Activity of Charybdea.—41. a. About five o’clock in the morning a Charybdea was taken in the tow. It was in good condition swimming incessantly round and round without change of direction, in a jar of about twenty centimeters in diameter. It came to the surface every now and then, after eight to fifteen pulsations. The tentacles and the phacelli were of a lilac shade. If a pencil was placed in its way it would pulsate against it repeatedly without any effort to dodge around it.
| 6.58 | A. M., | 124 | pulsations | were | counted | to the | minute. |
| 8.00 | “ | 124 | “ | “ | “ | “ | “ |
| 9.25 | “ | 136 | “ | “ | “ | “ | “ |
| 10.15 | “ | 131 | “ | “ | “ | “ | “ |
| 11.00 | “ | 146 | “ | “ | “ | “ | “ |
At 10.15 it went around the dish in eight seconds, taking eighteen or nineteen pulsations. If a bright platinum spatula or a black pencil was placed in its circuit it would repeatedly butt against it each time it came around. After the second or third pulsation against it, however, it seemed to have some sense to change its direction.
b. The pedalia have no perceptible action of their own. They move inwards slightly toward the axis at each pulsation, but scarcely as much as one would suppose from their attachment to the pulsating margin. It seems as if they were for “winging” the moving animal more than for anything else.
c. The velarium is loose and it flaps. It seems to take part in swimming something more than the passive diaphragm function,—i. e., it straightens out during the recovery after each contraction of the bell.
Aurelia and Polyclonia.
[The following experiments were performed at Port Henderson, Jamaica, in 1896.]
42. May 12th. An Aurelia was pulsating normally at the rate of twenty-five or twenty-six pulsations to the half-minute. One lithocyst was cut out, when a few contractions, evidently caused by the stimulus of cutting, followed; then, rest. In the first minute there were only about five pulsations. In two or three minutes rhythmic pulsations were resumed. Four minutes after the cutting there were nineteen pulsations to the half-minute. About twenty minutes after there were nine to the half-minute, in groups of six and three.
A Polyclonia, about four and one-half inches (115 mm.) in diameter, gave twenty-six or twenty-seven regular pulsations to the half-minute. After one otocyst was removed, pulsations continued, but in groups with intervals of pause: e. g., thirteen, pause; ten, pause; six. Three minutes after the removal of the lithocyst there were 5, 3, 1, 3, 5, or seventeen pulsations to the half-minute. Eleven minutes after the operation there were fifteen to the half-minute. The removed lithocyst and surrounding tissue gave contractions.