(3) Special lectures on sex-hygiene independent of biology or general hygiene are at best makeshifts, and not without dangers. I fear the effect of the abrupt introduction to sex problems by special lectures, especially for girls who may be shocked much more than the average boys can be. I heartily sympathize with parents and school officials who object to special lectures that suddenly focus attention on problems of sexual health. It seems to me that special lectures should be given only when no other method of teaching is possible. This applies especially to young people who are not in schools. While I have stressed biological nature-study as offering the ideal basis for the broadest kind of sex-education, I realize that there are cases where such study cannot be held prerequisite to some aspects of sex-hygiene that young people should know. However, we should aim to make such cases the exceptions and not the rule. Some good may be accomplished by teaching certain facts of sex-hygiene frankly and directly to those who have absolutely no knowledge of nature-study and biology; but after watching the reactions of groups of boys who were receiving such information, I have been convinced that even with a limit of one hour for instruction a biological setting is decidedly important in that it gives an indirect approach. (4) Special books and pamphlets are useful when, and only when, the above methods are impossible, but certain cautions are desirable (see Sec. 22). [Sidenote: Difficulty in ethical-social teaching.] The third aim involves some difficult educational problems. Since we confess that we know so little concerning efficient methods for ethical, moral, or social teaching, it is evident that we must be far from a satisfactory plan for dealing with instruction which is intended to oppose most powerful instinctive tendencies and long-established habits of sensuality. Clearly the third aim sets no easy task for the educator; but since the possible solution of sex problems must turn on the sex actions of the individual in relation to society, the ethical-social aspects of sex-education must not be evaded because the way is not yet entirely clear. The fact is that a good beginning has been made, especially in teaching concerning social diseases, heredity, and eugenics. [Sidenote: Social hygiene and ethics.]