COMMERCIAL SPONGES. 49 
The Cliona bores into shells, causing 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 
tubulifera 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. 
BRANCH II.—PORIFERA. 
The sponges are many-celled animals, with three cell-layers, without a 
true digestive cavity, supported usually by calcareous or silicious spicules, 
the body-mass permeated by ciliated passages, or containing minute cham 
bers lined by ciliated, collared, monad-like cells. No true mouth-opening, 
but usually an irregular system of inhalent pores opening into. the cell-lined 
chambers or passages through which the food is introduced in currents of 
sea-water, the waste particles passing out of the body by a single, but more 
usually, many cloacal openings (oscula). Sponges are 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. Caleispongiw. 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 2. Carneospongie. 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.) 
