=The eugenic difficulty.=--But it will be already evident to the reader that, though Spencer's law offers hope and warrant to the eugenist, it also poses him with a permanent and ineradicable difficulty which is inherent in natural necessity--viz., the difficulty that, in consequence of the operation of this law, those very classes or members of a society whose parenthood he most desires must be, in general, the least fertile. Throughout the animal world the lesser fertility of higher species is no real handicap to them, as we know; but where the conditions of selection are so profoundly modified as in human society, the case is very different. Furthermore, amongst mankind individuality has often grown, and does grow, to such an extent that parenthood disappears altogether. Indeed, Spencer's law expresses itself--and the eugenist must qualify his hopes by the fact--in the practical infertility of many[25] of the most highly individualised and even unique personalities, that is to say, in the ranks of what we call genius. To this subject we must return. A notable section in Mr. Galton's great work, _Inquiries into Human Faculty_, states very plainly the difficulty for the eugenist involved in Spencer's law, under its more statistical aspect. What are the relative effects of early and late marriages? Mr. Galton proves, mathematically, that in a very few generations a group of persons who marry late will be simply bred down and more than supplanted by those who marry early. Now no one will dispute that the less individualised, the lower types, the more nearly animal, do in general marry earlier, and are more fertile. Here, then, is an anti-eugenic tendency in human society, depending really upon Spencer's law and requiring us to recognise and counteract it by throwing all the weight we can upon the side of progress, which means _increasing to our utmost the survival-value and the effective fertility of the higher types_.