Suppose the blastula opened out on the flat, like the Mercator projection of a globe on a flat map. Suppose that _a_ is a small element of it. Suppose that the rectangles _b c d e_, _F G H e_, _I J c L_, _M N O e_, and as many more as we care to make, represent the pieces of the blastular wall separated by our operation--they all contain the element _a_, but this is in a different position in each case. There are really an infinite number of such parts of the blastula and _a_ occupies an infinitely variable position in each of them. This demonstration is very important, so let us make it as clear as possible: Driesch’s logical proof of vitalism may be stated as follows:-- The different parts of the blastula are going to become different parts of an embryo. The part _a_, occupying a definite position in the entire blastula, is going to become a definite part, having a definite position, in the embryo; But each partial blastula becomes an entire embryo and the same part _a_ occupies a different position in each. Therefore _any_ part of the blastula may become _any_ part of the embryo. Now if a mechanism is involved, it must, according to our ideas of mechanism, be one which is different in its parts, for each part of it produces a different result from the others; But since any part of the mechanism may produce any of the different results contained in the embryo, every one of its parts must be similar to every other one. That is, all the parts of the mechanism are the same, though the hypothesis requires that they should be different. We conclude, then, that a mechanism such as we understand a mechanism to be in the physical sciences cannot be present in the developing ovum. Nevertheless, an _organisation_, using this term as an ill-defined one for the present, must exist in the ovum, or the system of undifferentiated cells into which the ovum divides, during the first stages of segmentation. In certain animals, Ctenophores (Chun, Driesch, and Morgan), and Mollusca (Crampton), for instance, separation of the blastomeres in the first stages of segmentation produces different results from those mentioned above. In these cases the isolated blastomeres develop as partial embryos, that is, the latter are incomplete in certain respects, and this incompleteness corresponds, in a general way, to the incompleteness of the part of the ovum undergoing development. We have thus the apparently contradictory results: (1) each of the first few blastomeres resulting from the first divisions of the ovum is similar to the entire ovum, and develops like it; and (2) each of the first few blastomeres is different from the others, and from the entire ovum, and develops differently from the others, and from the entire ovum.