Mutation Theory Criticised 
purple beech seems to be a mutation which has 
originated at least three times over. 
Every one interested in biological theory 
should read both Species and Varieties and Plant 
Breeding by De Vries, works which are of 
incalculable value to the horticulturist and agri- 
culturist as well as to the biologist. 
While not wishing to detract in any way from 
the truly splendid work done by De Vries, we 
feel constrained to bring several charges against 
him. 
Firstly, he suffers from the complaint that 
seizes nine out of ten originators of new theories. 
He pushes his theory to extreme lengths; he 
allows his imagination to run away with him. 
We do not think that on the evidence available 
he is justified in asserting that every species 
passes through alternating periods of comparative 
quiescence and periods in which it throws off, 
as mutations, swarms of elementary species. He 
is justified in asserting that discontinuous varia- 
tion is by no means an uncommon phenomenon, 
but further than this it does not seem safe to go 
at present. 
Secondly, he ought to lay more stress on the 
fact that Oenothera lamarckiana is a plant which 
does not appear to be known in the wild state, 
and that it is therefore possibly a hybrid plant, 
and the so-called elementary species which it 
gives off may be merely the varieties out of 
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