350 



CALVIN B. BRIDGES 



Expectation called for an equality of the four genetic classes 

 which occurred in culture Ml 14, but as the not-eosin whiting 

 males and females are indistinguishable from the wild-type flies, 

 the 1:1:1:1 ratio became converted into a 2 : 1 : 1 ratio. From 

 the whiting females and males which appeared in culture Ml 14 

 a pure stock of whiting was made up. This double recessive 

 stock was indistinguishable in appearance from the stock of the 

 sex-linked white. 



Two of the whiting males of culture Ml 14 were tested by out- 

 crossing to eosin females. The Fi flies were standard eosin in 

 color (table 8), and the F2 raised from two pairs of these Fi flies 



TABLE 8 



was of the ordinary 3 : 1 type, the whiting reappearing among the 

 females and males equally (table 8). It is evident that whiting 

 has excellent viability, for in most of these cultures it slightly 

 exceeds expectation, the greatest departure being in the above 

 cases where it reappeared as 32 instead of 25 per cent of the F2 

 flies. 



The sex-linked genes white, eosin, and cherry are all allelo- 

 morphs of each other. Cherry and eosin females are almost 

 identical in color, but cherry males are of the same color as cherry 

 females and are easily separated from eosin males. A series of 

 tests was run to observe the effect of the whiting gene when acting 

 with these allelomorphs. The previous experiments in which 



