190 NATURAL HISTORY OP 



ACTINOZOA (ANTHOZOA). 



II. ALCYONARIA. 



Description. 



There are few species of the Alcyonaria found in 

 British seas, but those which are obtained there are very- 

 representative. The Alcyonaria differ from the Zoan- 

 tharia in being always compound, and yet not assuming 

 a truly coralline form. The polyps have eight short 

 fringed tentacles and septa arranged in multiples of 4, 

 which, however, are not paired. The British species 

 are distributed amongst five families, each of which 

 has characteristics sufficiently striking to require de- 

 tailed mention. The families are the AlcyonidcB, Gor- 

 gonidce, PemiatididcB, Virgidaridce, and FunicuUnidce. 



Before, however_, setting out the family differences, 

 the polyps, which are alike in all the families, should 

 be described. Each polyp is a transparent animal, in 

 shape when extended somewhat like a truncated cone, 

 and having eight pinnately fringed tentacles surround- 

 ing the mouth. Plate XV., fig. 1. The body wall is ex- 

 tended above round the tentacles into a calyx with 

 pointed processes. This wall_, like that of the Zoan- 

 tharia, consists of an ectoderm, m esoderm, and endoderm, 

 with the usual layers of muscular fibres between the en- 

 doderm and mesoderm. The tentacles are eight hollow 

 extensions of the body wall. They are fringed pinnately 

 on each side by eight or ten hollow pinnules. The ecto- 

 derm of the tentacles contains the usual armament of 

 thread-cells, which are oval in shape,and contain spirally 

 coiled threads. There is no distinct disc, as in the 



