SURFACE TENSION AND CELL-DIVISION 



243 



hardly be mentioned that the existence of any form of mechani- 

 cal membrane, or the presence of elements (e. g. other cells) 

 capable of exerting a pressure in any particular direction 

 will materially alter the system which is under discussion. 



It can hardly be doubted that the elongation of the cell-axis 

 is associated in some way with the elongation of the astral 



figure. Since the latter process goes on continuously during 

 mitosis and does not begin with the elongation of the whole 

 cell, it follows that the elongation of the cell is probably the 

 result and not the cause of the elongation of the astral figure. 

 If this conclusion is correct the cell can be divided into three 

 parts ; a central cylindrical portion ABDC (Text-fig. 8) which 

 is tending to increase the length of its shorter axis, and two 

 convex ends to this cylinder AEB and CFD. Until the ratio 



AC 



T-D approaches | the form of the cell will not change, but as 



