My Tropic Isle Part 9

An oyster (OSTREA DENDOSTREA FOLIUM), too mean of proportions, too dull and commonplace of colour to be termed pretty, worth nothing, and justifying, in appearances its worthlessness, is remarkable for the exercise of a certain sort of deliberate wit in accordance with special conditions. Nature provides various species of the great oyster family with respective methods of holding their own in the sea, and in the case under review she permits the individual to exercise a choice of two different methods of fixture as chance and the drift of circ.u.mstances decide its location. From the bases of the valves spring three or more pairs of hook-like processes which, if Fate decides upon a certain coral host, encircle a slim "twig," creating for the mollusc a curious resemblance to a short-limbed sloth hugging tightly the branch of a tree.

When the spat happens to settle in places where coral is not available the hooks or arms are but crudely developed. It becomes a club-footed cripple, its feet adherent by agglutination or fusion to a rock or other and larger mollusc, dead or alive. In fact, the shrewd little oyster responds to its environment, clasping a twig with claws or cementing itself to an unembraceable host in accordance as contingencies insist.

Another mollusc (AVICULA LATA), sometimes found in company with the clinging oyster, resembles, when the fragile valves are expanded, a decapitated b.u.t.terfly, brick-red in colour, with an overs.h.i.+rt of fine and elaborate network, orange tinted. The interior is scarcely less attractive, the nacre having a pink and bluish l.u.s.tre, while the "lip" is dark red. This is found (in my experience) only in a.s.sociation with a certain species of coral (GORGONIA), which flourishes in strong currents on a stony bottom three or four fathoms deep. Apart from the unusual shape and pleasing colours of the sh.e.l.l, it is remarkable because it seems to be actually incorporated with its host. The foot of the mollusc is extended into a peduncle, consisting of fibres and tendons, by which the animal is a fixture to a spur of coral. At the point of union (to facilitate which there is a hiatus in the margins of the peduncle) the sarcode or "flesh" of the coral is denuded, its place being occupied by ligaments, which by minute ramifications adhere so intimately to the coral stock or stem that severance therefrom cannot be effected without loss of life to the mollusc.

On a single spray of ruddy Gorgonia several of these commensal molluscs may occur in various stages of development--the smaller no bigger than the wing of a fly and almost as frail, the larger three and four inches long, and each whatsoever its proportions securely budded on and growing from a spur, while frequently the valves of the large are bossed with limpets and other enc.u.mbrances. In appearance the sh.e.l.l represents a deformity in usurpation of a thin pencilate "growth" of coral a foot long, for the exterior colouration is that of the coral. Quite independent of their host for existence, these molluscs are not to be stigmatised as parasites, though the individual spur to which each is attached is invariably destroyed by the union, merely sufficient remaining for the support of the intruder. Natural science provides many ill.u.s.trations of symbiosis, or the intimate a.s.sociation of two distinct organisms. This example may be out of the common, and therefore worthy of inclusion in a general reference to the life of the coral reef.

A third species, rare in a certain sense only, is of a most retiring, not to say secretive, disposition. For several years I sought in vain a living specimen of a flattened elongated bivalve (VALSELLA), buff-coloured externally, very l.u.s.trous within, with a hinge the centre of which resembles a split pearl. The blacks could offer no information beyond that which was delightfully indefinite. "That fella plenty alonga reef. You look out. B'mbi might you catch 'em!" "Tom," who never wilfully parades his ignorance, boldly a.s.serted that they favoured rocks, but he had no name for them, and no living specimen was ever forthcoming to substantiate confident opinions.

An exceptionally low tide revealed several hitherto cautiously preserved secrets of the reef, among them the location of a species of sponge, dark brown, some semi-spherical, some turreted in fantastic fas.h.i.+on. Embedded upright in the sponges, like almonds in plum-puddings, so that merely the extremities of the valves were visible as narrow slits, were the long-sought-for molluscs. Judging by the extreme care of the species for its own protection--for it is ill-fitted in model and texture for a rough-and-tumble struggle for existence--one is inclined to the opinion that it must have many enemies. The valves are frail and brittle, and only when they gape are they revealed, and the gape is self consciously polite. The sponge embraces the slender mollusc so maternally that rude yawning is forbidden. It may lisp only and in smooth phrases, such as "prunes" and "prisms"; and, moreover, the host further insures it against molestation by the diffusion of an exceptionally powerful odour, which, though to my sense of smell resembles phosphorus, is, I am informed on indubitable authority, derivable from the active form of oxygen known as ozone. Experimentally I have placed these molluscs in fresh water, to find it quickly dyed to a rich amber colour while acquiring quite remarkable pungency. Even after the third change the water was impregnated.

