SEXUAL SELECTION %9 



manifest that if the convergence were strongly pronounced 

 and the confluence complete, the indentation at the conver- 

 gent end would tend to disappear. 



The tail-feathers in both species of peacock are entirely 

 destitute of ocelli, and this apparently is related to their 

 being covered up and concealed by the long tail- coverts. 

 In this respect they differ remarkably from the tail- feathers 

 of Polyplectron, which in most, of the species are orna- 

 mented with larger ocelli than those on the tail- coverts. 

 Hence I was led carefully to examine the tail-feathers of 

 the several species, in order to discover whether their ocelli 

 showed any tendency to disappear; and to my great satis- 

 faction this appeared to be so. The central tail-feathers of 

 J*, napoleonis have the two ocelli on each side of the shaft 

 perfectly developed; but the inner ocellus becomes less and 

 less conspicuous on the more exterior tail-feathers, until a 

 mere shadow or rudiment is left on the inner side of the 

 outermost feather. Again, in P. malaccense, the ocelli on 

 the tail-coverts are, as we have seen, confluent; and these 

 feathers are of unusual length, being two-thirds of the 

 length of the tail-feathers, so that in both these respects 

 they approach the tail-coverts of the peacock. Now, in 

 P. malaccense the two central tail-feathers alone are or- 

 namented, each with two brightly- colored ocelli, the inner 

 ocellus having completely disappeared from all the other 

 tail-feathers. Consequently the tail-coverts and tail-feathers 

 of this species of Polyplectron make a near approach in 

 structure and ornamentation to the corresponding feathers 

 of the peacock. 



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

 which the magnificent train of the peacock has been ac- 

 quired, hardly anything more is needed. If we picture to 

 ourselves' a progenitor 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 ordinary gallinaceous bird with short 

 tail-coverts, merely spotted with some color, we shall see 



