﻿MATURATION, 
  ETC., 
  OF 
  THE 
  EGC4 
  OF 
  THE 
  AXOLOTL. 
  453 
  

  

  Cerebratulus, 
  van 
  der 
  Striclit's 
  of 
  Tliysanozoon 
  (second 
  polar 
  

   spindle), 
  and 
  Griffin's 
  of 
  Thalassema. 
  The 
  cleavage 
  centro- 
  

   sonie 
  of 
  the 
  Axolotl, 
  on 
  the 
  other 
  hand, 
  resembles 
  that 
  of 
  

   Ascaris. 
  At 
  first 
  small, 
  it 
  increases 
  in 
  volume, 
  and 
  then 
  gives 
  

   off 
  fine 
  rays, 
  which 
  become 
  continuous 
  with 
  the 
  older 
  astral 
  

   rays 
  outside. 
  These 
  rays 
  then 
  degenerate 
  to 
  form 
  the 
  centro- 
  

   sphere, 
  in 
  the 
  middle 
  of 
  which 
  a 
  " 
  reduced 
  " 
  centrosome 
  (to 
  

   use 
  Boveri's 
  expression) 
  is 
  found. 
  This 
  divides 
  for 
  the 
  next 
  

   mitosis, 
  and, 
  like 
  the 
  centrosome 
  of 
  Ascaris, 
  contains 
  a 
  minute 
  

   centriole. 
  

  

  Lillie 
  describes 
  in 
  the 
  maturation 
  and 
  fertilisation 
  spindles 
  

   of 
  Unio 
  an 
  inner 
  radiate 
  sphere 
  immediately 
  outside 
  the 
  

   centrosome, 
  between 
  which 
  and 
  the 
  aster 
  proper 
  is 
  a 
  second 
  or 
  

   outer, 
  also 
  radiate 
  sphere. 
  In 
  the 
  anaphase 
  the 
  inner 
  sphere 
  

   enlarges, 
  while 
  the 
  centrosome 
  divides, 
  a 
  spindle 
  being 
  formed 
  

   between 
  the 
  halves. 
  Then, 
  while 
  the 
  inner 
  sphere 
  disinte- 
  

   grates 
  together 
  with 
  the 
  outer 
  sphere 
  and 
  aster, 
  each 
  

   centrosome 
  grows 
  to 
  form 
  the 
  inner 
  sphere 
  of 
  the 
  next 
  gene- 
  

   ration, 
  one 
  central 
  particle 
  remaining 
  as 
  the 
  centrosome. 
  

   Lillie's 
  inner 
  sphere 
  is 
  clearly 
  a 
  derivative 
  of 
  the 
  centrosome, 
  

   and 
  its 
  whole 
  history 
  shows 
  very 
  clearly 
  that 
  a 
  part 
  — 
  the 
  

   outer 
  part 
  — 
  of 
  the 
  centrosome 
  may 
  in 
  the 
  course 
  of 
  its 
  life 
  

   assume 
  a 
  radial 
  structure. 
  This, 
  as 
  pointed 
  out 
  above, 
  is 
  

   admitted 
  by 
  Boveri, 
  and, 
  I 
  think, 
  follows 
  from 
  my 
  own 
  

   observations. 
  

  

  Vejdovsky's 
  interpretation 
  of 
  the 
  corresj^onding 
  changes 
  in 
  

   Rhynchelmis 
  is 
  very 
  different. 
  The 
  substance 
  of 
  the 
  sphere, 
  

   which 
  is 
  cytoplasmic 
  in 
  origin, 
  assumes 
  a 
  radiate 
  arrangement 
  

   under 
  the 
  influence 
  of 
  the 
  central 
  body 
  or 
  centriole 
  (he 
  admits 
  

   no 
  centrosome) 
  . 
  The 
  central 
  portion 
  of 
  this 
  sphere, 
  or 
  centro- 
  

   plasm, 
  as 
  Vejdovsky 
  calls 
  it, 
  undergoes 
  degeneration 
  only 
  

   once 
  more 
  to 
  assume 
  a 
  radial 
  arrangement 
  about 
  each 
  half 
  of 
  

   the 
  dividing 
  centriole. 
  The 
  central 
  body, 
  therefore, 
  under- 
  

   goes 
  no 
  increase 
  of 
  size, 
  and 
  exhibits 
  no 
  alteration 
  of 
  struc- 
  

   ture. 
  The 
  changes 
  are 
  entirely 
  confined 
  to 
  the 
  surrounding- 
  

   cytoplasm 
  (centroplasm) 
  , 
  and 
  are 
  merely 
  called 
  forth 
  by 
  the 
  

   activity 
  of 
  the 
  centriole. 
  

  

  