VI.] SPECIES AST) TUFE. 155 



twenty-four million years ago. On tlie other hand, he 

 seems to consider that specific change has been more rapid 

 than generally supposed, and exceptionally stable during 

 the last score or so of thousand years. 



Now, first, with regard to the time required for the 

 evolution of all organic forms by merely accidental, 

 minute, and fortuitous variations, the useful ones of which 

 have been preserved : 



]Mr. jNIurphy ^ is of opinion that tliere has not been time 

 enough. He says, " I am inclined to think that geological 

 time is too short for the evolution of the higher forms of 

 life out of the lower by that accumulation of impercep- 

 tibly slow variations to which alone Darwin ascribes the 

 whole process." 



'• Darwin justly mentions the greyhound as being equal 

 to any natural species in the perfect co-ordination of its 

 parts, ' all adapted for extreme fleetness and for running- 

 down weak prey.' " "Yet it is an artificial species (and not 

 physiologicaUy a species at all), formed by long-continued 

 selection under domestication ; and there is no reason to 

 suppose that any of the variations which have been selected 

 to form it have been other than gradual and almost imper- 

 ceptible. Suppose that it has taken five hundred years to 

 form the greyhound out of his wolf-like ancestor. This is 

 a mere guess, but it gives the order of the magnitude." 

 Now, if so, " how long would it take to obtain an elephant 

 from a protozoon, or even from a tadpole-like fish ? Ought 

 it not to take much more than a million times as 



long ? 



?> o 



Mr. Darwin ^ would compare with the natural origin of 



1 "Habit and Iiitolligence," vol. i. p. 344. -' ibij. vol. i. p. 345. 



» "Origan of Species," 5tli edition, p. 353. 



