G. SPONGIA. 
149 
LAKE. 
4. Ephydatia lacustris. Spreading’, and fragile ; 
branches upright, cylindrical, and obtuse. 
In the lakes of the north of Europe. 
SPONGIA. 
Spongy, inarticulated, and porous Polypidoms, 
formed of fibres crossed and interwoven in every di- 
rection, never tubular, but covered with a fugitive 
and gelatinous matter, which according to some au- 
thors is irritable. 
The preceding description of the Spongias, in ge- 
neral, being found every way applicable to the Ephy- 
datias, established the opinion of their alliance to that 
genus. 
The marine Spongias are characterised as a very 
porous mass, lobed, ramified, turbinated or tubu- 
lous, formed of horny or leathery fibres, which are 
flexible, interwoven or agglutinated together, and in a 
living state coyered with a gelatinous, irritable, and 
very fugitive matter. 
It is difficult to define the characters which con- 
stitute the various species of the Spongia ; the form 
alone is insufficient, without an additional detail on 
the nature, the quantity, the arrangement, and the co- 
lour of their fibres. 
Considered in relation to their substance, or rather 
their texture, the differences they exhibit are consider- 
