Spirazines 25 



molecules can never be accomplished by one con- 

 tinuous process, but even if it could be thus accom- 

 plished there would have to be an abrupt change 

 in the nature of the process after the completion 

 of one molecule in order to initiate the formation 

 of the next one. 



However, there is no experimental evidence 

 that the protoplasmic structures of living cells are 

 built up of discrete molecules, or that they are of 

 utmost chemical complexity. In regard to their 

 supposed molecular constitution, it might be 

 stated that most proteins, and especially those 

 which form the nuclear or actively growing por- 

 tions of living cells, require special chemical 

 treatment to bring them into solution, whereas 

 those which will dissolve in water, as for example 

 the albumins, are probably no longer integral 

 portions of the cell structure but may consist of 

 free colloidal bodies which have grown out from 

 the nuclear material and have become detached. 

 In regard to their supposed chemical complexity, 

 a distinction should be made between two-dimen- 

 sional complexity and three-dimensional complex- 

 ity. Although it seems impossible to explain 

 growth and reproduction if we assume that proto- 

 plasmic materials possess three-dimensional com- 

 plexity, yet it seems comparatively easy to ex- 

 plain these processes if we assume that they 



