. The cell and protoplasm ... Cells; Protoplasm; Cytology; Cytoplasm. 202 THE CELL AND PROTOPLASM follow the lines of orientation of the equally-spaced virus particles. The theor}^ of factoids makes it possible to go a long way in the explanation of the mechanism of cell division, for it provides secondary forces affecting the poles of the factoids which are due not to any imme- diate reaction between these poles, but to the whole field of orientation of the tac- toid itself. These forces overcome the dif- ficulty implicit in the earlier crude elec- trical or diffusion theory of spindle for- m
. The cell and protoplasm ... Cells; Protoplasm; Cytology; Cytoplasm. 202 THE CELL AND PROTOPLASM follow the lines of orientation of the equally-spaced virus particles. The theor}^ of factoids makes it possible to go a long way in the explanation of the mechanism of cell division, for it provides secondary forces affecting the poles of the factoids which are due not to any imme- diate reaction between these poles, but to the whole field of orientation of the tac- toid itself. These forces overcome the dif- ficulty implicit in the earlier crude elec- trical or diffusion theory of spindle for- mation because they admit of considerable geometrical variation; they do not act in straight lines but along the flow lines of the long particles and consequently may follow curved or even sinuous tracks. Not only do long particles suspended in an un- oriented medium tend to form factoids, but any enclosure of this medium in the tactoid itself takes on a tactoid shape which may be termed a negative tactoid (Fig. 2, B). The poles of the negative tactoid have a tendency to move apart as the orientation of the tactoid becomes more pronounced, and also tend to move bodily into the equatorial plane of the original tactoid. On the basis of a few very simple hypoth- eses, it is therefore possible to give a simple account of the external mechanisms of cell division: 1. That tlie cell (probabl}' the nucleus) contains protein material which under suitable ionic and chemical conditions ag- gregates into long particles of dimensions of the order of 1000 A x 100 A. 2. That structures exist in the cell toward which these particles tend to set themselves at right angles, , cell walls, centrosomes, and centromeres. A. Fig. 2. Tactoids of dificroit sizes. A, ])ositive tactoids; P., negative Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly r
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Keywords: ., bookauthoramericanassociation, bookcentury1900, booksubjectcells
