ALASKA NEMERTEANS 59 



Nephridia. The nephridial canals are short, and reach forward to 

 the brain. Anteriorly each nephridium lies above the lateral nerve, 

 but farther back the branches ramify both above and below the nerve. 

 Near the anterior end of each of the main canals a large efferent duct 

 passes outside of the lateral nerve, and bends downward and outward 

 to open to the exterior on the lateral margin of the body. In one in- 

 stance a double efferent canal was observed. 



The head is provided with large cephalic glands which open on the 

 tip of the snout. The cerebral sense organs are large. They lie 

 mainly in front of the brain, although their posterior ends extend 

 backward beside and lateral to the brain lobes. Each connects with 

 the exterior by a canal which runs anteriorly to open on the lateral 

 margin of the head. 



A broad intestinal caecum reaches into the anterior fourth of the 

 esophagal region. It lies below the esophagus, and sends off a few 

 wide lobes on each side, but these reach dorsally only a little above the 

 lateral nerve. The esophagus opens into the caecum far behind the 

 anterior sexual glands, and nearly as far back as the middle of the 

 body. The reproductive pouches lie both above and below the intes- 

 tine. 



As will be seen from the above description, this species agrees 

 closely with the typical species of Tetrastemma in size, general appear- 

 ance, and in the details of the internal anatomy. It differs from 

 known species of the genus only in the fragmented nature of its eyes 

 and in the number of nerves in the proboscis. It seems extremely 

 probable, however, that when more of the described species have been 

 examined in this regard, some of them will be found to contain more 

 or less than ten proboscidial nerves. The eyes certainly resemble 

 those of Tetrastemma more closely than they do those of any de- 

 scribed species of Amphiporus. 



Habitat. Found among hydroids in about four fathoms in Glacier 

 Bay, and between tides at Orca, Prince William Sound. Not com- 

 mon. 



21. TETRASTEMMA CAECUM sp. nov. 



A small species which I shall refer provisionally to this genus was 

 found by Ritter in considerable numbers at Kadiak. The species is 

 especially remarkable, and quite aberrant from most other species of 

 Tetrastemma , both in lacking ocelli and in being hermaphroditic. 

 The body is rounded and of almost even diameter throughout. The 

 head has a pair of inconspicuous, oblique, lateral furrows. 



