r the mutual relations of
plants and animals. For, as species spread themselves gradually over the
globe, they are exposed from time to time to variations in climate, and
to changes in the quantity and quality of their food; they meet with new
plants and animals which assist or retard their development, by
supplying them with nutriment, or destroying their foes. The nature,
also, of each locality, is in itself fluctuating; so that, even if the
relation of other animals and plants were invariable, the habits and
organization of species would be modified by the influence of local
revolutions.

Now, if the first of these principles, _the tendency to progressive
development_, were left to exert itself with perfect freedom, it would
give rise, says Lamarck, in the course of ages, to a graduated scale of
being, where the most insensible transition might be traced from the
simplest to the most compound structure, from the humblest to the most
exalted degree of intelligence. But, in consequence of the perpetual
interference of the _external causes_ before mentioned, this regular
order is greatly interfered with, and an approximation only to such a
state of things is exhibited by the animate creation, the progress of
some races being retarded by unfavorable, and that of others accelerated
by favorable, combinations of circumstances. Hence, all kinds of
anomalies interrupt the continuity of the plan; and chasms, into which
whole genera or families might be inserted, are seen to separate the
nearest existing portions of the series.

_Lamarck's theory of the transformation of the orang-outang into the
human species._--Such is the machinery of the Lamarckian system; but the
reader will hardly, perhaps, be able to form a perfect conception of so
complicated a piece of mechanism, unless it is exhibited in motion, so
that we may see in what manner it can work out, under the author's
guidance, all the extraordinary effects which we behold in the present
state of the animate creation. I have only space for exhibiting a small
part of the entire process by which a complete metamorphosis is
achieved, and shall therefore omit the mode by which, after a countless
succession of generations, a small gelatinous body is transformed into
an oak or an ape; passing on at once to the last grand step in the
progressive scheme, by which the orang-outang, having been already
evolved out of a monad, is made slowly to attain the attributes and
dignity o