In his Mémoires 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 Système des Animaux sans Vertèbres (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 leçons j’ai toujours insiste sur ces considérations.” Are we to infer from this that these evolutionary views were expressed in his first course, or in one of the earlier courses of zoölogical 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 himself in these fields of thought, and one so inflexible and unyielding in holding to an opinion once formed as he, must have arrived at such views only after long reflection. There is also every reason to suppose that Lamarck’s theory of descent was conceived by himself alone, from the evidence which lay before him in the plants and animals he had so well studied for the preceding thirty years, and that his inspiration came directly from nature and not from Buffon, and least of all from the writings of Erasmus Darwin.
FOOTNOTES:
[158] See the comparative summary of the views of the founders of evolution at the end of Chapter XVII.
[159] While Rousseau was living at Montmorency “his thought wandered confusedly round the notion of a treatise to be called ‘Sensitive Morality or the Materialism of the Age,’ the object of which was to examine the influence of external agencies, such as light, darkness, sound, seasons, food, noise, silence, motion, rest, on our corporeal machine, and thus, indirectly, upon the soul also.”—Rousseau, by John Morley (p. 164).
[160] Butler’s Evolution, Old and New (p. 244), and Isidore Geoffroy St. Hilaire’s Histoire naturelle générale, tome ii., p. 404 (1859).
[161] After looking in vain through both volumes of the Recherches for some expression of Lamarck’s earlier views, I found a mention of it in Osborn’s From the Greeks to Darwin, p. 152, and reference to Huxley’s Evolution in Biology, 1878 (“Darwiniana,” p. 210), where the paragraphs translated above are quoted in the original.