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ME'I HODS OF OCEANOGRAPHÏCAL RESEARCH
269
from the sea near Plymouth.
It Was thought that this
represented a true picture of the density of population
until an ingenious laboratory method for counting the
organisms present was devised.
In the laboratory half
a cubic centimetre of water taken from
was added
to a large volume of sterilized sea water.
This large
volume was then divided into seventy parts, each of which
was put into a separate ask.
These seventy
were
then allowed to stand for several days; and on examination
it was found that “ cultures ” of various organisms had
.
grown in them.
On the assumption. that each culture of
each species must have sprung from at least one individual
.
of its kind, which must have been present in the original
half cubic centimetre, it was found that the original
number Of orgaisms present in the sea' water was at least
464-per cubic centimetrè—a considerable advance on the
f0urteen
found by the centrifuge method, which was
evideny not fully efcient.
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