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  ORGANISM 
  AND 
  MECHANISM 
  

  

  great 
  complexity, 
  it 
  is 
  not 
  unfair 
  to 
  recall 
  some 
  of 
  the 
  dif- 
  

   ficulties, 
  that 
  the 
  supposed 
  mechanism, 
  has 
  to 
  form 
  in 
  

   fertilisation 
  a 
  working 
  unity 
  with 
  another 
  mechanism 
  as 
  

   complex 
  as 
  itself; 
  that 
  it 
  has 
  thereafter 
  to 
  divide 
  over 
  and 
  

   over 
  again; 
  that 
  a 
  part 
  is 
  sometimes 
  as 
  good 
  as 
  a 
  whole; 
  

   and 
  so 
  on. 
  It 
  is 
  sometimes 
  easy 
  to 
  get 
  twins 
  from 
  one 
  egg 
  

   by 
  shaking 
  the 
  first 
  two 
  cleavage-cells 
  apart, 
  and 
  even 
  at 
  

   the 
  four-cell 
  stage 
  of 
  the 
  lancelet's 
  development 
  the 
  same 
  

   method 
  may 
  result 
  in 
  quadruplets. 
  It 
  almost 
  seems 
  as 
  if 
  we 
  

   here 
  reached 
  a 
  Euclidean 
  reductio 
  ad 
  absurdum 
  of 
  a 
  mecha- 
  

   nistic 
  interpretation. 
  

  

  The 
  central 
  problem 
  of 
  development 
  is 
  differentiation, 
  

   and 
  the 
  biological 
  study 
  of 
  this 
  is 
  not 
  more 
  than 
  incipient. 
  

   We 
  cannot 
  even 
  elucidate 
  the 
  fact 
  that 
  the 
  two 
  cells 
  into 
  

   which 
  a 
  germ-cell 
  divides 
  are 
  sometimes 
  exactly 
  alike 
  and 
  

   sometimes 
  distinctly 
  different. 
  Out 
  of 
  apparent 
  simplicity 
  

   there 
  gradually 
  emerges 
  obvious 
  complexity. 
  As 
  Roux 
  puts 
  

   it, 
  there 
  is 
  a 
  self-manifestation 
  of 
  intrinsic 
  manifoldness. 
  

   What 
  was 
  a 
  clear 
  drop 
  a 
  few 
  hours 
  ago 
  is 
  now 
  a 
  manifest 
  

   organism 
  with 
  nerve 
  and 
  sense-organ, 
  food-canal 
  and 
  muscle. 
  

   It 
  is 
  the 
  most 
  wonderful 
  thing 
  in 
  the 
  world. 
  Sometimes 
  the 
  

   whole 
  scene 
  has 
  changed 
  when 
  we 
  return 
  to 
  observation 
  

   after 
  the 
  interruption 
  of 
  an 
  hour's 
  lecture. 
  Be 
  it 
  under- 
  

   stood 
  that 
  no 
  theory 
  explains 
  it, 
  but 
  while 
  the 
  biological 
  

   interpretation 
  may 
  try 
  with 
  some 
  success 
  to 
  bring 
  devel- 
  

   opment 
  into 
  line 
  with, 
  say, 
  the 
  organism's 
  characteristic 
  self- 
  

   repairing 
  activity, 
  the 
  mechanistic 
  interpretation 
  has 
  not 
  

   yet 
  begun 
  its 
  task. 
  It 
  is 
  a 
  mere 
  impious 
  opinion 
  that 
  devel- 
  

   opment 
  will 
  one 
  day 
  be 
  described 
  in 
  terms 
  of 
  mechanics. 
  

  

  Another 
  prominent 
  fact 
  in 
  development 
  is 
  its 
  regulated- 
  

   ness 
  or 
  correlation. 
  Driesch 
  and 
  others 
  have 
  directed 
  at- 
  

   tention 
  to 
  the 
  power 
  the 
  embryo 
  often 
  shows 
  of 
  righting 
  it- 
  

  

  