ALCYONARIANS 



199 



elongated at right angles to this. There are usually six simple non- 

 retractile tentacles, 6-10 mesenteries, and two ill-defined siphonoglyphs. 

 The mesenteries are without muscle-banners. The two longest, 

 running at right angles to the elongated stoniodacum, bear gonads. 

 The development is unknown. 

 Examples : — 



Antipatkes (arborescent). Cirripaihcs (whip-like). Lciopaihes 

 (with twelve mesenteries). Dendruhrachia (with eight pinnate re- 

 tractile tentacles). 



Alcyonaria 



In the Alcyonarian polyp there are eight tentacles, 

 almost always pinnate, and eight mesenteries attached to 



-rp 



Fig. 105. — Corallium rubrum, a corner of a colony. — 

 After Lacaze-Duthiers. 



A., Anthocodia or retractile portion^ of a polyp; r.p., com- 

 pletely retracted polyp, with the verruca or calyx portion 

 left protruding ; C., ccenenchyma ; T., pinnate tentacles. 



the stomodaeum. In Bourne's Acrossota the tentacles 

 have no pinnules. There is one longitudinal ciliated 

 groove (siphonoglyph or sulcus) in the stomoda?um (ven- 

 trally). The mesenteries bear retractor muscles, all 

 situated on the sulcar aspect (see Fig. loi), and each mesen- 

 tery bears a mesenteric filament. The two dorsal (asulcar) 



