ting the infinite
variability of species, and the progressive development in past time of
the organic world. The reader must bear in mind that when I made this
analysis of the 'Philosophie Zoologique' in 1832, I was altogether
opposed to the doctrine that the animals and plants now living were the
lineal descendants of distinct species, only known to us in a fossil
state, and ... so far from exaggerating, I did not do justice to the
arguments originally adduced by Lamarck and Geoffroy St. Hilaire,
especially those founded on the occurrence of rudimentary organs. There
is therefore no room for suspicion that my account of the Lamarckian
hypothesis, written by me thirty-five years ago, derived any colouring
from my own views tending to bring it more into harmony with the theory
since propounded by Darwin."[334] So little difference did Sir Charles
Lyell discover between the views of Lamarck and those of his successors.

With the identity, however, of the main proposition which, both Lamarck
and Mr. Darwin alike endeavour to establish, the points of agreement
between the two writers come to an end. Lamarck's great aim was to
discover the cause of those variations whose accumulation results in
specific, and finally in generic, differences. Not content with
establishing the fact of descent with modification, he, like his
predecessors, wishes to explain how it was that the fact came about. He
finds its explanation in changed surroundings--that is to say, in
changed conditions of existence--as the indirect cause, and in the
varying needs arising from these changed conditions as the direct cause.

According to Lamarck, there is a broad principle which underlies
variation generally, and this principle is the power which all living
beings possess of slightly varying their actions in accordance with
varying needs, coupled with the fact observable throughout nature that
use develops, and disuse enfeebles an organ, and that the effects,
whether of use or disuse, become hereditary after many generations.

This resolves itself into the effect of the mutual interaction of mind
on body and of body on mind. Thus he writes:--

"The physical and the mental are to start with undoubtedly one and the
same thing; this fact is most easily made apparent through study of the
organization of the various orders of known animals. From the common
source there proceeded certain effects, and these effects, in the outset
hardly separated, have in the