place; these have the effect of keeping unchanged the retinal relations of the image cast by the illuminated spot, and being undiscriminated in the consciousness of the observer the position of the point of regard is apprehended by him as stationary. The biological importance of such facile and unconscious adjustment of the mechanism of vision to the moving object needs no emphasis; but the relation of these obscure movements of the eyes to the process of determining the plane of the subjective horizon should be pointed out. The sense of horizontality in the axes of vision is a transient experience, inner conviction being at its highest in the first moments of perception and declining so characteristically from this maximum that in almost every case the individual judgment long dwelt upon is unsatisfactory to the observer. This change I conceive to be a secondary phenomenon due to the appearance of the visual wanderings already described. VIII. The influence of sensory reflexes in the eye upon the process of visual orientation was next taken up in connection with two specific types of stimulation. At top and bottom of the vertical screen were arranged dark lanterns consisting of electric bulbs enclosed in blackened boxes, the fronts of which were covered with a series of sheets of white tissue-paper, by which the light was decentralized and reduced in intensity, and of blue glass, by which the yellow quality of the light was neutralized. Either of these lanterns could be illuminated at will by the pressure of a button. All other experimental conditions remained unchanged. The observers were directed to pay no special regard to these lights, and the reports show that in almost every case they had no conscious relation to the judgment. The results are presented in the following table: TABLE X. Light Below. Light Above. Observer. Const.Err. Av.Dev. M.Var. Const.Err. Av.Dev. M.Var. _C_ (40) +156.37 156.37 19.67 +169.85 169.85 19.22 _D_ (20) + 39.30 43.30 17.95 + 46.65 47.35 15.41 _F_ (30) + 19.47 19.47 8.83 + 58.37 58.37 7.83 _G_ (50) + 66.11 112.76 14.65 +117.86 117.86 13.10 _H_ (30) -147.63 147.63 21.07 -105.30 105.30 30.31 _J_ (20) + 1.90 31.95 22.33 + 44.40 44.40 20.55 Average: + 22.59 85.28 17.42 + 55.30 90.52 17.74