﻿LECTURE 
  X 
  

   MENDEL'S 
  LAW 
  OF 
  BALANCED 
  CROSSES 
  

  

  In 
  the 
  scientific 
  study 
  of 
  the 
  result 
  of 
  crosses, 
  

   the 
  most 
  essential 
  point 
  is 
  the 
  distinction 
  of 
  the 
  

   several 
  characters 
  of 
  the 
  parents 
  in 
  their 
  combi- 
  

   nation 
  in 
  the 
  hybrids 
  and 
  their 
  offspring. 
  

   From 
  a 
  theoretical 
  point 
  of 
  view 
  it 
  would 
  be 
  

   best 
  to 
  choose 
  parents 
  which 
  would 
  differ 
  only 
  

   in 
  a 
  single 
  point. 
  The 
  behavior 
  of 
  the 
  differen- 
  

   tiating 
  character 
  might 
  then 
  easily 
  be 
  seen. 
  

  

  Unfortunately, 
  such 
  simple 
  cases 
  do 
  not 
  read- 
  

   ily 
  occur. 
  Most 
  species, 
  and 
  even 
  many 
  ele- 
  

   mentary 
  species 
  are 
  distinguished 
  by 
  more 
  than 
  

   one 
  quality. 
  Varieties 
  deviating 
  only 
  in 
  one 
  

   unit-character 
  from 
  the 
  species, 
  are 
  more 
  com- 
  

   mon. 
  But 
  a 
  closer 
  inspection 
  often 
  reveals 
  

   some 
  secondary 
  characters 
  which 
  may 
  be 
  over- 
  

   looked 
  in 
  comparative 
  or 
  descriptive 
  studies, 
  

   but 
  which 
  reassume 
  their 
  importance 
  in 
  experi- 
  

   mental 
  crossings. 
  

  

  In 
  a 
  former 
  lecture 
  we 
  have 
  dealt 
  with 
  the 
  

   qualities 
  which 
  must 
  be 
  considered 
  as 
  being 
  due 
  

   to 
  the 
  acquisition 
  of 
  new 
  characters. 
  If 
  we 
  

  

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