The Descent of Man

other ornaments, of which the female partakes
to a slight degree; for these are almost certainly
due to characters primarily acquired by the
male having been more or less transferred to
the female. But what are we to conclude with
respect to certain birds in which, for instance,
the eyes differ slightly in colour in the two
sexes? (44. See, for instance, on the irides of a
Podica and Gallicrex in 'Ibis,' vol. ii. 1860, p.
206; and vol. v. 1863, p. 426.) In some cases the
eyes differ conspicuously; thus with the storks
of the genus Xenorhynchus, those of the male
are blackish- hazel, whilst those of the females
are gamboge-yellow; with many hornbills (Buceros),
as I hear from Mr. Blyth (45. See also
Jerdon, 'Birds of India,' vol. i. pp. 243-245.), the
males have intense crimson eyes, and those of
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 colour of the