Chap. VIII. SEXUAL SELECTION. 295 



for the two sexes, though not quite alike, resemble each 

 other more closely than do the sexes of the aboriginal 

 parent-species, yet they acquire their characteristic 

 plumage late in life, for the chickens are distinctly 

 pencilled. Turning to other characters besides colour : 

 the males alone of the wild parent-species and of most 

 domestic breeds possess a fairly well developed comb, but 

 in the young of the Spanish fowl it is largely developed 

 at a very early age, and apparently in consequence of 

 this it is of unusual size in the adult females. In the 

 Game breeds pugnacity is developed at a wonderfully 

 early age, of which curious proofs could be given ; and 

 this character is transmitted to both sexes, so that the 

 hens, from their extreme pugnacity, are now generally 

 exhibited in separate pens. With the Polish breeds the 

 bony protuberance of the skull which supports the crest 

 is partially developed even before the chickens are 

 hatched, and the crest itself soon begins to grow, though 

 at first feebly ; 31 and in this breed a great bony protu- 

 berance and an immense crest characterise the adults of 

 both sexes. 



Finally, from what we have now seen of the relation 

 which exists in many natural species and domesticated 

 races, between the period of the development of their 

 characters and the manner of their transmission — for 

 example the striking fact of the early growth of the 

 horns in the reindeer, in which both sexes have horns, 

 in comparison with their much later growth in the 

 other species in which the male alone bears horns 



31 For full particulars and references on all these points respecting 

 the several breeds of the Fowl, see ' Variation of Animals and Plants 

 under Domestication,' vol. i. p. 250, 256. In regard to the higher 

 animals, the sexual differences which have arisen under domestication 

 are described in the same work under the head of each species. 



