120 DIl. J. S. BOWERBANK ON THE SPONGIADjE. [Feb. 6, 



they are broad ; and in one large specimen its breadth is nearly- 

 double its height. The surface-characters are also variable ; some- 

 times, especially in young specimens, they are quite smooth, at 

 others strongly, but irregularly papillated. The apices of the pa- 

 pillae in some are round or flat, and in others they terminate in acute 

 thread-like points. In fact neither the form nor the surface of 

 the sponge affords any reliable specific characters. Some of the 

 specimens attached firmly to fragments of shells were destitute 

 of root-like appendages, and their bases were rounded off like 

 the other parts of the sponge ; others exhibited a broad base 

 with one or two smooth impressions, threw out round their margins 

 short hook-like fleshy claspers with expanded terminations, by which 

 they secured a firm seat on the smooth bodies to which they fixed 

 themselves. In one case the attachment thrown out was a fleshy 

 cylinder an inch in length and 2 lines in diameter, with a flat termi- 

 nation nearly 4 lines in breadth. 



These modes of locating themselves are not peculiar to this spe- 

 cies, but may be observed in many others of the same genus in 

 cases where they are needed. 



When a section of a mature sponge is made, there is the appearance 

 of a thick dermal rind, frequently 3 lines in thickness ; it is composed 

 of innumerable, closely packed,large, subsphero-attenuato-stellate spi- 

 cula, the radii being acutely conical ; and this form, in diminished 

 quantities, is found in the interstitial membranes in all parts of the 

 sponge. 



The dermal membrane is thin ; it is profusely furnished with 

 minute clavate subsphero-stellate spicula, which are so numerous 

 and so closely packed as completely to obscure their forms, in situ, 

 excepting at the extreme edges of the piece of membrane under ex- 

 amination. No other forms of spicula could be detected in the 

 membrane. 



The skeleton-fasciculi radiate in compact curved lines from a cen- 

 tral solid spherical mass nearly 4 inch in diameter. It is composed 

 of condensed sarcode in which is imbedded a large quantity of 

 acuate spicula, smaller than those of the skeleton, but of the same 

 form ; they are disposed without any approach to regularity ; and 

 from the surface of this mass the skeleton-fasciculi radiate in every 

 direction. The hemispherical bases of their spicula all either pene- 

 trate its surface for a short distance, or they are in close conjunction 

 with it. The spicula of the skeleton-fasciculi are exceedingly nu- 

 merous at their commencement at the basal centre of the sponge. 



The interstitial membranes are also abundantly supplied with spi- 

 cula ; the tension ones are rather few in number, but the retentive 

 ones are very numerous. The retentive spicula of the interstitial 

 membranes of most sponges are of the same form and size as those 

 of the dermal membrane ; but this is not the case in the sponge in 

 course of description, in which they vary distinctly from the dermal 

 ones, a very few of which may be occasionally detected dispersed on 

 the membranes at no great distance from the dermal rind. In the 

 deeply seated membranes they all appear to be attenuato-stellate 



