﻿PLATE 
  I. 
  

  

  Figure 
  1. 
  — 
  Eggs 
  two 
  hours 
  and 
  seven 
  minutes 
  after 
  fertili- 
  

   zation. 
  It 
  is 
  now 
  perfectly 
  spherical, 
  with 
  an 
  external 
  mem- 
  

   brane, 
  and 
  the 
  gerrainative 
  vesicle 
  is 
  not 
  visible. 
  

  

  Figure 
  2. 
  — 
  The 
  same 
  egg 
  two 
  minutes 
  later. 
  It 
  is 
  now 
  

   elongated 
  ; 
  one 
  end 
  is 
  wider 
  than 
  the 
  other, 
  and 
  a 
  transparent 
  

   area 
  at 
  the 
  broad 
  end 
  marks 
  the 
  point 
  where 
  the 
  polar 
  glob- 
  

   ules 
  are 
  about 
  to 
  appear. 
  At 
  the 
  opposite 
  end 
  the 
  external 
  

   membrane 
  is 
  wrinkled 
  by 
  waves 
  which 
  run 
  from 
  the 
  nutritive 
  

   towards 
  the 
  formative 
  pole 
  in 
  rapid 
  succession 
  for 
  about 
  fif- 
  

   teen 
  seconds. 
  

  

  Figure 
  3. 
  — 
  The 
  same 
  egg 
  two 
  minutes 
  later. 
  

  

  Figure 
  4. 
  — 
  The 
  same 
  egg 
  two 
  minutes 
  later. 
  The 
  yolk 
  has 
  

   become 
  pear-shaped. 
  The 
  polar 
  globule 
  has 
  appeared 
  at 
  the 
  

   formative 
  pole, 
  in 
  the 
  middle 
  of 
  the 
  broad 
  end 
  of 
  the 
  pear, 
  

   and 
  the 
  nutritive 
  end 
  of 
  the 
  egg 
  is 
  now 
  less 
  granular 
  than 
  

   the 
  formative 
  end. 
  

  

  Figure 
  5. 
  — 
  The 
  same 
  egg 
  two 
  minutes 
  later. 
  Three 
  equi- 
  

   distant 
  furrows 
  have 
  made 
  their 
  appearance, 
  separating 
  it 
  into 
  

   a 
  single 
  mass 
  at 
  the 
  nutritive 
  pole, 
  and 
  two 
  at 
  the 
  formative 
  

   pole. 
  At 
  this 
  stage 
  the 
  three 
  masses 
  are 
  about 
  equal 
  in 
  size. 
  

  

  Figure 
  6. 
  — 
  The 
  same 
  egg 
  two 
  minutes 
  later. 
  The 
  first 
  mi- 
  

   cromere, 
  c, 
  is 
  now 
  perfectly 
  separated, 
  and 
  smaller 
  than 
  the 
  

   second, 
  J, 
  and 
  each 
  is 
  smaller 
  than 
  the 
  macromere, 
  a. 
  

  

  Figure 
  7. 
  — 
  ^The 
  same 
  egg 
  one 
  minute 
  later. 
  Both 
  micro- 
  

   meres 
  are 
  separated 
  and 
  are 
  spherical, 
  as 
  is 
  also 
  the 
  macromere. 
  

   This 
  stage 
  ends 
  the 
  first 
  period 
  of 
  activity. 
  

  

  Figure 
  8. 
  — 
  The 
  same 
  egg 
  forty-five 
  seconds 
  later. 
  The 
  two 
  

   inicromeres 
  have 
  begun 
  to 
  fuse 
  with 
  each 
  other, 
  and 
  the 
  second 
  

   micromere, 
  h, 
  is 
  also 
  partially 
  fused 
  with 
  the 
  macromere, 
  a. 
  

  

  Figure 
  9. 
  — 
  The 
  same 
  egg 
  one 
  minute 
  later. 
  The 
  first 
  mi- 
  

   cromere, 
  c. 
  has 
  also 
  bee-un 
  to 
  unite 
  with 
  the 
  macromere. 
  

  

  