﻿ON 
  SOME 
  MOVEMENTS 
  AND 
  REACTIONS 
  OP 
  HYDUA. 
  595 
  

  

  Minor 
  deviations 
  are 
  numerous^ 
  but 
  all 
  fall 
  readily 
  into 
  tlie 
  

   above 
  scheme. 
  One 
  Hydra, 
  for 
  instance, 
  was 
  stimulated 
  at 
  

   the 
  tip 
  of 
  a 
  tentacle 
  while 
  body 
  and 
  tentacles 
  were 
  expand- 
  

   ing. 
  The 
  tentacle 
  stimulated 
  contracted 
  sharply, 
  but 
  the 
  

   rest 
  of 
  the 
  organism 
  kept 
  on 
  expanding. 
  It 
  was 
  only 
  after 
  

   this 
  tentacle, 
  now 
  contracted, 
  was 
  stimulated 
  a 
  number 
  of 
  

   times 
  that 
  the 
  whole 
  Hydra 
  contracted. 
  After 
  a 
  short 
  period 
  

   of 
  rest 
  it 
  expanded 
  again. 
  The 
  stimulation 
  was 
  repeated 
  in 
  

   the 
  same 
  manner 
  as 
  before, 
  and 
  the 
  same 
  result 
  was 
  obtained 
  

   step 
  by 
  step. 
  It 
  is 
  a 
  fact 
  worth 
  noting 
  here 
  that 
  in 
  most 
  

   Hydras 
  an 
  exact 
  repetition 
  of 
  a 
  stimulus, 
  after 
  an 
  interval 
  of 
  

   several 
  minutes, 
  reproduces 
  the 
  same 
  sequence 
  of 
  events 
  as 
  

   at 
  first. 
  

  

  In 
  another 
  Hydra 
  I 
  could 
  make 
  the 
  tentacles 
  conti-act 
  one 
  

   by 
  one 
  by 
  means 
  of 
  stimulation 
  at 
  their 
  tips, 
  until 
  all 
  were 
  

   contracted. 
  The 
  body 
  in 
  the 
  meanwhile 
  remained 
  expanded, 
  

   and 
  contracted 
  only 
  after 
  the 
  last 
  tentacle 
  to 
  contract 
  has 
  

   been 
  stimulated 
  a 
  number 
  of 
  times. 
  In 
  other 
  specimens 
  

   repeated 
  stimulation 
  of 
  one 
  tentacle 
  first 
  caused 
  the 
  contrac- 
  

   tion 
  of 
  this 
  one, 
  then 
  of 
  some 
  other, 
  or 
  several 
  others, 
  until 
  all 
  

   were 
  contracted. 
  Finally, 
  the 
  body 
  also 
  contracted. 
  There 
  is 
  

   seemingly 
  no 
  constant 
  relation 
  between 
  the 
  tentacle 
  stimulated 
  

   and 
  the 
  one 
  immediately 
  succeeding 
  it 
  in 
  contraction. 
  This 
  

   latter 
  is 
  sometimes 
  the 
  one 
  standing 
  next 
  to 
  the 
  one 
  stimu- 
  

   lated, 
  but 
  by 
  no 
  means 
  always. 
  Quite 
  as 
  frequently 
  it 
  is 
  the 
  

   one 
  opposite, 
  or 
  any 
  other 
  one 
  of 
  the 
  circle. 
  There 
  occurred 
  

   cases 
  where 
  the 
  body 
  contracted 
  simultaneously 
  Avith 
  the 
  

   last 
  arms 
  to 
  contract; 
  but 
  in 
  no 
  case, 
  where 
  the 
  stimulus 
  was 
  

   applied 
  to 
  a 
  tentacle, 
  did 
  the 
  body 
  contract 
  and 
  leave 
  some 
  of 
  

   the 
  tentacles 
  expanded 
  ; 
  that 
  is, 
  a 
  stimulus 
  applied 
  to 
  one 
  

   tentacle 
  did 
  not 
  radiate 
  to 
  the 
  body 
  without 
  also 
  radiating 
  to 
  

   all 
  the 
  other 
  tentacles. 
  It 
  did 
  often 
  radiate 
  to 
  these 
  tentacles 
  

   without 
  reaching 
  the 
  body. 
  This 
  indicates 
  that 
  there 
  is 
  a 
  

   particularly 
  intimate 
  connection 
  for 
  the 
  transmission 
  of 
  

   stimuli 
  between 
  the 
  individual 
  tentacles; 
  such 
  connection 
  

   would 
  necessarily 
  be 
  through 
  the 
  hypostome. 
  This 
  is, 
  of 
  

   course, 
  far 
  from 
  assuming 
  that 
  these 
  parts 
  are 
  more 
  sensitive 
  

  

  