NEMERTEANS 



197 



Anteriorly the rings usually encircle the whole body, but farther 

 back they are merely indicated on ventral surface by very fine grayish 

 lines of much less distinctness than on dorsal surface. In intestinal 

 region they are sometimes separated by more than twice the diameter 

 of body when moderately extended. 



In some individuals the white rings are very indistinct, in others they 

 are merely indicated on dorsal surface and are not present at all below, 

 while they are wanting entirely in the posterior portions of the body. 

 The fact that fission usually takes place through these white rings indi- 

 cates that there must be some peculiarity of the body walls in these 

 regions other than a lack or differentiation of pigment. This is true 

 of other species of the genus and of other genera, notably Carinella. 

 Body is often constricted at these points previous to rupture. 



After preservation the delicate white rings disappear, and the body 

 assumes a slaty black appearance, sometimes more grayish below, and 

 with the distinct terminal white border. 



Size. — Length commonly 7-15 cm.; width about 2-6 mm. 



Body Walls. — Cephalic glands not well developed. Cutis glands 

 limited to a rather thin but dense layer external to the outer longi- 

 tudinal muscles. They do not encroach on this muscular layer to any 

 great extent even in the intestinal region, nor do they sink in among 

 the muscular fibers. The pigment to which the color of the body is 

 due resides in the connective tissue among the cutis glands. 



Nephridial and Blood Systems. — The nephridia are well devel- 

 oped, and extend through more than half the esophageal region. 

 They reach anteriorly well toward the mouth, and send large branches 

 among the esophageal lacunae. In each of two specimens sectioned 

 there was a single pair of large efferent ducts a little in front of the 

 middle of the esophageal region. In another specimen a single acces- 

 sory duct was found on one side, situated a considerable distance behind 

 the normal pair and toward the posterior end of the nephridia. The 

 single pair of efferent ducts is usually situated somewhat anterior to 

 the middle of the nephridial region. 



Cephalic and esophageal blood lacunae large; numerous large blood 

 lacunae also surround the mouth. Proboscis sheath vessel leaves the 

 rhynchocoel a little in front of the intestinal region. 



Nervotis system and sense organs show few deviations from those of 

 related species. There is a large commissure of the esophageal nerves 

 just in front of the mouth. The cephalic furrows are very deep and 

 long. Frontal sense organs are present and well developed. They are 

 situated in three well marked pits, of which one is situated above the 



