76 SEXUAL SELECTION : BIRDS. [Part II. 



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, while 

 the females, as described by Mr. Sclater in a most inter- 

 esting 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. nudlcollis) 

 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-br*own, and the male of this species is pro- 

 vided 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. 70 



The colored plumage and certain other ornaments of 

 the males when adult are either retained for life or are 

 periodically renewed during the summer and breeding-sea- 

 son. " At this season the beak and naked skin about the 

 head frequently change color, as with some herons, ibises, 

 gulls, one of the bell-birds just noticed, etc. In the white 

 ibis, the cheeks, the inflatable skin of the throat, and the 

 basal portion of the beak, then become crimsqn. 71 In one 

 of the rails, Gallicrex cristatus, a large red caruncle is de- 

 veloped during this same 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-sea- 

 son, these horny crests are shed, like horns from the heads 



10 Mr. Sclater, 'Intellectual Observer,' Jan. 1867. '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,' 1867, p. 394. 



