Heredity and Sex 77 



be possible for the character to leave one X and attach 

 itself to the othe x, as apparently takes place in IheTemale 

 when the coinbination 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-mnged, 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 -Ys. Now, its gametes are of four sorts, as indicated. 

 The tirst 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 s ort could result only from 

 t he attachment of R and L to the same .Y , leaving the other 

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

 This k ind, which transmits neither red eyes nor long wings , 

 w ould represent the ne w g ametic com bi nation — whi te eye d 

 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 oft'spring, 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, 



