58 
In  the  region  of  the  caudal  zone  the  intestinal  canal  shows  a  pe- 
cularity ,  first  pointed  out  by  Perrieb  ,  but  as  I  believe  overlooked  by 
Beddard  ,  viz.  the  termination  of  the  lamellar  typhlosolis  on  this  spot. 
As  above  referred  to,  Perrier  thinks  the  dilatation  of  the  body 
to  be  only  due  to  this  pecularity  and  I  quite  agree  with  him,  that 
this  region  of  the  intestinal  canal  is  always  bulged  by  alimentary 
substance,  in  variance  with  Beddard,  who  found  the  intestine  here 
empty  of  debris. 
On  examining  the  alimentary  tract  of  Urochaeta,  I  observed 
another  peculiarity,  singularly,  not  noted  neither  by  Perrier  nor 
by  Beddard,  viz.  that  it  is  spirally  coiled;  this  spiral  begins 
almost  behind  the  clitellum  and  continues  till  the  caudal  extremity. 
Each  coil  of  the  spiral  corresponds  to  four  segments,  so  that  in 
the  anterior  portion  of  the  body,  where  the  segments  have  a  greater 
longitudinal  diameter  than  farther  backwards ,  the  coils  are  also  longer 
than  in  the  posterior  body-region.  The  intestine  appears  not  to  be 
coiled  in  a  true  spiral,  but  to  move  rather  backward  in  a  com- 
pressed zigzag  line;  for  the  dorsal  vessel  and  the  typhlosolis,  which 
are  connected  with  the  dorsal  median  line  of  the  intestine,  remain 
in  this  situation.  If  it  were  a  true  spiral,  the  dorsal  vessel  and  ty 
phlosolis  in  one  half  of  the  coils  ought  to  be  situated  ventrally.  Sohmarda 
in  his  diagnosis  of  Pontoscolex  also  says  :  „der  darm  der  einzige  species  ist 
schraubenförmig  gewunden,  mit  ausnähme  des  oberen  theiles."  This  con- 
firms Beddard's  Suggestion  about  the  identity  of  this  genus  withUrochaeta. 
A  spiral  condition  of  the  alimentary  canal  is  described  in  Didymo- 
gaster  by  Fletcher  l)  and  in  Plagiochaeta  by  Benham  2)  ;  Benham 
states,  that  in  the  latter  worm  it  is  a  true  spiral.  I  have  however 
some  doubt  as  to  the  exactness  of  this  assertion,  because  the  dorsal 
vessel,  which  from  its  origin  is  connected  with  the  dorsal  median 
line  ol  the  intestine,  appears  to  retain  that  position  ;  unfortunately  the 
typhlosolis  is  absent  in  this  species. 
Periohaetidae. 
Within  the  last  years  a  considerable  number  of  species  are  referred 
to  the  genus  Perichaeta,  which,  though  agreeing  rather  well  with 
1)  Proc.  Linn.  Society  of  N.  S.  Wales,  2e  S.  Vol.  I,  1886,  p.  554,  Pl.  XI,  fig.  8. 
2)  Quartl.  Journ.  of  Micr ose.  Science,  Vol.  XXXIII,  1892,  p.  294,  pl.  XV,  fig.  21. 
