384 The Descent of Man. Part II. 



every part of the body. The feathers on the throat and breast 

 are sometimes developed into beautiful ruffs and collars. The 

 tail-feathers are frequently increased in length ; as we see in the 

 tail-coverts of the peacock, and in the tail itself of the Argus 

 pheasant. With the peacock even the bones of the tail have 

 l>een modified to support the heavy tail-coverts. 66 The body of 

 the Argus is not larger than that of a fowl ; yet the length from 

 the end of the beak to the extremity of the tail is no less than 

 five feet three inches, 67 and that of the beautifully ocellated 

 secondary wing-feathers nearly three feet. In a small African 

 night-jar (Cosmetoruis vexillurius) one of the primary wing- 

 feathers, during the breeding -season, attains a length of twenty- 

 six inches, whilst the bird itself is only ten inches in length. In 

 another closely-allied genus of night-jars, the shafts of the elon- 

 gated wing-feathers are naked, except at the extremity, where 

 there is a disc. 68 Again, in another genus of night-jars, the 

 tail-feathers are even still more prodigiously developed. In 

 general the feathers of the tail are more often elongated than 

 those of the wings, as any great elongation of the latter impedes 

 flight. "We thus see that in closely -allied birds ornaments of 

 the same kind have been gained by the males through the 

 development of widely different feathers. 



It is a curious fact that the feathers of species belonging to 

 very distinct groups have been modified in almost exactly the 

 same peculiar manner. Thus the wing-feathers in one of the 

 above-mentioned night-jars are bare along the shaft, and ter- 

 minate in a disc ; or are, as they are sometimes called, spoon or 

 racket- shaped. Feathers of this kind occur in the tail of a 

 motmot (tiumomota superciliaris), of a king-fisher, finch, hum- 

 ming-bird, parrot, several Indian drongos (Dicrurus and Edolius, 

 in one of which the disc stands vertically), and in the tail of 

 certain birds of paradise. In these latter birds, similar feathers, 

 beautifully ocellated, ornament the head, as is likewise the case 

 with some gallinaceous birds. In an Indian bustard (Sypheotides 

 auritus) the feathers forming the ear-tufts, which are about four 

 inches in length, also terminate in discs. 69 It is a most singular 

 fact that the motmots, as Mr. Salvin has clearly shewn, 70 give to 

 their tail feathers the racket-shape by biting off the barbs, 

 and, further, that this continued mutilation has produced a 

 certain amount of inherited effect. 



66 Dr. W. Marshall, 'Uber den Vog- 1864, p. 114. Livingstone, ' Expedi- 

 elschwanz,' ibid. B. I. Heft 2, 1872. tion to the Zambesi,' 1865, p. 66. 



67 Jardine's ' Naturalist Library : 69 Jerdon, ' Birds of India,' vol, 

 Birds,' vol. xiv. p. 166. iii. p. 620. 



•» Sclater, in the 'Ibis,' vol. vi. 70 < Proc. Zoolog. Soc' 1873, p. 429. 



>l 



