﻿180 
  ANIMAL 
  BEHAVIOUR 
  

  

  facts 
  : 
  (1) 
  The 
  movements 
  of 
  one 
  animalcule 
  are 
  often 
  quite 
  

   different 
  from 
  those 
  of 
  another, 
  even 
  in 
  the 
  same 
  medium: 
  

   so 
  soon 
  is 
  the 
  note 
  of 
  individuality 
  struck. 
  (2) 
  The 
  restless 
  

   roving 
  is 
  not 
  at 
  random, 
  and 
  when 
  food 
  is 
  scarce 
  it 
  is 
  in- 
  

   tensified, 
  passing 
  insensibly 
  into 
  ' 
  hunting 
  '. 
  (3) 
  Many 
  of 
  

   the 
  simplest 
  animals 
  exhibit 
  quite 
  definite 
  reactions 
  to 
  stim- 
  

   uli. 
  They 
  respond 
  by 
  particular 
  movements 
  to 
  changes 
  in 
  

   temperature, 
  in 
  illumination, 
  and 
  in 
  the 
  chemical 
  composition 
  

   of 
  the 
  medium. 
  As 
  there 
  is 
  no 
  nervous 
  system, 
  but 
  simply 
  

   a 
  specific 
  inborn 
  protoplasmic 
  organisation, 
  we 
  may 
  use 
  the 
  

   phrase 
  unicellular 
  organic 
  reaction 
  for 
  what 
  is 
  in 
  a 
  far-off 
  

   way 
  comparable 
  to 
  the 
  reflex 
  action 
  of 
  a 
  higher 
  animal. 
  

  

  The 
  adherents 
  of 
  the 
  mechanistic 
  school 
  point 
  out 
  that 
  the 
  

   Amo3ba 
  is 
  a 
  reservoir 
  of 
  energy 
  which 
  is 
  tapped 
  by 
  various 
  

   stimuli 
  such 
  as 
  the 
  freshness 
  of 
  the 
  water, 
  the 
  chemical 
  

   composition, 
  the 
  temperature, 
  and 
  the 
  illumination. 
  Its 
  

   locomotion 
  represents 
  the 
  natural 
  outflow 
  of 
  the 
  stored 
  en- 
  

   ergy, 
  and 
  the 
  direction 
  of 
  its 
  journeying 
  depends 
  on 
  the 
  con- 
  

   tinually 
  varying 
  stimuli 
  with 
  which 
  it 
  meets. 
  But 
  when 
  we 
  

   really 
  study 
  the 
  Amoeba, 
  as 
  Professor 
  Jennings 
  (1906) 
  has 
  

   done, 
  the 
  possibility 
  of 
  any 
  simple 
  description 
  of 
  its 
  doings 
  

   disappears. 
  Its 
  general 
  condition 
  has 
  much 
  to 
  do 
  with 
  its 
  

   reactions; 
  the 
  direction 
  of 
  movement 
  is 
  not 
  wholly 
  deter- 
  

   mined 
  by 
  the 
  position 
  of 
  the 
  stimulus 
  or 
  the 
  part 
  of 
  the 
  body 
  

   on 
  which 
  it 
  acts; 
  the 
  moving 
  Amoeba 
  shows 
  in 
  its 
  transient 
  

   differentiation 
  a 
  trafficking 
  with 
  time; 
  what 
  it 
  has 
  done 
  is 
  

   an 
  important 
  factor 
  in 
  determining 
  what 
  it 
  will 
  do 
  ; 
  the 
  

   types 
  of 
  reaction 
  are 
  not 
  stereotyped 
  ; 
  it 
  is 
  not 
  possible 
  to 
  

   predict 
  the 
  movements 
  from 
  a 
  knowledge 
  of 
  the 
  direct 
  re- 
  

   sults 
  of 
  the 
  external 
  influence. 
  So 
  the 
  life 
  of 
  the 
  Amreba 
  

   is 
  not 
  such 
  a 
  simple 
  affair 
  as 
  some 
  would 
  make 
  out. 
  We 
  

   require 
  a 
  kind 
  of 
  description 
  different 
  from 
  that 
  which 
  

  

  