294 



MUSEUM OF ANIMATED NATURE. 



[Bernicles. 



mouth is furnished with later*! horny, tithed, and ar- 

 ticulated jaw». The branchi* are on each side of 

 the base of the first cirrhi. The nervous system con- 

 liists of a double cordon, with Kani;lia, giving off 

 llbres to every part. But leaving these eeneraliia- 

 tions, let us take one of these animals and examine 

 it, with a view to a more clear ami definite idea of 

 the ?roup in question. We will take the Common 

 Bprnicle, Penlalasmis anatifera (I,epas anatifera, 

 Linn.). The Bernicle, Fig. 30(>G, is widely spread, 

 anl clustei-s of these strange creatures may be seen 

 adherent to floating logs of wood, the timbers of 

 wrecked vessels, the sides of rocks, and other ob- 

 jects alTording a secure attachment. Each indivi- 

 dual consists of a body enclosed in a shell, not unlike 

 that of a mussel in figure, and of a fleshy worm-like 

 •tern or peduncle, the extremity of which is fixed to 

 the object upon which the animal is stationed. This 

 stem is tubular, tolerably firm, and has a fleshy feel ; 

 it is composed exteriorly of a fine coriaceous outer 

 membrane, bedewed with a watery fluid, and be- 

 neath this, of an inner membrane of considerable 

 density, apparently consisting of muscular fibres, 

 running for the most part in parallel longitudinal 

 lines. That these fibres are muscular we may con- 

 clude from the animal having the power of contract- 

 ing the stem, or of twisting it in various directions. 

 Within the tube there is a fluid secretion. 



The body, as we have said, is enclosed in a shell ; 

 and this shell is composed of five pieces. Four 

 pieces are lateral, two on each side ; while between 

 the valves down the back is interposed a single nar- 

 row slip uniting them together. Their colour is 

 white, more or less tinged with purplish blue. 

 .\long the anterior margin the valves are but par- 

 tially''c'>nnected by membrane, leaving a large fis- 

 sure, through which emerge the plumose and jointed 

 arms or cirrhi. 



Removing the shell so as to expose the body, we 

 find it enveloped in a fine membranous mantle ; at 

 its apical portion are the jointed cirrhi in two rows, 

 each row consisting of six pairs of these appendages, 

 and each rises from a single stem or footstalk at the 

 base. The apical pairs are the longest ; the othei-s 

 decrease in rotation. They are based on decided 

 articulations of the body, and the shortest pair are 

 regarded by some as the analogues of the jaw-feet 

 (pieds-machoires) of Crustacea. In each of the 

 cirrhi is a double canal, for establishing a circulat- 

 ing current, traversing all their joints. Between the 

 base of the shortest cirrhi, or pieds-miichoires, are 

 certain pyramidal fleshy appendages, like the radii of 

 a minute starfish, and which are regarded as bran- 

 chiae, though the cirrhi are also, perhaps, aerating 

 organs. 



The mouth is placed at the lower part of the fis- 

 sure through which the cirrhi are protruded, and 

 terminates a raised tubercle or prominence. It is 

 furnished with a horny lip, having minute palpi, 

 and with three pairs of mandibles, of which the two 

 external are horny and serrated, the internal soft 

 and membranous. In these triple jaws, we trace a 

 decided analogy to the Crustacea, while the cirrhi 

 represent the true and false limbs of these animals, 

 and the fleshy appendages their branchiae. 



From the symmetrical arrangement of the cirrhi we 

 might expect to find a similar disposition of the 

 nervous system, and accordingly, as in Crustacea, we 

 find it homogangliate— that is, composed of ganglia 

 or knots, and symmetrical nervous threads. Four oeso- 

 phageal ganglia give origin to four nervous cords 

 proceeding to the muscles and viscera. A double 

 cord, connected by ganglia, is continued down the 

 ventral aspect of the body, supplying the cirrhi. 



The mouth leads to a short firm oesophagus, which 

 receives a supply of saliva from two large glands, 

 and enters a capacious stomach with sacculated 

 walls, and surrounded by the liver — a mass of minute 

 sacculi : the alimentary canal is simple ; it runs 

 along the dorsal aspect of the body, and terminates 

 at the root of a tail-like prolongation, between the 

 two longest cirrhi. 



The food of the Bernicles consists of small Crus- 

 tacea and raollusks; these are entangled by the 

 many-jointed plumose cirrhi, which are perpetually 

 thrown out and folded again, so as to serve the pur- 

 pose of a casting net, and drag the prey to the mouth, 

 where it is seized and crushed. 



