OF  THE  EEPEODHCTIVE  OEOAHS  OF  THE  ANNELIDS. 
123 
They  are  present  alike  in  the  male  and  in  the  female.  In  structure  they  consist  of 
follicles  filled  with  large  fatty  particles,  difiering  most  widely  from  the  true  sperm-cells. 
The  office  of  this  median  glandular  mass  is  undoubtedly  to  supply  the  lubricating  and 
cementing  fluid  by  which  the  animal  forms  and  moulds  its  tube. 
The  testes  in  the  male  Terehella  are  the  lateral  pouches  or  true  segmental  organs,  as 
in  the  female  they  are  ovaria.  In  this  genus,  as  in  Arenicola^  the  generative  products 
in  both  sexes  are  early  introduced  into  the  general  cavity,  in  the  fluid  of  which  they 
rapidly  become  developed. 
In  concluding  his  remarks  upon  the  Terebellidae,  the  author  is  anxious  to  recapitulate 
one  or  two  points.  That  the  lateral  pouches  are  the  real  reproductive  organs  is  certain 
from  these  facts : — 
At  a particular  season  they  are  crowded  with  ova  (in  the  female)  and  sperm-cells  (in 
the  male).  These  products  respectively  are  less  developed  than  those  contained  in  the 
general  cavity;  but  as  to  their  being  one  and  the  same  bodies  in  the  two  places,  there  is 
no  doubt.  Next,  there  is  the  negative  evidence  of  the  absence  of  any  other  organ  in 
the  body  entitled  to  be  called  a genital  apparatus.  And  thirdly,  there  is  the  incontro- 
vertible proof,  derived  from  the  structure  and  segmental  position  of  the  organ,  that  it  is 
the  homologue  of  that  part  in  the  Hirudinei  in  which  the  ova  are  formed  and  afterwards- 
lodged  throughout  the  entire  period  of  their  intra-matemal  life.  The  segmental  organ 
of  the  Terebellidse,  as  will  be  afterwards  proved,  bears  a most  intimate  analogy  to  that 
of  the  Sipuncuhdae  amongst  the  Echinoderms. 
Sabellidce  and  Serpulidce. — The  system  of  the  segmental  organs  in  these  families  pre- 
sents several  peculiarities.  In  the  true  Terebellidse  these  organs  were  found  to  be 
restricted  to  the  thoracic  or  anterior  portion  of  the  body.  In  the  genera  Sabella  and 
Serpula  the  case  is  reversed ; they  are  absent  in  the  thoracic  and  present  only  in  the 
abdominal  portion.  They  are  far  more  numerously  repeated  in  these  families  than  in 
the  Terebellidse.  As  formerly  stated,  the  ova  and  sperm-cells  in  the  latter  escape  into 
and  float  freely  in  the  general  cavity  of  the  body.  This  is  not  the  case  in  Serpula  and 
Saiella.  Although  the  generative  elements  escape  out  of  the  channel  of  the  organ 
(fig.  13,  a db)  (probably  at  c),  they  do  not  pass  into  the  free  space  of  the  perigastric 
chamber,  there  to  float  about,  as  in  Arenicola  and  Terebella.  They  are  bounded  by  a 
delicate  membrane  or  bag  (as  represented  in  the  case  of  Chlorcema,  fig.  2?>eee),  the 
ca'vity  of  which  is  intersected  by  vessels  and  areolar  tissue,  and  filled  with  a glutinous 
fluid,  quite  unlike  the  chylaqueous  fluid,  by  which  the  ova  are  fixed  and  tied  together, 
generally  into  rows.  To  what  part  of  the  ciliated  tube  {a  db,  fig.  13)  in  Sabella  it  is  at- 
tached, it  is  impossible  to  determine  with  exactness;  but  that  it  is  not  the  ovary,  but 
only  a receptacle  for  the  ova,  will  be  afterwards  shown  to  be  highly  probable,  from  the 
conditions  under  which  it  occurs  in  Chlormma  and  some  Nereids. 
In  Sabella  and  Serpula  the  organ  is  the  same  in  figure  and  structure.  It  is  a looped 
tube  (fig.  13),  the  fundus  of  which  [d]  is  dilated,  as  compared  with  the  two  limbs ; with 
one,  the  ingoing  limb,  is  connected  a dense  tuft  of  looped  vessels  {f,  g,  e).  The  interior 
is  highly  ciliated. 
