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QL 
366 

M66 
1917 
Sp  Coll 


,,^  X.N  ffiDDUOTION  TO  THE 

STUDY  OF  THE   PEOTOZOA 

WITH  SPECIAL  REFERENCE  TO 
THE  PARASITIC  FORMS 


BY 


E.  A.  MINCHIN,  M.A.,  PH.D.,  F.B.S. 

PROFESSOH     OF      PROTOZOOLOGY      IN      THE      UNIVERSITY     OF     LONDON 


>,   KOV 


ILLUSTRATED 


MARINE 
BIOLOGICAL 

LABORATORY 


LI5RARY 


O^S  HGi-c,  f-'ASS. 
W.  H.  0    !. 


SECOND   IMPRESSION 


LONDON 

—  J^DWARD     ARNOLD 
1917 


*          [All  rjyhts  rfferv 


PREFACE 

THIS  book,  as  its  name  implies,  is  intended  to  serve  as  an  intro- 
duction to  the  subject  with  which  it  deals,  and  not  in  any  way  as  a 
complete  treatise  upon  it.  The  science  of  "  protozoology,"  as  it  is 
now  generally  termed,  covers  a  vast  field,  and  deals  with  an  immense 
series  of  organisms  infinitely  varied  in  form,  structure,  and  modes  of 
life.  In  recent  years  the  recognition  of  the  importance  of  the 
Protozoa  to  mankind  in  various  ways,  and  especially  from  the 
medical  point  of  view,  has  focussed  attention  upon  them,  and  has 
brought  about  a  great  increase  of  our  knowledge  concerning  these 
forms  of  life.  To  set  forth  adequately  and  in  full  detail  all  that  is 
now  known  about  the  Protozoa  would  be  a  task  that  could  not  be 
attempted  in  a  volume  of  this  size,  but  would  require  a  work  many 
times  larger. 

The  aim  of  the  present  work  is  essentially  didactic — that  is  to  say, 
it  is  intended  to  furnish  a  guide  to  those  who,  having  at  least  some 
general  knowledge  of  biology,  desire  a  closer  acquaintance  with  the 
special  problems  presented  by  the  Protozoa.  First  and  foremost, 
it  attempts  to  define  the  position  of  these  organisms  in  Nature,  and 
to  determine,  as  far  as  possible,  in  this  way  exactly  what  should  be 
included  under  the  term  "  Protozoa,"  and  what  should  be  excluded 
from  the  group.  Secondly,  its  function  is  to  guide  the  student 
through  the  maze  of  technicalities  necessarily  surrounding  the  study 
of  objects  unfamiliar  in  daily  life,  and  requiring,  consequently,  a 
vocabulary  more  extensive  than  that  of  common  language  ;  and 
with  this  aim  in  view,  care  has  been  taken  to  define  or  explain  fully 
all  technical  terms,  since  confusion  of  thought  can  be  avoided  only 
by  a  clear  understanding  of  their  exact  significance  and  proper 
application.  Thirdly,  it  aims  at  introducing  the  student  to  the 
vast  series  of  forms  comprised  in  the  Protozoa  and  their  systematic- 
classification,  based  on  their  mutual  affinities  and  inter-relationships, 
so  far  as  these  can  be  inferred  from  their  structural  peculiarities  and 
their  life-histories.  And,  incidentally,  attention  has  been  drawn 
specially  to  those  parts  of  the  subject  where  the  Protozoa  throw 


vi  PREFACE 

great  light  on  sonic  of  the  fundamental  mysteries  of  living  matter — 
as,  for  example,  sex  —  and  a  special  chapter  dealing  with  the 
physiology  of  the  Protozoa  has  been  added. 

In  so  wide  a  field  it  is  almost  necessary  to  exercise  some  favour- 
itism in  the  choice  of  objects,  and  greater  stress  has  been  laid  in 
this  work  upon  the  parasitic  forms,  both  on  account  of  the  many 
interesting  biological  problems  which  they  present,  and  also  because 
they  come  into  closer  relationship  with  the  practical  needs  of  human 
life  than  the  non-parasitic  species.  The  author  wishes,  however, 
to  point  out  clearly  that  he  is  not  a  medical  man,  but  one  who 
approaches  the  study  of  the  parasitic  Protozoa  solely  from  the 
standpoint  of  a  naturalist  who  is  more  concerned,  so  to  speak,  with 
the  interests  of  the  parasite  than  with  those  of  the  host.  Conse- 
quently, purely  medical  problems — such  as,  for  example,  the 
symptoms  and  treatment  of  diseases  caused  by  trypanosomes  and 
other  Protozoa' — are  not  dealt  with  in  this  book,  since  the  author 
deems  it  no  part  of  his  task  to  attempt  to  instruct  medical  men 
concerning  matters  with  which  they  are  better  acquainted  by  their 
training  and  experience  than  himself.  The  needs  of  medical  men 
have,  however,  been  specially  kept  in  view,  and  the  author  hopes 
that  the  book  will  succeed  in  supplying  them  with  useful  informa- 
tion, at  least  from  a  general  zoological  or  biological  standpoint. 

In  a  science,  such  as  protozoology,  which  is  growing  actively  and 
receiving  continually  new  additions,  and  in  which  most  of  the  data 
are  based  upon  an  elaborate  and  delicate  technique,  there  are 
necessarily  many  controversial  matters  to  be  dealt  with.  In  such 
cases  the  points  at  issue  have  been  reviewed  critically,  and  the 
author  has,  wherever  possible,  attempted  to  give  a  lead  by  indicating 
more  or  less  decisively  what  is,  in  his  opinion,  the  most  probable 
solution  of  the  problem  under  discussion.  Such  judgments,  how- 
ever, are  not  intended  to  be  put  forward  in  a  dogmatic  or  polemical 
spirit,  since  the  author  recognizes  fully  that  any  conclusion  now 
reached  may  be  upset  entirely  by  fresh  evidence  to  the  contrary. 

The  vast  literature  of  the  Protozoa  would,  if  cited  in  full,  easily 
fill  by  itself  a  volume  of  the  size  of  the  present  one.  It  has  been 
necessary,  therefore,  to  restrict  the  limits  of  the  bibliography  as 
much  as  possible,  both  by  selecting  carefully  the  memoirs  to  be 
cited  and  by  abbreviating  their  titles.  The  works  selected  for 
reference  comprise,  first,  comprehensive  treatises  which  deal  with 
the  subject,  or  with  some  part  of  it  in  a  general  way,  and  in  which 
full  references  to  older  works  will  be  found  ;  secondly,  classical 
memoirs  on  particular  subjects,  also  containing,  as  a  rule,  full 
bibliographies  ;  and,  thirdly,  such  memoirs  of  recent  date  as  have 


PREFACE  vii 

been  deemed  worthy  of  citation.  In  the  many  cases  where  the 
same  authors  have  published  several  works  on  a  given  subject,  only 
the  last  of  them  is  cited — for  example,  the  volume  of  researches 
published  recently  by  Mathis  and  Leger  (473)  covers  the  ground  of 
the  earlier  memoirs  published  by  these  authors,  which  are  therefore 
not  cited  ;  similarly,  the  memoir  upon  amoebae  by  Nagler  (95) 
covers  the  earlier  work  of  Hartrnarm  and  Nagler  upon  Amoeba 
diploidea.  Since  it  was  quite  impossible  to  make  the  bibliography 
in  any  way  exhaustive,  the  aim  has  been  to  make  it,  like  the  rest 
of  the  book,  introductory  to  the  subject.  It  is  hoped  that  any 
reader  who,  desirous  of  pursuing  further  some  special  subject, 
consults  the  references  cited  will  find  in  them  and  in  the  further 
works  quoted  in  them  the  means  of  acquiring  complete  information 
with  regard  to  modern  knowledge  concerning  all  the  points  in 
question.  The  following  classes  of  memoirs  are  not  cited,  however, 
in  the  bibliography,  unless  there  was  some  special  reason  for  doing 
so  :  faunistic  works,  papers  describing  new  species,  and  writings  of 
a  polemical  character. 

New  memoirs  on  Protozoa  are  being  published  continually,  so 
rapidly,  and  in  so  many  different  periodicals  (some  of  them  very 
difficult  to  obtain),  that  the  author  fears  he  may  himself  have 
overlooked  many  such,  especially  of  those  publications  which  have 
appeared  very  recently,  while  the  book  was  in  course  of  preparation. 
T\>r  such  omissions,  some  of  which  have  already  come  under  his 
notice,  he  can  but  apologize,  and  at  the  same  time  promise  that 
they  shall  be  rectified  in  future  editions,  if  the  patronage  of  those 
interested  in  the  subject  enables  further  editions  of  this  book  to  be 
published.  The  present  edition  does  not,  however,  profess  to  deal 
with  works  published  later  than  1911. 

In  order  to  further  the  object  of  making  this  book  a  guide  to  the 
technicalities  of  the  subject,  the  plan  has  been  adopted  of  printing 
in  heavier  black  type  in  the  index  the  numbers  of  those  pages  on 
which  the  term  cited  is  fully  explained,  or,  in  the  case  of  taxonomic 
names,  is  referred  to  its  place  in  the  systematic  classification.  In 
this  way  the  index  can  be  used  as  a  glossary  by  anyone  wishing  to 
ascertain  the  significance  of  a  technical  term,  or,  though  necessarily 
to  a  more  limited  extent,  the  systematic  position  of  a  genus,  family, 
or  order  of  the  Protozoa.  All  that  is  necessary  for  this  purpose  is 
to  look  up  the  word  in  the  index,  and  then  to  turn  to  the  page  or 
pages  indicated  by  black  type. 

The  author  has,  in  a  few  cases,  modified  the  technical  terminology 
in  current  use,  or  has  made  additions  to  it.  The  adjective  in  general 
use  relating  to  chromatin  is  "  chromatic,"  with  its  various  deriva- 


viii  PREFACE 

lives  ("achromatic,"  etc.);  since,  however,  these  adjectives  have- 
a  totally  different  meaning  and  use  in  optics,  they  have  been  altered 
to  chromatinic,  etc.,  in  so  far  as  they  relate  to  chromatin.  New 
terms  used  in  this  book  are  chromidiosome  (p.  65,  footnote),  endosome 
(p.  73),  as  an  equivalent  to  the  German  Binnenkorper,  and  cjregarinula 
(p.  169). 

In  conclusion,  it  is  the  author's  pleasant  duty  to  return  thanks  to 
those  of  his  colleagues  who  have  kindly  rendered  him  assistance  in 
his  task.  He  is  especially  indebted  for  much  help  and  many 
valuable  suggestions  and  criticisms  to  Dr.  H.  M.  Woodcock,  whose 
unrivalled  knowledge  of  recent  bibliography  has  been  throughout  of 
the  utmost  assistance  ;  and  to  Dr.  J.  D.  Thomson  and  Miss  Muriel 
Robertson  for  many  helpful  discussions  upon  matters  of  fact  or 
theory.  Dr.  A.  G.  Bagshawe,  Professor  J.  B.  Farmer,  F.R.S.,  Mr. 
W.  F.  Lanchester,  Dr.  C.  J.  Martin,  F.R.S.,  and  Dr.  P.  Chalmers 
Mitchell,  F.R.S.,  have  kindly  read  through  some  of  the  chapters,  and 
have  given  valuable  advice  and  criticism.  In  justice  to  these  gentle- 
men, however,  it  should  be  stated  that  they  are  in  no  way  responsible 
for  any  of  the  theoretical  opinions  put  forward  by  the  author.  The 
majority  of  the  figures  have  been  specially  drawn  from  the  original 
sources,  or  from  actual  preparations  by  Mr.  R.  Brook-Greaves  and 
Miss  Mabel  Rhodes,  to  both  of  whom  the  author's  best  thanks 
are  due. 

LISTER  INSTITUTE  OF  PREVENTIVE 
MEDICINE,  CHELSEA,  S.W., 
July  1,  1912. 


CONTENTS 


CHAPTER  PAGES 

I.  INTRODUCTORY — THE  DISTINCTIVE  CHARACTERS  OF  THE  PROTOZOA 

AND    OF   THEIR   PRINCIPAL   SUBDIVISIONS  -  -  1 — 12 


II.  THE  MODES  OF  LIFE  OF  THE  PROTOZOA  ...        13 — 28 

The  Four  Types  of  Nutrition,  13-15  ;  Problems  of  Parasitism, 
15-28. 


[II.  THE    ORGANIZATION    OF    THE    PROTOZOA — EXTERNAL    FORM    AND 

SKELETAL  STRUCTURES  ....        29 — 39 


IV.  THE    ORGANIZATION    OF    THE    PROTOZOA    (continued) — THE    PROTO- 
PLASMIC BODY  -  .....        40     11 


V.  THE  ORGANIZATION  OF  THE  PROTOZOA  (continued) — DIFFERENTIATIONS 

OF  THE  ECTOPLASM  AND  ENDOPLASM  -  45 — 64 

A.  Ectoplasmic  Organs — (1)  Protective,  45;   (2)  Kinetic   and 
Locomotor,  46  ;  (3)  Excretory,  60  ;  (4)  Sensory,  61. 

