G. GORGONIA. 197 



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All the Gorgonias appear in their organisation to 

 consist of two substances ; the interior is sometimes 

 horny and hard, sometimes more soft and brittle, like 

 the blea {alburnum) of some trees and of many biennial 

 plants. This interior substance seems to be composed 

 of concentric layers, formed of longitudinal fibres. M. 

 Lamark has given it the name of ^:re(Axis). When 

 the rind or exterior is thick, the axe is proportionably 

 smaller and more compact ; but larger and of a softer 

 consistence, when the rind is thin. The surface, be- 

 sides, is marked with lines and pores, by means of 

 which, doubtless, a communication is kept up between 

 the outer and innermost parts of the animated mass. 

 In short, this axe in Polypidoms appears destined to 

 perform functions analogous to those recognized in 

 the skeletons of vertebrous animals, or the articulated 

 and horny envelopements of insects ; and it undoubt- 

 edly makes part of the animal, as the animal cannot 

 exist without it. 



The growth of the axe in the Gorgonias appears to 

 proceed by layers, placed one upon the other. They 

 frequently enclose in their interior, portions of the 

 fleshy envelope, by some unknown cause deprived 

 of life; this phenomenon seems to be effected in 

 the same manner that the bark of trees is renewed 

 when a part has previously experienced any injury. 



The rind envelopes the axe throughout its whole 

 extent ; it is fleshy in the living state of the Poly- 

 pidom, and we feel justified in the presumption 

 that it is then irritable and susceptible: by desic- 

 cation it becomes chalky and earthy, and will dis- 

 solve in acids ; it always eftervesces with them. 



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