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:
[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).
[52] De Saporta and Marion, L'Évolution des cryptogames, 1881, p. 37.
[53] On fixation and parasitism in general, see the work of Houssay, La Forme et la vie, Paris, 1900, pp. 721-807.
[54] Cope, op. cit. p. 76.
[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.).
[56] Archives de physiologie, 1892.
[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.
[58] Cuvier said: "The nervous system is, at bottom, the whole animal; the other systems are there only to serve it." ("Sur un nouveau rapprochement à établir entre les classes qui composent le regne animal," Arch. du Muséum d'histoire naturelle, Paris, 1812, pp. 73-84.) Of course, it would be necessary to apply a great many restrictions to this formula—for example, to allow for the cases of degradation and retrogression in which the nervous system passes into the background. And, moreover, with the nervous system must be included the sensorial apparatus on the one hand and the motor on the other, between which it acts as intermediary. Cf. Foster, art. "Physiology," in the Encyclopaedia Britannica, Edinburgh, 1885, p. 17.