OF  THE  EEPEODUCTIVE  OEGANS  OF  THE  ANNELIDS. 
103 
fused  heap  of  glands  into  an  orderly  system  of  parts,  and  moreover,  to  bring  the  sexual 
apparatus  of  this  Annelid  vsdthin  the  pale  of  definite  homologies. 
Every  ring  in  the  body  of  this  worm  (except  a few  at  the  head  and  tail)  contains  two 
segment  organs,  one  on  either  side  of  the  intestine : they  are  convoluted,  tubular  organs, 
arising  from  the  ventral  aspect  of  the  general  cavity  near  the  median  line,  curving 
upwards  round  the  intestine  and  terminating  in  a fan-shaped  ciliated  extremity,  which 
is  bridled  to  the  septum  near  its  dorsalmost  edge.  Those  segmental  organs  which  are 
situated  anteriorly  to  the  gizzard  are  very  much  larger  and  more  distinct  than  those 
which  are  placed  behind  it. 
It  is  desirable  in  the  first  place  to  obtain  a clear  idea  of  an  ordinary  or  non-generative 
segmental  organ  in  this  worm.  The  folio-wing  description  is  drawn  from  minute 
researches  conducted  with  care  by  the  author  himself.  Not  having  seen  the  original 
paper  of  Gegenbatjer*  on  this  subject,  he  cannot  say  how  far  his  o-wn  account  may  agree 
with  or  differ  from  that  of  this  anatomist. 
The  season  of  the  year,  the  state  of  the  weather,  have  much  to  do  with  the  condition 
in  which  these  organs  are  found.  All  the  specimens  upon  which  the  following  exami- 
nations were  instituted  were  taken  in  the  months  of  July  and  August,  from  a rich, 
loamy,  highly-cultivated  garden  soil. 
This  fact  it  is  material  to  know,  since  nowhere,  in  the  ordinary  fields  and  meadows, 
does  this  worm  attain  the  same  size  and  plumpness.  The  generative  nisus  does  not 
seem  to  reach  its  climax  until  the  worm  has  arrived  at  a certain  period  of  age  and  ful- 
ness of  growth,  so  that,  out  of  100  specimens  examined,  only  ten  or  fifteen  may  be  found 
in  that  condition  which  is  required  for  the  successful  prosecution  of  these  researches. 
The  accompanying  illustration  (fig.  5)  of  an  ordinary  segmental  organ  of  an  Earth-worm 
was  constructed  from  dissections  instituted  on  at  least  fifty  individuals:  so  exceed- 
ingly difiicult  was  the  inqufry,  that  only  a small  fragment  of  this  extraordinarily  com- 
plex tube  (extending  from  a to  fig.  5)  could  be  traced  in  each  individual.  It  was 
found  to  be  impossible  to  make  such  a section  of  the  annuli  as  would  afford  a com- 
plete -view  of  the  entire  apparatus.  Not-withstanding  these  difficulties,  the  following 
* Note,  added  April  2Tth,  1858. — I have  just  procured  that  number  of  the  Zeitschrift  fur  Wiss,  ZooL, 
for  September  1852,  which  contains  Gegenbauee’s  paper  “ Ueber  die  sogenannten  Eespirationsorgane  des 
Eegenwurms.”  It  affords  me  the  greatest  pleasure  to  find  that  the  description  given  in  the  text,  and  drawn 
exclusively  from  my  own  unaided  observations,  agrees  almost  in  every  minute  particular  with  the  description 
and  figures  of  Gegenbatjee.  It  is  gratifying  to  find  one’s  self  in  agreement  with  so  accurate  an  observer 
on  so  extremely  difficult  a point  in  minute  anatomy.  Our  concord,  however,  ceases  at  this  point.  Gegen- 
bauee’s  accoimt  of  the  complex  hotryoidal  vascular  system  of  the  segmental  organs  of  Lumhricus  is  little 
more  than  a passing  reference.  He  seems  neither  to  have  deciphered  its  anatomy  nor  recognized  its  homo- 
logical  significance.  He  speaks  of  the  “ schleifenformigen  Organe”  as  intended,  in  function,  to  discharge  in  a 
direct  manner  the  fluid  of  the  general  cavity,  and  also  to  furnish  a peculiar  excretion  from  their  own  walls. 
Although  he  alludes  to  the  increased  size  presented  by  these  organs,  both  in  l/wmbricus  and  in  Scemt/ris,  in 
the  segments  containing  the  generative  masses,  he  overlooks  completely  the  organic  connexion  which  I have 
invariably  found  to  exist  between  the  one  and  the  other,  and  upon  which  connexion  I have  attempted  in 
this  memoir  to  explain  the  homology  of  the  reproductive  system  of  the  Annelids  in  general. 
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