Darwin and his disciples wish that even our ignorance on the subject of certain phenomena should be considered as in their favour. The question has often been argued on the ground of palæontology, and they have been asked to point out a single instance of those series which ought, according to them, to unite the parent species with its derivatives. They admit their inability; but they reply that the extinct fauna and flora have left very few remains; that we only know a small part of these ancient archives; that the facts which favour their doctrine are doubtless buried under the waves with submerged continents, etc. “This manner of treating the question,” Darwin concludes, “diminishes the difficulties considerably, if it does not cause them to disappear entirely.” But, I again ask the question, in what branch of human knowledge, except these obscure subjects, should we regard problems as solved, for the very reason that we possess none of the requisite knowledge for their solution? I do not intend to reproduce here the entire examination which I have made elsewhere of the transmutation theories in general, or of Darwinism in particular. The above observations will suffice, I hope, to show why I could not accept even the most seductive of these theories. In certain points they agree with certain general facts and give an explanation of a certain number of phenomena. But all without exception attain this result only by the aid of hypotheses which are in flagrant contradiction with other general facts, quite as fundamental as those which they explain. In particular, all these doctrines are based upon a gradual and progressive derivation, upon the confusion of race and species. Consequently they ignore an unquestionable physiological fact; they are entirely in opposition with another fact, which follows from the first, and is conspicuous from every point of view, the isolation, namely, of specific groups from the earliest ages of the world, and the maintenance of organic order through all the revolutions of the globe. Such are my reasons for refusing my adherence to Darwin’s theories. VII. The theory of the English naturalist is certainly the most vigorous effort which has been made to trace back the origin of the organic world by processes analogous to those which we have discovered in the genesis of the inorganic world, that is to say, in only having recourse to secondary causes. He has failed, as we see, like Lamarck. These eminent men will be succeeded by others who will attempt the solution of the same problem. Will they be more fortunate?