But, as a matter of historical fact, no morphologist, not even Geoffroy, deduced from the facts of his science any comprehensive theory of evolution. The pre-Darwinian morphologists were comparatively little influenced by the evolution-theories current in their day, and it was in the anatomist Cuvier and the embryologist von Baer that the early evolutionists found their most uncompromising opponents.
Speaking generally, and excepting for the moment the theory of Lamarck, we may say that the evolution-theories of the 18th and 19th centuries arose in connection with the transcendental notion of the Échelle des êtres, or scale of perfection. This notion, which plays so great a part in the philosophy of Leibniz, was very generally accepted about the middle of the 18th century, and received complete and even exaggerated expression from Bonnet and Robinet. Buffon also was influenced by it. Towards the beginning of the 19th century the idea was taken up eagerly by the transcendental school and by them given, in their theories of the "one animal," a more morphological turn. Their recapitulation theory was part and parcel of the same general idea.
One understands how easily the notion of evolution could arise in minds filled with the thought of the ideal progression of the whole organic kingdom towards its crown and microcosm, man. Their theory of recapitulation led them to conceive evolution as the developmental history of the one great organism.[337] Many of them wavered between the conception of evolution as an ideal process, as a Vorstellungsart, and the conception of it as an historical process. Bonnet, Oken, and the majority of the transcendentalists seem to have chosen the former alternative; Robinet, Treviranus, Tiedemann, Meckel, and a few others held evolution to be a real process.
We have already in previous chapters[338] briefly noticed the relation of one or two of the transcendental evolution-theories to morphology, and there is little more to be said about them here. They had as good as no influence upon morphological theory, nor indeed upon biology in general.[339] It is different with the theory of Lamarck, which, although it had little influence upon biological thought during and for long after the lifetime of its author, is still at the present day a living and developing doctrine.
Lamarck's affinity with the transcendentalists was in many ways a close one, but he differed essentially in being before all a systematist. Nor is the direct influence of the German transcendentalists traceable in his work—his spiritual ancestors are the men of his own race, the materialists Condillac and Cabanis, and Buffon, whose friend he was. The idea of a gradation of all animals from the lowest to the highest was always present in Lamarck's mind, and links him up, perhaps through Buffon, with the school of Bonnet. The idea of the Échelle des êtres had for him much less a morphological orientation than it had even for the transcendentalists, for he was lacking almost completely in the sense for morphology. Lamarck's scientific, as distinguished from his speculative work, was exclusively systematic, and it was systematics of a very high order. He introduced many reforms into the general classification of animals. He was the first clearly to separate Crustacea (1799), and a little later (1800) Arachnids, from insects. He reduced to a certain orderliness the neglected tribes of the Invertebrates, and wrote what was for long the standard work on their systematics—the Histoire naturelle des Animaux sans Vertèbres (1816-22). His speculative work on biology is contained in three publications, the small book entitled Considérations sur l'organisation des corps vivants (1802), the larger work of 1809, the Philosophie zoologique, and the introductory matter to his Animaux sans Vertèbres (vol. i., 1816).
It is no easy matter to give in short compass an account of Lamarck's biological philosophy. He is an obscure writer, and often self-contradictory.
In the first part of the Philosophie zoologique Lamarck is largely pre-occupied with the problem of whether species are really distinct, or do not rather grade insensibly into one another. As a systematist of vast experience Lamarck knew how difficult it is in practice to distinguish species from varieties. "The more," he writes, "we collect the productions of Nature, the richer our collections become, the more do we see almost all the gaps filled up and the lines of separation effaced. We find ourselves reduced to an arbitrary determination, which sometimes leads us to seize upon the slightest differences of varieties, and form from them the distinctive character of what we call a species, and at other times leads us to consider as a variety of a certain species individuals a little bit different, which others regard as forming a separate species."[340]
For Lamarck, as for Darwin later, the chief problem was not the evolution and differentiation of types of structure, but the mode of origin of species.
Lamarck is at great pains to show how arbitrary are our determinations of species, and how artificial the classificatory groups which we distinguish in Nature. Strictly speaking, there are in Nature only individuals, "... this is certain, that among her products Nature has in reality formed neither classes, nor orders, nor families, nor genera, nor constant species, but only individuals which succeed one another and resemble those that produced them. Now, these individuals belong to infinitely diversified races, which shade into one another under all the forms and in all the degrees of organisation, and each of which maintains itself without change, so long as no cause of change acts upon it" (p. 41).
But there is a natural order in the animal kingdom, a progression from the simpler to the more complex organisations, a natural Échelle des êtres.