. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. FIBERS OF FERTILIZED SEA URCHIN EGGS 491 O 0) O) O) ' o. 0 0 2345 Potential gradient (V/cm) Force (x10~5dyne) FIGURE 10. Generalized schematic reproduction of Figure 9. A: resistance due to tension of the fibers. B: internal viscous resistance of the fibers. C: viscous resistance due to perivitelline fluid. surface area of eggs) in which a largest optical section of eggs is located was estimated. In three eggs, the numbers were 108, 148 and 180. Therefore, 1000-1800 fibers will exist in the wh
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. FIBERS OF FERTILIZED SEA URCHIN EGGS 491 O 0) O) O) ' o. 0 0 2345 Potential gradient (V/cm) Force (x10~5dyne) FIGURE 10. Generalized schematic reproduction of Figure 9. A: resistance due to tension of the fibers. B: internal viscous resistance of the fibers. C: viscous resistance due to perivitelline fluid. surface area of eggs) in which a largest optical section of eggs is located was estimated. In three eggs, the numbers were 108, 148 and 180. Therefore, 1000-1800 fibers will exist in the whole perivitelline space of an Anthocidaris egg. When the electrophoretic force acting on the eggs was below X 10~5 dyne, the eggs did not show any movement. If the fibers within the stereoangle of 60 degrees at the cathodal side are effective to support the egg, the number of these fibers is estimated to be (=(2 - V5)/4) of the total fibers. That is, about 100 fibers will practically support the egg, if the number of the total fibers is 1500. This indicates that a single fiber could withstand the stretching force of 1 X 10~7 dyne. The nature of the structure responsible for such a resistance to stretching is still not clear, but if the resistance is due to the tension working at the protoplasmic surface of the fiber with the diameter perhaps as small as /urn, then the calculated tension will amount to X 10~3 dyne/cm, which approximates to the value of surface tension of a protoplasmic droplet in Nitella flexilis ( X 10~3 dyne/cm, cf. Kamiya and Kuroda, 1958). The centrifugal force acting on the egg when it is centrifuged at 125 g was calculated. By using Hiramoto's data (1954) on the density of the egg in H. pul- cherrimus () and that of the perivitelline fluid () determined in normal sea water, it came out to be X 10~3 dyne. This is forty times greater than the electrophoretic force under the potential gradient of V/cm that is the maximu
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