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Show 1873.] DR. J. S. BOWERBANK ON THE SPONGIADcE. 323 Hab. Fiji Islands (Sir E. Home). In the collection of the Royal College of Surgeons (see « Catalogue of Porifera,' part i. 1860, p. 127, B. 170), Examined in the dried state. The form of this sponge is somewhat like that of a pear, the basal end being the smaller one. It is 2\ inches in height, and 1\ inch at its greatest diameter. The natural base of the sponge is not present. The fractured termination is nearly circular, and is f of an inch in diameter; and there is every appearance of its having been supported, when perfect, on a short "stout pedicel. The surface is armed with numerous minute acerate or fusiformi-acerate spicula, which project from it about one third or half their length at right angles to its plane. The surface of the sponge in its present state has a large number of orifices, produced by the contraction of the tissues ; the true oscula visible are very small, of an oval form, not exceeding above a line in length and half a line in width, and are closed by the proper membrane of the organ. Immediately beneath the dermal membrane there is a thick stratum of membranous tissue and sarcode, in which the triradiate heads of the connecting-spicuia are immersed. I could not detect in this stratum the slightest indication of the presence of gemmules. The dermal membrane is crowded with the subtuberculated fusiformi-cylindrical spicula ; and very few indeed of the pores were in an open condition. Some of these appeared to have intermarginal cavities beneath them somewhat resembling those apparent in the dermal crust of Geodia and Pachymatisma ; but I could not satisfactorily determine the fact of their existence, the tissues in which they are situated having been greatly disarranged by the contraction incurred by drying; under more favourable circumstances it is very probable that such intermarginal cavities will be found to exist. This sponge exhibits in its structure very nearly the extremes in magnitude of the spicula. While those of the skeleton and connecting system are more than usually large and stout, the defensive ones and those of the membranous and sarcodous systems are unusually minute, and the stellate ones especially so, requiring a linear power of not less than 800 or 1000 to demonstrate their forms in a satisfactory manner : many of them do not exceed J-$Q-Q inch in extreme diameter; and the fusiformi-cylindrical spicula average J-JJVO" in length by Ysh^'o ^ncn greatest diameter. The interstitial membranes are abundantly covered with sarcode, in which there are a vast number of spherical nucleated cells, varying in diameter from -J^Q inch to xoooo inch. E C I O N E M I A DENSA, Bowerbank. (Plate X X X .) Sponge massive or subcyathiform, sessile ; surface sinuous and uneven, asperated. Oscula simple, dispersed. Pores inconspicuous. Dermal membrane thin, pellucid, abundantly spiculous; spicula tuberculated, subcylindrical, occasionally fusiform, short and minute. Skeleton-fasciculi numerous and large; spicula fusiformi-cylindrical, long and stout, variable in form and proportion. Connecting-spicuia 21* |
