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Show 18 DR. J. S. BOWERBANK ON THE SPONGIADcE. [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. Hab. 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 cloacse, 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 prolongation of the layer of large acerate spicula. W h e n 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 oscular 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 remarkable ; and in their closely packed state they form a most efficient 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 its 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. This 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 |