﻿MANUAL 
  OF 
  FISH-CULTURE. 
  217 
  

  

  of 
  the 
  milt 
  they 
  are 
  cleauetl 
  and 
  the 
  superfluous 
  milt 
  washed 
  off 
  by 
  

   introducing 
  a 
  gentle 
  stream 
  of 
  water 
  into 
  the 
  bag 
  and 
  rolling 
  the 
  eggs 
  

   from 
  side 
  to 
  side. 
  

  

  It 
  frequently 
  happens 
  that 
  fish 
  held 
  in 
  tanks 
  to 
  mature 
  deposit 
  their 
  

   eggs 
  during 
  the 
  night. 
  In 
  such 
  cases 
  the 
  eggs 
  are 
  found 
  on 
  the 
  bottom 
  

   of 
  the 
  tank 
  the 
  next 
  morning. 
  They 
  are 
  usually 
  in 
  clusters 
  and 
  when 
  

   examined 
  with 
  the 
  microscope 
  it 
  will 
  be 
  found 
  that 
  practically 
  every 
  

   egg 
  is 
  fertilized. 
  

  

  After 
  the 
  eggs 
  have 
  been 
  taken 
  and 
  fertilized 
  the 
  number 
  is 
  calcu- 
  

   lated 
  by 
  measuring 
  in 
  a 
  glass 
  graduate 
  and 
  computing 
  47,8l'G 
  eggs 
  

   to 
  the 
  liquid 
  ounce. 
  The 
  average 
  number 
  of 
  eggs 
  is 
  about 
  500,000 
  to 
  

   a 
  fish. 
  On 
  March 
  6, 
  1897, 
  30 
  ounces, 
  or 
  1 
  ,462,000 
  eggs, 
  were 
  taken 
  

   from 
  a 
  fish 
  20 
  inches 
  long 
  and 
  11 
  inches 
  wide, 
  its 
  weight 
  being 
  3 
  J 
  

   pounds 
  after 
  the 
  eggs 
  were 
  taken. 
  

  

  Flatfish 
  eggs 
  may 
  be 
  hatched 
  in 
  several 
  kinds 
  of 
  apparatus, 
  but 
  the 
  

   Chester 
  jar 
  is 
  most 
  used, 
  in 
  combination 
  with 
  the 
  McDonald 
  tidal 
  box 
  

   employed 
  in 
  incubating 
  cod 
  eggs. 
  From 
  400,000 
  to 
  500,000 
  eggs 
  are 
  

   usually 
  placed 
  in 
  each 
  jar. 
  The 
  top 
  of 
  the 
  jar 
  is 
  covered 
  with 
  cheese- 
  

   cloth 
  held 
  in 
  place 
  by 
  rubber 
  bands. 
  The 
  jar 
  Is 
  then 
  inverted 
  and 
  

   placed 
  in 
  a 
  tidal 
  box. 
  The 
  usual 
  complement 
  of 
  each 
  box 
  is 
  2 
  jars. 
  A 
  

   wooden 
  frame 
  of 
  1-inch 
  strips 
  is 
  placed 
  lengthwise 
  on 
  the 
  bottom 
  of 
  

   the 
  box 
  for 
  the 
  jars 
  to 
  rest 
  on, 
  so 
  as 
  to 
  raise 
  them 
  and 
  allow 
  the 
  free 
  

   circulation 
  of 
  the 
  water. 
  A 
  hole 
  in 
  the 
  bottom 
  of 
  the 
  jar 
  allows 
  the 
  

   air 
  to 
  pass 
  in 
  and 
  out 
  as 
  the 
  water 
  inside 
  rises 
  and 
  falls. 
  The 
  inner 
  

   compartment, 
  with 
  a 
  bottom 
  of 
  cheese-cloth, 
  used 
  in 
  cod-hatching 
  is 
  

   omitted. 
  

  

  As 
  in 
  using 
  the 
  jars 
  the 
  eggs 
  are 
  generally 
  on 
  the 
  bottom 
  all 
  the 
  

   time, 
  the 
  experiment 
  has 
  been 
  tried 
  of 
  employing 
  the 
  McDonald 
  box 
  

   with 
  the 
  automatic 
  current 
  in 
  order 
  to 
  keep 
  the 
  eggs 
  in 
  circulation. 
  It 
  

   having 
  been 
  found 
  that 
  the 
  current 
  commonly 
  used 
  for 
  cod 
  eggs 
  caused 
  

   the 
  eggs 
  to 
  pile 
  up 
  in 
  the 
  end 
  nearest 
  the 
  outlet, 
  a 
  stream 
  was 
  intro- 
  

   duced 
  into 
  each 
  end 
  of 
  the 
  box 
  and 
  the 
  water 
  was 
  allowed 
  to 
  escape 
  in 
  

   all 
  directions 
  through 
  a 
  perforated 
  nozzle; 
  the 
  water 
  was 
  kept 
  about 
  3 
  

   inches 
  deep 
  in 
  the 
  bottom 
  of 
  the 
  box 
  by 
  using 
  a 
  quantity 
  sufficient 
  to 
  

   prevent 
  the 
  breakiiig 
  of 
  the 
  siphon. 
  By 
  this 
  means 
  a 
  constant 
  current 
  

   is 
  formed, 
  the 
  eggs 
  develop 
  nicely, 
  and 
  the 
  fry 
  hatch, 
  but 
  the 
  current 
  

   necessary 
  to 
  keep 
  the 
  eggs 
  in 
  circulation 
  is 
  strong 
  enough 
  to 
  kill 
  the 
  

   fry 
  by 
  forcing 
  them 
  against 
  the 
  sides 
  of 
  the 
  box. 
  This 
  experiment 
  is 
  

   therefore 
  not 
  considered 
  a 
  success. 
  

  

  The 
  period 
  of 
  incubation 
  wlien 
  the 
  mean 
  water 
  temperature 
  is 
  37° 
  or 
  

   38° 
  F. 
  is 
  17 
  or 
  18 
  days. 
  

  

  The 
  fry 
  of 
  the 
  flatfish, 
  although 
  much 
  smaller 
  than 
  those 
  of 
  the 
  cod, 
  

   are 
  much 
  more 
  lively, 
  and 
  are 
  straightened 
  out 
  when 
  first 
  hatched. 
  

   Unlike 
  the 
  young 
  cod, 
  they 
  do 
  not 
  float 
  on 
  the 
  surfiice, 
  but 
  are 
  scat- 
  

   tered 
  through 
  the 
  water 
  from 
  top 
  to 
  bottom, 
  many 
  being 
  seen 
  among 
  

   the 
  eggs 
  on 
  the 
  bottom 
  of 
  the 
  jars. 
  Unlike 
  the 
  adults, 
  the 
  flatfish 
  fry 
  

  

  