Interest in the mollusc became secondary upon the discovery of the host and in consideration of the part it plays in the production of one of the special effects of coral reefs; but the mollusc serves another and timely purpose--purely personal and yet not to be disregarded. It indicates a dilemma with which the wilful amateur in the first-hand study of conchology is confronted. Although, as I have said, no local knowledge of ident.i.ty was available, reference to a well-disposed expert secured the information that its t.i.tle in science is VULSELLA LINGULATA; that some twenty species are known; that they all a.s.sociate with sponges, and that possibly different species inhabit different kinds of sponges. It may seem unpardonably gratuitous on the part of one professedly ignorant to offer general observations upon natural phenomena; but as I find myself among the great majority who do not know and who may be more or less interested and anxious to learn, I claim justification in describing that which to me is novel and rare. In this splendid isolation I cannot hope to illuminate primary investigations with the searching light in which science basks unblinkingly, for the nearest library of text-books is close on a thousand miles away. Nor can I keep all my observations to myself. There are some which, like murder, "will out," conscious though I am of meriting the censure of the learned.

With this off my mind, let me return to the tenement sponges, which may be likened to so many independent and flouris.h.i.+ng manufactories of ozone.

Apart from the odour of brine common to every ocean and the scents of the algae and some of the flowering plants of the sea, which are similar all over the world, a coral reef has a strong and specific effluence. The skeletonless coral (ALCYONARIA) has a sulphurous savour of its own, and the echini and beche-de-mer are also to be separately distinguished by their fumes. Anemones, great and small, seem to disperse a recognisable scent as from a mild and watery solution of fish and phosphorus. But of all the occupants of the reef none are so powerful or so characteristic in this respect as sponges. Puissant and aggressive, these exhalations are at times so strong as to almost make the eyes water, while exciting vivid reminiscences of old-fas.h.i.+oned matches and chemical experiments.

Substantial, wholesome, and clean--though generated by a wet, helpless creature having no personal charms, and which, having pa.s.sed the phase of life in which it enjoyed the gift of locomotion, has become a plant-like fixture to one spot--the gas mingles with other diffusions of the reef, recalling villanous salt-petre and sheepdips and brimstone and treacle to the stimulation of the mental faculties generally.

Invariably an afternoon's exploration of the coral reef is followed by a drowsy evening and a night of exceptionally sweet repose. No ill dreams molest the soothing hours during which the nervous system is burnished and lubricated, and you wake refreshed and invigorated beyond measure. I have endeavoured to account for the undoubted physical replenishment and mental exhilaration largely from the breathing of air saturated with emanations from the coral and sea things generally.

In the course of three hours' parade and splas.h.i.+ng in the tepid water, ever so many varieties of gas more or less pungent and vitalising--gas which seems to search and strengthen the mechanism of the lungs with chemically enriched air, to tonic the whole system, and to brighten the perceptive faculties, have been imbibed. Exercise and the eagerness with which wonders are sought out and admired may account in part for present elation and balmy succeeding sleep, but the vital functions seem, if my own sensations are typical, to receive also a general toning up. Twice a month at least a man should spend an afternoon on a coral reef for the betterment of body and brain. On the face of it this is counsel of perfection. Only to the happy few is such agreeable and blest physic proffered gratis. Yet the whole world might be brighter and better if coral reefs were more generously distributed. Breathing such subtle and st.u.r.dy air, men would live longer; while the extravagant life of the reef, appealing to him in fine colours and strange shapes, would avert his thoughts from paltry and mean amus.e.m.e.nts and over-exciting pleasures.

The pomp of the world he would find personated by coral polyps; its vanities by coy and painted fish; its artfulness represented by crabs that think and plan; its scavenging performed by aureoled worms.

Although students of conchology are familiar with several species of LIMA, I am eager to include it in these haphazard references, because my first acquaintance with a living specimen afforded yet another experience of the versatility of the designs of Nature. It is truly one of the "strange fellows" which Nature in her time has framed. Living obscurely in cavities, under stones, inoffensive and humble, the Lima enjoys the distinction of being, the permanent exemplification of the misfit, its body being several sizes too large as well as too robust for its fragile, sh.e.l.ly covering. The valves are obtusely oblong, while the animal is almost a flattened oval, the mantle being fringed with numerous bright pink tentacles, almost electrical in their sensitiveness.

Though anything but rotund, so full in habit (comparatively speaking) is the body of the lima that the valves cannot compress it. Except at the hinges they are for ever divorced, an unfair proportion of the bulging body being exposed naked to the inclemency and hostility of the world.

