To inform the embryo any principle, whether it is the rational soul or a force derived from the parental organism, must have organs; and if organs are present, then the embryo is fit to receive the human soul, as the only objection to its presence is a supposed lack of organs. To use other principles when the human soul itself could be present would be a _multiplicatio entium sine necessitate_, which is a condition repugnant to the universal method of the Creator. It has been said that the vital activity in the fertilized ovum does not proceed from the rational soul because, "in the first place, it results from the fusion of two vital activities, neither of which is rational; secondly, it results in the formation, by fission, and differentiation, of two distinct and separate living cells, each containing within itself a principle of vital activity. Now this principle of vital activity cannot be a rational soul, for each cell has its own principle of activity, and in man there is but one soul." In the first place, that vital activity does _not_ result from the fusion of two vital activities neither of which is rational. It results _after_ the nuclei come together, by particular creation, and replaces their activity--the generation of the last vital force is the corruption of the first that existed in the separate nuclei, not a derivative of that first force. Again, when the embryo is in the two, four, eight cell stage, and so on, there are not two, four, eight vital principles present, but one. Substantial unity is essential to life of any kind, no matter how low its grade; and if each cell had an independent vital principle, any form of resultant life in the mass would be impossible. An aggregation has no unity of substance; there would be as many substances or natures as there are individual beings in the aggregate, no matter whether ordered or in a mob, consequently no life at all as a life. The embryo in the two-cell stage is not made up of two independent organisms, any more than the right and left halves of an adult man are two independent organisms. The cells in the two-cell stage of the embryo are the right and left halves of the body, not two individuals, as has been proved repeatedly by biologists. Roux[42] punctured with a hot needle one of the cells in the two-cell stage of a frog embryo without killing the embryo, and it grew into a half-frog larva. Analogous results were obtained by operating in the four-cell stage. Later, Pflüger, Schultze, Enders, and Morgan corroborated the work of Roux. Newport[43] discovered this fact sixty years ago. [42] Virchow's Archiv (1888), 114. [43] _Phil. Trans._, 1854.