hat
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 sea water, "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 _seaweed 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 1500 feet or more, with
its file-fish, sharks, gurnards, cod, and sword-fish.

More than twenty years later, M.M. 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 a l'Histoire
Naturelle du Littoral de la France," published in 1832.

They divide the area included between highwater-mark and lowwater-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 their
observations were made) into four zones, each characterized by its
peculiar invertebrate inhabitants. Beyond the fourth region they
distinguish a fifth, which is never uncovered, and is inhabited by
oysters, scallops, and large starfishes and other animals. Beyond this
they seem to think that animal life is absent.[3]

[Footnote 3: "Enfin plus has encore, c'e