Differences of opinion are most apparent in the theory of heredity, where there is a struggle between Darwin's view, that even acquired characteristics are inherited, and Galton's and Weissmann's conviction that this is not the case. In connection with this stands, also, the question of the marriage of consanguineous relations; some regard these marriages as dangerous, _per se_, for the posterity; others only as dangerous from the point of view that the same family trait is often found in both parents, and so becomes strongly impressed on the children. For example, congenital shortsightedness of both parents develops into blindness of the children, their stupidity becomes idiocy, their melancholy, insanity. The Occident has gradually abolished the Oriental marriage law to which Moses gave validity, while other Oriental legislators, for example, Manes and Mohammed, are still followed to a great extent. In China, too, similar prohibitions have a binding power. Here and there the feeling of the significance of heredity has vaguely appeared in some Occidental writers. Sir Thomas More, like Plato, required a physical examination before entering into marriage. It was not until the nineteenth century that the question of the rights of the child in this respect began to be noticed. It was Robert Owen who in one way awakened the general right feeling in favour of children, by investigations begun in 1815. They showed that children under eight years old were forced to work by blows from leather whips, to work from fifteen to sixteen hours a day, with the result that a fourth or fifth of them ended as cripples. Another Englishman, Malthus, published in 1798 an essay on the _Principle of Population_, and directed the attention of society to the conditions which had caused him to write his work. He pointed to the deficiency of food supply produced by over-population and the obstacles it offered to legitimate marriages. Again, these conditions, he showed, resulted partly in great mortality among children, partly in the murder of children. Malthus saw the significance of selection and the danger of degeneration. With perfect calmness of conscience he met the storm he had evoked. Personally a blameless and tender hearted man, Malthus, as all other reformers of moral ideas, had to allow the shameless accusations of corruption and immorality to pass over his head. Harriet Martineau, who advocated Malthus's views, had the same experience. When she wrote her novels on this subject she knew very well to what she was exposing herself; but this remarkable woman, who died unmarried and childless, was at an early period of her life filled with a feeling for the holiness of the child. When nineteen years old, at the time of the birth of a small sister, she fell on her knees and devoutly thanked God that she had been allowed to be the witness of the great wonder of the development of the human being from the beginning. The same feeling