In the first chapter is discussed the practical importance of "Play," not only in offering the opportunity for sensory, central, and motor development in the child, but for releasing the broader life energies of the adult whose mind is confined by specializing work. It is shown that the fundamental motives of the play life are to be found in religion. The next three chapters, on "Serviceable Memory," "Mental Efficiency," and "Mental Health," are full of sound practical advice. The first contains a clear and attractive presentation of the principles of remembering, so arranged as to exemplify the rules which it inculcates. The second emphasizes the importance of the wave form of attention in all mental work, the superiority of efferent to afferent response as an educational process, and the acquirement of mastery by a transfer of control from higher to lower mental levels. There is also good counsel with regard to the best time and manner in which to rest, although the author's deductions from the physiological "curve of sleep" appear somewhat hasty. "Mental Health" is defined in terms of our mental "members" in the classical way, and the "Ten Maxims of Wise Living," which are given, are selected from the history of moral philosophy rather than from current psychotherapeutic results. The chapter on "Mental Law" is the most interesting one for the theoretical psychologist, and discusses in a general but illuminating manner, principles of perception and of perseveration which are of interest to the psychological psychiatrist. The chapter on "Law in Illusion" seems disproportionately long, but gives an interesting description and analysis of three different types of illusions: those based on "units of direction," the over-estimation of "cylinder height," and upon the "size-weight" error. In connection with the second, the results of original investigations in the author's laboratory are presented. It is shown that a knowledge of the complex but definite principles underlying illusions can be made practically serviceable, for example, in tests of mental normality. The final chapter deals with a specific illustrative problem in "Mental Measurement," viz. the determination of a subject's fitness for a musical career. A detailed analysis of the problem is offered, and it is shown that the elemental questions involved can be answered by the methods of the psychological laboratory, but that these answers require expert interpretation before they can be made practically applicable. The author's style is engaging and clear. LEONARD THOMPSON TROLAND. AN OUTLINE OF PSYCHOBIOLOGY. By Knight Dunlap, Associate Professor of Psychology in the Johns Hopkins University. Baltimore, The Johns Hopkins Press, 1914. Pp. 121, octavo; illustrated.