﻿424 
  J. 
  W. 
  JENKINSON. 
  

  

  the 
  sperm-aster, 
  and 
  separated 
  from 
  the 
  sperm-head 
  ; 
  this 
  

   body, 
  I 
  think, 
  may 
  be 
  the 
  last 
  remains 
  of 
  the 
  sti-ucture 
  in 
  

   question, 
  though 
  it 
  is 
  possible 
  that 
  it 
  is 
  the 
  remnant 
  of 
  the 
  

   tail. 
  

  

  But 
  whether 
  it 
  dissolves 
  in 
  this 
  fashion, 
  or 
  whether 
  it 
  is 
  

   withdrawn 
  into 
  the 
  sperm 
  nucleus 
  — 
  as 
  I 
  suppose 
  is 
  a 
  not 
  

   impossible 
  view 
  — 
  of 
  its 
  actual 
  disappearance 
  there 
  cannot 
  be 
  

   the 
  shadow 
  of 
  a 
  doubt. 
  In 
  a 
  stage 
  which 
  is, 
  to 
  judge 
  by 
  the 
  

   further 
  shortening 
  and 
  thickening 
  of 
  the 
  sperm-head 
  and 
  by 
  its 
  

   increased 
  vacuolation, 
  more 
  advanced 
  than 
  that 
  just 
  under 
  dis- 
  

   cussion, 
  no 
  sign 
  of 
  the 
  middle-piece 
  can 
  be 
  seen 
  (fig. 
  18) 
  ; 
  the 
  

   centre 
  of 
  the 
  sperm-aster 
  is 
  occupied, 
  as 
  before, 
  merely 
  by 
  a 
  

   vacuolated 
  mass. 
  The 
  tail 
  has 
  also 
  now 
  disappeared. 
  

  

  4. 
  Formation 
  of 
  the 
  pronuclei; 
  appearance 
  of 
  

   the 
  definitive 
  centrosome. 
  

  

  (a) 
  The 
  female 
  pronucleus. 
  — 
  The 
  chromosomes 
  left 
  in 
  the 
  

   egg 
  lie 
  in 
  a 
  small, 
  clear 
  area. 
  At 
  first 
  they 
  converge 
  by 
  

   their 
  apices 
  (fig. 
  8), 
  as 
  in 
  the 
  anaphase, 
  but 
  presently 
  

   become 
  arranged 
  in 
  a 
  tangled 
  skein, 
  without, 
  however, 
  losing 
  

   their 
  individuality. 
  A 
  little 
  later 
  still 
  a 
  nuclear 
  membrane 
  

   appears, 
  surrounding 
  the 
  chromosomes 
  (fig. 
  28, 
  a.). 
  These 
  

   lie 
  in 
  an 
  achromatic 
  network 
  ; 
  but 
  whether 
  this 
  is 
  derived 
  

   from 
  the 
  chromosomes 
  or 
  not 
  I 
  cannot 
  say. 
  It 
  certainly 
  stains 
  

   differently, 
  but 
  at 
  the 
  same 
  time 
  the 
  surfaces 
  of 
  the 
  chromo- 
  

   somes 
  are 
  everywhere 
  produced 
  into 
  small, 
  tooth-like 
  pro- 
  

   cesses, 
  which 
  lends 
  some 
  colour 
  to 
  the 
  view 
  that 
  the 
  achromatic 
  

   network 
  is 
  in 
  reality 
  the 
  result 
  of 
  the 
  continued 
  outgrowth 
  

   of 
  these. 
  

  

  The 
  chromosomes 
  become 
  broken 
  up 
  into 
  at 
  first 
  coarse 
  

   (fig. 
  28, 
  h. 
  and 
  c), 
  but 
  ultimately 
  very 
  fine 
  fragments, 
  which 
  

   are 
  evenly 
  distributed 
  over 
  the 
  achromatic 
  reticulum; 
  these 
  

   small 
  granules 
  seem 
  to 
  lose 
  much 
  of 
  their 
  staining 
  capacity 
  

   (fig. 
  28, 
  d. 
  and 
  e.). 
  It 
  is 
  not 
  possible 
  to 
  speak 
  very 
  

   positively, 
  but 
  it 
  seems 
  as 
  though 
  a 
  great 
  deal 
  of 
  the 
  chro- 
  

   matin 
  had 
  gone 
  into 
  solution 
  in 
  the 
  nuclear 
  sap. 
  In 
  any 
  case 
  

  

  