SEX 



"3 



repels femaleness produces no visible effect, and its pres- 

 ence or absence can only be determined by the introduc- 

 tion 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 transmis- 

 sion by the mother, the father's contribution to the off- 

 spring being identical for each sex. The mother trans- 

 mits 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 re- 

 semble 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 fe- 

 maleness the possibility of ever receiving a double dose of 

 this factor. We know that in some cases, as, for example, 



