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.
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.