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  cient 
  to 
  aft'ect 
  the 
  mature 
  animal, 
  but 
  tliat 
  in 
  this 
  case 
  the 
  

   water 
  continued 
  fresh, 
  or 
  practically 
  so, 
  for 
  too 
  long 
  a 
  period, 
  

   thus 
  killing 
  the 
  oysters 
  by 
  endosmose. 
  

  

  From 
  the 
  observations 
  of 
  density, 
  then, 
  it 
  may 
  be 
  assumed 
  

   that 
  the 
  density 
  of 
  the 
  water 
  in 
  these 
  localities 
  at 
  least 
  cannot 
  

   fall 
  below 
  1.01 
  for 
  any 
  protracted 
  period 
  without 
  destroying 
  

   the 
  oysters. 
  

  

  Whether 
  the 
  changes 
  in 
  density 
  affect 
  the 
  spatting 
  can 
  only 
  

   be 
  ascertained 
  by 
  continuing 
  the 
  observations 
  for 
  a 
  number 
  

   of 
  seasons, 
  or 
  by 
  direct 
  experiment 
  with 
  the 
  spat 
  artificially 
  

   raised. 
  

  

  During 
  the 
  summer 
  I 
  have 
  examined, 
  under 
  the 
  microscope, 
  

   374 
  oysters, 
  of 
  which 
  212 
  were 
  females 
  and 
  162 
  males, 
  or 
  the 
  

   percentage 
  of 
  females 
  to 
  males 
  was 
  0.56. 
  

  

  The 
  oysters 
  were 
  not 
  all 
  examined 
  at 
  the 
  same 
  time, 
  nor 
  

   were 
  they 
  all 
  from 
  the 
  same 
  bed, 
  but 
  the 
  percentage 
  in 
  each 
  

   of 
  the 
  lots 
  examined, 
  twelve 
  in 
  number, 
  does 
  not 
  vary 
  greatly 
  

   from 
  the 
  percentage 
  given 
  above. 
  

  

  I 
  am 
  of 
  the 
  opinion, 
  therefore, 
  that 
  about 
  60 
  per 
  cent, 
  of 
  

   the 
  oysters 
  in 
  a 
  community 
  are 
  females. 
  A 
  larger 
  number 
  of 
  

   observations 
  is, 
  however, 
  desirable. 
  

  

  In 
  making 
  these 
  examinations 
  I 
  have 
  never 
  seen 
  both 
  ova 
  

   and 
  sj)ermatozoa 
  in 
  the 
  same 
  animal, 
  though 
  I 
  have 
  made 
  

   many 
  careful 
  observations 
  in 
  order 
  to 
  detect 
  the 
  presence 
  of 
  

   either. 
  I 
  have 
  also 
  carefully 
  examined 
  the 
  gills 
  and 
  mantles 
  

   of 
  a 
  large 
  number, 
  and 
  have 
  never 
  found 
  an 
  embryo 
  oyster 
  

   within 
  the 
  shell. 
  

  

  As 
  these 
  observations 
  were 
  made 
  during 
  the 
  spawning 
  sea- 
  

   son, 
  I 
  do 
  not 
  think 
  it 
  possible 
  that 
  the 
  spat, 
  if 
  they 
  are 
  at 
  any 
  

   time 
  contained 
  within 
  the 
  gills 
  or 
  mantle, 
  could 
  have 
  escaped 
  

   my 
  notice. 
  

  

  The 
  observations 
  as 
  to 
  the 
  sex 
  of 
  the 
  oyster 
  were 
  continued 
  

   late 
  in 
  the 
  season, 
  and 
  though 
  the 
  ova 
  and 
  spermatozoa 
  in 
  a 
  

   number 
  of 
  oysters 
  was 
  in 
  apparently 
  good 
  condition 
  as 
  late 
  

   as 
  the 
  1st 
  of 
  October, 
  yet 
  those 
  products 
  of 
  generation 
  ap- 
  

   peared 
  in 
  best 
  condition 
  in 
  the 
  largest 
  number 
  of 
  animals 
  dur- 
  

   ing 
  July. 
  

  

  A 
  considerable 
  disintegration 
  of 
  the 
  eggs 
  was 
  noticed 
  by 
  

  

  