NEW SPECIES OF NEMERTEAN. 



123 



Cl 



~dv 



ventral ly in the brain region to be again separated after a short 

 space. At the posterior end of the brain region they are again 

 united by a broad median lacuna which gives rise to the proboscis 

 sheath vessel posteriorly (Fig. 4). Behind the mouth the lat- 

 eral lacunae send off a great many an- 

 astomosing blood spaces beside and be- 

 neath the esophagus. On the walls of 

 these blood spaces delicate branches of 

 the nephridial tnlntlcs ramify in all direc- 

 tions. From the pair of nephridial canals 

 which lie on the lateral walls of the 

 lateral blood spaces numerous efferent 

 ducts pass through the muscular layers 

 to the dorso-lateral aspects of the body 

 as usual. These ducts are probably vari- 

 able in number for in the single specimen 

 sectioned there were thirteen on one side 

 and only seven on the other. In addition 

 to the seven ducts of this side were two 

 incomplete or rudimentary ducts (Fig. 

 4, ed] which did not connect with the 



FIG. 4. Diagram of blood vascular system and 

 nephridia. The two cephalic lacunas (<:/) unite an- 

 teriorly by a rather broad anastomosis. In the brain 

 region are two other anastomoses of the cephalic 

 lacunae, from the posterior of which the dorsal vessel 

 (dv] and the lateral vessels (fa) originate. The lateral 

 vessels give rise to profusely branched anastomosing 

 lacunae (,?/) beside and beneath the esophagus. Dor- 

 sal vessel leaves the wall of proboscis sheath in the 

 midst of nephridial region (.r). The nephridia (nep} 

 lie on the lateral walls of lateral vessels about hal 

 way between mouth and intestinal region, and send 

 numerous branches among the esophagal lacunae. 

 They open to exterior through numerous efferent 

 ducts (eel ) on each side. In this specimen there were thirteen on one side and 

 seven on the other. There are, however, two rudimentary ducts (/') on the side 

 with the smaller number. 



nephridial canals at all and are apparently the remains of formerly 

 functional ducts which, for some reason or other, have become 

 degenerated and no longer functional. Similar rudimentary effer- 

 ent ducts have been noticed in several other forms. 



