﻿440 
  J. 
  W. 
  JENKINSON. 
  

  

  their 
  behaviour 
  can 
  be 
  explained 
  simply 
  by 
  comparison 
  with 
  

   these. 
  

  

  After 
  the 
  separation 
  of 
  the 
  chromosomes 
  the 
  general 
  

   spindle-fibres 
  remain 
  behind. 
  An 
  achromatic 
  equatorial 
  plate 
  

   (the 
  cell 
  plate) 
  is 
  now 
  clearly 
  visible 
  (fig. 
  41), 
  though 
  indi- 
  

   cations 
  of 
  it 
  may 
  indeed 
  be 
  seen 
  in 
  the 
  metaphase 
  (fig. 
  40), 
  

   This 
  plate 
  consists 
  of 
  a 
  thickening 
  and 
  union 
  of 
  the 
  fibres 
  in 
  

   the 
  equatorial 
  plane. 
  Axially, 
  the 
  spindle-fibres 
  are 
  perpen- 
  

   dicular 
  to 
  this 
  plate 
  ; 
  outside 
  the 
  axis 
  they 
  make 
  an 
  angle 
  with 
  

   it, 
  more 
  peripherally 
  still 
  they 
  curve 
  outwards 
  and 
  lie 
  parallel 
  

   with 
  it. 
  Where 
  the 
  fibres 
  meet 
  the 
  plate 
  they 
  are 
  thickened. 
  

   It 
  looks 
  as 
  though 
  two 
  opposing 
  sets 
  of 
  alveoli 
  had 
  here 
  met 
  

   and 
  fused. 
  What 
  relation, 
  if 
  any, 
  this 
  equatorial 
  plate 
  bears 
  

   to 
  the 
  subsequent 
  cytoplasmic 
  division 
  I 
  cannot 
  say. 
  

  

  In 
  the 
  telophase 
  the 
  nucleus 
  becomes 
  once 
  more 
  completely 
  

   reticular, 
  and 
  the 
  plasmosomes 
  reappear. 
  Its 
  polar 
  surface 
  is 
  

   deeply 
  indented 
  (fig. 
  35). 
  The 
  division 
  of 
  the 
  centrosome, 
  

   the 
  degeneration 
  of 
  the 
  centrosphere, 
  the 
  formation 
  of 
  lai-ge 
  

   vacuoles 
  round 
  the 
  nucleus 
  have 
  already 
  been 
  described. 
  

  

  6. 
  Remarks 
  on 
  the 
  work 
  of 
  Fick 
  and 
  Michaelis. 
  

  

  The 
  foregoing 
  account 
  dilfers 
  seriously 
  from 
  that 
  given 
  by 
  

   Fick 
  in 
  one 
  important 
  particular, 
  the 
  origin 
  of 
  the 
  definitive 
  

   centrosome. 
  

  

  After 
  describing 
  the 
  formation 
  of 
  the 
  sperm-aster 
  about 
  

   the 
  middle-piece, 
  and 
  showing 
  that 
  the 
  latter 
  becomes 
  

   separated 
  from 
  the 
  sperm-head, 
  swells 
  up 
  and 
  loses 
  the 
  

   distinctness 
  of 
  its 
  outline 
  (in 
  all 
  of 
  which 
  I 
  am 
  able 
  to 
  agree 
  

   with 
  him 
  entirely), 
  Fick 
  proceeds 
  as 
  follows 
  : 
  " 
  Die 
  Attrak- 
  

   tions-sphare 
  zieht 
  ilire 
  Strahlen 
  ein, 
  ballt 
  sich 
  zusammen 
  zu 
  

   einer 
  intensiv 
  roth-gefjirbten 
  Kugel 
  oder 
  zu 
  einem 
  Unregel- 
  

   massig 
  gestalteten 
  abgerundet 
  eckigen 
  Klumpen, 
  ganz 
  

   ahnlich 
  wie 
  die 
  von 
  Boveri 
  bei 
  Ascaris 
  abgebildeten 
  Archo- 
  

   plasmaklumpen." 
  

  

  This, 
  preceding 
  the 
  sperm, 
  divides 
  to 
  form 
  the 
  centrosomes 
  

   (though 
  he 
  does 
  not 
  apply 
  this 
  term 
  to 
  them) 
  of 
  the 
  fertilisa- 
  

  

  