All these, during the long ages since they first started in life, have been learning to make use of some area in the wide expanse of water spread over our globe, and it remains for us now to see how they have succeeded. Where shall we make our start? If we begin at home in the rivers we should have to work, as it were, backwards, for the sea is the chief home of fishes, and the rivers only the refuge of a few stray kinds. The sea-shore would be, perhaps, our truest starting-point, but then we should have to travel two different ways. Will it not be best to dive down first into the silent depths of the ocean, and learn what little is known of those which have taken refuge there? Thence we can rise up to the open sea, from there swim in to the shore, and then up the rivers and back to our own land-home. It makes but little difference where we take our plunge into the deep sea, for changes of climate are scarcely or not at all known there, and the fish seem to wander over every part. Wherever it may be, then,--let us say in the seas of the Tropics, which have given us most of our specimens--let us dive down, down, till we reach about 1800 feet (300 fathoms). ... “For who can know What creatures swim in secret depths below, Unnumber’d shoals glide thro’ the cold abyss Unseen, and wanton in unenvied bliss.” We shall be groping more and more in darkness as we go, for the sunlight scarcely reaches beyond 1000 feet, and we have left its last rays behind us, and the water is growing icy cold. How strange, then, that the first fish we meet should have large wide-open eyes! This is the Beryx,[25] shaped something like a perch, but about a foot and a half long, and genealogists ought to look at him with respect, for his ancestors (see heading of Chapter) are almost the oldest known bony fish, and lived in the chalk seas. Has he come down here because the upper world was too rough for him? If so, he has found comparative stillness, for he is far beneath the turmoil of the waves, and only the slowly creeping currents make any movement around him. But he has not escaped from the struggle for life, for not only is a good-sized shark coming his way, but a huge monster of the bony race, six feet long,[25] with wide-opened jaw, sharp pointed teeth, and large keen eyes, is wandering near in search of prey, devouring large and small fish with great impartiality.