quate training for experts in psycho-educational and psycho-social diagnosis. The need of extensive research is, of course, paramount. The field is almost virgin soil. But it is doubtful if this need will be adequately met until the work is organized by a properly financed research foundation, or by a government bureau. It is a matter of great surprise to workers in this field who know its large possibilities that it has been totally neglected by the existing foundations and by the government bureaus. This is all the more surprising in view of the fact that there are few fields of investigation which offer larger immediate practical returns on the investment made. Norms established for mental traits can be put to immediate practical use in the grading, classification, and social and educational care of human beings. Surely it is as important properly to care for human beings as to care for animals and plants. The government could well afford to include $100,000 for the psychological investigation of children, in the annual budget of the Bureau of Education. The need of trained and experienced psychological examiners should be obvious. Shall we leave the official mental examination of children to amateurs but insist that our official inspectors of horses and cows must possess the highest technical training? Practically, it will be difficult to induce scientific students to spend three or four years in thorough preparation for this basic and difficult type of public service as long as they are obliged to compete with poorly trained workers whose services can be secured at grade-teachers' salaries, and as long as school, court, and institutional authorities consider that the work of mental classification can be adequately done by psychological amateurs who have learned to give the Binet tests. The moment, however, the true rôle of the Binet tester is understood,- she sustains the same relation to the psychologist as the nurse sustains to the physician, and in this capacity performs a very useful service,— the field will open for the professionally trained, and possibly the officially certified, psychological examiner. J. E. W. W. THE INTRODUCTION HE graded class system of instruction was instituted on on the assumption that children of the same age are approximately equal in mental capacity, and therefore can be most economically, and successfully, taught in groups by uniform methods and a uniform subject matter. Experience has shown that this supposition is only partly true. The pedagogical studies of retardation and the clinical studies of mental backwardness and feeblemindedness conducted in the schools during the last decade or two have demonstrated that pupils of the same age and the same extent of schooling may vary from one year to five years or more in their mental capacity and pedagogical attainments, and that the number of children who thus deviate from the normal is larger than was once thought to be the case. In consequence of these discoveries public-school administrators have begun to realize that the problem of the exceptional child has become one of the most important administrative problems in the schools. In the effort to solve this problem we have attempted to adapt the instruction to the varying needs of each variant pupil, although mainly thus far only to the needs of the child of subnormal capacity. Children of inferior capacity or deficient attainments have been segregated in small numbers in special classes, and provided with specially trained teachers and a special program of work. But it has happened inevitably -as has been so convincingly shown in this book that the differentiations have not always been very accurately made, and that children varying greatly in their type of mental handicap and in their degree of mental capacity have been congregated in the same classes. It is obvious that a type of education suited to |