For some years Forbes's theory was very generally accepted, and the results of Darwin's and Dana's investigations, showing that corals could not live beyond a depth of fifteen fathoms, seemed to confirm it. But, quite recently, facts derived from new and unlooked-for sources of information have given a check to this theory. Commerce has come to the aid of science (rewarding her for the gift first received at her hands), and the telegraph cables, alive with the secrets of sea and land, have brought us tidings from the deep. Dr. Wallich, the naturalist who in 1860 accompanied the expedition to explore the bed of the Atlantic, previous to laying the telegraphic cable, first called attention again to this subject. He brought up various animals, highly organized, from a depth of about nineteen hundred fathoms.
Yet, in spite of this positive evidence added to the former observations of Ehrenberg, and to those of Sir James Ross, who, in the Antarctic Sea, brought up an Euryale on a sounding-line from a depth of eight hundred to a thousand fathoms, naturalists were slow to believe that the distribution of animal life in the ocean was not limited to the shallow depths assigned by Edward Forbes. In the Mediterranean and in the Red Sea, from depths of eighteen hundred to two thousand fathoms, living animals have been brought up on the telegraph wires, not of doubtful infusorial character, hovering on the border-land between animal and vegetable life, but of considerable size, as, for instance, one or two kinds of Crustacea, Cockles, stocks of Bryozoa and tubes of Annelids. When the cable between France and Algiers was taken up from a depth of eighteen hundred fathoms, there came with it an Oyster, Cockle-shells, Annelid tubes, Bryozoa and Sea-fans. As these animals were growing upon it, there could be no doubt that they had their normal life and development at this depth, and since they are carnivorous, they tell also of the existence of other animals with them on which they feed.
The dredge, which thus far has played an important part in zoölogical researches, is destined to revolutionize many of our accepted theories, if we can judge of its future by the brilliant results of the last few years.
From 1861 to the present time the Swedish government has sent several expeditions to Spitzbergen and Greenland. They carried on dredging operations most successfully to a depth of twenty-six hundred fathoms. For some years past Lovén, Koren, and Danielssen, the elder and younger Sars, and other Scandinavian naturalists, have made systematic dredgings along the coast of Norway, which, though not extending below four hundred fathoms or thereabouts, have yet furnished most astounding results.
The United States Coast Survey has, in connection with an exploration of the Gulf Stream, been the first to establish a systematic series of dredgings at great depths, continued during several years. The results have proved conclusively that there exists everywhere, in the deep sea, modified, of course, according to the nature of the bottom and the temperature, a most varied fauna, totally distinct from that characteristic of the shores and of shallower waters. Since 1867 Count Pourtales has had charge of these investigations, first established many years ago by Professor Bache and continued by his successor Professor Peirce. He has dredged across the Gulf Stream between Florida and Cuba to a depth of about seven hundred fathoms, collecting an immense number of marine animals entirely unknown before, and characteristic of the different belts of depth, having a most extraordinary geographical distribution, many of the species being found in Florida, the Azores, the Faroe Islands, and the west coast of Norway.
The English Admiralty has for two summers detailed a vessel admirably fitted for such purposes, intrusting the scientific direction of the expedition to Dr. Carpenter, Professor Thomson, and Mr. Jeffreys. Their dredgings, carried on to the enormous depth of two thousand four hundred and thirty-five fathoms, have in every respect corroborated the conclusions drawn from the collections made by Count Pourtales and the Scandinavian naturalists, who, not content with so thoroughly exploring their own coast, have even sent a ship of war to dredge across the whole Atlantic.
These discoveries only show how much yet remains to be done before we shall fully understand the laws of marine life. But we already have ample evidence that the same beneficent order controls the distribution of animals in the ocean as on land, appointing to all its inhabitants their fitting home in the dim waste of waters.