Of the blood-vessels little is known. With regard 

 to the reproduction of these creatures, the eggs are 

 seen enclosed at certain times within the hollow of 

 the peduncle, where they appear of a blue colour, 

 and render the pedicle opaque ; from this they pass 

 through a minute conduit into the cavity of the 

 mantle, where they are arranged like two leaflets, 

 attached to the septum between the body and the 

 peduncle. They are enclosed in a film, out of which 

 they fall when ready to hatch. At first these leaflets 

 of eggs are small, and blue; as they increase, they 

 lose that tint and assume a tinge of pink, and at last 

 become nearly white. 



We may now turn to our specimens. Figs. 3067 

 to 3074 are illustrative of the organization of the 



Bernicles. They are from a shell-less species of 

 the genus Alepas. 



Fig. 3067 : A is a gelatinous production of the 

 homy envelope which serves to attach the peduncle. 

 B', a small individual affixed, as is often seen, to 

 the pedicle of the parent. B, the first membrane of 

 the pedicle. C, the convex part, containing the body 

 of the animal. D, the fissure from which the cirrhi 

 protrude. F, the cirrhi. E, the termination of the 

 pedicle, where the eggs stop. G, the eggs arrived 

 within the mantle. 



Fig. 3068, the same letters refer to the same parts 

 as in Fig. 3067. H, the part of the feet which sus- 

 tains the cirrhi. 



Fig. 3069, the same, with the interior more ex- 

 posed. e,e, the canal which carries off the peduncle 

 within the mantle ; b, a nutrient vessel to the pe- 

 duncle and eggs ; g, g, the membrane of the mantle, 

 which intercepts direct communication between the 

 peduncle and the cavity of the mantle. J repre- 

 sents the body enclosed in its proper envelope. 



Fig. 3070, the same more displayed. B, B, the 

 muscular tube open, in which the eggs are seen. 

 e, e, the course of the egg-duct in the thickness of 

 the second envelope : g, g, g, the envelope opened 

 and turned back. J, J, J, the proper membrane of 

 the body of the animal. It is between this mem- 

 brane and that of the envelope, ff, g', that the eggs 

 are found. 



Fig. 3071, a side view of the Common Bernicle 

 (Pentalasmis anatifera) taken out of the shell, en- 

 veloped in its proper membrane. V, the cervical 

 ganglion ; t/, the nerve which is given off from it to 

 go to the muscles of the skin. J, the two levator 

 muscles of the lower lip. K, K, branchiae ; /(, a 

 horny tubercle on each side of the egestive orifice. 

 U', the extremity of the articulated tube, tipped 

 with fine hairs. It contains a canal opening at its 

 extremity by a minute orifice, and receives at its 

 base two vesiculae. 



Fig. 3072, anterior view of the same, showing the 

 articulated disposition of the body, each ring of 

 which corresponds to a pair of feet. S, the adductor 

 muscle of the valves; F, the cirrhi. 



Fig. 3073, the digestive apparatus. D, the mouth ; 

 d, the oesophagus ; d', the stomach ; d", the little 

 tube communicating with a kind of sacculus, rf'", 

 of the same structure as the stomach. T, alimentary 

 canal ; h, terminal aperture. U U, certain vesiculae, 

 uniting in a single canal and terminating at U' by 

 a small orifice. 



Fig. 3074, disposition of the nervous system. 1, 

 first oesophageal ganglion, with branches, v, v', r", 

 destined to muscles of the dorsal part. V, salivary 

 glands supplied by a minute nerve. Z, nervous 

 ganglia ; 2, 3, 4, 5, 6, other ganglia giving nerves to 

 the feet ; g' and y, two threads given to the arti- 

 culated or caudal tube ; x corresponds to the centre 

 of the oesophagus, which has been removed. 



It is from Mr. Thompson that we learn the ex- 

 traordinary fact that the young bernicles and other 

 Cirrhopods on emerging from the egg are quite free, 

 and very different from their parents. They possess 

 locomotive organs, consisting of a large anterior 

 pair of limbs, provided with a sucker, and hooks for 

 the purpose of mooring themselves at pleasure to 

 various objects — and also of six pairs of swimming- 

 limbs, acting in concert like oars. Besides these 

 they have a tail bent under the body, consisting of 

 two joints and terminating in four bristles ; this is an 

 additional locomotive organ. Thus endowed they 

 swim along in a series of bounds, the oars and tail 

 going in measured time successive impulses. They 

 have, moreover, large lateral eyes set on peduncles, 

 and the body is covered with a sort of shell, as we 

 see in certain Crustacea (Cyclops, &c.), which they 

 closely resemble, and for which Mr. Thompson ait 

 first mistook them. 



In due time a metamorphosis takes place ; the 

 shell is thrown off, the eyes disappear, the limbs 

 become transformed to cirrhi, the regular valves 

 develop themselves, the peduncle shoots forth, and 

 the animal becomes permanently fixed. 



