524 THE DESCENT OF MAN. 



pigeon has likewise produced a vast number of distinci 

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

 the two sexes are identically alike. 



Therefore if other species of G alius and Columba wen 

 domesticated and varied it would not be rash to predici 

 that similar rules of sexual similarily and dissimilaritj 

 depending on the form of transmission would hold good ii 

 both cases. In like manner the same form of transmissioi 

 has generally prevailed under nature throughout the sanii 

 groups, although marked exceptions to this rule occur 

 Thus within the same family, or even genus, the sexes mai 

 be identically alike or very different in color. Instancei 

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

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

 pheasants the sexes of almost all the species are wonder 

 fully dissimilar, but are quite alike in the eared pheasan 

 or Crossoptilon auritum. In two species of Chloephaga 

 a genus of geese, the male cannot be distinguished fron 

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

 are so unlike that they might easily be mistaken for distinc 

 species. * 



The laws of inheritance can alone account for the fol 

 lowing cases in which the female acquires late in lifi 

 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. Blytli in 

 forms me that the females of Oriolus mela7iocepUalus an( 

 of some allied species when sufficiently mature to bree( 

 differ considerably in plumage from the adult males; bu 

 after the second or third moults they differ only in thei 

 beaks having a slight greenish tinge. In the dwarf bittern 

 (Ardetta), according to the same authority, ^' the mal< 

 acquires his final livery at the first moult; the female no 

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

 sents an intermediate garb, which is ultimately exchangee 

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

 female Falco peregrmus acquires her blue plumage mon 

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

 the drongo shrikes (Dicrurus macrocercus) the male, whil< 

 almost a nestling, molts his soft brown plumage anc 

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



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



