346 
In  Goat  2  and  the  Pretoria  rabbit,  tadpoles  appeared  ;  and  the  one 
trypanosome  seen  in  a  fresh  preparation  from  Dog  5  was  also  of  this 
variety. 
Diagnosis 
It  may  be  questioned  if  these  two  forms  are  really  of  the  same 
species.  We  think  they  are.  Whether  inoculations  were  made  with 
tadpole  or  long,  the  results  in  white  rats  and  guinea-pigs  were 
invariably  negative.  Both  forms  existed  at  a  farm  where  all  animals 
were  herded  together  and  where  an  autochthonous  case  is  believed 
to  have  occurred ;  *  and  examples  of  both  varieties  have  been  seen 
in  films  where  one  or  other  preponderated.  Further,  the  history  of 
Sheep  I,  which  we  consider  was  ‘  clean  ’  at  the  time  of  inoculation, 
indicates  a  change  in  morphology  rather  than  a  re-infection  at  our 
camp,  situated  nearly  200  miles  from  the  only  locality  in  which  a 
trypanosome  non-pathogenic  to  small  animals  was  seen.  That  the 
tadpole  was  not  T.  dimorphon  is,  we  think,  clearly  indicated  by  the 
failure  to  infect  rats  and  guinea-pigs  with  doses  of  10  to  30  c.cm.  of 
blood  showing  trypanosomes. 
In  morphological  characters  the  ‘  long  form  is  almost  indis- 
guishable  from  T.  vivax  and  T.  cazalboui ;  it  is  certainly  less  actively 
motile  than  the  Broken  Hill  T.  vivax,  but  no  reliance  should  be 
placed  on  such  a  variable  quality.  No  reference  has  been  made  by 
Ziemann,  Laveran  or  other  writer  on  this  species,  to  the  occurrence 
of  any  form  recalling  the  tadpole  dimorphon  in  naturally  infected 
or  sub-inoculated  animals ;  Laveran  has  had  a  unique  opportunity 
of  observing  such  forms  did  they  occur  in  T.  cazalboui. 
The  tadpole  forms  correspond  by  morphology  and  animal  reaction 
to  the  original  descriptions  of  T.  nanum  given  by  Laverant  and 
Balfour,!  and  to  that  of  Wenyon,§  who  appears  to  have  regained 
this  species  in  the  Anglo-Egyptian  Soudan.  The  last  named  writer 
has  also  described  ‘  long  ’  forms  of  ‘  about  20  5  of  which  are 
taken  up  by  the  free  flagellum,’  and  in  fig.  39  shows  forms  which 
by  their  rounded  posterior  extremity,  situation  of  the  blepharoplast. 
*  Vide  page  333. 
t  Laveran.  C.  R.  Sop.  Biol.,  1905,  Vol.  LVII,  pp.  292-294. 
X  Balfour.  Second  Report  of  the  Wellcome  Laboratory,  1906,  p.  122. 
§  Wenyon.  Third  Report  of  the  Wellcome  Laboratory,  1908,  p.  I37' 
