198 Evolution and Adaptateon 
A remarkable bird of South America, the bell-bird, has a 
peculiar note that “can be distinguished at the distance of 
nearly three miles and astonishes every one who hears it. 
The male is pure white, whilst the female is dusky- 
green; and white is a very rare color 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 offer- 
ing 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. zudicollis) 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 color. In a third 
species (C. tricarunculatus) the head and neck alone of the 
male are white, the rest of the body being chestnut-brown, 
and the male of this species is provided with three filamentous 
projections half as long as the body —one rising from the 
base of the beak, and the two others from the corners of the 
mouth.” 
The most familiar case of sexual difference amongst North 
American birds is that of the scarlet tanager, in which the 
male is scarlet with jet-black wings, while the female is an 
inconspicuous yellow-green color. Amongst domesticated 
animals the peafowl shows the most beautiful case of sexual 
differences. The magnificent tail of the male can be lifted 
up, so as to be seen to best advantage when the male faces 
the observer. Moreover the wild form, living in the forests 
of India, has the same gorgeous train. 
