63C- THE DESCENT OF MA.N 



both sexes have been rendered beautiful independently; 

 and not that one sex has partially transferred its beauty 

 to the other. The male apparently has acquired his bright 

 colors through sexual selection 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 

 difficulty 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 

 the females in number, while 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 

 exceeded the females in number, but that during another 

 lengthened period the females had far exceeded the males, 

 we could understand how the males at one time, and the 

 females at another, might have been rendered beautiful by 

 the selection of the brighter-colored individuals of either 

 sex; both sexes transmitting their characters to their young 

 at a rather earlier age than usual. Whether this is the true 

 explanation I will not pretend to say; but the case is too 

 remarkable to be passed over without notice. 



We have now seen in all six classes that an intimate 

 relation exists between the plumage of the young and the 

 adults, either of one sex or both. These relations are fairly 

 well explained on the principle that one sex — this being in 

 the great majority of cases the male — first acquired through 

 variation and sexual selection bright colors or other orna- 

 ments, and transmitted them in various ways, in accordance 

 with the recognized laws of inheritance. Why variations 

 have occurred at different periods of life, even sometimes 

 with species of the same group, we do not know, but with 

 respect to the form of transmission one important determin- 

 ing cause seems to be the age at which the variations first 

 appear. 



From the principle of inheritance at corresponding ages, 

 and from any variations in color which occurred in the 

 males at an early age not being then selected — on the con- 



