ALASKA NEMERTEANS 8l 



Proboscis. — The proboscis is pale red, and of moderate size for the 

 genus. Its musculature consists of an inner circular, a longitudinal, 

 and a very thin outer circular muscular layer. It is, therefore, differ- 

 ent from those of nearly all the species of the family Lineidce.^ in that 

 the inner longitudinal muscular layer is wanting. There are fibers 

 passing between the inner circular layer and the thin outer circular 

 layer, but these fibers do not form such distinct crosses as are char- 

 acteristic of most of the members of the family. The internal epi- 

 thelium is thick and highly glandular. The nerve plexus beneath this 

 layer is unusually conspicuous, and lies directly internal to the circular 

 muscular layer. The proboscis is very often retained in place after the 

 animal has been killed. The muscular layers of the proboscis sheath 

 are rather thick, and the circular muscular fibers often cross into the 

 circular muscles of the body in the median line. 



In the anterior portion of the head a rich growth of glands pene- 

 trates the other tissue nearly to the central proboscis sheath. These 

 glands mostly open directly outward on the whole circumference of 

 the head, although a few open on the tip of the snout. Back of the 

 lateral slits the glands are restricted to the cutis. In the region of the 

 mouth the cutis glands are separated from the outer epithelium hy a 

 layer of interlaced fibers of connective tissue, forming a basement layer 

 of double the thickness of the epithelium. In the intestinal region the 

 cutis glands are much reduced, and scattered. The outer muscular 

 layer of the body is about as thick as the two inner muscular layers 

 combined. 



The mouth is much elongated, and its anterior end reaches forward 

 as far as the posterior ends of the cephalic slits. The intestinal pouches 

 are deep and narrow, and are forked distally. 



Nephridia. — The nephridial canals are profusely branched, and lie 

 in contact with the blood spaces around the esophagus in front of the 

 middle esophagal region. Their extent longitudinally, however, is 

 short. The main nephridial canals lie in the angles between the 

 esophagus and the proboscis. Near their posterior extremities a large 

 efferent duct passes obliquely upward on each side and opens on the 

 latero-dorsal aspect of the body. As described by Biirger^ in C. 

 marglnatus., one of the efferent ducts often lies far behind the other. 

 Posterior to the efferent ducts the nephridial canals are smaller, and 

 their branches end a short distance farther back. The blood lacunze 

 in the head in the specimens sectioned were very much reduced in size. 



'Fauna u. Flora Neapel, Monogr. 22, p. 622. 

 Proc. Wash. Acad. Sci., March 1901. 



