The Making of Species 
ences not only can, but have actually been pro- 
duced by the selection of such variations. This 
objection is based upon the assumption that 
breeders have in the past dealt only with fluc- 
tuating variations. This assumption does not 
appear to be justified. It is exceedingly prob- 
able that most, if not all, the varieties of 
domesticated animals have originated in muta- 
tions. Take, for instance, the modern turbit 
pigeon; this has been derived from the old 
Court-bec, described and figured over two 
centuries ago by Aldrovandus. 
De Vries goes so far as to assert that the 
various races of pears are all mutations; that 
each distinct flavour is a mutation, and that it is 
impossible to produce a new flavour by selecting 
fluctuating variations. Thus it would appear 
that in every case of the production of a new 
breed a mutation has occurred which has 
attracted the fancy of some breeder, and he 
has seized upon this and perpetuated it. 
All the evidence available tends to show that 
there is a limit—and one which is quickly 
reached—to the amount of change that can 
be produced by the selection of fluctuating or 
continuous variations. We, therefore, seem 
driven to the belief that evolution is based on 
the kind of variation which Professor Bateson 
terms “discontinuous variation” and Professor 
De Vries calls “ mutation.” 
72 
