822 
ME.  HANCOCK  OX  THE  OEOAXIZATIOX  OE  THE  BEACHIOPODA. 
as  two  rather  delicate  tubes ; and  thus  buried  run  for  some  distance  towards  each  other, 
and  terminate  at  the  external  surface  in  two  small  diagonal  slits',  one  a shoid  way  on 
either  side  from  the  median  line,  a little  below  the  mouth.  The  expanded  poidion  is 
yellowish,  and  the  tubular  of  a full  red  colour.  The  walls  have  a glandular  appearance, 
the  inside  being  velvety  from  the  numerous  minute  ^illi  which  crowd  the  suiTace. 
From  the  nature  of  these  organs  it  seems  probable  that  the  ova,  on  their  passage 
outwards,  may  receive  some  external  covering ; or  perhaps,  having  to  subseiwe  the  func- 
tion of  renal  organs,  as  suggested  to  me  by  Professor  Huxley,  their  walls  are  neces- 
sarily glandular.  Be  this,  however,  as  it  may,  they  seem  to  be  primarily  for  effecting 
the  discharge  of  the  eggs,  and  therefore  the  denomination  of  oriducts  appears  appro- 
priate. In  corroboration  of  this  riew  of  their  function  it  may  be  stated,  that  in  two 
instances,  in  which  the  ova  were  mature,  they  were  found  in  vast  numbers  strewed  about 
the  perivisceral  chamber,  and  in  one  of  the  oviducts  several  had  penetrated  almost  to 
the  external  orifice.  The  expansion  of  the  inner  aperture  may  be  for  the  better  securing 
the  ova  as  they  fall  into  the  chamber;  and  it  is  not  improbable  that  ciliary  cnrrents 
may  direct  their  course  to  this  receptacle.  Arrived  there,  they  are  probably  carried 
onward  by  some  peristaltic  action  of  the  parts,  for  such  would  seem  necessary ; as  the 
tubular  portion,  being  buried  in  the  parietes,  will  be  kept  in  a state  of  collapse  by  the 
pressure  of  the  fluid  in  the  perivisceral  chamber.  The  passage  is  undoubtedly  so  con- 
structed as  to  be  opened  and  closed  as  the  economy  of  the  animal  requires. 
ClECULATOEY  AND  EeSPIEATOEY  SySTEMS. 
The  circulatory  apparatus  has  been,  up  to  a very  recent  period,  entii'ely  misimderstood. 
Professor  Huxley’s  paper,  which  appeared  in  the  Proceedings  of  the  Royal  Society  in 
1854,  threw  the  first  gleam  of  light  upon  this  most  intricate  portion  of  the  anatomy  of 
these  animals.  In  1852  I had  discovered  that  the  Cuvierian  hearts  open  externally, 
and  in  my  communication  on  the  subject  submitted  to  the  British  Association  in  1856^, 
it  was  stated  that  these  organs  were  really  oviducts,  or  perhaps  kidneys,  and  formed  no 
part  of  the  circnlatory  apparatus,  but  that  the  true  blood-propelling  organ  was  the  pyri- 
form vesicle,  described  by  Professor  Huxley  as  appended  to  the  stomach.  Further 
research  has  only  tended  to  confirm  the  accuracy  of  these  vieAvs,  which  now  appear  to 
be  incontrovertible. 
This  vesicle  or  heart  is  present  in  all  the  Bmc1iio])oda  that  I have  examined,  and  when 
in  an  expanded  state  is  of  considerable  size.  In  the  articulated  species  it  is  appended 
to  the  middle  line  of  the  stomach,  immediately  behind  the  central  gastro-parietal  band, 
and  projects  freely  into  the  peririsceral  cavity,  reaching  dorni  almost  to  the  anterior 
margin  of  the  oviducts : the  free  extremity  is  the  larger  one.  When  in  this  state,  the 
walls,  though  rather  thin,  are  firm,  smooth,  opake,  and  do  not  collapse ; they  are  com- 
posed of  two  layers,  the  inner  of  which  is  distinctly  muscular,  the  fibres  running  in 
various  directions,  but  principally  radiating  from  centres ; the  outer  layer  is  delicate, 
‘ Plate  LXIV.  fig.  3.  ^ Transactions  of  the  Sections,  p.  94. 
