MALACOLOGY. 



extent amphibious, being capable of breathing air by 

 the organs of respiration, yet living in water which 

 they rarely quit voluntarily, such as the Lymnaea 

 planorbis. The greater number constantly inhabit 

 salt and fresh water, being incapable of existing out of 

 it ; these distinctions are anatomically defined in the 

 aquatic and terrestrial species, possessing a particular 

 structure of respiratory organ ; but it is not so easily 

 observed what characters distinguish such of them as 

 possess branchiae of the same structure, and are 

 capable of existing either in salt or fresh water with 

 the same ease, or only in the one or the other. The 

 location of marine molluscs is extremely various ; a 

 great portion of them live on the sea-coast, on rocks, 

 iu the sand, or at the embouchure of rivers ; these 

 are called littoral species ; others are only to be found 

 at a distance from the shore in great depths of water ; 

 these are called pelasgic ; others, as we have already 

 stated, float on the surface of the waters, or attached 

 to various submerged bodies. Others live in the 

 sand or mud ; some make a dwelling in wood or 

 stone. But it is almost needless to observe that the 

 terrestrial species are much less variable in their 

 habits, and that it is generally in moist places that 

 they are most plentifully found ; some, however, seek 

 a dry soil for their habitation, and, under the disad- 

 vantageous circumstances to their comfort of too 

 much heat or too great cold, they conceal themselves 

 under ground, in the holes of trees, or other sheltered 

 spots, where, during the noxious season, vitality is for 

 a season partially suspended ; and they hybernate like 

 some others of the animal creation, remaining in a state 

 of torpor the whole time, from which, however, they 

 may be roused, though the experiment ill-conducted 

 would occasion instant death. 



The specFes of nourishment necessary to the exist- 

 ence of molluscs varies according not only to the 

 nature of their formation anatomically, but greatly 

 also with respect to their localities. They subsist 

 either on animal or vegetable substances, dead or 

 alive, fresh, or in a state of putrescence ; but each 

 species, each genus even, and yet more certainly, 

 each family, confines itself to one or other of these 

 nutriments. All the known CRYFTODIBRANCHIATA 

 the Sepia, Octopus, &c., seek their food in living 

 animals, which they tear to pieces, by means of the 

 hard parts of their mouth ; and in that state probably 

 swallow them without further mastication. The 

 SIPHONOBRANCHIATA, the Murex, and its congeners 

 appear all of them to be carnivorous ; it is notjikely 

 however, that they often swallow their prey whole 

 they may suck it by means of their toothed trunk, or 

 otherwise reduce its substance, but they cannot mas- 

 ticate it, being unprovided with true organs for thai 

 faculty. The AsiPHONOBRANcmATA,TVoc/ms,&c.seem 

 to be less generally carnivorous, perhaps not at all so 

 taking their food, either animal or vegetable, in a pu- 

 trid state, their proboscis-formed' trunk being more 

 adapted to sucking than masticating, this is certain 

 with regard to the terrestrial Cyclostoma. The PULMO- 

 BRANCHIATA, Li/mncea, Physa, &c., are, on the con 

 trary, decidedly phytophagous, or vegetable feeders 

 they cut and masticate the food they subsist upon ir 

 small pieces, which they swallow by slow degrees 

 they possess a mouth provided with one tooth of a 

 cutting shape, to which is opposed the lingual mass 

 it is however asserted that the Tcstacclla swallows 

 whole worms, drawing them gradually into the intes 

 tinul canal. The CHISMOBRANCHIATA, Sigaretus, &c. 



*ith the MoNOPLEUROBHANcniATA.and Berthella,pro" 

 lablyfeedin the same manner as theasiphonobranchia, 

 ince they possess no appearance of teeth in the 

 mouth. The PTEROPODS, Alalanta, do not appear to 

 iave the power of mastication, for the above reason, 

 and merely take their food by suction. The same 

 nay be said of the CYCLOBRANCHIATA, Dons, &c., and 

 veu generally of the PoLYBRANCHiATA,GVai<cMs, &c., 



Glaucus Fosteri. 



though in this last order there are some genera, such 

 as the Tritons and Scyllcea, in which two jaws exist, 



Scyllsea pelaglca. 



acting laterally like scissors, enabling them conse- 

 quently at least to cut or separate their food in small 

 portions. The NUCLEOBRANCHIATA, Carinaria, Ptero- 

 trachia, appear to feed upon small animals ; the CER- 

 VIBRANCHIATA, Patella, probably do the same, but 

 the greatest portion of their nourishment is most 

 likely derived from decomposed matter. In all the 

 class of Accjjhalophora, Terebratu/a, Lingula, &c., 

 the same mode of feeding is obviously necessary, 

 since their mouths, being entirely soft in all its parts, 

 cannot make the slightest impression on any substance 

 possessing consistence, which seems to confirm the 

 idea that they only subsist upon animal or even vege- 

 table particles, resulting from things, in a state of 

 decomposition, conveyed by the fluid element which 

 enters into the cavity of the mantle destined for re- 

 spiration ; neither is it impossible to conceive that they 

 may derive a great portion of their nourishment from 

 the innumerable microscopic animalcule existing in 

 the water they inhabit, which, being of the greatest 

 softness, require no masticatory process for prepara- 

 tion as food. 



From the nature of the aliment, and the very 

 different circumstances under which it is obtained, 

 it is equally evident that molluscs must employ 

 various methods of supplying the first want of 

 nature. Those species which, like the Sepia and even 

 the Testacella, prey upon fugitive animals, pursue, 

 catch, and destroy them ; when impelled by hunger, 

 some wait for their victims, lying in ambuscade, display- 

 ing a bait or temptation formed by some portion of their 

 weapons of destruction, and exercising in this opera- 

 tion a degree of what is termed instinct, very similar 

 to that of animals of a more exalted grade iu creation. 



