determined tendency of
evolution to advance in a few directions, is a law for the whole of the
animate world. In active response to the stimuli and influences of the
environment the organism expresses itself in "organic growth" without any
relation to utility. Butterflies in particular, and especially their
markings and coloration, are taken as illustrations. In the Darwinian
theory of "mimicry" these played a brilliant part. The great resemblance
to leaves, to dried twigs, or to well-protected species which are secure
from enemies, was regarded as the most convincing proof of the operation
of natural selection. But Eimer shows that markings, striping, spots, the
development of pattern, and the alleged or real resemblances to leaves,
are really subject to definite laws of growth, in obedience to which they
gradually appear, developing according to their own internal laws, varying
and progressing altogether by internal necessity, and without any
reference to advantage or disadvantage, In association with this
orthogenesis, Eimer recognises halmatogenesis, correlation and
"genepistasis" (coming to a standstill at a fixed and definite stage), and
these seem to him to make the Darwinian theory utterly impossible. The
text and the illustrations of the book show how, in the sequence of
evolution (according to Eimer's laws of transformation), the groupings of
stripes, bands, and eye-spots must have appeared on the butterfly's wing,
how convex or concave curvings of the contour must have come about at
certain points, so that the form of a "leaf" and the lines of its venation
resulted, how the eye-spots must have been moulded and shunted, so that
they produced the effect of rust or other spots on withered leaves.
Particular interest attaches to the detailed arguments against the idea
that the butterfly must receive some advantage from its "mimicry." Even
the Darwinians have to admit that in a whole series of cases the advantage
is not obvious. They talk with some embarrassment of "pseudomimicry." Some
butterflies that are supposed to be protected have the protective markings
on the underside, so that these are actually hidden when the insects are
flying from pursuing birds. Many of the leaf-like butterflies are not
wood-butterflies at all, but meadow species,(47) and so Eimer's arguments
continue.

A specially energetic fellow-worker on Eimer's line is W. Haacke, a
zoologist of Jena, author of "Gestaltung und Vererbung," and "Die