The adult organisation of Paragordius varius. 409 
symmetrically arranged on the two sides of the body (N.2 Fig. 2, 
Pl 3%::3Fig. 15, Plisa8): 
At the plane where the cephalic nerves meet together a trans- 
verse fibrous commissure (Fig. 23, Pl. 38) joins them lying close to 
the ventral surface of the parenchym sheath (Par) of the oesophagus 
(Oes), and this may be called the ventral commissure of the 
cephalic ganglion. This commissure (V. Com Figs. 16, 23), which is 
composed entirely of nerve fibres, sends its fibres dorsad around the 
sides of the intestine, and as a pair of large fibrous trunks these 
penetrate the tissue of the capsule of the eye, and there ramify as 
will be described in another place; these may be termed the dorsal 
nerves’ (Dors:Nt Figs.) 2,18, 16, 7, (Pl dts) Big2u16, Pls238). oft the 
cephalic ganglion, and together are probably comparable to the dorsal 
fibre commissure of other Gordiacea, but modified by the presence 
of the huge eye; there appears to be no direct commissure above the 
intestine uniting these nerves. 
The nerve cells (chromophobic cells) of the cephalic ganglion 
extend as far forward as the point of separation of the two cephalic 
nerves; this most anterior portion of the nerve cell mass is also the 
widest from side to side, and the narrowest dorso-ventrally. There is 
thus a wide bridge of chromophobic nerve cells (Fig. 15, Pl. 38) con- 
necting the roots of the cephalic nerves (Ceph. N), this bridge of 
nerve cells being separated from the intestine above as well as from 
the hypodermis below by parenchym. At the plane of the ventral 
commissure (Fig. 23, Pl. 38) the nerve cell mass (Chb. C) has a dorso- 
ventral thickness equal to that of the fibrous tracts (roots of the 
cephalic nerves) on either side of it; but behind this commissure the 
fibre tracts come to meet over the mass of nerve cells, so that the 
latter more posteriorly become restricted to the medio-ventral region. 
Thus the cephalic ganglion of Paragordius is the but little modified 
anterior termination of the nerve cord. Anteriorly it bifurcates (Fig. 7, 
Pl. 37), the forks being the forward continuations of the lateral fibre 
tracts, the median fibre tract not being represented at this anterior 
region. Each such cephalic nerve (Ceph. N) terminates anteriorly 
against the hypodermis of the ventro-lateral surface of the hypodermis ; 
and from the ventral side of the more posterior part of the each 
cephalic nerve two smaller ventral nerves pass to the hypodermis. 
There is one transverse fibrous commissure below the oesophagus, and 
from this commissure two large nerves, the dorsal nerves, pass dorsad 
on each side of the oesophagus into the tissue of the eye sheath, but 
27* 
