100 COLOUR 
the distribution of colouring matter in transverse lines or bars is the 
phylogenetically older method, because natural and sexual selection 
cannot well have affected the hidden parts of the feathers. On 
the other hand, the striated downy or first plumage of the Galline 
and Ratitze has been already, by Darwin, taken to be a very old 
stage. This appearance, however, as in Struthio, is not due to 
striation of the single feathers, but to juxtaposition of colourless 
and deeply pigmented downs. To judge from the growth of a 
feather, the production of crossbars seems to be the older stage, 
since they will result from the intermittent deposition of pigment, 
while, on the other hand, the production of shaft-streaks is not yet 
satisfactorily explained. At any rate, it must be borne in mind 
that possibly various groups of birds have gone independently 
through such stages, and that what is primitive or archaic in one 
need not be so in all. But a strong proof of the soundness of 
Darwin’s views is that we are able to trace the pattern of the most 
beautifully-adorned feathers of the Argus-Pheasant or of the Peacock 
step by step backwards to longitudinal stripes, spots, crossbars, and 
lastly to insignificant and simple irregular little dots. 
Natural and sexual selection, whether combining or striving 
against each other, have worked marvels in plumage. Significant 
colours, as for instance total blackness or whiteness, could be 
developed only when higher intellectual qualities, bodily size and 
strength, or occasionally even special smallness, guaranteed the 
safety of the bird. The females and the young mostly retain a 
more sombre garb, and thus remain on a phylogenetically lower 
level. It takes the large Gulls several years to change from a 
mottled brownish and grey appearance into the beautifully dark 
and white colours. ‘The same applies to the white shoulders of 
certain Eagles; and many other instances, too well known to be 
repeated here, shew clearly how the changes of bygone ages of the 
ancestors are recapitulated in the yearly moult of the growing 
individual until with maturity its present stage of perfection is 
reached—but only its present stage, because its descendants in turn 
will be different, either still more beautiful or still better adapted 
to the ever-changing conditions of life. ‘This consideration implies 
that whole-coloured birds, like Swans and Ravens, have reached their 
limit so far as coloration is concerned ; since both black and white 
are very conspicuous and are correlated with a considerable amount 
of intellectual development. The very early assumption of the 
black plumage by the nestlings of Ravens and Crows is a strong 
argument for their relatively highest position on the hypothetical 
avine tree. Albinos are notoriously shy. The females of birds 
which breed in holes, as Rollers, Kingfishers, and Parrots, are fre- 
quently as beautifully coloured as the males, because they need 
no protection through colour while sitting on the nest. In the 
