CI MMUS. [TEsnurs.] Cl RRITEDIA, or C1RRHIPEDA (Leptis of Liumeus, CierSopodrz of Cuvier and Feruseac, Cirrhipedes of Lamarck, Nematopodes of De Blainville, Cirripedes of Latreille), a well-defined natural group of 31arine Invertebrate Animals, whose place in the system has occa sioned much doubt end difference of opinion among zoologists. In the earlier times the most absurd stories were propagated and believed in relation to one of the most common genera, Pcntalasmis anatifera (Lepel., anatifera of Linnaeus), the Common or Duck Barnacle. To the references on this head in the article BERNICLE-GOOSE, we may add the testimony of Sir Robert Moray to show how long the delusion lasted, and in what positive terms a witness can state the thing that is not. " 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 waterfowl, to my best remembrance." So widely spread has been this delusion, that it is stated that the Roman Catholics are permitted, in France at least, to eat the Berniele-Goose upon fast.days and during the whole of Lent, in consequence of its supposed marine origin.
Organisation, and place in the Natural System.—Linnaeus placed the Cirripcdia, with the generic name of Lepas, among the Multivalves of his Vermes (Testacca), between Odeon and Pholas; and, aupposiug that the form existed without a shell, found a situation for it under the name of Triton, between Terebella and Lemma. Cuvier, in the. first and also in the last edition of the Regne Animal,' says that the existence of these Tritons is not confirmed, and that we must suppose that Linnaeus had only seen the animal of an Anatifa (Pentalaranis), which had been taken out of its shell. Rang, however, thinks that he has found the Linrreln genus Triton in certain specimens brought home by Messrs. Lesson and Garnot, Quoy and Gaimard, and has published it under the name of Alepas. Bruguieres divided the genus Lepaa into two ; the first, Anat ifa, a barbarous word for A nal ifera (the Anatifes of the French), comprising the Pedunculated Cirripedes ; and the second, Balanua, the Sessile species. envier, under the name of Cirrhopoda, made these animals the sixth class of his Mollusks, which he places between the Brachiopoda and the first class (Ann6lides) of his third great division of the animal kingdom, namely, the Articu lated Animals, and in the Regne Animal' they appear between Orbicula and Serpula. Lamarck, under the name of Cirrhipeda, his tenth class of Invertebrate Animals, arranges them between the seden tary Annelides and his Conchifera, dividing them into two orders : 1st, tho Sessile Cirripedes ; 2nd, the Pedunculated Cirripedes. In his system they stand between Ma/A/as and Aapergillum. Latreille, though he does not disturb this arrangement, evidently considers them as related to the Oat recede, among the Branchiopodous Crusta ceans. He says that tho Sessile Cirripedes seem to represent the ani mals which terminate the Ac6phales Enferm6s of Cuvier. He observes that the two tubular processes of Orion represent the two tubes of some of the A cephcda, though with different uses, the tentacula being converted into jaws. The cirri ho considers as a kind of feet anala gous to the sub-abdominal appendages of many Crustaceans, espe cially those of the A mphipoda, and is of opinion that we may also compare them to those of many Annelides. The oviduct, he remarks, has some resemblance to that of Phalangium. Finally, he expresses a conjecture, that nature, to form the Cirripedes, has borrowed different organs from animals of several classes. Mr. William Sharp 31`Leay, in his profound and philosophical work, ' Hone Entomologicn,' con siders that Pentalasmis exhibits the greatest affinity with the Odra coda; but he seems to be of opinion that there exists an affinity between the shell of Balanua and that of Echinua, and sanctions Latreille's opinion that the articulated cirri have their analogues in the arms of the Radiato, particularly of COntatula. Dr. Leach, who has described several genera unnoticed till his time, divided the class into two orders : 1st, Campylosomata, comprising the Pednnculated section ; and 2nd, Acamptusomata, including the Sessile species. M. de Blainvillo makes the Cirripedes the first class (Nematopoda) of his sub-type Malentozoaria, a group which corresponds to the Multi valves of Linnfrus, after separating from them the genus Pholas, so that Do Blainville's Malentozoaria consist of the Cirripedes and Chitons. The Cirripedes, he thinks, have an evident relation to the Bivalve Mollusks, by means of their calcareous envelope, in which he recognises the pieces of the shell of the Pho/ades, and even the ana logue of the tube of the neighbouring genera. He also considers the relationship further indicated by the recurred position of the animal fixed head downwards (la tete en bas) ; but he also considers that their relations to certain animals of the type Entemozoaria are nume rous, by means of the horny, locomotive, articulated appendages which are bronchial, at least at the root, becoming, towards the mouth, true horny denticulated jaws. Mr. Thompson, in his 'Zoological Researches,' considers the Cirripedes to be true Crustacea, and that in the first state of these animals they not only possess perfect freedom and power of motion, but organs of sight. On the 23th April 1823, Mr. Thompson states that he took in a small muslin towing-net while crossing the ferry at Passage, among other minute creatures, a small translucent animal, one-tenth of an inch long, of a somewhat elliptical form, but very slightly compressed laterally, and of a brownish tint.
