SEXUAL SELECTION 305 



wMch ti.e characters are usually transferred in an equal 

 degree to both sexes) varied into pale blue, could lie by 

 long-continued selection make a breed in whicli the males 

 alone should be of this tint, while the females remained un- 

 changed? I will here only say that this, though perhaps 

 not impossible, would be extremely difficult; for the natural 

 result of breeding from the pale-blue males would be to 

 change the whole stock of both sexes to this tint. If, how- 

 ever, variations of the desired tint appeared, which were 

 from the first limited in their development to the male sex, 

 there would not be the least difficulty in making a breed 

 with the two sexes of a different color, as indeed has been 

 effected with a Belgian breed, in which the males alone are 

 streaked with black. In a similar manner, if any variation 

 appeared in a female pigeon, which was from the first sex- 

 ually limited in its development to the females, it would be 

 easy to make a breed with the females alone thus charac- 

 terized; but if the variation was not thus originally limited, 

 the process would be extremely difficult, perhaps impossible. " 



On the Relation between the Period of Development of a 

 Character and its Transmission to One Sex or to Both Sexes. — - 

 Why certain characters should be inherited by both sexes, 

 and other characters by one sex alone, namely, by that sex 

 in which the character first appeared, is in most cases quite 

 unknown. We cannot even conjecture why, with certain 

 sub- breeds of the pigeon, black striae, though transmitted 

 through the female, should be developed in the male alone, 

 while every other character is equally transferred to both 

 sexes. Why, again, with cats, the tortoise-shell color 



3' Since the publication of the first edition of this work, it has heen highly 

 satisfactory to me to find the following remarks ("The Field," Sept. 1872) from 

 so experienced a breeder as Mr. Tegetmeier. Aiter describing some curious 

 cases in pigeons, of the transmission of color by one sex alone, and the forma- 

 tion of a sub-breed with this character, he says: "It is a singular circumstance 

 that Mr. Darwin should have suggested the possibility of modifying the sexual 

 colors of birds by a course of artificial selection. When he did so, he was in 

 ignorance of these facts that I have related ; but it is remarkable how very 

 closely he suggested the right method of procedure." 



