TUKBINATED SHELL FISH. 



363 



habitant from enlarging. How the soft slime 

 of the snail hardens, at the bottom of the sea, 

 into the stony substance of a shell, is not easy 

 to conceive. This slirne must at least be pos- 

 sessed of very powerful petrifying powers. 



All animals of the snail kind, as was ob- 

 served before, are hermaphrodites ; each con- 

 taining the instruments of generation double. 

 But some of the sea kinds copulate in a differ- 

 ent manner from those of the garden. The 

 one impregnates the other ; but, from the po- 

 sition of the parts, is incapable of being im- 

 pregnated by the same in turn. For this rea- 

 son it is necessary for a third to be admitted 

 as a partner in this operation : so that, while 

 one impregnates that before it, another does 

 the same office by this ; which is itself im- 

 pregnated by a fourth. In this manner, Mr 

 Adanson has seen vast numbers of sea-snails 

 united together in a chain impregnating each 

 other. The Bulin and the Coret perform the 

 offices of male and female at the same time. 

 The orifices in these are two, both separated 

 from each other: the opening by which the 

 animal performs the office of the male being 

 at the origin of the horns ; that by which it is 

 passive, as the female, being farther down 

 upon the neck. It may also be observed, as 

 a general rule, that all animals that have this 

 orifice, or verge, as some call it, on the right 

 side, have their shells turned from the right 

 to the left ; on the contrary, those which have 

 it on the left side, have their shells turned from 

 left to right, in a contrary direction to the 

 former. 



But this is not the only difference between 

 land and sea-snails. Many of the latter en- 

 tirely want horns; and none of them have 

 above two. Indeed, if the horns of snails be 

 furnished with eyes, and if, as some are will- 

 ing to think, the -length of the horn, like the 

 tube of a telescope, assists vision, these ani- 

 mals that chiefly reside in the gloomy bottom 

 of the deep, can have no great occasion for 

 them. Eyes would be unnecessary to crea- 

 tures whose food is usually concealed in the 

 darkest places; and who, possessed of very 

 little motion, are obliged to grope for what 

 they subsist on. To such, I say, eyes would 

 rather be an obstruction than an advantage ; 

 and, perhaps, even those that live upon land 

 are without them. 



Those that have seen the shells of sea-snails, 

 need not be told that the animal which produ- 

 ces them is larger than those of the same de- 

 nomination upon land. The sea seems to have 

 the property of enlarging the magnitude of all 

 its inhabitants; and the same proportion that 

 a trout bears to a shark, is often seen to obtain 

 between a shell bred upon the land, and one 

 bred in the ocean. Its convolutions are more 

 numerous. The garden-snail has but five 



turns at the most ; in the sea-snail the convo- 

 lutions are sometimes seen amounting to ten. 



There is a difference also in the position of 

 the mouth in the garden and the water snail. 

 In the former, the mouth ia-plaeed crosswise, 

 as in quadrupeds; furnished with jaw-bones, 

 lips, and teeth. In most of the sea-snails, the 

 mouth is placed longitudinally in the head ; 

 and in some obliquely, or on one side. Others, 

 of the Trochus kind, have no mouth whatso- 

 ever; but are furnished with a trunk, very 

 long in some kinds, and shorter in others. 



Snails of the Trochus kind, furnished thus 

 with an instrument of offence, deserve our par- 

 ticular attention. The trunk of the Trochus 

 is fleshy, muscular, supple, and hollow. Its 

 extremity is bordered with a cartilage, and 

 toothed like a saw. The snails that are pre- 

 vided with this may be considered as the pre- 

 dacious tribe among their fellows of the bot- 

 tom. They are among snails what the tiger, 

 the eagle, or the shark, is among beasts, birds, 

 or fishes. The whole race of shelled animals 

 avoid their approach ; for their habitations, 

 however powerfully and strongly built, though 

 never so well fortified, yield to the superior 

 force of these invaders. Though provided 

 with a thick clumsy shell themselves, yet they 

 move with greater swiftness at the bottom 

 than most other shell-fish, and seize their prey 

 with greater facility. No shell so large but 

 they will boldly venture to attack; and, with 

 their piercing auger-like trunk, will quickly 

 bore it through. No efforts the other animal 

 makes can avail : it expands itself, and rises 

 to the surface ; but the enemy rises with it : 

 it again sinks to the bottom, but still its des- 

 troyer closely adheres. In this manner the 

 carnivorous shell-fish, as some naturalists call 

 it, sticks for several days, nay, weeks, to its 

 prey, until, with its trunk, it has sucked out 

 all the substance, or until it drops off, when 

 the other begins to putrefy. 



Thus it would seem, throughout nature, 

 that no animal is so well defended but that 

 others are found capable of breaking in upon 

 its intrenchments. The garden-snail seems 

 tolerably well guarded ; but the wall of its 

 shell is paper itself, in comparison with that 

 which fortifies some of the sea-snail kind. 

 Beside this thick shell, many of them are also 

 furnished with a lid, which covers the mouth 

 of the shell, and which opens and shuts at the 

 animal's pleasure. \Vhen the creature hunts 

 for food, it opens its box, gropes or swims 

 about; and, when satisfied, drops its lid, and 

 sinks to the bottom : there it might be sup- 

 posed to remain in perfect security; but the 

 trochus soon finds the way to break into the 

 thickest part of its inclosure, and quickly de- 

 stroys it with the most fatal industry. 



The being liable to the attacks of the trochus 



