1 66 MANUAL OF ZOOLOGY. 



and are not simply rounded. Numerically, the Alcyonaria 

 agree with the extinct order Rugosa ; but the latter invariably 

 possess a well- developed sclerodermic corallum, the thecae of 

 which exhibit either septa or tabulae, or both combined. 



With the exception of two genera (Haimeia and Hartea\ 

 both of which are possibly founded upon immature forms, the 

 Alcyonaria are all composite, the tubular polypes being united 

 by a ccenosarc, and their body-cavities being placed in com- 

 munication by means of anastomosing canals, which ramify in 

 the coenosarc, and permit of a free circulation of nutrient fluids. 

 The form of the colony differs greatly in different cases, but 

 none possess the power of independent locomotion, most being 

 rooted to foreign objects, or sunk in the mud, whilst some float 

 freely in the sea. The polypes, in most of the essential points 

 of their organisation, agree with those of the Zoantharia, the 

 mouth opening into a tubular stomach, which in turn com- 

 municates freely with the body-cavity, and the stomach-sac 

 being connected with the body-wall by means of a series of 

 vertical membranous laminae or " mesenteries." The mesen- 

 teries, however, are only eight in number, and are not paired, 

 one of the tentacles corresponding with and opening into each 

 intermesenteric chamber. A corallum may be wanting, and 

 when present its structure varies. In some cases, lastly, it has 

 been shown that the actinosoma normally consists of two kinds 

 of polypes one sexual, the other sexless and permanently 

 rudimentary. The Alcyonaria are divided into five families 

 viz., the Alcyonidce, the Tubiporidcz, the Pennatulid^ the Gor- 

 gonidce, and the Helioporida. 



FAMILY I. ALCYONID^E. This family is characterised by 

 the possession of a fixed actinosoma, which is provided with a 

 sclerodermic corallum in the form of calcareous spicula embedded 

 in the tissues. The spicules are mostly fusiform in shape, and 

 are generally present both in the polypes themselves and in 

 the connecting ccenosarc ; but there is no central solid axis. 



Alcyonium may be taken as the type of the family, and it 

 is well known to fishermen under the name of "Dead-men's 

 fingers." It forms spongy-looking, orange-coloured crusts or 

 lobate masses, which are attached to submarine objects, and 

 are covered with little stellate apertures, through which the 

 delicate polypes can be protruded and retracted at will. The 

 polypes communicate with one another by an anastomosing 

 system of aquiferous tubes, and the corallum is in the form 

 of cruciform, calcareous spicula scattered through its sub- 

 stance. In the allied Sarcodictyon the actinosoma is creeping 

 and linear. 



