Permanence and Evolution. 17 



no evidence that they vary in any degree, either 

 in cattle or in any other animals, I do not see 

 of what use immense periods of time would be 

 to the theorist. Darwin in one place (" Animals 

 and Plants," p. 233) seems conscious of this, 

 and says that it has been objected that the 

 differences between domestic pigeons can throw 

 no light upon those between wild Columbae, 

 because they do not differ in the same respects ; 

 to which he replies that man would only select 

 such differences as were externally conspicuous. 

 But, if so, where is the positive evidence of the 

 other modifications being producible ? I do not 

 well see how we can have any, and therefore in 

 those cases the general presumption of perma- 

 nence must prevail. There is also perhaps no 

 reason why granting natural races to be modi- 

 fiable at all, they should all be modifiable 

 in exactly the same degree. 



Another question here suggests itself. When 

 we are dealing with the gradual upheaval 



C 



