MENDELISM AND SEX 151 



Since the pink-eyed condition is really due to 

 the absence of black pigment, we may regard the 

 alternative factors as being blackness = B and 

 absence of blackness = h. In such case, we should 

 substitute the symbol h for that of P in the table 

 above. Similarly we may regard {infra page 156) 

 maleness as simply a condition which is left when 

 femaleness is withdrawn. In other words, maleness 

 is simply absence of femaleness. 



The two cases, namely, the currant moth and the 

 canary, which we have last considered, are instances 

 of what may be described as sex-limited inheritance : 

 that is, a certain character in its inheritance is trans- 

 mitted by the germ-cells which are carrying either 

 maleness or femaleness, but not by both. There is 

 thus conceivably a process of repulsion between 

 this particular character and one of the sexes, when 

 the factors which determine both are brought into 

 association, in the ripening germ-cells. In both 

 the cases we have just considered it is femaleness 

 which exerts this repelling influence upon the par- 

 ticular character. 



There is one further case apparently similar 

 which came under my notice in the course of some 

 experiments with poultry. Certain recessive white 

 fowls carry the hidden factor which, meeting colour, 

 produces grey-white feathers barred with blue-black. 

 This " barred " character is spoken of in the " fancy " 

 as the " cuckoo" character. When recessive white hens 

 carrying "cuckoo" are crossed with black cocks, the off- 

 spring consist simply of "cuckoo" cocks and black hens. 



