Franklin Story Conant

“ In Medusæ it is a common thing to find that in certain definite places of the gastro-vascular system two endodermal surfaces that were primarily separated by a space have come together and fused into a single lamella or plate. Such a structure is called indifferently a cathammal plate, an endodermal lamella, or a vascular lamella. In the adult animal the vascular lamellæ are by virtue of their very nature formations “with a past.” They are scaffolding left in the completed structure, giving us clues as to the way in which that structure was brought about ”

“ It seems in place for me, therefore, to give in the briefest possible way a general idea of their structure, and to pass then at once to the points in which my work has led me to different conclusions from those of Claus and Schewiakoff. In brief, then, the knob of the sensory club consists of a thick, complex mass of nerve fibres, more or less imbedded in which lie the special sensory organs, surrounding the ampulla-like terminal enlargement of the canal. The surface between the special organs is covered with less specialized sensory epithelium. The sensory organs are seven in number. ”

“ We have next to describe the marginal system. The vascular lamellæ mentioned above in every case connected endoderm of one cavity with endoderm of another; those of the margin have the noteworthy difference that they run from endoderms of some part of the [32] gastro-vascular system to ectoderm of the surface. The outermost cells of the endodermal lamellæ make direct connection with the ectodermal cells, without the usual intervention of a layer of gelatine.
The marginal lamella of Charybdea lies, as the name implies, just on the bell margin where the edge is curving round into the velarium. ”

“ The vascular lamellæ of the internal system are the most prominent and morphologically the most important. They comprise the four vertical strips of fusion that separate the four stomach pockets in the interradii (ivl in the figures of the series of cross-sections of Charybdea and Tripedalia, Nos. 6-15 and 21-29) , and four curved horizontal cross-pieces at the top of these which separate the stomach from the stomach pockets, and would make the separation complete did they not leave in each perradius a free space between their ends, which makes possible the gastric ostia. ”

“ When all the rest of the margin grew down and away from the four sensory clubs, fusing below them to form the present intact edge of the bell, the four portions of the nerve ring that lay in the perradii were left at the level of the sensory clubs, and the originally straight nerve ring was thus bent into a bow in each quadrant. The finer structure of the nerve will be treated of in the special part to be devoted to the nervous system. ”

“ The granular deeply staining cytoplasm, the clear non-staining nucleus with its bright nucleolus and the nucleolus-like yolk nucleus, all show beyond doubt that these freely floating cells originate in the ovary.
In some of my preparations these cells are found not only floating free, but wandering through the tissues. Fig. 70 shows two such wandering cells fixed just as they were making their way either through the digestive epithelium into the gelatine of the floor of the stomach, or from the gelatine into the epithelium. ”

“ The supporting cells like those referred to before, are cone-shaped, having a proximal fibrous process that runs into the underlying stratum of nerve fibres, and on the surface of the retina a broad distal pigmented termination. The sensory cells are spindle-shaped, the proximal processes becoming continuous with fibres of the underlying nervous mass, while the distal process runs up to the surface of the retina (the part toward the lens) in between the ends of the supporting cell. The two kinds of cells are accordingly designated as pigment and visual. ”

“ At any rate the gelatinous lobes in the case of Chirodropus on the one hand, and on the other hand the sinuous outline of the margin still mapped out by the lamella in Chirodropus, Chiropsalmus and Tripedalia, are certainly very suggestive of an ancestral Cubomedusa in which there was no velarium, but sixteen free marginal lobes instead. Two more indications favor slightly the same view. In both Charybdea and Tripedalia a small notch is seen in the edge of the velarium in the perradius (Fig. 44) . Its constancy suggests that it may not be a chance or meaningless feature. ”

“ If the long cells with the fibres are, on the other hand, considered [50] the visual cells of Schewiakoff, then again we find nonconformity to a spindle-shaped type, and nuclei not always at a lower level. The matter of alternation of nuclei at different levels seems to me any way too slight a distinction upon which to base a difference in function. It is a necessary mechanical consequence of the crowding together of many cells on one surface. And in many cases in perfectly radial sections through the retina I find the nuclei fewer in number and arranged in very nearly a single level. ”

