COE: NEMERTEANS OF WEST AND NORTHWEST COASTS. 139 



utmost extent. The body is always more or less contracted when 

 studied, and the folds are always present in preserved specimens, 

 but it remains possible that when the worms are living and the body 

 is in its fully extended condition the folds would entirely disappear. 

 In certain parts of the body they are much higher than in others, 

 and are also higher on the ventral than on the dorsal side (PI. 10, 

 %. 65) . 



Where the genital pouches are fully developed they encroach to 

 some extent on the intestinal space, and there is sometimes an indi- 

 cation of an alternation betAveen the sexual pouches and the intes- 

 tinal folds, but the relation is merely su])erticial. 



Nephridia. — The nephridial tubules are limited to a short space 

 about midway between the head and anterior sexual glands. This 

 can hardly be called the esophageal, but is more properly the 

 stomach region, as stated above. The usual delicate nephridial 

 tubules form a sort of primitive "nephridial gland" by entering 

 into close relation with the outer, ventral wall of the lateral blood 

 vessels. As in Carixoma and Carinella, there are numerous fine 

 tubules which press inward, causing corresponding infoldings in the 

 wall of the blood vessel (PI. 5, fig. 48, a). The nephridial tubules 

 extend forward nearly to the anterior border of the dark band seen 

 on the body in preserved specimens and reach backward only 

 about half-way to the end of the thickening of the circular muscle, 

 and as far as the anterior ends of the lateral sense organs. Their 

 extent is, therefore, remarkably limited. On each side at about the 

 middle of the region of the nephridial tubules a single large duct 

 (PI. 5, fig. 48) passes off and extends posteriorly on the dorsal side 

 of the blood vessel (PL 7, fig. 56) almost as far as the end of the 

 thickening of the circular muscle. It then bends obliquely dorsally 

 to open on the dorso-lateral surface of the body as usual. In its 

 middle portions the main nephridial duct is larger than the core of 

 the lateral nerve, but is much smaller toward its posterior opening. 

 The diagram (PL 5, fig. 48) will illustrate these conditions. 



Blood vascular system. — The blood system consists principally 

 of large cephalic lacunae and a single pair of lateral vessels with 

 outgrowths into the wall of the rhynchocoel. It is, therefore, very 

 similar to that of Carinella. The cephalic blood spaces are remark- 

 ably large, and more or less subdivided into numerous connected 

 chambers by strands of connective tissue and muscle which pass 



