﻿OYSTERS 
  AND 
  METHODS 
  OF 
  OYSTER-CULTURE. 
  277 
  

  

  by 
  the 
  body, 
  or 
  visceral 
  mass, 
  which 
  is 
  made 
  up 
  mainly 
  of 
  the 
  light-colored 
  repro- 
  

   ductive 
  organs 
  and 
  the 
  dark-colored 
  digestive 
  organs, 
  packed 
  together 
  in 
  one 
  

   continnoiis 
  mass. 
  

  

  If 
  the 
  oyster 
  has 
  been 
  opened 
  very 
  carefully, 
  a 
  transparent, 
  crescent-shaped 
  space 
  

   will 
  be 
  seen 
  between 
  the 
  muscle 
  and 
  the 
  visceral 
  mass. 
  This 
  space 
  is 
  the 
  pericar- 
  

   dium, 
  and 
  if 
  the 
  delicate 
  membraue 
  which 
  forms 
  its 
  sides 
  be 
  carefully 
  cut 
  away, 
  the 
  

   heart, 
  re 
  and 
  an, 
  may 
  be 
  fouud 
  without 
  any 
  difficulty 
  lying 
  in 
  this 
  cavitj- 
  and 
  pulsat- 
  

   ing 
  slowly. 
  If 
  the 
  oyster 
  has 
  been 
  opened 
  roughly, 
  or 
  if 
  it 
  has 
  been 
  out 
  of 
  water 
  for 
  

   some 
  time, 
  the 
  rate 
  of 
  beating 
  may 
  be 
  as 
  low 
  as 
  one 
  a 
  minute, 
  or 
  even 
  less, 
  so 
  the 
  heart 
  

   must 
  be 
  watched 
  attentively 
  for 
  some 
  time 
  in 
  order 
  to 
  see 
  one 
  of 
  the 
  contractions. 
  

  

  In 
  front 
  of 
  the 
  gills, 
  that 
  is, 
  between 
  them 
  and 
  the 
  hinge, 
  there 
  are 
  four 
  fleshy 
  

   flaps 
  — 
  the 
  lips, 
  p, 
  two 
  on 
  each 
  side 
  of 
  the 
  body. 
  They 
  are 
  much 
  like 
  the 
  gills 
  in 
  

   appearance, 
  and 
  they 
  are 
  connected 
  with 
  each 
  other 
  by 
  two 
  ridges, 
  which 
  run 
  across 
  

   the 
  middle 
  of 
  the 
  body 
  close 
  to 
  the 
  anterior 
  end, 
  and 
  between 
  these 
  folds 
  is 
  the 
  large 
  

   oval 
  mouth, 
  m, 
  which 
  is 
  thus 
  seen 
  to 
  be 
  situated, 
  not 
  at 
  the 
  open 
  end 
  of 
  the 
  shell, 
  

   but 
  as 
  far 
  away 
  from 
  it 
  as 
  possible. 
  As 
  the 
  oyster 
  is 
  immovably 
  fixed 
  upon 
  the 
  

   bottom, 
  and 
  has 
  no 
  arms 
  or 
  other 
  structures 
  for 
  seizing 
  food 
  and 
  carrying 
  it 
  to 
  the 
  

   mouth, 
  the 
  question 
  how 
  it 
  obtains 
  its 
  food 
  at 
  once 
  suggests 
  itself. 
  If 
  a 
  fragment 
  of 
  

   one 
  of 
  the 
  gills 
  is 
  examined 
  with 
  a 
  microscope 
  it 
  will 
  be 
  found 
  to 
  be 
  covered 
  with 
  very 
  

   small 
  hairs, 
  or 
  cilia, 
  arranged 
  in 
  rows, 
  plate 
  viii, 
  fig. 
  3, 
  c. 
  Each 
  of 
  these 
  cilia 
  is 
  

   constantly 
  swinging 
  back 
  and 
  forth 
  with 
  a 
  motion 
  somethiug 
  like 
  that 
  of 
  an 
  oar 
  in 
  

   rowing. 
  The 
  motion 
  is 
  quick 
  and 
  strong 
  in 
  one 
  direction 
  and 
  slower 
  in 
  the 
  other. 
  

   As 
  all 
  the 
  cilia 
  of 
  a 
  row 
  swing 
  together 
  they 
  act 
  like 
  a 
  line 
  of 
  oars, 
  only 
  they 
  are 
  

   fastened 
  to 
  the 
  gill, 
  and 
  as 
  this 
  is 
  immovable 
  they 
  do 
  not 
  move 
  forward 
  through 
  the 
  

   water, 
  but 
  produce 
  a 
  current 
  of 
  water 
  in 
  the 
  opposite 
  direction. 
  This 
  action 
  is 
  not 
  

   directed 
  by 
  the 
  animal, 
  for 
  it 
  can 
  be 
  observed 
  for 
  hours 
  in 
  a 
  fragment 
  cut 
  out 
  of 
  

