Very learned men, in former days, have
even entertained the notion that all the formed things found in rocks
are of this nature; and if no such conception is at present held to be
admissible, it is because long and varied experience has now shown
that mineral matter never does assume the form and structure we find
in fossils. If any one were to try to persuade you that an oyster-shell
(which is also chiefly composed of carbonate of lime) had crystallized
out of sea-water, I suppose you would laugh at the absurdity. Your
laughter would be justified by the fact that all experience tends to
show that oyster-shells are formed by the agency of oysters, and in no
other way. And if there were no better reasons, we should be justified,
on like grounds, in believing that Globigerina is not the product of
anything but vital activity.
Happily, however, better evidence in proof of the organic nature of the
Globigerinae than that of analogy is forthcoming. It so happens that
calcareous skeletons, exactly similar to the Globigerinae of the chalk,
are being formed, at the present moment, by minute living creatures,
which flourish in multitudes, literally more numerous than the sands of
the sea-shore, over a large extent of that part of the earth's surface
which is covered by the ocean.
The history of the discovery of these living Globigerinae, and of the
part which they play in rock building, is singular enough.
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