104 MENDELISM CHAP. 



factor which repels femaleness produces no visible 

 effect, and its presence or absence can only be deter- 

 mined by the introduction of a third factor, that for 

 pigmentation. 



This conception of the nature of the Brown 

 Leghorn hen leads to a curious paradox. We have 

 stated that the Silky cock transmits the pigmented 

 condition, but transmits it to his daughters only. 

 Apparently the case is one of unequal transmission 

 by the father. Actually, as our analysis has shown, 

 it is one of unequal transmission by the mother, the 

 father's contribution to the offspring being identical 

 for each sex. The mother transmits to the daughters 

 her dominant quality of femaleness, but to balance 

 this, as it were, she transmits to her sons another 

 quality which her daughters do not receive. It is 

 a matter of common experience among human 

 families that in respect to particular qualities the 

 sons tend to resemble their mothers more than the 

 daughters do, and it is not improbable that such 

 observations have a real foundation for which the 

 clue may be provided by the Brown Leghorn hen. 



Nor is this the only reflection that the Brown 

 Leghorn suggests. Owing to the repulsion between 

 the factors for femaleness and for pigment inhibition, 

 it is impossible by any form of mating to make a 

 hen which is homozygous for the inhibitor factor. 

 She has bartered away for femaleness the possibility 

 of ever receiving a double dose of this factor. We 

 know that in some cases, as, for example, that of the 

 blue Andalusian fowl, the qualities of the individual 

 are markedly different according as to whether he 

 or she has received a single or a double dose of a 



