The author’s answer is, that this phenomenon is a consequence of the well-known fact that we overestimate small angles, and underestimate large ones. The presence of the lines has nothing to do with the optical illusion, as the inserted cut, in which the lines are omitted, shows. (Cut 2.) The optical illusion is also not present when the lines are rectangularly attached, as is Cut 3. These facts prove that angular _inclination_ is the decisive factor. The following cuts show this, the first in a more and the second in a less marked degree. (Cuts 4, 5.) The simplest case in which the explanatory factor of this phenomenon is involved, is that of the estimation of the distance of an isolated point from the extremities of a short straight line. The estimation of this distance is dependent upon our estimation of the angle made by lines drawn from the point to the extremities of a short line. If this estimation is false, it produces by an exact trigonometrical law, an error in the estimation of the corresponding distance. This explains all. In our first figure the factor of illusion is eight times presented: hence its marked character. The second article consists of a rather long series of experiments on the so-called “flatternde Herzen” by Adolph Szili. The third article is on the foundations of a psychology of the blind, by a blind man, Friedrich Hitschmann, of Vienna. This article contains a number of interesting facts concerning the sensory, intellectual, and emotional life of blind people, and affords a great many valuable hints for the development of the special psychology which the author has in view. The first article of No. 6 of the _Zeitschrift_ is a very exhaustive one, some sixty pages in length, filled with special and technical investigations concerning the dioptrics of the eye. When light passes from one refracting medium into another it is partially reflected at the dividing surface, and transmits by reflection the objects from which it has proceeded. This is also the case with the human eye, which is itself a lens. The refracted pictures are the only pictures of importance to the possessor of the eye; but just as in the construction of optical instruments, the reflected or “lost” images are of supreme importance to the optician in the determination of the properties of his productions, so these same pictures in the human eye are of supreme importance to the physiologist and the psychologist. This is the subject of Dr. Tscherning’s researches.