PRECIS OF CONTENTS xiii 



CHAPTER X 



SUMMARY AND CONCLUSIONS 



The fundamental divergences in evolutionary theory — the organism as the 

 product of variation guided by environmental change and as endowed 

 with an internal momentum. Limitations of our knowledge. The 

 origin of groups and the production of adaptation are the outstanding 

 features of evolution. The apparent unitary nature of the evolutionary 

 process ; are group-formation and adaptation produced by the same 

 process ? The evolutionary relationship between specialisation and 

 organisation. Natural selection and the unitary concept of evolution. 

 Discussion of the evidence for the efficiency of natural selection. The 

 role of Lamarckism and ' induced ' mutations. The importance of 

 certain ' orthogenetic ' phenomena. Summary of the main theories 

 of evolution. The ' spread ' of variants an acid test of evolutionary 

 theories. Difficulty of regarding organisation as a product of natural 

 selection. 



