6 CLASSIFICATION AND ADAPTATION 



evolution has taken place, that the history of 

 organisms has been a process of descent with modi- 

 fication. If the animals and plants whose remains 

 are preserved as fossils, or at any rate forms closely 

 related to these, were not the ancestors of existing 

 forms, there are only two other possibilities : either 

 the existing forms came into existence by new 

 creations after the older forms became extinct, 

 or the ancestors of existing forms, although they 

 coexisted with the older forms, never left any fossil 

 remains. Each of these suppositions is incredible. 



In view of these plain facts and their logical 

 conclusion it is curious to notice how -Darwin in his 

 Origin of Species constantly mingles together argu- 

 ments to prove the proposition that evolution has 

 occurred, that the structure and relations of existing 

 animals can only be explained by descent with 

 modification, with arguments and evidence in 

 favour of natural selection as the explanation and 

 cause of evolution. In the great controversy about 

 evolution which his work aroused, the majority of 

 the educated public were ultimately convinced of the 

 truth of evolution by the belief that a sufficient cause 

 of the process of change had been discovered, 

 rather than by the logical conclusion that the 

 organisms of a later period were the descendants 

 of those of earlier periods. Even at the present 

 day the theory of natural selection is constantly 

 confused with the doctrine of evolution. The 

 fact is that the investigation of the causes of evolu- 

 tion has been going on and has been making progress 

 from the time of Darwin, and from times much earlier 

 than his, down to the present day. 



Bionomics show that every type must be adapted 



