It is hoped that the publication in translation of the work of Binet and Simon in which these tests first appeared, along with the complete series of tests as extended and revised during the lifetime of the former, will tend to remove this twofold misapprehension, and make the educationalist, as well as the wider public interested in social questions, acquainted with the real purpose which underlay the devisal or invention of the tests, and so enable all to perceive that their relative value, as measuring stages of intelligence, must be judged by the purpose for which they were devised. Now, the main purpose of the authors in the devisal of these tests is to furnish to the teacher a _first_ means by which he may single out mentally backward children, who, upon further examination, may also be found to have some mental defect or peculiarity which prevents them from fully profiting by the education of the ordinary school, and who probably would benefit more by being educated in a special school or in a special class. But the final selection, it is contended, of defective children for special education demands the experience of the doctor and of the psychologist, as well as the knowledge of the teacher, and the aid of all three is necessary in the devisal of courses of study for the mentally defective. Especially important is the division of mentally defectives into two main classes--the feeble-minded and the ill-balanced. The latter, as a rule, are easily marked out from the normal child, and, if not specially looked after, may in later life become a menace to society. The feeble-minded, on the other hand, may easily escape the notice of the teacher, and may pass through the ordinary school unaffected and unimproved, enter into society, and propagate their kind. Both classes require the special care of the community, and their proper education and training are of the gravest importance for the welfare and stability of society. In this selection and education of mentally defective children, three positions of Billet and Simon are worthy of consideration. In the first place, it is contended that a physical examination alone can never allow us to dispense with a direct examination of the intelligence, and that "anthropometry, stigmata, and physical appearance must take a second place as means of discovering in school the feeble-minded and the ill-balanced." Again, "mental deficiency and want of balance are peculiar mental conditions which it is often impossible to connect with definite pathological changes." Hence the examination of the medical man is not decisive. It must be accompanied and reinforced by that of the psychologist. In the second place, it is affirmed that in the devisal of schemes of training for mental defectives, we must take into account that the dominant features in their life are the "senses, the concrete perceptions, and motor ability," and that "in the education of defectives the workshop