The Descent of Man

very rare colour in terrestrial species of moderate
size and inoffensive habits. The male, also,
as described by Waterton, has a spiral tube,
nearly three inches in length, which rises from
the base of the beak. It is jet-black, dotted over
with minute downy feathers. This tube can be
inflated with air, through a communication
with the palate; and when not inflated hangs
down on one side. The genus consists of four
species, the males of which are very distinct,
whilst the females, as described by Mr. Sclater
in a very interesting paper, closely resemble
each other, thus offering an excellent instance
of the common rule that within the same group
the males differ much more from each other
than do the females. In a second species (C.
nudicollis) the male is likewise snow-white,
with the exception of a large space of naked
skin on the throat and round the eyes, which
during the breeding-season is of a fine green
colour. In a third species (C. tricarunculatus)
the head and neck alone of the male are white,