CHAPTER XIII
ANIMAL LIFE IN THE SEA
The primitive idea of the ocean was that it was a vast desert, and a strange disbelief in its being inhabited by more than the very few forms that everybody was compelled to recognize persisted up to quite modern times among those who should have known better. Pliny boldly asserted, for example, that nothing remained in the Mediterranean Sea unknown to him after he had made a list of 176 marine animals! But now we know that the sea teems with living beings as densely as do the fresh waters or the air. In it began the life of the globe, for the fossil records of the rocks show that the first animals lived in the ocean, and that ages passed before any of them began to people the newly formed lands and breathe the atmosphere instead of the air in the water; and, abundant as oceanic life now is, the paleozoic seas held immensely greater hordes, of which many forms were giants as compared with those of our day. Some of the old straight chambered shells were twelve feet long; and I have seen fossil ammonites, extinct relatives of our coiled pearly nautilus, which when alive must have been too heavy for a man to lift. The fishes, too, could tell great stories of the glory of their ancestors in size and strength and numbers. Some of them wore solid coats of mail upon their heads, and could do battle even with the huge swimming reptiles that were the dreaded tyrants of the Mesozoic deep.
Life in the ocean in those old geologic days was a long guerrilla warfare—every animal guarding against attack, and at the same time watching sharply for an opportunity to seize and prey upon some weaker companion. As for the foraminifers and other microscopic creatures, they were countless, and their skeletons, singly invisible, have by accumulation built up great masses of rock, like the chalk-beds of England and France.
Though lessened in numbers and reduced in size, because the land has gradually won over to its side many sorts of animals which in former ages were exclusively confined to the water, and for other reasons, the sea still holds its share of every “branch” and “class” (except birds, and it may almost claim some of them, such as the albatross, penguins, and petrels), and a majority of the “orders” of animal life. Glance at the catalogue: Foraminifers, sponges, and polyps are chiefly confined to salt water; starfishes, urchins (or sea-eggs), and the like, wholly so: mollusks (next higher) are principally oceanic, and the majority of the crabs inhabit salt water. Among the last-named one species, the common horse-foot (Limulus) of our shores, remains as the solitary representative of that immense and varied group, the trilobites, which so crowded the Paleozoic sea-bottom that some rocks—for instance, the limestones of Iowa—are packed almost as full of their fossils as is a raisin-box of raisins.
None of the insects is truly marine, yet some of them are seafaring, truly, for they spend their lives on drifting sea-wrack, or on beaches just out of reach of the tides; but most of the true worms are dwellers in the mud of sea-shores and sea-bottoms. No one knows of any land fishes; but I need not tell you that fishes throng in the fresh waters as well as in the salt, and that many species inhabit both at different seasons.
In respect to the reptiles, of which the ancient oceans contained gigantic and horrid types, I do not know any now that are truly oceanic except the turtles, if you leave out the “sea-serpent,” of which we hear so many wonderful and not quite satisfactory tales. You will hear of “sea-snakes” in the East Indies, but they are only certain kinds of serpents which swim well, and pass the most of their time in the salt water, as several species of our own country do in the rivers and ponds; all the oriental sea-snakes are venomous.
It is in this manner, too, that we may count certain birds, such as the petrels, auks, penguins, albatrosses, frigate-birds, and their kin, as belonging to the ocean. They spend all their life flying over the waves, seeking their food there, and some of them rarely go ashore, except to lay their eggs and hatch their young on remote rocks, resting and sleeping on the billows, when not busy at their hunting. In the highest rank of all, however, the mammals, several families are natives of the “great deep”—the whales, dolphins, and porpoises, the seals and walruses, and the manatees and dugongs. But all these must come to the surface to breathe, not having gills like fishes, but true lungs.
As it is only within the last thirty years that machinery suitable for deep-sea dredging has been invented, so it is only lately that we have been able to learn much as to the population of the ocean beneath the surface layer and marginal shallows. Now by means of beam-trawls, dredges, tangle-bars, etc., worked by steam-machinery on shipboard, naturalists may scrape up the bottom-ooze and obtain living objects or their bony relics at the depth of even 3000 to 4000 fathoms or more than four miles, for living beings are found in these profound abysses. Many scientific expeditions, such as those of the English exploring steamer Challenger, about 1874, have carried out these dredging investigations, and the United States Fish Commission possesses the large, specially built, sea-going Albatross, provided with all the necessary apparatus for deep-sea exploration. By means of these and other vessels an enormous amount of study—all useful in ascertaining the habits and methods of reproduction of food-fishes—has been carried on by American marine naturalists.