COMMERCIAL SPONOES. 49 



The Cliona bores into shells, caiasing them to disinte- 

 grate. For example, Cliona sulphurea of Verrill has been 

 found by him boring into various shells, such as the oyster, 

 mussel, and scallop ; it also spreads out on all sides, envelop- 

 ing and dissolving the entire shell. It has even been found 

 to penetrate one or two inches into hard statuary marble. 



Of the marketable sponges there are six species, with nu- 

 merous varieties. They are available for our use from being 

 simply fibrous, having no silicious spicules. The Mediter- 

 ranean sponges are the best, being the softest; those of the 

 Red Sea are next in quality, while our West Indian species 

 are coarser and less durable. Our glove-sponge {Spongia 

 tubuiifera Duch. and Mich.) corresponds to Spongia Adriat- 

 ica Schmidt, which is the Turkey cup-sponge and Levant 

 toilet sponge of the Mediterranean. Spongia gossypina 

 Duch, and Mich, the wool sponge of Florida and the Baha- 

 mas, corresponds to S. equina Schmidt, the horse or bath 

 sponge of the Mediterranean. 



BBANCH II.— PORIFERA. 



The sponges are many-ceUed animals, with three ceU-layers, without a 

 true digestive cavity, supported umuMy iy calcareous or silicious spicules, 

 the body-mass permeated by ciliated passages, or containing minute cham^ 

 bers lined by ciliated, collared, m/mad-like ceUs. No true mouth-opening, 

 but usuaUy an irregular system of inlialent pores opening into the cell-lined 

 chambers or passages through whicJi the food is introduced in currents of 

 sea-water, tlie waste partides passing out of the body by a single, but more 

 usually, many doacal opehings {os&uia). Sponges a/re hermaphroditic, mul- 

 tiplying by fertilized eggs, the germ passing through a morula and a gastrula 

 stage. (The characters of the Class the same as those of the Branch.) 



Order 1. Calcispongim. Animal supported by a framework of calcare- 

 ous spicules, disposed in lines or columns at right angles to 

 the walls ; with cell-lined radiating canals. (Sycon.) 



Order 3. Cameospongim. Mesoderm exceedingly thick ; the ciliated 

 cells restricted to cell-lined chambers. Either no solid 

 framework, as in Halisarca, or usually a well-developed 

 fibrous or silicious framework. (Spongilla, Spongia, Hya- 

 lonema, Euplectella.) 



