BIRDS-GRADATION OP CHARACTERS. 435 



given me by Mr. Ward, of a specimen mounted as in the act of 

 display, it may be seen that on the feathers which are held per- 

 pendicularly, the white marks on the ocelli, representing light 

 reflected from a convex surface, are at the upper or further end, 

 that is, are directed upwards; and the bird whilst displaying 

 himself on the ground would naturally be illuminated from above. 

 But here comes the curious point, the outer feathers are held 

 almost horizontally, and their ocelli ought likewise to appear as 

 If illuminated from above, and consequently the white marks ought 

 to be placed on the upper sides of the ocelli; and wonderful as is 

 the fact they are thus placed! Hence the ocelli on the several 

 feathers, though occupying very different positions with respect 

 to the light, all appear as if illuminate^ from above, just as an 

 artist would have shaded them. Nevertheless they are not il- 

 luminated from strictly the same point as they ought to be; for 

 the white marks on the ocelli of the feathers which are held 

 almost horizontally, are placed rather too much towards the 

 further end; that is they are not sufficiently lateral. We have, 

 however, no right to expect absolute perfection in a part rendered 

 ornamental through sexual selection, any more than we have 

 in a part modified through natural selection for real use; for 

 instance in that wondrous organ the human eye. And we know 

 what Helmholtz, the highest authority in Europe on the subject, 

 has said about the human eye; that if an optician had sold him 

 an instrument so carelessly made, he would have thought himself 

 fully justified in returning it.^= 



We have now seen that a perfect series can be followed, from 

 simple spots to 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 passed 

 through by the extinct progenitors of the species; but they prob- 

 ably give us the clue to the actual steps, and they at least prove 

 to demonstration 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 ad- 

 mits 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 elliptic ornaments. These latter ornaments have been 



^2 'Popular Lectures on Scientific Subjects,' Eng. trans. 1873, pp. 219, 

 227, 269, 390. 



