HEEEDITY 



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-RX-L, 



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



One of the uniting gametes, X-E, is formed 

 by the red-eyed, short- winged parent ; the other, 

 X-L, is formed by the long-winged, white- 

 eyed parent. The zygote resulting 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 

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