﻿514 
  J. 
  BRETLAND 
  FARMER 
  AND 
  J. 
  E. 
  S. 
  MOOKE. 
  

  

  reference 
  to 
  the 
  spindle-fibres, 
  i. 
  e. 
  to 
  the 
  forces 
  that 
  effect 
  

   their 
  final 
  separation. 
  la 
  the 
  majority 
  of 
  cases 
  a 
  chromo- 
  

   some 
  is 
  as 
  a 
  straight 
  or 
  twisted 
  structure, 
  projecting 
  radially 
  

   from 
  the 
  equatorial 
  plane. 
  Then 
  each 
  monovalent 
  half 
  is 
  

   attached 
  at 
  or 
  near 
  one 
  end 
  to 
  a 
  sheaf 
  of 
  achromatic 
  spindle- 
  

   fibres, 
  and 
  the 
  two 
  halves 
  (i. 
  e. 
  the 
  monovalent 
  constituents) 
  

   of 
  each 
  chromosome 
  slide 
  over 
  each 
  other 
  and 
  travel 
  towards 
  

   the 
  appropriate 
  pole. 
  As 
  soon 
  as 
  this 
  migration 
  commences 
  

   the 
  longitudinal 
  fission 
  once 
  more 
  becomes 
  apparent, 
  and 
  the 
  

   rod 
  splits 
  open 
  along 
  the 
  greater 
  part 
  or 
  even 
  the 
  whole 
  of 
  

   its 
  length, 
  so 
  as 
  to 
  give 
  rise 
  to 
  the 
  V-shaped 
  daughter 
  

   chromosomes. 
  Each 
  limb 
  of 
  the 
  V 
  represents 
  the 
  original 
  

   half 
  of 
  the 
  spireme 
  thread 
  that 
  was 
  formed 
  during 
  the 
  pro- 
  

   phase. 
  Gregoire 
  ^ 
  was 
  the 
  first 
  to 
  recognise 
  that 
  this 
  V- 
  

   shaped 
  form 
  is 
  due 
  to 
  the 
  re-opening 
  of 
  a 
  previously 
  effected 
  

   longitudinal 
  fission. 
  But 
  he 
  considered 
  that 
  two 
  longitudinal 
  

   fissions 
  occurred 
  during 
  the 
  prophase, 
  and 
  that 
  the 
  appearance 
  

   in 
  question 
  was 
  due 
  to 
  the 
  re-opening 
  of 
  the 
  second 
  of 
  these. 
  

   Although 
  we 
  cannot 
  accept 
  the 
  interpretation 
  in 
  that 
  form, 
  

   since 
  we 
  have 
  shown 
  that 
  the 
  supposed 
  second 
  split 
  really 
  

   represents 
  the 
  first 
  (and 
  only) 
  one 
  in 
  a 
  disguised 
  form, 
  it 
  is 
  

   obvious 
  that 
  Gregoire 
  was 
  correct 
  in 
  his 
  main 
  contention, 
  

   viz. 
  , 
  that 
  the 
  production 
  of 
  the 
  V 
  depended 
  on 
  the 
  re-opening 
  

   of 
  a 
  previously 
  effected 
  fission. 
  And 
  the 
  interpretation 
  

   receives 
  a 
  striking 
  confirmation 
  from 
  certain 
  types 
  of 
  

   chromosomes 
  that 
  are 
  occasionally 
  to 
  be 
  observed 
  in 
  the 
  

   diaster 
  of 
  lilies. 
  The 
  chromosomes 
  in 
  question 
  assume 
  

   the 
  forms 
  of 
  V's, 
  but 
  each 
  is 
  seen 
  to 
  be 
  completely 
  split 
  

   throughout 
  its 
  entire 
  length. 
  Such 
  a 
  figure 
  is 
  produced 
  when 
  

   a 
  heterotype 
  chromosome 
  becomes 
  attached 
  by 
  the 
  middle 
  

   instead 
  of 
  by 
  the 
  end, 
  to 
  the 
  spindle-fibres 
  (c/. 
  Figs. 
  

   15, 
  16, 
  17). 
  The 
  whole 
  daughter 
  chromosome 
  is 
  then 
  bent 
  

   over 
  into 
  a 
  y-shaped 
  structure 
  instead 
  of 
  forming 
  a 
  rod-like 
  

   body. 
  Hence 
  the 
  longitudinal 
  fission, 
  on 
  its 
  re-appearance, 
  

   gives 
  rise 
  to 
  the 
  figures 
  of 
  split 
  V~shaped 
  bodies. 
  

  

  ' 
  V. 
  Gregoire, 
  " 
  Les 
  Cineses 
  Polliniques 
  cliez 
  les 
  Liliacees," 
  'La 
  Cellule,' 
  

   t. 
  xvi. 
  

  

  