﻿ON 
  SOME 
  MOVEMENTS 
  AND 
  REACTIONS 
  OF 
  HYDRA. 
  611 
  

  

  straca, 
  annelids, 
  insect 
  larvjB, 
  and 
  the 
  like, 
  wliich 
  form 
  the 
  

   ordinary 
  food 
  of 
  Hydra. 
  The 
  difficulty 
  increases 
  in 
  snch 
  a 
  

   case 
  as 
  came 
  to 
  my 
  notice 
  recently, 
  where 
  a 
  Hydra 
  grisea 
  

   made 
  an 
  attempt, 
  partially 
  successful, 
  to 
  swallow 
  an 
  annelid 
  

   fully 
  fifty 
  times 
  its 
  own 
  bulk 
  (Fig. 
  5). 
  The 
  extent 
  to 
  which 
  

   the 
  tissues 
  of 
  the 
  Hydra 
  were 
  stretched 
  during 
  this 
  perfoi'm- 
  

   ance 
  is 
  almost 
  beyond 
  belief. 
  Another 
  Hydra 
  from 
  the 
  same 
  

   dish 
  attempted 
  the 
  same 
  gastronomic 
  feat 
  on 
  a 
  leech 
  (Clepsine) 
  

   certainly 
  five 
  hundred 
  times 
  its 
  own 
  bulk. 
  Needless 
  to 
  say 
  

   this 
  one 
  did 
  not 
  succeed. 
  It 
  seems 
  to 
  me 
  Ave 
  must 
  assign 
  the 
  

   leading 
  role 
  in 
  swallowing 
  to 
  pseudopodia. 
  I 
  hope, 
  however, 
  

   to 
  obtain 
  direct 
  evidence 
  on 
  this 
  point 
  from 
  sections 
  before 
  

   long. 
  

  

  The 
  food 
  having 
  reached 
  the 
  lower 
  portion 
  of 
  the 
  digestive 
  

   tract, 
  rests 
  here 
  until 
  digestion 
  is 
  complete, 
  except 
  for 
  the 
  

   fact 
  that 
  it 
  is 
  churned 
  up 
  and 
  down 
  the 
  cavity 
  more 
  or 
  less 
  as 
  

   the 
  Hydra 
  expands 
  and 
  contracts. 
  Digestion 
  completed, 
  the 
  

   insoluble 
  residue 
  is 
  discarded 
  through 
  the 
  mouth. 
  This 
  

   ejection 
  I 
  have 
  seen 
  performed 
  several 
  times, 
  and 
  in 
  every 
  

   case 
  the 
  food 
  was 
  forced 
  out 
  by 
  a 
  very 
  sudden 
  squirt 
  that 
  

   threw 
  the 
  debris 
  to 
  some 
  distance. 
  

  

  During 
  these 
  experiments 
  it 
  was 
  soon 
  noticed 
  that 
  Hydras 
  

   would 
  not 
  always 
  attempt 
  to 
  capture 
  food 
  that 
  was 
  offered. 
  

   Hydi-as 
  taken 
  from 
  a 
  dish 
  in 
  which 
  food 
  was 
  abundant 
  were 
  

   commonly 
  quite 
  indifferent 
  to 
  any 
  food 
  offered 
  them, 
  no 
  

   matter 
  what 
  its 
  character. 
  The 
  same 
  Hydra 
  were 
  then 
  kept 
  

   in 
  a 
  dish 
  of 
  filtered 
  water 
  for 
  a 
  week, 
  thus 
  being 
  deprived 
  of 
  

   all 
  food 
  material. 
  At 
  the 
  end 
  of 
  this 
  period 
  they 
  swallowed 
  

   very 
  readily 
  any 
  food 
  offered 
  them, 
  the 
  process 
  of 
  ingestion 
  

   often 
  being 
  over 
  in 
  less 
  than 
  half 
  a 
  minute. 
  Hydra, 
  there- 
  

   fore, 
  does 
  not 
  react 
  to 
  offered 
  food 
  at 
  all 
  times, 
  but 
  only 
  after 
  

   a 
  period 
  of 
  abstinence. 
  It 
  is 
  an 
  intermittent, 
  not 
  a 
  constant 
  

   feeder. 
  It 
  sounds 
  very 
  simple 
  to 
  say 
  that 
  Hydra 
  will 
  not 
  

   feed 
  except 
  when 
  hungry. 
  Nevertheless, 
  a 
  determination 
  of 
  

   the 
  fact 
  is 
  not 
  superfluous. 
  The 
  case 
  is 
  different 
  for 
  instance 
  

   in 
  Planaria; 
  Pearl 
  ('08, 
  p. 
  668-9) 
  found 
  in 
  these 
  that 
  the 
  

   food-seeking 
  reaction 
  was 
  not 
  at 
  all 
  affected 
  by 
  conditions 
  of 
  

  

  