1853.] Reproduction of the Coronet in Sabella vesiculosa. capsules, exactly resembling in essential points those of certain Medusa, were imbedded in its substance. These capsules, transparent and colourless, were of a long oval shape, from to inch in length, and contained a thread closely coiled. When the pressure reached a certain point the capsule shot forth from one end the elastic thread, which in a moment started out like a spring to a length thirty times as great as that of the capsule; sometimes in a straight line, sometimes in a serpentine, or, as he rather believes, a spiral form. These capsules did not burst, but at the instant of the propulsion of their filament a crack was distinctly heard. He cut off carefully with fine-pointed scissors two or three tentacles from one fully expanded, and submitted them to the same scrutiny. The rounded head of the tentacle appeared rather rough or hairy at first, but as pressure began to flatten it, filiferous capsules were seen protruding from the outline, which increased in number as the pressure proceeded, until an amazing multitude appeared, and the whole substance of the tentacle head was seen to be composed of these capsules as thick as spicula in a sponge, with only a small quantity of gelatinous matter to hold them together: To see these thousands of little vesicles discharging their missiles in rapid succession, like the flights of arrows in any ancient battles, was an astonishing sight. . . . . If, indeed, these projected bristles are so many darts injected into the bodies of those minute animals which are the prey of the madrepore, accompanied, as we must suppose each puncture to be, to insure its effect, with a fatal poisondoes not their presence in the convoluted bands of the interior militate against the supposition that these bands are ovaries, especially as I have seen the curious manner in which these are appressed to the swallowed morsel? Is it unreasonable to conjecture that their office may be accessory to that of the tentacles, destroying what may remain of life in the victim, after it has been inclosed by the lips, and is consequently out of the reach of the tentacles? Mr. Gosse adds that this inference was confirmed by the results of further investigations. It may be interesting to those who 395 visit the spot to learn that, at the great recess of the tides in October, our naturalist observed that the rocks and caves all about Ilfracombe were studded at low-water mark with this madrepore. He obtained at this time a considerable number of them, many being of large size and great beauty. Double specimens were numerous, triple ones not uncommon, and one was four-fold, the bodies being all agglomerated into one, and the plated disks with the fleshy parts alone being separated; these diverged in the form of a cross. Mr. Gosse discovered another beautiful scarlet and gold madrepore, which proved to be of the genus Balanophyllia of Mr. Searles Wood, among the rocks that run out from the Tunnels, which he has named Balanophyllia regia, described and figured. The largest that he found was smaller than C. Smithii, and he shows that this coral approaches much nearer to the Actinia than does C. Smithii. Those who have read the able report of Dr. Williams, of Swansea, 'On the British Annelida' (1852) -and few zoologists have not-will remember that he does not notice any power of reproduction in sabella, and that he even seems to doubt the existence of that power in the whole class (p. 247 of the report); but Mr. Gosse makes out a good case of the reproduction of the coronet in Sabella vesiculosa. At the time of preparing this note for press (writes he) the Sabelle have been in captivity about four months, more than three of which have been spent in London. Some have died, but the others are still apparently in good health. No increase has taken place in the young ones, in the number of filaments in their coronets, nor, so far as I can perceive, in the dimensions of their tubes. species is probably slow of growth and long-lived. The man who showed me the group in the rock had himself known them to be there for several years past, and they were as large when he first discovered them as at last. The An interesting circumstance, however, has occurred, illustrative of the faculty which the creature has of reproducing its organs. When the specimens were transferred to London, I found that the confinement in close jars had been well nigh fatal to several. Two were disposed to desert their tubes, but I pushed them back with gentle force, and these presently recovered, though their fans were very flaccid at first. Those of two other tubes, which were attached, side by side, to the same fragment of rock, did not protrude the fans at all, and though I watched day by day it was in vain, for these beautiful organs appeared no more, and I concluded that the animals had died. I did not, however, remove the tubes from the vase of water, but allowed them to lie week after week upon the bottom, remarking all the time with curiosity, yet without suspicion of the actual state of the case, that neither the tubes nor, as far as I could see, the contents, showed any tendency to decomposition, nor did the water become offensive. At length, on the 4th of January, about two months after the disappearance of the animals, I was surprised to see issuing, from each tube, a new fandisk, the filaments very delicate, of a translucent white, and about a quarter of an inch long, curled at their tips. Each formed a nearly flat disk, about as large as a sixpence, divided into two semicircles, but without any appearance of the spiral volutes. There were about twenty-two filaments in each moiety, and the bases of all formed a ring, apparently as large as the old neck, but this part I could not see distinctly. The disks of the two animals agreed precisely in appearance with each other. It is manifest that each