Because they are bound to the shells by two muscles, which arise from the pillar, and having penetrated the body below its spiral part, run forward under the stomach, and spread their fibres in several slips, which interlace with those of the muscles proper to the foot, the substance of which they enter. It is obvious from this direction, that on their contraction, the body of the snail must be drawn within the shell. When it wishes to re-issue, the head and foot are forced out by circular fibres, which surround the body immediately above the foot. - Cuvier.
Blumenbach says "Whether the black points, at the extremities of what are called the horns of the common snail, are organs which really possess the power of vision, is still problematical." - Compar. Anat.
Because the slime enables the slug to attach one part of its body more firmly to the surface on which it is moving", while it drags up the remainder to a new position.
In England the rustic maiden once read her fortune in the meanders of a snail:
Last May-day fair I search'd to find a snail, That might my lover's name reveal;
She placed it on " the milk-white emhers spread," when
Slow crawl'd the snail; and, if I right can spell, In the soft ashes mark'd a curious L. Oh ! may this wondrous omen lucky prove, For L: is found in Luhberkin and love. - Gay.
Because the snails have then retired to torpidity, previous to which they have formed an operculum or lid from the mouth of the shell, by which they attach themselves, and at the same time close up even all access of the air. The winter lid of some snails resembles a piece of card paper.
All the land testacea (shell animals) appear to have the power of becoming torpid at pleasure, and independent of any alterations of temperature. Thus, snails, if placed in a box at midsummer, will attach themselves to its sides, and remain in this dormant state for several years. Even in their natural haunts, they are often found in this state during the summer season, when there is a continued drought. With the first shower, however, they recover, and move about, and at this time the conchologist ought to be on the alert.
Because the skin or film with which they are covered, is then removed.
Because the shell is gradually formed by the snail, by aid of a fold or membrane, to be perceived where the body rises into the shell. This part is denominated
PART VIII G the collar, from the manner in which it surrounds the body, and it is the organ which secretes the shell. The animal is born with the rudiments of its future covering, and by its gradual increase of growth is enabled to push the collar for a space, and from time to time beyond the original margin. In these operations, a thin layer of membraneous and calcareous matter is excreted and deposited, which is gradually thickened by successive layers being laid on within the first, by the repeated protrusions and retractions of the collar. This portion being formed, the animal commences another, and finishes it in the same manner; and the extent of each portion is marked as above. There is not, as has been implied, a regular and alternate deposition of a layer of membrane, and a layer of lime ; but, in all shells, the animal and earthy matters are obviously secreted and deposited at the same moment, and in commixture.