B.  Endoplasmic  Organs,  62. 

VI.  THE  ORGANIZATION  OF  THE  PROTOZOA  (continued) — THE  NUCLEAR 
APPARATUS — CHROMATIN,  NUCLEUS,  CHROMIDIA,  CENTEO- 
SOMES,  AND  BLEPHAROPLASTS  -  -  65 — 99 

VII.  THE  REPRODUCTION  OF  THE  PROTOZOA  ...  -     100 — 124 

Types  of  Fission,  100  ;  Division  of  the  Nucleus,  101  ;  Division 
of  the  Cell-Body,  122. 

VIII.  SYNGAMY  AND  SEX  IN  THE  PROTOZOA   -  -  -    125 — 161 

Nature  of  the  Sexual  Process,  125 ;  Occurrence  of  Sexual 
Phenomena  and  their  Importance  in  the  Life  of  the  Organism, 
128  ;  Maturation  and  Reduction,  142  ;  Examples  of  Syngamy 
and  Reduction  in  Protozoa,  147  ;  Theories  of  the  Origin  and 
Significance  of  the  Syngamic  Process,  154. 

ix 


x  CONTENTS 

CHAPTER  PAGES 

IX.  POLYMORPHISM  AND  LIFE-CYCLES  OF  THE  PROTOZOA  -  -     162 — 185 
A.   Polymorphism,  162-176  ;  B.  Life-Cycles,  177-185. 


X.  THE  GENERAL  PHYSIOLOGY  OF  THE  PROTOZOA  -     186 — 211 

(1)  Nutrition  and  Assimilation,  187;  (2)  Respiration,  195; 
(3)  Excretion  and  Secretion,  197  ;  (4)  Transmutation  of 
Energy,  199  ;  (5)  Reactions  to  Stimuli  and  Environments, 
201 ;  (6)  Degeneration  and  Regeneration,  208. 


XI.  SYSTEMATIC  REVIEW  OF  THE  PROTOZOA:  THE  SARCODINA        -     212 — 256 

A.  Rhizopoda — I.    Amoebaea,    218  ;    II.    Foraminifera,    231  ; 
III.  Xenophyophora,  237  ;  IV.  Mycetozoa,  239. 

B.  Actinopoda — V.  Heliozoa,  244  ;  VI.  Radiolaria,  249. 


XII.  SYSTEMATIC  REVIEW  OF  THE  PROTOZOA  :  THE  MASTIGOPHORA      257 — 279 

I.  Flagellata,   257  ;   II.   Dinoflagellata  seu  Peridiniales,   276  ; 
III.  Cystoflagellata  seu  Rhynchoflagellata,  278. 


XIII.    THE    H^MOFLAGELLATES    AND    ALLIED    FORMS  -       280 — 322 

I.  Trypanosoma,  283  ;  II.  Trypanoplasma,  309  ;  III.  Crithidia, 
312  ;  IV.  Leptomonas,  313  ;  V.  Leishmania,  316  ;  VI.  Prowa- 
zekia,  319. 


XIV.  THE  SPOROZOA  :  I.  THE  GREGAEINES  AND  COCCIDIA      -  -     323 — 355 

I.  Gregarinoidea,  326  ;  II.  Coccidia,  341. 

Comparison  of  the  Life-Cycles  of  Gregarines  and  Coccidia,  354. 


XV.  THE  SPOROZOA:  II.  THE  H^IMOSPORIDIA         -  -  -     356 — 397 

(1)  Haemamrebse,  357;  (2)  Halteridia,  365;  (3)  Leucocytozoa, 
369  ;  (4)  Haemogregarines,  371 ;  (5)  Piroplasms,  378 ;  Affinities 
of  the  Haemosporidia,  388  ;  of  the  Telosporidia,  395. 


XVI.  THE  SPOROZOA:  III.  THE  NEOSPORIDIA  •  -     398 — 429 

I.   Myxosporidia,   399 ;   II.    Actinomyxidia,   409 ;   III.   Micro- 
sporidia,  411  ;  IV.  Sarcosporidia,  419  ;  V.  Haplosporidia,  423. 
Incertce  Sedis,  425. 


XVII.  The  INFUSORIA  -  -     430 — 461 

I.  Ciliata,  430;  II.  Acinetaria,  455. 


CONTENTS  xi 

CHAPTER  PAGES 

XVIII.  AFFINITIES    AND    CLASSIFICATION    OF   THE   MAIN   SUBDIVISIONS — 

DOUBTFUL  GROUPS  -  -    462 — 474 

General  Phylogeny  of  the  Protozoa,  463. 
Spirochsetes,  466  ;  Chlamydozoa,  470. 

BIBLIOGRAPHY     ...  .    475 — 504 

INDEX      -  ....    505—517 


AN  INTRODUCTION  TO  THE  STUDY 
OF  THE  PROTOZOA 


CHAPTER  I 

INTRODUCTORY --THE   DISTINCTIVE   CHARACTERS   OF    THE 
PROTOZOA  AND  OF  THEIR  PRINCIPAL  SUBDIVISIONS 

THE  Protozoa  are  a  very  large  and  important  group  of  organisms, 
for  the  most  part  of  minute  size,  which  exhibit  a  wide  range  of 
variation  in  structural  and  developmental  characters,  correlated 
with  the  utmost  diversity  in  their  modes  of  life.  Nevertheless, 
however  greatly  adaptation  to  the  conditions  of  life  may  have 
modified  their  form,  structure,  or  physiological  properties,  a  certain 
type  of  organization  is  common  to  all  members  of  the  group.  The 
most  salient  feature  of  the  Protozoa  is  their  unicellular  nature  ; 
that  is  to  say,  the  individual  in  this  subdivision  of  living  beings  is 
an  organism  of  primitive  character,  in  which  the  whole  body  has 
the  morphological  value  of  a  single  "  cell,"  a  mass  of  protoplasm 
containing  nuclear  substance  (chromatin)  concentrated  into  one  or 
more  nuclei.  However  complex  the  structure  and  functions  of  the 
body,  the  organs  that  it  possesses  are  parts  of  a  cell  ("  organellse  "), 
and  are  never  made  up  of  distinct  cells  ;  and  at  least  one  nucleus 
is  present,  or  only  temporarily  absent,  as  a  constant  integral  part 
of  the  organism.  The  unicellular  nature  of  the  Protozoa,  though  a 
constant  character,  cannot,  however,  be  used  by  itself  to  define 
the  group,  since  it  is  also  a  peculiarity  of  many  other  distinct  types 
of  simple  living  things. 

As  an  assemblage  of  organisms  of  primitive  nature  from  which, 
in  all  probability,  the  ordinary  plants  and  animals  have  originated 
in  the  remote  past  by  divergent  processes  of  evolution,  the  Protozoa, 
have  always  possessed  very  great  interest  from  the  purely  scientific 
and  philosophical  point  of  view.  Of  recent  years,  however,  they 
have  also  acquired  great  practical  importance  from  the  relations 
that  have  been  discovered  to  exist  between  Protozoa  of  parasitic 
habit  and  many  diseases  of  man  and  animals.  Hence  the  study  of 
the  Protozoa  has  received  an  immense  impetus,  and  has  been 

1 


2  THE  PROTOZOA 

cultivated  zealously  even  by  many  who  are  not  professed  biologists, 
with  the  result  that  our  knowledge  of  these  organisms  has  made 
very  great  strides  in  the  last  two  decades,  and  is  advancing  so 
rapidly  that  it  becomes  increasingly  difficult  for  any  single  person 
to  keep  pace  with  the  vast  amount  of  new  knowledge  that  is  pub- 
lished almost  daily  at  the  present  time. 

While  the  attention  that  is  now  focussed  upon  the  Protozoa  has 
led  to  a  most  gratifying  increase  of  scientific  and  medical  knowledge 
concerning  particular  forms,  it  tends  frequently  to  a  certain  vague- 
ness in  the  notions  held  with  regard  to  the  nature  and  extent  of 
the  group  as  a  whole.  This  is  owing  largely  to  the  fact  that  many 
are  now  attracted  to  the  study  of  the  Protozoa  whose  aims  are 
purely  practical,  and  who  investigate  only  a  limited  number  of 
species  in  minute  detail,  without  having  an  adequate  foundation 
of  general  knowledge  concerning  other  forms.  Hence  it  is  important 
to  attempt  to  frame  a  general  definition  of  the  Protozoa,  or  at  least 
to  characterize  these  organisms  in  such  a  way  as  to  enable  a  dis- 
tinction to  be  drawn  between  them  and  other  primitive  forms  of 
life.  This  object  may  be  attained  logically  in  two  ways  —  either  by 
considering  the  distinctive  characters  of  the  group,  or  by  enu- 
merating the  types  of  organisms  which  constitute  it  ;  in  more 
technical  phraseology,  by  determining  either  the  connotation  or  the 
denotation  of  the  term  Protozoa.  To  attempt  this  task  will  be 
the  object  of  the  present  chapter. 

The  name  Protozoa  was  first  used  in  1820*  as  an  equivalent 
of  the  German  word  Urthiere,  meaning  animals  of  a  primitive  or 
archaic  type.  This  fitting  designation  superseded  rapidly  the  older 
term  Infusoria  (Infiisionsthierchen),  used  to  denote  the  swarms 
of  microscopic  organisms  which  make  their  appearance  in  organic 
infusions  exposed  to  the  air.  The  word  Infusoria  is  now  em- 
ployed in  a  restricted  sense,  as  the  name  of  one  of  the  principal 
subdivisions  of  the  Protozoa  (pp.  12  and  430). 

The  first  attempt  at  a  scientific  definition  of  the  Protozoa  was 
given  by  von  Siebold,  who  defined  them,  from  a  strictly  zoological 
standpoint,  as  unicellular  animals.  This  definition,  or  a  modifica- 
tion of  it,  is  still  the  one  given,  as  a  rule,  in  zoological  textbooks  ; 
and  from  this  time  onwards  the  animal  kingdom  was  subdivided 
universally  into  the  Protozoa  and  the  Metazoa.  The  Protozoa, 
as  organisms  in  which  the  individual  is  a  single  cell,  are  regarded 
as  those  which  come  first  (TT^WTOS)  in  the  ascending  scale  of  animal 
life,  or  in  the  course  of  organic  evolution  ;  the  Metazoa,  in  which 
the  individual  is  an  organism  composed  of  many  cells,  come  after 
the  simpler  forms  of  life  in  rank  and  time. 


*  For  the  detailed  history  of  the  growth  of  scientific  knowledge  of  the  Protozoa. 
.see  Biitschli  (2),  pp.  i-xviii. 


DISTINCTIVE  CHARACTERS  OF  THE  PROTOZOA       3 

Siebold's  generalization  was  a  great  step  in  advance,  introducing 
clear  and  orderly  ideas  into  the  place  of  the  chaotic  notions  pre- 
viously held,  and  setting  definite  limits  to  the  group  Protozoa  by 
excluding  from  it  various  types  of  organisms,  such  as  Sponges, 
Rotifers,  etc.,  which  had  hitherto  been  classed  as  Protozoa,  but 
which  were  now  referred  definitely  to  the  Metazoa.  Nevertheless 
Siebold's  definition  presents  many  difficulties,  especially  when  con- 
sidered from  a  wider  standpoint  than  that  of  the  zoologist.  This 
will  be  apparent  if  the  two  words  of  the  definition  given  above, 
;'  unicellular  animals,"  be  considered  critically. 

1.   "  Unicellular."-—  Accepting  the  standpoint  of  the  cell-theory,  it 
has  already  been  noted  that  many  other  organisms  besides  Protozoa 
must  be  regarded  as  single  cells.     Moreover,  it  is  found  that  many 
organisms  which  must  be  classed  as  Protozoa  appear  constantly  in 
a  multicellular  condition  ;  such  are  the  well-known  genus   Volvox 
and  its  allies,  besides  examples  of  other  orders.     In  all  cases  of  this 
kind,  however,  the  constituent  cells  are  morphologically  equivalent, 
and  are  to  be  regarded  as  complete  individuals  more  or  less  inde- 
pendent, showing  as  a  rule  no  differentiation,  or,  if  any,  only  into 
reproductive   and    vegetative   individuals  ;    and    the    multicellular 
organism  as  a  whole  is  to  be  regarded  as  a  colony  of  unicellular 
individuals  primitively  similar  but  secondarily  differentiated,  it  may 
be,  in  relation  to  special  functions.     Such  multicellular  Protozoa 
present,  in  fact,  a  perfect  analogy  with  the  colonial  forms  seen  in 
many  groups  of  animals  higher  in  the  scale,  especially  the  Coelentera, 
where  also  the  members  of  a  colony,  primitively  equivalent  and 
similar  amongst  themselves,  may  become  differentiated  secondarily 
for  the  performance  of  distinct  functions  by  a  process  of  division 
of  labour  among  different  individuals.     It  is  not  possible  to  con- 
found the  multicellular  Protozoa  with  the  Metazoa,  in  which  the 
organism  is  not  only  composed  of  many  cells,  but  exhibits  also 
cell-differentiation  based  on   mutual  physiological  dependence  of 
the  cells  on  one  another,  leading  to  the  formation  of  distinct  tissues  ; 
that  is  to  say,  aggregations  or  combinations  of  numerous  cells,  all 
specialized  for  the  performance  of  a  particular  function,  such  as 
contraction,  secretion,  and  so  forth. 

