VERMES. 



ending in the ovjduft. The penis forms a tube nearly a3 

 long as that of the onchidium, but without any enlargement 

 or acceffory tube. 



The openings of the fexual organs are remote from each 

 other in the hyalxa and pneumodermon, although united in 

 the fame individual ; but the animals are too fmall for a 

 detailed defcription. 



Gajhropoda lu'ith feparate Sexes. — This feparation certainly 

 exifts in the buccinum undatum. The male is recognized, 

 even externally, by a flcfhy penis as large as a finger, com- 

 prefled, broader at the end, and terminated by a fmall 

 tubercle, which is perforated by the orifice of the vas 

 deferens. It adheres to the right fide of the neck, and 

 folds back into the pulmonary cavity, but the animal often 

 extends it, without any intention of copulating. The vas 

 deferens traverfes its whole length, making fevcral folds and 

 zigzags ; it enters the right fide of that part of the body 

 which fills the (hell, makes a large packet of tortuous t\irns, 

 becomes gradually fmaller, and ends at the tefticle, a yel- 

 lowifh, foft, glandular mafs, occupying with the liver the 

 higheft turns of the fhell. 



Nothing fimilar to this penis is found in the female ; the 

 neck is fmooth, but on the right fide of the pulmonary 

 cavity, between the body and the reftum, a large canal is 

 feen, the extremity of the oviduft. The orifice is fmall : 

 on opening it we find a large tube with thick glandular 

 parietes, calculated no doubt to furnirti an exterior covering 

 for the ova. It opens a little within the edge of the pul- 

 monary cavity by a fmall aperture. 



In the murex tritonis, there is a Cmilar feparation of 

 fexes, and a penis equally flefhy and prominent. Inftead, 

 however, of having a complete vas deferens in its interior, 

 there is a fimple groove on the furface, continued on the 

 body, as far as the portion which fills the fhell. The penis 

 is proportionally Ihorter and thinner than in the buccinum. 

 The female has an oviduft fimilar to that of the female 

 buccinum. 



The ftrombus has a mere tubercle projefting flighlly at 

 the right fide of its very fmall foot. The femuial fluid is 

 conveyed to it alfo by a groove. 



The penis of the voluta is flefhy, conical, always pro- 

 jefting, but not perforated : the femen arrives by a groove, 

 which however ends at its bafis, without going to the point. 



In thofe genera with feparate fexes, the oviduft is wanting 

 when there is a penis with its groove ; this groove occupy- 

 ing the place of the oviduct. 



There is an hermaphrodite fpecies ; but it feems formed 

 rather on the model of thofe juft defcribed, than on that of 

 the fpecies in the former divifion. It is the hehx vivipara 

 of frefii water. It has an ovidnft and a groove, placed fide 

 by fide, and ending refpeftively at the ovary and tefticle. 

 The latter is clofely joined to the oviduft : its groove ter- 

 minates externally at the very edge of the foot, under the 

 right hern ; and there is no penis but the prominence which 

 this edge may form when extended. The oviduCl is of great 

 fize and length when filled with fmall living individuals. 



This animal is ovo-viviparous. In the \^per part of its 

 ovidudl we find eggs not hatched, refembling fmall globules 

 of a whitifh glairy matter, in which with a glafs the 

 animal can be feen covered by its fhell. In theie ova the 

 fmall pedicle may be Hill feen, by which they were attached 

 to the ovary. 



The acephala are all hermaphrodites, and impregnate 

 themfelves without any copulation. We difcover no other 

 generative organs but an ovary, extending over the two fides 

 of the body, immediately under the fliin, penetrating be- 



tween the tendons of the mufcles, and fometimes between 

 the two membranes of the cloak. The fize and colour' 

 vary according as the animal is more or lefs advanced in 

 geftation. At a certain period a milky liquor is feen in it, 

 which is probably a feminal fluid defigned to fecundate the 

 ova. When the latter are advanced, they pafs into the 

 fpaces between the two vafcular laminae, compofing each of 

 the four plates of the branchias, and fometimes diftend them 

 in an extraordinary manner, for the number is truly pro- 

 digious in fome fpecies. The eggs of the ovo-viviparous 

 fpecies, as the frefh-water mufcle, are hatched in the 

 branchise. When we obferve the little mufcles with a 

 glafs, we fee them open and fhut their valves with great 

 afiivity. 



No orifice has yet been difcovered, by which they could 

 pafs out ; probably they efcape by lacerating the tiffue at 

 the edges of the branchia; between their pulmonary veffels. 



The organs of generation in the naked acephala, as the 

 biphori and afcidia:, and in the branchiopoda, as the tere- 

 bratulx and lingulas, have not been carefully inveftigated. 



The cirropoda, or balani and anatifae, differ very much 

 from the acephala, and approach in their male organs, as in 

 feveral others, to the cruflacea. On each fide of their in- 

 teftinal canal there is a white ferpentine tube, fuppofed to" 

 be the tefticle, and ending towards the bafis of the redlum., 

 Yet thefe animals are hermaphrodites, and their ovaries are 

 two nialTes placed between the trunk and the cloak, and 

 connefted in their fituation only by veffels and cellular 

 tifl"ue. , 



Generative Organs of Worms. — This clafs exhibits the 

 three combinations, which are found in the moUufca ; fome 

 have the fexes feparate ; others united, fo that they fecun- 

 date themfelves in an infulated manner ; in a third divifion 

 they are united, but there is a reciprocal copulation. 



The leech exemplifies the latter modification ; it has a 

 very confiderable penis, compofed of a thick and long 

 mufcular tube, hollow internally, which can be protruded 

 like the penis of the fnail, while it is prolonged backwards 

 into a flender and merely membranous tube. There are 

 two tefticles, each compofed of numerous convolutions of a 

 fingle, foft, whitifh canal, with glandular fides, and of a 

 fliort, ftraight, and mufcular vas deferens. Thefe two tubes 

 appear to terminate at the bafis of the mufcular part of the 

 penis, and the feminal fluid probably flows along the 

 grooves of its furface, when it is unrolled. Near it is a 

 cavity opening externally, and ferving apparently to receive 

 the penis of the other individual. The orifices of thefe 

 parts are near each other, and near the anterior extremity 

 of the body. 



The earth-worm exhibits two orifices on its under fur- 

 face, near the anterior extremity, and not, as fome have 

 defcribed, at the fwelling in the middle of the body. They 

 correfpond internally to two or three foft, oval, glandular 

 cavities. There are feveral fmaller ones around them. 

 Thefe feem to be the organs of generation ; but we cannot 

 point out their funftions. Willis mentions that the large 

 cavities are fometimes filled with eggs ; but we fee true 

 ovaries, in the form of fmall inteftines, arranged in three or 

 four pairs, and fwelled by ova, fo as to referable rows of 

 beads. No external or internal organ of copulation can be 

 found ; yet it is popularly known that earth-worms remain 

 clofely embraced for the purpofe of fecundation. 



In the anterior part of the body of the lumbricus marinus 

 there are five greyifh facculi on each fide, fufpended by 

 veffels and cellular fubftance, and appearing analogous to 

 thofe of the earth-vi'orra. The ova mufl efcape from the 



facculi 



