﻿254 
  REPORT 
  OF 
  COMMISSIONER 
  OF 
  FISH 
  AND 
  FISHERIES. 
  

  

  whereas 
  the 
  latter 
  would. 
  (3) 
  Copepods 
  and 
  other 
  small 
  crustacea, 
  

   and 
  various 
  larval 
  forms 
  which 
  are 
  so 
  very 
  common 
  at 
  times 
  in 
  all 
  

   salt 
  and 
  brackish 
  waters, 
  forni 
  no 
  appreciable 
  part 
  of 
  the 
  oyster's 
  diet, 
  

   yet 
  these 
  would 
  be 
  included 
  in 
  a 
  chemical 
  analysis. 
  (4) 
  While 
  an 
  

   oyster 
  depends 
  wholly 
  upon 
  what 
  the 
  currents 
  bring 
  within 
  reach 
  of 
  

   its 
  cilia, 
  it 
  does 
  not 
  passively 
  accept 
  all 
  that 
  is 
  brought. 
  I 
  have 
  

   abundant 
  reason 
  for 
  believing 
  that 
  the 
  oyster 
  possesses 
  a 
  limited 
  

   amount 
  of 
  selective 
  power 
  in 
  feeding 
  and 
  is 
  able 
  in 
  a 
  measure 
  to 
  dis- 
  

   card 
  objectionable 
  forms. 
  Very 
  active 
  creatures, 
  like 
  small 
  Crustacea 
  

   and 
  larviB, 
  are 
  seldom 
  caught, 
  being 
  able 
  to 
  free 
  themselves 
  from 
  the 
  

   incurrent 
  streams 
  of 
  water 
  set 
  up 
  by 
  the 
  ciliary 
  movements 
  of 
  the 
  

   oyster. 
  

  

  From 
  the 
  above 
  facts 
  it 
  can 
  be 
  readily 
  seen 
  that 
  before 
  any 
  deter- 
  

   mination 
  of 
  the 
  food 
  value 
  of 
  the 
  water 
  of 
  a 
  certain 
  locality 
  can 
  be 
  

   made 
  it 
  must 
  be 
  known 
  what 
  forms 
  existing 
  there 
  constitute 
  the 
  

   oyster's 
  diet, 
  and 
  the 
  conclusions 
  must 
  be 
  based 
  upon 
  the 
  abundance 
  

   of 
  these 
  forms 
  and 
  not 
  upon 
  the 
  abundance 
  of 
  organic 
  forms 
  in 
  gen- 
  

   eral. 
  The 
  method 
  followed 
  in 
  these 
  investigations, 
  which 
  proves 
  to 
  

   be 
  fairly 
  accurate, 
  was 
  carried 
  out 
  as 
  follows: 
  A 
  liter 
  of 
  water 
  was 
  

   carefully 
  collected 
  1 
  foot 
  from 
  the 
  bottom 
  in 
  the 
  locality 
  under 
  con- 
  

   sideration. 
  This 
  was 
  done 
  by 
  lashing 
  a 
  bottle 
  of 
  1 
  liter 
  capacity 
  1 
  

   foot 
  from 
  the 
  end 
  of 
  a 
  pole. 
  When 
  the 
  pole 
  was 
  thrust 
  to 
  the 
  bottom 
  

   the 
  cork 
  was 
  drawn 
  by 
  a 
  string 
  attached 
  to 
  it, 
  and 
  when 
  the 
  bottle 
  

   had 
  filled 
  it 
  was 
  brought 
  to 
  the 
  surface 
  and 
  unlashed, 
  recorked, 
  and 
  

   labeled. 
  A 
  number 
  of 
  oysters 
  were 
  then 
  tonged 
  from 
  the 
  same 
  locality" 
  

   and 
  three 
  were 
  chosen 
  which 
  had 
  a 
  length 
  of 
  not 
  less 
  than 
  3 
  and 
  not 
  

   more 
  than 
  4 
  inches. 
  The 
  contents 
  of 
  their 
  stomachs 
  were 
  removed 
  by 
  

   means 
  of 
  a 
  medicine 
  dropper 
  thrust 
  into 
  the 
  stomach 
  after 
  one 
  shell 
  

   had 
  been 
  removed, 
  a 
  very 
  simple 
  process 
  when 
  the 
  position 
  of 
  the 
  

   stomach 
  is 
  known. 
  The 
  stomach 
  contents 
  were 
  examined 
  as 
  soon 
  

   after 
  removal 
  as 
  practicable. 
  The 
  amount 
  taken 
  from 
  three 
  oysters 
  

   was 
  found 
  to 
  be 
  seldom 
  more 
  than 
  10 
  cc. 
  When 
  less, 
  water 
  was 
  added; 
  

   when 
  more, 
  it 
  was 
  allowed 
  to 
  settle 
  and 
  the 
  clear 
  surface 
  liquid 
  was 
  

   removed, 
  the 
  examination 
  thus 
  beginning 
  each 
  time 
  with 
  10 
  cc. 
  of 
  

   the 
  food 
  solution. 
  This 
  liquid 
  was 
  violently 
  shaken 
  in 
  a 
  bottle 
  and 
  

   1 
  cc. 
  quickly 
  removed 
  and 
  put 
  into 
  a 
  Rafter 
  cell,^ 
  where 
  it 
  was 
  care- 
  

   fully 
  examined 
  and 
  the 
  number 
  of 
  food 
  forms 
  estimated, 
  the 
  process 
  

   being 
  repeated 
  twice. 
  From 
  the 
  three 
  estimates 
  thus 
  obtained 
  the 
  

   amount 
  of 
  oyster 
  food 
  in 
  the 
  entire 
  10 
  cc. 
  was 
  calculated, 
  and 
  this 
  

   divided 
  by 
  3 
  gave 
  the 
  amount 
  per 
  oyster. 
  

  

  The 
  specimen 
  of 
  water 
  was 
  allowed 
  to 
  stand 
  for 
  eighteen 
  to 
  twenty- 
  

   four 
  hours, 
  until 
  all 
  the 
  sediment 
  and 
  organisms 
  (except 
  small 
  Crusta- 
  

   cea 
  and 
  swimming 
  larvae) 
  had 
  settled 
  and 
  formed 
  a 
  definite 
  layer 
  on 
  

  

  a 
  If 
  it 
  be 
  desired 
  to 
  determine 
  the 
  food 
  resources 
  of 
  a 
  locality 
  in 
  which 
  no 
  oysters 
  are 
  found 
  it 
  is 
  

   only 
  necessary 
  to 
  plant 
  a 
  few 
  oysters 
  a 
  few 
  days 
  before 
  the 
  examination 
  is 
  made. 
  

  

  bThe 
  Rafter 
  cell 
  and 
  the 
  method 
  of 
  using 
  it 
  are 
  described 
  on 
  pages 
  366-367 
  of 
  J. 
  I. 
  Peck's 
  report 
  on 
  

   "The 
  Sources 
  of 
  Marine 
  Food," 
  U. 
  S. 
  F. 
  C. 
  Bull, 
  for 
  1895. 
  

  

  