Another simple observation is interesting in this connection. If at any time, except when the eyes are quite fresh, one closes one's eyes and attends to the after-images, some will be found which are so faint as to be just barely distinguishable from the idioretinal light. If the attention is then fixed on one such after-image, and the eyes are moved, the image will suddenly disappear and slowly emerge again after the eyes have come to rest. This disappearance during eye-movements can be observed also on after-images of considerable intensity; these, however, flash back instantly into view, so that the observation is somewhat more difficult. Exner,[2] in speaking of this phenomenon, adds that in general "subjective visual phenomena whose origin lies in the retina, as for instance after-images, Purkinje's vessel-figure, or the phenomena of circulation under discussion, are almost exclusively to be seen when the eye is rigidly fixed on a certain spot: as soon as a movement of the eye is made, the subjective phenomena disappear." [2] Exner, Sigmund, _Zeitschrift f. Psychologie u. Physiologie der Sinnesorgane_, 1890, I., S. 46. The facts here mentioned in no wise contradict a phenomenon recently discussed by McDougall,[3] wherein eye-movements revive sensations which had already faded. Thus an eye-movement will bring back an after-image which was no longer visible. This return to vividness takes place after the movement has been completed, and there is no contention that the image is seen just during the movement. [3] McDougall, W., _Mind_, N.S., X., 1901, p. 52.