ONCE upon a time, in a solar system belonging to the constellation Andromeda, a planet a million times the size of our Earth bore on its surface a very advanced human race. The eyes of its inhabitants were constructed differently from ours and received radiations which are dark to us. Also, instead of five senses those human organisms possessed twelve. Their subtle and far-seeing industry had invented instruments of great space-penetrating power, and they had succeeded in determining at immense distances the volumes, masses, densities, physical and chemical constitutions, the movements, and the intrinsic nature of worlds at present quite indiscernible to us. Amidst the glories of a sumptuous civilisation, those human beings, whose form did not at all resemble ours, thought, in spite of their progress in astronomy, that they were the centre, the final goal, and the justification for the existence of the universe. Some of their philosophers had indeed put forward the idea of a probability of inhabited worlds, but this idea, received with scepticism by most of the learned men and resolutely rejected by the theologians, was only accepted by the most liberal spirits with a reservation concerning the intellectual superiority of their race, considered as the necessary and normal type of all humanity. To them it seemed impossible that Nature should create anything other or better than what had been established in their own world; the zoology of their own planet set a standard, and living beings, they thought, could not be organised otherwise than as they knew them. To their minds, the area accessible to their observation included all the possible manifestations of the forces acting throughout the cosmos. It was only possible to have twelve senses, neither more nor less. There came a time when some transcending genius discovered among the stars of the constellation which terrestrial astronomers call Centaurus the star which we call the Sun and around which we gravitate. He noticed round this star nine principal spheres circulating round it, and, by some secret sympathy, he directed his attraction chiefly to the globe which we now inhabit. The star--our own Sun--and the nine planets we have just mentioned were invisible in our sense of the word. They only emitted dark rays, black light. For a long time already, in fact, the Sun had been extinct, and the humanities who had lived on the surface of the Earth, of Mars, Venus, Mercury, Jupiter, Saturn, Uranus, and Neptune, of the trans-Neptunian planet and its sisters, had died in turn and had been gradually erased from the great book of universal life.