XII.

The Potter

1 THE POTTER (Terebella figulus)2Terebella littoralis

Havingvisited the sea-side a few weeks since, along with some 'aquarian naturalists,' among other objects we managed to capture a very fineTerebella Figulus, commonly called the 'Potter.' The specimen measured about five inches in length, and was nearly as thick as a common drawing pencil. I could discover no signs whatever of any tube in the rocky basin in which the Annelid was situated, a circumstance that struck me as being rather curious.

On returning home, my much-valued prize was placed in a tumbler of large dimensions, the base of which I strewed with newly-pounded shells and gravel. By the following morning all the fine or powdered portion of the 'Silver Willies' had been collected and used in the construction of a tube, sufficient in length to cover half the contracted body of the industrious little mason. After labouring for a fortnight, the tube was gradually extended across the bottom of the vase in a cylindrical form, but eventually it assumed a semi-circular shape, being builtupon the glass, and elevated by gentle stages up each side of the vessel until the level of the water was reached, when all further labours ceased for a time.

After the lapse of a few days the building operation was resumed, and the tube carried fully an inch further, at right angles to its former position. The opposite end of the structure was next extended at an angle of 45° from the base of the vase, to a height of about two inches. Then commenced a very curious phenomenon. Some of the tentacles were incessantly elevated and extended across the vessel, until they touched the opposite end of the tube, with what object I could not then conceive. The design, however, was afterwards made evident: in less than two days the animal succeededin making both ends of its tube meet together, so as to form a continuous circle. I happened to be watching the mason, when the last stroke of his labial trowel was given to the building, and shall never forget the cautious way in which the animal crept for the first time over the newly-completed portion of the work, and the seeming delight with which it continued to glide, hour after hour, over the entire circuit of its dwelling-place.

Sometimes its body would be long drawn out, until the tips of the tentacula would reach, and apparently tickle the extreme point of the tail; then a race would commence, in character exactly resemblingthat so often witnessed with the kitten, or the playful whelp, when either of these animals foolishly imagine that the tip of their tail is adorned with some coveted tit-bit.

The branchial organs of my specimen were very beautiful objects, being formed of three blood-red spiral tufts, the effect of which were heightened by their being placed in contact with the drab, coloured cephalic[10]tentacles, which seemed to be almost innumerable. These latter organs, although apparently so useless when seen closed, are in reality of the greatest importance to theTerebella, for they not only act as auxiliary organs of respiration, and aid most materially in building its dwelling-place, but also constitute the real organs of locomotion.

'They consist,' says Dr. Williams, 'of hollow flattened, tubular filaments furnished with strong muscular parietes. The band may be rolled longitudinally into a cylindrical form, so as to enclose a hollow cylindrical space, if the two edges of the band meet, or a semi-cylindrical space if they only meet imperfectly. This inimitable mechanism enables each filament to take up and firmly graspat any point of its lengtha molecule of sand, or, if placed in a linear series, a row of molecules. But so perfect is the disposition of the muscular fibres at the extreme free end of each filament, that it is giftedwith the twofold power of acting on the sucking and muscular principle.

'When the tentacle is about to seize an object, the extremity is drawn in, in consequence of the sudden reflux of fluid in the hollow interior. By this movement a cup-shaped cavity is formed, in which the object is securely held by atmospheric pressure. This power is, however, immediately aided by the contraction of the circular muscular fibres. Such, then, are the marvellous instruments by which these peaceful worms construct their habitation, and probably sweep their vicinity for food.'

The foregoing beautifully and accurately describes the tentacular cirri. The use of these organs in the formation of the tube in which the Annelid dwells, I will now endeavour to make clear, from close personal observation.

It is an extremely interesting sight to watch a Terebella extend its tentacles in all directions in search of building materials, catching up the surrounding molecules (sometimes visible along the whole length of each filament), and then, by a strong muscular contraction, bringing the collected atoms to the opening of the tube, around which, as is generally supposed, they are then immediately attached by a secretion which is exuded from the body of the animal. Such, however, is not the case.

When the filaments bring their 'subscriptions,' the material thus gathered, instead of being used at oncefor building purposes,is, in reality, first eaten by the animal, and, after undergoing a kind of mastication, becomes coated with a salivary secretion, and is then ejected in mouthfuls at the extremity of the tube, which, by such means, becomes gradually elongated. The shell work, when deposited as above mentioned, is held in position, and prevented from falling over the outside of the cavity, by the filaments which are made to hang down in a most ingenious manner; the animal, at the same time, putting itself in motion, allows the slimy surface of its body to press and rub against the new addition to the tube, which is thus effectually strengthened and soldered together.

