﻿LOBSTEK 
  AND 
  CLAM 
  INVESTIGATIONS. 
  223 
  

  

  tvibution 
  to 
  clearly 
  detinod 
  areas. 
  These 
  conditions 
  are 
  constantly 
  

   changing- 
  and 
  shifting 
  the 
  regions 
  vrhere 
  clams 
  may 
  become 
  established. 
  

  

  Conditions 
  controUing 
  the 
  dlstrloidlon, 
  and 
  yroioth 
  of 
  the 
  ijoxing: 
  

  

  The 
  egg 
  develops 
  into 
  ix 
  swimming 
  larva 
  which 
  finall}^ 
  settles 
  to 
  the 
  

   i)ottom 
  and 
  attaches 
  by 
  means 
  of 
  a 
  b3'ssus. 
  It 
  is 
  some 
  time 
  before 
  the 
  

   clam 
  is 
  a])le 
  to 
  burrow. 
  In 
  the 
  meantime 
  it 
  is 
  exposed 
  to 
  many 
  

   dangers. 
  The 
  young 
  appear 
  scattered 
  on 
  beaches 
  and 
  flats, 
  but 
  at 
  

   times 
  are 
  segregated 
  in 
  numbers 
  so 
  great 
  that 
  the}^ 
  have 
  scarcely 
  room 
  

   for 
  lodgment. 
  Such 
  a 
  localit}^ 
  was 
  found 
  at 
  West 
  Falmouth, 
  Mass. 
  

   These 
  segregations 
  occur 
  below 
  the 
  low-tide 
  mark, 
  and 
  are 
  accounted 
  

   for 
  by 
  the 
  rapidity 
  of 
  narrow 
  currents 
  where 
  the 
  water 
  bears 
  many 
  

   swimming 
  embryos. 
  There 
  seems 
  to 
  be 
  no 
  relation 
  between 
  such 
  l)eds 
  

   of 
  young 
  and 
  the 
  beds 
  of 
  mature 
  clams 
  on 
  the 
  beaches 
  above 
  them, 
  the 
  

   latter 
  ])eing 
  recruited 
  only 
  from 
  the 
  few 
  small 
  clams 
  that 
  chance 
  to 
  

   settle 
  between 
  tide 
  lines 
  and 
  there 
  establish 
  themselves. 
  

  

  On 
  the 
  West 
  Falmouth 
  bed 
  the 
  maximum 
  size 
  on 
  July 
  1<), 
  18U9, 
  was 
  

   aliout 
  11 
  mm., 
  the 
  minimum 
  about 
  1 
  mm., 
  though 
  smaller 
  clams 
  

   might 
  have 
  been 
  found 
  with 
  a 
  finer 
  sieve 
  than 
  the 
  one 
  used. 
  The 
  

   larger 
  clams 
  were 
  p'robably 
  from 
  five 
  to 
  seven 
  weeks 
  old. 
  Several 
  

   observations 
  on 
  the 
  growth 
  were 
  made 
  from 
  time 
  to 
  time 
  until 
  Sep- 
  

   tember. 
  On 
  August 
  10 
  the 
  maximum 
  length 
  was 
  about 
  20 
  mm. 
  

   Very 
  small 
  individuals 
  still 
  appeared, 
  though 
  few 
  in 
  number, 
  showing 
  

   that 
  the 
  breeding 
  season 
  was 
  not 
  yet 
  entireh^ 
  ended. 
  

  

  Even 
  at 
  the 
  height 
  of 
  the 
  breeding 
  season, 
  earl}^ 
  in 
  July, 
  some 
  clams 
  

   were 
  dying. 
  B}^ 
  August 
  16 
  ver}^ 
  few 
  remained 
  alive. 
  The 
  expla- 
  

   nation 
  of 
  their 
  destruction 
  seems 
  to 
  be 
  (1) 
  lack 
  of 
  sufficient 
  food 
  and 
  

   (2) 
  the 
  contamination 
  of 
  the 
  water 
  i>y 
  the 
  decaving 
  bodies 
  of 
  dead 
  

   clams. 
  

  

  The 
  set 
  varies 
  in 
  different 
  3'ears, 
  sometimes 
  being 
  great, 
  sometimes 
  

   small. 
  

  

  Conditions 
  deterniining 
  existence 
  and 
  rapidity 
  of 
  growth 
  in 
  arti^ji- 
  

   cial 
  heds: 
  

  

  Experiments 
  were 
  made 
  to 
  determine 
  the 
  rate 
  of 
  growth 
  under 
  many 
  

   different 
  conditions. 
  The 
  methods 
  are 
  described 
  in 
  detail. 
  Woods 
  

   Hole 
  harbor 
  was 
  not 
  a 
  favorable 
  locality 
  for 
  showing 
  the 
  possil)le 
  

   rapidit3^of 
  growth. 
  At 
  the 
  head 
  of 
  the 
  harbor, 
  where 
  there 
  was 
  prac- 
  

   tically 
  no 
  current, 
  series 
  of 
  clams 
  (each 
  of 
  which 
  was 
  measured) 
  from 
  

   19 
  to 
  2t 
  inches 
  in 
  length 
  were 
  planted. 
  At 
  the 
  end 
  of 
  a 
  year 
  these 
  

   extremes 
  of 
  the 
  series 
  had 
  increased 
  in 
  volume 
  556 
  and 
  28 
  per 
  cent, 
  

   respectively. 
  In 
  another 
  localit}' 
  where 
  there 
  was 
  some 
  current, 
  

   clams 
  from 
  1 
  inch 
  to 
  1| 
  inches 
  had 
  increased 
  1,150 
  and 
  711 
  per 
  cent 
  

   in 
  volume. 
  In 
  one 
  bed 
  placed 
  where 
  the 
  currents 
  wore 
  most 
  rapid, 
  

   clams 
  exactlv 
  1 
  inch 
  long 
  were 
  planted, 
  and 
  in 
  a 
  j^ear 
  had 
  increased 
  

   1,337 
  per 
  cent 
  in 
  volume. 
  The 
  conclusion 
  was 
  reached 
  that 
  the 
  rate 
  

   of 
  growth 
  depends 
  directl}' 
  upon 
  the 
  amount 
  of 
  food. 
  

  

  