28 A]!^TIIOZOA HYDROIDA. 



I arrange the British species of this order under the follow- 

 ing tribes, families, and genera : — 



* Ovisacs or bulbules naked, bud-like, pullulating from the bases of 



the tentacula. Tubulakina, Ehrenberg. (Tubularia, Linnceus. 

 TubulariadiB, Johnston. Les Tubulaires, Van Beneden.) 



Family I. — Polypes naked, or with only a rudimentary polypi- 

 dom. CORYNIDJ^. 

 t Polypes naked 



The tentacula scattered. Clava. 



The tentacula in one row. Hydractinia. 



t t Polypes with a horny cuticle 



The tentacula with globose tips. CoRrNE. 



The tentacula filiform. Cordylophora. 



Family II. — Polypidom fistular : the tentacula whorled, TU- 

 BULARIADjE. 



t The tentacula in a single whorl. Eudendrium. 

 t t The tentacula in a double whorl 



Polypidom rooted. Tubularia. 



Polypidom unrooted and deciduous. Corymorpha. 



* * Ovisacs in the form of horny capsules or vesicles scattered on the 



polypidoms and deciduous. Sertularina, Ehrenberg. (Sertu- 

 laria, LinncBus.^ 



Family III.— Cells of the polypes sessile. SUET ULA EI A DjE. 

 t Cells biserial 



Cells alternate, tubular. Halecium. 



Cells vasiform, everted. Sertularia. 



Cells conico-tubular, appressed. Thuiaria. 



t t Cells uniserial 



The branchlets plumose or pectinate. Plumularia. 



The branchlets whorled. Antennularia. 



Family IV Polype-cells on ringed stalks. CAMPANULA- 



EIADJE. 

 Cells alternate, campanulate. Laomedea. 



Cells irregular or whorled. Campanularia. 



* * * Polypes propagating by buds and ova, which develop them- 



selves on and in the body of the parent. Hydrina, Ehrenberg. 

 (Hydra, Linnceus. HYDRAiniE, Johnston.) 



One genus only. Hydra. 



