Chap. XVI. Birds — Young like Adult Males. 475 



been of 110 service to them, and would not have been selected ; 

 and moreover, if dangerous, would have been eliminated. Thus 

 the females 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 

 modified, will best exhibit any such effects. These changes 

 and all others will have been kept uniform by the free inter- 

 crossing 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 coloured plumage. 



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

 adult male, the youwj of both stxes in their first phi/naye resemble 

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

 the females are here brighter coloured or more conspicuous than 

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

 the adult males iD stead 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. 

 Wallace, who first called attention to the singular relation which 

 exists between the less bright colours of the males and their 

 performing the duties of incubation, lays great stress on this 

 point, 13 as a crucial test that obscure colours have been acquired 

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

 different 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 Gallinaceaa. In most of the species the female is 

 more distinctly coloured and brighter than the male, 14 but in 

 some few species the sexes are alike. In Turnix taigoor of India 

 the male " wants the black on the throat and neck, and the 

 " whole tone of the plumage is lighter and less pronounced than 

 " that of the female." The female appears to be noisier, and is 

 certainly much more pugnacious than the male; so that the 



13 'Westminster Review,' July, 178, 180, 186, and 188. In the 

 1867, and A. Murray, ' Journal of British Museum specimens of the 

 Travel,' 1868, p. 83. Australian Plain-wanderer (Pedio* 



14 For the Australian species, see nonius torquutus) may be seen, 

 Qould's ' Handbook,' &c, vol. ii. pp. shewing similar sexual differences. 



