﻿MATURATION, 
  ETC., 
  OF 
  THE 
  EGG 
  OF 
  THE 
  AXOLOTL. 
  481 
  

  

  Tig. 
  32. 
  — 
  Later. 
  The 
  terminal 
  vacuoles 
  are 
  reduced. 
  The 
  pronuclei 
  are 
  

   elongated 
  parallel 
  to 
  tlie 
  spindle 
  axis. 
  A 
  pigmented 
  cord 
  still 
  connects 
  the 
  

   centrosomes. 
  Plasmosomes 
  as 
  in 
  the 
  last. 
  

  

  Pig. 
  33. 
  — 
  Later 
  still. 
  The 
  centrosomes 
  are 
  much 
  enlarged, 
  and 
  the 
  terminal 
  

   vacuoles 
  have 
  disappeared. 
  From 
  each 
  centrosonie 
  pass 
  out 
  a 
  number 
  of 
  fine 
  

   " 
  inner 
  " 
  astral 
  rays 
  (see 
  text). 
  Note 
  the 
  round 
  vacuoles 
  at 
  the 
  equator. 
  

  

  Pig. 
  34. 
  — 
  Only 
  one 
  pronucleus 
  is 
  shown 
  ; 
  the 
  chromosomes 
  are 
  forming 
  in 
  

   it. 
  The 
  achromatic 
  reticulum 
  is 
  coarse, 
  and 
  bears 
  granular 
  thickenings. 
  The 
  

   spindle 
  is 
  much 
  longer, 
  the 
  centrosomes 
  smaller 
  and 
  reticular 
  (aceto-corrosive 
  

   preparation), 
  and 
  the 
  inner 
  astral 
  rays 
  exceedingly 
  fine. 
  

  

  Fig. 
  35. 
  — 
  Resting 
  nucleus 
  of 
  one 
  of 
  the 
  first 
  two 
  blastomeres 
  ; 
  iu 
  it 
  are 
  

   seen 
  plasmosomes, 
  finely 
  divided 
  chromatic 
  granules, 
  and 
  an 
  achromatic 
  

   reticulum. 
  On 
  its 
  polar 
  — 
  the 
  right 
  — 
  side 
  is 
  a 
  depression, 
  and 
  on 
  the 
  same 
  

   side 
  two 
  small 
  centrosomes. 
  It 
  lies 
  in 
  a 
  clear, 
  much 
  vacuolated 
  area. 
  

  

  Fig. 
  35 
  6^. 
  — 
  Division 
  of 
  the 
  centrosomes 
  in 
  the 
  anaphase 
  of 
  the 
  fertilisation- 
  

   spindle. 
  The 
  centrosomes 
  are 
  flattened 
  against 
  one 
  another; 
  each 
  is 
  lobed 
  

   and 
  contains 
  a 
  centriole. 
  Chroino-acetic 
  preparation. 
  

  

  Fig. 
  36. 
  — 
  Early 
  stage 
  in 
  the 
  formation 
  of 
  the 
  chromosomes 
  by 
  linear 
  aggre- 
  

   gation 
  of 
  granules. 
  Li 
  the 
  female 
  proneucleus 
  (on 
  tlie 
  left) 
  a 
  plasniosome 
  is 
  

   still 
  visible. 
  In 
  the 
  male 
  pronucleus 
  there 
  is 
  a 
  very 
  coarse 
  granular 
  network 
  

   of 
  chromatin 
  crowded 
  together 
  in 
  the 
  centre 
  of 
  the 
  pronucleus. 
  In 
  both 
  

   pronuclei 
  the 
  achromatic 
  reticulum 
  is 
  coarse. 
  

  

  Fig. 
  37. 
  — 
  Transverse 
  section 
  of 
  the 
  fertilisation 
  spindle 
  in 
  early 
  metaphase 
  

   showing 
  two 
  distinct 
  sets 
  of 
  chromosomes. 
  

  

  Fig. 
  38. 
  — 
  Formation 
  of 
  the 
  equatorial 
  portion 
  cf 
  the 
  spindle 
  from 
  the 
  

   achromatic 
  reticulum 
  of 
  (one 
  of 
  the) 
  pronuclei. 
  The 
  continuity 
  of 
  the 
  extra- 
  

   and 
  intra-nuclear 
  fibres 
  through 
  the 
  openings 
  in 
  the 
  membrane 
  of 
  the 
  upper 
  

   pronucleus 
  is 
  readily 
  seen. 
  Centrospheres 
  and 
  centrosomes 
  as 
  iu 
  the 
  next 
  

   figure. 
  Pronuclei 
  as 
  in 
  Pig. 
  34. 
  

  

  Pig. 
  39. 
  — 
  Early 
  metaphase. 
  Aceto-corrosive 
  preparation. 
  The 
  inner 
  rays 
  

   have 
  undergone 
  reticular 
  degeneration 
  and 
  now 
  form 
  the 
  centrospheres. 
  In 
  

   each 
  centrosphere 
  is 
  an 
  ill-defined 
  reticular 
  centrosome. 
  Tlie 
  spindle-fibres 
  

   are 
  undulating, 
  united 
  by 
  anastomoses, 
  and 
  pass 
  continuously 
  from 
  pole 
  to 
  

   pole. 
  Outside 
  the 
  spindle 
  is 
  a 
  mantle 
  of 
  equatorial 
  astral 
  rays 
  ; 
  these 
  are 
  

   closely 
  pressed 
  together 
  and 
  pigmented. 
  The 
  chromosomes 
  lie 
  unevenly 
  in 
  

   the 
  equatorial 
  plane. 
  

  

  Fig. 
  40. 
  — 
  Metaphase. 
  Aceto-chromic 
  preparation. 
  The 
  cliromosomes 
  

   are 
  split, 
  lying 
  in 
  the 
  equator. 
  To 
  each 
  pair 
  of 
  chromosomes 
  is 
  attached 
  a 
  

   pair 
  of 
  special 
  fibre-bundles 
  (" 
  Zugfasern 
  "). 
  The 
  centrospheres 
  are 
  reticular 
  

   and 
  contain 
  each 
  a 
  homogeneous 
  lobed 
  centrosome 
  ; 
  inside 
  each 
  of 
  these 
  

   the 
  centriole 
  lias 
  divided. 
  

  

  