If, then, such be the case; if even now there are civilized countries and classes of people who openly profess prudential reasons as the best for marrying, it will only require a better education of public opinion to enable men to advance to the position that the physical and mental vigor of the resulting children is a motive to be consciously considered in the selection. We may first reach the stage of avoiding an hereditary taint as people now fly an infectious disease. Such avoidance would ultimately stamp out or reduce to a minimum this evil, and the race would escape a great part of the direst and most hopeless of its physical miseries. Then the systematic and deliberate desire that there should be healthy children will discover many conditions now unknown, when so many of our unions are the result of chance or avarice, or, still worse, of passion. Men of science will begin to make observations on the difference of physical antecedents which cause such curious differences in children of the same house. And the day will come when, from a body of such observations, valuable practical rules may be deduced. We may thus improve our race as the Spartans did in old Greece; and they, we know, were perfectly successful in obtaining what they sought--a high average of physical strength and beauty. All this, we may hope, will only be the introduction to a far more important, but far more difficult, problem--the determining of the conditions which produce genius. There is no reason to doubt that these conditions are mainly transient, for genius is no fixed heritage, the most splendid instances coming from obscure and ordinary parents. Nor does the mere combination of the suitable parents work its effect uniformly without other more limited conditions. For we find the great leaders of the world sometimes the only child, sometimes eldest, sometimes youngest, or in the middle of a family of brothers and sisters as obscure as their parents. The careful observation, then, not only of the parents, but of the particular passage in their life which produced an intellectually splendid offspring, is one upon which we cannot expect light for a long time, and until people have become accustomed to regard the general improvement of the race of far greater importance than they now do. If such results could be obtained even approximately--if, even in one case out of ten, intellectual excellence could be produced as we reproduce physical perfections--then, indeed, the perfectibility of mankind would no longer be a vague dream, but would show some signs of a partial fulfilment.