Origin of Species Variorum

of escaping destruction from predacious birds and insects, and was consequently oftener preserved;— "the less perfect degrees of resemblance being generation after generation eliminated, and only the others left to propagate their kind." So that here we have an excellent illustration of the principle of natural selection.

Mr. Wallace has recently described several equally striking cases of mimicry in the Lepidoptera of the Malay Archipelago, and other cases could be given with other orders of insects. Mr. Wallace has also given one instance of mimicry amongst birds, but we have no such cases with the larger animals. The much greater frequency of mockery with insects than with other animals, is probably the consequence of their small size; insects cannot defend themselves, excepting indeed the kinds that sting, and I have never heard of an instance of these mocking other insects, though they are mocked: insects cannot escape by flight from the larger animals; hence they are reduced, like most weak creatures, to trickery and dissimulation.

But to return to more ordinary cases of analogical resemblance: as members of distinct classes have often been adapted by successive slight modifications to live under nearly similar circumstances,— to inhabit, for instance, the three elements of land, air, and water,— we can perhaps understand how it is that a numerical parallelism has sometimes been observed between the sub-groups in distinct classes. A naturalist, struck by a parallelism of this nature in any one class, by arbitrarily raising or sinking the value of the groups in other classes (and all our experience shows that this valuation has hitherto been arbitrary), could easily extend the parallelism over a wide range; and thus the septenary, quinary, quaternary, and ternary classifications have probably arisen.