The  essential  feature  of  the  Protozoa,  as  contrasted  with  the 
higher  animals  or  plants,  is  to  be  sought  in  the  independence  and 
physiological  completeness  of  the  cell-individual.  The  Metazoa 
are  tissue-animals,  in  which  the  primitive  individuality  of  the  cell, 
is  subordinated  to,  or  has  a  restraint  imposed  upon  it  by,  the 
corporate  individuality  of  the  cell -aggregate.  In  the  Protozoa  the 
cells  are  complete  individuals,  morphologically  and  physiologically 
of  equal  value.  If,  however,  as  feAv  will  doubt,  the  Metazoa  have 
been  evolved  from  simple  unicellular  ancestors,  similar  to  th<> 


4  THE  PROTOZOA 

Protozoa,  then  there  must  have  existed  an  unbroken  series  of 
transitions  between  these  two  types  of  living  beings.  Hence,  as 
in  all  attempts  to  classify  living  beings,  sharp  verbal  distinctions 
between  Protozoa  and  Metazoa  are  rendered  possible  only  through 
the  extinct/ion  of  intermediate  forms,  or  by  ignoring  such  forms  if 
known  to  exist.  It  is  expedient  rather  to  recognize  distinct  types 
of  organization  characteristic  of  the  Protozoa  and  the  Metazoa 
respectively,  and  to  compare  and  contrast  them,  than  to  attempt 
to  limit  these  groups  by  precise  definitions. 

2.  "  Animals."-  -This  part  of  the  definition  raises  more  difficulties 
than  their  cellular  nature.  In  the  higher  forms  of  life  the  distinc- 
tion between  animals  and  plants  is  an  obvious  and  natural  one  ;  it 
is  by  no  means  so  in  the  lower  organisms.  In  the  ranks  of  the 
simplest  living  creatures,  those  of  animal  nature  are  not  marked 
off  by  any  sharply  defined  structural  or  other  features  from  those  of 
vegetable  nature,  and  cannot  be  separated  from  them  in  any  scheme 
of  classification  which  claims  to  be  founded  upon,  or  to  express,  the 
true  natural  affinities  and  relationships  of  the  objects  dealt  with. 
As  will  be  explained  more  fully  in  the  next  and  subsequent  chapters, 
the  distinction  between  animal  and  vegetable  is,  at  its  first  appear- 
ance, nothing  but  a  difference  in  the  mode  in  which  the  organisms 
obtain  their  living.  Forms  that  are  obviously  closely  allied  in  all 
their  characters  may  differ  in  this  respect,  and  in  some  cases  even 
one  and  the  same  species  may  nourish  itself  at  one  time  as  a  plant, 
at  another  as  an  animal,  according  to  circumstances.  In  short,  the 
difference  between  plant  and  animal  is  primarily  a  distinction  based 
upon  habits  and  modes  of  life,  and,  like  all  such  distinctions,  does 
not  furnish  characters  that  can  be  utilized  for  systematic  classifica- 
tion until  the  mode  of  life  has  continued  so  long,  and  the  habit  has 
become  so  engrained,  as  to  leave  an  impress  upon  the  entire 
structural  characteristics  of  the  organism. 

The  Protozoa  cannot  therefore  be  defined  strictly  and  con- 
sistently as  organisms  of  animal  nature,  for,  though  the  vast  majority 
of  them  certainly  exhibit  animal  characteristics,  it  is  impossible  to 
exclude  from  the  group  many  which  live  temporarily  or  permanently 
after  the  manner  distinctive  of  the  vegetable  kingdom,  and  which 
are  plants,  to  all  intents  and  purposes,  leading  on  in  an  unbroken 
series  to  the  simplest  algae. 

For  this  reason  it  has  been  proposed  to  unite  all  the  simplest  and 
most  primitive  forms  of  life  in  one  "kingdom"  under  the  title 
Protista  (Protistenreich,  Haeckel),  irrespective  of  their  habit  of  life 
and  metabolism,  whether  animal  or  vegetable.  The  kingdom 
Protista  is  then  to  be  considered  as  equivalent  in  systematic  value 
to  the  animal  and  vegetable  kingdoms,  which  in  their  turn  are 
restricted  in  their  application  to  true  animals  and  plants  as  ordinarily 


DISTINCTIVE  CHARACTERS  OF  THE  PROTOZOA 


understood.  The  term  Protista  thus  unites  under  a  single 
systematic  category  the  vast  assemblage  of  simple  and  primitive 
living  beings  from  which  the  animal  and  vegetable  kingdoms  have 
taken  origin,  and  have  developed,  by  a  continuous  process  of 
natural  evolution,  in  different  directions  in  adaptation  to  divergent 
modes  of  life. 

The  conception  of  a  Protistan  kingdom  separate  from  the  animal  and 
vegetable  kingdoms  is  open  to  the  objection  that  it  contains  organisms 
which  are  indubitably  of  animal  or  vegetable 
nature  respectively.  The  relations  of  the 
Protista  to  other  living  things  may  be  repre- 
sented graphically  by  the  accompanying  dia- 
gram (Fig.  1),  where  the  circle  represents  the 
Protista,  the  two  triangles  the  animal  and 
vegetable  kingdoms  respectively.  It  is  seen 
that  the  separation  of  the  Protista  as  a 
systematic  unity  cuts  across  the  ascending 
series  of  evolution  ;  to  express  it  figuratively, 
it  is  a  transverse  cleavage  of  the  phylogenetic 
"  tree."  A  truly  natural  classification  of  living 
things,  however,  is  one  which  expresses  their 
genetic  affinities  and  follows  their  pedigrees 
and  lines  of  descent ;  it  should  represent  a 
vertical  cleavage  of  the  ancestral  tree.  Judged 
by  this  standard,  the  kingdom  of  the  Protista 
•can  only  be  regarded  as  a  convenient  makeshift 
or  compromise,  rather  than  as  a  solution  of  a  FIG.  1. — Graphic  representa- 
difficult  problem — that,  namely,  of  giving  a  tion  of  the  relation  of  the 
natural  classification  of  the  most  primitive 
forms  of  life. 


animal  and  vegetable  king- 
doms to  the  kingdom  of  the 
Protista  (Protistenreich). 
The  Protozoa  are  represented 
by  the  portion  of  the  triangle 
representing  the  animal 
kingdom  which  lies  within 
the  circle  representing  the 
Protista. 


Whether  the  kingdom  Protista  be 
accepted  or  not  as  a  natural  and  valid 
division  of  living  beings,  it  is  imperative 
to  subdivide  it  further,  not  only  on 
account  of  its  vast  extent  and  unwieldy 
size,  but  also  because  it  comprises  organisms  very  diverse  in  nature, 
requiring  for  their  study  the  application  of  methods  of  technique 
and  investigation  often  entirely  different  in  kind.  Hence  in  actual 
practice  the  Protista  are  partitioned  among  at  least  three  different 
classes  '  of  scientific  workers — zoologists,  botanists,  and  bacteri- 
ologists— each  studying  them  by  special  methods  and  to  some  extent 
from  different  points  of  view. 

It  is  necessary,  therefore,  to  consider  from  a  general  standpoint 
the  principal  types  of  organization  comprised  in  the  kingdom 
Protista,  and  we  can  recognize  at  the  outset  two  chief  grades  of 
structure,  bearing  in  mind  always  that  transitional  forms  between 
them  must  exist,  or  at  least  must  have  existed. 

In  the  first  grade,  which  is  represented  by  the  Bacteria  and  allied 
groups  of  organisms,  a  type  of  organization  is  found  which  is 
probably  the  more  primitive,  though  by  many  regarded  as  the 


6 


THE  PROTOZOA 


result  of  degeneration  and  specialization.  These  organisms  do  not 
conform  to  the  type  of  structure  of  the  cell,  as  this  word  is  usually 
understood,  since  they  do  not  exhibit,  speaking  generally,  a  division 
of  the  living  body  substance  into  a  nucleus  distinct  from  the 
cytoplasm  ;*  but  the  chromatin  is  distributed  through  the  proto- 
plasmic body  in  the  condition  of  scattered  lumps  or  granules 
("  chromidia  "),  and  in  many  cases  it  constitutes,  apparently,  the 
whole  or  a  very  large  proportion  of  the  substance  of  the  body. 


f?m$jjtm&?)   <% 

^fm^r  ® 


r 


B 

FIG.  2. — Amosba  proteus.  A,  An  individual  in  active  movement ;  the  arrows 
indicate  the  direction  of  the  currents  in  the  protoplasm  ;  at  r  is  seen  a  pseudo- 
podium  which  is  nearly  completely  retracted  and  has  assumed  a  rnulberry- 
like  appearance  ;  c.v.,  contractile  vacuole,  ;  /.,  fsecal  matter  extruded  at  the 
end  of  the  body  posterior  in  movement ;  the  nucleus  is  obscured  by  the 
opacity  of  the  protoplasm.  B,  An  individual  in  the  act  of  capturing  its  prey 
(P1),  an  Infusorian  (Urocentrnm)  ;  two  pseudopodia  have  flowed  round  it, 
as  shown  by  the  arrows,  and  met  at  the  point  c,  enclosing  the  prey  ;  another 
Infusorian  (P2)  is  seen  in  a  food  vacuole  in  the  body;  N.,  nucleus;  other 
letters  as  in  A.  After  Leidy  (226),  magnified  200  diameters. 

Further,  the  body  in  organisms  of  the  bacterial  type  is  of  definite 
form,  limited  in  many  cases  by  a  rigid  envelope  or  cuticle,  and 
special  organs  of  locomotion  are  either  absent  or  present  in  the 
form  of  so-called  "  flagella,"  structures  perhaps  different  in  nature 
from  the  flagella  of  truly  cellular  organisms.  But  the  most  remark- 
able and  significant  feature  of  organisms  of  the  bacterial  type  is 
seen  in  the  many  different  modes  of  metabolism  and  assimilation 

:  The  significance  of  the  terms  "  nucleus,"  "  cytoplasm,"  "  chromidia,"  etc.,, 
will  be  explained  more  fully  in  subsequent  chapters. 


DISTINCTIVE  CHARACTERS  OF  THE  PROTOZOA       7 

seen  to  occur  amongst  them.  Although  their  metabolism  is  in 
general  distinctly  of  a  vegetative  or  saprophytic  type,  it  often 
exhibits  peculiarities  not  found  in  any  true  plant.* 

In  the  second  grade  of  the  Protista,  the  organism  possesses  the 
characteristics  of  a  true  cell,  in  that  the  body  shows  a  differentia- 
tion of  the  living  substance  into  two  quite  distinct  parts — the 
cytoplasm,  or  general  body-protoplasm,  in  which  is  lodged  at  least 
one  nucleus,  a  body  representing  a  concentration  and  organiza- 
tion of  the  chromatin-substance.  In  some  cases  the  nuclear  sub- 
stance or  chroinatin  niav  be  in  the  scattered,  chromidial  condition 

tj 


end-----,  ^fa^ 


/////mi 

/      ,-:          •  >          •     f     j      f      * 


FIG.  3.  —  Actinosphcerium  eichhornii.  ect.,  Ectoplasm;  end.,  endoplasm  ;  c.v.1,  a 
contractile  vacuole  at  its  full  size  ;  c.v.2,  a  contractile  vacuole  which  has  just 
burst  ;f.v.,f.v.,  food  vacuoles  ;  D.,  a  large  diatom  engulfed  in  the  protoplasm  ; 
ps.,  pseupopodia  ;  N.,  one  of  the  numerous  nuclei.  After  Leidy  (226),  magni- 
fied 250  diameters. 

during  certain  phases  of  the  life-history,  but  such  a  condition  is 
comparatively  rare  and  probably  always  temporary.  The  body- 
protoplasm  may  be  limited  by  a  firm  envelope,  or  may,  on  the  other 
hand,  be  naked,  in  which  case  the  body-form  may  be  quite  in- 
definite. Organs  of  locomotion,  when  present,  are  of  various  kinds  ; 
and  these  organs  may  serve  also  for  the  capture  and  ingestion  of 
food.  And,  finally,  the  metabolism  is  always  one  of  the  four  types 

*  For  a  summary  and  review  of  different  modes  of  metabolism  among  bacterial 
organisms,  see  article  "  Fermentation  "  in  Thorpe's  "  Dictionary  of  Applied 
Chemistry  "  (Longmans). 


8 


THE  PROTOZOA 


described  in  more  detail  in  the  next  chapter— namely,  animal-like 
(holozoic),  plant-like  (holophytic),  fungus-like  (saprophytic),  or  at 
the  expense  of  some  other  living  organism  (parasitic). 

The  cellular  organisms  that  constitute  the 
second  or  higher  grade  of  the  Protista  are 
commonly  partitioned  between  botanists  and 
zoologists  as  Protophyta  (unicellular  algae  and 
fungi)  and  Protozoa  respectively.  It  has  been 
pointed  out  already,  however,  that  this 


c/r^iJ 

^s 

E**^ 


o«Vooly<\0 

te^ll^ 

m$££m 


w 


FIG.  4. — Euglena  spi- 
rogyra.  ces.,  CEsopha- 
gus;st.,  stigma;  c.r., 
reservoir  of  the  con- 
tractile vacuole;  P,P, 
paramylum  -  bodies  ; 
N.,  nucleus.  After 
Stein. 


