﻿GROWTH 
  AND 
  MIGRATION 
  OF 
  FRESH-WATER 
  MUSSELS. 
  19 
  

  

  MIGRATION. 
  

  

  No 
  end 
  of 
  speculation 
  has 
  been 
  carried 
  on 
  as 
  to 
  the 
  traveling 
  

   ability 
  of 
  mussels. 
  The 
  long 
  undulation 
  tracks, 
  often 
  found 
  upon 
  

   the 
  pond 
  or 
  stream 
  floor, 
  together 
  with 
  other 
  field 
  observations, 
  

   and 
  the 
  active 
  movements 
  of 
  specimens 
  kept 
  in 
  aquaria 
  have 
  afforded 
  

   data 
  for 
  discussion. 
  While 
  gathering 
  information 
  concerning 
  growth, 
  

   I 
  have 
  constantly 
  kept 
  in 
  mind 
  the 
  migration 
  question, 
  as 
  it 
  was 
  

   easy 
  to 
  carry 
  on 
  the 
  two 
  together. 
  

  

  As 
  already 
  indicated, 
  the 
  main 
  reason 
  for 
  tagging 
  a 
  large 
  number 
  

   of 
  mussels 
  was 
  the 
  feeling 
  that 
  many 
  would 
  be 
  lost 
  through 
  migration; 
  

   and 
  further 
  to 
  guard 
  against 
  this 
  migration 
  in 
  the 
  Chikaskia 
  I 
  inclosed 
  

   the 
  specimens 
  in 
  good-sized 
  pens. 
  

  

  SHOOFLY. 
  

  

  The 
  extent 
  of 
  actual 
  ftiigration 
  is 
  best 
  shown 
  in 
  considering 
  definite 
  

   plantings. 
  Lot 
  D 
  (see 
  p. 
  8) 
  of 
  the 
  Shoofly 
  is 
  good 
  for 
  this 
  purpose. 
  

   The 
  168 
  Quadrulse 
  planted 
  here 
  were 
  from 
  the 
  Chikaslda, 
  where 
  

   they 
  were 
  collected 
  from 
  the 
  sand 
  bars 
  in 
  shallow 
  water. 
  From 
  

   track-mark 
  evidence 
  these 
  specimens 
  had 
  been 
  actively 
  moving 
  

   about 
  on 
  the 
  sandy 
  bottom, 
  stimulated 
  to 
  activity 
  by 
  unfavorable 
  

   environmental 
  conditions. 
  

  

  The 
  164 
  specimens 
  were 
  spread 
  out 
  on 
  a 
  small 
  portion 
  of 
  the 
  

   bottom 
  of 
  the 
  Shoofly 
  (p. 
  8), 
  June 
  16, 
  1910, 
  and 
  left 
  free 
  to 
  move. 
  

   June 
  14 
  and 
  15, 
  1911, 
  I 
  reclaimed 
  139 
  of 
  these 
  specimens, 
  or 
  84.8 
  

   per 
  cent, 
  in 
  about 
  three 
  hours' 
  work. 
  Twelve 
  of 
  these 
  specimens 
  

   were 
  reserved 
  for 
  records. 
  On 
  September 
  11, 
  1911, 
  a 
  cold 
  rainy 
  day, 
  

   I 
  again 
  checked 
  over 
  lot 
  D, 
  and 
  this 
  time 
  I 
  secured 
  93 
  specimens 
  in 
  

   about 
  one 
  hour's 
  time; 
  the 
  water 
  was 
  so 
  cold 
  that 
  collecting 
  was 
  

   exceedingly 
  difficult. 
  Three 
  specimens 
  not 
  found 
  in 
  June 
  were 
  

   found 
  on 
  this 
  date, 
  bringing 
  the 
  total 
  number 
  reclaimed 
  from 
  the 
  

   original 
  planting 
  up 
  to 
  142. 
  When 
  we 
  consider 
  that 
  the 
  water 
  was 
  

   cloudy 
  and 
  from 
  3 
  to 
  4 
  feet 
  deep 
  the 
  experienced 
  field 
  collector 
  will 
  

   know 
  that 
  specimens 
  could 
  not 
  be 
  recovered 
  in 
  these 
  numbers 
  unless 
  

   they 
  were 
  on 
  the 
  very 
  spot 
  °' 
  where 
  they 
  were 
  planted. 
  Lots 
  A 
  and 
  

   B 
  in 
  the 
  Shoofly 
  gave 
  similar 
  results, 
  although 
  I 
  did 
  not 
  attempt 
  to 
  

   recover 
  these 
  as 
  thoroughly 
  as 
  in 
  the 
  case 
  of 
  lot 
  D. 
  

  

  Lot 
  C 
  in 
  the 
  Shoofly 
  is 
  of 
  especial 
  interest, 
  as 
  these 
  specimens 
  

   were 
  all 
  A. 
  grandis 
  (floater). 
  Of 
  this 
  lot 
  12 
  specimens 
  were 
  found 
  

   directly 
  on 
  the 
  site 
  where 
  they 
  were 
  planted. 
  While 
  this 
  is 
  rather 
  

   a 
  small 
  per 
  cent 
  in 
  comparison 
  with 
  lot 
  D, 
  I 
  was 
  surprised 
  to 
  find 
  46 
  

   per 
  cent 
  of 
  A. 
  grandis 
  (floater), 
  as 
  it 
  is 
  well 
  known 
  to 
  be 
  an 
  active 
  

  

  « 
  It 
  has 
  been 
  suggested 
  that 
  since 
  lot 
  D 
  specimens 
  were 
  transplanted 
  the 
  inactivity 
  may 
  have 
  been 
  due 
  

   to 
  the 
  changed 
  environment. 
  The 
  relatively 
  rapid 
  growth 
  and 
  hke 
  inactivity 
  of 
  lots 
  A 
  and 
  B, 
  Shoofly 
  

   specimens, 
  which 
  might 
  very 
  well 
  be 
  considered 
  as 
  control 
  lots, 
  should 
  quiet 
  any 
  apprehensions 
  on 
  this 
  

   point. 
  

  

  