﻿460 
  Mutations 
  

  

  ently 
  lost 
  character. 
  The 
  elementary 
  species, 
  

   on 
  the 
  other 
  hand, 
  must 
  have 
  arisen 
  by 
  the 
  pro- 
  

   duction 
  of 
  new 
  qualities, 
  each 
  new 
  acquisition 
  

   constituting 
  the 
  origin 
  of 
  a 
  new 
  elementary 
  

   form. 
  

  

  Moreover 
  we 
  have 
  seen, 
  that 
  such 
  improve- 
  

   ments 
  and 
  such 
  losses 
  constitute 
  sharp 
  limits 
  

   between 
  the 
  single 
  unit-forms. 
  Every 
  type, 
  of 
  

   course, 
  varies 
  around 
  an 
  average, 
  and 
  the 
  ex- 
  

   tremes 
  of 
  one 
  form 
  may 
  sometimes 
  reach 
  or 
  

   even 
  overlap 
  those 
  of 
  the 
  nearest 
  allies, 
  but 
  

   the 
  offspring 
  of 
  the 
  extremes 
  always 
  return 
  to 
  

  

  i 
  

  

  the 
  type. 
  The 
  transgression 
  is 
  only 
  temporary 
  

   and 
  a 
  real 
  transition 
  of 
  one 
  form 
  to 
  another 
  

   does 
  not 
  come 
  within 
  ordinary 
  features 
  of 
  fluc- 
  

   tuating 
  variability. 
  Even 
  in 
  the 
  cases 
  of 
  ever- 
  

   sporting 
  varieties, 
  where 
  two 
  opposite 
  types 
  

   are 
  united 
  within 
  one 
  race, 
  and 
  where 
  the 
  suc- 
  

   ceeding 
  individuals 
  are 
  continually 
  swinging 
  

   from 
  one 
  extreme 
  to 
  the 
  other, 
  passing 
  through 
  

   a 
  wide 
  range 
  of 
  intermediate 
  steps, 
  the 
  limits 
  

   of 
  the 
  variety 
  are 
  as 
  sharply 
  defined 
  and 
  as 
  free 
  

   from 
  real 
  transgression 
  as 
  in 
  any 
  other 
  form. 
  

  

  In 
  a 
  complete 
  systematic 
  enumeration 
  of 
  the 
  

   real 
  units 
  of 
  nature, 
  the 
  elementary 
  species 
  and 
  

   varieties 
  are 
  thus 
  observed 
  to 
  be 
  discontinous 
  

   and 
  separated 
  by 
  definite 
  gaps. 
  Every 
  unit 
  

   may 
  have 
  its 
  youth, 
  may 
  lead 
  a 
  long 
  life 
  in 
  the 
  

   adult 
  state 
  and 
  may 
  finally 
  die. 
  But 
  through 
  

  

  