Some of the Loiver Metazoans 397 



The Corals. — Some members of the class Anthozoa secrete a limy 

 shell for the protection of the soft body parts. These are the corals. 

 Some corals occurring in deep water produce very handsome shells, 

 which are used as jewelry and are known as the "precious corals." 

 Others produce the large coral reefs which are confined to tropical 

 waters where the annual temperature is above 70° F. The famous 

 barrier reef of Australia has a great variety of animal life associated 

 with the myriad forms of corals that exist there. 



Fig. 131. — Various coelenterates. a, Physalia, a siphonophore, Portuguese man- 

 of-war; b, Velella, a siphonophore, by-the-wind-sailor; c, Gorgonia, an anthozoan, 

 sea fan; d, Polyorchis, a hydrozoan; e, Acropora, an anthozoan, a branched coral; 

 /, Fungla, an anthozoan, the mushroom coral; g, Montipora, an anthozoan, a stony 

 coral; h, Meandrina, an anthozoan, the brain coral. 



THE PHYLUM CTENOPHORA 



The comb jellies or ctenophores are all marine forms which in 

 many respects are not much advanced in structure over the coelenter- 

 ates. The gastrovascular cavity, the lack of organs, the gelatinous 

 mesenchyme, and the general relations of the body parts all show the 



