676 THE DESCENT OF MAN 



With fowls, variations of color, limited in their transmis- 

 sion to the male sex, habitually occur. When this form of 

 inheritance prevails, it might well happen that some of the 

 Buccessive variations would be transferred to the female, 

 who would then slightly resemble the male, as actually 

 occurs in some breeds. Or again, the greater number, but 

 not all, of the successive steps might be transferred to both 

 sexes, and the female would then closely resemble the male. 

 There can hardly be a doubt that this is the cause of the 

 male pouter pigeon having a somewhat larger crop, and of 

 the male carrier pigeon having somewhat larger wattles than 

 their respective females ; for fanciers have not selected one 

 sex more than the other, and have had no wish that these 

 characters should be more strongly displayed in the male 

 than in the female, yet this is the case with both breeds. 



The same process would have to be followed, and the 

 same difficulties encountered, if it were desired to make a 

 breed with the females alone of some new color. 



Lastly, our fancier might wish to make a breed with 

 the two sexes differing from each other, and both from the 

 parent species. Here the difficulty would be extreme, un- 

 less the successive variations were from the first sexually 

 limited on both sides, and then there would be no diffi- 

 culty. We see this with the fowl; thus the two sexes of 

 the pencilled Hamburghs differ greatly from each other, 

 and from the two sexes of the aboriginal Qallus banhiva; 

 and both are now kept constant to their standard of excel- 

 lence by continued selection, which would be impossible 

 unless the distinctive characters of both were limited in 

 their transmission. The Spanish fowl offers a more curi- 

 ous case; the male has an immense comb, but some of the 

 Buccessive variations, by the accumulation of which it was 

 acquired, appear to have been transferred to the female; 

 for she has a comb many times larger than that of the 

 females of the parent species. But the comb of the female 

 differs in one respect from that of the male, for it is apt to 

 lop over; and within a recent period it has been ordered by 



