652 
The Influence of Light on the [November, 
IV. THE INFLUENCE OF LIGHT ON THE 
COLOURATION OF ANIMALS. 
R. LEWIS, in a paper lately read before the Ento- 
mological Society, gave the outlines of a provisional 
theory of the part due to light in the production 
and distribution of the colours of animals. Some of his 
ideas, though they cannot he regarded as demonstrated, are 
of an exceedingly interesting nature, and deserve attention. 
It will of course be admitted that Natural Selection, 
Sexual Selection, and Mimetism, — though they may weed 
out individuals whose colours are ill adapted for conceal- 
ment, or are unattractive to their destined mates, and may, 
on the other hand, give an advantage to such as happen to 
be more favoured in these respeCts, — cannot in themselves 
produce colouring-matters to be modified. This is easily 
shown by a reference to the colours prevalent in different 
groups of animals. We see, e.g., mammals — such as the 
lion and many of the antelopes — assuming the colour of the 
deserts which they inhabit. But we do not see any mam- 
malian species which haunt luxuriant grass-lands, thickets, 
&c., approximating to the green colour there prevailing, as 
do many birds, reptiles, and inseCts. We therefore judge that 
the mammalian system, whilst it is able to ring the changes 
among greys, blacks, browns, drabs, yellows, fawn-colours, 
&c., is unable to produce greens, however advantageous such 
a colour might prove. 
From the general absence of colour in the interior of 
animals, or, in other words, its concentration upon their 
outer surface, Mr. Lewis argues that light must play a con- 
siderable part in the production of the pigments or the 
structural arrangements which gave rise to such colours.* 
We cannot, however, admit that colours are invariably 
absent in the inner parts of animals.- Familiar instances to 
the contrary are the cochineal, the lac, and the kermes 
inseCts, the colours given out by certain of the Heteroptera 
when crushed, the coloured secretions of beetles of the genus 
Timarcha, and the yellow and orange matters emitted by 
most Lepidoptera in emerging from the pupa. 
* We refer here to the peculiar arrangements in, e.g., the plumage of 
humming {birds, which occasion interference colours in the absence of any 
pigment. 
