on of organic life, and
at the same time to deduce from the numerical predominance of certain
forms, the greater heat or uniformity of the ancient climate. The
arguments in favor of the latter conclusion are without any force,
unless we can assume that the rules followed by the Author of Nature in
the creation and distribution of organic beings were the same formerly
as now; and that, as certain families of animals and plants are now most
abundant in, or exclusively confined to regions where there is a certain
temperature, a certain degree of humidity, a certain intensity of light,
and other conditions, so also analogous phenomena were exhibited at
every former era.

If this postulate be denied, and the prevalence of particular families
be declared to depend on a certain order of precedence in the
introduction of different classes into the earth, and if it be
maintained that the standard of organization was raised successively, we
must then ascribe the numerical preponderance, in the earlier ages, of
plants of simpler structure, _not to the heat_, or other climatal
conditions, but to those different laws which regulate organic life in
newly created worlds.

Before we can infer a warm and uniform temperature in high latitudes,
from the presence of 250 species of ferns, some of them arborescent,
accompanied by lycopadiacae of large size, and araucariae, we must be
permitted to assume, that at all times, past, present, and future, a
heated and moist atmosphere pervading the northern hemisphere has a
tendency to produce in the vegetation a predominance of analogous forms.

It should moreover be borne in mind, when we are considering the
question of development from a botanical point of view, that naturalists
are by no means agreed as to the existence of an ascending scale of
organization in the vegetable world corresponding to that which is very
generally recognized in animals. "From the sponge to man," in the
language of De Blainville, there may be a progressive chain of being,
although often broken and imperfect; but if we seek to classify plants
according to a linear arrangement, ascending gradually from the lichen
to the lily or the rose, we encounter incomparably greater difficulties.
Yet the doctrine of a more highly developed organization in the plants
created at successive periods presupposes the admission of such a
graduated scale.

We have as yet obtained but scanty information respecting the state of
the ter