CCELENTKRATA : ALCYONARIA. 



127 



ing fringes are short. The polypes have eight tentacles. Tht 

 sclerobasis is in the form of a long calcareous rod, like a knit- 

 ting-needle, and part of it is usually naked. No spicula are 

 found in the tissues of Virgularia. In the nearly-allied Pavo- 

 nana the polype-mass is quadrangular in shape. 



Fig. 34. — Fennatuia pkospJiorea 

 (after Johnston). 



Fig. 35 — PeiinatuIidEe, 

 Virgularia tnirabilis. 

 a A portion of the 

 stem in the living con- 

 dition^ enlarged ; b 

 Portion of the stem in 

 its dead condition. 



Family IV. GoRGONiDi*.. - — In the Gorgonidm, or " Sea- 

 shrubs," there is an arborescent ccenosarc permanently rooted 

 and provided with a grooved, or sulcate, branched sclerobasis, 

 whidi is sometimes associated withi true tissue - secretions, 

 termed " dermo-sclerites." 



The sclerobasis of the Gorgonidce varies a good deal in its 

 composition. In some it is corneous, and these have often 

 been confounded with the AntipathidcB, amongst the Zoantharia. 

 The distinction, however, between them is easy, when it is 

 remembered that the polypes in the Gorgonidce have tentacles 

 in multiples of four, whilst in the Antipathidce they are in sixes. 

 The sclerobasis, too, in the former is always marked by groove.s, 

 whereas in the latter it is always either smooth or spinulous. 



