468 WESLEY R. COE AND STANLEY C. BALL 
mens shows numerous convolutions. In the vast majority of 
specimens of this and related species the proboscis has been dis- 
charged from the body and lost before preservation. In two of 
specimens which we have studied, however, this organ was intact, 
and in sections shows the characteristic Metanemertean structure 
(figs. 10 and 11). 
Between the outer, thin, flattened epithelial layer (fig. 11, ep) 
and the inner layer of columnar epithelium (ep’) there are the 
usual outer and inner (cmp, cmp’) layers of circular muscles and 
a much thicker intervening layer of longitudinal muscles (lmp), 
the latter being divided by the nervous layer (pn) into two layers 
of approximately equal thickness. In the nervous layer are 
about twenty rather well-demarcated proboscidial nerves con- 
nected by a nervous plexus, giving the proboscis a_ highly 
developed innervation. In 21 specimens studied by Brinkmann 
(17, 17a) the number varied from 18 to 24. 
The two specimens in which the proboscis was present were 
very carefully studied after clearing in suitable medium, and one 
was sectioned. The armature was found to consist of a minute, 
slender, curved or hook-shaped basis, bearing a row of about 
ten to twelve tiny, conical stylets. 
At its posterior end the proboscis is provided with a retractor 
of such strength that when the proboscis is spasmodically ex- 
tended, instead of being normally everted, the retractor and the 
terminal end of the proboscis remain attached to the sheath. 
Cravens and Heath (’06) found the same condition in N. pelagica. 
The attachment of the retractor to the proboscis sheath lies some 
little distance in front of the posterior end of the latter. 
ALIMENTARY CANAL 
Mouth and proboscis openings are widely separated, as shown 
in figure 17, the former opening on the ventral and the latter 
on the dorsal side of the anterior end’ of the body. The buccal 
cavity has the surface epithelium thrown into deep folds (fig. 
17, m) which enable the lips to be enormously distended during 
the ingestion of food. The narrow oesophagus passes backward 
