The very interesting and important phenomena of impregnation have only been known to us in detail for thirty years. It has been shown conclusively, after a number of delicate investigations, that the individual development of the embryo from the stem-cell or fertilised ovum is controlled by the same laws in all cases. The stem-cell divides and subdivides rapidly into a number of simple cells. From these a few simple organs, the germinal layers, are formed at first; later on the various organs, of which there is no trace in the early embryo, are built up out of these. The biogenetic law teaches us how, in this development, the original features of the ancestral history are reproduced or recapitulated in the embryonic processes; and these facts in turn can only be explained by the unconscious memory of the plasm, the "_mneme_ of the living substance" in the germ-cells, and especially in their nuclei. One important result of these modern discoveries was the prominence given to the fact that the personal soul has a beginning of existence, and that we can determine the precise moment in which this takes place; it is when the parent cells, the ovum and spermatozoon, coalesce. Hence what we call the soul of man or the animal has not pre-existed, but begins its career at the moment of impregnation; it is bound up with the chemical constitution of the plasm, which is the material vehicle of heredity in the nucleus of the maternal ovum and the paternal spermatozoon. One cannot see how a being that thus has a beginning of existence can afterwards prove to be "immortal." Further, a candid examination of the simple cell-soul in the unicellular infusoria, and of the dawn of the individual soul in the unicellular germ of man and the higher animals, proves at once that psychic action does not necessarily postulate a fully formed nervous system, as was previously believed. There is no such system in many of the lower animals, or any of the plants, yet we find psychic activities, especially sensation, irritability, and reflex action everywhere. All living plasm has a psychic life, and in this sense the psyche is a partial function of organic life generally. But the higher psychic functions, particularly the phenomena of consciousness, only appear gradually in the higher animals, in which (in consequence of a division of labour among the organs) the nervous system has assumed these functions.