COLLECTION OF NEMEETEANS FROM SINGAPORE. 123 



The muscle layers in the oesophageal region are well 

 developed, the external longitudinal layer {mlo.) being more 

 than double the thickness of the circular layer {mc), whilst 

 this in turn is about twice as thick as the internal longitu- 

 dinal layer [mil.) . Further back the circular layer becomes 

 relatively smaller, and near the posterior end the outer longi- 

 tudinal layer becomes very sparse. The horizontal layer 

 over the mouth is well marked. The dorso-ventral muscles 

 between the intestinal diverticula are strong. There is no 

 diagonal muscle layer. 



The vascular system anteriorly forms a well-marked 

 head loop. There is in addition a small dorsal portion sepa- 

 rated off. The rest of the vascular system is formed on the 

 usual type for the family as described by Oudemans (6) and 

 Coe (4). The proboscis vessel leaves the proboscis sheath 

 about 6'5 mm. from the anterior end. 



The alimentary canal is of the usual type. The intes- 

 tinal diverticula are very deep, and Avith a very narrow 

 lumen (fig. 15). There is no ventral gutter posteriorly. 



The proboscis shows the usual three layers of muscles, 

 i. e. outer longitudinal, circular, and inner longitudinal, the 

 last named being the thickest. Outside the circular muscles 

 is a well-marked nerve layer. There are two muscle crosses 

 (fig. 13, mcr.) dorsally and ventrally. The epithelium either 

 dorsally or ventrally (which it is impossible to determine) is 

 considerably thickened and highly glandular. The outer 

 borders of the cells are here rendered conspicuous by the 

 presence of a dark greenish pigment. 



The proboscis sheath extends to within a millimetre of 

 the posterior end, though it is here much reduced. 



The generative organs appear as thin- walled sacs 

 between the intestinal diverticula. There is no trace of 

 sexual products. 



The excretory system commences about 3 mm. from the 

 tip of the snout, and extends over the same distance. The 

 tubules, except at the anterior portion, are exclusively ventral 

 to the level of the side stems. Anteriorly there is a single 



