REPORT ON THE ACTINIARIA. 121 



a layer of sand 5 millimetres thick (even in PL II. fig. 10 the soft part of the wall is too 

 large in proportion to the layer of sand granules). Where the sand grains are absent the 

 fundamental substance is homogeneous and furnished with two different forms of cells, 

 small branched cells and larger roundish ones, the latter being entirely filled with strongly 

 refractive concrement-like granules. The tissue between the sand granules (PL XIV. fig. 8), 

 on the other hand, appears rather fibrous, and even the corpuscles of connective tissue are 

 fusiform in shape. The direction of the fibres and the fusiform cells is parallel to the 

 surface of the body. In most parts the sand granules are so thickly compacted that the 

 fundamental substance is entirely covered. 



There are no ectodermal vessels in the wall, but the supporting fibres are very 

 numerous ; they are richly furnished with granular protoplasm, are very fine and 

 branched on the endodermal side, whilst towards the ectoderm they become lost among 

 the sand granules. 



The mesodermal circular muscle, which is strongly developed as in the other Zoanthese, 

 is not confined merely to the inverted part of the wall, but extends a good way down 

 into the outer section. It is strongest where it begins close to the oral disk and lies 

 in the non- encrusted section of the wall, it then becomes narrower and gradually 

 approaches the endoderm, till the lower end almost touches the epithelium. It consists 

 of bundles of fibrillse, which give repeatedly waved figures in transverse section ; several 

 bundles are united into roundish bundles of the second order, which remain farther apart 

 from one another. 



Whilst the wall is very thick and firm, all the inner parts consist of delicate, easily 

 torn lamellae. The oral disk only is tolerably strong, and foreign bodies (sponge spicules, 

 sand granules) are enclosed here and there in its supporting lamella. It is covered by a 

 smooth layer of ectodermal radial muscles, and the margin bears two rows of tentacles ; 

 I could not determine the number of the tentacles accurately because of the strong con- 

 traction, but there were probably about sixty of them. 



Before the oral disk passes into the oesophagus, which is of considerable size, it rises 

 into a thin, sharp-margined lip, which is repeatedly indented at the edge. A large 

 number of longitudinal ridges of the oesophagus, which correspond to the origins of the 

 perfect septa, spring from these indentations. 



The oesophageal groove is remarkably distinct ; it is distinguished by its depth, and is 

 enclosed by two broad folds, almost as hard as cartilage. Gray probably had these folds 

 in mind when he specially mentions that in Sphenopus marsujiinUs " the laniinas of 

 the stomach have a cartilaginous edge." They extend a little way beyond the lower 

 margin of the stomach and form a projection, resembling the prow of a boat. 



The arrangement of the septa agrees essentially with that already described in detail 

 for Zoanthus, sp. ? Two small directive septa lie at the dorsal end of the oesophagus, 

 two large directive septa at the ventral end, which is easily recognised by the oesophageal 



(ZOOL. CHALL. EXP. PART XV. 1882.) P 16 



