314 Proceedings of the Royal Society of Edinburgh. [Sess. 
Commencing at a point slightly median or dorsal to the pulmonary 
aperture, there is a distinct but shallow groove in the skin which leads 
obliquely forwards and downwards, ending just below the ventral lip of the 
genital pore. 
On looking at the left side of the specimen just behind the posterior 
tentacle it is at once obvious that certain parts of the genital apparatus are 
repeated ; indeed, there is no difficulty in recognising a penis and its retractor 
muscle, a vas deferens and a flagellum. These may be first described as 
they are seen in the general dissection, shown in fig. 2. 
The additional penis (P.S.) is as well developed as the normal one, and 
opens to the exterior by means of a slit-like aperture as large as the normal 
genital pore on the right side. The retractor muscle (M.Retr.P.S.) is 
inserted in the usual position at the inner end of the penis ; only a short 
portion is shown at that point in the figure, the remainder (M.Retr.P.S'.) 
is seen attached to the body wall, its origin being close to that of the 
retractor of the right penis. Enclosing the bases of these retractors there 
is a thin connective tissue sheath (Sh.), folded at the middle so as to divide 
the enclosed area into two compartments, one for each retractor. When 
the flaps of the body wall are replaced in their normal position the origins 
of the retractor muscles are seen to be a little to the left of the mid-dorsal 
line, and so placed that the muscles would gradually diverge from one 
another to their respective penes. The two penes are symmetrically placed 
with regard to the median plane of the head, and, as already stated, are 
equally developed. 
The extra vas deferens (V.D.S.) is seen in connection with the inner 
end of the penis, and may be followed along the whole length of that organ 
until it disappears beneath one of the large retractor muscles of the anterior 
end ; this muscle (M.Retr.) is inserted into the body wall by means of two 
diverging portions which enclose the distal part of the penis and the 
proximal part of the vas deferens. 
Arising from the vas deferens near the middle of its length is a well- 
developed flagellum (Fl.S.), the terminal portion of which was accidentally 
severed and lost during the initial stages of the dissection in class, before 
the abnormality had been observed. At the point of origin of the flagellum, 
which is situated somewhat further from the penis than in the case of the 
normal flagellum, there is a sudden increase in the diameter of the vas 
deferens, its distal part being about twice as wide as the proximal 
part. The ocular tentacle (Tent.P.L.) and its retractor muscle pass to the 
outer side of the penis and neighbouring portion of the vas deferens, as is 
the case on the right side. 
