﻿f)'.) 
  

  

  Fig, 
  8, 
  PL 
  I. 
  The 
  unimprcgnated 
  ovum 
  or 
  egg, 
  freshly 
  

   taken 
  from 
  the 
  female 
  and 
  divested 
  from 
  the 
  mucous 
  coat- 
  

   ing, 
  presents 
  a 
  vitelline 
  membrane 
  or 
  shell 
  entirely 
  filled 
  

   with 
  liighly 
  refractile 
  oil 
  globules 
  of 
  very 
  nearly 
  unitVivni 
  

   size. 
  These 
  oil-globules 
  constitute 
  the 
  vitellus. 
  

  

  The 
  vitelline 
  membrane 
  has 
  upon 
  one 
  side 
  a 
  very 
  promi- 
  

   nent 
  depression 
  or 
  pit— 
  the 
  micropyle 
  — 
  witli 
  an 
  undoubted 
  

   opening 
  or 
  pore 
  at 
  the 
  bottom. 
  Figs. 
  1 
  and 
  2, 
  PI. 
  I. 
  

  

  This 
  micropyle 
  at 
  first 
  indents 
  the 
  mass 
  of 
  oil-globules, 
  

   but 
  as 
  soon 
  as 
  the 
  egg 
  passes 
  into 
  water, 
  some 
  of 
  it 
  is 
  ab- 
  

   sorbed, 
  and 
  the 
  vitellus 
  shrinks 
  in 
  balk 
  and 
  occupies 
  a 
  

   smaller 
  space 
  in 
  the 
  centre 
  of 
  the 
  egg. 
  Fig. 
  2, 
  PI. 
  I. 
  

  

  From 
  the 
  absorption 
  of 
  water 
  the 
  micropyle 
  soon 
  becomes 
  

   obliterated 
  and 
  its 
  place 
  simply 
  indicated 
  at 
  first 
  by 
  a 
  slight 
  

   protrusion 
  of 
  tlie 
  vitelline 
  membrane. 
  Fig. 
  3, 
  PI. 
  I, 
  after- 
  

   wards 
  by 
  a 
  puckering 
  of 
  the 
  surface, 
  Fig. 
  4, 
  PI. 
  I, 
  which 
  is 
  

   observed 
  in 
  some 
  eggs 
  when 
  the 
  embryo 
  is 
  very 
  far 
  advanced. 
  

   In 
  many, 
  or 
  perhaps 
  most 
  eggs, 
  however, 
  all 
  traces 
  of 
  the 
  

   position 
  of 
  the 
  micropyle 
  disappear 
  soon 
  after 
  impregnation. 
  

  

  The 
  absorption 
  of 
  water 
  sliglitly 
  increases 
  the 
  size 
  of 
  the 
  

   ovum/al 
  though 
  very 
  sliglitly, 
  the 
  great 
  change 
  being 
  the 
  

   concentration 
  of 
  the 
  yolk-mass. 
  This 
  distention 
  of 
  the 
  vitel- 
  

   line 
  membrane 
  of 
  course 
  has 
  very 
  much 
  to 
  do 
  with 
  tlie 
  dis- 
  

   appearance 
  of 
  the 
  micropyle. 
  The 
  micropyle 
  is 
  not 
  constant 
  

   in 
  position 
  as 
  regards 
  the 
  stalk 
  of 
  the 
  mucous 
  sack, 
  noi' 
  as 
  

   regards 
  the 
  position 
  of 
  the 
  embryo, 
  sometimes 
  being 
  over 
  the 
  

   bead, 
  sometimes 
  over 
  the 
  tail^ 
  sometimes 
  to 
  one 
  side. 
  

  

  This 
  latter 
  relationship, 
  however, 
  is 
  of 
  no 
  special 
  import- 
  

   ance, 
  since 
  the 
  yolk-mass 
  is 
  movable, 
  and 
  the 
  position 
  of 
  the 
  

   micropyle, 
  with 
  relation 
  to 
  the 
  embryo, 
  tiius 
  a 
  constantly 
  

   changing 
  one, 
  with 
  every 
  motion 
  of 
  the 
  e<^(^. 
  After 
  the 
  

   absorption 
  of 
  water, 
  the 
  concentration 
  of 
  the 
  yolk-mass, 
  and 
  

   the 
  filling 
  out 
  of 
  the 
  vitelline 
  membrane, 
  the 
  vitellus 
  or 
  

   yolk-mass 
  becomes 
  somewhat 
  changed 
  in 
  character 
  ; 
  the 
  oil- 
  

   globules 
  unite 
  one 
  into 
  another 
  directly, 
  forming 
  larger 
  

   spheres 
  in 
  the 
  centre 
  of 
  the 
  mas-i, 
  with 
  sinallei- 
  onei 
  filling 
  

  

  