374 
EDWIN LINTON 
I take them to represent a subdermal nerve plexus. They He in 
the body-wall, probably closely associated with the muscular 
layers. This was evident in the living and active specimens. 
When the worm was contracting actively and the mesenchyme 
was thrown into constant motion so that the various structures 
which were lying in it, even such stable bodies as the pharynx 
and eyes, were constantly shifting their position, the reticulum 
remained unchanged and moved only with those movements of 
the worm which involved the outer body wall 
Alimentary tract 
The mouth, although very minute, may occasionally be seen 
in specimens that are lying free in sea water and viewed under 
low magnification. When the worm, in making its characteristic 
movements described below, turns the head sharply to one side, 
a view of the ventral surface in profile is often obtained. A notch 
in the outline of the ventral surface indicates the position of the 
mouth. This position is somewhat variable on account of the 
extreme mobility of the body-wall. In one that was watched for 
some time there appeared to be a longitudinal furrow leading 
from near the level of the anterior border of the pharynx to the 
anterior end of the body. The sides of this furrow were capable 
of being pressed together, thus extemporizing a gullet (fig. 5). 
The mouth proper appeared to be near the anterior edge of the 
pharynx. It was variable in shape, usually ovate with the larger 
end in front; sometimes it was circular. The furrow and the 
mouth are, of course, cihated, as is the whole surface of the body. 
The pharynx is near the anterior end and is subglobular. In 
the living worm it was seen performing swallowing movements, 
and in one case where the pharynx had been entirely separated 
from the body in a crushed specimen it continued to contract 
convulsively for some minutes. 
The esophagus is short, scarcely as long as the pharynx. In 
a horizontal section measuring 1 mm. in length, the pharynx 
was 0.05 mm-, from the anterior end, and measured 0.07 mm. in 
- diameter, and the esophagus was about 0.05 mm. in length. The 
