WE have a tendency to remain geometric and anthropocentric and to believe that everything is created on the terrestrial model. Not long ago, at one of the scientific soirées of the Solar Festival which I founded in 1904, and which is almost always illustrated by a conference of learned men of philosophical attainments, I requested my eminent friend Edmond Perrier, Member of the Institut and Director of the Paris Museum, to discuss the question of the population of the planets in the light of the latest achievements of science, in which he is past master. His reasoning was, that the same matter, the same forces, the same laws, exist on the Earth, Venus, Mars, Jupiter, etc., and that therefore the evolution of life is everywhere the same, arrested in one place and developed in another according to the conditions and circumstances, and that all organisms on all the planets can only have terrestrial forms. Our palæontology would be repeated everywhere. It seems to me that this idea, shared, by the way, by other learned naturalists, is really too “naturalist,” too terrestrial, too classical, too professional, too narrow, too little in harmony with the grandeur of the universe, with the immensity of its energy and the variety of vital manifestations found on our small planet. On the contrary, the diversity of beings, already so prodigious on our little globe, must be, so to speak, infinite, and the extra-terrestrial living forms cannot be cast in the same mould. There is no reason, for instance, why all the beings of the universe should be limited to our five senses. There are inevitable differences: gravitation, density, food-supply, atmosphere, temperature, light, the years, seasons and days, etc., etc.--causes so different cannot fail to produce absolutely different effects. A savant is a man accustomed to discussions and delighted to provoke them, because he knows that they contribute to the advancement of science; the naturalists whose views I dispute will not bear me any ill-will, and this is not the first time that they will pardon me for being a recalcitrant microbe.