II CNIDAEIA 69 



Hydroid form. Medusa form. 



mouth and tentacles, and they are sur- 

 rounded by a chitinous periderm. It is 

 as little known in this case as in that 

 of the Hydrocorallia, whether these 

 gonophores are degenerate Mcdusce which 

 remain sessile, or simple sexually differ- 

 entiated Rydropolyp buds. 



Sub-Order 4. 

 Wanting. Trachomedusffi. 



CraspcdoU Medusas with auditory or- 

 gans (tentaculocysts), with endodermal 

 otolith cells, which sometimes stand 

 freely on the margin of the umbrella, 

 sometimes enclosed in auditory capsules. 

 Ocelli generally wanting. Gonades 

 always in the course of the radial canals. 

 Number of radial canals 4, 6, or 8, never 

 more ; between them often blind centri- 

 petal canals. Direct development with 

 metamorphosis. Olindias Millleri, Eho- 

 paJoiicma velalum, Aglantha digitalis, 

 Gcryoiiia proboscidalis, Carniarina 

 hastata. 



Sub-Order 5. 

 Wanting. NaroomedusEe. 



Craspedote Jfcdiiscc with auditory or- 

 gans, always standing freely on the 

 margin of the umbrella, with endodermal 

 otolith cells. Ocelli mostly wanting. 

 Tentacles at some distance from the 

 margin of the umbrella, inserted on the 

 exumbrella, bound to the umbrella mar- 

 gin by clasps (peronia), which divide it 

 into a number of collar lobes. Gonades 

 on the gastric peduncle, often spreading 

 from it peripherally in radial gastric 

 pouches. Radial canals sometimes 

 wanting, sometimes spreading out in the 

 shape of flat gastric pouches. Circum- 

 ferential canal sometimes obliterated. 

 Number of tentacles, lobes, and pouches 

 variable ; seldom 4, generally 8 or more, 

 up to 32. Development usually direct, 

 with metamorphosis. Ounina, Pcrjan- 

 tha, ^gineta, ^ginopsis, Sohnaris. 



Order 3. Siphonophora. 



Polymorphic, freely swimming Hydrozoa stocks, whose individuals or persons, 

 Craspedote Mcdasa, are modified for special functions. 



