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  extent 
  by 
  working 
  upon 
  it. 
  The 
  dredges 
  or 
  other 
  implements 
  

   used 
  open 
  the 
  bed 
  and 
  spread 
  it, 
  thus 
  giving 
  more 
  room 
  for 
  

   development, 
  and 
  allowing 
  a 
  greater 
  amount 
  of 
  food 
  to 
  reach 
  

   the 
  animals. 
  

  

  The 
  mortality 
  is 
  great 
  in 
  all 
  thickly 
  populated 
  tracts 
  and 
  

   in 
  any 
  closely 
  united 
  community, 
  and 
  it 
  is 
  evident 
  that 
  the 
  

   removal 
  of 
  any 
  of 
  the 
  brood 
  oysters 
  could 
  not 
  be 
  effected 
  

   without 
  destroying 
  the 
  fecundity 
  of 
  the 
  bed, 
  did 
  not 
  this 
  very 
  

   removal 
  influence 
  the 
  mortality 
  among 
  the 
  young 
  so 
  as 
  to 
  al- 
  

   low 
  a 
  larger 
  number 
  to 
  come 
  to 
  maturity. 
  But 
  this 
  removal 
  

   of 
  brood 
  oysters 
  may 
  become 
  so 
  great 
  that 
  the 
  most 
  violent 
  

   exertions 
  of 
  nature 
  to 
  supply 
  others 
  are 
  unequal 
  to 
  the 
  de- 
  

   mand. 
  

  

  It 
  must 
  also 
  be 
  evident 
  that 
  as 
  soon 
  as 
  the 
  number 
  of 
  brood 
  

   oysters 
  is 
  thus 
  diminished, 
  even 
  to 
  the 
  slightest 
  extent, 
  the 
  

   fecundity 
  of 
  the 
  bed 
  is 
  impaired. 
  

  

  This 
  impairment 
  constantly 
  increases, 
  influencing, 
  as 
  it 
  does, 
  

   both 
  old 
  and 
  young. 
  As 
  the 
  number 
  of 
  the 
  latter 
  decrease, 
  

   so 
  will 
  the 
  number 
  of 
  the 
  former, 
  and 
  as 
  that 
  number 
  is 
  again 
  

   and 
  again 
  diminished, 
  the 
  number 
  of 
  yonng 
  produced 
  by 
  them 
  

   must 
  constantly 
  diminish. 
  Thus 
  the 
  cause 
  for 
  the 
  destruction 
  

   of 
  the 
  fecundity 
  of 
  the 
  bed, 
  and 
  the 
  gradual 
  extinction 
  of 
  the 
  

   animals 
  upon 
  it, 
  can 
  be 
  readily 
  understood 
  and 
  as 
  easily 
  com- 
  

   prehended 
  as 
  the 
  fact 
  that 
  the 
  fecundity 
  and 
  preservation 
  of 
  

   the 
  productive 
  powers 
  of 
  a 
  bed 
  depends 
  npon 
  the 
  number 
  of 
  

   mature, 
  spawn-bearing 
  oysters 
  upon 
  it. 
  

  

  It 
  is 
  not 
  meant 
  by 
  this 
  that 
  none 
  but 
  the 
  mature 
  oysters 
  

   are 
  capable 
  of 
  reproduction, 
  as 
  such 
  is 
  not 
  the 
  case, 
  oysters 
  of 
  

   even 
  six 
  or 
  nine 
  months' 
  growth 
  having 
  been 
  observed 
  by 
  me 
  

   with 
  ripe 
  ova 
  and 
  spermatozoa 
  in 
  them, 
  but 
  the 
  main 
  depend- 
  

   ence 
  must 
  be 
  placed 
  upon 
  the 
  adults 
  in 
  the 
  community, 
  as 
  the 
  

   spawn 
  of 
  the 
  young 
  growth 
  is 
  not 
  considerable 
  when 
  com- 
  

   pared 
  with 
  that 
  of 
  the 
  other 
  class. 
  

  

  Without 
  a 
  knowledge 
  of 
  the 
  number 
  of 
  oysters 
  on 
  a 
  bed 
  

   it- 
  is 
  impossible 
  to 
  say 
  what 
  number 
  should 
  be 
  removed, 
  and 
  

   as 
  an 
  attainment 
  of 
  the 
  knowledge 
  of 
  the 
  number 
  on 
  the 
  bed 
  

   is 
  almost 
  impossible, 
  all 
  that 
  can 
  be 
  done 
  is 
  to 
  keep 
  the 
  pro- 
  

   portions 
  between 
  the 
  young 
  and 
  the 
  mature 
  as 
  nearly 
  the 
  

  

  