212 SCIENCE PROGRESS 



that a similar equatorial lowering of surface tension sets up the 

 streaming movements which lead to the division of the proto- 

 plasmic material in a cell. This is explicable on the hypothesis 

 that choline or soaps of choline are liberated in the cell by the 

 cleavage of lecithin or similar phosphatides in the region of 

 the nucleus. 



I have thought it right to mention that there are theories 

 of this nature in the air, but whether they are feasible is one of 

 the many problems for the future which we all hope will be 

 cleared up when bio-chemistry and other branches of biological 

 study are founded more and more firmly on the bed-rock of 

 experiment. 



