94 T. H. MORGAN AND ELETH CATTELL 



Despite the large number of individuals (2677), there are no 

 cases of crossing-over for color in the last case. If such occurred 

 in the females, they would be masked by the presence of the domi- 

 nant factor, R, present in all female-producing sperm. Concern- 

 ing the crossing-over of wing characters, it will be noted that LRY 

 cf = 335, while SRY cf = 118; and LRBr ^ = 73, while SRBr 

 c? = 17; and the on other hand, SWB d^ = 108, while LWB c^ 

 = 63 and SWN cf = 221, while LWN c^ = 191. The sum of 

 the 'straight' cases is 737, while that of the cross-overs is 398, or 

 approximately 2 to 1. 



LONG, RED, BLACK BY SHORT, WHITE, YELLOW 



When LRB females are paired with SWY males, the offspring 

 are LRN d^'s and 9 's. The second generation is given below: 



LRB 9 by SWY d^ 



F, 



LRN 9 94 

 LRN d^ 111 



F, 



The expectation is as follows : 



p LRByX - LRByX 



' SWYbX - ...Yb 



