214 CLASS III.— ORDER II. 



Gorgonias of the two last sections, whose polypi ap- 

 pear in small papillous risings or tubercles, nor with 

 the first, whose very thin rind almost wholly dissolves 

 in acids, whilst that of the Plexauras scarcely effer- 

 vesces with them : in short, the nature of the fleshy 

 envelope, its great thickness, the stiffness of the 

 branches, their form, and the largeness of the polypi, 

 which never project, and still more the existence of 

 real cells, will always distinguish the Plexauras from 

 others of the Gorgonian order. 



In these Polypidoms is found a membrano-granu- 

 lous substance, of the colour of violet, which ap- 

 pears to unite the rind with the axe, and adheres to 

 these two parts, or sometimes to one alone, or first 

 to one and then to the other ; its thickness is not 

 considerable ; the internal part is slightly striated ; 

 the external surface is marked with numerous deep 

 furrows, longitudinal and parallel. This membrane 

 is in all probability of great importance during 

 the existence of the animal ; it is scarcely apparent 

 in the Gorgonias; it visibly exists in the Isidias, 

 and also in the Corallinas. It is perhaps destined 

 to connect the myriads of animalcula which com- 

 pose the swarms inhabiting the deep, and to effect a 

 mutual communication between these singular beings, 

 every individual of which seems to enjoy a peculiar 

 life, whilst the mass is endued with a general exist- 

 ence independent of that of the individuals : or it 

 may be destined to supply the increase of the inte- 

 rior, by adding new layers to the axe that sustains 

 the fleshy envelope or rind ; its adherence to both the 

 envelope and the axe renders this hypothesis not im- 

 probable, particularly as the cells do not penetrate so 

 deeply through the fleshy rind. 



