﻿THE 
  MAIOTIC 
  PHASE 
  IN 
  ANIMALS 
  AND 
  PLANTS. 
  537 
  

  

  just 
  as 
  it 
  isiu 
  the 
  pre 
  maiotic 
  divisions, 
  audit 
  is 
  this 
  splitting 
  

   in 
  the 
  segments 
  of 
  the 
  chromosomes 
  which 
  constitutes 
  the 
  

   longitudinal 
  fission 
  seen 
  in 
  the 
  daughter 
  elements 
  as 
  they 
  

   recede 
  from 
  one 
  another. 
  

  

  In 
  the 
  cockroach 
  after 
  the 
  first 
  maiotic 
  (heterotype) 
  division 
  

   has 
  been 
  completed 
  the 
  resulting 
  nuclei 
  pass 
  into 
  a 
  condition 
  

   of 
  almost 
  complete 
  rest. 
  That 
  is 
  to 
  say, 
  the 
  nuclei 
  again 
  

   return 
  to 
  the 
  state 
  in 
  which 
  there 
  is 
  merely 
  a 
  coarse 
  chromatic 
  

   reticulum 
  where 
  it 
  is 
  impossible 
  to 
  trace 
  the 
  daughter 
  

   chromosomes 
  any 
  further, 
  and 
  it 
  is 
  consequently 
  only 
  after 
  a 
  

   considerable 
  period 
  that 
  the 
  second 
  maiotic 
  (homotype) 
  

   division 
  is 
  brought 
  about. 
  In 
  this 
  (the 
  last 
  division 
  of 
  the 
  

   series), 
  as 
  in 
  the 
  ordinary 
  pre 
  maiotic 
  divisions, 
  the 
  sixteen 
  

   chromosomes 
  emerge 
  each 
  from 
  definite 
  chromatic 
  condensa- 
  

   tions, 
  wherein 
  the 
  chromatin 
  becomes 
  again 
  arranged 
  in 
  

   two 
  thick 
  streaks 
  or 
  bands, 
  the 
  chromosomes 
  presenting 
  

   the 
  appearance 
  of 
  so 
  many 
  short 
  split 
  rods; 
  and 
  as 
  division 
  

   proceeds 
  these 
  pass 
  on 
  to 
  the 
  spindle 
  and 
  divide 
  in 
  the 
  

   ordinary 
  pre-maiotic 
  manner. 
  

  

  Thus, 
  although 
  it 
  would 
  seem 
  to 
  be 
  strongly 
  suggested 
  that 
  

   the 
  ordinary 
  longitudinal 
  split 
  of 
  the 
  segments 
  in 
  the 
  synaptic 
  

   spirem 
  thread 
  constitutes 
  the 
  fission 
  by 
  means 
  of 
  which 
  the 
  

   reduced 
  number 
  of 
  chromosomes 
  in 
  the 
  second 
  maiotic 
  mitosis 
  

   are 
  ultimately 
  divided, 
  this 
  is 
  not 
  absolutely 
  demonstrated 
  

   in 
  the 
  Periplaneta 
  itself. 
  

  

  V. 
  E 
  1 
  a 
  s 
  m 
  o 
  b 
  r 
  a 
  n 
  c 
  h 
  s 
  . 
  

  

  (a) 
  The 
  pre-maiotic 
  phase. 
  

  

  In 
  view 
  of 
  the 
  remarkable 
  character 
  of 
  the 
  reduction 
  

   process 
  as 
  it 
  appears 
  to 
  be 
  carried 
  out 
  in 
  the 
  typical 
  arthropod 
  

   example 
  constituted 
  by 
  the 
  cockroach, 
  we 
  have 
  re-examined 
  

   the 
  elasmobranch 
  material 
  which 
  had 
  been 
  obtained 
  and 
  

   already 
  described 
  by 
  one 
  of 
  us 
  ^ 
  in 
  1894 
  ; 
  such 
  a 
  re-examiua- 
  

  

  ' 
  Moore, 
  J. 
  E. 
  S., 
  " 
  On 
  the 
  Structural 
  Clianges 
  iu 
  the 
  Reproductive 
  Cells 
  

   during 
  the 
  Spermatogenesis 
  of 
  Elasmobranchs," 
  'Quart. 
  Journ. 
  Micr. 
  Sci.,' 
  

   vol. 
  38, 
  new 
  series. 
  

  

  VOL. 
  48, 
  PAKT 
  4. 
  — 
  Nl.:W 
  SKIilliS. 
  39 
  

  

  