MOLLUSCA. 131 



oviduct, and, after pursuing an independent course for some time, 

 opens into a hollow muscular tube, the penis, which receives at 

 the same point the flagelhim, a long and hollow filament. The 

 penis opens into the genital atrium, a shallow depression common 

 to both male and female ducts, and opening to the exterior below 

 the optic tentacle by the genital opening. A narrow band-like 

 muscle, the retractor penis, takes origin in the lung-floor, and is 

 inserted into the penis. 



(3) Special Female Organs. The oviduct is a wide, somewhat 

 twisted tube, with folded and pouched walls, along one side of 

 which the spermiduct runs. The tongue-shaped albumen-gland, 

 which varies very much in size, according to the time of year, 

 opens into its commencement. Where the spermiduct assumes an 

 independent course, the oviduct merges into a muscular, smooth- 

 walled tube, the vagina, which opens into the genital atrium. A 

 tubular organ, the spermotheca (receptaculum seminis), consisting 

 of right and left branches, opens into the hinder end of the 

 vagina. The right and shorter branch ends in a berry-like 

 dilatation. 



In Helix pomatia the lefVbranch is only represented by a small projection. 



Two tuft-like mucous glands open into the side of the vagina 

 somewhat further forwards, and in front of this an extremely 

 muscular pouch, the dart-sac, which can be everted from the 

 genital opening, communicates with it. This sac contains an 

 elongated calcareous body, the spiculum amoris, which is sharply 

 pointed and possesses four slightly twisted lateral ridges. 



It is doubtful whether the dart-sac really belongs to the female organs, 

 Imt its position would seem to indicate this. 



The hermaphrodite gland is made up of numerous branched 

 tubules lined by germinal epithelium. Some of these germinal 

 cells develop into rounded ova, which possess a well-marked 

 germinal vesicle with germinal spot, but are devoid of a vitelline 

 membrane. Other germinal cells pass into the cavities of the 

 tubules, and as mother-sperm-cells divide repeatedly to produce 

 bunches of sperms (spermatozoa), each of which has an irregularly 

 oval head, and long vibratile tail. 



The breeding season is early summer. As in most hermaphro- 

 dite animals cross-fertilization takes place, and self-fertilization is 

 prevented, in this case by the sperms maturing before the ova. 



