﻿THE 
  M 
  ATOXIC 
  PHASE 
  IN 
  ANIMALS 
  AND 
  PLANTS. 
  547 
  

  

  as 
  miicli 
  later 
  we 
  reach, 
  in 
  the 
  prophase 
  of 
  the 
  hetero- 
  

   type 
  mitosis, 
  a 
  condition 
  of 
  things 
  wherein 
  the 
  full 
  number 
  

   of 
  the 
  pre-maiotic 
  chromosomes 
  are 
  really 
  separated 
  out, 
  

   although 
  disguised 
  by 
  the 
  fact 
  that 
  the 
  pair 
  represented 
  

   by 
  a 
  disjointed 
  loop 
  always 
  remain 
  associated. 
  The 
  different 
  

   forms 
  which 
  this 
  association 
  may 
  take 
  give 
  rise, 
  as 
  we 
  have 
  

   seen, 
  to 
  all 
  sorts 
  of 
  different 
  figures 
  ; 
  thus, 
  in 
  the 
  later 
  stages 
  

   of 
  the 
  division 
  we 
  sometimes 
  encounter 
  heterotype 
  chromo- 
  

   somes 
  having 
  the 
  appearance 
  of 
  loops 
  twisted 
  upon 
  them- 
  

   selves 
  ; 
  or 
  again, 
  we 
  may 
  have 
  a 
  pair 
  of 
  rods 
  open 
  at 
  both 
  

   ends, 
  joined 
  at 
  both 
  ends 
  in 
  the 
  form 
  of 
  a 
  ring, 
  or 
  lying 
  over 
  

   one 
  another 
  at 
  right 
  angles 
  in 
  the 
  form 
  of 
  a 
  cross. 
  But 
  in 
  

   whatever 
  form 
  the 
  heterotype 
  chromosomes 
  appear 
  they 
  are 
  

   always 
  obviously 
  to 
  be 
  interpreted 
  as 
  pairs 
  of 
  somatic 
  rods 
  

   attached 
  or 
  associated 
  together. 
  

  

  In 
  the 
  succeeding 
  stages 
  of 
  the 
  division, 
  when 
  the 
  chromo- 
  

   somes 
  are 
  definitely 
  attached 
  to 
  the 
  spindle, 
  the 
  individual 
  

   somatic 
  elements 
  of 
  which 
  each 
  chromosome 
  is 
  composed 
  

   become 
  simply 
  separated 
  from 
  one 
  another 
  and 
  pass 
  into 
  the 
  

   daughter 
  cells. 
  And 
  in 
  some 
  cases, 
  as 
  in 
  the 
  cockroach, 
  

   while 
  this 
  separation 
  is 
  in 
  progress, 
  and 
  the 
  chromosomes 
  

   become 
  lengthened 
  out 
  upon 
  the 
  spindle, 
  the 
  original 
  longi- 
  

   tudinal 
  split 
  in 
  each 
  is 
  again 
  quite 
  clearly 
  evident. 
  Such 
  

   figures 
  explain 
  at 
  once 
  the 
  real 
  meaning 
  of 
  the 
  longitudinal 
  

   fission 
  which 
  has 
  frequently 
  been 
  observed 
  in 
  the 
  daughter 
  

   elements 
  as 
  they 
  divaricate 
  from 
  one 
  another 
  during 
  the 
  

   heterotype 
  diaster. 
  

  

  The 
  second 
  maiotic 
  (or 
  homotype) 
  mitosis 
  follows 
  im- 
  

   mediately 
  upon 
  the 
  heterotype 
  (first 
  maiotic) 
  division. 
  In 
  the 
  

   cases 
  studied 
  by 
  us 
  it 
  consists 
  clearly 
  in 
  the 
  completion 
  of 
  

   that 
  initial 
  longitudinal 
  fission 
  of 
  the 
  spirem 
  that 
  was 
  

   accepted 
  (but 
  not 
  finished) 
  during 
  the 
  prophase 
  of 
  the 
  first 
  

   of 
  the 
  two 
  maiotic 
  divisions. 
  

  

  Thus 
  the 
  essential 
  peculiarities 
  of 
  the 
  maiotic 
  phase 
  can 
  be 
  

   explained 
  as 
  follows: 
  They 
  are 
  due 
  to 
  the 
  coherence 
  in 
  

   pairs 
  of 
  pre-maiotic 
  chromosomes 
  and 
  to 
  the 
  inter- 
  

   calation 
  of 
  a 
  special 
  form 
  of 
  chromosome-distribu- 
  

  

  