134 bulletin: museum of comparative zoology. 



serving agents, so as to produce the dark color in a worm which 

 was whitish in hfe. In the anterior portion of the band, where the 

 color is deepest, these gland cells are more closely placed (PL 7, fig. 

 56) and reach nearer the outer surface, but more posteriorly (PI. 8, 

 fig. 57) they gradually become more scattered and of smaller size. 

 The band thus fades out gradually posteriorly, as described above, 

 and as is well known in Carhstella. 



Body musculature. — The musculature of the body resembles that 

 of Carinoma in its general aspects, but differs in many particulars. 

 It also resembles — perhaps even more closely — that of certain 

 species of Carixella, notably C. linearis. 



The main longitudinal muscular layer is well developed through- 

 out the body. The circular layer outside this likewise continues 

 throughout the length of the body, but is everywhere thin and incon- 

 spicuous. Between the longitudinal and the outer circular muscles 

 a double set of diagonal muscles can be distinguished in the esopha- 

 geal region, as in Carinoma (PL 12, fig. 79). An internal circular 

 layer extends throughout the esophageal region, reaching a great 

 thickness and then suddenly almost disappearing at the beginning of 

 the intestinal region, as in Carinoma. 



In the vicinity of the nephridiopores there is a marked infolding 

 on the dorsal surface of the body, which presses the longitudinal 

 muscles in the dorsal half of the body toward the lateral margins. 

 In many cases the infolding is so marked as to bring the two circu- 

 lar layers into contact, so that for a short space immediatel}'^ above 

 the proboscis sheath the longitudinal muscles do not appear at all 

 (PL 8, fig. 57). As described below, this infolding is caused by 

 contraction of the fibrous crossings between the two circular muscu- 

 lar layers. 



The inner circular muscle is very thin immediately behind the 

 mouth, bvit increases rapidly in thickness throughout the esophageal 

 region. It reaches its maximum thickness in the nephridial region, 

 where it becomes from one half to two thirds as thick as the layer 

 of longitudinal muscles. Immediately behind the nephridial region 

 it disappears almost completely, although a few fibers continue to 

 surround the proboscis sheath and intestine. Behind the posterior 

 end of the proboscis sheath careful examination shows that this 

 inuscle still continues as a very delicate circular layer closely sur- 

 rounding the intestine almost as far as the posterior end of the body. 



