. no DIVERSIONS OF A NATURALIST It is not every one who has the chance of seeing living ship's barnacles (Lepas), but anyone can pick up a stone or bit of rock on the seashore with live sea-acorns or acorn-barnacles (Balanus) adherent to it. Each is like a little truncated volcano (Fig. I i), the sides of which correspond to the pair of larger shells of the ship's barnacle, fused together and grown into a cone-like wall. The acorn-barnacle has no stalk, but adheres by its broad base to the stone. Just within the shelly crater are four small hinged plates or valves in pairs, identical with the
. no DIVERSIONS OF A NATURALIST It is not every one who has the chance of seeing living ship's barnacles (Lepas), but anyone can pick up a stone or bit of rock on the seashore with live sea-acorns or acorn-barnacles (Balanus) adherent to it. Each is like a little truncated volcano (Fig. I i), the sides of which correspond to the pair of larger shells of the ship's barnacle, fused together and grown into a cone-like wall. The acorn-barnacle has no stalk, but adheres by its broad base to the stone. Just within the shelly crater are four small hinged plates or valves in pairs, identical with the smaller shelly bits of the ship's barnacle. When you first see your specimen, the valves are tightly closed. After a few minutes in a glass of sea- water they open right and left, and up jumps—jack-in-the-box-wise—a tuft of Fig. ii. —A large bowing and scraping feelers or tentacles, British Sea-acorn, like those of the ship's barnacle. If Balanus porcatus, disturbed, they shoot inwards, and the allied to the Ship's , , . ... Barnacle. /, the valves close on them like a spring trap- feather - like legs door. issuing from the tf^Z* Now, these clawing, feathery little plumes are found, when we examine them with a hand-glass, to be six pairs in number, and each of them is Y-shaped, like the swimmerets of a lobster. The arms of the Y are built up of many little joints and covered with coarse hairs. As a result of the study of the young condition of the ship's barnacle and the sea-acorn, we find that these six pairs of Y-shaped plumes are six pairs of legs corresponding to those of the mid-body (some of the walking legs and some of the foot-jaws) of the lobster, and that the shelly hinged plates of the barnacles correspond to the over- hanging sides of the " head " of the lobster and prawn,
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectnaturalhistory, booky
