140 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
already described as lying anterior to the nerve ring. Immediately 
beneath the inner band of the radial nerve is the pseudohaemal 
canal of Hamann, the canal sous-nervien of Hérouard, for which I 
propose the name hyponeural canal (W’pn.r.). The radial canal of 
the water-vascular system, as is well known, lies beneath the hypo- 
neural canal. In the connective tissue of the wall between these 
two canals is the radial haemal lacuna (svg. 7.). 
Outer band.— The structure of the outer band, as in other 
holothurians, is similar to that of the nerve rmg. The nuclei which 
are embedded within the mass of longitudinal fibrillae resemble 
closely those of the nerve ring. Like Hamann, I have found them 
most numerous in the anterior part of the nerve band. The linear 
arrangement of nuclei observed in the nerve ring is also noticeable 
here, but, from the comparative infrequency of the nuclei, less 
obviously. 
The nuclei of the covering epithelium are distributed over the 
whole external surface of the outer band, but are especially abundant 
in two parallel columns (Ze//sdulen), one on either side of the 
median line, as Semon originally found to be the case in Synapta. 
In sections stained successively with haematoxylin and eosin the 
fibers of the covering epithelium are brought out sharply, being 
colored with the eosin. As they are very nearly perpendicular to 
the length of the radial nerve or nerve ring, they can readily be 
followed from the nucleus through the entire thickness of the 
outer band to the connective-tissue partition, in which they terminate. 
In no case in which these fibers are thus clearly demonstrated can 
there be any doubt that they run across the nerve band indepen- 
dently of each other and without branching. My observations 
respecting this point differ from those of Teuscher, Semon, and 
Hérouard, all of whom have inclined to the view that these fibers 
branch. I am led to adopt the view of Hamann that they are 
purely supporting structures. If the nerve band is somewhat 
compressed in the direction of the length of these fibers, they 
appear exceedingly sinuous (Plate 3, fig. 41 ) both in the radial 
nerve and in the nerve ring. This would seem to indicate, as 
Hérouard has suggested, that they are not perceptibly elastic. 
Some of the nuclei of the covering epithelium are connected 
with processes which run outward across the epineural canal and 
terminate in the outer wall of this space. These fibers have 
their greatest diameter next the nucleus with which they are in 
