diverse combinations, we should rather be surprised that pronounced talent in a specific direction can persist in a family for two and a half centuries than that it should do so very rarely. For reducing division is always combining the existing mental qualities anew, and amphimixis is adding fresh ones to them. Thus germinal selection, that is, the free, spontaneous, but definitely directed variation of individual groups of determinants, is at the root of those striking individual peculiarities which we call specific talents; but it can attain to the highest level only rarely and in isolated cases, because these talents are not favoured by personal selection, and therefore the excessively highly developed determinants upon which they depend may be dispersed in the course of generations; they may sink to smaller majorities, or even to minorities, in which case they will no longer manifest themselves in visible mental qualities. We deduced the process of germinal selection on the basis of the assumption that the nutrition of all the parts and particles of the body, therefore also of the determinants and biophors of the germ-plasm, is subject to fluctuations. We regarded the resulting variations of these last and smallest units of the germ-plasm as the ultimate source of all hereditary variation, and therefore the basis of all the transformations which the organic world has undergone in the course of ages and is undergoing still. We have still to inquire whether we can give any more precise account of the nature of these units of the germ-plasm. If I mistake not, we may say at least so much, that all variations are, in ultimate instance, quantitative, and that they depend on the increase or decrease of the vital particles, or their constituents, the molecules. For this reason I have hitherto always spoken of only two directions of variation--a plus or a minus direction from the average. What appears to us a qualitative variation is, in reality, nothing more than a greater or a less, a different mingling of the constituents which make up a higher unit, an unequal increase or decrease of these constituents, the lower units. We speak of the simple growth of a cell when its mass increases without any alteration in its composition, that is, when the proportion of the component parts and chemical combinations remains unchanged; but the cell changes its _constitution_ when this proportion is disturbed, when, for instance, the red pigment-granules which were formerly present but scarcely visible increase so that the cell looks red. If there had previously been no red granules present, they might have arisen through the breaking up of certain other particles--of protoplasm, for instance, in the course of metabolism, so that, among other substances, red granules of uric acid or some other red stuff were produced. In this case also the qualitative change would depend on an increase or decrease of certain