DECORATION. 379 



same group the protuberances may have cores of bone, or be 

 quite destitute of them, with intermediate gradations connecting 

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

 variations of the most different kinds have served for the de- 

 velopment through sexual selection of these ornamental appen- 

 dages. Elongated feathers or plumes spring from almost 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 

 been modified to support the heavy tail-coverts." 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,"' and that of the beautifully ocellated sec- 

 ondary wing-feathers nearly three feet. In a small African night- 

 jar (Cosmetornis vexillarius) 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 elongated wing- 

 feathers are naked, except at the extremity, where there is a 

 disc.™ Again, in another genus of night-jars, the tail-feathers 

 are even still more prodigiously developed. In general the feath- 

 ers 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 (Eumomota superciliaris), of a king-fisher, finch, hum- 

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

 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.™ It is a most singular 



ee Dr. W. Marshall, 'Uber den Vogelschwanz,' ibid. B. I. Heft 2, 1872. 

 " Jardine's 'Naturalist Library: Birds,' vol. xiv. p. 166. 

 "" Sclater, in the 'Ibis,' vol. vi. 1864, p. 114. Livingstone, 'Expedition 

 to the Zambesi,' 1S65, p. 66. 

 " Jerdon, 'Birds of India,' vol. iii. p. 620. 



