﻿AND 
  STARCH 
  CHARACTERS 
  IN 
  CORN 
  179 
  

  

  or 
  a 
  means 
  of 
  swamping 
  out 
  existing 
  variations 
  involves 
  the 
  

   consideration 
  of 
  the 
  complicated 
  and 
  far 
  reaching 
  mechanical 
  

   and 
  chemical 
  interrelations 
  of 
  the 
  cell 
  structures 
  concerned 
  in 
  the 
  

   preparation 
  for, 
  and 
  achievement 
  of, 
  cell 
  or 
  gametic 
  fusion 
  and 
  the 
  

   pairing 
  of 
  the 
  chromosomes. 
  It 
  is 
  obvious 
  that 
  we 
  must 
  dis- 
  

   tinguish 
  at 
  least 
  two 
  somewhat 
  independent 
  sets 
  of 
  conditions 
  

   which 
  determine 
  the 
  character 
  of 
  the 
  embryonic 
  progeny 
  in 
  sexual 
  

   reproduction. 
  First, 
  the 
  degree 
  of 
  similarity 
  or 
  difference 
  in 
  the 
  

   ancestry 
  of 
  the 
  gametes 
  which 
  are 
  to 
  combine 
  and, 
  second, 
  the 
  

   very 
  processes 
  of 
  synapsis, 
  maturation 
  and 
  union 
  of 
  the 
  gam- 
  

   etes. 
  To 
  be 
  sure 
  each 
  of 
  these 
  sets 
  of 
  conditions 
  determines 
  the 
  

   other 
  In 
  large 
  degree. 
  First, 
  the 
  complicated 
  nature 
  of 
  the 
  pro- 
  

   cesses 
  of 
  reproduction 
  set 
  a 
  limit 
  to 
  the 
  degree 
  of 
  difference 
  allow- 
  

   able 
  In 
  the 
  gametes 
  beyond 
  which 
  even 
  if 
  fertilization 
  occurs 
  

   embryo 
  abortion 
  may 
  at 
  once 
  follow. 
  Second, 
  owing 
  to 
  the 
  com- 
  

   plexity 
  of 
  the 
  fertilization 
  process 
  the 
  degree 
  of 
  compatibility 
  In 
  

   the 
  gametes 
  may 
  Influence 
  the 
  probable 
  range 
  of 
  variation 
  In 
  the 
  

   progeny 
  as 
  well 
  as 
  their 
  general 
  vegetative 
  vigor 
  and 
  fertility 
  or 
  

  

  sterility 
  when 
  grown. 
  

  

  It 
  seems 
  to 
  me 
  probable 
  that 
  the 
  constitutional 
  differences 
  

   In 
  the 
  gametes 
  are 
  more 
  likely 
  to 
  be 
  responsible 
  for 
  the 
  wider 
  and 
  

   so-called 
  suddenly 
  achieved 
  variations 
  known 
  as 
  mutations, 
  sports, 
  

   monstrosities, 
  etc., 
  while 
  the 
  complex 
  nature 
  of 
  the 
  reduction, 
  

   , 
  mating, 
  fusion, 
  and 
  pairing 
  prcesses 
  may 
  well 
  be 
  regarded 
  as 
  

   responsible 
  for 
  those 
  fluctuating 
  normal 
  variations 
  which 
  it 
  has 
  

   been 
  so 
  much 
  the 
  fashion 
  recently 
  to 
  confuse 
  with 
  the 
  not 
  directly 
  

   heritable 
  variations 
  due 
  to 
  the 
  external 
  environment. 
  

  

  It 
  is 
  not 
  at 
  all 
  Impossible 
  of 
  course 
  that 
  external 
  environmental 
  

   conditions 
  of 
  temperature, 
  and 
  nutrition, 
  toxic 
  effects, 
  etc., 
  may 
  m- 
  

   fluence 
  the 
  complex 
  of 
  reproductive 
  processes 
  and 
  thus 
  affect 
  the 
  

   degree 
  of 
  congenital 
  variation. 
  The 
  demonstration 
  of 
  this, 
  

   however, 
  by 
  such 
  studies 
  as 
  those 
  of 
  alcoholism, 
  malnutrition, 
  

   etc., 
  in 
  their 
  influence 
  on 
  the 
  offspring 
  of 
  sexual 
  reproduction 
  

   have 
  so 
  far 
  led 
  to 
  no 
  very 
  conclusive 
  results. 
  

  

  It 
  is 
  clear 
  then, 
  it 
  seems 
  to 
  me, 
  that 
  the 
  cytological 
  discoveries 
  

   as 
  to 
  the 
  nature 
  of 
  synapsis, 
  chromosome 
  reduction, 
  gametic 
  

   fusion 
  and 
  chromosome 
  pairing 
  indicate 
  that 
  fluctuatmg 
  variation 
  

   may 
  be 
  expected 
  as 
  a 
  direct 
  result 
  of 
  the 
  complexity 
  of 
  these 
  

  

  