236 ARTHUR 5. SHIPLEY. 
has in some cases been seen to exude from the pores of the 
glands. 
The external circular layer of muscles is well developed in 
the introvert, and in the anterior half of the body; but about 
the middle of the body it fades away, so that the posterior end 
is provided only with longitudinal muscles (fig. 7). The cir- 
cular muscles are arranged in bundles, but the longitudinal 
are in a continuous sheet. 
Both the cutis and the external and internal layers of 
muscles take part in the thickening of the skin which exists 
at the junction of the proboscis and the body. 
The body-wall is lined by an endothelium, which extends over 
the internal organs. In the living specimens, according to 
Koren and Danielssen, it can be distinctly seen that this endo- 
thelium is ciliated, and that the cilia, by their action, keep 
the perivisceral fluid in motion. 
Tuer GENERAL ANATOMY. 
If a longitudinal incision be made in the body-wall of 
Oxchnesoma, and the sides reflected, the arrangement of the 
internal organs and their relation to one another become at 
once evident without further dissecting. These relations are 
clearly shown in fig. 8, which I have borrowed from Koren 
and Danielssen’s ‘Fauna Littoralis Norvegie.’ It will be 
seen that the esophagus is very long and loosely coiled, in 
order to allow for the extension of the introvert. The intestine, 
whose diameter is larger than the csophagus or rectum, is 
also much coiled. The anus is situated rather too far forward 
to the right of the ventral nerve-cord. 
There is only a single retractor muscle, which has its origin 
at the extreme posterior end of the body, where the skin is 
thickened and produced into a blunt point (fig. 7). The other 
end of this muscle is inserted into the wall of the cesophagus 
immediately below the brain. The muscle-fibres which com- 
pose this retractor muscle are bigger than those of the mus- 
cular sheaths in the skin. They are fusiform, with a rather 
flattened transverse section and a faint longitudinal striation. 
