An EXPLANATION of the TWENTY-THIRD PLATE
FIG. 1.
The Teeth of a Snail
THE upper Jaw-Bone and Teeth of a Garden-Snail are here magnified for our Ob-
servation.
The whole was a small bended hard Bone, the Teeth all joining together like the Teeth
of a Rbinoceros ; which perhaps is the only known Animal besides that has them in that
manner.
The Part A B C D, which grew out of the upper Chap of the Snail G G G, was
found to be much whiter and less furrowed, than the lower and blacker Part of it
H I I H K K H, which was shaped exactly like Teeth ; the Bone growing thinner and
tapering towards an Edge at K K K. It seemed to have nine Teeth or prominent Parts,
some smaller than others, but all joined together by thinner interposing Parts of the same
Bone.
This very Snail, just before its Dissection, was seen feeding on a Rose-Leaf, and biting out
half round Pieces, not unlike the Figure of a Capital C, nor much differing from it in
Bigness.
Though a Snail is known to every Body, there are some Particulars belonging to it may
not be amiss to mention. Its Way of moving from place to place, though destitute of
Feet, is effected by two large muscular Skins, that are lengthned by letting out ; after
which, their Fore-part is shortned into Folds, and the hinder Part falls into the same
Contraction : Then the Fore-part extends, and draws along the Shell. A glutinous
Slime emitted from the Body, enables it, at the same time, to adhere firmly and securely
to all Kinds of Surfaces, which is an Advantage few Animals that have Feet can pre-
tend to.
Snails are oviparous, but their Way of Coupling is extraordinary. They are all Her-
maphrodites, each possessing the generative Parts of both Sexes, which are employed mu-
tually in Coitu. These Parts are situated on the Left-side of the Head, and are only dis-
coverable when they are generating, which usually engages them about twelve Hours, and
from which they can hardly be separated without hurting the Parts.
The Manner of their coming together, as related by Dr. LISTER, is very extraordi-
nary. --When they are disposed to approach each other, they signify their mutual Incli-
nations in a Manner peculiar to themselves. One launches against the other a kind of little
D?t, which has four Wings or minute Edges. The Weapon flies from the Animal who
shot it, and either lodges in the other, or falls down by him, after making a slight Wound ;
upon which, this Creature in his turn dispatches another Dart at the Aggressor : But this
little Combat is immediately succeeded by a Reconciliation. The Substance of the Dart is
like Horn, and the Animals are stocked with them at the Seasons when tbese Approaches
are made, and which happen each Year thrice in six Weeks, or once every fifteen Days.
Some Days after, each makes its Way into the Earth, and lays its Eggs in Knots of about
thirty in Number, near four Inches deep. The Place they chuse is commonly moist and
shady. In about a Month the Eggs are hatched, and the young Snails appear above
Ground, with their Shells compleatly formed, of a Minuteness proportionable to their
little Bodies and the Dimensions of the Eggs that inclosed them.
|
Malpigbi A?at. de Colcb. M?oires de? Academic des Sciences, 1709. |
These Shells increase
from time to time by the Addition of new Circles, but continue always to be the Center
even when the Animals are arrived at their full Growth. If they are broken by any
Accident, a slimy Exsudation from the Body repairs them again in a few Days.
Tis said no Cold either of Nature or Art can sreeze the Juice of Snails, which perhaps
is owing to its Viscosity, as we find the Berries of Misletoe, whose Juices are of that
Qulity, are so far from being frozen by, that they ripen in the coldest Weather.
A Snail's Heart may be found just against a round Hole near its Neck, which opens
and shuts as it either stands still or moves, and is supposed by Dr. HARVEY to be the
Place of its Respiration : It will sometimes beat a Quarter of an Hour after Diffection :
But without that Trouble it may be seen by the Microscope through the transparent Shell
of a new-hatched Snail performing its Contractions and Dilatations with the utmost Re-
gularity.
