74 
SEXUAL SELECTION: BIRDS. 
PABi 1 
The barbs of the feathers in various widely-disti° c 
birds are filamentous or plumose, as with some HeroO-' 
Ibises, Birds of Paradise and Gallinaceae. In oth e | 
eases the barbs disappear, leaving the shafts bare; °’ 11 
these in the tail of tho Paradhea apoda attain a lengt ' 1 
of thirty-four inches . 66 Smaller feathers when th fl 
denuded appear like bristles, as on the breast of 
turkey-cock. As any fleeting fashion in dress con 11 ’’ 
to be admired by man, so with birds a change 0 
almost any kind in the structure or colouring of t' 1<J 
feathers in the male appears to have been admired W 
the female. The fact of the feathers in widely 
tinet groups, having been modified in an analog 011 ’ 
manner, no doubt depends primarily on all the feath 01 " 
having nearly the same structure and manner of deV^ 
lopment, and consequently tending to vary in the 
manner. We often see a tendency to analogous vari 9 ' 
bility in the plumage of our domestic breeds belong! 0 ' 
to distinct species. Thus top-knots have appeared ,jl 
several species. In an extinct variety of the turk°)’ 
the top-knot consisted of bare quills surmounted wi^ 
plumes of down, so that they resembled, to a certa' 1 ' 
extent, the racket-shaped feathers above described. I 11 
certain breeds of the pigeon and fowl the feathers il1 ' 1 
plumose, with some tendency in the shafts to be nak°^’ 
In the Sebastopol goose the scapular feathers are great!.' 
elongated, curled, or even spirally twisted, with 
margins plumose . 67 
In regard to colour hardly anything need here 
said ; lor every one knows how splendid are the th '* 5 
66 Wallace, in ‘Annals and Mag. of Nat. Hist.’ vol. xx. 1857, p. ilb 
and in his 1 Malay Archipelago,’ vol. ii. 1869, p. 390. 
67 See ray work on * The Variation of Animals and Plants nnd et 
Domestication’ vol. i. p. 289, 293. 
