559 
forms  without  a  flagellum,  in  all  these  stages  a  blepharoplast  was 
present  and  could  be  clearly  seen. 
In  other  forms  a  new  flagellum  connected  with  the  blepharoplast 
was  observed.  Whereas  the  original  flagellum  was  thin  and  wavy, 
the  new  flagellum  appeared  very  much  thicker  and  bnstle-like  (Figs. 
II,  12),  but  it  seemed  to  become  thinner  as  its  length  increased 
(Fig.  13).  Up  to  this  point,  forms  observed  in  stained  specimens  had 
always  been  controlled  by  examination  of  living  parasites.  Judging 
from  the  different  size  of  the  oval-shaped  Herpeloinonas-\\kQ  forms 
of  the  developmental  stages  of  T.  lewisi  (Figs,  ii  and  15),  one  can 
assume  that  these  forms  increase  in  size. 
If  lice,  containing  a  small  number  of  these  Herpeio^uonas-like 
forms,  were  taken  from  the  rat  and  kept  alive  for  a  varying  interval 
(we  were  not  able  to  keep  lice  alive  for  longer  than  seventy-two 
hours),  a  marked  multiplication  of  the  forms  took  place  in  the  gut 
(Fig.  18).  Many  of  the  latter,  possessing  only  one  nucleus  and  one 
blepharoplast,  showed  two  flagella.  We  are  inclined  to  regard  these 
bi-flagellated  forms  as  the  first  stage  in  the  process  of  division. 
The  division  appears  to  start  with  a  broadening  or  rounding  up 
of  the  blepharoplast  (Figs.  14,  15).  Afterwards,  the  nucleus  divides 
and  the  cytoplasm  of  the  parasite  splits  longitudinally  into  two 
daughter  cells  (Fig.  lO). 
Sometimes,  however,  before  one  division  has  come  to  an  end,  a 
second  division  has  already  commenced  (Fig.  17).  When  these  forms 
occur  in  large  numbers,  they  can  often  be  seen  to  be  agglomerated 
in  great  clusters,  with  the  flagellum  always  directed  inwardly  (Fig. 
18).  Very  great  variation  in  the  shape  and  structure  of  the 
Herpetoinonas-Wke.  forms  was  noticed  (Figs,  ig,  20). 
In  specimens  stained  with  safranine-methylene  blue,  bright 
granules  in  varying  numbers  can  very  often  be  seen  (Figs.  21,  22). 
Now  and  again  the  nucleus  of  these  forms  degenerates  (Figs.  23,  24, 
25).  In  Fig.  26  there  is  only  a  light  area  with  irregular  red  granules 
in  the  position  of  the  nucleus. 
The  stages  depicted  in  Figs.  27  and  28  are  suggestix  e  of  con¬ 
jugation  forms.  Although  analogous  appearances  were  seen  in  fresh 
specimens  and  kept  under  observation  for  several  hours,  no  further 
changes  occurred. 
