OF  THE  EEPEODUCTIVE  OEGANS  OF  THE  ANNELIDS. 
113 
The  other,  more  medianly  situated,  and  bilateral  also,  consists  of  two  series  (one  on 
either  side)  of  spherical  white  little  bodies,  tied  together  by  an  intermediate  thread, 
which  unite  at  a common  point  anteriorly. 
A third  element  should  be  noticed,  namely,  the  small  sacculus  which,  immediately 
behind  the  anterior  mass  of  the  united  testes,  lies  also  on  the  median  line. 
Now  the  first  of  these  three  systems  of  organs  has  been  described  as  belonging  to  the 
reproductive  system  by  no  other  writer  than  the  author  of  this  paper*. 
By  Duges  they  have  been  described  as  the  Respiratory  Sacculi ; by  De  Quatrepages, 
in  Hirudo  vacca  and  other  species  of  this  genus,  as  the  “ Poches  secre trices  laterales  avec 
leur  coecum,”  and  by  Leydig  simply  (in  Neplielis)  as  the  analogues  of  the  ciliated  tubes 
of  the  Rotifera ; by  Muller,  Meckel,  Siebold,  and  Milne-Ed wards  and  others,  as  the 
“internal  branchiae”  or  aquiferous  vessels.  Not  one  of  these  distinguished  anatomists 
appears  at  any  time  to  have  discovered  the  existence  of  ova  in  these  variously  designated 
organs.  No  suspicion,  therefore,  as  to  their  ovarian  character,  could  have  existed. 
Gegexbauer  and  Leydig  are  the  only  physiologists  who  have  caught  even  a glimpse  at 
their  true  homology.  Thus  stands  at  the  present  time  the  question  as  to  the  history 
of  the  reproductive  system  and  of  the  segmental  organs  in  the  genus  Hirudo.  It  must 
be  confessed  that  much  information  remains  to  be  acquired.  The  author  hopes  that  the 
following  contribution  Avill  go  far  to  supply  this  admitted  desideratum. 
The  testes  and  the  copulative  median  pouch  have  hitherto  been  regarded  as  consti- 
tuting the  entire  reproductive  apparatus  of  the  Leech  family.  The  vermiform  processes 
appended  to  the  fundus  of  the  pouch  have  been  described  as  the  ovary,  and  the  pouch 
itself  as  the  uterus.  It  will  now  be  demonstrated,  for  the  second  time,  that  this  idea 
with  respect  to  the  ovarian  system  of  this  family,  involves  a very  complete  and  radical 
error. 
It  may  be  desirable  to  commence  by  admitting,  that  the  minute  membranous  organs, 
which  in  the  Hirudinei  exist  in  pairs  (one  on  either  side  of  the  stomach)  in  each  ring  of 
the  body,  are  the  equivalents  or  homologues  of  the  ciliated  tubes  or  segmental  organs, 
as  already  described  in  Limihiicm  and  Ahzsf. 
* In  my  Eeport  to  the  British  Association  in  1851,  I described  at  length  the  anatomy  of  the  reproductive 
system  of  the  common  Leech.  As  no  reference  whatever  has  been  made  to  that  description  by  any  subsequent 
writer  (see  the  last  edition  of  Dr.  Caepentee’s  ‘Principles,’  &c..  Professor  Owen’s  ‘ Lectures  on  the  Inver- 
tebrata’),  except  Mr.  Eymee  Jones  (‘Animal  Kingdom,’  last  edition,  1856),  in  this  country,  I resolved  to 
apply  myself  during  the  past  two  summers  to  the  renewed  investigation  of  the  subject.  The  result  is  tliat 
I have  again  and  again,  in  every  essential  respect,  demonstrated  the  correctness  of  my  first  account.  Some 
of  these  demonstrations  have  been  recently  witnessed  by  Dr.  Caepentee  and  Mr.  Busk.  An  error  or 
two  of  minute  detail  and  of  interpretation,  as  contained  in  the  original  report,  are  corrected  in  the  improved 
description  given  in  the  text.  In  one  important  respect,  however,  the  reproductive  system  of  tlie  Leech, 
although  descriptively  resolved,  was  utterly  incomprehensible  to  me  in  a homological  sense,  for  I had  not 
then  discovered  that  the  ovaria  (and  their  appendages)  of  this  Annelid  are  really  tlie  equivalents  of  the 
ciliated  tubes  of  Lumhricus  and  Nais. 
t As  the  following  passage  from  a recent  paper  by  Leydig  (“  Ueber  den  Bau  und  die  systematische  SteL 
