146 COE 



the fluid in the proboscis sheath. This is not very conspicuous in the 

 esophageal region, where the proboscis fills most of the space in its 

 sheath, but in the intestinal region the proboscis sheath is seen to be 

 filled with a clear red fluid. The red color does not reside in the cor- 

 puscles, but exists in the fluid itself, while the corpuscles are nearly 

 colorless. Occasionally an individual has the intestinal region grayish 

 in color, and in such cases the proboscis sheath is very conspicuous as 

 a wavy longitudinal, blood-red band about one-fourth the diameter of 

 the body. 



After preservation the esophageal region becomes almost colorless, 

 but the intestinal tract gives a decidedly greenish color to the rest of 

 the body. 



Proboscis. When extruded the proboscis appears of a reddish color 

 due to the red rhynchocoel fluid within it, but when this fluid is pressed 

 out the proboscis remains colorless. It is of fairly large size, and is 

 provided with four or six pouches of accessory stylets in addition to the 

 central stylet (pi. xvm, fig. 2; pi. xxi, fig. 3). The basis of the 

 latter is rather long and slender, slightly narrower anteriorly, but of 

 fairly even diameter throughout (pi. xvm, figs. 4, 5 ; pi. xxi, figs. 

 48). The stylet itself is moderately slender and about half as long 

 as the basis, or sometimes a little more than half as long. There are 

 usually two or three accessory stylets in each of the four or six pouches. 

 All the stylets, both central and accessory, show a peculiar darker or 

 more opaque portion about the head (pi. xxi, figs. 4-9). This 

 darker portion extends perhaps one-sixth the length of the stylet. 

 Measurements in a single specimen are : Basis of central stylet 0.36 

 mm. long, o.i in average width ; stylets about 0.17-0.2 mm. in length. 



In each of three specimens sectioned the proboscis was provided 

 with ten large and distinct nerves. A fourth individual showed an 

 abnormal condition in that there were twelve distinct nerves in a short 

 region of the proboscis, although there was but the usual number 

 (ten) both anteriorly and posteriorly to this region. A fifth specimen 

 showed eleven nerves. The nerves are often one-half to three-fourths 

 as great in diameter as the thickness of the longitudinal muscular 

 layer. Muscular and epithelial layers as usual, but the basement 

 layer beneath the internal epithelium is so very much thickened that it 

 practically equals the circular muscular layer in thickness. 



Proboscis sheath reaches fully one-half the entire length of the 

 body, but does not extend into the posterior one-third of the animal. 

 In this respect the present species agrees well with the other members 

 of the genus from Alaska. Muscular layers of proboscis sheath enor- 