FIG.  5. — Trichomonas  eberthi,  from  the  intestine  of  the 
common  fowl,  fll.,  Anterior  flagella,  three  in  number ; 
p. ft.,  posterior  flagellum,  forming  the  edge  of  the 
undulating  membrane ;  chr.L,  "  chromatinic  line," 
forming  the  base  of  the  undulating  membrane;  chr.b., 
"  chromatinic  blocks  "  ;  bl.,  blepharoplast  from  which 
all  four  flagella  arise ;  m.,  mouth-opening ;  N.,  nucleus  ; 
ax.,  axostyle.  After  Martin  and  Robertson. 


DISTINCTIVE  CHARACTERS  OF  THE  PROTOZOA        9 


method  of  subdividing  them  is  purely  arbitrary  and  artificial  ;  it 
leads  to  the  result  that  many  forms  are  claimed  by  both  sides,  and 
are  always  to  be  found  described  in  both  botanical  and  zoological 
treatises.  It  is  nevertheless  convenient  for 
many  reasons  to  retain  the  group  Protozoa,  even 
though  we  are  obliged  to  include  in  it  some 
forms  which  are  plants  in  every  sense  of  the 
word.  The  systematist  who  desires  to  give  a 
rigidly  logical  definition  of  the  Protozoa  is, 
then,  confronted  with  a  dilemma  :  either  to 
exclude  from  it  forms  with  plant-like  metab- 
olism which  naturally  belong  to  it,  or,  by 
admitting  such  forms,  to  impair  the  universal 
applicability  of  the  definition  given.  Such 
difficulties  arise  in  every  attempt  to  apply 
rigid  verbal  definitions  to  natural  groups  of 
living  things  ;  they  are  the  direct  outcome  of 
the  fact  that  all  organisms  have  undergone  and 
are  undergoing  a  process  of  evolution,  whereby 
they  adapt  themselves  to  new  conditions  of 
life  and  acquire  new  characters,  as  a  result  of 
which  any  two  forms  now  distinct  are  or 
have  been,  connected  by  intermediate  forms. 


B 

FIG.  6. — Trypanosoma  remaki  of  the  pike.    A,  Slender 
form    ("  var.    parva ").      B,    Stout    form    ("  var. 
magna  ").     After  Minchin,  x  2,000. 


FIG.  7.  -  -  Gregarina 
polymorpha,  parasite 
of  the  digestive  tract 
of  the  mealworm  ; 
"  syzygy  "  of  two 
individuals  attached 
to  one  another.  In 
each  individual,  N., 
nucleus;  pr.,  proto- 
rnerite,  or  anterior 
segment  of  the  body; 
d.,  deutomerite,  or 
posterior  segment. 
After  Schneider. 


10 


THE  PROTOZOA 


The  attempt,  therefore,  made  in  the  following  paragraph  to  give 
a  diagnosis  of  the  Protozoa  must  not  be  regarded  as  a  definition 
of  the  group  in  the  rigidly  logical  sense,  but  merely  as  the  construc- 
tion of  a  general  type,  the  characters  of  which  are  liable  to  a 
certain  amount  of  variation  in  special  cases — a  compromise  between 
the  claims  of  logic  and  the  versatility  of  Nature. 

The  Protozoa,  then,  are  Protista 
in  which  the  organization  is  of  the 
cellular  type,  with  nucleus  distinct 
from  the  cytoplasm.  They  are  uni- 
cellular, in  the  sense  that  the  cell 
constitutes  an  entire  individual, 
which  may  exist  singly  and  in- 
dependently or  in  the  form  of  cell- 
colonies  ;  but  in  the  latter  case  the 
cells  are  not  subordinated  to  the 
individuality  of  the  entire  cell- 
aggregate  by  the  formation  of 


n-. 


-  »  !  .•» 

iH 

.  •-.& 

1  i  :ty$ 
~  •"•*• 

Ht 

•»f^&i^M^ 

FIG.  8. — Stentor  roesdii,  fully  expanded. 
oes.,  (Esophagus;  N,  band-like  macro- 
nucleus  ;  c.v.,  contractile  vacuole,  con- 
nected with  a  long  feeding- canal  (/.c.) 
stretching  down  the  body ;  H,  gelat- 
inous house  into  which  the  animal 
can  retract  itself  completely ;/.,  fibres 
attaching  the  extremity  to  the  stalk 
to  the  house.  After  Stein. 


c.v- 


an. 


FIG.  9.  —  Nyctotherus  cordiformis, 
parasite  of  the  rectum  of  the  frog. 

""  N,  Macronucleus  ;  n,  micronucleus  ; 
gr.,  mass  of  granules  in  front  of  the 

^  macronucleus ;  ces.,  oesophagus;  c.v., 

f^  contractile      vacuole  ;      an.,      anus 

L_  (cytopyge).     After  Stein. 


tissues.  The  body  protoplasm  is  naked  or  clothed  with  a  firm 
envelope,  which  is  usually  not  of  the  nature  of  cellulose.  Proto- 
plasmic organs  are  usually  present  for  purposes  of  locomotion  and 
for  the  capture  and  ingestion  of  food.  Chlorophyll  is  usually 
absent  as  a  cell -constituent,  and  the  metabolism  is  usually  of  the 
animal  type.  To  these  characters  it  may  be  added,  though  not 
as  special  peculiarities  of  Protozoa,  that  reproduction  takes  place 


DISTINCTIVE  CHARACTERS  OF  THE  PROTOZOA     11 


and  that 


tfi-. 


always  by  some  form  of  fission — that  is  to  say,  division  of  the  body 
into  smaller  parts  ;  that  the  phenomena  known  as  "  syngamy  "  and 
"  sex  "  occur,  perhaps  universally,  throughout  the  group 
it  is  very  characteristic  of 
Protozoa,  as  compared  with 
other  Protista,  to  exhibit  in 
their  life-history  a  develop- 
mental cycle,  more  or  less 
complicated,  in  the  course  of 
which  the  organism  may  appear 
under  very  different  forms  at 
different  stages  in  its  develop- 
ment. 

The  Protozoa,  as  thus  under- 
stood, are  commonly  divided 
into  four  main  subdivisions, 
termed  "classes."  Other 
methods  of  classifying  the 
Protozoa  have  been  suggested, 
which  will  be  considered  later ; 
for  the  present  the  old- 
established  subdivisions  are 
sufficient  for  our  purpose. 

CLASS  I.,  SARCODIXA.* — 
Protozoa  in  which  the  proto- 
plasmic body  is  naked  or  non- 
corticate  -  -  that  is  to  say, 
without  a  limiting  envelope 
in  the  form  of  a  cuticle, 
membrane,  or  stiff  cortical 
layer  ;  consequently  the  body 
tends  to  be  either  more  or  less 
spherical  in  floating  forms,  or 
to  have  an  irregular,  con- 
tinually changing  shape  in 
creeping  forms.  Organs  serving 
for  locomotion  and  capture  of 
food  are  furnished  by  tem- 
porary extensions  of  the  living 
pi-otoplasm,  termed  pseudo- 
podia.  A  skeleton  or  shell 
may  be  present.  Examples 


FIG.  10. — Acineta  grandis.  st.,  Stalk  ;  th.f 
theca  ;  s.,  suctorial  tentacles.  After 
Saville  Kent. 


The  name  is  derived  from  sarcode,  the  term  coined  by  Dujardin  to  denote 
u-mg  substance   subsequently  named  by  von  Mohl  protoplasm,  the  term  now 
universally  employed. 


12  THE  PROTOZOA 

• 

are  Amoeba  (Fig.  2),  Diffl.ugia  (Fig.  16),  Adinosphcerium 
(Fig.  3),  etc. 

CLASS  II.,  MASTIGOPHORA.* — Protozoa  in  which  the  organs  of 
locomotion  and  food-capture  in  the  adult  are  flagella,  slender  fila- 
ments which  are  capable  of  performing  active  whip-like,  lashing 
movements.  The  body-protoplasm  may  be  naked  or  corticate. 
Examples  are  Euglena  (Fig.  4),  Trichomonas  (Fig.  5),  Trypanosoma 
(Fig.  6),  etc. 

CLASS  III.,  SPOROZOA. — Protozoa  occurring  always  as  parasites 
of  other  organisms,  and  without  definite  organs  for  locomotion  or 
ingestion  of  food  in  the  adult  condition.  The  reproduction  takes 
place,  typically,  by  formation  of  resistant  seed-like  bodies,  termed 
spores,  containing  one  or  more  minute  germs,  termed  sporozoites. 
Examples  are  Gregarina  (Fig.  7),  Coccidium  (Fig.  152),  the  malarial 
parasites  (Fig.  156),  etc. 

CLASS  IV.,  INFUSORIA. — Protozoa  in  which  the  organs  of  loco- 
motion and  food-capture  are  cilia,  small  vibratile  filaments  dis- 
tinguished from  flagella  by  their  smaller  size,  by  differences  in 
their  mode  of  movement,  and  by  being  present  usually,  in  primitive 
forms  at  least,  in  great  numbers  like  a  fine  fur  over  the  whole  or 
a  part  of  the  surface  of  the  body.  The  cilia  may  be  present  through- 
out life  (subclass  Ciliata),  or  only  in  the  early  stages  of  the  life- 
history  (subclass  Acinetaria).  The  body -protoplasm  is  always  cor- 
ticate. Examples  are  Stentor  (Fig.  8),  Nyctotherus  (Fig.  9),  Acineta 
(Fig.  10),  etc. 

Bibliography. — For  a  list  of  general  works  on  Protozoa,  see  p.  476. 
*  Derived  from  the  Greek  /ido-nf,  a  whip,  equivalent  to  the  Latin  flagettum. 


CHAPTER  II 
THE  MODES  OF  LIFE  OF  THE  PROTOZOA 

PROTOZOA,  as  simple  protoplasmic  organisms,  can  only  exist  in  an 
active  state  in  a  fluid  medium.  Hence  the  free-living,  non-parasitic 
forms  are  aquatic,  either  marine  or  fresh-water  in  habitat.  A 
certain  number  of  species,  however,  are  semi-terrestrial  in  their  mode 
of  life,  creeping  on  damp  surfaces  or  living  in  a  minimum  of 
moisture.  Examples  of  such  forms  are  the  Amoebae,  etc.,  found  in 
the  soil,  or  Mycetozoa,  which  in  the  plasmodial  phase  (p.  239)  creep 
ort  tree-trunks,  logs,  and  so  forth.  None  of  these  forms,  however, 
can  remain  active  in  perfectly  dry  surroundings,  but  pass  into  a 
resting  state  when  desiccated. 

It  has  been  stated  already  that  the  methods  by  which  Protozoa 
gain  their  livelihood  vary  greatly  in  different  cases.  Considered 
generally,  these  methods  may  be  classified  under  four  types  : 

I.  The  majority  of  Protozoa  nourish  themselves  after  the  manner 
of  animals — that  is  to  say,  they  are  entirely  dependent  for  food  and 
sustenance  on  other  organisms  which  they  capture,  devour,  and 
digest.     Such  forms  are  said  technically  to  be  holozoic,  a  word  sig- 
nifying "  completely  animal-like  ";  they  are  unable  to  utilize  simpler 
chemical  substances  in  order  to  build  up  the  protein  constituents 
of   the  living   body,    but  require   proteins   ready-made   for   their 
sustenance. 

II.  A  certain  number   of  Protozoa — all,  with  rare   exceptions, 
belonging  to  the  class  Mastigophora — possess   in  their  body-sub- 
stance peculiar  colour-bearing  corpuscles,  so-called  cJiromatopJiores  or 
chromoplasts,  containing  chlorophyll  or  a  pigment  of  allied  nature, 
by  means  of  which  they  are  able  to  decompose  carbon  dioxide  in 
the  sunlight,  liberating  the  oxygen  and   making  use  of  the  carbon 
in  order  to  build  up  the  protein  and  other  constituents  of  the  living 
body.     Such  organisms  are  entirely  similar  in  their   metabolism 
to  the  ordinary  green  plants,  and  are  hence  termed  holophytic.  or 
"  completely  plant-like." 

The  holophytic  condition,  in  which  the  chlorophyll-bodies  form  an  integral 
part  of  the  structure  of  the  body,  and  are  to  be  regarded  simply  as  proto- 
plasmic organs,  must  be  distinguished  carefully  from  a  state  of  things  often 

13 


14  THE  PROTOZOA 

found  in  holozoic  Protozoa  of  all  classes — namely,  the  presence  in  the  body 
substance  of  symbiotic  independent  organisms  of  vegetable  nature,  as  described 
below. 

III.  A  certain  number  of  Protozoa  that  have  no  chlorophyll  or 
similar  pigment  in  their  bodies  are,  nevertheless,  free  from  the 
necessity  of  preying  upon  other  organisms  in  order  to  obtain  their 
sustenance,  since  they  are  able  to  live  upon  organic  substances  in 
solution,  the  products  of  the  metabolism  or  decay  of  other  living 
organisms.     Such  forms  are  termed  saprophytic  (or  saprozoic).  since 
their  mode  of  life  is  similar  to  that  of  a  saprophyte,  such  as  a  fungus. 
It  is  not  necessary  that  they  should  be  supplied  with  ready-made 
proteins  in  their  food,  since  they  are  able  to  build  up  their  protein 
constituents  from  substances  of  simpler  chemical  nature.     Many 
examples  of  saprophytic  forms  are  found  amongst  the  free-living 
Flagellata. 

