In its practical aspect, this laboratory problem takes the form of the construction of a course of study which harmonizes with the natural history of the growth of the child in capacity and experience. The question is the selection of the kind, variety, and due proportion of subjects, answering most definitely to the dominant needs and powers of a given period of growth, and of those modes of presentation that will cause the selected material to enter vitally into growth. We cannot admit too fully or too freely the limits of our knowledge and the depths of our ignorance in these matters. No one has a complete hold scientifically upon the chief psychological facts of any one year of child life. It would be sheer presumption to claim that just the material best fitted to promote this growth has as yet been discovered. The assumption of an educational laboratory is rather that enough is known of the conditions and modes of growth to make intelligent inquiry possible; and that it is only by acting upon what is already known that more can be found out. The chief point is such experimentation as will add to our reasonable convictions. The demand is to secure arrangements that will permit and encourage freedom of investigation; that will give some assurance that important facts will not be forced out of sight; conditions that will enable the educational practice indicated by the inquiry to be sincerely acted upon, without the distortion and suppression arising from undue dependence upon tradition and preconceived notions. It is in this sense that the school would be an experimental station in education. What, then, are the chief working hypotheses that have been adopted from psychology? What educational counterparts have been hit upon as in some degree in line with the adopted psychology?