[   387  ] 
XLII.  Remarks  on  the  Entozoa,  and  on  the  structural  Differences  existing  among  them :  in- 
cluding Suggestions  for  their  Distribution  into  other  Classes.  By  Richard  Owen,  Esq., 
F.R.S.  8f  Z.S.,  Assistant  Conservator  of  the  Museum  of  the  Royal  College  of  Surgeons 
in  London. 
Communicated  May  26,  1835. 
In  investigating  the  nature  of  the  small  human  Entozoon  which  I  have  called  Tri- 
china, considerable  difficulty,  extrinsic,  or  superadded  to  the  subject  itself,  was  expe- 
rienced, from  the  habit  of  considering  all  such  internal  parasites  as  belonging  to,  or 
constituting,  a  distinct  class  of  animals.  It  is  true  that  it  was  easy  to  determine  in  Tri- 
china the  absence  of  trachecE,  of  branchia,  and  of  every  other  kind  of  respiratory  organs, 
as  well  as  of  any  true  circulating  organs,  and  that  not  even  a  vestige  of  a  nervous  chord 
existed  in  this  worm-like  animal.  But  its  reference  to  the  Entozoa  was  not  therefore  less 
a  matter  of  doubt ;  for  other  negative  characters  presented  themselves  in  relation  to  the 
digestive  system,  and  to  the  mechanism  for  adhesion  or  suction,  which  no  less  prevented 
its  association  with  already  known  Entozoa,  than  the  first-mentioned  deficiencies  sepa- 
rated it,  in  common  with  the  Entozoa,  from  Worms  of  a  higher  type  of  organization. 
The  greater  part  of  Cuvier's  definition  of  the  class  Entozoa  is  devoted  to  the  account 
of  their  localities,  and  the  remedies  used  against  them,  and  to  a  consideration  of  their 
mode  of  production  ;  while  the  character  itself  of  the  class  is  altogether  a  negative  one. 
"  On  n'apercoit  aux  vers  intestinaux  ni  trachees,  ni  branchies,  ni  aucun  autre  organe 
de  la  respiration,  et  ils  doivent  eprouver  les  influences  de  I'oxygene  par  I'intermediaire 
des  animaux  qu'ils  habitent.  lis  n'ofirent  aucune  trace  d'une  vraie  circulation,  et  Ton 
n'y  voit  que  des  vestiges  de  nerfs  assez  obscurs,  pour  que  plusieurs  naturalistes  en  aient 
mis  I'existence  en  doute."  Cuvier  then  adds  :  "  Lorsque  ces  caracteres  se  trouvent  re- 
unis  dans  un  animal,  avec  une  forme  semblable  a  celle  de  cette  classe,  nous  I'y  rangeons, 
quoiqu'il  n'habite  pas  dans  I'interieur  d'une  autre  espece^" 
In  consistency  with  this  proposition,  the  Vibriones  of  Miiller  ought  to  have  ranked  in 
the  '  Regne  Animal'  with  the  Entozoa ;  and  it  would  be  difficult  to  determine  what  mo- 
dification of  external  form  should  exclude  a  species  defective  in  respiratory  or  circu- 
lating organs  from  that  class  which,  even  in  Cuvier's  system,  includes  animals  of 
almost  every  variety  of  shape.  Fortunately,  however,  the  presence  of  external  vibra- 
tile  cilia,  which  are  in  some  degree  subservient  to  respiration,  afibrds  a  good  character 
for  distinguishing  the  simpler  Infusoria  from  the  Entozoa,  although  with  this  limitation 
those  species  of  non-ciliated  Vibriones^,  which  do  not  occasion  currents  when  placed  in 
a  coloured  fluid,  would  still  rank  with  the  Intestinal  Worms. 
'  Rfegne  Anim.,  nouv.  ed.,  torn.  iii.  p.  246. 
-  Amblyura  Serpentulus,  Ehr. ;  Anguillula  Aceti,  Auct. ;  and  Ang.  Glutinis,  Auct.  or  the  common  Vinegar-eel 
and  Paste -eel. 
