112  DE.  T.  WILLIAMS’S  EESEAECHES  ON  THE  STEHCTL^E  AND  HOMOLOGY 
The  first  impression  is,  that  they  must  be  connected  with  the  reproductive  masses ; but 
in  what  way  and  what  physiological  sense  \ It  has  already  been  demonstrated  that  the 
ovaria  and  testes  respectively,  in  their  several  segments,  are  anatomically  developed  from 
the  ciliated  tubes.  But  this  fact  throws  no  light  upon  the  use  of  the  tubes  themselves.  Is 
it  possible  that  they  can  act  as  the  conduits  by  which  the  generative  products  are  con- 
veyed into  the  perigastric  cavity  1 No,  it  is  not  possible,  for  the  cilia  by  which  the  tubes 
are  lined  act  in  the  reverse  direction,  tending  rather  to  carry  outwards,  and  that  Avith 
great  force,  any  body  that  may  perchance  be  thrown  into  the  channels  of  the  tubes. 
This  fact  is  sustained  by  another  fact,  viz.  that  in  N^ais  and  Litmbricus  neither  the  ova 
nor  the  sperm-cells  have  ever,  under  any  circumstances,  been  discovered  in  the  general 
cavity  of  the  body.  On  these  and  other  grounds  it  is  then  probable  that  the  augmented 
size  of  the  ciliated  tubes  in  the  “ generative  region  ” may  be  ascribed  to  two  causes : 1st,  to 
the  fact  that  they  are  the  roots  from  which  the  ovarian  and  testicular  masses  arise ; and, 
2nd,  that  by  means  of  their  open  ciliated  ends,  they  may  effect  the  discharge  of  a larger 
quantity  of  the  cavitary  fluid  from  the  segments  in  which  they  are  situated ; and  the  more 
rapid  elimination  of  this  fluid  from  this  region  is  most  probably  concerned  in  the  more 
energetic  nutrition  chai’acteristic  of  the  generative  segments  *. 
Hirudmei. — The  segmental  organ  in  the  Leech  tribe  exists  under  very  readily  demon- 
strated conditions.  Two  genera  of  this  family  will  be  here  selected  for  the  purposes  of 
illustration,  viz.  the  common  officinal  Leech  {Sanguisuga  medicinalis)^  and  the  Sea  Leech 
{Alhione  muricata). 
The  method  to  be  observed  in  the  dissection  of  these  Annelids  is  the  same  ■with  that 
recommended  in  the  case  of  Lumbricus. 
After  pinning  the  common  leech  down  carefully  to  the  trough  and  opening  the  body 
by  a longitudinal  incision  along  the  dorsal  aspect,  pinning  down  again  the  integuments, 
the  whole  stomach  and  its  diverticula  must  be  minutely  picked  away.  The  dissection 
should  be  repeatedly  washed  with  very  gentle  streams  of  fresh  cold  water,  in  order  to 
remove  the  blood  which  obscures  everything.  The  object  being  thus  carefully  cleansed 
and  then  floated  in  water,  a full  and  complete  view  of  the  segmental  ovarian  and  the 
median  testicular  systems  will  present  itself.  It  is  most  important  that  at  this  stage  the 
anatomist  should  well  and  clearly  instruct  himself  as  to  the  relative  extent  and  relative 
anatomical  places  of  these  two  systems. 
The  one  consists  of  a bilateral  series,  of  extremely  delicate  floating  pearly  membranous 
organs,  equalling  in  the  number  of  their  pairs  that  of  the  annuli  marked  on  the  integu- 
ments. 
'*  In  a paper  in  Mulleb’s  Archiv,  1844,  on  the  genitalia  of  Lumbricus  terrestris,  H.  Meckel  remarks 
that  there  are  three  pairs  of  testes  with  sacculi  and  three  pairs  of  ovaries,  the  latter  being  intimately  joined 
to  the  former.  This  statement  seems  to  show  that  the  results  arrived  at  by  Meckel  closely  correspond 
with  the  description  contained  in  the  text.  They  do  so  only  as  regards  the  distribution  of  the  masses  of  the 
ovaries  and  testes.  To  Meckel,  however,  the  existence  of  the  ciliated  tubes  Avas  unknown,  nor  does  he 
suspect  the  importance  of  the  septa  in  separating  the  ovaries  and  testes  into  segmental  independent  groups. 
