s of animals, and Erasmus Darwin in his _Zoonomia_
(1794) brought forward as one of the strongest proofs of evolution, "the
essential unity of plan in all warm-blooded animals."[336]

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 _Echelle des
etres_, 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