CLASSIFICATION OF ACTINIARIA 261 



the latter condition fairly frequent among advanced forms. Not more 

 than one tentacle comnumicates with each exo- and endocoel. The 

 sphincter, if present, is mesogloeal. Acontia are often present, and 

 are the typical special stinging organs of the group ; sometimes they are 

 rudimentary and hard to detect. Secondary mesenteries appear in 

 exocoels, not endocoels. Ectodermal muscle in the body-wall is excep- 

 tional. Mesenterial musculature is typically well developed; at its best 

 very strong. 



The ten families of Mesomyaria arid the contained genera are 

 defined in Part I of this paper. The only modification required 

 is, that the word ' Mesomyaria ' be substituted for the word 

 ' Actiniina ' in the family definitions there given. ' Actiniina ' 

 was used provisionally, pending the working out and publica- 

 tion of the groups set up in Part II. 



• Sub-tribe 4. Endomyaria, mihi. 



Nynantheae with a definite base save in one case, but it may be 

 reduced or rather physa-like, or slit-like, or converted into a float, &c. 

 Usually there are basilar muscles. Form variable, body-wall either 

 smooth or with verrucae or acrorhagi or vesicles, which may become 

 complex outgrowths — more than one of these things may be present in 

 the same animal. There is not the same tendency to ponderous body- 

 walls (though of course these are sometimes fairly thick) and knobs 

 and crests of mesogloea as in some Mesomyaria. Ectodermal muscle 

 in the body-wall is exceptional. Cinclides do occur, but their distribu- 

 tion is little known. The tentacles are simple or complicated in various 

 ways (see Part 11, Text-figs. 14 and 19), but do not have basal meso- 

 gloeal swellings. Their longitudinal musculature is less often mesogloeal 

 than in Mesomyaria. At their best development, in forms of warm 

 seas, they may form complex tufts and give a frill-like or seaweed-like 

 effect (see Part II, Text-fig. 19, and Text-fig. 18 for vesicles). In some 

 forms not more than one tentacle joins each endocoel and exocoel. In 

 others there is more than one on some or all of the endocoels, but not 

 more than one on each exocoel. In still others the exocoels also may have 

 more than one — so that sometimes there are many per endo- and exo- 

 coel. Sometimes the tentacles are reduced to sessile vesicular structures. 

 The sphincter, if present, is endodermal of some grade, may be very strong 

 and circumsci'ibed at its best though often weak or diffuse, &c. There 

 are never any acontia. Secondary mesenteries develop in exocoels. 

 Mesenterial musculature is typically well developed; at its best very 

 strong. 



