﻿OYSTERS 
  AND 
  METHODS 
  OF 
  OYSTER-CULTURE. 
  291 
  

  

  independently 
  of 
  its 
  fellows 
  or 
  in 
  conjunction 
  with 
  tbem. 
  As 
  shown 
  

   in 
  plate 
  xvi, 
  the 
  starfish 
  feeding 
  upon 
  oysters 
  or 
  other 
  lamellibranchs 
  

   arches 
  itself 
  over 
  the 
  nibs 
  or 
  lips 
  of 
  the 
  mollusk 
  so 
  that 
  some 
  of 
  its 
  arms 
  

   are 
  on 
  one 
  side 
  and 
  some 
  on 
  the 
  other. 
  In 
  this 
  positicm 
  a 
  large 
  number 
  

   of 
  the 
  sucker 
  feet 
  are 
  attached 
  to 
  each 
  valve, 
  and 
  when 
  they 
  contract 
  

   a 
  stress 
  is 
  produced 
  in 
  opposite 
  directions 
  and 
  opposed 
  to 
  the 
  force 
  of 
  

   the 
  adductor 
  muscle 
  which 
  tends 
  to 
  keep 
  the 
  valves 
  of 
  the 
  oyster 
  

   closed. 
  Dr. 
  Schiemenz 
  has 
  shown 
  by 
  actual 
  measurement 
  that 
  in 
  this 
  

   manner 
  there 
  is 
  exerted 
  a 
  force 
  sufficient 
  to 
  overcome 
  any 
  resistance 
  

   which 
  the 
  oyster 
  may 
  ofler. 
  It 
  is 
  eventually 
  tired 
  out 
  by 
  the 
  x)ersist- 
  

   ence 
  of 
  its 
  enemy, 
  its 
  shell 
  is 
  forced 
  open, 
  the 
  stomach 
  of 
  the 
  starfish 
  

   is 
  inserted, 
  and 
  within 
  a 
  few 
  hours 
  the 
  valves 
  only 
  remain. 
  

  

  Another 
  annoying 
  and 
  frequently 
  very 
  destructive 
  enemy 
  of 
  the 
  

   oyster 
  is 
  the 
  boring-sponge, 
  Cliona 
  sulphurea. 
  It 
  differs 
  from 
  the 
  

   enemies 
  before 
  enumerated 
  in 
  that 
  it 
  consumes 
  the 
  shell 
  and 
  not 
  the 
  

   soft 
  i:)arts 
  of 
  the 
  unfortunate 
  oyster. 
  The 
  young 
  sponge 
  lives 
  in 
  galleries 
  

   excavated 
  in 
  the 
  substance 
  of 
  either 
  dead 
  or 
  living 
  shells 
  which 
  are 
  

   soon 
  reduced 
  to 
  a 
  honey-combed 
  condition, 
  when 
  they 
  may 
  be 
  crumbled 
  

   to 
  powder 
  between 
  the 
  fingers. 
  When 
  they 
  attack 
  a 
  living 
  oyster, 
  

   as 
  the 
  galleries 
  penetrate 
  the 
  inner 
  face 
  of 
  the 
  shell, 
  an 
  irritation 
  of 
  

   the 
  mantle 
  is 
  produced, 
  causing 
  an 
  increased 
  amount 
  of 
  shell 
  deposit 
  

   at 
  that 
  point. 
  If 
  the 
  inside 
  of 
  such 
  a 
  shell 
  be 
  examined 
  it 
  will 
  be 
  found 
  

   to 
  be 
  covered 
  with 
  blister-like 
  shell 
  deposits, 
  sealing 
  up 
  the 
  openings 
  to 
  

   the 
  galleries, 
  and 
  many 
  curious 
  distortions 
  follow 
  from 
  the 
  destruction 
  

   of 
  the 
  hinge 
  area 
  and 
  the 
  portion 
  of 
  the 
  shell 
  to 
  which 
  the 
  adductor 
  

   muscle 
  is 
  attached. 
  Although 
  the 
  oyster 
  itself 
  is 
  not 
  attacked, 
  yet 
  it 
  

   becomes 
  poor, 
  thin, 
  and 
  watery 
  and 
  often 
  dies 
  from 
  the 
  exhaustion 
  

   induced 
  by 
  the 
  constant 
  etfort 
  to 
  keep 
  its 
  shell 
  intact. 
  

  

  The 
  older 
  specimens 
  of 
  the 
  boring-sponge 
  are 
  large, 
  dense, 
  yellow 
  

   masses, 
  often 
  G 
  or 
  7 
  inches 
  in 
  diameter 
  and 
  usually 
  inclosing 
  the 
  shells, 
  

   etc., 
  to 
  which 
  they 
  were 
  originally 
  attached. 
  All 
  stages 
  intermediate 
  

   between 
  those 
  described 
  can 
  usually 
  be 
  found 
  upon 
  infested 
  oyster- 
  

   beds. 
  The 
  older, 
  more 
  massive 
  forms 
  often 
  suftbcate 
  the 
  oyster 
  through 
  

   the 
  denseness 
  of 
  their 
  growth. 
  

  

  In 
  addition 
  to 
  the 
  various 
  forms 
  already 
  enumerated 
  there 
  is 
  a 
  large 
  

   population 
  upon 
  the 
  oyster-beds 
  which 
  is 
  not 
  injurious. 
  This, 
  of 
  course, 
  

   includes 
  many 
  of 
  the 
  minute 
  food 
  Ibrms, 
  together 
  with 
  some 
  of 
  the 
  fishes 
  

   and 
  crabs. 
  The 
  latter, 
  at 
  least 
  on 
  the 
  Atlantic 
  coast, 
  can 
  not 
  be 
  

   regarded 
  as 
  very 
  destructive, 
  but 
  on 
  the 
  contrary 
  they 
  serve 
  as 
  scav- 
  

   engers, 
  removing 
  dead 
  matter 
  troni 
  the 
  beds 
  when 
  it 
  might 
  otherwise 
  

   become 
  foul 
  and 
  fatal 
  to 
  the 
  oysters. 
  It 
  will 
  be 
  seen 
  that 
  the 
  popula- 
  

   tion 
  of 
  the 
  oyster-beds 
  is 
  large 
  and 
  extremely 
  comi)Iex. 
  The 
  social 
  

   relations 
  of 
  the 
  various 
  forms 
  are 
  exceedingly 
  intricate 
  and 
  have, 
  in 
  

   the 
  cburse 
  of 
  evolution, 
  become 
  nicely 
  adjusted 
  in 
  a 
  system 
  of 
  reciprocity. 
  

   The 
  law 
  of 
  the 
  oyster 
  beds 
  is 
  "give 
  and 
  take," 
  each 
  of 
  a 
  large 
  number 
  

   of 
  organisms 
  giving 
  something 
  for 
  the 
  general 
  welfare 
  and 
  taking 
  what 
  

   it 
  needs 
  for 
  its 
  own 
  well 
  being. 
  

  

  