REPORT ON THE ACTINIARIA. 27 



rows were closely identical. The number of the papillae varies between six and seven. 

 From this observation it may be inferred that with increasing growth an addition to the 

 rows of papillae occurs, proportional to the additions to the pairs of mesenteries. In 

 connection with this is the fact that the rows of papillae correspond to the intra- 

 mesenterial chambers. 



Two examples of the present species were taken from the same locality as the one 

 example of Amphianthus bathybium, Station 241. This renders it necessary to weigh 

 the possibility that the differences which have been made of importance, are perhaps 

 only of secondary significance, and that all the specimens may be referred to one species. 

 Owing to the limited material, the cpiestion could not well be decided. 



From the minuteness of the organism, anatomical investigation could only be 

 effected by means of longitudinal and transverse sections ; to this purpose I devoted 

 two complete examples, the one from Station 241, the other from Station 244, besides 

 quadrants of specimens from Stations 241 and 56. It resulted that the papillae were 

 proved to be solid outgrowths of the body-wall, and, like it, consist of an extremely 

 fibrous mesogloea. The fibres are generally interlacing, as is for the most part normal 

 among Actiniae, so that the tissue appears finely granular ; they also here and there 

 show a tendency to arrangement into bundles. In transverse sections, therefore, a 

 reticulate figuring appears round the endodermal lining ; this can be rendered clearer 

 by staining, when it appears that small branches of the fibrils cross the course of the 

 rest of the fibrils in a longitudinal direction. Similarly, one sees numerous radial fibres 

 also in the peripheral parts of the body-wall, and a corresponding radial striation is 

 thus produced. 



The sphincter is completely embedded in the connective-tissue of the body-wall, 

 and consists of small mesoglceal muscle-bundles composed of few, but powerful, fibres. 

 In some places only two or three fibres are united in a bundle, or a single fibre even 

 may run in the connective-tissue. The individual bundles are enclosed in such numbers 

 in the mesogloea as to be separated from the two epithelial surfaces by only a narrow 

 layer. In transverse section, the muscle in most cases' forms a club-shaped figure, being 

 of weak development below and broadening out strongly upwards ; this increase in 

 breadth is so considerable that the whole upper end of the body-wall is strongly thickened. 

 Even in the youngest specimens the sphincter was completely formed, and inclosed in 

 the mesogloea. As it is separated from the endodermal circular musculature by the 

 insertion of a layer of connective-tissue, it seems that in the course of further growth 

 the bundles can only increase by division of the bundles of fibrils. 



The musculature of the oral disc and tentacles is purely ectodermal, but very 

 markedly pleated. The number of tentacles corresponds to the number of mesenteries, 

 and this is different in the different individuals investigated. In the youngest specimen 

 from Station 244, the two first cycles were already formed, and of the third traces 



