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  the 
  body, 
  are 
  covered 
  with 
  cilia, 
  so 
  that 
  food 
  once 
  fairly 
  

   in 
  the 
  mouth 
  will 
  be 
  carried 
  by 
  their 
  action 
  down 
  to 
  the 
  

   cavity 
  of 
  the 
  stomach, 
  where 
  it 
  is 
  carried 
  into 
  the 
  folds 
  

   and 
  deep 
  pouches 
  in 
  its 
  walls 
  and 
  even 
  into 
  the 
  openings 
  

   of 
  the 
  bile 
  ducts, 
  to 
  undergo 
  digestion 
  or 
  solution, 
  so 
  as 
  

   to 
  be 
  fitted 
  in 
  its 
  passage 
  through 
  the 
  intestine, 
  to 
  be 
  

   taken 
  into 
  the 
  circulation, 
  and 
  finally 
  disposed 
  of 
  in 
  

   building 
  up 
  the 
  structures 
  of 
  the 
  body. 
  

  

  Along 
  with 
  the 
  food 
  which 
  is 
  taken, 
  a 
  very 
  laige 
  

   amount 
  of 
  undigestible 
  dirt 
  or 
  inorganic 
  matter 
  is 
  car- 
  

   ried 
  in. 
  which 
  in 
  a 
  great 
  measure 
  fills 
  up 
  the 
  intestine 
  

   together 
  with 
  tlie 
  refuse 
  or 
  waste 
  fi-om 
  the 
  body. 
  This 
  

   material, 
  when 
  examined, 
  reveals 
  the 
  fact 
  that 
  the 
  oyster 
  

   subsists 
  largely 
  on 
  diatoms, 
  a 
  low 
  tyj^e 
  of 
  moving 
  plants 
  

   which 
  swim 
  about 
  in 
  the 
  water 
  encased 
  in 
  minute 
  sand- 
  

   stone 
  cases 
  or 
  boxes 
  of 
  the 
  most 
  delicate 
  beauty 
  of 
  work- 
  

   manship. 
  These, 
  when 
  found 
  in 
  the 
  intestine, 
  have 
  

   usually 
  had 
  their 
  living 
  contents 
  dissolved 
  out 
  by 
  the 
  

   action 
  of 
  the 
  digestive 
  juices 
  of 
  the 
  stomach. 
  I 
  have 
  

   found 
  in 
  our 
  owm 
  species 
  of 
  oyster 
  the 
  shells 
  of 
  three 
  

   different 
  genera 
  of 
  diatoms, 
  viz. 
  : 
  Campylodiscus, 
  Cosci- 
  

   nodismis 
  and 
  Navicula. 
  The 
  first 
  is 
  a 
  singularly 
  bent 
  

   form 
  ; 
  the 
  second 
  is 
  discoidal, 
  and 
  the 
  last 
  boat-shaped, 
  

   and 
  all 
  are 
  beautifully 
  marked. 
  Of 
  these 
  three 
  types, 
  I 
  

   saw 
  a 
  number 
  of 
  species, 
  especially 
  of 
  the 
  latter, 
  but 
  as 
  I 
  

   was 
  not 
  an 
  authority 
  upon 
  the 
  systematic 
  history 
  of 
  any 
  

   of 
  them, 
  I 
  had 
  to 
  neglect 
  the 
  determination 
  of 
  the 
  species. 
  

   No 
  doubt 
  many 
  more 
  forms 
  are 
  taken 
  as 
  food 
  by 
  the 
  

   oyster, 
  since 
  I 
  saw 
  other 
  forms 
  in 
  which 
  the 
  living 
  matter 
  

   inside 
  the 
  silicious 
  cases 
  was 
  brown, 
  the 
  same 
  as 
  in 
  most 
  

   of 
  the 
  preceding 
  forms, 
  Avhich 
  I 
  have 
  indicated. 
  Some 
  

   of 
  these 
  brown 
  forms 
  Avere 
  so 
  plentiful 
  as 
  to 
  color 
  a 
  con- 
  

   siderable 
  surface 
  whereon 
  they 
  grew, 
  of 
  the 
  same 
  tint 
  as 
  

   themselves. 
  But 
  in 
  no 
  instance 
  have 
  I 
  found 
  any 
  indi- 
  

   cations 
  of 
  the 
  animal 
  of 
  the 
  oyster 
  becoming 
  colored 
  by 
  

   feeding 
  on 
  these 
  diatoms, 
  as 
  it 
  is 
  said 
  the 
  Euroj)ean 
  

   oyster 
  does 
  when 
  feeding 
  on 
  Namcula 
  ostrearla, 
  which 
  

  

  