EYE COLOR IN DROSOPHILA MELANOGASTER 



343 



colors are: eosin female, heterozygous cream female, eosin male, 

 heterozygous cream male, cream female, cream male (diagram 1, 

 page 273). The females were first separated from the males. 

 Then in each sex the pure creams were separated from the others, 

 and finally the more difficult separation of heterozygous cream 

 from eosin was undertaken. The separation of the creams from 

 other colors is accurate, but the final separation, that of the 

 heterozygous creams from the eosins must be regarded as only a 

 close approximation. The sharp 1:2:1 ratio (160 : 318 : 148) 

 which was obtained from this separation probably represents 

 among the eosins a fair number of the darkest heterozygotes, 

 while the lightest of the pure eosins were likewise classified among 



TABLE 2 



The f 2 offspring given by Fi pairs from the cross of a cream II male to an eosin 



female 



the heterozygotes. Probably 10 per cent of the combined eosin 

 and heterozygous cream class overlapped enough so that the 

 separations might or might not correspond to genetic differences. 

 One test of the correctness of the classification of intermediates 

 was made. From culture M79 a heterozygous male and a heter- 

 ozygous female were selected, and the results (culture M95) 

 showed that both individuals were of the supposed type. 



No attempt has been made to secure a stock homozygous for 

 the cream gene but without eosin. The cultures and experiments 

 in which such not-eosin creams must have constituted one-fourth 

 of the wild-type flies prove that such a stock could not be dis- 

 tinguished by inspection from a wild stock. 



