﻿14 
  

  

  GROWTH 
  AND 
  MIGRATION 
  OF 
  FRESH-WATER 
  MUSSELS. 
  

  

  Table 
  6. 
  — 
  Increase 
  in 
  One 
  Year 
  op 
  Specimens 
  from 
  Lot 
  B, 
  Weighing 
  

   OVER 
  200 
  Grams, 
  Selected 
  at 
  Random 
  prom 
  20 
  Specimens 
  One 
  Year 
  from 
  

   Date 
  op 
  Planting. 
  

  

  Table 
  7. 
  — 
  Increase 
  in 
  One 
  Year 
  of 
  Specimens 
  from 
  Lot 
  A, 
  Weighing 
  

   OVER 
  200 
  Grams, 
  Selected 
  at 
  RiVNDOM 
  prom 
  68 
  Specimens 
  Reclaimed 
  One 
  

   Year 
  from 
  Date 
  op 
  Planting. 
  

  

  Averages 
  for 
  One 
  Year. 
  

  

  a 
  Per 
  cent 
  of 
  aggregate 
  increa.se. 
  

  

  The 
  specimens 
  under 
  100 
  grams 
  make 
  the 
  largest 
  increase 
  in 
  

   weight 
  and 
  length; 
  those 
  under 
  200 
  grams, 
  the 
  second; 
  and 
  those 
  

   over 
  200, 
  or 
  fully 
  mature 
  specimens, 
  fall 
  short. 
  A 
  point 
  of 
  special 
  

   interest 
  in 
  connection 
  with 
  tables 
  6 
  and 
  7 
  lies 
  in 
  the 
  fact 
  that 
  w^hile 
  

   per 
  cent 
  of 
  gam 
  in 
  length 
  is 
  almost 
  negligible, 
  weight 
  goes 
  steadily 
  

   forward 
  in 
  fairly 
  good 
  proportion. 
  From 
  averages 
  in 
  tables 
  4 
  and 
  5, 
  

   an 
  average 
  yearly 
  growth 
  for 
  a 
  young 
  undulata 
  (tlii'ee-ridge) 
  might 
  

   be 
  put 
  at 
  25 
  grams 
  in 
  weight 
  and 
  from 
  5 
  to 
  25 
  millimeters 
  in 
  length; 
  

   at 
  this 
  rate 
  it 
  would 
  take 
  about 
  eight 
  years 
  to 
  reach 
  the 
  weight 
  of 
  

   200 
  grams 
  and 
  a 
  length 
  of 
  90 
  to 
  100 
  millimeters; 
  as 
  later 
  growth 
  is 
  

   slower, 
  about 
  12 
  to 
  15 
  years 
  would 
  be 
  a 
  fau* 
  estimate 
  for 
  the 
  age 
  of 
  a 
  

   Shoofly 
  Creek 
  undulata 
  (tlu-ee-ridge) 
  of 
  300 
  grams 
  in 
  weight 
  and 
  110 
  

   to 
  120 
  millimeters 
  in 
  length. 
  

  

  