DARWIN'S THEORY. 17 



should be regarded as distinct species ; and, perhaps, 

 others which a person, so judging, would be not too 

 bold in accounting as belonging to different genera. 

 The argument of Darwin is, 



" How possibly can there be fixed species, or immut- 

 able species, when the individuals, which represent 

 those species, vary and change so greatly ? A species 

 is made up of individuals ; and, when those individuals 

 change, the species, also, must necessarily change." 



And, again, he argues, if difference in structural 

 build is what alone constitutes the distinction between 

 species, why, then, should not the great differences in 

 structural build, between varieties of what has hereto- 

 fore been known, or taken, to be one species, be taken 

 as specific distinctions ? 



Having detailed, at large, these- facts of variation, 

 from which Darwin purposes to deduce his theory, the 

 necessity of some inquiry into the natural forces at 

 work in inducing these improvements, occurred to 

 Darwin. Some aspect of these variations — either 

 founded upon a scientific analysis of the phenomena, 

 or, else, gratuitously assumed — -had necessarily to be 

 taken for granted, as a basis for further research. The 

 question, for instance, whether these variations are 

 amenable to any limit ; the question, too, whether it be 

 legitimate to estimate the amount of improvement 

 possible to occur in millions of years, by means of these 

 variations, from the amount of development known to 

 have taken place during the last one hundred years ; 

 could not be resolved, unless some view was taken. 

 Darwin admits — aye, explicitly states — that he has not 



