J34 
SEXUAL SELECTION : BIRDS. 
Part II. 
development of a perfect ocellus does not require a 
long course of variation and selection. 
With birds and many other animals it seems, from 
the comparison of allied species, to follow, that cir- 
cular spots are often generated by the breaking up 
and contraction of stripes. In the Tragopan pheasant 
faint white lines in the female represent the beautiful 
white spots in the male ; and something of the 
same kind may be observed in the two sexes of the 
Argus pheasant. However this may be, appearances 
strongly favour the belief that, on the one hand, a dark 
spot is often formed by the colouring-matter being 
drawn towards a central point from a surrounding 
zone, which is thus rendered lighter. And, on the other 
hand, that a white spot is often formed by the colour 
being driven away from a central point, so that it accu- 
mulates in a surrounding darker zone. In either case 
an ocellus is the result. The colouring matter seems 
to be a nearly constant quantity, but is redistributed,, 
either centripetally or centrifugally. The feathers of 
the common guinea-fowl offer a good instance of white 
spots surrounded by darker zones; and wherever the 
white spots are large and stand near each other, the 
surrounding dark zones become confluent. In the same 
wing-feather of the Argus pheasant dark spots may 
be seen surrounded by a pale zone, and white spots 
by a dark zone. Thus the formation of an ocellus 
in its simplest state appears to be a simple affair. 
By what further steps the more complex ocelli, which 
wonderful amount of variation in the coloration and shape of the wings 
of this butterfly, in his ‘Rhopalocera Africse Australis,’ p. 186. See 
also an interesting paper by the Rev. H. H. Higgins, on the origin, 
of the ocelli in the Lepidoptera in the ‘ Quarterly Journal of Science,! 
July, 1868, p. 325. 
Jerdon, ‘Birds of. India,’ vol. iii. p. 517. 
