the. Actiniarian Family Aliciidse. o 



vesicles, being smaller and showing a long spiral thread 

 coiled up inside. Tiiey are mostly limited to the uj)[>er 

 naked part of the column. The mesogloea is thrown into 

 deep plaitings to support a strong endodermal muscle. 



The vesicles have a broad ectoderm, which, in limited 

 j)laces, evidently corresponding witii the thickenings at the 

 tips, is crowded with enormous nematocysts rounded at each 

 end. These are clear or contain granular matter, and have 

 only a very short sj)iral thread ; nearer tlie origin of the 

 vesicles — that is, on the peduncle — they are smaller and have 

 a long spiral thread as in the column-wall. Numerous 

 strongly staining elongated bodies occur in the deeper part of 

 the ectoderm, evidently developing nematocysts *. The 

 mesogloea is thin, and the endoderm, iiowdecomj)osed, contains 

 much granular pigment matter. 



SpJiincter muscle. — The sphincter muscle is of the same 

 character as that found in Alicia costce, i. e. endodermal, 

 diffuse, and elongated. The ])laitings of the mesogloea are, 

 however, better developed than in that species, becoming 

 more dendriform and thinning out for some distance. The 

 material does not admit of a determination of the exact limits 

 of the muscle, but it appears to commence just below the 

 tentacles and to extend into the region of the vesicles, being 

 merely a concentration of the circular endodermal muscle 

 occurring throughout the column- wall. 



lentaclis. — The ectoderm of the tentacles is thick and 

 richly supplied with nematocysts like those of the column- 

 wall and arranged at right angles to and close to the surface. 

 An occasional larger one, similar to the vesicular form, may 

 be met with. The mesogloea is broad, and forms small 

 dendriform outgrowths on its internal border for the support 

 of the strong circular endodermal muscle. 



(Esophagus. — The ectoderm of the oesophagus is a deep 

 layer and much folded. It contains numerous elongated 

 stinging-cells and many large cells with pigmented granular 

 contents, arranged in a nearly central zone. 



The mesogloea is narrow and supports a weak ectodermal 

 and endodermal musculature. 



Mesenteries. — Twenty-four pairs of mesenteries are present, 

 similar in arrangement to those of A. costce^ viz. : six perfect 

 pairs, two pairs being directives ; six pairs forming a second 

 cycle, alternating with the first ; and twelve pairs in a third 



* In the description of A. cosiee it is stated (' Annals,' 1895, xv. p. 216) 

 that the vesicles are not batteries of nematocysts. A re-examination of 

 the sections in the light of other forms shows that they must be so regarded, 

 the so-called gland-cells being developing stinging-cells. 



