REPRODUCTION 25 



the action of these forces a drop of liquid 

 rounds up and becomes spherical when- 

 ever it is free to do so. But when these 

 forces are disturbed by localized chemical 

 action they may cause a constriction of 

 the drop which may result in its division 

 into two parts. The same forces seem 

 to operate in the case of the cell and in 

 addition there may be changes in the 

 consistency of the protoplasm. There 

 seems, therefore, to be nothing in such 

 cases which we may not hope to explain 

 on a physicochemical basis. 



For the more complicated cases, where 

 division of the nucleus occurs, we have 

 at present no satisfactory explanation. 

 We need not, however, concern ourselves 

 with these cases at present, since our 

 purpose is to reduce each life process to 

 its simplest form and try to see whether 

 we can explain it on a physicochemical 

 basis. If we succeed in this we may be 

 content to leave the more complicated 

 cases to future investigation. 



In sexual reproduction there is a fusion 



