If, now, we should wish to express this in terms of finality, we should have to say that consciousness, after having been obliged, in order to set itself free, to divide organization into two complementary parts, vegetables on one hand and animals on the other, has sought an issue in the double direction of instinct and of intelligence. It has not found it with instinct, and it has not obtained it on the side of intelligence except by a sudden leap from the animal to man. So that, in the last analysis, man might be considered the reason for the existence of the entire organization of life on our planet. But this would be only a manner of speaking. There is, in reality, only a current of existence and the opposing current; thence proceeds the whole evolution of life. We must now grasp more closely the opposition of these two currents. Perhaps we shall thus discover for them a common source. By this we shall also, no doubt, penetrate the most obscure regions of metaphysics. However, as the two directions we have to follow are clearly marked, in intelligence on the one hand, in instinct and intuition on the other, we are not afraid of straying. A survey of the evolution of life suggests to us a certain conception of knowledge, and also a certain metaphysics, which imply each other. Once made clear, this metaphysics and this critique may throw some light, in their turn, on evolution as a whole. FOOTNOTES: [Footnote 51: This view of adaptation has been noted by M.F. Marin in a remarkable article on the origin of species, "L'Origine des espèces" (_Revue scientifique_, Nov. 1901, p. 580).] [Footnote 52: De Saporta and Marion, _L'Évolution des cryptogames_, 1881, p. 37.] [Footnote 53: On fixation and parasitism in general, see the work of Houssay, _La Forme et la vie_, Paris, 1900, pp. 721-807.] [Footnote 54: Cope, _op. cit._ p. 76.] [Footnote 55: Just as the plant, in certain cases, recovers the faculty of moving actively which slumbers in it, so the animal, in exceptional circumstances, can replace itself in the conditions of the vegetative life and develop in itself an equivalent of the chlorophyllian function. It appears, indeed, from recent experiments of Maria von Linden, that the chrysalides and the caterpillars of certain lepidoptera, under the influence of light, fix the carbon of the carbonic acid contained in the atmosphere (M. von Linden, "L'Assimilation de l'acide carbonique par les chrysalides de Lépidoptères," _C.R. de la Soc. de biologie_, 1905, pp. 692 ff.).] [Footnote 56: _Archives de physiologie_, 1892.] [Footnote 57: De Manacéine, "Quelques observations expérimentales sur l'influence de l'insomnie absolue" (_Arch. ital. de biologie_, t. xxi., 1894, pp. 322 ff.). Recently, analogous observations have been made on a man who died of inanition after a fast of thirty-five days. See, on this subject, in the _Année biologique_ of 1898, p. 338, the résumé of an article (in Russian) by Tarakevitch and Stchasny.]