But far more remarkable changes take place in the growth of the shell
in a family of signal beauty, of which I discern a specimen in yonder
cavernous hollow. The family I speak of is that of the Cowries; and
this individual represents the only species that is indigenous to our
seas--the little Furrowed Cowry.[8] Let us pause awhile to admire it,
for it is one of the very loveliest of our marine animals.
The shell itself is doubtless familiar to most of my readers, for it
is to be picked up on every sandy beach. It varies in size from that
of a split pea to that of a large horsebean. It is elegantly marked
all over with transverse ridges. These ridges are porcellaneous white,
and the alternate furrows between are purplish, or flesh-coloured. The
larger specimens commonly display three spots of dark brown, arranged
lengthwise. But probably few are aware how very elegant a creature
it is when tenanted by its living inhabitant, and crawling at ease
in clear water. The foot, on which it glides with a slow but smooth
motion over the surface of the rock on which it habitually dwells,
or, if you please, on the bottom of the saucer of sea-water in which
you are examining it, is a broad expansion spreading out to twice the
superficies of the base of the shell. Above this is the fleshy mantle,
which is so turned up as closely to invest the shell, conforming to
its shape, and even fitting into the grooves between the ridges. This
mantle can be protruded, at the will of the animal, so far that the two
sides meet along the top of the shell, and completely cover it, or it
can be completely retracted within the wrinkled lips beneath; and it
is capable of all gradations of extension between these limits. From
the front of the shell protrudes the head, armed with two straight
and lengthened tentacles, answering in function and appearance to the
upper pair of horns in a snail; except that the little black points
which constitute the visual organs are not in this case placed at the
tips, but on a little prominence on the outside of the base of each
tentacle. Above and between these, which diverge at a considerable
angle, projects the proboscis, a rather thick fleshy tube, formed by
a flat lamina, with its edges bent round so as to meet along the
under side. The interior of this proboscis is lined with delicate
cilia, by whose constant vibrations a current of water is drawn into
the tube and poured over the surface of the gills, for the purpose
of respiration. This current may be readily perceived by any one who
will take the trouble to watch, with a pocket-lens, a Cowry crawling
along the side of a phial filled with sea-water. By placing the vessel
between your eye and the light, and fixing your attention on the front
of the proboscis, you will presently perceive the minute particles of
floating matter (always held in suspension, even in clear water) drawn
in various directions towards the tube, with a motion which increases
in velocity as they approach, and at length rapidly sucked in, and
disappearing one after another within. It is an interesting sight to
see, and one that cannot be looked on without delight and admiration
at this beautiful contrivance of Divine Wisdom, for the incessant
breathing of the respiratory organs in water charged with vivifying
oxygen.
Let us look at the vivid hues of all these organs. The foot, which
expands to so great a length and breadth behind the shell, is of a buff
or pale orange ground-colour, delicately striated with longitudinal
undulating veins of yellowish white. The mantle which embraces the
shell is of a pellucid olive, thickly mottled and spotted with black,
and studded with glands protruded through its substance, of light
yellow; and is often edged with a narrow border of red. The proboscis
is vermilion-red, varying in brilliancy in different individuals. The
tentacles are of a paler tint of the same colour, speckled with yellow.
Such, then, is the beauty of the animal which inhabits this familiar
and plain little shell,--a beauty of which those who know it only in
cabinets can hardly form an idea; while, as the observer gazes on it
placidly gliding along, he cannot avoid an emotion of surprise that
such an amplitude of organs can be folded within the narrow compass of
the shell, and protruded through so contracted an aperture.