The winds and waves not unfrequently bear into our harbours fragments
of spars, old water-casks, or planks, from the hull of some ill-fated
ship foundered in the inhospitable ocean, which are teeming with life.
Conspicuous on such “flotsam and jetsam,” as our ancient maritime
law-codes term these relics, we mark the Necked Barnacles,[137] so
long believed by our ancestors, with a most implicit credence, to be
legitimately descended from, and to be in turn the regular and normal
parents of, a certain species of goose, common enough on our northern
shores. That myth may, however, be dismissed with a mere recollection.
In this form the neck or stalk is greatly developed, frequently
reaching to eight inches and upwards in length, with a thickness of
half an inch. Externally it is very tough and leathery, yet it is
sufficiently flexible to be jerked vigorously in various directions,
and thrown into contorted curves, by means of muscles that run through
it. The lower part adheres firmly to the support, which is generally
wood, and I believe only in a floating condition. The bottoms of ships
in warm climates are generally much infested with these parasites,
which acquire a great size in the course of a voyage of only a few
months.
The valves resemble delicate shells, and are elegantly painted with
various tints of light blue varied with white, the edges of the valves
being often rich scarlet or orange. The hand is deep purplish black,
the fingers stout and massive; but not differing in their structure or
in their mode of use, from those of their sessile fellows.
Perhaps the most interesting of all our native forms of these
Cirripedes--for true parasitism is always a subject of peculiar
interest--is that little species[138] which invariably selects as its
support the stony walls of a coral. Our beautiful Cup-coral, so common
at extreme low-water level on both the north and south coasts of Devon
and Cornwall, is the favourite species of the _Pyrgoma_. So far as my
experience goes, extending over a very extensive series of specimens, I
think about one in six of these corals carries the parasite, generally
situated either on, or just without, the margin of the cup. I say,
“generally,” because Mr. Guyon has lately recorded what he thinks an
exception to the rule, in two _Pyrgomata_ situated on the rock close
to the base of the coral. But Mr. Holdsworth, an excellent authority,
considers that the exception is more apparent than real. The number of
these little intruders varies from one upwards. I possess specimens,
one of which carries nine, the other eleven; the appearance of the
ovate barnacles, each with its conspicuous orifice, crowded all round
the edge of the coral, is exceedingly curious and novel. Mr. Holdsworth
mentions, however, that he has seen fourteen _Pyrgomata_ attached to a
single _Caryophyllia_, which was dredged in Plymouth Sound.[139]