362 
The  nucleus  is  round  and  lies  slightly  on  the  aflagellar  side  of  the 
middle.  The  undulating  membrane  exists,  but  is  not  well  developed, 
and  the  rim  ceases  with  the  body,  or  may  be  continued  in  a  few 
instances  for  as  much  as  4  /*. 
In  this  dog,  the  long  forms  greatly  exceeded  in  number  the  short, 
at  the  time  of  examination.  Intermediate  forms  were  very 
uncommon. 
(b)  In  experimental  animals. 
(i)  In  the  rats,  guinea-pigs  and  dogs  both  forms  were  seen  but 
the  short  was  usually  in  numerical  excess  of  the  large  ;  this  latter  was 
not  seen  in  certain  slides  from  Dog  ii,  and  in  some  others  it  was 
very  rare.  In  Rat  i  they  co-existed  in  almost  equal  numbers. 
(ii)  The  extreme  rarity  of  occurrence  in  the  blood  of  sheep  and 
goats  precluded  a  study  of  the  forms  ;  in  smears  made  from  gland 
punctures  they  respond  to  the  '  short  ’  forms,  but  the  length  is  greater 
(average  23-2) ;  the  free  flagellum  was  rudimentary. 
(iii)  In  cattle.  In  fresh  preparations  the  motility  was  found  to 
vary  from  day  to  day,  and  also  in  individual  trypanosomes.  Most 
commonly  the  form  which  re-appeared  was  almost  as  active  as  that 
to  which  we  have  referred  as  T.  vivax\  less  frequent  were  those 
trypanosomes  whose  gliding  movements  without  corpuscular  dis¬ 
placement  could  be  watched  while  crossing  a  field.  Only  rare  were 
those  even  temporarily  remaining  in  a  single  field. 
In  stained  preparations  we  have  only  seen  one  form.  This 
trypanosome  showed  morphological  variations  from  those  in  other 
animals  inoculated  with  this  strain.  It  measured  from  2175  to  25-5  v- 
in  length  (average  22-4  /i)  and  from  27  to  4'5  /U  in  breadth  (average 
3'3  jx).  The  following  is  the  mean  of  made  measurements  :  — 
Extremity  to  Blepharoplast  Nucleus  to  body 
Blepharoplast  to  Nucleus  Nucleus  extremity  Free  Flagellum 
07  5-8  3-3  7-3  5-52 
The  body  is  rounded  or  bluntly  conical  at  the  posterior  extremity, 
and  tapers  gradually  from  the  widest  point,  which  is  close  to  the 
region  of  the  blepharoplast.  The  cytoplasm  is  commonly  homogeneous 
and  free  from  chromatic  granules  or  vacuoles.  The  blepharoplast  is 
