BIRDS. 549 



vividly colored than the adults, but many of the feathers 

 on the lower surface are edged with brown* a vestige 

 probably of a former state of the plumage. Frequently in 

 the same group of birds, even within the same genus 

 for instance, in the Australian genus of paroquets 

 (Platycercus), the young of some species closely resemble, 

 while the young of other species differ consider- 

 ably from, their parents of both sexes, which are alike, f 

 Both sexes and the young of the common jay are closely 

 similar; but in the Canada jay (Perisoreus canadensis) the 

 yaung diifer so much from their parents that they were 

 formerly described as distinct species. J 



I may remark before proceeding that, under the present 

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

 the conclusions 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 cha 4 ac,ers 

 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 th ; 3 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 of some few species are in a slight degree more 

 brightly colored than the females. It is again passible that the 

 females may have selected the more beautiful males, these males 

 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 con- 

 cerned, in accordance with the general rule throughout the animal 

 kingdom, that is, on the males; and that these have transmitted their 



*Jerdon, "Birds of India," vol. i, pp. 222, 228. Gould's "Hand- 

 book to the Birds of Australia," vol. i, pp. 124, 130. 

 | Gould, ibid, vol. ii, pp. 37, 46, 56. 

 JAudubon, " Ornith. Biography," vol. ii, p. 55. 



