Comparative anatomy / by C.Th. v. Siebold and H. Stannius ; translated from the German, and edited with notes and additions recording the recent progress of the science by Waldo I. Burnett.

  • Karl Theodor Ernst von Siebold
Date:
1854
Catalogue details

Licence: Public Domain Mark

Credit: Comparative anatomy / by C.Th. v. Siebold and H. Stannius ; translated from the German, and edited with notes and additions recording the recent progress of the science by Waldo I. Burnett. Source: Wellcome Collection.

Provider: This material has been provided by The University of Glasgow Library. The original may be consulted at The University of Glasgow Library.

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    These poisonous and prehensile organs are destroyed by use, which is also true of the nettling organs. But this loss is probably repaired by their speedy reproduction. This last circumstance may explain the various descriptions given them by different authors, for, probably they have been observed at dissimilar stages of development.,3) 3 Erdl, who has discovered a great number of these nettling organs, saw, in some cases, the thread directly continuous with the neck of the vesicle ; in others, these necks appeared furnished with spines directed backwards •, exactly as Wagner had before described, and as Kolliker had often ob- * [§ 28, note 3.] These nettling organs of the Polypi have recently been very successfully studied by A gassiz, who has enjoyed the most enviable advantages with the Polypi and Acalephae of the North American coast. He has changed the entire aspect of the subject, besides almost exhausting it for future research. His special studies were made on the coral polyp of our southern coast, the Astrangia Danae, Agass. The complexity of structure of these lasso-cells, as he has very appropriately termed them, is truly wonderful for such minute forms. As I have also studied these forms, I will use my own language, in the description of what Prof. Agassiz has seen. There are several varieties of these cells or capsules, depending upon the ar- rangement and structure of the lasso ; sometimes this last is a simple coil, sometimes it is coiled about a staff which is erected from the base, but which is also a part of the proje?tile apparatus. In the first case, the lasso is much the longer and may be fifty or seventy-five times the length of the vesicle; while, in the second case, it rarely exceeds the length of this last by more than sixteen or twenty times. In all cases, the essential feature of these organs is the lasso or internal coil, which is of a most curious structure. In the first place, it is, in general terms, only an inverted portion of the vesicle or cell itself, an internal instead of an external cilium, coiled up in a regular manner. When thrown out, there- fore, it is wholly inverted, and its projection consists of an instantaneous turning of the whole inside out. But the lasso, delicate as it is, has still more delicate structures on its surface. These consist of barbels arranged in regular spiral rows, which extend to the very extremity of the lasso. At this last served (Beitrage z. Kenntniss d. Geschlechtsver- haitnisse u. d. Samenfliissigkeit wirbelloser Thiere, 1841, p. 44, fig. 14). Erdl asks if these variations of form are not coincident with an increasing or decreasing activity of the sexual organs (see Muller's Arch. 1842, p. 305). * point, they almost elude the highest and best micro- scopic powers. These barbels all point backwards when the lasso is extended, and serve, no doubt, as teeth, to prevent it from slipping on the objects over which it is thrown. But these most delicate struc- tures, which in beauty transcend that of all other tissues, can be better appreciated by figures than by the most minute description; see Agassiz's Memoir on Astrangia Danae (forthcoming in the “Smithsonian Contributions to Knowledge”), PI. VI. These observations, however, were made in 1848; see Proceed. Amer. Assoc. Advancem. Sc. 1848, p. 68. From my own observations there would, indeed, be nothing to add on the special points studied by Agassiz ; but a remark or two may be made as to the development of these forms. The lasso-vesicle is, originally, only an epithelial cell, of a spheroidal shape. It soon elongates, its contents become cloudy, after which, the coil is seen, very faintly marked, lying on the inner wall. It would seem probable, therefore, that its forma- tion was somewhat similar to that of the spiral vessels in plants, although it is true that the lasso- coils and these spiral vessels are analogous only in form and position, and not in structure. The details of the formation are unknown. These lasso-cells are more widely distributed among the Radiata than hitherto supposed. Agas- siz (as he has informed me by letter) has observed them on most of the Polypi and Acalephae, and even with some of the Mollusca, and although their general structure is the same, there are points of difference of even a zoological value. Editor.