ON HsEMONAIS LAURENTII. 775 



the anterior part of the body. Here in many cases the cells which contain the 

 brown particles are disintegrating ; and in the prostomium and round the pharynx 

 the cells have disappeared, leaving only loose aggregates of brownish-coloured grains. 



The new segments produced in the budding zone at first contain no chloragogen. 

 It begins to appear in the prostomium of the newly formed head soon after separa- 

 tion, and could be seen in an animal in which the dorsal setae had disappeared as far 

 back as segment xii. 



The alimentary canal differs from that of many Naididse, and reminds the 

 observer of the condition in the Tubificidse, in showing no obvious differentiation into 

 cesophagus, stomach, and intestine. The pharynx, in segments ii-iv, is invested 

 by chloragogen at both ends, but free in the middle (fig. l). A transverse section 

 through the middle of its length (fig. 2) shows that its lumen has here the shape of 

 the letter T inverted (j_) — in other words, there is a dorsal diverticulum with a 

 median cavity which is narrow from side to side ; the dorsal diverticulum and the 

 dorsal wall of the main tube are heavily ciliated, while the ventral wall of the 

 pharynx shows no cilia, and the cells are not so high. 



On the sides of the pharynx are a number of gland-cells, arranged in groups of 

 three, four, or more, the groups separated by muscular strands passing outwards 

 from the pharyngeal wall to the parietes (figs. 1, 2). In a vertical longitudinal 

 section which cuts the lateral wall of the pharynx tangentially (fig. l) the arrange- 

 ment of these groups of cells is well seen, and the appearance resembles that of 

 the acini of an ordinary racemose gland in the higher animals. The individual 

 cells are usually elongated, pyriform or fusiform, and are continued by means of 

 a narrower neck into the epithelial layer of the pharynx, to which they thus 

 properly belong. It is very possible, however, that some of the cells in this situa- 

 tion are of peritoneal origin and have no direct connection with the pharyngeal 

 lining epithelium. 



The oesophagus is narrow as far back as segment xii or thereabouts ; it then 

 begins to dilate, and the intestine may be said to be established in xiii or xiv. The 

 intestine is characterised by being dilated in each segment and constricted at the 

 septa. The histological characters of the epithelium also change : in the oesophagus 

 the cells are long, but of rather unequal height, and groups of two or three are united 

 together to form minute papilliform elevations ; in the first part of the intestine the 

 cells take up more of the eosin stain, are not on the whole so tall or so irregular, and 

 have numerous spaces between their bases ; but I am not satisfied that these differences 

 are constant. 



The anus is dorsal, and a strong ascending ciliary current is very obvious in the 

 posterior part of the gut. The margin of the anus may be slightly puckered, and in 

 the best-marked cases there is a slight eversion of the epithelial lining of the intestine, 

 which appears as a dorsal and ventral lip at the anal orifice. The term " eversion " 

 is in strictness not applicable, since the projections are epithelial only ; there is no 



