﻿PEOPAGATION 
  OF 
  FRESH-WATER 
  MUSSELS. 
  37 
  

  

  in 
  those 
  species. 
  The 
  drum 
  or 
  sheepshead, 
  Aplodinotus 
  grunniens, 
  

   is 
  found 
  infected 
  commonly 
  with 
  the 
  glochidia 
  of 
  Lampsilis 
  Isevis- 
  

   sima, 
  L. 
  gracilis, 
  L. 
  alata, 
  Plagiola 
  donaciformis, 
  and 
  others. 
  The 
  

   drum 
  is 
  a 
  mussel-eating 
  fish 
  (see 
  Forbes 
  and 
  Richardson, 
  1908), 
  so 
  

   that 
  we 
  have 
  an 
  explanation 
  of 
  the 
  presence 
  of 
  the 
  larva 
  of 
  these 
  

   thin-shelled 
  and 
  so 
  readily 
  eaten 
  mussels 
  upon 
  its 
  gills. 
  In 
  the 
  

   above 
  example 
  we 
  have 
  several 
  species 
  of 
  mussels 
  parasitic 
  upon 
  

   one 
  species 
  of 
  fish. 
  From 
  many 
  examiuations 
  of 
  the 
  channel 
  cat- 
  

   fish, 
  Ictalurus 
  punctatus, 
  I 
  have 
  found 
  only 
  one 
  species 
  of 
  mussel, 
  

   viz, 
  Q. 
  pustulosa; 
  this 
  seems 
  to 
  be 
  the 
  other 
  extreme. 
  

  

  The 
  failure 
  to 
  obtain 
  gill 
  infection 
  with 
  certain 
  species 
  has 
  been 
  

   mentioned 
  (see 
  introduction). 
  I 
  have 
  observed 
  a 
  similar 
  immunity 
  

   in 
  examinations 
  for 
  natural 
  infections 
  on 
  the 
  gills 
  of 
  the 
  gar 
  pike, 
  

   Lepidosieus 
  platostomus, 
  the 
  dogfish, 
  Amia 
  calva 
  Linnaeus, 
  and 
  the 
  

   suckers, 
  the 
  Catostomidse. 
  Upon 
  obtaining 
  fuller 
  data 
  such 
  cases 
  

   may 
  perhaps 
  prove 
  to 
  have 
  their 
  parasitic 
  species, 
  at 
  present 
  unknown. 
  

   It 
  is 
  to 
  be 
  noted 
  that 
  these 
  reported 
  cases 
  of 
  immunity 
  refer 
  to 
  gill 
  

   infection 
  and 
  that 
  the 
  absence 
  of 
  these 
  possibly 
  does 
  rot 
  preclude 
  

   infection 
  of 
  fins. 
  We 
  have 
  not 
  found 
  infections 
  on 
  the 
  gills 
  of 
  the 
  

   gizzard 
  shad, 
  Dorosoma 
  cepedianum, 
  but 
  Mr. 
  A. 
  F. 
  Shira 
  has 
  found 
  

   the 
  fins 
  of 
  tliis 
  species 
  infected.'* 
  

  

  Lefevre 
  and 
  Curtis, 
  in 
  seeking 
  an 
  explanation 
  of 
  immunity, 
  raise 
  

   the 
  question 
  as 
  to 
  whether 
  the 
  factors 
  are 
  chiefly 
  mechanical 
  or 
  are 
  

   an 
  liistological 
  response 
  of 
  the 
  fish's 
  tissues. 
  In 
  my 
  opinion 
  both 
  of 
  

   these 
  operate, 
  and 
  there 
  is 
  still 
  another 
  factor, 
  viz, 
  the 
  failure 
  of 
  

   glochidia 
  to 
  fasten 
  when 
  the 
  appropriate 
  host 
  is 
  not 
  found. 
  The 
  

   histological 
  response 
  begins 
  with 
  the 
  hypertrophy 
  resulting 
  in 
  the 
  

   formation 
  of 
  the 
  cyst 
  ; 
  this 
  occurs 
  in 
  most 
  cases 
  whether 
  the 
  parasite 
  

   is 
  retained 
  or 
  not. 
  If 
  not, 
  the 
  cyst 
  is 
  shed 
  by 
  a 
  process 
  of 
  desqua- 
  

   mation 
  of 
  the 
  external 
  epithelium. 
  I 
  have 
  observed 
  this 
  in 
  gUl 
  

   infections 
  only. 
  A 
  stream 
  of 
  water 
  of 
  not 
  great 
  force 
  will 
  remove 
  

   the 
  outer 
  layers 
  of 
  epithelium 
  of 
  an 
  infected 
  gill 
  about 
  to 
  shed 
  the 
  

   glochidia. 
  Such 
  a 
  catarrhal 
  reaction 
  is 
  presumably 
  the 
  result 
  of 
  the 
  

   irritation 
  set 
  up 
  by 
  the 
  glochidium. 
  The 
  question 
  arises 
  as 
  to 
  what 
  

   prevents 
  such 
  a 
  reaction 
  in 
  cases 
  of 
  successful 
  implantation. 
  Is 
  it 
  

   merely 
  absence 
  of 
  immunity 
  in 
  the 
  host, 
  or 
  does 
  the 
  glochidium 
  

   supply 
  an 
  active 
  agent 
  in 
  the 
  nature 
  of 
  an 
  anaesthetic 
  to 
  prevent 
  

   the 
  irritation 
  that 
  would 
  be 
  expected 
  ? 
  Mr. 
  Thaddeus 
  Surber 
  once 
  

   called 
  my 
  attention 
  to 
  an 
  apparent 
  case 
  of 
  acquired 
  immunity 
  in 
  

   some 
  sunfishes 
  which 
  received 
  glochidia 
  upon 
  the 
  first 
  infection 
  but 
  

   not 
  the 
  second. 
  This 
  is 
  a 
  matter 
  that 
  should 
  be 
  investigated, 
  as 
  

   the 
  existence 
  of 
  such 
  a 
  possibility 
  would 
  prevent 
  the 
  use 
  of 
  fish 
  more 
  

   than 
  once 
  successfully 
  in 
  artificial 
  propagation. 
  

  

  o 
  Since 
  writing 
  this, 
  I 
  have 
  found 
  iafections 
  by 
  Q 
  heros 
  upon 
  the 
  fins 
  of 
  this 
  species, 
  also 
  infections 
  hf 
  

   other 
  mussels 
  upon 
  the 
  gills 
  of 
  the 
  gar-pike 
  and 
  the 
  dogfish. 
  (See 
  table 
  2.) 
  

  

  