﻿THE 
  MAIOTIC 
  PJJASE 
  IN 
  ANIMALS 
  AND 
  PLANTS. 
  511 
  

  

  in 
  tlie 
  development 
  of 
  tlie 
  cliromatin 
  element 
  in 
  the 
  spireme, 
  

   as 
  is 
  shown 
  both 
  by 
  staining 
  reactions, 
  and 
  by 
  its 
  intimate 
  

   relation 
  with 
  the 
  spireme 
  during 
  the 
  progress 
  of 
  differentia- 
  

   tion 
  and 
  growth 
  of 
  the 
  latter. 
  About 
  this 
  time 
  the 
  nucleus 
  

   attains 
  to 
  its 
  largest 
  size, 
  85 
  fi 
  being 
  an 
  average 
  measurement 
  

   of 
  the 
  diameter 
  in 
  Lilium 
  caudidum. 
  As 
  the 
  contraction 
  

   proceeds, 
  which 
  it 
  does 
  with 
  great 
  rapidity, 
  the 
  original 
  

   longitudinal 
  fission 
  ceases 
  to 
  be 
  noticeable 
  and 
  is 
  only 
  visible 
  

   in 
  exceptionally 
  favourable 
  cases. 
  But 
  a 
  rearrangement 
  of 
  

   the 
  thread, 
  first 
  correctly 
  explained 
  by 
  Schaffuer 
  in 
  the 
  case 
  

   of 
  L. 
  Philadelphicum, 
  now 
  sets 
  in. 
  Parts 
  of 
  the 
  thread 
  

   forming 
  the 
  spireme 
  become 
  pulled 
  into 
  parallel 
  positions. 
  

   This 
  is 
  specially 
  well 
  seen 
  in 
  those 
  places 
  where 
  at 
  the 
  bend 
  

   of 
  a 
  convolution 
  an 
  attachment 
  to 
  the 
  nuclear 
  periphery 
  has 
  

   taken 
  place. 
  Often 
  the 
  nuclear 
  wall 
  is 
  drawn 
  inwards 
  at 
  these 
  

   spots. 
  Thus 
  a 
  close 
  and 
  parallel 
  approximation 
  of 
  lengths 
  of 
  

   the 
  entire 
  spireme 
  thread 
  is 
  effected, 
  and 
  this 
  parallel 
  

   arrangement 
  has 
  been 
  commonly 
  interpreted 
  as 
  representing 
  

   the 
  parallel 
  split 
  halves 
  of 
  the 
  spireme 
  thread. 
  Such 
  an 
  

   interpretation 
  is, 
  however, 
  shown 
  to 
  be 
  unsound 
  by 
  a 
  careful 
  

   study 
  of 
  the 
  stages 
  just 
  described. 
  Sometimes 
  in 
  one 
  or 
  both 
  

   sides 
  of 
  the 
  narrow 
  V-shaped 
  figures 
  thus 
  produced 
  the 
  

   original 
  fission 
  can 
  still 
  be 
  traced, 
  and 
  this 
  is 
  especially 
  the 
  

   case 
  when 
  free 
  ends 
  of 
  the 
  thread 
  can 
  be 
  observed. 
  For 
  at 
  

   this 
  time, 
  and 
  possibly 
  earlier, 
  the 
  definitive 
  chromosomes 
  begin 
  

   to 
  be 
  recognisable, 
  though 
  often 
  each 
  one 
  is 
  still 
  connected 
  

   by 
  strands 
  of 
  linin 
  with 
  those 
  lying 
  next 
  to 
  it. 
  This 
  relic 
  

   of 
  the 
  original 
  fission 
  has 
  been 
  recognised 
  by 
  others, 
  but 
  it 
  

   has 
  been 
  commonly 
  interpreted 
  as 
  due 
  to 
  the 
  occurrence 
  of 
  a 
  

   second 
  longitudinal 
  fission. 
  No 
  such 
  second 
  fission, 
  how- 
  

   ever, 
  really 
  takes 
  place 
  at 
  all. 
  

  

  As 
  a 
  consequence 
  of 
  the 
  bending 
  over 
  of 
  the 
  spireme 
  

   thread, 
  or 
  rather 
  parts 
  of 
  it 
  which 
  give 
  rise 
  to 
  the 
  chromo- 
  

   somes, 
  the 
  segments 
  when 
  isolated 
  very 
  often 
  exhibit 
  the 
  

   form 
  of 
  a 
  loop, 
  open 
  at 
  one 
  end, 
  with 
  sides 
  either 
  parallel 
  to 
  

   each 
  other 
  or, 
  more 
  commonly, 
  twisted 
  over 
  one 
  another 
  

   (Figs, 
  9, 
  11). 
  But 
  it 
  by 
  no 
  means 
  follows 
  that 
  all 
  the 
  bivalent 
  

  

  