418 GASTEROPODA. 



zig-zag folds, it reaches the extremity of that organ, where it ter- 

 minates by a small orifice. 



Equally simple is the structure of the generative system in the 

 females of the PECTINIBRANCHIATE Gasteropods. A large ovary 

 occupies the same position as the testis of the male, and shares with 

 the liver the interior of the windings of the shell. The oviduct 

 generally follows the same course as the vas deferens of the other 

 sex, and is provided with thick and glandular walls. The eggs, 

 which are very numerous, are arranged in long gelatinous ribands, 

 and, after extrusion, are glued in various ways to the surface of 

 rocks, sea-weed, or even to the shells of other Mollusca. Some- 

 times in the siphoniferous tribes, as for example in the common 

 welk (Buccinum), the ova are enclosed in tough coriaceous capsules 

 secreted by a glandular organ in the vicinity of the oviduct. These 

 capsules contain several eggs a-piece, and are joined together in large 

 bunches, such as the waves continually cast up upon every beach. 



(456.) The HETEROPOD Gasteropoda are hermaphrodite. In 

 Pterotrachea the female organs consist of a distinct ovary, uterus, 

 spermatheca, and an auxiliary gland, all lodged in the visceral sac- 

 culus appended to the back. The ovary (Jig. 188, p) is of con- 

 siderable, size, and gives origin to a slender oviduct, which near its 

 termination communicates with the receptacle for the ova, called the 

 uterus (g). The spermatheca (r) joins the canal leading from the 

 uterine cavity to the exterior of the body, which likewise receives 

 the secretion of two small glandular sacs (k) apparently destined 

 to furnish some investment to the eggs prior to their expulsion. 



The male parts are situated in the general cavity of the body, 

 quite apart from the female apparatus. The testicles seem to be 

 represented by two wavy cseca (Jig- 188, <), which terminate at 

 the root of a small intromittent organ (s) placed at a short distance 

 behind the opening of the vulva. 



(457.) All the TECTIBRANCHIATA, INFEROBRANCHIATA, 

 NUDIBRANCHIATA, and the PULMONATED GASTEROPODS are 

 hermaphrodite, having both a male and female generative apparatus 

 arranged upon the same principles as those of the snail, which 

 have already been described at length ; and to enumerate the 

 variations which occur in the relative position and organization of 

 different parts of the reproductive system in all the genera com- 

 posing these extensive orders would scarcely answer any useful pur- 

 pose, even were it practicable within the limits of this work. 



(458.) Many families of Gasteropoda, as for example the Nu- 



