Ch. XVI. the young like adults of same sex. 221 
nut-brown colour with a golden-red head, is the male, 
whilst the other, which is elegantly variegated with 
green and w^hite with a metallic-green head, is the fe- 
male. Now the young from the first resemble to a 
certain extent the adults of the corresponding sex, the 
resemblance gradually becoming more and more com- 
plete. 
In considering this last case, if as before we take the 
plumage of the young as our guide, it would appear 
that both sexes have been independently rendered 
beautiful ; and not that the one sex has partially trans- 
ferred its beauty to the other. The male apparently 
has acquired his bright colours through sexual selec- 
tion in the same manner as, for instance, the peacock or 
pheasant in our first class of cases ; and the female in 
the same manner as the female Ehynchaea or Turnix 
in our second class of cases. But there is much diffi- 
culty in understanding how this could have been 
effected at the same time with the two sexes of the 
same species. Mr. Salvin states, as we have seen in 
the eighth chapter, that with certain humming-birds 
the males greatly exceed in number the females, whilst 
with other species inhabiting the same country the 
females greatly exceed the males. If, then, we might 
assume that during some former lengthened period the 
males of the Juan Fernandez species had greatly ex- 
ceeded the females in number, but that during another 
lengthened period the females had greatly exceeded 
the males, we could understand how the males at one 
time, and the females at another time, might have been 
rendered beautiful by the selection of the brighter- 
coloured individuals of either sex ; both sexes transmit- 
ting their characters to their young at a rather earlier 
age than usual. Whether this is the true explanation I 
