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  one 
  differential 
  unit 
  in 
  the 
  parents, 
  we 
  may 
  

   give 
  it 
  in 
  the 
  following 
  manner. 
  In 
  fertiliza- 
  

   tion, 
  the 
  characters 
  of 
  both 
  parents 
  are 
  not 
  uni- 
  

   formly 
  mixed, 
  but 
  remain 
  separated 
  though 
  

   most 
  intimately 
  combined 
  in 
  the 
  hybrid 
  

   throughout 
  life. 
  They 
  are 
  so 
  combined 
  as 
  to 
  

   work 
  together 
  nearly 
  always, 
  and 
  to 
  have 
  nearly 
  

   equal 
  influence 
  on 
  all 
  the 
  processes 
  of 
  the 
  whole 
  

   individual 
  evolution. 
  But 
  when 
  the 
  time 
  ar- 
  

   rives 
  to 
  produce 
  progeny, 
  or 
  rather 
  to 
  produce 
  

   the 
  sexual 
  cells 
  through 
  the 
  combination 
  of 
  

   which 
  the 
  offspring 
  arises, 
  the 
  two 
  parental 
  

   characters 
  leave 
  each 
  other, 
  and 
  enter 
  sepa- 
  

   rately 
  into 
  the 
  sexual 
  cells. 
  From 
  this 
  it 
  may 
  be 
  

   seen 
  that 
  one-half 
  of 
  the 
  pollen-cells 
  will 
  have 
  

   the 
  quality 
  of 
  one 
  parent, 
  and 
  the 
  other 
  the 
  qual- 
  

   ity 
  of 
  the 
  other. 
  And 
  the 
  same 
  holds 
  good 
  for 
  

   the 
  egg-cells. 
  Obviously 
  the 
  qualities 
  lie 
  latent 
  

   in 
  the 
  pollen 
  and 
  in 
  the 
  egg, 
  but 
  ready 
  to 
  be 
  

   evolved 
  after 
  fertilization 
  has 
  taken 
  place. 
  

  

  Granting 
  these 
  premises, 
  we 
  may 
  now 
  ask 
  as 
  

   to 
  the 
  results 
  of 
  the 
  fertilization 
  of 
  hybrids, 
  

   when 
  this 
  is 
  brought 
  about 
  by 
  their 
  own 
  pollen. 
  

   We 
  assume 
  that 
  numerous 
  pollen 
  grains 
  fer- 
  

   tilize 
  numerous 
  egg 
  cells. 
  This 
  assumption 
  at 
  

   once 
  allows 
  of 
  applying 
  the 
  law 
  of 
  probability, 
  

   and 
  to 
  infer 
  that 
  of 
  each 
  kind 
  of 
  pollen 
  grains 
  

   one-half 
  will 
  reach 
  egg-cells 
  with 
  the 
  same 
  qual- 
  

  

  