EYE COLOR IN DROSOPHILA MELANOGASTER 



345 



TABLE 3 

 F-i from the cross of cream II male to curved female 



A more efficient experiment than this last was carried out by 

 making all the flies of the experiment eosin, in which case the 

 2:1:1:0 ratio involved all the offspring, rather than only a 

 quarter as in culture 70. A stock of eosin black was made up 

 (black being a second chromosome mutant) and a female of this 

 stock was outcrossed to a cream II male. The Fi and Fo results 

 are given in table 4. All of the Fi flies and half the Fo flies were 

 of the intermediate color of the heterozygous cream. In the F2 

 these intermediates were classified along with the pure eosins so 

 that the cream was treated as though a strict recessive. 



The F2 ratio of 442 : 217 : 207 : is a very close approximation 

 to a 2 : 1 : 1 : ratio and proves that the gene for cream is in the 

 second chromosome (cream II). 



TABLE 4 



Pi mating, cream II cT X eosin black ? ; Fi mating, heterozygous cream II 9 X Fi 



heterozygous cream II d' 



