384 THE DESCENT OF MAN. 



bell-bird (Chasmorbynchus niveus) of S. America, the note of 

 which can be distinguished at the distance of nearly three miles. 

 and astonishes every one when first hearing 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 communi- 

 cation 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, v/hich 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 colored plumage and certain other ornaments of the adult 

 males are either retained for life, or are periodically renewed 

 during the summer and breeding-season. At this same season 

 the beak and naked skin about the head frequently change color, 

 as with some herons, ibises, gulls, one of the bell-birds just no- 

 ticed, &c. In the white ibis, the cheeks, the inflatable 

 skin of the throat, and the basal portion of the beak then be- 

 come crimson.™ In one of the rails, Gallicrex cristatus, a large red 

 caruncle is developed during this period on the head of the male. 

 So it is with a thin horny crest on the beak of one of the pelicans, 

 P. erythrorhynchus ; for after the breeding-season, these horny 

 crests are shed, like horns from the heads of stags, and the shore 

 of an island in a lake in Nevada was found covered with these 

 curious exuviffi." 



Changes of color in the plumage according to the season de- 

 pend, firstly on a double annual moult, secondly on an actual 

 change of color in the feathers themselves, and thirdly on their 



■"= Mr. Sclater, 'Intellectual Observer,' Jan. 1S67. 'Waterton' s Wan- 

 derings,' p. 118. See also Mr. Salvin's Interesting paper, with a plate, 

 in the 'Ibis,' 1865, p. 90. 



" 'Land and Water,' 1S67, p. 394. 



" Mr. D. G. Elliot, in 'Proc. Zool. Soc' 1S69, p. 589. 



