442 THE ANATOMY OF INVERTEBRATED ANIMALS. 



penis. In Peronla, the vas deferens and the oviduct open 

 too-ether b}' the genital aperture, and, as in some Branchio- 

 gasteropods, a groove, along which the seminal fluid is con- 



FiG. 12-2.— Diajrrara exhibiting the disposition of the intestine, nervous system, etc., 

 in a common Suail {H:U.r).—a, mouth; b. tooth : c. odontophore ; d. gullet ; e. its 

 dilatation into a sorr of crop;/, stomach: g. coiled termination of the visceral 

 mass ; the latter is also close to tlie commencement of the intestine, which will be 

 seen to lie on the neural side of the oesophagus ; h, rectum ; i. anus ; ^^ renal ,>^ac ; 

 I, heart: m, lung, or mjdified pallial chamber; «, its external aperture; o, thick 

 edire of the mantle united with the sides of the bodv; p. foot; r, s, cerebral, pedal, 

 and parieto -splanchnic ganglia aggregated round the gullet. 



ducted, leads to the outer openinir of the eversible penis (Fig-. 

 123, I., II.). 



In connection with the female genital aperture, there is 

 always a spermatheca.^ or sac (which is sessile in the Slugs, 

 but in the Snails is placed at the extremity of a long duct), 

 for the reception of the semen of the other individual when 

 copulation takes place. 



The HdlcidrB alone possess, in addition, the so-called sac 

 of the dart^ a short muscular b:ig, in which pointed chitinous 

 or calcified bodies— the spicida amorls — are formed ; and 

 certain glandular cieca, generally arranged in two digitate 

 bundles, termed mucous glands] which give rise to a milky 

 secretion. Sometimes prostatic glands are developed on the 



