28. When the pedalia were cut off from one, the power of direct motion was entirely gone. It swam in circles, turned summersaults, changed its course continually, the oral end getting ahead of the aboral end, or trying to do so. The whole power of balancing was gone. It seemed excited by the operation and swam continually. [Repeated.]
29. The pedalia can be made to contract inwards by stroking their outer edge with a needle. This was noted last year and has been seen several times this year. Their inner edge is not so sensitive.
Touching a sensory club caused the pedalia to contract inwards in two cases.
The pedalia could be made to contract by giving the subumbrella a prick,—generally a rather severe one was necessary. The upper part of the subumbrella seems not so sensitive as the lower part and the proboscis, and the base of the stomach did not give any reflex at all (two specimens). One of the two could be made to give the reflex only with much difficulty. This was a very lively one. It would even stand severe pricks on the nerve, or even through the region of the sensory clubs, without contracting the pedalia or stopping pulsations.
Cutting the frenula seemed not to affect the ability to swim well. Cutting in this region brings about the reflex of the pedalia.
In the preceding fish the velarium was cut away wholly in some places, in other places it was left only as ragged strips. The pedalia became very strongly contracted and the tentacles were brought inside the bell. Pulsations that seemed strong produced much less progress than with the velarium intact. [Repeated.]
30. One with the whole margin cut off still gave pulsations. Upon the removal of the region of the radial ganglia, however, pulsations were seen no more.
The velarium in the above continued to give twitchings. The four pedalia were cut off with plenty of the tissue at their bases to insure the removal of interradial ganglia, and twitchings of the velarium with irregular contractions continued. No full contraction all around the velarium was noticed. When all the tissue was trimmed off as nearly as possible down to the velarium, the latter still gave twitchings and irregular contractions as before,—even more so as if excited by the operation. The power of originating contractions evidently resides in the velarium or in the ganglion cells of the frenula just as it does in the proboscis and the floor of the stomach.
Small pieces cut from between the pedalium corners and the frenula, so as to have tissue on them from neither, could contract by themselves. (See also for Pedalia, Experiments [15], [23], [41b]; Velarium [18], [41c].)