Page:Popular Science Monthly Volume 3.djvu/470

456 Mylius, in his treatise "De Animalium origine et migratione populorum" argues that, since there are innumerable species of animals in America which do not exist elsewhere, they must have been made and placed there by the Deity: Buffon no less forcibly insists upon the difference between the Fauna? of the Old and New World. But the first attempt to gather facts of this order into a whole, and to coordinate them into a series of generalizations, or laws of Geographical Distribution, is not a century old, and is contained in the "Specimen Zoologiæ Geographicæ Quadrupedum Domicilia et Migrationes sistens," published, in 1777, by the learned Brunswick professor, Eberhard Zimmermann, who illustrates his work by what he calls a "Tabula Zoographica," which is the oldest distributional map known to me.

In regard to matters of fact, Zimmermann's chief aim is to show that, among terrestrial mammals, some occur all over the world, while others are restricted to particular areas of greater or smaller extent; and that the abundance of species follows temperature, being greatest in warm and least in cold climates. But marine animals, he thinks, obey no such law. The Arctic and Atlantic Seas, he says, are as full of fishes and other animals as those of the tropics. It is, therefore, clear that cold does not affect the dwellers in the sea as it does land animals, and that this must be the case follows from the fact that seawater, "propter varias quas continet bituminis spiritusque particulas," freezes with much more difficulty than fresh water. On the other hand, the heat of the Equatorial sun penetrates but a short distance below the surface of the ocean. Moreover, according to Zimmermann, the incessant disturbance of the mass of the sea, by winds and tides, so mixes up the warm and the cold that life is evenly diffused and abundant throughout the ocean.

In 1810, Risso, in his work on the Ichthyology of Nice, laid the foundation of what has since been termed "bathymetrical" distribution, or distribution in depth, by showing that regions of the sea-bottom of different depths could be distinguished by the fishes which inhabit them. There was the littoral region between tide-marks with its sand-eels, pipe-fishes, and blennies; the sea-weed region, extending from low water-mark to a depth of 450 feet, with its wrasses, rays, and flat-fish; and the deep-sea region, from 450 feet to 1,500 feet or more, with its file-fish, sharks, gurnards, cod, and sword-fish.

More than twenty years later, MM. Audouin and Milne Edwards carried out the principle of distinguishing the Faunae of different zones of depth much more minutely, in their "Recherches pour servir à l'Histoire Naturelle du Littoral de la France," published in 1832.

They divide the area included between high-water mark and low-water mark of spring tides (which is very extensive, on account of the great rise and fall of the tide on the Normandy coast about St. Malo, where the observations were made) into four zones, each characterized by its peculiar invertebrate inhabitants. Beyond the fourth