by the order and state of things which she has
constituted in each organisation and in each particular system of
organs.

"2. Every animal faculty, of whatever nature it may be, is an organic
phenomenon, and results from a system of organs or an organ-apparatus
which gives rise to it and upon which it is necessarily dependent.

"3. The more highly a faculty is developed the more complex is the
system of organs which produces it, and the higher the general
organisation; the more difficult also does it become to grasp its
mechanism. But the faculty is none the less a phenomenon of
organisation, and for that reason purely physical" (p. 104).

According to these "axioms" function is a direct and mechanical effect
of structure.

The curious thing is that in spite of his avowed materialism, Lamarck's
conception of life and evolution is profoundly psychological, and from
the conflict of his materialism and his vitalism (of which he was
himself hardly conscious), arise most of the obscurities and the
irreductible self-contradiction of his theory.

Lamarck divided animals (psychologically!) into three great
groups--apathetic or insensitive animals, animals endowed with
sensation, and intelligent animals. The first group, which comprise all
the lower Invertebrates, are distinguished from other animals by the
fact that their actions are directly and mechanically due to the
excitations of the environment; they have no principle of reaction to
external influences, but passively prolong into action the excitations
they receive from without. They are _irritable_ merely. The second group
are distinguished from the first by their possessing, in addition to
irritability, a power which Lamarck calls the _sentiment interieur_. He
has some difficulty in defining exactly what he means by it:--"I have no
term to express this internal power possessed not only by intelligent
animals but also by those that are endowed merely with the faculty of
sensation; it is a power which, when set in action by the feeling of a
need, causes the individual to act at once, _i.e._, in the very moment
of the sensation it experiences; and if the individual is of those that
are endowed with intelligence it nevertheless acts in such a case
entirely without premeditation and before any mental operation has
brought its _will_ into play" (p. 24).

It is the power we call instinct in animals (p. 25), and it implies
neither consciousness nor will. It acts by tran