The animal does not always wait until the opening of the tube is reached, but gently disgorging while lying at its ease, it then pushes forward by aid of its head and tentacles the mass of building material, which soon becomes distributed and moulded to its proper shape.

If your specimen should happen to build a complete tube, its mode of working cannot be well seen; but should it economize its labours, and run its house up in a semi-circular form against the transparent side of the vessel, as the animal I write of did, you will be enabled to see distinctly every movement that goes on in the interior.

It seems somewhat singular that the Terebella should possess the power of turning itself within itstube, so as to be able to extend its habitation from either end at will. I have very often watched the operation with emotions of pleasure, not unmixed with wonder.

Wishing to test the powers and intelligence of my specimen, I dropped within its tube, which was curved in shape lengthways, some particles of sand, and a pebble which nearly filled up the 'bore' of the cylinder. The great annoyance occasioned by this intrusion to the master of the house was painfully evident. For a whole day the Terebella endeavoured to push out the objectionable matter by means of its head and cephalic tentacula, but without success; for although the mass frequently neared, it never touched or toppled over the mouth of the aperture, and consequently fell to its original position at the bottom of the tube as soon as the animal removed the pressure.

Apparently despairing of its efforts, though still oftener repeated, being eventually prosperous, the poor Annelid literally 'turned tail,' and very coolly proceeded to elongate the opposite end of its dwelling. This operation did not last long; for in the course of a few hours, on peering again into the vessel, I saw that the humble and insignificant worm had mustered up courage to 'face the enemy' once more, and had, in fact, apparently conceived a new idea, the wisdom of which was soon made palpable; for slowly, but surely, most of the arenaceous particleswere eaten, and nothing being left but the pebble, it was speedily and triumphantly ejected from the tube, and the sand soon after employed for building purposes. The Terebella having completed its laborious and well-executed task, seemed to be quite exhausted, and lay to all appearance lifeless for the succeeding four and twenty hours.

When walking along the sandy beach, myriads of peculiar objects may be seen swayed to and fro by the roll of the waves. Frequently, when the tide has receded, these tubes remain sticking out of the sand to the height of two or three inches, each terminating in a tuft, like the end of a piece of cord that had been teazed out.

Within such a fragile habitation dwells theTerebella littoralis, the most common species of the marine tubiculous Annelids. I have very often tried, by aid of my fingers only, or a strong spade, to capture one of these creatures, but have never been successful, even in a solitary instance. Yet several authors tell their readers the task is perfectly easy. Mr. Lewes, for instance, made me feel ashamed of my previous manipulative efforts when I read his vivid description of a Terebella hunt, and caused me lately to journey a distance of six miles to try my hand again, with no better result than hitherto.

I have lately seen a specimen ofT. littoraliswhich a friend of mine was so fortunate as to capture. The tube of the animal, instead of being inits usual position, was situated in a pool, and offered a most rare prize to its discoverer, it being the only one he had ever caught. The tube, being of great length, was cut down to about six inches and transferred to a shallow glass tank, in which was introduced some pounded shells. The beautiful Annelid soon made itself at home, and commenced to repair the damage done to its habitation by collecting these particles, by means of its tentacula, which were thrown out to an extraordinary distance in all directions.

The result of the animal's labours was soon apparent by a most amusing white patch being added to each end of its dark tube.

As soon as this operation was completedmon amicarefully tore up the patched garment, and ejected the defenceless Terebella into the vessel, wherein was placed a piece of glass tube that measured an inch in length. Strange to state, the animal instantly crept into this object, and soon made itself quite at home and comfortable. When the building materials were placed near, they were collected andattached to each end of the glass cylinderby the little architect, who doubtless was the first of its 'family' who could boast of such a noble mansion,—which ultimately assumed a very remarkable aspect from the variously-coloured 'mortar' that was employed in its construction. Above and below the transparent centre came patchesof red, white, and blue material, composed respectively of broken tile, pounded shells, and coloured glass. Such a 'concourse of atoms' was surely never before combined, either 'fortuitously' or otherwise, in the construction of so common an object as the tube of an Annelid.

The branchiæ of the above mentioned specimen presented a most exquisite appearance, resembling the perfect skeleton of a leaf, supposing that to be dyed a brilliant crimson colour, and made to exhibit incessant life-like motion even in its most delicate and minute ramifications.

