transformations ; instead of a logical sequence of ideas they 

 posit a transforming and progressive development. Zool- 

 ogy constructs a system of specific and generic concepts, 

 "an animal kingdom with logical relations." Our concepts 

 are derived from natural objects, but in reality do not per- 

 fectly correspond to them. The phylogenetic school com- 

 mits the capital mistake of presenting a transformation 

 which can be realized only in logical concepts, as an actu- 

 ally occurring process, and of confounding an abstract 

 operation with concrete fact. "The logical transformation 

 of the concept ape into the concept man is no genealogical 

 j-rocess." The mathematician may logically 'develop' the 

 concept of a circle from that of a polygon, but it by no 

 means follows that the circle is phjlo-genetically derived 

 from the polygon. 



Because the concept of species is variable, the species 

 themselves, according to Darwin,, should be subject to a 

 continual flux; whereas the real cause of the variability 

 which he observed lies in the discrepancy between objective 

 facts and their logical tabulation, in the narrowness of our 

 concepts and in the lack of adequate means of expression. 

 He thus makes natural objects responsible for our logical 

 limitations. 



With regard to organisms the Descent-school con- 

 founded the purely logical signification of the word "re- 

 lated" with that of blood or family affinity. But surely 

 when they speak of the relation of forms in the crystal 

 systems, they do not refer tO' genetic connection. To-day 



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