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intermediate torrid regions. In the admirable "Introduction to the Flora
of New Zealand," by Dr. Hooker, analogous and striking facts are given
in regard to the plants of that large island. Hence, we see that certain
plants growing on the more lofty mountains of the tropics in all parts
of the world, and on the temperate plains of the north and south, are
either the same species or varieties of the same species. It should,
however, be observed that these plants are not strictly arctic forms;
for, as Mr. H.C. Watson has remarked, "in receding from polar toward
equatorial latitudes, the Alpine or mountain flora really become less
and less Arctic." Besides these identical and closely allied forms, many
species inhabiting the same widely sundered areas, belong to genera not
now found in the intermediate tropical lowlands.

These brief remarks apply to plants alone; but some few analogous facts
could be given in regard to terrestrial animals. In marine productions,
similar cases likewise occur; as an example, I may quote a statement
by the highest authority, Prof. Dana, that "it is certainly a wonderful
fact that New Zealand should have a closer resemblance in its crustacea
to Great Britain, its antipode, than to any other part of the world."
Sir J. Richardson, also, speaks of the reappearance on the shores of New
Zealand, Tasmania, etc., of northern forms of fish. Dr. Hooker informs
me that twenty-five species of Algae are common to New Zealand and to
Europe, but have not been found in the intermediate tropical seas.

From the foregoing facts, namely, the presence of temperate forms
on the highlands across the whole of equatorial Africa, and along the
Peninsula of India, to Ceylon and the Malay Archipelago, and in a less
well-marked manner across the wide expanse of tropical South America, it
appears almost certain that at some former period, no doubt during
the most severe part of a Glacial period, the lowlands of these great
continents were everywhere tenanted under the equator by a considerable
number of temperate forms. At this period the equatorial climate at the
level of the sea was probably about the same with that now experienced
at the height of from five to six thousand feet under the same latitude,
or perhaps even rather cooler. During this, the coldest period, the
lowlands under the equator must have been clothed with a mingled
tropical and temperate vegetation, like that described by Hooker as
growing luxur