38 CCELENTERATA AND 



rooted by a creeping stolon. Hydrothecae biserial, alter- 

 nate, orifice toothed. Operculum of several pieces. 



$. polyzonias. 



Diphasia. Plant-like. Stem branching, jointed, rooted 

 by a creeping stolon. Hydrothecae opposite, pair on each 

 internode. Valve-like operculum. Gonothecae scattered, 

 different in male and female. 



D.fattax. 



Sertularia (Dynamena) . Plant-like; stem branching, 

 jointed, rooted by creeping stolon. Hydrothecae biserial, 

 opposite or alternate. No operculum. Gonothecae scat- 

 tered . 



tS. pumila. 



Antennularia . Plant-like. Stems simple or branching, 

 with verticillate branchlets and rooted by a mass of fibres 

 Hydrotheese cup-shaped. Nematophores bithalmic on 

 stem. 



A. sp.? 



Plumularia. Hydrothecae sessile, unilateral. With 

 nematophores or minute cups which contain an extensile 

 offshoot from the ccenosarc, with or without nematocysts. 

 Gonozooids fixed. 



P. Verrillii. 



Aglaophenia. Plumose, simple or branched, rooted. 

 Hydrothecae cup-formed. Nematophores on the Hydro- 

 thecae. Gonothecae in the form of corbulae. 



A. arbor ea. 



Order II. Trachy medusae. 



Sense-bodies with a hood. With a bell-cavity and ve- 

 lum. Medusas transparent, of small size resembling in 

 many particulars the Hydroida. Body disk-like, spheri- 

 cal, conical ; colorless. Walls sometimes rigid, sometimes 

 flexible. Marginal tentacles stiff, sometimes easily decid- 



