Now, however, we must turn aside to look at other objects. Attached
to the base of the Lobster-horn, we find several examples of an
interesting Cirripede.[135] It is of a dirty buff, or drab hue,
semi-transparent, in outline something like a butcher’s cleaver, handle
and blade, or still more like a silver butter-knife, but much
thicker in proportion; the handle represented by the cartilaginous and
flexible stalk, the blade by the compressed valves. These vary much
in regularity of form, some being nearly oval, little wider than the
stalk, others angular and much wider. The body throws itself vigorously
about on the stalk, when disturbed. The valves open, and out comes a
widely radiating hand, of brilliantly glassy fingers, the joints and
comb-like bristles of which glitter and sparkle as I hold it up in a
tumbler of sea-water, examining it with a lens, with a lamp behind. It
remains some seconds expanded, as if enjoying contact with the water;
or perhaps, if I may draw inferences from some slight twitchings,
feeling and testing for the accidental presence of invisible atoms that
might serve it for food; then suddenly the fingers close together, and
the hand is drawn in with a snap, as if it had taken some prize, though
the lens had revealed nothing there. Soon it opens again, and exhibits
the same manœuvres. A front view of the hand, the bristle-like fingers
radiating in all directions, is a very attractive object for a low
magnifying power. There are several tiny ones in another group, the
bodies of which are not bigger than hempseed; these make their grasps
apparently at random, with regular alternation, much as the commoner
Barnacles do.
Of these latter we have no lack, many of the rough shells and small
pebbles being incrusted with crowded colonies of the commonest Acorn
Barnacle.[136] We see the same species, by tens of thousands, covering
roods and roods of the seaward surfaces of our rough rocks between
tide-marks. They rarely exceed one-third of an inch in diameter at
base; but there is a much more massive kind, rough with ridges and
furrows, and hence called _porcate_, occasionally found adhering to the
jutting angles of rocks hereabout, and much more commonly on the coast
of South Wales, around Tenby.
These Acorn Barnacles have no foot-stalk, but adhere by the whole
broad base to the rock or shell, on which a floor either of strong
stone, or of thin membrane is formed, and from whose margin the stony
plates arise, enclosing a more or less conical chamber, with an orifice
at the summit. If we look in at this during the life of the animal,
we discern, a little below the rim, some angular valves, which meet
with a straight suture, and close the interior. These are moveable,
however; and under water they open like folding-doors, and a hand of
many fingers, each composed of many joints, modelled on the same plan
as that of the _Scalpellum_, but less delicate, protrudes, which makes
its cast for prey, and is withdrawn beneath the again-closed valves.