DE VBIES' "MUTATION" 86 



Stood it, to the origin of new species by the 

 gradual accumulation of those almost imper- 

 ceptible variations usually described as "fluc- 

 tuations/' Whatever conflict there may be 

 between Darwinism and mutation must be 

 ascribed to Wallace. As DeVries clearly rec- 

 ognizes, Darwin is in no way responsible. 

 "Darwin," says DeVries, "recognized both 

 lines of evolution." 



The diflference between "fluctuations" and 

 "mutation'^ is illustrated by DeVries recalling 

 Galton's simile of a polyhedron — an example 

 of which is a solid piece of glass covered with 

 many small flat faces. When it comes to rest 

 on any particular face, it is in stable equili- 

 brium. Small disturbances may make it oscil- 

 late, but it returns always to the same face. 

 These oscillations are like fluctuating varia- 

 tions. A greater disturbance may cause the 

 polyhedron to roll over on to a new face, 

 where it comes to rest again, only showing 

 the ever present fluctuations around the new 

 center. The new position corresponds to a 

 mutation. One of the disabilities of this illus- 

 tration is that some fluctuations represent a 

 greater disturbance from the given position 

 than some mutations. The essential difference 

 is that in the fluctuation it rocks back again 



