shell-fish gather together—­two or three varieties appear to browse upon the leaves and bark of the mangroves; some excavate galleries in the living trunks.  The insidious cobra does not wear any calcareous covering beyond the frail tiny bivalves which guard the head—­a scandalously small proportion of its naked length—­but lines its tunnels with the materials whence shell is made, smooth and white as porcelain.  How this delicate creature with less of substance than an oyster—­a mere worm of semi-transparent, stiff slime—­bores in hard wood along and across the grain, housing itself as it proceeds, and never by any chance breaking in upon its neighbours, though the whole of the trunk of the tree be honeycombed, savours of another wonder.  Authorities consider the bivalve shell too delicate and frail to be employed in the capacity of a drill, and one investigator has come to the conclusion that the rough fleshy parts of the animal, probably the foot or mantle, acting as a rasp, forms the true boring instrument.  Thus, the skill of a worm in excavating tunnels in wood puzzles scientists; and the cobra is certainly among the least conspicuous of the denizens of a mangrove swamp, and perhaps far from the most wonderful.

The most remarkable if not the strangest denizens of the spot are two species of the big-eyed walking and climbing fish (PERIOPHTHALMUS KOELREUTERI and P. Australis) which ascend the roots of the mangrove by the use of ventral and pectoral fins, jump and skip on the mud and over the surface of the water and into their burrows with rabbit-like alertness.  They delight, too, in watery recesses under stones and hollows in sodden wood.  Inquisitive and most observant they might be likened to Lilliputian seals, as they cling, a row of them, to a partially submerged root, and peer at you, ready to whisk away at the least sign of interference.  They climb along the arching roots, the better to reconnoitre your movements and to outwit attempts at capture.  Their eyes—­in life, reflecting gems—­are so placed that they command a complete radius, and if you think to sneak upon them they dive from their vantage points and skip with hasty flips and flops to another arching root, which they ascend, and resume their observation.  It must not be assumed that the climbing fish—­which seems to be more at home on the surface of the water than below—­climbs up among the branches.  A foot or so is about the limit of its upper wanderings.

Then, too, in what is generally regarded as a noisome, dismal, mangrove swamp, birds of cheerful and pleasing character congregate.  Several honey-eaters, the little blue turtle dove, the barred-shouldered dove, the tranquil dove, the nutmeg pigeon, the little bittern, the grey sandpiper, the sordid kingfisher, the spotless egret, the blue heron, the ibis—­all and others frequent such places, and in their season, butterflies come and go.  In most of its aspects a mangrove swamp is not only the scene of one of Natures most vigorous and determined processes, but to those who look aright, a theatre of many wonders, a museum teeming with objects of interest, a natural aviary of gladsome birds.