V 



THEORIES OF EVOLUTION 



It would be gratifying if all studies of evolution 

 and all controversies on the subject could begin 

 with the same well-established foundation of facts, 

 but this is, unfortunately, impossible. The vitalists 

 still hold sway with the mechanists, the selection- 

 ists and mutationists have very nearly monopolized 

 the field, and the Lamarckians have trailed along 

 with dogged persistency in spite of the unfeeling 

 reception of their views by a large part of the 

 biological world. There is often misunderstanding 

 between the various schools of thought. The facts 

 of nature do not vary, but our knowledge of them 

 is such an exceedingly uncertain thing that in ex- 

 pressed views on evolution we must be critical of 

 everything involved. Theories may be attractive 

 and yet be unsoundly based; even apparently logi- 

 cal conclusions drawn from carefully safeguarded 

 experiments may be proved unsound by the use 

 of additional facts, sometimes of the most obvious 

 nature. And when we add to these difficulties the 

 utter impossibility of securing agreement even 

 among scientists on the significance of established 



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