THE NORWEGIAN POLAR EXPEDITION. 435 



portance as a means of supplying nourishment to the marine animals 

 of the western Arctic Ocean. This food supply, microscopic algae 

 chiefly Diatomeae, while very abundant on the surface of the Siberian 

 Sea, diminishes gradually towards the west. "Indeed," says Sars, "with- 

 out 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 Cala- 

 noid 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, here- 

 tofore 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 objec- 

 tion, its publication in such beautiful form and high price as necessarily 

 places this series beyond the means of many scientific students. 



