﻿60 
  

  

  a 
  stati(inary 
  one. 
  I 
  never 
  failed 
  to 
  find 
  the 
  structure 
  

   present, 
  which 
  I 
  have 
  just 
  described, 
  on 
  young 
  spat 
  ; 
  

   after 
  a 
  time, 
  as 
  the 
  oyster 
  becomes 
  older, 
  the 
  umbonal, 
  

   portion 
  of 
  the 
  shell 
  together 
  with 
  the 
  larval 
  shell 
  is 
  vi^orn 
  

   off 
  or 
  is 
  dissolved 
  aAvay 
  by 
  the 
  carbonic 
  acid 
  in 
  solution 
  

   in 
  the 
  water, 
  so 
  that 
  it 
  is 
  not 
  to 
  be 
  found 
  on 
  the 
  adult 
  

   shell. 
  

  

  In 
  examining 
  the 
  collection 
  of 
  oysters 
  in 
  the 
  museum 
  

   of 
  the 
  Academy 
  of 
  Natural 
  Sciences 
  of 
  Philadelphia, 
  I 
  

   found 
  that 
  I 
  could 
  very 
  easily 
  detect 
  the 
  presence 
  of 
  this 
  

   larval 
  shell, 
  and 
  of 
  about 
  the 
  same 
  size, 
  in 
  the 
  ''spat" 
  of 
  

   four 
  othei' 
  species, 
  viz 
  : 
  (Jatrea 
  equestrls 
  Say, 
  from 
  Flor- 
  

   ida 
  ; 
  (). 
  coiicJiaphila, 
  (California 
  ; 
  0. 
  cvcullata, 
  Viti 
  

   Islands, 
  Pacific 
  ; 
  a 
  species 
  which 
  was 
  also 
  bored 
  by 
  a 
  

   Cliona 
  ; 
  O. 
  penmiana, 
  Peru. 
  The 
  presence 
  of 
  this 
  fea- 
  

   ture, 
  together 
  wi'th 
  others, 
  will 
  enable 
  conchologists 
  to 
  

   distinguish 
  the 
  young 
  from 
  adults, 
  some 
  of 
  the 
  former 
  

   no 
  doubt 
  having 
  supplied 
  a 
  basis 
  upon 
  which 
  to 
  found 
  

   species. 
  

  

  THK 
  KATE 
  OF 
  <4 
  1J<)W'I'H 
  OF 
  THE 
  SPAT. 
  

  

  Upon 
  comparing 
  the 
  spat 
  obtained 
  from 
  our 
  collectors 
  

   which 
  were 
  put 
  out 
  in 
  the 
  pond 
  at 
  St. 
  Jerome's 
  Creek, 
  

   with 
  that 
  of 
  the 
  same 
  age 
  as 
  figured 
  l)y 
  Coste, 
  and 
  

   Mobius 
  of 
  the 
  European 
  oyster, 
  I 
  find 
  that 
  our 
  species 
  

   grows 
  with 
  three 
  or 
  four 
  times 
  the 
  rapidity 
  of 
  the 
  for- 
  

   mer. 
  For 
  instance, 
  Mobius 
  figures 
  a 
  European 
  oyster 
  

   twelve 
  to 
  fifteen 
  months 
  old, 
  which 
  measures 
  only 
  li 
  

   inches 
  in 
  diameter, 
  contrasting 
  this 
  with 
  the 
  size 
  of 
  the 
  

   American 
  at 
  71) 
  to 
  82 
  days 
  old 
  and 
  measuring 
  from 
  I4 
  to 
  

   nearly 
  2 
  inches 
  in 
  diameter, 
  we 
  see 
  how^ 
  immeasurably 
  

   our 
  species 
  surpasses 
  that 
  of 
  Europe 
  in 
  vigor 
  and 
  raj)id- 
  

   ity 
  of 
  growth. 
  

  

  Fig. 
  8 
  shows 
  the 
  single 
  si>ecimen 
  obtained 
  from 
  ^ 
  

   the 
  collectors 
  placed 
  in 
  the 
  large 
  l)ox 
  or 
  fiannel 
  ^o 
  

   pen, 
  and 
  supp(>sed 
  to 
  be 
  one 
  of 
  a 
  lot 
  of 
  artificially 
  

   impregnated 
  spawn 
  put 
  into 
  the 
  box 
  seventeen 
  jTf^-^ 
  g 
  

  

  