4 
W. J. Dakin 
Kawitz' figures both surfaces of the visceral ganglion. On the ventral 
surface the anterior ends of the two dorso-central lobes are depicted 
(»Corpora oblonga« Rawitz') but their shape and size is quite incorrect. 
The two lateral lobes called by Rawitz »corpora semilunaria « are wrongly 
shaped and both sides are illustrated as alike. The large ventro-central 
lobe is Rawitz' corpus centrale posterius and it is figured by him as smaller 
than either of the anterior portions of the dorso-central lobes. The two 
nerves (fig. 1 os.h.n) which arise from the lateral grooves were not seen 
by him at all, for they are neither figured nor described, and the other 
nerves are shown as if alike on both sides of the ganghon. The lobes of 
the dorsal surface in Rawitz' figures disagree, in a similar way, with 
mine and I have not recognised his corpora cuneiformia as separate lobes. 
The small pigmented body (fig. 2 h) must equal Rawitz' corpus centrale 
anterius, for these is no other lobe in that position. Sections show that 
these lobes are simply superficial divisions (figs. 4,8) and none are cut 
off completely from the rest of the ganglion, the deepest division occurr- 
ing between the dorso-central lobes. The centrai mass of the ganglion 
is quite continuous and as in other molluscs is formed of a mass — 
the Punktsubstanz, Marksubstanz, or Neuropil — enclosed by a 
cortex of ganglion cells. This cortex is not everywhere of the same thick- 
ness, nor are the ganglion cells of the same size. The dark pigment occurs 
most abundantly where the cortex is made up of large ganglion cells. 
The two dorso-central lobes for example are composed almost entirely 
of ganghon cells of the largest size (fig. 11) and there is little neuropil. 
On the other hand the cortex is thin over the ventro-central lobe and the 
same applies to the lateral lobes. The intermediate lateral grooves have 
a covering of large ganghon cells (not so large as those of the dorso-central 
lobes) and are slightly pigmented. Finally, there is a coUection of larger 
ganglion cells on the under surface (dorsal) of the ventro-central lobe 
(fig. 2 v.c.l) which is also pigmented. Further details of the microscopie 
structure will be given after reference has been made to the course of the 
nerves which have their origin in the visceral ganglion. 
Commencing at the anterior end, and taking the more superficial 
nerves, we have first the cerebro-visceral connectives to consider. They 
enter the ganghon at the anterior ends of the lateral regions and by 
reason of their thickness, can be traced on the dorsal surface. 
Just at the point of entrance, however, and on the outer side, a num- 
ber of fibres are given off which pass directly into the branchial nerve 
(fig. 1 hr') which leaves the ganglion dose to the connective. The point 
of origin of the branchial nerves has just been referred to. They arise 
