THE ORIGIN OF SPECIES. 23 



that the genius of an Agassiz will be found equal to the 

 work of constructing, upon the mental and material 

 foundations combined, a theory of Nature as theistic 

 and as scientific as that which he has so eloquently 

 expounded. 



To conceive the possibility of " the descent of 

 species from species by insensibly fine gradations" 

 during a long course of time, and to demonstrate its 

 compatibility with a strictly theistic view of the uni- 

 verse, is one thing ; to substantiate the theory itself 

 or show its likelihood is quite another thing. This 

 brings us to consider what Darwin's theory actually 

 is, and how he supports it. 



That the existing kinds of animals and plants, or 

 many of them, may be derived from other and earlier 

 kinds, in the lapse of time, is by no means a novel 

 proposition. Not to speak of ancient speculations of 

 the sort, it is the well-known Lamarckian theory. 

 The first difficulty which such theories meet with is 

 that in the present age, with all its own and its inher- 

 ited prejudgments, the whole burden of proof is nat- 

 urally, and indeed properly, laid upon the shoulders 

 of the propounders ; and thus far the burden has been 

 more than they could bear. From the very nature of 

 the case, substantive proof of specific creation is not 

 attainable ; but that of derivation or transmutation of 

 species may be. He who affirms the latter view is 

 bound to do one or both of two things : 1. Either to 

 assign real and adequate causes, the natural or neces- 

 sary result of which must be to produce the present 

 diversity of species and their actual relations ; or, 2. 

 To show the general conformity of the whole body of 



