Chap. XIY. 
GEADATION OF CHAKACTEKS. 
151 
colours apparently became less bright; and then the 
ornamentation of the plumes had to be gained by 
improyements in the pattern and shading ; and this 
process has been carried on until the wonderful ball- 
and-socket ocelli haye been finally developed. Thus we 
can understand — and in no other way as it seems to 
me — the present condition and origin of the ornaments 
on the wing-feathers of the Argus pheasant. 
From the light reflected by the principle of grada- 
dation ; from what we know of the laws of variation; 
from the changes which have taken place in many 
of our domesticated birds ; and, lastly, from the cha- 
racter (as we shall hereafter more clearly see) of the 
immature plumage of young birds — we can sometimes 
indicate with a certain amount of confidence, the pro- 
bable steps by which the males have acquired their 
brilliant plumage and various ornaments ; yet in many 
cases we are involved in darkness. Mr. Gould several 
years ago pointed out to me a humming-bird, the 
Urosticte henjamini, remarkable from the curious dif- 
ferences presented by the two sexes. The male, besides 
a splendid gorget, has greenish-black tail-feathers, with 
the four central ones tipped with white ; in the female, 
as with roost of the allied species, the ihiee outer tail- 
feathers on each side are tipped with white, so that the 
male has the four central, whilst the female has the six 
exterior feathers ornamented with white dips. What 
makes the case curious is that, although the colouring 
of the tail differs remarkably in both sexes of many 
kinds of humming-birds, Mr. Gould does not know a 
single species, besides the Urosticte, in which the male 
has the four central feathers tipped with white. 
The Duke of Argyll, in commenting on this case,^^ 
‘ The Reign of Law,M867, p. 2t7. 