'And now your view upon the ocean turn,And there the splendour of the waves discern;Cast but a stone, or strike them with an oar,And you shall flames within the deep explore;Or scoop the stream phosphoric as you stand,And the cold flames shall flash along your hand,When lost in wonder, you shall walk and gazeOn weeds that sparkle, and on waves that blaze.'

Thereare certain narrow-minded persons who raise objections to men of science prying into the secrets of nature, and profanely, as they think, attempting to explain the design and purpose of the great Creator.

But to the intelligent and right thinking man, no employment could be found more elevating or ennobling than this; and whether he be a fellow-worker himself, or merely an approving observer of the labours of others, still he feels, and conscientiously believes in the words of Milton, that—

"The desire which tends to knowThe works of God, thereby to glorifyThe great Workmaster, leads to no excessThat merits blame, but rather merits praiseThe more it seems excess."

When such a one contemplates the atmosphere, for instance, with its 'wonderful phenomena of clouds, rain, and sunshine, that alternately shield, moisten, and warm the face of the earth, he feels awed by the grandeur of the exquisite system of machineryby which such beautiful results are accomplished. To him also the sea, with its physical geography, becomes as the main-spring of a watch; its waters, and its currents, and its salts, and its inhabitants with their adaptations, as balance wheels, cogs, and pinions, and jewels. Thus he perceives that they too are according to design; that they are the expression of one thought, a unity with harmonies, which one intelligence only could utter.' To his eye all created things possess an interest doubly great, not only from their marvellous structure, but from the mission they are destined to fulfil in this lower world.

What peculiar mission the Acalephæ (which we are now about to consider) were destined to fulfil it has long puzzled men of science to explain. Nor can this be wondered at, when we remember the amazing number of these creatures, and also the extreme delicacy of their structure. Some indeed appear almost as if they were formed by the sportive combination of air and water, as if the sea-breeze ruffling the face of ocean caused bubbles innumerable to arise, which becoming mysteriously endowed with life, thenceforth existed as Medusæ.

They have, indeed, frequently been spoken of as 'animated sea-water,' or 'living jelly.' These expressions seem most appropriate when we remember, that if one of these creatures be placed upon a plate of glass, and allowed to remain exposed to the sun'srays, the only thing that will remain to testify to the existence of this singularly graceful object is a thin film, that a stroke of the sponge or finger will remove in an instant.

The most satisfactory explanation that has been offered as to the use and purpose of the Medusæ is, thatthey serve as the principal food of whales and other Cetacea. To these marine monsters—frequently found from 70 to 110 feet long—we can imagine a few hundreds of jelly-fish would be considered a small meal. The supply, however, is ever equal to the demand, as we shall see hereafter.

I may here be permitted to explain that, in most large fishes, the jaws are completely filled with formidable teeth, as in the shark, for instance. This rapacious monster—which has been aptly termed the tiger of the sea by us, and which the French, in allusion to the deadly character of its habits, have named Requin, or Requiem, the rest or stillness of death—possesses a most marvellous dental apparatus.

Its teeth are not, as might be supposed, fixed in sockets, but attached to a cartilaginous membrane. The teeth, in fact, are placed one behind the other in a series of rows; the first of which, composed of triangular cutting teeth, stands erect and ready for use. But as the membrane continues to grow and advance forward, it slowly perishes, and the teeth drop off, their place being taken by the next row which formerly stood second. These, in the courseof time, are succeeded by a third series, which are again followed by others.

Now, whales possess no such weapons. Their enormous mouths are not filled with 'tusks or grinders, but fitted instead with vast numbers of oblique laminæ of a softer substance, usually denominated whalebone, which is admirably adapted for the crushing and masticating of soft bodies.'

To give an idea of the amazing extent of the harvests of 'whale food,' as the Medusæ are termed, that abound in various parts of the ocean, we need only quote the evidence of various navigators on the subject. One (Lieut. Maury), for example, states, that on the coast of Florida he met with a shoal of these animals, that covered the sea for many leagues, through which his vessel, bound for England, was five or six days in passing. The most singular part of the story is that, on his return some sixty days after, he fell in with the same shoal off the Western Islands, and here again he was three or four days in getting clear of them.

The Western Islands here mentioned are, it seems, the great resort for whales; and 'at first there is something curious to us in the idea that the Gulf of Mexico is the harvest field, and the Gulf Stream the gleaner which collects the fruitage planted there, and conveys it thousands of miles off to the living whales at sea. But, perhaps, perfectly in unison is it with the kind and providential care of that great, goodBeing who feeds the young ravens when they cry, and caters for the sparrow.'

