20 Darwinism and Other Essays. 



Whether, therefore, it is practicable for us to- 

 day to explain every minute peculiarity of any 

 one particular species by an appeal to natural se- 

 lection alone is not the main point to be consid- 

 ered in estimating the success of the Darwinian 

 theory. The question has a scientific interest of 

 its own which is very great, but it is not the main 

 question. The main point is that, admitting nat- 

 ural selection to be a vera causa at all (and this 

 no one denies), the stability of species is proved 

 to be but a contingent and temporary affair. The 

 old notion of an absolute fixity of species is over- 

 thrown once for all, and with it the only sem- 

 blance of an argument that could ever have been 

 alleged in behalf of the hypothesis of special cre- 

 ations. For in considering nearly allied forms, 

 like the lion, tiger, and leopard, their actual con- 

 sanguinity would never have been doubted for a 

 moment but for the inability of naturalists to un- 

 derstand how the type which appears so constant, 

 when viewed through a short period of time and 

 amid unchanging conditions, should after all be 

 variable. Unable to imagine any probable cause 

 or method of variation by which the descendants 

 of a common feline ancestor should have acquired 

 the divergent characters of lions and leopards, the 

 naturalist either gave up the problem as insoluble, 



