Cutting the nerve causes the pedalia to forcibly contract inwards.
Side, Subumbrella.—24. A whole side was cut out, the transverse cut being above the sensory organ so as to take off [leave off] the radial ganglion also. This pulsated, or rather contracted, nicely. The upper end had been cut just through the suspensorium. It especially gave twitchings like the twitchings of the stomach. The piece was then halved transversely, when the upper part containing the portion of the suspensorium twitched as before while the lower part was not seen to contract again. This was repeated with the same result, except that a portion of the lower part gave a slight contraction several times. The part that contracted was at the upper end of the piece, i. e., nearest the suspensorium. The contractions were also more longitudinal than transverse, as the regular contractions would be.
The piece connected with the sensory clubs of course pulsated nicely. Upon cutting off the sensory club from the stalk, pulsation ceased, but twitching of the velarium continued. This was repeated with the same effect.
In the same animal, in cutting off the sides, the stomach was left, the cut being through the gastric ostium. The floor of the stomach was now cut off by cutting out the four interradial points of attachment. The stomach and the proboscis gave vigorous contractions and tied themselves all up so that I could not cut off the proboscis.
The four pieces of the floor of the stomach left on the interradii gave contractions nicely. The phacelli continued their squirming movements.
25. Cutting off the whole aboral end of the animal excites to very rapid pulsations of the remaining part. The stream, as shown by particles in the water, is apparently stronger out the aboral end than past the velarium.
It seems that I get no good evidence that the subumbrella is able to contract of itself without connection with special nerve centers. In the one case noted (Experiment [31]) I could not be sure but that the part that contracted was intimately associated with the suspensorium or frenulum.
26. A piece of the subumbrella cut off and having, so far as I could determine, no connection with ganglia, frenula, or suspensoria, gave contractions. Another piece was not seen to contract.
A small piece of the subumbrella connected with a club can contract. The proboscis can give contractions of itself when cut off with the base of the stomach. Even a cut-off lip can twitch by itself. A portion of the subumbrella by itself also showed twitchings. (See also Experiments [18], [19], [25], [26], [29], [47], [49].)
Pedalia, Velarium, Radial and Interradial Ganglia.—27. The pedalia with their tentacles were cut off at their bases to insure cutting out the interradial ganglia. The animal could pulsate well enough, but intermittently and without much progress (the velarium, of course, being injured). Cutting one pedalium caused the others to contract.