40 bulletin: museum of comparative zoology. 



In Carinoma there is a pair of large dorso lateral vessels (PI. 13, 

 figs. 81, 82) in addition to those found in Carinella. These 

 originate from the lateral vessels in the mouth region and extend to 

 the nephridial region in the parenchyma beside the proboscis sheath. 

 They join the lateral vessels in or near the nephridial region. The 

 rhynchocoel vessels (PI. 13, fig. SI, rev) are usually very conspicuous. 

 In this genus there are also metamerically arranged transverse ves- 

 sels in the posterior portion of the body which unite the lateral 

 vessels above the intestine at regular intervals. 



B. Hoplonemertea. — In this order there is a single dorsal or 

 dorso-median vessel in addition to the pair of lateral vessels. The 

 dorsal vessel arises from a union of the lateral vessels in the brain 

 region and usually passes directly through the walls of the proboscis 

 sheath. It then continues as a ridge on the floor of the rhynchocoel 

 for a short distance, back of which it passes ventrally through the 

 wall of the proboscis sheath beneath which it continues to the 

 posterior end of the body. In some species of Geonemertes and 

 Tetrastemma the dorsal vessel does not enter the proboscis sheath. 

 The pair of cephalic vessels extend forward fi-om the union of the 

 lateral vessels in the brain region and unite at their anterior ends 

 (PI. 1, fig. 13). 



There are also metamerically arranged transverse vessels connect- 

 ing the three longitiidinal vessels above the intestine in the middle 

 and posterior portions of the body. A pair of such transverse 

 vessels lies above and lateral to each pair of intestinal lobes, and 

 therefore, as a rule, alternate with the genital pouches. In Pelag- 

 ONEMERTES the dorsal vessel is wanting. 



The vessels described are entirely without branches in many 

 hoplonemerteans, although in a number of forms from the Pacific 

 coast (Amphiporus nebulosus and A. gelatinosns, for example) the 

 lateral vessels undoubtedly branch repeatedly in the anterior eso- 

 phageal region. Previously it has been generally stated (see Burger 

 '95, p. 291) that such branches do not occur in any of the Hoplone- 

 mertea as here defined. 



C. Bdellonemertea. — In Malacobdella the three longitudinal 

 vessels branch profusel}^, their ramifications frequently anastomosing 

 and penetrating all parts of the parenchyma and musculature. No 

 other nemerteans exhibit so com])lex a network of anastomosing 

 lacunae and tubules, which unite beneath as well as above the ah- 



