108 



MANUAL OF ZOOLOGY. 



the sea-bottom. 



a 



Fig. 28. Pennatulidae. 

 Vii-gulai-ia mirabilis. 



a. A portion of the 

 stem in the living 

 condition, enlarged. 



b. Portion of the stem 

 in its dead condition. 



like lateral pinnae, which bear the polypes ; whilst its proximal 

 end is smooth and fleshy, and is probably sunk in the mud of 

 ~~ ^~" This latter portion of the coenosarc is, like- 

 wise, strengthened by a long, slender, styli- 

 form sclerobasis, resembling a rod in shape, 

 whilst spicula occur also in the tentacles 

 and ectoderm. Some Pennatulcz are phos- 

 phorescent. 



In Virgularia (fig. 28), which, like Pen- 

 natula, occurs not uncommonly in British 

 seas, the actinosoma is much longer and 

 more slender than in the preceding, and 

 the polype-bearing fringes are short. The 

 polypes have eight tentacles. The scle- 

 robasis is in the form of a long calcareous 

 rod, like a knitting-needle, and part of it 

 is usually naked. No spicula are found in 

 the tissues of Virgularia. 



FAMILY IV. GORGONID^;. In the Gor- 

 gonidce, or ' Sea-shrubs,' there is an arbores- 

 cent ccenosarc permanently rooted and pro- 

 vided with a grooved, or sulcate, branched sclerobasis, which 

 is sometimes associated with 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 Antipathidcs, 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 

 grooves, whereas in the latter it is always either smooth or 

 spinulous. In Isis and Hopsea the sclerobasis consists of 

 alternate calcareous and horny segments, branches being de- 

 veloped in the former from the calcareous, and in the latter 

 from the horny segments. 



In Corallium rubruin, the 'red coral ' of commerce, the 

 sclerobasis is unarticulate, or unjointed, and is entirely cal- 

 careous. It is the most familiar member of the family, and is 

 largely imported for ornamental purposes. Bed coral consists 

 of a branched densely calcareous sclerobasis, which is finely 

 grooved upon its surface, and is of a bright red colour. The 

 corallum is invested by a coenosarc, also of a red colour, 

 which is studded by the apertures for the polypes, which are 

 white, and possess eight pinnately- fringed tentacles. The 

 entire coenosarc is channelled out by a number of anastomosing 



