CHAPTER XIII 



COELENTEKATA {CONTINUED) : ANTHOZOA = ACTINOZOA GENEEAL 



CHARACTERS ALCYONARIA 



CLASS III. ANTHOZOA = ACTINOZOA 



Among the familiar objects included in this class are the Sea- 

 anemones, the Stony Corals (Madrepores), the Flexible Corals, the 

 Precious Coral, and the Sea-pens. "With the exception of a few- 

 species of Sea-anemone, Anthozoa are not commonly found on 

 British sea-shores ; but in those parts of the tropical world wdiere 

 coral reefs occur, the shore at low tide is carpeted with various 

 forms of this class, and the sands and beaches are almost entirely 

 composed of their broken-down skeletons. 



The majority of the Anthozoa are colonial in habit, a large 

 number of individuals, or zooids as they are called, being organi- 

 cally connected together by a network of nutritive canals, and 

 forming a communal gelatinous or stony matrix for their pro- 

 tection and support. Whilst the individuals are usually small 

 or minute, the colonial masses they form are frequently large. 

 Single colonies of the stony corals form blocks of stone whicli 

 are sometimes live feet in diameter, and reach a height of two 

 or three feet from the ground. From the tree or slirub-like form 

 assumed by many of the colonies they were formerly included in 

 a class Zoophyta or animal-plants. 



But whether the individual polyps are large or small, whether 

 they form colonies in the adult condition or remain independent, 

 they exhibit certain characters in common which distinguish 

 them not only from the other Coelenterata, but from all other 

 animals. When an individual zooid is examined in the living 

 and fully expanded condition, it is seen to possess a cylindrical 



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