SEX INHERITANCE 



83 



taining the normal allelomorphs of all these factors. 

 In the case of all the factor-pairs, except abnormal 

 and bar, the normal allelomorph dominates. There- 

 fore, the females will appear normal for all characters 

 except abnormal and bar, which are dominant. 



In the cat, Doncaster has discovered a sex linked 

 factor affecting the coat color. In man several char- 

 acters, such as color blindness, haemophilia, and 

 others less certainly identified have been found to 

 follow the same scheme. 



A comparison of sex linkage in Abraxas with that 

 in Drosophila shows that the mode of inheritance of 

 sex linked characters is identical in these two cases, 

 but the sex relations are exactly reversed. In the 

 Abraxas type sex linked inheritance takes place in 

 accord with the plan that the female is heterozygous 

 in sex production. If the chromosome that carries 

 this sex differentiator is called Z, and its mate in 

 the female W, the formula for the male would be ZZ 

 and that for the female WZ. The scheme follows: 



WZ ZZ 



Inheritance in Abraxas is illustrated in the follow- 

 ing diagrams (Figs. 30 and 31), in which the common 



