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The ability of filter feeders to discriminate between particles of different kinds was given an experimental basis in the work of Harvey (1937), who found that Calanus feeding in a mixed suspension of Lauderia and Chaetocerus would take little of the latter. Marshall & Orr (1955) could not confirm these observations and in experiments with mixed suspensions of various plant cells found no clear evidence of any selection mechanism, as also did Ryther (1954) using Daphnia.
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Michael R. Reeve (1963) studied this question.
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