When in a state of perfect repose it resembled a very minute mussel, and lay upon ono of its sides at the bottom of the vessel of sea-water in which it was placed ; at this time all the members of the animal were withdrawn within the shell, which appeared 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 limbs. These were of two descriptions, namely, anteriorly a large and very strong pair, provided with a cup-like sucker and hooks, serving solely to attach the animal to rocks, stones, &c. ; and, posteriorly, six pairs of natatory members, so articulated as to act in concert, and to give a very forcible stroke to the water, caus ing the animal, when swimming, to advance by a succession of bounds after the same manner as the Water-Flea (Daphnia) and other Nen °cull, but particularly Cyclops, whose swimming-feet are extremely analogous. [BRANCHIOPODA.] The tail, usually bent up under the belly, is extremely short, composed of two joints, and terminating in four seta;, and is employed to assist in progression and in changing the position from a state of repose. The greatest peculiarity however in the structure is in the eyes, which, although constantly shielded by the valves of the shell, are pedunculated as in the Crab and Lobster, and placed entirely at the sides of the body. Mr. Thompson observes that this animal, but for its pair of peduneulated eyes, would find a place as a new genus of Ostracoda; that its members approximate it to Argulus on the one hand and to Cyclops on the other—genera which are widely separated ; while the eyes show its relationship to the Decapoda (crabs, lobsters, &c.) The individuals presented no variation indicative of a difference of sex ; and this, with their anoma lous organisation, induced a belief that they were the lame or dis guised states of some crustaceous animal, or (as it had been previously ascertained that the Cirripedes were Crustacea) that they were the males of these, Mr. Thompson not being disposed to believe that the two sexes were united in the same individual. What follows being of the last importance, we give in the author's own words :—" Under the foregoing impressions, some of them 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 May 1st, and on the night of the 8th the author had the satisfaction to find that two of them had thrown off their exuvia (exuvice), and, wonderful to say, were firmly adhering to the bottom of .the vessel, and changed to young barnacles, such as are usually seen intermixed with grown specimens on rocks and stones at this season of the year. (Balanua pusillus, Penn.) In this stage the su tures between the valves of the shell and of the operculum were visible, and the movements of the arms of the animal within, although these last were not yet completely developed ; the eyes also were still per ceptible, although the principal part of the colouring-matter appeared to have been thrown off with the exuvium (exuvize). On the 10th another individual was seen in the act of throwing off its shell, and attaching itself as the others to the bottom of the glass. It only remains to add, that as the secretion of the calcareous matter goes on in the compartments destined for the valves of the Shelly covering, the eyes gradually disappear, from the increasing opacity thence pro duced, and the visual ray is extinguished for the remainder of the animal's life ; the arms at the same time acquire their usual ciliated appearance. Thus, then, an animal originally natatory and locomo tive, and provided with a distinct organ of sight, becomes permanently and immoveably fixed, and its optical apparatus obliterated, and fur nishes not only a new and important physiological fact, but is the only instance in nature of so extraordinary a metamorphosis." "During the whole of the spring and summer months," says Mr. Thompson, "the water teems with these exuvia (exuviac) of Tritones (the animal inhabitant, according to Linnaeus, of the barnacles) : it is impossible to avoid drawing up numbers every time a towing-net is thrown out, nay the tide is at times discoloured from their abundance ; but to be certain that these are really such, let a stone with several barnacles upon it be kept in sea-water, regularly renewed, towards the latter end of April or the beginning of May, and with due attention many of them may be observed in the act of throwing off exuvia (exuviw) in every respect identical ; let it be recollected, however, that these are the casts of the animal alone, and not of the valves of the shell or of the opereulum." isre G. B. Sowerby (' Genera of Shells,' Scalpelluna') thus writes on the subject of Mr. Thompson's disco very :—" Without describing the facts, or entering upon the arguments with which he supports this opinion " (that is, that the Cirripedia are Crustacea), " we must be permitted to say that we do not think that ho has fully demonstrated it ; at the same time, considering that, as far as we hitherto knew, the Cirripedes were all attached, the circum stance of their being free when very young accounts well to our mind for the fact of each species being found attached to peculiar situations, which would only be compatible with the notion of their being at one time free agents, and possessed of an instinctive volition determining their choice of situation." Professor Owen, iu the ' Catalogue of the Museum of the College of Surgeons' (' Cirripeda '), speaks of the dis covery without expressing any doubt.