   the 
  gill, 
  and 
  if 
  such 
  a 
  fragment 
  bo 
  supplied 
  with 
  fresh 
  sea 
  water 
  the 
  motion 
  will 
  

   continue 
  until 
  it 
  begins 
  to 
  decay. 
  While 
  the 
  oyster 
  lies 
  undisturbed 
  on 
  the 
  bottom, 
  

   with 
  its 
  muscle 
  relaxed 
  and 
  its 
  shell 
  open, 
  the 
  sea 
  water 
  is 
  drawn 
  on 
  to 
  the 
  gills 
  by 
  

   the 
  action 
  of 
  the 
  cilia, 
  for 
  although 
  each 
  cilium 
  is 
  too 
  small 
  to 
  be 
  seen 
  without 
  a 
  

   microscope, 
  they 
  cover 
  the 
  gills 
  in 
  such 
  great 
  numbers 
  that 
  their 
  united 
  action 
  pro- 
  

   duces 
  quite 
  a 
  vigorous 
  stream 
  of 
  water, 
  which 
  is 
  drawn 
  through 
  the 
  shell 
  and 
  is 
  then 
  

   forced" 
  through 
  vei-y 
  small 
  openings 
  on 
  the 
  surlaces 
  of 
  the 
  gills 
  into 
  the 
  water 
  tubes 
  

   inside 
  the 
  gills, 
  and 
  through 
  these 
  tubes 
  into 
  the 
  cavity 
  above 
  them, 
  and 
  so 
  out 
  of 
  

   the 
  shell 
  again. 
  As 
  the 
  stream 
  of 
  water 
  passes 
  through 
  the 
  gills 
  the 
  blood 
  is 
  aerated 
  

   by 
  contact 
  with 
  it. 
  

  

  The 
  food 
  of 
  the 
  oyster 
  consists 
  entirely 
  of 
  minute 
  animal 
  and 
  vegetable 
  organisms 
  

   and 
  small 
  particles 
  of 
  organized 
  matter. 
  Ordinary 
  sea 
  water 
  contains 
  an 
  abundance 
  

   of 
  this 
  sort 
  of 
  food, 
  which 
  is 
  drawn 
  into 
  the 
  gills 
  with 
  the 
  water, 
  but 
  as 
  the 
  water 
  

   strains 
  through 
  the 
  pores 
  into 
  the 
  water 
  tubes 
  the 
  food 
  particles 
  are 
  caught 
  on 
  the 
  

   surface 
  of 
  the 
  gills 
  by 
  a 
  layer 
  of 
  adhesive 
  slime, 
  which 
  covers 
  all 
  the 
  soft 
  parts 
  of 
  

   the 
  body. 
  As 
  soon 
  as 
  they 
  are 
  entangled 
  the 
  cilia 
  strike 
  against 
  them 
  in 
  such 
  a 
  way 
  

   as 
  to 
  roll 
  or 
  slide 
  them 
  along 
  the 
  gills 
  toward 
  the 
  mouth. 
  When 
  they 
  reach 
  the 
  

   anterior 
  ends 
  of 
  the 
  gills 
  they 
  are 
  pushed 
  oif 
  and 
  fall 
  between 
  the 
  lips, 
  and 
  these 
  

   again 
  are 
  covered 
  with 
  cilia, 
  which 
  carry 
  the 
  particles 
  forward 
  until 
  they 
  slide 
  

   into 
  the 
  mouth, 
  which 
  is 
  always 
  wide 
  open 
  and 
  ciliated, 
  so 
  as 
  to 
  draw 
  the 
  food 
  

   through 
  the 
  a^sophagus 
  into 
  the 
  stomach. 
  Whenever 
  the 
  shell 
  is 
  ojien 
  these 
  cilia 
  

   are 
  in 
  action, 
  and 
  as 
  long 
  as 
  the 
  oyster 
  is 
  breathing 
  a 
  current 
  of 
  food 
  is 
  sliding 
  into 
  

   its 
  mouth. 
  

  

  The 
  cilia 
  and 
  particles 
  of 
  food 
  are 
  too 
  small 
  to 
  be 
  seen 
  without 
  a 
  microscope, 
  but 
  

   if 
  finely 
  ])owdered 
  carmine 
  be 
  sprinkled 
  over 
  the 
  gills 
  of 
  a 
  fresh 
  oyster, 
  which 
  has 
  

   been 
  carefully 
  opened 
  and 
  placed 
  in 
  a 
  shallow 
  dish 
  of 
  sejf 
  water, 
  careful 
  observation 
  

   will 
  show 
  that 
  as 
  soon 
  as 
  the 
  colored 
  particles 
  touch 
  the 
  gills 
  they 
  begin 
  to 
  slide 
  

   along 
  with 
  a 
  motion 
  which 
  is 
  quite 
  uniform, 
  but 
  not 
  much 
  faster 
  than 
  that 
  of 
  the 
  

   minute-hand 
  of 
  a 
  watch. 
  This 
  slow, 
  steady, 
  gliding 
  motion, 
  without 
  any 
  visible 
  

  

  