﻿580 
  Mutations 
  

  

  of 
  the 
  highest 
  importance 
  and 
  admits 
  of 
  only 
  

   two 
  explanations. 
  One 
  is 
  that 
  intermediates 
  

   may 
  be 
  assumed 
  to 
  have 
  preceded 
  the 
  existent 
  

   developed 
  form, 
  and 
  to 
  have 
  died 
  out 
  after- 
  

   wards. 
  But 
  why 
  should 
  they 
  have 
  done 
  so, 
  

   especially 
  in 
  cases 
  of 
  recent 
  changes? 
  On 
  the 
  

   other 
  hand 
  the 
  intermediates 
  may 
  be 
  lacking 
  

   because 
  they 
  have 
  never 
  existed, 
  the 
  change 
  

   having 
  taken 
  place 
  by 
  a 
  sudden 
  leap, 
  such 
  as 
  the 
  

   mutations 
  described 
  in 
  our 
  former 
  lectures. 
  It 
  

   is 
  manifest 
  that 
  the 
  assumption 
  of 
  hypothetical 
  

   intermediates 
  could 
  only 
  gain 
  some 
  probability 
  

   if 
  they 
  had 
  been 
  found 
  in 
  some 
  instance. 
  Since 
  

   they 
  do 
  not 
  occur, 
  the 
  hypothesis 
  seems 
  wholly 
  

   unsupported. 
  

  

  The 
  second 
  point 
  is 
  the 
  constancy 
  of 
  the 
  new 
  

   type. 
  Seeds 
  should 
  be 
  saved 
  and 
  sown. 
  If 
  the 
  

   plant 
  fertilizes 
  itself 
  without 
  the 
  aid 
  of 
  insects, 
  

   as 
  do 
  some 
  evening-primroses, 
  the 
  seed 
  saved 
  

   from 
  the 
  native 
  locality 
  may 
  prove 
  wholly 
  pure, 
  

   and 
  if 
  it 
  does 
  give 
  rise 
  to 
  a 
  uniform 
  progeny 
  the 
  

   constancy 
  of 
  the 
  race 
  may 
  be 
  assumed 
  to 
  be 
  

   proved, 
  provided 
  that 
  repeated 
  trials 
  do 
  not 
  

   bring 
  to 
  light 
  any 
  exceptions. 
  If 
  the 
  offspring 
  

   shows 
  more 
  than 
  one 
  type, 
  cross-fertilization 
  is 
  

   always 
  to 
  be 
  looked 
  to 
  as 
  the 
  most 
  probable 
  

   cause, 
  and 
  should 
  be 
  excluded, 
  in 
  order 
  to 
  sow 
  

   pure 
  seeds. 
  Garden-experiments 
  of 
  this 
  kind, 
  

   and 
  repeated 
  trials, 
  should 
  always 
  be 
  combined 
  

  

  