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  ORGANISM 
  AND 
  MECHANISM 
  

  

  host 
  that 
  will 
  enable 
  them 
  to 
  continue 
  their 
  life-history. 
  

   When 
  they 
  touch 
  the 
  mollusc 
  they 
  work 
  their 
  way 
  into 
  it 
  and 
  

   exhibit 
  a 
  remarkable 
  succession 
  of 
  multiplications 
  and 
  meta- 
  

   morphoses. 
  The 
  point 
  is 
  that 
  a 
  minute, 
  brainless 
  creature 
  

   responds 
  at 
  once 
  to 
  the 
  one 
  stimulus 
  which 
  will 
  enable 
  it 
  

   to 
  continue 
  its 
  life. 
  

  

  These 
  instances 
  have 
  been 
  taken 
  from 
  different 
  levels: 
  

   the 
  swallow 
  is 
  very 
  intelligent 
  and 
  yet 
  instinctive, 
  the 
  bee 
  

   is 
  very 
  instinctive 
  and 
  yet 
  intelligent, 
  the 
  larval 
  mussel 
  has 
  

   just 
  the 
  beginnings 
  of 
  a 
  nervous 
  system, 
  the 
  larval 
  fluke 
  

   has 
  none. 
  Our 
  point 
  is 
  that 
  we 
  can 
  find 
  objectively 
  analo- 
  

   gous 
  kinds 
  of 
  behaviour 
  at 
  all 
  levels 
  of 
  nervous 
  organisation, 
  

   and 
  that 
  we 
  have 
  to 
  do 
  with 
  a 
  general 
  capacity 
  of 
  living 
  

   creatures 
  the 
  capacity 
  of 
  enregistering 
  past 
  experiences 
  

   and 
  experiments, 
  either 
  individual 
  or 
  racial, 
  so 
  that 
  present 
  

   behaviour 
  is 
  influenced 
  by 
  them 
  in 
  very 
  specific 
  ways. 
  

   There 
  are 
  several 
  characteristic 
  features 
  in 
  behaviour 
  which 
  

   appear 
  to 
  be 
  beyond 
  all 
  mechanical 
  description. 
  The 
  be- 
  

   haviour 
  is 
  made 
  up 
  of 
  a 
  succession 
  of 
  acts 
  which 
  are 
  cor- 
  

   related 
  in 
  a 
  particular 
  sequence. 
  At 
  any 
  one 
  moment 
  there 
  

   are 
  chemical 
  and 
  physical 
  processes 
  going 
  on, 
  about 
  which 
  

   we 
  know 
  or 
  may 
  know 
  a 
  good 
  deal, 
  but 
  it 
  is 
  the 
  bond 
  of 
  

   union 
  that 
  eludes 
  the 
  chemist 
  and 
  physicist. 
  To 
  take 
  items 
  

   in 
  the 
  process 
  and 
  reduce 
  them 
  (as 
  far 
  as 
  we 
  can) 
  to 
  physi- 
  

   cal 
  and 
  chemical 
  common 
  denominators 
  is 
  interesting 
  in 
  its 
  

   way, 
  and 
  for 
  certain 
  purposes 
  useful, 
  but 
  it 
  does 
  not 
  make 
  

   any 
  clearer 
  the 
  interlinking, 
  the 
  co-ordination, 
  of 
  all 
  the 
  

   items 
  in 
  a 
  piece 
  of 
  behaviour. 
  When 
  we 
  consider 
  the 
  larval 
  

   liver-fluke 
  arrested 
  by 
  contact 
  with 
  the 
  fresh-water 
  snail 
  

   with 
  a 
  particular 
  species 
  of 
  water-snail, 
  or 
  the 
  larval 
  mussel 
  

   arrested 
  by 
  the 
  proximity 
  of 
  a 
  minnow, 
  or 
  a 
  stickleback, 
  or, 
  

   it 
  may 
  be, 
  by 
  one 
  and 
  only 
  one 
  particular 
  species 
  of 
  fish, 
  

  

  