10 



ORDERS AND SUB-ORDERS OF POLYZOA. 



Orders. 



Lophophore bilateral ; mouth 

 with au epistome. 



PHYLACTOL^MATA.* 



Lophophore orbicular, or 

 nearly so ; no epistome. 



QYMNOLillMATA.t 



Arras of lophophore free or ' 

 obsolete. 



Arms of lophophore united at 

 the extremities. 



Poh'pide only partially re- 

 tractile ? 



Polypide completely retractile ; 

 evagination of tentacular 

 sheath imperfect. 



Polypide completely retractile; 

 evagination perfect ; orifice 

 of cell destitute of move- 

 able appendage. 



Polypide completely retractile; 

 evagination perfect ; a circle 

 of setae attached to the in- 

 invertible portion, and act- 

 ing as an operculum in the 

 retracted state. 



Polypide completely retractile; 

 evagination perfect; orificeof 

 the cell with a moveable lip. 



Sub-orders. 



LopooPEA (^fresh-water). 



PedicellinkaJ (marine). 

 Urnatellea§ (fresh- water). 



Paludicellea (fresh-water). 

 CvcLOSTOMATA (marine). 



Ctenosto.mata (marine) 



Cheilostomata|| (marine). 



* Phylactolamata (from ^uXauffw, to guard, and Xai'^ia, the gullet, in allusion to the epistome 

 placed at the entrance of the alimentary canal) corresponds in part with the Hippocrepia of Gervais. 

 The Hippocrepia of the French zoologist, however, constitute in reality an artificial group. Being 

 essentially characterised by the possession of a crescentic lophophore, they necessarily exclude not only 

 Pedicellina, but even Fredericdla, whose relations with the species furnished with a crescentic 

 lophophore are of the most intimate kind. Hippocrepianism, therefore, though of great interest as a 

 morphological fact, tending, as will be afterwards shown, to throw much light on certain homological 

 questions, cannot be employed as the determining character of groups more comprehensive than those 

 of generic rank. 



t GymnolcEmata (from yv^ivoq, naked, and \aipa, in allusion to the absence of an epistome) 

 corresponds to part of the Infundibulata of Gervais. 



X For the structure of Pedicellina, see Note, p. 19. 



§ The location of Urnatella among the Gymnolrematous Polyzoa must for the present be viewed 

 as a provisional expedient, subject to alteration as its structure becomes better known. See the 

 description of the genus farther on. 



II The terms Cydostomata, Ctenostomata, and Cheiloslomata, were proposed by Busk, to indicate 

 the primary subdivisions of the marine Gymuolsematous Polyzoa. (Voyage of " The Rattlesnake," 

 vol. i. Appendix, p. 346.) 



