fade, but seems to suffer a sudden and total eclipse; whereas the
second streak flashes out suddenly _in situ_, but at a lesser
brilliancy than the other, and very slowly fades away.

These observations thoroughly confirmed those of Schwarz. And one
could not avoid the conviction that Schwarz's suggestion of the two
streaks being separate localizations of the same retinal stimulation
was an extremely shrewd conjecture. The facts speak strongly in its
favor; first, that when the arc of movement is rather long, there is a
distinct feeling of succession between the appearances of the falsely
and the correctly localized images; second, that when both streaks are
seen, the correct streak is always noticeably dimmer than the false
streak.

It is of course perfectly conceivable that the feeling of succession
is an illusion (which will itself then need to be explained), and that
the streak is seen continuously, its spacial reference only undergoing
an instantaneous substitution. If this is the case, it is singular
that the correctly seen streak seems to enter consciousness so much
reduced as to intensity below that of the false streak when it was
eclipsed. Whereas, if a momentary anæsthesia could be demonstrated,
both the feeling of succession and the discontinuity of the
intensities would be explained (since during the anæsthesia the
after-image on the retina would have faded). This last interpretation
would be entirely in accordance with the observations of
McDougall,[17] who reports some cases in which after-images are
intermittently present to consciousness, and fade during their
eclipse, so that they reappear always noticeably dimmer than when they
disappeared.