POLYZOA. 



243 



roKiD^, has the cokiiiy hinielhir ami irrogidar, iiRTusliiio; the surfaces of suh-inariiie 

 objects, or iii)rig]it and branching. In Cellepora an aviculariuni exists in llie median 

 line, just beliind the posterior margin 

 of the mouth of the cell, while in Cel- 

 lejwruria it is absent. The Retepor- 

 iD^K are graceful forms, in whicli the 

 cells miite to form a flat, loaf-like col- 

 ony, whieh is perforated with numer- 

 ous oval openings. 



Order II. — PIIYLACTOLJ:- 

 MATA. 



This order eniljraces the fresh-water 

 Polyzoa proper, none of its members 

 being found in the sea. They have p 



the tentacles arranged on a horseshoe- 

 shaped lophophore, while the mouth may bo closed by a tongue-shaped lid, known as 

 the epistome, which is ])lacod just above the rudimentary brain. In size these forms 



are much larger than their marine lelatives, while their general a]ipoarance is much 

 more imiform. They are found beneath stones in running brooks, attached to sub- 

 merged logs in lakes and ponds, and in the case of Cristatclhi the whole colony is free, 

 and has the power of motion as a whole. The number of species known, from the 



