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Or to the organs of circulation? We have among the Copepoda, the Cyclopidae and Corycaeidae without a heart, side by side with the Calanidae and Pontellidae with a heart. And in the same way among the Ostracoda, the Cypridinae, which I find possess a heart, place themselves side by side with Cypris and Cythere which have no such organ. Or to the respiratory apparatus?
In the Corycaeidae, Claus found all the ventral ganglia fused together into a single broad mass, and in the Calanidae a long ventral chain of ganglia, the former, therefore, in this respect resembling the Spider Crabs and the latter the Lobster; but no one would dream on this account of supposing that there was a relationship between the Corycaeidae and the Crabs, or the Calanidae and the Lobsters.
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