﻿MATURATION, 
  ETC., 
  OP 
  THK 
  EGG 
  OF 
  THE 
  AXOLOTL. 
  429 
  

  

  merely 
  iu 
  connection 
  witli 
  but 
  tlirougli 
  the 
  active 
  agency 
  of 
  

   the 
  sperm-nucleus. 
  

  

  It 
  cannot 
  indeed 
  be 
  said 
  that 
  the 
  centrosome 
  is, 
  literally, 
  of 
  

   intra-nuclear 
  origin, 
  for 
  no 
  formed 
  body 
  at 
  all 
  like 
  it 
  is 
  ever 
  

   observable 
  in 
  the 
  interior 
  of 
  the 
  sperm-nucleus. 
  What 
  does 
  

   however 
  seem 
  to 
  me 
  probable 
  is 
  this, 
  that 
  this 
  body 
  is 
  pro- 
  

   duced 
  through 
  the 
  precipitation 
  of 
  albumins 
  or 
  globulins 
  

   present 
  in 
  the 
  cytoplasm 
  by 
  nucleic 
  acid 
  or 
  nucleins 
  emerging 
  

   from 
  the 
  nucleus, 
  a 
  view 
  which 
  coincides 
  with 
  that 
  advanced 
  

   by 
  Fischer 
  of 
  the 
  formation 
  of 
  the 
  centrosome 
  in 
  general. 
  

  

  The 
  origin 
  of 
  the 
  pigment, 
  on 
  the 
  other 
  hand, 
  is 
  a 
  matter 
  

   about 
  which 
  I 
  hardly 
  care 
  to 
  advance 
  any 
  conjectures 
  ; 
  but 
  I 
  

   think 
  it 
  is 
  certain 
  that 
  it 
  is 
  too 
  abundant 
  to 
  allow 
  us 
  to 
  

   suppose 
  that 
  it 
  has 
  been 
  dragged 
  in 
  by 
  the 
  spermatozoon 
  on 
  

   its 
  entrance 
  into 
  the 
  egg 
  ; 
  besides 
  it 
  is 
  absent 
  in 
  the 
  previous 
  

   stages. 
  

  

  I 
  cannot 
  conclude 
  this 
  paragraph 
  without 
  alluding 
  to 
  some 
  

   preparations 
  I 
  have 
  which 
  may 
  be 
  considered 
  to 
  favour 
  the 
  

   reprecipitation 
  hypothesis 
  mentioned 
  first. 
  In 
  these 
  a 
  dense 
  

   (fig. 
  26, 
  a.) 
  granular 
  mass, 
  undeniably 
  like 
  a 
  centrosome, 
  is 
  

   found 
  in 
  company 
  with 
  a 
  sperm-nucleus 
  (fig. 
  26, 
  h.), 
  which 
  is 
  in 
  

   an 
  earlier 
  stage 
  of 
  development 
  than 
  that 
  in 
  which 
  the 
  

   centrosome 
  usually 
  first 
  makes 
  its 
  appearance; 
  further, 
  the 
  

   nuclear 
  membrane 
  is 
  quite 
  intact 
  in 
  these 
  preparations. 
  

   Against 
  this 
  interpretation 
  I 
  must 
  urge 
  that 
  the 
  middle-piece 
  

   is 
  certainly 
  absent 
  at 
  an 
  earlier 
  stage 
  still, 
  that 
  nucleic 
  acid 
  

   may 
  diffuse 
  through 
  without 
  actually 
  bursting 
  the 
  nuclear 
  

   membrane, 
  and 
  that 
  there 
  is 
  no 
  reason 
  why 
  the 
  production 
  of 
  

   the 
  centrosome 
  by 
  the 
  other 
  method 
  should 
  not 
  have 
  taken 
  

   place 
  precociously. 
  

  

  5. 
  Union 
  of 
  the 
  pronuclei. 
  The 
  fertilisation 
  spindle. 
  

  

  Preceded 
  by 
  its 
  centrosome, 
  sphere, 
  and 
  aster, 
  the 
  sperm- 
  

   nucleus 
  makes 
  its 
  way 
  into 
  the 
  interior 
  of 
  the 
  egg. 
  The 
  

   female 
  pronucleus 
  has 
  meanwhile 
  been 
  moving 
  away 
  from 
  its 
  

   position 
  at 
  the 
  animal 
  pole, 
  and 
  sooner 
  or 
  later 
  the 
  two 
  

  

  