BIEDS. 637 



mnch duller. In the guinea-fowl the two sexes are indis- 

 tinguishable. There is no improbability in the plain, 

 though peculiarly spotted, plumage of this latter bird 

 having been acquired through sexual selection by the 

 males, and then transmitted to both sexes; for it is not 

 essentially different from the much more beautifully 

 spotted plumage, characteristic of the males alone of the 

 Tragopan pheasants. 



It should be observed that in some instances the trans- 

 ference of characters from the male to the female has been 

 effected apparently at a remote period, the male having 

 subsequently undergone great changes without transferring 

 to the female any of his later gained characters. For in- 

 stance, the female and the young of the black grouse 

 (Tetrao tetrix) resemble pretty closely both sexes and the 

 young of the red grouse {T. scoticus); and we may conse- 

 quently infer that the black grouse is descended from some 

 ancient species, of which both sexes were colored in nearly 

 the same manner as the red grouse. As both sexes of this 

 latter species are more distinctly barred during the breed- 

 ing-season than at any other time, and as the male differs 

 slightly from the female in his more strongly pronounced 

 red and brown tints,* we may conclude that his plumage 

 has been influenced by sexual selection, at least to a certain 

 extent. If so, we may further infer that the nearly similar 

 plumage of the female black grouse was similarly produced 

 at some former period. But since this period the male 

 black grouse has acquired his fine black plumage with his 

 forked and outwardly curled tail-feathers; but of these char- 

 acters there has hardly been any transference to the female, 

 excepting that she shows in her tail a trace of the curved 

 fork. 



We may therefore conclude that the females of distinct 

 though allied species have often had their plumage rendered 

 more or less different by the transference of various degrees 

 of characters acquired by the males through sexual selec- 

 tion both during former and recent times. But it deserves 

 especial attention that brilliant colors have been transferred 

 much more rarely than other tints. For instance, the 

 male of the red-throated blue-breast (Cyanecula suecica) 

 has a rich blue breast, including a sub- triangular red mark; 



Macgillivray, "Hist. British Birds." vol. i, pp. 172-174. 



