﻿MATUBATrO>J, 
  ETC., 
  OF 
  THE 
  EGG 
  OF 
  THE 
  AXOLOTL. 
  427 
  

  

  — 
  probably 
  under 
  the 
  immediate 
  influence 
  of 
  the 
  middle- 
  

   piece 
  — 
  from 
  the 
  cytoplasm 
  of 
  the 
  eg-g-. 
  If 
  so, 
  this 
  is 
  a 
  fact 
  of 
  

   the 
  very 
  highest 
  physiological 
  importance 
  in 
  the 
  process 
  of 
  

   fertilisation. 
  I 
  must 
  however 
  defer 
  the 
  full 
  discussion 
  of 
  it 
  

   to 
  another 
  part 
  of 
  this 
  paper. 
  

  

  The 
  sperm-nucleus 
  lies 
  a 
  little 
  to 
  one 
  side 
  — 
  the 
  outer 
  side 
  — 
  

   of 
  the 
  sperm-aster 
  ; 
  and 
  as 
  soon 
  as 
  the 
  large 
  vacuoles 
  are 
  

   formed 
  projects 
  slightly 
  into 
  them. 
  These 
  then 
  appear 
  as 
  a 
  

   system 
  of 
  clear 
  spaces 
  partially 
  surrounding 
  the 
  inner 
  side 
  of 
  

   the 
  sperm-nucleus 
  and 
  preceding 
  it 
  in 
  its 
  progress 
  into 
  the 
  

   interior 
  of 
  the 
  ovum 
  to 
  meet 
  the 
  female 
  pronucleus. 
  The 
  path, 
  

   generally 
  termed 
  the 
  " 
  copulation 
  " 
  path, 
  which 
  the 
  sperm- 
  

   nucleus 
  now 
  pursues 
  is 
  not 
  as 
  a 
  rule 
  in 
  the 
  same 
  straight 
  

   line 
  as 
  its 
  earlier 
  " 
  penetration 
  " 
  path, 
  but 
  makes 
  an 
  angle 
  

   with 
  it. 
  

  

  It 
  is 
  during 
  this 
  stage, 
  when 
  the 
  sperm-nucleus 
  is 
  already 
  

   coarsely 
  reticular, 
  that 
  the 
  definitive 
  centrosome 
  appears 
  

   (figs. 
  19 
  — 
  21). 
  This 
  is 
  a 
  large 
  rounded 
  body, 
  composed 
  of 
  

   a 
  granular 
  substance 
  staining 
  faintly 
  with 
  carmine, 
  and 
  not 
  

   very 
  deeply 
  with 
  iron-heematoxylin. 
  Occasionally 
  one 
  or 
  

   more 
  intensely-staining 
  granules 
  may 
  be 
  discerned 
  in 
  its 
  

   interior. 
  Its 
  diameter 
  is 
  about 
  one-quarter 
  or 
  one-third 
  that 
  

   of 
  the 
  sperm-nucleus. 
  It 
  is 
  always 
  surrounded 
  by 
  a 
  cloud 
  of 
  

   pigment 
  which 
  may 
  be 
  so 
  dense 
  as 
  to 
  entirely 
  obscure 
  the 
  

   centrosome 
  within 
  (fig. 
  23) 
  ; 
  this 
  can, 
  however, 
  easily 
  be 
  

   demonstrated 
  after 
  depigmentation 
  with 
  the 
  fumes 
  of 
  nitric 
  

   acid 
  (fig. 
  22). 
  It 
  lies 
  in 
  front 
  of 
  the 
  sperm-nucleus, 
  between 
  

   it 
  and 
  the 
  system 
  of 
  vacuoles. 
  When 
  the 
  sperm-nucleus 
  

   comes 
  to 
  project 
  into 
  the 
  vacuoles 
  the 
  centrosome 
  occupies 
  

   approximately 
  the 
  centre 
  of 
  the 
  system. 
  

  

  This 
  body 
  is 
  also 
  found 
  in 
  connection 
  with 
  the 
  accessory 
  

   sperm-nuclei, 
  where 
  it 
  has 
  exactly 
  the 
  same 
  character 
  and 
  

   behaves 
  in 
  precisely 
  the 
  same 
  manner 
  (figs. 
  19, 
  22, 
  23, 
  24). 
  

  

  The 
  centrosome 
  very 
  soon 
  divides 
  in 
  a 
  direction 
  which 
  is 
  at 
  

   right 
  angles 
  to 
  the 
  " 
  sperm 
  " 
  path 
  (fig. 
  22) 
  . 
  Preliminary 
  to 
  

   division 
  it 
  becomes 
  elongated 
  and 
  constricted 
  (figs. 
  20, 
  21). 
  

   The 
  halves 
  may 
  be 
  at 
  first 
  connected 
  by 
  fibrillee. 
  In 
  one 
  case 
  

  

  