1867.] DR. J. S. BOWERBANK ON HYALONEMA MIRABILE. 31 



stitial spiculum (PI. 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, nnmistakeably connects the two as portions of 

 the same individual. 



The quadrihamate spicula are a variet}' 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 dis- 

 persed on the interstitial membranes (PI. V. fig. 1.5). 



From tlic few patches of sarcode remaining attached to parts of the 

 skeleto.i, 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 //. 7ni- 

 rabile, 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 

 Avithin the precincts of the sponge their escape would be almost im- 

 possible. The powerful cultelliform radii of the fimbriated birotu- 

 tulate spicula entering their bodies Avonld securely hold them as prey ; 

 and every writhing effort they made would contribute to their de- 

 struction 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 de- 

 scribed are admirably adapted to the purposes that 1 have assigned 

 to them. 



I cannot agree with Dr. Gray in considering Ihjalonema as allied 

 to either the Gorgoniadin or the Zoanthidce. ^e know of no com- 

 pound polypidom, among the Coralliidce or Zoanthidce^ or any other 

 division of Zoophyta, in which there is any approach to the secre- 

 tion of a siliceous skeleton. In all of them, however varied the 

 form may be, that part of tlie animal is either purely keratose or 

 kerato-calcareous, while in Hyahmema 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 ten- 

 tacula 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 ol' the oscular mamillse on the 

 spiral cloacal appendage of the animal is very like the polypidom 

 of some GorgonicB ; but this similarity is not enough to justify 

 the assumption that it belongs to that tribe of zoophytes, espe- 

 cially as, in Pachymatisma JoJmstonia and other sponges, we find 



