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  ANIMAL 
  BEHAVIOUR 
  

  

  and 
  guards 
  against 
  its 
  occurrence. 
  Beavers 
  cut 
  a 
  canal 
  right 
  

   through 
  an 
  island 
  in 
  a 
  big 
  river 
  a 
  task 
  not 
  practically 
  justi- 
  

   fied 
  till 
  it 
  is 
  completed. 
  It 
  is 
  strictly 
  impossible 
  to 
  prove 
  

   that 
  these 
  animals 
  really 
  put 
  two 
  and 
  two 
  together 
  as 
  we 
  

   do 
  in 
  perceptual 
  inference, 
  but 
  no 
  less 
  generous 
  interpreta- 
  

   tion 
  seems 
  adequate. 
  

  

  When 
  Dr. 
  G. 
  T. 
  Romanes's 
  chimpanzee 
  was 
  asked 
  for 
  a 
  

   number 
  of 
  straws 
  up 
  to 
  five, 
  it 
  used 
  to 
  pick 
  up 
  the 
  required 
  

   number 
  and 
  present 
  them 
  with 
  the 
  ends 
  exposed 
  between 
  

   finger 
  and 
  thumb. 
  When 
  it 
  was 
  right 
  it 
  got 
  its 
  reward. 
  Some- 
  

   times, 
  however, 
  if 
  asked 
  for 
  four 
  straws, 
  it 
  would 
  gather 
  three 
  

   to 
  save 
  time 
  and 
  double 
  one 
  of 
  them 
  so 
  that 
  four 
  ends 
  showed. 
  

   When 
  a 
  reward 
  was 
  refused 
  on 
  such 
  occasions, 
  it 
  would 
  

   straighten 
  out 
  the 
  doubled 
  straw, 
  pick 
  up 
  another 
  one, 
  and 
  

   present 
  the 
  required 
  number. 
  In 
  a 
  case 
  of 
  this 
  sort 
  we 
  are 
  

   inclined 
  to 
  admit 
  intelligence, 
  for 
  it 
  was 
  rather 
  subtle 
  and 
  

   novel, 
  and 
  we 
  know 
  that 
  the 
  chimpanzee 
  has 
  a 
  highly 
  de- 
  

   veloped 
  brain. 
  

  

  But 
  pass 
  to 
  one 
  of 
  Miss 
  Drzewina's 
  experiments 
  with 
  

   hermit-crabs. 
  She 
  removed 
  them 
  from 
  their 
  borrowed 
  shells 
  

   and 
  gave 
  them 
  similar 
  shells 
  which 
  had 
  been 
  plastered 
  up. 
  

   The 
  hermit-crabs 
  spent 
  a 
  long 
  time 
  trying 
  to 
  get 
  into 
  these 
  

   closed 
  shells. 
  Eventually, 
  however, 
  they 
  gave 
  it 
  up 
  as 
  hope- 
  

   less, 
  as 
  of 
  course 
  it 
  was. 
  When 
  some 
  shells 
  of 
  the 
  same 
  

   sort, 
  but 
  empty, 
  were 
  put 
  into 
  the 
  aquarium 
  the 
  hermit- 
  

   crabs 
  would 
  not 
  look 
  at 
  them. 
  The 
  established 
  association 
  

   was 
  too 
  strong. 
  Yet 
  when 
  some 
  other 
  shells 
  of 
  a 
  different 
  

   shape 
  were 
  introduced, 
  the 
  hermit-crabs 
  tried 
  them 
  at 
  once. 
  

   The 
  question 
  is 
  whether 
  this 
  also 
  was 
  intelligent 
  behaviour, 
  

   or 
  whether 
  it 
  illustrated 
  what 
  we 
  do 
  not 
  understand, 
  a 
  profit- 
  

   ing 
  by 
  experience 
  on 
  a 
  lower 
  than 
  an 
  intellectual 
  level, 
  such 
  

   as 
  must 
  form 
  the 
  basis 
  of 
  the 
  very 
  effective 
  agency 
  of 
  the 
  

  

  