publication of his "Zoological Philosophy" ("Philosophie
Zoologique"). The Lamarckian theory of the hereditary transmission
of characters acquired by use, disuse, etc., has still a following,
though it is controverted by the schools of Darwin and Weissmann.
Lamarck died on December 18, 1829.

_I.--The Ladder of Life_

If we look backwards down the ladder of animal forms we find a
progressive degradation in the organisation of the creatures comprised;
the organisation of their bodies becomes simpler, the number of their
faculties less. This well-recognised fact throws a light upon the order
in which nature has produced the animals; but it leaves unexplained the
fact that this gradation, though sustained, is irregular. The reason
will become clear if we consider the effects produced by the infinite
diversity of conditions in different parts of the globe upon the
general form, the limbs, and the very organisation of the animals in
question.

It will, in fact, be evident that the state in which we find all animals
is the product, on the one hand, of the growing composition of the
organisation which tends to form a regular gradation; and that, for the
rest, it results from a multitude of circumstances which tend
continually to destroy the regularity of the gradation in the
increasingly composite nature of the organism.

Not that circumstances can effect any modification directly. But changed
circumstances produce changed wants, changed wants changed actions. If
the new wants become constant the animals acquire new habits, which are
no less constant than the wants which gave rise to them. And such new
habits will necessitate the use of one member rather than another, or
even the cessation of the use of a member which has lost its utility.

We will look at some familiar examples of either case. Among vegetables,
which have no actions, and therefore no habits properly so called, great
differences in the development of the parts do none the less arise as a
consequence of changed circumstances; and these differences cause the
development of certain of them, while they attenuate others and cause
them to disappear. But all this is caused by changes in the nutrition of
the plant, in its absorptions and transpirations, in the quantity of
heat and light, of air and moisture, which it habitually receives; and,
lastly, by the superiority which certain of its vital movements may
assert over the others. T