SEXUAL SELECTION 503 



three inches in length, which rises from ttie 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, while_J;he 

 females, as described by Mr. Sclater inA--very^interesting 

 paper, closely resemble each other^^iMis ofEering an excel- 

 lent instance of the common vyM that within the same 

 group the males differ much more from each other than 

 do the females. In a second species {G. nudicoUis) the male 

 is likewise snow-white, with the exception of a large space 

 of naked skin on the throat and round the eyes, which dur- 

 ing the breeding season is of a fine green color. In a third 

 species {O. 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 filamen- 

 tous projections half as long as the body — one rising from 

 the base of the beak, and the other two 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 fre- 

 quently 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 crimson." In one of the 

 rails, Oallicrex eristatus, 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 



■" Mr. Sclater, "Intellectual Observer," January, 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," ISet, p. 394. 



