188 PROCEEDINGS OF THE ACADEMY OF [1887. 



Gemmule spicules general^ cylindrical, much aud variably curved; 

 somewhat sparsely spined ; spines more numerous near the extrem- 

 ities, Avhere they are long, acute, and frequently recurved. Upon 

 the gemmules they vary from a horizontal to a nearly erect position, 

 according to the thickness of the crust, and for the same reason 

 are sometimes wanting and at others very numerous. 



Hah. On stones and timbers everywhere ; preferring running 

 water. 



Measurements. Diameter of gemmules 0.02 inches. Average 

 length of skeleton spicules about 0.0108 inches. 



Remarks. — SpongUla lacustris is certainly not introduced in 

 this connection on account of any claims I desire to make as to au- 

 tliorship or discovery ; but rather in the way of recantation or con- 

 fession that in times past I have so frequently mistaken this name- 

 child of the great Linnaeus, clucking to it as one of my own little brood. 

 Indeed it is to save others from a similar experience that I am par- 

 ticular to make this identification. 



This species was one of the earliest known ; though for years the 

 distinction between it and Spongilla (now Meyenia,) fiuvmtilis was 

 far from clear. It has been found in nearly all parts of the world 

 where any sponges have been discovered. While many of the fresh 

 water sponges appear to shun the light S. lacustris comes out boldly 

 and flourishes in the full sunshine. For this rea^^on and because of 

 its resultant brilliant green color and its consj)icuous branching 

 habit, this sponge is better known than any other, and is more fre- 

 quently gathered by the non-expert collector. I have received it 

 from nearly all my correspondents in the United States and from 

 almost every locality in which any have been collected. 



In every })lace it prefers rapidly running water, where its growth 

 is strong and vigorous. Perhaps my finest specimens were gathered 

 at a place in Chester Creek, Pennsylvania, where the stream was 

 narrowed to a width of ten or twelve feet, rushing between large 

 masses of rock, many of which were coated with the sessile sponge 

 and beautifully fringed with tapering finger-like processes, one half 

 inch or more in diameter by several inches in length. In standing 

 pools, on the contrary, it grows in slender cylindrical branches; a.s 

 in the subsiding reservoirs on Fairmount Hill, Philadelphia, where 

 it appears in slender, flaccid, yellow-green branches, with hardly 



