of age,
and which he allowed to remain, as then stated, for eighteen years, or
whether he inserted it when reading the proofs in 1794. It would seem as
if it were the expression of his views when a botanist and a young man.

In his _Memoires de Physique et d'Histoire naturelle_, which was
published in 1797, there is nothing said bearing on the stability of
species, and though his work is largely a repetition of the
_Recherches_, the author omits the passages quoted above. Was this
period of six years, between 1794 and 1800, given to a reconsideration
of the subject resulting in favor of the doctrine of descent?

Huxley quotes these passages, and then in a footnote (p. 211), after
stating that Lamarck's _Recherches_ was not published before 1794, and
stating that at that time it presumably expressed Lamarck's mature
views, adds: "It would be interesting to know what brought about the
change of opinion manifested in the _Recherches sur l'Organisation des
Corps vivans_, published only seven years later."

In the appendix to this book (1802) he thus refers to his change of
views: "I have for a long time thought that _species_ were constant in
nature, and that they were constituted by the individuals which belong
to each of them. I am now convinced that I was in error in this respect,
and that in reality only individuals exist in nature" (p. 141).

Some clew in answer to the question as to when Lamarck changed his views
is afforded by an almost casual statement by Lamarck in the addition
entitled _Sur les Fossiles_ to his _Systeme des Animaux sans Vertebres_
(1801), where, after speaking of fossils as extremely valuable monuments
for the study of the revolutions the earth has passed through at
different regions on its surface, and of the changes living beings have
there themselves successively undergone, he adds in parenthesis: "_Dans
mes lecons j'ai toujours insiste sur ces considerations._" Are we to
infer from this that these evolutionary views were expressed in his
first course, or in one of the earlier courses of zooelogical
lectures--_i.e._, soon after his appointment in 1793--and if not then,
at least one or two, or perhaps several, years before the year 1800? For
even if the change in his views were comparatively sudden, he must have
meditated upon the subject for months and even, perhaps, years, before
finally committing himself to these views in print. So strong and bold a
thinker as Lamarck had already shown h