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  PROPAGATION 
  OF 
  FRESH-WATEE 
  MUSSELS. 
  

  

  glochidia 
  would 
  be 
  too 
  widely 
  distributed 
  to 
  make 
  heavy 
  infection 
  

   possible. 
  We 
  find 
  the 
  heaviest 
  infections 
  Math 
  glochidia 
  of 
  the 
  

   niggerhead, 
  which 
  hves 
  in 
  swiftly 
  flowing 
  water. 
  It 
  would 
  be 
  quite 
  

   reasonable 
  to 
  expect 
  adaptations 
  here 
  comparable 
  to 
  those 
  seen 
  be- 
  

   tween 
  insects 
  and 
  plants, 
  not 
  necessarily 
  as 
  elaborate 
  as 
  that 
  between 
  

   the 
  rein-orchids 
  TIabenaria 
  and 
  fertiHzing 
  moths, 
  but 
  something 
  of 
  

   that 
  nature 
  would 
  be 
  equally 
  advantageous 
  to 
  a 
  species 
  of 
  mussel. 
  

   The 
  expected 
  features 
  in 
  such 
  a 
  relation 
  would 
  be 
  some 
  attractive 
  

   agent 
  in 
  the 
  mussel, 
  the 
  perception 
  by 
  the 
  latter 
  of 
  the 
  fish's 
  presence, 
  

   and 
  the 
  reaction 
  of 
  extruding 
  the 
  glochidia. 
  Mussel 
  beds 
  are 
  knovra 
  

   to 
  offer 
  attractions 
  to 
  fishes 
  because 
  of 
  the 
  associated 
  fife 
  in 
  their 
  

   vicinity, 
  such 
  as 
  worms, 
  crustaceans, 
  and 
  the 
  like. 
  During 
  the 
  sum- 
  

   mer 
  of 
  1912, 
  Dr. 
  W. 
  P. 
  Herrick 
  called 
  my 
  attention 
  to 
  at 
  least 
  three 
  

   instances 
  of 
  fish 
  (sunfish 
  in 
  each 
  case) 
  being 
  taken 
  in 
  his 
  crates 
  which 
  

   contained 
  five 
  mussels. 
  We 
  have 
  abundant 
  evidence 
  of 
  attractions 
  

   to 
  some 
  species 
  of 
  fish, 
  e. 
  g., 
  catfish 
  and 
  sheepshead, 
  in 
  the 
  food 
  

   which 
  the 
  thin-shelled 
  species 
  of 
  mussels 
  supply 
  (Forbes 
  and 
  Rich- 
  

   ardson, 
  1908, 
  quoted 
  above, 
  and 
  Kendall, 
  1910). 
  Tliis 
  is 
  a 
  rather 
  

   vicarious 
  ofl'ering, 
  and 
  it 
  is 
  not 
  known 
  to 
  be 
  made 
  by 
  the 
  heavier- 
  

   shelled 
  species 
  among 
  which 
  we 
  have 
  found 
  cases 
  of 
  narrowly 
  re- 
  

   stricted 
  parasitism. 
  It 
  is 
  among 
  these 
  that 
  we 
  would 
  expect 
  some 
  

   special 
  adaptations. 
  

  

  Type 
  of 
  infection. 
  — 
  In 
  observations 
  upon 
  natural 
  infections 
  I 
  have 
  

   found 
  that 
  in 
  general 
  the 
  hooked 
  glochidia 
  were 
  to 
  be 
  found 
  upon 
  the 
  

   fins 
  and 
  the 
  bookless 
  upon 
  the 
  gills, 
  as 
  has 
  been 
  reported 
  by 
  others, 
  

   chiefly 
  frorn 
  artificial 
  infection 
  (Harms, 
  1909; 
  Lefevre 
  and 
  Curtis, 
  

   1912). 
  I 
  find, 
  however, 
  there 
  are 
  some 
  apparently 
  constant 
  excep- 
  

   tions. 
  I 
  have 
  mentioned 
  above 
  the 
  observations 
  that 
  the 
  bookless 
  

   glochidium 
  of 
  the 
  washboard 
  mussel, 
  Quadrula 
  heros, 
  was 
  found 
  to 
  

   be 
  a 
  fin-infecting 
  species. 
  Its 
  considerable 
  size 
  apparently 
  adapts 
  it 
  

   to 
  this 
  mode 
  of 
  infection. 
  The 
  presence 
  of 
  a 
  larval 
  thread 
  also 
  sug- 
  

   gests 
  a 
  possible 
  relation 
  to 
  this 
  habit 
  because 
  of 
  the 
  presence 
  of 
  that 
  

   organ 
  in 
  the 
  fin-infecting 
  hooked 
  glochidia. 
  In 
  support 
  of 
  this 
  is 
  

   the 
  recent 
  discovery 
  of 
  fin 
  infection 
  in 
  nature 
  by 
  the 
  small 
  bookless 
  

   glochidium 
  of 
  Unio 
  gihhosus, 
  which 
  has 
  a 
  larval 
  thread. 
  

  

  I 
  have 
  rarely 
  seen 
  natural 
  infections 
  of 
  gills 
  by 
  hooked 
  glochidia; 
  

   in 
  two 
  cases 
  they 
  were 
  evidently 
  unsuccessful, 
  the 
  glochidia 
  having 
  

   died, 
  and 
  were 
  embedded 
  in 
  hypertrophied 
  tissue 
  at 
  the 
  base 
  of 
  the 
  

   gUls, 
  apparently 
  in 
  process 
  of 
  shedding. 
  The 
  third 
  and 
  fourth 
  

   instances 
  were 
  apparently 
  successful 
  infections 
  of 
  single 
  glochidia, 
  

   in 
  one 
  case 
  on 
  the 
  heavy 
  gills 
  of 
  a 
  catfish, 
  Leptops 
  olivarus, 
  and 
  in 
  

   the 
  other 
  on 
  the 
  sturgeon. 
  

  

  Another 
  case 
  was 
  a 
  heavy 
  infection 
  on 
  the 
  gills 
  of 
  Pomolobus 
  

   chrysochloris 
  by 
  a 
  glochidium 
  which 
  is 
  hooked, 
  but 
  the 
  hook 
  is 
  not 
  

  

  