192 



THE INVERTEBRATA 



parent remain connected by their extrathecal portions, and this con- 

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

 the colony are filled up by calcareous material secreted by the coeno- 

 sarc and called coenenchyme , 



P. 



Mo. 



Fa 



Fu. 



M. 



Fig. 143. 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. Meandrina, the brain coral ; Mo. Monti- 

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



The polyps of the Zoantharia attain a higher physiological grade 

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

 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 of the 



