20
After the statements which have just been made, it can
scarcely be said that the theory of Natural Selection is
quite so definite or self-consistent as it is generally sup
posed to be. It is not quite certain that he who reads it
as he runs will be sure to read aright, or that the wayfaring
man will not be liable to err therein.
Now, in the first place, let me say that it is quite natural
that there should be differences of opinion among different
persons, and the first thing one has to remember is that
Natural Selection may be held with various modifica
tions. Some may believe that it is the one only method
of the transmutation of species, others may hold that
possibly there are many methods, among which Natural
Selection is one. Some may follow Ray Lankester
and Weismann, others may follow Darwin and Romanes.
On this and other points we have modifications of the
theory which almost amount to rival theories, and the
attempt to reconcile the two would be a mere waste of
time.
In the second place, a discrepancy, if it exists, may arise
from the fact that even an eminent specialist sometimes
writes from the point of view of the logical exponent of a
theory, and sometimes in the character of a careful observer
of nature. Both statements may be correct in their own
field. Assuming certain data as the axioms of a theory,
a man may reason as to what the result must be : looking
out on nature, he may honestly record what the fact
actually is : and he may not be quite aware of the discrep
ancy which exists between the two sets of statements.
This may explain Mr. Darwin’s treatment of the question
whether variations are small or large.
Mr. Darwin asserts that Natural Selection deals only
with slight variations ; that on the theory of Natural
Selection the variations must be slight ; and in nature