﻿MATURATION, 
  ETC., 
  OF 
  THE 
  EGG 
  OF 
  THE 
  AXOLOTL. 
  435 
  

  

  ceiitrosomes 
  are 
  flattened 
  against 
  one 
  another; 
  the 
  direction 
  

   of 
  their 
  division 
  is 
  at 
  right 
  angles 
  to 
  tlie 
  axis 
  of 
  the 
  spindle. 
  

   This 
  division 
  takes 
  place 
  as 
  a 
  rule 
  during 
  the 
  anaphase, 
  Lut 
  1 
  

   have 
  found 
  the 
  centrosome 
  doubled 
  at 
  an 
  earlier 
  stage. 
  

  

  The 
  cycle 
  of 
  changes 
  which 
  this 
  cell-organ 
  passes 
  through 
  

   would 
  then 
  appear 
  to 
  be 
  as 
  follows 
  : 
  — 
  At 
  first 
  a 
  small 
  body, 
  

   the 
  centrosome 
  begins 
  to 
  swell 
  by 
  absorption 
  of 
  the 
  watery 
  

   contents 
  of 
  the 
  adjacent 
  vacuoles; 
  then 
  spindle 
  fibres 
  and 
  

   astral 
  rays 
  begin 
  to 
  grow 
  out 
  at 
  its 
  expense 
  in 
  turn 
  ; 
  finally, 
  

   while 
  the 
  large 
  centrosphere 
  is 
  being 
  formed 
  by 
  the 
  reticular 
  

   degeneration 
  of 
  these 
  rays 
  the 
  centrosome 
  once 
  more 
  returns 
  

   to 
  its 
  original 
  volume 
  and 
  divides. 
  If 
  we 
  choose, 
  with 
  Boveri, 
  

   to 
  look 
  on 
  the 
  centrosphere 
  as 
  simply 
  an 
  enlarged 
  centrosome 
  — 
  

   and 
  I 
  think 
  that, 
  with 
  certain 
  reservations, 
  there 
  is 
  much 
  to 
  

   be 
  said 
  for 
  this 
  view 
  — 
  then 
  we 
  shall 
  regard 
  the 
  small 
  cor- 
  

   puscle 
  found 
  in 
  its 
  centre 
  as 
  a 
  " 
  reduced 
  " 
  centrosome 
  in 
  his 
  

   sense, 
  as 
  coming 
  into 
  being 
  by 
  a 
  condensation 
  of 
  the 
  central 
  

   portion 
  of 
  the 
  larger 
  body. 
  

  

  Though 
  I 
  have 
  not 
  made 
  any 
  extended 
  observations 
  on 
  the 
  

   behaviour 
  of 
  the 
  centrosomes 
  during 
  segmentation, 
  I 
  may, 
  

   perhaps, 
  be 
  allowed 
  to 
  give 
  an 
  account 
  here 
  of 
  what 
  little 
  I 
  

   have 
  been 
  able 
  to 
  make 
  out. 
  

  

  In 
  the 
  telophase 
  of 
  the 
  first 
  division 
  two 
  small 
  centrosomes 
  

   may 
  be 
  found 
  on 
  the 
  polar 
  side 
  of 
  the 
  nucleus 
  (fig. 
  35) 
  ; 
  they 
  

   are 
  usually 
  extremely 
  hard 
  to 
  detect, 
  mainly, 
  I 
  fancy, 
  because 
  

   they 
  lie 
  in 
  a 
  depression 
  of 
  the 
  nuclear 
  membrane. 
  The 
  

   centrosphere 
  has, 
  as 
  such, 
  totally 
  disappeared, 
  and 
  with 
  it 
  the 
  

   astral 
  rays. 
  Its 
  place 
  is 
  occupied 
  by 
  a 
  large 
  highly 
  vacuolated 
  

   area 
  surrounding 
  the 
  nucleus, 
  and 
  resembling 
  exactly 
  the 
  

   system 
  of 
  vacuoles 
  formed 
  in 
  connection 
  with 
  the 
  sperm- 
  

   nucleus. 
  

  

  In 
  the 
  metaphase 
  of 
  the 
  dividing 
  nuclei 
  of 
  blastomeres 
  a 
  

   large 
  centrosphere 
  is 
  present 
  at 
  each 
  spindle 
  pole, 
  and 
  in 
  the 
  

   centre 
  of 
  this 
  is 
  a 
  reticular 
  centrosome 
  (I 
  have 
  at 
  my 
  

   disposal 
  only 
  material 
  preserved 
  with 
  aceto-corrosive) 
  which 
  

   can 
  barely 
  be 
  distinguished 
  from 
  the 
  surrounding 
  reticulum. 
  

   These 
  facts 
  seem 
  to 
  me 
  to 
  indicate 
  that 
  the 
  centrosomes 
  of 
  the 
  

  

  