That infinite world of life which every where surrounds us was almost unknown until lately. Swammerdam and others, who formerly recognized it, were stopped at their first step; and it was as lately as the year 1830, that the magician Uhrenberg looked, revealed, and classified it. He studied the figure of these invisibles, their organization, their manners; he saw them absorb, digest, chase, and fiercely battle. Their generation remained a mystery to him. What is the nature of their amours? _Have_ they any amours? For creatures so elementary, would nature go to the expense of a complicated generation? Or do they spring up spontaneously, and, in vulgar phrase, "like mushrooms?" A great question! at which more than one naturalist smiles and shakes his head. One is so certain of having solved the great mystery of the world and secured, laid down, once and forever, the true laws of life! It is for Nature to obey! When, a hundred years ago, Réaumur was told that the female silk worm could produce alone and without the male, he denied it in the brief phrase--"Out of nothing, nothing comes." But the fact, often denied but always proved, is now thoroughly established and admitted, not only as to the silk worm, but as to the bee, certain butterflies, and still other creatures. In all times, in every nation, both the learned and unlearned have said, "Out of death cometh life." It was especially supposed that the imperceptible animalculæ immediately sprang up from the wrecks of death. Even Harvey, who first laid down the law of generation, did not venture to contradict that ancient belief, for though he said every body comes from the egg, he immediately added--_or from the dissolved body of a preceding life_. It is precisely the theory which has been so brilliantly revived by the experiments of M. Ponchet. He has established the fact that from the remains of the infusoriæ and other creatures, there proceeds a fecund jelly, the "prolific membrane" from which spring, not new beings, indeed, but the germs, the eggs from which new creatures will spring. We live in an age of miracles. This is not to astonish us. Any one would formerly have been laughed at who had ventured to say that some animals, disobedient to the general laws of nature, take the liberty to breathe through their paws. The noble labors of Milne Edwards have brought this to light. And Cuvier and Blainville had observed, it is said, that other creatures, destitute of the regular organs of circulation, supply their place by the intestines, but those great naturalists deemed the fact so enormous and so incredible, that they did not venture to publish it. It is now perfectly established by Milne Edwards, M. de Quatrefages, &c.