﻿LOBSTER 
  AND 
  CLAM 
  INVESTIGATIONS. 
  215 
  

  

  which 
  we 
  now 
  possess. 
  Here 
  we 
  simply 
  describe 
  the 
  conditions 
  so 
  far 
  

   us 
  we 
  know' 
  them 
  and 
  show 
  the 
  approximate 
  increase, 
  and 
  the 
  number 
  

   of 
  clams 
  planted 
  (8,500 
  in 
  the 
  IT 
  beds) 
  is 
  great 
  enoug-h 
  to 
  make 
  our 
  

   result 
  reliable. 
  

  

  The 
  errors 
  are 
  slight. 
  They 
  arise 
  in 
  two 
  or 
  three 
  waj^s, 
  and 
  tend 
  to 
  

   balance 
  each 
  other. 
  (1) 
  The 
  unit 
  of 
  the 
  scale 
  of 
  measurement 
  was 
  an 
  

   eighth 
  of 
  an 
  inch. 
  If 
  a 
  clam 
  l^eing 
  measured 
  for 
  planting 
  was 
  slightly 
  

   less 
  than 
  1^ 
  inches 
  in 
  length, 
  it 
  was 
  placed 
  in 
  the 
  1-inch 
  group. 
  This 
  

   method 
  was 
  also 
  followed 
  in 
  measuring 
  clams 
  aftergrowth. 
  (2) 
  When 
  

   the 
  mean 
  of 
  a 
  series 
  after 
  growth 
  was 
  determined, 
  a 
  decimal 
  above 
  0.5 
  

   was 
  expressed 
  by 
  the 
  next 
  highest, 
  and 
  when 
  below 
  0.5 
  by 
  the 
  next 
  

   lowest 
  unit 
  in 
  the 
  scale. 
  Thus 
  if 
  the 
  mean 
  size 
  in 
  a 
  given 
  series 
  were 
  

   20.6 
  eighths, 
  it 
  would 
  be 
  called 
  2§, 
  if 
  20.4, 
  2| 
  inches. 
  

  

  The 
  decrease 
  of 
  the 
  percentage 
  of 
  growth 
  shown 
  in 
  the 
  table, 
  from 
  

   the 
  smaller 
  to 
  the 
  larger 
  individuals, 
  is 
  not 
  perfectly 
  regular. 
  This 
  

   may 
  have 
  been 
  because 
  the 
  number 
  in 
  some 
  series 
  was 
  much 
  greater 
  

   than 
  in 
  others, 
  and 
  also 
  because 
  the 
  conditions 
  on 
  one 
  bed 
  were 
  not 
  

   exactl}'^ 
  like 
  those 
  on 
  another. 
  Some 
  beds 
  were 
  each 
  day 
  longer 
  

   exposed 
  than 
  others, 
  and 
  there 
  may 
  have 
  been 
  other 
  differences 
  in 
  the 
  

   surroundings. 
  

  

  Am.oimt 
  of 
  variation 
  in 
  a 
  single 
  series. 
  — 
  The 
  variation 
  in 
  length 
  of 
  

   the 
  individuals 
  of 
  a 
  single 
  series 
  was 
  considerable. 
  For 
  example, 
  in 
  

   a 
  series 
  of 
  140 
  clams, 
  w;hich 
  were 
  2| 
  inches 
  long 
  when 
  planted, 
  the 
  

   series 
  when 
  dug 
  included 
  clams 
  from 
  2| 
  to 
  3f 
  inches 
  in 
  length. 
  A 
  few 
  

   seemed 
  to 
  have 
  grown 
  very 
  little. 
  It 
  is 
  possible 
  that 
  some 
  may 
  have 
  

   been 
  overlooked 
  in 
  preparing 
  the 
  beds 
  for 
  planting, 
  and 
  that 
  these 
  

   clams 
  were 
  not 
  those 
  planted, 
  but 
  small 
  forms 
  already 
  present 
  and 
  not 
  

   removed. 
  From 
  the 
  pebbl}^ 
  nature 
  of 
  the 
  surface 
  it 
  was 
  not 
  easy 
  to 
  

   detect 
  all 
  the 
  siphon 
  holes. 
  On 
  account 
  of 
  the 
  difficulty 
  in 
  removing 
  

   all 
  small 
  clams 
  in 
  preparing 
  the 
  beds, 
  these 
  afterwards 
  appearing 
  in 
  

   the 
  series, 
  probably 
  the 
  calculated 
  percentage 
  of 
  growth 
  is 
  less 
  than 
  

   it 
  would 
  have 
  been 
  if 
  the 
  beach 
  when 
  planted 
  had 
  been 
  perfectly 
  clear 
  

   of 
  clams. 
  On 
  the 
  other 
  hand 
  it 
  was 
  comparatively 
  easy 
  to 
  note 
  the 
  

   presence 
  of 
  large 
  clams, 
  and 
  probal)Iy 
  few^ 
  of 
  them 
  were 
  left. 
  

  

  In 
  one 
  bed 
  in 
  another 
  locality 
  the 
  ground 
  was 
  most 
  carefullj^ 
  dug 
  

   and 
  examined 
  for 
  small 
  clams. 
  Practically 
  all 
  must 
  have 
  been 
  

   removed. 
  The 
  clams 
  planted 
  here 
  were 
  all 
  exactly 
  1 
  inch 
  long, 
  but 
  

   at 
  the 
  end 
  of 
  a 
  year 
  the 
  length 
  varied 
  from 
  2^ 
  to 
  2^ 
  inches. 
  

  

  Growtli 
  in 
  a 
  slow 
  current. 
  — 
  Over 
  the 
  beds 
  first 
  described 
  there 
  was 
  

   practically 
  no 
  current, 
  but 
  only 
  a 
  rise 
  and 
  fall 
  of 
  the 
  tide. 
  The 
  fol- 
  

   lowing 
  table, 
  prepared 
  as 
  was 
  the 
  first, 
  shows 
  the 
  approximate 
  increase 
  

   on 
  several 
  beds 
  placed 
  on 
  a 
  beach 
  near 
  the 
  entrance 
  to 
  the 
  harbor, 
  

   where 
  the 
  current 
  was 
  more 
  marked 
  than 
  at 
  its 
  head. 
  The 
  current 
  

   here, 
  however, 
  was 
  not 
  at 
  all 
  strong, 
  and 
  was 
  discerned 
  only 
  by 
  the 
  

   bending 
  of 
  the 
  eel-grass 
  below 
  the 
  beds. 
  On 
  the 
  best 
  clam 
  bottoms 
  in 
  

  

  