﻿191 
  

  

  maxinnim 
  number 
  about 
  the 
  end 
  of 
  July, 
  and 
  decreases 
  after- 
  

   wards. 
  

  

  The 
  mortality 
  after 
  the 
  23d 
  of 
  August 
  was 
  very 
  great, 
  fully 
  

   50 
  per 
  cent, 
  perishing 
  from 
  some 
  unknown 
  cause, 
  which, 
  

   though 
  unknown, 
  is 
  certainly 
  natural. 
  

  

  We 
  did 
  not 
  notice 
  any 
  evidence 
  of 
  the 
  destructive 
  effects 
  of 
  

   drills 
  or 
  other 
  animals, 
  though 
  as 
  their 
  agency 
  would 
  only 
  be 
  

   discovered 
  by 
  the 
  evidence 
  of 
  the 
  holes 
  in 
  the 
  upper 
  valves, 
  

   but 
  as 
  those 
  valves 
  were 
  never 
  present, 
  it 
  cannot 
  be 
  said 
  with 
  

   certainty 
  that 
  the 
  destruction 
  was 
  not 
  due 
  to 
  them. 
  What- 
  

   ever 
  the 
  cause, 
  the 
  fact 
  is 
  that 
  50 
  per 
  cent, 
  perished 
  in 
  the 
  

   first 
  six 
  weeks 
  of 
  their 
  existence. 
  

  

  The 
  tiles 
  have 
  shown 
  that 
  the 
  increase 
  in 
  size 
  is 
  much 
  

   greater 
  than 
  was 
  supposed, 
  and 
  are 
  the 
  first 
  and 
  only 
  authen- 
  

   tic 
  evidence 
  upon 
  that 
  point 
  which 
  has 
  been 
  produced 
  with 
  

   regard 
  to 
  the 
  American 
  oyster. 
  

  

  Again, 
  it 
  is 
  conclusively 
  shown 
  by 
  these 
  tiles, 
  and 
  some 
  

   others 
  that 
  were 
  dredged 
  up 
  from 
  the 
  AVoman's 
  Marsh 
  Rocks 
  

   (Hurdle 
  No. 
  24), 
  that 
  the 
  greatest 
  attachment 
  is 
  on 
  the 
  lower 
  

   concave 
  side, 
  and 
  consequently 
  that 
  whatever 
  may 
  be 
  the 
  

   movements 
  of 
  the 
  embryo 
  oyster 
  before 
  attachment, 
  during 
  

   the 
  period 
  just 
  prior 
  to 
  it, 
  they 
  are 
  near, 
  if 
  not 
  on 
  the 
  bot- 
  

   tom, 
  and 
  in 
  seeking 
  their 
  place 
  of 
  attachment 
  they 
  must 
  rise. 
  

   In 
  this 
  they 
  are 
  similar 
  to 
  the 
  European 
  variety. 
  

  

  The 
  selection 
  of 
  the 
  lower 
  sides 
  of 
  the 
  tiles 
  and 
  the 
  inte- 
  

   rior 
  of 
  the 
  "boxes" 
  may 
  be 
  an 
  effort 
  of 
  nature 
  to 
  provide 
  

   some 
  protection 
  for 
  the 
  young 
  brood 
  by, 
  to 
  a 
  certain 
  extent, 
  

   inducing 
  them 
  to 
  seek 
  dark 
  and 
  secluded 
  points 
  for 
  attach- 
  

   ment, 
  or 
  the 
  large 
  niimber 
  found 
  in 
  such 
  places 
  may 
  be 
  due 
  

   to 
  the 
  inability 
  of 
  the 
  various 
  enemies 
  of 
  the 
  spat 
  to 
  get 
  at 
  

   them 
  when 
  thus 
  protected. 
  

  

  It 
  is 
  a 
  matter 
  of 
  very 
  great 
  regret 
  that 
  we 
  have 
  not 
  a 
  large 
  

   number 
  of 
  specimens 
  and 
  observations 
  for 
  comparison, 
  as 
  all 
  

   the 
  future 
  investigations 
  in 
  this 
  field 
  would 
  be 
  greatly 
  assisted 
  

   by 
  an 
  accurate 
  knowledge 
  of 
  the 
  rate 
  of 
  decrease 
  in 
  number 
  

   and 
  increase 
  in 
  size 
  of 
  the 
  oysters, 
  and 
  it 
  is 
  to 
  be 
  hoped 
  that 
  

   the 
  hurdle 
  in 
  the 
  Bio- 
  Annemessex 
  will 
  be 
  allowed 
  to 
  remain 
  

  

  