﻿176 
  REPORT 
  OF 
  COMMISSIONER 
  OF 
  FISH 
  AND 
  FISHERIES. 
  

  

  On 
  the 
  securing 
  of 
  a 
  proper 
  food 
  supply 
  depends 
  not 
  only 
  the 
  pre- 
  

   vention 
  of 
  cannibalism, 
  but 
  also, 
  as 
  we 
  shall 
  see 
  later, 
  what 
  is 
  of 
  far 
  

   more 
  importance 
  — 
  the 
  length 
  of 
  time 
  required 
  to 
  pass 
  through 
  the 
  

   early 
  stages 
  and 
  the 
  escape 
  from 
  the 
  growth 
  of 
  diatoms. 
  

  

  In 
  the 
  experiments 
  at 
  Woods 
  Hole 
  the 
  fry 
  were 
  fed 
  for 
  the 
  most 
  part 
  

   finely 
  chopped 
  lobster 
  liver, 
  clams, 
  and 
  menhaden. 
  None 
  of 
  these 
  

   proved 
  an 
  ideal 
  food; 
  perhaps 
  that 
  of 
  most 
  value 
  was 
  the 
  clams. 
  

   Further 
  experiments 
  to 
  discover 
  a 
  suitable 
  food 
  for 
  the 
  fry 
  are 
  

   greatly 
  to 
  be 
  desired, 
  as 
  on 
  this 
  depends 
  to 
  a 
  large 
  extent 
  the 
  practi- 
  

   cability 
  of 
  rearing 
  the 
  fry 
  at 
  all 
  successfully. 
  A 
  further 
  discussion 
  

   of 
  this 
  important 
  question 
  will 
  be 
  found 
  under 
  a 
  later 
  section 
  of 
  this 
  

   paper. 
  

  

  DIATOMS. 
  

  

  It 
  was 
  the 
  abundant 
  growth 
  of 
  diatoms 
  on 
  the 
  surface 
  of 
  the 
  body 
  

   and 
  on 
  the 
  appendages 
  that 
  first 
  led 
  to 
  a 
  consideration 
  of 
  the 
  causes 
  of 
  

   death 
  of 
  the 
  fry. 
  It 
  was 
  supposed 
  that 
  the 
  growth 
  was 
  a 
  parasitic 
  

   fungus, 
  but 
  microscopic 
  examination 
  soon 
  showed 
  that 
  it 
  was 
  merely 
  

   an 
  external 
  growth 
  of 
  a 
  few 
  protozoa 
  and 
  alga3, 
  and 
  very 
  many 
  diatoms 
  

   of 
  a 
  few 
  well-defined 
  species. 
  These 
  did 
  not 
  at 
  all 
  endanger 
  the 
  life 
  of 
  

   the 
  lobster, 
  except 
  in 
  so 
  far 
  as 
  they 
  were 
  a 
  mechanical 
  obstruction 
  to 
  

   his 
  movements. 
  They 
  did 
  not 
  penetrate 
  his 
  chitinous 
  shell 
  and 
  were 
  

   all 
  thrown 
  ofi' 
  at 
  each 
  molt. 
  

  

  CORRELATION 
  OF 
  THE 
  LIFE 
  HISTORY 
  OF 
  THE 
  FRY 
  AND 
  THE 
  PRESENCE 
  

   OF 
  DIATOMS. 
  

  

  Absence 
  of 
  diatoms 
  on 
  adult 
  lobsters 
  and 
  on 
  eggs 
  lohen 
  attached' 
  to 
  the 
  

   female. 
  — 
  The 
  lobsters 
  and 
  eggs 
  examined 
  came 
  from 
  the 
  immediate 
  

   vicinity 
  of 
  Woods 
  Hole, 
  from 
  Gloucester, 
  Mass., 
  Block 
  Island 
  and 
  

   Narragansett 
  Pier, 
  R. 
  L, 
  and 
  from 
  Noank, 
  Conn., 
  and 
  no 
  diatoms 
  Vv'ere 
  

   found 
  on 
  the 
  adults 
  or 
  on 
  the 
  eggs 
  when 
  attached 
  to 
  the 
  swimmerets 
  

   of 
  the 
  female. 
  On 
  the 
  stalks 
  by 
  which 
  the 
  eggs 
  are 
  attached 
  to 
  the 
  

   appendages 
  of 
  the 
  female 
  there 
  are 
  frequently 
  colonies 
  of 
  a 
  vorticella 
  

   {Zoothamnium 
  elega-ns 
  D'Udekem), 
  but 
  these 
  are 
  seldom 
  found 
  on 
  the 
  

   eggs 
  and 
  never 
  on 
  the 
  fry, 
  and 
  so 
  have 
  no 
  bearing 
  on 
  the 
  problem 
  

   under 
  consideration. 
  

  

  Diatoms 
  on 
  the 
  eggs 
  and 
  fry 
  in 
  the 
  hatcldng-jars. 
  — 
  When 
  the 
  eggs 
  

   are 
  placed 
  in 
  the 
  McDonald 
  hatching-jars 
  the 
  diatoms 
  make 
  their 
  

   appearance 
  within 
  twenty-four 
  hours. 
  The 
  species 
  that 
  first 
  appears, 
  

   in 
  fact 
  the 
  only 
  species 
  that 
  appears 
  on 
  the 
  eggs 
  while 
  in 
  the 
  jars, 
  is 
  

   Licmophora 
  tincta., 
  the 
  one 
  destined 
  to 
  be 
  the 
  most 
  abundant 
  through- 
  

   out 
  the 
  life 
  of 
  the 
  ivy 
  (pi. 
  iv, 
  fig. 
  1). 
  

  

  In 
  cases 
  where 
  the 
  fry 
  hatch 
  within 
  twent3^-four 
  hours 
  after 
  the 
  

   eggs 
  are 
  placed 
  in 
  the 
  jars, 
  some 
  of 
  them, 
  in 
  a 
  few 
  hours 
  after 
  emerg- 
  

   ing 
  from 
  the 
  eggshell, 
  have 
  a 
  considerable 
  number 
  (Itt- 
  25) 
  of 
  diatoms 
  

  

  