476 THE DESCENT OF MAN. 



parents of both sexes, which are alike.^' Both sexes and the 

 young of the common jay are closely similar; but in the Canada 

 jay (Perisoreus canadensis) the young differ so much from their 

 parents that they were formerly described as distinct species.^" 



I may remark before proceeding that, under the present and 

 next two classes of cases, the facts are so complex and the con- 

 clusions so doubtful, that any one who feels no especial interest 

 in the subject had better pass them over. 



The brilliant or conspicuous colors which characterize many 

 birds in the present class, can rarely or never be of service to 

 them as a protection; so that they have probably been gained 

 by the males through sexual selection, and then transferred to 

 the females and the young. It is, however, possible, that the 

 males may have selected the more attractive females; and if 

 these transmitted their characters to their offspring of both sexes, 

 the same results would follow as from the selection of the more 

 attractive males by the females. But there is evidence that this 

 contingency has rarely, if ever, occurred in any of those groups 

 of birds in which the sexes are generally alike; for, if even a 

 few of the successive variations had failed to be transmitted to 

 both sexes, the females would have slightly exceeded the males 

 in beauty. Exactly the reverse occurs under nature; for, in 

 almost every large group in which the sexes generally resemble 

 each other, the males in some few species are in a slight degree 

 more brightly colored than the females. It is again possible that 

 tue females may have selected the more beautiful males, these 

 ma-es having reciprocally selected the more beautiful females; but 

 it is doubtful whether this double process of selection would be 

 likely to occur, owing to the greater eagerness of one sex than the 

 other, and whether it would be more efficient than selection on one 

 side alone. It is, therefore, the most probable view that sexual 

 selection has acted, in the present class, as far as ornamental 

 characters are concerned, in accordance with the general rule 

 throughoul the animal kingdom, that is, on the males; and that 

 these have transmitted their gradually acquired colors, either 

 equally or almost equally, to their offspring of both sexes. 



Another point is more doubtful, namely, whether the suc- 

 cessive variations iirst appeared in the males after they had be- 

 come nearly mature, or whilst quite young. In either case sexual 

 selection must have acted on the male when he had to compete 

 with rivals for the possession of the female; and in both cases 

 the characters thus acquired have been transmitted to both sexes 

 and all ages. But these characters, if acquired by the males 



2s Gould, Ibid. vol. ii. pp. 37, 46, 56. 



-' Audubon, 'Ornith. Biography,' vol. ii. p. 55. 



