■74 
SEXUAL SELECTION: BIEDS. 
Part II. 
The barbs of the feathers in various widely-distinct 
birds are filamentous or plumose, as with some Herons, 
Ibises, Birds of Paradise and Gallinaceae. In other 
cases the barbs disappear, leaving the shafts bare ; and 
these in the tail of the Paradisea ajpoda attain a length 
of thirty-four inches.^® Smaller feathers when thus 
denuded appear like bristles, as on the breast of the 
turkey-cock. As any fleeting fashion in dress comes 
to be admired by man, so with birds a change of 
almost any kind in the structure or colouring of the 
feathers in the male appears to have been admired by 
the female. The fact of the feathers in widely dis- 
tinct groups, having been modified in an analogous 
manner, no doubt depends primarily on all the feathers 
having nearly the same structure and manner of deve- 
lopment, and consequently tending to vary in the same 
manner. We often see a tendency to analogous varia- 
bility in the plumage of our domestic breeds belonging 
to distinct species. Thus top-knots have appeared in 
several species. In an extinct variety of the turkey, 
the top-knot consisted of bare quills surmounted with 
plumes of down, so that they resembled, to a certain 
extent, the racket-shaped feathers above described. In 
certain breeds of the pigeon and fowl the feathers are 
plumose, with some tendency in the shafts to be naked. 
In the Sebastopol goose the scapular feathers are greatly 
elongated, curled, or even spirally twisted, with the 
margins plumose.^^ 
In regard to colour hardly anything need here be 
said ; for every one knows how splendid are the tints 
Wallace, in ‘Annals and Mag. of Nat. Hist.’ vol. xx. 1857, p. 416 ; 
and in his ‘ Malay Archipelago,’ vol. ii. 1869, p. 390. 
See my work on ‘The Variation of Animals and Plants under 
Domestication,’ vol. i. p. 289, 293. 
