Practically we see the significance of these differences. No manufacturer thinks of making one size of overall in the hope that it will fit each of these men. He adapts his garment to their size, and he knows approximately how many of each size will be called for in the course of ordinary business. If these same men could be taken one by one into a music studio and have their voices tested for range, the same interesting variations would be found. There would be a few very high tenors, a few exceptionally low bassos, and a crowd with medium range with fillers-in all along the line. If we were interested in carrying the experiment still further we might apply the speed test. In a 100-yard dash a few men would be found to be particularly fast, a few others would trail away behind at a snail's pace, while the big crowd of men would make the distance in "average time." Of course, it would be foolish to attempt to make tenors of all these men--equally foolish to try to make speeders of them all. In these practical matters we appreciate the wisdom of letting each man fit into that niche for which he is qualified. Nor are these differences confined to the field of physical characteristics and achievements. Tests by the hundred have demonstrated beyond all question that they hold equally well of mental capabilities. In the past children have gone to school at the age of six. They have remained there because they were six. At seven they were in grade two, and so on up through the grades of our public schools. Tests and measurements now, however, are showing that such a procedure works both a hardship and an injustice on the pupils. Some boys at six are found as capable of doing work in grade two as other boys at eight. Some boys and girls at six are found wholly incapable of doing what is required in grade one. One of the most promising prospects ahead educationally is that we shall be able to find out just the capacity of a child regardless of his age, and fit him into what he can do well, making provisions for his passing on as he shows capability for higher work. Not only has this matter of individual differences been found to apply generally in the various grades of our schools--it has been found to have significant bearing upon achievements in particular subjects. For all too long a time we have held a boy in grade four until he mastered what we have called his grade four arithmetic, spelling, geography, grammar, history, etc. As a matter of fact, many a boy who is a fourth-grader in grammar may be only a second-grader in arithmetic--a girl, for whom fourth grade arithmetic is an impossibility, because of her special liking for reading, may be seventh grade in her capacity in that subject. In the specific subjects, individual differences have been found to be most marked. Surely it is unfair to ask a boy "born short" in history to keep up to the pace of a comrade "born long" in that