﻿Studies 
  on 
  Synapsis. 
  

  

  321 
  

  

  the 
  typical 
  resting 
  cells. 
  At 
  this 
  stage 
  the 
  individual 
  chromosomes 
  become 
  

   attenuated, 
  at 
  first 
  retaining 
  their 
  parallel 
  arrangement 
  ; 
  and 
  in 
  this 
  con- 
  

   dition 
  as 
  well 
  as 
  in 
  the 
  succeeding 
  stage, 
  when 
  they 
  become 
  scattered 
  in 
  the 
  

   nucleus 
  without 
  orientation 
  with 
  respect 
  to 
  the 
  spindle, 
  it 
  is 
  possible 
  to 
  make 
  

   quite 
  certain 
  that 
  they 
  remain 
  undivided 
  (fig. 
  35). 
  The 
  scattered 
  thread- 
  

   like 
  telophase 
  chromosomes 
  then 
  become 
  more 
  granular, 
  less 
  definite 
  in 
  

   outline, 
  assuming 
  a 
  zigzag 
  delineation, 
  in 
  which 
  condition 
  they 
  merge 
  into 
  

   the 
  reticulum 
  (fig. 
  36). 
  

  

  The 
  process 
  by 
  which 
  the 
  prophase 
  chromosomes 
  are 
  built 
  up 
  has 
  been 
  

   fully 
  described 
  by 
  Farmer 
  and 
  Moore. 
  It 
  is 
  described 
  by 
  them 
  in 
  the 
  

   following 
  terms 
  : 
  " 
  mitosis 
  is 
  ushered 
  in 
  by 
  the 
  increasingly 
  chromatic 
  appear- 
  

   ance 
  of 
  the 
  cells 
  .... 
  at 
  first 
  the 
  cells 
  which 
  are 
  preparing 
  for 
  division 
  

   present 
  an 
  even 
  granulation 
  of 
  the 
  chromatin 
  within 
  their 
  nuclei, 
  and 
  this 
  in 
  

   its 
  consistency 
  strongly 
  suggests 
  a 
  foam 
  structure 
  of 
  the 
  ordinary 
  type 
  ; 
  but 
  

   after 
  a 
  time 
  the 
  chromatin 
  confusion, 
  as 
  it 
  were, 
  sorts 
  itself 
  out 
  into 
  obvious 
  

   condensations 
  or 
  fiocculent 
  areas, 
  and 
  it 
  is 
  apparently 
  unquestionable 
  that 
  

   each 
  of 
  these 
  clouds 
  is 
  individually 
  the 
  forerunner 
  of 
  one 
  of 
  the 
  future 
  

   chromosomes. 
  The 
  gradual 
  condensation 
  which 
  occurs 
  in 
  each 
  cloud 
  proceeds 
  

   moreover 
  in 
  such 
  a 
  manner 
  that 
  the 
  chromatic 
  granules 
  become 
  arranged 
  in 
  

   two 
  distinct 
  rows 
  or 
  tracts. 
  So 
  that 
  by 
  the 
  time 
  the 
  individual 
  chromosomes 
  

   have 
  attained 
  to 
  some 
  sharpness 
  of 
  definition 
  they 
  appear 
  also 
  as 
  if 
  they 
  had 
  

   been 
  longitudinally 
  split 
  from 
  end 
  to 
  end." 
  Apart 
  from 
  the 
  negative 
  

   generalisation 
  that 
  there 
  is 
  no 
  stage 
  at 
  which 
  the 
  prochromosomes 
  are 
  

   undivided, 
  this 
  account 
  is 
  unexceptionable. 
  That 
  the 
  fiocculent 
  prochromo- 
  

   somes 
  of 
  the 
  prophase 
  are, 
  however, 
  at 
  first 
  undivided, 
  can 
  be 
  shown 
  in 
  smear 
  

   preparations, 
  as 
  would 
  be 
  expected 
  from 
  what 
  occurs 
  in 
  the 
  preceding 
  

   telophase. 
  

  

  In 
  any 
  case, 
  the 
  premeiotic 
  divisions 
  of 
  Periplaneta, 
  unlike 
  the 
  archesporial 
  

   divisions 
  of 
  Osmunda, 
  do 
  not 
  show 
  an 
  increasingly 
  intimate 
  association 
  of 
  

   half-chromosomes, 
  resulting 
  in 
  the 
  organisation 
  of 
  the 
  complete 
  univalent 
  

   chromosome 
  in 
  anticipation 
  of 
  the 
  metaphase 
  ; 
  on 
  the 
  contrary, 
  the 
  cleavage 
  

   of 
  the 
  chromosomes 
  in 
  Periplaneta 
  exhibits 
  progressive 
  differentiation, 
  

   beginning 
  in 
  the 
  inception 
  of 
  the 
  prophase 
  itself. 
  This 
  distinction 
  is 
  

   doubtless 
  correlated 
  with 
  the 
  different 
  behaviour 
  of 
  the 
  chromosomes 
  in 
  the 
  

   telophases 
  of 
  the 
  two 
  cases 
  ; 
  it 
  may 
  therefore 
  be 
  said 
  that 
  behaviour 
  of 
  the 
  

   chromosomes 
  in 
  the 
  telophase 
  of 
  the 
  premeiotic 
  mitosis 
  amply 
  confirms 
  the 
  

   conclusion 
  that 
  each 
  loop 
  of 
  the 
  leptotene 
  bouquet 
  is 
  equivalent 
  to 
  a 
  whole 
  

   univalent. 
  The 
  modification 
  of 
  the 
  process 
  which 
  occurs 
  in 
  the 
  last 
  

   premeiotic 
  division 
  is 
  correctly 
  described 
  by 
  Morse. 
  

  

  