﻿Theories 
  of 
  Evolution 
  13 
  

  

  planting 
  one 
  in 
  a 
  garden, 
  varietal 
  differences 
  

   at 
  once 
  arise 
  and 
  are 
  often 
  designated 
  in 
  sys- 
  

   tematic 
  works 
  under 
  different 
  varietal 
  names. 
  

   Secondly 
  all 
  individual 
  differences 
  which 
  are 
  of 
  

   a 
  fluctuating 
  nature 
  are 
  to 
  be 
  combined 
  into 
  a 
  

   group. 
  But 
  with 
  these 
  we 
  shall 
  deal 
  later. 
  

  

  Apart 
  from 
  these 
  minor 
  points 
  the 
  subdi- 
  

   visions 
  of 
  the 
  systematic 
  species 
  exhibit 
  two 
  

   widely 
  different 
  features. 
  I 
  will 
  now 
  try 
  to 
  

   make 
  this 
  clear 
  in 
  a 
  few 
  words, 
  but 
  will 
  return 
  

   in 
  another 
  lecture 
  to 
  a 
  fuller 
  discussion 
  of 
  this 
  

   most 
  interesting 
  contrast. 
  

  

  Linnaeus 
  himself 
  knew 
  that 
  in 
  some 
  cases 
  all 
  

   subdivisions 
  of 
  a 
  species 
  are 
  of 
  equal 
  rank, 
  to- 
  

   gether 
  constituting 
  the 
  group 
  called 
  species. 
  

   No 
  one 
  of 
  them 
  outranks 
  the 
  others; 
  it 
  is 
  not 
  

   a 
  species 
  with 
  varieties, 
  but 
  a 
  group 
  consisting 
  

   only 
  of 
  varieties. 
  A 
  closer 
  inquiry 
  into 
  the 
  

   cases 
  treated 
  in 
  this 
  manner 
  by 
  the 
  great 
  master 
  

   of 
  systematic 
  science, 
  shows 
  that 
  here 
  his 
  varie- 
  

   ties 
  were 
  exactly 
  what 
  we 
  now 
  call 
  elementary 
  

   species. 
  

  

  In 
  other 
  cases 
  the 
  varieties 
  are 
  of 
  a 
  deriva- 
  

   tive 
  nature. 
  The 
  species 
  constitutes 
  a 
  type 
  that 
  

   is 
  pure 
  in 
  a 
  race 
  which 
  ordinarily 
  is 
  still 
  grow- 
  

   ing 
  somewhere, 
  though 
  in 
  some 
  cases 
  it 
  may 
  

   have 
  died 
  out. 
  From 
  this 
  type 
  the 
  varieties 
  are 
  

   derived, 
  and 
  the 
  way 
  of 
  this 
  derivation 
  is 
  usual- 
  

   ly 
  quite 
  manifest 
  to 
  the 
  botanist. 
  It 
  is 
  ordina- 
  

  

  