306 MANUAL OF ZOOLOGY. 



DIVISIONS OF THE POLYZOA. The Polyzoa are Divided into 

 two divisions or orders the Phylactol&mata (fig. 124, 3), dis- 

 tinguished by the possession of a bilateral horse-shoe-shaped 

 lophophore, and of an " epistome " arching over the mouth ; 

 and the Gymnol&ntata (fig. 124, 2), in which the lophophore is 

 orbicular, and there is no epistome. 



TABLE OF THE DIVISIONS OF THE POLYZOA. 



ORDER I. PHYLACTOL^EMATA. 



Lophophore bilateral ; mouth with an epistome. 

 Sub-order I. Lophopea (fresh-water). 



Arms of lophophore free or obsolete ; consistence horny, sub-cal- 

 careous. 

 Sub-order 2. Pedicellinea (marine). 



Arms of lophophore united at their extremities ; consistence soft, 

 fleshy. 

 Sub-order 3. Rhabdopleiirea (marine). 



Coencecium branched, adherent, membranous, with a solid chili- 

 nous rod on its adherent side, to which the polypites are attached 

 by their funiculi. Lophophore completely hippocrepian, with a 

 peculiar shield-like body on its haemal side. No epistome (?). 



ORDER II. GYMNOL^EMATA. 



Lophophore orbicular, or nearly so ; no epistome. 

 Sub-order 4. Paludicellea (fresh-water). 



Polypide completely retractile ; evagination of tentacular sheath 

 imperfect ; consistence horny or sub-calcareous. 

 Sub-order 5. Cheilostomata (marine). 



Polypide completely retractile ; evagination perfect ; orifice of cell 

 sub-terminal, of less diameter than the cell, and usually closed with a 

 movable lip or shutter, sometimes by a contractile sphincter ; cells 

 not tubular ; consistence calcareous, horny, or fleshy. 

 Sub-order 6. Cyclostomata (marine). 



Cell tubular ; orifice terminal, of the same diameter as the cell, 

 without any movable apparatus for its closure; consistence cal- 

 careous. 

 Sub-order 7. Ctenostomata (marine). 



Orifice of the cell terminal, furnished with a usually setose fringe 

 for its closure ; cells distinct, arising from a common tube ; consist- 

 ence horny or carnose. 



CHAPTER XLIII. 



TUN 1C AT A. 



CLASS II. TUNICATA (Ascidioida). The members of this class 

 of the Molluscoida are defined as follows : Alimentary canal 

 suspended in a double-walled sac, but not capable of protru- 



