Chap. XIV. 
YARIABILITt. 
129 
of the genus Xenorhynclms those of the male are 
blackish-haze], whilst those of the females are gam- 
boge-yellow ; with many hornbills (Buceros), as I hear 
from Mr. Blyth/^ the males have intense crimson, and 
the females white eyes. In the Buceros hicornis, 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 colour of the eyes have been preserved or aug- 
mented through sexual selection in the males? This 
is very doubtful; for Mr. Bartlett shewed me in the 
Zoological Gardens that the inside of the mouth of this 
Buceros is black in the male and flesh-coloured in the 
female ; and their external appearance 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 yellowish-brown in the 
male, and into bright red in the female. The male 
has also a small, longitudinal, leaden-coloured, fleshy 
crest or comb. With many gallinaceous birds the 
comb is highly ornamental, and assumes vivid colours 
during the act of courtship ; but what are we to think 
of the dull-coloured 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 appendages cannot be attractive to the female, 
when we remember that with savage races of man 
See also Jerdon, ‘Birds of India,’ vol. i. p. 243-245. 
‘ Zoology of the Yoyage of H.M.S. Beagle/ 1841, p. 6. 
YOL. II. K 
