ALASKA NEMERTEANS 27 



The pair of blood lacuna in the head are rather small, and pass 

 backward in numerous branches. The dorsal vessel in the proboscis 

 sheath has several communications with the lateral vessels in the 

 esophagal region. 



In the region of the brain a great abundance of sub-muscular glands 

 appears, occupying the whole lateral aspects of the body and reaching 

 far backward. As usual, they are multicellular. Their ducts pierce 

 the muscles and integument of the body wall to open on the sides of 

 the body in enormous numbers. Farther back they are restricted to a 

 narrow region in each section just lateral to the nerve cords, and open 

 somewhat ventrally from the lateral edge. They continue in dimin- 

 ished numbers, but of large size, backward beyond the point where 

 the esophagus opens into the intestine (pi. xn, fig. 3). 



Alimentary canal. A pair of remarkably narrow intestinal caeca 

 reach forward well toward the brain. Their diameter for a long dis- 

 tance back is insignificant compared with that of the esophagus. 

 They occupy positions ventro-laterally to the proboscis sheath and 

 above the esophagus. Occasional pouches are sent off laterally into 

 the tissues above the nerve cords. Farther back they become larger 

 and extend laterally beyond the ventrally placed nerve cords. Towards 

 the middle of the esophagal region the pouches become paired with 

 considerable regularity. A well developed network of muscular fibers 

 and connective tissue reaches between the pouches from the muscular 

 layer above to that below the alimentary canal. The pouches lie close 

 together still farther back, and near the posterior end of the esophagal 

 region extend on each side below the esophagus and open together 

 from opposite sides. The two intestinal caeca are thus connected to- 

 gether. From this point backward the esophagus decreases rapidly in 

 size, the caecum becomes large and is divided into numerous pouches 

 by fibrous partitions extending between the muscular layers above and 

 below, and eventually the esophagus opens into the intestine by a 

 narrow slit in its dorsal wall (pi. xn, fig. 3). 



Reproductive organs. Far in front of the opening of the esoph- 

 agus into the intestine the reproductive glands make their first appear- 

 ance. The anterior pouches are scattered, and lie above the intestinal 

 caeca well towards the sides of the body. These open directly on the 

 dorso-lateral surfaces. Farther back similar ones appear below the in- 

 testinal canal, and these open ventrally (pi. xn, fig. 3). In the intes- 

 tinal region the glands are very numerous and are scattered just inside 

 the muscular layers all over the body dorsally, ventrally and laterally. 

 As many as 20 to 30 glands in a male are met with in a single section. 



