The Making of Species 
grandparents of Linus I. had exceptionally long 
hair. 
Coming now to birds we find several undoubted 
examples of mutations, or new forms which have 
come suddenly into being. 
The black-winged peafowl, whose peculiarities 
were commented on by Darwin, afford a striking 
example of this phenomenon. These birds breed 
true when mated together, and are known to 
have arisen from common peafowl in no less 
than nine instances. The cocks have the wings 
(except the primary quills), black glossed with 
blue and green, and have the thighs black, 
whereas, in the ordinary peacock, the same part 
of the wing is nearly all mottled black and pale 
buff, and the thighs are drab. The black-winged 
hen, on the other hand, is nearly white, but has 
a black tail and black speckling on the upper 
surface of the body, while her primary quills are 
cinnamon coloured as in male peafowl, not 
drab as in the normal hens. The young are 
white when hatched, the young cock gradually 
assuming the dark colour as he matures. 
This mutation, which, in one case quoted by 
Darwin, increased among a flock of peafowl 
until the black-winged supplanted the ordinary 
kind, is so distinct in appearance in all stages 
that it was formerly supposed to be a true species 
(Pavo nigripennis), of which the wild habitat was 
unknown. 
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