466 G. HERBERT FOWLER. 



over each of the six chief pairs of mesenteries, and six addi- 

 tional (? entoccelic) tentacles between them. In the histo- 

 logical condition of my specimens no difference is apparent 

 between the stomodseum and the oral disc. The contortion of 

 the specimen was so considerable that I am unable to speak 

 to the presence of siphonoglyphs. 



It is in the arrangement of the mesenteries and their muscles 

 that the chief interest of Octineon consists. Their exact 

 number appears to vary considerably in different specimens : 

 generally there are about thirty-five to forty-five ; but as they 

 are almost all devoid of filaments and of generative organs, 

 their exact number probably has no particular significance. 

 They are generally, but not always, in pairs of approximately 

 equal breadth. 



There are, however, always twelve larger mesenteries, which 

 we may safely term " primary," which appear to reach the 

 stomodseum, and to extend downwards to be inserted on the 

 pedal disc. In spite of its Zoanthid habit of forming a sandy 

 incrustation of foreign bodies embedded in the raesogloea, 

 Octineon is therefore a Hexactinian, as possessing twelve 

 primary mesenteries; but the next point that I wish to bring 

 out is, that of these twelve Hexactinian mesenteries only eight 

 carry the extraordinarily powerful retractor muscles, and that 

 these muscles are arranged in the manner characteristic of a 

 third group, the Edwardsise. We have therefore, in Octineon, 

 an Actiniarian with the characteristic habit of a Zoanthid, with 

 the twelve mesenteries of a Hexactinian, and the eight muscles 

 of an Edwardsid. 



The section, fig. 11, is taken near the apex of the cone, and 

 exhibits the twelve primary mesenteries. From the central tube, 

 which is the inturned body-wall, they are cut off by the large 

 stoma represented in fig. 23. In these mesenteries at this 

 height, as in all the inferior mesenteries, the fact that a single 

 layer of weak muscle-fibres occurs on the extremely thin meso- 

 gloea lamina is recognisable. (An obvious exception is notice- 

 able in the mesenteries 3, 3, and will be referred to below.) 



There are in all four types of mesenteries present (fig. 12) : — 



