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Show 1867.] DR. J. S. BOW'ERBANK ON HYALONEMA MIRABILE. 31 stitial spiculum (Pl. V. fig. 14). The occurrence of this peculiar form of spiculum in the inner surface of the coriaceous dermis of the spiral column, and also dispersed amid the tissues of the basal mass of the sponge, unmistakeably connects the two as portions of the same individual. The quadrihamate spicula are a variety of form that I have not seen before. The hami are comparatively very long and slender. They are exceedingly minute, requiring a linear power of at least 700 to define them well. They are irregularly and rather sparingly dispersed on the interstitial membranes (Pl. V. fig. 15). From the few patches of sarcode remaining attached to parts of the skeleton, it is probable that it has been both dense and abundant. The fragments preserved are of a deep amber-colour. It is probable that there are more species of the genus than the one described above, as among the material brought up from 2200 fathoms by the soundings in the Indian Ocean, from the ' Herald,' I have seen three distinct varieties of form of multihamate birotulate spicula of a very similar size and character to those found in H. mirabile, but with such structural variations as to indicate their origin in different species. The internal structures of this sponge are strongly indicative of carnivorous habits. The loosely constructed reticulated skeleton would readily admit of the entrance of small annelids ; and when once within the precincts of the sponge their escape would be almost impossible. The powerful cultelliform radii of the fimbriated birotu-tulate spicula entering their bodies would securely hold them as prey ; and every writhing effort they made would contribute to their destruction by a succession of impalements on the spiculated rays of the numerous spiculated cruciform spicula around them, bleeding them to death from numerous punctured and lacerated wounds for the nutrimentation of the sponge; and it will readily be seen that every one of these elaborately constructed organs that I have described are admirably adapted to the purposes that 1 have assigned to them. I cannot agree with Dr. Gray in considering Hyalonema as allied to either the Gorgoniadee or the Zoanthidee. W e know of no compound polypidom, among the Coralliidce or Zoanthidee, or any other division of Zoophyta, in which there is any approach to the secretion of a siliceous skeleton. In all of them, however varied the form may be, that part of the animal is either purely keratose or kerato-calcareous, while in Hyalonema the whole of the skeleton is siliceous ; and this fact alone should have served to distinguish it from Gorgonia. I do not know of any zoophytes which have tentacula upon the polype-cases instead of upon the retractile polype; and in Zoanthus their position is undoubtedly upon the latter-named part of the animal. The form of the oscular mamillae on the spiral cloacal appendage of the animal is very like the polypidom of some Gorgoniee; but this similarity is not enough to justify the assumption that it belongs to that tribe of zoophytes, especially as, in Pachymatisma Johnstonia and other sponges, we find |