﻿374 
  ^' 
  T. 
  Young. 
  

  

  gins 
  to 
  show 
  a 
  slight 
  indentation 
  in 
  one 
  side 
  as 
  tho 
  it 
  were 
  about 
  

   to 
  divide 
  in 
  its 
  turn. 
  Now 
  it 
  is 
  difficult 
  to 
  understand 
  how 
  

   such 
  a 
  constriction 
  as 
  this 
  can 
  be 
  caused 
  by 
  mechanical 
  pressure 
  

   in 
  a 
  cell 
  which 
  lies 
  free 
  from 
  other 
  cells, 
  or 
  as 
  an 
  artifact 
  due 
  to 
  

   fixation 
  when 
  neighboring 
  cells 
  do 
  not 
  show 
  similar 
  artifacts. 
  

   Similar, 
  tho 
  less 
  marked 
  constrictions 
  I 
  have 
  seen 
  in 
  several 
  cells. 
  

   Still 
  stronger 
  evidence 
  of 
  amitosis 
  is 
  seen 
  in 
  Fig. 
  38 
  where 
  is 
  shown 
  

   a 
  spermatogonium 
  one 
  end 
  of 
  which 
  is 
  partly 
  cut 
  off 
  from 
  the 
  rest 
  

   of 
  the 
  cell, 
  the 
  separation 
  between 
  the 
  two 
  parts 
  appearing 
  with 
  

   diagrammatic 
  clearness. 
  The 
  division 
  line 
  touches 
  one 
  end 
  of 
  the 
  

   nucleus, 
  and 
  possibly 
  a 
  fragment 
  of 
  the 
  latter 
  has 
  been 
  cut 
  off 
  with 
  

   the 
  new 
  cell. 
  Outside 
  of 
  this 
  the 
  latter 
  is 
  anucleate. 
  It 
  is 
  

   difficult 
  to 
  explain 
  this 
  condition 
  as 
  a 
  result 
  of 
  mechanical 
  pressure 
  

   or 
  fixation, 
  as 
  anything 
  in 
  fact 
  but 
  an 
  unequal 
  amitosis, 
  the 
  amount 
  

   of 
  nuclear 
  mattor 
  passing 
  into 
  the 
  new 
  cell, 
  being 
  very 
  small 
  if 
  any. 
  

   A 
  similar 
  condition 
  is 
  represented 
  in 
  Fig. 
  37. 
  Here 
  the 
  cell 
  a 
  

   has 
  been 
  nearly 
  separated 
  from 
  h 
  and 
  c 
  by 
  two 
  cleavages 
  passing 
  

   nearly 
  at 
  right 
  angles 
  to 
  each 
  other, 
  only 
  one 
  of 
  which, 
  that 
  be- 
  

   tween 
  a 
  and 
  h, 
  is 
  clearly 
  shown 
  in 
  the 
  figure. 
  But 
  are 
  not 
  such 
  

   irregular 
  divisions 
  as 
  are 
  here 
  shown 
  artifacts 
  rather 
  than 
  normal 
  

   division 
  planes? 
  If 
  they 
  were 
  I 
  should 
  expect 
  to 
  find 
  them 
  of 
  more 
  

   frequent 
  occurrence 
  in 
  tissues 
  similarly 
  fixed, 
  and 
  I 
  should 
  also 
  

   expect 
  to 
  find 
  other 
  evidence 
  of 
  imperfect 
  fixation, 
  which 
  is 
  not 
  

   the 
  case. 
  Further 
  this 
  explanation 
  will 
  hardly 
  apply, 
  as 
  I 
  have 
  

   already 
  stated, 
  to 
  Fig. 
  38. 
  This 
  case 
  is 
  thus 
  supported 
  by 
  the 
  

   preceding 
  and, 
  as 
  will 
  shortl}^ 
  appear, 
  by 
  the 
  succeeding 
  one 
  as 
  well. 
  

   Further 
  evidence 
  is 
  furnished 
  by 
  Fig. 
  40. 
  Here 
  are 
  shown 
  two 
  pairs 
  

   of 
  cells 
  ab 
  and 
  cd, 
  one 
  of 
  which 
  ah 
  has 
  just 
  completed, 
  and 
  the 
  

   other 
  of 
  which 
  .cd 
  is 
  just 
  completing 
  its 
  division. 
  In 
  either 
  case 
  

   the 
  nearly 
  straight 
  edges 
  of 
  the 
  cells 
  along 
  the 
  line 
  of 
  division, 
  the 
  

   closeness 
  with 
  which 
  these 
  edges 
  correspond 
  to 
  one 
  another, 
  and 
  

   the 
  fact 
  that 
  in 
  one 
  case 
  the 
  cells 
  are 
  barely 
  separated 
  at 
  one 
  point, 
  

   is 
  at 
  least 
  very 
  strongly 
  suggestive 
  of 
  the 
  amitotic 
  division 
  of 
  these 
  cells, 
  in 
  

   the 
  absence 
  of 
  any 
  evidence 
  whatsoever 
  of 
  a 
  recent 
  mitosis. 
  But 
  may 
  not 
  

   mitosis 
  have 
  already 
  occurred 
  and 
  the 
  nuclei 
  have 
  passed 
  into 
  the 
  resting 
  

   condition 
  before 
  the 
  division 
  of 
  the 
  cell 
  body? 
  Such 
  an 
  interpretation 
  is 
  not 
  

   of 
  course 
  impossible, 
  but 
  in 
  view 
  of 
  the 
  two 
  preceding 
  cases 
  and 
  of 
  

   the 
  total 
  absence 
  of 
  any 
  mitoses 
  whatever 
  in 
  thousands 
  of 
  cases 
  

   examined 
  I 
  consider 
  it 
  highly 
  improbable. 
  Further, 
  may 
  not 
  the 
  

   form 
  of 
  the 
  edges 
  of 
  the 
  cells 
  to 
  which 
  I 
  have 
  called 
  attention 
  be 
  

  

  