120  DE.  T.  WILLIAMS’S  EESEAECHES  ON  THE  STEHCTUEE  AXD  HOMOLOGY 
lateral  process  (?^),  (ypens  into  the  canity  of  the  lody.  It  is  by  tbis  last  process  tbat 
the  ova  in  the  female  and  the  sperm-cells  in  the  male  reach  the  perigastric  chamber. 
As  far  as  the  commencement  of  this  lateral  process,  the  generative  products  are  con- 
veyed by  the  cilia-excited  water-current  already  explained;  but  how  they  are  made 
at  this  particular  point  to  turn  towards  n,  the  opening  leading  into  the  perigastric 
chamber,  instead  of  escaping  externally  with  the  water-stream  through  B,  can  only  be 
explained  by  ascribiag  to  this  spot  a vital  sphincteric  selective  office.  The  only  link 
that  is  wanting  in  the  chain  of  evidence  proving  that  the  ova  are  formed  in  and  then 
pass  out  from  the  segmental  organ  into  the  perigastric  chamber,  is  just  the  opening  from 
the  former  into  the  latter.  The  ova  in  the  female  and  the  sperm-cells  in  the  male  are 
abundantly  and  constantly  found  in  the  fluid  of  the  general  cavity,  and  the  author  has 
repeatedly,  in  the  series  of  observations  which  he  has  instituted  upon  this  subject, 
actually  seen,  in  large  crowds,  the  ova  in  the  outgoing  limb  [h  B).  The  ova  at  this 
point  consist  of  clean  pellucid  germinal  vesicles.  The  vitellus  has  not  yet  appeared. 
After  they  have  sojourned  for  some  time  in  the  general  cavity,  the  latter  begins  to  show 
itself.  Now  although  the  author,  in  consequence  of  the  pecuhar  difficulties  of  the 
subject,  has  never  been  able  to  demonstrate  clearly  the  mode  by  which  the  generative 
products  pass  from  the  segmental  organs  into  the  perigastric  ca\dty,  he  is  compelled  to 
beheve  that  this  passage  is  made,  from,  the  fact  that  the  ova,  at  one  stage,  are  actually 
seen  in  the  segmental  organ,  at  another,  in  the  general  cavity  of  the  body.  To  complete 
the  chain  of  evidence  it  is  only  necessary  to  demonstrate  the  mode  in  which  they  escape 
from  the  one  place  into  the  other.  The  segmental  organ  is  the  true  ovary  in  the  female 
and  the  true  testes  in  the  male.  It  is  not  difficult  to  prove  this  proposition.  The 
ingoing  limb  of  the  organ  (as  far  as  the  point  (Z ) is  a highly  glandular  structure ; its 
vessels  are  densely  packed  and  specially  arranged ; its  walls  are  thick  and  stromatous ; 
at  its  mid-point  (^)  is  a noted  glandular  development.  From  the  vascular  system  of  this 
gland  proceeds  the  great  vascular  organ  stretching  from  g^  to  g^. 
To  the  one  side  of  this  great  vascular  system  there  are  appended  peculiar  ceecal 
pouches  [e  e) ; from  the  other  {ff),  a dense  capillary  plexus.  This  vascular  appendage 
is  the  morphological  equivalent  of  the  blood-system  connected  with  the  ovogenetic  limb 
of  the  segmental  organ  of  the  Leech  {f  flg.  9),  and  of  the  botryoidal  apparatus  of  vessels 
{h  h,  flg.  5)  connected  with  the  segmental  organ  of  Lambincus. 
It  is  impossible  that  this  most  singular  system  of  vessels  can  discharge  any  other 
function  than  the  following : viz.  [a)  it  is  the  receptacle  of  an  extra  supply  of  blood  to 
an  organ  susceptible  of  periodical  expansion ; (^)  it  excretes  something  from  the  blood- 
proper  into  the  cavity  of  the  segmental  organ  [m),  which  is  essential  to  the  fiudher 
development  of  the  generative  products.  In  Arenicola  it  is  quite  certain  that  the  o^  a 
and  sperm-cells  pass  through  the  last  stage  of  their  development  in  the  perigastric 
chamber.  How  they  escape  out  of  this  chamber  has  never  yet  been  proved  *. 
* Eathke  and  Grube  have  argued  that  Arenicola  is  androgynous.  He  Qttatreeages,  however,  from 
his  knowledge  of  the  development  of  the  spermatic  particles,  has  long  recognized  the  existence  of  sepai’ate 