of the tenants of these tubes-full-grown animals-has undergone first the loss and then the reproduction of the tentacular disk. Perhaps the accident which befel the first specimen that fell under my notice may be one to which the species is not unexposed, naturally, and hence it is a merciful provision that an organ so easily lost, yet so essential, should be replaceable. the We must refer those of our readers who would amuse themselves with Medusa fishing to the graphic account of those transparently beautiful acalephans, commencing at p. 392, and the correct and beautiful illustrations of many of the family scattered through the amusing pages, particularly plates of Chrysaora cyclonota, and Equorea Forbesiana, the latter named after the well-known, gifted president of the Geological Society of London, in unfeigned honour and respect for a naturalist of the highest eminence, whose pen and pencil have alike served to elucidate, above all his compeers, these lovely forms.' Mr. Gosse adopted the plan recommended by Professor Forbes for transferring the captives to the jar-viz., turning the bag of the net inside out into the water within the jar, and letting the animals float off; and no better mode can be adopted. While we write, the seas of our southern coasts are swarming with whole fleets of these lovely but tingling 'jelly-fishes.' Even at Southampton squadrons of them float about the pier at high tide, and go up the Hamble with the flood. As examples of Mr. Gosse's researches with reference to the testaceous mollusca, we select the burrowing sessile Pholas and the active Pecten. And first, let us take Pholas dactylus. A The respiration of many of the bivalve mollusca is effected by means of a siphon, the two extremities of which are situated close together, and are often united so as at first to appear hut one tube. glance at the very tip, however, even in this case, shows that there are two openings, one of which is a little smaller than the other, and commonly this subordinate orifice diverges at a slight angle from the principal one. The latter is the entrance, the former the exit, for the water, a perpetual change of which is absolutely indispensable to the life of the animal. The interior of these tubes is said to be lined with innumerable delicate cilia, by the action of which the surrounding water is drawn towards the entering orifice, and conveyed in a strong current through the tube over the surface of the gills. Then, having been deprived of its oxygen, it is poured through the other tube, and expelled in a jet at its extremity, by a similar machinery. This is not only a breathing but a clearing apparatus, and the double siphonal tube is principally developed in those species which burrow, whether in sand, mud, wood, or stone: As the burrowing bivalve usually, if not always, dwells in the interior of the passage it has excavated, it is needful that there should be a communication with the external water, and hence a hole is always found extending to the surface of the material bored. The entering and departing currents keep this passage clear; a process which, in mud or sand, might seem at first not very easy of accomplishment. It is facilitated, however, by the faculty which the boring bivalves have of lengthening the siphonal 1853.] Pholas dactylus-Pecten Opercularis. tubes at will; and the degree to which this may be accomplished depends on the depth of the cavity which the species is accustomed to make. If we take one of the stone-boring mollusca a Pholas or a Saxicava, for example-from its excavation, without injuring the animal, and place it in a glass vessel of sea water, it will not be difficult to detect the currents in question, even with the naked eye, though a lens of moderate power will render them more distinctly appreciable. The vessel should be so placed as that the light may be nearly, but not exactly, opposite to the eye. By this arrangement the minute atoms of floating matter are illuminated, while the background is dark; and these by their motion clearly reveal the currents of the fluid in which they are suspended. A few moments' practice will enable even an unaccustomed eye to perceive the atoms converging from all points around, with an even but increasing velocity, towards the principal tube, down which they disappear, like the streams of passengers and traffic in the neighbourhood of a great city, converging towards it as to a common centre of attraction by a hundred different routes. The current of the expelling tube is even still more marked in its character: a forcible jet of water is continuously ejected from this orifice, which draws the surrounding particles into its vortex, and shoots them forward to a distance of many inches. It is by the expulsive force of this anal current, chiefly, that the passage is kept free from the deposit of mud and other substances, which would otherwise soon choke it up. But how are the delicate tissues of the viscera to be traversed, and how is the entrance of these guarded against the particles of matter which float in an indiscriminating current, and from their form or other qualities might be noxious? Mark the beautiful contrivance provided for this necessity:— The margin of the entering siphon, and sometimes, though more rarely, of the ejecting one, is set round with a number of short tentacular processes, varying indeed in their length, but the longest scarcely more than equalling half the diameter of the mouth of the tube. In Sacicava rugosa, which bores through and through with small holes the hardest limestone of our coasts, these tentacular appendages are found fringing both the tubes. The tentacles in this species are simple, and appear as if cut off trans 397 versely; and some are not more than half as long as the others, with which they irregularly alternate. The object of this diversity in length will be manifested presently. . . . It is