12  DR.  R.  E.  GRANT  ON  THE  NERVOUS  SYSTEM  OF  BEROE  PILEUS. 
regular  and  rapid  vibrations  of  these  very  minute  organs  in  the  lowest  forms  of  animal 
organization,  depend  on  volition  directed  at  once  to  thousands  of  millions  of  muscles. 
When  the  tentaculum  of  a  Flustra  is  cut  off  from  the  polypus,  I  have  observed  it  swim 
like  a  straight  worm,  or  a  Vorticella,  through  the  water  by  the  action  of  the  cilia  still 
continuing ;  and  it  was  observed  by  Fabricius,  that  when  the  Beroe  is  broken  to  pieces 
these  continue  to  live,  and  to  swim  about  by  the  action  of  the  cilia  still  kept  up.  The 
tubular  feet  which  project  from  the  ambulacra  of  the  Asterias,  rise  and  sink  in  constant 
succession  by  the  entrance  and  exit  of  water  sent  into  them  by  vessels  destined  for  that 
office.  The  same  mechanism  is  observed  in  Echinus  and  in  Holothuria,  (the  forms  of 
w^hich,  as  well  as  the  arrangement  of  the  feet,  closely  resemble  those  of  the  Beroe,)  and 
the  tubular  tentacula  of  Actinia  rise  by  the  injection  of  water  into  them  from  their  base. 
It  appears  therefore  highly  probable  that  the  motions  of  the  cilia  of  the  Beroe  are  inti- 
mately connected  with  the  streams  passing  along  the  bands  ;  and  should  the  rapid 
vibrations  of  these  singular  organs  in  the  lowest  animals  depend  on  the  undulations  of 
water  conveyed  through  elastic  tubes  along  their  bases,  one  of  the  most  remarkable 
phenomena  of  animal  motion,  though  one  of  the  most  frequent,  will  lose  much  of  its 
present  marvellous  character,  and  prove  another  instance  of  the  striking  similarity  of 
the  phenomena  of  the  simplest  organic  beings  to  those  which  occur  in  the  inorganic 
world. 
PLATE  11. 
Fig.  1.  Beroe  Pileus,  Lam.  (twice  the  natural  size). 
