﻿590 
  

  

  C4b;0RGE 
  WAGNER. 
  

  

  now 
  looseu 
  their 
  hold. 
  The 
  result 
  in 
  either 
  case 
  is 
  the 
  same. 
  

   By 
  one 
  such 
  manoeuvre 
  Hydra 
  sometimes 
  travels 
  a 
  distance 
  

   several 
  times 
  its 
  own 
  length 
  when 
  contracted. 
  Hydra 
  is 
  

   further 
  able 
  to 
  make 
  slower 
  journeys 
  by 
  gliding 
  about 
  on 
  its 
  

   foot 
  without 
  aid 
  fx'om 
  the 
  tentacles. 
  This 
  movement 
  is 
  very 
  

  

  i^a^ 
  

  

  Fig. 
  2. 
  — 
  Dia<Train 
  showing 
  movement 
  of 
  a 
  Hydra 
  viridis 
  in 
  

   absence 
  of 
  any 
  directive 
  stimulus. 
  The 
  fisjures 
  represent 
  positions 
  

   of 
  the 
  Hydra 
  when 
  observations 
  were 
  made. 
  For 
  further 
  ex|)lana- 
  

   tion 
  see 
  text. 
  

  

  slow, 
  and 
  noticeable 
  only 
  on 
  very 
  close 
  observation. 
  Never- 
  

   theless, 
  Hydra 
  ti'avels 
  considerable 
  distances 
  by 
  means 
  of 
  it. 
  

   It 
  has 
  been 
  stated 
  above 
  that 
  Hydra 
  is 
  often 
  found 
  hanging 
  

   from 
  the 
  surface 
  film. 
  A 
  slight 
  touch 
  to 
  such 
  a 
  Hydra 
  will 
  

   usually 
  loosen 
  its 
  hold 
  and 
  cause 
  it 
  to 
  fall 
  to 
  the 
  bottom, 
  but 
  

   this 
  is 
  not 
  always 
  the 
  case. 
  Trembley 
  (1. 
  c. 
  Mem. 
  1, 
  p. 
  77, 
  et 
  

  

  