﻿614 
  GEORGE 
  WAGNEK. 
  

  

  Having 
  at 
  baud 
  some 
  Hydras 
  that 
  had 
  been 
  without 
  food 
  

   for 
  twelve 
  days 
  I 
  started 
  to 
  repeat 
  the 
  same 
  series 
  of 
  experi- 
  

   ments 
  on 
  them. 
  To 
  my 
  surprise 
  they 
  all 
  responded 
  with 
  a 
  

   typical 
  food 
  reaction 
  when 
  immersed 
  in 
  pure 
  filtered 
  beef-tea. 
  

   Shortly 
  after 
  this 
  was 
  poured 
  over 
  them 
  the 
  tentacles 
  began 
  

   vigorous 
  movements, 
  which 
  were, 
  however, 
  but 
  little 
  corre- 
  

   lated. 
  The 
  mouth 
  opened 
  wide, 
  and 
  remained 
  open 
  for 
  a 
  

   minute 
  or 
  so, 
  then 
  it 
  closed, 
  and 
  apparently 
  some 
  of 
  the 
  beef- 
  

   tea 
  had 
  been 
  taken 
  in, 
  for 
  the 
  body 
  could 
  be 
  seen 
  to 
  be 
  con- 
  

   siderably 
  expanded 
  just 
  back 
  of 
  the 
  hypostome. 
  In 
  some 
  

   cases 
  this 
  expansion 
  even 
  travelled 
  backward. 
  In 
  fact 
  there 
  

   was, 
  in 
  every 
  case, 
  a 
  very 
  typical 
  food 
  reaction. 
  

  

  What 
  is 
  more, 
  the 
  same 
  food 
  reaction 
  was 
  secured 
  by 
  means 
  

   of 
  a 
  solution 
  of 
  quinine. 
  In 
  this 
  case, 
  however, 
  the 
  quinine 
  

   very 
  strongly 
  affected 
  the 
  entoderm 
  after 
  the 
  mouth 
  was 
  

   opened, 
  and 
  the 
  Hydra 
  soon 
  perished 
  with 
  its 
  mouth 
  wide 
  

   open. 
  Quinine 
  is 
  a 
  strong 
  poison 
  to 
  most 
  of 
  the 
  lower 
  inver- 
  

   tebrates. 
  So 
  much 
  the 
  more 
  remarkable 
  is 
  the 
  fact 
  that 
  it 
  

   should 
  be 
  able 
  to 
  call 
  forth 
  a 
  food 
  reaction. 
  

  

  These 
  experiments 
  then 
  give 
  us 
  the 
  evidence 
  that 
  there 
  

   may 
  be 
  three 
  factors 
  concerned 
  in 
  the 
  production 
  of 
  a 
  food 
  

   reaction. 
  These 
  factors 
  are 
  a 
  state 
  of 
  hunger 
  in 
  the 
  Hydra, 
  

   a 
  chemical 
  stimulus, 
  and 
  a 
  mechanical 
  stmmlus. 
  The 
  first 
  

   two 
  must 
  be 
  present 
  to 
  produce 
  the 
  reaction. 
  The 
  third 
  is 
  or 
  

   is 
  not 
  necessary, 
  depending 
  upon 
  the 
  intensity 
  of 
  the 
  first 
  

   factor 
  — 
  hunger. 
  A 
  food 
  reaction 
  may 
  thus 
  be 
  brought 
  about 
  

   in 
  two 
  ways 
  : 
  first, 
  by 
  the 
  combined 
  action 
  of 
  a 
  chemical 
  and 
  

   a 
  physical 
  stimulus, 
  in 
  presence 
  of 
  a 
  moderate 
  degree 
  of 
  

   hunger; 
  second, 
  by 
  a 
  chemical 
  stimulus 
  alone, 
  when 
  the 
  

   hunger 
  has 
  become 
  intense. 
  

  

  While 
  keeping 
  Hydra 
  under 
  observation 
  for 
  a 
  number 
  of 
  

   months 
  it 
  was 
  noticed 
  that 
  ostracods 
  formed 
  no 
  part 
  of 
  their 
  

   food, 
  though 
  these 
  Crustacea 
  were 
  fairly 
  numerous 
  in 
  the 
  

   aquaria 
  in 
  which 
  the 
  Hydra 
  were 
  kept. 
  It 
  was 
  further 
  

   noticed 
  that 
  an 
  ostracod 
  could 
  come 
  freely 
  in 
  contact 
  with 
  

   Hydra 
  at 
  any 
  time 
  without 
  calling 
  forth 
  any 
  attempt 
  at 
  

   capturing 
  it. 
  This 
  was 
  the 
  case 
  even 
  when 
  the 
  H)'dra 
  had 
  been 
  

  

  