﻿188 
  REPORT 
  OF 
  COMMISSIONER 
  OF 
  FISH 
  AND 
  FISHERIES. 
  

  

  Protozoa. 
  — 
  On 
  man}^ 
  fry 
  are 
  found, 
  more 
  or 
  less 
  abundantly, 
  speci- 
  

   mens 
  of 
  the 
  stalked 
  protozoan, 
  Ephelota 
  coronata 
  Strethill 
  Wright. 
  

   This 
  protozoan 
  was 
  observed 
  on 
  fry 
  at 
  Woods 
  Hole 
  on 
  June 
  17 
  and 
  July 
  

   3, 
  1902, 
  and 
  was 
  probably 
  more 
  or 
  less 
  abundant 
  throughout 
  the 
  season. 
  

   At 
  Wickford 
  it 
  was 
  especially 
  abundant 
  early 
  in 
  July 
  (1-8), 
  sometimes 
  

   as 
  many 
  as 
  %'^-) 
  individuals 
  being 
  found 
  on 
  one 
  fr3^ 
  

  

  Ormtacea. 
  — 
  ^One 
  specimen 
  of 
  a 
  tube-dwelling 
  amphipod 
  was 
  observed 
  

   at 
  Woods 
  Hole 
  on 
  the 
  ])ack 
  of 
  the 
  carapace 
  of 
  a 
  fry 
  in 
  the 
  fourth 
  stage. 
  

   (PI. 
  IV, 
  tig. 
  5.) 
  In 
  no 
  case 
  were 
  the 
  algae, 
  protozoa, 
  or 
  Crustacea 
  so 
  

   abundant 
  that 
  they 
  caused 
  any 
  serious 
  inconvenience 
  to 
  the 
  fry. 
  

  

  SUGGESTIONS 
  FOR 
  THE 
  PREVENTION 
  OF 
  THE 
  GROWTH 
  OF 
  DIATOMS 
  ON 
  

  

  THE 
  FRY. 
  

  

  As 
  will 
  be 
  seen 
  from 
  a 
  consideration 
  of 
  the 
  foregoing 
  facts, 
  the 
  

   successful 
  rearing 
  of 
  lobster 
  fr}^ 
  depends 
  to 
  a 
  large 
  extent 
  on 
  the 
  

   discovery 
  of 
  some 
  method 
  of 
  combating 
  or 
  getting 
  rid 
  of 
  the 
  growth 
  

   of 
  diatoms. 
  The 
  following 
  suggestions 
  are 
  derived 
  from 
  these 
  

   observations: 
  

  

  Filtering 
  the 
  water 
  in 
  which 
  the 
  fry 
  are 
  kept. 
  — 
  This 
  method 
  of 
  

   removing 
  diatoms 
  could 
  of 
  com-se 
  be 
  applied 
  only 
  to 
  the 
  water 
  in 
  the 
  

   hatching 
  jars; 
  it 
  would 
  l)e 
  a 
  practical 
  impossibility 
  to 
  filter 
  the 
  water 
  

   in 
  which 
  the 
  f 
  r}^ 
  are 
  kept 
  in 
  the 
  rearing 
  apparatus. 
  Inasmuch 
  as 
  we 
  

   have 
  learned 
  that 
  the 
  troublesome 
  species 
  of 
  diatoms 
  are 
  present 
  in 
  

   the 
  water 
  as 
  it 
  flows 
  into 
  the 
  hatchery, 
  however, 
  and 
  that 
  in 
  many 
  

   cases 
  the 
  diatoms 
  become 
  well 
  established 
  on 
  the 
  fr}" 
  before 
  the 
  latter 
  

   are 
  removed 
  from 
  the 
  jars, 
  it 
  would 
  certainly 
  retard 
  and 
  to 
  a 
  large 
  

   extent 
  prevent 
  the 
  rapid 
  growth 
  of 
  diatoms 
  during 
  the 
  tirst 
  molts 
  of 
  

   the 
  fry 
  if 
  the 
  water 
  supplied 
  to 
  the 
  hatching 
  jars 
  were 
  filtered. 
  No 
  

   very 
  elaborate 
  filter 
  would 
  be 
  required. 
  It 
  would 
  not 
  be 
  necessary 
  to 
  

   remove 
  the 
  smallest 
  organisms, 
  such 
  as 
  bacteria, 
  though 
  this 
  would 
  

   certainly 
  be 
  an 
  advantage 
  for 
  other 
  i-easons. 
  Experiment 
  would 
  

   determine 
  the 
  sort 
  of 
  a 
  filter 
  required. 
  It 
  might 
  be 
  that 
  a 
  settling 
  

   basin. 
  would 
  be 
  all 
  that 
  is 
  necessary 
  for 
  the 
  removal 
  of 
  both 
  diatoms 
  

   and 
  their 
  spores. 
  

  

  Selection 
  of 
  other 
  localities 
  for 
  the 
  rearing 
  apparatus. 
  — 
  Experi- 
  

   mental 
  rearing 
  of 
  the 
  fry 
  has 
  been 
  practiced 
  at 
  but 
  few 
  localities 
  — 
  

   Orrs 
  Island, 
  Me., 
  Annisquam, 
  Mass., 
  Gloucester, 
  Mass., 
  Woods 
  Hole, 
  

   Mass., 
  and 
  Wickford, 
  R. 
  I. 
  Diatoms 
  occurred 
  in 
  all 
  these 
  localities, 
  

   but 
  were 
  somewhat 
  less 
  abundant 
  at 
  Annisquam 
  and 
  Wickford. 
  

   Whether 
  this 
  was 
  due 
  to 
  a 
  difl:'erence 
  in 
  the 
  temperature 
  of 
  the 
  water 
  — 
  

   the 
  temperature 
  at 
  Annisquam 
  and 
  Wickford 
  was 
  somewhat 
  higher 
  

   than 
  at 
  the 
  other 
  localities 
  — 
  or 
  to 
  other 
  conditions, 
  can 
  be 
  determined 
  

   onlv 
  by 
  experiment. 
  It 
  may 
  be 
  that 
  there 
  are 
  other 
  places 
  along 
  

   the 
  coast 
  where 
  greater 
  differences 
  of 
  temperature 
  or 
  other 
  local 
  con- 
  

  

  