POLYPES. 177 



especially those having a jointed axis, present 

 some analogy to the vertebrated animals, in 

 which the muscles cover the bones. It should 

 seem, from the solid and compact substance 

 generated by them, that these Polypes absorb 

 from the searwater a greater quantity of the 

 matter which is converted into carbonate of lime 

 than the rest of the class, so as to enable them 

 to condense' it into the smallest compass, and 

 therefore Providence has gifted them with the 

 faculty of making up in virtue, so to speak, what 

 they may want in volume. A single-stemmed 

 species, however, belonging to the flexible ge- 

 nus Antipathes, found by Professor Eschscholtz, 

 on the north-west coast of America, was ten feet 

 long. The foot, or base by which the common 

 coral is attached to the rocks, as indeed is the 

 case with the whole section to which it belongs, 

 is remarkably expanded ; it rises at first with a 

 single stem of varying magnitude, which soon 

 divides into a. small number of branches, in their 

 turn dividing and subdividing irregularly into a 

 great number of others, so as to resemble a leaf- 

 less shrub, rising to the height of about eighteen 

 inches. After pearls, this is the most precious 

 production of the ocean, and has always been a 

 valuable article of commerce. As well as the 

 common sponge, it is principally the produce of 

 the Mediterranean, and is formed with such rapi- 

 dity, that a place which has been quite exhausted 



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