﻿Stitches 
  ore 
  Synapsis. 
  

  

  327 
  

  

  accessory 
  chromosomes 
  in 
  the 
  female 
  behave 
  in 
  all 
  respects 
  like 
  the 
  

   autosomes. 
  

  

  (6) 
  In 
  its 
  earliest 
  stages, 
  the 
  heterotype 
  prophase 
  differs 
  from 
  the 
  pre- 
  

   meiotic 
  reticulate 
  nucleus 
  in 
  the 
  organisation 
  of 
  the 
  chromatin 
  in 
  the 
  form 
  of 
  

   elongated, 
  finely 
  beaded 
  filaments, 
  forming 
  an 
  intricate 
  tangle. 
  

  

  (7) 
  The 
  polarised 
  leptotene 
  threads 
  of 
  the 
  early 
  bouquet 
  are 
  present 
  in 
  

   the 
  full 
  diploid 
  number. 
  

  

  (8) 
  Parallel 
  conjugation 
  of 
  leptotene 
  threads 
  takes 
  place 
  in 
  the 
  bouquet 
  

   stage 
  at 
  the 
  point 
  of 
  maximal 
  contraction. 
  

  

  (9) 
  The 
  diplotene 
  loops 
  of 
  the 
  post-synaptic 
  spireme 
  become 
  straightened 
  

   and 
  abbreviated, 
  in 
  anticipation 
  of 
  their 
  transformation 
  into 
  heterotype 
  

   chromosomes. 
  

  

  (10) 
  In 
  both 
  cases 
  two 
  of 
  the 
  bivalents 
  retain 
  their 
  looped 
  condition 
  till 
  

   the 
  transformation 
  of 
  the 
  remainder 
  has 
  already 
  made 
  considerable 
  progress, 
  

   and 
  it 
  is 
  suggested 
  that 
  the 
  differential 
  rate 
  of 
  metamorphosis 
  of 
  annular 
  

   heterotype 
  chromosomes 
  has 
  given 
  rise 
  to 
  the 
  appearance 
  that 
  the 
  latter 
  are 
  

   formed 
  through 
  the 
  union 
  of 
  the 
  free 
  ends 
  of 
  a 
  diplotene 
  loop. 
  

  

  (11) 
  The 
  heterotype 
  chromosomes 
  are 
  formed 
  by 
  the 
  opening 
  out 
  of 
  the 
  

   shortened 
  diplotene 
  rods 
  along 
  the 
  line 
  of 
  cleavage, 
  so 
  as 
  to 
  assume 
  eventually 
  

   the 
  form 
  of 
  stretched 
  rings. 
  

  

  (12) 
  From 
  the 
  fact 
  that, 
  in 
  the 
  oocyte, 
  the 
  splitting 
  of 
  the 
  diplotene 
  

   filaments 
  appears 
  to 
  correspond 
  with 
  the 
  plane 
  in 
  which 
  conjugation 
  takes 
  

   place, 
  it 
  is 
  inferred 
  that 
  segregation 
  of 
  homologous 
  chromosomes 
  is 
  effected 
  

   in 
  the 
  heterotype 
  mitosis. 
  

  

  (13) 
  A 
  comparison 
  has 
  been 
  made 
  of 
  the 
  events 
  of 
  the 
  meiotic 
  phase 
  in 
  

   Periplaneta 
  and 
  Osmunda, 
  as 
  set 
  forth 
  in 
  Miss 
  Digby's 
  most 
  recent 
  work 
  ; 
  

   the 
  existence 
  of 
  a 
  single 
  contraction 
  phase 
  in 
  animals, 
  and 
  the 
  character 
  

   of 
  the 
  telophase 
  in 
  premeiotic 
  divisions, 
  indicate 
  that 
  there 
  is 
  no 
  valid 
  

   basis 
  for 
  the 
  comparison 
  of 
  the 
  initial 
  processes 
  in 
  animals 
  and 
  plants. 
  

  

  (14) 
  The 
  elimination 
  of 
  " 
  chromatin 
  " 
  particles 
  in 
  the 
  diffuse 
  stage 
  of 
  the 
  

   oocyte 
  nucleus 
  has 
  been 
  fully 
  investigated 
  ; 
  it 
  has 
  been 
  shown 
  that 
  the 
  

   formation 
  of 
  yolk 
  is 
  consequent 
  upon 
  the 
  elimination 
  of 
  material 
  from 
  the 
  

   plasmosome, 
  and 
  the 
  suggestion 
  is 
  made 
  that 
  similar 
  nuclear 
  particles 
  in 
  

   other 
  animals 
  arise 
  from 
  the 
  plasmosome. 
  

  

  This 
  research 
  was 
  conducted 
  in 
  Prof. 
  MacBride's 
  laboratory 
  at 
  the 
  

   Imperial 
  College 
  of 
  Science 
  ; 
  acknowledgment 
  is 
  made 
  to 
  Profs. 
  MacBride, 
  

   Doncaster, 
  and 
  Dobell 
  — 
  to 
  the 
  former 
  for 
  his 
  kindness 
  in 
  reading 
  the 
  MS., 
  

   and 
  to 
  the 
  two 
  last 
  named 
  for 
  bibliographical 
  references. 
  

  

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