VERMES. 



but fmalkr. We obfcrve in tlie gizzard a narrow groove, 

 leadiii" direftly from the lirft (lomach into the third, and 

 probably fubfervient to fomething hke rumination. The 

 intelline is fhort and uniform. The aliment is moulded, in 

 the third ilomach, into long whitidi cords. 



The aplyiia has a ilill more curious ilomach : it is alfo 

 four-fold. The a;fophagus, at lirft narrow, dilates fud- 

 denly to form the Krit ilomach or crop, which is a large thin 

 membranous bag, makuig a nearly fpiral turn, and having 

 no glandular appearance. Then follows a iliort cylindrical 

 gizzard, with mufcular and very itrong parietes : they are 

 covered internally with a very extraordinary kind of armour, 

 to which there is nothing exaftly fimilar, although the ofleous 

 pieces belonging to the Ilomach of the bullxa bear fome 

 analogy to it. Let us conceive pyramids with rhomboidal 

 bafes, whole irregular faces are united into an apex divided 

 into two or three obtufc points. Their fubftance is femi- 

 cartilaginous, and compofed of ftrata parallel to the bafis. 

 There are about twelve large ones, arranged in quincunces 

 on three rows, and fome fmaller, placed at the upper edge 

 of the gizzard. Thefe pyramids adhere fo flightly to the 

 mucous furface, that the llighteft contact difplaces them, no 

 trace of membrane, or any other union, being perceptible. 

 The places to which they adhered are, liowever, marked by 

 fmooth prominent furfaees, while the intervals are flightly 

 hollowed and ftriated. Tiie aj)ices of thefe pyramids come 

 together in the middle of the gizzard, and tiiey muft con- 

 fequently comminute the food which paiFes along the fpace 

 between them. The third Ilomach is broad, but not fo long 

 as the former, and has an equally fmgular covering, confiding 

 of fmall pointed hooks attached to one iide of the cavity, al- 

 moft as flightly as the pyramids are to tlie preceding ilomach. 

 Their points are turned towards tiie gizzard, and no other 

 ufc can be afllgned to them but tiiat of (lopping the paffage 

 of the aliment when infufiiciently triturated : licre, indeed, 

 the form of the alimentary fubflances is no longer recog- 

 nizable. • Near the pylorus are two fmall prominent mem- 

 branous crillx, between which the orifice of the fourth ilo- 

 mach is feen, and that of the hepatic veflels. The former, 

 as in the cuttle-fidi, might be called a caecum. This caecum 

 is as long as the third ftomach : its diameter is fmall, its 

 fides fimple, without any internal projeftions, and it is ab- 

 folutely hid in the liver. The inteftinal canal is of uniform 

 diameter, with tiiin tranfparcnt fides, more fo than thofe of 

 the third ftomach, and dillinguiflied from it by this circum- 

 ftance : it makes two great convolutions enveloped in the 

 lobes of the liver, and terminates at the anus, in the middle 

 of the right fide of the body, by a reftum which pafles 

 tranfverl'ely. Its internal furface exhibits neither papillx 

 nor valves ; it has no fenfible conftriftion nor dilatations. 



The moft ftrongly armed of all known ftomachs is tliat of 

 the bulla lignaria and aperta ; there are three flat ftony 

 pieces ; two of iimilar form, triangular, broader and late- 

 ral, one narrower, rhomboidal and middle, united by muf- 

 cular fibres, wliich liave the power of approximating them. 

 Thefe hard fubftances are larger in the bulla lignaria, and 

 rather differently made. Draparnaud found tfiat this ap- 

 paratus had ben confidered as a fliell, and had given rife to 

 the eftablifhment of the genus tricla or giocnia. ■ 



In the Pteropoda. — Two of the fmall genera which com- 

 pofe this order, -vn. the clio and pneumodermon, have 

 ftomachs of the fame kind : they are fimple membranous 

 bags, furrounded by the liver, and receiving bile from nu- 

 merous orifices. Tlie third genns, hyala'a, has a dilatation 

 of the cefophagus, followed by a fiiort cylindrical gizzard : 

 both have internal longitudinal plates. The two firll genera 



have a fliort itraight intelline : the hyala:a has three convolu- 

 tions included in the liver. 



