During the past decade educators everywhere have been expressing the earnest wish that some man competent to do the work should organize the vast amount of material already accumulated relating to human ontogeny, and interpret it for a theory of education. To accomplish this herculean task one should have considerable familiarity with the methods of investigation and with the more important principles of a number of sciences, especially of biology, palaeontology, pathology, psychology,
... ogy, physiology, sociology; and to these there should be added an intimate acquaintance with education, in its historical, theoretical, and practical aspects, and with the history of philosophy, religion, and what has come to be known as childstudy. In the effort to meet this pressing popular demand there have been a number of attempts within the past half dozen years to organize and evaluate the data in hand concerning special phases of ontogeny, as motor development, linguistic development, and the like. In addition we have been given a few books which have dealt, the majority of them in a very general and quite elementary way, with development as a whole. In method, some have confined themselves very largely to tables and graphs and surfaces of frequency, while others have left statistics aside altogether, and have presented us with generalizations and educational interpretations. These efforts, meritorious as they may be, singly and collectively, still most of them seem preliminary and fragmentary in comparison with Hall's Adolescence. In this book we get the broadest view that has yet been taken, so far as I know, in discussing ontogenetic problems.