STRUCTUEE AND ECONOMY OF TETHEA. 419 



Many of these masses appear to me to break up into 

 the constituent elements of the intermediate masses of the 

 sponge, while others near the denuded portion of the surface 

 are arranged and developed into new rind. Some of these 

 ova-like bodies have a distinct covering of silicious granules, 

 and if we are to be guided by the analogy of Spongilla, they 

 must be the sources of the ciliated or locomotive particles 

 which, ejected from the parent, move off to become fixed and 

 developed as independent individuals. 



