﻿Theories 
  of 
  Evolution 
  3 
  

  

  subspecies 
  and 
  varieties. 
  If 
  an 
  origin 
  by 
  nat- 
  

   ural 
  laws 
  is 
  conceded 
  for 
  the 
  latter, 
  it 
  must, 
  on 
  

   this 
  ground 
  be 
  granted 
  for 
  the 
  first 
  also. 
  In 
  

   this 
  discussion 
  he 
  simply 
  returned 
  to 
  the 
  pre- 
  

   Linnean 
  attitude. 
  But 
  his 
  material 
  was 
  such 
  

   as 
  to 
  allow 
  him 
  to 
  go 
  one 
  step 
  further, 
  and 
  this 
  

   step 
  was 
  an 
  important 
  and 
  decisive 
  one. 
  He 
  

   showed 
  that 
  the 
  relation 
  between 
  the 
  various 
  

   genera 
  of 
  a 
  family 
  does 
  not 
  exhibit 
  any 
  fea- 
  

   tures 
  of 
  a 
  nature 
  other 
  than 
  that 
  between 
  the 
  

   species 
  of 
  a 
  genus. 
  What 
  has 
  been 
  conceded 
  

   for 
  the 
  one 
  must 
  needs 
  be 
  accepted 
  for 
  the 
  

   other. 
  The 
  same 
  holds 
  good 
  for 
  the 
  large 
  

   groups. 
  The 
  conviction 
  of 
  the 
  common 
  origin 
  

   of 
  closely 
  allied 
  forms 
  necessarily 
  leads 
  to 
  the 
  

   conception 
  of 
  a 
  similar 
  descent 
  even 
  in 
  remote 
  

   relationships. 
  

  

  The 
  origin 
  of 
  subspecies 
  and 
  varieties 
  as 
  

   found 
  in 
  nature 
  was 
  not 
  proved, 
  but 
  only 
  gen- 
  

   erally 
  recognized 
  as 
  evident. 
  A 
  broader 
  

   knowledge 
  has 
  brought 
  about 
  the 
  same 
  state 
  of 
  

   opinion 
  for 
  greater 
  groups 
  of 
  relationships. 
  

   Systematic 
  affinities 
  find 
  their 
  one 
  possible 
  ex- 
  

   planation 
  by 
  the 
  aid 
  of 
  this 
  principle; 
  without 
  

   it, 
  all 
  similarity 
  is 
  only 
  apparent 
  and 
  accidental. 
  

   Geographic 
  and 
  paleontologic 
  facts, 
  brought 
  to- 
  

   gether 
  by 
  Darwin 
  and 
  others 
  on 
  a 
  previously 
  

   unequalled 
  scale, 
  point 
  clearly 
  in 
  the 
  same 
  di- 
  

   rection. 
  The 
  vast 
  amount 
  of 
  evidence 
  of 
  all 
  

  

  