PART OP THE GREAT BARRIER REEF OF AUSTRALIA.

Chiefly composed of star-corals, many cf them resembling human skulls. The Great Barrier Reef of Australia, consisting of innumerable detached reefs and coral-islets, is over 1,200 miles in length. 759

of the Worldy6o The Living Animals

its tropical allies. The Australian coast produces giant species which may measure no less than from 18 inches to 2 feet across their expanded disks. These giant anemones are further interesting on account of the circumstance that they are self-constituted "harbours of " refuge to sundry species of fishes and crabs, which nestle among their tentacles like birds in a leafy bower. The anemones are themselves bright in colour, but the associated fishes are even more so. In an example which was photographed by the writer on the Western Australian coast, the anemone was olive-green, with the tips of the tentacles bright mauve. The fishes, of which three examples were present, were brilliant orange-scarlet with white bands. In addition to the fishes a small flat-clawed crab shared the sheltering hospitality of the anemone. Some of the tropical coral-reef-frequenting anemones, which have their tentacles beautifully branched, must be cautiously handled, in consequence of their notable stinging properties. All sea-anemones and corals are, in fact, provided with peculiar stinging-cells, with which they benumb and thus make an easy capture of the living organisms on which they prey. While the majority of the sea-anemones live single or individually separate lives, there are some which form aggregations or colony-stocks of numerous units. These compound growths are brought about by repeated budding, or the sub-division or fission, without , of an originally single individual. It complete separation, is by a similar process of recurrent sub-division that the wonderful fabrications of the coral-polyps are built up. An ordinary coral-animal or polyp, as previously

Photo ly W. SavMe-Kent, F.Z.S., Mtlford-on-Sea.

PORTION OF A STAG'S-HORN CORAL.

Each minute circular cell represents the situation in life of a small sea-anemone-like anima], or coral-polyp. stated, differs in no respect from a sea-anemone, excepting for the possession of a calcareous skeleton secreted within its basal tissues, including portions of the membranous radiating partitions. Some coral-animals, like the majority of the Anemones, are solitary, and form single attached or loosely lying corals. The well-known MUSHROOM-CORAL is one of the latter. One species observed, which was photographed through the water by the writer as it lay expanded in a tide- Pkotoby W. Saville-Kent. F.Z.S.] [Mllford-on-Sea. pool on the Australian Great A CLUMP OF STAG'S-HORN CORAL. Barrier Reef, might easily be The life-colours of this coral are a delicate cream with brilliant magenta tips.

Corals, Sea-anemones, and Jelly-fishes 761

itmistaken for a big sea-anemone allied to the dahlia-anemone. On being disturbed, however, immediately shrinks back upon its base, ejecting all the water with which its expanded tissues were filled, and revealing the presence of the hard radiating coral beneath. Each of the calcareous radii, which are now cleai'ly defined through the thin semi-transparent skin, corresponds in position with one of the internal membranous partitions, and also with the origin of one of the tentacles. off from the parent, which attach themselvesNew mushroom-corals are produced as buds thrown and secrete a foot-stalk, to which they remain affixed, like the young of the feather star-fish, for the earlier epoch of their existence. Ultimately, however, they become detached, and, falling from their stalks, lie loosely on the sea-bottom, after the manner of their parents. The huge

Photo by W. Saville-Kent, y.Z.S. [Milfonl-on-Sea.

BLEACHED CORALS FROM THE GREAT BARRIER REEF.

Branching stag's-horn corals are chiefly represented in this group. Several of the large solitary mushroom-corals may, however, be observed in the foreground.

coral-masses commonly known as MADREPORES, out of which coral-islands and reefs are constructed, all commence as a single coral-animal, with its contained skeleton analogous to the coral-mushroom-coral, though in all instances much smaller. The buds developed by the polyp in these instances remain attached to the parent. If they spread out laterally, the}' build up by accumulation the large flattened or sub-spherical masses known as BRAIN- CORALS and STAR-CORALS, which are most abundant on coast-line reefs, or form the bases of the outer barrier-reefs. Where, on the other hand, the budding is terminal or oblique, branching tree-like growths such as the STAG'S-HORN CORALS, with their innumerable allies and variations, are produced. The colours of the coral-polyps are as brilliant and diverse as those of ordinary sea-anemones, living reefs, whereon a number of different species are 90

of the World762 The Living Animals

in & condition of healthy growth, yielding a spectacular effect that vies with that of any floral parterre. Sometimes large areas, acres upon acres in extent, may be covered with one almost uniform purple, green, brown, or other coloured growth of the branching stag's-horn is not unlike that of a heath-covered common.species. The aspect presented

In addition to the solid, calcareous-skeletoned Madrepores, or "Stony Corals," as they are often termed, there are a number of species in which a skeleton composed only of loosely aggregated calcareous spicules is produced. The so-called

-^FLEXIBLE CORALS, or SEA-FANS,

belong to this category, as also the precious CORAL OF COMMERCE. In the last-named species the solid, brilliantly coloured skeleton so much prized as an article of jewellery is deposited as a supplementary basis outside the tissues by which the star-patterned skeletons of the stony corals are secreted. A group which demands brief notice is that of the HYDROID POLYPS. These include the majority of the JELLY-FISHES, a few coral-secreting species, and the organisms whose seaweed-like horny skeletons, known as SEA- FIRS, are, in common with those of Sea-mats, included among the flotsam and jetsam on every sea-beach. In the Photo by W. Savillc-Kcnt, F.Z.S.} [Milford-on-Sea.

