﻿Periodic 
  Mutations 
  693 
  

  

  natively 
  mutating 
  and 
  constant 
  species. 
  Some 
  

   lines 
  may 
  be 
  mutating 
  at 
  the 
  present 
  moment; 
  

   others 
  may 
  momentarily 
  be 
  constant. 
  The 
  mu- 
  

   tating 
  lines 
  will 
  probably 
  sooner 
  or 
  later 
  revert 
  

   to 
  the 
  inactive 
  state, 
  while 
  the 
  powers 
  of 
  de- 
  

   velopment 
  now 
  dormant 
  may 
  then 
  become 
  awak- 
  

   ened 
  on 
  other 
  branches. 
  

  

  The 
  view 
  of 
  permanency 
  represents 
  life 
  as 
  

   being 
  surrounded 
  with 
  unavoidable 
  death, 
  the 
  

   principle 
  of 
  periodicity, 
  on 
  the 
  contrary, 
  fol- 
  

   lows 
  the 
  idea 
  of 
  resurrection, 
  granting 
  the 
  

   possibility 
  of 
  future 
  progression 
  for 
  all 
  living 
  

   beings. 
  At 
  the 
  same 
  time 
  it 
  yields 
  a 
  more 
  hope- 
  

   ful 
  prospect 
  for 
  experimental 
  inquiry. 
  

  

  Experience 
  must 
  decide 
  between 
  the 
  two 
  main 
  

   theories. 
  It 
  demonstrates 
  the 
  existence 
  of 
  poly- 
  

   morphous 
  genera, 
  such 
  as 
  Drab 
  a 
  and 
  Viola 
  and 
  

   hundreds 
  of 
  others. 
  They 
  clearly 
  indicate 
  a 
  

   previous 
  state 
  of 
  mutability. 
  Their 
  systematic 
  

   relation 
  is 
  exactly 
  what 
  would 
  be 
  expected, 
  if 
  

   they 
  were 
  the 
  result 
  of 
  such 
  a 
  period. 
  Perhaps 
  

   mutability 
  has 
  not 
  wholly 
  ceased 
  in 
  them, 
  but 
  

   might 
  be 
  found 
  to 
  survive 
  in 
  some 
  of 
  their 
  mem- 
  

   bers. 
  Such 
  very 
  rich 
  genera 
  however, 
  are 
  not 
  

   the 
  rule, 
  but 
  are 
  exceptional 
  cases, 
  indicating 
  

   the 
  rarity 
  of 
  powerful 
  imitative 
  changes. 
  

  

  On 
  the 
  other 
  hand, 
  species 
  may 
  remain 
  in 
  a 
  

   state 
  of 
  constancy 
  during 
  long, 
  apparently 
  dur- 
  

   ing 
  indefinite, 
  ages. 
  

  

  