﻿Unbalanced 
  Crosses 
  251 
  

  

  For 
  our 
  present 
  purposes 
  we 
  are 
  to 
  deal 
  with 
  

   hybrids 
  only 
  in 
  so 
  far 
  as 
  they 
  afford 
  the 
  means 
  

   of 
  a 
  still 
  better 
  distinction 
  between 
  elementary 
  

   species 
  and 
  varieties. 
  I 
  will 
  try 
  to 
  show 
  that 
  

   these 
  two 
  contrasting 
  groups 
  behave 
  in 
  quite 
  a 
  

   different 
  manner, 
  when 
  subjected 
  to 
  crossing 
  

   experiments, 
  and 
  that 
  the 
  hope 
  is 
  justified 
  

   that 
  some 
  day 
  crosses 
  may 
  become 
  the 
  means 
  of 
  

   deciding 
  in 
  any 
  given 
  instance, 
  what 
  is 
  to 
  be 
  

   called 
  a 
  species, 
  and 
  what 
  a 
  variety, 
  on 
  physio- 
  

   logic 
  grounds. 
  It 
  is 
  readily 
  granted 
  that 
  the 
  

   labor 
  required 
  for 
  such 
  experiments, 
  is 
  perhaps 
  

   too 
  great 
  for 
  the 
  results 
  to 
  be 
  attained, 
  but 
  then 
  

   it 
  may 
  be 
  possible 
  to 
  deduce 
  rules 
  from 
  a 
  small 
  

   series 
  of 
  experiments, 
  which 
  may 
  lead 
  us 
  to 
  a 
  

   decision 
  in 
  wider 
  ranges 
  of 
  cases. 
  

  

  To 
  reach 
  such 
  a 
  point 
  of 
  view 
  it 
  is 
  necessary 
  

   to 
  compare 
  the 
  evidence 
  given 
  by 
  hybrids, 
  with 
  

   the 
  conclusions 
  already 
  attained 
  by 
  the 
  com- 
  

   parison 
  of 
  the 
  differentiating 
  characteristics 
  of 
  

   allied 
  forms. 
  

  

  On 
  this 
  ground 
  we 
  first 
  have 
  to 
  inquire 
  what 
  

   may 
  be 
  expected 
  respecting 
  the 
  internal 
  nature 
  

   and 
  the 
  outcome 
  of 
  the 
  process 
  of 
  crossing 
  in 
  

   the 
  various 
  cases 
  cited 
  in 
  our 
  former 
  discussion. 
  

  

  We 
  must 
  always 
  distinguish 
  the 
  qualities, 
  

   which 
  are 
  the 
  same 
  in 
  both 
  parents, 
  from 
  those 
  

   that 
  constitute 
  the 
  differentiating 
  marks 
  in 
  

   every 
  single 
  cross. 
  In 
  respect 
  to 
  the 
  first 
  

  

  