524 OLWEN M. EEES. 



tives. The number of mesenteries reaching the CBSophagus was about 

 24 pairs, including the directives. 



. The column wall is strong, the mesogloea being much thicker than the 

 ectoderm. The ectoderm has a spongy appearance and contains a large 

 number of gland cells, which are arranged near the outer margin, and 

 most of them contain a granular substance like those of S. viduata. 

 The opening of the cinclides is like that described and figured by Carlgren 

 for S. viduata ; the canal consists exclusively of ectoderm, endoderm only 

 beginning at the inner end. 



The mesogloea has a fibrous appearance when examined under a low 

 power of the microscope, but under the high ]5ower, the cavities of the 

 cells give it an almost spongy appearance. The cells become smaller 

 and the whole mesogloea becomes stronger near the endodermal margin, 

 and this gives rise to an endodermal muscle. As in S. viduata this is 

 fairly well developed and much folded in transverse section. The folds 

 are not branched and are irregular in shape. In the upper part of the 

 column the muscle is differentiated into a mesogloeal sphincter which is 

 very strong especially at the top, diminishing downwards. There are 

 numerous mesogloeal processes projecting into the endoderm, and they are 

 deeply set and are often branched. These projections are not present 

 in the sphincter muscle of S. viduata as figured in " Nordische Actinien." 

 The endoderm of the column wall is of about the same thickness as the 

 ectoderm and contains numerous zooxanthellse ; and the number of 

 these increases on the mesenteries, especially in the region near the 

 oesophagus. 



The primary mesenteries all have a large and well-developed retractor 

 muscle. 



As in S. viduata and S. undata, the muscle cushions of the directive 

 septa are quite near the oesophagus, while those of the remaining septa 

 are nearer the middle of the septa. The former are more concentrated 

 and higher than the latter, w^hich are extensive and more shallow. The 

 retractor muscle is of the usual shape and contains a large number of 

 arborescent folds. 



In the largest specimen (c) this muscle in section was divided up into 

 a number of folds, each fold being supplied with numerous mesogloeal 

 fibres, as shown in the figure (Fig. 1). In this way the whole septum is 

 very much elongated. 



The parieto-basilar muscle is well developed and appears very long 

 in cross section, and most of the mesogloeal processes arise from the side 

 on which the retractor muscle occurs. These processes are not numerous 



