The molluscs are no less profusely scattered over the tropical seas and coasts than the higher organised crustaceans. There we find those mighty cephalopods, whose long fleshy processes, as thick as a man’s thigh, are able, it is said, to seize the fisherman in his boat and drag him into the sea; and there is the abode of the tridacna, whose colossal valves, measuring five feet across, attain a weight of five hundred pounds, and serve both as receptacles for holy water in Catholic churches and to collect the rain in the South Sea Islands. The rarest and most beautiful of shells, the royal Spondylus, the Carinaria vitrea, the Scalaria pretiosa, the Cypræa aurora, and a host of Volutes, Harps, Marginelles, Cones, &c., of the most exquisite colouring, are all inhabitants of the warmer waters; and the most costly gift of the sea, the oriental pearl, is the produce of a mollusc which is found scattered over many parts of the Indian and Pacific Oceans. On descending still lower in the scale of marine life, we find the jelly-fish disporting in the tropical waves in hosts as brilliant as the skies. Some are formed like a mushroom, others assume the shape of a belt or girdle; others are globular, while some are circular, flat, or bell-shaped; and others again resemble a bunch of berries. In colour, perhaps the most delicate is the lovely Velella, with its pellucid crest, its green transparent body and fringe of purple tentacles; but it is surpassed in size and gorgeousness by the Physalia, or ‘Portuguese man-of-war,’ whose large air-sack, with its splendid vertical comb, shines in every shade of purple and azure. The greatest marvels of the tropical ocean are, however, beyond comparison, the wondrous buildings of the Lithophytes, or stone polyps, the reefs and coral islands. Here we see them forming vast barriers which fringe the shores for hundreds and hundreds of miles; there they rise in circular atolls over the blue waves, like bridal rings dropped from the heavens upon the surface of the seas. All is wonderful in these amazing constructions--their puny architects, the lagoons they encircle, the power with which they resist the most furious breakers, the little world of plants drifted over the waters, which ultimately covers them with a verdant crown, and invites man to settle on these gardens of the ocean. There the tall cocoa-palm rocks its feathered crest in the breeze, affording both shade and fruit to the islander, and there the sea-bird finds a resting-place after its wide flight over the deserts of the equatorial sea. [Illustration: POLYNESIAN FISHERMEN.] CHAPTER XXII. THE PAPUANS AND POLYNESIANS.