MUTATIONS IN EYE-COLOR OF DROSOPHILA. 341 



involved is the C factor, which in the female can appear in duplex where it rivet 

 dark eosin, while in simplex, as in the heterozygous females, and in all males it 

 gives the light eosin color. On the other hand, the factors V and P while essential 

 for the production of the eosin color may be present either in simplex or in duplex 

 without any distinguisfiable difference in shade. 



When (dark) eosin females are mated to orange males there result red-eved 

 females and (light) eosin males. The red females could only be produced if th< 

 new mutant contained both the V and P factors, since previous experimc nt 

 had shown that the orange male lacks these factors. Since the males were not 

 red, the male-producing sperm of the orange-eyed fly lacks orange. In other 

 words, the factor for orange is sex-linked. The analysis of the last cross i 



therefore, as follows : 



VP0CX—VP0CX Dark-eosin 9 



vpOCX — v poc Orange 0" 



VPoCX vpOCX Red 9 



VPoCX vpoc Light-eosin <? 



Crosses Within the Eosin Stock. 



Dark-eosin 9 by Eosin d" . 



When the eosin females of the darker eye color are mated to eosin males 

 female offspring have Dark-eosin eyes and the males Light-eosin eyes : 



Dark-eosin 9 by eosin c? 



The analysis is as follows 



Dark-eosin 9 765 

 Light-eosin cf 836 



VP0CX—VP0CX Dark-eosin 9 



VPoCX—Vpoc Light-eosin <? 



VP0CXVP0CX Dark-eosin 9 



VPoCXVpoc Light-eosin c? 



9 



Light-eosin 9 by Eosin tf. 

 The parallel cross, in which both males and females have Light-eosin eyes, 



gave four classes of offspring as shown below: 



Dark-eosin 9 420 



T . 1 . ^ , . 1 Light-eosin 9 3o7 



Light-eosin 9 by eosin tf = i T .\. • ^ ™ 



Lieht-eosm cf 370 



The analysis gives 



Light 

 White-eosin cf 344 



VPoCX—VPocX Light-eosin 9 



VPoCX — Vpoc Light-eosin & 



VP0CXVP0CX Dark-eosin 9 



VPoCXVPocX Light-eosin 9 



VPoCXVpoc Light-eosin cf 



VPocXVpoc White-eosin <? 



