102 REV. F. A. WALKER, D.D., F.L.S., 
likewise results not from a flat surface, but from the different 
depths of layers in the flesh. The varying rose and lily tints 
proceed from the more or less free circulation of the blood ; 
the bluish tint well known to painters, proceeds from the 
vesicles when seen under the skin, and similarly blue veins 
present a false appearance, because the blood is red; it is the 
skin that thus dyes what lies beneath it; and blue eyes owe 
their shade to the brown pigment that lines the other side of 
the iris. Fishes, on the other hand, owe their lustre,—causing 
the contents of the fishing-net to resemble an immense opal,— 
not to the scales but to thin layers below the scales and under 
the skin and round the blood-vessels, that look like so many 
threads of silver running through the flesh. Of these plates 
or layers, with the addition of glass and glue, false pearls 
are manufactured. ‘The exceptional brightness of colouring 
displayed by male animals during the spring season, and at 
nesting time, far exceeding their hue at any other period of 
the year, is well known; to quote a few examples out of many, 
that of the yellow-hammer among’ birds, of the common newt 
among reptiles, and of the stickleback among fishes. 
Whiteness, be it remarked, is never a sign of strength, even 
if the said whiteness results from constitutional variety, as 
much as from age or illness. Hoar hairs sometimes result 
from sudden fright, or dangerous fever, or long continuance 
of severe headaches, as well as from advanced years; but 
from whatever cause, it is always a sign of decrepitude. And 
there are albino varieties of the cat, the rat, the guinea-pig, 
the mouse, the crow, &c., as well as of human beings; but 
this peculiarity is almost invariably accompanied with some 
constitutional defect, that of red eyes in nearly if not quite 
all the creatures above mentioned. White cats, morever, 
are said to be always deaf. 
And human albinoes, such as I saw, too, very many years 
ago in the streets of London, are reported to lack vigour of 
intellect, and certainly presented a pitiable appearance with 
their red, raw, and inflamed eyes, seemingly unable to bear 
thedaylight. Similarly, thewhitevarietiesofthecommonorchis, 
and hyacinth, &ec., are never of such vigorous growth, or so free 
for blossoming, as the ordinary types, while they certainly are 
far rarer. Age replaces the colouring matter in the hair 
(when it turns white) with small air-bubbles, and so, too, the 
briluant white of feathers is due to the air which fills them ; 
and the plumage of domestic poultry often turns whiter at each 
successive moult, just as much as the hair of human beings 
or the coats of horses at the approach of age. It would be 
