NEMERTEANS 



261 



half the length of the body, but 

 the rhynchocoel extends to the 

 tail. The proboscis has twelve 

 nerves. The armature consists of 

 a main stylet on a base not longer 

 than itself and two reservoirs, each 

 with from four to seven stylets. 



The relative positions of the 

 stomach, excretory organs and 

 branches of the anterior caecum 

 are believed to vary with the 

 degree of contraction of the body. 

 Thus in one series of sections the 

 stomach wall is visible some 

 distance before the brain, showing 

 that the alimentary canal has the 

 power of independent movement 

 and that not much reliance can 

 be placed in distinguishing charac- 

 ters based on position. The anterior 

 caecum has branches which are 

 first seen close behind the excre- 

 tory tubules (Fig. 35). 



The vascular system consists of 

 two lateral vessels forming a head 

 loop and passing one on each side 

 of the rhynchocoel through the 

 brain region. They unite with a 

 dorsal vessel by a transverse con- 

 nection and pass down the body 

 ventral to the nerves. 



There is a convoluted excretory 

 tubule on each side close behind 

 the cerebral organ, lying above 

 the nerve and opening to the ex- 

 terior by a single dorso-lateral 

 duct. 



The brain is of good size. The 

 dorsal ganglia are larger than the 

 ventral and lie immediately over 

 them. At the posterior end of the 

 ventral ganglia there maybe a con- 



Fig. 35. Amphiporus lecointei, Biirger. Diagram from a graphic 

 reconstruction of the head and anterior end of the body to show 

 the relations of the brain, cerebral organs, excretory and 

 alimentary systems, ac, anterior caecum; co, cerebral organ; 

 csg, cerebral subepithelial glands; dg, dorsal ganglion; e, eye- 

 spots; ex, excretory tubule; hg, head glands; In, lateral nerve; 

 phg, opening of the head gland; rd, rhynchodaeum. 



Fig. 36. Outline drawings (x 3 approx.) of Amphiporus 

 marioni (A), A. lecointei (B), A. gerlachei (C), and A. falk- 

 landicus (D). 



