The Descent of Man

in the common peacock; but M. Hegt of Amsterdam
informs me, that with young birds of
the previous year, of both species, compared on
April 23rd, 1869, there was no difference in the
development of the spurs. The spurs, however,
were as yet represented merely by slight knobs
or elevations. I presume that I should have
been informed if any difference in the rate of
development had been observed subsequently.)
The male and female Peacock differ conspicuously
from each other in almost every part of
their plumage, except in the elegant head-crest,
which is common to both sexes; and this is developed
very early in life, long before the other
ornaments, which are confined to the male. The
wild-duck offers an analogous case, for the
beautiful green speculum on the wings is
common to both sexes, though duller and somewhat
smaller in the female, and it is developed
early in life, whilst the curled tail-feathers
and other ornaments of the male are developed
later. (45. In some other species of the Duck