SPONGE WEAVERS. 125 



the size and form of these cavities, and their precise 

 location. In some they are distributed in a general, 

 manner throughout the internal canal-system ; whilst 

 in others they are confined to sphaeroidal chambers, 

 excavated within the substance of the body of the 

 sponge, but freely communicating with the inflowing 

 and outflowing streams. 



The second element is the common gelatinous 

 base, or hyaline mucous-like stratum, in which 

 the two other elements are imbedded. Although 

 of the same consistence throughout, this stratum 

 consists of two layers ; that is, of an investing 

 membrane in which no monad chambers exist, 

 and a deeper, thicker substratum in which they are 

 immersed. 



The third element consists of the innumerable 

 amoeboid bodies, or cells, scattered more or less 

 abundantly throughout the substance of the mucous- 

 like stratum. These bodies have no distinct cell- 

 wall, and unless specially sought after, are scarcely to 

 be distinguished from the stratum in which they are 

 imbedded. They vary much in outline, each fur- 

 nished with a refractive nucleus, and are best seen in 

 the investing membrane. "Like Amoeba they are 

 constantly undergoing a change of outline, and may 

 also be observed to shift their position from one part 

 to another of the matrix. Oftentimes their long, 

 slender pseudopodia, radiating towards those of their 



