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  ADAPTIVENESS 
  AND 
  PURPOSIVENESS 
  

  

  eggs. 
  The 
  young 
  marsupials 
  are 
  born 
  prematurely 
  and 
  can- 
  

   not 
  even 
  suck 
  ; 
  the 
  mother 
  places 
  them 
  in 
  her 
  external 
  pocket 
  

   of 
  skin 
  and 
  has 
  a 
  special 
  arrangement 
  for 
  forcing 
  the 
  milk 
  

   into 
  their 
  mouth. 
  They 
  meet 
  this, 
  so 
  to 
  speak, 
  with 
  a 
  special 
  

   adaptation 
  that 
  prevents 
  the 
  milk 
  going 
  down 
  the 
  wrong 
  way. 
  

  

  There 
  are 
  also 
  inter-organismal 
  adaptations 
  between 
  crea- 
  

   tures 
  of 
  different 
  kinds, 
  of 
  which 
  the 
  crowning 
  examples 
  

   are 
  to 
  be 
  found 
  in 
  the 
  way 
  certain 
  flowers 
  and 
  certain 
  in- 
  

   sects 
  are 
  suited 
  for 
  making 
  the 
  best 
  of 
  one 
  another. 
  Very 
  

   striking 
  also 
  are 
  the 
  numerous 
  mutually 
  helpful 
  associations 
  

   which 
  have 
  been 
  established 
  partnerships, 
  commensalism, 
  

   and 
  symbiosis, 
  in 
  which 
  there 
  is 
  sometimes 
  two-sided 
  adapta- 
  

   tion. 
  The 
  case 
  is 
  repulsive, 
  but 
  the 
  parasite 
  is 
  often 
  adapted 
  

   to 
  its 
  drifting 
  life 
  of 
  ease 
  and 
  to 
  making 
  much 
  of 
  its 
  host, 
  

   which, 
  in 
  turn, 
  is 
  often 
  adapted 
  so 
  that 
  it 
  hardly 
  suffers 
  

   at 
  all 
  from 
  its 
  guest. 
  In 
  the 
  mimetic 
  resemblance 
  of 
  one 
  

   creature 
  to 
  another 
  there 
  is 
  again 
  adaptation, 
  often 
  of 
  almost 
  

   incredible 
  subtlety. 
  

  

  In 
  Lido-Pacific 
  crabs 
  of 
  the 
  genus 
  Melia 
  a 
  delicate 
  sea- 
  

   anemone 
  is 
  often 
  carried 
  on 
  the 
  forceps, 
  and 
  probably 
  serves 
  

   to 
  paralyse 
  the 
  crab's 
  prey 
  with 
  its 
  batteries 
  of 
  stinging 
  

   cells. 
  It 
  is 
  quaintly 
  suggestive 
  of 
  a 
  tool, 
  and 
  its 
  occasional 
  

   absence 
  shows 
  that 
  it 
  is 
  not 
  vitally 
  necessary. 
  But 
  the 
  part- 
  

   nership 
  or 
  commensalism 
  is 
  probably 
  of 
  very 
  old 
  standing, 
  

   since 
  the 
  denticles 
  of 
  the 
  forceps 
  are 
  elongated 
  into 
  needles 
  

   which 
  are 
  adaptively 
  suited 
  to 
  keeping 
  a 
  firm 
  grip 
  of 
  the 
  

   ' 
  tool 
  '. 
  

  

  We 
  are 
  accustomed 
  to 
  the 
  idea 
  of 
  adaptations, 
  but 
  perhaps 
  

   we 
  are 
  not 
  sufficiently 
  appreciative 
  of 
  their 
  nicety. 
  When 
  

   winter 
  sets 
  in, 
  the 
  North 
  American 
  ruffed 
  grouse 
  puts 
  on 
  

   snow-shoes 
  a 
  row 
  of 
  projecting 
  plates 
  on 
  each 
  side 
  of 
  each 
  

   toe 
  so 
  that 
  the 
  bird 
  can 
  tread 
  on 
  the 
  loose 
  snow 
  without 
  

  

  