But Dr. Scoresby, in his work on the Arctic Regions, by aid of figures conveys the most vivid idea of the myriads of these creatures that float in the bosom of the ocean. This writer discovered that the olive-green colour of the waters of the Greenland sea was caused by the multitudes of jelly-fish contained therein. On examination he found that 'they were about one-fourth of an inch asunder. In this proportion a cubic inch of water must contain 64; a cubic foot, 110,592; a cubic fathom, 23,887,872; and a cubical mile, 23,888,000,000,000,000! From soundings made in the situation where these animals were found, it is probable the sea is upwards of a mile in depth; but whether these substances occupy the whole depth is uncertain. Provided, however, the depth which they extend be but 250 fathoms, the above immense number of one species may occur in a space of two miles square. It may give a better conception of the amount of Medusæ in this extent, if we calculate the length of time that would be requisite with a certain number of persons for counting this number. Allowing that one person could count 1,000,000 in seven days, which is barely possible, it would have required that 80,000 persons should have started at the creation of the world to complete the enumeration at the present time! What a prodigious idea this fact gives of the immensityof creation, and of the bounty of Divine Providence, in furnishing such a profusion of life in a region so remote from the habitations of man. But if the number of animals be so great in a space of two miles square, what must be the amount requisite for the discolouration of the sea through an extent of perhaps 20,000, or 30,000 square miles.'

These creatures may be appropriately termed the glow-worms of the ocean, for it is to them that the phosphorescence of the sea is mainly attributable.

Sir Walter Scott, in his poem of the 'Lord of the Isles,' thus alludes to this phenomenon:—

'Awaked before the rushing prow,The mimic fires of ocean glow.Those lightnings of the wave.Wild sparkles crest the broken tides,And, flashing round the vessel's sides,With elfish lustre lave;While far behind their livid lightTo the dark billows of the nightA gloomy splendour gave.'

Hugh Miller also gives a beautiful prose description of the luminosity of our own seas, but we must resist the temptation to introduce it here.

The appearance of the Greenland Seas is principally owing to the presence of the minute species of Acalephæ, but there are many others that grow to an immense size. Specimens of these may be frequently seen cast on the sea-beach by the force of the waves. When in their native element they form the swimmer's dread, owing to a peculiar stinging power which they possess.

The Medusæ have been divided into groups, and distinguished according to their different organs of locomotion. The common idea is that all jelly-fishes are like mushrooms or miniature umbrellas. Such, it is true, is their general form, but others abound both in our own and in foreign seas, that possess a totally different appearance. For instance, some move by means of numerous cilia, or minute hairs that are attached to various parts of their bodies. By the exercise of these organs the creatures glide through the water, and hence they are calledciliograde Acalephæ.

One of the most remarkable examples of this class is seen in the Girdle of Venus (Cestum veneris). 'This creature is a large, flat, gelatinous riband, the margins of which are fringed with innumerable cilia, tinted with most lively irridescent colours during the day, and emitting in the dark a phosphorescent light of great brilliancy. In this animal, too, which sometimes attains the length of five or six feet, canals may be traced running beneath each of the ciliated margins.'

This animal, as it glides rapidly along, has the appearance of an undulating riband of flame. Most likely it is the species to which Coleridge alludes in the following passage:—

'Beyond the shadow of the shipI watched the water snakesThey moved in tracks of shining white,And when they reared, the elfish lightFell off in heavy flakes.* * * *Within the shadow of the shipI watched their rich attire—Blue, glossy green, and velvet black,They curled and swam; and every trackWas a flash of golden fire.'

Another of this class is the common Beroë (Cydippe pileus); its body is melon-shaped, and covered over by rows or bands of cilia, placed similarly to the treads on a water wheel, one above another. These are entirely under the will of the little gelatine. It can use each or all of them, and thus row itself along at pleasure. But perhaps the most singular portion of this creature is what has been termed its fishing apparatus, though by some writers it is considered merely to be the means by which the Beroë anchors its body to any desired spot. It consists of two exceedingly slender filaments or streamers, which measure many times the length of the Beroë itself. Some writers, again, fancy that these organs are used to propel the animal. This must be an erroneous notion, for if they were cut off, the creature would still continue to move with the same power as before. Nay more, if the little Cydippe be cut into pieces, and the ciliated bands be attached to each fragment, the latter will swim about with the same power as when connected with the entire animal.

