[   9  ] 
II.  On  the  Nervous  System  o/Beroe  Pileus,  Lam.,  and  on  the  Structure  of  its  Cilia.  By 
Robert  E.  Grant,  M.D.,  F.R.S.  Ed.,  L.S.,  G.S.,  Z.S.,  &fc.,  Professor  of  Comparative 
Anatomy  and  Zoology  in  the  University  of  London. 
Communicated  January  8,  1833. 
In  the  month  of  September  last  I  obtained  on  the  coast  of  Sheppey,  in  the  Thames,  a 
specimen  of  the  globular  Beroe,  Beroe  Pileus,  Lam.,  a  species  which  lias  been  observed 
occasionally  on  the  coasts  of  England  and  Scotland,  and  which  I  had  once  before  met 
with  on  the  coast  of  StafFa.  It  constitutes  the  genus  Pleurobrachia  of  Dr.  Fleming, 
and  the  Eucharis  of  Peron  and  M.  Blainville.  I  found  this  little  animal  floating  with 
myriads  of  minute  Equorece  and  other  Medusaria  in  the  harbour  of  Sheerness.  The 
boatmen,  who  seemed  to  be  familiar  with  it  under  the  name  of  the  spawn  of  the  Sea- 
egg  {Echinus),  which  it  somewhat  resembles  in  its  globular  and  ribbed  form,  assured 
me  that  often  in  hot  and  calm  weather  they  swarm,  with  the  little  Medusa,  in  such 
numbers  as  to  cover  the  surface  of  the  water  in  all  this  part  of  the  estuary  of  the  Thames. 
The  animal  has  a  regular  oval  form,  with  its  longest  diameter,  from  the  mouth  to  the 
anus,  about  six  lines,  and  its  breadth  about  four  lines.  The  general  texture  of  the  body 
is  quite  transparent  and  colourless.  The  eight  equidistant  bands  which  support  the 
cilia,  extend  along  the  surface  from  the  margins  of  the  mouth  to  the  anus,  and  appear 
more  firm  in  their  texture  and  less  transparent,  than  the  rest  of  the  body.  There  are 
four  prominent  membranous  lobes  placed  around  the  mouth,  which  the  animal  can 
retract  at  pleasure.  The  mouth  and  oesophagus  are  wide  ;  and  the  latter  continues  so 
to  the  stomach,  which  extends  to  the  centre  of  the  body.  The  intestine  continues 
straight,  equal,  and  narrow,  from  the  stomach  to  the  anus,  which  has  a  prominent  cir- 
cular margin.  The  digestive  organs  contained  no  perceptible  food,  but  Fabricins  has 
often  observed  minute  Crustacea  in  that  cavity.  The  ovaries  consisted  of  two  lengthened 
clusters  of  small  spherical  gemmules,  of  a  lively  crimson-red  colour,  extending  along 
the  sides  of  the  intestine  and  stomach.  Their  bright  red  colour  contrasted  beautifully 
with  the  glassy  transparency  of  the  general  texture  of  the  animal ;  and  I  have  generally 
observed  that  the  lively  hues  presented  by  the  Acalepha,  depend  on  the  bright  opaque 
colours  of  their  reproductive  gemmules,  which  are  often  red,  sometimes  yellow,  or 
brown,  or  purple.  The  two  tentacula  are  remarkable  in  this  species  of  Beroe  for  their 
complex  structure,  and  their  peculiar  movements.  They  extend  from  two  curved  tubes 
placed  near  the  sides  of  the  stomach,  which  pass  obliquely  downwards  and  outwards  to 
terminate  between  two  of  the  bands  at  some  distance  above  the  mouth.  They  are  about 
four  times  the  length  of  the  animal,  and  consist  of  two  thin  white  filaments,  round,  and 
VOL.  I.  C 
