No. 533] INHERITANCE IN COLIAS PHILODICE 



273 



Homozygous White Female x Heterozygous Yellow Male 



50 per cent, yellow, heterozygous, 50 per cent, pure white, 

 9. Homozygous White Female x Homozygous White Male 



homozygous white. 



That the germ cells in the white female, which I have 

 shown to be heterozygous for color, and which is pre- 

 sumably also heterozygous for the sex determiner, are 

 really segregated in oogenesis into four distinct groups 

 is strongly indicated by the realization of the results of 

 this hypothesis as shown in f f 3 and 4. In this segre- 

 gation there is no real "coupling," the sex determiner 

 (x) being equally distributed among the white and the 

 yellow gametes, but the chances are also equal that any 

 gamete may receive the x factor, and become a male 

 zygote when fertilized, or lack it, and become on fertil- 

 ization a female organism. 



As would be expected, there are similarities between 

 Colias and Abraxas* in the method of inheritance of the 

 white female variety in each. The female in both is 

 heterozygous for sex, producing in equal numbers eggs 

 which give rise to males and to females when fertilized 

 by the like sperms of the homozygous male. But there 

 are striking differences between the two forms in inherit- 

 ance, e. g. t the dominance of the type color in Abra-xas, 

 compared with its dominance in the male only in Colias, 

 white being dominant in the female ; females of the type 

 form that are homozygous for color are found in Colias, 

 but not in Abraxas, in which all the type females are 

 heterozygous, just as are all the white females of Colias 

 that have hitherto been bred. The segregation of the 



