THE VISCERAL MASS IN ANTEDON ROSACEUS. 309 



The mouth is oval, runs obliquely downwards, and is now for the first 

 time very distinctly bounded. The beginning of the anal cone is 

 visible as a small conical papilla placed interradially. 



In sections the alimentary canal is seen to be fairly well developed; 

 it contains food refuse, indicating that it has begun to be used again. 

 The epidermis covering the depressed area round the mouth is now 

 composed of columnar, nucleated cells, and passes gradually into the 

 inner lining of the oesophagus, the cells of which are still more colum- 

 nar. The walls of the stomach are also composed of the usual two 

 layers, an inner layer of columnar, nucleated cells, and an outer layer 

 of connective tissue j this outer layer is connected with the loose con- 

 nective tissue filling the body cavity. In the specimen now described 

 the cells forming the inner wall of the alimentary canal have become 

 columnar right up to the anus. The anus is very minute and situated 

 on the top of a small papilla. The columnar cells lining the cavity 

 of the anus are very small and pass gradually into the epidermic cells 

 covering the rudimentary anal cone ; the epidermic layer at this point 

 is thickened. In the region of the stomach the walls of the alimen- 

 tary canal are beginning to become folded, especially on the axial side, 

 and on this side also the glandular layer is thicker. 



In another specimen of this date, which appears not to have ad- 

 vanced quite so far in regeneration, the alimentary canal, as it ap- 

 proaches the anus, narrows very much ; its inner wall, which in the 

 first part of its course is composed of the usual columnar cells, here 

 consists of a layer of very minute cells, such as line the whole of the 

 canal at an earlier date, and identical with the cells covering the 

 general surface of the disc. In thickness this inner layer is very 

 irregular and the cells composing it appear to be rapidly proliferating. 

 At its extreme end they block up the lumen of the canal, so that the 

 latter appears solid, and the end of the canal fuses indistinguishably 

 with the layer of similar cells covering the general surface of the disc. 

 At the point of fusion there is a thick mass of these minute round 

 cells, forming a little elevation on the surface of the disc. This indi- 

 cates the position of the future anal cone. In this specimen I have 

 been able to fiud no distinct anal opening. These facts appear to me 

 to support the view that the alimentary canal is formed by invagi- 

 nation from its oral end. 



Twelve days. — No great advance has been made on the condition 

 presented by a nine days specimen. In one specimen the pentagon 