Believing these little creatures to be the larvae of 

 some crustaceous animal, .some of them, says Mr. 

 Thompson, "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 he 

 examined at any time by means of a common mag- 

 nifying glass; they were taken May 1, and on the 

 night of the 8th the author had the satisfaction to 

 find that two of them had thrown off their exuviae, 

 and, wonderful to say, were firmly adhering to the 

 bottom of the vessel and changed to young bar- 

 nacles, such as are usually seen intermixed with 

 grown specimens on rocks and stones at this season 

 of the year (Balanus pusillus, Penn.). In this 

 stage the sutures between the valves of the shell 

 and of the operculum were visible, and the move- 

 ments of the arms of the animal within, although 

 these last were not yet completely developed ; the 

 eyes also were still perceptible, although the prin- 



cipal part of the colouring-matter appeared to have 

 been thrown off with the exuvium (exuviie). 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 

 produced, 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 loco- 

 motive, and provided with a distinct organ of sight, 

 becomes permanently and immovably fixed, and its 

 optic apparatus obliterated ; and furnishes not only 

 a new and important physiological fact, but is the 

 only instance in nature of so extraordinary a meta- 

 morphosis. 



"During the whole of the spring and summer 

 months the water teems with these exuviae of 

 Tritones (the animal inhabitant, according to 

 LinnsDUs, 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, regulaily 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 exuviae 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 operculum." 



These researches were followed up by Mr. 

 Thompson, and in a paper read before the Royal 

 Society on the 5th of March, 1835, he detailed his 

 discovery of similar transformations in the young of 

 the pedunculated Barnacles (see ' Phil. Trans.' PI. II. 

 1835). His first observations have been confined to 

 the young of the sessile Balani. The following is 

 an abstract of the paper : — 



"The larvae of this tribe, like those of the Balani, 

 have the external appearance of bivalve monoculi, 

 furnished with locomotive organs, in the form of 

 three pairs of members ; the most anterior of which 

 are simple, and the other bifid. The back of the 

 animal is covered by an ample shield, terminating 

 anteriorly in two extended horns, and posteriorly in 

 a single elongated spinous process. Thus they 

 possess considerable powers of locomotion, which, 

 with the assistance of an organ of vision, enable 

 them to seek their future permanent place of 

 residence. The author is led from his researches to 

 the conclusion that the Cirripedes do not constitute, 

 as modern naturalists have considered them, a 

 distinct class of animals, but that they occupy a 

 place intermediate between the Crustacea decapoda 

 — with which the Balani have a marked affinity — 

 and the Crustacea entomostraca, to which the 

 Lepades are allied ; and that they have no natural 

 affinity with the testaceous mollusca, as was sup- 

 posed by Linnaeus, and all the older systematic 

 writers on zoology." 



With respect to the inference deduced, viz., that 

 these animals are not related to the testaceous mol- 

 lusca, there is, as we have said, much difference of 

 opinion, but the point at issue we shall not attempt 

 to moot. Turning first to the Bernicles, or pedun- 

 culated species, we may observe that they are widely 

 spread, and adhere to submarine bodies in consider- 

 able numbers. They have been found not only on 

 floating wood, the hulls of ships, bottles, and other 

 articles drifting about, but on shells, on turtles, 

 whales, and even sea-snakes. We have seen a 

 large log of timber completely covered by them, 

 so that it was hidden entirely ; to see thousands of 

 these creatures all compacted in close array, writh- 

 ing and twisting about, was a singular spectacle ; it 

 reminded us of Medusa's head, serpaitibus lior- 

 ridum. 



It would appear that the growth of these animals 

 is very rapid, for a ship perfectly free from them 

 will otten return after a short voyage covered with 

 them below the water-line. The negroes of Goree 

 are said to eat a large species of Pentalasmis, which 

 it is reported is of delicate flavour. 



We may now turn to our pictorial specimens 

 illustrative of the genera into which the peduncu- 

 lated group is divided, and first we notice Alepas. 



In the genus Alepas the general figure of the 

 body is oval and compressed. There is no shell, it». 

 place being taken by a subgelatinous and somewhat 

 transparent envelope, continuing itself with the pe- 

 duncle. The individual on which M. Rang founded 

 the genus was attached to the umbrella of a Me- 

 dusa. Fig. 3075 represents the Alepas parasita. 



The next genus, Gyranolepas, is divided by Dr. 

 Leach into two subgenera, Otion and Cineras. The 

 pedicle is long, the shell merely rudimentary. In 

 Otion there are two auriform tubes attached to the 

 outer investment of the body. Fig. 307G represents 

 the Otion Cuvieri (Gymnolepas Cuvieri). It is a 



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