PHYLUM CCELENTERATA. Radially symmetrical animals with only one body-cavity the gastrovasculat space which 

 serves alike for digestion and circulation. 



A. With nematocysts. 



Class i. HYDROZOA. Coelenterata in which the medusa has a velum and the polyp is without an oesophagus and 



mesenteries. 



Order i. HYDRIDA. Solitary polyps without medusa stage. Ex. Hydra. 

 Order 2. HYDROMEDUS^i. Forms generally possessing both polyp and medusa stages. 



/Campanularidse. Ex. Campanularia, Obelia. 

 Sub-order i. Calyptoblastea (Leptomedusre). /Sertularidae. Ex. Sertularia. 



(Plumularidae. Ex. Plumularia, Antennnlaria. 



Sub-order i. Gymnoblastea (Anthomedusae). Ex. Pennaria, Tttbularia, Hydractinia, Lizzia. 

 Order 3. NARCOMEDUS/E. Ex. Mgina. 

 Order 4. TRACHYMEDUSJE. Ex. Geryonia. 



Order 5. SIPHONOPHORA. Free-swimming polymorphic colonies. Ex. Diphyes, Physopkora, Physalia, Velella. 

 Order 6. HYDROCORALLIN^. Colonial forms with calcareous skeleton. Ex. Millepora, Stylaster. 



Class i. ACALEPH.S. Medusae of large size with gastral filaments and endodermal gonads : without true velum. 

 Ex. Lucernaria, Aurelia, Pelagia, Rhiwstoma. 



Class 3. ACTINOZOA. Polyps with oesophagus and mesenteries. Without medusa stage. 



Order i. ALCYONARIA. With eight pinnate tentacles and eight mesenteries. Ex. Alcyonium, Pennatula, \ 



Gorgonia, Tubipora. 

 Order 2. ZOANTHARIA. With smooth tentacles. These are usually secondary and tertiary mesenteries. 



Ex. Actinia, Peachia (sea anemones), Lophohelia, Fungia, Madrepora. 



B. Without nematocysts. 



Class 4. CTENOPHORA. Ccelenterates with a secondarily acquiied bilateral symmetry. Eight meridional rows of 

 vibratile plates formed of fused cilia. With oesophagus. Ex. Pleurobrachia, Beroe, Cestus. 



