The most general fact in the life of insects, and the great law of their existence, is the Metamorphosis. Changes which in other creatures are obscure, are in them exceedingly conspicuous. The three ages of the insect appear to be three creatures. Who would have dared to assert that the grub, with its heavy luxuriance of digestive organs and its great hairy feet, was identical with a winged and ethereal being, the butterfly? He dared to say, and by the most delicate anatomy he demonstrated, that the larva, the pupa, and the butterfly represented three conditions of the same individual, three natural and legitimate evolutions of its life. How did learned Europe welcome this novel science of metamorphoses? That was the question. Swammerdam, young and without authority, without any position in the academy or university, lived in his cabinet. Scarcely anything of his works was published during his life, nor even fifty years afterwards, so that his discoveries might circulate and advantage all, rather than himself and his fame. Holland remained indifferent. Eminent professors in the University of Leyden were opposed to him; and took umbrage at the fact that a simple student placed himself by his discoveries on a level with them, or even above them. The miserable and necessitous condition in which his father left him was not calculated to recommend him greatly in a country like Holland. In his costly labours he was supported by the generosity of his friends. At Leyden it was Van Horn, his professor of anatomy, who defrayed all his expenses. At this epoch two illustrious academies were founded,--the Royal Society of London and the _Académie des Sciences_ of Paris. But the former, specially inspired by the genius of Harvey, a pupil of Padua, turned its gaze towards Italy, and addressed its inquiries to the distinguished and very accurate observer, Malpighi, who furnished at its request the anatomy of the silkworm. I know not why the Englishmen turned aside from Holland, and did not also interrogate the genius of Swammerdam. He was honoured only in France. It was here, in the neighbourhood of Paris, that he made the first public demonstration of his discovery. His friend Thévenot, the famous traveller and publisher of travels, collected around him at Issy different classes of _savants_, linguists, orientalists, and, before all, inquiring students of Nature. Such was the origin of the _Académie des Sciences_. One might justly say that the revelation of the illustrious Hollander inaugurated its cradle.