DESCRIPTION OF BFHYDATTA BLEMBINGIA. 73 



lacustris and Epliydatia fluviatilis, denizens of our 

 own rivers, are green in colour only when tliey grow in bright 

 sunlight, this is what we would have expected in the case of 

 a sponge which grew in a joool of water scarcely ever brightened 

 by direct sunlight. 



The halnts of growth of Epliydatia blembingia are 

 peculiar. In reality it is an encrusting sponge, though some 

 specimens have a massive appearance. But this is due to the 

 habit of growing on such supports as blades of grass and 

 branching weeds of various kinds which inhabit the same 

 pool of water as the sponge. It never seems to produce 

 independent branches, which, when present, give a sponge a 

 kind of bush-like appearance, as Spongilla lacustris does. 

 If, at first, a specimen appears to branch, on closer examina- 

 tion the apparent branching reveals itself as the result of 

 creeping over a branched support. Consequently, in spite of 

 its massive appearance, Epliydatia blembingia is an 

 encrusting sponge. The biggest specimens measure no more 

 than about an inch across (PI. 1, fig. 1). 



The surface texture of the preserved sponge is somewhat 

 woolly, an appearance caused by the spicule fibres which sup- 

 port the otherwise smooth dermal mend^rane. The fibres 

 often penetrate the mendjrane, owing undoubtedly to its being- 

 rubbed off their extreme points. 



To sum up, Ephydatia blembingia may be described as 

 a pale flesh-coloured sponge, with encrusting habits, creeping 

 over branched vegetable supports, and consequently irregular 

 in shape and woolly in texture. 



The oscula, not to speak of the dermal ostia, are so small 

 as to be invisible without the aid of the microscope. The 

 openings represented in fig. 1 are those of the inhalant canals 

 seen through the dermal membrane. 



(2) Skeleton. — The skeleton consists almost entirely of 

 spicules, which I shall now proceed to describe. 



A. Spicules, — In order to facilitate the description of this 

 most important element of the skeleton, I shall arrange the 

 spicules under three heads. 



