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  slate 
  covered 
  with 
  a 
  dense 
  colony 
  of 
  ascidians 
  ; 
  in 
  this 
  

   condition 
  a 
  great 
  percentage 
  of 
  available 
  surface 
  is 
  lost 
  

   which 
  ought 
  to 
  serve 
  for 
  the 
  attachment 
  of 
  spat. 
  The 
  

   surfaces 
  so 
  occupied 
  would 
  also 
  be 
  comparatively 
  clean 
  

   were 
  it 
  not 
  for 
  these 
  organisn)s 
  which 
  actually 
  become 
  a 
  

   serious 
  annoyance. 
  They, 
  like 
  the 
  oyster, 
  affix 
  them- 
  

   selves 
  to 
  the 
  slates 
  while 
  still 
  in 
  the 
  free 
  swimming 
  larval 
  

   stage, 
  since 
  the 
  surfaces 
  designed 
  for 
  the 
  oyster 
  are 
  equal- 
  

   ly 
  well 
  adapted 
  to 
  them. 
  The 
  barnacles 
  which 
  also 
  affix 
  

   themselves 
  in 
  great 
  numbers 
  become 
  a 
  nuisance 
  for 
  the 
  

   same 
  reason. 
  The 
  larval 
  l)arnacle 
  is 
  an 
  extremely 
  active 
  

   little 
  creature 
  and 
  dashes 
  al)()ut 
  in 
  the 
  water 
  with 
  great 
  

   rapidity. 
  As 
  soon 
  as 
  it 
  has 
  completed 
  this 
  stage 
  of 
  its 
  

   growth, 
  it 
  betakes 
  itself 
  to 
  some 
  object 
  to 
  the 
  sui-face 
  of 
  

   which 
  it 
  attaches 
  itself 
  by 
  the 
  head 
  end, 
  when 
  a 
  singular 
  

   change 
  takes 
  place, 
  at 
  the 
  end 
  of 
  which 
  it 
  is 
  foand 
  that 
  

   it 
  has 
  begun 
  the 
  construction 
  of 
  the 
  curious 
  conical 
  shell 
  

   which, 
  it 
  inhabits. 
  They 
  grow 
  very 
  rapidly, 
  so 
  that 
  in 
  a 
  

   couple 
  of 
  months 
  the 
  shell 
  will 
  already 
  measure 
  over 
  half 
  

   an 
  inch 
  in 
  diameter. 
  In 
  this 
  way 
  farther 
  inroads 
  are 
  

   made 
  upon 
  the 
  room 
  wliich 
  should 
  be 
  taken 
  up 
  l)y 
  oys- 
  

   ters. 
  

  

  Of 
  course, 
  the 
  larger 
  types 
  are 
  not 
  alcme 
  in 
  taking 
  up 
  

   space, 
  since 
  infusorious, 
  bryoza, 
  polyps, 
  etc., 
  are 
  also 
  cul- 
  

   pable, 
  as 
  well 
  as 
  algae, 
  such 
  as 
  diatoms 
  and 
  the 
  higher 
  

   forms. 
  The 
  only 
  remedy 
  for 
  this 
  accumulation 
  of 
  ani- 
  

   mal 
  growths 
  on 
  the 
  surfaces 
  of 
  the 
  slates 
  and 
  other 
  col- 
  

   lecting 
  apparatus, 
  will 
  be 
  to 
  have 
  the 
  frames 
  which 
  hold 
  

   the 
  slate 
  in 
  position 
  so 
  arranged 
  that 
  each 
  tile, 
  shingle 
  or 
  

   slate 
  can 
  be 
  removed, 
  in 
  order 
  that 
  it 
  may 
  be 
  readily 
  over- 
  

   hauled 
  and 
  these 
  organisms 
  removed 
  from 
  the 
  surfaces 
  

   which 
  it 
  is 
  desired 
  shall 
  remain 
  clean. 
  This 
  work 
  would 
  

   have 
  to 
  be 
  done 
  at 
  intervals 
  of 
  every 
  two 
  or 
  three 
  weeks, 
  

   and 
  should 
  Ix^ 
  conducted 
  with 
  gi-eat 
  caie 
  so 
  as 
  not 
  to 
  re- 
  

   move 
  the 
  oysters 
  wliicli 
  have 
  affixed 
  tliemselves 
  along 
  

   with 
  the 
  other 
  things 
  wliicli 
  it 
  is 
  the 
  intention 
  to 
  destroy. 
  

   The 
  removal 
  of 
  the 
  smaller 
  forms 
  from 
  the 
  sui'faces 
  of 
  

  

  