The Descent of Man

does not appear that intermediate gradations
have been observed in this or the following
cases. In the males alone of one of the Australian
parrakeets "the thighs in some are scarlet,
in others grass-green." In another parrakeet of
the same country "some individuals have the
band across the wing-coverts bright-yellow,
while in others the same part is tinged with red.
(37. Gould, 'Handbook to Birds of Australia,'
vol. ii. pp. 32 and 68.) In the United States some
few of the males of the scarlet tanager (Tanagra
rubra) have "a beautiful transverse band of
glowing red on the smaller wing- coverts" (38.
Audubon, 'Ornithological Biography,' 1838, vol.
iv. p. 389.); but this variation seems to be somewhat
rare, so that its preservation through
sexual selection would follow only under usually
favourable circumstances. In Bengal the
Honey buzzard (Pernis cristata) has either a
small rudimental crest on its head, or none at
all: so slight a difference, however, would not
have been worth notice, had not this same spe-