CHAPTER XV. 



PHYLUM III: CCELENTERATA. 



190. General Survey. This branch of animals is found 

 almost wholly in salt water. There is one small group 

 of them (the Hydras) that live wholly in fresh water 

 and a small number of examples that live in brackish 

 water or, if in fresh water, quite near the seashore. This 

 suggests that these latter types are just now gradually 

 making a transition from salt to fresh water. 



This is one of the most beautiful and varied of the 

 lower branches of animals. It includes the jelly-fishes, 

 the sea anemones, the corals, and the sea-fans. Many 

 of these are very delicate and beautifully colored; and 

 they often occur with great luxuriance on rocky bottoms 

 of the warmer seas, unless too deep. Here they look 

 like gardens of many colored plants. With the exception 

 of the jelly-fishes and a few others, they are like the 

 sponges in being attached, in forming great colonies by 

 budding, and in secreting supporting skeletons. They 

 differ from them in being more branched, in having 

 waving tentacles, and in great diversity of color. The 

 branching habit gives them an added likeness to plants. 

 In addition, the group is especially interesting to the 

 student because of the following facts: 



i. The body, especially in the region of the tentacles, 

 is covered with minute nettling cells (Fig. 46, n) with 

 which they paralyze their prey and perhaps protect 

 themselves. 



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