﻿[13] 
  DEVELOPMENT 
  OF 
  OSSEOUS 
  FISHES. 
  . 
  r 
  )01 
  

  

  of 
  the 
  bottom 
  of 
  each 
  jar 
  by 
  means 
  of 
  a 
  glass 
  funnel. 
  Beyond 
  au 
  occa 
  

   sional 
  siphoning-off 
  of 
  the 
  sediment 
  on 
  the 
  bottom 
  of 
  the 
  trough 
  and 
  

   the 
  cloth 
  covers 
  of 
  the 
  jars, 
  the 
  eggs 
  require 
  no 
  attention 
  until 
  hatched. 
  

  

  Heretofore 
  great 
  mortality 
  has 
  been 
  caused 
  by 
  the 
  use 
  of 
  metal 
  in 
  the 
  

   construction 
  of 
  hatching 
  vessels 
  and 
  strainers. 
  Since 
  the 
  adoption 
  of 
  

   glass, 
  wood, 
  and 
  cloth 
  as 
  the 
  only 
  materials 
  used 
  in 
  the 
  construction 
  of 
  

   the 
  hatching 
  apparatus 
  here 
  described, 
  combined 
  with 
  the 
  very 
  gentle 
  

   movement 
  to 
  which 
  the 
  eggs 
  are 
  subjected, 
  complete 
  success 
  has 
  been 
  

   attained. 
  The 
  eggs 
  are 
  caused 
  to 
  oscillate 
  up 
  and 
  down 
  through 
  a 
  

   space 
  of 
  only 
  5 
  inches 
  from 
  the 
  level 
  of 
  a 
  to 
  that 
  of 
  b, 
  and, 
  withal, 
  so 
  

   gently 
  that 
  they 
  suffer 
  no 
  hurtful 
  shocks 
  of 
  any 
  kind 
  whatever. 
  Cap- 
  

   tain 
  Chester's 
  device 
  will 
  doubtless 
  be 
  used 
  with 
  great 
  advantage 
  in 
  the 
  

   propagation 
  of 
  the 
  Spanish 
  mackerel. 
  In 
  twenty-four 
  hours 
  the 
  em- 
  

   bryos 
  of 
  the 
  latter 
  would 
  be 
  ready 
  to 
  be 
  set 
  free 
  from 
  the 
  apparatus; 
  

   whereas 
  it 
  requires 
  eleven 
  or 
  twelve 
  days 
  to 
  hatch 
  the 
  eggs 
  of 
  the 
  cod, 
  

   with 
  the 
  temperature 
  of 
  the 
  water 
  ranging 
  from 
  45° 
  to 
  48° 
  Fahr. 
  

  

  Each 
  of 
  the 
  jars 
  J 
  is 
  17 
  inches 
  high 
  by 
  9 
  inches 
  in 
  diameter, 
  and 
  will 
  

   hold 
  from 
  one-half 
  to 
  one 
  million 
  of 
  cod 
  eggs 
  ; 
  so 
  that 
  an 
  apparatus 
  of 
  

   the 
  style 
  shown 
  above, 
  and 
  occupying 
  not 
  much 
  over 
  a 
  square 
  yard 
  of 
  

   space, 
  would 
  accommodate 
  from 
  two 
  to 
  four 
  millions 
  of 
  ova, 
  in 
  four 
  

   jars. 
  

  

  These 
  results 
  and 
  experiments 
  show 
  that 
  violent 
  movement 
  of 
  the 
  

   eggs 
  of 
  the 
  cod 
  is 
  of 
  no 
  advantage; 
  that 
  such 
  movement 
  is, 
  on 
  the 
  con- 
  

   trary, 
  injurious 
  if 
  not 
  mortal 
  when 
  continuously 
  maintained. 
  The 
  

   requisite 
  conditions 
  for 
  the 
  successful 
  hatching 
  of 
  this 
  important 
  food- 
  

   fish 
  having 
  been 
  settled, 
  the 
  great 
  station 
  of 
  the 
  Fish 
  Commission 
  at 
  

   Wood's 
  Holl 
  affords 
  unlimited 
  opportunities 
  for 
  conducting 
  the 
  work 
  

   for 
  at 
  least 
  three 
  months 
  of 
  the 
  year, 
  during 
  which 
  time 
  from 
  five 
  hun- 
  

   dred 
  to 
  one 
  thousand 
  millions 
  of 
  eggs 
  might 
  readily 
  be 
  hatched 
  out 
  by 
  

   the 
  aid 
  of 
  the 
  Chester 
  apparatus 
  and 
  set 
  free 
  in 
  the 
  adjacent 
  waters. 
  

  

  The 
  proper 
  specific 
  gravity 
  of 
  the 
  sea-water 
  has 
  a 
  great 
  deal 
  to 
  do 
  

   with 
  the 
  healthy 
  development 
  of 
  the 
  eggs 
  of 
  the 
  cod. 
  By 
  accident 
  a 
  

   broken 
  valve 
  admitted 
  fresh 
  water 
  to 
  the 
  pumps 
  which 
  supplied 
  our 
  

   salt-water 
  tanks, 
  causing 
  the 
  specific 
  gravity 
  of 
  the 
  water 
  to 
  fall 
  from 
  

   1.0256 
  to 
  1.021 
  or 
  1.022. 
  In 
  the 
  latter 
  densities 
  the 
  eggs 
  immediately 
  

   sank, 
  but 
  rose 
  at 
  once 
  if 
  placed 
  in 
  sea-water 
  of 
  the 
  specific 
  gravity 
  first 
  

   mentioned. 
  The 
  break 
  in 
  the 
  valve 
  through 
  which 
  fresh 
  water 
  was 
  

   added 
  to 
  that 
  which 
  was 
  pumped 
  from 
  the 
  harbor 
  for 
  use 
  in 
  our 
  hatch- 
  

   ing 
  troughs, 
  caused 
  us 
  to 
  lose 
  over 
  two 
  millions 
  of 
  good 
  eggs. 
  After 
  

   this 
  unfortunate 
  experience, 
  and 
  also 
  judging 
  from 
  the 
  fact 
  that 
  ever 
  

   since 
  the 
  break 
  in 
  the 
  valve 
  has 
  been 
  mended 
  no 
  eggs 
  have 
  sunk 
  or 
  

   subsided 
  to 
  the 
  bottom, 
  we 
  have 
  concluded 
  that 
  the 
  cod 
  egg, 
  in 
  order 
  

   that 
  it 
  may 
  develop 
  normally, 
  must 
  float 
  at 
  or 
  near 
  the 
  surface. 
  Under 
  

   no 
  other 
  conditions 
  does 
  it 
  seem 
  possible 
  to 
  get 
  them 
  to 
  develop 
  regu- 
  

   larly 
  and 
  without 
  serious 
  losses. 
  

  

  It 
  was 
  also 
  found 
  in 
  the 
  course 
  of 
  subsequent 
  experience 
  that 
  the 
  

   constant 
  flow 
  of 
  cold 
  water 
  around 
  the 
  jars 
  immersed 
  in 
  the 
  troughs 
  

  

  