﻿2 
  Descent 
  

  

  bringing 
  the 
  theory 
  of 
  common 
  descent 
  to 
  its 
  

   present 
  high 
  rank 
  in 
  scientific 
  and 
  social 
  phi- 
  

   losophy. 
  

  

  Two 
  main 
  features 
  in 
  his 
  work 
  have 
  contrib- 
  

   uted 
  to 
  this 
  early 
  and 
  unexpected 
  victory. 
  One 
  

   of 
  them 
  is 
  the 
  almost 
  unlimited 
  amount 
  of 
  com- 
  

   parative 
  evidence, 
  the 
  other 
  is 
  his 
  demonstration 
  

   of 
  the 
  possibility 
  of 
  a 
  physiological 
  explanation 
  

   of 
  the 
  process 
  of 
  descent 
  itself. 
  

  

  The 
  universal 
  belief 
  in 
  the 
  independent 
  crea- 
  

   tion 
  of 
  living 
  organisms 
  was 
  revised 
  by 
  

   Linnaeus 
  and 
  was 
  put 
  upon 
  a 
  new 
  foundation. 
  

   Before 
  him 
  the 
  genera 
  were 
  supposed 
  to 
  be 
  

   created, 
  the 
  species 
  and 
  minor 
  forms 
  having 
  

   arisen 
  from 
  them 
  through 
  the 
  agency 
  of 
  ex- 
  

   ternal 
  conditions. 
  In 
  his 
  first 
  book 
  Linnaeus 
  

   adhered 
  to 
  this 
  belief, 
  but 
  later 
  changed 
  his 
  

   mind 
  and 
  maintained 
  the 
  principle 
  of 
  the 
  sep- 
  

   arate 
  creation 
  of 
  species. 
  The 
  weight 
  of 
  his 
  

   authority 
  soon 
  brought 
  this 
  conception 
  to 
  uni- 
  

   versal 
  acceptance, 
  and 
  up 
  to 
  the 
  present 
  time 
  

   the 
  prevailing 
  conception 
  of 
  a 
  species 
  has 
  been 
  

   chiefly 
  based 
  on 
  the 
  definition 
  given 
  by 
  Linnaeus. 
  

   His 
  species 
  comprised 
  subspecies 
  and 
  varieties, 
  

   which 
  were 
  in 
  their 
  turn, 
  supposed 
  to 
  have 
  

   evolved 
  from 
  species 
  by 
  the 
  common 
  method. 
  

  

  Darwin 
  tried 
  to 
  show 
  that 
  the 
  links 
  which 
  

   bind 
  species 
  to 
  genera 
  are 
  of 
  the 
  same 
  nature 
  

   as 
  those 
  which 
  determine 
  the 
  relationship 
  of 
  

  

  