CuAP. X\'i. Birds — Yotmg like both Adults. 485 



srion be lost, as the males would prevail, wliich r. taiDed their imniatiire 

 drisi- fur thu longest pevi"d. and thus the chaructir of the speciis 

 Wdiilil ultJiu t ly he modified. ^° Jf. on the other hand, tlie young uever 

 fiuiceuleii in olMaiiiing a female, 'be habit of early reproduction would 

 pirhi.ps be sooner or later eliminated, from being superfluous and 

 entailing waste of power. 



The plumage of ceitain birds goes on increasing in beauty during 

 many y( ars atter they are fully mature ; this is the c a.,e with ihe train 

 (>f the peacoi'k, with some of the biids of paiadise, and with the crest 

 mid plumeb of certain heions, for instance, the Ardea ludavicana.'"' 

 Hut it is doubtful whether the continued development of snoh feathers 

 is the result of the selection of successive beneticial varL.tious (though 

 t is is the most probable view with birds of paradise) or merely of con- 

 tinuous growth. Most fishes contiaue increasing in size, as long us tl,ey 

 are in good hciilth iind have plenty of food ; und a soiuewhai similar 

 law may p evail with the plumes of birds. 



Clas.-^ V. IVften the adults of both sexes Jia/ve a distinct ivinter and 

 fummer plumage, whether or not the male differs from the female, the 

 young resimhle ihe adults of both sexes in their winter dress, or much 

 more ranhj in their summer dress, or they resemble the females alone. 

 Or the young may have an intermediate cliaroffter ; or, again, tliey may 

 differ greatly from the adults in both their seasonal plumages. — The cases 

 in tliis cla.-s are singularly complex; nor is this surprising, as they 

 depend on inheritance, limitjd in a greater or lesd degree in three 

 dilferent ways, namely, by sex, age, and the season of the year. In 

 some cases the individuals of the same species pass through at least 

 li\e distinct states of pluirage. With the sjiecies, in which the maie 

 differs from the female during the summer stasiin alone, or, which is 

 rarer, dur.ng both s asons,'" the young generally resemble the females, 

 ■ — as with the so-called goldfinoh of North America, and apparently 

 with the splendid Maluri of Australia.''^ With .hose species, tlie sexes 

 (if which ate alike during both the summer and winter, the young may 



'" Other animals, belonging to *^ Jerdon, * Birds of India,' vol. 



quite distinct classes, are either iii. p. 507, on the peacock. Dr. 



habitually or occasionally capable Marshall, thinks that the older and 



of breeding before they have fully iiiore brilliant males of birds of 



acquired , their adult characters, paradise, have an advantage over 



This is the case with the young the younger males; see * Archives 



males of the salmon. Several am- Neerlandaises,' torn. vi. 1871.' — On 



phibians have been known to breed Ardea, Audubon, ibid. vol. iii. p. 



whilst retaining their larval struc- 139. 



ture. Fritz Miiller has shewn *^ .For illustrative cases see vol. 



(' Facts and Arguments for Darwin,* iv. of Macgillivray's * Hist. Brit. 



Eng. trans. 1869, p. 79) that the Birds ;'on Tringa, &c., pp. 229, 271 ; 



males of several amphipod crusta- on the Mache'.es, p. 172; on the 



ceans become sexually mature whilst Charadrius hiaticula, p. 118 ; on the 



young ; and I infer that this is a Charadrius pluviatis, p. 94. 



case of premature breeding, because *^ For thegoldfinchof N.America, 



they have not as yet acquired their Fringilla tristis, Linn., see Audubon, 



fully-developed claspers. All such ' Ornith. Biography,' vol. i. p. 172, 



f.icts are highly interesting, as For the Maluri, Gould's ' Hanilbooii 



1: earing on one means by which tc the Birds of Australia,* vol. i. p 



Kpt3cies may undergo great modifi- 318. 

 cations of character. 



