. General physiology; an outline of the science of life. ELEMENTARY VITAL PHENOMENA 237 pseudopodia that are short and blunt, incised, thick and finger- shaped, slender and thorn-like, straight and radiating, long and thread-like, dichotomously branched, or reticulate. But all these varieties, which are united with one anotherby innumerable trans- itions, are produced in the same manner, namely, by protoplasm streaming out into the medium centrifugally from the central cell- body. In organisms possessing long, filose pseudopodia, such as Foraminifera {, Orhitolites, Fig. 98), the protoplas
. General physiology; an outline of the science of life. ELEMENTARY VITAL PHENOMENA 237 pseudopodia that are short and blunt, incised, thick and finger- shaped, slender and thorn-like, straight and radiating, long and thread-like, dichotomously branched, or reticulate. But all these varieties, which are united with one anotherby innumerable trans- itions, are produced in the same manner, namely, by protoplasm streaming out into the medium centrifugally from the central cell- body. In organisms possessing long, filose pseudopodia, such as Foraminifera {, Orhitolites, Fig. 98), the protoplasm must travel a long way from the centre to the tip of the constantly. Fig. 97.—Pigment-cells from the skin of the frog; /, extended ; //, slightly contracted; III, strongly contracted ; IV, wholly contracted ; the clear spot in the centre of the cell-body is the nucleus. lengthening process ; in these fine threads the microscope shows the protoplasm with its granules flowing like the water of a slow stream. This extremely fascinating phenomenon constantly charms the observer and has been vividly described by Dujardin ('41), Max Schultze ('54), and Haeckel ('62), as granular or 'protoplasmic streaming. In the retraction of such pseudopodia the proto- plasmic particles must again travel over the same path in the reverse or centripetal direction. In pseudopodia that are extended to a considerable distance and remain extended for a considerable time, two currents, a centrifugal and a centripetal, are always. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Verworn, Max, 1863-1921; Lee, Frederic S. (Frederic Schiller), 1859-1939. London, Macmillan and co. , limited; New York, The Macmillan company
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