88 REY. F. A. WALKER, D.D., F.L.S., 
affect a later stage, and that only the pupal, and in this case, 
as far as my informant can see, the larval colours cannot be 
produced artificially. 
There is no evidence for colours being due to the presence 
of chemicals, although, no doubt, advantage is taken of their 
presence to produce certain colours ; but in the vast majority 
of cases the colours are due to arrangements of molecules, 
&c., and not to peculiar or uncommon elements. None of 
these have been shown to exist in insects. 
It is not believed that the fact of the insect beholding the 
surroundings could ever account for resemblances, but that it 
is a case of survival of the better-adapted variations. In 
certain cases colour is modified by beholding surround- 
ings, although, in the case of larve, it is more probably by 
feeling the colours through the skin, and not through the 
eyes. But in these cases we have no explanation of the origin 
of colour, for it is more than doubtful whether the result can 
be inherited. 
In the case of the changing colour of the chameleon, trout, 
&c., it is obvious that the results cannot be transmitted, only 
the power of changing, and it is believed that it is also the 
same with the results arrived at in insects. 
The blue sky and sea cannot account for blue in animals, 
for the two colours depend upon such different chemical sub- 
stances, and often different optical principles. Nor is there 
any evidence for any colour tending to produce a similar 
colour in other bodies. 
Those who desire more detailed information on this topic, 
and kindred subjects, are referred to Mr. Edward Poulton’s 
papers in the Proceedings ef the Royal Society for 1885 and 
1886 on the special colour-relation between Smerinthus 
ocellatus and its food-plants, the outcome of laborious investi- 
gation, accompanied by varied experiments, modifications of 
colour produced and noted by feeding larve on leaves of 
different trees, and also on leaves of different sizes and 
shapes, as well as different kinds; also the contrivance of 
fastening leaves together, so that some larve should only see the 
upper surface, others only the under, and as the upper sur- 
face differs in tint from the under, a varied result is expected 
and, in many cases, obtained. The experiment has also been 
varied by feeding some larvae which had been given a dif- 
ferent tint artificially by removing the “bloom” from the 
under surface, and, to test whether the ocelli formed the im- 
pressionable part of the larvae by investigating the effect 
upon colour of covering those organs with some innocuous 
opaque pigment. 
