﻿12 
  PROPAGATION 
  OF 
  FRESH- 
  WATER 
  MUSSELS. 
  

  

  breeding 
  of 
  the 
  lieavier-t-helled 
  species. 
  Tliis 
  attraction 
  of 
  the 
  fish 
  

   would 
  serve 
  to 
  furnish 
  the 
  liost 
  and 
  also 
  increase 
  the 
  chances 
  of 
  the 
  

   young 
  mussels 
  being 
  shed 
  there 
  by 
  the 
  fish, 
  thus 
  partly 
  accounting 
  for 
  

   the 
  segregation 
  of 
  mussels. 
  Tlie 
  fishermen 
  on 
  the 
  Mississippi 
  take 
  

   advantage 
  of 
  this 
  appetite 
  in 
  the 
  catfish 
  by 
  baiting 
  nets 
  with 
  the 
  

   "meats" 
  of 
  the 
  mussels 
  which 
  the 
  clammers 
  or 
  mussel 
  fishermen 
  

   remove 
  from 
  the 
  shells. 
  

  

  Artificial 
  infection. 
  — 
  The 
  finding 
  of 
  glochidia 
  of 
  Q. 
  pustnlosa 
  on 
  

   catfisiies 
  in 
  natural 
  infection 
  suggested 
  testing 
  these 
  fishes 
  in 
  experi- 
  

   ments 
  in 
  artificial 
  infection. 
  

  

  In 
  these 
  experiments 
  four 
  species 
  of 
  catfish 
  were 
  tried 
  and 
  five 
  

   other 
  kinds 
  of 
  fish. 
  The 
  results 
  of 
  some 
  of 
  these 
  experiments 
  are 
  

   shown 
  in 
  table 
  1. 
  

  

  When 
  exposed 
  to 
  infection 
  in 
  the 
  same 
  tank 
  and 
  thus 
  under 
  the 
  

   same 
  conditions, 
  the 
  difference 
  in 
  susceptibility 
  between 
  the 
  catfish 
  

   and 
  tlie 
  other 
  species 
  was 
  very 
  marked 
  and 
  the 
  difference 
  in 
  implanta- 
  

   tion 
  still 
  more 
  so. 
  The 
  catfish 
  in 
  general 
  received 
  them 
  more 
  quickly 
  

   and 
  retained 
  the 
  glochidia, 
  while, 
  though 
  abundant 
  on 
  the 
  gills 
  of 
  

   some 
  of 
  the 
  other 
  species, 
  they 
  disappeared 
  before 
  the 
  end 
  of 
  the 
  

   second 
  day. 
  

  

  The 
  results 
  in 
  the 
  case 
  of 
  the 
  different 
  species 
  of 
  catfisli 
  were 
  not 
  

   imiform. 
  The 
  duration 
  of 
  the 
  parasitic 
  period 
  seems 
  to 
  vary 
  slightly 
  

   in 
  the 
  different 
  species 
  and 
  tliere 
  is 
  evidence 
  of 
  immunity 
  in 
  some 
  

   individuals 
  of 
  Leptops 
  olivaris. 
  The 
  greatest 
  variation 
  in 
  duration 
  

   of 
  parasitism 
  occurred 
  in 
  the 
  case 
  of 
  the 
  bullheads 
  Ameiurus 
  melas 
  

   and 
  A. 
  nebvlosus. 
  (See 
  table 
  1, 
  experiments 
  V-22 
  and 
  VI-1.) 
  The 
  

   long 
  period, 
  17 
  days, 
  can 
  be 
  explained 
  by 
  the 
  lower 
  temperature 
  

   (average 
  72.1° 
  F.); 
  but 
  the 
  temperature 
  of 
  75.1° 
  F. 
  for 
  the 
  shorter 
  

   period 
  of 
  6 
  to 
  8 
  days 
  is 
  no 
  higher 
  tlian 
  those 
  in 
  which 
  the 
  parasitism 
  

   is 
  of 
  much 
  longer 
  duration. 
  

  

  The 
  experiments 
  with 
  Ictalurus 
  punctatus 
  gave 
  more 
  definite 
  and 
  

   regular 
  results 
  than 
  with 
  any 
  of 
  the 
  other 
  species. 
  The 
  majority 
  of 
  

   the 
  experim.ents 
  were 
  conducted 
  between 
  June 
  18 
  and 
  August 
  14, 
  

   duiing 
  a 
  season 
  when 
  the 
  water 
  temperatures 
  were 
  more 
  uniform 
  

   than 
  usual. 
  This 
  probably 
  accounts 
  for 
  the 
  uniformity 
  in 
  the 
  

   parasitic 
  period, 
  which 
  was 
  determined 
  as 
  9 
  to 
  12 
  days. 
  The 
  mini- 
  

   mum 
  period 
  on 
  a 
  fish 
  is 
  less 
  readily 
  determined 
  than 
  the 
  maximum; 
  

   taking 
  this 
  into 
  account 
  it 
  is 
  probable 
  that 
  the 
  period 
  may 
  be 
  less 
  

   than 
  9 
  days 
  for 
  some. 
  This 
  seems 
  a 
  remarkably 
  short 
  period 
  when 
  

   we 
  consider 
  cases 
  of 
  winter-breeding 
  mussels 
  carried 
  over 
  six 
  months 
  

   by 
  the 
  fish. 
  

  

  The 
  young 
  mussels 
  after 
  dropping 
  from 
  the 
  fish 
  were 
  secured 
  and 
  

   their 
  structure 
  and 
  habits 
  noted." 
  

  

  o 
  During 
  these 
  early 
  stages 
  I 
  observed 
  cases 
  of 
  ingestion 
  by 
  a 
  turbellarian 
  very 
  abundant 
  in 
  the 
  aquarium 
  

   This, 
  with 
  the 
  number 
  of 
  empty 
  shells 
  found, 
  indicates 
  a 
  high 
  mortality 
  among 
  them. 
  

  

  