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Updated: June 12, 2025
Professor Haeckel, to whom Schleicher addresses himself, previously took occasion, in his splendid monograph on the 'Radiolaria',* to express his high appreciation of, and general concordance with, Mr. Darwin's views.
Dickie, of Aberdeen, sent these materials to Ehrenberg, who made out that the residuum of the melted ice consisted for the most part of the silicious cases of diatomaceous plants, and of the silicious spicula of sponges; while, mixed with these, were a certain number of the equally silicious skeletons of those low animal organisms, which were termed Polycistineoe by Ehrenberg, but are now known as Radiolaria.
The sea-garden exhibits were all completed and were among the museum's most popular cases, and the curator was engaged in preparing some exquisite models of the Radiolaria, those magical creatures of the sea, which are so small that they can be seen only with a powerful microscope, but which look like living snow-crystals, although a thousand times more beautiful.
I know of no more solid and important contributions to biology in the past seven years than Haeckel's work on the Radiolaria, and the researches of his distinguished colleague Gegenbaur, in vertebrate anatomy; while in Haeckel's Generelle Morphologie there is all the force, suggestiveness, and, what I may term the systematizing power, of Oken, without his extravagance.
Nevertheless, the positive and negative evidence all points the other way. The skeletons of the full-grown, deep-sea Globigerinae are so remarkably solid and heavy in proportion to their surface as to seem little fitted for floating; and, as a matter of fact, they are not to be found along with the Diatoms and Radiolaria, in the uppermost stratum of the open ocean.
In the great intermediate zone, occupying some 110° of latitude, which separates the circumpolar Arctic and Antarctic areas of silicious deposit, the Diatoms and Radiolaria of the surface water and the sponges of the bottom do not die out, and, so far as some forms are concerned, do not even appear to diminish in total number; though, on a rough estimate, it would appear that the proportion of Radiolaria to Diatoms is much greater than in the colder seas.
In accordance with the existing state of things, the Radiolaria and Diatoms would have a universal distribution, the latter gathering most thickly in the polar regions, while the Foraminifera would be largely, if not exclusively, confined to the intermediate zone; and, as a consequence of this distribution, a bed of "chalk" would begin to form in the intermediate zone, while caps of silicious rock would accumulate on the circumpolar regions.
Ehrenberg, in fact, had shown that the extensive beds of "rotten-stone" or "Tripoli" which occur in various parts of the world, and notably at Bilin in Bohemia, consisted of accumulations of the silicious cases and skeletons of Diatomaceoe, sponges, and Radiolaria; he had proved that similar deposits were being formed by Diatomaceoe, in the pools of the Thiergarten in Berlin and elsewhere, and had pointed out that, if it were commercially worth while, rotten-stone might be manufactured by a process of diatom-culture.
These silicious bodies belong partly to the lowly vegetable organisms which are called Diatomaceae, and partly to the minute, and extremely simple, animals, termed Radiolaria. It is quite certain that these creatures do not live at the bottom of the ocean, but at its surface where they may be obtained in prodigious numbers by the use of a properly constructed net.
I know of no more solid and important contributions to biology in the past seven years than Haeckel's work on the "Radiolaria," and the researches of his distinguished colleague Gegenbaur, in vertebrate anatomy; while in Haeckel's "Generelle Morphologie" there is all the force, suggestiveness, and, what I may term the systematising power, of Oken, without his extravagance.
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