496 THE DESCENT OF MAN 



times the fleshy appendages about the head of the male 

 Tragopan pheasant (^Geriornis Temminckii) swell into a large 

 lappet on the throat and into two horns, one on each side 

 of the splendid topknot; and these are then colored of the 

 most intense blue which I have ever beheld.*" The African 

 hornbill {Bticorax ahyssiniciis) inflates the scarlet bladder- 

 like wattle on its neck, and with its wings drooping and 

 tail expanded "makes quite a grand appearance." " Even 

 the iris of the eye is sometimes more brightly colored in 

 the male than in the female ; and this is frequently the case 

 with the beak, for instance, in our common blackbird. In 

 Buceros corrugatus, the whole beak and immense casque are 

 colored more conspicuously in the male than in the female; 

 and "the oblique grooves upon the sides of the lower man- 

 dible are peculiar to the male sez." °* 



The head, again, often supports fleshy appendages, fila- 

 ments, and solid protuberances. These, if not common to 

 both sexes, are always confined to the males. The solid 

 protuberances have been described in detail by Dr. W. 

 Marshall,'* who shows that they are formed either of can- 

 cellated bone coated with skin, or of dermal and other 

 tissues. With mammals true horns are always supported 

 on the frontal bones, but with birds various bones have 

 been modified for this purpose ; and in species of the same 

 group the protuberances may have cores of bone, or be 

 quite destitute of them, with intermediate gradations con- 

 necting these two extremes. Hence, as Dr. Marshall justly 

 remarks, variations of the most different kinds have served 

 for the development through sexual selection of these orna- 

 mental appendages. Elongated feathers or plumes spring 

 from almost every part of the body. The feathers on 

 the throat and breast are sometimes developed into beau- 



*^ See Dr. Murie's account with colored figures in "Proc. Zoolog. Soc," 

 I8t2, p. 730. 



«' Monteiro, "Ibis," vol. iv., 1862, p. 339. 



^ "Land and Water," 1868, p. 217. 



** "TJeber die Schadelhoclcer, " etc., "Niederiandischen Archiv fiir Zoolo- 

 gie," B. I. Heft 2, 1872. 



