My Tropic Isle - Edmund James Banfield (little bear else holmelund minarik .txt) 📗

cluster of capsules is hollow and that water flushes it throughout. In appearance it resembles a combination of the pineapple and the corncob, and to the base a portion of the coral-stem to which it had been anchored by its considerate parent was firmly attached.

When the cluster of capsules (the substance of which is tough, semi-transparent, gelatine, opal-tinted, soon to be sea-stained a yellowish green) is slowly expelled from the parent's body--I have been witness to the birth--each contains about one-sixth ounce of vital element, fluid and glistening. Physical changes in this protoplasm manifest themselves in the course of a few days. The central portion becomes a little less fluid, and from an inchoate blur a resemblance to a diaphanous shell develops and floats, cloud-like, in a perfectly limpid atmosphere. Gradually it becomes denser though still translucent, as it seemingly absorbs some of the fluid by which it is surrounded. The model of the future animal, exact even to the dainty contours and furrows around that which represents the spire of the ultimate shell, is still without trace of visible organs. That, however, its substance is highly complex is obvious, for as imperceptible development progresses the exterior is transformed into a substance resembling rice tissue-paper--an infinitely fragile covering--which from day to day insensibly toughens in texture and becomes separate from the animal. Faint opaque, transverse ribs are at this stage apparent, though disappearing later on. Opacity is primarily manifested at the aperture of the infant mollusc where a seeming resemblance to an operculum forms, possibly for the protection of vital organs during nascency. This plaque of frail armour is, however, soon dismantled, and of course much more happens in the never-ceasing process than is revealed to the uninitiated.

As the calcareous envelope becomes opaque and solid, the animal within loses its transparent delicacy, and coincidentally the apex of the capsule opens slightly. In the meantime the fluid contents have disappeared, as if the animal had resulted from its solidification. The animal, too, is a very easy fit in its compartment, and incapable, in its extreme fragility of withstanding the pressure of a finger. Now it begins to increase rapidly in bulk and sturdiness; the shell becomes hard, and as the exit widens it screws its way out of a very ragged cradle, emerging sound and whole as a bee from its cell, all its organs equipped to ply their respective offices.

With pardonable affectation of vanity it has finally fitted itself for appearance in public by the assumption of three or four buff and brown decorations upon its milk-white shell, which quickly blend into a pattern varying in individuals, of blotches and clouds in brown, yellow, and white. In maturity the mollusc weighs several pounds, its shell has a capacity for as much as two gallons of water, and is coloured uniformly buff, while in old age infantile milk-white reasserts itself.

It is not for such as I am in respect of the teachings of science to say whether the development of the perfect animal from a few drops of translucent jelly--as free from earthly leaven as a dewdrop--is to be more distinctly traced, in the case of this huge mollusc than in other elementary forms. All that it becomes an unversed student of life's mysteries to suggest is that this example gives bold advertisement to the marvellous process.

Many of the secrets of life are written in script so cryptic and obscure that none but the wise and greatly skilled may decipher it, and they only, when aided by the special equipment which science supplies. In this case the firm but facile miracle is recorded in words that he that runs may read. Independent of microscope the unskilled observer may trace continuity in the transformation of jelly to life.

The sea-drop, lovely in its purity, knowing neither blemish nor flaw, becomes an animal with form and features distinctive from all others, with all essential organs, means of locomotion, its appetite, its dislikes, its care of itself, its love for its kind, its inherent malice towards its enemies--all evolved in a brief period from the concentrated essence of life.

"If, as is believed, the development of the perfect animal from protoplasm epitomises the series of changes which represent the successive forms through which its ancestors passed in the process of evolution" (these are the words of Professor Francis Darwin) what a graphic, what a luminous demonstration of evolution is here presented!

In a brief previous reference to this mollusc it was stated that the infants in their separate capsules were in a state of progressive development from the base to the apex of the cluster, those in the base being the farther advanced. Investigations lead to a revision of such statement. No favour seems to be enjoyed by first-born capsules. Development is equable and orderly, but as in other forms of life the contents of certain capsules seem to start into being with a more vigorous initial impulse than others, and these mature the more speedily. A sturdy infant may be screwing its way out of its cradle, while in a weakly and degenerate brother alongside the thrills of life may be far less imperative.

The pictures illustrate isolated scenes in the life-history of the mollusc, which in a certain sense offers a solution to, the conundrum stated by job "Who, hath begotten the drops of dew?"

PROTECTIVE COLORATION

July 17, 1909.

Found a small cowry shell of remarkable beauty on dead coral in the Bay. At first sight it appeared as a brilliant scarlet boss on the brown coral, and upon touching it the mantle slowly parted and was withdrawn, revealing a shell of lavender in two shades in irregular bands and irregularly dotted with reddish brown spots; the apertures were richly stained with orange, and the whole enamel exceedingly lustrous. Most of the molluscs of the species conceal themselves under mantles so closely resembling their environments as to often render them invisible. In this case the disguise assumed similitude to a most conspicuous but common object of anomalous growth, seeming to be a combination of slime and sponge.


CHAPTER XIV



SOME CURIOUS BIVALVES

Though certain species of molluscs have their respective habitats, and that which is considered rare in one part may be common in another, there are few which have not a general interest for the scientific conchologist. Collectors prize shells on account of their rarity and beauty; the man of science because of the assistance they afford in the working out of the universal problems of nature. Neither a collector nor a scientific student, my attitude towards marine objects is that of a mere observer--an interested and often wonder-struck observer--so that when I classify one species of mollusc as common and another as rare I am judging them in accordance with my own environment and information, not from a general knowledge of one of the most entertaining branches of natural history. From this standpoint I may refer to four or five species which stand out from the rest in interest and comparative rarity.

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 circumstances 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 butterfly, brick-red in colour, with an overshirt of fine and elaborate network, orange tinted. The interior is scarcely less attractive, the nacre having a pink and bluish lustre, while the "lip" is dark red. This is found (in my experience) only in association 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 shell, 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 encumbrances. In appearance the shell 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 illustrations of symbiosis, or the intimate association 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 lustrous 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 asserted 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 fashion. 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.