NEMERTEANS 185 



region varied from ochre through deep buff to olive brown, sometimes 

 showing a median dorsal longitudinal stripe of darker, more brownish 

 color. These were filled with mature sexual products. 



In all these varieties the brain region was indicated by its more rosy 

 color, and this was sometimes quite conspicuous. The lateral and 

 anterior margins of head were always very pale or colorless. The 

 esophageal region showed clearly the two divisions of the esophageal 

 walls, as seen through the somewhat translucent body walls. The 

 ventral surface of head is much paler than dorsal surface, while 

 throughout remainder of body the ventral differs from the dorsal sur- 

 face in color mainly in having a duller and more whitish tinge. A paler 

 median dorsal line in intestinal region, indicating the position of the 

 proboscis sheath, is often present. 



Proboscis straw color or slightly yellowish. 



Size. Small, pale-colored individuals were 8-15 mm. long; 

 others 20-40 mm., while those from deeper water were often 80-120 

 mm. in length, with a diameter of 2-3 mm. 



Ocelli. On each side of tip of head is a transverse row of irregular 

 pigment masses (pi. xvn, figs. 3,4). These are very variable in shape, 

 in size, and in number, and vary in color from blood red to purple or black. 

 There are commonly three to seven irregular groups of pigment granules 

 on each side, and of these the more anterior are the larger. Those of the 

 two sides are separated by a fairly wide pale area above the proboscis 

 pore, and extend as a single row along each antero-lateral margin of 

 the head. Commonly the ocellus lying most anteriorly is much larger 

 than any of the others, while the three or four most posterior ones are 

 represented by minute dots only. The number of ocelli may not be 

 the same on the two sides, and perhaps in the majority of cases it is 

 impossible to determine the exact number because the pigment granules 

 are so much scattered. Often there is an irregular row of scattered 

 pigment masses, grouped irregularly, but not arranged into definite 

 ocelli. These appear to have arisen from a fragmentation of ocelli 

 which have previously existed. 



Whether the ocelli should be blood red, wine color, purple or black, 

 seemed to be an individual peculiarity, and was not always correlated 

 with the color of the body or the environment under which the animal 

 lived. It is to be noted, however, that most of the individuals dredged 

 among the red seaweeds had wine-colored or purple ocelli. 



As seen in sections, only the anterior pair of ocelli usually possess a 

 well-developed visual apparatus, with distinct, cup-shaped retina hav- 

 ing long, spindle-shaped sensory cells. They lie very deep in the 



