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A COURSE ON ZOOLOGY. 



titions. These partitions correspond in number to the 

 tentacles of the polyp. Since the corals multiply by 

 breeding, and remain united in colonies, large polyparies 

 are often found, consisting of as many little cups as there 

 are creatures in the polypary. The form of the mass 

 differs according to the species, but, since the breeding 

 takes place in the same manner in each species, it follows 

 that the form of the coral mass is also constant for each. 



FIG. 106. 



A, branch of dendrophyllia ; B, part of a stock of red coral, with (a) fully 

 extended polyp, and (6, b) two polyps partly extended. 



Most of these creatures dwell in the sea, but there are 

 a few species found in fresh water. The calcareous 

 polyps grow only in warm seas, and there increase in 

 such abundance that they form islands of vast extent. 

 The well-established origin of these islands and the 



