This, Professor Bastian readily concedes, notwithstanding it cuts the Darwinian _plexus_ squarely in the middle. He says: "Both Gruithuisen and Tréviranus agree that the infusoria met with have never presented similar characters when they have been encountered in different infusions; nor have they been uniform in the same infusion, when different portions of it have been _exposed to the incidence of different conditions_. The slightest variations in the quality or quantity of the materials employed, are invariably accompanied by the appearance of different organisms--these being oftentimes strange and peculiar, and unaccompanied by any of the familiar forms." Other writers of equal eminence in this field of investigation have not only observed the same characteristics, but encountered the same difficulties in classification, from the very great diversity obtaining even in the nearest allied forms. So great is this diversity, and so multitudinous the different forms, that little certainty or value can be attached to the classifications already made. Even Professor O.F. Müller, after he had convinced himself that he had discovered not less than twelve different species belonging to a single genus, was subjected to the mortification of seeing Ehrenberg cut them all down to mere modifications of one and the same species. We refer to these several statements of fact for the purpose of emphasizing the true genesis of life as supplemented by "the incidence of different conditions," on which all vital manifestations depend. The presence of the germinal principles of life in the earth is emphatically averred in the Bible genesis. And we have only to connect the doctrine of "conditional incidence" with this averment, to account for all the vital phenomena which so profoundly puzzle these gentlemen while prying into the mysteries of the ephemeromorphic world. Whatever may be the character of any infusion, or to whatever incidence of conditions it may be subjected, it will produce _some_ form of life; not because it contains this or that morphological cell, destructible at a temperature of 100° C--that to which it is experimentally subjected before microscopic examination,--but because every organic infusion, whether undergoing the required heat-test or not, contains vital units--those as indestructible by heat as by glacial drift--which burgeon forth into life whenever the proper conditions of environment obtain. The slightest variation, in either the quantity or quality of the material employed in the infusion, is, as these eminent microscopists agree, invariably accompanied by the appearance of different forms of life, just as the slightest change in soil-conditions, such as that produced by the presence of one species of tree with another in natural truffle-grounds, will result in the appearance of another and altogether different plant, as well as truffle tuber.