"All too full in the bud" for those frail unpuritanical stays, the animal seems to be at a palpable disadvantage in the battle of life, yet the lima is equipped with special apparatus for the maintenance of its right to live. By the expansion and partial closing of the valves it swims or is propelled with a curiously energetic, fussy, mechanical action, while the ever-active pink rays--a living, nimbus--beat rhythmically, imperiously waving intruders off the track.

The appearance and activities of the creature are such as to establish the delusion that it is not altogether amicable in its att.i.tude towards even such a b.u.mptious and authoritative product of Nature as man. Its agitated demonstrations--whatever their vital purpose may be--to the superficial observer are danger signals, a means of self-preservation, as a subst.i.tute for the hard calcareous armour bestowed upon other molluscs.

The fussy red rays may impose upon enemies a sense of discretion which constrains them to avoid the lima, which, though hostile in appearance, is one of the mildest of creatures. The tentacles, too, have a certain sort of independence, for they occasionally separate themselves from the animal upon the touch of man, adhering to the fingers, while maintaining harmonic action, just as the tip of a lizard's tail wriggles and squirms after severance.

Most of the blocks of submerged, denuded coral are the homes of certain species of burrowing molluscs, the most notable of which are the "date mussels" (LITHOPHAGA). The adult of that designated L. TERES is over two inches long and half an inch in diameter; glossy black, with the surface delicately sculptured in wavy lines; the interior nacreous, with a bluish tinge. This excavates a perfectly cylindrical tunnel, upon the sides of which are exposed the stellar structure of the coral. A closely related species (STRAMINEA), slightly longer, and generally of smooth exterior, partially coated with plaster, muddy grey in colour, adds to the comfort and security of existence by lining its tunnel with a smooth material, a distinction which cannot fail to impress the observer. In each case the mollusc is a loose fit in its burrow, having ample room for rotation, but the aperture of the latter is what is known as a ca.s.sinian oval, and generally projects slightly above the surface of the coral.

The animal is a voluntary life prisoner, for the aperture has the least dimension of the tunnel. The genus is known to be self luminous--a decided advantage in so dark and narrow an habitation. It seems to me to be worthy of special note that an animal enclosed by Nature in tightly fitting valves should also be endowed with the power of mixing plaster or secreting the enamel with which its tunnel is lined and of depositing it with like regularity and, smoothness to that exhibited in its more personal covering which grows with its growth. The mollusc in its burrow in the depths of a block of coral, white as marble, with its own light and its self-constructed independent wall, appeals to my mind as evidence of the care of Nature for the preservation of types, while from such retiring yet virile creatures man learns earth-s.h.i.+fting lessons. A quotation from Lyell's "Principles of Geology" says that the perforations of Lithophagi in limestone cliffs and in the three upright columns of the Temple of Jupiter Serapis at Puzzuoli afford conclusive evidence of changes in the level of sea-coasts in modern times--the borings of the mollusc prove that the pillars of the temple must have been depressed to a corresponding depth in the sea, and to have been raised up again without losing their perpendicularity.

The date-mussels play an important part in the conversion of sea-contained minerals into dry land. Ma.s.sive blocks of lime secreted by coral polyps being weakened by the tunnels of the mussels are the more easily broken by wave force; and being reduced finally to mud, the lime, in a.s.sociation with sand and other const.i.tuents, forms solid rock.

A feature of another of the coral rock disintegrating agents is its extreme weakness. It is a rotund mollusc with frail white valves, closely fitting the cavity in which it lives. As it cannot revolve, the excavation of the cavity is, possibly, effected by persistent but necessarily extremely slight "play" of the valves; but the animal appears to be quite content in its cramped cell with a tiny circular aperture (generally so obscured as to be invisible), through which it accepts the doles of the teeming, incessant sea.

CHAPTER XV

BARRIER REEF CRABS

"Reasoning, oft admire How Nature, wise and frugal, could commit Such dispositions with superfluous hand."

MILTON.

So much of the time of the Beachcomber is spent sweeping with hopeful eyes the breadths of the empty sea, policing the uproarious beaches, overhauling the hordes of roguish reefs, and the medley concealed in cosy caves by waves that storm at the bare mention of the rights of private property, that he cannot avoid casual acquaintance with the scores of animated things which ceaselessly woo him from the pursuit of his calling. Should he be inclined to ignore the boldly obvious distractions from serious affairs, there are others, not readily discernible, which have singularly direct and successful methods of fixing attention upon themselves.

