315 
1906-7.] Helix pomatia with Paired Male Organs. 
The penial nerve on both sides leaves the cerebral ganglion (C.G.) 
laterally, anterior to the root of the ocular nerve, and passes into the 
interval between the penis and vas deferens, being supported by a connective 
tissue sheet which partially binds these two structures together. The 
nerve divides into three or four branches, which pass into the penis near 
the middle of its length. The nerve to the right penis really originates in 
the pedal ganglion, and traverses the cerebro-pedal connective and a portion 
of the cerebral ganglion before becoming free as the penial nerve (N.P.), 
seen in the figure. The actual origin of the left penial nerve (N.P.S.) 
could not be determined by dissection, so the nerve, the cerebral ganglion, 
and the cerebro-pedal and cerebro-pleural connectives were excised and 
sectioned. The preservation of the tissues enclosed within the sheath of 
the ganglion was, however, so defective that the complete course of the 
penial nerve fibres could not be followed. The left penial and ocular nerves, 
on being traced back into the cerebral ganglion, are seen to penetrate the 
sheath of the ganglion close together and then unite, but soon after this 
the tissue is so badly preserved that the two bundles of fibres are no longer 
distinguishable. Whether the penial nerve fibres arise from the ocular 
nerve, as is apparently the case, or whether they actually arise from the 
pedal ganglion, is unfortunately impossible to decide. In the majority of 
normal specimens there is, on the left side, a nerve given off from the 
cerebral ganglion just anterior to the ocular nerve, and reaching the body 
wall immediately behind the ocular tentacle — that is, in the region of the 
supplementary penis in the abnormal specimen. It is possible that in the 
abnormal specimen this nerve has been elevated along with the up-growth 
of the supernumerary organs. 
Dissection of the tissues around the base of the extra penis and vas 
deferens permits their further course to be traced (see fig. 3). The penis 
passes through the body wall and opens to the exterior by a slit-like pore 
(G.O.S.), but probably the portion of the tube immediately internal to the 
aperture is to be regarded as atrium (see below, pp. 316, 317). The vas 
deferens (V.D.S.), followed from the inner end of the penis, courses alongside 
the penis until it reaches the body wall, along which it runs obliquely dorsally 
for a short distance ; it then comes into close association with the skin, so 
close, indeed, that it was at first believed that the tube actually perforated 
the skin and opened externally by a minute pore. Further examination, 
checked by sections of this region, proves that there is no actual opening to 
the exterior ; the vas deferens ends blindly in the sub-epidermal tissue and 
is bound to the epidermis by a short cord of connective tissue (Con.T.). 
On reference to fig. 1 it is seen that the left genital aperture (G.O.S.) is 
