icking {36}
walking-leaf insect and the real leaf it mimics, or the original progenitor
of both the bamboo insect and the bamboo itself. As these last most
remarkable cases have certainly nothing to do with heredity,[31] it is
unwarrantable to make use of that explanation for other protective
resemblances, seeing that its inapplicability, in certain instances, is so
manifest.

Again, at the other end of the process it is as difficult to account for
the last touches of perfection in the mimicry. Some insects which imitate
leaves extend the imitation even to the very injuries on those leaves made
by the attacks of insects or of fungi. Thus, speaking of one of the
walking-stick insects, Mr. Wallace says:[32] "One of these creatures
obtained by myself in Borneo (_Ceroxylus laceratus_) was covered over with
foliaceous excrescences of a clear olive-green colour, so as exactly to
resemble a stick grown over by a creeping moss or jungermannia. The Dyak
who brought it me assured me it was grown over with moss although alive,
and it was only after a most minute examination that I could convince
myself it was not so." Again, as to the leaf butterfly, he says:[33] "We
come to a still more extraordinary part of the imitation, for we find
representations of leaves in every stage of decay, variously blotched, and
mildewed, and pierced with holes, and in many cases irregularly covered
with powdery black dots, gathered into patches and spots, so closely
resembling the various kinds of minute fungi that grow on dead leaves, that
it is impossible to avoid thinking at first sight that the butterflies
themselves have been attacked by real fungi."

Here imitation has attained a development which seems utterly beyond the
power of the mere "survival of the fittest" to produce. How this double
mimicry can importantly aid in the struggle for life seems puzzling indeed,
but much more so how the first faint beginnings of the imitation of {37}
such injuries in the leaf can be developed in the animal into such a
complete representation of them--_a fortiori_ how simultaneous and similar
first beginnings of imitations of such injuries could ever have been
developed in several individuals, out of utterly indifferent and
indeterminate infinitesimal variations in all conceivable directions.

[Illustration: PLEURONECTIDAE, WITH THE PECULIARLY PLACED EYE IN DIFFERENT
POSITIONS.
(_From Dr. Traquair's paper in the "Transactions of the Linnean S