144 SEXUAL SELECTION: BIRDS. [Paet II. 



usual to become confluent into stripes ; on the contrary, 

 they are often broken up into smaller spots, so that two 

 or three rows run down to each ocellus. 



We have now seen that a perfect series can be 

 followed, from two almost simple spots, at first quite 

 distinct from each other, to one of the wonderful 

 ball-and-socket ornaments. Mr. Gould, who kindly gave 

 me some of these feathers, fully agrees with me in 

 the completeness of the gradation. It is obvious that 

 the stages in development exhibited by the feathers 

 on the same bird do not at all necessarily show us the 

 steps which have been passed through by the extinct pro- 

 genitors of the species ; but they probably give us the 

 clew 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 ren- 

 dering it probable that female birds prefer the more at- 

 tractive males, no one who admits the agency of sexual 

 selection will deny that a simple dark spot with some 

 fulvous shading might be converted through the approxi- 

 mation and modification of the adjoining spots, together 

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

 elliptic ornaments. These latter ornaments have been 

 shown to many persons, and all have admitted that they 

 are extremely pretty, some thinking them even more 

 beautiful than the ball-and-socket ocelli As the second- 

 ary plumes became lengthened through sexual selection, 

 and as the elliptic ornaments increased in diameter, their 

 colors apparently became less bright ; and then the orna- 

 mentation of the plumes had to be gained by improve- 

 ments in the pattern and shading; and this process has 

 been carried on until the wonderful ball-and-socket ocelli 

 have been finally developed. Thus we can understand — 

 and in no other way, as it sterns to me — the present con- 



