I believe it is well for boys of adolescent years to know a few leading facts regarding female structure and function, but such knowledge is best learned from oral description by a well-balanced teacher. Diagrams and (in some schools) a demonstrated dissection of a cat or other animal will be helpful. The meaning of the ovaries as sources of the egg-cells and of the uterus as the place for development of the fertilized egg-cell should be explained in a serious way that will help boys get some fundamental ideas as to what motherhood means Boys, moreover, should be informed concerning the existence of the periodic disturbance in the other sex, for unless they know they are sure at times to misunderstand their sisters and other girls. Professor W.S. Hall has stated the essential information in "Chums" (for boys twelve to sixteen), but his comparison of periodicity in the two sexes is not strictly accurate, for there are not in men any sexual cycles that are strictly comparable with the menstrual cycles of women. [Sidenote: No pictures.] It is probably best, as urged by several writers, that the life-like illustrations, some of them photographic, in books of human anatomy be kept away from boys of early adolescent age. Diagrams can be made to explain all that is necessary, and without the danger of stimulation that might come from the illustrated medical books. [Sidenote: Embryology.] The embryological facts of human biology are very impressive to boys and young men who know little of science. I believe that no other line of scientific facts is so likely to claim a serious and respectful attitude. The ideal way for giving a popular glimpse at human development is with a small series of lantern slides or photographs from embryological works. Unfortunately, there is no available popular treatment of the main facts of human development, but teachers trained in biology can easily glean the facts for the preparation of a short lecture. [Sidenote: Social diseases.] Since the venereal diseases are due to micro-organisms, I believe that they should be introduced in connection with the study of bacteria and other germs, either in school courses or in popular lectures. Such instruction should be very brief. Sec. 29. _Scientific Facts for Girls_ [Sidenote: Girls more innocent.]