﻿LOBSTER 
  AND 
  CLAM 
  INVESTIGATIONS. 
  177 
  

  

  on 
  their 
  appendao-es. 
  Others 
  remain 
  perfectly 
  clean. 
  In 
  the 
  hatching- 
  

   jans 
  the 
  growth 
  of 
  diatoms 
  never 
  becomes 
  abundant 
  either 
  on 
  the 
  

   eggs, 
  egg-stalks, 
  or 
  ivy. 
  

  

  Diatoms 
  <m 
  the 
  fry 
  in. 
  the 
  rearing 
  apparatus.— 
  A.s 
  soon 
  as 
  the 
  eggs 
  

   or 
  fry 
  are 
  placed 
  in 
  the 
  bags 
  of 
  the 
  rearing 
  apparatus, 
  the 
  growth 
  of 
  

   diatoms 
  is 
  greatly 
  accelerated, 
  and 
  eggs, 
  egg-stalks, 
  and 
  fry 
  are 
  soon 
  

   covered 
  with 
  them 
  (pi. 
  iv, 
  figs. 
  3, 
  6, 
  and 
  7). 
  The 
  fry 
  become 
  brownish 
  

   and 
  shaggy 
  to 
  the 
  naked 
  eye, 
  are 
  impeded 
  in 
  the"ir 
  movements 
  and 
  

   in 
  their 
  feeding, 
  and 
  soon 
  perish 
  unless 
  the 
  act 
  of 
  molting 
  intervenes 
  

   to 
  rid 
  them 
  of 
  their 
  unpleasant 
  burden. 
  

  

  As 
  already 
  stated, 
  in 
  the 
  hatching 
  jars 
  but 
  one 
  species 
  of 
  diatom 
  is 
  

   present 
  {Licmophora 
  tincta). 
  Upon 
  removal 
  to 
  the 
  rearing 
  bags 
  the 
  

   number 
  of 
  species 
  increases, 
  and 
  although 
  Licmophora 
  thicta 
  is 
  always 
  

   the 
  most 
  abundant 
  at 
  Woods 
  Hole, 
  other 
  species 
  also 
  are 
  present 
  in 
  

   large 
  numbers. 
  A 
  list 
  of 
  the 
  species 
  and 
  their 
  relative 
  abundance 
  

   will 
  be 
  found 
  in 
  a 
  later 
  section. 
  

  

  ^ 
  Diatoms 
  on 
  the 
  different 
  stages 
  of 
  the 
  fry. 
  —Th^ 
  eggs 
  and 
  fry 
  of 
  the 
  

   first, 
  second, 
  and 
  third 
  stages 
  become 
  badly 
  covered 
  and 
  in 
  many 
  cases 
  

   killed 
  by 
  the 
  diatoms. 
  When 
  an 
  individual 
  survives 
  and 
  molts 
  to 
  

   the 
  fourth 
  stage 
  he 
  is 
  less 
  liable 
  to 
  infection. 
  He 
  is 
  now 
  a 
  more 
  active 
  

   swimmer. 
  He 
  swims 
  not 
  merely 
  to 
  keep 
  afloat, 
  but 
  to 
  go 
  swiftly 
  from 
  

   place 
  to 
  place, 
  to 
  retreat 
  from 
  danger, 
  or 
  to 
  capture 
  his 
  food. 
  His 
  

   shell 
  is 
  harder, 
  his 
  limbs 
  and 
  appendages 
  are 
  larger, 
  less 
  feathery, 
  

   less 
  adapted 
  for 
  the 
  attachment 
  of 
  the 
  diatoms. 
  His 
  manner 
  of 
  life 
  

   is 
  changed. 
  He 
  now 
  seeks 
  the 
  bottom 
  and 
  crawls 
  about 
  and 
  hides 
  

   under 
  stones, 
  shells, 
  and 
  seaweed, 
  or 
  even 
  burrows 
  in 
  the 
  sand— 
  a 
  

   manner 
  of 
  life 
  that 
  enables 
  him 
  to 
  free 
  himself 
  to 
  a 
  large 
  extent 
  from 
  

   any 
  extei-nal 
  growth. 
  But 
  even 
  in 
  this 
  fourth 
  stage 
  certain 
  individu- 
  

   als 
  become 
  covered 
  with 
  diatoms, 
  particulai-ly 
  when 
  they 
  do 
  not 
  have 
  

   access 
  to 
  a 
  sandy 
  bottom. 
  Individuals 
  of 
  the 
  fourth 
  stage 
  have 
  been 
  

   observed 
  with 
  a 
  growth 
  of 
  algte 
  one-half 
  inch 
  long, 
  and 
  in 
  one 
  case 
  

   an 
  amphipod 
  tube, 
  with 
  its 
  living 
  occupant, 
  was 
  closely 
  attached 
  to 
  

   the 
  carapace 
  (pi. 
  iv, 
  fig. 
  5). 
  In 
  this 
  stage, 
  however, 
  diatoms 
  are 
  not 
  so 
  

   troublesome 
  and 
  probably 
  are 
  never 
  the 
  cause 
  of 
  death, 
  particularly 
  if 
  

   the 
  fry 
  are 
  transferred 
  to 
  cars 
  with 
  a 
  sandy 
  or 
  gravelly 
  bottom. 
  

  

  DIATOMS 
  AND 
  THE 
  PROCESS 
  OF 
  MOLTING. 
  

  

  As 
  is 
  well 
  known, 
  the 
  process 
  of 
  molting 
  usually 
  takes 
  but 
  a 
  few 
  

   moments. 
  Not 
  infrequently, 
  however, 
  something^ 
  goes 
  wrong, 
  the 
  

   fry 
  becomes 
  entangled 
  in 
  the 
  old 
  shell, 
  the 
  struggle 
  is 
  quite 
  prolonged, 
  

   and 
  often 
  the 
  lobster 
  dies 
  in 
  the 
  process. 
  The 
  method 
  of 
  molting 
  is 
  

   the 
  same 
  in 
  all 
  stages 
  of 
  the 
  lobster; 
  the 
  old 
  skin 
  splits 
  across 
  *the 
  

   back 
  between 
  the 
  thorax 
  and 
  the 
  abdomen 
  and 
  the 
  body 
  is 
  worked 
  out 
  

   from 
  this 
  opening, 
  leaving 
  the 
  old 
  shell 
  with 
  all 
  the 
  appendages 
  

   mtact. 
  If 
  the 
  old 
  shell 
  is 
  covered 
  with 
  diatoms, 
  some 
  of 
  these 
  are 
  

  

  F. 
  C. 
  1903 
  12 
  

  

  