difications which have
in each case been due to one of the three main desires above specified,
namely, reproduction, subsistence, and self-defence.

Lamarck concludes the chapter with some passages which show that he was
alive--as what Frenchman could fail to be after Buffon had written?--to
the consequences which must follow from the geometrical ratio of
increase, and to the struggle for existence, with consequent survival of
the fittest, which must always be one of the conditions of any wild
animal's existence. The paragraphs, indeed, on this subject are taken
with very little alteration from Buffon's work. As Lamarck's theory is
based upon the fact that it is on the nature of these conditions that
the habits and consequently the structure of any animal will depend, he
must have seen that the shape of many of its organs must vary greatly in
correlation to the conditions to which it was subjected in the matter of
self-protection. I do not see, then, that there is any substantial
difference between the positions taken by Dr. Erasmus Darwin and by
Lamarck in this respect.

"Let us conclude," he writes, "by showing the means employed by nature
to prevent the number of her creatures from injuring the conservation of
what has been produced already, and of the general order which should
subsist.[248]

. . . . . .

"In consequence of the extremely rapid rate of increase of the smaller,
and especially of the most imperfect, animals, their numbers would
become so great as to prove injurious to the conservation of breeds, and
to the progress already made towards more perfect organization, unless
nature had taken precautions to keep them down within certain fixed
limits which she cannot exceed."[249]

This seems to contain, and in a nutshell, as much of the essence of what
Mr. Herbert Spencer and Mr. Charles Darwin have termed the survival of
the fittest in the struggle for existence, as was necessary for
Lamarck's purpose.

To Lamarck, as to Dr. Darwin and Buffon, it was perfectly clear that the
facts, that animals have to find their food under varying circumstances,
and that they must defend themselves in all manner of varying ways
against other creatures which would eat them if they could, were simply
some of the conditions of their existence. In saying that the
surrounding circumstances--which amount to the conditions of
existence--determined the direction in which any plant or animal should
be slowly modified, L