ALASKA NEMERTEANS 63 



body of one specimen still measured 15 x 18 mm. It is one of the 

 largest Nemerteans of the coast. 



Ocelli. — There are many minute ocelli arranged in an irregular 

 group on each side of the tip of the head. The number of such ocelli 

 is commonly 40 or more in each of the two groups. 



The mouth is a small rounded pore, and is situated several milli- 

 meters back from the tip of the head in large individuals. The pro- 

 boscis-pore is also minute, and is situated subterminally as usual. 



Proboscis. — The proboscis sheath reaches some distance into the 

 esophagal region, but is very short vv^hen compared vv^ith the length of 

 the body. The proboscis is short and vv^eak. Its muscular and epi- 

 thelial layers are as in other species of the genus. 



The cephalic glands are enormously developed. They occupy a 

 large proportion of the area in the anterior portion of the head, sur- 

 round the brain on all sides, and extend still further backwards into 

 the anterior end of the esophagal region. Here they lie in the outer 

 longitudinal muscular layer around the whole circumference of the body. 



Body walls. — The outer longitudinal muscular layer about equals in 

 thickness the other two muscular layers combined. In the intestinal 

 region the inner longitudinal muscular layer becomes extremely thin on 

 the lateral aspects of the body, and is much reduced dorsally. It is only 

 on the ventral side that this layer retains its comparative thickness. 

 The cutis is thinner than in most species of the genus, and especially 

 is this true of its inner, fibrous layer. This layer is, throughout most 

 of the body, reduced nearly to the condition of a thin membrane. It 

 is commonly not much thicker than the muscular layer beneath the 

 body epithelium. The epithelium itself is thin in comparison with the 

 massive muscular layers of the body. 



The blood lacunce in the head lie directly above the brain, as in other 

 species of the genus. They are, however, remarkably large, and 

 are crossed in various directions by numerous bundles of muscular 

 tissue, which tend to subdivide the lacunae into numerous smaller 

 spaces. The longitudinal blood vessels are as usual. The dorsal vessel 

 passes out of the proboscis sheath early in its course. 



Nephridia. — Situated in anterior and middle portions of esophagal 

 region. Several efferent ducts on each side. These are small in 

 diameter and pass above the nerve cords, opening on the lateral aspects 

 of the body dorsal to the lateral margins. 



Cerebral sense organs. — The dorsal lobes of the brain greatly exceed 

 the ventral lobes in size, and lie somewhat lateral as well as above 

 them. The cerebral sense organs are voluminous. They extend for- 