From the filaments here described, others more slender still depend at regular intervals, which curl up like vine tendrils upon the principal stem. Thewhole can be spontaneously elongated or slowly withdrawn within the body of the Beroë, where they lie enclosed in two sheaths until again required for use.

These interior 'sheaths,' which resemble in shape the drone of a bag-pipe, are easily seen, being almost the only parts which are not perfectly transparent. They are whitish in colour, and semiopaque. (Plate 6 contains a sketch of the Beroë, drawn from nature.)

I may mention that the paddles, with their comb-like array of cilia, flap successively in regular order from the top to the bottom of each row. This wave-like movement takes place simultaneously in all the rows, when the animal is in full vigour.

The organs of progression in thePulmonigradeAcalephæ, as their name imports, bear certain resemblance to the lungs in respiration. They move by the expansion and contraction of their umbrella-shaped bodies. Graceful and elegant indeed are the motions of these creatures. I have seen small specimens about the size of a sixpence, advance, in three springs, from the bottom to the top of a large vase in which they were confined.

In descending they turn over and allow themselves to sink gradually as if by their own weight.

The third division of the Acalephæ is termedPhysograde. The most common member of this group is thePhysalus, so well known to all sailorsunder the name of the Portuguese Man-of-War. It is buoyed up by air bladders—in fact, its entire body appears as one bladder, which the animal is enabled to contract or expand at will. At first glance thePhysalusappears to belong to quite a different family—suffering under some maltreatment; for from its lower side, what seem a number of entrails, of all shapes and sizes, hang down. When the upper surface or crest of its swimming bladder projects above the waves, it has a beautiful appearance, spangled with rays of purple, blue, and gold. This formation acts as a kind of sail, by means of which the creature is enabled to glide along with considerable speed.

This Physalus is a somewhat mysterious being, and zoologists have not as yet been able to determine many points connected with its structure and development.

TheCirrigradeAcalephæ, too, are a singular family. They exhibit a higher stage of development than those already alluded to, and possess a kind of skeleton embedded within their gelatinous bodies.

ThePorpitaandVelellaare examples of this class, but for detailed descriptions I must refer the reader to larger works which treat on the subject.

I cannot conclude this brief and imperfect sketch of the Acalephæ without noticing their singular mode of reproduction. Nothing can appear more marvellous than this process when first brought beforeone's attention. It far excels the wildest dreams of fiction; and were it not so well authenticated by naturalists who have devoted labour and valuable time to gain ocular demonstration of the fact, we might well hesitate to believe the statements laid before us in their works.

For example, a Polype, asHydra GelatinosaorHydra Tuba(found on buoys, oyster shells, &c., long submerged), will, it may be in a simple aquarium, produce a number of small objects which, on being examined through the microscope, are found to be, not young Polypes, but Jelly-fish! In process of time, the latter, by a wondrous law of nature, will produce in their turn, not Medusæ, but Polypes!

'Imagine,' says Mr. Lewes, 'a lily producing a butterfly, and the butterfly in turn producing a lily, and you would scarcely invent a marvel greater than this production of Medusæ was to its first discoverers. Nay, the marvel most go further still, the lily must first produce a whole bed of lilies like its own fair self before giving birth to the butterfly, and this butterfly must separate itself into a crowd of butterflies, before giving birth to the lily.'

Let me now, by entering briefly into detail, endeavour to make the reader acquainted with the leading features of this mysterious subject, known as 'the alternation of generations.'

The adult Medusæ, then, gives birth to a numberof oval gemmæ or buds, appropriately so called by most writers, which appear like minute jelly bubbles, covered with numberless vibratile cilia. These organs, ten thousand times more delicate, we may imagine, than the eyelashes of some infant member of fairy land, are ever in constant motion. The currents produced thereby serve to propel the little animal to some stray pebble or stalk of sea-weed, situated at a respectful distance from its gelatinous relative. On some such object the young bud attaches itself, and proceeds to vegetate.

The body gradually lengthens, and becomes enlarged at its upper extremity; from this portion of the animal four arms appear surrounding a kind of mouth. The arms lengthen, and are soon joined by four others. These organs, as also the inner surface of the lips and of the stomach, are covered with cilia, and become highly sensitive. They are used in the same manner as the tentacula of the Actiniæ, namely, for the capture of food. There is this difference, be it observed, between the two animals, that while the infant Medusæ labours incessantly to gain its daily meals, the zoophyte remains still, and trusts to chance for every meal that it enjoys.

