ked curvature of the fore-rim of the fore-wings and the
consequent more extended form, that are produced by the action of
artificial heat. Manifestly this is a matter of vital importance for
the solution of the question: heat, whether artificial or natural,
produces a difference in growth, which results in a change of form and
coloring. There is consequently no room for natural selection or the
struggle for existence.

The leaf-like form is generally associated with the dark, faded colors
of dry leaves, and when this similarity disappears even bright colors
appear on the fore-wings. In many cases the resemblance to leaves is
very imperfect; different forms of the same species live side by side
and among them are to be found those, the resemblance of which to
leaves is extremely slight. All these facts, and especially the
frequently recurring retrogression of the leaf-like appearance, justify
serious doubt regarding the Darwinian assumption, that adaptation was a
necessity for the forest-butterflies on account of the protection which
it provided.

An eye witness furthermore declares that the butterflies that resemble
leaves most closely do not always alight on withered leaves, on which
they would be almost invisible, but frequently rest on a green
background, against which they show off very clearly, and therefore
could not long escape the keen eye of birds. Besides, these butterflies
are but seldom pursued by the birds, of which there is question here,
and hence are in no need of protection.

The longer Eimer devoted his attention to the origin of this
resemblance the more "the poetic picture of the imitated leaf" vanished
out of sight, and he became convinced that it involved the necessary
expression of the lines of development, which the respective beings
were bound to follow, and that there was no question of imitation.

Apart from the resemblance to leaves, by reason of regular changes of
color, design, and wing-structure, numerous non-related butterflies
often develop such wonderful similarities--which are not, as hitherto
supposed, imitations or disguises produced by selection, but are either
the outcome of an entirely independent uniformity of development or, at
least, of its consequence--that it must be admitted that external
similarity may arise by different means and in various ways. These
relations of similarity are of such frequent recurrence because of the
limited number of directions of development in