150 SEXUAL selection: BIEDS. PartIL 



smaller and less perfect than on the other feathers, 

 with the upper parts of the external black rings de- 

 ficient, as in the case just mentioned. The imperfec- 

 tion here seems to be connected with the fact that the 

 spots on this feather shew less tendency than 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 fol- 

 lowed, 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 com- 

 pleteness of the gradation. It is obvious that the stages 

 in development exhibited by the leathers on the same 

 bird do not at all necessarily shew us the steps which 

 have been 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 demonstra- 

 tion 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, will deny that a sim23le dark spot with 

 some fulvous shading might be converted, through 

 the approximation and modification of the adjoining- 

 spots, together with some slight increase of colour, 

 into one of the so-called elliptic ornaments. These 

 latter ornaments have been shewn 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 secondary plumes be- 

 came lengthened through sexual selection, and as 

 the elliptic .ornaments increased in diameter, their 



