﻿276 
  REPORT 
  OF 
  COMMISSIONER 
  OF 
  FISH 
  AND 
  FISHERIES. 
  

  

  ANATOMY. 
  

  

  The 
  following 
  poi)ular 
  description 
  of 
  the 
  anatomy 
  of 
  the 
  oyster 
  is 
  

   extracted 
  from 
  the 
  writings 
  of 
  Professors 
  Brooks 
  and 
  Ryder: 
  

  

  The 
  general 
  structure 
  of 
  an 
  oyster 
  may 
  be 
  roughly 
  represented 
  by 
  a 
  long, 
  narrow 
  

   memorandum 
  book, 
  with 
  the 
  back 
  at 
  one 
  of 
  the 
  narrow 
  ends 
  instead 
  of 
  one 
  of 
  the 
  

   long 
  ones. 
  The 
  covers 
  of 
  such 
  a 
  book 
  represent 
  the 
  two 
  shells 
  of 
  the 
  oyster, 
  and 
  the 
  

   back 
  represents 
  the 
  hinge, 
  or 
  the 
  area 
  where 
  the 
  two 
  valves 
  of 
  the 
  shell 
  are 
  fastened 
  

   together 
  by 
  the 
  hinge 
  ligament. 
  (Plate 
  i, 
  lig. 
  1 
  I.) 
  This 
  ligament 
  is 
  an 
  elastic, 
  dark- 
  

   brown 
  structure, 
  which 
  is 
  placed 
  in 
  such 
  a 
  relation 
  to 
  the 
  valves 
  of 
  the 
  shell 
  that 
  it 
  

   tends 
  to 
  throw 
  their 
  free 
  ends 
  a 
  little 
  apart. 
  In 
  order 
  to 
  understand 
  its 
  manner 
  of 
  

   working, 
  open 
  the 
  memorandum 
  book 
  and 
  place 
  between 
  its 
  leaves, 
  close 
  to 
  the 
  back, 
  

   a 
  small 
  piece 
  of 
  rubber 
  to 
  represent 
  the 
  ligament. 
  If 
  the 
  free 
  ends 
  of 
  the 
  cover 
  are 
  

   pulled 
  together 
  the 
  rubber 
  will 
  be 
  compressed 
  and 
  will 
  throw 
  the 
  covers 
  apart 
  as 
  

   soon 
  as 
  they 
  are 
  loosened. 
  The 
  ligament 
  of 
  the 
  oyster 
  shell 
  tends, 
  by 
  its 
  elasticity, 
  

   to 
  keep 
  the 
  shell 
  open 
  at 
  all 
  times, 
  and 
  while 
  the 
  oyster 
  is 
  lying 
  undisturbed 
  upon 
  

   the 
  bottom, 
  or 
  when 
  its 
  muscle 
  is 
  cut, 
  or 
  when 
  the 
  animal 
  is 
  dying 
  or 
  dead, 
  the 
  

   edges 
  of 
  the 
  shell 
  are 
  separated 
  a 
  little. 
  

  

  The 
  shell 
  is 
  lined 
  by 
  a 
  thin 
  membrane, 
  the 
  mantle 
  (plate 
  i, 
  fig. 
  1, 
  mt), 
  which 
  folds 
  

   down 
  on 
  each 
  side, 
  and 
  may 
  be 
  compared 
  to 
  the 
  leaf 
  next 
  the 
  cover 
  on 
  each 
  side 
  of 
  

   the 
  book. 
  The 
  next 
  two 
  leaves 
  of 
  each 
  side 
  roughly 
  represent 
  the 
  four 
  gills, 
  g, 
  the 
  

   so-called 
  "beard" 
  of 
  the 
  oyster, 
  which 
  hang 
  down 
  like 
  leaves 
  into 
  the 
  space 
  inside 
  

   the 
  two 
  lobes 
  of 
  the 
  mantle. 
  The 
  remaining 
  leaves 
  may 
  be 
  compared 
  to 
  tlie 
  body 
  or 
  

   visceral 
  mass 
  of 
  the 
  oyster. 
  

