REPORT ON THE ACTINIARIA. 53 



specimens of one species, wliicli 1 will here describe on account of the stiil<iug appearance 

 of the body. 



The body of Stephanidium is in diameter l"5-2"2 mm., and about 1 mm. high in 

 the contracted condition. Tlie epithelium had been stripped off at most points, and 

 remained only on the lowest parts of the body-wall, the mesogloea thus being exposed 

 over a wide extent, and allowing the mesenteries to be seen through it. The resulting 

 appearance is drawn in PL I. fig. 14, and was oHginally interpreted as follows: — 1 

 believed that the surface was indented by deep furrows corresponding to the 

 mesenteries ; the ridges lying between these furrows become narrower, from a definite 

 part of the body-wall outwards ; they are extremely unequal in breadth, a broader and 

 a narrower ridge alternating regularly with one another, and to every broader ridge 

 corresponds, at the upper edge of the body-wall, a special structure of the following 

 nature : the edge of the body-wall is elevated into a kind of battlement (PI. III. fig. 7), 

 on the outer side of which are situated roundish or oval bodies, which call to mind the 

 marginal spherules of Actinia mesembryanthemum. The longitudinal ridge of the body- 

 wall meets the spherule, splits into two forks, and surrounds the structure from below. 



Sections through the animal, however, showed that the body-wall is smooth, and 

 that the appearance of furrows was caused by the insertions of the mesenteries. On 

 the other hand, the spherules are really present, and form evaginations of the body- wall, 

 above a spot which is marked by the position of the circular muscle (PI. III. fig. 1). The 

 latter, in spite of the contracted condition of the Actinian, is of weak development, 

 and is merely a part of that endodermal circular muscle-layer which is at other points 

 hardly recognisable, but is here elevated into small folds. It is most obvious at those 

 places where it traverses the thickness of a mesenterial insertion ; here the endodermal 

 muscle-layer is not recognisable, but mesogloeal muscle-rings are embedded in the 

 region of the sphincter, largest at the upper end, and becoming gradually less obvious 

 in a downward direction, till one meets mth small groups of only two or three fibres, 

 or even with completely isolated fibres. 



Of the tentacles and oral disc it can only be said that the ectodermal muscle- 

 layer is strongly pleated. 



The mesenteries, the number of which may be learnt even by superficial observa- 

 tion, amount to twenty-six, and are differentiated, as in the Zoantheae, into macro- 

 and micro-mesenteries. Of their arrangement, despite much trouble, I have not yet 

 arrived at a completely clear comprehension, but I could demonstrate the probability 

 that the directives of the one side are macro-mesenteries, those of the other micro- 

 mesenteries, that dorsal and ventral mesenterial zones meet with micro-mesenteries, and 

 that one pair is more developed on the one side than on the other. 



The mesenteries (probably only macro-mesenteries) bore ripe male generative 

 organs. I was unable to recognise a siphonoglyphe. 



