484 THE DESCENT OF MAN. 



dered 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 ornaments, and transmitted them 

 in various ways, in accordance with the recognized laws of in- 

 heritance. 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 

 determining 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 contrary being often 

 eliminated as dangerous — whilst similar variations occurring 

 at or near the period of reproduction have been preserved, it 

 follows that the plumage of the young will often have been left 

 unmodified, or but little modified. We thus get some insight 

 into the coloring of the progenitors of our existing species. In 

 a vast number of species in five out of our six classes of cases, the 

 adults of one sex or of both are bright colored, at least during 

 the breeding-season, whilst the young are invariably less brightly 

 colored than the adults, or are quite dull colored; for no in- 

 stance is known, as far as I can discover, of the young of dull- 

 colored species displaying bright colors, or of the young of bright- 

 colored species being more brilliant than their parents. In the 

 fourth class, however, in which the young and the old resemble 

 each other, there are many species (though by no means all), 

 of which the young are bright-colored, and as these form whole 

 groups, we may Infer that their early progenitors were likewise 

 bright. With this exception, if we look to the birds of the world, 

 it appears that their beauty has been much increased since that 

 period, of which their immature plumage gives us a partial rec- 

 ord. 



On the Color of the Plumage in relation to Protection. — It will 

 have been seen that I cannot follow Mr. Wallace in the belief 

 that dull colors, when confined to the females, have been in 

 most cases specially gained for the sake of protection. There 

 can, however, be no doubt, as formerly remarked, that both sexes 



