148 SEXUAL SELECTION: BIRDS. [Part IL 



they first appearcrl. Since my remarks appeared, the sub- 

 ject of sexual coloration has been discussed in some very 

 interesting papers by Mr. Wallace," who believes that in 

 almost all cases the successive variations tended at first to 

 be transmitted equally to both sexes ; but that the female 

 was saved, through natural selection, from acquiring the 

 conspicuous colors of the male, owing to the danger which 

 she would thus have incurred during incubation. 



This view necessitates a tedious discussion on a diffi- 

 cult point, namely, whether the transmission of a charac- 

 ter, which is at first inherited by both sexes, can be subse- 

 quently limited in its transmission, by means of selection, 

 to one sex alone. We must bear in mind, as shown in the 

 preliminary chapter on sexual selection, that characters 

 which are limited in their development to one sex are 

 always latent in the other. An imaginary illustration will 

 best aid us in seeing the difficulty of the case : we may 

 suppose that a fancier wished to make a breed of pigeons, 

 in which the males alone should be colored of a pale blue, 

 while the females retained their former slaty tint. As with 

 pigeons characters of all kinds are usually transmitted to 

 both sexes equally, the fancier would have to try to con- 

 vert this latter form of inheritance into sexually-limited 

 transmission. All that he could do would be to persevere 

 in selecting every male pigeon which was in the least 

 degree of a paler blue ; and the natural result of this pro- 

 cess, if steadily carried on for a long time, and if the pale 

 variations were strongly inherited or often recurred, would 

 be to make his whole stock of a lighter blue. But our 

 fancier would be compelled to match, generation af^er gen- 

 eration, his pale-blue males with slaty females, for he wishes 

 to keep the latter of this color. The result would generally 

 be the production either of a mongrel piebald lot, or 



* ' Westminster Review,'' July, 1867. 'Journal of Travel,' vol. i. 

 1868, p. 73. 



