﻿320 
  

  

  Mr. 
  L. 
  T. 
  Hogben. 
  

  

  The 
  Premeiotic 
  Telophase. 
  

  

  That 
  the 
  oogonial 
  chromosomes 
  do 
  not 
  exhibit 
  cleavage 
  either 
  in 
  the 
  

   telophase 
  or 
  earlier 
  in 
  the 
  anaphase 
  is 
  very 
  certain 
  in 
  Periplaneta 
  ; 
  but 
  since 
  

   mitoses 
  are 
  rare 
  in 
  the 
  ovarioles 
  full 
  details 
  as 
  to 
  the 
  genesis 
  of 
  the 
  nuclear 
  

   reticulum 
  are 
  difficult 
  to 
  obtain. 
  In 
  Farmer 
  and 
  Moore's 
  account 
  of 
  the 
  

   spermatogenesis 
  of 
  this 
  species 
  the 
  events 
  of 
  the 
  premeiotic 
  telophase 
  are 
  not 
  

   described 
  ; 
  while 
  Morse 
  figures 
  at 
  this 
  stage 
  a 
  homogeneous 
  mass 
  of 
  iron 
  

   haemotoxylin 
  which 
  hardly 
  sheds 
  any 
  further 
  light 
  on 
  the 
  question. 
  In 
  

   general 
  it 
  may 
  be 
  said 
  that 
  zoological 
  writers 
  with 
  very 
  few 
  exceptions 
  have 
  

   paid 
  little 
  attention 
  to 
  it, 
  though 
  in 
  the 
  case 
  of 
  plants 
  it 
  appears 
  that 
  a 
  proper 
  

   understanding 
  of 
  the 
  premeiotic 
  telophase 
  provides 
  the 
  key 
  to 
  the 
  earlier 
  

   processes 
  of 
  synapsis. 
  It 
  is 
  obvious 
  that 
  to 
  attempt 
  a 
  recomparison 
  of 
  the 
  

   maturation 
  prophases 
  in 
  animals 
  and 
  plants, 
  it 
  is 
  above 
  all 
  things 
  essential 
  to 
  

   gain 
  such 
  an 
  understanding. 
  The 
  clumping 
  together 
  of 
  the 
  chromosomes 
  of 
  

   the 
  spermatogonial 
  telophase 
  shown 
  in 
  the 
  illustrations 
  to 
  so 
  many 
  papers, 
  

   is 
  in 
  the 
  opinion 
  of 
  the 
  present 
  writer 
  purely 
  an 
  artifact 
  due 
  to 
  bad 
  fixation, 
  

   inappropriate 
  staining, 
  and 
  in 
  general 
  to 
  a 
  failure 
  to 
  recognise 
  that 
  almost 
  

   every 
  stage 
  of 
  cell 
  history 
  requires 
  separate- 
  technical 
  attention. 
  All 
  acid 
  

   fixatives, 
  and 
  in 
  particular 
  the 
  sublimate 
  mixtures, 
  produce 
  a 
  swelling, 
  which 
  

   is 
  admittedly 
  advantageous 
  in 
  estimating 
  the 
  chromosome 
  numbers 
  of 
  

   metaphase 
  plates, 
  where 
  each 
  chromosome 
  is 
  widely 
  separated 
  from 
  its 
  

   neighbours 
  ; 
  but 
  as 
  chromosomes 
  pass 
  to 
  the 
  poles 
  of 
  the 
  spindle, 
  they 
  become 
  

   approximated 
  more 
  closely, 
  so 
  that 
  it 
  is 
  desirable 
  to 
  use 
  acid-free 
  mixtures 
  

   such 
  as 
  platinic 
  formol, 
  which 
  produce 
  a 
  shrinkage 
  rather 
  than 
  a 
  swelling 
  of 
  

   the 
  individual 
  elements. 
  By 
  such 
  methods 
  it 
  is 
  possible 
  not 
  only 
  to 
  recognise 
  

   the 
  telophase 
  chromosomes 
  individually 
  but 
  to 
  ensure 
  that 
  any 
  evidence 
  of 
  

   cleavage 
  which 
  would 
  be 
  obscured 
  by 
  swelling 
  does 
  not 
  escape 
  observation. 
  

   One 
  further 
  point 
  should 
  be 
  added, 
  it 
  is 
  useless 
  to 
  study 
  the 
  telophase 
  in 
  

   Haidenhein 
  preparations 
  ; 
  a 
  transparent 
  stain 
  such 
  as 
  gentian 
  violet 
  (corrected 
  

   with 
  a 
  light 
  filter) 
  is 
  to 
  be 
  preferred. 
  

  

  The 
  arc-shaped 
  chromosomes 
  of 
  the 
  spermatogonial 
  metaphase 
  display 
  

   median 
  fibre 
  attachment 
  until 
  the 
  anaphase 
  ; 
  and 
  no 
  indication 
  of 
  cleavage 
  is 
  

   to 
  be 
  seen 
  (figs. 
  32, 
  33). 
  On 
  reaching 
  the 
  poles 
  of 
  spindle 
  the 
  chromosomes 
  

   become 
  arranged 
  with 
  their 
  long 
  axis 
  in 
  the 
  plane 
  that 
  is 
  parallel 
  with 
  the 
  

   axis 
  of 
  the 
  spindle 
  itself. 
  This 
  circumstance 
  greatly 
  facilitates 
  the 
  study 
  of 
  

   their 
  behaviour, 
  in 
  sections 
  transversely 
  cut 
  with 
  reference 
  to 
  the 
  spindle, 
  

   the 
  telophase 
  chromosomes 
  appear 
  as 
  points, 
  the 
  number 
  of 
  which 
  is 
  about 
  

   thirty-two 
  (c/. 
  figs. 
  33, 
  34). 
  The 
  appearance 
  of 
  the 
  nuclear 
  membrane 
  pre- 
  

   cedes 
  the 
  dissolution 
  of 
  the 
  spindle, 
  though 
  no 
  spindle 
  remains 
  are 
  found 
  in 
  

  

  