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.