POLYPIFERA. 



31 



Fig. 36. 



Gorgonia nobills. A small detached portion magnified. 



When this Gorgonia was exposed to a red 

 heat, it crackled and emitted a thick smoke, 

 with the smell of burnt horn. The shape 

 was soon destroyed, and a compact coal re- 

 mained. By continuing the red heat, a very 

 small portion of white matter was obtained, 

 which, as far as the quantity would allow, 

 proved to be muriate of soda with some 

 carbonate of the same. 



The results of the experiments on certain 

 Gorgonias, such as Ceratophyla, Flabellum 

 suberosa, pectinata, and setosa, were not a 

 little remarkable ; for when the two portions 

 which compose these Gorgoniae, viz. the 

 horny stem and the cortical substance with 

 which it is coated, were examined separately, 

 it was proved, 



1st, That the stems of these Gorgoniae con- 

 sist of a substance analogous to horn, and 

 that the horny matter contains a quantity of 

 the phosphate of lime, but scarcely any of the 

 carbonate. 



2d, That the cortical part consists prin- 

 cipally of the carbonate of lime, with very 

 little or none of the phosphate ; and the car- 

 bonate is deposited in and upon a soft flexible 

 membranaceous substance, which seems much 

 to approach the nature of cuticle. 



The coral of commerce, Corallium rubrum, 

 is, perhaps, one of the most interesting 



examples of this division of Polypiferous 

 zoophytes. In its living state this animal 

 resembles a short stunted tree fixed to the 

 surface of the rock by a broadly expanded 

 base, from which it rises, at first with a single 

 stem of varying magnitude, which soon di- 

 vides into branches so as to resemble a leaf- 

 less shrub rising to the height of about 18 

 inches. The central axis of the coral is of 

 stony hardness, insomuch, indeed, that to this 

 circumstance it owes its principal value in 

 commerce, on account of the high polish of 

 which it is susceptible. In the growing coral 

 this stony centre is entirely invested with a 

 fleshy cortex that constitutes the living por- 

 tion of the zoophyte whereby the central 

 stem is deposited, and the whole external 

 surface is studded at intervals with polypes, 

 in structure exactly resembling those of the 

 Alcyonidae, both in the number of their 

 arms and general structure. During the au- 

 tumnal months gemmules are formed in the 

 ovaria of these polypes, which are described 

 as being at first white, but afterwards of a 

 bright red colour ; these detach themselves 

 separately from the little white groups with 

 which they were originally connected by fila- 

 ments or umbilical cords. They escape thus 

 into the body of the polype, behind its sto- 

 mach, where they are seen to be perfectly 



