﻿Studies 
  on 
  Synapsis, 
  

  

  313 
  

  

  cells 
  (figs. 
  17, 
  18a). 
  One 
  of 
  the 
  bivalent 
  filaments 
  of 
  this 
  stage 
  is 
  distinguish- 
  

   able 
  by 
  its 
  singular 
  form, 
  and 
  smaller 
  than 
  the 
  rest 
  ; 
  it 
  is 
  possible 
  that 
  it 
  

   represents 
  the 
  accessory 
  pair 
  (fig. 
  185). 
  The 
  constituent 
  halves 
  of 
  the 
  

   bivalents 
  now 
  become 
  widely 
  separated 
  in 
  the 
  region 
  midway 
  from 
  the 
  

   extremities 
  of 
  the 
  filament 
  (fig. 
  19). 
  And- 
  as 
  the 
  confused 
  stage 
  supervenes, 
  

   the 
  axis 
  of 
  each 
  filament 
  becomes 
  shorter, 
  the 
  interspace 
  widens, 
  until 
  each 
  

   half 
  is 
  separated 
  along 
  its 
  entire 
  length 
  from 
  its 
  fellow, 
  becoming 
  con- 
  

   temporaneously 
  more 
  sharply 
  curved 
  and 
  more 
  granular 
  in 
  appearance. 
  

   Thus 
  the 
  bivalent 
  elements 
  pass 
  into 
  the 
  reticulate 
  condition 
  characteristic 
  

   of 
  the 
  growth 
  phase 
  of 
  the 
  egg 
  as 
  transversely 
  divided 
  rings, 
  such 
  as 
  are 
  

   described 
  on 
  the 
  heterotype 
  spindle 
  of 
  the 
  male 
  by 
  Farmer 
  and 
  Moore. 
  But 
  

   it 
  will 
  be 
  observed 
  that 
  their 
  mode 
  of 
  formation 
  is 
  very 
  different 
  : 
  the 
  ring 
  is 
  

   formed 
  by 
  the 
  opening 
  out 
  of 
  the 
  diplotene 
  cleavage, 
  and 
  not 
  by 
  the 
  union 
  

   of 
  loops 
  by 
  their 
  free 
  ends 
  as 
  described 
  in 
  Farmer 
  and 
  Moore's 
  account 
  of 
  the 
  

   spermatogenesis 
  of 
  the 
  species. 
  The 
  validity 
  of 
  the 
  alternative 
  interpreta- 
  

   tion 
  will 
  be 
  fully 
  discussed 
  in 
  dealing 
  with 
  the 
  reduction 
  divisions 
  in 
  the 
  

   male. 
  Since, 
  in 
  general, 
  the 
  bivalents 
  emerge 
  from 
  the 
  diffuse 
  stage 
  in 
  the 
  

   same 
  form 
  which 
  they 
  exhibit 
  before 
  its 
  onset 
  ; 
  and 
  since 
  the 
  heavily 
  yolked 
  

   ova 
  of 
  Perip]aneta 
  did 
  not 
  yield 
  any 
  critical 
  data 
  regarding 
  the 
  details 
  of 
  

   polar 
  mitosis 
  the 
  nuclear 
  history 
  of 
  the 
  oocyte 
  may 
  be 
  here 
  concluded, 
  by 
  

   observing 
  that 
  as 
  the 
  bivalents 
  become 
  more 
  granular 
  in 
  form 
  (fig. 
  21) 
  they 
  

   merge 
  into 
  reticular 
  units, 
  eventually 
  losing 
  their 
  visible 
  individuality 
  

   altogether. 
  As 
  in 
  other 
  insects, 
  the 
  cytoplasm 
  of 
  the 
  oocyte 
  from 
  this 
  point 
  

   onwards 
  undergoes 
  enlargement. 
  This 
  stage 
  also 
  synchronises 
  with 
  other 
  

   events 
  in 
  the 
  egg 
  : 
  firstly, 
  the 
  mitochondria 
  which 
  are 
  well 
  preserved 
  in 
  

   unacidified 
  chromosmic 
  preparations 
  cease 
  to 
  congregate 
  around 
  the 
  centro- 
  

   some 
  as 
  in 
  the 
  young 
  oocytes 
  and 
  oogonia 
  (fig. 
  8), 
  migrate 
  from 
  the 
  neigh- 
  

   bourhood 
  of 
  the 
  nucleus, 
  and 
  become 
  dispersed 
  uniformly 
  in 
  the 
  surrounding 
  

   cytoplasm 
  ; 
  secondly, 
  infection 
  by 
  the 
  symbiotic 
  bacteria 
  . 
  {Bacillus 
  cuenoti) 
  

   described 
  by 
  Mercier(14), 
  and 
  indicated 
  in 
  fig. 
  28, 
  usually 
  occurs 
  at 
  this 
  

   point, 
  a 
  well-defined 
  zone 
  of 
  symbionts 
  being 
  seen 
  in 
  the 
  periphery 
  of 
  the 
  egg- 
  

   by 
  the 
  time 
  it 
  assumes 
  a 
  definite 
  outline 
  (fig. 
  22) 
  ; 
  finally, 
  the 
  plasmosome 
  is 
  

   seen 
  to 
  undergo 
  changes 
  to 
  be 
  described 
  hereinafter. 
  

  

  In 
  concluding 
  this 
  account 
  of 
  the 
  nuclear 
  history 
  of 
  the 
  ovarian 
  oocyte, 
  

   attention 
  may 
  now 
  be 
  directed 
  to 
  the 
  criticism 
  of 
  those 
  opponents 
  of 
  para- 
  

   synapsis, 
  such 
  as 
  Meves, 
  Fick, 
  and 
  Duesberg, 
  who, 
  while 
  emphasising 
  like 
  the 
  

   telosynaptic 
  school 
  the 
  importance 
  of 
  an 
  understanding 
  of 
  the 
  premeiotic 
  pro- 
  

   phase, 
  appear 
  to 
  recognise 
  that 
  the 
  interpretation 
  of 
  the 
  early 
  events 
  of 
  the 
  

   heterotype 
  nucleus 
  in 
  terms 
  of 
  a 
  normal 
  prophase 
  can 
  only 
  be 
  accepted 
  for 
  

   animals 
  by 
  rejecting 
  the 
  doctrine 
  of 
  synapsis 
  itself. 
  Duesberg 
  after 
  affirming, 
  

  

  