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Show 1867.] DR. J. S. BOWERBANK ON HYALONEMA MIRABILE. 25 imbedded in such large quantities in the latter tissue might, by a great stretch of imagination, be thought to have been selected from other extraneous matters around and thus appropriated ; but this solution of their presence in the valvular structure of the supposed polype, deeply imbedded in its sarcodous membranes, is certainly inadmissible. In the valvular structures they are in a position in which secretion alone can account for their presence ; and their appearance under such circumstances incontrovertibly connects them with the corium on which the so-called polypes are based ; so, in like manner, their abundant presence in the inner corium, and still more profuse occurrence in the basal sponge, connects the corium and basal sponge unmistakeably together. W e have therefore, by means of these peculiar and very striking forms of spicula, a sequence of proof of a most conclusive character that the whole of the structures present in the most perfect specimens of Hyalonema are parts of one and the same animal. Professors Brandt, Bocage, and Max Schultze, in their respective papers on Hyalonema, believed that they had detected tentacula within the heads of the oscular projections ; and the former two have each figured what they regard as those organs with powers of about 4 or 5 linear. The figures of the supposed tentacles of the first and second named authors differ exceedingly; and if each be correct, their supposed polypes cannot belong to the same genus. The former author does not seem to have much faith in the reality of what he depicts, as in the description of the figure 8. tab. 2, in his work, he writes, " quoad tentacula expansa idealis." I have no doubt that by soaking the oscular projections in a solution of caustic potass, and by pressure or a little clever manipulation on the softened and half-destroyed tissues of the valvular structure within them, their motive fibres, which pass inward from the inner surface towards the central diaphragm, may be loosened and withdrawn from the apical orifice, and so disposed by pressure or otherwise as to readily deceive an observer whose mind was previously occupied by a foregone conclusion. I am well acquainted with the polype-cases of Zoanthus couchii in the form of Dysidea papnllosa, Johnston. They are stout open tubes, composed of sand cemented together by animal matter, and they have nothing within them like the elaborate keratose valvular apparatus that we find in the distal ends of the oscular projections in Hyalonema; in fact their apices are permanently open when the polypes, their former occupants, are destroyed. Nor have they at any time any appearance of tentacles upon them. Those organs at all times appertain to the soft retractile polypes, and not to the poly-pidoms that they inhabit. It has been suggested that Hyalonema really consists of the basal spongeous mass, the spiral column of spicula, and the inner sheath that surrounds it; while the outer sheath is a parasitical Zoanthoid Coral. But a careful examination of the two sheaths surrounding the column affords such evidences of the identity of their structures as to forcibly negative this supposition. |