THE ESSEX FIELD CLUB.
257
In ignorance of the optical effect producible by this arrangement of
colour he had in 1880 and since, in common with other naturalists, attempted
to explain the white colours of the undersides of birds, &c., as being of purely
physical origin. That explanation he now unreservedly withdrew in favour
of protection by concealment.
With reference to the work on colour adaptability in individuals, as shown
by the illustrations of caterpillars, he thought that the lecturer had been too
modest in concealing his own share in this most important work. Although
he (the President) had by observation arrived at the conclusion that such
adaptability existed and had claimed natural selection as an efficient cause of
the phenomenon it was only the experimental investigations of Prof. Poulton,
carried on with such consummate skill and patience, that had placed these
deductions on a solid basis of irrefutable facts. As an example of conceal-
ment by adventitious means he reminded them that they in Essex had the
well-known case of the larva of the Essex Emerald Moth (Geometra smarag-
daria ; see Essex Naturalist, vol. I., p. 120).
The President also expressed concurrence with the strictures which the
lecturer had imposed upon the conclusions drawn from the experiments of
those who, like Plateau, had actually tasted insects having warning colours
and because they could find no unpleasant taste had inferred that the whole
theory of distastefulness was erroneous. It was impossible to institute a
comparison between the senses of taste and smell of man and of insect-eating
birds and animals. Distastefulness might be associated with quite other
characters than those of taste or smell as interpreted by our senses.
Cantharidin, for example, a product of the blister-beetle, would be an
extremely unpleasant thing for a bird or animal to get into its mouth
although possessed of no distinctive smell as far as we know. An insect
producing this compound as an active defensive principle might derive the
full advantage of having warning colours without any nauseous smell or taste
at all. The danger would only be realised after the insect had been taken into
the mouth by its enemy. Hence the value in such cases of dangar signals.
The President went on to say that the development of the Miillerian
theory of mimicry in the hands of Prof. Poulton was a source of immense
gratification to him since he (the speaker) as the lecturer had told them, had
been very largely responsible for the adoption and promulgation of that
theory in its initial form in this country. It was the late Charles Darwin
who had first sent him in 1879 the publication, Kosmos, containing Fritz
Miiller's modest little paper, accompanied by one of his characteristic post-
cards asking him to see if there was anything in it. On looking through the
paper he came at once to the conclusion that there was a very great deal in it
—how much, they had perhaps been able to realize from the Hope Professor's
remarks that evening. Although he was himself a firm believer in the appli-
cation of Darwinian principles to the cases comprised under the general
term "Mullerian Mimicry," he thought it desirable to point out, by way of
answer to those who had from the beginning opposed the new ideas with the
charge of being too theoretical, that quite apart from the question of the
truth of the theory, its utility under the influence of Prof. Poulton had now
been demonstrated beyond cavil. Inspired by the new idea the lecturer had
set observers and collectors systematically at work in [various parts of the