lander: anatomy of hemiukus ceenatus. 11 



Digestive System. 



There is no prepliarynx, the pharjnx opening directly into the dorso- 

 posterior part of the oral sucker. The pharynx is relatively quite large, 

 varying from 0.108 mm. to 0.126 mm. in diameter and from 0.117 mm. 

 to 0.144 mm. in length. 



There is a short oesophagus, in spite of frequent statements to the 

 contrary. In preserved specimens it turns dorsally from the posterior 

 end of the pharynx, then bends anteriorly and extends to about the 

 middle of the dorsal surface of the pharynx, where it bifurcates to join the 

 intestinal coeca. It is provided with a thick lining resembling cuticula, 

 which also extends a short distance into each of the coeca, where it 

 ceases abruptly at the beginning of the intestinal epithelium (Plate 3, 

 Fig. 35, eta'.). 



The intestinal coeca (Fig. 1) pass from the end of the oesophagus a 

 short distance toward either side of the body, then turning backwards 

 extend to near the posterior end of the appendix. There is a slight con- 

 striction between the transverse and longitudinal portion of each coecum 

 (Fig. 35). The condition of the intestinal epithelium is almost identical 

 with that described by Juel ('89) for the species of Apoblema which he 

 studied. In the anterior transverse portion of the coeca it has the appear- 

 ance of long, closely j^acked threads with a few small conical granular 

 masses next to the basement membrane (Plate 3, Fig. 35). As Juel sug- 

 gests, I believe these are the basal portions of the epithelial cells whose 

 inner portions have become modified into the fine protoplasmic threads. 

 Looss ('94, p. 142) describes a similar condition of the intestinal epithe- 

 lium of several distoraes and speaks as though the entire epithelium was 

 so modified. Looss shows nuclei in his figure ; Juel does not. I do not 

 find any nuclei in this part of the epithelium, but deeply staining bodies 

 are present, the significance of which will presently be discussed. The 

 epithelium of the greater part of the coeca consists of slender, nearly 

 cylindrical cells, usually becoming smaller toward their free ends (Plate 2, 

 Fig. 25 ; Plate 3, Fig. 36), but, as Juel states, in some places the cells 

 appear to have fused together into a common mass. According to Juel 

 many of the cells contain each a small nucleus, but many appear to be 

 without nuclei. I have been unable to distinguish any nuclei in the 

 epithelial cells of Hemiurus crenatus, but 1 have found in every specimen 

 sectioned, as well as in several preparations examined without sectioning, 

 numerous, deeply staining, spherical, oval, or club-shaped, nucleus-like 



