1S78.] Colouration of the Organic World. 37 
change which blacks undergo will not seem surprising if we 
reflet that in Nature, as well as in Art, they generally con- 
sist of an intense olive or brown to which a deep blue or 
purple is superadded. The latter hues, being the more fugi- 
tive, fade first on exposure to light, and thus a dirty olive or 
a rusty brown must remain. 
These changes are in partial harmony with what we 
observe in the vegetable kingdom. A dull, dirty brown is 
the ultimate goal towards which leaves, flowers, and fruits, 
as well as inserts, tend while fading; but those splendid 
intermediate changes which we find in autumnal foliage 
have nothing analogous in the decaying colours of inserts. 
It is curious that in the manufacture of those artificial 
colours which now play so important a part in tinctorial 
operations a corresponding rule holds good. If these dyes, 
during their elaboration, are submitted to a heat too high or 
too prolonged, the product becomes dusky, and a dirty 
brownish grey is the final result. 
We must further note how, in the animal and vegetable 
kingdoms, pure and bright colours are connected with the 
highest vitality only. We plant the dusky seed in the earth 
amidst the dark remains of decomposing organic matter, 
and as it grows up we see it put on higher and higher 
colours, till, in the culminating moment of its life, in the 
aCt of inflorescence, prismatic hues are all but universal. 
Then begins the process of decay, attended by a degradation 
of colour. Similar changes may be traced in animals. 
Externally we need merely compare the dull-coloured larva 
with the brilliant imago, or the sombre-coated nestling 
with the brighter plumage of the mature bird. Internally 
we may contrast the intensely-vitalised scarlet arterial blood 
with the darker-coloured and more contaminated venous 
blood, and still further with excrementitious matters. The 
great truth to which we are here calling attention has not 
altogether escaped the notice of Mr. Wallace, who writes — 
“ The very frequent superiority of the male bird or inseCt in 
brightness or intensity of colour, even when the general 
tints and colouration are the same, now seems to me to he 
due to the greater vigour and activity and the higher vitality 
of the male. The colours of an animal usually fade during 
disease or weakness, while robust health and vigour add to 
their intensity.* This intensity of colouration is most 
manifest in the male during the breeding season, when the 
* Those who are brought practically in contadt with animals have long been 
familiar with the fadt that a “ dull coat ” is indicative of disease, or at least of 
weakness. 
