V. Consequently each personality owes his bodily and spiritual qualities to both parents; by heredity the nucleus of the ovum contributes a portion of the maternal features, while the nucleus of the spermatozoon brings a part of the father’s characteristics.
By these empirical facts of conception, moreover, the further fact of extreme importance is established, that every man, like every other animal, has a beginning of existence; the complete copulation of the two sexual cell-nuclei marks the precise moment when not only the body, but also the “soul,” of the new stem-cell makes its appearance. This fact suffices of itself to destroy the myth of the immortality of the soul, to which we shall return later on. It suffices, too, for the destruction of the still prevalent superstition that man owes his personal existence to the favor of God. Its origin is rather to be attributed solely to the “eros” of his parents, to that powerful impulse that is common to all polycellular animals and plants, and leads to their nuptial union. But the essential point in this physiological process is not the “embrace,” as was formerly supposed, or the amorousness connected therewith; it is simply the introduction of the spermatozoa into the vagina. This is the sole means, in the land-dwelling animals, by which the fertilizing element can reach the released ova (which usually takes place in the uterus in man). In the case of the lower aquatic animals (fishes, mussels, medusæ, etc.) the mature sexual elements on both sides are simply discharged into the water, and their union is let to chance; they have no real copulation, and so they show none of those higher psychic “erotic” functions which play so conspicuous a part in the life of the higher animals. Hence it is, also, that all the lower, non-copulating animals are wanting in those interesting organs which Darwin has called “secondary sexual characters,” and which are the outcome of sexual selection: such are the beard of man, the antlers of the stag, the beautiful plumage of the bird of paradise and of so many other birds, together with other distinctions of the male which are absent in the female.
Among the above theses as to the physiology of conception the inheritance of the psychic qualities of the two parents is of particular importance for psychological purposes. It is well known that every child inherits from both his parents peculiarities of character, temperament, talent, acuteness of sense, and strength of will. It is equally well known that even psychic qualities are often (if not always) transmitted from grandparents by heredity—often, in fact, a man resembles his grandparents more than his parents in certain respects; and that is true both of bodily and mental features. All the chief laws of heredity which I first formulated in my General Morphology, and popularized in my Natural History of Creation, are just as valid and universal in their application to psychic phenomena as to bodily structure—in fact, they are frequently more striking and conspicuous in the former than in the latter.
However, the great province of heredity, to the inestimable importance of which Darwin first opened our eyes in 1859, is thickly beset with obscure problems and physiological difficulties. We dare not claim, even after forty years of research, that all its aspects are clear to us. Yet we have done so much that we can confidently speak of heredity as a physiological function of the organism, which is directly connected with the faculty of generation; and we must reduce it, like all other vital phenomena, to exclusively physical and chemical processes, to the mechanics of the protoplasm. We now know accurately enough the process of impregnation itself; we know that in it the nucleus of the spermatozoon contributes the qualities of the male parent, and the nucleus of the ovum gives the qualities of the mother, to the newly born stem-cell. The blending of the two nuclei is the “physiological moment” of heredity; by it the personal features of both body and soul are transmitted to the new individual. These facts of ontogeny are beyond the explanation of the dualistic and mystic psychology which still prevails in the schools; whereas they find a perfectly simple interpretation in our monistic philosophy.
