128 bulletin: museum of comparative zoology. 



rounded, or emarginate according to state of contraction ; often 

 flattened dorso-ventrally and shovel-shaped; marked off from parts 

 immediately following by a pair of faintly indicated lateral, trans- 

 verse grooves. Ocelli wanting. 



Color. — General color of the body milk white and more or less 

 translucent throughout. This color is somewhat affected, however, 

 by the intestinal canal which is often pale yellowish or sometimes 

 brownish. In the brain region there is often a rosy tinge. The 

 esophagus shows an anterior translucent portion, while its pos- 

 terior half is opaque white. Proboscis is small; white in color. 



After preservation in formalin or in alcohol, there is commonly a 

 marked differentiation of color in the anterior portion of the body, 

 perfectly similar to the well known dark band which occurs in most 

 species of Carinella after preservation. About 5 mm. of the ante- 

 rior end of a medium-sized specimen is pure white, and this is fol- 

 lowed by a sharply marked brownish or pale brick red band (PI. 5, 

 figs. 46, 47). This shades off gradually posteriorly, precisely as in 

 Carinella, so that its exact width cannot be determined, but the 

 brownish tinge is conspicuous for 2 mm. or more in a specimen 

 which measures 20 ram. long and 1^ mm. wide after preservatiou. 

 In serial sections the position of this band can easily be distinguished 

 with the naked eye because of the differential staining of the integ- 

 ument where it is present. This effect is apparently produced by a 

 differentiation in the chemical nature of the glandular secretions, 

 and not to any special pigment. Anteriorly, where the color is 

 deepest, the layer of peculiarly stained glands occupies the inner 

 two thirds of the integument, but the layer becomes gradually 

 thinner posteriorly, until there are only a few scattered glands at 

 the beginning of the intestinal region. The band is of the same 

 thickness ventrally as dorsally, and begins anteriorly near the for- 

 ward end of the nephridial region. 



The lateral sense organs are easily distinguished with a hand lens 

 on preserved specimens. They lie on the lateral margins of the 

 body near the posterior border of the reddish brown band, and each 

 appears as an oval depression bordered with a white or colorless rim 

 (PI. 5, figs. 46, 47). Naturally the sense organs show most con- 

 spicuously in those specimens which have the brownish band of the 

 deepest color. The body usually shows an annular constriction just 

 posterior to the sense organs, due to contraction of the powerful 

 circular muscles. 



