ACTINOZOA. 



91 



the polypes of the Alcyonaria is, in essential anatomical features, the 

 same as in the Sea-anemones, but the organism commonly consists 

 of two sets of polypes, which differ from one another in structure 

 and in function. A regular coral may or may not be present, and 

 when present, varies much in its character ; but most Alcyoiiarians 

 possess numerous microscopic spicules of lime in their tissues. 



Of the various different organisms included under this order, one 

 of the best known is the " Dead-men's-fingers," or Alcyonium, which 

 occurs commonly on both sides of the North Atlantic. It forms 

 spongy-looking masses of a yellow or orange colour, attached to shells 

 and other marine objects. The whole mass is covered with little 

 star-shaped apertures, through which the delicate polypes can be 



Fig. 53. — Colony of Vereiillum 

 cyiwTnorium, of the natural size, 

 with the polypes protruded. 



Fig. 54. — Pennatula sulcata, seen 

 from the dorsal side. Slightly 

 reduced, after KoUiker. 



protruded and retracted at will. Another well-known member of 

 this order — the type of another family — is the "Sea-rod " ( Virgularia), 

 which has the form of a long rod-shaped body of a light flesh colour, 

 supported upon a calcareous rod (sclerobasis), somewhat like a knit- 

 ting-needle, which is covered by the ccenosarc. From the cosnosarc 

 are given out lateral processes, each of which bears numerous polypes. 

 Closely allied to Virgularia is the " C!ock's-comb " (Pennatula) ; but 

 in this the lower end of the coenosarc is naked and fleshy (fig. 54), 



