Living matter may be roughly compared to an electric pile, the elements of which are capable of regenerating indefinitely. This continual exchange of the elements of living bodies and the medium in which they are placed, is one of the conditions of life. Life is the continued organization, while the molecules constituting the organized body (organism) are in a state of mobile equilibrium, or a continual renovation. A grain of vegetation, or an animal (Rotifera) slowly dried, might not manifest any vital property for a long time. Far from constituting an example opposed to our definition, it on the contrary goes to corroborate it. Whilst the chemical elements which compose it could not act one upon the other, it was necessary that they should be dissolved: Corpora non agunt nisi sulta. One might compare these organisms to a pile where nothing except the fluid is wanting. The eggs of certain animals (birds, etc.), that require a certain heat in order to develop completely, furnish us a case analogous to those chemical actions which could not be accomplished in a perfect manner except by a sufficient elevation of temperature. The long discussions that have taken place in the last few years on this question, the attempted efforts to demonstrate or refute the heterogenic doctrine, have but indifferently served the purposes of science. They have made us at least to see more clearly the impotence of chemistry and physiology alone to solve the biological problem. It is impossible for anyone to study with care the organization of the Infusoria, and even the Protista, and believe that beings so complex are formed by spontaneous generation. The size of an animal or a vegetable signifies nothing in this question. The imperfections of the micrographic investigation have alone permitted the notion of the creation of beings such as the Paramecia, the Mucidina, etc. Even in the more inferior Protista, the Bacteria, and other Schizomycites, the hypothesis of heterogeny is reversed by the simple observation that these beings present a very complicated metamorphosis. An evolution, that is to say a series of supposed forcible metamorphoses, a special condition of the germ, resulting from heredity, consequently proves a generation dependent on other than anterior organisms. This reasoning, however, demonstrates in an unobjectionable manner that the first living beings were formed independent of all preëxisting organization, and that these beings were as little organized as possible. The latest progress in chemistry and in biology permits us to raise the veil partly in recovering the obscure origin of living matter. ANIMAL-VEGETABLES, PROTISTA.