ught in animals and plants invisible to the
naked eye; it would have done much towards giving to organisms of all
kinds certain leading traits. But it has done more than this. By causing
the first differentiations of those clusters of units out of which
visible animals in general arose, it fixed the starting place for
organization, and therefore determined the course of organization; and,
doing this, gave indelible traits to embryonic transformations and to
adult structures.

* * * * *

Though mainly carried on after the inductive method, the argument at the
close of the foregoing section has passed into the deductive. Here let
us follow for a space the deductive method pure and simple. Doubtless in
biology _a priori_ reasoning is dangerous; but there can be no danger in
considering whether its results coincide with those reached by reasoning
_a posteriori_.

Biologists in general agree that in the present state of the world, no
such thing happens as the rise of a living creature out of non-living
matter. They do not deny, however, that at a remote period in the past,
when the temperature of the Earth's surface was much higher than at
present, and other physical conditions were unlike those we know,
inorganic matter, through successive complications, gave origin to
organic matter. So many substances once supposed to belong exclusively
to living bodies, have now been formed artificially, that men of science
scarcely question the conclusion that there are conditions under which,
by yet another step of composition, quaternary compounds of lower types
pass into those of highest types. That there once took place gradual
divergence of the organic from the inorganic, is, indeed, a necessary
implication of the hypothesis of Evolution, taken as a whole; and if we
accept it as a whole, we must put to ourselves the question--What were
the early stages of progress which followed, after the most complex form
of matter had arisen out of forms of matter a degree less complex?

At first, protoplasm could have had no proclivities to one or other
arrangement of parts; unless, indeed, a purely mechanical proclivity
towards a spherical form when suspended in a liquid. At the outset it
must have been passive. In respect of its passivity, primitive organic
matter must have been like inorganic matter. No such thing as
spontaneous variation could have occurred in it; for variation implies
some habitual course