258 J. H. ASH WORTH. 



dorsal vessel ; these are the blood-vessels or sinuses (see 

 below) similar to those described in Arenicola. 



About the level of the fourteenth to sixteenth sette the 

 stomach passes gradually into the intestine, which is a 

 cylindrical tube narrowing slightly towards the anus. 



The ventral wall of the anus is slightly notched in the 

 middle line, and on each side of the notch is a protuberance 

 from which the two anal cirri arise (fig. 6). 



As pointed out above (p. 255), it is moderately certain that 

 the stomach, and to a less extent the anterior part of the 

 intestine, are swung backwards and forwards during diges- 

 tion. In addition to this the passage of the contained sand, 

 etc., is aided by the strong peristaltic movements of the 

 anterior part of the intestine which have been observed by 

 Danielssen (1859, p. 70). 



The alimentary canal of most of the specimens was dis- 

 tended with fine sand and debris in which quartz grains, 

 spicules, frustules of diatoms, and Foraminifera were clearly 

 recognisable. 



Histology. — Tlie oesophagus is lined throughout by cili- 

 ated columnar cells. There are no gland-cells in this part of 

 the alimentary canal. The ciliated cells are supported by a 

 thin layer of muscle-fibres. The walls of the oesophageal 

 pouches are raised internally into a number of folds, which 

 are at first mere ridges, but increase in size with the growth 

 of the animal. Each fold consists of two layers of epithelial 

 cells, between which is a blood-sinus, slightly enlarged, near 

 the inner edge of each fold (fig. 23) . 



On the external surface of the pouches there is a network, 

 apparently a blood-sinus, with which the sinuses of the folds 

 are continuous. The cells lining the cavity of the cesopha- 

 geal pouches are cubical or flattened^ and are not ciliated. 

 The protoplasm of these cells usually contains an enormous 

 number of minute spherical granules (or cavities from which 

 the granules have been dissolved), which give rise to the 

 glandular secretion (fig. 24). The latter may often be seen 

 in masses of considerable size in sections of the hinder 