COMMON HYDRA, or FRESH- A QUEENSLAND STAR-CORAL.

WATER POLYP, an exceptional This species in life is of a pale lemon-yellow tint. fresh-water representative of this group is presented. It may be likened to a tiny sea-anemone, having, when extended, a slender foot-stalk and long thread-like tentacles. Like a sea-anemone, it will shrink up is more simple than that of when disturbed into a mere button of jelly. Its organisation the anemone, its body-cavity being a simple sac, without any intucking of the orifice, or strengthening by supplementary membranous partitions. A similar simple structural plan is characteristic -of all the organisms belonging to the series. An interesting phenomenon connected with the fresh-water hydra is the circumstance, demonstrated now over a century ago, that, if one of these animals be cut up into little pieces, each separate fragment is capable of repairing itself and growing into a new polyp. first sight to possess but The JELLY-FISHES, or MEDUSAS, arid their allies would appear at little structurally in common with the Coral-polyps and Sea-anemones. In their most familiar form they are represented by a more or less translucent bell-shaped body, which drifts with the current or propels itself through the water by its alternate expansions and contractions. In the centre of the lower surface, occupying the position of the bell's clapper, a polyp-like, circle of tentacles, tubular mouth is usually discernible, and this is frequently surrounded by a sometimes simple and sometimes elaborately ramified. Long, thread-like tentacles are also commonly developed around the margin of the swimming-bell.

Corals, Sea-anemones, and Jelly-fishes 763 a3 The larger number of the jelly-

| fishes are, as a matter of fact,

transitional phases only of the fixed hydroid polyps previously referred to. i In certain instances the body of the

| fixed polyp becomes elongated, and

splits up horizontally into a series

| of jelly-fishes, or medusas, resembling

a pile of saucers, which consecutively

| break away and lead a free-roving

al existence. In other forms a compound tree-like growth gives birth {to medusa-like buds, like the flowers on a plant, which ultimately become detached and swim away. What are known as the CoMB-BEARING JELLY-FISHES—their locomotive organs consisting of comb-like bands of vibratile hairs—are especially noteworthy. -In some of these the body From 18 inches to 2 feet in diameter when expanded. Bright apple-green in is nearly spherical oh EAE, one of colour, and with almost spherical bead-like tentacles. the species, in reference to its shape, being popularly known as the SEa- LEMON. A notable feature of these medusas is their remarkable glass-like transparency, their presence in the water in many instances being recognisable only by the prismatic glimmerings of their rows of vibratile hairs when the light falls upon them at a favourable angle. The most remarkable member of this particular group is undoubtedly the form known as Venus’s GirDLE. This species takes. the form of a long, ribbon-like band of transparent jelly. The edges of the ribbon are clothed with vibratile hairs, and the mouth is situated in the centre of one of the edges. The animal progresses by the action of its hairs alone, or may be assisted by the twistings and undulations of its ribbon-like body. Many jelly-fishes possess an unenviable reputation with reference to their stinging properties. The so-called PorTUGUESE Man-or-war is one of the more noteworthy of these. - ers": = 4 The organism consists of an ovately eee geome rae a ae pointed air-bladder, which floats on numerous nutritive polyps and a mass _ in search of food, but always return to shelter among the anemone's tentacles. Photo-of capturing-filaments, or tentacles. ierepu caban turoun Chelwater: —t Photo by W. Saville-Kent, F.Z.S.] [Milyord-on-seu.

A GIANT ANEMONE FROM THE GREAT BARRIER REEF.

A GIANT SEA-ANEMONE.

The Living Animals of the World

CHAPTER VII.

SPONGES AND ANIMALCULES.

as a group standing on the borderland rTIHE SPONGES are regarded i between the Polyps and the lowly organisms which follow. The familiar BATH- and TOILET-SPONGES of commerce represent but an insignificant fraction in comparison with the many hundred species which find no place in the world's market. Toilet-sponges owe their intrinsic value to the relative fineness and elasticity of their component fibrous skeletons. In these particular species the skeleton is composed of a substance akin to horn. In other sponges the skeleton may consist of horny fibres mixed with flinty spicules, or it may be of flint only, or of spicules of carbonate of lime. Finally, there are sponges which possess no internally supporting skeleton, fibrous or spicular, and whose substance is consequently little more than gelatinous. All these numerous forms, however, agree with one another in the identity of their most essential vital elements. In the living sponge the skeleton, fibrous or otherwise, is embedded within a gelatinous matrix by whose component cells it is excreted. Externally the sponge-body is perforated over the greater portion of its extent by minute holes or pores, while one or more holes of relatively large size occupy the summit of the sponge, or are scattered here and there among the numerous smaller pores. The smaller pores represent incurrent apertures, and lead to chambers

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