472 DR. J. MURIE ON THE DERMAL AND VISCERAL STRUCTURES 
Colour is not restricted to one shade; for, from the pure snowy whiteness of the 
clumps in Egretta alba, through the grey tints of Ardea cinerea, brownish tinge of 
Cancroma, up to the almost black stripes of Rhinochetus, there is an infinity of gra- 
dations. The most I can affirm, after examination of many species and specimens, is 
that the colours of powder-bearing plumes and brushy stumps bear a relation to, and, 
indeed, are harmonious in tint with, the rest of the true down-feathers. 
Fig. 4. A down-feather from outside the thigh; and fig. 5. Powder-down plume 
from the shoulder, of Rhinochetus jubatus, compared. Nat. size. 
Length, proximity, and volume of the tuftlets present extremes. They obtain often 
only as little, short, downy (camel-hair-pencil-like) brushes, isolated, singly, or sprinkled 
here and there in lines and limited territories, well exemplified in the Parrots and 
Cockatoos (vide fig. 11, Pl. LVI.). At other times, and markedly in confined spots on 
the rump and belly, they are met with as closely aggregated filiform plumes, one, two, 
or more inches in length, and with an areal base as varied in extent, admirably shown 
in Podargus heretofore mentioned (woodcut, fig. 6, p. 483), and in the better-known 
breast- and rump-patches of the Egrets and Herons. Thus their combined roots may 
be roundish, angular, or in linear strips, broad or narrow, short or long, separate from 
or intermingled with the contour- and true down-feathers, as the case may be. 
But from these somewhat negative characters I return to others of a more positive 
kind. In all, with a slight differentiation, the powder-downs are to all intents and 
purposes essentially down-feathers, differing materially from the strong-quilled wing- 
and tail-plumage, from the other stiffish contour-feathers, from the semiplumes and 
filo-plumes of Nitzsch’s terminology. In all, growth from the root or within the basal 
sheath is continuous, and minute powdery substance is constantly emitted. Lastly, as 
