VII. HYDR^, JELLYFISHES, SEA ANEMONES, 

 CORAL POLYPS 



Brajsich III. — Coelenterata (koilos, hollow; enteron, 

 intestine) 



The Coelenterata, which include the corals, jellyfishes, 

 sea anemones, etc., occur, without exception, in the water, 

 and the majority of them are found in the sea. In general 

 they are much more complex in structure and development 

 than the sponges, but resemble the sponges in several 

 respects, namely, in the tendency to reproduce by budding 

 and form colonies; in their fixed mode of life; and in the 

 possession of one body cavity. Perhaps the corals are the 

 most familiar examples of this group, but there are many 

 other little-known members, the characters of which will 

 be better understood after the study of a few leading 

 types. 



An Example of the Branch — the Fresh-w.\ter 

 Hydra 



Where the hydra lives. — The fresh- water hydra lives in 

 ponds, pools, (Utches, and streams where there is an abun- 

 dance of water plants, such as duckweed, algse (pond scum), 

 etc. There are two species of hydra3 that are common, 

 the green hydra and the brown hydra. 



External features. — The hydra has a long, cylindrical 

 body attached to some i^art of a suijmerged water plant 

 or other object by the posterior end, while the anterior end 

 sways free in the water. The mouth is situated at the 



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