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Page:Popular Science Monthly Volume 57.djvu/445

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435
THE NORWEGIAN POLAR EXPEDITION.

portance as a means of supplying nourishment to the marine animals of the western Arctic Ocean. This food supply, microscopic algæ chiefly Diatomeæ, while very abundant on the surface of the Siberian Sea, diminishes gradually towards the west. "Indeed," says Sars, "without such a constant conveyance of nourishing matter, there could be no such rich animal life in the Polar Sea."

A very remarkable fact was the presence of certain pelagic Copepoda, which hitherto had only been observed in southern waters, and a Calanoid of the genus Hemicalanus Claus, previously known only from the Mediterranean and tropical parts of the Atlantic and Pacific oceans. Two species of the genus Oncoea, which accord perfectly with species in the Bay of Naples, were found in great abundance north of the New Siberian Islands. Another copepod, of the genus Lubbockia Claus, heretofore only known in the Mediterranean and tropical oceans, was found in the same locality, with which was a small perfectly hyaline copepod of the very remarkable genus Mormonilla, of which heretofore only two species have been recorded, both in the tropical Pacific and south of the equator.

Perhaps the most remarkable forms are those mentioned by Doctor Sars, when he says: "The very close and apparently genetic relationship between the two polar species of the amphipodous genus Pseudalibrotos and those occurring in the Caspian Sea, is another remarkable instance which seems fully to corroborate the correctness of the assumption of geologists as to a direct connexion in olden times between this isolated basin and the North Polar Sea."

Both species, taken near 85° N., are regarded as the primitive types from which the Caspian forms are descended. The more remarkable of the Arctic forms, P. Nanseni, is reproduced on page 430.

To conclude, this volume is a most valuable contribution to the scientific literature of the Arctic regions. It has but one marked objection, its publication in such beautiful form and high price as necessarily places this series beyond the means of many scientific students.