﻿OYSTER 
  INDUSTRY 
  OF 
  NORTH 
  CAROLINA. 
  325 
  

  

  When 
  the 
  free 
  larva 
  of 
  the 
  oj'ster 
  settles 
  down 
  into 
  the 
  fixed 
  state, 
  the 
  left 
  lobe 
  of 
  

   the 
  mantle 
  stretches 
  beyond 
  its 
  valve, 
  and, 
  applying 
  itself 
  to 
  the 
  surface 
  of 
  the 
  stone 
  

   or 
  shell 
  to 
  which 
  the 
  valve 
  is 
  to 
  adhere, 
  secretes 
  shelly 
  matter, 
  which 
  serves 
  to 
  cement 
  

   the 
  valve 
  to 
  its 
  support. 
  As 
  the 
  animal 
  grows 
  the 
  mantle 
  deposits 
  new 
  layers 
  of 
  

   shell 
  over 
  its 
  Avhole 
  surface, 
  so 
  that 
  the 
  larval 
  shell 
  valves 
  become 
  separated 
  from 
  

   the 
  mantle 
  by 
  the 
  new 
  layers 
  (plate 
  ix, 
  fig. 
  3, 
  S), 
  which 
  crop 
  out 
  beyond 
  their 
  

   margins 
  and 
  acquire 
  the 
  characteristic 
  prismatic 
  and 
  nacreous 
  structure. 
  The 
  sum- 
  

   mits 
  of 
  the 
  outer 
  faces 
  of 
  the 
  umbones 
  thus 
  correspond 
  with 
  the 
  places 
  of 
  the 
  larval 
  

   valves, 
  which 
  soon 
  cease 
  to 
  be 
  discernible. 
  After 
  a 
  time 
  the 
  body 
  becomes 
  convex 
  

   on 
  the 
  left 
  side 
  and 
  flat 
  on 
  the 
  right; 
  the 
  successively 
  added 
  new 
  layers 
  of 
  shell 
  mold 
  

   themselves 
  upon 
  it, 
  and 
  the 
  animal 
  acquires 
  the 
  asymmetry 
  characteristic 
  of 
  the 
  

   adult. 
  « 
  

  

  The 
  horny 
  convex 
  shell 
  of 
  the 
  fry 
  (phite 
  ix, 
  fig. 
  3, 
  Z) 
  may 
  be 
  seen, 
  

   for 
  a 
  considerable 
  time 
  after 
  attachment, 
  at 
  the 
  umbo 
  or 
  beak 
  of 
  the 
  

   developing- 
  shell 
  of 
  the 
  spat 
  (plate 
  ix, 
  fig-. 
  3, 
  aS*). 
  The 
  under 
  or 
  

   attached 
  valve 
  of 
  the 
  latter 
  at 
  first 
  conforms 
  closely 
  to 
  the 
  surface 
  to 
  

   which 
  it 
  has 
  become 
  attached, 
  being 
  usuall}^ 
  flat, 
  but 
  afterwards, 
  as 
  a 
  

   rule, 
  becoming 
  deep 
  and 
  strong-ly 
  concave, 
  through 
  an 
  upgrowing 
  

   along 
  the 
  edges. 
  

  

  nXATIOX, 
  SET, 
  OR 
  SPATTING. 
  

  

  At 
  the 
  time 
  of 
  fixation 
  the 
  fry 
  will, 
  under 
  proper 
  conditions, 
  attach 
  

   itself 
  by 
  its 
  left 
  valve 
  to 
  anv 
  hard 
  or 
  tirm 
  bod}^ 
  with 
  which 
  it 
  may 
  come 
  

   in 
  contact. 
  

  

  The 
  first 
  essential 
  is 
  that 
  the 
  surface 
  should 
  be 
  clean 
  and 
  that 
  it 
  

   should 
  remain 
  so 
  a 
  sufficient 
  length 
  of 
  time 
  to 
  enable 
  the 
  young 
  oyster 
  

   to 
  establish 
  itself 
  firml3^ 
  So 
  long 
  as 
  this 
  condition 
  obtains, 
  the 
  nature 
  

   of 
  the 
  material 
  seems 
  to 
  matter 
  but 
  little. 
  In 
  most 
  bodies 
  of 
  water 
  the 
  

   spat 
  fixes 
  itself 
  at 
  all 
  levels 
  from 
  the 
  surface 
  to 
  the 
  bottom, 
  but 
  in 
  cer- 
  

   tain 
  parts 
  of 
  the 
  coast 
  its 
  place 
  of 
  attachment 
  is 
  confined 
  to 
  the 
  zone 
  

   between 
  high 
  and' 
  low 
  water, 
  the 
  mid-tide 
  mark 
  being 
  the 
  place 
  of 
  

   maximum 
  fixation. 
  It 
  has 
  been 
  suggested 
  that 
  this 
  was 
  due 
  to 
  the 
  

   density 
  of 
  the 
  water 
  preventing 
  the 
  sinking 
  of 
  the 
  fr^-. 
  There 
  are 
  a 
  

   number 
  of 
  objections 
  to 
  this 
  theory, 
  but 
  no 
  better 
  one 
  has 
  been 
  offered, 
  

   and 
  it 
  may 
  receive 
  provisional 
  acceptance. 
  

  

  At 
  the 
  time 
  of 
  its 
  attachment 
  the 
  oyster 
  fry 
  measures 
  about 
  one- 
  

   eightieth 
  or 
  one-ninetieth 
  of 
  an 
  inch 
  in 
  diameter. 
  The 
  valves 
  of 
  the 
  

   shell 
  are 
  strongly 
  convex 
  and 
  symmetrical, 
  and 
  are 
  composed 
  of 
  a 
  

   horny 
  material 
  quite 
  different 
  from 
  the 
  finished 
  shell 
  of 
  the 
  adult. 
  

  

  The 
  mantle, 
  a 
  thin 
  flap 
  of 
  tissue 
  which 
  envelops 
  the 
  body 
  of 
  the 
  

   oyster 
  on 
  each 
  side, 
  projects 
  freely 
  from 
  between 
  the 
  lips 
  of 
  the 
  valves 
  

   and 
  is 
  the 
  organ 
  which 
  secretes 
  the 
  shell. 
  Upon 
  its 
  outer 
  surface 
  suc- 
  

  

  rtHuxley, 
  Thomas 
  H.: 
  Oysters 
  and 
  the 
  Ovster 
  Question. 
  The 
  English 
  Illustrated 
  Magazine, 
  Lon- 
  

   don, 
  Oct., 
  1883, 
  and 
  Nov., 
  1883, 
  vol. 
  1, 
  pp. 
  47-55 
  and 
  112-121. 
  

  

  