VERMES. 



all animals, in which it has been hitherto difcovered, with 

 the refpiratory apparatus ; the air wliich enters the latter 

 loaded with odorous effluvia atling on the olfaftory nerves 

 in its paflage. This analogy would lead us to look for the 

 nofe in fimilar iituations in invertebral animals. No fuch 

 organ, however, has yet been difcovered in this great divi- 

 fion of the animai kingdom ; a.though in fome inftances 

 there are ftroug proofs that fuch a fenfe exifts. (See 

 Insects, in Anatomy. ) In moUufca and worms we have 

 ilill fewer direft arguments for the exiilence of the fenfe, 

 than in infefts. We fhould not perhaps expeft it in in- 

 teiUnal worms, as it could anfwer no purpofe ; nor in fuch 

 tcitaceous animals and corals, &c. as have no power of 

 locomotion. 



Organ ofTaJlc The fepis, fnails, and mod gafteropodous 



inollufca, have a cartilaginous tongue, the fingular ftrufture 

 of which will be fpoken of in defcribing the organs of 

 maRication, &c. It has no motions except fuch as are 

 connefted with deglutition. Its anterior part is fixed 

 below the mouth ; and it it incapable of embracing fapid 

 bodies. The acephalous mollufca do not appear to have 

 any tongue ; perhaps they exercife the fenfe of taile by 

 thofe tcntacula, fo fimilar to papillse, with which their 

 cloaks are furniftied at the parts, where the water, which is 

 the vehicle of their aliments, enters. 



There is no tongue, properly fpeaking, in worms ; though 

 lome have given that name to the probofcis of the tha- 

 laffema, echinorhynchus, &c. The zoophytes have alfo no 

 tongue ; but the tentacula, which furround their mouth, 

 are frequently fo fine, and of fo deUcate a fubftance, as to be 

 very well calculated for the feat of tafte. 



Organs of Digeflion. 



Organs of Maflicatton in the Mollufca. — As this clafs hardly 

 ptyffelTes in any inftance an oifeous or at afl fohd head, their 

 jaws, when they have any, cannot be articulated with, or 

 reft upon the head. Although the cephalopoda poffefs a 

 kind of cranium, they do not conftitutc an exception to 

 this rule ; the parts compofing their mouth are fufpended 

 in the ring formed by this cranium. 



The jaws of the mollufca confift of horny, or fometimes 

 ftony fubftance, fixed in an oval flefiiy mafs, enveloping the 

 mouth, and compofed of the mufcles of the jaws, and of 

 thofe concerned in deglutition. The mufcular fibres be- 

 longing to this mafs are not very diftinft, although we per- 

 ceive in them different direftions, by which they are calcu- 

 lated to approximate or feparate the jaws. The latter differ 

 confiderably in form. All the cephalopoda poffefs two, 

 which refemble exaftly the homy mandibles of a bird. 

 They are convex, hooked, and very fharp-pointed. They 

 confift of a double plate of a thick hard horn, of a deep- 

 brown colour, of which the edges, oppofed to each other at 

 the triturating part, become very thin, while they are 

 hidden at their bafis in the flefhy mafs already mentioned. 

 This inftrument is employed to break the crabs and other 

 teflaceous animals which are ufed for food. 



The form and number of the jaws are not fo conftant in 

 the gafteropoda. The common flugs and fnails have only 

 one, which correfponds to the upper ; it is crefcent-lhaped, 

 and the concave edge is denticulated. 



In the tritonia, the jaws may be bcfl; compared to the 

 fhcars emploved in {hearing (heep. Inftcad, however, of 

 playing on a common fpring, the two plates move by a 

 joint ; and they are (lightly curved, inftead of being plane. 

 Tliefe jaws are lateral, and move from right to left ; the 

 cutting-edge of one Aides over that of the otlier, and they 

 are very fharp. 



We fee nothing in the aplyfia but a thin horny phfe, of 

 no great ftrength, covering th interior of each fide of the 

 mouth. Even this flight induration is not obferved in the 

 onchidium. 



The gafteropodous mollufca, poffelling a long or (hort 

 probofcis, have no jaws at all ; this is the cafe with the 

 buccinum, murex, voluta, buUaea, &c. ; and among the 

 naked gafteropoda, with the doris, fcvl!";? Sec. We merely 

 find in fome cafes, that the fides cf the bottom of the 

 probofcis are covered with cartilaginous plates ; there are 

 fuch in the doris. The ofcabrio has no mafticating organ : 

 neither have the pteropoda, as the hyalasa, clio, pneumo- 

 dermon, &c. 



None of the acephalous mollufca have jaws, nor any 

 thing fubfervient to maftication properly fo called. The 

 teredos employ, for piercing wood, the valves of their (heDs, 

 which fome naturalifts have called their teeth ; but about 

 the true nature of which it is impoffible to doubt, when the 

 teredo is compared to the pholas, the genus moft analogous 

 to it. The valves of the former feem merely a miniature 

 reprefentation of thofe belonging to the latter ; as Adanfon 

 obferved long ago. 



The naked acephala, as the falpa (biphore), afcidia, 8cc. 

 have no apparatus for dividing their food. The cirropoda, 

 as the balanus and lepas, have veftiges of jaws, difpofed in 

 pairs. The lepas, for example, has two denticulated pairs, 

 and a thin oae fimply rounded. 



Organs of Mqflicatlon in the Vermes. — Some of this clafs 

 have lateral jaws as ftrong as thofe of any infeft or crutla- 

 ceous animal, and even very fimilar to them in form. In a 

 large fpecies of nereis, for example, the opening of the 

 oefophagus is furnifhed with eight calcareous pieces, which 

 feem to fupply the place of mandibles, jaws, and lower lip. 

 The two upper are flattened, arched, and pointed hooks, 

 difpofed like the branches of a pair of forceps, united 

 behind, and articulated upon a horny, elaftic, femilunar 

 plate fituated above the oefophagus. The two following 

 are broader, but not fo long ; they have fix denticuU 

 direfted backwards ; they are articulated towards the pof- 

 terior third and below the hooks, which reft upon them '\i\ 

 their whole length. The third jaw on each fide is placed 

 below and exteriorly ; it is Ihorter arid embraces the firft 

 jaws, as in the bowl of a fpoon. It is found, on attentive 

 examination, to be compofed of three fmall pieces placed 

 near together ; the internal has its edge denticulated with 

 twelve fmall triangular points, like the teeth of a faw : the 

 middle is placed forwards, and forms the pofterior edge of a 

 prominent rounded eminence, fituated at the opeamg of the 

 mouth ; the laft is external, and terminated by a fingle 

 point. The two lower pieces, which feem to ferve for a 

 lower lip, are the longeft, flattened horizontally, fofter at 

 their edge, which confifts of a horny and rather flexible 

 fubftance. All the parts juft fpecified are furrounded by a 

 ftratum of mulcular fibres detained to move them. 



In other fmall fpecies of nereis, the opening of the 

 oefophagus is very mufcular, covered with wrinkles and 

 points of a horny firm texture, arranged in a circular 

 manner, and on fcveral lines, which are capable of rubbing 

 on each other. Two principal rugae, fituated towards the 

 upper part, fupport two larger horny pieces of a round 

 form. At the lower and back part are two arched iiooks, 

 which come together hke the branches of forceps. In 

 other fpecies we alfo obferve two hooks ; but the homy 

 points are not arranged in the fame manner. They are 

 collefted in fix groups in mufcular eminences, of which 

 three are anterior and three pofterior. It appears that the 

 animal has the power of inverting this part of the afopha- 



