46 



SEX-LINKED INHERITANCE IN DROSOPHILA. 



which we could use as an index, but, so far as we have been able to see, 

 there is no such constant accessory character in the case of the dot. 

 Unlike club, dot is markedly sex-limited in its effect; that is, there is 

 a diflference of expression of the gen in the male and female. This 

 difference recalls the sexual dimorphism of the eosin eye. 



BOW. 



In an F2 generation from rudimentary males by wild females there 

 appeared, August 15, 1912, a single male whose wings instead of being 

 flat were turned down over the abdomen (fig. c). The curvature was 

 uniform throughout the length of the wing. A previous mutation, arc, 

 of this same type had been found to be a recessive character in the 

 second group. The new mutation, bow, is less extreme than arc and 

 is more variable in the amount of curvature. When the bow male was 

 mated to wild females the offspring had straight wings. 



Fig. C. — Bow wing. 



Table 21.— Pi bow d'd' X wild 9 9 . 



