inally
assume a single common parent-form (the monophyletic hypothesis), or
several (the polyphyletic hypothesis), is wholly immaterial to the
essence of the theory of descent; and it is equally immaterial to its
fundamental idea what mechanical causes are assumed for the
transformation of the varieties. This assumption of a transformation
or metamorphosis of species is, however, indispensable, and the theory
of descent is very properly called also the "metamorphosis
hypothesis," or "doctrine of transmutation;" as well as Lamarckism,
after Jean Lamarck, who first founded it in 1809.

III. The doctrine of elimination, or the selection theory, as the
doctrine especially of "choice of breed or selection," assumes that
almost all, or at any rate most, organic species have originated by a
process of selection; the artificial varieties under conditions of
domestication--as the races of domestic animals and cultivated
plants--through artificial choice of breeds; and the natural varieties
of animals and plants in their wild state by natural choice of breeds:
in the first case, the will of man effects the selection to suit a
purpose; in the second, it is effected in a purposeless way by the
"struggle for existence." In both cases the transformation of the
organic forms takes place through the reciprocal action of the laws of
inheritance and of adaptation; in both cases it depends on the
survival or selection of the better-qualified minority. This theory of
elimination was first clearly recognised and appreciated in its full
significance by Charles Darwin in 1859, and the selection-hypothesis
which he founded on it is Darwinism properly so called.

The relation that these three great theories, which are frequently
confounded, bear to one another may, according to the present position
of science, be simply defined as follows:--I. Monism, the universal
theory of development, or the monistic progenesis-hypothesis, is the
one only scientific theory which affords a rational interpretation of
the whole universe and satisfies the craving of our human reason for
causality, by bringing all natural phenomena into a mechanical
causal-connection as parts of a great uniform process of evolution.
II. The theory of transmutation, or descent, is an essential and
indispensable element in the monistic development hypothesis, because
it is the one only scientific theory which rationally explains the
origin of organic species--that is to say, by t