The emotion of sex-love, so plainly traceable to the reproductive instinct, has its evolution in each normal individual. It develops through various stages as do other instincts. It does not make its appearance for the first time at the period of adolescence, as has been thought. Extended and varied experience in the public schools has furnished me with very favorable opportunities for making observations upon children who were allowed to mix freely regardless of sex. Most of the observations were made in schools which, with very few exceptions, had outdoor recesses during which the plays and games brought both sexes together under no restraint other than the ordinary social ones with perhaps some modifications by the particular regimen of the school concerned. The observations relative to the subject of love between the sexes were begun fifteen years ago. The first observations were made incidentally and consisted mainly of those love affairs between children, that needed my attention as one officially concerned. However, many were unquestionably innocent and harmless. My observations have not been limited to children under school conditions. About one-third of the number of cases which I have personally observed have been concerning children who were under the ordinary social or industrial conditions. During the past fifteen years, from time to time, I have collected as many as eight hundred cases observed by myself. In addition to these I have seventeen hundred cases as returns from a syllabus which I circulated among the students in my pedagogy and psychology classes at the Northern Indiana Normal School, at Valparaiso, Ind., in 1896. The syllabus is as follows: I. _Love between children of about the same age and of opposite sex._ Give as completely as you can the details of any such cases you know of; age of each child; length of time the love continued; whether it was mutual; what broke it up; any signs of jealousy; any _expressions_ of love such as confessions, caresses, gifts, etc.; any ideas of marriage; actions in presence of each other free or shy, when alone, when in the presence of others; any tendency of either child to withhold demonstrations and be satisfied to love at a distance; any other details you may have noticed. II. _Love between children and those of opposite sex who are much older._ Give complete details on such points as indicated in I, with whatever differences the disparity in age would naturally make. III. Give fully, frankly, and as accurately as you can the details of your own childish love affairs. IV. Give your name (this may be left blank), age, and sex.