s to correspond to them maintains
itself, gliding through the meshes of the sieve, what does not perishes."
It is an old idea of the naturalistic philosophies, dating from
Empedocles, which Darwin worked up into the theory of "natural selection"
through "the survival of the fittest" "in the struggle for existence." Of
course the assumption necessary to his idea is that the forms of life are
capable of variation, and of continually offering in ceaseless flux new
properties and characters to the sieve of selection, and of being raised
thereby from the originally homogeneous to the heterogeneous, from the
simple to the complex, from the lower to the higher. This is the theory of
descent, and it is, of course, an essential part and the very foundation
of Darwin's theory. But it is _the doctrine of descent based upon natural
selection_ that is Darwinism itself.

The Characteristic Features of Darwinism.

We do not propose to expound the Darwinian theory for the hundredth time;
a knowledge of it must be taken for granted. We need only briefly call to
mind the characteristic features and catchwords of the theory as Darwin
founded it, which have also been the starting points of subsequent
modifications and controversies.

All living creatures are bound together in genetic solidarity. Everything
has evolved through endless deviations, gradations, and differentiations,
but at the same time by a perfectly continuous process. Variation
continually produced a crop of heterogeneous novelties. The struggle for
existence sifted these out. Heredity fixed and established them. Without
method or plan variations continue to occur (indefinite variations). They
manifest themselves in all manner of minute changes ("fluctuating"
variations). Every part, every function of an organism may be subject
individually to variation and selection. The world is strictly governed by
what is useful. The whole organisation as well as the individual organs
and functions bear the stamp of utility, at least, they must bear it if
the theory is correct. In the general continuity the transitions are
always easy; there are no fundamentally distinct "types," architectural
plans, or groups of forms. Where gaps yawn the intermediate links have
gone amissing. There is no fundamental difference between _genus_,
_species_, and _variety_. Even the most complicated organ such as the eye,
the most puzzling function such as the instinct of the bee, may be
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