﻿CHROMOSOMES 
  OF 
  TUADESOANTIA. 
  VIRGINICA. 
  567 
  

  

  become 
  reconstituted. 
  Sometimes 
  they 
  are 
  found 
  in 
  the 
  

   equatorial 
  zone, 
  but 
  often 
  they 
  lie 
  near 
  the 
  cell 
  periphery 
  or 
  

   even 
  in 
  the 
  cytoplasm. 
  They 
  do 
  not 
  appear, 
  however, 
  to 
  

   give 
  rise 
  to 
  small 
  pollen 
  grains, 
  at 
  least 
  as 
  a 
  rule, 
  but 
  perhaps 
  

   in 
  most 
  cases 
  they 
  degenerate. 
  

  

  In 
  one 
  example 
  it 
  was 
  clear 
  that 
  the 
  chromatic 
  fragment 
  

   thus 
  left 
  in 
  the 
  cytoplasm 
  originated 
  as 
  a 
  detached 
  fragment 
  

   of 
  a 
  chromosome. 
  

  

  III. 
  HoMOTYPE 
  Mitosis. 
  

  

  After 
  the 
  telophase 
  of 
  the 
  heterotype 
  division 
  the 
  nuclei 
  do 
  

   not 
  revert 
  to 
  a 
  resting 
  condition. 
  The 
  chromosomes 
  cannot, 
  

   however, 
  be 
  identified 
  as 
  separate 
  structures. 
  They 
  swell, 
  

   and 
  undergo 
  those 
  regressive 
  changes 
  that 
  if 
  completed 
  would 
  

   bring 
  about 
  the 
  resting 
  condition. 
  Here 
  and 
  there 
  signs 
  of 
  

   a 
  double 
  or 
  parallel 
  arrangement 
  of 
  chromatin 
  granules 
  sug- 
  

   gests 
  a 
  persistence 
  of 
  the 
  longitudinal 
  fission. 
  Then 
  the 
  

   mitotic 
  activity 
  is 
  again 
  resumed, 
  the 
  chromatic 
  thread-work 
  

   shortens 
  and 
  contracts, 
  and 
  the 
  chromosomes 
  themselves 
  be- 
  

   come 
  easily 
  recognised, 
  although 
  it 
  is 
  difficult 
  and 
  generally 
  

   impossible 
  to 
  distinguish 
  any 
  signs 
  of 
  longitudinal 
  fission 
  at 
  

   this 
  stage. 
  They 
  are 
  thinner 
  and 
  longer 
  structures 
  than 
  

   those 
  met 
  with 
  in 
  the 
  prophase 
  of 
  the 
  former 
  division, 
  and 
  

   they 
  exhibit 
  curious 
  varicosities 
  over 
  their 
  entire 
  length. 
  

   Finally, 
  when 
  they 
  are 
  arranged 
  upon 
  the 
  spindle 
  they 
  adopt 
  

   the 
  same 
  form 
  of 
  grouping 
  as 
  that 
  characteristic 
  of 
  somatic 
  

   cells. 
  As 
  in 
  the 
  latter 
  the 
  longitudinal 
  fission 
  now 
  becomes 
  

   unmistakeable, 
  and 
  the 
  two 
  halves 
  are 
  then 
  separated 
  and 
  

   distributed 
  to 
  the 
  two 
  daughter 
  nuclei. 
  

  

  It 
  thus 
  becomes 
  evident 
  that 
  the 
  essential 
  phases 
  in 
  the 
  

   heterotype 
  mitosis 
  whereby 
  reduction 
  by 
  a 
  sorting 
  out 
  of 
  entire 
  

   chromosomes 
  is 
  effected, 
  are 
  to 
  be 
  regarded 
  as 
  an 
  intercalated 
  

   series 
  of 
  events 
  breaking 
  the 
  ordinary 
  rhythmical 
  sequences. 
  

   The 
  longitudinal 
  fission 
  begins 
  during 
  the 
  prophase 
  of 
  the 
  

   heterotype 
  mitosis, 
  but 
  its 
  natural 
  outcome 
  is 
  postponed 
  

   whilst 
  the 
  train 
  of 
  events 
  runs 
  off 
  on 
  a 
  loop-line, 
  the 
  track 
  

  

  