General physiology; an outline of the science of life . ricted by acircular groove, the plane of which stands at right angles to theaxis of the two nuclear poles. The groove becomes deeper anddeeper, until finally the whole cell divides into two equal halves,each of which possesses a nucleus ; the latter surrounds itself witha new nuclear membrane, the spindle-fibres completelydisappearing, and thus returns to its resting-stage. Thus by thedivision of the mother-cell two daughter-cells have arisen, andthese continue the growth on their own behalf (Fig. 72, F).But during the division a phenomen
General physiology; an outline of the science of life . ricted by acircular groove, the plane of which stands at right angles to theaxis of the two nuclear poles. The groove becomes deeper anddeeper, until finally the whole cell divides into two equal halves,each of which possesses a nucleus ; the latter surrounds itself witha new nuclear membrane, the spindle-fibres completelydisappearing, and thus returns to its resting-stage. Thus by thedivision of the mother-cell two daughter-cells have arisen, andthese continue the growth on their own behalf (Fig. 72, F).But during the division a phenomenon has appeared in theprotoplasm. Simultaneously with the appearance of the spindle,the poles of which are formed by the centrosomes, two star-shaped figures begin to appear in the protoplasm, by the latterarranging itself at each pole like rays around the centrosomeas a centre; the centrosomes thus become surrounded exactlylike two suns by a closed circle of rays (Fig. 73). As the spindle-fibres become indistinct the protoplasmic rays also ELEMENTARY VITAL PHENOMENA 195 This mode of mitotic nuclear division is the same in the differentforms of cells, almost without exception and even to the finestdetails. But the division of the cell as a whole does not alwaysproceed in exactly the same manner. Deviations from the typeoccur in various cases, especially in the division of egg-cells thatcontain much nutrient material (yolk). With O. Hertwig (92)
Size: 1533px × 1630px
Photo credit: © The Reading Room / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1800, bookdecade1890, bookidgen, booksubjectphysiology
