﻿MATUIiATION, 
  ETC., 
  OF 
  THE 
  EGG 
  OF 
  THE 
  AXOLOTL. 
  411 
  

  

  sie 
  aucli 
  vom 
  Fixirimgsmittel 
  conserviit 
  werden." 
  Within 
  

   this 
  real 
  structure 
  alterations 
  are 
  undoubtedly 
  produced 
  (let 
  

   me 
  instance 
  the 
  frequently 
  described 
  microsomal 
  structure 
  of 
  

   astral 
  rays 
  and 
  the 
  minute 
  — 
  reticular 
  or 
  alveolar 
  — 
  structure 
  

   of 
  cytoplasm) 
  ; 
  these 
  must 
  remain 
  as 
  a 
  permanent 
  source 
  of 
  

   difficulty 
  which 
  will 
  always 
  prevent 
  us 
  from 
  deciding 
  where 
  

   nature 
  leaves 
  off 
  and 
  art 
  begins. 
  There 
  are 
  other 
  cell 
  struc- 
  

   tures 
  again 
  about 
  which 
  we 
  should 
  preserve 
  a 
  frankly 
  open 
  

   mind. 
  I 
  should 
  certainly 
  be 
  prepared 
  to 
  admit 
  for 
  example 
  

   that 
  the 
  achromatic 
  reticulum 
  of 
  the 
  nucleus 
  was 
  artificial. 
  

  

  Secondly 
  Fischer 
  has 
  criticised 
  the 
  current 
  views 
  of 
  the 
  

   nature 
  of 
  the 
  centrosome, 
  aster, 
  and 
  spindle. 
  This 
  criticism 
  

   falls 
  into 
  two 
  parts 
  ; 
  the 
  first 
  is 
  an 
  attack 
  on 
  the 
  iron- 
  

   htematoxylin 
  method 
  as 
  diagnostic 
  of 
  the 
  centrosome 
  and 
  

   centriole, 
  the 
  second 
  is 
  a 
  theory 
  of 
  the 
  formation 
  of 
  centro- 
  

   somes 
  and 
  asters. 
  The 
  centrosome 
  is 
  regarded 
  as 
  produced 
  

   through 
  a 
  precipitation 
  of 
  the 
  albumins 
  of 
  the 
  cell 
  by 
  nucleic 
  

   acid, 
  the 
  nucleus 
  opening 
  for 
  the 
  purpose 
  at 
  the 
  poles. 
  The 
  

   asters 
  are 
  also 
  looked 
  upon 
  as 
  precipitation 
  products. 
  Fischer 
  

   has 
  shown 
  that 
  a 
  radial 
  structure 
  can 
  be 
  artificially 
  made 
  in 
  

   two 
  ways. 
  In 
  the 
  first, 
  which 
  he 
  terms 
  " 
  Fremdstrahlung,'' 
  

   elder 
  pith 
  cells 
  are 
  injected 
  with 
  solutions 
  of 
  proteid 
  and 
  then 
  

   fixed. 
  Asters 
  are 
  found 
  in 
  the 
  cells, 
  bnt 
  only 
  when 
  some 
  

   small 
  nodule 
  is 
  present 
  to 
  form 
  a 
  centre 
  for 
  the 
  radiations. 
  

   In 
  the 
  second 
  method 
  — 
  " 
  Selbststrahlung"— 
  the 
  rays 
  are 
  

   formed 
  in 
  a 
  proteid 
  solution 
  about 
  a 
  crystal 
  of 
  sublimate 
  or 
  

   a 
  drop 
  of 
  osmic 
  exuding 
  from 
  a 
  capillary 
  tube. 
  He 
  suggests 
  

   that 
  in 
  the 
  living 
  cells 
  asters 
  originate 
  around 
  the 
  centrosome 
  

   by 
  one 
  or 
  other 
  of 
  these 
  processes. 
  In 
  the 
  first 
  case 
  the 
  pre- 
  

   cipitating 
  reagent 
  is 
  either 
  the 
  nucleic 
  acid 
  of 
  the 
  nucleus 
  or 
  

   the 
  fixative 
  employed 
  ; 
  in 
  the 
  second 
  it 
  is 
  the 
  centrosome 
  

   itself. 
  Further, 
  centrosome, 
  aster, 
  and 
  spindle 
  (formed 
  by 
  

   the 
  conjunction 
  of 
  two 
  asters) 
  are 
  looked 
  upon 
  as 
  entirely 
  

   passive, 
  mere 
  incidental 
  accompaniments 
  of 
  the 
  activities 
  of 
  

   the 
  cell 
  ; 
  for 
  the 
  movements 
  of 
  the 
  chromosomes 
  are 
  attributed 
  

   by 
  Fischer 
  to 
  the 
  ordinary 
  streaming 
  and 
  growth 
  motions 
  of 
  

   the 
  cytoplasm. 
  

  

  