﻿466 
  J. 
  W. 
  JKNKINSON. 
  

  

  This, 
  however, 
  is 
  by 
  no 
  means 
  the 
  case 
  ; 
  tor 
  in 
  the 
  tirst 
  

   place 
  a 
  drop 
  of 
  distilled 
  water 
  will 
  produce 
  an 
  aster 
  in 
  eg^- 
  

   yolk 
  or 
  albumen 
  ; 
  and 
  further, 
  the 
  asters 
  can 
  be 
  made 
  much 
  

   more 
  readily, 
  as 
  already 
  pointed 
  out, 
  on 
  a 
  glass 
  slide 
  and 
  in 
  

   a 
  thin 
  film, 
  or 
  at 
  the 
  surface 
  of 
  a 
  liquid, 
  than 
  in 
  the 
  bulk 
  of 
  

   a 
  liquid, 
  and 
  in 
  the 
  latter 
  much 
  better 
  when 
  there 
  are 
  solids 
  

   present. 
  

  

  It 
  is 
  quite 
  evident 
  then 
  that 
  though 
  a 
  central 
  excess 
  of 
  

   osmotic 
  pressure 
  may 
  be 
  to 
  a 
  certain 
  extent 
  responsible 
  for 
  the 
  

   production 
  of 
  the 
  aster, 
  surface-tension 
  phenomena 
  of 
  a 
  very 
  

   complicated 
  nature 
  have 
  still 
  to 
  be 
  reckoned 
  with. 
  More 
  

   than 
  this 
  as 
  to 
  the 
  physical 
  nature 
  of 
  the 
  process 
  it 
  is 
  impos- 
  

   sible 
  to 
  say. 
  There 
  seems 
  to 
  be 
  an 
  important 
  difference 
  

   between 
  these 
  asters 
  and 
  the 
  well-known 
  " 
  cohesion 
  figures 
  " 
  

   of 
  Tomlinson. 
  No 
  doubt 
  both 
  are 
  capillary 
  phenomena, 
  but 
  

   while 
  Tonilinson's 
  figures 
  are 
  formed 
  at 
  the 
  surface 
  these 
  

   grow 
  out 
  beneath 
  it 
  in 
  the 
  thickness 
  of 
  the 
  film. 
  Surface- 
  

   tension 
  relations 
  with 
  both 
  air 
  and 
  glass 
  are 
  thus 
  apparently 
  

   excluded. 
  My 
  asters 
  also 
  are 
  quite 
  dissimilar 
  to 
  the 
  "strain" 
  

   asters 
  produced 
  by 
  Biitschli 
  (1898) 
  in 
  gelatin 
  under 
  the 
  stress 
  

   of 
  a 
  contracting 
  air-bubble, 
  and 
  made 
  by 
  Hardy 
  with 
  a 
  small 
  

   globule 
  of 
  mercury 
  rolled 
  on 
  a 
  thin 
  film 
  of 
  albumen. 
  Dr. 
  

   Ramsden 
  has 
  pointed 
  out 
  to 
  me 
  that 
  the 
  latter 
  is 
  nothing- 
  

   more 
  than 
  the 
  wrinkling 
  of 
  a 
  solid 
  surface 
  membrane, 
  and 
  

   can 
  hardly 
  be 
  compared 
  with 
  any 
  radiations 
  formed 
  in 
  the 
  

   bulk 
  of 
  a 
  fluid. 
  

  

  It 
  only 
  remains 
  to 
  be 
  considered 
  whether 
  any 
  hypothesis, 
  

   however 
  tentative, 
  can 
  be 
  based 
  on 
  these 
  experiments 
  which 
  

   shall 
  elucidate 
  the 
  natural 
  asters 
  which 
  we 
  observe 
  in 
  the 
  

   living 
  cell. 
  

  

  We 
  have 
  seen 
  that 
  when 
  the 
  spermatozoon 
  reaches 
  the 
  

   interior 
  of 
  the 
  ovum 
  a 
  clear 
  yolk-free 
  area 
  is 
  formed 
  round 
  it, 
  

   in 
  the 
  centre 
  of 
  which 
  the 
  middle-piece 
  gradually 
  dissolves. 
  

   The 
  behaviour 
  of 
  the 
  middle-piece 
  in 
  the 
  egg 
  seems 
  quite 
  

   comparable 
  with 
  the 
  behaviour 
  of 
  a 
  small 
  crystal 
  of 
  salt 
  or 
  

   other 
  substance 
  in 
  a 
  drop 
  of 
  egg-yolk 
  ; 
  here 
  also 
  a 
  clear 
  

   yolk-free 
  area 
  is 
  formed 
  round 
  the 
  dissolving 
  particle. 
  

  

  