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-bee, 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 



