, instead of 



