462 F. W. GAMBLE AND J. H. ASHWORTH. 



large branch (not yet traced in A. Claparedii) to the oeso- 

 phageal pouch, and then runs forwards supplying the lateral 

 walls of the oesophagus^ breaking up into capillaries near the 

 second diaphragm. On each side of the nerve-cord there is a 

 small vessel, which accompanies the cord along the whole 

 length of the body. In front the neural vessels arise in the 

 triangular area between the oesophageal nerve connectives by 

 the union of capillaries from the ventral region of the oto- 

 cysts. They receive several branches from the ventral vessel 

 (see above). From these neural vessels small branches are 

 given off which supply the body-wall in their vicinity. 



The vessels of the body-wall are much more highly de- 

 veloped in A. Grubii and A, ecaudata (and especially in 

 the former) than in A. marina. There are two chief vessels : 

 (1) a dorsal longitudinal, or parietal vessel, which runs along 

 the whole length of the body, except at the extreme anterior 

 end, at the level of the insertion of the notopodial setae ; (2) 

 a nephridial longitudinal vessel, which is present only in and 

 immediately in front of and behind the nephridial region, and 

 runs just ventral to the level of the nephridiopores. An- 

 teriorly the parietal vessel is distinguishable just behind the 

 first setee, and the nephridial vessel immediately behind the 

 second diaphragm, where the two are united by a transverse 

 connection (PI. 25, fig. 44). The two vessels run parallel to 

 each other through the nephridial region, but behind this the 

 nephridial vessel gradually decreases in size, and in the 

 anterior part of the gill region (about the level of the second 

 or third gill) disappears entirely. The dorsal longitudinal, 

 or parietal vessel receives blood chiefly from the afferent 

 nephridial vessels. These arise from the ventral, vessel, and 

 on approaching the nephridium bifurcate, one branch passing 

 to this organ and the other going to the parietal vessel. An- 

 teriorly the parietal vessel on each side is connected to the 

 dorsal vessel by the branch which supplies the first nephridium. 

 The second nephridium is supplied with blood by a small 

 branch from the parietal vessel. In A. Grubii the afferent 

 vessels situated in the three segments following the last 



