Strictly speaking, entoptic phenomena are concerned with the autovisualization of certain structures within the eye through the propitious arrangement of incident light. These structures may be normal to the eye or they may be pathologic imperfections, such as opacities in the vitreous or lenticular flaws. Pressure and traction on the retina and the optic nerve may cause subjective awareness of these structures by evoking from their highly differentiated pathways various sensations resembling those induced by light : There must be included under the heading of entoptic, therefore, a number of phenomena which result from these nonspecific (inadequate) stimuli. The general subject has been covered thoroughly in the works of von Helmholtz, Duke-Elder and Adler and in the recent "Traité d'ophtalmologie." It is the purpose of this paper to dwell chiefly on several observations and explanations which are wholly or in part original in character. The data have been accumulated during the