﻿ON 
  SOME 
  MOVEMENTS 
  AND 
  REACTIONS 
  OF 
  HYDEA. 
  609 
  

  

  latter 
  result 
  is 
  a 
  true 
  response 
  to 
  stimulus; 
  the 
  former 
  is 
  a 
  

   purely 
  lueclianical 
  effect, 
  due 
  to 
  the 
  fact 
  that 
  the 
  severely- 
  

   injured 
  cells 
  ceased 
  growing 
  and 
  the 
  continued 
  growth 
  on 
  

   the 
  opposite 
  side 
  forced 
  the 
  root 
  to 
  curve 
  toward 
  the 
  injured 
  

   side. 
  The 
  response 
  to 
  a 
  chemical 
  in 
  Hydra 
  is 
  probably 
  a 
  

   mechanical 
  result 
  of 
  this 
  kind, 
  except 
  that 
  in 
  place 
  of 
  growth 
  

   it 
  is 
  movement 
  that 
  is 
  checked. 
  

  

  Food 
  Reactions. 
  

  

  The 
  process 
  of 
  taking 
  in 
  food 
  as 
  it 
  occurs 
  in 
  Hydra 
  has, 
  as 
  

   far 
  as 
  I 
  know, 
  been 
  described 
  in 
  detail 
  only 
  by 
  Hartog 
  ('80), 
  

   although 
  Trembley 
  has 
  a 
  long 
  general 
  discussion 
  of 
  it. 
  

   Hartog's 
  note 
  on 
  the 
  subject 
  was 
  unknown 
  to 
  me 
  until 
  after 
  

   I 
  had 
  studied 
  the 
  process 
  myself 
  and 
  written 
  out 
  a 
  desci'ip- 
  

   tion 
  that 
  coincides 
  in 
  large 
  part 
  with 
  his. 
  

  

  If 
  a 
  Hydra 
  that 
  has 
  been 
  kept 
  without 
  food 
  for 
  a 
  week 
  or 
  

   ten 
  days 
  has 
  a 
  bit 
  of 
  raw 
  meat 
  placed 
  on 
  or 
  very 
  near 
  one 
  of 
  

   its 
  tentacles 
  the 
  course 
  of 
  events 
  is 
  about 
  as 
  follows 
  : 
  — 
  The 
  

   tentacle 
  first 
  touching 
  the 
  meat 
  fastens 
  itself 
  to 
  it, 
  apparently 
  

   by 
  means 
  of 
  some 
  secretion, 
  and 
  then 
  contracts. 
  The 
  other 
  

   tentacles 
  begin 
  rather 
  active 
  movements, 
  which, 
  however, 
  

   show 
  little 
  correlation. 
  Nevertheless, 
  soon 
  all 
  the 
  tentacles 
  

   find 
  their 
  way 
  to 
  the 
  meat, 
  become 
  fastened 
  to 
  it, 
  and 
  

   contract. 
  There 
  is, 
  however, 
  so 
  little 
  definiteness 
  in 
  all 
  these 
  

   movements 
  that 
  the 
  meat 
  often 
  falls 
  away 
  from 
  the 
  tentacles. 
  

   In 
  such 
  cases 
  the 
  Hydra 
  makes 
  no 
  very 
  great 
  effort 
  to 
  find 
  it 
  

   again. 
  Vague 
  movements 
  of 
  the 
  tentacles 
  may 
  continue 
  for 
  

   some 
  time; 
  sometimes 
  they 
  even 
  strike 
  simultaneously 
  toward 
  

   the 
  hypostome, 
  as 
  if 
  clutching 
  for 
  something. 
  

  

  In 
  other 
  cases, 
  however, 
  the 
  food 
  is 
  by 
  the 
  movement 
  of 
  

   the 
  tentacles 
  brought 
  to 
  the 
  hypostome. 
  As 
  soon 
  as 
  this 
  is 
  

   touched 
  by 
  the 
  meat, 
  sometimes 
  even 
  some 
  seconds 
  before, 
  

   the 
  mouth 
  begins 
  to 
  open, 
  and 
  its 
  edges 
  fasten 
  to 
  the 
  meat. 
  

   Immediately 
  the 
  tentacles 
  loosen 
  their 
  hold 
  and 
  swing 
  away 
  

   from 
  the 
  mouth. 
  They 
  play 
  no 
  further 
  part 
  in 
  the 
  swallowing. 
  

   It 
  is 
  usually 
  stated 
  that 
  they 
  push 
  the 
  food 
  into 
  the 
  mouth, 
  

  

  