﻿616 
  GEOKGE 
  WAGNER. 
  

  

  penetrate 
  the 
  epidermis 
  of 
  the 
  prey 
  is 
  incorrect. 
  They 
  argue 
  

   that 
  the 
  nature 
  of 
  the 
  nematocyst 
  is 
  too 
  fragile 
  to 
  permit 
  of 
  

   such 
  a 
  result. 
  The 
  nematocysts, 
  according 
  to 
  their 
  views, 
  

   merely 
  adhere 
  to 
  the 
  outside 
  of 
  the 
  captured 
  animal. 
  

   Clrenacher 
  ('95) 
  is, 
  as 
  far 
  as 
  I 
  know, 
  the 
  only 
  one 
  who 
  has 
  

   published 
  a 
  direct 
  observation 
  on 
  this 
  subject, 
  reproducing 
  

   from 
  memory 
  a 
  drawing 
  of 
  an 
  observation 
  made 
  many 
  years 
  

   previously. 
  It 
  represents 
  a 
  single 
  nematocyst 
  that 
  has 
  pene- 
  

   trated 
  the 
  cuticle 
  of 
  a 
  Culex 
  larva. 
  Opportunities 
  for 
  such 
  

   observations 
  are 
  not 
  so 
  frequent 
  as 
  might 
  be 
  supposed. 
  

   Professor 
  Jennings 
  was 
  so 
  fortunate, 
  however, 
  as 
  to 
  procure 
  

  

  Tig. 
  G. 
  — 
  Insect 
  larva 
  pierced 
  wiili 
  uematocysts. 
  (Copied 
  from 
  a 
  

   drawing 
  bv 
  Mrs. 
  Jennings.) 
  

  

  a, 
  specimen 
  that 
  settles 
  the 
  point 
  for 
  Hydra 
  very 
  conclusively. 
  

   The 
  victim, 
  a 
  fly 
  larva, 
  is 
  thickly 
  covered 
  with 
  Hydra 
  nemato- 
  

   cysts, 
  and 
  these 
  can 
  be 
  plainly 
  seen 
  to 
  penetrate 
  the 
  skin, 
  and 
  

   project 
  into 
  the 
  interior 
  of 
  the 
  larva 
  (Fig. 
  6). 
  Not 
  only 
  the 
  

   point, 
  but, 
  in 
  some 
  cases, 
  the 
  lateral 
  barbs 
  also 
  have 
  pene- 
  

   trated. 
  The 
  specimen 
  was 
  taken 
  from 
  among 
  the 
  tentacles 
  

   of 
  a 
  Hydra 
  just 
  as 
  the 
  latter 
  was 
  preparing 
  to 
  swallow 
  it. 
  

  

  The 
  effect 
  of 
  the 
  nematocysts 
  is 
  almost 
  instantaneous 
  para- 
  

   lysis 
  or 
  even 
  death 
  of 
  the 
  animal 
  attacked. 
  It 
  seems, 
  more- 
  

   over, 
  to 
  be 
  effective 
  on 
  Hydra 
  itself. 
  On 
  one 
  occasion, 
  seeing 
  

   a 
  Hydra 
  grisea 
  Avith 
  its 
  mouth 
  widely 
  open, 
  I 
  quickly 
  

   thrust 
  a 
  second 
  Hydra 
  into 
  it. 
  The 
  first 
  one 
  made 
  an 
  attempt 
  

   to 
  swallow 
  it, 
  but 
  did 
  not 
  get 
  very 
  far, 
  for 
  the 
  victim 
  began 
  

  

  