Nor have we any
right to suppose that the seas of the world have always been so freely open
from south to north as they are at present. 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 considerations, 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 knowledge effected by the discoveries of
the last dozen years, it seems to me to be about as rash to dogmatize on
the succession of organic forms throughout the world, as it would be for a
naturalist to land for five minutes on a 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 more serious. I
allude to the manner in which species belonging to several of the main
divisions of the animal kingdom 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 are descended from a single
progenitor, apply with equal force to the earliest known species.
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