COLLECTION OF NEMRRTEANS FROM STNGAPOEE. 125 



being- more than double tlie thickness of the circular layer, 

 whilst this in turn is about four times as thick as the inner 

 longitudinal layer. There is a layer of longitudinal fibres 

 between the proboscis slieath and alimentary canal (cf. 

 Lineus versicolor, Burger [3], p. 638). There is no dia- 

 gonal muscle layer. 



The vascular system anteriorly shows a network of small 

 lacunae instead of a head loop. From this network the main 

 cephalic vessel, just before the brain, is situated dorsally to 

 the proboscis shenth (as in the Eupoliidfe). The oesophageal 

 vessels are merged into a single large lacuna on each side in 

 the posterior region of the oesophagus, about 8 mm. from the 

 tip of the snout. 



The alimentary canal presents no special features. A 

 ventral gutter is present in the intestinal i-egion, which com- 

 mences about 1'5 cm. from the tip of the snout. It is very 

 conspicuous. 



The proboscis is extremely thin. It contains no muscle 

 crosses. 



In the proboscis sheath the circular layer is extremely 

 thick in the mouth region. The proboscis sheath is not found 

 in the posterior 3 cm. of the body. 



The generative sacs contain developed ova. 



The excretory system commences 3*4 mm. behind the 

 snout, and extends over 38 mm. The tubules do not extend 

 much, either dorsally or ventrally, over the level of the side 

 stems. There are ten ducts on the left side and five on the 

 right (fig. 35) . They open to the exterior just above the level 

 of the side stems. 



The nervous system is built on the usual type. The 

 median dorsal nerve is well marked. 



The cerebral organ is well developed and rounded in 

 transverse section. The dorsal glands are more strongly 

 developed than the ventral (fig. 27, a — d). The connective 

 tissue contains a bright yellow pigment {pg.). The dorsal 

 lobe of the dorsal ganglion stretches over the anterior portion 

 of the organ. The head slits are deep, though not reaching 



