BIRDS. 509 



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

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

 the penciled Hamburghs differ greatly from each other, 

 and from the two sexes of the aboriginal Gallus bankiva; 

 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 curious case; the male 

 has an immense comb, but some of the successive varia- 

 tions, 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 would 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 ex- 

 tremely difficult and complex, perhaps an impossible pro- 

 cess, to change one form of transmission into the other 

 through selection. Therefore, without distinct evidence 

 in each case, I am unwilling to admit that this has been 

 effected in natural species. On the other hand, by means 

 of successive variations, which were from the first sexually 

 limited in their transmission, there would not be the least 

 difficulty in rendering a male bird widely different in color 

 or in any other character from the female; the latter being 

 left unaltered, or slightly altered, or specially modified for 

 the sake of protection. 



As bright colors are of service to the males in their 

 rivalry with other males, such colors would be selected 

 whether or not they were transmitted exclusively to the 

 same sex. Consequently the females might be expected 

 often to partake of the brightness of the males to a greater 

 or less degree; and this occurs with a host of species. 



