﻿12 
  

  

  are 
  probably 
  covered 
  with 
  cilia 
  in 
  more 
  or 
  less 
  active 
  

   motion, 
  for 
  all 
  the 
  portions 
  of 
  the 
  lining 
  of 
  the 
  stomach 
  

   and 
  intestine 
  examined 
  by 
  me 
  appeared 
  to 
  be 
  provided 
  

   with 
  a 
  ciliary 
  covering. 
  The 
  faeces 
  of 
  the 
  oyster 
  are 
  not 
  

   extruded 
  in 
  the 
  form 
  of 
  a 
  cylinder 
  as 
  in 
  many 
  other 
  

   mollusks, 
  but 
  have 
  the 
  form 
  of 
  a 
  demicylinder 
  with 
  one 
  

   side 
  excavated 
  in 
  a 
  groove-like 
  manner, 
  as 
  shown 
  in 
  

   section 
  in 
  Fig. 
  I, 
  2, 
  the 
  peculiar 
  form 
  being 
  due 
  to 
  the 
  

   presence 
  of 
  thelongitudinal 
  folds 
  in 
  the 
  intestine, 
  as 
  shown 
  

   in 
  a 
  cross-section 
  of 
  the 
  latter 
  in 
  Fig. 
  I, 
  1. 
  In 
  Unio, 
  the 
  

   fresh-water 
  mussel, 
  a 
  similar 
  arrangement 
  is 
  said 
  to 
  

   exist, 
  according 
  to 
  Bronn 
  ; 
  (Klass. 
  u. 
  Ord. 
  des 
  Their- 
  

   reichs. 
  Ill, 
  p. 
  864.) 
  

  

  The 
  course 
  of 
  the 
  intestine 
  as 
  sketched 
  above 
  is 
  most 
  

   nearly 
  in 
  accord 
  with 
  Clark's 
  account 
  ; 
  the 
  figures 
  given 
  

   by 
  Sir 
  Everard 
  Home* 
  of 
  the 
  intestine 
  of 
  Ostrea 
  edulis 
  

   are 
  also 
  in 
  close 
  agreement, 
  but 
  the 
  proper 
  relation 
  of 
  

   the 
  mouth 
  and 
  palps 
  was 
  evidently 
  not 
  understood. 
  

   Home's 
  figure, 
  however, 
  fully 
  justifies, 
  with 
  other 
  evi- 
  

   dence, 
  the 
  criticism 
  made 
  in 
  AVoodward's 
  Manual 
  of 
  the 
  

   Mollusca, 
  regarding 
  the 
  inaccuracy 
  of 
  Poli'sf 
  tiguresof 
  the 
  

   same 
  j)arts. 
  

  

  The 
  systemic 
  heart 
  is 
  that, 
  organ 
  which 
  serves 
  to 
  pro- 
  

   pel 
  and 
  continually 
  redistribute 
  the 
  colorless 
  blood 
  of 
  

   the 
  oyster 
  through 
  the 
  body 
  for 
  its 
  nourishment, 
  and 
  

   through 
  the 
  gills 
  that 
  the 
  blood 
  itself 
  may 
  discharge 
  into 
  

   the'^water 
  the 
  poisonous 
  gases 
  with 
  which 
  it 
  is 
  load- 
  

   ed 
  in 
  passing 
  through 
  the 
  l)ody, 
  and 
  receive 
  a 
  fresh 
  

   supply 
  of 
  oxygen 
  as 
  fresh 
  supplies 
  of 
  water 
  pass 
  through 
  

   the 
  gills. 
  The 
  heart 
  consists 
  of 
  three 
  chambers; 
  the 
  

   ui)I)er 
  and 
  largest 
  is 
  the 
  ventricle 
  oe, 
  and 
  the 
  two 
  small- 
  

   er, 
  lowermost, 
  brownish, 
  paired 
  chambers 
  are 
  called 
  

   auricles 
  (lu 
  ; 
  the 
  three 
  chambers 
  lie 
  in 
  a 
  crescent-shaped 
  

   space, 
  the 
  pericardial 
  space 
  Per, 
  just 
  forward 
  of 
  the 
  

   adductor 
  muscle. 
  The 
  ventricle 
  tie, 
  is 
  almost 
  globular; 
  

  

  *Philos. 
  Trans. 
  1827. 
  pi. 
  IV. 
  

  

  fTestacea 
  Utriiisque€iciliae 
  eorumque 
  Historia 
  et 
  Anatome, 
  U. 
  Tab. 
  XXIX, 
  fig. 
  3. 
  Parma, 
  

  

  1795, 
  Fnl. 
  

  

  