434 The Descent of Man. Tart II. 



As far, then, as gradation throws light on the steps by which 

 the magnificent train of the peacock has been acquired, hardly 

 anything moru is needed. If we picture to ourselves a progeni- 

 tor of the peacock in an almost exactly intermediate condition 

 between the existing peacock, with his enormously elongated 

 tail-coverts, ornamented with single ocelli, and an ordinarj 

 gallinaceous bird with short tail-coverts, merely spotted with 

 some colour, we shall see a bird allied to Polyplectron — that is, 

 with tail-coverts, capable of erection and expansion, ornamented 

 with two partially confluent ocelli, and long enough almost to 

 conceal the tail-feathers, the latter having already partially lost 

 their ocelli. The indentation of the central disc and of the 

 surrounding zones of the ocellus, in both species of peacock, 

 speaks plainly in favour of this view, and is otherwise in- 

 explicable. The males of Polyplectron are no c\mbt beautiful 

 birds, but their beauty, when viewed from a little distance, 

 cannot be compared with that of the peacock. Many female 

 progenitors of the peacock must, during a long line of descent, 

 have appreciated this superiority ; for they have unconsciously, 

 by the continued preference of the most beautiful males, rendered 

 the peacock the most splendid of living birds. 



Argus pheasant. — Another excelltnt case for investigation is 

 offered by the ocelli on the wing-feathers of the Argus pheasant, 

 which are shaded in so wonderful a manner as to resemble balls 

 lying loose within sockets, and consequently differ from ordinary 

 ocelli. No one, I presume, will attribute the shading, which has 

 excited the admiration of many experienced artists, to chance 

 — to the fortuitous concourse of atoms of colouring matter. 

 That these ornaments should have been formed through the 

 selection of many successive variations, not one of which was 

 originally intended to produce the ball-and-socket effect, seems 

 as incredible, as that one of Raphael's Madonnas should have 

 been formed by the selection of chance daubs of paint made by a 

 loDg succession of young artists, not one of whom intended at 

 first to draw the human figure. In order to discover how the 

 ocelli have been developed, we cannot look to a long line of 

 progenitors, nor to many closely-allied forms, for such do not 

 now exist. But fortunately the several feathers on the wing 

 suffice to give us a clue to the problem, and they prove to de- 

 monstration that a gradation is at least possible from a mere 

 spot to a finished ball-and-socket ocellus. 



The wing-feathers, bearing the ocelli, are covered with dark 

 stripes (fig. 57) or with rows of dark spots (fig. 59), each stripe 

 or row of spots running obliquely down the outer side of the 



