272 



LAWSON, ON HELIX ASPERSA AND HORTENSTS. 



D 



EXPLANATION OF THE PLATE. 



A. The entire reproductive apparatus, natural size — a, albu- 

 men-gland ; c, caecum ; d, dart-sac ; o, ovary ; ov, oviduct ; 

 p, penis; ou, outlet; v, vagina; vm, multified vesicles; s, sperm- 

 sac; sd, spermatheca-duct ; t, testis; u, uterus; vd, vas 

 deferens. 



B. Vertical section tlirougli the dart-sac, enlarged, repre- 

 senting the follicle, papilla, dart, protective valve, and orifice 

 of vagina. 



C. Outline view of the testis, greatly magnified. 



D. A lobule of the ovary, enormously enlarged, exhibiting 

 the absence of included lobule, and the isolated zoosperms at 

 the aperture. 



E. Transverse section through the stilette, exhibiting the 

 trenchant outline and central perforation. 



BIBLIOGRAPHY. 



Berthelen. — Ann. des Sci. Nat. 



BuRDACH. — Quelques considerations sur le nidamentum. 



Carus. — Beitrage zur genauern kenntniss der geschlichts- 



organe und functionen einiger Gasteropoden. Miill, Arch., 



1835. 



