ZOANTHARIA 169 



stitutes the coenosarc of the colony. The gaps between the thecae of 

 the colony are filled up by calcareous material secreted by the coenosarc 

 and called coenenchyme. 



The polyps of the Zoantharia attain a higher physiological grade 

 than those found elsewhere in the coelenterates. The sea anemones, 



P. 



Mo. 



Fa. 



Fu. 



M. 



Fig. 139. Photograph of a pool on a coral reef (Great Barrier Reef), showing 

 various types of zoantharian corals. Fa. Favia, with circular thecae ; Fu. the 

 free coral Fungia, a single polyp; M. Meandrtna, the brain coral; Mo. 

 Montipora, a branched coral ; P. Pontes. (Photograph by Dr S. M. Manton.) 



like Hydra, in the absence of any external skeleton, are capable of 

 locomotion, especially in the case of burrowing forms. The muscles 

 of the body are arranged in such a way as to bring about many 

 different kinds of movements. Thus, while the longitudinal muscles 