in Pholas dactylus, a noble species of large size, that excavates the softer rocks of our shores, that this apparatus is developed with peculiar beauty, and its use is made most clearly manifest. The tentacular filaments are in this case also confined to the oval tube. They are numerous, each forming a little tree, with pinnate branches, bearing no small resemblance to the flowers of feathery branchiæ, that expands around the mouth of a Holothuria. These branched tentacula are ordinarily bent down across the mouth of the tube, the longest of them just meeting in the centre; alternating with these are placed others of similar structure, but inferior size; and the interstices are occupied by others smaller still, and simply pinnate; so that when the whole occupy their ordinary transverse position, the small ones fill up the angles of the larger, and the branches of all form a network of exquisite tracery, spread across the orifice, through the interstices or meshes of which the current of entering water freely percolates, while they exclude all except the most minute floating atoms of extraneous matter. The painted scallop* is taken in great abundance with the dredge off the harbour in the neighbourhood of Brixham, and when properly stewed these pectens appear as a highly savoury and luscious dish at the tables of the richer classes, under the name of 'Quins,' a name probably derived from the great actor and epicure, who appears to have been a most judicious appreciator of everything delicious to the taste and Mr. comforting to the stomach. Gosse obtained two or three small from under the flat stones specimens for a very different purpose, and gives a most interesting account of its structure and habits from one which he kept for some days in a glass phial of seawater, the transparency of the vessel enabling him to watch its motions with advantage : An object of unwonted beauty indeed it is. Its ordinary condition is to lie with its valves separated to the distance of about one sixth of an inch. The open space is occupied by what seems a fleshy cushion, extending from one valve to the other all round, but just within their edge. It is of a delicate * Pecten opercularis. flesh-colour, with mottlings of dark brown, making a kind of irregular pattern with transverse bands. A close examination, however, shows that this substance is divided into two parts, for when the animal is quite at ease, it is seen to gape, with a fissure parallel to the valves, widely enough to give us a peep into the internal structure. This is, in fact, the mantle, of which these two parts are the thick and glandular edges. Around its circumference, on each portion, just where it is in contact with the valve, there are set a great number of tentacles-delicate, threadlike organs, tapering to a fine point, and of a pellucid white appearance; they are capable of being protruded and retracted at the will of the animal. I have occasionally seen some of them extended to a length equal to the diameter of the shell. They are more commonly contracted to about one fourth of that length, or even much less, with the points curled up; but frequently the animal protrudes them to their utmost extent, bending them back above the edges of the shell, and waving them slowly in every direction. Sometimes one or two only are protruded, and the others kept short. Along the very edge of each division of the mantle, bordering the fissure, is another row of similar tentacles, smaller in their dimensious. But the most beautiful appearance is yet to be described! In the line of the larger tentacles, and alternating with them, is seen a row of minute circular points, of high refrac tive power, possessing all the brilliancy of precious stones. They look, indeed, like diamonds of the first water, each set in a ring or socket of black substance, which greatly enhances their beauty. They are about half as numerous again as the radiating grooves of the shell, but are not set with perfect regularity. They are still less uniform in size, some having a diameter twice as great as the others. These are believed to be eyes, and certainly they are well placed for enabling the animal to watch the world around it. It is very sensitive, withdrawing its tentacles and mantle, and bringing the valves of its shell together, on any shock being given to the vessel in which it is kept. I observe, however, that it will not actually close the valves unless it be repeatedly disturbed, or unless the shock be violent, contenting itself with narrowing the opening to the smallest space ap preciable; yet even then the two rows of gem-like eyes are distinctly visible, peering out from the almost closed shell, the two appearing like one undu lating row, from the closeness of their contiguity. Those who are familiar. with the pincushions, so frequently made between the valves of these very scallop shells, can hardly fail to be struck with the resemblance borne by the living animal to its homely but useful substitute; and the beautiful eyes themselves might be readily mistaken for two rows of diamond-headed pins, carefully and regularly stuck along the two edges of the pincushion. A friend to whom I showed it when nearly closed, compared it not unaptly to a lady's ring set with brilliants. Active as the creature is, there seems to be a necessity for its having its quiet time, and Mr. Gosse saw it lying at its moorings. It was adhering by one valve (the flat one) to the side of the glass phial, at some distance from the bottom : On close examination with a lens, I discovered that it was attached by a very delicate byssus. Curious to ascertain how it contrived to mount from the bottom to this position, touched it slightly, and caused it to loose its hold. In the course of half an hour, I found that it had resumed the same position again. I again disturbed it, and began to watch its motions. It was lying with the convex