464. WESLEY R. COE AND STANLEY C. BALL 
(fig. 4). The nuclei of these muscles are often conspicuous about 
the middle of their length (figs. 8, 9). The dorsoventral muscles 
closely invest the proboscis sheath and anchor it in place in the 
delicate parenchyma. Many of the bundles pass out radially 
from this organ into the muscular layers of the body walls. 
The character of the musculature clearly indicates that the 
animal is a sluggish swimmer, depending for locomotion largely 
on the movements of the caudal fin, and that it has little capacity 
for changing the shape of its body or exhibiting the rapid undula- 
tions characteristic of littoral species. The special musculature 
of the tentacles and the function of these organs will be described 
below. 
Parenchyma. As is other pelagic nemerteans, the abundance © 
of the gelatinous parenchyma which surrounds the internal or- 
gans (figs. 6, 8, 14) and separates them widely gives the animal 
its translucent appearance and adapts it to its pelagic existence. 
THE TENTACLES, OR NUCHAL CIRRI 
The most remarkable feature of this genus, other than the 
reproductive organs, is the lateral outgrowths from the body 
walls immediately back of the head. ‘The original description 
by Verrill (’92) records a different state of development of these 
appendages in each of the four specimens which he had for study. 
The smallest specimen had short, blunt tentacles, only about half 
as long as the breadth of the head; another had slender tapering 
tentacles as long as the diameter of the body, while in the largest 
individual they were more than twice as long as the width of 
the head, with slender, lash-like, somewhat coiled tips. 
A specimen which has more recently come into our hands has 
the tentacles about midway between the extremes described by 
Verrill, or one and one-half times as long as the width of the head 
(fig. 1). We have found, as was to have been expected, that all 
these five specimens are males, and that those with the tentacles 
most highly developed have the spermaries in the most advanced 
stages, while those with the short tentacles are still immature. 
It seems obvious, therefore, as has already been pointed out 
by Brinkmann (’12), that these appendages represent secondary 
