28 DR. J. S. BOWERBANK ON HYALONEMA MIRABILE. [Jan. 10, 



ingly long and comparatively few in number, and do not appear to 

 be connected ■nith the parietes of the organ ; while in Ciocahjpta 

 they are short and very numerous, and the axis is connected with 

 the sides of the cloaca. Thus, when we consider the spiral column 

 and its delapidated dermal coating alone, as it is usually received 

 from the Japanese, and without reference to the basal mass of sponge 

 belonging to it in its natural condition, the species presents an ex- 

 ceedingly anomalous appearance ; but when the entire animal is con- 

 sidered and compared with other sponges, the anomaly is dissipated, 

 and it is seen to present very few anatomical and no physiological 

 differences from a numerous series of well-known sponges. 



The dermal membrane of the basal portion of the sponge in the 

 British Museum has been nearly entirely destroyed, a few fragments 

 only remaining /» situ. It appears to have been thin, pellucid, and 

 aspiculous, or with a few adventitious spicula attached to its surface. 

 The numerous inflato-fusiformi-acerate external defensive spicula 

 do not appear to perforate it in the natural condition of the sponge ; 

 but the fragments of the membrane in situ were so small as scarcely 

 to allow of speaking on this point decisively. 



The spicula of the skeleton are exceedingly variable in length and 

 proportions, and are often curved to a very considerable extent, or 

 they are tlexuous ; and amongst them there are occasionally found 

 exceedingly large fusiformi-acerate spicula, the diameters of whicli 

 are equal to that of six or seven of the ordinary s])icula of the ske- 

 leton ; and at irregular intervals we find very large attenuato-rect- 

 angulated hexradiate spicula, which probably served to connect the 

 flakes or layers of the skeleton together (PI. V. lig. 1 a). 



I found but one small group of the external defensive spicula in situ ; 

 but this was exceedingly characteristic. The spicula (Pi. V. fig. 5) 

 are very numerous and closely packed together in parallel lines, and 

 they are apparently projected about half their length beyond the outer 

 surface of the mass of the skeleton. These spicula represent the shaft 

 of an attenuated rcctangulated hexradiate spiculum, with the inflation 

 at about the middle of the shaft, whence the four lateral radii of 

 that form of spiculum would spring. But the striking peculiarity 

 of their structure is the mode of their adaptation as external defen- 

 sive spicula, by tlie projection from all jiarts of the distal half of the 

 shaft of numerous small spines at ascending angles of about 20 de- 

 grees to the long axis of the spiculum ; while on the proximal half 

 of the spiculum there is rarely even the rudiment of a sj)ine to be 

 detected. The central inflation of the spiculum is usually projected 

 beyond the external surface of the mass of the skeleton. A secondary 

 series of defensive spicula are projected from the surface of the mass 

 of the skeleton, and these consist of spiculated cruciform spicula as- 

 cendingly and entirely spinous. They are also exceedingly nume- 

 rous, their cruciform bases all being nearly in the same plane, and 

 their spicular radii nearly parallel to each other, the apices reaching 

 to about the central inflations of the large external defensive spicula. 

 These secondary external defensive spicula are in reality the internal 

 defensive spicula of thg sponge. They are perfectly novel in their 



