254 POLYZOA. 



The POLYZOA are divisible into two Orders : 



I. INFUNDIBULATA. Natives of the sea. Polypes compound, the mouth sur- 

 rounded with ciliated filiform retractile tentacula, which form an uninterrupted 

 circle : ova ciliated. 



II. HYPPOCREPIA. Lacustrine or natives of fresh water. Polypes compound, the 

 mouth surrounded with ciliated retractile tentacula, interrupted or depressed on 

 one side, so as to assume a crescentic or horse-shoe form : ova unciliated. 



*,* The name which this class should bear is still disputed. Bryozoa, conferred 

 on it in 1834 by Ehrenberg (see Agassiz's Nomenclator Zoologicus), is the one in 

 common use. Mr. Thompson says that he discovered the class in 1820, but his 

 memoir has no date. It was not published previous to 1832, nor later than 1834 ; 

 and my belief is that it was published in 1833: hence the adoption of his name 

 Polyzoa. Agassiz is wrong, both in assigning the invention of this name to Gray, 

 and in his date of its introduction to science. 



