EVOLUTIONARY THEORIES SINCE DARWIN 247 



which he has not determined as yet, instability comes 

 into the species and it varies in quite a number of 

 directions. Each of these variations may be the start- 

 ing point of a new species. DeVries believes that 

 he has at least half a dozen mutants of his new Even- 

 ing Primrose. 



This theory of Mutation has been eagerly seized 

 upon by many botanists. The zoologists have not 

 accepted it quite so enthusiastically. If this is the 

 chief method by which species transform, it seems 

 strange that we do not find more mutations than we 

 do. Perhaps we do not look carefully enough; per- 

 haps we shall find them a little later. Just at present 

 it seems premature to believe that all evolution is 

 by mutation, although quite possibly some of it is. 

 The main apparent advantage of mutation is that it 

 hastens the time in which a new species may arise. 



There are certain difficulties which run back into 

 the problem, and which must first be reasonably 

 solved before a clear understanding of the idea of 

 evolution is possible. The first of these is as to the 

 nature of life. What is life? The reply of the biolo- 

 gist will probably be that so far as its material side 

 is concerned, it must be answered in terms of physics 

 and chemistry. As to any side not material, if it 

 have any such side, science says that the chemist can 

 have nothing to say. The chemist may have an 



