or  THE  EEPEODUCTIVE  OEOANS  OF  THE  ANNELIDS. 
101 
behind,  as  in  the  common  Earth-worm,  a thickened  ring  or  band  around  the  body.  It 
is  bounded  by  abrupt  limits,  and  implicates  four  or  six  of  the  annuli  of  the  body. 
When  this  portion  of  the  integument  is  closely  examined,  it  proves  to  depend  upon  an 
extraordinary  development  of  the  cutaneous  follicles.  On  the  abdominal  aspect  of  this 
thickened  portion,  suctorial  cups  are  formed,  by  aid  of  which,  during  the  congress  of  the 
individuals,  mutual  contact  is  maintained ; but  the  generative  segments  internally  have 
no  relation  with  this  suctorial  ring  of  integument,  nor  has  this  latter  part  anything  to  do 
with  the  time  genitalia.  It  is  like  the  thumb  of  the  Frog ; it  is  simply  a provision  for 
the  mutual  apposition  of  two  individuals.  The  enlarged  follicles  of  this  cutaneous  ring 
discharge  also  another  function ; they  supply  that  peculiar  glutinous  secretion  which 
affords  (in  such  a remarkable  manner  in  the  cases  of  Inimbricus  terrestris  and  L.  com- 
planatus)  a protecting  capsule  to  the  ova  as  they  escape  from  the  body.  This  peculiar 
hj^ertrophy  of  the  integuments  in  the  region  of  the  reproductive  segment  occurs  also 
in  every  species  of  Nais. 
lAimhricus  Jordanii  is  a minute  worm  of  pure  white  colour.  The  integuments  are 
transparent  enough  to  enable  the  eye  to  read  the  interior  organs.  The  ordinary  seg- 
mental organs  are  present,  in  pairs  (fig.  3 A.  m,  m),  in  every  annulus  of  the  body;  they  do 
not  however  float  freely  in  the  fluid  of  the  general  cavity,  as  in  Nais.  They  are  attached 
to  the  side  of  the  intestine  by  means  of  threads  or  delicate  membranes,  the  trumpet- 
shaped extremity  being  fixed  to  a determinate  point. 
All  those  organs  which  are  distributed  throughout  that  part  which  is  posterior  to  the 
generative  segments  are  in  the  ordinary  condition  (fig.  3 A.  w,  m).  The  internal  end  [j)  of 
the  tube  in  this  worm  is  figured  after  a pattern  intermediate  between  that  of  Nais  and  that 
of  Lumbricus.  It  is  less  trumpet-shaped  than  the  latter,  and  more  so  than  the  former. 
In  this  little  terrestrial  Annelid,  as  in  the  aquatic  Nais,  only  two  segmental  organs, 
one  on  either  side,  are  specially  evolved  into  the  reproductive  condition ; in  other 
words,  only  one  ring  of  the  body  is  implicated  in  this  function;  bearing  in  this  re- 
spect a striking  resemblance  to  the  instance  of  Nais,  and  differing  no  less  strikingly 
from  that  of  the  common  Earth-worm,  in  which  six  or  eight  pairs  of  these  organs 
experience  this  special  enlargement.  In  L.  Jordanii,  as  in  Nais,  the  generative  tubes 
(fig.  3 A.  « ^ and  a^  e)  are  considerably  developed  when  measured  by  the  standard  of 
the  ordinary  non-generative  ones  [m,  m).  The  utricular  ends  [g,  c)  are  far  more  elongated 
than  in  Nais,  but  they  bear  precisely  the  same  relation  to  the  ovarian  masses  [b,  b)  as  is 
observed  in  the  latter.  The  intermediate  tube  [d)  is  extremely  coiled  and  elongated; 
the  free  ciliated  extremity  exhibits  a distinctive  form ; it  is  pear-shaped  [e,  i) ; it  is  very 
long,  provided  with  veiy  thick  walls ; and  at  the  extremity  it  is  furnished  with  a lip, 
highly  ciliated  (1),  which  appears  to  be  adapted  to  favour  the  ingress  of  the  chyl- 
aqueous  fluid  into  the  bore  of  the  segmental  organ. 
By  easy  manoeuvres  a clear  sight  of  the  reproductive  masses  may  be  obtained  in  all 
their  relations.  Under  skilfully-regulated  pressure,  the  entire  system  will  burst  its 
MDCCCLVIII.  p 