  

  Although 
  the 
  oyster 
  lies 
  upon 
  the 
  bottom, 
  with 
  one 
  shell 
  above 
  and 
  one 
  below, 
  the 
  

   shells 
  are 
  not 
  iipon 
  the 
  top 
  and 
  bottom 
  of 
  the 
  body, 
  but 
  upon 
  the 
  right 
  and 
  left 
  

   sides. 
  The 
  two 
  shells 
  are 
  symmetrical 
  in 
  the 
  young 
  oyster 
  (plate 
  viii, 
  fig. 
  2), 
  but 
  after 
  

   it 
  becomes 
  attached 
  the 
  lower 
  or 
  attached 
  side 
  grows 
  faster 
  than 
  the 
  other 
  and 
  

   becomes 
  deep 
  and 
  sjioon-shaped, 
  while 
  the 
  free 
  valve 
  remains 
  nearly 
  flat. 
  In 
  nearly 
  

   every 
  case 
  the 
  lower 
  or 
  deep 
  valve 
  is 
  the 
  left. 
  As 
  the 
  hinge 
  marks 
  the 
  anterior 
  

   end 
  of 
  the 
  body, 
  an 
  oyster 
  which 
  is 
  held 
  on 
  edge, 
  with 
  the 
  hinge 
  away 
  from 
  the 
  

   observer 
  and 
  the 
  flat 
  valve 
  on 
  the 
  right 
  side, 
  will 
  be 
  placed 
  with 
  its 
  dorsal 
  surface 
  

   uppermost, 
  its 
  ventral 
  surface 
  below, 
  its 
  anterior 
  end 
  away 
  from 
  the 
  observer, 
  and 
  

   its 
  posterior 
  end 
  toward 
  him, 
  and 
  its 
  right 
  and 
  left 
  sides 
  on 
  his 
  right 
  and 
  left 
  hands, 
  

   respectively. 
  

  

  In 
  order 
  to 
  examine 
  the 
  soft 
  parts, 
  the 
  oyster 
  should 
  be 
  opened 
  by 
  gently 
  working 
  

   a 
  thin, 
  flat 
  knife 
  blade 
  under 
  the 
  posterior 
  end 
  of 
  the 
  right 
  valve 
  of 
  the 
  shell, 
  and 
  

   pushing 
  the 
  blade 
  forward 
  until 
  it 
  strikes 
  and 
  cuts 
  the 
  strong 
  adductor 
  muscle, 
  M, 
  

   which 
  passes 
  from 
  one 
  shell 
  to 
  another 
  and 
  pulls 
  them 
  together. 
  As 
  soon'as 
  this 
  

   muscle 
  is 
  cut 
  the 
  valves 
  separate 
  a 
  little, 
  and 
  the 
  right 
  valve 
  may 
  be 
  raised 
  up 
  and 
  

   broken 
  off 
  from 
  the 
  left, 
  thus 
  exposing 
  the 
  right 
  side 
  of 
  the 
  body. 
  The 
  surface 
  of 
  

   the 
  body 
  is 
  covered 
  by 
  the 
  mantle, 
  a 
  thin 
  membrane 
  which 
  is 
  attached 
  to 
  the 
  body 
  

   over 
  a 
  great 
  part 
  of 
  its 
  surface, 
  but 
  hangs 
  free 
  like 
  a 
  curtain 
  around 
  nearly 
  the 
  whole 
  

   circumference. 
  13y 
  raising 
  its 
  edge, 
  or 
  gently 
  tearing 
  the 
  whole 
  right 
  half 
  away 
  

   from 
  the 
  body, 
  the 
  gills, 
  g, 
  will 
  be 
  exposed. 
  These 
  are 
  four 
  parallel 
  plates 
  which 
  

   occupy 
  the 
  ventral 
  half 
  of 
  the 
  mantle 
  cavity 
  and 
  extend 
  from 
  the 
  posterior 
  nearly 
  

   to 
  the 
  anterior 
  end 
  of 
  the 
  body. 
  Their 
  ventral 
  edges 
  are 
  free, 
  but 
  their 
  dorsal 
  edges 
  

   are 
  united 
  to 
  each 
  other, 
  to 
  the 
  mantle, 
  and 
  to 
  the 
  body. 
  The 
  s^iace 
  above, 
  or 
  dorsal 
  

   to 
  the 
  posterior 
  ends 
  of 
  the 
  gills, 
  is 
  occupied 
  by 
  the 
  oval, 
  firm 
  adductor 
  muscle, 
  M, 
  

   the 
  so-called 
  " 
  heart." 
  For 
  some 
  time 
  I 
  was 
  at 
  a 
  loss 
  to 
  know 
  how 
  the 
  muscle 
  

   came 
  to 
  be 
  called 
  the 
  "heart," 
  but 
  a 
  friend 
  told 
  me 
  that 
  he 
  had 
  always 
  supposed 
  

   that 
  this 
  was 
  the 
  heart, 
  since 
  the 
  oyster 
  dies 
  when 
  it 
  is 
  injured. 
  The 
  supposed 
  

   "death" 
  is 
  simply 
  the 
  opening 
  of 
  the 
  shell, 
  when 
  the 
  animal 
  loses 
  the 
  poAver 
  to 
  

   keep 
  it 
  shut. 
  Between 
  this 
  muscle 
  and 
  the 
  hinge 
  the 
  space 
  above 
  the 
  gills 
  is 
  occupied 
  

  

  