438 THE DESCENT OF MAN. 



and these in the tail of the Paradisea apoda attain a 

 length of thirty-four inches;* in P. Papiiana (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 feathers in widely distinct groups having 

 been modified in an anologous 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 dis- 

 tinct 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 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 

 are greatly elongated, curled, or even spirally twisted, with 

 the margins plumose, f 



In regard to color, hardly anything need here be said, 

 for every one knows how splendid are the tints of many 

 birds and how harmoniously they are combined. The 

 colors are often metallic and iridescent. Circular spots 

 are sometimes surrounded by one or more differently 

 shaded zones and are thus converted into ocelli. Nor need 

 much be said on the wonderful difference between the 

 sexes of many birds. The common peacock offers a strik- 

 ing instance. Female birds of paradise are obscurely col- 

 ored and destitute of all ornaments, while the males are 

 probably the most highly decorated of all birds, and in so 

 many different ways that they must be seen to be appre 

 ciated. The elongated and golden-orange plumes which 

 spring from beneath the wings of the Paradisea apoda 

 when vertically erected and made to vibrate are described 



* Wallace, in "Annals and Mag of Nat. Hist.," vol. xx, 1857, p. 

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



f See my work on "The Variation of Animals and Plants under 

 Domestication," vol. i, pp. 289, 293. 



