﻿MATURATION, 
  ETC., 
  OF 
  THE 
  EGG 
  OF 
  THE 
  AXOLOTL. 
  419 
  

  

  divisions, 
  and 
  in 
  the 
  first 
  polar 
  body, 
  tliougli 
  sometimes 
  I 
  

   have 
  seemed 
  to 
  make 
  sixteen, 
  sometimes 
  only 
  fourteen. 
  In 
  

   the 
  fertilization 
  spindle 
  I 
  have 
  counted 
  about 
  thirty 
  chromo- 
  

   somes. 
  

  

  This 
  disagrees 
  with 
  the 
  computations 
  of 
  Fick, 
  who 
  counts 
  

   eight 
  in 
  the 
  polar 
  divisions, 
  and 
  of 
  KoUiker, 
  who 
  has 
  

   given 
  the 
  number 
  in 
  the 
  dividing 
  nuclei 
  of 
  blastouieres 
  as 
  

   twelve. 
  

  

  B. 
  Fertilization. 
  

   1. 
  General 
  outline 
  of 
  fertilization. 
  

  

  The 
  spermatozoon 
  may 
  enter 
  the 
  egg 
  at 
  any 
  point 
  in 
  the 
  

   animal 
  hemisphere. 
  Its 
  entry 
  is 
  accompanied 
  by 
  the 
  forma- 
  

   tion 
  at 
  the 
  surface 
  of 
  a 
  deep 
  pit 
  or 
  funnel 
  filled 
  with 
  a 
  plug, 
  

   the 
  entrance 
  cone. 
  

  

  The 
  sperm 
  lies 
  at 
  the 
  bottom 
  of 
  this 
  funnel, 
  and 
  a 
  clear 
  

   area 
  — 
  the 
  sperm-sphere 
  — 
  rapidly 
  forms 
  round 
  the 
  head 
  and 
  

   middle-piece. 
  

  

  The 
  last 
  named 
  disappears; 
  as 
  it 
  disappears 
  the 
  sperm- 
  

   sphere 
  assumes 
  a 
  radiate 
  structure, 
  the 
  sperm-aster, 
  and 
  the 
  

   centre 
  of 
  this 
  soon 
  becomes 
  occupied 
  by 
  large 
  vacuoles. 
  The 
  

   sperm 
  head 
  becomes 
  gradually 
  transformed 
  into 
  an 
  oval 
  

   sperm- 
  nucleus 
  which, 
  preceded 
  by 
  its 
  aster, 
  moves 
  into 
  the 
  

   interior 
  of 
  the 
  egg 
  and 
  meets 
  with 
  the 
  female 
  pronucleus. 
  

  

  The 
  definitive 
  centrosome 
  is 
  formed 
  in 
  connection 
  with 
  the 
  

   sperm 
  nucleus, 
  probably 
  from 
  it. 
  This 
  centrosome 
  divides. 
  

   The 
  fertilization 
  spindle 
  is 
  then 
  formed 
  between 
  the 
  two 
  

   centrosomes, 
  the 
  male 
  and 
  female 
  pronuclei 
  breaking 
  up 
  

   independently 
  into 
  chromosomes 
  in 
  its 
  equator. 
  

  

  I 
  cannot 
  state 
  the 
  time 
  occupied 
  by 
  these 
  processes 
  with 
  

   very 
  great 
  certainty. 
  The 
  female 
  axolotl 
  begins 
  depositing 
  

   her 
  ova 
  soon 
  after 
  midnight 
  or 
  early 
  in 
  the 
  morning, 
  and 
  

   continues 
  laying 
  at 
  short 
  intervals 
  throughout 
  the 
  early 
  part 
  

   of 
  the 
  day. 
  It 
  is 
  necessary 
  to 
  watch 
  the 
  animal 
  closely 
  and 
  

   remove 
  each 
  batch 
  of 
  eggs 
  as 
  soon 
  as 
  it 
  is 
  laid 
  ; 
  but 
  even 
  so 
  

   the 
  time 
  of 
  laying 
  can 
  only 
  be 
  ascertained 
  approximately. 
  

  

  