Roseate or sombre your humour as you patrol the reefs, it is liable to be changed in a flash into clas.h.i.+ng tints by inadvertent contact with a warty ghoul of a sea-urchin, a single one of whose agonising spines never fails to bring you face to face with one of the vividest realities of life. A slim but shapely mollusc known as Terebellum or augur, to mention another conceited little disturber of your meditations, stands on its spire in the sand, and screws as you tread, cutting, a delightfully symmetrical hole in the sole of your foot, and retaining the core--perfect as that of a diamond drill.

Many and varied are the inconspicuous creatures with office to remind the barefooted trespa.s.ser that no charter of the isles and their wrecks is flawless, and that they are prepared to inflict curious pains and limping penalties for every incautious intrusion on their domicile. Few of the denizens of the unkempt coral gardens are more remarkable than the crabs.

By reef and sh.o.r.e I have come literally into contact with so many quaint specimens, and they have so often afforded exhilarating diversion and sent brand-new startling sensations scurrying along such curious and complicated byways, that courtesy bids me tender a portrait of one of the family which (in appearance only) may be described as a dandy, and to tell of two or three others whose intimacy is invariably enlivening.

Shall I dispose of the dandy first? Perhaps it were better so, for I confess to a very slight acquaintances.h.i.+p with him, and as I am ignorant, too, of its ceremonious as well as familiar t.i.tle, the pleasure of a formal introduction is denied. In the portrait the ruling pa.s.sions--modesty and meekness--are graphically displayed. When it lies close--and it moves rarely, and then with a gentle lateral swaying--the fancy dress of seaweed is a garment of invisibility. It is far more true to character alive than as a museum specimen, for its natural complexion is a yellowish grey, the neutral tint of the blending of sand and coral mud upon which it resides. The preserving fluid added a pinkish tinge to the body and limbs. Blame, therefore, the embalmer for the over-conspicuous form which is not in the habit of the creature as it lived. Neither are the plumes those of pomp and ceremony, but merely the insignia of self-conscious meekness--the masquerade under which the shrinking crab moves about, creating as little din and stir as possible, in an ever-hungry world. With such unfaltering art does it act its part that it is difficult to realise the crab's real self unless aided by mischance. Conscious of the terrors of discovery, it rocks to and fro, that its plumes may sway, as it were, in rhythm with the surge of the sea. Can there be such a thing as an unconscious mimic? If not, then the portrait is that of an ideal artist.

Those who know only the great flat, ruddy crabs with ponderous pincers and pugnacious mien, which frequent fish shop windows, can form but a very unflattering opinion of the fancy varieties which people every mile of the Barrier Reef.

The struggle for existence in this vast, crowded, and most cruel of arenas is so appalling that the great crab family has been battered by circ.u.mstances into weird and fantastic forms. Only a few come up to the human conception of the beautiful either in figure or colouring. While some shrink from observation, others, though themselves obscure to the vanis.h.i.+ng-point, seem to be endowed with a vicious yearning for notoriety.

A certain cute little pursuer of fame is absolutely invisible until you find it stuck fast to one of your toes with a serrated dorsal spur a quarter of an inch long. It is invisible, because Nature sends it into this breathing world masquerading, as she did Richard III, deformed, unfas.h.i.+oned, scarce half made-up. In general appearance it closely resembles a crazy root-stalk of alga--green and not quite opaque, and clinging to such alga it lives, and lives so placidly that it cannot be distinguished from its prototype except by the sense of touch. When you pick it gingerly from between your toes there is a malicious gleam in the pin-point black eyes, and then you understand that it is one of the many inventions designed for the torment of trespa.s.sers.

I have often sought specimens of this poor relation of the fish-shop window aristocrat, but invariably in vain, until I have found myself suddenly shouting "Eureka!" while balancing myself on one foot eager for the eas.e.m.e.nt of the other, and the giggling demeanour of the imp as it parts company with his spur gives a sort of comic relief to the thrilling sensations of the moment. Upon examination this imp seems to be an example of arrested development. Whimsical fate has played upon it a grim practical joke, flattering it primarily by resemblance to a grotesquely valorous unicorn, and then, having changed her mood to mere pettishness, finished it offhand by adding a section of semi-animate seaweed.

Although among the commonest of the species, the grey sand crab, which burrows bolt-holes in the beaches, is by no means an uninteresting character. Surrounded by enemies, and yet living on the bare, coverless beach, its faculties for self-preservation are exceptionally refined.

