﻿150 
  REPORT 
  OF 
  COMMISSIONER 
  OF 
  FISH 
  AND 
  FISHERIES. 
  

  

  The 
  overflow 
  from 
  tbe 
  collectors 
  is 
  guarded 
  by 
  a 
  wire- 
  gauze 
  or 
  cbeese- 
  

   cloth 
  strainer. 
  A 
  safe 
  and 
  iutercliaugeable 
  device 
  consists 
  of 
  a 
  stout 
  

   wire 
  frame, 
  over 
  whicli 
  a 
  cheese-cloth 
  bag 
  is 
  drawn 
  and 
  tied. 
  A 
  

   3 
  inch 
  rubber 
  hose 
  is 
  attached 
  to 
  the 
  opening 
  in 
  the 
  frame. 
  The 
  

   strainer 
  is 
  put 
  inside 
  among 
  tlie 
  fry, 
  and 
  the 
  outflow 
  in 
  an 
  overflow 
  cup. 
  

   The 
  overflow 
  cup 
  is 
  set 
  at 
  the 
  proper 
  height 
  to 
  control 
  the 
  water 
  level 
  

   in 
  the 
  collector-tank. 
  Long-handled 
  nets 
  of 
  fsrinch 
  mesh 
  are 
  required 
  

   to 
  remove 
  egg 
  lumps 
  or 
  other 
  matter 
  from 
  the 
  jars. 
  

  

  THE 
  AUTOMATIC 
  HATCHING- 
  JAR. 
  

  

  The 
  United 
  States 
  Fish 
  Commission, 
  in 
  the 
  development 
  of 
  its 
  

   work, 
  had 
  presented 
  to 
  it 
  the 
  necessity 
  of 
  dealing 
  with 
  the 
  eggs 
  of 
  the 
  

  

  whiteflsh 
  and 
  the 
  shad 
  upon 
  a 
  

   scale 
  unprecedented 
  in 
  the 
  his- 
  

   tory 
  of 
  fish-culture. 
  Millions 
  

   were 
  to 
  be 
  handled 
  instead 
  of 
  

   thousands, 
  and 
  the 
  removal 
  of 
  

   dead 
  eggs 
  by 
  hand 
  picking 
  was 
  

   no 
  longer 
  to 
  be 
  considered. 
  

   After 
  successive 
  experiments 
  

   the 
  McDonald 
  automatic 
  hatch- 
  

   ing-jar 
  was 
  devised, 
  and 
  it 
  is 
  

   now 
  generally 
  employed. 
  

  

  The 
  most 
  meritorious 
  feature 
  

   of 
  this 
  apparatus 
  is 
  that 
  it 
  

   prevents 
  the 
  development 
  of 
  

   the 
  saprolegnious 
  fungus, 
  which 
  

   caused 
  so 
  great 
  a 
  mortality 
  in 
  

   some 
  other 
  forms 
  of 
  hatching 
  

   contrivances 
  in 
  which 
  all 
  the 
  ova 
  

   were 
  not 
  in 
  continual 
  movement. 
  

   The 
  very 
  gradual, 
  gentle, 
  and 
  

   continual 
  rolling 
  movement 
  of 
  

   the 
  ova 
  upon 
  each 
  other 
  in 
  the 
  

   jar 
  api^arently 
  i)re 
  vents 
  the 
  

   spores 
  of 
  the 
  fungus 
  from 
  ad- 
  

  

  Automatic 
  shad-hatching 
  jar. 
  

  

  hering. 
  The 
  cleanliness 
  of 
  the 
  apparatus 
  is 
  also 
  advantageous, 
  and 
  as 
  

   the 
  material 
  of 
  which 
  it 
  is 
  made 
  is 
  glass, 
  the 
  progress 
  of 
  development 
  

   can 
  be 
  watched 
  satisfactorily 
  from 
  the 
  outside 
  of 
  the 
  jar 
  with 
  a 
  hand 
  

   glass 
  or 
  pocket 
  lens 
  of 
  moderate 
  power. 
  

  

  The 
  jar 
  consists 
  of 
  a 
  cylindrical 
  glass 
  vessel, 
  of 
  7 
  quarts' 
  capacity, 
  

   with 
  hemispherical 
  bottom, 
  supported 
  upon 
  three 
  glass 
  legs. 
  The 
  top 
  

   is 
  made 
  with 
  threads 
  to 
  receive 
  a 
  screw-cap. 
  It 
  is 
  closed 
  by 
  a 
  metallic 
  

   disk, 
  i^erforated 
  with 
  two 
  holes 
  five-eighths 
  inch 
  in 
  diameter 
  — 
  one 
  in 
  

   the 
  center 
  admits 
  the 
  glass 
  tube 
  that 
  introduces 
  the 
  water 
  into 
  the 
  

   jar, 
  the 
  other, 
  equally 
  distant 
  from 
  the 
  central 
  hole 
  and 
  the 
  edge 
  of 
  

  

  