188 



ZOOLOGY. 



hv a single channel ; some are known to be more than tin 

 leagues in diameter. 



21. Almost all coral animals irihahit the sea; never- 

 theless some are found in liv-h 

 waters. 'Those which have tin- 

 coral case simply fleshy or horny, 

 are spread over all climates ; but 

 it is only in the seas of hot climates, 

 or nearly so, that we find an 

 abundance of the coral polyp with 

 a rocky cover in g or coral case. 



Sometimes these aggregated 

 polyps deposit in the interior of 

 the common tissue by which they 

 arc united, a horny or calcareous 

 matter, constituting a sort of in- 

 terior stalk, which branches out 

 like a tree, in proportion as the 

 animated mass sends forth new 

 branches It is in this way that 

 the coral of commerce is formed 

 (Fig. 166) of which snch use is 

 made in the fabrication of orna- 

 ments . there is an active fishery 

 for this substance on the coa>t of 

 Algeria. 



The actinia? belong to this divi- 

 sion of the animal kingdom ; they 

 are also called sea anemones 

 (Fig. 1-15) ; they have a fleshy 

 body, and are found in great num- 

 bers on the rocks of our <o:i>t : 

 the caryophylli and the astreir. 

 which, more than all other-. 

 in the formation of coral reel's 

 (Fig. 167); the coral animal itself 

 (Fig. K'.i));tlie veivtilli ( Fiir. 173), 

 which do not adhere to the >oil. 

 hut are simply buried in the sand by one of the extremities 

 of the common stalk, belong to this division. Most zoolo- 

 gists also class with them the hydra, of which we have 

 already spoken ( :317'. 



Fig. 473. Polyps 

 (Verretilli). 



