“Ye shall know them by their fruits. Do men gather grapes of thorns, or figs of thistles?... Wherefore by their fruits ye shall know them.” These classical words surely have a special value for the eugenist. As we have said, it is his particular necessity, alike in theory and in practice, to “know” the real nature, the innate, inherent, germinal characters, of the individuals who may or may not be parents: and these, as we have seen, are frequently obscured by the action of the environment--as, for instance, in the population of the slums on the one hand, or the man of factitious culture on the other hand. But “by their fruits ye shall know them.” In general, the children inherit what was innate in their parents, and in many an instance the surest way in which you could ascertain what the parent really was by nature--what, as we say, Nature “meant” him to be--is by a study of his children. Only, of course, we must take the children very young indeed, before environment has made its mark upon them also, for better or for worse. Thus, when we find the new-born baby of some pallid, half-starved, stunted mother in the slums, to be healthy and vigorous and beautiful,[27] by this fruit we shall know what the mother might and should have been. A healthy baby goes far to demonstrate that the stock is healthy. This is one of the cardinal truths which emerge from the study of infant mortality, and it may be perhaps permitted to warn some students of race-culture of the errors into which they are bound to fall if they do not reckon with what the student of infant mortality is constantly asserting: viz., that the babies of the slums, seen early, before ignorance and neglect have had their way with them, are physically vigorous and promising in certainly not less than ninety per cent. of cases. This primarily demonstrates, of course, the murderous nature of our infant mortality; but it also demonstrates to the eugenist that these classes are perhaps not so unworthy as he may fancy. By their new-born babies ye shall know them. It is under the influence of such considerations that the present writer, for one, is somewhat chary of predictions and proposals based upon the relative fertility of different classes of the community or of the masses as compared with the classes. Directly the eugenist begins to talk in terms of _social_ classes (as Mr. Galton has never done), he is skating on thin ice, and if it lets him through, he will find the remains of many of his rash predecessors beneath it.[28] In fine, then, if we observe the distinction between the innate and the acquired, which is the distinction between the transmissible and the intransmissible, this is so far from denying the fact of heredity at all as in reality to emphasise its potency whilst undoubtedly diminishing its range.