502 THK DESCENT OF MAN. 



exhibited by the feathers on the same bird do not at all 

 necessarily show us the steps passed through by the extinct 

 progenitors of the species; but they probably give us the 

 clue to the actual steps, and they at least prove to demon- 

 stration that a gradation is possible. Bearing in mind how 

 carefully the male Argus pheasant displays his plumes 

 before the female, as well as the many facts rendering it 

 probable that female birds prefer the more attractive males, 

 no one who admits the agency of sexual selection in any 

 case will deny that a simple dark spot with some fulvous 

 shading might be converted, through the approximation 

 and modification of two adjoining spots, together with 

 some slight increase of color, into one of the so-called ellip- 

 tic ornaments. These latter ornaments have been shown 

 to many persons, and all have admitted that they are beau- 

 tiful, some thinking them even more so than the ball-and- 

 socket ocelli. As the secondary plumes became lengthened 

 through sexual selection, and as the elliptic ornaments 

 increased in diameter, their colors apparently became less 

 bright; and then the ornamentation of the plumes had to 

 be gained by an improvement in the pattern and shading ; 

 and this process was carried on until the wonderful ball- 

 and-socket ocelli were finally developed. Thus we can 

 understand and in no other way as it seems to me the 

 present condition and origin of the ornaments on the 

 wing-feathers of the Argus pheasant. 



From the light afforded by the principle of gradation 

 from what we know of the laws of variation from the 

 changes which have taken place in many of our domesti- 

 cated birds and, lastly, from the character (as we shall 

 hereafter see more clearly) of the immature plumage of 

 young birds we can sometimes indicate, with a certain 

 amount of confidence, the probable steps by which the 

 males have acquired their brilliant plumage and various 

 ornaments; yet in many cases we are involved in complete 

 darkness. Mr. Gould several years ago pointed out to me 

 a humming-bird, the Urosticte benjamini, remarkable for 

 the curious differences between the sexes. The male, 

 besides a splendid gorget, has greenish-black tail-feathers 

 with the four central ones tipped with white; in the female, 

 as with most of the allied species, the three outer tail- 

 feathers on each side are tipped with white, so that the 



