This leads us to inquire how life appeared on the earth. The debate between the heterogenists and the panspermists has been long vain, because the question has been laid before them in insoluble terms. In order to resolve it, therefore, we must take ourselves back in thought thousands of thousands of centuries in the past. A thin crust of red-hot lava, hardly solidified, extended over the incandescent nucleus of our globe. An eternity then passed before the fiery sphere was forever confined within its coffin of granite. The metalloids dominant in this chaos of affinities and repulsions were then floating in an irrespirable atmosphere along with a mass of aqueous vapors. At the end of many millions of years, the waters definitely took their place around the globe. But who can ever tell what useless abortions, to be destroyed as soon as they were created, arose in these oceans saturated with anomalous substances? The first germs of life doubtless arose from the thick proliferous stratum which was developed under the pressure of a dense atmosphere in contact with liquids still warm, incessantly traversed by electric currents of unimaginable intensity. It was a sprout that arose everywhere at once. But in those innumerable spontaneous efforts, continued during the enormous length of time required to purify the atmosphere from its acrid vapors and the seas from their foreign matters, only a small number of these germs achieved a beginning of vegetation. This, according to Madame Royer's theory, was the way life began on the globe. The author next examines the complete series of the phases of evolution gone through by the species, and then the development of the mental faculties, the chief feature of difference which in the view of some thinkers creates a gap between man and the rest of the animal kingdom. She demonstrates that the primary qualities of mind are identical in all living creatures, even in those of least development. The intelligence of man is simply superior to the mental organism of the animal. This is, however, only a relative superiority, not differing in nature from the animal's intelligence, but only in form and intensity.