﻿204 
  EEPOET 
  OF 
  COMMISSIONEE 
  OF 
  FISH 
  AND 
  FISHERIES. 
  

  

  which 
  ran 
  parallel 
  to 
  the 
  shores, 
  over 
  the 
  area 
  occupied 
  by 
  the 
  

   small 
  clams. 
  The 
  current 
  in 
  the 
  center 
  of 
  the 
  ba}^ 
  was 
  slow, 
  on 
  

   account 
  of 
  the 
  great 
  mass 
  of 
  eelgrass 
  which 
  tilled 
  it, 
  so 
  that 
  a 
  large 
  

   part 
  of 
  the 
  water 
  entering 
  and 
  leaving 
  took 
  this 
  course 
  near 
  the 
  

   shores. 
  These 
  streams 
  seemed 
  to 
  be 
  like 
  that 
  part 
  of 
  a 
  river 
  which 
  

   has 
  reached 
  its 
  base 
  level, 
  for 
  apparently 
  they 
  neither 
  deposited 
  nor 
  

   eroded. 
  In 
  the 
  broad 
  upper 
  part 
  of 
  the 
  bay 
  the 
  water 
  was 
  quiet 
  and 
  

   a 
  large 
  quantity 
  of 
  fine 
  silt 
  was 
  deposited, 
  making 
  it 
  impossible 
  for 
  

   clams 
  of 
  any 
  age 
  to 
  exist. 
  

  

  It 
  is 
  probably 
  generally 
  true, 
  as 
  in 
  this 
  case, 
  that 
  small 
  clams 
  are 
  

   found 
  crowded 
  in 
  great 
  numbers 
  only 
  where 
  currents 
  are 
  compara- 
  

   tively 
  rapid. 
  This 
  has 
  seemed 
  to 
  be 
  the 
  condition 
  in 
  other 
  localities 
  

   where 
  they 
  have 
  been 
  found. 
  At 
  the 
  lower 
  ends 
  of 
  these 
  strips 
  they 
  

   were 
  crowded 
  most 
  closely, 
  and 
  the 
  currents 
  were 
  most 
  rapid 
  here, 
  

   though 
  still 
  not 
  so 
  swift 
  as 
  to 
  disturb 
  the 
  bottom. 
  Toward 
  the 
  upper 
  

   ends 
  of 
  the 
  strips 
  clams 
  became 
  gradually 
  less 
  numerous, 
  -where, 
  also, 
  

   the 
  velocity 
  of 
  the 
  currents 
  was 
  diminished. 
  

  

  It 
  is 
  important 
  to 
  notice 
  that 
  the 
  small 
  clams 
  were 
  not 
  entirely 
  con- 
  

   fined 
  to 
  the 
  beds 
  below 
  the 
  low-water 
  mark. 
  With 
  a 
  fine 
  sieve 
  it 
  was 
  

   possible 
  to 
  find 
  them 
  between 
  tide 
  lines. 
  They 
  were 
  not 
  numerous, 
  

   however. 
  It 
  has 
  been 
  stated 
  that 
  the 
  densely 
  packed 
  beds 
  below 
  low- 
  

   water 
  mark 
  appear 
  in 
  few 
  localities. 
  Yet 
  from 
  almost 
  any 
  clam 
  bed 
  

   between 
  tide 
  lines 
  in 
  the 
  early 
  summer 
  a 
  few 
  of 
  the 
  young 
  may 
  be 
  

   obtained. 
  The 
  number 
  is 
  insignificant 
  as 
  compared 
  with 
  that 
  where 
  

   3^oung 
  clams 
  are 
  segregated 
  in 
  a 
  bed 
  by 
  themselves. 
  It 
  is 
  probablj^ 
  

   these 
  scattered 
  young 
  that 
  make 
  good 
  the 
  annual 
  losses 
  of 
  a 
  clam 
  bed, 
  

   and 
  not 
  the 
  numbers 
  of 
  the 
  crowded 
  lower 
  bed, 
  even 
  where 
  it 
  is 
  

   present 
  and 
  in 
  close 
  proximity. 
  

  

  Such 
  a 
  separation 
  of 
  young 
  below 
  low 
  tide 
  and 
  adults 
  between 
  tide 
  

   lines 
  as 
  shown 
  at 
  West 
  Falmouth 
  seems 
  strange, 
  and 
  the 
  further 
  

   history 
  of 
  this 
  lower 
  bed 
  is 
  equall}' 
  remarkable. 
  

  

  We 
  may 
  attempt 
  to 
  explain 
  the 
  position 
  of 
  the 
  young 
  in 
  the 
  follow- 
  

   ing 
  way: 
  For 
  several 
  weeks 
  during 
  the 
  breeding 
  season 
  in 
  1889 
  

   (May, 
  June, 
  and 
  July), 
  when 
  this 
  large 
  ''set" 
  occurred, 
  the 
  embr3'os 
  

   undoubtedly 
  swam 
  in 
  vast 
  numbers 
  in 
  the 
  water. 
  It 
  is 
  probably 
  safe 
  

   to 
  say 
  that 
  during 
  such 
  a 
  season 
  millions 
  of 
  embryos 
  grow 
  from 
  the 
  

   eggs 
  of 
  a 
  single 
  large 
  female. 
  These 
  embr3^os 
  swim, 
  and 
  it 
  is 
  possible 
  

   that 
  the 
  course 
  taken 
  by 
  them 
  may 
  be 
  influenced 
  by 
  differences 
  in 
  the 
  

   intensity 
  of 
  light, 
  changes 
  in 
  the 
  temperature 
  of 
  water 
  or 
  air, 
  or 
  by 
  

   differences 
  in 
  the 
  specific 
  gravity 
  of 
  the 
  water. 
  But 
  their 
  movements 
  

   must 
  be 
  very 
  largely 
  determined 
  by 
  tide 
  currents, 
  and 
  it 
  is 
  not 
  easy 
  

   to 
  imagine 
  that 
  these 
  other 
  conditions 
  are 
  the 
  causes 
  of 
  this 
  peculiar 
  

   distribution, 
  or 
  that 
  they 
  have 
  any 
  important 
  influence 
  upon 
  it. 
  

  

  We 
  will 
  probably 
  find 
  our 
  explanation 
  in 
  the 
  action 
  of 
  a 
  definite 
  

   current 
  of 
  water 
  which 
  contains 
  swimming 
  embryos. 
  Imagine 
  a 
  wide 
  

  

  