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 Society, 1865."_)] Another instance which may be cited is the asymmetrical condition of the heads of the flat-fishes (Pleuronectidae), such as the sole, the flounder, the brill, the turbot, &c.

In all these fishes the two eyes, which in the young are situated as usual one on each side, come to be placed, in the adult, both on the same side of the head.