“ The cone-shaped streaks of pigment in the vitreous body belong to the underlying pigment cells, in fact are direct continuations of them, and at their distal ends they are prolonged into fibrous processes lying in canals of the vitreous body exactly like the visual fibres of Schewiakoff. ”

“ The reproductive organs of both males and females of Cunina proboscidea are said to produce, besides the usual distinctively sexual elements, neutral amœboid germ cells, which wander into the endoderm of the stomach and circular canal, and also penetrate into the gelatine of the subumbrella. ”

“ It seemed hardly probable from an a priori standpoint that in an animal like the crab there should be any necessity for an elaborate nervous mechanism to regulate the beat of the heart, but their experiments placed the matter beyond any doubt, and have since served to call attention to this animal as a promising organism for the study of some of the fundamental problems in the physiology of the heart. ”

“ The suspensoria are much more developed than in Charybdea, so that the interradial funnels lying between are more marked. In a corresponding way the frenula are larger and stouter (Figs. 28, 29, frn) . The musculature shows no new features and differs only in being comparatively more strongly developed and having a more pronounced striation. The nerve ring follows the same looped course from the margin in each interradius up to the level of the sensory clubs in the perradius. ”

“ Stomach. The shape of the stomach is approximately that of a biconvex lens, as seen in Fig. 4, which represents a Charybdea cut in halves longitudinally in the perradius. The lumen of the proboscis (the buccal stomach according to Haeckel’s terminology) communicates directly by a funnel-shaped enlargement with the stomach proper, or central stomach of Haeckel. The term basal stomach is carried over by Haeckel from the Stauromedusæ, where it has considerable significance, to the Cubomedusæ, and applied to the upper part of the central stomach. ”

“ The islands rise but slightly above the level of the waters, and the thick vegetation that covers them, for the most part mangroves, grows out into the water on all sides, forming a fringe of overhanging boughs. ”

“ Fig. 64 is a drawing of the first cut through the vitreous body of Charybdea, and in among the sections of the pigment streaks are seen sections of processes lying within clear spaces exactly as Schewiakoff figures his visual fibres (’89, Taf. II, Fig. 18) . That the fibres occur is indisputable, but as to the cells [53] to which they belong I can say nothing except that from such evidence as I have given in the preceding paragraph I conclude that they come from pigmented retinal cells of not very different type within the retina from the others, if different at all. ”

“ With its tentacles streaming gracefully behind, an actively swimming Charybdea presents a fanciful resemblance to a [8] comet or meteor. When an attempt is made to capture one, it will often escape by going down into deeper water—as indeed do other jelly-fish. Escape from observation is all the more easy by reason of the entire absence of pigment excepting for the small amount in the sensory clubs. The yellowish or brownish color usually stated as common in the Cubomedusæ is nowhere present in C. Xaymacana. ”

“ They apparently must lie imbedded in some clear, watery fluid that does not show in the preserved material. The processes of the epithelial cells give the fibres the appearance of lying in alveoli, or being divided into strands, and one of these strands (ax) is always discernible among the others by reason of its more numerous or finer or more compactly massed fibres. This is the “axis” of Claus. Here and there in its course appear ganglion cells having their long axis in the longitudinal direction of the nerve. ”

“ This sheltered bay is dotted with small mangrove islands which toward the head of the bay become so numerous as virtually to convert it into a mangrove swamp. The water is shallow and discolored with organic matter, showing that the tide does not exercise much influence here, and the bottom is for the most part a black mud, deep enough to make wading very uncomfortable but not impossible near shore. ”

“ From my inability to demonstrate sensory cells in the nerves of Charybdea, I by no means wish to deny their existence; for that remains to be proved, or disproved, by macerations. At any rate, [41] they cannot be so numerous as has been supposed. The position of the nuclei shows that.
The epithelium of the nerve is said by Claus to be ciliated. It has been suggested by Schewiakoff that probably in such cases the sensory cells bear one long cilium, while the supporting cells have many smaller cilia. ”