IX. 



THE DEVELOPMENT HYPOTHESIS. 



IN a debate upon the development hypothesis, lately nar 

 rated to me by a friend, one of the disputants was de- 

 scribed as arguing, that as, in all our experience, we know 

 no such phenomenon as transmutation of species, it is un- 

 philosophical to assume that transmutation of species e\ er 

 takes place. Had I been present, I think that, passing over 

 his assertion, which is open to criticism, I should have re- 

 plied that, as in all our experience we have never known a 

 species created^ it was, by his own showing, unphilosophical 

 to assume that any species ever had been created. 



Those who cavalierly reject the Theory of Evolution, as 

 not adequately supported by facts, seem quite to forget 

 that their own theory is supported by no facts at all. Like 

 the majority of men who are born to a given belief, they 

 demand the most rigorous proof of any adverse belief, but 

 assume that their own needs none. Here we find, scattered 

 over the globe, vegetable and animal organisms numbering, 

 of the one kind (according to Humboldt), some 320,000 

 species, and of the other, some 2,000,000 species (see Car- 

 penter) ; and if to these we add the numbers of animal and 

 vegetable species that have become extinct, we may safelj 

 estimate the number of species that have existed, and are 