The eyes are elongated ovals, based on singularly mobile pivots, while the pupils resemble the bubble of a spirit-level. Not only is the range of vision a complete circle, but the crab seems able to concentrate its gaze upon any two given points instantly and automatically. To spite all its skill as a digger, to set at naught its superb visual alertness, the sand crab has a special enemy in the bird policeman which patrols the beach. Vigilant and obnoxiously interfering, the policeman has a long and curiously curved beak, designed for probing into the affairs of crabs, and unless the "hatter" has hastily stopped the mouth of its shaft with a bundle of loose sand--which to the prying bird signifies "Out! Please return after lunch!"--will be disposed of with scant ceremony and no grace, for the manners of the policeman are shocking.

This quick-footed sand-digger enhances its reputation by the performance of feats of subtlety and skill. Its bolt-hole is sometimes three feet deep, generally on an incline. Piled in a mound the spoil would inevitably betray the site of the operations to the policeman, thus seriously facilitating the duties of that official towards the suppression of the species. From remote depths the crab carries a bundle of sand. You remember the trenchant way in which Pip's sister cut the bread and b.u.t.ter, her left hand jamming the loaf hard and fast against her bib? Just so the crab with its bundle of loose sand, though it has the advantage in the number of limbs which may be pressed into service.

The feat of carrying an armful of sliding sand in proportion to bulk about one-third of the body, is far away and beyond the capacities of human beings, but to the crab, which has acquired the trick of temporary consolidation by pressure, it is merely child's play. Arrived at the mouth of the shaft, it elevates its eyes (which in the dark have rested in neatly fitting recesses) for the purpose of a cautious yet sweeping survey. Seeing nothing alarming, it emerges with the alertness of a jack-in-the-box, races several inches, and scatters the load broadcast as the sower of seed who went forth to sow. Then, as suddenly, the crab pauses and flattens itself--its body merging with its surroundings almost to invisibility--preparatory for a spurt for home. During these exertions the intellect of the crab has been concentrated for outwitting the vigilance of enemies, for the plodding policeman is not singular in appreciation. The lordly red-backed sea-eagle occasionally condescends to such humble fare, and the crab must needs be alert to evade the scrutiny with which the eagle searches the sand.

This pa.s.sing reference to the wit and deftness of the crab would be quite uncomplimentary in default of special notice of the plug of sand with which it stops its burrow. As a rule it is about an inch thick, and in content far more than a crab could carry in a single load. How does the creature, working from below and with such refractory material, so arrange that the plug shall be flush with the surface and sufficiently consolidated to retain its own weight? Of what art in loose masonry has the crab the unique secret? Shakespeare speaks of stairs of sand, and Poe laments the "how few" grains of golden sand which crept through his fingers to the deep; but who but a crab possesses the secret for the building of a roof of the material which is the popular emblem of instability and s.h.i.+ftiness?

The impartial student must not restrict his notions as to the possibilities of sand to the admirable accomplishments of crabs. He may also inspect with profit the handicraft of a lowly mollusc which agglutinates sand-grains into a kind of plaque, in the substance of which numerous eggs are deposited.

To attribute manual dexterity and a calculating mind to a mere crab, is, no doubt, an insult to the intelligence of those who "view all culogium on the brute creation with a very considerable degree of suspicion and who look upon every compliment which is paid to the ape as high treason to the dignity of man." But the truthful historian of the capabilities of crabs, the duty of one who stands sponsor to some of the species and who has the hardihood to indite some of the manifestations of their intelligence, wit, and craft, must discard the prejudices of his race, abandon all flattering sense of superiority, forbear the smiles of patronage, and contemplate them from the standpoint of fellows.h.i.+p and sympathy.

In this spirit he watches another expert digger which has a sharp-edged shovel affixed to the end of each of its eight legs, and is so deft in their use that it disappears in the sand on the instant of detection, without visible effort, and almost as quickly as a stone sinks in water.

Unless a crab is a giant in armour, or is endowed with almost supernatural alertness, or is an artist in the art of mimicry, or unless it cultivates some method of rapid disappearance, it has little chance of holding its own in the battle raging unceasingly over the vast areas of the Great Barrier Reef.

CHAPTER XVI

THE BLOCKADE OF THE MULLET

"Up with a sally and a flash of speed As if they scorned."

The rains which came at the New Year flooded all the creeks of the Island. Acc.u.mulations of sand usually form beds through which the sweet water slowly mingles with the salt, but with the violence and impetus of a downpour of ten inches during the night, each torrent had cut a channel, through which it raced from the seclusion of the jungle to the free, open sea. Twice in the twenty-four hours the impa.s.sive flowing tide subdued the impertinence of each of the brawlers, smothered its gurgling, and forced it back among the ferns and jungle and banana-plants which crowded its banks.