The explanation of this phenomenon is found in the method employed to dispell the illusion. It was suggested that, at the moment of the appearance of the phenomenon, the child be requested to fixate the end of the father's index finger which was revolved, in the air, to form various geometrical figures. This had the desired effect. Clearly we have here a case of the object altering its apparent size without altering its distance. Under normal conditions a change in size is followed by a corresponding change in the distance. It is probable that we have here inadequate convergence and that the optic axes do not intersect at the object but beyond, so that the axes are more or less parallel. Thus the feeling of convergence is less intense than experience teaches is necessary to perceive the object as such a size and at such a distance. If degree of convergence is a criterion for distance and if distance is a measure for the apparent size of an object then we have the conditions necessary for the appearance of the illusion. Here we have the retinal image constant for the apparent and the real size of the object (head). Obviously the retinal processes are constant for the two interpretations of magnitude and the ambiguity is due to the concomitant factor of convergence. The conditions necessary to decrease the real size of an object while still maintaining an unaltered image are produced without artificial means. Wheatstone, a long time ago, arranged his stereoscope so that a negative correlation obtained between the degree of convergence and size of the retinal image.[3] [3] Philosophical Transactions, 1852. Very interesting is the fact that Stratton demonstrated by artificial means what was naturally the case in that of the boy reported in the Annals referred to above. Wheatstone demonstrated by artificial means what was naturally the case in that of the girl here reported. REVIEWS FEEBLE-MINDEDNESS, ITS CAUSES AND CONSEQUENCES. By H. H. Goddard. The Macmillan Co., N. Y., 1914. 599 pp., illustrated.