SECT. iv. G OR G ONIID^E. 125 



drical throughout its whole length. The covering is 

 white, and nearly smooth; the cups containing the 

 polypes either have no salient border, or are deeply 

 sunk in the coat. 



The Gorgons known as sea-fans live in warm seas, and 

 are of numerous species. Not only all their branches, 

 but all their branchlets and twigs, spread in the flat 

 form of a fan, are soldered together so as to form a net 

 with open meshes ; the coating is thin, and the polypes 

 are placed bilaterally. 



The stems and branches of the Isidse, which form 

 the third group of Gorgoniidae, are composed of a series 

 of calcareous cylinders, separated by either horny or 

 cork-like nodes ; the polypes are only born in the bark 

 of the former. In the genus Isis the calcareous cylinders 

 are deeply striated by straight or wavy lines. This race 

 of animals are mostly inhabitants of warm seas ; but 

 they once lived in a colder climate. Some species of 

 them are preserved in a fossil state in the cretaceous 

 earth in Belgium, and in the plastic clay near London. 



There is but one genus of the Coralline Gorgon, and 

 the type of that is the common red ornamental coral of 

 commerce found in the Mediterranean Sea only. Dr. 

 Carpenter has discovered that the solid calcareous stem 

 of the Corallium rubrum is made up of aggregations of 

 spicules closely resembling those of the other Alcyonian 

 zoophytes, but of an intense red, sometimes rose colour 

 or whitish. The stem and branches are delicately striated 

 along their length, and covered with a soft substance of 

 the same colour as the stem, into which the polypes 

 retreat when alarmed ; but when fishing for food, with 

 their eight white tentacles expanded, the red stem and 

 branches appear as if they were studded with stars. Prof, 

 de Lacaze Duthiers, who was appointed by the French 

 Government to investigate the natural history of the 

 red coral with a view to the regulation of the fishery at 



