NEMERTEANS 199 



Ocelli. None. 



Size. Length of the few individuals found 40-80 mm. ; diameter 

 about 2-3 mm. 



Proboscis sheath extends to the posterior end of the body, and is 

 well developed throughout. The circular muscles of the proboscis 

 sheath increase to a remarkable degree near the posterior end of the 

 stomach region, but the fibers do not extend beneath the alimentary 

 canal as in several species described above. After reaching a great 

 thickness at the posterior end of the stomach region they suddenly de- 

 crease to a very thin layer at the commencement of the intestinal 

 region. It will be observed that although the fibers do not surround 

 the alimentary canal, yet the thickening of the circular layer occurs in 

 exactly the same region as in L. rubescens and other species, and is 

 probably homologous with the inner circular muscles of those species. 



Proboscis. There are only two muscular layers present, the inner 

 longitudinal muscles being completely wanting. Both the dorsal and 

 ventral fibrous crossings between the circular muscles and the outer 

 fibrous layer are well developed. A rather thick basement layer is 

 situated between the nervous plexus and the inner epithelium. Another 

 peculiarity of the proboscis in the single specimen sectioned is that 

 there is a marked differentiation of the epithelium on one side through- 

 out its whole length. This narrow strip of differentiated cells is quite 

 conspicuous in each cross section, from the fact that in it the epithelium 

 is much higher than elsewhere and behaves very differently to stains 

 than do the other cells. This specialized area is composed of very 

 slender cells, strongly resembling the sensory cells found in various 

 parts of the body, and having numerous small nuclei among their bases. 



Body Walls. The cutis glands form a compact layer beneath the 

 integument, and do not sink inward among the fibers of the outer 

 longitudinal muscles as they do in many related species. Pigment 

 which gives the brownish color to the body after preservation is 

 situated in the connective tissue among the cutis glands. 



Cephalic glands are well developed, and extend posteriorly nearly 

 to the brain. Cephalic furrows are narrow, and are not deep. Except 

 at their posterior ends, they reach less than half the distance from 

 surface to rhynchodaeum or brain. 



Alimentary Canal. The two divisions of the esophagus described 

 for Lineus rubescens, L. flavescens and other forms are also well 

 marked in the present species. The change from esophagus proper to 

 stomach is abrupt, and the two sections are separated by a conspicuous 

 sphincter of connective tissue. The position of this sphincter is at 



