The White Sponge of Syria, called Venetian, is esteemed for its lightness, the regularity of its form, and its solidity. In its rough state it is brown in colour, of a fine texture, compact and firm. Purified, it becomes flaxen and of a looser texture. The orifice of the great channels which traverse it are edged with rough and bristly hairs.
(From Dr. Grant.)
Fig. 11. Spongia oculata, showing the orifices and currents outwards. 2. Anastomosing horny substance of Spongia communis. 3. Siliceous spiculum of S. papillaris. 4. Of S. cineria. 5. S. panicea. 6. Calcareous spiculum of S. compressa. 7. Transverse section of a canal of S. papillaris, showing the structure of the ova passing along the canal. 8. Ovum of S. panicea seen laterally—the ciliæ anterior. 9. The same seen on the end, with a circle produced by the ciliary action. 10. Young Spongia papillaris.
The Brown Barbary Sponge, called the Marseillaise, when first taken out of the water, presents itself as an elongated flattened body, gelatinous, round in shape, and charged with blackish mud. It is then hard, heavy, coarse, but compact, and of a reddish colour. By a simple washing in water it becomes round, still remaining heavy and reddish. It presents many gaps, the intervals of which are occupied by a sinuous and tenacious network. It is valuable for domestic use, because of the facility with which it absorbs water, and its great strength.
Other sorts of sponges are very abundant. The Blonde Sponge of the Archipelago, often confounded with the Venetian; the Hard Barbary Sponge, called Gelina, which only comes by accident into France; the Salonica Sponge is of middling quality; finally, the Bahama Sponge, from the Antilles, is wanting in flexibility and a little hard, and so is sold at a low price, having few useful properties to recommend it.
Many species of Spongia are described as inhabiting British seas, but none of any commercial value. Regarding them as apolypiferous zoophytes, Dr. Grant has pointed out certain principles of analysis on which they may be grouped, according to the arrangement of the horny fibres, the calcareous and siliceous spiculæ, and the distribution and formation of their pores and orifices.
I. Groups of which the Constituent Structure is known.
Spongia.—Mass soft, elastic, more or less irregular in shape, very porous, traversed by many tortuous canals, which terminate at the surface in distinct orifices. Substance of the skeleton cartilaginous, fibres anastomosed in all directions, without any earthy spicula.—Example, S. communis (Fig. 11 [2]).