﻿254 
  Retrograde 
  Varieties 
  

  

  their 
  qualities 
  from 
  both 
  parents 
  ; 
  for 
  each 
  sin- 
  

   gle 
  mark 
  they 
  possess 
  at 
  least 
  two 
  units. 
  Prac- 
  

   tically 
  but 
  not 
  absolutely 
  equal, 
  these 
  two 
  op- 
  

   ponents 
  always 
  work 
  together 
  and 
  give 
  to 
  the 
  

   offspring 
  a 
  likeness 
  to 
  both 
  parents. 
  No 
  un- 
  

   paired 
  qualities 
  occur 
  in 
  normal 
  offspring 
  ; 
  these 
  

   constitute 
  the 
  essential 
  features 
  of 
  the 
  hybrids 
  

   of 
  species 
  and 
  are 
  at 
  the 
  same 
  time 
  the 
  cause 
  of 
  

   their 
  wide 
  deviations 
  from 
  the 
  ordinary 
  rules. 
  

  

  Turning 
  now 
  to 
  the 
  varieties, 
  we 
  likewise 
  

   need 
  discuss 
  their 
  differentiating 
  marks 
  only. 
  

   In 
  the 
  negative 
  types, 
  these 
  consist 
  of 
  the 
  ap- 
  

   parent 
  loss 
  of 
  some 
  quality 
  which 
  was 
  active 
  in 
  

   the 
  species. 
  But 
  it 
  was 
  pointed 
  out 
  in 
  our 
  last 
  

   lecture 
  that 
  such 
  a 
  change 
  is 
  an 
  apparent 
  loss. 
  

   On 
  a 
  closer 
  inquiry 
  we 
  are 
  led 
  to 
  the 
  assumption 
  

   of 
  a 
  latent 
  or 
  dormant 
  state. 
  The 
  presumably 
  

   lost 
  characters 
  have 
  not 
  absolutely, 
  or 
  at 
  least 
  

   not 
  permanently 
  disappeared. 
  They 
  show 
  

   their 
  presence 
  by 
  some 
  slight 
  indication 
  of 
  the 
  

   quality 
  they 
  represent, 
  or 
  by 
  occasional 
  revers- 
  

   ions. 
  They 
  are 
  not 
  wanting, 
  but 
  only 
  latent. 
  

  

  Basing 
  our 
  discussion 
  concerning 
  the 
  process 
  

   of 
  crossing 
  on 
  this 
  conception, 
  and 
  still 
  limiting 
  

   the 
  discussion 
  to 
  one 
  differentiating 
  mark, 
  we 
  

   come 
  to 
  the 
  inference, 
  that 
  this 
  mark 
  is 
  present 
  

   and 
  active 
  in 
  the 
  species, 
  and 
  present 
  but 
  dor- 
  

   mant 
  in 
  the 
  variety. 
  Thus 
  it 
  is 
  present 
  in 
  both, 
  

   and 
  as 
  all 
  other 
  characters 
  not 
  differentiating 
  

  

  