What in Reinke’s case came about almost unperceived, Driesch did with full consciousness and intention, following the necessity laid upon him by his own gradual personal development and by his consistent, tenacious prosecution of the problem. The acuteness of his thinking, the concentration of his endeavours through long years, his comprehensive knowledge and mastery of the material, the deep logicalness and consistent evolution of his “standpoints,” and his philosophical and theoretical grasp of the subject make him probably the most instructive type, indeed, we may almost say, the very incarnation of the whole disputed question. In 1891 he published his “Mathematisch—mechanische Betrachtung morphologischer Probleme der Biologie,” the work in which he first touched the depths of the problem. It is directed chiefly against the merely “historical” methods in biology, used by the current schools in the form of Darwinism. Darwinism and the Theory of Descent have been so far nothing more than “galleries of ancestors,” and the science ranged under their banner is only descriptive, not explanatory. Instead of setting up contingent theories we must form a “conception” of the internal necessity, inherent in the substratum itself, in accordance with which the forms of life have found expression—a necessity corresponding to that which conditions the form-development of the crystal. Experimental investigations and discoveries, and further reflection, resulted, in 1892, in his “Entwicklungsmechanische Studien,” and led him to insist on the need for what the title of his next year’s work calls “Biologie als selbständige Grundwissenschaft.” In this work two important points are emphasised. The first is, that biology must certainly strive after precision, but that this precision consists not in subordination to, but in co-ordination with physics. Biology must rank side by side with physics as an “independent fundamental science,” and that in the form of tectonic. And the second point is, that the teleological point of view must take its place beside the causal. Only by recognising both can biology become a complete science.