24 
ON A NEW SPECIES OF ENTEROPNEUSTA, 
from the " cord hollows." I have never been able to trace these 
hollows in the roots as continuous canals throughout the whole 
length of even the first "root," and am convinced that in none of 
the " roots " of this species does a continuous canal exist such as 
Spengel describes for the first "roots" in Ft. minuta, claviyra, 
aperta, and bahamensits. Similar though smaller hollows may 
exist in the " roots " succeeding the first, but just as in the first 
" root " the hollows do not stand in continuous connection, but 
are interrupted by anastomosing strands or in some cases by 
branching cells with large nuclei. I have likewise never observed 
the " collar hollows " to pass into the roots. 
The roots end dorsally just as Spengel describes (fig. 16, rt.). 
The outer limiting membrane and the fibrous layer of the root 
unite with the similar layers of the epidermis; while the cellular 
tissue of the root projects in a cone-like mass between the epidermal 
cells, the apex of the cone reaching to within a short distance from 
the outer surface. The apex of this cone-like mass of tissue is 
composed of a network of fine strands enclosing clear spaces, and 
with a few very small nuclei in the angles where the strands meet. 
Below this clear tissue and continuous with it, there occur more 
deeply staining branched cells which are directly continuous with 
the central tissue of the "roots." 
Nerve Stems of Trunk : These are related exactly as in the 
described species, and the circular commissure placing the fibrous 
layer of the collar cord in connection with that of the ventral stem 
can be readily seen in horizontal sections occupying the deep 
groove between collar and trunk. The cells covering the circular- 
fibre ring are entirely destitute of gland cells, and consequently 
are sharply marked off from the adjacent epidermal cells. 
The dorsal stem in the branchial region is situated somewhat 
below the level of the adjacent epidermis (fig. 20, dnv.), but 
posterior to this region it forms a distinct ridge. The ventral 
stem, on the other hand, occupies over its whole extent the bottom 
of a shallow longitudinal groove (figs. 20, 24, vn.). The fibrous 
layer of the dorsal stem is, as in Ft. minuta, somewhat triangular 
in transverse section; it is thickest in the middle, and laterally 
