CHAPTER II 



COELENTERATA 



THE Protozoa are regarded as forming a phylum of the Animal 

 Kingdom. The Metazoa are resolved into a series of phyla, 

 and each phylum is divided into classes, orders, families, 

 genera, and species. 



The phylum Porifera sponges may he said to belong 

 to the Metazoa ; some regard the sponges as allied to the 

 Coelenterata, and others are of the opinion that they are an 

 independent offshoot of the Protozoa. 



Phylum COELENTERATA Types 



Class HYDEOZOA .... Hydra 



Obelia 

 CTENOPHORA 

 SCYPHOZOA 

 ACTINOZOA 



Under the name Coelenterata are included Hydra and 

 its allies in fresh water, and marine Zoophytes (Hydrozoa) ; 

 also jelly fish (Scyphozoa) and sea anemones and corals 

 (Actinozoa). Ctenophores are mostly planktonic jelly-fish- 

 like organisms allied to Hydrozoa and to the Planaria. 



The characteristic features of the class Hydrozoa and of 

 the Coelenterates are well illustrated by the fresh-water polyp, 

 Hydra, and its allies the zoophytes found in the sea. 



Hydra. There are three species of the fresh-water Hydra : 

 Hydra vulgaris, colourless, spread apparently over all the world ; 

 H. Jusca (oligactis), brown or reddish in colour, common 

 all over the northern hemisphere, and rare to the south ; 

 H. viridis, green, also common in the northern hemisphere, 



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