Studies of mentality, so well advanced for infants and so well begun for lower grades, are still very meager for adolescent stages so far as they bear on growth in the power to deal with arithmetic, drawing and pictures, puzzles, superstitions, collections, attention, reason, etc. Enough has been done to show that with authority to collect data on plans and by methods that can now be operated and with aid which should now be appropriated by school boards and teachers' associations, incalculable pedagogic economy could be secured and the scientific and professional character of teaching every topic in upper grammar and high school and even in the early college grades be greatly enhanced. To enter upon this laborious task in every branch of study is perhaps our chief present need and duty to our youth in school, although individual studies like that of Binet[21] belong elsewhere. (C) The studies of memory up the grades show characteristic adolescent changes, and some of these results are directly usable in school. Bolton[22] tested the power of 1,500 children to remember and write dictated digits, and found, of course, increasing accuracy with the older pupils. He also found that the memory span increased with age rather than with the growth of intelligence as determined by grade. The pupils depended largely upon visualisation, and this and concentrated attention suggested that growth of memory did not necessarily accompany intellectual advancement. Girls generally surpassed boys, and as with clicks too rapid to be counted, it was found that when the pupils reached the limits of their span, the number of digits was overestimated. The power of concentrated and prolonged attention was tested. The probability of error for the larger number of digits, 7 and 8, decreased in a marked way with the development of pubescence, at least up to fourteen years, with the suggestion of a slight rise again at fifteen. In comprehensive tests of the ability of Chicago children to remember figures seen, heard, or repeated by them, it was found that, from seven to nine, auditory were slightly better remembered than visual impressions. From that age the latter steadily increased over the former. After thirteen, auditory memory increased but little, and was already about ten per cent behind visual, which continued to increase at least till seventeen. Audiovisual memory was better than either alone, and the span of even this was improved when articulatory memory was added. When the tests were made upon pupils of the same age in different grades it was found in Chicago that memory power, whether tested by sight, hearing, or articulation, was best in those pupils whose school standing was highest, and least where standing was lowest.