VARIA TION. 23 



rant the conclusion of the mutability of species. 

 While, then, most naturalists regard the mutability of 

 species as no longer questionable, it is a conclusion 

 which has not been definitely proved. 



It will be admitted at the outset, on all sides, that 

 no unquestionable instance has been observed of one 

 species being derived from another. This is not 

 surprising, even if the mutability of species be 

 granted. It has been only twenty-five years since 

 naturalists have perceived the importance of the 

 question, and this is far too short a time for changes 

 of importance to occur. But there is even a greater 

 difficulty than this. Whenever it is shown that one 

 form has given rise to another, it is, of course, a very 

 simple matter to say that they are simply two forms 

 of the same species. It is, therefore, impossible at 

 present to place the matter beyond question. Two 

 very distinct animals are studied, which are every- 

 where acknowledged to be distinct species. After 

 careful study and experiment, it is found that one 

 may be converted into the other, and from this time 

 these two species are regarded simply as different 

 forms of one and the same species; and thus the 

 whole force of the proof is lost by this circular 

 argument. 



Variation. 



That species are absolutely immutable no one will 

 pretend to claim. It is repeatedly proved by facts 

 of every-day observation that species are subject to 

 a certain amount of variation and change. Every 

 one is aware of the effect of food, climate, hardship 



