ransformation--and
reduces it to mechanical principles. III. The theory of Selection or
Darwinism is, up to the present time, the most important of the
various theories which seek to explain the transformation of species
by mechanical principles, but it is by no means the only one. If we
assume that most species have originated through natural elimination,
we also now know, on the other hand, that many forms distinguished as
varieties are hybrids between two different varieties, and can be
propagated as such; and it is equally well worthy of consideration
that other causes are in activity in the formation of species of
which, up to the present time, we have no conception. Thus it is left
to the judgment of individual naturalists to decide what share is to
be attributed to natural selection in the origin of species, and even
at the present day authorities differ widely on the subject. Some give
it a large share, and some a very small one in the result. Moritz
Wagner, for instance, would substitute his own migration-hypothesis
for Darwin's theory of selection; while I regard the action of
migration, which acts as isolation or separation, as merely a special
mode of selection. But these differing estimates of Darwinism are
quite independent of the absolute import of the doctrine of descent
or of transformation, for the latter is as yet the only theory which
rationally explains the origin of species. If we discard it, nothing
remains but the irrational assumption of a miracle, a supernatural
creation.

In this crucial and unavoidable dilemma, Virchow has declared himself
publicly in favour of the latter, and against the former hypothesis.
Every one who has attentively followed his occasional utterances on
the theory of descent during the last decade with an unprejudiced eye
and an unbiassed judgment, must be convinced that he fundamentally
rejects it. Still, his dissent has always been so obscured, and his
judgment on Darwinism in particular so wrapped in ambiguities, that an
opportune conversion to the opposite side seemed not impossible; and
many, even among those who stood near to Virchow--his friends and
disciples--did not know to what point he was in fact an opponent of
the evolution hypothesis in general. Virchow took the last step
towards clearing up this matter at Munich; for after his Munich
address there can be no farther doubt that he belongs to the most
decided opponents of the whole theory of evolution, includ