Between the 'failures' and the cases when a band of light was seen, no change in the conditions had been introduced except 'an increase of the illumination.' Suppose now this change made just the difference between a stimulation which left _no_ appreciable _after-image_, and one which left _a distinct one_. And is it even possible, in view of the extreme rapidity of eye-movements, that a retinal stimulation of any considerable intensity should not endure after the movement, to be _then_ perceived, whether or not it had been first 'perceived during the movement'? Both of Dodge's experiments are open to the same objection. They do not admit of distinguishing between consciousness of a retinal process during the moment of stimulation, and consciousness of the same process just afterward. In both his cases the stimulation was given during the eye-movement, but there was nothing to prove that it was perceived at just the same moment. Whatever the difficulties of demonstrating an anæsthesia during movement, an experiment which does not observe the mentioned distinction can never disprove the hypothesis. [Illustration: Fig. 2.] For the sake of a better understanding of these bands of light of Dodge, a perimeter was equipped in as nearly the manner described by him (_ibid._, p. 460) as possible. Experiments with the eye moving past a very narrow illuminated slit confirmed his observations. If the light behind the slit was feeble, no band was seen; if moderately bright, a band was always seen. The most striking fact, however, was that the band was not localized behind the slit, but was projected on to that point where the eye came to rest. The band seemed to appear at this point and there to hover until it faded away. This apparent anomaly of localization, which Dodge does not mention, suggests the localization which Schwarz describes of his streaks. Hereupon the apparatus was further modified so that, whereas Dodge had let the stimulation take place only during the movement of the eye across a narrow slit between two walls, now either one of these walls could be taken away, allowing the stimulation to last for one half of the time of movement, and this could be either the first or the second half at pleasure. A plan of the perimeter so arranged is given in Fig. 2.