Lauterborn  (17)  has  coined  the  useful  term  sapropelic  (from  the  Greek 
7rrj\6s,  mud)  to  denote  a  mode  of  life  which  must  be  regarded  as  a  special 
type  of  the  saprophytic  method,  partly  also  of  the  holozoic — namely,  the 
mode  of  life  of  those  fresh- water  organisms  that  live  in  a  mud  or  ooze  composed 
almost  entirely  of  the  decaying  remains  of  dead  plants  and  other  debris  of 
a  similar  nature.  A  very  characteristic  fauna  occurs  under  these  conditions. 

IV.  Finally,  many  Protozoa  of  all  classes  live  as  parasites — that 
is  to  say,  at  the  expense  of  some  other  living  being,  which  is  termed 
the  host. 

These  four  modes  of  life  can  be  used  only  to  a  very  limited  extent 
for  classificatory  purposes  ;  it  is  only  possible  to  do  so  in  those 
cases  where  a  particular  habit  of  life,  long'  continued,  has  resulted 
in  definite  structural  characteristics,  and  more  especially  in  the 
loss  of  organs  requisite  for  other  modes  of  life — as,  for  example,  in 
the  case  of  the  subdivision  Phytoflagellata,  of  the  order  Flagellata, 
where  the  holophytic  habit  has  become  so  ingrained  that  only 
structural  features  proper  to  vegetable  life  are  retained. 

In  other  cases  it  is  clear  that  a  given  habit  of  life  in  different 
organisms  does  not  necessarily  indicate  close  affinity  between  them. 
In  the  first  place,  we  find  closely  allied  forms  living  in  different 
ways.  Examples  of  all  the  four  methods  of  metabolism  described 
above  are  to  be  found  in  the  single  order  Flagellata,  and  through- 
out the  Protozoa  there  are  commonly  to  be  found  parasitic  forms 
closely  allied  to  free-living  forms.  In  the  second  place,  different- 
types  of  metabolism  may  be  found  as  transitory  phases  in  the  life 
of  one  and  the  same  individual  or  species.  Thus  the  common 
Euglena  (Fig.  4),  a  flagellate  possessing  chromatophores  and  living 
normally  in  a  holophytic  manner,  is  able  to  maintain  itself  as  a 
saprophyte  if  deprived  of  the  sunlight  necessary  for  a  holophytio 
mode  of  life  (p.  188)  Striking  examples  of  variability  in  the 
mode  of  nutrition  are  seen  also  in  the  section  Chryso  monad  inn.  of 


THE  MODES  OF  LIFE  OF  THE  PROTOZOA  15 

the  Flagellata,  where  a  given  species  may  be  either  holozoic  or 
holophytic,*  according  to  circumstances. 

The  bionomics  of  Protozoa — that  is  to  say,  their  relations  to  their 
environment  and  to  other  organisms — constitute  a  very  important 
branch  of  knowledge,  both  practical  and  theoretical,  especially  in 
the  case  of  parasitic  forms.  Considering  the  subject  from  the  point 
of  view  of  the  four  modes  of  life  already  described,  it  is  clear,  in 
the  first  place,  that  the  holophytic  forms  are  entirely  independent 
of  all  other  living  organisms,  and  require  for  their  continued 
existence  only  sunlight  and  a  suitable  environment,  containing  the 
necessary  inorganic  substances,  at  a  temperature  which  permits 
the  continuance  of  vital  processes  and  activities. 

Saprophytic  organisms,  however,  in  so  far  as  they  require  for 
their  sustenance  materials  produced  by  living  bodies,  are  dependent 
directly  or  indirectly  upon  other  organisms  for  their  existence. 
Purely  holozoic  forms,  also,  cannot  exist  without  other  forms  of 
life  upon  which,  or  upon  the  products  of  which,  they  can  feed. 
But  neither  holozoic  nor  saprophytic  organisms  are  dependent, 
as  a  rule,  upon  any  other  particular  form  of  life,  but  only  upon  living 
things  generally  ;  though  in  some  cases  such  forms  may  be  specialized 
in  their  nutrition  to  such  an  extent  as  to  be  unable  to  exist  without 
some  particular  food. 

A  parasitic  form,  on  the  other  hand,  is  entirely  dependent,  as  a 
rule,  for  its  existence  on  some  particular  organism  or  limited  group 
of  organisms  which  constitute  its  host  or  hosts.  It  must,  however, 
be  understood  clearly  that  an  organism  living  in  or  upon  the  body 
of  another  organism  is  not  necessarily  a  parasite  by  any  means. 
In  the  first  place,  a  distinction  must  be  drawn  bet\veen  parasitism 
and  symbiosis,  by  which  is  meant  an  association  of  two  organisms 
for  mutual  benefit,  f  Good  examples  of  symbiosis  are  seen  in 
some  of  the  Sarcodina,  Radiolaria,  and  Foraminifera,  the  proto- 
plasm of  which  contains  constantly  intrusive  organisms,  known  as 
zoochlorettce  or  zooxanthellce,  according  as  they  contain  a  green  or  a 
yellow  pigment.  Zoochlorellse  are  green  algae  of  the  order  Proto- 
coccacece ;  zooxanthellae  are  holophytic  flagellates  of  the  suborder 
Cryptomonadina — e.g.,  Cryptomonas  schaudinni,  symbiotic  in  the 
foraminifer  Peneroplis  (Winter,  28).  These  organisms  penetrate 

'  For  example,  the  species  Cliromulina  flavicans.    See  Biitschli  (2),  vol.  ii.,  p.  865. 

t  The  term  "  symbiosis  "  is  often  much  misused,  especially  by  medical  writers, 
by  whom  it  is  commonly  applied  to  any  association  of  two  distinct  organisms  ; 
for  instance,  "  pure  mixed  cultures  "  of  amoebfe  with  some  species  of  bacillus, 
where  the  amoebae  are  simply  feeding  on  the  bacteria,  are  often  spoken  of  as 
"  symbiosis,"  although  the  advantage  is  clearly  only  on  one  side  in  such  an  asso- 
ciation. It  should  be  understood  that  the  term  "  S3rmbiosis  "  is  a  technical  term 
of  long  standing  in  biology,  and  is  used  not  merely  in  its  strict  etymological  sig- 
nificance of  ''  living  together/'  but  in  the  special  and  restricted  sense  of  "  living 
together  for  the  mutual  benefit  of  the  two  organisms  concerned." 


16  THE  PROTOZOA 

into  the  body  of  their  host,  lose  their  flagella,  and  nourish  them 
selves  by  means  of  their  pigment,  which  has  the  nature  and  proper- 
ties of  plant-chlorophyll  ;  that  is  to  say,  it  decomposes  carbon  dioxide 
in  the  sunlight  and  liberates  oxygen.  The  carbon  dioxide  is 
obtained  from  the  respiratory  processes  of  the  host,  which  in  its 
turn  utilizes  the  oxygen  produced  by  the  symbionts  (p.  197),  and 
thus  each  organism  supplies  the  needs  of  the  other.  When  the 
host  enters  upon  its  reproductive  processes  and  breaks  up  into  a 
vast  number  of  swarm-spores,  the  symbionts  develop  flagella  and 
swim  off,  doubtless  to  seek  for  lodging  elsewhere. 

It  is  a  matter  of  convenience  to  distinguish  as  epizoic  those 
organisms  which  live  upon,  or  are  attached  to,  and  as  entozoic 
those  which  live  within,  the  body  or  substance  of  the  particular 
form  of  life  with  which  they  are  associated.  Epizoic  forms  may 
be  entirely  harmless  to  the  creature  upon  which  they  occur  ;  they 
may  simply  utilize  its  body  as  a  coign  of  vantage  where  they  readily 
obtain  their  food,  which  may  consist  in  some  cases  of  nutritious 
substances  dropped  or  rejected  by  the  animal  that  carries  them  ; 
or  they  may  obtain  the  benefits  of  shelter  or  transport,  especially 
when  the  epizoic  form  in  question  is  itself  of  sedentary  habit. 
Every  naturalist  is  acquainted  with  the  sea-anemones  that  live 
habitually  upon  hermit-crabs,  probably  to  the  advantage  of  both 
animals — at  all  events,  to  the  detriment  of  neither.  There  are 
many  similar  cases  among  Protozoa.  The  appendages  of  Crustacea, 
especially  of  the  Cladocera  and  Copepoda,  are  often  thickly  beset 
with  sessile  Vorticellids  and  Acinetaria,  which  obtain  a  convenient 
lodging,  but  provide  their  own  board.  Other  forms  occur  similarly 
on  the  stems  of  hydroids,  as,  for  example,  Acineta  papillifera  on 
Cordylopliora  lacustris.  Amoebae  are  found  creeping  on  the  exterior 
of  Calcareous  Sponges,  nourishing  themselves  on  diatoms  and  other 
organisms.  Similar  instances  could  be  multiplied  indefinitely. 

On  the  other  hand,  epizoic  forms  may  be  dangerous  parasites, 
nourishing  themselves  at  the  expense  of  the  animal  they  infest, 
and  sometimes  inflicting  much  damage  upon  it.  It  can  be  easily 
understood  that  an  epizoic  form  which  at  first  lived  harmlessly  upon 
some  animal,  drawing  its  supplies  of  food  from  the  surrounding 
medium,  might  acquire  the  habit  ultimately  of  obtaining  its  nourish- 
ment from  the  living  substratum  upon  which  it  has  planted  itself. 
Examples  of  epizoic  parasites  are  the  flagellate  Costia  necatrix 
(p.  272)  and  the  ciliate  Ichthyophthirius  multifiliis  (p.  450),  both  of 
which  are  epizoic  parasites  of  fishes,  attaching  themselves  to  the 
skin  and  destroying  the  epidermis  ;  as  a  result,  the  way  is  left  open 
for  fungi  and  bacteria  to  penetrate  the  skin,  and  so  produce  ulcera- 
tion  and  suppuration,  which  may  be  fatal. 

All  certain  instances  of  Protozoa  acting  as  external  parasites  are 


THE  MODES  OF  LIFE  OF  THE  PROTOZOA  17 

found  amongst  aquatic  animals,  and  it  can  be  readily  understood 
that  a  delicate  protoplasmic  organism  could  only  pass  from  one 
host  to  another  in  a  fluid  medium,  or  by  the  help  of  special  mechan- 
isms adapted  to  aerial  transport  or  transmission  by  contact.  It 
should  be  mentioned,  however,  that  some  human  contagious  skin- 
diseases  are  suspected  to  be  due  to  the  agency  of  parasites  of  the 
nature  of  Protozoa.* 

Like  the  epizoic  forms,  there  are  many  entozoic  Protozoa  which 
inhabit  the  bodies,  and  especially  the  intestines,  of  other  animals, 
but  which  are  in  no  way  to  be  regarded  as  parasites  ;  they  feed 
merely  on  various  substances  to  be  found  there,  such  as  waste 
particles  of  food,  excreted  or  fsecal  matter,  or  on  other  organisms, 
such  as  bacteria,  yeasts,  and  the  like — in  short,  on  substances  which 
from  the  point  of  view  of  the  host  are  superfluous,  or  even  harmful. 
Many  examples  of  such  organisms  could  be  cited  ;  a  good  one  is  the 
common  Chlamydophrys  stercorea,  found  in  the  fseces  and  digestive 
tract  of  man  and  many  animals.  The  common  intestinal  flagellates 
belonging  to  the  genus  Trichomonas  (Fig.  5)  and  other  genera  are, 
similarly,  not  to  be  regarded  as  true  parasites  in  any  sense  of  the 
word.  The  common  LopJiomonas  blattarum  (Fig.  45)  from  the 
intestine  of  the  cockroach  feeds  chiefly  upon  bacteria  and  yeasts. 
Many  of  these  intestinal  Protozoa  are  perhaps  useful,  rather  than 
harmful,  to  their  hosts. 

On  the  other  hand,  the  vast  majority  of  organisms,  Protozoa  or 
otherwise,  that  live  in  the  interior  of  other  living  creatures  are  there 
for  no  good  or  useful  purpose  ;  their  habitat  is  alone  sufficient  to 
render  them  suspect.  Two  modes  of  parasitism  may  be  distin- 
guished from  a  general  point  of  view.  On  the  one  hand,  the  para- 
site may  merely  intercept  the  food-  of  the  host  and  rob  it  of  its 
sustenance.  On  the  other  hand,  the  parasite  may  nourish  itself 
upon  the  living  substance  or  vital  fluids  of  its  host. 

Organisms  which  rob  the  host  of  its  food  may  do  so  in  one  of  two 
ways.  They  may  appropriate  the  raw  food-material,  which  they 
then  ingest  and  devour  after  the  strictly  holozoic  method  of  feeding  ; 
examples  of  this  mode  of  life  are  possibly  to  be  found  in  the  extensive 
infusorian  fauna  to  be  found  in  the  stomachs  of  ruminants.  Or 
they  may  absorb  the  fluid  products  of  the  digestion  of  the  host  by 
diffusion  through  the  surface  of  the  body  of  the  parasite  ;  examples 
of  this  mode  of  parasitism  are  to  be  seen,  probably,  in  the  case  of 
the  Gregarines  so  common  in  the  guts  of  insects.  Parasites  of  the 

*  For  example,  the  so-called  Coccidioides  immitis,  a  name  given  to  bodies  found 
in  certain  South.  American  skin  diseases ;  see  Blanchard  (633),  p.  168.  Molluscum 
contagiosum  has  also  been  attributed  to  parasites  referred  by  some  to  the  Protozoa. 
In  both  these  instances,  however,  the  exact  nature  of  the  parasitic  bodies  is  far 
from  clear  ;  the  parasite  of  molluscum  contagiosum  should  probably  be  referred 
to  the  Chlamydozoa  (p.  470). 


