Even at this day, if the Malay Archipelago were converted
into land, the tropical parts of the Indian Ocean would form a large
and perfectly enclosed basin, in which any great group of marine
animals might be multiplied; and here they would remain confined,
until some of the species became adapted to a cooler climate, and were
enabled to double the southern capes of Africa or Australia, and thus
reach other and distant seas.
From these and similar considerations, but chiefly from our ignorance
of the geology of other countries beyond the confines of Europe and
the United States; and from the revolution in our palaeontological
ideas on many points, which the discoveries of even the last dozen
years have effected, it seems to me to be about as rash in us to
dogmatize on the succession of organic beings throughout the world, as
it would be for a naturalist to land for five minutes on some one
barren point in Australia, and then to discuss the number and range of
its productions.
ON THE SUDDEN APPEARANCE OF GROUPS OF ALLIED SPECIES IN THE LOWEST
KNOWN FOSSILIFEROUS STRATA.
There is another and allied difficulty, which is much graver. I allude
to the manner in which numbers of species of the same group, suddenly
appear in the lowest known fossiliferous rocks. Most of the arguments
which have convinced me that all the existing species of the same
group have descended from one progenitor, apply with nearly equal
force to the earliest known species.
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