Fresh sets of arms continue to be developed successively upon the little jelly fish, until the whole amount in number to twenty-five or thirty. 'And the body, originally about the size of a grain of sand, becomes a line, or the twelfth part of an inch in length.'

Thus far there appears nothing particularly striking or improbable in the history of the Medusæ; the next stage, however, exhibits matter for our 'special wonder.'

The young Acaleph now throws off its animal existence, and sinks into a plant or compound polype.

The lower part of the body swells, and from thence, what may be termed astolen, is thrown out. On the upper surface of the stolen one and even two buds are often formed. 'As the bud enlarges it becomes elongated, and bends itself downwards to reach the surface of the stone to which the elongated extremity adheres; after this the attached end is gradually separated from the body of the parent. When thus detached, a small opening presents itself at its upper end, its interior gradually becomes hollowed out, and cilia grow upon it, and tentacula begin to sprout around the mouth, exactly in the same manner as in the buds formed on the upper surface of the stolens.'

Thus, from a single bud numberless other buds are formed, each being endowed with equally prolific powers. If the parent be cut in half transversely, the cut will close in, attach itself to some object, and produce stolens and buds! If cut longitudinally, and the cut edges be allowed to touch each other, they will again adhere, and exhibit no trace of their ever having been divided. If the cut edges of each division be not kept apart they will approximate andadhere together, and thus two separate animals will be produced, each gifted with the power of throwing out stolens and buds with the same prodigality as if they had never been disunited!

How long this budding process of necessity continues we cannot tell. It may be only during the winter season. These creatures in their perfect condition are generally found crowding our seas during the summer months; most probably, therefore, as Sars and Steenstrup state, it is at the commencement of spring that they undergo the last portion of this 'transformation strange.'

Still, this cannot be taken as a general rule. Dr. Reid, who for a period of two years kept colonies of Medusæ, and assiduously watched the various stages of their development, found that the larvæ of one colony, which was obtained in September 1845, did not split transversely into young Medusæ in the spring of 1846, as he expected them to do, but continued to produce stolens and buds abundantly.

On the other hand, the larvæ of the other colonies, which this gentleman obtained in July, began to yield young Medusæ about the middle of March. This process takes place in the following manner: A 'bud' having arrived at maturity, it becomes 'cylindrical,' considerably elongated, and much diminished in diameter, its outer surface being marked with a series of transverse wrinkles.

These wrinkles, or rings, which frequently amountto thirty or forty in number, are first formed at the top, and slowly extend downwards. Gradually as these furrows become deeper, the tentacula waste away, and upon the margin of the upper ring eight equi-distant rays are formed. The process continuing, in the space of a fortnight or so each groove or ring is in like manner furnished with rays. The Medusæ now present an appearance exactly resembling a series of cups piled up one within the other. Strange to state, each little cup becomes eventually endowed with life! As the uppermost segment is completely developed, it rests upon the slender lips of the one beneath. It then glides off from its old resting-place, and swims freely about in the water. Quickly it aspires to the rippling surface above, and by a series of graceful evolutions accomplishes its object. Once among the dancing waves and exposed to the rays of a cheering sun, our little Medusa assumes its complete form; and as a beautifulModecra formosa, it may be destined at some time or other to be the prize of an ardent zoologist, who, I venture to assert, could not compliment it in more poetical language than Professor Forbes has already done. This delightful author, describing the little gem in question, says, 'It is gorgeous enough to be the diadem of sea fairies, and sufficiently graceful to be the night-cap of the tiniest and prettiest of mermaidens.' Or as an adultCyanea capillata, our once insignificant jelly-bag may perhaps appear, andby an exercise of its urticating powers, send some unhappy swimmer smarting and trembling to his home.

While the Medusæ column proceeds to throw off from its uppermost part living segments of itself, its lower half, or stem, continues to grow, but does not become ringed, for as the budding process ceases, the last formed cup rests on newly-formed tentacula! Then again stolens are thrown out, on which young Medusæ are formed, as before described.

Contemplating such mysteries as these, the mind becomes bewildered and the spirits humbled.

'Imagination wastes its strength in vain,And fancy tries and turns within itself,Struck with the amazing depths of Deity.'

