Chap. XV. Birds — Sexually Limited Inheritance, 44.7 



inheritance prevails, it might well happen that some of the 

 successive 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 colour. 



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 w r ould be extreme, unless the suc- 

 cessive variations were from the first sexually limited on both 

 sides, and then there would be no difficulty. 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 abori- 

 ginal Gallus bankiva ; and both are now kept constant to their 

 standard of excellence by continued selection, which would be 

 impossible unless the distinctive characters of both were limited 

 in their transmission. The Spanish fowl offers a more curious 

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

 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 the fancy that this should always be the case, 

 and success has quickly followed the order. Now the lopping of 

 the comb must be sexually limited in its transmission, otherwise 

 it would prevent the comb of the male from being perfectly 

 upright, which would be abhorrent to every fancier. On the 

 other hand, the uprightness of the comb in the male must 

 likewise be a sexually-limited character, otherwise it w^ouid 

 prevent the comb of the female from lopping over. 



From the foregoing illustrations, we see that even with almost 

 unlimited time at command, it would be an extremely difficult 

 and complex, perhaps an impossible process, to change one form 

 of transmission into the other through selection. Therefore, 



