COELENTERATA 



With a single continuous coelenteron or gastro-vascular 

 cavity. With tentacles and nettle cells. With two cellular 

 layers and a mesoglea. 



Class 1. Hydrozoa. 



Coelenteron simple, without septa. Gonads 

 usually ectodermal. Fully formed medusae 

 have a velum. (Craspedote medusae.) 



Order 1. Leptolinae. 



With a fixed zoophyte stage. 

 Suborder 1. Anthomedusae. (Gymnoblastea.) 



Without hydrothecae or gonothecae. The 

 medusa bears gonads on the manubrium. 

 (Bougainvillia, Eudendrium, Clava, Hydra, 

 Hydractinia, Pennaria, Tubularia.) 

 Suborder 2. Leptomedusae. (Calyptoblastea.) 



With hydrothecae and gonothecae. The 

 medusa bears gonads on the radial canal. 

 (Campanularia, Gonionemus, Obelia, Sertu- 

 laria, Tima.) 



Order 2. Trachylinae. 



Without fixed zoophyte stage, 

 Suborder 1. Trachymedusae. 



Tentacles from the margin of the umbrella. 

 Gonads on the radial canals. (Petasus.) 

 Suborder 2. Narcomedusae. 



Tentacles from the exumbrella. Gonads on the 

 manubrium. (Aeginopsis.) 



Order 3. Hydrocorallina. 



Massive calcareous exoskeleton. (Millepora.) 



Order 4. Siphonophora. 



Pelagic. Colonial. "" Colony usually shows ex- 

 treme polymorphism of its zooids. (Physalia.) 

 Class 2. Scyphozoa. 



Body wall of polyp thrown into four ridges 

 (Taenioles) which project into the coelenteron. 

 Medusa generally without velum and with gas- 

 tric tentacles (acraspedote medusae). Medu- 

 soid form predominating. 



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