﻿CHKOMOSOMES 
  OF 
  TEADESOANTIA 
  VIRGINIOA. 
  563 
  

  

  nucleolus 
  in 
  fixed 
  preparations 
  indicates 
  a 
  precipitation 
  of 
  

   the 
  coagulable 
  constituents 
  which 
  during 
  life 
  probably 
  were 
  

   of 
  a 
  fluid 
  or 
  viscous 
  consistence. 
  Hence, 
  when 
  the 
  solidified 
  

   matter 
  is 
  thrown 
  down, 
  the 
  light 
  aureole 
  represents 
  the 
  fluid, 
  

   non-precipitable 
  remainder. 
  Slowly 
  the 
  bands 
  of 
  linin, 
  which 
  

   contain 
  the 
  chromatin, 
  continue 
  to 
  swell 
  up 
  till 
  their 
  apparent 
  

   individuality 
  is 
  lost, 
  as 
  the 
  equal 
  spacing 
  of 
  the 
  stainable 
  

   substance 
  necessarily 
  obliterates 
  the 
  criteria 
  of 
  boundaries. 
  

   But 
  it 
  does 
  not 
  follow 
  that 
  this 
  obliteration 
  extends 
  to 
  the 
  

   real 
  morphological, 
  and 
  still 
  less 
  to 
  the 
  physiological, 
  limi- 
  

   tations. 
  

  

  II. 
  The 
  Heteeotype 
  Mitosis. 
  

  

  The 
  cells 
  of 
  the 
  sporogenous 
  tissue 
  in 
  the 
  anther, 
  just 
  before 
  

   they 
  enter 
  upon 
  the 
  two 
  final 
  (maiotic^) 
  mitoses 
  by 
  which 
  the 
  

   pollen 
  grains 
  will 
  be 
  formed, 
  are 
  bound 
  together 
  into 
  a 
  compact 
  

   tissue. 
  The 
  nuclei 
  of 
  the 
  cells 
  are 
  large, 
  but 
  they 
  do 
  not 
  

   exhibit 
  that 
  even 
  distribution 
  of 
  chromatin 
  which 
  is 
  often 
  

   met 
  with 
  in 
  other 
  cells. 
  The 
  nucleus 
  when 
  carefully 
  examined 
  

   is 
  seen 
  to 
  contain 
  fibrils 
  of 
  chromatic 
  linin. 
  ISometimes 
  

   (fig. 
  26) 
  these 
  are 
  so 
  arranged 
  as 
  to 
  simulate 
  more 
  granular 
  

   arrangement, 
  but 
  closer 
  inspection 
  shows 
  the 
  case 
  to 
  be 
  

   otherwise. 
  It 
  is 
  quite 
  certain 
  that 
  during 
  these 
  early 
  stages 
  

   of 
  prophase 
  there 
  is 
  no 
  continuous 
  spireme 
  present. 
  The 
  

   ends 
  of 
  the 
  stainable 
  threads 
  can 
  be 
  clearly 
  recognised. 
  On 
  

   the 
  other 
  hand, 
  there 
  is 
  nothing 
  recalling 
  that 
  diii'erentiation 
  

   into 
  broad 
  chromatic 
  bands 
  which 
  forms 
  so 
  characteristic 
  

   a 
  feature 
  of 
  the 
  ordinary 
  somatic 
  prophase. 
  It 
  is 
  not 
  cleai 
  

   that 
  one 
  is 
  justified 
  in 
  laying 
  too 
  much 
  stress 
  on 
  this 
  

   difference. 
  It 
  may 
  depend 
  on 
  accidental 
  circumstances, 
  

   such, 
  for 
  example, 
  as 
  the 
  length 
  of 
  time 
  that 
  elapses 
  between 
  

   the 
  telophase 
  of 
  one 
  mitosis 
  and 
  the 
  prophase 
  of 
  the 
  next. 
  

  

  Soon 
  the 
  fibrillar 
  structure 
  becomes 
  more 
  dense, 
  and 
  the 
  

   separate 
  fibrils 
  cannot 
  with 
  certainty 
  be 
  any 
  longer 
  identified. 
  

  

  1 
  See 
  Farmer 
  and 
  Moore 
  "Ou 
  the 
  Maiotic 
  Phase 
  (Reduction 
  Divisions) 
  in 
  

   Animals 
  and 
  Plants," 
  ' 
  Q. 
  J. 
  M. 
  S./ 
  1904. 
  

  

  