206 SEXUAL SELECTION: BIRDS. [Part II. 



the case. Audubon speaks of the breeding of the imma- 

 ture males of Ibis tantalus as a rare event, as does Mr. 

 Swinhoe, in regard to the immature males of Oriolus. 38 If 

 the young of any species in their immature plumage were 

 more successful in winning partners than the adults, the 

 adult plumage would probably soon be lost, as the males 

 which retained their immature dress for the longest period 

 would prevail, and thus the character of the species would 

 ultimately be modified. 39 If, on the other hand, the young 

 never succeeded in obtaining a female, the habit of early 

 reproduction would perhaps be sooner or later quite elim- 

 inated, from being, superfluous and entailing waste of 

 power. 



The plumage of certain birds goes on increasing in 

 beauty during many years after they are fully mature ; 

 this is the case with the train of the peacock, and with 

 the crest and plumes of certain herons ; for instance, the 

 Ardea Ludovicana ; *? but it is very doubtful whether 

 the continued development of such feathers is the result of 



3S See- the last foot-note. 



39 Other animals, belonging to quite distinct classes, are either habit- 

 ually or occasionally capable of breeding before they have fully acquired 

 their adult characters. This is the case with the young males of the 

 salmon. Several amphibians have been known to breed while retaining 

 their larval structure, Fritz Miiller has shown (' Facts and Arguments 

 for Darwin,' Eng. Trans. 1869, p. 79) that the males of several amphipod 

 crustaceans become sexually mature while young ; and I infer that this 

 is a case of premature breeding, because they have not as yet acquired 

 their fully-developed claspers. All such facts are highly interesting, as 

 bearing on one means by which species may undergo great modifications 

 of character, in accordance with Mr. Cope's views, expressed under the 

 terms of ¥he " retardation and acceleration of generic characters ; " but 

 I cannot follow the views of this eminent naturalist to their full extent. 

 See Mr. Cope, " On the Origin of Genera," from the ' Pros, of Acad. Nat. 

 Sc. of Philadelphia,' Oct. 1868. 



• 40 Jerdon, ' Birds of India,' vol. iii. p. 507, on the peacock. Audu- 

 bon, ibid. vol. iii, p. 139, on the Ardea. 



