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  ANIMAL 
  BEHAVIOUR 
  

  

  Oiie 
  of 
  the 
  criteria 
  of 
  organisms 
  is 
  the 
  power 
  of 
  retention 
  

   or 
  registration 
  which 
  eventually 
  finds 
  remarkable 
  expression 
  

   in 
  human 
  memory, 
  and 
  the 
  general 
  view 
  we 
  wish 
  to 
  suggest, 
  

   as 
  a 
  clue 
  to 
  the 
  maze 
  of 
  animal 
  behaviour, 
  is 
  that 
  there 
  

   has 
  been 
  at 
  level 
  after 
  level 
  a 
  process 
  of 
  automatisation 
  or 
  

   organisation, 
  which 
  makes 
  for 
  economy 
  of 
  time 
  and 
  energy, 
  

   and 
  also, 
  if 
  it 
  does 
  not 
  go 
  too 
  far, 
  leaves 
  the 
  organism 
  free 
  

   for 
  experiment 
  and 
  initiative. 
  So 
  in 
  established 
  reactions, 
  

   in 
  reflex 
  actions, 
  and 
  in 
  tropisms 
  we 
  see 
  enregistrations 
  

   which 
  are, 
  in 
  a 
  way, 
  off 
  the 
  main 
  line 
  of 
  advance. 
  

  

  Besides 
  established 
  reactions, 
  reflex 
  actions, 
  and 
  tropisms 
  

   there 
  are 
  rhythmic 
  activities 
  adjusted 
  to 
  external 
  periodici- 
  

   ties, 
  such 
  as 
  change 
  of 
  position 
  in 
  shore 
  animals 
  when 
  the 
  

   tide 
  goes 
  out 
  or 
  comes 
  in. 
  That 
  these 
  may 
  be 
  more 
  than 
  

   tropisms 
  is 
  shown 
  by 
  cases 
  where 
  the 
  rhythm 
  is 
  so 
  engrained 
  

   in 
  the 
  creature's 
  constitution 
  that 
  it 
  persists 
  for 
  a 
  time 
  in 
  

   periodic 
  expression 
  even 
  when 
  the 
  external 
  stimulus 
  has 
  

   ceased. 
  The 
  interesting 
  green 
  worms 
  called 
  Convolutas, 
  

   well-known 
  on 
  some 
  flat 
  beaches, 
  such 
  as 
  that 
  of 
  Roscoff, 
  

   come 
  up 
  to 
  the 
  surface 
  of 
  the 
  sand 
  when 
  the 
  tide 
  goes 
  out, 
  

   and 
  retreat 
  again 
  when 
  the 
  tide 
  comes 
  in. 
  Bohn 
  has 
  found 
  

   that 
  they 
  will 
  continue 
  doing 
  this 
  for 
  a 
  couple 
  of 
  weeks 
  

   in 
  an 
  aquarium 
  away 
  from 
  the 
  sea. 
  Similarly, 
  some 
  hermit- 
  

   crabs 
  which 
  make 
  for 
  the 
  light 
  at 
  high 
  tide 
  and 
  away 
  from 
  

   the 
  light 
  at 
  low 
  tide 
  have 
  been 
  observed 
  doing 
  this 
  for 
  some 
  

   time 
  at 
  the 
  proper 
  hours 
  in 
  a 
  tideless 
  aquarium. 
  

  

  It 
  is 
  a 
  question 
  for 
  expert 
  discussion 
  and 
  further 
  experi- 
  

   ment 
  how 
  far 
  the 
  conception 
  of 
  tropisms 
  will 
  carry 
  us 
  as 
  

   an 
  interpretation 
  of 
  the 
  ways 
  of 
  the 
  lower 
  animals. 
  Loeb 
  

   believes 
  it 
  will 
  cover 
  most 
  cases; 
  Jennings 
  thinks 
  its 
  scope 
  

   is 
  narrowly 
  limited. 
  Just 
  as 
  tropisms 
  differ 
  from 
  ordinary 
  

   reflexes 
  in 
  being 
  usually 
  adjustments 
  of 
  the 
  animal 
  as 
  a 
  

  

  