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 
