SECTION III 



INFLUENCE OF ADAPTATION IN THE FORMATION OF SPECIES 



Is everything adapted ? 



FROM the preceding considerations it appears to me, therefore, 

 that leaving aside Kolliker's hypothesis, neither Nageli's view, 

 which ascribes to the principle of utility an almost infini- 

 tesimal effect, nor Weismann's, which regards adaptation as 

 all-powerful, can be unreservedly accepted. The truth lies 

 between them. Weismann in his latest paper explains every- 

 thing as adaptive. As an example of such complete adapta- 

 tion he describes the whale. 



He alludes to Nageli in his remark that he can perfectly 

 understand that it is more natural to a botanist than to a 

 zoologist to take refuge in internal forces of evolution. " The 

 relations of form to function, the adaptation of the organism 

 to the internal and external conditions of life, are less con- 

 spicuous in plants, less easily observed, indeed are often only 

 to be discovered by the most careful and acute investigation. 

 The temptation is therefore greater to regard everything as 

 due to causes acting from within." And he says further : 

 " In any case, animal biology cannot point out too emphatically 

 how exactly and to the minutest detail form and function go 

 together, how completely adaptation to definite conditions of 



