OF  THE  EEPEODUCTIVE  OEGAJN'S  OF  THE  ANNELIDS. 
135 
be  more  beautiful  than  a portion  of  this  tubular  network  (taken  from  the  female  organ). 
The  individual  tubes  are  bridled  (A  e)  on  one  side,  and  glandular  (A  d)  on  the  other. 
A similar  structure  is  exhibited  by  the  male  tubes  (B  d). 
The  author  thinks  it  probable  that  if  the  roots  or  attached  ends  (a,  a,  fig.  28)  of  these 
organs  could  only  be  followed  through  the  integuments  to  their  extreme  outlets,  they 
would  be  found  to  di\dde  into  two  limbs,  an  ingoing  and  an  outgoing ; a fact  which 
would  account  for  the  clearly  divided  ciliary  currents,  as  they  are  seen  in  the  dilated 
portions  (A,  B)  of  the  organs  (see  arrows).  If  this  fact  of  the  bifurcation  of  the  tube 
were  clearly  determined,  there  would  be  no  difficulty  whatever  in  connecting  the  seg- 
mental organs  of  Aphrodita  -with  their  homologues  in  the  typical  Annelids.  In  the 
absence  of  proof  yxpon  this  point,  however,  they  must  be  described  as  commencing  in  a 
single  tube,  the  internal  extremity  of  which  divides  into  a numerous  system  of  branches. 
None  of  these  branches  communicate  openly  with  the  general  cavity  of  the  body.  It  is 
therefore  probable  that  these  organs  are  exclusively  dedicated  to  the  office  of  repro- 
duction. They  seem  unfitted  to  discharge  any  subsidiary  function. 
Now  there  are  several  features  in  the  history  of  the  segmental  system  of  Aphrodita, 
which  irresistibly  suggest  certain  definite  inferences  as  to  its  morphology.  In  the  first 
place,  the  indi\idual  organs  are  segmentally  or  annularly  repeated ; in  the  second,  they 
constitute  a symmetrical  bilateral  series.  They  arise  from  either  side  of  the  median 
ventral  line.  They  float  in  the  fluid  of  the  perigastric  cavity  (accidentally  tangled 
around  the  gastric  cseca).  The  ova  in  the  female,  and  the  sperm-cells  in  the  male,  are 
seen  with  perfect  clearness  in  the  interior  of  then.'  branching  tubuli.  The  significance 
of  these  facts  cannot  for  a moment  be  disputed.  If  there  be  any  basis  of  truth  or  fact 
in  the  science  of  comparative  anatomy  whereon  to  rest  the  doctrine  of  equivalent  forms 
(morphology),  it  cannot  be  denied  that  the  branched  segmental  organs  of  Aphrodita  are 
only  another  example,  under  the  guise  of  an  unusual  variation,  of  the  typical  segmental 
organ  as  now  described  in  the  Annelids  in  general. 
In  Sigalion,  Pholoe  and  Polynoe,  this  system  occurs  under  precisely  the  same  charac- 
ters as  those  just  indicated  in  Aphrodita.  If  there  be  any  difference,  it  is  marked  only 
by  the  number  and  complexness  of  the  branches  (fig.  27  A,  B). 
The  blood-vascular  system  in  all  the  Aphroditadse  is  almost,  if  not  entirely  wanting ; 
upon  this  special  point  the  author  has  instituted  numerous  and  careful  observations. 
In  no  instance  whatever  amongst  this  family  has  he  ever  succeeded  in  detecting  the 
faintest  trace  of  a blood-vascular  system,  except  in  Pholoe  inornata.  In  this  little 
Aphrodite  a vessel  may  be  seen,  carrying  a colourless  fluid,  in  contact  with  and  parallel 
to  the  ventral  nervous  chord,  slowly  undulating  with  pulsations.  Practically  this  fluid- 
system  is  wanting  in  the  Aphroditadse ; it  can  therefore  play  no  part  in  the  generative 
functions.  As  will  be  subsequently  shown,  this  fact,  added  to  a mass  of  others,  will 
compel  the  morphologist  to  admit  a close  zoological  affinity  between  the  aberrant 
Annelids  and  the  Asteriadea  and  Echinidea  among  the  Echinoderms. 
T 2 
