﻿364 
  

  

  Mr. 
  W. 
  Bateson. 
  

  

  division 
  cannot 
  be 
  the 
  one 
  critical 
  moment. 
  The 
  suggestion 
  has 
  been 
  made 
  

   that 
  germ-cells 
  of 
  the 
  missing 
  kinds 
  may 
  be 
  in 
  reality 
  formed 
  and 
  perish, 
  

   before 
  reaching 
  a 
  functional 
  stage. 
  As 
  regards 
  the 
  Oenotheras, 
  where 
  

   shrivelled 
  pollen 
  grains 
  abound, 
  this 
  conjecture 
  is 
  very 
  plausible 
  and 
  probably 
  

   correct 
  ; 
  but 
  when 
  as 
  in 
  the 
  other 
  cases 
  here 
  quoted, 
  the 
  pollen 
  grains 
  are 
  

   uniformly 
  sound, 
  the 
  hypothesis 
  is 
  inapplicable 
  and 
  without 
  evidential 
  

   support. 
  Moreover, 
  even 
  if 
  it 
  were 
  true 
  that 
  certain 
  classes 
  of 
  germ-cells 
  

   perish 
  in 
  one 
  or 
  other 
  of 
  the 
  sexes, 
  that 
  would 
  hardly 
  alleviate 
  the 
  difficulty, 
  

   for 
  this 
  differential 
  viability 
  would 
  remain 
  to 
  be 
  be 
  accounted 
  for, 
  being 
  itself 
  

   a 
  phenomenon 
  of 
  segregation. 
  

  

  Begonia 
  Davisii* 
  is 
  another 
  curious 
  illustration 
  in 
  which 
  segregation 
  must 
  

   occur 
  even 
  earlier. 
  This 
  plant 
  is 
  a 
  wild, 
  true-breeding 
  species, 
  with 
  ordinary 
  

   single 
  flowers. 
  All 
  the 
  pollen 
  grains 
  however 
  carry 
  doubleness, 
  and 
  used 
  on 
  

   the 
  female 
  flowers 
  of 
  doubles 
  give 
  offspring 
  all 
  double 
  (single 
  being 
  the 
  

   dominant). 
  The 
  pollen 
  of 
  this 
  plant 
  is 
  as 
  uniform 
  and 
  perfect 
  as 
  those 
  of 
  any 
  

   species 
  I 
  have 
  ever 
  seen. 
  We 
  must 
  therefore 
  conclude 
  that 
  the 
  segregation 
  

   by 
  which 
  singleness 
  separates 
  from 
  doubleness 
  is 
  effected 
  not 
  later 
  than 
  the 
  

   formation 
  of 
  the 
  rudiments 
  of 
  the 
  male 
  and 
  female 
  flowers. 
  Cytological 
  

   investigation 
  may 
  no 
  doubt 
  show 
  that 
  the 
  distinctions 
  between 
  the 
  genetic 
  

   properties 
  of 
  the 
  male 
  and 
  female 
  are 
  associated 
  with 
  visible 
  nuclear 
  

   differences, 
  but 
  I 
  see 
  no 
  reason 
  for 
  anticipating 
  that 
  such 
  differences 
  must 
  

   exist. 
  Cells 
  which 
  differ 
  in 
  their 
  genetic 
  potentialities 
  must 
  of 
  course 
  differ 
  

   .in 
  physical 
  constitution, 
  but 
  there 
  is 
  no 
  reason 
  to 
  suppose 
  that 
  this 
  difference 
  

   need 
  be 
  in 
  any 
  way 
  dependent 
  on 
  chromosome 
  structure. 
  

  

  As 
  regards 
  Campanula 
  carpatica 
  " 
  pelviformis" 
  and 
  Begonia 
  Davisii 
  

   experiment 
  has 
  shown 
  that 
  the 
  peculiar 
  kind 
  of 
  segregation 
  which 
  they 
  

   exhibit 
  may 
  recur 
  in 
  their 
  offspring. 
  In 
  the 
  Begonia, 
  if 
  the 
  female 
  of 
  Davisii 
  

   be 
  fertilised 
  with 
  pollen 
  of 
  an 
  ordinary 
  double 
  tuberous 
  Begonia, 
  the 
  double- 
  

   ness 
  so 
  introduced 
  stays 
  on 
  the 
  male 
  side 
  just 
  as 
  the 
  doubleness 
  of 
  its 
  own 
  

   male 
  does, 
  and 
  a 
  plant 
  so 
  bred 
  has 
  its 
  pollen 
  all 
  double. 
  But 
  if 
  the 
  male 
  of 
  

   Davisii 
  be 
  used 
  on 
  the 
  female 
  of 
  an 
  ordinary 
  single, 
  there 
  is 
  no 
  restriction 
  of 
  

   doubleness 
  to 
  either 
  sex 
  of 
  the 
  offspring. 
  The 
  peculiarity 
  of 
  Davisii 
  must 
  

   therefore 
  be 
  attributed 
  to 
  the 
  special 
  properties 
  of 
  its 
  female 
  side. 
  The 
  

   Campanula 
  case 
  is 
  complex 
  and 
  has 
  not 
  yet 
  been 
  fully 
  explored, 
  but 
  at 
  least 
  

   from 
  the 
  female 
  side 
  of 
  pelviformis 
  plants 
  have 
  been 
  raised 
  which 
  retain 
  the 
  

   properties 
  of 
  the 
  mother 
  as 
  regards 
  the 
  distribution 
  of 
  the 
  white 
  and 
  blue 
  

   colours. 
  

  

  We 
  have 
  at 
  the 
  John 
  Innes 
  Institution 
  been 
  lately 
  investigating 
  a 
  similar 
  

   case 
  in 
  flax, 
  which 
  though 
  comparable 
  has 
  some 
  special 
  features. 
  A 
  dwarf 
  

   * 
  ' 
  Jour. 
  Gen.,' 
  vol. 
  8, 
  p. 
  199 
  (1919). 
  

  

  