In his work on “Organic Regulations,” Driesch collects from the most diverse biological fields more and more astonishing proofs of the activity of the living as contrasted with physico-chemical phenomena, and of the marvellous power the organism has to “help itself” and to attain the typical form and reach the end aimed at, even under the greatest diversity in the chain of conditions. The material here brought forward is enormous, and the author’s grasp of it very remarkable; and not the least of the merits of the book is, that the bewildering wealth and diversity of these phenomena, which are usually presented to us as isolated and uncoordinated instances, is here definitely systematised according to their characteristic peculiarities, and from the point of view of the increasing distinctness of the “autonomy” of the processes. The system begins with the active regulatory functions of living matter in the chemistry of metabolism (see particularly the phenomena of immunisation), and ascends through different stages up to the regulations of regeneration. There could be no more impressive way of showing how little life and its “regulations” can be compared to the “self-regulations” of machines, or to the restoring of typical states of equilibrium and of form in the physical and chemical domain, to which the mechanists are fond of referring. The facts thus empirically brought together are then linked together in a theory, and considered epistemologically. We may leave out of account all that is included in the treatment of modern idealism, immanence-philosophy, and solipsism. All this does not arise directly out of the vitalistic ideas, though the latter are fitted into an idealistic framework. Extremely vivid is the excursus on respiration and assimilation. (All processes of building up and breaking down take place within the organism under conditions notoriously different from those obtaining in the laboratory. It is radically impossible to speak of a living “substance” according to the formula CxHyOz, which assimilates and disassimilates itself [sibi].) Excellent, too, are Driesch’s remarks on materialistic elucidations of inheritance and morphogenesis. It is quite impossible to succeed with epigenetic speculations on a material basis (_cf._ Haacke). Weismann is so far right, he admits, from his materialistic premisses when he starts with preformations. But his theory, and all others of the kind, can do nothing more than make an infinitely small photograph of the difficulty. They “explain” the processes of form-development and the regeneration of animals and plants, by constructing infinitely small animals and plants, which develop their form and regenerate lost parts. And Driesch holds it to be impossible to distribute a complicated tectonic among the elements of an equipotential system. In denying the materialistic theory of development, Driesch again determinedly “traverses” his own earlier views. He does this, too, when he