OF  THE  EEPEODHCTIVE  OEGANS  OF  THE  ANNELIDS. 
107 
The  Sexual  System  of  the  Earth-worm,  Lumbricus  terrestris,  appears,  on  a superficial 
inspection,  to  consist  of  an  inextricably  confused  mass  of  ovaria  and  testes,  bound  to 
and  centred  in  a particular  region  of  the  body  without  rule,  law,  or  intelligible  order*. 
But  the  results  arrived  at  by  the  numerous  anatomists  who  have  laboured  on  this  subject 
are  still  more  confused  and  contradictory.  Sir  E.  Home,  Duges,  Meckel,  Hoffmeistek, 
De  Quateefages,  D’Udekem,  and  lastly,  and  more  especially  and  recently,  Meissnee  and 
Heeing,  amongst  many  others,  may  be  named  in  this  category.  They  have  bequeathed 
to  us  no  consistent  account  of  the  reproductive  organs  of  this  worm.  These  organs  have 
proved  a puzzle  to  anatomists  of  every  age ; and  they  are  so  to  this  day,  notwithstanding 
the  meritorious  researches  of  those  whose  names  have  been  mentioned. 
The  author  is  fully  impressed  with  the  difficulties  which  beset  the  investigation.  He 
has  not  therefore  ventured  upon  conclusions  with  respect  to  the  subject  in  dispute, 
without  great  care,  caution  and  labour. 
He  now  beheves,  however,  that  he  has  seized  the  true  clue  which  will  conduct  the 
patient  dissector  to  a complete  and  satisfactory  solution  of  this  long- vexed  problem. 
He  will  proceed  at  once  to  state  the  results  of  his  own  researches,  indicating  in  notes 
the  points  whereon  he  differs  from  other  observers. 
The  dissection  of  the  Earth-worm  requires  great  manipulative  skill  and  experience. 
The  animal  should  be  pinned  down  (with  the  back  upwards)  to  a cork-bottomed  vessel. 
The  posterior  half  of  the  body  may  be  cut  off  as  unnecessary  for  our  purpose.  By 
means  of  a curve-scissors  a longitudinal  incision  should  then  be  made  along  the  dorsal 
median  line.  The  point  of  the  instrument  should  run  in  the  hollow  axis  of  the  intestine. 
The  integuments  should  then  be  pinned  down  and  slightly  stretched.  A gentle  stream 
oi  fresh  water  should  now  be  allowed  to  fall  on  the  worm  thus  opened.  This  will  carry 
away  the  contents  of  the  intestine,  and  float  the  delicate  parts  without  arresting  ciliary 
action.  If  the  operation  thus  far  has  been  carefully  performed,  the  object  is  ready  for 
examination.  The  eye  should  be  first  carefully  carried  along  the  septa,  or  the  mem- 
branous partitions  between  the  annular  chambers.  It  will  be  seen  that  these  mem- 
branous septa,  when  clearly  traced  out  by  the  aid  of  the  handle  of  the  scalpel,  divide 
with  great  regularity  the  reproductive  masses  into  segmental  groups.  This  point  impli- 
cates a principle  of  great  anatomical  importance.  It  establishes  this  fact,  viz.  that  the 
contents  of  each  ring  or  annulus  are  distinct  from,  and  structurally  independent  of,  those 
of  the  adjacent  rings  or  annuli f. 
It  countenances  the  idea  of  the  zooidal  individuality  of  each  annulus.  An  annulus 
in  the  generative  region  is  a perfect  organism  in  its  nervous,  hsemal,  visceral,  fluid  and 
reproductive  parts,  not,  however,  an  hermaphrodite  organism. 
* See  plate  21  bis,  in  the  volume  “ Sur  les  Annelides,”  ‘Eegne  Animal,’  which  is  taken  from  the  dissec- 
tions of  Lumbricus  trapezoides  by  De  Quateeeages. 
+ Lest  the  dissector  who  undertakes  to  repeat  these  researches  should  be  led  hastily  astray,  it  is  here 
proper  to  explain  that  it  is  meant  only  those  parts  which  take  their  origin  in  the  individual  segments,  not 
those  masses  which  by  growth  swell  beyond  the  dimensions  of  several  annuli. 
