&CYPHOZOA. 



ORDER I. OCTOCORALLA. 



303 



In these the separate polyps are small, and each has but 

 eight septa and eight tentacles. They produce but little 

 coral, but rather those kinds of coral which are known as 

 sea-fans and sea-whips. One form is especially noticeable 

 since it produces the precious red coral so often carved into 

 beads, etc. 



ORDER II. HEXACORALLA . 



As the name indicates, the septa and tentacles here occur 

 in multiples of six. Here belong all the sea-anemones and 

 the true corals which produce coral-reefs and islands. The 



FIG. 137. Sea-anemone (Metridium). From Emerton. 



reef-building species are limited in their distribution by 

 temperature, for they cannot live where the temperature of 

 the water falls below 60 Fahr. (13 C.). 



