498 THE DESCENT OF MAN 



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

 some gallinaceous birds. In an Indian bustard {Sypfieotidea 

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

 four inches in length, also terminate in disks."* It is a most 

 singular fact that the motmots, as Mr. Salvin has clearly 

 shown," give to their tail-feathers the racket-shape by 

 biting o£E the barbs, and, further, that this continued muti- 

 lation has produced a certain amount of inherited effect. 



Again, the barbs of the feathers in various widely dis- 

 tinct birds are filamentous or plumose, as with some herons, 

 ibises, birds of paradise, and Gailinacese. In other cases 

 the barbs disappear, leaving the shafts bare from end to 

 end; and. these in the tail of the Paradisea apoda attain a 

 length of thirty-four inches ;" in P. Papuana (Fig. 47) they 

 are much shorter and thin. 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 coloring of the feathers in the male appears to 

 have been admired by the female. The fact of the feath- 

 ers in widely distinct groups having been modified in an 

 analogous manner, no doubt depends primarily on all the 

 feathers having nearly the same structure and manner of 

 development, and consequently tending to vary in the same 

 manner. We often see a tendency to analogous variability 

 in the plumage of our domestic breeds belonging to distinct 

 species. Thus topknots have appeared in several species. 

 In an extinct variety of the turkey, the topknot consisted 

 of bare quills surmounted with plumes of down, so that 

 they somewhat resembled 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 



•9 .Terdon, "Birds of India," vol. iii. p. 620. 

 ■"> "Proo. Zoolog. See," 1873, p. 429, 



" Wallace, in "Annals and Mag. of Na^.. Hist.," vol. xi., 1857, p. 416; and 

 in his "Malay Archipelago," vol. ii., 1869, p. 390. 



