﻿458 
  J. 
  W. 
  JENKINSON. 
  

  

  of 
  the 
  continued 
  jiersistence 
  of 
  the 
  centrosome 
  from 
  the 
  

   spermatid 
  to 
  the 
  completely 
  fertilised 
  ovum, 
  we 
  may 
  l)e 
  

   taking 
  the 
  first 
  step 
  towards 
  re-establishing 
  on 
  a 
  securer 
  

   basis 
  Boveri's 
  original 
  generalisation. 
  

  

  The 
  rehabilitated 
  theor}'- 
  of 
  the 
  ])rime 
  activity 
  of 
  the 
  

   spermatozoon 
  in 
  renewing 
  the 
  ovum's 
  lost 
  power 
  of 
  cell- 
  

   division 
  might 
  then 
  be 
  enunciated 
  as 
  follows 
  : 
  — 
  On 
  contact 
  

   with 
  the 
  egg 
  an 
  apparatus 
  — 
  the 
  entrance-cone 
  — 
  is 
  produced 
  

   for 
  ensuring 
  the 
  entrance 
  of 
  the 
  sperm; 
  the 
  organ 
  respon- 
  

   sible 
  for 
  this 
  is 
  the 
  acrosome. 
  In 
  the 
  interior 
  of 
  the 
  egg 
  

   a 
  sperm-sphere 
  appears 
  which 
  imparts 
  (as 
  Ziegler's 
  experi- 
  

   ment 
  has 
  shown) 
  a 
  second 
  stimulus 
  to 
  the 
  cytoplasm; 
  the 
  

   organ 
  which 
  is 
  now 
  concerned 
  is 
  the 
  middle-piece. 
  When 
  

   the 
  pronuclei 
  have 
  met 
  a 
  spindle, 
  formed 
  directly 
  by 
  the 
  

   divided 
  sperm-centrosome, 
  completes 
  the 
  process 
  of 
  nuclear 
  

   and 
  cell-division. 
  Since, 
  however, 
  all 
  these 
  three 
  organs 
  

   either 
  are, 
  or 
  are 
  derived 
  from 
  centrosomes, 
  the 
  supreme 
  

   physiological 
  importance 
  of 
  the 
  centrosome 
  in 
  the 
  act 
  of 
  

   fertilisation 
  is 
  vindicated 
  to 
  the 
  full. 
  

  

  IV. 
  Experimental. 
  

  

  In 
  this 
  section 
  I 
  propose 
  to 
  give 
  a 
  brief 
  account 
  of 
  some 
  

   experiments 
  I 
  have 
  made 
  in 
  the 
  hope 
  of 
  throwing 
  some 
  light 
  

   on 
  the 
  nature 
  of 
  the 
  physical 
  processes 
  concerned 
  in 
  the 
  act 
  

   of 
  fertilisation, 
  that 
  is 
  to 
  say 
  in 
  the 
  restoration 
  to 
  the 
  ovum 
  

   of 
  its 
  lost 
  power 
  of 
  cell-division. 
  

  

  We 
  have 
  seen 
  that 
  not 
  only 
  in 
  the 
  Axolotl, 
  but 
  also 
  in 
  a 
  

   large 
  number 
  of 
  other 
  forms 
  the 
  following 
  phenomena 
  have 
  

   been 
  observed 
  during 
  fertilisation 
  : 
  — 
  

  

  1. 
  The 
  formation 
  round 
  the 
  spermatozoon 
  of 
  an 
  entrance- 
  

   funnel 
  filled 
  with 
  a 
  plug 
  — 
  the 
  entrance-cone 
  — 
  consisting 
  of 
  

   some 
  coagulable, 
  apparently 
  watery 
  material. 
  

  

  2. 
  (a) 
  The 
  appearance 
  of 
  a 
  clear 
  area 
  devoid 
  of 
  yolk- 
  

   granules 
  round 
  the 
  sperm-head 
  and 
  middle-piece 
  Avhen 
  the 
  

   latter 
  has 
  reached 
  the 
  interior 
  of 
  the 
  egg. 
  

  

  (b) 
  The 
  vacuolation 
  of 
  this 
  clear 
  area 
  and 
  sinmltaneous 
  

  

  