ME. Gr. J. EOMANES ON THE LOCOMOTOE SYSTEM OE MEDUSiE. 
703 
stimulation is being applied in the bell somewhere ; for every time any portion of 
tissue below the cut a is irritated, the polypite actively dodges about from one part of 
the bell to another, applying its extremity now to this place and now to that one, as if 
seeking in vain for the offending body. If the stimulation is persistent, the polypite 
will every now and then pause for a few seconds, as if trying to decide from which 
direction the stimulation is proceeding, and will then suddenly move over and apply 
its extremity, perhaps, to the point that is opposite to the one which it is endeavouring 
to find. It will then suddenly leave this point and try another, and then another 
and another, and so on, as long as the stimulation is continued. Moreover, it is 
important to observe that there are gradations between the ability of the polypite to 
localize correctly and its inability to localize at all — these gradations being determined 
by the circumferential distance from the end of the cut at which the stimulus is applied, 
and also by the radial distance between the cut and the point of stimulation. For 
instance, in figure 1 suppose a cut AB, ^ of an inch long, to be made pretty close to 
the margin and concentric with it, then a stimulus applied at the point c , just below 
the middle point of A B, would have the effect of making the polypite move about 
to various parts of the bell, without being able in the least degree to localize the 
seat of irritation. But if the stimulus be applied at d, the polypite will probably 
be so far able to localize the seat of irritation as to confine its movements, in its search 
for the offending body, to perhaps the quadrant of the bell in which the stimulation 
is being applied. If the stimulation be now applied at e, the localization on the part 
of the polypite will be still more accurate; and if applied at f (that is, almost beneath 
one end of the cut AB) the polypite may succeed in localizing quite correctly. 
These facts may also be well brought out by another mode of section, which is 
described in my former paper as “ cutting round a greater or less extent of the mar- 
ginal tissue, leaving one end of the resulting strip free, and the other end attached 
in situ.” If this form of section be practised on Tiarojpsis indicans , as represented at 
g , k in the figure, it may always be observed that irritation of a distant point in the mar- 
ginal strip, such as g or h, causes the polypite to move in various directions, without any 
special reference to that part of the bell which the irritated point of the marginal strip 
would occupy if in situ. But if the stimulation be applied only one or two millims. 
from the point of attachment of the marginal strip, as at i, the polypite will confine its 
localizing motions to perhaps the proper quadrant of the bell ; and if the stimulus be 
applied still nearer to the attachment of the severed strip, as at j, the localizing 
motions of the polypite may become quite accurate. 
Again, with regard to radial distance, if the cut AB in the figure were situated higher 
up in the bell, as at AB', and the arc, c, d, e, f, of the margin irritated as before, the 
polypite would be able to localize better than if, as before, the radial distance between 
AB and c, d, e,f were less. The greater this radial distance, the better would be the 
localizing power of the polypite ; so that, for instance, if the cut A'B' were situated 
nearly at the base of the polypite, the latter organ might be able to localize correctly 
