18 DR. J. S. BOWERBANK ON THE SPONGIADjE. [Jail. 7, 



spicula equiangular, triradiate ; radii short and stout ; reposing on a 

 closely packed stratum of very large and strong fusiformi-acerate 

 dermal spicula disposed in lines in accordance with the long axis of 

 the branch. Skeleton — interstitial structures sparingly spiculous ; 

 spicula inequitriradiate, variable in size and form. 



Colour in the dried state cream-white. 

 Ilab. Port Elizabeth (Capt. Charles Tyler). 

 Examined in the dried state. 



The basal attachment of the sponge has been destroyed ; but the 

 whole mass of closely compressed branches appear to spring from 

 one basal mass or sessile attachment, dividing and subdividing into 

 a complex mass of ramuli, each terminated with a fsecal orifice ; the 

 cloacae, of which these orifices are the terminations, are continuous 

 from the extreme proximal end of each branch to the distal end of 

 each of its ramuli. The terminal orifices are rarely ciliated ; but 

 when they are so furnished the ciliary fringe is composed of a pro- 

 longation of the layer of large acerate spicula. When a longitudinal 

 section of one of the ramuli is made and mounted in Canada balsam, 

 the interior of the sponge forms a very interesting object, the whole 

 of the inner surface of the cloaca being occupied with beautiful oscu- 

 lar reticulation ; the rete is formed of broad flat threads of closely 

 felted triradiate spicula ; and within each area there is a well-defined 

 osculum. In other well-known species of Leuconia we find a series 

 of defensive spicula projected from the oscular surface, the points of 

 these organs being usually inclined towards the mouth of the cloaca ; 

 but in this species no such spicula could be detected. 



The dermal membrane is exceedingly delicate ; it is furnished 

 with numerous equiangular triradiate spicula; and in the present 

 state of the sponge it is closely adherent to the dense stratum of 

 large fusiformi-acerate spicula beneath it. The disproportion of the 

 comparatively enormous spicula of which it is composed is very re- 

 markable ; and in their closely packed state they form a most effi- 

 cient protection to the delicate interstitial structures beneath them. 

 One of these large spicula separated with others from the sponge 

 and mounted in Canada balsam presented a striking instance of the 

 vitality of these organs. It had evidently been fractured near ita 

 middle while in its natural position during the life of the animal ; 

 the broken surfaces have been cemented together and a strong 

 angular ridge thrown out to strengthen the reunited parts. Thi9 

 spiculum is represented in Plate IV. fig. 3. The reuniting of 

 the soft parts of sponges is of exceedingly common occurrence; but 

 this is the only instance among sponges analogous to the uniting of 

 fractured bones among the higher classes of animals that I have 

 hitherto observed. The interstitial structures between the dermal 

 surfaces and the parietes of the cloaca are but sparingly spiculous ; 

 the spicula are inequitriradiate, having two short and one long ray. 

 The two short ones are applied to the surface of either the cloaca or 

 the inside of the dermal stratum ; and their apices are slightly curved 

 backwards, so as to bring them into about the same plane ; while the 



