102  DE.  T.  WILLIAMS’S  EESEAECHES  ON  THE  STEHCTTJEE  ANT)  HOMOLOGY 
boundaries  and  float  in  the  neighbouring  fluid.  It  will  be  observed  at  once  that  a most 
constant  and  intimate  organic  connexion  exists  between  the  masses  (/,  g and  h,  h)  and 
the  coiled  tubes  of  their  respective  sides.  The  ova  on  the  one  side,  and  the  sperm-cells 
on  the  other,  may  be  actually  seen  by  the  eye,  on  many  occasions,  rolling  to  and  firo  in 
the  interior  of  the  dilated  portions  of  the  tubes  (a,  «^). 
To  this  Annelid  no  further  reference  will  be  necessaiy,  since  in  every  particular  the 
sexual  system  conforms  vnth  the  type  of  that  of  Nais.  In  the  young  of  this  worm  the 
ordinary  segmental  organ  exhibits  the  form  shown  at  flg.  3,  B. 
It  seems  to  the  author  that  a candid  review  of  the  preceding  facts  must  inevitahly 
conduct  to  the  conclusion  that,  in  this  species  (which  is  evidently  intermediate  between 
Nais  and  the  common  Earth-worm),  the  ovaries  on  the  one  side  and  the  testes  on  the 
other  are  not  only  organically  connected  with,  but  are  ingrafted  upon,  and  developed 
from,  the  standard  or  normal  segmental  organ. 
In  the  course  of  his  researches  the  author  has  accidentally  fallen  upon  other  species 
of  Lumbrici,  more  or  less  favourable  to  the  study  of  this  question.  In  L.  Kanii^  mihi, 
in  the  young  state,  the  segmental  organ  may  frequently  he  discovered  in  a condition 
highly  favourable  to  the  present  investigation  (see  flg.  4 A).  In  that  annulus  in  which  the 
contained  ciliated  tubes  are  destined  to  become  the  generative  organs,  the  latter  appear 
at  first  under  the  character  represented  at  c (fig.  4 B).  From  one  side  of  the  mid-portion 
of  the  tube  (as  at  4 C)  may  be  observed  to  bulge  minute  pear-shaped  vesicles,  filled  uith 
a semigelatinous  fluid.  Regarded  as  a whole,  it  is  impossible  to  doubt  that  this  organ  is 
one  of  the  segmental  organs.  If  this  be  admitted,  the  conclusion  cannot  be  resisted,  that 
the  vesicular  outgrowth  (c)  is  really  the  ovary  or  the  testes  in  process  of  development. 
But  in  the  same  individual  the  other  and  ordinary  segmental  organs  have  altogether  a dif- 
ferent form  and  structure  (fig.  4 A.  a a,  a,  and  B).  Thus  is  adduced  another  well-attested 
fact,  in  confirmation  of  the  view  maintained  in  this  paper,  viz.  that  the  reproductive 
organs  in  Aais  and  Lumbricus  are  in  reality  nothing  but  a modification  of  the  “ segmental 
organs  ” or  “ ciliated  tubes  ” which  exist,  in  pairs,  in  every  annulus  of  the  body. 
Earth-worm. — The  anatomy  of  the  reproductive  system  in  the  Earth-worm  has  been 
made  a subject  of  express  investigation  by  many  competent  comparative  anatomists. 
The  points  in  difference  between  the  author  and  other  observers  Avill  be  indicated  as 
we  proceed. 
The  anatomy  of  this  system  in  the  Earth-worm  has  ever  been  held  as  almost  an 
insoluble  enigma.  No  intelligible  clue  whereby  to  unravel  the  intricate  glandular  mass 
has  ever  been  discovered.  Without  such  a clue  the  problem  never  can  be  consistently 
solved.  It  is  hoped  that  such  a clue  ox  princijgle  is  afforded  m the  succeeding  accoimt. 
It  rests  upon  the  fact  that  between  the  reproductive  masses  and  the  ciliated  segmental 
tubes  there  exists  a necessary  and  regular  connexion,  and  that  the  glandular  masses  of 
the  adjacent  segments  are  distinct  from  and  independent  of  one  another.  A knowledge 
of  this  leading  principle  of  arrangement  enables  the  anatomist  at  once  to  convert  a con- 
