524 THE DESCENT OF MAN. 



pigeon has likewise produced a vast number of distinct 

 breeds and sub-breeds, and in these, with rare exceptions, 

 the two sexes are identically alike. 



Therefore if other species of Gallus and Columba were 

 domesticated and varied it would not be rash to predict 

 that similar rules of sexual similarily and dissimilarity 

 depending on the form of transmission would hold good in 

 both cases. In like manner the same form of transmission 

 has generally prevailed under nature throughout the same 



iroups, although marked exceptions to this rule occur, 

 'hus within the same family, or even genus, the sexes may 

 be identically alike or very different in color. Instances 

 have already been given in the same genus, as with spar- 

 rows, fly-catchers, thrushes and grouse. In the family of 

 Eheasants the sexes of almost all the species are wonder- 

 Lilly dissimilar, but are quite alike in the eared pheasant 

 or Crossoptilon auritum. In two species of Chloephaga, 

 a genus of geese, the male cannot be distinguished from 

 the females except by size; while in two others the sexes 

 are so unlike that they might easily be mistaken for distinct 

 species. * 



The laws of inheritance can alone account for the fol- 

 lowing cases in which the female acquires late in life 

 certain characters proper to the male, and ultimately 

 comes to resemble him more or less completely. Here pro- 

 tection can hardly have come into play. Mr. Blyth in- 

 forms me that the females of Oriolus melanocephalus and 

 of some allied species when sufficiently mature to breed 

 differ considerably in plumage from the adult males; but 

 after the second or third moults they differ only in their 

 beaks having a slight greenish tinge. In the dwarf bitterns 

 (Ardetta), according to the same authority, " the male 

 acquires his final livery at the first moult; the female not 

 before the third or fourth moult; in the meanwhile she pre- 

 sents an intermediate garb, which is ultimately exchanged 

 for the same livery as that of the male." So, again, the 

 female Falco peregrinus acquires her blue plumage more 

 slowly than the male. Mr. Swinhoe states that with one of 

 the drongo shrikes (Dicrurus macrocercus) the male, while 

 almost a nestling, molts his soft brown plumage and 

 becomes of a uniform glossy greenish-black; but the female 



*The "Ibis," vol. vi, 1864, p. 122. 







