e
disintegrated by the action of the atmosphere and the waters; the
sediment deposited in the bottom of the seas was thrown to the surface;
continents were enlarged, higher mountain ranges upheaved, the coasts
worn into greater irregularity of outline; and everywhere the soil
became more composite, the surface more uneven, the landscape more
variegated.

Corresponding changes have taken place in the climate. At first the
temperature of the earth was much warmer than now, and uniform in all
parallels of latitude, as is shown by the fossil remains. Now we have a
great diversity of climate, whether we contrast the polar with the
torrid regions, or the different seasons of the temperate zone with each
other.

The same law of increasing diversity obtains in the fauna and flora of
the various periods of geological history. The earliest fossil record of
animal life is witness to the simplicity of organic structure. Among
vertebrated animals, fishes first appear, next reptiles, then birds;
still higher, the lower type of animals which suckle their young; and as
the strata become more recent, still higher forms of mammalia, till we
reach the upper tertiary, in which geologists have discovered the
remains of many animals of complex structure nearly allied to those
which are now in existence. In the historic period appear many organic
forms of still greater complexity, with man at the head of the
zoological series.

In this glance of zoological progress, we discover increasing
complication of two kinds; for while the individual structure has been
constantly becoming more complex, there are now in existence the
analogues of the lowest fossil types, which, with the highest, and with
all the intermediate, present a maze and vastness of complication,
which, in comparison with the homogeneity of the aggregate of early
structure, is sufficiently obvious and impressive.

There is in this view, still another outline of increasing complexity.
At first the same types prevailed all over the earth's surface; but as
the soil, atmosphere, and climate changed, and the animal structure
became more complex and varied, the limits of particular species became
more and more localized, till the earth's surface presented zoological
districts, with the fauna of each peculiar to itself.

But, what of unitization? Here, there appears to be divergence only, and
that continually increasing.

Guyot says that 'the unity reappears with the creation of