ANTHOZOA ASTEROIDA. 143 



teum.* A cross section of the stem or of a principal branch 

 will show the layers to be disposed concentrically round a 

 central medulla, the layers more or less compactly pressed 

 according to the nature of the species (fig. 32). The whole 

 section presents a certain resemblance to a similar section of 

 a dicotyledonous tree (fig. 33) : the medulla in position and 

 outward appearance is a pith ; the horny axis is the wood ; 

 and the fleshy crust has been denominated the bark;f nor 

 perhaps could fault be found with this language, since it is 

 sufficiently illustrative, had it not been the mother of some 

 very erroneous notions, and a great means of their propagation 

 and continuance. Thus Linnaeus, in his definition of Gor- 

 gonia, calls the axis a vegetating stem : and as if this was not 

 sufficiently explicit, we find Pallas entering into detail, and 

 telling us that the concentric circles are produced by succes- 

 sive transmutations of the fleshy crust, in the same manner 

 that the circles of the wood of trees are formed by transfor- 

 mations of the inner layers of the bark. J And this opinion, 

 if we may judge from their language, has been adopted by 



Fig. 32 



* " L'ecorce des Gorgoniees ne se lie pas immediatement a 1'axe, elle en est 

 separee par une membrane d'une nature particuliere, si mince dans le genre Gorgonia, 

 qui'l est tres-difficile de 1'apercevoir ; elle est plus apparente dans les Plexaures et les 

 Eunicees." Polyp. Corall. Flex. p. 391. Couch, lib. cit. p. 47. 



t Lin. Syst. 1829. 



J Elench. p. 162. He seems, however, to have had his suspicions that the theory 

 was questionable, for he adds " Quanquam diversissima corticis natura, ejusdemque 

 facilis a ligno separatio, suggerere possent : hujus strata potius ex deposito intus succo 

 fieri, aut lignum, prout ossa animalium sanguineorum intra periosteum, generari, 

 augeri, durescere." 



