1873.] DR. J. S. BOWERBANK ON THE SPONGIAD.E. 11 



exceed an inch in diameter. Originally it had been nearly sphe- 

 rical in form ; it was in the dried state when I examined it. 

 When alive it would probably have been about two inches in dia- 

 meter ; and, judging its surface characters by those of the well- 

 known British species T. lyncurium, which in many points it 

 closely resembles in its anatomical characters, it would in the living 

 state have presented a smooth surface, and in the dried state, as 

 shown by the section figured and the microscopical sections in 

 Canada balsam in my possession, it would have been abundantly 

 furnished with large depressed tubercles. 



The oscula and pores are not distinguishable ; nor could I de- 

 tect the slightest indication of a dermal membrane. The dermal 

 rind is more than usually thick in this species of the genus. The 

 closely packed mass of the thick stratum of large sphero-stellate 

 spicula, and their enveloping membranes, of which it is composed, 

 would naturally prove a serious impediment to the inhalant opera- 

 tions of the sponge. To remedy this obstruction, the inhalation is 

 effected through numerous very deep cylindrical depressions, which 

 are found between the corymbose distal terminations of the skeleton- 

 fasciculi ; these depressions form cylindrical sacs the depth of which 

 is three or four times their own diameter, and extending nearly or 

 quite to the inner surface of the dermal rind. Similar but more 

 highly developed organs exist in several species of Geodia, as in G. 

 Barretti and M'Andrewi, through which aerating and nutrient 

 streams have access to the interior of the sponge. 



The skeleton-fasciculi radiate from a central mass composed of 

 numerous loosely compacted bundles of spicula of the same form 

 as those of the skeleton, but very much smaller ; these fasciculi do 

 not appear to have any definite arrangement, but cross each other 

 in every direction. The skeleton-fasciculi proceeding from the 

 central mass are large and closely compacted, and in this state 

 they enter the inner surface of the dermal rind, and commence 

 separating and radiating to form the corymbose terminations at the 

 distal surface of the dermal rind of the sponge ; and they expand 

 to such a degree that the large dermal tubercles thus formed are 

 in very close conjunction on the surface. 



The stellate spicula of this species are very remarkable. The ex- 

 treme diameter of a fully developed one of the largest description is 

 j^-g inch, and the radii are, comparatively, exceedingly large and 

 stout. The number of these organs is very great ; and in the dermal 

 rind they are so closely packed that the rays of each pass between 

 those of the adjoining ones, and the whole become, as it were, ce- 

 mented into a solid mass. 



The two smaller ones are also exceedingly abundant on the inter- 

 stitial membranes. They occur in about equal quantities, thickly 

 dispersed over the membranes. The largest of the two, the cylindro- 

 stellate ones, have an average extreme diameter of -j-pj-g- inch ; while the 

 smaller cylindro-stellate ones do not exceed Ts ^ 7 inch in diameter, 

 being less than one-third of the greatest diameter of a skeleton-spicu- 

 lum, which measured -j-^-ij inch. 



