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Thus he establishes a third primary division of the living world, distinct from both animals and plants, under the name of the Protista, to include the Myxomycetes, the Diatomaceae, and the Labyrinthulae, which are commonly regarded as plants, with the Noctilucae, the Flagellata, the Rhizopoda, the Protoplasta, and the Monera, which are most generally included within the animal world.
That unicellular algae, like the Diatomaceae, living in a medium which may contain only one part in 10,000 by weight of dissolved silica, or even less than that amount, should be able to separate this substance to form their exquisitely ornamented frustules is one of the most striking facts in natural history, whether we regard it in its physiological or its chemical aspects.
These are plants growing in sea or fresh water, or on damp surfaces, with a filamentous, or more rarely a leaf-like pulverulent or gelatinous thallus; the last two forms essentially microscopic. Consisting frequently of definitely arranged groups of distinct cells, either of ordinary structure or with their membrane silicified Diatomaceae. We note three forms of fructification: 1.
There are also great masses of limestone growing in some seas, chiefly composed of corals and shells, or, as in the depths of the Atlantic, of chalky mud made up of foraminifera and diatomaceae. As to the dry land, so far from being the receptacle of fresh accessions of matter, it is exposed almost everywhere to waste away.
Reproduced by division and by resting spores produced in sporangia formed after the conjugation of two cells and union of their contents, and by zoospores formed in the vegetative cells or in the germinating resting spores. Diatomaceae. Multiplied by division and by the formation of new larger individuals out of the contents of individual conjugated cells; perhaps also by spores and zoospores.
This stone, when examined with a powerful microscope, is found to consist of the siliceous plates or frustules of the above-figured Diatomaceae, united together without any visible cement. At every stroke, therefore, that we make with this polishing powder, several millions, perhaps tens of millions, of perfect fossils are crushed to atoms.
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.
An attentive study of the conditions favorable to the propagation of the diatomaceae might perhaps help us to profit directly by the productivity of this organism, and, at the same time, disclose secrets of nature capable of being turned to valuable account in dealing with silicious rocks, and the metal which is the base of them.
The waters of the ocean, all along the borders of the icy barrier, produce in amazing abundance the family of water-plants named Diatomaceae. The Diatoms are so called from their faculty of multiplying themselves indefinitely by splitting into two; and so rapidly is this process performed, that in a month a single diatom may produce a thousand millions.
In certain geological formations, the diatomaceae deposit, at the bottom of fresh-water ponds, beds of silicious shields, valuable as a material for a species of very light firebrick, in the manufacture of water-glass and of hydraulic cement, and ultimately, doubtless, in many yet undiscovered industrial processes.
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