Quarterly journal of microscopical science . 1-64 •77 1 -35 1-70 •80 115 1-38 •83 1-80 2 1,-, 2-00 2-9 •90•91 Average XY AB 65 AverageAB~ * Prior to any visible change in the appearance of the cell the XY ratio .-p is progressively increasing from the beginning of the formation of the astral figure ; it then passes through thecritical value at which the furrow appears and continues toincrease until complete cell-division is effected. SURFACE TENSION AND CELL-DIVISION • It is somewhat rash, perhaps, to press too far the analogyof the astral figure to the rings in Plateaus experiment. Itis
Quarterly journal of microscopical science . 1-64 •77 1 -35 1-70 •80 115 1-38 •83 1-80 2 1,-, 2-00 2-9 •90•91 Average XY AB 65 AverageAB~ * Prior to any visible change in the appearance of the cell the XY ratio .-p is progressively increasing from the beginning of the formation of the astral figure ; it then passes through thecritical value at which the furrow appears and continues toincrease until complete cell-division is effected. SURFACE TENSION AND CELL-DIVISION • It is somewhat rash, perhaps, to press too far the analogyof the astral figure to the rings in Plateaus experiment. Itis obvious that the mechanical model is a limited one, and thatsubsequent work may show that regions of differential viscositysuch as are suggested by Chamberss J work may be foundto be involved. Yet in the particular case of a cell whichpossesses a structure curiously fitted to play the part ofPlateaus rings, division is found to proceed on just those linesdemanded by the above analysis. Text-fig. 9 shows the division Text-fk;. Division of C o 1 e p s h irt us (after Doflein). The undivided form agives rise to two daughter individuals by passing through stage b. of the protozoon Coleps hirt us. The body is covered byfour hard skeletal plates Px-P4. When division occurs thedistal ends of the cell remain fixed in form owing to the existingplates, and between plates P3 andP4 the cell becomes elongatediii exactly the form demanded by the hypothesis put the stage of division illustrated a well-marked cleavagefurrow has formed and the Plateau ratio is about -8. Summary. Cell-division may be accounted for by the movement of thetwo asters away from each other. The appearance of thecleavage furrow \& due to an equilibrium between the efifeciof this movement on the protoplasm and the surface the fell-surface. The behaviour of the cell under these foii- precisely similar to a drop of oil subjected to similar condi-tions. There is do necessity to postula
Size: 3174px × 787px
Photo credit: © The Reading Room / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1800, bookdecade1850, bookpublisheroxfor, bookyear1853