The above may be deemed one of the most interesting zoological theories that has ever been promulgated in modern times. It was founded by Chamisso, and termed the 'alternation of generation,' but was much improved and extended by the researches of Steenstrup. Professor Owen, however, had previously reduced the theory to a fixed and definite scientific form, under the title of 'Parthenogenesis.' Another author, not viewing the Medusæ in the various stages of development as an aggregation of individuals, 'in the same sense that one of the higher animals is an individual,' proposes that each Medusa be considered as an individual, developed into so many 'zooids.'

Into this abstract question, of course, I cannot enter. The reader who would wish to know more of the subject than I have faintly shadowed forth in this chapter, may consult Steenstrup's Memoir, published by the Ray Society; Dr. Reid's admirable papers in the 'Magazine of Natural History' 2d series; Lewes' 'Sea-Side Studies;' and the learned works of Professor Owen.

MEDUSÆ IN VARIOUS STAGES OF DEVELOPMENT.

'The inhabitants of the watery element were made for wise men to contemplateand fools to pass by without consideration.'—Isaak Walton.

Onefine morning during the month of January, on peering into my largest tank I perceived, attached to the upper portion of the marble arch (centre piece), a peculiar object that had evidently been deposited during the preceding night, but by whom or by what means I knew not. It resembled a fungoid growth, or riband of flesh, plaited up and attached at one edge to the stone. At every undulation of the water the object moved to and fro with an extremely graceful motion.

By careful and close examination it was seen to be covered with a film, that gradually expanded until it burst, and thus gave means of escape to thousands of minute white granules. On submitting these to the microscope, a most wondrous sight met my astonished eyes. Each dot or granule proved to be a transparent shell, resembling the periwinkle or rather the nautilus in shape; containing an animal whose excited and rapid movements were amusing to witness. From out the opening of the shell appearednow and again two rings of cilia. When these organs were about to be put into action, they reminded me of two circular tubes of gas connected together, and each containing innumerable perforations, which were sometimes suddenly and entirely lit up by a torch being applied to one end.

Theciliamay be distinctly seen to play at a certain point, and then gradually extend round the circumference of the rings. When the whole are in full action their movements are so extremely swiftas to appear devoid of motion, and thus bear a resemblance to rings of flame.

The result of the movements of the cilia was always evident in the vigorous evolutions of the little embryos, for the microscope filaments, while in action, caused the animal to roll about in all directions in a confined circle. When this envelope burst, the little nautiline dashed out, and then—then it was of little use attempting to get a view of the animal again, so rapid and violent were its movements to and fro, never resting for one instant on any spot, and least of all the spot wished. By the aid of blotting-paper, I sometimes reduced the quantity of water in the watch glass; and the animal, thus being compelled to confine its evolutions to a narrower stage, was more often within the field of view.

On visiting the sea-shore shortly after the discovery of the egg cluster just described, I perceived attached to numberless stones and large bouldersthick clusters, composed of the self-same objects! Beside them were lying confused heaps ofsea-slugs, evidently exhausted with their hatching exertions. Anything more repulsive to the eye than those animal heaps exhibited it would be difficult to conceive. Yet, at the same time, I know of no sight more pleasing than to watch theDorisin its healthy state, gliding along with outspread plume on the under surface of the water, or up the sides of the tank, more especially if it be observed through a powerful hand lens.

These remarks will perhaps convey some new information to the young naturalist, embracing as they do the leading facts connected with the wondrous embryotic development of many marine animals. The reader will already be prepared to learn that the vivacious little animal, moving by aid of cilia and enclosed in ashell, was in reality the youthful stage of that slow creeping gasteropod theDoris, which, in its mature form, is possessed of no cilia, nor any shelly covering whatever.

I should not have introduced this subject so familiarly did I not feel anxious to make my readers aware how easy it is for each of them to conduct experiments in the early stages of embryotic development, and to gain practical evidence of the wonders which this study unfolds.

'What,' eloquently asks Mr. Lewes, 'can be more interesting than to watch the beginnings of life, totrace the gradual evolution of an animal from a mass of cells, each stage in the evolution presenting not only its own characteristics, but those marks of affinity with other animals which make the whole world kin? To watch the formation of the blood-vessels, to see the heart first begin its tremulous pulsations, to note how life is from the first one incessant struggle and progress—these keep us with fascinated pertinacity at our studies.'

The remarkable fact above mentioned, of the young of the Nudibranchiate Gasteropoda being furnished with a shell is exhibited not only in Doris, but in Eolis, Tritonia, Aplysia, &c., while the embryos of the Purpura, Nerita, Trochus, &c., are likewise in their youthful state furnished with cilia, by the agency of which these animals swim freely about in their native element.

