﻿GROWTH 
  AND 
  MIGRATION 
  OF 
  FRESH-WATER 
  MUSSELS. 
  

  

  13 
  

  

  June 
  28 
  to 
  Sept. 
  26, 
  1910 
  

   Sept. 
  26 
  to 
  Apr. 
  11, 
  1911 
  

   Apr. 
  11 
  to 
  June 
  20, 
  1911. 
  

  

  Length. 
  

  

  2.4 
  

   .1 
  

   .3 
  

  

  For 
  comparison 
  with 
  these 
  averages 
  we 
  have 
  the 
  results 
  from 
  

   lot 
  E, 
  which 
  I 
  have 
  not 
  tabulated, 
  for 
  14 
  specimens: 
  7 
  lachrymosa 
  

   (maple-leaf); 
  4 
  undulata 
  (three-ridge); 
  and 
  3 
  pustulosa 
  (warty-back, 
  

   pimple-back) 
  . 
  In 
  this 
  case 
  the 
  April 
  reclaiming 
  was 
  not 
  done. 
  

  

  Time. 
  

  

  Length. 
  

  

  June 
  23 
  to 
  Sept. 
  26, 
  1910. 
  

   Sept. 
  26 
  to 
  June 
  23, 
  1911. 
  

  

  Mm. 
  

   1.0 
  

   .55 
  

  

  The 
  second 
  period 
  shows 
  a 
  gain 
  in 
  the 
  growth 
  for 
  lot 
  E 
  over 
  lot 
  F. 
  

   The 
  explanation 
  is 
  one 
  of 
  food 
  and 
  possibly 
  oxygen, 
  and 
  appears 
  

   later 
  (p. 
  24) 
  under 
  the 
  discussion 
  of 
  migration. 
  

  

  The 
  following 
  four 
  tables 
  show 
  proportional 
  rate 
  of 
  growth, 
  at 
  

   different 
  ages, 
  of 
  a 
  single 
  species, 
  Q. 
  undulata 
  (three-ridge). 
  The 
  

   fact 
  that 
  lot 
  D 
  mussels 
  were 
  transplanted 
  (p. 
  5) 
  brings 
  in 
  an 
  additional 
  

   factor 
  (footnote, 
  p. 
  23), 
  but 
  I 
  am 
  not 
  sure 
  that 
  this 
  is 
  material. 
  In 
  

   making 
  these 
  comparisons 
  weight 
  and 
  length 
  are 
  used. 
  

  

  Table 
  4. 
  — 
  Increase 
  in 
  One 
  Year 
  of 
  Specimens 
  from 
  Lot 
  D, 
  Weighing 
  Less 
  

  

  THAN 
  100 
  Grams. 
  

  

  Table 
  5. 
  — 
  Increase 
  in 
  One 
  Year 
  op 
  Specimens 
  from 
  Lot 
  D, 
  Weighing 
  

  

  under 
  200 
  Grams. 
  

  

  a 
  No 
  record. 
  

  

  