In the Acephala. — We generally find in this family a mem- 

 branous ftomach, following a very fliort cefophagus, fur- 

 rounded on all fides by the liver, which adheres to it inti- 

 mately, and in which it appears to be excavated. Its pa- 

 rietes are very irregular, forming feveral fmall cul-de-facs, 

 at the bottom of which the bile is received : for in all the 

 order that fluid enters the ftomach immediately. The 

 bfliary apertures have fomewhat valvular edges, to prevent 

 the food from entering the dufts. The inteftine makes fe- 

 veral convolutions, chiefly out of the liver, and moft fre- 

 quently in the fubftance of the mufcles of the foot, in which 

 it is in a manner incafed. Towards its origin, in fome 

 fpecies, the inteftinal canal has dilatations, which might be 

 taken for fecond ftomachs. In others there is a true iecond 

 ftomach, which is a kind of caecum near the pylorus. The 

 greateft fingularity, which is alfo abfolutely peculiar to fome 

 acephala, is a part long ago defcribed by Willis, Swam- 

 merdam, and others, but more particularly by Poli, under the 

 name of tiie cryftalline ftilette. It is probably traiifparent 

 and cartilaginous ; elongated, pointed at one end, and obtufe 

 at the other. It is compofed of lamina, included one in the 

 other, and contained in a flieath clofely applied to the com. 

 mencement of the inteftine, but open towards the ftomach, 

 fo as to allow the point of the ftilette to penetrate that cavity. 

 On this point is articulated a body of fimilar texture, divided 

 into fome conical eminences, and occupying the entrance of 

 the ftomach : it is difficult to afiign the ufc of fuch an 

 organ. 



The folen has a fecond ftomach, long and flender, and 

 occupying half the length of the foot, into which it pene- 

 trates : the inteftine begins at the fide of the origin of the 

 latter, and proceeds parallel to it. The oyftcr has alfo a fe- 

 cond ftomach, fituated between the branchiae and the mufcle 

 that clofes the fticll : the inteftine rifes from it near its com- 

 mencement, and proceeds in an oppofite direftion. 



According to Poli, the inteftinal canal is Ihorter in the 

 genera fixed to one fpot, as the oyfter and fpondylus, than 

 in thofe which are capable of locomotion, as the cardium 

 and venus. Yet the frefli-water mufcle has it fliort ; it 

 makes a '.ingle fold in the foot, and returns backwards to 

 defcend to the anus. The fame arrangement is found in the 

 mya piftnrum. On leaving the fecond ftomach, in the 

 oyfter, the inteftine afcends, furrounds the liver, and then 

 goes backwards. It is nearly the fame in the fpondylus. In 

 the eatable mufcle fmytilusefcnlentus), it defcends along the 

 back, afcends again, goes round the liver, and then defcends 

 to the anus. It is very fliort, making only two flio-ht curves, 

 in the venus decu-fiata ; but in the cardium cdiJe (common 

 cockle) it makes .feven or eight fpiral turns in the foot, 

 and is more than five times the length of the body. It is 

 equally long, but rather differently arranged, in the maftra 

 piptrata, where its commencement is very large, and might 

 eafily pafs for a fecond ftomach. It is the fame in fome of 

 the genus venus, and in the orbicular tellinae : the common 

 tellinx have moreover a kind of cxcum at the end of this 

 dilatation. 



\n moll of the acephala the reftum' pafles through the 

 middle of the heart, but the oyfter is an exception. 



There are fome remarkable varieties rtfpeding the anus. 

 In thofe which have no tubes to the clonk, and which walk 

 or fpin like the frefli-water and fea muftles, it opens by a 

 flefliy didc or fphinCler, between the two edges of the cloak. 

 In thofe which have thefe tubes, the anus itfelf makes 

 another, iituatcd more internally, projeding into the cavity 



of 



