VERMES. 



the tefticle to be the ovary : having afterwards found the 

 true ovary, he called the teftis the bag of glue. The large 

 part of the oviduft adhering to the teftis he called the 

 uterus ; and not feeing that the vas deferens belongs exclu- 

 ilvely to the teftis, and has only an external attachment to 

 the oviduft, he admitted a communication between the 

 uterus and penis. 



The fize of the penis varies in the different fpecies of 

 fnails : fome have it longer than the body, when extended. 



Thefe organs in the teftacella do not differ remarkably 

 from thofe of the fnail. 



The ovary of the tritonia is more voluminous, the oviduft 

 larger in proportion, and the tefticle irregularly lobed and 

 fhaped like a ball. 



In the doris, the oviduft, after joining the teftis, appears 

 to unite with the canal of the bladder, and to form with it a 

 common canal. In the doris folea, from the Indian feas, 

 it feems even to enter the bladder itfelf ; which would con- 

 firm the notion of tliis part being defigned to furnifh a cover- 

 ing for the ova. The tefticle is rounded, and touches the 

 common cavity. A fmall acceffory bladder is connefted to 

 the canal of the bladder. 



In the bulimus ftagnalis (helix, Linn.) the conneftion 

 between the oviduct and tefticle is not fo clofe. The vas 

 deferens can be diftinguifhed throughout, at firft large and 

 expanded into a refervoir much plaited, and capable of con- 

 taining a large quantity of fluid. At parting out, the canal 

 is fmall, enters the flefh near the end of the oviduft, then 

 comes out again to end in the bottom of the fac of the penis, 

 which is organized as in the Aug. 



The ovary and tefticle of the fnail are arranged as in the 

 flug. The neck of the bladder is much longer, and con- 

 nefted to the broad portion of the oviduft, as far as the 

 point of its union with the tefticle. The lower part of its 

 neck is broad, and receives the orifice of the oviduft. It 

 moreover receives the apertures of two parts, which do not 

 cxift in the flug ; viz. two ramified organs, each of which 

 terminates in fifteen or twenty fmall caeca, containing a 

 white milky liquor. This might be confidered as feminal 

 fluid, and the organs as veficulae feminales, but they have no 

 immediate conneftion with the vas deferens. The latter 

 terminates in the fide of the penis, near its entry into the 

 common cavity. The penis therefore is not perforated at 

 its bottom, as in the flug : it is alfo much longer ; but pro- 

 bably it cannot be unfolded in its whole length, perhaps 

 only as far as the point at which the vas deferens enters : 

 this would then become its external extremity. 



The fnail has another remarkable part, not found in the 

 (lug ; W2. the fac of tlie dart. It is oblong, with thick 

 mufcular parietes : at the bottom there is a papilla, from 

 which proceeds a pointed dagger-ftiaped dart, with four 

 cutting edges. The fubftance of this fingular part is cal- 

 careous : it is renewed when loft. Snails prick each other 

 with it, at any part of the fltin indifferently, when they are 

 about to copulate. They feem too to dread it ; for as foon 

 as one perceives the other's dart, he withdraws immediately 

 into the fliell. The objeft of fuch a proceeding cannot be 

 conjeftured. Copulation docs not take place, until after 

 both individuals have brought out their darts : it refembles 

 that of the flug. 



The length of the penis protruded in copulation, 

 and the number of caeca, vary in the different fpecies of 

 fnails. 



The parmacella has the fame organs as the fnails. Its 

 veficulx are oval and undivided, and terminate dircftly in 

 the common cavity. The fac of the dart is nearer to the 



Vol. XXXVII. 



prepuce of the penis ; and the vas deferens opens in the bot- 

 tom of the latter. 



The fecond feftion of hermaphrodite gafteropoda in- 

 cludes thofe, in whom the penis paffes out at fome point of 

 the body diftant from the oviduft. The vas deferens is ftiU 

 united to the oviduft, and communicates with the penis 

 only by the intervention of a groove excavated in the ex- 

 ternal furface of the body. This groove is on the right 

 fide of the neck in the aplyfia; under the right edge of the 

 cloak in the onchidium, ice. 



The ovary of the aplyfia is an oval mafs, occupying all 

 the pofterior part of the abdomen, and in its ordinary ftate 

 of a whitifli colour. The oviduft arifes from it by feveral 

 veffels, coming from the different parts of the mafs, like the 

 excretory tubes of a gland, and uniting into one canal. 

 The latter, having run along the right fide of the tefticle, 

 fuddenly becomes fmaller, turns round the apex of that 

 gland, and forms a canal which, having been clofely joined 

 for fome time to the vas deferens, terminates by openir.g in 

 it, after receiving a fmall blind inteftine, apparently analo- 

 gous to the ramified organs of the fnail. 



The tefticle is of a beautiful yellow, and refembles an 

 elliptic fpheroid furrounded by a fpiral band. Its middle 

 is tolerably compaft, and feems nearly homogeneous. The 

 fpiral band is itfelf divided into a principal finely ftriated 

 band, of which the ftrise are probably fo many veffels, and 

 two fmooth borders, which are excretory tubes. The fu- 

 perior is the vas deferens common to the whole tefticle, 

 ierving to convey the feminal fluid. 



The common cord going to the exterior of the body is 

 at firft divided into two canals. That which comes from 

 the teftis is formed of a thin membrane much plaited : the 

 other, from the oviduft, has thicker parietes. From the firft 

 third of their length they communicate freely by means of 

 a flit : yet the diftinftion between them is marked by a 

 projefting membranous feptum. The oval bladder opens, 

 towards the fecond thread, by a fmall particular duft. 

 Beyond this orifice, the double canal forms a prominence, 

 vifible externally, on the right fide of the body : its open- 

 mg is continuous with a deep groove formed in the right 

 fide of the neck, and continued into the body of the penis. 

 Does this groove conduft the feminal fluid of one aplyfia 

 into the body of another ? The folution of the mode of 

 fecundation in thefe animals depends on the anfwer to that 

 queftion. 



The onchidium refembles the aplyfia in the feparation of 

 the organs. The oviduft, after being joined to the tef- 

 ticle, is united to the canal of the bladder, near its neck ; 

 and the common canal goes out at the fame point as the vas 

 deferens. From their orifice a groove extends, on the right 

 fide, along the under part of the cloak, to that of the penis 

 fituated at the right fide of the head. The latter com- 

 municates firft with a cavity having two cul-de-facs. In the 

 bottom of one of them a cylindrical tube enters, which tra- 

 vcrfes an elhptical mufcular enlargement, and extends be- 

 yond it to a length more than five times that of the body. 

 Near its entrance into the cavity, this tube conceals a fliarp 

 horny point. The other cul-de-fac receives the end of a 

 tube fliorter and much flcnderer than the preceding, with- 

 out any enlargement. This has alfo a fmall horny point in 

 the correfponding fituation. The ufe of thefe organs is not 

 known. 



The oviduft is diftinft throughout from the tefticle and 



the canal of the bladder in the bullxa, although the three 



organs have their iffue at the fame point. There it alfo an 



acceffory veficula, coming out with them, and a fmaller one 



G ending 



