Heredity and Sex 77 



be possible for the character to leave one X and attach 

 itself to the other, as apparently takes place in the female 

 when the combination of two sex-limited characters in the 

 same gamete is secured through a cross. The combination 

 is apparently secured in this way: 



Gametes uniting, X-R and X L 



Zygote formed, X-R - X-L 



Its gametes, X-R and X-L, or X-R-L and X. 



One of the uniting gametes, X-R, is formed by the 

 red-eyed, short-winged parent; the other, X-L, is formed 

 by the long-winged, white-eyed parent. The zygote result- 

 ing is a red-eyed individual, since it contains R; it is long 

 winged, since it contains L; it is a female, since it contains 

 two Xs. Now, its gametes are of four sorts, as indicated. 

 The first two sorts result from simple separation of the 

 two Xs, each with its associated character, R in one case, 

 L in the other. But the third sort could result only from 

 the attachment of R and L to the same X, leaving the other 

 X without either R or L as the fourth kind of gamete. 

 This kind, which transmits neither red eyes nor long wings, 

 would represent the new gametic combination white eyed 

 and with short wings. 



The experimental evidence that gametes of these four 

 sorts are formed by females of the origin described is as 

 follows: When such a female is mated with a long-winged, 

 white-eyed male, there are obtained female offspring, all 

 of which are long winged, but half of them are red eyed, 

 half white eyed. The male offspring, however, are of four 

 sorts, viz., red short, white long, red long, and white short. 

 This result harmonizes with the hypothesis advanced. 

 For if the gametes of the female are X-R, X-L, X-R-L, 



