[265] I have noticed the following cases in Audubon’s ‘Ornith. Biography. The Redstart of America’ (_Muscicapa ruticilla_, vol. i. p. 203). The _Ibis tantalus_ takes four years to come to full maturity, but sometimes breeds in the second year (vol. iii. p. 133). The _Grus Americanus_ takes the same time, but breeds before acquiring its full plumage (vol. iii. p. 211). The adults of _Ardea cærulea_ are blue and the young white; and white, mottled, and mature blue birds may all be seen breeding together (vol. iv. p. 58): but Mr. Blyth informs me that certain herons apparently are dimorphic, for white and coloured individuals of the same age may be observed. The Harlequin duck (_Anas histrionica_, Linn.) takes three years to acquire its full plumage, though many birds breed in the second year (vol. iii. p. 614). The White-headed Eagle (_Falco leucocephalus_, vol. iii. p. 210) is likewise known to breed in its immature state. Some species of Oriolus (according to Mr. Blyth and Mr. Swinhoe, in ‘Ibis,’ July, 1863, p. 68) likewise breed before they attain their full plumage. [266] See the last footnote. [267] 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 Müller 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 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 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. [268] Jerdon, ‘Birds of India,’ vol. iii. p. 507, on the peacock. Audubon, ibid. vol. iii. p. 139, on the Ardea. [269] For illustrative cases see vol. iv. of Macgillivray’s ‘Hist. Brit. Birds;’ on Tringa, &c., p. 229, 271; on the Machetes, p. 172; on the _Charadrius hiaticula_, p. 118; on the _Charadrius pluvialis_, p. 94. [270] For the goldfinch of N. America, _Fringilla tristis_, Linn., see Audubon, ‘Ornith. Biography,’ vol. i. p. 172. For the Maluri, Gould’s ‘Handbook of the Birds of Australia,’ vol. i. p. 318. [271] I am indebted to Mr. Blyth for information in regard to the Buphus; see also Jerdon, ‘Birds of India,’ vol. iii. p. 749. On the Anastomus, see Blyth, in ‘Ibis,’ 1867, p. 173.