1904] + COPELAND—VARIATION OF CALIF ORNIA PLANTS 419 
a proper subject for discussion by those who recognize no ground 
for it. 
The mutation theory does not, as some of its supporters seem to 
believe, do away with the doctrine of natural selection. This doc- 
trine is that among more living things than can live and bear progeny 
those best adapted to the existing environment will survive. It 
assumes, what is the fact, that the existing organisms differ. The 
mutation theory would explain the origin of the differences, saying 
that from their first appearance they are too wide and fundamental 
to fall in the category of “individual variations.”’ The more prevalent 
idea since Darwin has been that these minor, incessantly appearing 
differences were the raw material for nature to select among, and 
that by the constant survival of the individuals with the slightest 
advantages new Taces, varieties, and species might arise; but every 
Partisan of natural selection recognizes variation as prerequisite to 
any evolution. The apparent issue is: “are the differences whose per- 
Petuation gives rise to new species the ordinary individual variations, 
or the less usual but more considerable mutations?” But a question 
Which should obviously be settled first is: “are individual variations 
and mutations distinct 2” 
Since I do not believe that the differences between the offspring 
of common parents differ fundamentally among themselves, It 1s 
but ‘atural that I should be unable to frame a definition of a mutation 
Which would really distinguish it from the general run of ppemanare 
For the Most authoritative definition I have consulted DE VRIES'S 
Mationstheorie. To my surprise, I have read the book, and then 
— Carefully re-read the general part, without finding anywhere 
‘nything that has the force or form of a definition. 
3 In the introduction, where “es sich darum handelt, den 
i beiden Grundformen der Variabilitait so klar wie méglich darzu 
sell he says: ‘‘Die Mutationen sind Vorginge, tiber deren Natur 
"I noch sehr wenig wissen. Die bekanntesten Beispielen — 
Mutationen sind die sogenannten spontanen Abinderungen ( single 
"atiations ’), durch welche scharf unterschiedene neue Varietaten 
eeianae Man nennt sie auch wohl Sprungvariationen Shs sie 
‘Sain he Says (p. 22): “Die letzteren [single variations] sind - - 
®% Spontane Abinderungen, unseren Mutationen entsprec 
Unterschied 
