The laws and mechanics of circulation, with the principle involved in animal movement . o produce these varied changes of form in thecell, it is manifest that the cell-contents, the molecules equallywith the masses, would have to change their relative positions,even to the nucleus (a, o), which occupies the root of a largebranched process in g ; while in the subsequent condition (h), MOLECULAR MOVEMENTS IN CELLS. 447 in which the animal is fully contracted, restoring the originalspheroidal condition (a), the nucleus occupies a nearly centralposition. In other words, we have definite actions an
The laws and mechanics of circulation, with the principle involved in animal movement . o produce these varied changes of form in thecell, it is manifest that the cell-contents, the molecules equallywith the masses, would have to change their relative positions,even to the nucleus (a, o), which occupies the root of a largebranched process in g ; while in the subsequent condition (h), MOLECULAR MOVEMENTS IN CELLS. 447 in which the animal is fully contracted, restoring the originalspheroidal condition (a), the nucleus occupies a nearly centralposition. In other words, we have definite actions and limita-tions in the protoplasmic substance, the movements directedto special objects, whether it relate to feeding or locomotion,in the entire absence of muscles or nerves, or any form-elementsfor producing them. Now, then, by looking from this to theactions taking place in the cells of compound organisms, inwhich muscles and nerves are developed, it will at once beseen that the same principle for producing motion is main-tained, and must be so in the very nature of things. In the. Fig. 187.—Devouring Blood-Cells of a Naked Sea-Snail (Thetis) very much connection with the blood-cells of this snail, I was the first to observe the impor-tant fact that the blood-cells of invertebrate animals are uncovered lumps of proto-plasm, and, like the Amoebae, by means of their peculiar movements can absorbmatter, can, therefore, eat. When at Naples (on the 10th of May, 1859) I hadinjected the blood-vessels of one of these snails with pulverized indigo dissolved inwater. I was much astonished to find after a few hoursthat the blood-cells them-selves were more or less filled with fine particles of indigo. By repeated experi-mental injections, I was able to watch the absorption of the coloring matter into theblood-cells, which was accomplished exactly as by Amoebse. (See Monograph ofRadiolaria, 1862, pp. 104, 105.)—Haeckel. muscles, for example, in which changes of form in t
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