The Cirrhipeds are well known under the names of Barnacles and Acorn-shells, being found attached to rocks, ships’ bottoms, and pieces of timber which have been under the water for a length of time. They also at times fix themselves on the shells of the larger Mollusca, and on the backs of whales, tortoises, &c. These creatures, from their singular formation, have often proved a stumbling-block in the way of the systematic naturalist, who, from their anomalous characters, was unable to refer them to any part of his system; and although their true nature, which has more recently been discovered by a British naturalist, was partially suspected by Lamarck, (without, however, any definite idea on the subject,) we have still placed them immediately after the Conchifera, although, as we shall presently show, they ought more properly to be ranged with the Crustacea, that is, the crab and lobster tribes, and in future systems this no doubt will be the case.
After noticing their resemblance in many respects to the Crustacea, Lamarck thus expresses himself. “In fact, when I established the class of Crustacea, I formed the first order of this class, (the Cirrhipeds,) under the name of sightless Crustacea, but a few years afterwards I separated them and placed them at the end of the Mollusca, but this was no better. If, for example, we consider those characters which furnish their most important organs, we shall find that the Cirrhipeds, without any doubt, most nearly resemble the Crustacea, for they have the same system of nerves, they have jaws analogous to those of the Crustacea, and their tentacula resemble the antennÆ of the shrimps.” To prove that they really were Crustacea, was a task that devolved upon a British naturalist, I. V. Thomson, Esq., a surgeon in his Majesty’s forces. The manner in which this discovery took place, we shall notice further on.
The Cirrhipeds have obtained their name from the hairy feelers, or tentacula, with which they are provided; the name Cirrhipeda being derived from two Latin words,—cirrhus, hair, and pes, the foot; these appendages, being figuratively called feet, although they have, in reality, but little relation to that organ of motion.
They have been separated into two orders; namely, Cirrhipeda pedunculata, which are attached to any object by a tube of a leathery nature, as, for instance, the Barnacle,—and Cirrhipeda sedentaria, which are fixed directly to the rock, like the Acorn-shell.
ORDER CIRRHIPEDA PEDUNCULATA.
(Cirrhipeda with a Footstalk.)
The Smooth Barnacle, (Anatifa lÆvis.)
The curious popular error, that the Barnacle contained the young of a species of goose, which was thence called the Barnacle Goose, has lasted for many ages, and still prevails among the uneducated, on the shores of many of the European seas. One reason of the continuance of this error in several Roman Catholic countries, is the permission granted by the priest to its members, to eat this goose on fish-days, because it is considered, on account of its supposed watery origin, to partake more of the character of a fish than a fowl. To show the extent to which an erroneous belief may be carried, we may quote the following notice sent by Sir Robert Moray to the Royal Society, and printed by them in their Transactions. He says, “The pedicle seems to draw and convey the matter which serves for the growth and vegetation of the shell and the little bird within it.” “In every shell that I opened, I found a perfect sea-fowl; the little bill like that of a goose, the eyes marked; the head, neck, breast, wings, tail, and feet formed; the feathers everywhere perfectly shaped, and blackish-coloured; and the feet like those of other water-fowl, to my best remembrance!” “Nor did I ever see any of the little birds alive, nor met with anybody that did; only some credible persons have assured me that they have seen some as big as their fist!!”
ORDER CIRRHIPEDA SEDENTARIA,
(Sedentary Cirrhipeds.)
The Acorn-Shell, (Balanus.)
Mr. Thomson describes his discovery of the real nature of the Cirrhipeds in these words. “On April 28, 1823, which the author had devoted to the investigation of some marine productions, he was returning home without any addition to his stock of knowledge, when, casually throwing out a small muslin towing-net, on crossing the ferry at Passage, such a capture of marine animals was made, as furnished a treat which few can ever expect to meet, and could hardly be excelled for the variety, rarity, and interesting nature of the animals taken.” After mentioning the names of several very rare species, he continues “and others perfectly nondescript, and incapable of being associated in any of our classifications of the Crustacea; of this description is the little animal about to be described.
Balanus, (The Acorn-Shell Barnacle.)
“There is a small translucent animal one-tenth of an inch long, of a somewhat elliptic form, moderately compressed, and of a brownish hue. When in a state of perfect repose, it resembles a very minute mussel, and lies upon one of its sides at the bottom of the vessel of sea-water in which it is placed. At this time all the members of the animal are withdrawn within the shell, which appears to be composed of two valves, united by a hinge along the upper part of the back, and capable of opening from one end to the other along the front, to give occasional exit to the legs. The limbs are of two descriptions; namely, in front a large and very strong pair, provided with a cup-like sucker and hooks, &c., and at the hinder part of the body, six pair of swimming-members, so articulated as to act in concert, and to give a very forcible stroke to the water, so as to cause the animal, when swimming, to advance by a succession of bounds, after the manner of the water flea.
- Fig. 1. Larva of Barnacle, natural size.
- 2. " " "magnified, seen from above.
- 3. " " "highly magnified, seen from side;
- a, swimming-members;
- b, front limb, with sucker.
- 4. Eye, much magnified.
- 5. Perfect Young Barnacle, natural size.
- 6. """ full grown.
“The greatest peculiarity, however, in the structure of this animal, is the eyes; which, although constantly shielded by the valves of the shell, are placed on footstalks, as in the crab and lobster, in front, at the sides of the body.
“Some of these curious creatures were collected in the Spring of 1826; and, in order to see what changes they might undergo, were kept in a glass vessel, covered by such a depth of sea-water, that they could be examined at any time by means of a common magnifying glass; they were taken on May the 1st, and on the night of the 8th, the author had the satisfaction to find that two of them had thrown off their exuviÆ[4], and, wonderful to say, were firmly adhering to the bottom of the vessel, and changed into young Barnacles! such as are usually seen intermixed with grown specimens, on rocks and stones, at this season of the year. The eyes were still perceptible, although the principal part of the black colouring-matter appeared to have been thrown off with the exuviÆ. On the 10th, another individual was seen in the act of throwing off its shell, and attaching itself, like the others, to the bottom of the glass.”
