﻿THE 
  MAIOTIC 
  PHASE 
  IN 
  ANIMALS 
  AND 
  PLANTS. 
  509 
  

  

  each 
  other. 
  It 
  forms 
  a 
  colourless 
  thready 
  at 
  first 
  infiltrated 
  

   with 
  chromatin 
  throughout, 
  but 
  the 
  latter 
  soon 
  collects 
  into 
  

   serial 
  beads 
  so 
  as 
  to 
  give 
  rise 
  to 
  the 
  well-known 
  alternation 
  of 
  

   stainable 
  (chromatin) 
  and 
  non-staining 
  (linin) 
  discs. 
  The 
  

   numerous 
  small 
  nucleoli 
  previously 
  seen 
  have 
  disappeared 
  

   and 
  become 
  replaced 
  by 
  one 
  or 
  more 
  relatively 
  large 
  ones. 
  

   At 
  first 
  irregularly 
  coiled 
  in 
  the 
  nucleus, 
  the 
  differentiating 
  

   spireme 
  next 
  aggregates 
  towards 
  one 
  side, 
  and 
  there 
  

   forms 
  what 
  we 
  may 
  designate 
  as 
  " 
  the 
  first 
  contraction 
  

   figure" 
  (Fig. 
  2). 
  The 
  thread 
  becouies 
  densely 
  coiled 
  in 
  the 
  

   vicinity 
  of 
  the 
  nucleolus, 
  exhibiting 
  a 
  highly 
  characteristic 
  

   arrangement. 
  This 
  figure 
  has 
  often 
  been 
  dismissed 
  as 
  the 
  

   result 
  of 
  imperfect 
  fixation, 
  but 
  there 
  exists 
  strong 
  evidence 
  

   to 
  show 
  that 
  it 
  represents 
  a 
  normal 
  occurrence 
  in 
  the 
  life 
  

   history 
  of 
  these 
  cells. 
  Miss 
  Sargant 
  states 
  she 
  has 
  observed 
  

   it 
  in 
  the 
  liviug 
  spore 
  mother-cells 
  of 
  lilies, 
  and 
  we 
  have 
  

   not 
  unfrequently 
  seen 
  it 
  in 
  the 
  corresponding 
  cells 
  of 
  

   Tradescantia, 
  Osmunda, 
  and 
  several 
  Liverworts, 
  as 
  

   well 
  as 
  in 
  some 
  animal 
  spermatocytes. 
  It 
  is 
  a 
  style 
  that 
  

   persists 
  for 
  some 
  time, 
  but 
  as 
  it 
  passes 
  away 
  the 
  filament 
  

   again 
  becomes 
  more 
  loosely 
  coiled 
  and 
  diffused, 
  especially 
  

   about 
  the 
  periphery 
  of 
  the 
  nuclear 
  cavity. 
  It 
  is 
  perhaps 
  a 
  

   fact 
  of 
  some 
  significance 
  that 
  the 
  nucleus 
  at 
  this 
  stage 
  is 
  

   relatively 
  large, 
  the 
  average 
  diameter 
  in 
  the 
  case 
  of 
  pollen- 
  

   mother-cells 
  of 
  Lilium 
  candidum 
  being 
  32 
  /u, 
  as 
  com- 
  

   pared 
  with 
  diameter 
  29 
  fx 
  reached 
  by 
  the 
  nuclei 
  at 
  the 
  con- 
  

   traction-figure 
  stage 
  just 
  described. 
  

  

  A 
  certain 
  degree 
  of 
  polarity 
  is 
  observed 
  to 
  characterise 
  the 
  

   spireme 
  thread 
  as 
  a 
  whole 
  at 
  this 
  stage, 
  for 
  the 
  convolutions 
  

   are 
  absent 
  from, 
  or 
  at 
  least 
  scarce 
  in, 
  one 
  region 
  of 
  the 
  

   nucleus, 
  and 
  this 
  seems 
  to 
  be 
  related 
  to 
  the 
  emergence 
  from 
  

   the 
  stage 
  of 
  contraction. 
  The 
  region 
  of 
  comparative 
  freedom 
  

   from 
  convolution 
  is 
  about 
  diametrically 
  opposite 
  to 
  the 
  spot 
  

   at 
  which 
  the 
  aggregation 
  previously 
  had 
  occurred. 
  

  

  The 
  longitudinal 
  fission 
  of 
  the 
  thread 
  is 
  now 
  to 
  be 
  seen 
  

   (figs. 
  3, 
  4) 
  . 
  At 
  first 
  the 
  beads 
  or 
  discs 
  of 
  chromatin 
  lengthen 
  

   out 
  somewhat 
  in 
  the 
  plane 
  of 
  cross-section 
  of 
  the 
  thread 
  ; 
  

  

  