| OCR Text |
Show 1869.] DR. J. s. B O W E R B A N K O N SILICEO-FIBROUS SPONGES. 93 with elongo-attenuato-stellate spicula, may frequently be seen in situ. I he connecting spicula are very numerous beneath the dermal membrane of this surface, and their closely intermingled ternate heads form a strong and very complicated dermal network. Occasionally the oscula run from two or three to six or seven in a line, on a slightly elevated ridge ; but in other respects there is no approximation to a definite arrangement. The pores are situated each in a single area, the margin of which is slightly thickened and elevated • the areas are visible by the aid of a lens of 2 inches focus ; they are very numerous, and about equidistant from each other ; the greater portion of them were in a closed condition. The expansile dermal system of this sponge affords excellent specific characters: the furcated attenuato-patento-ternate connecting spicula are large and strong, and their shafts comparatively long, and the central canals in both the shaft and the radii are lar°*e and well defined ; the furcations of their ternate heads are closely intermingled, forming a fine but very irregular and complex dermal network. They vary very considerably iu size and proportions: one of the largest measured fe inch in length, and -fe inch in the extreme expansion of its ternate head ; one of the smallest measured yPa inch in length, and in extreme expansion of its ternate head 151 inch. The elongo-attenuato-stellate retentive spicula of the dermal membrane are very minute ; two of the largest measured T-fer inch and -jifes inch in length. Their shafts are rarely straight; they have usually two or three angular bends. The radii are long, slender, and exceedingly acutely terminated. Their structure and profuse dispersion on the surface of the membrane renders them a most effective protection against the insidious attacks of voracious enemies on that organ. Those on the oscular surface are larger than those of the inhalant one. The skeleton is also strikingly characteristic. The fibre is somewhat compressed; it is perfectly smooth excepting the umbones with which it is studded at intervals; they project from half to once their own diameter from its surface, are nearly cylindrical in form and have either a flat or a hemispherical apex. In the dried condition of the sponge, when closely adherent to the inner surface of the dermal membrane, they may at first sight be readily mistaken for pores ; their form and general appearance is unlike any corresponding organs of a similar description in any other known species of this tribe of sponges. A iew gemmules were observed; they were somewhat globular, with a broad attachment; with a power of 308 linear they appeared to be filled with minute semitransparent molecules. Their general character is very much that of the similar organs in Iphiteon panicea oi the Porto-Rico specimen in the Museum of the Jardin des Plantes. When portions of the interior of the skeleton of this sponge are immersed in water, and examined beneath the microscope, the sarcode is found to be abundant in the interstices of the skeleton, sometimes completely filling the interstitial spaces, and quite ignorim-*' |
