This experiment leaves it impossible to doubt that the conjecture of Schwarz, that the correct image is only the false one seen over again, is perfectly true. It would be interesting to enquire what it is that conditions the length of the false streak. It is never more than one third that of the correct streak (Fig. 3:1; except of course under the artificial conditions of Fig. 3:3) and may be less. The false streak seems originally to _dart out_ from the light, as described by Lipps, visibly growing in length for a certain distance, and then to be suddenly eclipsed or blotted out _simultaneously_ in all its parts. Whereas the fainter, correct streak flashes into consciousness _all parts at once_, but disappears by fading gradually from one end, the end which lies farther from the light. Certain it is that when the false streak stops growing and is eclipsed, some new central process has intervened. One has next to ask, Is the image continuously conscious, suffering only an instantaneous relocalization, or is there a moment of central anæsthesia between the disappearance of the false streak and the appearance of the other? The relative dimness of the second streak in the _first moment_ of its appearance speaks for such a brief period of anæsthesia, during which the retinal process may have partly subsided. We have now to seek some experimental test which shall demonstrate definitely either the presence or the absence of a central anæsthesia during eye-movements. The question of head-movements will be deferred, although, as we have seen above, these afford equally the phenomenon of twice-localized after-images. IV. THE PENDULUM-TEST FOR ANÆSTHESIA. A. Apparatus must be devised to fulfil the following conditions. A retinal stimulation must be given during an eye-movement. The moment of excitation must be so brief and its intensity so low that the process shall be finished before the eye comes to rest, that is, so that no after-image shall be left to come into consciousness _after_ the movement is over. Yet, on the other hand, it must be positively demonstrated that a stimulation of this _very same_ brief duration and low intensity is amply strong enough to force its way into consciousness if no eye-movement is taking place. If such a stimulation, distinctly perceived when the eye is at rest, should not be perceptible if given while the eye is moving, we should have a valid proof that some central process has intervened during the movement, to shut out the stimulation-image during that brief moment when it might otherwise have been perceived.