d than the vanished _h_ of shape 4). This explanation is
rendered more probable by the very rare appearance of shape 5, which
must certainly emerge if ever the eye were to move more slowly than
the pendulum.

The critical fact is, however, that shape 4 _does_ appear to a trained
subject in about one half the trials--a very satisfactory ratio when
one considers the difficulty of timing the beginning of the movement
and its rate exactly to the pendulum.

Lastly, in some cases no image appears at all. This was at first a
source of perplexity, until it was discovered that the image of the
dumb-bell, made specially small so as to be contained within the area
of distinct vision, could also be contained on the blind-spot. With
the pendulum at rest the eye could be so fixed as to see not even the
slight halo which diffuses in the eye and seems to lie about the
dumb-bell. It may well occur, then, that in a movement the image
happens to fall on the blind-spot and not on the fovea. That this
accounts for the cases where no image appears, is proved by the fact
that if both eyes are used, some image is always seen. A binocular
image under normal convergence can of course not fall on both
blind-spots. It may be further said that the shape 4 appears as well
when both eyes are used as with only one. The experiment may indeed as
well be carried on with both eyes.

Some objections must be answered. It may be said that the image of _h_
happens to fall on the blind-spot, _e_ and _e_ being above and below
the same. This is impossible, since the entire image and its halo as
well may lie within the blind-spot. If now _h_ is to be on the
blind-spot, at least one of the end-circles _e_, _e_ will be there
also, whereas shape 4 shows both end-circles of the dumb-bell with
perfect distinctness.

Again, it cannot properly be urged that during the movement the
attention was distracted so as not to 'notice' the handle. The shape
of a dumb-bell was specially chosen for the image so that the weaker
part of the stimulation should lie between two points which should be
clearly noticed. Indeed, if anything, one might expect this central,
connecting link in the image to be apperceptively filled in, even when
it did not come to consciousness as immediate sensation. And it
remains to ask what it is which should distract the attention.

In this connection the appearance under reflex eye-movement compares
interestingly with that under voluntary. If the w