very far from being the case that all thought and knowledge moves in this one direction, and that the content of our minds can ever find exhaustive expression through it alone.” In his “Theory of Dominants,”(96) Reinke, the botanist of Kiel, has attempted to formulate his opposition to the physico-chemical conception of life into a vitalistic theory of his own. Among biologists who confess themselves supporters of the mechanical theory, there are some who expressly reject explanations in terms of chemical and physical principles, and emphasise, more energetically than others, that these can only give rise to vital phenomena and complex processes of movement, on the basis of a most delicately differentiated structure and architecture of the living substance in its minute details, and from the egg onwards. They have created the strict “machine theory,” and they may be grouped together as the “tectonists.” “A watch that has been stamped to pieces is no longer a watch.” Thus the merely material and chemical is not the essential part of the living; it is the tectonic, the machinery of structure that is essential. The fundamental idea in this position is precisely that of Lotze. It is not a “mystical,” vital principle, that sets up, controls, and regulates the physical and chemical processes within the developed or developing organism. They receive their direction and impulse through the fact that they are associated with a given peculiar mechanical structure. This theory certainly contains all the monstrosities of preformation in the germ, the mythologies of the infinitely small, and it suffers shipwreck in ways as diverse as the number of its sides and parts. But it has the merit of clearly disclosing the impossibilities of purely chemical explanations. Reinke’s “Theory of Dominants” started from such tectonic conceptions, and so originally did Driesch’s Neovitalism, of which we shall presently have to speak.