Experimental studies on nuclear and cell division

Abstract

During several seasons extensive experiments were made on the segmenting eggs of Crepidula plana. These experiments included a study of the influence on nuclear and cell division of hypertonic and hypotonic sea water, of ether, alcohol, etc., of the lack of oxygen, of the electric current, and of pressure and shaking. The following general conclusions may be drawn from this work:

1. Under the same treatment the effects may be extremely varied, owing, probably, to the different stages of cell division acted upon.

2. A dividing cell is much more easily disturbed or rendered abnormal than is a resting one; the mitotic figure in particular is very easily altered and most of the abnormalities observed arise from this source.

3. The earlier stages of cleavage are much more easily altered than are the later ones.

4. Certain general abnormalities occur after the most varied treatment, e. g., the general results both of concentration and of dilution of sea water are to produce polyasters and to prevent the cleavage of the yolk.

5. On the whole the results of the hypertonic solutions are the same whether they are produced by evaporation of the sea water or by the addition of NaCl, MgCl₂, or KCl to sea water; in short, these salts exert no specific action on cell division.

6. The most general modification of the mitotic figure is the production of polyasters, multipolar spindles, and as a consequence, multiple nuclei. In many cases the cells are filled with asters and irregular mitotic figures, during division, while in the resting stage they are filled with equally numerous resting centrosomes and nuclei.

7. The movements of the chromosomes are in many cases interrupted, so that they remain scattered along the spindle, while the cytoplasmic movements are frequently stopped or altered.