United States or Portugal ? Vote for the TOP Country of the Week !
Most of the wrigglers, however, feed on algæ, diatoms, Protozoa and other minute plant or animal forms which are swept into the mouth by curious little brush-like organs whose movements keep a stream of water flowing toward the mouth.
On the 4th of February, in lat. 52°, 29' S., long., 71° 36" E., a little to the north of the Heard Islands, the tow-net, dragging a few fathoms below the surface, came up nearly filled with a pale yellow gelatinous mass. This was found to consist entirely of Diatoms of the same species as those found at the bottom.
Large groups of the simpler animals contain chlorophyll, and decompose carbonic acid under the influence of light, as plants do. Large groups of the simpler plants, as you may observe in the diatoms from any stagnant pool, are no less actively locomotive than the minute creatures classed as animals seen along with them.
Like the Globigerina ooze, then, which it succeeds to the southward in a band apparently of no great width, the materials of this silicious deposit are derived entirely from the surface and intermediate depths. It is somewhat singular that Diatoms did not appear to be in such large numbers on the surface over the Diatom ooze as they were a little further north.
It may be he will still, with the utmost nonchalance, be pushing out his pseudopodia, and ingesting diatoms when the fretful transitory life of humanity has passed altogether from the earth. One may catch him in specimen tubes by the dozen; but still, when one thinks of this, it is impossible to deny him a certain envious, if qualified, respect.
He was a shy, lonely, rather ineffectual man, provided with just enough income to keep off the spur of necessity, and not enough nervous energy to make him seek any exacting employments. He might have collected stamps or coins, or translated Horace, or bound books, or invented new species of diatoms. But, as it happened, he grew orchids, and had one ambitious little hothouse.
The towns of Berlin in Europe and of Richmond in the United States are actually built upon ground called "infusorial earth," composed almost entirely of valves of these minute diatoms which have accumulated to a thickness of more than eighty feet! Those under Berlin are fresh-water forms, and must have lived in a lake, while those of Richmond belong to salt-water forms.
Collier?" asked Paul; "other animals smaller still?" "No, my boy," was the reply, "on plants called diatoms. There are over four thousand species of these plants known, which are so small that the microscopic animals readily engulf them.
The little spindle-shaped things in the centre are diatoms and may be disregarded since they are probably vegetable rather than animal. But the right-hand side you will see an undoubted amoeba, moving sluggishly across the field. The upper screw is the fine adjustment. Look at it for yourselves." Summerlee did so and acquiesced.
But if the Radiolaria and Diatoms are thus rained upon the bottom of the sea, from the superficial layer of its waters in which they pass their lives, it is obviously possible that the Globigerinæ may be similarly derived; and if they were so, it would be much more easy to understand how they obtain their supply of food than it is at present.
Word Of The Day