GOETHE'S SPECULATIONS. QI 
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 orignal type. In regard to 
the most important of all animal groups, namely that of 
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 
