FARR: CYTOKINESIS OF POLLEN-MOTHER-CELLS 309 



certain that the ions of many inorganic salts are to be found within 

 the cell, and these are known to have a relatively high speed of 

 diffusion, and hence might be thought of as accumulating upon 

 the membranes of the cell. If, as there is some evidence to indi- 

 cate, the plasma membrane is colloidal and if it may be inferred 

 that the same is true of the nuclear membrane, this colloidal 

 condition would serve to increase very much the amount of ionic 

 material which might be adsorbed upon the membranes. It is 

 not difficult then to see how great numbers of ions might accumu- 

 late there, and if they are of like sign they would give to that 

 membrane an electric charge. 



If, for example, the nuclear sap were markedly acid and the 

 cytoplasm be markedly alkaline, there will accumulate upon the 

 plasma membrane charges of one sign, while upon the nuclear 

 membrane there will accumulate predominately charges of the 

 opposite sign. It seems thus possible from a physico-chemical 

 standpoint that such membranes may have acquired opposite 

 charges. But for the purpose of this discussion, it makes no 

 difference how these membranes may have received their charges; 

 it is simply proposed to show that they, at least at certain stages, 

 behave as if so charged. 



As noted above, the nuclei of like charge would repel each other 

 and hence take up a tetrahedral arrangement within the cell. 

 The charges upon the plasma membrane and nuclear membranes 

 would not necessarily be neutralized by contact of the membranes 

 since the ions are adsorbed. 



The mutual repulsion of the nuclei and their attraction for the 

 plasma membrane opposed by the repulsion between different 

 areas of the plasma membrane will tend to transform the perfect 

 sphere into a tetrahedron with four equal triangular faces, each 

 parallel to the plane of three of the nuclei. Now the center of 

 each of these triangular faces will be attracted equally by each of 

 these three nuclei and also to some degree by the fourth. The 

 resultant of these four forces will tend to draw this point toward 

 this fourth nucleus; and the latter will exert relatively more force 

 of attraction upon this point than any one of the other three nuclei; 

 for, though it is farther away, it is working in the direction along 

 which the point will move. This portion of the plasma membrane 

 will tend to move toward the fourth nucleus, that is, toward the 



