EVOLUTIOI:^ AND ITS CONSEQUENCES. 21 



this induces opposite electricity on the external surface, which, as 

 in the muscular cell, causes compression, and therefore extension 

 of the stratum. This extends itself beyond its contents, which 

 may be attenuated, filling the space, or contracting, forms the 

 nucleus. 



This view will not, however, account for nucleus and cell- 

 division, which are the subsequent and principal exhibitions of 

 growth-force. Perhaps the following suggestions may throw some 

 light on it. Should a polar tendency appear in the nucleus, were 

 the protoplasm of the proper viscidity, the poles being of like 

 electric name, would tend to separate by repulsion, thus forming 

 the hour-glass shape so well known, and afterward division. 

 This nucleus division would inevitably be followed by division 

 of the cell-wall, if its inner face were electrified in opposition to 

 the nucleus. For the wall being attracted toward it equally all 

 round, the separation of the two nuclei would be followed by an 

 incurvature of the walls opposite the interval between the nuclei, 

 in order that each should maintain a position equidistant from 

 its center. Further divergence would result in the completion 

 of the cell-wall of each, apart from the other. This process 

 would be supported by nutrition of the cell, which proceeds by 

 the passage through the cell-wall to the nucleus, of additional 

 protoplasm from the blood. Of course, the prime question is as 

 to whether polarity can appear in the nucleus. That growth 

 is first polar appears probable on consideration of the globular 

 and discoidal forms of the lower animals, and that this principle 

 lies at the basis of the growth of the higher is rendered equally 

 probable by the phenomena of symmetry of different kinds, as 

 bilateral, anteroposterior, etc. The electricity supplied to the 

 outer sheaths of muscular fibrillae is, according to Dubois Eey- 

 mond, positive. That covering the surface of the nucleus must 

 be thought to be positive also, if it be effected in opposition to the 

 inner wall of the cell-wall, which is known to be negative by ex- 

 periment. But in that case it would be difficult to perceive why 

 it should not fill the cell by attraction to the wall. If, on the 

 other hand, it be a generator of negative electricity, it would re- 

 tain its integrity and induce a temporary change in the wall. 

 The transmission of protoplasm through the cell-wall to the 

 nucleus would produce an accumulation of electricity to be dis- 

 charged in extension, or a disturbance of equilibrium, to be fol- 

 lowed by polarity and division ; but the conditions under which 



