MOLLUSCOIDA. 



187 



CHAPTER XIX. 



MOLLUSCOIDA. 



Class I. Polyzoa. 



The members of this class are the lowest of all the Mollusca, and 

 they are generally known by the popular names of " Sea-mosses " 



Fig. \Z\.~Flustra foliacea, one of the Sea-mats, a Portion of the colony, natural 

 size ; b A fragment magnified, to show tlte cells in which the separate polypides are 

 contained. 



and " Sea-mats." They are invariably compound, forming associated 

 growths or colonies, often more or less plant-like in form (fig. 131), 



