﻿504 
  J. 
  BRETLAND 
  FARMER 
  AND 
  J. 
  E. 
  S. 
  MOORE. 
  

  

  teresfcing, 
  since 
  it 
  puts 
  the 
  facts 
  of 
  reduction 
  for 
  this 
  plant 
  

   in 
  a 
  light 
  as 
  diagrammatic 
  as 
  Korschelts' 
  investigations 
  had 
  

   already 
  done 
  for 
  Ophryotrocha. 
  

  

  Perhaps 
  one 
  may 
  venture 
  to 
  suggest 
  that 
  the 
  A.rthropoda^ 
  

   and 
  other 
  forms, 
  in 
  Avhich 
  the 
  transverse 
  division 
  has 
  been 
  

   assigned 
  to 
  the 
  homotype 
  mitosis 
  (Hacker 
  and 
  others) 
  are 
  

   worth 
  re-examination 
  from 
  the 
  new 
  point 
  of 
  view. 
  It 
  must 
  

   be 
  remembered 
  that 
  the 
  location 
  of 
  the 
  transverse 
  plane 
  of 
  

   separation 
  in 
  a 
  symmetrical 
  tetrad 
  is 
  not 
  an 
  easy 
  matter; 
  and 
  

   the 
  assertion 
  that, 
  in 
  the 
  heterotype 
  mitosis, 
  it 
  lies 
  in 
  the 
  

   longitudinal 
  axis 
  of 
  the 
  spindle, 
  can 
  only 
  be 
  maintained 
  pro- 
  

   vided 
  it 
  can 
  be 
  shown 
  that 
  the 
  developing 
  chromosome 
  

   retains 
  its 
  primary 
  orientation 
  unchanged 
  from 
  the 
  time 
  at 
  

   which 
  the 
  transverse 
  and 
  longitudinal 
  planes 
  could 
  be 
  dis- 
  

   tinguished. 
  Otherwise 
  some 
  unaltering 
  mark 
  is 
  required 
  to 
  

   enable 
  the 
  observer 
  to 
  fix 
  the 
  planes 
  in 
  some 
  other 
  way. 
  The 
  

   difficulty 
  of 
  deciding 
  as 
  to 
  the 
  particular 
  plane 
  affected 
  is 
  at 
  

   once 
  rendered 
  obvious 
  on 
  reflecting 
  how 
  the 
  remarkable 
  

   movements 
  of 
  the 
  chromosomes 
  themselves, 
  just 
  prior 
  to 
  

   their 
  congregation 
  on 
  the 
  spindle, 
  may 
  affect 
  their 
  ultimate 
  

   orientation. 
  

  

  We 
  have 
  made 
  no 
  pretence^ 
  in 
  this 
  brief 
  introduction, 
  of 
  

   dealing 
  exhaustively 
  with 
  the 
  immense 
  mass 
  of 
  literature 
  that 
  

   has 
  grown 
  up 
  around 
  the 
  problems 
  connected 
  with 
  reduction. 
  

   That 
  formed 
  no 
  part 
  of 
  our 
  task. 
  We 
  desired 
  merely 
  to 
  

   indicate 
  some 
  of 
  the 
  principal 
  trends 
  of 
  opinion 
  in 
  these 
  

   matters, 
  and 
  to 
  point 
  out 
  that 
  it 
  is 
  plainly 
  desirable 
  to 
  ascer- 
  

   tain 
  whether 
  or 
  no 
  some 
  reconciliation 
  between 
  the 
  various 
  

   conflicting 
  views 
  may 
  not 
  be 
  possible. 
  For 
  when 
  one 
  reflects 
  

   on 
  the 
  widespread 
  occurrence 
  of 
  the 
  phenomena 
  in 
  question, 
  

   extending 
  as 
  it 
  does 
  to 
  all 
  the 
  metaphyta 
  and 
  metazoa 
  (if 
  we 
  

   exclude 
  certain 
  suggestive 
  cases 
  of 
  parthenogenesis) 
  it 
  is 
  

   clear 
  that 
  we 
  are 
  in 
  the 
  face 
  of 
  a 
  fact 
  of 
  fundamental 
  im- 
  

   portance 
  whatever 
  its 
  true 
  significance 
  may 
  ultimately 
  turn 
  

   out 
  to 
  be. 
  And 
  furthermore, 
  our 
  own 
  comparative 
  studies 
  of 
  

   karyokinesis 
  in 
  plants 
  and 
  animals, 
  extending 
  over 
  many 
  

   years, 
  have 
  impressed 
  us 
  with 
  the 
  remarkable 
  similarities 
  

  

  