﻿Theories 
  of 
  Evolution 
  19 
  

  

  show 
  that 
  he 
  was 
  quite 
  right, 
  and 
  that 
  the 
  

   cause 
  of 
  the 
  divergence 
  of 
  opinions 
  is 
  due 
  

   simply 
  to 
  the 
  very 
  incomplete 
  state 
  of 
  knowl- 
  

   edge 
  concerning 
  both 
  processes. 
  If 
  both 
  are 
  

   critically 
  analyzed 
  they 
  may 
  be 
  seen 
  to 
  comprise 
  

   the 
  same 
  factors 
  and 
  further 
  discussion 
  may 
  be 
  

   limited 
  to 
  the 
  appreciation 
  of 
  the 
  part, 
  which 
  

   each 
  of 
  them 
  has 
  played 
  in 
  nature 
  and 
  among 
  

   cultivated 
  plants. 
  

  

  Both 
  natural 
  and 
  artificial 
  selection 
  are 
  part- 
  

   ly 
  specific, 
  and 
  partly 
  intra-specific 
  or 
  individ- 
  

   ual. 
  Nature 
  of 
  course, 
  and 
  intelligent 
  men 
  first 
  

   chose 
  the 
  best 
  elementary 
  species 
  from 
  among 
  

   the 
  swarms. 
  In 
  cultivation 
  this 
  is 
  the 
  process 
  of 
  

   variety-testing. 
  In 
  nature 
  it 
  is 
  the 
  survival 
  of 
  

   the 
  fittest 
  species, 
  or, 
  as 
  Morgan 
  designates 
  it, 
  

   the 
  survival 
  of 
  species 
  in 
  the 
  struggle 
  for 
  ex- 
  

   istence. 
  The 
  species 
  are 
  not 
  changed 
  by 
  this 
  

   struggle, 
  they 
  are 
  only 
  weighed 
  against 
  each 
  

   other, 
  the 
  weak 
  being 
  thrown 
  aside. 
  

  

  Within 
  the 
  chosen 
  elementary 
  species 
  there 
  

   is 
  also 
  a 
  struggle. 
  It 
  is 
  obvious, 
  that 
  the 
  fluc- 
  

   tuating 
  variability 
  adapts 
  some 
  to 
  the 
  given 
  

   circumstances, 
  while 
  it 
  lessens 
  the 
  chances 
  of 
  

   others. 
  A 
  choice 
  results, 
  and 
  this 
  choice 
  is 
  

   what 
  is 
  often 
  exclusively 
  called 
  selection, 
  either 
  

   natural 
  or 
  artificial. 
  In 
  cultivation 
  it 
  produces 
  

   the 
  improved 
  and 
  the 
  local 
  races 
  ; 
  in 
  nature 
  little 
  

   is 
  known 
  about 
  improvement 
  in 
  this 
  way, 
  but 
  

  

  