﻿AIATUIJATION, 
  ETC., 
  OF 
  THK 
  EGG 
  OF 
  THI'! 
  AXOLOTF.. 
  467 
  

  

  Subsequently 
  the 
  sperm-spliere 
  assumes 
  a 
  radiate 
  struc- 
  

   ture. 
  I 
  suggest 
  that 
  this 
  structure 
  is 
  due 
  to 
  the 
  outgrowth 
  

   of 
  tubular 
  processes 
  from 
  the 
  central 
  dissolved 
  mass. 
  These 
  

   outgrowths, 
  filled 
  with 
  a 
  slight 
  coagulum, 
  constitute 
  the 
  

   alveoli 
  or 
  iuter-fibrillar 
  spaces 
  ; 
  the 
  intervening 
  tracts 
  of 
  the 
  

   substance 
  of 
  the 
  sphere 
  the 
  inter-alveolar 
  lamella? 
  or 
  fibres. 
  

  

  In 
  addition 
  to 
  these 
  rays, 
  however, 
  other 
  rays 
  are 
  formed, 
  

   passing 
  outwards 
  between 
  the 
  yolk-granules. 
  These 
  external 
  

   rays 
  I 
  must 
  regard 
  as 
  originating 
  by 
  a 
  diiferent 
  process 
  ; 
  

   I 
  believe 
  that 
  they 
  represent 
  the 
  paths 
  along 
  which 
  water 
  is 
  

   being 
  withdrawn 
  from 
  the 
  cytoplasm. 
  Biitschli 
  (1894) 
  has 
  

   described 
  such 
  rays 
  round 
  the 
  contractile 
  vacuole 
  of 
  Balan- 
  

   tidium 
  and 
  some 
  other 
  Protozoa. 
  The 
  water 
  thus 
  continually 
  

   withdrawn 
  from 
  the 
  egg 
  becomes 
  concentrated 
  in 
  the 
  large 
  

   vacuoles 
  which 
  Ave 
  have 
  seen 
  occupying 
  the 
  centre 
  of 
  the 
  sphere. 
  

  

  It 
  is 
  at 
  this 
  moment 
  that 
  the 
  definitive 
  centrosome 
  makes 
  

   its 
  appearance. 
  Its 
  probable 
  origin 
  through 
  precipitation 
  of 
  

   the 
  albumins 
  of 
  the 
  egg-cell 
  by 
  the 
  nucleic 
  acid 
  or 
  nucleins 
  

   of 
  the 
  sperm- 
  nucleus 
  has 
  already 
  been 
  discussed. 
  It 
  has 
  

   also 
  been 
  shown 
  that 
  the 
  spindle-fibres 
  appear 
  to 
  grow 
  out 
  

   from 
  the 
  centrosomes, 
  and 
  that 
  as 
  the 
  spindle 
  is 
  gradually 
  

   developed 
  so 
  the 
  centrosomes 
  gradually 
  enlarge. 
  It 
  seems 
  to 
  

   me 
  that 
  the 
  physical 
  interpretation 
  suggested 
  above 
  of 
  the 
  

   formation 
  of 
  the 
  sperm-aster 
  is 
  applicable 
  here 
  also, 
  only 
  that 
  

   the 
  active 
  hygi^oscopic 
  particle 
  is 
  now 
  the 
  centrosome 
  instead 
  

   of 
  the 
  middle-piece. 
  Accepting 
  this 
  view, 
  we 
  regard 
  the 
  

   spindle-fibres 
  and 
  such 
  parts 
  of 
  the 
  astral 
  rays 
  as 
  come 
  into 
  

   being 
  at 
  this 
  stage 
  as 
  inter-alveolar 
  lamellae, 
  the 
  alveoli 
  

   themselves 
  as 
  outgrowths 
  of 
  the 
  dissolved 
  substance 
  of 
  the 
  

   centrosome. 
  The 
  intra- 
  nuclear 
  portion 
  of 
  the 
  spindle 
  arises 
  

   by 
  the 
  extension 
  of 
  the 
  tubular 
  outgrowths 
  into 
  the 
  cavity 
  of 
  

   the 
  nucleus, 
  the 
  membrane 
  being 
  first 
  dissolved. 
  The 
  fibres 
  

   are 
  then 
  formed 
  from 
  tracts 
  of 
  achromatic 
  substance, 
  just 
  as 
  

   outside 
  they 
  are 
  formed 
  from 
  the 
  cytoplasm. 
  

  

  Assuming 
  that 
  the 
  centrosome 
  — 
  and 
  the 
  middle-piece 
  is 
  

   also 
  a 
  centrosome 
  — 
  contains 
  nucleic 
  acid 
  or 
  even 
  nuclein 
  we 
  

   have 
  in 
  it 
  an 
  agent 
  capable 
  of 
  producing 
  these 
  effects 
  ; 
  meta- 
  

  

  