| OCR Text |
Show 290 DR. J. S. BOWERBANK ON THE SPONGIADcE. [Apr. 6, they are about as numerous on the interstitial membranes as on dermal one. The bidentate equianchorate ones are rather rare; they are not readily found in situ amidst the numerous minute grains of sand adherent to the membranes ; but they are readily found among the spicula prepared by the aid of nitric acid, but they require the application of a power of about 400 linear to render them distinctly to the eye; they ara stout and short in their proportions. The interstitial membranes are usually rather sparingly spiculous; but occasionally the spicula are clustered together in considerable quantities. HALICHONDRIA CRASSA, Bowerbank. Sponge massive, sessile. Surface uneven and very rugged, with numerous irregular thin ridges and elevations, coarsely reticulated. Oscula simple, dispersed. Pores inconspicuous. Dermal membrane spiculous ; tension-spicula acuate, same size and form as those of the skeleton, not very numerous : retentive spicula, two descriptions of bihamate, simple and contort, large and small, and bidentate equianchorate minute, and few in number. Skeleton-rete multispicu-lous, coarse, and strong ; areas large and irregular ; spicula acuate, rather short and stout. Interstitial membranes spiculous; spicula same as those of the dermis. Colour, in the dried state, dull pale green. Hab. Straits of Malacca (Commodore Parish). Examined in the dried state. I received a single specimen of this sponge from my friend Commodore Parish, who obtained it from the Straits of Malacca. It is a rough-looking mass, very irregular in form, about 1| inch in diameter, and half an inch in thickness, and it has several specimens of Balanus imbedded in its substance. Its surface is full of sharp, thin, elevated ridges and deep depressions ; and all parts of its surface are coarsely reticulated, the reticulation being more or less visible to the unassisted eye, and very apparent by the aid of a lens of 2 inches focus. This coarse reticulation arises in the dried specimen from the very coarse and open character of the skeleton-structures immediately beneath the dermis. The oscula are rather numerous; and some of them exceed a line in diameter. The dermal membrane is in some parts rather sparingly, and in others profusely, furnished with its respective spicula; the tension ones, like those of the skeleton, are purely acuate. Of the bihamate retentive spicula there are two distinct sizes-one comparatively large (that is to say, measuring on an average ^- inch in length), while the minuter set of these forms measured only -y-fV-f inch in length. These minute forms could not be detected in situ ; but in the remains of the membranes rendered transparent by the action of nitric acid and mounting in Canada balsam, and with a power of about 700 linear, they were distinctly visible. The bidentate equianchorate retentive spicula were also minute ; they varied in length from ^Lj inch to -gfe inch, and required a power of about 400 |
