"
The greater number of the oceanic microscopic forms hitherto discovered have
been silicious-shelled, although the analysis of sea water does not yield
silica as the main constituent, and it can only be imagined to exist in it
in a state of suspension. It is not only at particular points in inland
seas, or in the vicinity of the land, that the ocean is densely inhabited by
living atoms, invisible to the naked eye, but samples of
p 343
water taken up by Schayer on his return from Van Diemen's Land (south of the
Cape of Good Hope, in 57 degrees latitude, and under the tropics in the
Atlantic) show that the ocean in its ordinary condition, without any
apparent discoloration, contains numerous microscopic moving organisms,
which bear no resemblance to the swimming fragmentary silicious filaments of
the genus Chaetoceros, similar to the Oscillatoriae so common in our fresh
waters. Some few Polygastria, which have been found mixed with sand and
excrements of penguins in Cockburn Island, appear to be spread over the
whole earth, while others seem to be peculiar to the polar regions.*
[footnote] *See Ehrenberg's treatise 'Ueber das kleinste Leben im Ocean',
read before the Academy of Science at Berlin on the 9th of May, 1844.
[Dr.
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