18  THE  PROTOZOA 

type  that  may  be  denoted  as  food-robbers  are  in  general  very 
harmless  to  their  hosts. 

Those  parasites,  however,  that  nourish  themselves  on  the  sub- 
stance of  the  host  may  produce  the  most  dangerous  effects  on  its 
health  and  well-being.  As  in  the  case  of  the  food-robbers,  parasites 
of  this  kind  may  absorb  their  food  in  one  of  two  ways.  They  may 
devour  solid  portions  of  the  host's  body  in  a  holozoic  manner  ;  an 
example  of  this  is  seen  in  Entamceba  liistolytica  (Fig.  90),  the  parasite 
of  amoebic  dysentery,  which  devours  portions  of  the  host's  tissue, 
such  as  epithelial  cells,  or  blood-corpuscles.  But  more  usually  the 
parasites  absorb  their  nourishment  in  a  fluid  form  through  the 
surface  of  their  body,  doubtless  by  the  help  of  enzymes  secreted  by 
them.  Hence  it  is  typical  of  true  parasites  to  have  lost  all  trace 
of  special  organs  for  the  capture,  ingestion,  or  digestion,  of  solid 
food. 

Just  as  in  the  epizoic  mode  of  life  a  harmless  or  even  beneficial 
commensalism  may  degenerate  by  insensible  gradations  into 
dangerous  parasitism,  so  the  same  is  true  of  the  entozoic  habit. 
An  organism  which  begins  by  being  a  scavenger  readily  becomes  a 
food-robber.  LopJiomonas,  for  instance,  may  be  seen  to  contain 
starch-grains  and  other  substances  which  probably  belong  to  the 
food  of  its  host.  A  further  but  easy  gradation  leads  to  the  entozoic 
organism  devouring  portions  of  its  host.  A  good  example  of  this  is 
seen  in  two  of  the  entozoic  amoebae  of  the  human  intestine  :  the 
common  Entamceba  coli  (Fig.  89)  appears  to  be  chiefly  a  scavenger, 
harmless  to  its  host,  and  not  deserving  the  reproach  of  parasitism  ; 
on  the  other  hand,  E,  histolytica  is  a  dangerous  parasite.  So  also 
an  entozoic  organism,  which  begins  by  merely  absorbing  the  pro- 
ducts of  digestion,  may  end  by  absorbing  the  substance  of  its  host. 
It  is  highly  probable  that  in  many  entozoic  organisms  the  mode  of 
feeding  may  vary  according  to  circumstances,  and  that  an  organism 
which  may  be  a  harmless  commensal  under  some  conditions  may 
become  a  more  or  less  dangerous  parasite  under  others. 

The  entozoic  Protozoa  which  are  truly  parasitic  may  inhabit  a 
variety  of  situations  in  the  bodies  of  their  hosts.  In  some  cases  the 
host  is  another  species  of  Protozoon,  into  the  body  of  which  the 
intruder  penetrates,  living  either  in  the  cytoplasm  or  the  nucleus. 
Amoebae  are  ver}7  subject  to  the  attacks  of  intranuclear  parasites, 
and  the  young  stages  of  many  Acinetans  are  parasitic  upon  other 
Infusoria.  When  the  host  is  one  of  the  Metazoa,  the  invading 
organism  may  be  in  like  manner  intracellular  or  intranuclear  in 
habitat ;  or  it  may  penetrate  into  the  tissues,  living  amongst  and 
between  the  constituent  cells  ;  or  it  may  inhabit,  finally,  one  of  the 
internal  cavities  of  the  body,  such  as  the  digestive  tract,  general 
body-cavity,  spaces  containing  blood  or  lymph,  cavities  of  the  renal 


THE  MODES  OF  LIFE  OF  THE  PROTOZOA  19 

or  urinary  organs,  etc.,  either  living  free  in  the  cavity  it  inhabits,  or 
attached  to  the  lining  epithelium. 

As  diverse  as  the  modes  of  parasitism  among  Protozoa  are  the 
effects  they  produce  on  their  hosts.  Some  parasites  produce  no 
perceptible  disturbance  in  the  well-being  of  their  host ;  even  when 
they  destroy  cells  and  portions  of  tissues,  the  damage  may  be  slight, 
and  is  quickly  made  good  without  appreciable  permanent  injury 
being  done.  From  this  condition  of  more  or  less  perfect  harmless- 
ness  there  is  a  continuous  gradation  in  the  ascending  capacity  for 
harmfulness,  culminating  in  species  which  bring  about  the  death  of 
their  hosts  with  greater  or  less  rapidity.  Hence  parasitic  Protozoa 
are  commonly  distinguished  as  pathogenic  or  non-pathogenic  ;  but 
since  there  is  no  precise  limit  to  the  degree  of  sickness  or  indis- 
position which  justifies  the  application  of  the  term  "  pathogenic," 
it  is  perhaps  more  convenient  to  distinguish  them  as  lethal  or  non- 
lethal.  It  is  not  possible,  however,  to  lay  down  hard-and-fast 
distinctions  in  these  matters,  since  a  parasite  which  is  not  lethal 
under  some  circumstances  may  become  so  under  others  ;  for  instance, 
an  animal  living  a  free  and  natural  life  may  be  quite  well  able  to 
resist  the  attacks  of  parasites  to  which  it  succumbs  in  captivity. 
Moreover,  it  must  be  borne  in  mind  that  such  terms  as  "lethal "  or 
:'  pathogenic  "  can  only  be  applied  to  a  parasite  in  its  relation  to  a 
particular  host,  since,  as  will  be  shown  below,  a  parasite  which  is 
harmful  to  one  host  may  be  harmless  to  another. 

It  is  far  from  clear  in  what  way  the  pathogenic  effects  of  parasitic 
Protozoa  are  produced.  If  the  action  and  reaction  of  host  and 
parasite  were  relations  dependent  simply  on  the  number  or  relative 
total  bulk  of  parasites  present  in  a  given  host,  the  problems  of 
parasitism  would  be  comparatively  simple  ;  but  in  many  cases  this 
is  obviously  very  far  from  being  the  case.  The  effect  produced  by 
a  given  species  of  parasite  upon  a  given  species  of  host  is  a  specific 
reaction,  which  differs  markedly  when  one  of  the  two  dramatis 
personce  is  changed.  It  is  not  uncommon  to  find  insects  with  their 
digestive  tract  or  body-cavity  crammed  with  parasitic  Gregarinr>s 
of  relatively  large  size,  but  apparently  none  the  worse  for  it.  On 
the  other  hand,  large  mammals  may  succumb  to  the  effects  of 
minute  parasites  in  relatively  scanty  numbers — in  the  sense,  that 
is.  that  the  aggregate  bulk  of  the  parasites  may  be  infinitesimal 
compared  to  the  bulk  of  the  host.  A  better  comparison  is  furnished 
by  considering  closely-allied  species  of  parasites  and  hosts  respec- 
tively. A  rat  may  have  its  blood  swarming  with  Trypanosoma 
lewlsi,  without  apparently  being  any  the  worse  for  it.  On  the  other 
hand,  in  a  man  dying  of  sleeping  sickness,  caused  by  T.  gambiense, 
or  in  a  ruminant  dying  of  nagana  (tsetse-fly  disease),  caused  by 
T.  brucii.  the  trypanosomes  may  be  so  scanty  as  to  be  exceedingly 


20  THE  PROTOZOA 

difficult  to  detect.*  These  facts  suggest  strongly  that  the  parasites 
produce  specific  toxins  ;  but  the  "  sarcocystine  "  produced  by  para- 
sites of  the  genus  Sarcocystis  (Sarcosporidia)f  is  almost  the  only  case 
up  to  the  present,  in  which  a  toxin  has  been  isolated  from  a  Pro- 
tozoan parasite.  Laveran  and  Pettit  (19),  however,  claim  to  have 
obtained  "  trypanotoxins  "  from  trypanosomes. 

Considering  the  facts  of  parasitism  generally,  as  a  problem  of 
natural  history,  two  guiding  principles  must  be  borne  in  mind 
clearly  :  the  first  is  that  any  organism,  parasitic  or  otherwise,  tends 
to  be  adapted  in  the  best  possible  manner  to  the  circumstances  of 
its  natural  environment ;  the  second  is  that,  so  long  as  a  parasite  is 
entirely  dependent  on  its  host  for  its  existence,  it  is  to  its  utmost 
disadvantage  to  bring  about  the  death  of  its  host.  When,  therefore, 
a  given  parasite  is  constantly  lethal  to  a  particular  host  or  hosts, 
one  of  two  explanations  must  be  sought  for  :  either  the  case  is  one 
of  a  disharmony — that  is  to  say,  of  imperfectly-adjusted  relations 
between  the  host  and  parasite  ;  or  the  parasite  must  obtain  from 
the  death  of  the  host  advantages  in  the  matter  of  the  continuance 
of  the  species  sufficient  to  compensate  for  the  temporary  loss 
through  destruction  of  individuals. 

The  conditions  to  which  a  parasite  requires  to  be  adapted  are 
different  in  many  ways  from  those  that  influence  the  life  of  a  free- 
living  organism.  When  once  a  parasite  has  obtained  a  footing  in 
its  proper  host,  the  problem  of  food-supply  is  solved  for  it,  since 
it  finds  itself  lodged  in  the  midst  of  abundant  nutriment  so  long  as 
its  host  lives.  On  the  other  hand,  if  the  species  is  to  be  main- 
tained, it  is  essential  that  the  parasite  should  be  able  to  infect  new 
hosts,  a  difficult  undertaking,  and  one  in  which  the  chances  are 
all  against  the  parasite  in  most  cases.  To  insure  dissemination  of 
the  species  a  large  number  of  offspring  must  be  produced,  and 
special  mechanisms  and  adaptations  may  be  necessary  to  insure 
their  reaching  their  destination.  Hence,  the  more  parasites  become 
specialized  and  adapted  to  their  peculiar  mode  of  life,  the  more  the 
organs  and  functions  of  nutrition  tend  to  become  simplified,  and 
the  greater  the  tendency  to  elaboration  and  extreme  fertility  of  the 
reproductive  function. 

Considered  generally,  a  parasitic  Protozoon  reproduces  itself 
within  a  given  host  with  one  of  two  results  :  in  the  first  place,  with 
that  of  overrunning  the  host  and  establishing  itself  there  ;  in  the 
second  place,  with  that  of  producing  forms  destined  to  infect  new 
hosts.  Forms  produced  in  the  first  manner  may  be  termed  the 
'  multiplicative  phases  "  ;  their  function  is  to  produce  a  stock  of 
the  parasite.  From  the  stock  are  given  off  what  may  be  termed 

*  Compare  Laveran  and  Mesnil  (391),  pp.  146-150. 

•f-  Laveran  and  Mesnil  (18)  ;  Teichmann  (25)  ;  Teichmann  and  Braun  (26). 


THE  MODES  OF  LIFE  OF  THE  PROTOZOA  21 

the  "  propagative  phases,"  which  as  a  rule  do  not  multiply  further 
in  the  host  in  which  they  are  produced,  but  await  their  chance  of 
being  transferred  to  a  new  host ;  and  if  such  a  chance  be  not  given 
to  them,  they  die  off  and  are  replaced  by  fresh  propagative  forms 
from  the  stock  (see  further  below,  Chapter  IX.,  p.  166). 

So  long  as  the  nutritive  or  multiplicative  function  is  the  most 
important  one  in  the  life  of  a  parasite,  and  until  it  has  matured  its 
propagative  phases,  the  death  of  the  host  is  the  greatest  disaster 
that  can  befall  it.  The  ideal  host,  from  the  point  of  view  of  a  para- 
site, is  one  that  is  "  tolerant  "  to  it — that  is  to  say,  one  that  can 
support  the  presence  of  the  parasite  and  keep  it  supplied  with  the 
nutriment  it  requires,  without  suffering  in  health  or  vigour  to  any 
marked  extent.  When  once,  however,  the  parasite  has  made  the 
necessary  provision  for  propagating  the  species,  the  life  or  death 
of  the  host  may  become  a  matter  of  indifference  to  the  parasite, 
or  may  even  in  some  cases  be  necessary  for  the  dissemination  of  the 
offspring.  This  will  be  apparent  from  a  consideration  of  the  methods 
by  which  parasitic  Protozoa  infect  new  hosts. 

