﻿CHROMOSOMES 
  OF 
  THADESCANTIA 
  VIKGINIOA. 
  561 
  

  

  filament 
  is 
  present. 
  In 
  many 
  cases 
  the 
  evidence 
  pointed 
  

   strongly 
  in 
  favour 
  of 
  the 
  existence 
  of 
  free 
  ends, 
  but 
  it 
  was 
  

   not 
  possible 
  to 
  make 
  out 
  any 
  relation 
  between 
  them 
  and 
  the 
  

   number 
  of 
  chromosomes 
  to 
  be 
  ultimately 
  produced. 
  At 
  this 
  

   stage 
  it 
  was, 
  however, 
  clear 
  that 
  the 
  arrangement 
  of 
  the 
  

   chromatin 
  within 
  the 
  linin 
  filament 
  (or 
  filaments) 
  was 
  of 
  that 
  

   intermittent 
  character 
  to 
  which 
  the 
  appearance 
  of 
  alternate 
  

   stainable 
  and 
  non-stainable 
  discs 
  is 
  due. 
  

  

  Closely 
  following 
  on 
  this 
  stage 
  the 
  granules 
  or 
  discs 
  of 
  

   chromatin 
  can 
  be 
  sometimes 
  made 
  out 
  to 
  be 
  double. 
  We 
  

   look 
  on 
  this 
  as 
  an 
  indication 
  of 
  that 
  longitudinal 
  fission 
  of 
  the 
  

   thread 
  which 
  only 
  reaches 
  its 
  climax 
  when 
  the 
  isolated 
  

   chromosomes 
  are 
  arranged 
  on 
  the 
  equatorial 
  plane 
  of 
  the 
  

   spindle 
  — 
  an 
  event 
  that 
  happens 
  long 
  after 
  the 
  stage 
  we 
  are 
  

   now 
  describing. 
  The 
  fission 
  is 
  not 
  very 
  easily 
  seen, 
  but 
  it 
  

   can 
  hardly 
  be 
  missed 
  if 
  looked 
  for. 
  

  

  During 
  the 
  next 
  phase 
  the 
  spireme 
  undergoes 
  a 
  remarkable 
  

   polarisation. 
  Loops 
  are 
  formed 
  in 
  such 
  a 
  way 
  as 
  to 
  make 
  

   the 
  "pole 
  field 
  ^' 
  (Rabl) 
  strikingly 
  obvious 
  (tig. 
  8). 
  Within 
  

   these 
  loops 
  the 
  signs 
  of 
  longitudinal 
  fission 
  can 
  sometimes 
  be 
  

   detected, 
  though 
  usually 
  only 
  with 
  difficulty. 
  The 
  nucleoli 
  

   at 
  this 
  stage 
  are 
  easily 
  recognised 
  as 
  scattered 
  through 
  the 
  

   region 
  occupied 
  by 
  the 
  polarised 
  spireme 
  thread, 
  and 
  we 
  

   think 
  the 
  relation 
  almost 
  irresistably 
  compels 
  one 
  to 
  associate 
  

   these 
  bodies 
  with 
  the 
  function 
  of 
  increasing 
  the 
  chromatin 
  

   within 
  the 
  linin 
  filament. 
  

  

  The 
  filamentous 
  structure 
  now 
  can 
  with 
  certainty 
  be 
  

   recognised 
  as 
  discontinuous 
  (figs. 
  8 
  — 
  10), 
  and 
  a 
  number 
  of 
  

   separate 
  loops 
  are 
  readily 
  distinguished. 
  It 
  is, 
  however, 
  not 
  

   easy 
  to 
  determine 
  whether 
  their 
  number 
  is 
  identical 
  with 
  that 
  

   of 
  the 
  chromosomes, 
  though 
  this 
  seems 
  sometimes 
  to 
  be 
  the 
  

   case. 
  The 
  double 
  arrangement 
  of 
  the 
  chromatic 
  beads 
  in 
  

   parallel 
  series 
  (indicating 
  fission) 
  was 
  often 
  observed 
  at 
  this 
  

   stage 
  (fig. 
  11). 
  

  

  The 
  chromosomes 
  now 
  become 
  capable 
  of 
  identification, 
  

   and 
  though, 
  as 
  we 
  have 
  said, 
  we 
  do 
  not 
  feel 
  able 
  to 
  speak 
  

   positively 
  as 
  to 
  whether 
  they 
  have 
  always 
  been 
  separated. 
  

  

  