Goethe's speculations. 91 



following passage : — " The triumph of physiological meta- 

 morphosis manifests itself where the whole separates and 

 transforms itself into families, the families into genera, the 

 genera into species, and then again into other varieties 

 down to the individual. This operation of nature goes on 

 ad infinitum ; she cannot rest inactive, but neither can she 

 keep and preserve all that she has produced. From seeds 

 there are always developed varying plants, exhibiting the 

 relations of their parts to one another in an altered manner." 



Goethe had, in truth, discovered two great mechanical 

 forces of nature, which are the active causes of organic 

 formations, his two organic formative tendencies — on the 

 one hand the conservative, centripetal, and internal forma- 

 tive tendency of Inheritance or specification ; and on the 

 other hand the progressive, centrifugal, and external form- 

 ative tendency of Adaptation, or metamorphosis. This 

 profound biological intuition could not but lead him natur- 

 ally to the fundamental idea of the Doctrine of Filiation, that 

 is, to the conception that the organic species resembling one 

 another in form are actually related by blood, and that they 

 are descended from a common original type. In regard to 

 the most important of all animal groups, namely that ot 

 Vertebrate animals, Goethe expresses this doctrine in the 

 following passage (1796 ) : — " Thus much then we have 

 gained, that we may assert without hesitation that all the 

 more perfect organic natures, such as fishes, amphibious 

 animals, birds, mammals, and man at the head of the last, 

 were all formed upon one original type, which only varies 

 more or less in parts which are none the less permanent, and 

 still daily changes and modifies its form by propagation." 



This sentence is of interest in more than one way. The 



