They are more easily seen, when the nucleus is about to undergo mitosis, at the ends of the spindle, where they form the centres towards which the radiating fibres in.
It has been shown that, in cells of Spiro gyra placed under special conditions, amitotic division can be induced, and that normal mitosis is resumed when they are placed again under normal conditions.
Mitosis.In indirect nuclear division the nucleus undergoes a series of complicated changes, which result in an equal division.
On the other hand, the complex structure of the nucleus with its separate units, the chromosomes, and possibly even smaller units represented by the chromatin granules, and the means taken through the complex phenomena of mitosis to ensure that an exact and equal division of the chromosomes shall take place, emphasizes the importance of the nucleus in heredity.
Some observers consider that the yeast nucleus possesses a typical nuclear structure, and exhibits division by mitosis, but the evidence for this is not very satisfactory.
Xxi.; On the Prophases of the Heterotype Mitosis in the Embryo-sac Mother-cell of Lilium, Ann.
When mitosis is about to take place, they separate from one another and pass to the poles of the nucleus, forming the achromatic spindle.
These appearances are probably due toa pathological mitosis, commonly found in cancer, in which there is an irregular diminution in the number of chromosomes; some are cast out and become degenerated or some pass over to one of the daughter cells, leaving a reduced number in the other, and thus give rise to asymmetrical mitosis.
385; Text-Book of Pathology (London,1894); Hansemann, " Pathological Mitosis," Arch.