BIRDS-YOUNG LIKE ADULT MALES. 469 



Finally, with respect to our present class of cases, the most 

 probable view appears to be that successive variations in bright- 

 ness or in other ornamental characters, occurring in the males 

 at a rather late period of life have alone been preserved; and 

 that most or all of these variations, owing to the late period of 

 life at which they appeared, have been from the first transmitted 

 only to the adult male offspring. Any variations in brightness 

 occurring in the females or in the young, would have been of no 

 service to them, and would not have been selected; and more- 

 over, if dangerous, would have been eliminated. Thus the fe- 

 males and the young will either have been left unmodified, or 

 (as is much more common) will have been partially modified 

 by receiving through transference from the males some of his 

 successive variations. Both sexes have perhaps been directly 

 acted on by the conditions of life to which they have long been 

 exposed: but the females from not being otherwise much modi- 

 fied, will best exhibit any such effects. These changes and all 

 others will have been kept uniform by the free intercrossing 

 of many individuals. In some cases, especially with ground 

 birds, the females and the young may possibly have been modified, 

 independently of the males, for the sake of protection, so as to 

 have acquired the same dull colored plumage. 



Class II. When the adult female is more conspicuous than the 

 adult male, the young of both sexes in their first plumage resemble 

 the adult male. — This class is exactly the reverse of the last, for 

 the females are here brighter colored or more conspicuous than 

 the males; and the young, as far as they are known, resemble 

 the adult males instead of the adult females. But the difference 

 between the sexes is never nearly so great as with many birds in 

 the first class, and the cases are comparatively rare. Mr. Wal- 

 lace, who first called attention to the singular relation which 

 exists between the less bright colors of the males and their 

 performing the duties of incubation, lays great stress on this 

 point,^^ as a crucial test that obscure colors have been acquired 

 for the sake of protection during the period of nesting. A dif- 

 ferent view seems to me more probable. As the cases are curious 

 and not numerous, I will briefly give all that I have been able to 

 find. 



In one section of the genus Turnix, quail-like birds, the female 

 is invariably larger than the male (being nearly twice as large 

 in one of the Australian species), and this is an unusual circum- 

 stance with the Gallinaceffi. In most of the species the female is 

 more distinctly colored and brighter than the male," but in 



^3 'Westminster Review,' July, 1867, and A. Murray, 'JournaJ of 

 Travel,' 1868, p. 83. 

 " For the Australian species, see Gould's 'Handbook,' &c., vol. 11. 

 81 



