on growth of markings and colour.



45



flank-feathers are ornamented with e-shaped submarginal markings ;

in Munia punctulata these markings are thickened (extending also

backwards over the breast), so that they produce a spotted appearance;

in Amadina erythrocephala the markings have become marginal and

more regular ; in Steganopleura they retain their outline, are con¬

fined to the sides of the body, but the base of the feathers is

blackened ; in the males of Taniopygia (in which they have changed

from black to cinnamon) they surround the feather, leaving only

subovate white spots; while in Bathilda, in which the sides and

breast are pale olive, they are transversely ovate and extend over

both areas, as in Munia punctulata. When flight-feathers are

spotted the result is probably obtained (as when they are barred) by

transverse outgrowth from the shaft-streak, subsequently more or less

broken up by longitudinal extension of the dark colouring, as in

Stictoptera.


Central black or dark brown spots are merely expansions of

the shaft-streak without longitudinal extension, and, of course, if the

shaft of the feather is pale it indicates at once the origin of twin

spots ; if I remember rightly some of the feathers of the Wonga-

wonga Pigeon show this character ; I was unfortunately unable to

save the skin of the bird which died in my possession.


I have already explained the probable origin of terminal pale

spots to feathers; they are usually modifications of a triangle, and,

therefore, clearly (I think) the result of the fork of the sagittate

development of the shaft-streak not being filled with dark pigment.


Why is it that wing- and tail-feathers are so frequently

many-banded, and why are the bands usually at about equal

distances apart ? I can see the necessity for this in the case of pro¬

tectively barred birds, in order to render the general appearance of

the plumage uniform ; and, of course, the regularity of the banding

may have been gradually acquired through natural selection ; but I

cannot understand how it is that the coverts in the wings of our

European Jay are rendered conspicuous by precisely similar, though

brightly coloured, banding.



