NEMERTEANS I 79 



of any retractor muscle of proboscis, and the absence of the inner lon- 

 gitudinal muscle of proboscis, are among the more important peculiari- 

 ties of the species. 



In the paper referred to will be found detailed histological descrip- 

 tions and figures of all the principal organs of the body. 



17. LINEUS RUBESCENS sp. nov. 

 pi. xiv, fig. i ; pi. xv, figs. 3, 4; pi. xxn, fig. i. 



Body very slender, rounded anteriorly, flattened in intestinal region ; 

 posterior extremity slender ; head long, rather broad ; cephalic furrows 

 correspondingly long, reaching posteriorly as far as the anterior end of 

 the mouth, which is situated well back from tip of snout. 



Size. A small species, the specimens obtained measuring only 

 10-15 mm. long, and less than I mm. in diameter. 



Color. Anterior portions of body, except tip of head, beautiful 

 pink, or rosy flesh color, occasionally bright pinkish red, sometimes 

 with tinge of blue. Tip of head, both above and below, whitish, al- 

 most colorless, sharply marked off from pink color behind. Intestinal 

 region deep flesh color or pale, purplish brown, or occasionally buff, 

 anteriorly, shading off to very pale pinkish towards posterior end of 

 body ; very pale posteriorly. Ventral surface paler, but of similar 

 color, pinkish in front, pinkish buff or pale flesh color posteriorly ; 

 often with still paler median line. Intestinal lobes flesh color or buff ; 

 occasionally brownish or purplish. Head can be so much contracted 

 that white tip will disappear. Brain appears pale flesh color. Space 

 between ocelli is grayish. A most striking peculiarity of the color in 

 the esophageal region is that it becomes purplish or, sometimes, 

 bright blue in formalin. I know of no other species of Nemertean 

 where the color changes from pinkish to bluish on preservation. 

 The bluish color is not permanent, however, and after remaining a few 

 weeks in formalin will have practically disappeared. But when such 

 specimens are cleared in cedar oil, a delicate bluish or bluish green color 

 reappears in the esophageal region, while the intestinal region remains 

 colorless, except the intestinal lobes, which are slightly brownish. The 

 nature and situation of the pigment are noted below. 



Ocelli. Situated in whitish area on tip of head is a row of two to 

 four (or, rarely, as many as six or eight) ocelli on each side (pi. xiv, 

 fig. i ; pi. xv, figs. 3, 4). These are irregular in shape, very dark 

 reddish or almost black in color, and closely placed in a single row. 

 The anterior ocellus on each side is usually the largest, but the ocelli 



