456 



T. H. MORGAN AND C. B. BRIDGES 



Eosin vermilion heterozygous for pink 



In the experiment on page 446, 373 eosin vermilion females 

 heterozygous for pink are recorded. Similar males heterozygous 

 in pink were also obtained. These flies inasmuch as they are 

 eosin derivatives show the peculiarity of eosin, namely, sexual 

 bicolorism, and because they are heterozygous in pink, both sexes 

 are lighter than the corresponding simple eosin vermilion. 



The dilution of the color due to heterozygosity was more readily 

 observed in the following cases, by direct comparisons. Some 

 of the 373 eosin vermilion females were mated in pairs to some 

 of the eosin vermilion males (picked out from the 716 double 

 class, page 446) and gave the following results: 



F2 eosin vermilion 9 



F2 eosin vermilion cf X w® v p 



Xw^vP— Xw^vp 

 X w*' V P — p — 



In both the males and females the class eosin vermilion is 

 separably darker than the class eosin vermilion heterozygous for 

 pink. The eosin vermilion pink classes are still lighter. Each 

 class of females is darker than the corresponding class of males. 

 To compare the eosin vermilion heterozygous for pink more 

 closely to the eosin vermilion pink an experiment was devised 

 to produce only these desired classes in males and in females. 

 One of the females of the 373 (page 446) was mated to an eosin 

 vermilion pink male as follows : 



