HEREDITY OF BODY COLOR IN DROSOPHILA 35 



There are 1711 grays and 357 blacks which is very nearly 

 5 to 1. 



^Vild (gray) by yellow 



The results of this cross have been already published (1911), 

 but may be given here for the sake of completeness. In both 

 cases the parents were ahke except for body color: 



^, „^ ^^ /Gray 9 654 \ ^'^^ l ^^5 



G9byYc^= (g,^J^705= Gray J 340 



^ -^ [ Yellow cf 194 



The sum of the males is here nearly equal to the females as 

 called for in the expectation (see below). It will be noted, 

 however, that the gray males in r2 greatly exceed the yellow 

 males, and that the gray males are considerably more than 

 half (268) the gray females. 



It may seem that the discrepancy in the yellow males is not 

 due to their viability alone, but rather that the gray-bearing 

 male-producing spermatozoa are more likely to fertilize the 

 eggs than are the yellow bearing sperm. The analysis is as 

 follows : 



Gray 9 BYBrX — BYBrX 

 Yellow cf bYBrX — bYBr 



Gray 9 BYBrX — bYBrX 

 ^' ' Gray d^ BYBrX —bYBr 



Gray 9 2 

 ' Gray d" 1 



Yellow d" 1. 



The reciprocal cross is as follows: 



f Gray 9 346 



V o K n ^ /G 9 397 J Gray d 259 



Y 9 by G d^ - ^ ^ 282 = 1 Yellow 9 226 



[ Yellow cT ; 230 



The excess of females in Fi is noticeable. The expectation 

 in Fo is equal numbers for all classes. The grays run ahead of 

 the yellows. There is a very noticeable deficiency in the gray 



