﻿LOBSTER 
  AND 
  CLAM 
  INVESTIGATIONS. 
  179 
  

  

  days, 
  at 
  different 
  times 
  during- 
  the 
  month, 
  the 
  following 
  species 
  were 
  

   found, 
  being 
  named 
  in 
  the 
  order 
  of 
  their 
  abundance: 
  

  

  Chaetoceros 
  sp. 
  

  

  Rhabdonema 
  adriaticum 
  Kiitzing. 
  

  

  Tabellaria 
  (Striatella) 
  unipunctata 
  Agardh. 
  

  

  Navicula 
  sp. 
  

  

  Rhabdonema 
  arcuatum 
  (Lyngby) 
  Kiitziug. 
  

  

  Licmoiahora 
  tincta 
  Grunow. 
  

  

  Pleurosigma 
  sp. 
  

  

  Rhizosolenia 
  gracilis 
  H. 
  L. 
  Smith. 
  

  

  Rhizosolenia 
  setigera 
  Brightwell. 
  

  

  Grammatophora 
  subtilUssima 
  Bailey. 
  

  

  Diatoma 
  hyalinum 
  Kiitzing. 
  

  

  Achnanthes 
  longipes 
  Agardh. 
  

  

  It 
  thus 
  appears 
  that 
  the 
  water 
  is 
  filled 
  with 
  living 
  diatoms 
  of 
  both 
  

   the 
  free-swimming 
  and 
  the 
  sessile 
  varieties, 
  the 
  latter 
  ready 
  to 
  become 
  

   attached* 
  whenever 
  opportunity 
  offers. 
  

  

  DIATOMS 
  ON 
  LOBSTER 
  FRY 
  IN 
  THEIR 
  NATURAL 
  HABITAT 
  AND 
  ON 
  

   OTHER 
  CRUSTACEA. 
  

  

  The 
  next 
  question 
  was, 
  Do 
  the 
  diatoms 
  become 
  attached 
  to 
  lobster 
  

   fry 
  when 
  the 
  latter 
  are 
  uncontined 
  — 
  that 
  is, 
  under 
  natural 
  conditions? 
  

   Onl}' 
  a 
  few 
  lobster 
  fry 
  could 
  be 
  obtained 
  for 
  examination. 
  One 
  taken 
  

   in 
  the 
  tow 
  near 
  the 
  Fish 
  Commission 
  wharf 
  early 
  in 
  June 
  did 
  not 
  show 
  

   any 
  diatoms. 
  One 
  of 
  the 
  third 
  stage 
  and 
  two 
  of 
  the 
  fourth 
  or 
  lifth 
  

   stage, 
  taken 
  at 
  the 
  surface 
  at 
  11 
  p. 
  m., 
  1-0 
  miles 
  south 
  of 
  No 
  Mans 
  Land, 
  

   on 
  July 
  30, 
  1902,. 
  showed 
  no 
  diatoms. 
  Other 
  Crustacea 
  hav^e 
  occasion- 
  

   ally 
  been 
  observed 
  to 
  be 
  covered 
  with 
  them. 
  A 
  copepod, 
  probably 
  

   Corynura 
  hampic^ii^ 
  covered 
  with 
  Licomophora 
  tincta, 
  was 
  taken 
  off 
  

   the 
  Fish 
  Commission 
  wharf 
  by 
  Mr. 
  Vinal 
  N. 
  Edwards 
  on 
  June 
  24, 
  

   1902 
  (plate 
  v, 
  figure 
  5). 
  On 
  September 
  10, 
  1902, 
  a 
  young 
  Limulua 
  

   poly2)he)nvs 
  was 
  taken 
  covered 
  with 
  another 
  diatom, 
  Rhahdonema 
  

   adriaticum 
  (pi. 
  v, 
  fig. 
  1). 
  A 
  large 
  number 
  of 
  copepods, 
  zneje, 
  young 
  

   squilla, 
  etc., 
  taken 
  in 
  the 
  tow 
  during 
  September, 
  were 
  examined, 
  but 
  

   with 
  the 
  above 
  exceptions 
  no 
  diatoms 
  were 
  found 
  on 
  Crustacea 
  under 
  

   natural 
  conditions. 
  

  

  Other 
  Crustacea 
  besides 
  lobsters, 
  however, 
  when 
  kept 
  in 
  confinement 
  

   are 
  subject 
  to 
  diatom 
  infection. 
  Dr. 
  M. 
  T. 
  Thompson, 
  during 
  the 
  

   summer 
  of 
  1900, 
  found 
  that 
  certain 
  experiments 
  with 
  larval 
  hermit 
  

   cnihs 
  (Gleucot/ioe) 
  had 
  to 
  be 
  abandoned 
  because 
  of 
  the 
  abundant 
  growth 
  

   of 
  diatoms 
  on 
  the 
  young 
  crabs. 
  

  

  If 
  any 
  conclusion 
  can 
  be 
  drawn 
  from 
  these 
  few 
  observations 
  it 
  is 
  

   that 
  although 
  the 
  water 
  is 
  filled 
  with 
  diatoms 
  ready 
  to 
  become 
  attached 
  

   when 
  opportunit}^ 
  offers, 
  they 
  do 
  not 
  ordinarily 
  attack 
  living 
  lobster 
  

   f 
  r^' 
  or 
  other 
  Crustacea, 
  unless 
  some 
  artificial 
  condition, 
  such 
  as 
  confine- 
  

   ment 
  or 
  weakened 
  vitality, 
  is 
  introduced. 
  

  

  