57 
Examining  the  different  layers  of  the  body-wall,  we  find,  that  the 
epidermis  in  the  caudal  zone  shows  an  entirely  different  structure  as 
in  other  body-segments,  by  the  absence  of  the  large  glandular  cells. 
As  proved  by  fig.  39  and  40,  the  epidermis  on  this  spot  consists  of 
slender,  colummar  cells,  with  an  oblong  oval  nucleus,  situated  at 
some  distance  from  their  base.  I  however  cannot  take  this  to  be  an 
embryonic  feature ,  as  was  done  by  Beddaed  ;  for  comparing  it  with  the 
epidermis  of  the  zone  of  growth  in  Nais,  Chaetogaster  and  Lum- 
briculus  f.  i.,  we  find  there  the  epidermis  modified  in  a  layer  of  pro- 
toplasma, wherein  a  great  number  of  roundish  nuclei  lie  in  several 
layers,  densely  crowded,  no  trace  of  cell- walls  being  visible.  The  mus- 
cular layers  too  do  not  show  an  embryonic  feature  at  all;  they  are 
not  so  thick  and  more  stretched  out  as  in  the  normal  segments, 
especially  at  the  dorsal  side,  but  this  of  course  corresponds  with  the 
dilated  state  of  the  caudal  zone,  The  ventral  nerve-cord,  which,  as 
known ,  takes  its  origin  from  the  ectoderm  and  in  embryonic  segments 
is  connected  with  it,  has  a  completely  normal  character  and  the  same 
can  be  stated  with  regard  to  the  wall  of  the  intestinal  canal.  As  to 
the  bristles,  they  are  for  the  greater  part  absent,  and  those  which  are 
present,  are  rather  small;  but  it  may  be  called  in  mind  that  in  the 
normal  segments  the  setae  also  drop  and  are  replaced  by  new  ones, 
and  it  may  be  suggested,  that  the  dilated  state  of  the  caudal  zone  is 
not  well  adapted  for  the  preservation  of  the  bristles.  The  characteristic 
nephridial  pores  also  did  not  show  any  signs  of  division  or  increase 
in  number,  neither  did  the  nephridia  themselves  nor  the  septa,  as 
was  already  pointed  out  by  Beddaed.  Moreover  I  found  in  young  exam- 
ples, being  only  20  m.m.  in  length,  the  number  of  segments  nearly 
complete,  about  200,  viz.  130  segments  in  front  of  the  caudal  zone, 
and  about  80  behind  it.  If  really  the  increase  of  segments  took  place 
in  the  caudal  zone,  in  such  young  examples  the  number  of  segments 
in  the  region  behind  that  spot,  ought  to  be  much  smaller. 
Though  I  regret  not  to  be  able  to  express  an  opinion  as  to  the 
real  value  of  the  caudal  zone  in  P.  corethrurus ,  I  believe  to  have  de- 
monstrated, that  there  is  no  sufficient  ground  to  accept  the  views  of 
Fe.  Müllee  and  Beddaed,  who  look  at  the  caudal  zone  as  a  place 
of  rapid  growth  ;  and  I  am  quite  agreeing  with  Peeeieb,  who  says  about 
this  suggestion  „ce  serait  une  curieuse  exception  dans  le  groupe  des 
Lombriciens  terrestres/ ' 