The physiological fact which is most material for a correct appreciation of individual psychogeny is the continuity of the psyche through the rise and fall of generations. A new individual comes into existence at the moment of conception; yet it is not an independent entity, either in respect of its mental or its bodily features, but merely the product of the blending of the two parental factors, the maternal egg-cell and paternal sperm-cell. The cell-souls of these two sexual cells combine in the act of conception for the formation of a new cell-soul, just as truly as the two cell-nuclei, which are the material vehicles of this psychic potential energy, unite to form a new nucleus. As we now see that the individuals of one and the same species—even sisters born of the same parents—always show certain differences, however slight, we must assume that these variations were already present in the chemical plasmatic constitution of the generative cells themselves.[17]
These facts alone would suffice to explain the infinite variety of individual features, of soul and of bodily form, that we find in the organic world. As an extreme, but one-sided, consequence of them, there is the theory of Weismann, which considers the amphimixis, or the blending of the germ-plasm in sexual generation, to be the universal and the sole cause of individual variability. This exclusive theory, which is connected with his theory of the continuity of the germ-plasm, is, in my opinion, an exaggeration. I am convinced, on the contrary, that the great laws of progressive heredity and of the correlative functional adaptation apply to the soul as well as to the body. The new characteristics which the individual has acquired during life may react to some extent on the molecular texture of the germ-plasm in the egg-cell and sperm-cell, and may thus be transferred to the next generation by heredity in certain conditions (naturally, only in the form of latent energy).
Although in the soul-blending at the moment of conception only the latent forces of the two parent souls are transmitted by the coalescence of the erotic cell-nuclei, still it is possible that the hereditary psychic influence of earlier, and sometimes very much older, generations may be communicated at the same time. For the laws of latent heredity or atavism apply to the soul just as validly as to the anatomical organization. We find these remarkable phenomena of reversion in a very simple and instructive form in the alternation of generations of the polyps and medusæ. Here we see two very different generations alternate so regularly that the first resembles the third, fifth, and so on; while the second (very different from the preceding) is like the fourth, sixth, etc. (Natural History of Creation). We do not find such alternation of generations in man and the higher animals and plants, in which, owing to continuous heredity, each generation resembles the next; nevertheless, even in these cases we often meet with phenomena of reversion, which must be reduced to the same law of latent heredity.
Eminent men often take more after their grandparents than their parents even in the finer shades of psychic activity—in the possession of certain artistic talents or inclinations, in force of character, and in warmth of temperament; not infrequently there is a striking feature which neither parents nor grandparents possessed, but which may be traced a long way back to an older branch of the family. Even in these remarkable cases of atavism the same laws of heredity apply to the psyche and to the physiognomy, to the personal quality of the sense-organs, muscles, skeleton, and other parts of the body. We can trace them most clearly in the reigning dynasties and in old families of the nobility, whose conspicuous share in the life of the State has given occasion to a more careful historical picture of the individuals in the chain of generations—for instance, in the Hohenzollerns, the princes of Orange, the Bourbons, etc., and in the Roman Cæsars.
The causal-nexus of biontic (individual) and phyletic (historical) evolution, which I gave in my General Morphology as the supreme law at the root of all biogenetic research, has a universal application to psychology no less than to morphology. I have fully treated the special importance which it has with regard to man, in both respects, in the first chapter of my Anthropogeny. In man, as in all other organisms, “the embryonic development is an epitome of the historical development of the species. This condensed and abbreviated recapitulation is the more complete in proportion as the original epitomized development (palingenesis) is preserved by a constant heredity; on the other hand, it falls off from completeness in proportion as the later disturbing development (cenogenesis) is accentuated by varying adaptation.”
While we apply this law to the evolution of the soul, we must lay special stress on the injunction to keep both sides of it critically before us. For, in the case of man, just as in all the higher animals and plants, such appreciable perturbations of type (or cenogeneses) have taken place during the millions of years of development that the original simple idea of palingenesis, or “epitome of history,” has been greatly disturbed and altered. While, on the one side, the palingenetic recapitulation is preserved by the laws of like-time and like-place heredity, it is subject to an essential cenogenetic change, on the other hand, by the laws of abbreviated and simplified heredity. That is clearly seen in the embryonic evolution of the psychic organs, the nervous system, the muscles, and the sense-organs. But it applies in just the same manner to the psychic functions, which are absolutely dependent on the normal construction of these organs. Their evolution is subject to great cenogenetic modification in man and all other viviparous animals, precisely because the complete development of the embryo occupies a longer time within the body of the mother. But we have to distinguish two periods of individual psychogeny: (1) the embryonic, and (2) the post-embryonic development of the soul.