The  passage  of  a  parasite  from  one  host  to  another  includes  two 
manoeuvres  :  the  passing  out  from  the  first  host,  and  the  passing 
into  the  second.  Primitively  it  may  be  supposed  that  this  migra- 
tion was  effected  simply  by  the  unaided  efforts  of  the  parasite  itself — 
that  is  to  say,  that  the  active  motile  parasite  would  force  its  way 
out  of  one  host,  move  freely  in  the  surrounding  medium,  and  sooner 
or  later  attack  and  penetrate  a  fresh  host.  This  primitive  method 
of  transference  doubtless  occurs  in  many  cases,  especially  amongst 
epizoic  forms  (e.g.,  Ichthyophthirius,  p.  450).  In  the  case  of  entozoic 
parasites  its  occurrence  is  less  common,  but  it  is  found  in  a  certain 
number  of  cases.  The  young  stages  of  many  Acinetaria,  parasitic 
in  Ciliata,  probably  seek  out  their  hosts  and  penetrate  into  them  ; 
after  a  period  of  juvenile  parasitism  they  leave  the  host's  body  and 
become  free-living,  non-parasitic  organisms.  Active  migration  of 
this  kind,  however,  is  very  rare  amongst  entozoic  parasites.  In  the 
first  place,  the  conditions  of  life  within  a  living  body,  in  the  midst  of 
organic  fluids,  are  so  different  from  those  in  the  open  water,  whether 
salt  or  fresh,  that  it  is  hardly  to  be  expected  that  a  delicate  unicellular 
organism  adapted  to  the  one  mode  of  life  could  stand  the  sudden 
change  to  the  other.  In  the  second  place,  it  is  clear  that  active 
migration  of  parasitic  Protozoa  could  only  be  effected  wThen  the  host 
is  an  aquatic  animal,  and  not  when  it  leads  a  terrestrial  life.  The 
only  instances  of  active  migration  known  with  certainty  to  occur 
in  the  case  of  Protozoa  parasitic  on  terrestrial  animals  are  those 
in  which  the  parasite  can  penetrate  a  mucous  membrane,  and  is 
thus  able  to  pass  from  one  host  to  another  when  two  such  surfaces 
are  in  contact.  In  this  way  the  trypanosome  of  dourine  in  horses 


22  THE  PROTOZOA 

(T.  equiperdum)  passes  from  one  host  to  another  during  coitus,  and 
the  transmission  of  the  parasite  of  syphilis  is  another  instance. 

Speaking  generally,  and  excluding  for  the  moment  those  cases 
in  which  the  transmission  is  brought  about  by  means  of  an  inter- 
mediary host,  the  propagative  phases  of  the  parasitic  Protozoa 
take  the  form  of  inactive,  resting  stages  in  which  the  body  of  the 
parasite  is  protected  against  adverse  external  conditions  by  tough 
protective  membranes.  In  the  form  of  resistant  cysts  or  spores, 
the  parasites  in  a  dormant  state  offer  a  passive  and  inert  resistance 
to  the  elements  ;  they  are  disseminated  like  seeds,  and  they  ger- 
minate when  they  reach  a  suitable  environment,  but  not  till  then. 

Many,  perhaps  the  majority  of  parasitic  Protozoa,  occupy  posi- 
tions in  the  body  of  the  host  whence  the  propagative  phases  can  pass 
without  difficulty  to  the  exterior.  This  is  the  case  when  the  para- 
site is  lodged  in  organs  which  have  ducts  or  passages  leading  directly 
or  indirectly  to  the  exterior — such  as,  for  instance,  the  digestive 
tract  and  its  dependencies,  or  the  urinary  organs  and  ducts.  In  all 
such  cases  the  propagative  stages  of  the  parasite  pass  harmlessly 
to  the  exterior.  The  host  may  in  this  manner  get  rid  entirely  of  its 
parasites,  without,  however,  necessarily  acquiring  immunity  to 
fresh  infections  ;  or,  on  the  other  hand,  the  parasite  may  keep  up  its 
numbers  in  the  host  by  continual  multiplication  to  produce  a  stock 
from  which  are  sent  forth  incessant  relays  of  the  propagative  phases 
destined  to  infect  new  hosts.  In  the  majority  of  parasitic  Pro- 
tozoa the  relations  to  the  host  are  of  this  type,  and  the  parasites  are 
neither  lethal  nor  pathogenic  tc  any  great  extent. 

On  the  other  hand,  there  are  many  instances  in  which  parasitic 
Protozoa  occupy  a  position  in  the  body  of  the  host  whence  escape 
by  anatomical  channels  is  not  possible.  This  is  the  case  when  the 
parasite  inhabits  some  closed  space  in  the  body,  such  as  the  ccelome 
or  general  body-cavity,  or  the  blood-system  ;  or  when  it  attacks 
deeply-situated  cells  or  tissues  of  the  body.  In  some  cases  where 
natural  means  of  exit  from  the  body  occur,  they  may  be  unsuitable 
for  the  dissemination  of  the  parasite,  as  in  the  case  of  those  forms 
parasitic  in  the  genital  organs  of  one  sex  of  the  host.  In  cases  of 
this  kind  there  are  at  least  six  known  methods  whereby  parasitic 
Protozoa  are  disseminated  and  transferred  to  fresh  hosts. 

1.  The  resistant  stages  of  the  parasite  may  be  set  free  by  the 
death  and  decajr  of  its  host.     This  appears  to  be  the  manner  in 
which  some  of  the  tissue-infecting  parasites  of  the  order  Myxo- 
sporidia,  especially  the  family  Myxobolidce,  are  disseminated  ;  they 
are  for  the  most  part  parasites  of  fishes,  and  are  often  very  deadly 
in  their  effects. 

2.  The  parasite  may  cause  tumours  and  ulcers,  which  suppurate, 
and  so  set  free  the  cysts  or  spores  of  the  parasite.     This,  again,  is 


THE  MODES  OF  LIFE  OF  THE  PROTOZOA  23 

an  effect  often  produced  by  tissue-parasites,  such  as  the  Myxobolidce, 
or  by  species  of  Microsporidia.  In  such  cases  also  the  parasite  is 
pathogenic  to  its  host,  and  frequently  lethal. 

3.  The  parasite  remains  in  the  host  until  the  latter  is  eaten  by 
some  animal  which  preys  upon  it.     The  propagative  phases  of  the 
parasite  are  able,  however,  to  resist  digestion  by  the  animal  that 
has  devoured  their  former  host,  and  pass  unaltered  through  its 
intestine,  to  be  finally  cast  out  with  the  dejecta.     This  is  almost 
certainty  the  method  by  which  the  common  Monocystis  of  the  earth- 
worm infects  its  host.     The  parasite  produces  resistant  spores  in 
the  worm  ;  the  worm  is  eaten  by  a  bird,  mole,  frog,  OF  some  other 
animal,  through  the  digestive  tract  of  which  the  spores  pass  un- 
altered ;  they  are  scattered  abroad  with  the  faeces,  and  may  then 
be  swallowed  by  another  earthworm,  in  which  they  germinate  and 
produce  an  infection. 

4.  As  in  the  last  case,  the  host,  together  with  its  parasites,  is 
devoured  by  some  animal,  in  which,  however,  the  parasite  is  not 
merely   carried   passively,   but   again  becomes   actively  parasitic. 
Hence  in  this  case  there  is  an  alternation  of -hosts,  one  of  the  two 
hosts  becoming  infected  by  devouring  the  other.     This  mode  of 
infection,  which  is  well  known  to  occur  commonly  among  parasitic 
worms,  such  as  Cestodes,  is  probably  also  frequent  among  Pro- 
tozoa ;  but  at  present  only  two  cases  of  it  are  known  with  certainty. 
One  is  that  of  the  species  of  the  genus  Aggregata  (vide  infra,  p.  353), 
parasites  of  crabs  and  cephalopods,  such  as  the  cuttle-fish  and  the 
octopus.      In  the  cephalopod  the  parasite  forms  resistant  spores 
which  pass  out  with  the  faeces,  and  may  then  be  devoured  by  crabs. 
In  the  crab  the  spores  germinate  and  give  rise  to  a  second  form  of 
the  parasite,  which  lives  and  multiplies  in  its  new  host.     If,  as  fre- 
quently happens,  the  crab  is  eaten  by  a  cephalopod,  the  parasite 
completes  its  life-cycle  by  becoming  once  more  a  parasite  of  the 
cephalopod.     Another  case  is  that  of  Hcemogregarina  muris  in  the 
rat-mite  (p.  376,  infra). 

5.  The  Protozoa  parasitic  in  the  blood  of  vertebrates  are  dis- 
seminated by  blood-sucking  invertebrates,  such  as  leeches,  ticks, 
or  insects,  which  take  up  the  parasites  by  sucking  the  blood  of  an 
infected  animal.     Later  on  the  parasite  may  be  inoculated  into  a 
second  vertebrate  host  by  the  invertebrate  when  it  sucks  blood  at 
a  later  feed.     In  some  cases  the 'transference  of  the  blood-parasite 
may  be  effected  in  a  purely  direct  and  mechanical  manner  by  the 
invertebrate,  but  in  most  cases  the  invertebrate  plays  the  part  of  a 
true  host,  in  which  the  parasite  multiplies  and  goes  through  a  cycle 
of  development.     Hence  in  such  cases  also  there  is  an  alternation 
of  hosts  and  a  complicated  life-cycle,  of  which  the  life-history  of 
the  malarial  parasite  is  a  good  example  (vide  infra,  p.  359).     It 


24  THE  PROTOZOA 

need  only  be  noted  here  that  in  such  cases  resistant  spores  or  cysts 
become  unnecessary  and  superfluous  for  the  propagation  of  the 
parasite,  and  tend  to  disappear  from  its  developmental  cycle. 

6.  In  some  cases  the  parasite  may  penetrate  the  ovary  of  its  host, 
pass  into  the  ova,  and  thus  infect  the  embryo  and  the  next  genera- 
tion. Transmission  of  this  kind  is  known  in  a  certain  number  of 
cases  ;  it  is  never  the  sole  method  of  transmission,  but  is  always 
supplementary  to  other  methods.  For  instance,  in  "  pebrine  "  of 
silkworms,  caused  by  Nosema  bombycis,  the  spores  of  the  parasite 
are  liberated  in  the  ordinary  way  from  the  caterpillar  either  with  the 
faeces  or  by  its  death,  and  are  then  eaten  accidentally  on  the  leaves 
by  other  silkworms  ;  but  a  certain  number  of  the  parasites  pene- 
trate into  the  ovary  and  form  spores,  which  pass  through  the  pupal 
and  imaginal  stages  of  the  host  into  the  next  generation  of  silk- 
worms, which  are  born  infected.  In  this  way  the  parasite  is  able 
to  tide  over  the  winter  season,  when  the  ordinary  method  of  infec- 
tion would  be  impossible.  The  blood-parasites  of  the  genus 
Piroplasma  (p.  384,  infra)  afford  another  example  of  gerniinative 
infection  in  the  ticks  which  transmit  them. 

To  turn  now  to  the  methods  by  which  parasitic  Protozoa  pene- 
trate into  new  hosts  ;  there  are  four  known  methods,  which,  after 
what  has  been  said,  can  be  summarized  very  briefly.  The  com- 
monest is  the  method  of  casual  or  coiitaminative  infection,  where 
the  host  infects  itself  accidentally  by  taking  up  the  propagative 
phases  of  the  parasite  from  its  surroundings — most  usually  by  way 
of  the  mouth,  with  the  food,  but  it  may  be  by  way  of  the  respira- 
tory organs.  Other  modes  of  infection  are  the  contagious,  as  in 
dourine,  already  mentioned  ;  the  inoculative,  as  in  malaria  and 
other  diseases  caused  by  blood-parasites  ;  and  the  so-called  "  heredi- 
tary "  or  "  gerniinative  "  method,  as  in  Nosema  bombycis  and  other 
cases. 

From  the  foregoing  summary  of  the  methods  by  which  parasitic 
Protozoa  are  propagated  from  one  host  to  another,  it  is  clear  that 
there  are  very  few  cases  in  which  it  is  of  direct  advantage  to  the 
parasite  to  cause  the  death  of  its  host.  Even  where  it  is  necessary, 
for  the  propagation  of  the  parasite,  that  the  host  should  be  destroyed 
by  some  other  animal,  as  in  the  case  of  the  Monocystis  of  the  earth- 
worm, the  interests  of  the  parasite  are  not  furthered,  and  may, 
indeed,  be  damaged,  if  it  cause  disease  or  death  to  the  host.  In 
the  case  of  blood-parasites,  transmitted  by  the  inoculative  method, 
it  may  be  necessary  for  the  propagation  of  the  parasite  that  the 
required  phases  should  be  sufficiently  abundant  in  the  blood  of  the 
vertebrate  host  to  insure  the  invertebrate  host  becoming  infected 
when  it  sucks  the  blood  ;  then  large  numbers  of  the  parasite  may  be 
detrimental  to  the  well-being  of  the  host  to  a  greater  or  less  extent, 


THE  MODES  OF  LIFE  OF  THE  PROTOZOA  25 

and  one  interest  of  the  parasite  may,  so  to  speak,  clash  with  another. 
But  in  all  cases  alike  it  is  perfectly  clear  that  the  death  of  the  host 
before  the  parasite  has  matured  its  propagative  phases  leads  simply 
to  the  extirpation  of  the  parasite,  and  is  a  suicidal  policy  on  its 
part,  a  glaring  disharmony  in  Nature.  This  conclusion  is  borne  out 
by  a  general  survey  of  the  facts  of  parasitism  in  the  Protozoa,  since 
the  vast  majority  of  these  parasites  are  quite  harmless  to  their 
hosts,  and  lethal  parasites,  greatly  in  the  minority  when  compared 
with  harmless  forms,  must  be  considered  as  exceptional  and  aberrant 
types  of  parasites,  from  a  general  point  of  view. 

