[   381  ] 
XL.  On  the  Anatomy  o/Distoma  clavatum,  Rud.    By  Richard  Owen,  Esq.,  F.R.S.  ^ 
Z.S.,  Assistant  Conservator  of  the  Museum  of  the  Royal  College  of  Surgeons  in  London. 
Communicated  May  26,  1835. 
In  former  papers^  I  gave  descriptions  of  two  Entozoa,  or  internal  animal  parasites,  of 
widely  different  degrees  of  organization :  the  one  manifesting  simply  a  homogeneous 
granular  pulp,  enveloped  in  a  transparent  thin  elastic  tegument ;  the  other  having  di- 
stinctly developed  nervous  ganglions  and  filaments,  a  muscular  tunic,  a  digestive  canal 
contained  in  an  abdominal  cavity,  ovaries,  oviduct,  and  fecundating  glands.  I  now 
propose  to  offer  a  few  observations  on  an  Entozoon  of  an  intermediate  grade  of  struc- 
ture, in  which  a  cellular  parenchyma  still  occupies  the  body,  where  no  distinct  ner- 
vous filament  can  be  traced,  but  in  which  a  complicated  system  of  nutritious  and  gene- 
rative canals,  with  external  organs  for  adhesion  and  locomotion,  are  developed. 
My  attention  was  first  called  to  the  species  of  Distoma  about  to  be  described  by  the 
following  circumstance.  In  the  series  of  the  Hunterian  collection  of  comparative  ana- 
tomy relating  to  the  digestive  functions,  there  is  a  preparation^  of  an  Acrite  Invertebrate 
animal,  of  a  round  elongated  form,  showing  at  one  extremity  a  sac  opening  externally 
by  a  minute  orifice  ;  and  at  the  opposite  end  a  larger  orifice  surrounded  by  a  suctorious 
disc,  behind  which,  and  at  a  little  distance  from  each  other,  are  two  other  orifices,  the 
posterior  being  of  large  size,  and  evidently  an  organ  of  adhesion.  From  the  manuscript 
catalogue  it  appeared  that  Mr.  Hunter  had  regarded  the  sac  as  the  stomach. 
I  was  for  some  time  uncertain  to  what  class  of  animals  this  singular  specimen 
could  belong,  but  was  inclined  to  refer  it  to  the  Trematode,  or  fluke-worms,  on  account 
of  the  suctorious  orifices  at  the  smaller  end ;  although  the  digestive  cavity,  which 
the  specimen  had  apparently  been  prepared  to  exhibit,  was  a  feature  in  its  organiza- 
tion which  appeared  to  remove  it  equally  from  that  and  any  other  order  of  the  Ster- 
elmintha.  Subsequently,  however,  on  looking  over  the  '  Spicilegia  Zoologica '  of 
Pallas,  I  found,  in  the  tenth  fasciculus,  a  figure  and  description  of  a  Worm  termed  Fas- 
ciola  ventricosa,  which  closely  resembled  the  animal  in  question.  The  general  form  and 
situation  of  the  different  orifices  were  the  same,  but  the  orifice  corresponding  to  that 
which  led  to  the  cavity  regarded  by  Mr.  Hunter  as  the  stomach,  Pallas  calls  the  anus. 
The  account  given  of  the  cellular  parenchyma  of  the  body,  of  its  dark-coloured  con- 
tents, and  yellow  ovula,  agreed  very  closely  with  the  appearances  in  the  Hunterian  speci- 
men, but  nothing  could  be  deduced  from  the  description  as  to  the  existence  of  any  cavity 
communicating  with  the  anus,  corresponding  to  that  which  the  Hunterian  specimen 
presented ;  and  the  figures  given  by  Pallas  illustrate  the  external  form  only.  The  size 
of  the  specimen  described  in  the  '  Spicilegia'  is  nearly  2  inches  in  length,  and  f  of  an 
>  Page  315  and  page  325.  «  No.  116. 
VOL.  1.  3  E 
