4. Lectures and class instruction should be provided only for carefully selected groups: almost nothing can be gained, and much may be lost, by presenting the subject before miscellaneous audiences. 5. At every age, in every class, there are likely to be individuals who need certain instruction not needed by the entire class: such instruction should be given privately. 6. Books dealing directly with human sex life should not be given to children before the age of puberty; some of the books most widely used are dangerous; instruction should come directly from parent or teacher. 7. Traveling exhibits, made up of concrete and vivid materials, and prepared with due consideration of all the accepted principles of sex education, may be used effectively and inexpensively to bring the truths before many thousands of adults in many places.[64] 8. Against commercialized prostitution, the educational campaign should be one of pitiless publicity: the public should know the names of all persons engaged in promoting the business, whether they are prostitutes (including female _and male), or liquor dealers, owners of houses, owners of real estate, lessees, proprietors, financial backers, policemen, or politicians; their connection with the traffic should be proclaimed by means as effective as the "tin-plate" signs for disorderly houses. 9. Reliable investigations should be made further to reveal the relationships between sexual immorality and venereal diseases, on the one hand, and, on the other hand, between sexual immorality and ignorance, low wages, injurious clothing, lack of wholesome amusements, low dance-halls, grills, moving-picture houses, vaudeville shows and so-called legitimate theaters, mental deficiency, armies and navies, and--most important of all--the liquor traffic; and the outcome of such investigations should be made known through persistent campaigns of public education. 10. The conclusions of every vice commission and of every other dependable investigation--not the details--must be kept before the public, until the truth is common knowledge that segregation never segregates; that safeguarding clinics never safeguard; that medical control never controls; that official protection of immorality increases immorality; and that, if there be any such thing as a necessary evil, it is not the shameless partnership of government and vice.[65] III. MATERIALS 1. Elementary nature-study for children and biological study for boys and girls of high-school age may lead gradually and safely to the teaching of plant and animal reproduction, provided that the subject is not left on the plane of animal life; it is a mistake to suppose that the teaching of biology necessarily promotes right conduct in matters of sex.