MR,  R.  OWEN  ON  THE  ANATOMY  OF  DISTOMA  CLAVATUM. 
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almost  cartilaginous  texture  at  the  bottom,  which  is  perforated  by  a  minute  orifice, 
through  which  the  fluids  absorbed  from  the  animal  infested  by  the  Distoma  pass  into 
the  digestive  tubes  ;  these  are  two  in  number,  and  are  continued,  slightly  enlarging  and 
diverging  from  one  another,  to  the  cells  at  the  posterior  part  of  the  body. 
About  2  lines'  distance  from  the  mouth,  on  the  concave  side  of  the  neck  or  narrow 
part  of  the  body,  there  is  a  small  transverse  slit,  concealed  by  the  wrinkles  of  the  in- 
tegument, forming  the  outlet  of  the  generative  organs.  The  large  cavity  behind  this 
slit  is  simply  for  adhesion,  and  does  not  communicate  with  the  interior  of  the  body : 
it  is  provided  with  a  strong  muscular  concave  disc,  the  margin  of  which  is  papillose  ; 
and  external  to  the  papilla  it  is  surrounded  by  a  circular  fold  of  the  integument.  The 
body  continues  to  enlarge  behind  the  acetabulum,  and  terminates  in  an  obtuse  clavate 
extremity.  On  closely  inspecting  this  part  a  minute  central  orifice  was  clearly  per- 
ceived, which  conducted  to  a  narrow  cavity  formed  between  two  layers  of  a  villous 
membrane,  extending  vertically  across  the  terminal  dilated  part  of  the  animal.  No 
communication  could  be  detected,  upon  the  most  minute  inspection,  between  this  cavity 
and  the  rest  of  the  body. 
Besides  the  cellular  parenchyma,  of  which  the  body  is  chiefly  composed,  the  three 
systems  of  canals,  digestive,  vascular,  and  generative,  which  the  Trematoda  usually 
possess,  are  present  in  their  ordinary  forms  and  positions ;  the  cells  at  the  smaller  end 
of  the  body  were  occupied,  in  this  specimen,  by  a  yellow  fluid,  containing  numerous 
ovula  of  the  same  colour,  many  of  which  had  thence  passed  into  the  tortuous  oviduct. 
Towards  the  posterior  part  of  the  body  the  cells  enlarge  in  size,  and  are  principally 
transverse  in  their  direction. 
The  clavate  end  of  the  body  is  occupied  by  two  large  lateral  cavities  in  addition  to 
the  mesial  one  above  mentioned.  The  side  cavities  were  filled  with  a  dark  brown  fluid, 
containing  minute  opake  particles  of  the  same  colour,  similar  in  appearance  to  partly 
digested  blood.  The  internal  surface  of  these  cavities  is  of  a  black  colour,  and  covered 
with  minute  folds  and  wavy  wrinkles.    The  dark-coloured  canals  which  meander  over 
the  lateral  parietes  of  the  body  take  their  origin  from  these  large  cavities,  which  also 
communicate  with  the  smaller  canals  anterior  to  them,  and  from  them  they  receive  the 
nutriment,  which  is  carried  backwards  by  the  two  alimentary  canals  from  the  mouth  ; 
so  that  they  hold  an  intermediate  position  between  the  alimentary  and  the  sanguiferous 
canals.    Analogous  reservoirs  have  been  observed  in  Amphistoma  conicum,  in  which 
they  have  been  denominated  by  Laurer  cisterna  chyli ;  and  similar  cavities  are  also  termed 
chyle  receptacles  {Chylusbehdlter)  by  Nordmann'  in  the  minute  Trematode  parasites  which 
he  has  detected  in  the  eyes  of  Fishes.  In  the  Distoma  clavatum,  however,  these  receptacles 
have  no  communication  with  the  mesial  cavity  or  the  posterior  aperture.  Nordmann 
observed  that  a  white  fluid  was  ejected  by  successive  spasmodic  actions  from  the  posterior 
aperture  of  Diplostomum  volvens,  which  corresponds  to  the  one  above  described  in  Di- 
'  "  Am  hintem  Ende  dieses  birnformigen  Organs  befindet  sich  eine  deutllche,  trichterformige  Offnung,  die 
durch  einen  Sphincter  geschlossen  werden  kann.  Man  konnte  es  vieDeicht  am  besten  mit  dem  Namen  eines 
Chylusbebalters  bezeichnen." — Micrograi)h.  Beitriige,  p.  38,  Hft.  1. 
3  E  2 
