1 66 



PHYLUM C(ELENTERA. 



pillar may be formed. The outer wall of the theca may 

 bear vertical ridges or costse, and these may be connected 

 with neighbouring costse of other polyps by horizontal 

 shelves or dissepiments. Both septa and costae correspond 

 to intermesenteric spaces. (See Shipley's Zoology of the 

 Invertebratci) pp. 68-71.) 



ANTI PATH ARI ANS 



Usually arborescent, sometimes whip-like colonies, of wide distribu- 

 tion in most seas, often called " black corals." A spinose hollow 

 horny axis is covered with ccenenchyma and regularly arranged polyps, 



Vi 



FIG. 83. Structure of Antipatharians. 



X. A group of polyps M., mouth ; t., tentacles. 



2. Axis without polyps and ccenenchyma, covered with spines 



q. Vertical section of a polyp A., axis ; /., tentacle ; g., gullet; 



m., mesentery; o., ovary ; m.f., mesenteric filaments. 

 4. Cross section of a polyp EC., ectoderm; M., mesoglcea ; 



EN., endoderm ; (7., gullet ; MS., mesenteries. 



without any trace of spicules. A polyp is usually oval in section, with 

 its long diameter in the line of the axis, and its gullet elongated at 

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

 tentacles, ten mesenteries,, and two ill-defined siphonoglyphes. The 

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

 right angles to the elongated stomodseum, bear gonads. The develop- 

 ment is unknown. 



