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  Mutations 
  

  

  points 
  are 
  in 
  need 
  of 
  correction 
  and 
  elaboration, 
  

   but 
  such 
  improvements 
  of 
  our 
  knowledge 
  will 
  

   gradually 
  increase 
  our 
  means 
  of 
  discovering 
  

   new 
  instances 
  and 
  new 
  proofs. 
  

  

  The 
  conception 
  of 
  mutation 
  periods 
  produc- 
  

   ing 
  swarms 
  of 
  species 
  from 
  time 
  to 
  time, 
  among 
  

   which 
  only 
  a 
  few 
  have 
  a 
  chance 
  of 
  survival, 
  

   promises 
  to 
  become 
  the 
  basis 
  for 
  speculative 
  

   pedigree-diagrams, 
  as 
  well 
  as 
  for 
  experimental 
  

   investigations. 
  

  

  