a vote of thanks to Professor Henslow after his lecture on "Present
Day Rationalism." Lord Kelvin's claim for a recognition of the fact
that in organic nature scientific thought is compelled to accept the
idea of some kind of directive power, and his statement that
biologists are coming once more to a firm acceptance of a vital
principle, drew from several distinguished men of science retorts
heated enough to prove beyond a doubt that the gulf between the two
main divisions of evolutionists is as wide to-day as it was when
Butler wrote. It will be well, perhaps, for the benefit of readers
who have not followed the history of the theory of evolution during
its later developments, to state in a few words what these two main
divisions are. All evolutionists agree that the differences between
species are caused by the accumulation and transmission of
variations, but they do not agree as to the causes to which the
variations are due. The view held by the older evolutionists,
Buffon, Erasmus Darwin and Lamarck, who have been followed by many
modern thinkers, including Herbert Spencer and Butler, is that the
variations occur mainly as the result of effort and design; the
opposite view, which is that advocated by Mr. Wallace in
"Darwinism," is that the variations occur merely as the result of
chance. The former is sometimes called the theological view,
because it recognises the presence in organic nature of design,
whether it be called creative power, directive force, directivity,
or vital principle; the latter view, in which the existence of
design is absolutely negatived, is now usually described as
Weismannism, from the name of the writer who has been its principal
advocate in recent years.

In conclusion, I must thank my friend Mr. Henry Festing Jones most
warmly for the invaluable assistance which he has given me in