76 
nearly  always  spheric  with  circular  out¬ 
line.  The  protoplasm  stains  more  intensely 
than  in  the  large  form.  There  is  no  clear  de¬ 
marcation  between  endo  and  ectoplasm;  the 
latter  is  limited  to  a  narrow  periplastic  layer 
which  forms  the  contour  of  the  organism. 
The  nucleus  is  also  spheric,  with  regular 
outline;  like  the  rest  of  the  cell  it  is  redu¬ 
ced  and  smaller  than  in  the  other  form.  The 
nucleus  shows  a  relatively  large  central  ca- 
ryosome,  containing  a  compact  mass  of  chro¬ 
matin,  generally  without  distinct  granula¬ 
tions  ;  sometimes  it  is  attached  to  the  nucle¬ 
ar  membrane  by  fine  linin  threads.  The  ca- 
ryosome  is  surrounded  by  a  liquid  zone, 
which  may  be  structureless,  or  contain 
achromatic  filaments,  or  chromatin  granules 
mostly  in  small  number.  Without,  at  the  edge 
of  the  nucleus,  sometimes  even  adhering  to 
the  membrane,  are  the  masses  of  chroma¬ 
tin  which  constitute  the  outer  nucleus. 
They  are  large  and  compact,  either  iso¬ 
lated  or  in  groups  ;  sometimes  they  are 
grown  together  and  form  a  thick  chromatic 
ring,  parallel  with  the  nuclear  membrane 
(PI.  19,  fig  2). 
The  changes  in  the  nucleus,  most  of 
which  may  be  interpreted  as  cyclic  variations 
of  the  caryosome,  are,  as  we  already  mentio¬ 
ned,  one  of  the  most  striking  features  of  this 
species.  The  following  seems  to  us  the  order 
in  which  the  different  phases  probably  occur: 
In  the  larger  form  there  are  many  fine; 
granules  in  the  periphery  of  the  nucleus 
sometimes  they  occupy  only  the  part  nearest 
to  the  membrane  (PI.  19,  fig.  1),  at  others 
they  are  a'so  found  in  the  liquid  zone 
(PI.  19,  fig.  7).  At  the  edge  of  the  nucleus 
these  fine  granules  gradually  melt  into  each 
other,  thus  forming  larger  ones;  they  are 
symmetrically  and  regularly  arranged  (PI.  19 
figs.  3  and  6).  A  fact,  which  seems  in  favour  of 
our  interpretation,  is  the  existence  of  forms 
similar  to  that  of  fig.  7,  already  refered  to.  The 
greater  part  of  the  nucleus  showi  large  gra¬ 
nules  at  the  very  edge,  while  in  the  remain¬ 
ing  part  the  granules  are  tine  and  have 
not  yet  reached  the  periphery.  When  at  the 
edge,  the  granules  unite  and  form  at  first 
larger  granulations,  then  compact  mas¬ 
ses  (PI.  19  figs  4  and  5)  ;  at  its  maximum, 
the  agglomeration  looks  like  that  shown 
in  fig.  12. 
While  the  granules  are  fusing,  the  caryo¬ 
some,  which  at  first  always  looks  small, 
also  grows  larger  (fig.  11).  In  this  drawing, 
the  large  size  of  the  caryosome  seems  to 
coincide  with  a  beginning  of  desaggregation 
in  the  external  chromatin.  This  may  be  pre¬ 
vious  to  its  expulsion,  as  the  stages,  repre¬ 
sented  in  figs.  9  and  10,  seem  to  prove. 
Occasionly,  we  noticed  a  chromatin  gra¬ 
nule  near  the  caryosome  (pi.  19,  figs.  3  and 
specially  7,  8  and  10)  ;  its  meaning  is  uncertain, 
but  we  find  that  HARTMANN  also  noticed 
one  in  Entamoeba  testudinis.  This  spe¬ 
cies  has  more  points  in  common  with  ours, 
as  may  be  seen  by  comparing  our  illustra¬ 
tions  with  his. 
Sometimes  there  are  netlike  formations 
in  the  liquid  nuclear  zone  (PI.  19,  figs. 
2,  4,  6,  7  and  8).  They  seem  more  de¬ 
veloped  in  the  period  eliminating  fine  chro¬ 
matin  granules  (fig.  6).  This  drawing  shows 
the  achromatic  network  only  in  that  part 
of  the  nucleus,  in  which  the  granules  are  mi¬ 
grating  to  the  periphery. 
The  species  which  comes  nearest  to  En¬ 
tamoeba  serpent  is,  is  the  one  described  by 
HARTMANN  (Memorias  do  Instituto  Os- 
waldo  Cruz,  vol.  2,  fase.  1,  pp.  3-10  PI.  1) 
under  the  name  of  Entamoeba  testudinis ;  but 
no  dimorphism  is  seen  in  this  species  and 
the  forms,  described  by  HARTMANN,  resem¬ 
ble  only  the  larger  form  of  our  species. 
Another  species,  found  in  reptilia,  is  Enta¬ 
moeba  lacertae  (HARTMANN  &  PROWAZEK 
1907  in  Archiv  f.  Protistenkunde,  Vol.  X,  p. 
314,  fig.  42).  The  authors  only  mention  its 
small  size  and  a  peculiar  stage  in  the  division 
of  the  nucleus.  Later  on,  (1914)  this  species 
was  studied  and  fully  described  by  DOBELL 
(Arch.  f.  Prot.  Vol.  34  pp.  146-159,  PI.  8). 
