168 W. E. BENHAM. 



body-wall (figs. 6, 8) ; a similar ventral tegumeiitary vessel 

 joins the ventral vessel in each somite^ and has a similar rela- 

 tion to the septum : these two vessels, however, only communi- 

 cate indirectly in the plexus on the body-wall. In addition 

 two pairs of intestinal vessels pass from the dorsal vessel to 

 the gut wall, and two or three pass from this to the ventral 

 vessel in the "mesentery" which attaches this to the gut 

 (fig. 8). 



From the dorsal tegumentary or peripheral vessel of Somite 

 XIV a longitudinal vessel runs forwards on the body- 

 wall (fig. 6), and a similar vessel from the ventral tegumentary 

 of this somite accompanies it. These two longitudinal tegu- 

 mentary trunks can be traced forwards to about the second 

 somite, where they break up into small branches, entering 

 the capillary plexus on the walls of the pharynx, to which 

 network the dorsal vessel also contributes. These longitu- 

 dinal trunks lie on the inner surface of the body-wall 

 throughout their course (fig. 9), and give off" branches to 

 the body-wall and nephridia in each segment, — behaving, in 

 fact, just as do the posterior metamerically arranged tegumen- 

 tary vessels given off from the median trunks. They give off no 

 branches to the gut wall. In the body-wall is an elaborate 

 capillary plexus (not reaching into the epidermis), receiving 

 constituents from the above-mentioned tegumentary vessels. 

 The nephridia are marked by their pink colour in the fresh state, 

 owing to a dense plexus of blood-vessels upon them, and even 

 with a hand-lens one can see the dilatations described by 

 Claparede, Lankester, and myself in Lumbricus upon the 

 nephridial and other somatic vessels. This is especially notice- 

 able in the clitellar region. 



The dorsal vessel has a dark red or rather a brownish-red 

 colour, owing to the chloragogen cells surrounding it com- 

 bining their brownish tint with the red colour of the blood. The 

 intestine appears beautifully red, owing partly to the feeble 

 development of granules in the chloragogen cells, but chiefly 

 to the presence of a perienteric blood-sinus (figs. 7, 8, 9) 

 instead of the more usual network of capillaries. This sinus 



