75 
microscopical  structure  is  similar  to  that  of  other  Perichaetidae.  The 
pit,  in  which  the  spermiducal  pores  lie,  is  due  to  the  absence  of 
the  clitellar  elements  in  the  epidermis  and  the  faint  development  of 
the  longitudinal  muscular  layer  in  this  area. 
The  nephridia  consist  of  several  loops  and  open  externally  with 
a  slender  excretory  duct,  without  a  coecum;  their  external  pores  do 
not  alternate  with  each  other.  The  nephridia,  situated  in  the  seg- 
ments anterior  to  the  XVIIIth.,  have  their  loops  higher  developed 
than  those  situated  more  backwards. 
21.  Perionyx  gruenewaldi  Michaelsen. 
Java:  Tjibodas. 
Sumatra:  Manindjau,  Singkarah,  Fort  de  Kock. 
This  species,  first  described  by  Michaelsen  from  Sangir,  and  cha- 
racterized by  the  presence  of  penial  setae,  can  at  once  be  distin- 
guished from  the  foregoing  species  by  its  colour;  the  violet-red  tint 
of  its  dorsal  side  is  obviously  separated  from  the  yellowish  colour 
of  the  ventral  and  lateral  sides ,  whereas  in  P.  violaceus  the  tint  of  the 
dorsal  and  that  of  the  ventral  side  gradually  pass  into  each  other.  Again  in 
this  species  the  pores  of  the  spermathecae  are  very  noticeable ,  situated 
upon  a  glandular  area;  in  some  examples  they  were  surrounded  by 
a  brown  ring  and  visible  even  to  the  naked  eye ,  whereas  in  P.  vio- 
laceus they  are  not  distinguishable  externally.  On  the  contrary  the 
dorsal  pores,  very  obvious  upon  the  clitellum  in  P.  violaceus,  appear 
to  be  hardly  discernible  in  this  species.  P.  gruenewaldi  also  appears 
to  be  of  a  larger  size  than  P.  violaceus  ;  the  largest  example  from  San- 
gir measured  85  mm.  in  length.  Our  largest  specimen  had  a  length 
of  75  mm.  P.  excavatus,  agreeing  with  P.  gruenewaldi  and  P.  viola- 
ceus in  the  number  of  spermathecae,  appears  to  be  distinguished  by 
a  smaller  number  of  setae  (36  à  40),  by  its  spermathecae  without  di- 
verticulum and  by  its  globular,  undivided  prostata. 
