236 CALVIN B. BRIDGES. 



THE MODIFICATION OF EOSIN EYE COLOR BY WHITE-OCELLI. 



An examination of the various stocks of eye color mutations 

 showed that there was a strong correlation between the eye color 

 and the ocellar color. The ocelli of white-eyed flies are entirely 

 colorless. The ocelli of vermilion-eyed flies show a slight trace 

 only of color. Indeed, in the case of vermilion, the vermilion 

 gene has a relatively greater effect upon ocellar color than upon 

 eye color. The ocellar color of pink is so faint that pink can 

 not be used in the same experiment with white-ocelli without 

 some confusion in classification. The ocellar color of the dark 

 eye 'sepia' is itself also darker. In the ten multiple allelomorphs 

 of the white series, the ocellar color is proportional to the eye 

 color. This direct effect of eye color genes on ocellar color 

 suggested that the reverse relation might also hold namely, 

 that the white-ocelli gene might dilute the eye color. A careful 

 examination of the eye color of white-ocelli flies did not show 

 any certain effect. White-ocelli was crossed to vermilion, and 

 the p2 vermilion white-ocelli flies were not distinguishable from 

 the simple vermilion flies. In the 2 of the cross between white- 

 ocelli and eosin, a definite modification of the eosin by the white- 

 ocelli gene was observed. In the case of the males, the eye color 

 of the double form was lighter in intensity and less yellow in 

 tone than that of the eosin brothers. In the females, the 

 change was in the same direction but was less marked in degree. 

 Probably 95 per cent, of the diluted males were separable from 

 the simple eosin, while only about 60 per cent, of the females were 

 thus separable. Eosin is known to be especially subject to 

 specific modification, 1 and the effects of the white-ocellar gene 

 give a color intensity and tone and a sexual difference practically 

 identical with those observed in the case of the modifier 

 'pinkish.' The gene for pinkish was, however, in the second 

 chromosome, and there are other differences between the two 

 cases. 



Jour. Exp. Zoo/., July, 1919. 



