58 EVOLUTION OF TO-DAY. 



Agassiz and Darwin recognized that there is a unity 

 in the organic world, and to prove this unity essen- 

 tially the same arguments were used by both. In 

 the interpretation of this unity only did they differ. 

 While Agassiz places the unity in the mind of the 

 Creator, Darwin finds an equally intelligible and a 

 much more natural explanation in the theory of 

 genetic descent. Agassiz' essay was thus as strong an 

 argument for evolution as it was for his own theory, 

 although, of course, he did not recognize this fact. 



Either of these theories is an explanation of clas- 

 sification, and either of them if admitted will account 

 for many or most of the facts. It is, moreover, by 

 no means impossible that both may be in a measure 

 right ; that types of the animal kingdom did exist in 

 the mind of the Creator, and that his method of ex- 

 pressing or materializing these types was by genetic 

 descent, or evolution. While then the two views are 

 not incompatible, we must recognize that the first is 

 not open to investigation, since it lies beyond the 

 realm of human knowledge. The evolutionist, more- 

 over, claims that whatever be our belief as to crea- 

 tion, the facts of the organic world are such as to in- 

 dicate that the introduction of species, families, etc., 

 into this world, has been by genetic descent, and that 

 the history of the organic world has been evolution. 

 The reasons for this claim we must now examine. 



The Relation of the Various Great and Small Types 

 is Expressed by a Branching Tree-like Structure. 



It has been in the first place urged by those who 

 argue for evolution, that upon the theory of types 