There is one exception to this, which occurs inChiton, the early stage of which has recently been shown by the observations of Mr. Clarke and Professor Loven to be peculiar, and more resembling that of an annelid than of a mollusc. In this case the animal can scarcely be said to undergo a metamorphosis; for the embryo, even within the egg, has nearly the form of the parent, and the appearance of the shell-plates is a mere matter of development.

I have never attempted to count the ova that were contained in any single riband of Doris spawn,in fact I considered the task an impossibility; but at a rough calculation, I concluded there would not be less than a million. Dr. Darwin, however, travelling in the Falkland Isles, met with a riband of spawn from a white Doris (the animal itself was three and a half inches long), which measured twenty inches in length, and half an inch in breadth! and by counting how many balls were contained in a tenth of an inch in the row, and how many rows in an equal length of riband, this gentleman reckoned that upon a moderate computation there could not be less than six millions of eggs. Yet, in spite of such amazing fecundity, this Doris was not common. 'Although,' says Dr. Darwin, 'I was searching under the stones, I saw only seven individuals. No fallacy is more common with naturalists, than that the numbers of an individual species depend on its powers of propagation.'

This apparent paradox is not difficult of explanation when we consider the number of enemies which are always hovering near, and ready with hungry mouths to snap up the infant embryos as soon as they begin to show signs of vitality. The Hermit-Crabs are especially fond of Doris spawn, so much so, indeed, that the writer could never retain any for hatching purposes while any of the Paguri were near. Mr. Peach says they (the young Dorides) have myriads of enemies in the smallInfusoria, which may be noticed, with a powerful microscope,hovering round them, and ready to devour them the instant weakness or injury prevents their keeping in motion the cilia, which serve both for locomotion and defence. Let them cease to move, a regular attack is made, and the animal is soon devoured; and it is interesting to observe several of the scavengers sporting with the empty shell, as if in derision of the havoc they have made.

The same difficulty of calculation does not exist, at least to any such extent, with the spawn of Eolis, which is laid in stringy coils. M. Gosse mentions a specimen ofE. papillosathat laid nine strings of spawn in his tank between the 20th of March and the 24th of May, all as nearly as possible of the same length. Each string contained about a hundred convolutions, each convolution about two hundred ova, and each ova including, on an average, two embryos, making a total progeny of forty thousand, produced from one parent in little more than two months.

I may mention that on no occasion have I ever found the spawn coils of either Doridiæ or Eolididæ in my tanks, or at the sea-shore, except during the months of January and February or March; neither have any of my specimens spawned more than once during an entire season. From noticing the same group of parent slugs congregated, and remaining, as I can affirm, for weeks near their egg clusters, evidently in a most enfeebled condition, it has occurredto me that on the Frith of Forth, at least, vast numbers of these animals do not long survive the hatching season.

Whether this be the case or not, it is a most singular fact that in this locality, a Doris more than one or two inches in length is scarcely ever to be met with.

There is at present in one of my tanks a specimen of the Doris of a pearly-white colour, a second, tinted white and pink, and two others which are quiteblack,—all being procured from the coast near Edinburgh. The last-mentioned animals are, I think, somewhat uncommon. When watching one of them in motion while the sun is shining down upon it, the hue of the creature changes from a black to a very deep purple, owing, no doubt, to its fleshy disc being many shades lighter than its body, which, being extended, and exhibited under a full glow of light, becomes semi-transparent. This peculiarity is not evident, of course, when the Doris is lying in a passive state, with all its gill-plumes closed up.

This sombre-coated gasteropod, although rare in some localities, is very plentiful in foreign parts, if the following may be received as an accurate narrative. 'On a reef of rocks near the island of Raiatea is a huge unshapely black or brown slug, here called 'Biche,' from six to seven inches long, and five to six broad. Is is caught in vast quantities, and not only regarded as a great delicacy by the natives,but being cured, has become a valuable article of commerce in the China market, whither it is carried from many insular coasts of the Pacific by American ships. We have seen a number of lads fill three canoes in two hours with these sea-snails.'

Thus uninviting as this slimy animal seems to our English taste, there is evidently no doubt of its being used by the Chinese as an article of food, and according to the evidence of certain authors, is esteemed by the 'barbarians' a high-class luxury; but then we must remember that the inhabitants of the land of gongs and chopsticks, have always been famed for their singular gastronomic tastes. One poet writes:—

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