SPONGIDA. 75 



When cleansed it becomes flaxen-coloured and of a looser texture. 

 The orifice of the great channels which traverse it are rough and 

 bristly. 



The brown Barbary sponge, when first taken out of the water, 

 presents itself as an elongated flattened body, gelatinous, and charged 

 with blackish mud. It is then hard, heavy, coarse, and of a reddish 

 colour. When well washed in water, it becomes round in shape, 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 is a 

 little harsh, and so is sold at a low price, having few useful properties 

 to recommend it. 



Many species of Sponge are described as inhabiting the British 

 seas, but none are of any commercial value. 



No very satisfactory classification of the Sponges has as yet been 

 made, although many recent writers have attempted with more or 

 less success to arrange the very numerous fomis now known into 

 definite groups. Among these we may mention Dr. J. E. Gray, Dr. 

 Bowerbank, and Professor Oscar Schmidt. With a few exceptions, 

 all sponges, as we have seen, contain spicules ; these are either 

 siliceous or calcareous. We may therefore divide the sponges into 

 two sections, the first being called 



Calcarea. 



Skeleton chiefly composed of calcareous spicules, which are 

 generally three-rayed. All the species are marine, and none appear 

 to attain large dimensions, while some of the very smallest sponges 

 known belong to this section. Grantia cojfipressa, one of our com- 

 monest British sponges, will serve as an example. 



SiLICEA. 



Skeleton mostly horny, most frequently strengthened with 

 siliceous spicules ; these sometimes absent; and, in at least one genus, 

 the sarcode becomes not even difierentiated into a horny skeleton. 

 The sponges belonging to this section are found both in fresh and 



