on ancestral characters in nestlings. 213



yellow ? If the blue is an optical effect produced by minute surface

striation, as in many metallic-blue or blue-glossed butterflies, it

cannot be eliminated without a structural modification of the

surface of the feathers or of the pigment which they contain, which

is inconceivable to my mind.*


As I remarked in a letter to our Editor, of November 29th,

1917 (see the February No., p. 108), it is quite possible that at

an early stage in bird-life, no pattern existed in the plumage: the

nestling coloration of many species certainly favours this view,

although that of the numerous protectively ornamented youngsters

would seem to refute it; but, if the colouring of the latter was

gradually acquired for purposes of concealment, there must have

been a time at which such colouring first became needful, previous

to which period the plumage may have been unmarked. If, then,

all danger were to be removed for a considerable period, one might

anticipate occasional reversion to a monochromatic character in the

newly-hatched young, and I have an idea that this occurs in certain

long-domesticated forms of fowls and ducks.


Some of the most gorgeously coloured birds, such as the

Gouldian Finch, are extremely soberly dressed in their infancy, in

that species the slight wash of green on the upper parts is the only

indication of its lovely adult colouring. To watch day by day the

change from one plumage to the other is very interesting, the new

feathers growing over the old before the latter drop out; at any rate

that was what happened to the birds imported in nestling plumage,

in those which I bred I could not get near enough to see whether

the same process was carried out.


{To he continued.)



* Strictly speaking, I suppose all colour is the result of a structural arrangement

of infinitesimal atoms reflecting certain light-rays; but I don’t see how

green, which is a combination of blue and yellow, can be so altered as to

lose a feature not due to pigment.



15



