Chap. XYI. THE YOUNG LIKE BOTH ADULTS. 
215 
played as important a part, as I believe it Has, in 
giving ornamental colours, plumes, &c., to the males, 
and, by means of equal transmission, to the females of 
many species. The objection would be a valid one, if 
the younger and less ornamented males were as suc- 
cessful in winning females and propagating their kind, 
as the older and more beautiful males. But we have 
no reason to suppose that this is the case. Audubon 
speaks of the breeding of the immature males of Ibis 
tantalus as a rare event, as does Mr. Swinhoe, in re- 
gard to the immature males of Oriolus.^^ 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.^^ 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 eliminated, from being super- 
fluous and entailing waste of power. 
The plumage of certain birds goes on increasing in 
See the last foot-note. 
Other animals, belonging to quite distinct classes, are either 
habitually 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 
whilst retaining their larval structure. Fritz Muller has shewn (‘ Facts 
and Arguments for Darwin,’ Eng. trans. 1869, p. 79) that the males of 
several amphipod crustaceans become sexually mature whilst 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 higlily 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 the “ 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 ‘ Proc. of Acad. Nat. Sc. of Philadelphia,’ Oct. 1868. 
