32 
ON A NEW SPECIES OF ENTEROPNEUSTA, 
and the underlying ciliated grooves, and into a posterior caudal 
region. 
In the abdominal region the ciliated grooves may be situated 
directly under the epidermal stripes or may be remote from it by 
a short distance, but always the portion of the longitudinal 
musculature between them is somewhat thinner than elsewhere. 
The cells of the epidermal stripes usually stain darker, and are 
somewhat lower than the adjacent cells, and in one case where the 
groove was situated immediately under the epidermal stripe there 
existed what appeared to be a special differentiation of the cells 
of the latter in the form of a small mass of cells with rounded 
nuclei and distinct nucleoli. In other respects the abdominal 
region of this species closely agrees with that of Pt. minuta. The 
wall of the gut in this region (fig. 25, i.) is thrown into numerous 
somewhat irregular transverse folds, and it becomes further removed 
from the longitudinal musculature so that the ccelom is very much 
more distinct than in the liver region and, as there, divided into 
two distinct halves only, however, in the anterior part of the 
region. The band-like cellular mass which Spengel has found in 
Pt. minuta and sarniensis in connection with the dorsal vessel and 
lying along the dorsal median line of the gut also exists in this 
species. It has here the form of a low band of cells of varying 
height lying as in the described species between the two lamella? 
of the boundary membrane of the gut and not limited laterally. 
Between the dorsal vessel and the cellular mass there passes a 
short mesentery, and by the separation of # this into two lamella? 
the cavity of the dorsal vessel comes into direct connection with 
the cellular mass. At these points the cells of the mass are not 
closely packed, and have a branching character exactly like the 
endothelial cells of the dorsal vessel with which they seem to be 
continuous. 
The caudal region of the hind body is essentially similar to that 
of Pt. minuta. As in the posterior part of the abdominal region, 
the two halves of the ccelom here stand in connection below the 
dorsal vessel. On the ventral side the ventral vessel disappears 
as a distinct structure at the beginning of this region, while the 
