Part 17 (1/2)
It is most interesting to watch a dense ma.s.s of living cirripedes so closely packed together that not a speck of the surface of the wood is left uncovered by them; their fleshy stalks overhanging each other, and often attached in cl.u.s.ters to those of some larger individuals; their plumose casting-nets ever gathering in the food that comes within their reach, and carrying towards the mouth any solid particles suitable for their sustenance. How much of insoluble matter barnacles will eliminate from the water is shown by the rapidity with which they will render turbid sea water clear and transparent. The most common species of these ”necked barnacles” bears the name of ”_Lepas anatifera_,” ”the duck-bearing _Lepas_.” It was so ent.i.tled by Linnaeus, in recognition of its having been connected with the fable, which, of course, met with no credit from him.
Fig. 39 represents the figure-head of a s.h.i.+p, partly covered with barnacles, which was picked up about thirty miles off Lowestoft on the 22nd of October, 1857. It was described in the _Ill.u.s.trated London News_, and the proprietors of that paper have kindly given me a copy of the block from which its portrait was printed.
[Ill.u.s.tration: FIG. 39.--A s.h.i.+P'S FIGURE-HEAD WITH BARNACLES ATTACHED TO IT.]
Others of the barnacles affix themselves to the bottoms of s.h.i.+ps, or parasitically upon whales and sharks, and those of the latter kind often burrow deeply into the skin of their host. Fig. 40 is a portrait of a _Coronula diadema_ taken from the nose of a whale stranded at Kintradwell, in the north of Scotland, in 1866, and sent to the late Mr.
Frank Buckland. Growing on this _Coronula_ are three of the curious eared barnacles, _Conchoderma aurita_; the _Lepas aurita_ of Linnaeus.
The species of the whale from which these Barnacles were taken was not mentioned, but it was probably the ”hunch-backed” whale, _Megaptera longimana_, which is generally infested with this _Coronula_. This very ill.u.s.trative specimen was, and I hope still is, in Mr. Buckland's Museum at South Kensington. It was described by him in _Land and Water_, of May 19th, 1866, and I am indebted to the proprietors of that paper for the accompanying portrait of it.
[Ill.u.s.tration: FIG. 40.--WHALE BARNACLE (_Coronula diadema_), WITH THREE _Conchoderma aurita_ ATTACHED TO IT.]
[Ill.u.s.tration: FIG. 41.--A YOUNG BARNACLE. (_Larva of Chthamalus stellatus._)]
The young Barnacle when just extruded from the sh.e.l.l of its parent is a very different being from that which it will be in its mature condition.
It begins its life in a form exactly like that of an entomostracous crustacean, and, like a Cyclops, has one large eye in the middle of its forehead. In this state it swims freely, and with great activity. It undergoes three moults, each time altering its figure, until at the third exuviation it has become enclosed in a bivalve sh.e.l.l, and has acquired a second eye. It is now ready to attach itself to its abiding-place; so, selecting its future residence, it presses itself against the wood, or whatever the substance may be, pours out from its two antennae a glutinous cement, which hardens in water, and thus fastens itself by the front of its head, is henceforth a fixture for life, and a.s.sumes the adult form in which most persons know it best.[97]
[97] If any of my readers wish to observe the development of young barnacles they may easily do so. The method I have generally adopted has been as follows: Procure a shallow gla.s.s or earthenware milk-pan that will hold at least a gallon. Fill this to within an inch of the top with sea-water, and place it in any shaded part of a room--not in front of a window. Put in the pan six or eight pebbles or clean sh.e.l.ls of equal height, say 1 or 2 inches, and on them lay a clean sheet of gla.s.s, which, by resting on the pebbles, is brought to within about 2 inches of the surface of the water. Select some limpets or mussels having acorn-barnacles on them; carefully cut out the limpet or mussel, and clean nicely the interior of the sh.e.l.l; then place a dozen or more of these sh.e.l.ls on the sheet of gla.s.s, and the barnacles upon them will be within convenient reach of any observation with a magnifying gla.s.s. If this be done in the month of March, the experimenter will not have to wait long before he sees young _Balani_ ejected from the summits of some of the sh.e.l.ls. Up to the moment of their birth each of them is enclosed in a little coc.o.o.n or case, in shape like a canary-seed, and most of them are tossed into the world whilst still enclosed in this. In a few seconds this casing is ruptured longitudinally, apparently by the struggles of its inmate, which escapes at one end, like a b.u.t.terfly emerging from its chrysalis, and swims freely to the surface of the water, leaving the split coc.o.o.n or case at the bottom of the pan. Some few of the young barnacles seem to be freed from the coc.o.o.n before, or at the moment of, extrusion. From three to a dozen or more of these escape with each protrusion of the cirri of the parent, and as the parturient barnacle will put forth its feathery casting net at least twenty times in a minute for an hour or more, it follows that as many as ten thousand young ones may be produced in an hour. These, as they are cast forth at each pulsation of the parent's cirri, fall upon the clean sheet of gla.s.s, and may be taken up in a pipette, and placed under a microscope, or removed to a smaller vessel of sea-water, for minute and separate investigation. It seems strange that animals which, like the oyster and the barnacles, are condemned in their mature condition to lead so sedentary a life, should in the earlier stages of their existence swim freely and merrily through the water--young fellows seeking a home, and when they have found it, although their connubial life must be a very tame one, settling down, and not caring to rove about any more for the remainder of their days. These young _Balani_ dart about like so many water-fleas, and yet, after a few days of freedom, they become fixed and immovable, the inhabitants of the pyramidal sh.e.l.ls which grow in such abundance on other sh.e.l.ls, stones, and old wood.
It is unnecessary for me to describe more minutely the anatomy of the Cirripedes; I have said enough to show the nature of the plumose appurtenances which, hanging from the dead sh.e.l.ls, were supposed to be the feathers of a little bird within; but it is difficult to understand how any one could have seen in the natural occupant of the sh.e.l.l, ”the little bill, like that of a goose, the eyes, head, neck, breast, wings, tail, and feet, like those of other water-fowl,” so precisely and categorically detailed by Sir Robert Moray. As Pontoppidan, who denounced the whole story, as being ”without the least foundation,” very truly says, ”One must take the force of imagination to help to make it look so!”