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 tlie Spongiadce the nearest approach to the structure of the 

 Gorgoniadce ; 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 HijaJonema is nearly assimilated 

 by the peculiarities of the structure of its spicula with the genera 

 Alci/oncellum, Quoy et Gaimard, and Dactylocahjx, 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, Ciocahjpta. That the long 

 spiral spiculous extension, or cloaca, of Ihjalonemo. is intimately 

 connected witli, and forms a part of, the skeleton of the sponge can- 

 not reasonably be doubted after a careful examination of the large 

 specimen in the British Museum, in wliich it will be seen that the 

 skeleton of the basal portion of the sponge enters between, and em- 

 braces 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 

 PI. 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 

 goecimen represented by fig. 2. PI. 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 co- 

 rium enters the basal mass of sponge. 



I liave not seen the specimen of Hyalonema mirahile in the Bris- 

 tol Museum ; but I am informed by my 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 IMuseum specimen, presented to Capt. Tyler at the time of 

 his inspection of it, I have obtained precisely the same forms of spi- 

 cula that exist in the basal portion of the British Museum specimen. 

 I have before stated that, among the specimens in the collection of 

 my friend Caj)t. 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 struc- 

 tures obtained from the two larger and more perfect specimens of 

 the sponge, and also with that represented by fig. 2. PI. IV. No 

 reasonable doubt can therefore be entertained that these, specimens 



