﻿PROPAGATION 
  OF 
  FRESH-WATER 
  MUSSELS. 
  15 
  

  

  shell 
  has 
  been 
  formed, 
  its 
  chances 
  of 
  survival 
  must 
  be 
  tremendously- 
  

   increased. 
  The 
  introduction 
  of 
  mussels 
  into 
  various 
  streams 
  when 
  

   at 
  this 
  stage 
  has 
  been 
  suggested 
  (Lefevre 
  and 
  Curtis, 
  1912). 
  This 
  

   would 
  have 
  the 
  advantage 
  over 
  the 
  method 
  of 
  using 
  the 
  fish 
  for 
  dis- 
  

   tributing 
  the 
  mussel 
  that 
  transportation 
  in 
  the 
  former 
  case 
  would 
  be 
  

   much 
  easier 
  and 
  the 
  fish 
  can 
  be 
  used 
  a 
  second 
  time. 
  In 
  this 
  connec- 
  

   tion 
  comes 
  up 
  the 
  question 
  whether 
  a 
  natural 
  or 
  an 
  artificial 
  distri- 
  

   bution 
  is 
  better. 
  It 
  seems 
  Hkely 
  that 
  conditions 
  of 
  introduction 
  

   under 
  control 
  would 
  be 
  better 
  then 
  the 
  probably 
  haphazard 
  distri- 
  

   bution 
  of 
  young 
  mussels 
  in 
  nature. 
  When 
  they 
  drop 
  off 
  the 
  gills 
  of 
  a 
  

   fish 
  their 
  finding 
  a 
  favorable 
  location 
  is 
  probably 
  to 
  a 
  large 
  extent 
  a 
  

   matter 
  of 
  chance. 
  (See, 
  however, 
  discussion 
  of 
  segregation 
  under 
  

   head 
  of 
  natural 
  infection, 
  p. 
  11, 
  12.) 
  

  

  In 
  the 
  study 
  of 
  the 
  juvenile 
  mussels 
  and 
  their 
  environment 
  an 
  

   attempt 
  has 
  been 
  made 
  to 
  determine 
  these 
  conditions. 
  For 
  Quadrula 
  

   pustulosa 
  apparently 
  a 
  good 
  current 
  of 
  water 
  with 
  proper 
  food 
  content 
  

   and 
  a 
  bottom 
  of 
  fine 
  gravel 
  are 
  demanded. 
  The 
  conditions 
  of 
  a 
  pond 
  

   are 
  easier 
  to 
  meet, 
  but 
  the 
  difficulties 
  presented 
  in 
  producing 
  the 
  con- 
  

   ditions 
  of 
  a 
  flowing 
  stream 
  seem 
  not 
  to 
  be 
  insuperable. 
  

  

  The 
  season 
  of 
  breeding 
  is 
  an 
  important 
  feature 
  from 
  the 
  practical 
  

   standpoint. 
  The 
  mussels 
  of 
  the 
  short-breeding 
  period 
  are 
  at 
  some 
  

   disadvantage 
  because 
  of 
  the 
  limited 
  working 
  season; 
  this, 
  however^ 
  is 
  

   offset 
  by 
  the 
  fact 
  that 
  during 
  breeding 
  months 
  mussels 
  and 
  fish 
  can 
  

   more 
  readily 
  be 
  obtained. 
  

  

  The 
  number 
  of 
  glochidia 
  per 
  mussel 
  is 
  a 
  feature 
  of 
  practical 
  impor- 
  

   tance 
  in 
  propagation. 
  As 
  this 
  species 
  has 
  an 
  estimated 
  average 
  of 
  

   about 
  200,000 
  or 
  about 
  one-fifth 
  as 
  many 
  as 
  the 
  "mucket," 
  L. 
  liga- 
  

   mentina, 
  it 
  wiU 
  be 
  seen 
  that 
  a 
  larger 
  number 
  of 
  gravid 
  mussels 
  is 
  

   necessary 
  for 
  a 
  given 
  number 
  of 
  fish 
  to 
  be 
  infected. 
  This 
  small 
  num- 
  

   ber 
  as 
  compared 
  with 
  some 
  other 
  species 
  is 
  somewhat 
  offset 
  by 
  the 
  

   abundance 
  of 
  the 
  species. 
  

  

  The 
  Pimple-back, 
  Quadrula 
  pmstulata 
  (Ijea). 
  [PI. 
  vi, 
  fig. 
  37, 
  38, 
  39.1 
  

   The 
  quite 
  similar 
  Q. 
  pustulata 
  I 
  have 
  studied 
  in 
  the 
  juvenile 
  stage, 
  

   finding 
  it 
  a 
  habitant 
  of 
  sand 
  bars, 
  having 
  10 
  records 
  for 
  this 
  location 
  

   with 
  only 
  2 
  for 
  mud 
  or 
  gravel. 
  The 
  natural 
  infections 
  so 
  far 
  identified 
  

   have 
  been 
  so 
  few 
  that 
  Httle 
  is 
  known 
  regarding 
  this 
  phase. 
  I 
  suc- 
  

   ceeded 
  in 
  artificially 
  infecting 
  the 
  following 
  fish 
  with 
  this 
  species: 
  

   Pomoxis 
  sparoides, 
  Micropterus 
  salmoides, 
  and 
  Lepomis 
  pallidus, 
  but 
  

   the 
  death 
  of 
  the 
  fish 
  before 
  the 
  end 
  of 
  the 
  experiment 
  precluded 
  the 
  

   obtaining 
  of 
  any 
  conclusive 
  results. 
  As 
  the 
  species 
  is 
  comparatively 
  

   uncommon 
  in 
  this 
  region 
  its 
  propagation 
  would 
  hardly 
  be 
  practicable 
  

   here. 
  

  

  The 
  glochidium 
  has 
  the 
  following 
  dimensions: 
  Height, 
  0.25 
  mm.; 
  

   length, 
  0.2 
  mm. 
  (See 
  Surber, 
  1912.) 
  

  

  