GENETICS PURPLE EYE COLOR DROSOPHILA 267 



orange-like color resembled the old 'orange' (vermilion pink) 

 genetically also, for it was proved by this Fo to be a double 

 recessive, vermilion purple, in which purple corresponds to 

 pink. 



It seems probable that the two eye-color mutations, ver- 

 milion and purple, present in the male first found were not of 

 simultaneous or related origin. There was a vague report that 

 the vestigial stock had contained vermilion at some time pre- 

 vious to this discovery. No vermilion or purple was found in it 

 subsequently, however. 



DESCRIPTION^ 



The purple eye color passes, in its development, through an 

 interesting cycle of changes closely parallel to those seen in the 

 ripening of a 'sweet' cherry. In the pupa the eye is at first 

 colorless, then it assumes a creamy tone, which in turn becomes 

 pinkish, passing progressively through a yellowish pink to pink 

 and to ruby. When the flies hatch the color is a transparent 

 rather deep ruby. This color rapidly deepens to garnet and 

 then passes on to a purplish tone. The typical purple color at 

 its maximum development — in flies about a day old, while 

 retaining much of its transparency, appears darker in tone than 

 the red of the wild type, purple being the first of such 'dark' 

 eye colors. As the fly becomes older this 'ripe-cherry' color is 

 progressively obscured, apparently by an increase in a flocculent 

 red pigment like that of the wild fly. The eye color thus be- 

 comes somewhat lighter than red again, though always dis- 

 tinguishable by a lesser opacity and by a light 'fleck' in place 

 of the hard dark fleck seen in the wild eye. With extreme old 

 age the color approaches still closer to red, but does not become 

 strikingly darker, as do pink and sepia, for example. In purples 

 of the same age fluctuations in color are not great. The sepa- 

 ration of purple from red is easy if done while the flies are mostly 

 under two days old, though the climax in the development of the 

 purplish tone offers the most favorable stage. 



^ For a colored figure of purple see plate 5, figure 8, of a forthcoming Carnegie 

 publication (No 286) by Bridges and Morgan. 



