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
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-coloured 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 coloured 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. 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. Westminster Review, July 1867, and A. Murray, Journal of
Travel, 1868, p. 83.), 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 circumstance with the
Gallinaceae. In most of the species the female is more distinctly
coloured and brighter than the male (14. For the Australian species,
see Gould s Handbook, etc., vol. ii. pp. 178, 180, 186, and 188. In
the British Museum specimens of the Australian Plain-wanderer
(Pedionomus torquatus) may be seen, shewing similar sexual
differences.), 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
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