General physiology; an outline of the science of life . Fig. 97.—Pigment-cells from the skin of the frog; /, extended ; //, slightly contracted; HI,strongly contracted ; / V, wholly contracted; the clear spot in the centre of the cell-body isthe nucleus. lengthening process ; in these fine threads the microscope shows theprotoplasm with its granules flowing like the water of a slowstream. This extremely fascinating phenomenon constantly charmsthe observer and has been vividly described by Dujardin (41),Max Schultze (54). and Haeckel (62), as granular or protoplasmicstreaming. In the retraction
General physiology; an outline of the science of life . Fig. 97.—Pigment-cells from the skin of the frog; /, extended ; //, slightly contracted; HI,strongly contracted ; / V, wholly contracted; the clear spot in the centre of the cell-body isthe nucleus. lengthening process ; in these fine threads the microscope shows theprotoplasm with its granules flowing like the water of a slowstream. This extremely fascinating phenomenon constantly charmsthe observer and has been vividly described by Dujardin (41),Max Schultze (54). and Haeckel (62), as granular or protoplasmicstreaming. In the retraction of such pseudopodia the proto-plasmic particles must again travel over the same path in thereverse or centripetal direction. In pseudopodia that are extendedto a considerable distance and remain extended for a considerabletime, two currents, a centrifugal and a centripetal, are alwavs. Fig. 98.—Orbitolites complanatus, a rhizopod-cell from the Red Sea (small specimen magnifiedabout forty times ; natural size of adults upon an average 5 mm.). The central protoplasmicbody is enclosed in a round, disc-shaped, calcareous shell, which consists of innumerablechambers arranged essentially in concentric rings. The protoplasm of each chamber containsone or more nuclei. At the periphery of the shell numerous fine, straight, filose pseudopodiaprotrude, often reaching in large specimens a length of almost 20 mm. ; these branch greatlyand amalgamate with one another. Very beautiful protoplasmic and granular streaming maybe seen upon them. ELEMENTARY VITAL PHENOMENA 239 noticed, in thick pseudopodia the former plainly upon the peri-phery, the latter in the axis of the strand. According as the formeror the latter preponderates, the pseudopodium gradually extends orshortens itself. If the two are equally strong, it remains extended,its length not changing. The phenomena of contra
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Keywords: ., bookcentury1800, bookdecade1890, bookidgen, booksubjectphysiology
