Still, though the whole ocean teems with life, both animals and plants are most abundant near the coast. Air-breathing animals, whether mammals or insects, are naturally not well adapted to live far from dry land. Even Seals, though some of them make remarkable migrations, remain habitually near the shore. Whales alone are specially modified so as to make the wide ocean their home. Of birds the greatest wanderer is the Albatross, which has such powers of flight that it is said even to sleep on the wing. Many Pelagic animals--Jelly-fishes, Molluscs, Cuttle-fishes, Worms, Crustacea, and some true fishes--are remarkable for having become perfectly transparent; their shells, muscles, and even their blood have lost all colour, or even undergone the further modification of having become blue, often with beautiful opalescent reflections. This obviously renders them less visible, and less liable to danger. The sea-shore, wherever a firm hold can be obtained, is covered with Sea-weeds, which fall roughly into two main divisions, olive-green and red, the latter colour having a special relation to light. These Sea-weeds afford food and shelter to innumerable animals. The clear rocky pools left by the retiring tide are richly clothed with green sea-weeds, while against the sides are tufts of beautiful filmy red algae, interspersed with Sea-anemones,--white, creamy, pink, yellow, purple, with a coronet of blue beads, and of many mixed colours; Sponges, Corallines, Starfish, Limpets, Barnacles, and other shell-fish; feathery Zoophytes and Annelides expand their pink or white disks, while here and there a Crab scuttles across; little Fish or Shrimps timidly come out from crevices in the rocks, or from among the fronds of the sea-weeds, or hastily dart from shelter to shelter; each little pool is, in fact, a miniature ocean in itself, and the longer one looks the more and more one will see. The dark green and brown sea-weeds do not live beyond a few--say about 15--fathoms in depth. Below them occur delicate scarlet species, with Corallines and a different set of shells, Sea-urchins, etc. Down to about 100 fathoms the animals and plants are still numerous and varied. But they gradually diminish in numbers, and are replaced by new forms. To appreciate fully the extreme loveliness of marine animals they must be seen alive. "A tuft of Sertularia, laden with white, or brilliantly tinted Polypites," says Hincks, "like blossoms on some tropical tree, is a perfect marvel of beauty. The unfolding of a mass of Plumularia, taken from amongst the miscellaneous contents of the dredge, and thrown into a bottle of clear sea-water, is a sight which, once seen, no dredger will forget. A tree of Campanularia, when each one of its thousand transparent calycles--itself a study of form--is crowned by a circlet of beaded arms, drooping over its margin like the petals of a flower, offers a rare combination of the elements of beauty.