﻿LOBSTER 
  AND 
  CLAM 
  INVESTIGATIONS. 
  189 
  

  

  ditions 
  might 
  still 
  further 
  reduce 
  the 
  growth 
  of 
  diatoms; 
  the 
  possi- 
  

   bility 
  of 
  finding 
  such 
  a 
  place 
  warrants 
  a 
  series 
  of 
  trials 
  in 
  several 
  

   localities. 
  It 
  must 
  be 
  borne 
  in 
  mind, 
  however, 
  that 
  Woods 
  Hole 
  fry 
  

   when 
  they 
  come 
  from 
  the 
  hatchery 
  are 
  infected 
  with 
  the 
  diatoms 
  and 
  

   that 
  they 
  are 
  liable 
  to 
  introduce 
  these 
  diatoms 
  to 
  any 
  locality 
  where 
  

   such 
  an 
  experiment 
  is 
  tried. 
  Fry 
  from 
  Gloucester, 
  on 
  the 
  other 
  

   hand, 
  are 
  apparently 
  free 
  from 
  infection 
  when 
  they 
  come 
  from 
  the 
  

   hatchery. 
  

  

  Changes 
  in 
  the 
  rearing 
  apparatus. 
  — 
  There 
  is 
  no 
  doubt 
  but 
  that 
  the 
  

   scrim 
  bags 
  are 
  to 
  a 
  large 
  extent 
  responsible 
  for 
  the 
  rapid 
  growth 
  of 
  

   diatoms 
  on 
  the 
  fry. 
  As 
  has 
  already 
  been 
  shown, 
  the 
  bags 
  rapidl})^ 
  

   become 
  foul 
  from 
  a 
  growth 
  of 
  diatoms 
  and 
  other 
  organisms 
  filtered 
  

   out 
  of 
  the 
  water 
  as 
  it 
  passes 
  through 
  them. 
  The 
  fry 
  are 
  continually 
  

   coming 
  in 
  contact 
  with 
  the 
  bags, 
  and 
  the 
  diatoms, 
  being 
  easily 
  dis- 
  

   lodged, 
  readily 
  become 
  attached 
  to 
  the 
  feathery 
  appendages 
  of 
  the 
  

   fry. 
  The 
  use 
  of 
  canvas 
  bags 
  with 
  copper 
  netting 
  windows, 
  as 
  tried 
  at 
  

   Wickford 
  in 
  the 
  experiments 
  of 
  1902, 
  seems 
  to 
  prevent 
  to 
  a 
  large 
  

   extent 
  the 
  rapid 
  fouling 
  of 
  the 
  bags 
  and 
  the 
  consequent 
  growth 
  of 
  

   diatoms 
  on 
  the 
  fry. 
  A 
  more 
  frequent 
  changing 
  of 
  the 
  bags 
  would 
  

   perhaps 
  bring 
  the 
  same 
  result, 
  but 
  this 
  method 
  is 
  hardly 
  practicable. 
  

   Perhaps 
  there 
  is 
  some 
  other 
  material 
  of 
  which 
  the 
  bags 
  might 
  be 
  made 
  

   on 
  which 
  the 
  diatoms 
  would 
  not 
  grow 
  so 
  easily, 
  or 
  there 
  may 
  be 
  some 
  

   preparation, 
  such 
  as 
  tar 
  or 
  oil, 
  with 
  which 
  the 
  bags 
  might 
  be 
  coated, 
  

   that 
  would 
  prevent 
  the 
  attachment 
  of 
  the 
  diatoms. 
  It 
  is 
  certain 
  that 
  

   the 
  cleaner 
  the 
  bags 
  the 
  longer 
  the 
  fry 
  remain 
  free 
  from 
  diatoms. 
  

   If 
  the 
  fry 
  were 
  received 
  clean 
  from 
  the 
  hatchery, 
  or 
  were 
  hatched 
  

   directly 
  in 
  the 
  bags 
  and 
  the 
  bags 
  were 
  kept 
  perfectly 
  clean, 
  there 
  

   would 
  be 
  little 
  trouble 
  from 
  diatoms. 
  

  

  Sunlight 
  and 
  shade. 
  — 
  Diatoms 
  are 
  chlorophyl 
  bearing 
  plants, 
  and 
  

   consequently 
  require 
  sunlight 
  for 
  their 
  best 
  and 
  most 
  rapid 
  develop- 
  

   ment. 
  Might 
  not 
  their 
  growth 
  be 
  restrained 
  b}^ 
  confining 
  the 
  fry 
  in 
  

   bags 
  shielded 
  from 
  the 
  direct 
  light 
  of 
  the 
  sun? 
  Several 
  experiments 
  

   were 
  made 
  to 
  determine 
  this 
  point. 
  On 
  June 
  22, 
  1902, 
  an 
  awning 
  was 
  

   placed 
  about 
  3 
  feet 
  above 
  the 
  level 
  of 
  the 
  vrater 
  over 
  certain 
  bags 
  con- 
  

   taining 
  fry 
  in 
  the 
  first 
  stage. 
  The 
  number 
  of 
  diatoms 
  on 
  the 
  fry 
  under 
  

   the 
  awning 
  steadily 
  decreased, 
  or 
  at 
  most 
  did 
  not 
  develop 
  further 
  than 
  

   their 
  original 
  condition, 
  and 
  the 
  difference 
  between 
  the 
  control 
  fry 
  

   in 
  the 
  sunlight 
  and 
  those 
  in 
  the 
  shade 
  was 
  easily 
  apparent 
  to 
  the 
  naked 
  

   eye. 
  Some 
  of 
  the 
  fry 
  that 
  molted 
  from 
  the 
  first 
  to 
  the 
  second 
  stage 
  

   were 
  without 
  a 
  trace 
  of 
  diatoms 
  apparent 
  to 
  the 
  naked 
  eye, 
  while 
  those 
  

   in 
  the 
  sunlight 
  showed 
  a 
  considerable 
  growth. 
  On 
  the 
  other 
  hand, 
  

   however, 
  the 
  fry 
  themselves 
  seemed 
  to 
  be 
  influenced 
  unfavorably 
  by 
  

   the 
  absence 
  of 
  sunlight. 
  They 
  had 
  less 
  pigment 
  in 
  their 
  shells 
  and 
  

   seemed 
  much 
  less 
  active 
  than 
  those 
  in 
  the 
  sunlight. 
  

  

  