OCR Text |
Show 772 DR. J. s. B O W E R B A N K O N T H E SPONGIADJE. [Nov. 21, punctiunculate, abundantly furnished with subfusiformi-spinulate spicula, radiating irregularly from the centres to the circumferences of the branches ; spicula very irregular in length. Colour, in the dried state, red. Hab. Sharks' Bay, Western Australia. Examined in the dried state. I obtained this interesting species from a dealer in natural-history specimens. It is 9 inches in height and 7 inches in greatest breadth. Its mode of growth is very singular. It consists of a number of separate irregularly shaped fan-like aggregations, by anastomosis of the smaller branches, all projected in nearly the same plane, the whole forming a complicated fan-shaped mass of branches, from many of which, in numerous parts, by a careful examination, minute leaves of fuci may be seen projected ; but whether these are separate and independent growths, or projections from an originally enveloped fucus, it is difficult to decide, as I could not trace any portions of the stem of a fucus in numerous sections made at right angles to the surface of the sponge, even when mounted in Canada balsam. From the very young condition of all these minute fuci, and there being two species of them, aud several other parasitical bodies, such as little Barnacles, embedded in some of the branches, I am inclined to believe the small fuci to be parasites on the sponge, and not the sponge on a fucus. The dermal surface is furnished with an irregular fibro-reticulate rete, the fibre of which does not appear to be so profusely furnished with spicula as those of the skeleton. The minute hispidation of the surface is produced by the projection of the spicula of the fibres of both the dermal rete and the skeleton immediately beneath it. This character is not visible, excepting in thin slices of the sponge made at right angles to the dermal surface when mounted in Canada balsam. The fibres of both the surface and the skeleton are very remarkable ; their surfaces are profusely punetiunculated ; this character is best seen in the fibres of the dermal rete, the surfaces of which are usually less abundantly spiculous than those of the skeleton. These minute dottings of the surfaces of the fibres require a power of not less than 300 linear, when sections of the sponge are mounted in Canada balsam, to render them distinctly to the eye. I have never seen this remarkable dotting of the surface of the fibres of a keratose sponge in any other species of sponge; and in the one in course of description it forms a very decisive specific character. The structure of the skeleton is very irregular and complicated. The fibres are stout and rigid, and are profusely furnished with their defensive spicula. These organs vary to great extent in their length and diameter; one of the largest measured -^ inch in length, while one of the numerous short ones measured only -^Vo inch in length ; the two forms are distributed on the fibres without the slightest approach to order. This sponge is a very remarkable species of the genus. It is unlike any of its numerous congeners. |