110  DE.  T.  WILLIAMS’S  EESEAECHES  ON  THE  STEUCTIJEE  AXD  HOMOLOGY 
segmental  organs  of  opposite  sides  of  the  same  ring  become  developed  into  opposite 
sexual  parts  (ovaries  and  testes*). 
The  second  generative  annulus  in  the  order  mentioned  is  exclusively  ovarian.  The 
greatest  care  should  be  taken  to  float  well  the  delicate  septa  in  order  to  define  distinctly 
the  annulus.  Having  done  this,  it  will  be  easy  to  prove  that  the  mass  {f)  and  the  base 
of  the  ciliated  tube  run  together,  and  become  blended  into  one  structure. 
The  most  minute  dissection  fails  in  the  attempt  to  isolate  the  duct  which,  it  may  be 
supposed,  leads  from  the  ovary.  When  the  gland  is  cut  out  deeply  in  connexion  with 
the  ciliated  tube,  it  is  found  to  surround  this  tube  as  shown  at  fig.  8 ; so  intimate  is  this 
connexion,  that  it  is  certain  that  (as  in  the  case  of  the  testes  and  tube  in  the  segment 
behind)  the  gland  and  the  tube  must  have  a common  outlet.  The  ovary  is  considerably 
smaller  than  the  testes.  Its  capsule  is  more  dense  and  vascular,  and  its  interior  strac- 
ture  is  much  more  thickly  supplied  with  blood.  The  vessels  in  the  structrne  of  the 
ovaries  have  a peculiar  arrangement ; they  run  parallel  with  the  lobuli  of  the  gland,  a 
dense  capillary  plexus  being  formed  between  the  larger  trunks. 
The  ciliated  tubes  of  this  ovarian  annulus  do  not  differ  in  size  or  structui’e  from  those 
of  the  testicular  annulus.  It  is  therefore  impossible  to  tell  why  on  the  one  an  ovary 
should  be  ingrafted,  and  on  the  other  a testis  f. 
In  the  common  Earth-worm  the  second,  third  and  fourth  generative  segments  (fig.  6 
f?,  e,f)  are  ovarian.  Each  ovarian  segment  is  anatomically  only  a repetition  of  the 
other ; all  are  constructed  upon  the  same  plan.  Some  slight  difference  in  the  size  and 
position  of  the  glandular  masses  may  be  observable ; there  is  none  in  their  ultimate 
relations. 
The  fifth  segment  (from  behind)  of  the  generative  rings  is  again  testicular.  In  gene- 
ral and  minute  structure  this  segment  is  precisely  the  same  as  the  fii’st.  At  this  point 
* In  the  plate  copied  from  his  MS.  and  published  in  the  grand  edition  of  the  ‘ Eegne  Animal  ’ (vol. 
Annelides,  pi.  21),  De  Quatrefages  indicates  the  most  posterior  of  the  generative  masses  in  Lumhricus 
trapezoides  as  the  testes,  the  anterior  group  being  the  ovaries. 
t Ewald  Heeix g,  in  his  account  of  the  ovaries  in  Lunibricus  agricola,  describes  and  figures  the  ovaria  as 
occupying  the  hindmost  of  the  generative  segments.  “ Durchschneidet  man  jetzt  den  Harm  an  der  beschrie- 
benen  Stelle,  so  erscheinen  die  Ovarien  unter  der  Loupe  als  zwei  flache,  ovale  oder  birnlormige,  in  einen 
raelir  weniger  langen  Eaden  auslaufende  Scheibchen,  die  an  die  vordere  Scheidewand  des  di’eizehnten  Seg- 
ments ungefahr  1 Mm.  von  der  Mittellinie,  0.  5.  Mm.  von  der  Bauchfliiche  init  ihrem  breiten  Ende  ange- 
heftet  frei  in  die  Leibeshohle  hineinragen,  so  dass  ihre  Elache  der  Bauchflache  parallel  geht.  Da  an  der- 
selben  Stelle  jederseits  auch  das  Schleifenformige  Organ  befestigt  ist,  so  isolirt  man  das  Ovarium  am 
besten,  wenn  man  jenes  fasst  und  beide  nebst  dem  angrenzenden  Theile  des  Septums  herausschneidet.  Auf 
einem  Glaschen  ist  es  dann  leicht  weiter  zu  isolireu.  Stets  Jlndet  man  den  Jiimmernden  Trichter  des  schlei- 
fenfdrviigen  Organs  an  der  Basis  des  Ovariwms  angeheftet."  Loc.  cit.  Judging  from  his  figures  as  to  the 
real  character  of  what  Heeixg  here  describes  as  the  ovaria,  and  guided  by  what  is  so  perfectly  and  clearly  de- 
monstrable in  Lumhricus  terrestris  (a  species  synonymous  with  his  Lumhricus  communis'),  it  appears  beyond 
doubt  that  this  observer  has  mistaken  some  other  structures  for  the  true  ovaria.  Heeixg’s  account  difters 
as  widely  from  the  statements  and  figures  of  De  Quatrefages,  with  respect  to  the  ovaiia  of  an  allied 
species,  as  they  do  from  my  own. 
