,388  MR.  R.  OWEN'S  REMARKS  ON  THE  ENTOZOA. 
The  difficulty  of  assigning  a  distinctive  character  to  the  Entozoa,  which  Rudolphi 
imagined  he  had  overcome  in  the  '  Historia  Entozoorum  '  by  denying  them  a  nervous 
system,  and  so  distinguishing  them  from  the  Annulate  Worms,  he  justly  allows  in  his 
subsequent  work,  the  '  Synopsis  Entozoorum'',  to  have  returned  in  its  full  force,  and 
proposes  therefore  to  separate  the  Nematoidea  from  the  other  orders  of  Entozoa,  and  to 
join  them  with  the  Annulata  {Annelides,  Cuvier),  in  which  class  of  Worms  he  thinks  they 
should  form  a  distinct  family.  The  remaining  Entozoa  (the  Vers  Intestinaux  Parenchy- 
mateux  of  Cuvier)  Rudolphi  leaves  among  the  Radiata  or  Zoophyta,  a  division  of  animals 
which  he  justly  terms  '  regnum  chaoticam.' 
With  respect  to  the  affinity  of  the  Nematoidea  to  the  Red-blooded  Worms,  the  im- 
portant differences  which  the  presence  in  the  latter  class  of  distinct  respiratory  organs 
and  of  vessels  circulating  red  blood  present,  obviously  forbid  the  junction  proposed  by 
Rudolphi,  at  least  in  any  attempt  at  a  natural  arrangement.  While  the  absence  of 
ganghons  on  the  nervous  chords,  which  supply  the  body  in  the  Nematoidea  with  the 
motive  and  sensitive  endowments,  bespeaks  a  difference  of  still  greater  importance. 
As  the  Nematoidea,  or  Vers  Intestinaux  Cavitaires,  differ  from  the  Vers  Parenchymateux 
in  the  presence  of  a  distinct  nervous  system,  as  widely  on  the  one  hand  as  they  do  from 
the  Annelida  in  the  form  of  that  system  on  the  other,  I  have  been  induced  to  join  them 
with  those  other  classes  of  the  Radiata  of  Cuvier  which,  while  they  are  distinguished 
from  the  rest  of  that  Division  of  the  Animal  Kingdom  by  the  undoubted  presence  of 
nerves,  agree  with  the  Nematoidea  in  manifesting  those  organs  in  the  form  of  simple, 
ungangliated,  disconnected  cords. 
In  attempting  therefore  a  more  natural  arrangement  of  the  Entozoa,  I  have  been  led 
to  propose  a  division  of  the  Radiata  of  the  '  Regne  Animal'  into  two  groups,  founded 
principally  on  the  two  conditions  which  the  nervous  system  presents,  the  molecular  and 
the  fiUform.  The  necessity  of  such  a  dismemberment  appears  to  have  been  felt  by  every 
naturalist  who  has  considered  the  natural  affinities  of  the  classes  which  are  included  in 
the  lowest  division  of  Cuvier's  system.  His  Radiata,  indeed,  embrace  animals  which 
differ  widely  from  one  another,  not  only  in  the  condition  of  the  nervous  but  of  many 
other  important  systems  of  their  organization ;  and,  as  the  division  now  stands,  an  ana- 
tomist is  unable  to  predicate  a  community  of  structure  in  either  the  locomotive,  ex- 
cretive, digestive,  sensitive,  or  generative  systems  of  the  various  classes  which  it  em- 
braces. 
The  learned  entomologist  Mr.  W.  S.  MacLeay  has  proposed,  in  the  sketch  of  the 
natural  affinities  which  he  has  given  in  the  second  volume  of  the  '  Horse  Entomologicse', 
to  limit  the  term  Radiata  to  the  Echinodermata  and  Acalepha  of  Cuvier,  which  alone,  a& 
he  justly  observes,  strictly  present  the  radiated  form  of  the  body,  and  to  form  a  distinct 
division  of  the  animal  kingdom,  to  include  the  Infusoria,  Cuv.,  Polypi,  Cuv.,  and  Paren- 
chymatous Entozoa  under  the  term  Acrita,  while  the  Intestinaux  Cavitaires  are  trans- 
ferred to  the  Annulose  or  Articulate  division  of  the  animal  kingdom ;  they  are  not,  in- 
»  p.  572. 
