As already suggested, a large part of the sex-instruction is simply an extension of biological science, hygiene, and ethics; and in secondary schools and colleges should be given by selected teachers of the regular staff and whenever possible as a part of regular courses. There may be some necessary modifications to this plan; for example, in Teachers College the course on sex-education and another series of lectures on sex-physiology and hygiene for women are open to students who do not take the biology courses in which the sex-instruction logically belongs. [Sidenote: Sex-hygiene and ethics.] The culminating stages of any complete scheme for formal sex-education of young people will be sex-hygiene considered in its strict sense as that special phase of sex-education which deals with problems of health, and sex-ethics which determines the responsibility of individuals for control of sexual instincts. While nature-study and biology and general hygiene may be organized so as to present the major portion of the facts which should be included in a complete scheme of sex-instruction in schools and colleges, the application of these facts to personal life is the most difficult problem of sex-education. In fact, it is the only real problem, for long before sex-education became a definite movement the most efficient science teachers were presenting the fundamental facts on which we now propose to build with certain hygienic and ethic instruction which directly touches the personal life of the student. As already said, the human application will require only a few lessons, preferably in connection with nature-study, biology, ethics, or hygiene. But although brief, such instruction is the keystone in the arch of sex-education, and it is very important that there be no serious mistakes in selecting the teachers. [Sidenote: Sex specialists not desirable.] I have mentioned special teachers as necessary for instruction with direct reference to specialists human life. I hasten to add that I still agree with the report of the special committee (Morrow, _et al._) of the American Federation for Sex Hygiene that it is not desirable that any teacher should make a specialty of this type of instruction and of no other. We do not want "sex specialists" in the schools (see pp. 10 and 20-23 of the Report of the Committee). It is important that all teachers should have general information regarding the sex problems of young people in order to be able to help individual pupils. Sec. 21. _Certain Undesirable Teachers for Special Hygienic and Ethical Instruction_