The Presidential Address. 89
in bequeathing to us the true spirit of inquiry into Nature's
laws by legitimate method. The lustre shed by our Honorary
Member upon the present age will not wax and wane with
the fluctuations of opinion as to the efficiency of the "sur-
vival of the fittest," but his influence will be felt throughout
generations of posterity by virtue of that plasticity of mind
which he conferred upon his contemporaries, compelling them
to reconsider old doctrines, and ultimately effecting a com-
plete revulsion in thought. In a Society such as this, com-
prising as it does many young and aspiring naturalists, it is
perhaps the more necessary to insist upon this moral con-
veyed by Darwin's teachings. It is true that there are some
eminent men of science who, although evolutionists, do not
admit the sufficiency of the Darwinian factors; but at the
same time they could not deny that their acceptance of
evolution in any form is entirely the result of Darwin's
influence. The discovery of the theory of selection was a
very great contribution to science, but the establishment of
the principle of evolution was a still greater contribution to
philosophy.
The question as to how far evolution can be legitimately
admitted to have taken place in the organic world is by some
considered to be open to discussion. It cannot be denied that
the proof that natural selection is competent to modify
species does not necessarily carry with it the proof that groups
of great dissimilarity, such, for example, as the vertebrates
and the molluscs, have sprung from a common stock. But
those who admit evolution in principle need feel no distrust
on this head, even if Palaeontology has not as yet supplied
the transitional links. In cases of this kind, however,
arguments of another order come in, and homology, embry-
ology, &c, may be appealed to for completing the evidence
that is wanting to bridge over the gaps in the chain of being.
On this point Darwin is very explicit:—" Throughout whole
classes various structures are formed on the same pattern,
and at a very early age the embryos closely resemble each
other. Therefore I cannot doubt that the theory of descent
with modification embraces all the members of the same