PREFACE 



The preparation of this small volume has been 

 the result of long dissatisfaction with the existing 

 treatment of the processes of evolution. Published 

 theories and discussions representing a wide range 

 of opinion are almost universally weak in the 

 treatment of certain problems which are clearly 

 fundamental. The logical solution of these prob- 

 lems is of the greatest importance, and even though 

 a final solution is at present impossible, the prob- 

 lems commend themselves to the attention of bi- 

 ologists. 



The problems of evolution arise mostly from 

 the interpretation of observed facts. While the 

 facts themselves cannot be a subject of serious 

 disagreement, their significance in this field is often 

 a matter of dispute. Philosophical inquiries here, 

 as elsewhere in scientific fields, are often sufficiently 

 removed from the facts to give a misleading plausi- 

 bility to theories of doubtful or limited value, 

 and a plausible theory is all too likely to assume 

 such importance in the minds of its supporters 

 that it may obscure other factors with which the 

 problem is associated. 



This difficulty may be met in two ways. On the 



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