1 II 



SKXLIAL DIMOLTII1SM 



one median at the base of the upper mandible, and one at 



t'ach an^'le of the gape. Mr. Osbert Salvin 1 has stated that 

 hr was unable to ascertain from dried specimens whether 

 there was any communication by which air could be passed 

 into these caruncles, but his own impression was that no 

 inflation takes place, and that the bird has no voluntary 

 control over the excrescences ; that they elongate or contract 

 only like the fleshy caruncle of the Common Turkey. It 

 must be remembered, however, that Waterton distinctly 

 mentions the erection of the appendage in C. niveus. 



Evidently further investigation is here required, but it 

 seems most probable that the appendages are erectile and 

 solid, having nothing to do with the voice. In other words, 

 they are probably composed of erectile tissue, and erected by 

 influx of blood. If this be the case they are probably erected 

 during sexual excitement. Salvin mentions that they only 

 appear with the adult plumage, and develop rapidly. In my 

 opinion their evolution is probably due to some mechanical 

 irritation connected with the habits of sexual maturity; 

 perhaps the males fight with their beaks, as in the case of 

 the Turkey. This suggestion is supported by the condition 

 found in a fourth species, C. variegatus, occurring in Trinidad 

 and neighbouring parts of South America. In this species 

 there are no caruncles on the upper side of the beak or head, 

 but the skin of the throat is bare of feathers and provided 

 with numerous slender caruncles, which seem, from Salvin's 

 paper, to be about 1J inch long in the adult, and to be absent 

 in the immature male. In C. nudicollis, also mentioned 

 above, although there are no actual caruncles, the skin of the 

 throat and around the eyes is destitute of feathers, bearing 

 only scattered black bristles ; this bare skin is of a green 

 colour in the breeding-season. 



It is unfortunate that we have no evidence from actual 



Note on the Costa-Rican Bell-Bird," Ibis. 1865. 



