NEMERTEANS OF HAWAIIAN - ISLANDS. 
983 
of an inner layer of longitudinal fibers and an outer, much thinner layer of circular fibers. Posterior 
end of proboscis attached to dorsal wall of sheath near its posterior end by strong longitudinal muscles. 
Fluid of rhynchocoele contains an abundance of large corpuscles, each with a conspicuous nucleus. 
Body walls. — The relative thickness of the various layers which constitute the body walls is shown 
in figs. 4 and 5. Glandular layer of cutis three to four times as thick as the underlying fibrous layer. 
Outer longitudinal muscular layer massive, far exceeding in thickness the circular and inner longitudi- 
nal muscular layers combined (figs. 4, 5). 
Cephalic glands.— As in most species of the genus, these glands are very voluminous. They occupy 
a great portion of the tissues of the head, and extend posteriorly for some distance into the esophageal 
region, where they are scattered 
among the bundles of the outer lon- 
gitudinal muscular layer, as figured 
for T. univittatum (fig. 1). 
Alimentary canal. — Mouth and 
esophagus as in related species. The 
esophagus opens posteriorly into a 
long chamber, the stomach, without 
diverticula, and this in turn passes 
gradually into the intestine proper. 
At its posterior end the esopha- 
gus is surrounded by a well-devel-' 
oped layer of circular muscles, form- 
ing a strong sphincter (fig. 4, icm). 
These muscles are very limited in 
extent as a distinct layer, although 
they can be followed well forward 
in the esophageal region. Imme- 
diately in front of the opening of the 
esophagus into the intestine (fig. 4) 
they become fully equal in thickness 
to the circular muscular layer of the 
body walls. They are doubtless per- 
fectly homologous with the inner 
circular muscular layer which sur- 
rounds the posterior end of the stom- 
ach in Zygeupolia, Micrura, and other 
forms, and which is apparently ho- 
mologous with the inner circular 
muscular layer of the Paleonemertea. 
The histological elements of the 
esophagus are sharply demarcated Fie. 5 .—Tseniosoma cingulatum sp. nov. Portion of transverse section of 
from those of the stomach as in body thr0u s h anterior end of stomach region, showing peculiar cyst of 
. , , ’ , fibrous tissue (a) containing two parasitic nematodes; a similar parasite (x) 
many other forms, and the change is shown in the outer longitudinal muscles; ibl) blood lacuna; (in) lateral 
from esophagus to stomach is his- nerve. Other reference letters as in fig. 1. x 58. 
tologically as well as anatomically 
abrupt. Nevertheless, in one of the specimens sectioned a narrow band of epithelial cells (fig. 4, a) char- 
acteristic of the stomach extends forward for a short distance along the dorsal wall of the esophagus ( e ) . 
The transition from stomach to intestine, on the other hand, is so very gradual, both histologic- 
ally and anatomically, that it is necessary to observe the arrangement of the blood vessels and the 
muscular layers in order to determine where the stomach region ends and the intestinal region begins. 
The intestinal lobes are even less developed than in T. univittatum, and consequently the central 
lumen of the intestine is very large. 
Blood vascular system . — Cephalic blood lacunae as in related species; esophageal lacunae voluminous, 
surrounding the lateral and ventral walls of the esophagus as closely placed anastomosing blood spaces 
of large size (figs. 4, 6, 7, el). In the stomach region these lacunae decrease in number and size and 
eventually unite into a single pair of vessels, which later join the pair of lateral vessels situated in the 
