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  Retrograde 
  Varieties 
  

  

  parents. 
  Partial 
  departures 
  are 
  rare 
  in 
  the 
  

   hybrids 
  themselves, 
  but 
  in 
  their 
  offspring 
  the 
  

   divergence 
  becomes 
  the 
  rule. 
  

  

  Segregation 
  seems 
  to 
  be 
  a 
  very 
  difficult 
  pro- 
  

   cess 
  in 
  the 
  vegetative 
  way, 
  but 
  it 
  must 
  be 
  very 
  

   easy 
  in 
  sexual 
  reproduction, 
  indeed 
  so 
  easy 
  as 
  

   to 
  show 
  itself 
  in 
  nearly 
  every 
  single 
  instance. 
  

  

  Leaving 
  this 
  first 
  generation, 
  the 
  original 
  

   hybrids, 
  we 
  now 
  come 
  to 
  a 
  discussion 
  of 
  their 
  

   offspring. 
  Hybrids 
  should 
  be 
  fertilized 
  either 
  

   by 
  their 
  own 
  pollen, 
  or 
  by 
  that 
  of 
  other 
  individ- 
  

   uals 
  born 
  from 
  the 
  same 
  cross. 
  Only 
  in 
  this 
  

   case 
  can 
  the 
  offspring 
  be 
  considered 
  as 
  a 
  means 
  

   of 
  arriving 
  at 
  a 
  decision 
  as 
  to 
  the 
  internal 
  na- 
  

   ture 
  of 
  the 
  hybrids 
  themselves. 
  Breeders 
  gen- 
  

   erally 
  prefer 
  to 
  fertilize 
  hybrids 
  with 
  the 
  pollen 
  

   of 
  their 
  parents. 
  But 
  this 
  operation 
  is 
  to 
  be 
  

   considered 
  as 
  a 
  new 
  cross, 
  and 
  consequently 
  is 
  

   wholly 
  excluded 
  from 
  our 
  present 
  discussion. 
  

   Hence 
  it 
  follows 
  that 
  a 
  clear 
  insight 
  into 
  the 
  

   heredity 
  of 
  hybrids 
  may 
  be 
  expected 
  only 
  from 
  

   scientific 
  experiments. 
  Furthermore 
  some 
  of 
  

   the 
  diversity 
  observed 
  as 
  a 
  result 
  of 
  ordinary 
  

   crosses, 
  may 
  be 
  due 
  to 
  the 
  instability 
  of 
  the 
  par- 
  

   ents 
  themselves 
  or 
  at 
  least 
  of 
  one 
  of 
  them, 
  since 
  

   breeders 
  ordinarily 
  choose 
  for 
  their 
  crosses 
  

   some 
  already 
  very 
  variable 
  strain. 
  Combining 
  

   such 
  a 
  strain 
  with 
  the 
  desirable 
  qualities 
  of 
  

   some 
  newly 
  imported 
  species, 
  a 
  new 
  strain 
  may 
  

  

  