The Descent of Man

ied on until the wonderful ball-and-socket
ocelli were finally developed. Thus we can understand—and
in no other way as it seems to
me—the present condition and origin of the
ornaments on the wing-feathers of the Argus
pheasant.
From the light afforded by the principle of gradation—from
what we know of the laws of
variation—from the changes which have taken
place in many of our domesticated birds—and,
lastly, from the character (as we shall hereafter
see more clearly) of the immature plumage of
young birds—we can sometimes indicate, with
a certain amount of confidence, the probable
steps by which the males have acquired their
brilliant plumage and various ornaments; yet in
many cases we are involved in complete darkness.
Mr. Gould several years ago pointed out
to me a humming-bird, the Urosticte benjamini,
remarkable for the curious differences between
the sexes. The male, besides a splendid gorget,