362 
REPRODUCTIVE ORGANS — PENIS. 
Its function in common with the flagellum is merely to accumu- 
late and agglutinate the spermatozoa together or enclose them within 
a Arm chitinous sheath or spermatophore which varies in its shape 
according to the species. 
The Penis (penis, a tail) is the masculine intromittent organ, and is 
only developed in our fauna amongst the Gastropoda, always occupy- 
ing the right side of the anterior part of the body in dextrally 
organized individuals. 
In the Streptoneura it is a permanently external outgrowth from 
the boily-wall, and may he a dorsal development as in Cyclostoma, 
with innervation by the sub-intestinal ganglion, a cephalic organ as 
in Vivipara, a pedal organ as in Valvata, or a pallial organ as in 
the exotic Ampullaria, their character being indicated by their 
inneiTation. 
The penis sheath to which the vas deferens conducts the spermatic 
fluid encloses the male intromittent organ, which occupies the distal 
end of the sac, and may he separated from the flagellum or epiphallial 
tract by a constricting muscular annulus. The sheath is usually a 
large somewhat fusiform or clavate sac, but assumes a gi’eat variety 
m. m. 
Fig. 6G0. Fig. G61. Fig 6G2 
Fig. G60. — I’ak'ata (Miill.), X 2, showing the permanently projecting male organ. 
Fig. G61.— Penis sheath of Helix ru/escciis Penn., opened to show the male intromittent 
organ, X 12. 
Fig. GG2. — Penis .sheath of Limneca /a/wi/Wi (Midi.), X 10, opened after pairing before com- 
plete retraction, showing how the sac becomes the intromittent organ by eversion. 
p. penis ; f.s. penis sheath ; v.d. vas deferens ; r. retractor muscle ; m.m. longitudinal muscular 
pillars, possibly protractors and guides. 
of shapes, and furnishes important characters utilized in classiflcation 
and in the differentiation of species, affording in the Succinece a 
ready means of separation between the doubtful intermediate speci- 
mens connecting Siicclnea putris and S. elegans. 
