﻿14 
  Descent 
  

  

  rily 
  by 
  the 
  disappearance 
  of 
  some 
  superficial 
  

   character 
  that 
  a 
  variety 
  is 
  distinguished 
  from 
  

   its 
  species, 
  as 
  by 
  the 
  lack 
  of 
  color 
  in 
  the 
  flowers, 
  

   of 
  hairs 
  on 
  stems 
  and 
  foliage, 
  of 
  the 
  spines 
  and 
  

   thorns, 
  &c. 
  Such 
  varieties 
  are, 
  strictly 
  speak- 
  

   ing, 
  not 
  to 
  be 
  treated 
  in 
  the 
  same 
  way 
  as 
  elemen- 
  

   tary 
  species, 
  though 
  they 
  often 
  are. 
  We 
  shall 
  

   designate 
  them 
  by 
  the 
  term 
  of 
  " 
  retrograde 
  

   varieties," 
  which 
  clearly 
  indicates 
  the 
  nature 
  of 
  

   their 
  relationship 
  to 
  the 
  species 
  from 
  which 
  they 
  

   are 
  assumed 
  to 
  have 
  sprung. 
  In 
  order 
  to 
  lay 
  

   more 
  stress 
  on 
  the 
  contrast 
  between 
  elementary 
  

   species 
  and 
  retrograde 
  varieties, 
  it 
  should 
  be 
  

   stated 
  at 
  once, 
  that 
  the 
  first 
  are 
  considered 
  to 
  

   have 
  originated 
  from 
  their 
  parent-form 
  in 
  a 
  

   progressive 
  way. 
  They 
  have 
  succeeded 
  in 
  at- 
  

   taining 
  something 
  quite 
  new 
  for 
  themselves, 
  

   while 
  retrograde 
  varieties 
  have 
  only 
  thrown 
  

   off 
  some 
  peculiarity, 
  previously 
  acquired 
  by 
  

   their 
  ancestors. 
  

  

  The 
  whole 
  vegetable 
  kingdom 
  exhibits 
  a 
  con- 
  

   stant 
  struggle 
  between 
  progression 
  and 
  retro- 
  

   gression. 
  Of 
  course, 
  the 
  great 
  lines 
  of 
  the 
  gen- 
  

   eral 
  pedigree 
  are 
  due 
  to 
  progression, 
  many 
  

   single 
  steps 
  in 
  this 
  direction 
  leading 
  together 
  to 
  

   the 
  great 
  superiority 
  of 
  the 
  flowering 
  plants 
  

   over 
  their 
  cryptogamous 
  ancestors. 
  But 
  pro- 
  

   gression 
  is 
  nearly 
  always 
  accompanied 
  by 
  re- 
  

   trogression 
  in 
  the 
  principal 
  lines 
  of 
  evolution, 
  

  

  