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CLASS XIII. POLYPI. 



Remarks. Animals of this class are called po- 

 lypi, because the tentacula which surround their 

 mouths, resemble, in some degree, those of the se- 

 pia, which the ancients called polypus. They are 

 always cylindric, terete or conic ; but the number 

 and form of their tentacula are very variable. 

 There is a cavity in all to receive food ; but it is 

 often a mere simple cavity or caliber. All ani- 

 mals of this class are capable of becoming com- 

 pound ; and by cutting them in a direction to se- 

 parate an individual, the cutting will live, like an 

 inocculated bud. But their species are reproduced 

 fey eggs. 



ORDER I. NUDATA. 



Having no hard covering, and not producing a 

 woody, horny or fleshy axis by combination. 



HYDRA, (sprouting polypus,) animal fixing it- 

 self by the base, linear, gelatinous, naked, con- 

 tractile and furnished with setaceous tentacula or 

 feelers ; inhabiting fresh waters, and producing 

 its deciduous offspring, buds or eggs, from the 

 sides. 



PEDICELLARIA, (stiff-stem,) body soft and seat- 

 ed on a rigid fixed peduncle ; aperture single. lu 

 sea. 



ORDER 2. POLYPETRA. 



Having stony cases, made chiefly of carbonate of 

 lime. This order embraces all the animals inhab- 

 iting coral rocks. 



