G. SPONOIA. 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 covered 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 

 tlieir texture, the difierences they exhibit are consider- 



