Driesch answers this question in the books published in subsequent years.(101) In these he attains his final standpoint, and makes it more and more secure. The “machine-theory,” and all others like it, are now definitely abandoned. They represent the uncritical dogmatism of a materialistic mode of thought, which binds all phenomena to substance, and refuses to admit any immaterial or dynamic phenomena. The alleged initial structure is nowhere to be found. The pursuit of things into the most minute details leads to no indication of it. The chromatin, in which the most important vital processes have their basis, is very far from having this machine-like structure; it is homogeneous. The formation of the skeleton, for instance, of a Plubeus larva is due to migratory spontaneously moving cells (comparable to the leucocytes of our own body, whose migrations and activities remind one much more of a social organism than of a machine). The organism arises, not from mechanical, but from “harmoniously-equipotential systems”: that is to say, from systems every element of which has equal functional efficiency; so that each individual part bears within itself in an equal degree the potentiality of the whole—an impossibility from the mechanical point of view. Driesch had given an experimental basis for this theory at an earlier stage, in his experiments on the initial stages of the development of sea-urchins, starfishes, zoophytes, and the like. A Planarian worm cut into pieces developed a new worm of smaller size from each part. A mutilated Pluteus larva developed a new food-canal, and restored the whole typical form. His experiment of 1892 went farther still, for he succeeded in separating the first four segmentation-cells of the sea-urchin’s egg; and from each cell obtained a developing embryo. These facts, he maintains, compel us to assume a mode of occurrence which is dynamically _sui generis_, a “prospective tendency” which is a sub-concept in the Aristotelian “Dynamis.” And the essential difference between this kind of operation and a mechanical operation is, that the same typical effect is always reached, even if the whole normal causal nexus be disturbed. Even when forced into circuitous paths the embryo advances towards the same goal. Thus “vitalism,” that is, the independence and autonomy of the vital processes, is proved. The effect required is attained through “action at a distance,” a mode of happening which is specifically different from anything to be found in the inorganic world, and which has its _directive_, for instance, in the regeneration of lost parts, _not_ in anything corporeal or substantial, but in the end to be attained.