Chap. VIII. Sexual Selection 231 



common With anima.ls under domestication, but whether in 

 nature I will not venture to say, one sex may lose characters 

 proper to it, and may thus come somewhat to resemble the 

 opposite sex ; for instance, the males of some breeds of the fowl 

 have lost their masculine tail-plumes and hackles. On the 

 other hand, the differences between the sexes may be increased 

 under domestication, as with merino sheep, in which the 

 ewes have lost tlieir horns. Again, characters proper to one 

 BOX may suddenly appear in the other sex ; as in those sub- 

 breeds of th,e fowl in wliich the hens acquire spurs whilst young ; 

 or, as in certain Polish sub-breeds, in which the females, as 

 there is reason to believe, originally acquired a crest, and sub- 

 sequently transferred it to the males. All these cases are in- 

 telligible on the hypothesis of pangenesis ; for they depend on 

 the gemmules of certain parts, although present in both sexes, 

 l)econiing, through the influence of domestication, either dormant 

 or developed in either sex. 



There is one difficult question which it will be convenient to 

 defer to a future chapter; namely, whether a character at first 

 developed in both sexes, could through selection be limited in 

 its developmeht to one sex alone. If, for instance, a breeder 

 observed that some of his pigeons (of which the characters are 

 usually transferred in an equal degree to both sexes) varied into 

 pale blue, could he by long-continued selection make a breed, 

 in which the males alone should be of this tint, whilst the females 

 remained unchanged ? I will here only say, that tliis, 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 desu'ed 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 colour, 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 sexually limited in its development to 

 the females, it would be easy to make a breed with the females 

 alone thus characterised ; but if the variation was not thus 

 originally limited, the process would be extremely difficult, per- 

 hups impossible.^ 



=' Since tiic publication of the perienced a breeder as Mr. Tegct- 



Nrst edition of this work, it hiis meier. After describing some cu- 



been highly satisfactory to me to rious cases in pigeons, of the trans- 



5nd the following remarks (the mission of colour by one sex alune, 



Field,' Sept. 1872) from so ex- and the formation of a sub-breed 



