246 



THE OCEAN WORLD. 



the Algerian coast. Other genera make their appearance on the 

 coast of Scotland, of Nonvay, in the Red Sea ; and in the Indian 

 Ocean they appear in great numbers. 



In the Alcyonidce, properly so called, the polypidom is very thick, 

 of a semi-cartilaginous consistence, granular, and rough to the touch. 



The genus Alcyonium is numerous in species which are widely 

 dispersed. A. digitaitmi is very common on our shores ; and on 

 many parts of the coast scarcely a stone or shell is dredged up from 

 deep water which does not serve as a support to some one or more 

 species of Alcyoniimi. It is known by various popular names by our 

 sea-side population, such as cows paps, from its resemblance to the 

 teats of the cow ; dead tnan's Jingers, from the occasional resemblance 

 of its finger-like lobes to a man's fingers. 



The outer skin of the polypidom is tough and coriaceous, studded 

 all over with star-like figures, which on examination are found to be 

 divided into eight rays, indicating the number of the polyps enclosed 

 in its semi-transparent membrane. Each polyp is dotted over with 

 minute calcareous bodies, and marked with eight longitudinal lines 

 or septa, stretching between the membrane and the central stomach, 

 which divide the intermediate space into an equal number of com- 

 partments. These lines not only extend to the base of the tentacula, 

 but run across the oral disc, and terminate in a central mouth. The 

 tentacula are short, obtuse, ciliated on the margins, and strengthened 

 at their roots by numerous calcareous spicula. The polyp cells are 

 oval, placed just under the investing membrane, and are the termi- 

 nating points of certain long canals which traverse the whole polypi- 

 dom. The polyps, which are distributed over the whole surface, can 

 withdraw into the cavities ; they are, besides, of extreme sensibility, 

 the least shock impresses itself on the tentacula, the impulse of a 

 wave even producing contraction, in response the animal imme- 

 diately retires to hide itself in the cell. 



We find, as we have said, on the coast, in the Channel, and in 

 the North Sea, Alcyotiium digitatmn, the mass of which is of a reddish 

 white, ferruginous, or orange colour. A. stellatum, found on the 

 shores of the Mediterranean, is expanded in its upper part, narrow 

 towards its base, very rough on the surface, and rose-coloured ; 

 A. palmatum is cylindrical, branching at the summit, of a deep red, 

 except at the base, where it is yellow — this is met with in the 

 Mediterranean. 



We may note as a type altogether different from any yet touched 

 upon the genus Nephtkya, in which the polypidom is a coriaceous 

 tissue bristling with spicula over its whole surface. In N. Chabrolii. 



