Illegitimacy is often due to ignorance of men as well as of women. Prominent physicians have cited from their notebooks cases of "protected" children in early adolescence who instinctively entered into sexual relationship in utter ignorance of the natural result. Such cases where the boy is entirely ignorant must be very rare; but there are probably many boys who do not really understand that the sexual act is very likely to lead to a ruined life for the girl companion and her offspring. Arthur Donnithorne, in "Adam Bede," did not forecast that his act would lead to the ruin of Hetty Sorrel and her condemnation for infanticide. [Sidenote: More than biology needed.] It is obvious that something more than the ordinary biological facts of reproduction must be included in sex-instruction that tries to prevent such tragedies. In another lecture we shall consider moral teaching, but here let us look at the cold facts of life that ought to be taught at some appropriate time to young people. Not only should they know the simple biological probability that sexual relationship will lead to reproduction, but they should be led to consider the relentless consequences of illegitimate propagation. On this latter point general literature, _e.g._, "Adam Bede" and "The Scarlet Letter," teaches some impressive lessons. Another point needs emphasis with the numerous young people, especially men, who are not controlled by moral laws, who know the probabilities of illegitimacy occurring, but who have acquired the popular impression that the order of nature is easily changed. Many physicians and social workers know girls who have gone down because they were persuaded to trust the efficiency of popular ways and means of avoiding the natural outcome of the sexual act. Hence, young people of both sexes should somehow learn that under the conditions that usually attend illicit union there is always a strong probability that the ways of nature cannot be easily circumvented. It is unlawful to explain, except to medical audiences, why this is so; but much illegitimacy will be prevented if it can be made widely known among young men and women that, according to reliable physicians, tragedies of illegitimacy are often due to misplaced confidence in popular methods of contraception. [Sidenote: Criminal operations.] There is yet another line of information that if widely known might have some bearing on the problem of illicit sexual relations: Physicians and social workers report that many young men and some women know the possibility of illegitimate pregnancy, but feel safe because they know the addresses of doctors and midwives who will perform criminal operations. The great danger of the operation, especially at the hands of such third-class doctors as would attempt to terminate pregnancy criminally, should be widely known by the general public, which only now and then gets a hint in the newspaper reports of a tragedy involving some unfortunate girl.