We do not yet know where life is most abundant,--whether on continents or in the unfathomed depths of the ocean. Through the excellent work of Ehrenberg, “Über das Verhalten des kleinsten Lebens,” we have seen the sphere of organic life extend, and its horizon widen before our eyes, both in the tropical parts of the ocean and in the fixed or floating masses of ice of the Antarctic seas. Siliceous-shelled Polygastrica, and even Coscinodiscæ, with their green ovaries, have been found alive enveloped in masses of ice only twelve degrees from the Pole; the small black Glacier flea (Desoria glacialis) and Podurellæ inhabit the narrow tubular holes examined by Agassiz in the Swiss glaciers. Ehrenberg has shown that on several microscopic Infusoria (Synedra, Cocconeis) others live as parasites, and that in the Gallionellæ such is their prodigious power of development, or capability of division, that in the space of four days an animalcule invisible to the naked eye can form two cubic feet of the Bilin polishing slate. In the sea, gelatinous worms, living or dead, shine like stars,[5] and by their phosphoric light change the surface of the wide ocean into a sea of fire. Ineffaceable is the impression made on my mind by the calm nights of the torrid zone, on the waters of the Pacific. I still see the dark azure of the firmament, the constellation of the Ship near the zenith, and that of the Cross declining towards the horizon, shedding through the perfumed air their soft and planetary lustre; while bright furrows of flashing light marked the track of the dolphins through the midst of the foaming waves.