313 
1906-7.] Helix pomatia with Paired Male Organs. 
folds into a larger female portion (CJD.F.), the walls of which are strongly 
plicated, and a smaller male portion (C.D.M.) which is covered by glandular 
prostatic tissue slightly folded or lobulated. After a course of about 
50 mm. the two portions of the common duct become completely separated 
as the oviduct and the vas deferens. 
The oviduct (Ovd.) runs forward for about 10 or 12 mm. and then 
merges into the wider vagina (V.), which leads into the common genital 
atrium (Atr.). The vagina bears a large clavate dart sac (D.S.) and two 
tufts of digitiform mucous glands (Muc.G.). In the figure these glands 
are to a large extent hidden by the dart sac ; they are not quite as large as 
in many other snails of the same collection examined, but, with this excep- 
tion, the reproductive organs are fully grown. Opening into the female 
genital canal near the point of junction of oviduct and vagina is the 
spermotheca or receptaculum seminis (R.S.), which bears a bulbous dilata- 
tion (R.S.J3.) at its inner end. In the natural position of the parts the 
tubular portion of the spermotheca lies alongside the common duct and is 
bound to it by connective tissue. 
The vas deferens (V.D.) has at first a somewhat sinuous course ; it then 
loops round the retracted posterior tentacle (Tent.P.R.), runs parallel to and 
practically along the whole length of the penis (P.), and bends round so as 
to enter the base of the latter, opening into it upon a knob-like muscular 
papilla which acts as a protrusible copulatory organ. This organ is enclosed 
in a thick muscular sheath, the inner surface of which, in the proximal part 
of the penis, has a rugose appearance. About the middle of the length of the 
penis, the sheath bears a muscular introversible tube. The part of the 
sheath distal to this is slightly thinner than the proximal part, but is also 
traversed by longitudinal folds. This inner sheath is surrounded by a 
much thinner outer one. The fibres of the thin, but strong, retractor penis 
muscle (M.Retr.P.) are chiefly inserted into the outer sheath close to the 
point of entry of the vas deferens into the penis. This muscle serves to 
retract the copulatory organ and also the penis as a whole. It arises from 
the posterior region of the mantle slightly to the left of the middle line. 
In the figure the greater part of the muscle is seen attached to the penis ; 
the remaining short portion is shown at M.Retr.P'. Just before entering 
the penis the vas deferens bears a long slender diverticulum, the flagellum 
(Fl.), which secretes the elongate spermatophore. 
The genital atrium (Atr.) is a short wide tube opening to the exterior 
by an aperture which, in non-excited specimens, is slit-like and about 
2*5 mm. long. This common genital pore is situated just behind and 
ventral to the posterior or ocular tentacle. 
