n's thought hesitated. Logically his theory proves, as Ray
Lankester pointed out, that the struggle for existence may have as its
outcome degeneration as well as amelioration: evolution may be
regressive as well as progressive. Then, too--and this is especially
to be borne in mind--each species takes its good where it finds it,
seeks its own path and survives as best it can. Apply this notion to
society and you arrive at the theory of multilinear evolution.
Divergencies will no longer surprise you. You will be forewarned not
to apply to all civilisations the same measure of progress, and you
will recognise that types of evolution may differ just as social
species themselves differ. Have we not here one of the conceptions
which mark off sociology proper from the old philosophy of history?

* * * * *

But if we are to estimate the influence of Darwinism upon sociological
conceptions, we must not dwell only upon the way in which Darwin
impressed the general notion of evolution upon the minds of thinkers.
We must go into details. We must consider the influence of the
particular theories by which he explained the mechanism of this
evolution. The name of the author of _The Origin of Species_ has been
especially attached, as everyone knows, to the doctrines of "natural
selection" and of "struggle for existence," completed by the notion of
"individual variation." These doctrines were turned to account by very
different schools of social philosophy. Pessimistic and optimistic,
aristocratic and democratic, individualistic and socialistic systems
were to war with each other for years by casting scraps of Darwinism
at each other's heads.

It was the spectacle of human contrivance that suggested to Darwin his
conception of natural selection. It was in studying the methods of
pigeon breeders that he divined the processes by which nature, in the
absence of design, obtains analogous results in the differentiation of
types. As soon as the importance of artificial selection in the
transformation of species of animals was understood, reflection
naturally turned to the human species, and the question arose, How far
do men observe, in connection with themselves, those laws of which
they make practical application in the case of animals? Here we come
upon one of the ideas which guided the researches of Gallon, Darwin's
cousin. The author of _Inquiries into Human Faculty and its
Development_,[247] has often e