﻿420 
  J. 
  W. 
  .TENKINSON. 
  

  

  In 
  this 
  way 
  1 
  have 
  found 
  that 
  the 
  entry 
  of 
  the 
  spermatozoon 
  

   and 
  the 
  formation 
  of 
  the 
  sperm-sphere 
  takes 
  about 
  two 
  hours, 
  

   the 
  formation 
  of 
  the 
  sperm-aster, 
  the 
  disappearance 
  of 
  the 
  

   middle-piece, 
  and 
  formation 
  of 
  the 
  two 
  pronuclei 
  about 
  five 
  

   hours. 
  About 
  seven 
  hours 
  after 
  laying 
  the 
  pronuclei 
  have 
  

   met, 
  while 
  the 
  definitive 
  centrosome 
  has 
  made 
  its 
  appearance 
  

   and 
  divided 
  into 
  two 
  ; 
  and 
  about 
  two 
  hours 
  later 
  the 
  fertiliza- 
  

   tion 
  spindle 
  is 
  complete. 
  These 
  observations 
  were 
  made 
  in 
  

   March, 
  1901. 
  

  

  Fick 
  makes 
  the 
  whole 
  time 
  much 
  shorter, 
  but 
  he 
  carried 
  

   on 
  his 
  work 
  later 
  in 
  the 
  year. 
  

  

  2. 
  The 
  entry 
  of 
  the 
  spermatozoon. 
  

  

  I 
  have 
  not 
  observed 
  the 
  actual 
  entrance 
  of 
  the 
  spermatozoon. 
  

  

  In 
  the 
  earliest 
  stage 
  in 
  my 
  possession 
  the 
  sperm 
  — 
  the 
  tail 
  

   of 
  which 
  is 
  taken 
  into 
  the 
  egg 
  with 
  the 
  head 
  — 
  is 
  seen 
  lying 
  

   in 
  a 
  clear 
  area 
  of 
  cytoplasm 
  in 
  the 
  midst 
  of 
  the 
  yolk-granules 
  

   (tig. 
  15). 
  This 
  clear 
  area, 
  which 
  I 
  will 
  call 
  the 
  sperm-sphere, 
  

   since 
  it 
  corresponds 
  to 
  what 
  has 
  been 
  described 
  under 
  that 
  

   name 
  by 
  other 
  authors, 
  lies 
  at 
  the 
  inner 
  end 
  of 
  a 
  deep 
  funnel- 
  

   shaped 
  depression 
  of 
  the 
  surface 
  of 
  the 
  egg. 
  The 
  superficial 
  

   pigment 
  of 
  the 
  egg 
  is 
  continued 
  down 
  the 
  sides 
  of 
  this 
  de- 
  

   pression 
  to 
  the 
  bottom 
  (fig. 
  A). 
  The 
  funnel 
  itself 
  is 
  occupied 
  

   by 
  a 
  plug 
  of 
  clear 
  hyaline 
  coagulum, 
  apparently 
  of 
  some 
  

   watery 
  substance, 
  which 
  projects 
  slightly 
  at 
  the 
  mouth 
  of 
  the 
  

   funnel, 
  and 
  is 
  here 
  surrounded 
  by 
  a 
  circular 
  groove; 
  its 
  

   outermost 
  layer 
  is 
  very 
  dense. 
  The 
  whole 
  is 
  covered 
  con- 
  

   tinuously 
  by 
  the 
  vitelline 
  membrane. 
  This 
  ping 
  is 
  the 
  

   entrance 
  cone 
  (wrongly 
  termed 
  by 
  earlier 
  observers 
  the 
  cone 
  

   of 
  attraction), 
  formed 
  on 
  contact 
  of 
  the 
  sperm 
  with 
  the 
  ovum 
  ; 
  

   it 
  has 
  been 
  observed 
  in 
  numerous 
  cases. 
  

  

  The 
  substance 
  of 
  the 
  plug 
  is 
  later 
  on 
  invaded 
  by 
  the 
  sur- 
  

   rounding 
  pigment 
  and 
  yolk-granules. 
  Its 
  position 
  in 
  the 
  egg 
  

   is 
  thus 
  marked 
  by 
  a 
  track 
  of 
  pigment, 
  which 
  may 
  be 
  termed 
  

   here, 
  as 
  it 
  has 
  been 
  in 
  other 
  cases, 
  the 
  " 
  penetration" 
  path 
  of 
  

   the 
  sperm. 
  

  

  