soft enough to permit of trawling.

It is obvious that between the dredge, the trawl, and the tangles, there
is little chance for any organism, except such as are able to burrow
rapidly, to remain safely at the bottom of any part of the sea which the
_Challenger_ undertakes to explore. And, for the first time in the
history of scientific exploration, we have a fair chance of learning what
the population of the depths of the sea is like in the most widely
different parts of the world.

And now arises the next question. The means of exploration being fairly
adequate, what forms of life may be looked for at these vast depths?

The systematic study of the Distribution of living beings is the most
modern branch of Biological Science, and came into existence long after
Morphology and Physiology had attained a considerable development. This
naturally does not imply that, from the time men began to observe natural
phenomena, they were ignorant of the fact that the animals and plants of
one part of the world are different from those in other regions; or that
those of the hills are different from those of the plains in the same
region; or finally that some marine creatures are found only in the
shallows, while others inhabit the deeps. Nevertheless, it was only after
the discovery of America that the attention of naturalists was powerfully
drawn to the wonderful differences between the animal population of the
central and southern parts of the new world and that of those parts of
the old world which lie under the same parallels of latitude. So far back
as 1667 Abraham 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 Faunae 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
Zoologiae Geographicae 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 t