484 THE DESCENT OF MAN. 



the females are white. In the Buceros bicornis, the hind 

 margin of the casque and a stripe on the crest of the beak 

 are black in the male, but not so in the female. Are we to 

 suppose that these black marks and the crimson color of 

 the eyes have been preserved or augmented through sexual 

 selection in the males? This is very doubtful; for Mr. 

 Bartlett showed me in the Zoological Gardens that the 

 inside of the mouth of this buceros is black in the male 

 and flesh -colored in the female; and their external appear- 

 ance or beauty would not be thus affected. I observed in 

 Chili * that the iris in the condor, when about a year old, 

 is dark-brown, but changes at maturity into a yellowish- 

 brown in the male, and into bright red in the female. The 

 male has also a small, longitudinal, leaden-colored, fleshy 

 crest or comb. The comb of many gallinaceous birds is 

 highly ornamental, and assumes vivid colors during the act 

 of courtship; but what are we to think of the dull-colored 

 comb of the condor which does not appear to us in the least 

 ornamental? The same question may be asked in regard to 

 various other characters, such as the knob on the base of 

 the beak of the Chinese goose (Anser cygnoides), which is 

 much larger in the male than in the female. No certain 

 answer can be given to these questions; but we ought to be 

 cautious in assuming that knobs and various fleshy appen- 

 dages cannot be attractive to the female, when we remem- 

 ber that with savage races of man various hideous 

 deformities deep scars on the face with the flesh raised 

 into protuberances, the septum of the nose pierced by sticks 

 or bones, holes in the ears and lips stretched widely open- 

 are all admired as ornamental. 



Whether or not unimportant differences between the 

 sexes, such as those just specified, have been preserved 

 through sexual selection, these diiferences, as well as all 

 others, must primarily depend on the laws of variation. On 

 the principle of correlated development, the plumage often 

 varies on different parts of the body, or over the whole 

 body, in the same manner. We see this well illustrated in 

 certain breeds of the fowl. In all the breeds the feathers 

 on the neck and loins of the males are elongated and are 

 called hackles; now when both sexes acquire a top-knot, 

 which is a new character in the genus, the feathers on the 



* " Zoology of the Voyage of H. M. S. ' Beagle,' " 1841, p. 6. 



