Physiology and histology of the Cubomedusæ / including Dr. F.S. Conant's notes on the physiology

by E. W. Berger

Concretions—Experiments [10], [11].—The four concretions were removed from each of four animals. Two of these (Experiments [10], and another (X), not appended, to save space) seemed to be little if at all affected by the operation. One of the two ([10]) swam actively, at first up and down more changeably than those intact, but later mostly near the surface. The other one also swam actively and showed nothing to indicate weakened sense-perception. The other two ([11]) did not stand the operation well, as Conant remarks, and immediately went to the bottom, where they remained, one swimming, while eight hours later one was still in good condition.

Several attempts with stronger light by removing the coat from the jar made no difference in the behavior of [10]; it continued to swim as heretofore. Upon a final trial, however, with removing the coat, it went to the bottom, thus showing a possible reaction to light; but when next seen it was keeping to the bottom.

That the concretions should function as organs of light sensation, as the first of the above animals might seem to indicate, I believe is out of the question.[a] The fact, too, that this same animal ([10]), together with another (X), swam actively, immediately changing their course upon coming to the surface, in reality behaving quite as normal animals, hardly permits us to conclude from the behavior of the other two ([11]) that the concretions function directly as organs of equilibrium or space relations. May these concretions not function simply as weights for keeping the sensory clubs with their eyes properly suspended? Since these concretions lie at the lowermost part of the clubs and in closed sacs and unsupported by cilia, it would seem that the above suggestion as to their being weights is not improbable. Direct observation (Experiment [20]) by Conant shows, furthermore, that the clubs always hang with a tendency for the concretions to be lowermost, regardless of the position of the animal.

Again, while they may function as weights, as just explained, the fact that the epithelium of the clubs is flagellated (a flagellum, continued as a nerve fiber, to each cell—see Histology), the supposition lies near that these flagella are the ones influenced by the concretions as the clubs bear against one side of the sensory niche or the other. A somewhat similar view seems to be held by other observers and is noted by Lang in his text-book (“The outer epithelium of the auditory body carries the auditory hairs”). It seems, then, that in functioning as weights for suspending the clubs, they may also serve at the same time for making the pressure of the club against the niche greater than if they were absent, and thus in part serve in equilibrium. On this supposition we should expect, furthermore, that after the removal of the concretions the animal would be little, if at all, affected, since the clubs themselves, without the concretions, would still be of sufficient weight to be influenced by gravity and thus to bear against the walls of the sensory niche. It must be noted, however, that Conant’s experiments upon equilibration in Charybdea are negative. Also, that Charybdea has any auditory sense is negatived by two attempts of Conant’s with a violin—one attempt with the violin near the animals, and another with it in contact with the dish. (From an unpublished note.) Hence, some other word such as sensory or equilibrating should perhaps be substituted for “auditory” in the above quotation.

Removing the concretions from Aurelia gave negative results very similar to those on Charybdea. (Experiment [42].)

Sensory Clubs—Experiments [12-19], [20], [24].—The entire sensory clubs were removed from a number of animals. A paralysis of pulsation followed by a rapid recovery was the usual result. In some instances, however, there was no paralysis, while in others no recovery followed paralysis. This is true in a general way whether one club only or all were removed. While no permanent paralysis followed the removal of one or two clubs, yet permanent paralysis did occur after the removal of a third club, as, of course, also after the removal of a fourth. It is evident, too, that as the removal of the clubs progressed recovery seemed to be weaker after each cutting, except in one case when pulsation seemed to be quickened after the removal of a second club. The pulsations after recovery seemed to be not so strong and regular, often quite feeble, and in one instance in groups. Pieces of tissue with a club attached and pulsating regularly, ceased pulsating after removal of the club, in one instance, however, still giving occasional contractions.

These results are quite the same as those of Romanes[I] on Aurelia, Cyanæa, etc., and of Eimer[IV] on Aurelia, Rhizostoma, Cotylorhyza, etc.[] In these forms Romanes sometimes obtained complete paralysis after the removal of the sensory clubs only, as also after the removal of the whole margin, though this was not marked in Aurelia. In Cyanæa and other forms motor centers seemed to be more abundant than in Aurelia, so that paralysis was oftener followed by recovery. He concludes that while the principal motor centers reside in the lithocysts, other centers doubtless exist that may function vicariously, but that the centers of the margin are more definitely limited to the marginal bodies in the Scyphomedusæ than in the Hydromedusæ, in which the whole margin seems to be replete with centers. He feels positive, furthermore, that no motor centers exist in Aurelia’s margin outside of the marginal bodies (lithocysts). Eimer’s results are essentially the same as Romanes’, so that for a more detailed comparison of the two, Romanes’ works should be consulted.

Romanes’ conclusion for the Hydromedusæ is that the motor centers are not so definitely localized in the marginal bodies, but in the margin generally, the excision of the marginal bodies alone producing only partial paralysis, as would also the removal of the margin from between the marginal bodies, but not so marked. For the Hydromedusæ he concludes, then, that all the centers of spontaneity are definitely localized in the margin, but not limited to the marginal bodies. To this he mentions one exception, namely, Staurophora laciniata, in which another center is found near the margin and two others in two opposite arms of the proboscis.

I made the remark in an abstract ([VI]) on Conant’s notes that Romanes did not obtain recovery of pulsation after removal of all the lithocysts in Aurelia. As noted above, he did obtain recovery, so that Conant’s results on Charybdea and also Aurelia (see Polyclonia and Aurelia) are quite in agreement with Romanes.

The paralysis following the removal of the clubs in Charybdea is evidently, primarily, the result of a loss of a part of its nervous mechanism (motor centers), and, secondarily, of nervous shock, and points to the existence of a definite nervous mechanism in the clubs. The histological evidence is here, as usual, corroborative of the physiological.