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Show 32 DR. J. S. BOWERBANK ON HYALONEMA MIRABILE. [Jail. 10, the oscula simulating the forms of the polypidom of many species of Gorgonia. The genus Grantia, with its calcareous skeleton, affords perhaps among the Spongiadce the nearest approach to the structure of the Gorgoniadee ; but there is no possibility of confounding these sponges with any known species of that group ; while, on the contrary side of the question, the basal portion of Hyalonema is nearly assimilated by the peculiarities of the structure of its spicula with the genera Alcyoncellum, Quoy et Gaimard, and Dactylocalyx, Stutchbury; and the singular cloacal appendage projected from the midst of the sponge has its physiological and, to a certain extent, its anatomical parallel in our British genus of sponges, Ciocalypta. That the long spiral spiculous extension, or cloaca, of Hyalonema is intimately connected with, and forms a part of, the skeleton of the sponge cannot reasonably be doubted after a careful examination of the large specimen in the British Museum, in which it will he seen that the skeleton of the basal portion of the sponge enters between, and embraces the long fibres of, the spiral organ, without the intervention of any part of the thick sandy cortex. This dermal coat in the British Museum specimen is in good preservation for several inches in length above the spongeous mass at its base ; but not a vestige of it remains within the mass, nor is there any space between it and that portion of the spiral column passing through it that serves to indicate that it had ever been present in that position ; on the contrary, the sponge embraces the base of the column closely and completely. But if any further evidence of their organic connexion were needed, we have it abundantly furnished by Capt. Tyler's specimen (represented in Pl. IV. fig. 1), in which it is seen that the dermal membrane of the small mass of basal sponge is continued from its distal end up the column, and that it is from this continuous membrane embracing the spiral column that the protuberant oscula are given off. In the specimen represented hy fig. 2. Pl. IV. the distal end of the basal sponge and the proximal one of the corium are coincident in their terminations, and it is distinctly observable that no part of the corium enters the basal mass of sponge. I have not seen the specimen of Hyalonema mirabile in the Bristol Museum ; but I am informed by m y friend Capt. Charles Tyler, who has seen it, that it has a basal mass of sponge very like that of the British Museum one. From portions of the basal mass of the Bristol Museum specimen, presented to Capt. Tyler at the time of his inspection of it, I have obtained precisely the same forms of spicula that exist in the basal portion of the British Museum specimen. I have before stated that, among the specimens in the collection of m y friend Capt. C. Tyler, there were three of the spiral columns that had portions of the basal mass closely adhering to them; and on microscopically examining these portions of the sponges they were found to agree in their organization in every respect with the structures obtained from the two larger and more perfect specimens of the sponge, and also with that represented by fig. 2. Pl. IV. No reasonable doubt can therefore be entertained that these specimens |