ence of a general law of evolution. This is his theory of
heterogeneous generation. "The fundamental idea of this hypothesis is
that under the influence of a general law of evolution creatures produce
from their germs others which differ from them" (p. 181). It is to be
noticed that Koelliker laid more stress upon the _Entwickelungsgesetz_
than upon the saltatory nature of variation, for he says a few pages
further on--"the notion at the base of my theory is that a great
evolutionary plan underlies the development of the whole organised
world, and urges on the simpler forms towards ever higher stages of
complexity" (p. 184). Saltatory evolution was not the essential point of
the theory:--"Another difference between the Darwinian hypothesis and
mine is that I postulate many saltatory changes, but I will not and
indeed cannot lay the chief stress upon this point, for I have not
intended to maintain that the general law of evolution which I hold to
be the cause of the creation of organisms, and which alone manifests
itself in the activity of generation, cannot also so act that from one
form others quite gradually arise" (p. 185). He put forward the
hypothesis of saltatory variation because it seemed to him to lighten
many of the difficulties of Darwinism--the lack of transition forms, the
enormous time required for evolution, and so on. It should be noted that
Koelliker regarded his principle of evolution as mechanical.

It would take too long to show in detail how a belief in innate laws of
evolution was held by the majority of Darwin's critics. A few further
examples must suffice.

Richard Owen, who in 1868[364] admitted the possibility of evolution, held
that "a purposive route of development and change, of correlation and
interdependence, manifesting intelligent Will, is as determinable in the
succession of races as in the development and organisation of the
individual. Generations do not vary accidentally, in any and every
direction; but in pre-ordained, definite, and correlated courses" (p.
808).

He conceived change to have taken place by abrupt variation, independent
of environment and habit, by "departures from parental type, probably
sudden and seemingly monstrous, but adapting the progeny inheriting such
modifications to higher purposes" (p. 797). He believed spontaneous
generation to be a phenomenon constantly taking place, and constantly
giving the possibility of new lines of evolution.

E. von Hartmann in