P. H. GOSSE, _del._ LEIGHTON, BROS.
DOG-WHELK. PELICAN’S FOOT. TOP. COWRY.
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The sensitive and muscular foot of our captive has already taken hold
of the glass side of its prison, and it is now smoothly mounting up
it. With a lens you may see that though it is one undivided area, yet
in the arrangement of its muscles, it is separated into two portions
by a line which runs down the middle; and that these two sides move
alternately. The muscles of the right half, for example, are moved a
little onward, and take a fresh hold of the ground, while those of
the left remain clinging; then the right half clings, while the left
relaxes and advances a little beyond the right, and again clings, when
the right makes its forward move. So that the effect is exactly that
of two feet advancing by alternate steps; and if your own two feet
were enclosed in one elastic stocking, your own progress would appear
very much like that of the _Trochus_. Indeed, some shell-fishes not
distantly allied to this, as the pretty little Pheasant-shell,[2] which
I occasionally find among these rocks, really have the foot divided
into two distinct and separate halves, in which this alternate motion
is, of course, more obvious.
Looked at from above, we discern that this foot thickens towards the
middle, where it is overlapped by a broad wing-like expansion on each
side. This, for manifest reasons, is known by the name of the cloak or
mantle. In all cases it performs important offices in the economy of
the animal, as I shall presently describe; and in this instance we see
it is adorned along its edges with certain lappets and long fleshy
taper threads (called _cirri_), which wave vivaciously to and fro as
the creature crawls. These are probably the seats of a delicate sense;
perhaps receiving impressions analogous to those of touch, from the
strokes they continually make on the surrounding fluid.
In front we see a distinct head, with a broad flat muzzle not
altogether unlike that of an ox. On each side of the back part of
this head, there is another long taper thread: these are called
tentacles, but neither in form nor in structure can we discern any
difference between these and the _cirri_ that fringe the mantle. In all
probability they are alike organs of a highly delicate sense of touch.