[305] Darwin _On the Origin of Species_, p. 518, London, 1861. “I believe that animals have descended from at most only four or five progenitors, and plants from an equal or less number. Analogy would lead me one step farther, namely, to the belief that all animals and plants have descended from some one prototype.” [306] Compare Darwin _On the Origin of Species_, p. 96, 1861. [307] _Histoire Naturelle Générale_, vol. ii, p. 421, 1859. [308] “The observation of species in a state of nature, by revealing to us a multitude of modifications more or less important, cannot show us any serious deviation from the types formed or preserved by the influence of the existing state of things.” Isidore Geoffroy, _Vie d’Étienne Geoffroy_, p. 349. [309] See Leibnitz, _Protogée_, transl. by Bertrand de Saint-Germain, Introduction, p. 61. [310] _Comptes rendus des séances de l’Académie_, February 22, 1858. [311] We shall be thanked for publishing here the following extract from a letter addressed to us by Isidore Geoffroy Saint-Hilaire, the 3rd of June, 1860, and which relates to all these questions. “I said, two or three years ago, as I have learnt from M. Lartet (who remembered the expression which I had myself forgotten), that the present movement of science tends to substitute in geology the idea of the _evolution_ of the globe for that of _revolutions_. M. Lartet has taken up this view, and adheres to it. It is of great importance to me, as regards my works on species, in which we must in this case substitute the notion of _evolution_ for that of _revolution_; _revolutions_ are here pretended creations, abruptly successive. It is time to have done with these views, which, instead of taking creation as having been once concluded, make at every instant the _Deus ex machinâ_ intervene.”