If we take a survey of the assumptions we have been compelled to make from the standpoint of the theory to explain the development of germ-cells, budding, and regeneration, it would seem as if it were contradictory to assume that, on the one hand, complete germ-plasm should be given to certain cell-series as inactive accessory idioplasm, and, on the other, that very numerous cells, at least in the lower Metazoa, should have received the idioplasm of budding, and still more numerous cells that of regeneration. But it is obvious that among the lower Metazoa the idioplasm of budding and the idioplasm of regeneration are equivalent; the same idioplasm, which, when liberated by stimuli unknown to us, co-operates from two or three germinal layers in the formation of a bud, effects, in response to the known stimulus of injury, the regeneration of the mutilated part. But germ-cells can never arise in the Metazoa from the partial budding-idioplasm or regeneration-idioplasm, because this is not complete germ-plasm, and because it can only give rise to budding or regeneration through the co-operation of two or more kinds of cells, while germ-cells always originate from _one_ cell and never arise from the fusion of cells. Germ-cells can thus only arise from the cells of the germ-track, and in no other way, no matter whether the germ-track lie in the ectoderm, as in the Hydromedusæ, or in the endoderm, as in true jellyfishes (Acalephæ) and the Ctenophores, or in the mesoderm, as in many higher groups of animals. It is only apparently that these cells belong to one particular layer, for in reality they are unique in kind, and they are simply assisted in their development by one or other cell-layer, from which they not infrequently emancipate themselves, as happens so notably in the Hydromedusæ. As we have already said, it is only among plants that we must think of budding as arising from cells which contain complete germ-plasm, for here there are no 'germinal layers' corresponding to those of animal development, and the cells of 'the growing point' must be equipped with the complete germ-plasm. The plant, like the Hydroid stock and the Siphonophore colony, is saved from death, in spite of the frequent loss of its members, mainly by the fact that it is capable of producing, at almost any part above the ground, buds which develop into new shoots, with leaves and the like. This makes a power of regeneration on the part of the individual leaves and flower-parts superfluous, but at the same time it implies that an enormous number of cells must be distributed over the whole surface of the plant, each of which can in certain circumstances become the starting-point of a bud. That is to say, each must contain, in a latent state, the complete germ-plasm which is necessary for the production of an entire plant.