456 F. W. GAMBLE AND J. H. ASHWORTfl. 



mesentery, connecting the alimentary canal to the body-wall 

 (see fig. 30, Mes. D.). In A. Grubii, A. ecaudata, and A. 

 cristata there are, immediately behind the heart, two small 

 strands, which look almost like thin nerves, but which are 

 composed of connective tissue, which arise from the ventral 

 walls of the stomach, and are inserted into the body-wall on 

 each side of the nerve-cord (PI. 25, fig. 44). During diges- 

 tion the stomach is swung to and fro by the movements of the 

 body, and the function of these strands of connective tissue 

 is probably to prevent the amplitude of the swing from being 

 too great, and causing the rupture of some of the delicate 

 branches of the ventral vessel, the main trunk of which is 

 attached to and moves with the alimentary canal. It will be 

 noticed that these strands (see fig. 44, Conn. Tiss.) are placed 

 at the boundary of the segment.^ 



8. Alimentary Canal. 



The alimentary canal of the four species at present under 

 consideration varies only in a few details from that of A. 

 marina. In each there is (1) an eversible buccal mass or 

 " proboscis," generally pinkish in colour owing to its contained 

 blood-vessels; (2) an oesophagus, brownish or pinkish in 

 colour, and often somewhat transversely wrinkled, bearing 

 glandular pouches just behind the level of the third dia- 

 phragm ; (3) a gastric region with yellow glandular walls and 

 numerous blood-vessels, extending from the level of the heart 

 to about that of the eleventh or twelfth setae (sixteenth in A. 

 ecaudata) ; and (4) an intestine, generally dark brown or 

 dark olive-green in colour, extending to the posterior end and 

 opening at the terminal anus. 



The alimentary canal of A. cristata very closely resembles 

 that of A. marina, the only difference being that in the 

 former the oesophageal pouches are relatively small. In 

 A. ecaudata the pharyngeal portion of the alimentary canal 

 is longer than in A. marina, due to the fact that in the 



^ See foot-note ou p. 519 re A. marina. 