valve downwards on the bottom of the phial. The first thing I observed was the thrusting forth of the delicate little foot, an organ which seemed to me appropriately named, when I marked its close resemblance in form to a human foot and leg, enveloped in a white stocking. What I may call the sole of this tiny foot was pressed against the side of the glass, feeling about from place to place, while with the lens I could distinctly see, in the part corresponding to the toe, the opening of the fleshy lips, or sides of the grooves, in which the threads of byssus are said to be formed. While it was thus engaged, my surprise was excited by seeing it suddenly throw itself with a jerk into an upright position; but the action was too startling to enable me to see how it was performed. I again laid it prone, and though for a moment it closed the valves, it presently opened them again, and performed a similar feat. This was followed by several leaps in different directions, in quick succession. But Mr. Gosse was still at a loss for the modus operandi, though it appeared to him certain that the ordinary supposition-viz., that the action is performed by the vigorous opening and shutting of the valves, was not the correct one; and, at 1853.] How the Pecten moves in the Sea. length, a favourable observation gave him a suspicion of what certainly appears to be the true means by which these butterflies of the ocean will flutter, as it were, for several feet along or below the surface of the glassy sea, as we have frequently seen: I perceived, (says Mr. Gosse) the lips of the mantle (which were held in contact, though the valves were considerably separated) suddenly open, to a partial extent, as if by blowing from within. At this instant there was a leap in the opposite direction, attended with a considerable agitation in the water. With this clue I observed more definitely. Having rendered the water a little turbid, in order the more distinctly to see any motion of the particles suspended in it, several leaps confirmed the notion that had suggested itself to me. The mode of proceeding is as follows: when the pecten is about to leap, it draws in as much water as it can contain within the mantle, while the lips are held firmly in contact. At this instant the united edges of the lips are slightly drawn inward, and this action gives sure warning of the coming leap. The moment after this is observed, the animal, doubtless by muscular contraction, exerts a strong force upon the contained water, while it relaxes the forced contact of the lips at any point of the circumference, according to its pleasure. The result is the forcible ejection of a jet of water from that point, which, by the resilience of its impact upon the surrounding fluid, throws the animal in the opposite direction, with a force proportioned to that of the jet d'eau. The action may be well imitated by the human mouth, blowing a stream of air from any determined point, while the lips are held firmly together at all other points. The resemblance, indeed, of the mantle to the human lips performing such an action (a resemblance perhaps more close than flattering) struck me as ludicrously faithful. Nor was the appearance less suggestive of a pair of bellows without a nose, of which the valves were the covers, and the mantle the leathers, discharging their contents from any part of their sides. That the pecten widely opens and forcibly closes its valves, if left uncovered by the water, is doubtless correct; I have seen my specimen perform such an action, and perhaps it might, by such means, jerk itself from place to place, with considerable agility. But I do not think so rude a mode of progression could enable it to select the 399 direction of its leaps, which, under water, appears to me to be determined with accurate precision. If the gem-like points be eyes, and we acknowledge that from the first opportunity of examination enjoyed by us many years ago on this very coast, we have always thought that they are visual organs, their locality secures the widest range with the least possible exposure. The death of Mr. Gosse's little pecten gave him the opportunity of submitting some of these gemmeous specks to the microscope. With a power of 220 diameters, he distinctly perceived a large lens, a glassy coat investing this, which itself was buried for more than half its volume in an investiture, apparently granular, of a yellowish-brown colour, having an ill-defined circle near its anterior side, of a blackish hue. Under pressure with the compressorium, the lens was manifestly circular; the coloured socket discharged dark granules, and from the darkest part a deep crimson pigment, which did Mr. not appear to be granular. Gosse has given a very interesting representation of one of these organs in his third plate, fig. 5. We have (p. 178) a very graphic account of a worm pipe-fish,* which our author kept alive for nearly three weeks; but we can only afford space for a very small portion of it, relating to curious points in its organization: In captivity the manners of this pretty little fish are amusing and engaging. Its beautiful eyes move independently of each other, which gives a most curious effect, as you watch its little face through a lens one eye being directed towards your face, with a quick glance of apparent intelligence, while the other is either at rest, or thrown hither and thither at various other objects; I was strongly reminded of that strange reptile, the chameleon. Another point of resemblance to that animal our little pipe-fish presents, in the prehensile character of its tail. It curves just the tip of this organ laterally round the stem or frond of some seaweed, and holds on by this half inch or so, while the rest of its body roves to and fro, elevating and depressing the head and foreparts, and throwing the body into the most graceful curves. The *Syngnathus lumbriciformis. |