n
of species as on the doctrine of homologies and the unity of
organization in the animal kingdom.

In fact, Geoffroy did not adopt the views peculiar to his old friend
Lamarck, but was rather a follower of Buffon. His views were preceded by
two premises.

The species is only "_fixe sous la raison du maintien de l'etat
conditionnel de son milieu ambiant_."

It is modified, it changes, if the environment (_milieu ambiant_)
varies, and according to the extent (selon la portee) of the variations
of the latter.[146]

As the result, among recent or living beings there are no essential
differences as regards them--"_c'est le meme cours d'evenements_," or
"_la meme marche d'excitation_."[147]

On the other hand, the _monde ambiant_ having undergone more or less
considerable change from one geological epoch to another, the atmosphere
having even varied in its chemical composition, and the conditions of
respiration having been thus modified,[148] the beings then living would
differ in structure from their ancestors of ancient times, and would
differ from them according "to the degree of the modifying power."[149]
Again, he says, "The animals living to-day have been derived by a series
of uninterrupted generations from the extinct animals of the
antediluvian world."[150] He gave as an example the crocodiles of the
present day, which he believed to have descended from the fossil forms.
While he admitted the possibility of one type passing into another,
separated by characters of more than generic value, he always, according
to his son Isidore, rejected the view which made all the living species
descend "_d'une espece antediluvienne primitive_."[151] It will be seen
that Geoffroy St. Hilaire's views were chiefly based on palaeontological
evidence. He was throughout broad and philosophical, and his eloquent
demonstration in his _Philosophie anatomique_ of the doctrine of
homologies served to prepare the way for modern morphology, and affords
one of the foundation stones on which rests the theory of descent.
Though temporarily vanquished in the debate with Cuvier, who was a
forceful debater and represented the views then prevalent, a later
generation acknowledges that he was in the right, and remembers him as
one of the founders of evolution.

FOOTNOTES:

[125] Mr. Morley, in his _Rousseau_, gives a startling picture of the
hostility of the parliament at the period (1762) when Buffon's works
appeared. Not only was Roussea