OCR Text |
Show 4 DR. J. S. BOWERBANK ON THE SPONGIADcE. [Jan. 7, and simple cylindro-stellate with comparatively long radii *, small ones cylindro-stellate with very short radii. Skeleton-spicula fusi-formi- cylindrical. Ovaria oval, variable in form. Colour light cream-yellow. Hab. Port Elliot, Australia (Mr. Ray). Examined in the dried state. I received this sponge with a considerable number of others of various genera from the Murray River, Australia, where they were collected by Mr. Ray. The specimen is an irregularly oval mass If inch long, 1| inch greatest breadth, and 1\ inch high. O n cutting off a portion of the sponge to examine its structure, I found the interior to be one large cavity, the parietes of the sponge not exceeding four lines at the thickest part, and near the basal portion about one line in thickness only, the excurrent canals running in a tortuous direction through the sponge to the oscula. The inner surface presented an irregular matting of spicula on membranous tissue, differing in no respect from other portions of the interior membranous structures. The occurrence of this large cavity is interesting, as a similarly cavernous condition prevails in the type specimen of the genus, Geodia gibberosa, in the Paris Museum. I do not consider this hollow condition of such specimens the normal state of the sponge, and I should not expect to find it of common occurrence in this or any other species of the genus; it is probable that it is only in young and incompletely developed specimens, or by the accidental action of drying, that it would be found to occur. The surface-characters of the sponge are unfortunately nearly obliterated, apparently by maceration and attrition. No portion of the dermal membrane is preserved. Sections at right angles to the surface exhibit the remains of a few large spicula that have passed through the dermal crust and have been projected about one-third of their length beyond the surface, which in its natural condition was therefore more or less hispid. The connecting spicula are few in number and very irregularly disposed, and the terminal radii are more frequently simple than they are dichotomous. The spicula of the skeleton vary considerably in their proportions ; and the greater part of the ovaries have the apices of the radial spicula of which they are composed more or less acute. From the whole of these circumstances combined, it may naturally be inferred that the specimen is not in a fully matured condition. The connecting spicula are exceedingly various in form. In their early state they are simple expando-ternate ones; as they advance in size one or more of the rays exhibit symptoms of bifurcating ; and you may thus trace their progressive development until they attain the size and proportions of the fully developed spiculum represented by Ag- 3, Plate I. In the completely developed condition they are not very numerous; nor, indeed, are they abundant in any state. The recurvo-ternate spicula are very slender in their proportions, and their shafts are usually exceedingly long. |