Thus our system of nature completes itself; thus, thanks to solar radiation, the two ends of the immense chain of organized beings whose place and part in the vast theatre of the worlds we have attempted to define are united. Life begins in the waters, its first appearance is in plants and zoophytes; for these two classes of living creatures obey the same laws, and appear to have the same origin. The sun, by sending his vivifying rays upon the earth, produces the formation of plants and zoophytes, which are the points of departure of organization. The _animated germ_ deposited by the sun in plants and zoophytes grows, passes from the zoophyte to the mollusc, or articulated animal, and then undergoes a further development, by passing from the mollusc or articulated animal to the fish. This germ of a soul thus becomes a rudimentary soul, provided with certain faculties. In the zoophyte and the mollusc it had only sensibility; in the fish, and then in the reptile, and the bird, it has attention and judgment. The faculties are augmented in proportion as the animal mounts higher in the organic scale. Arrived at its summit, the human being, the soul is in possession of all its faculties, and especially of memory, which during the animal stages of the ascent is obscure and uncertain. To accord sensibility to plants permits us to unite all the creatures of the living creation, and thus to complete our general system of terrestrial nature. [Illustration] FOOTNOTES: [15] "_Histoire des Plantes_," Paris, p. 111. [16] "_Contemplation de la Nature_ (_Œuvres d'Histoire Naturelle de Charles Bonnet._") Neuchâtel, 1781. [Illustration] CHAPTER THE THIRTEENTH. DOES MAN EXIST ELSEWHERE THAN ON THE EARTH?--DESCRIPTION OF THE PLANETS.--PLURALITY OF INHABITED WORLDS.