ent the work of Wallace and of Bates; for no two sets
of facts have done more to fix in ordinary intelligent minds a belief
in organic evolution and in natural selection as its guiding factor
than the facts of geographical distribution and of protective colour and
mimicry. The facts of geology were difficult to grasp and the public and
theologians heard more often of the imperfection than of the extent of
the geological record. The witness of embryology, depending to a great
extent upon microscopic work, was and is beyond the appreciation of
persons occupied in fields of work other than biology.

III.

From the influence in religion of scientific modes of thought we pass
to the influence of particular biological conceptions. The former effect
comes by way of analogy, example, encouragement and challenge; inspiring
or provoking kindred or similar modes of thought in the field of
theology; the latter by a collision of opinions upon matters of fact or
conjecture which seem to concern both science and religion.

In the case of Darwinism the story of this collision is familiar, and
falls under the heads of evolution and natural selection, the doctrine
of descent with modification, and the doctrine of its guidance or
determination by the struggle for existence between related varieties.
These doctrines, though associated and interdependent, and in popular
thought not only combined but confused, must be considered separately.
It is true that the ancient doctrine of Evolution, in spite of the
ingenuity and ardour of Lamarck, remained a dream tantalising the
intellectual ambition of naturalists, until the day when Darwin made it
conceivable by suggesting the machinery of its guidance. And, further,
the idea of natural selection has so effectively opened the door of
research and stimulated observation in a score of principal directions
that, even if the Darwinian explanation became one day much less
convincing than, in spite of recent criticism, it now is, yet its
passing, supposing it to pass, would leave the doctrine of Evolution
immeasurably and permanently strengthened. For in the interests of the
theory of selection, "Fur Darwin," as Muller wrote, facts have been
collected which remain in any case evidence of the reality of descent
with modification.

But still, though thus united in the modern history of convictions,
though united and confused in the collision of biological and
traditional opinion, yet evolution and nat