The  parasitic  Protozoa  of  lethal  properties  present  a  problem 
which  can  be  best  attacked  by  considering  and  comparing  two 
cases  of  closely  allied  parasites,  the  one  harmless,  the  other  lethal, 
to  their  hosts.  Very  instructive  cases  of  this  kind  are  furnished 
by  trypanosomes  (vide  infra,  p.  285).  The  common  parasite  of  the 
rat,  Trypanosoma  lewisi,  is  perfectly  harmless  as  a  rule  to  its  host, 
and  the  infection  runs  a  very  definite  course.  When  the  parasite  is 
introduced  into  the  blood  of  a  healthy  and  susceptible  rat,  it  enters 
at  once  upon  a  period  of  rapid  multiplication,  which  lasts  about 
twelve  days.  At  the  end  of  that  time  the  parasite  swarms  in  the 
rat's  blood,  without  perceptibly  affecting  its  general  health.  After 
about  twelve  or  thirteen  days  the  multiplication  of  the  parasite 
ceases  entirely  ;  the  swarming  period  lasts  generally  about  a  month, 
and  after  that  the  parasites  begin  steadily  to  diminish  and  dis- 
appear, until  after  a  variable  length  of  time,  usually  three  to  five 
months,  the  blood  is  quite  free  from  them,  and  the  rat,  cured  from 
the  attack,  is  now  quite  immune  to  the  parasite,  and  cannot  be 
infected  by  it  a  second  time. 

The  behaviour  and  effects  of  a  pathogenic  trypanosome,  such  as 
T.  brucii,  when  introduced  into  a  rat's  blood,  contrast  sharply 
with  that  just  described.  Not  only  do  the  trypanosomes  begin 
to  multiply  at  once,  but  they  never  cease  to  do  so  while  the  host 
remains  alive.  By  the  fifth  or  sixth  day  there  are  practically  more 
trypanosomes  in  the  blood  than  blood-corpuscles,  and  the  death 
of  the  host  soon  follows  when  this  stage  has  been  reached. 

Trypanosoma  lewisi  is  a  type  of  a  well-marked  group  of  try- 
panosomes, which  may  be  conveniently  denoted  the  lewisi-group 
(Fig.  11).  Such  are  T.  cuniculi  of  the  rabbit;  T.  duttoni  of  the 
mouse  ;  T.  rdbinowitsclii  of  the  hamster  ;  T.  blanchardi  of  the  dor- 
mouse ;  T.  microti  of  Microtus  artalis  ;  and  T.  elyomis  of  the  lerot 
(Eliomys  quercinus).  All  these  species  of  trypanosomes  are  ex- 
ceedingly similar  in  their  appearance  and  structure  ;  each  species, 
however,  appears  to  be  perfectly  specific  to  its  particular  species 
of  host.  The  trypanosome  of  the  rat,  for  instance,  will  not  flourish 
in  any  other  host,  not  even  in  a  mouse,  under  normal  circumstances. 


26 


THE  PROTOZOA 


Roudsky  suggests  that  all  this  group  of  trypanosomes  constitutes 
in  reality  a  single  species  ;  in  any  case,  it  is  reasonable  to  regard 
them  as  forms  recently  evolved  from  a  common  ancestor,  incipient 
species  which  have  not  advanced  beyond  the  stage  of  physiological 
differentiation. 

In  like  manner,  T.  brucii  is  a  type  of  a  group  of  trypanosomes 
which  may  be  termed  the  brucii-group  (Fig.  12)  ;  other  members 
of  it  are  T.  gambiense,  the  parasite  of  human  sleeping  sickness  ; 
T.  evansi,  causing  surra  in  horses  ;  T.  equiperdum,  of  dourine  in 
horses  ;  and  several  other  species.  These  forms  also  are  exceedingly 
similar  in  appearance  and  structure,  though  easily  distinguishable 
from  members  of  the  lewisi -group.  They  are  all  of  them  very 
lethal,  as  a  rule,  to  their  hosts  ;  and  they  differ  further  from  the  try- 


•c' 


FIG.  11. — Trypanosomes  of  the  leivisi-grouj).  A,  T.  lewisi  (rat) ;  B,  T.  duttoni 
(mouse)  ;  C,  T.  cuniculi  (rabbit)  ;  D,  T.  microti  (Microtus  arvalis)  ;  E,  T. 
elyomis  (Eliomys  quercinus)  ;  A  and  C,  from  preparations  ;  B,  after  Thiroux ; 
D,  after  Laveran  and  Pettit ;  E,  after  Franca.  All  figures  magnified  2,000 
diameters. 

panosomes  of  the  lewisi-group  in  the  fact  that  a  given  member  of 
the  brucii-grovLp  is  not  specific  to  a  particular  host,  but  can  flourish 
and  exert  its  lethal  powers  in  a  great  variety  of  vertebrate  hosts — 
a  fact  which,  coupled  with  their  very  similar  morphology,  renders 
the  exact  determination  of  the  species  of  this  group  very  difficult, 
and  often  a  matter  of  controversy.  AU  these  facts  point  to  the 
frrwcM-group  being  also  descended  from  a  common  ancestral  form  ; 
they  may  be  regarded  as  incipient  species  in  which  the  process  of 
evolution  has  not  yet  the  degree  of  physiological  specialization 
reached  in  the  lewisi-group.  This  view  receives  support  from  the 
fact  that  a  new  race  or  species  of  the  brucii-group  has  been  made 
known  this  year  (1911) — namely,  T.  rhodesiense,  a  trypanosome 
pathogenic  to  human  beings  which  appears  to  have  come  into 
existence  as  a  species  very  recently. 


THE  MODES  OF  LIFE  OF  THE  PROTOZOA 


27 


A  further  point  of  great  interest  in  this  connection  is  that 
T.  brucii  in  Africa  appears,  from  the  observations  of  Bruce,  to 
occur  as  a  natural  parasite  of  wild  game,  and  to  be  as  harmless  to 
these  its  natural  hosts  as  T.  lewisi  is  to  rats.  The  physiological 
difference  between  these  two  species  is  that  T.  lewisi  is  perfectly 
specific  to  its  natural  host,  whereas  T.  brucii  is  capable  of  flourish- 
ing in  others,  with  most  deadly  effects.  Hence  the  pathogenic 
properties  of  T.  brucii  would  appear  to  be  exerted  on  hosts  to  which 


FIG.  12. — Trypanosomes  of  the  brucii-gmup.  A,  B,  C,  T.  brucii  of  "nagana,"  three 
forms — slender,  intermediate,  and  stumpy  ;  D,  E,  F,  T.  gambiense  of  sleeping 
sickness,  the  three  corresponding  forms  ;  G,  H,  T.  evansi  of  "  surra,"  two  forms 
I,  T.  vivax  ;  J,  T.  nanum.  A  to  C,  I,  and  J,  after  Bruce,  Hamerton,  Bateman, 
and  Mackie  (411);  G  and  H,  after  Bruce  (404);  D  to  F,  from  preparations. 
All  figures  magnified  2,000  diameters. 

it  is  a  new  parasite,  and  not  on  those  to  which,  like  T.  lewisi,  it 
has  established  harmonic  relations  in  the  course  of  evolution. 
The  pathogenic  properties  of  T.  brucii,  and  doubtless  of  other 
similar  forms,  may  from  this  point  of  view  be  characterized* as  a 
disharmony  associated  with  the  first  steps  in  the  origin  of  species. 

The  problem  of  the  origin  of  diseases  caused  by  parasites  is 
essentially  a  problem  of  the  same  nature  as  the  origin  of  species. 
The  first  step  in  the  formation  of  new  species  is  a  process  of  varia- 
tion in  an  established  species.  Similarly,  in  the  process  of  forma- 


28  THE  PROTOZOA 

tion  of  new  species  of  parasites,  the  first  step  would  be  the  acquisi- 
tion by  the  parasite  of  the  power  of  living  in  hosts  other  than  that 
to  which  it  is  specific.  How  such  a  variation  might  arise  in  Nature 
is  impossible  to  conjecture  in  the  present  state  of  knowledge  ;  but 
some  experiments  that  have  been  carried  out  upon  T.  lewisi  show 
that  conditions  can  modify  the  apparent  fixity  of  its  characters. 
Roudsky  (22,  23)  found  that  after  prolonged  culture  on  artificial 
media,  and  subsequent  rapid  passages  through  rats,  it  was  possible 
to  infect  mice  with  T.  lewisi.  Wendelstadt  and  Fellmer  (27)  have 
shown  that  T.  lewisi,  if  inoculated  into  cold-blooded  vertebrates,  can 
persist  there  for  a  time,  and  then  becomes  virulent  to  rats.*  In 
both  cases  it  is  evident  that  the  normal  specific  properties  of  the 
parasite  have  been  induced  to  vary  by  changes  in  the  conditions  of 
life,  with  the  result  that  they  become  similar  to  those  characteristic 
of  the  pathogenic  trypanosom.es. 

If  it  be  true  that  a  parasite  attacking  a  new  host  is  at  first  patho- 
genic to  it,  but  tends  in  the  course  of  evolution  to  establish  more 
harmonic  relations  with  the  host,  the  question  arises  as  to  how 
such  relations  are  brought  about.  There  are  two  organisms  con- 
cerned, and  the  problem  affects  them  both.  In  the  case  of  the 
host  the  adaptation  to  the  effects  of  the  parasite  may  be  both 
individual  and  racial,  in  the  latter  case  to  be  perhaps  largely  ex- 
plained by  the  elimination  of  individuals  less  fitted  by  their  con- 
stitution to  resist  the  parasite.  In  the  case  of  the  parasite,  also,  the 
problem  may  be  considered  from  both  points  of  view ;  deadly  strains 
of  the  parasite  contribute  to  their  own  destruction.  Interesting 
observations  bearing  on  the  individual  adaptability  of  strains  of 
Scliizotrypanum  cruzi  have  been  made  by  Chagas  (425).  This  para- 
site, when  inoculated  into  guinea-pigs,  was  found  to  kill  them  in 
about  six  days  ;  this  is  its  initial  virulence  to  this  host.  After 
repeated  passages  through  guinea-pigs,  it  was  found  that  the  viru- 
lence diminished,  until  guinea-pigs  inoculated  with  strains  of  attenu- 
ated virulence  lived  as  much  as  six  weeks  before  they  succumbed 
to  the  effects  of  the  parasite.  If,  when  this  result  had  been  attained, 
the  parasite  was  given  a  single  passage  through  a  marmoset,  it  was 
then  found  to  have  regained  its  primary  virulence  to  guinea-pigs. 

The  study  of  the  exact  mechanism  of  the  physiological  relations 
between  parasites  and  their  hosts  is  the  task  of  the  investigations 
upon  immunity  and  kindred  problems  which  now  engross  so  largo 
a  share  of  the  attention  of  scientific  workers,  but  which  cannot  be 
considered  here  in  detail. 

Bibliography. — For  references,  see  p.  476. 
*  See  also  Sleeping  Sickness  Bulletin,  No.  22,  p.  412,  and  No.  24,  p.  81. 


CHAPTER  III 

THE  ORGANIZATION  OF  THE  PROTOZOA— EXTERNAL  FORM 
AND  SKELETAL  STRUCTURES 

A  UNICELLULAR  organism  of  any  kind  is  a  more  or  less  minute  mass 
or  corpuscle  of  the  living  substance,  protoplasm,  containing 
usiially  other  substances,  fluid,  solid,  or  even  in  some  rare  instances 
gaseous,  in  greater  or  less  amount — substances  which  are  either 
the  product  of  its  own  vital  activity  or  have  been  taken  up  into 
the  body  from  without.  As  will  be  shown  in  more  detail  in  the 
next  chapter,  protoplasm  is  a  substance  or  complex  of  substances 
which,  considered  in  the  aggregate,  exhibits  the  physical  properties 
of  a  viscid  fluid.  Some  samples  of  protoplasm  may  be  less,  others 
more  fluid,  but  the  essentially  fluid  nature  of  the  whole  mass  of 
protoplasm  composing  the  cell-body  is  very  obvious,  as  a  rule,  in 
the  case  of  Protozoa. 

A  drop  of  a  fluid  substance,  when  suspended  in  another  fluid  with 
which  it  is  not  miscible,  tends  immediately,  under  the  action  of  the 
physical  laws  of  surface-tension,  to  assume  the  geometrical  form  in 
which  the  surface  is  least  in  proportion  to  the  mass  ;  that  is  to  say, 
it  tends  to  become  a  perfect  sphere,  except  in  so  far  as  this  tendency 
may  be  altered  or  modified  by  the  contact  or  pressure  of  other 
bodies,  or  by  the  operation  of  other  forces  or  conditions  which 
oppose  the  action  of  surface-tension. 

The  sphere  may  therefore  be  regarded  as  the  primary  form  of 
the  living  cell — the  form,  that  is  to  say,  Avhich  the  organism  tends 
to  assume  under  the  influence  of  physical  forces  when  not  checked 
or  inhibited  in  their  operation  by  other  factors.  A  great  many 
Protozoa  exhibit  the  spherical  form  in  a  striking  manner,  especially 
those  species  which  float  more  or  less  freely  in  the  water,  such  as  the 
Heliozoa  (Fig.  3)  and  Radiolaria  (Fig.  13).  But  the  majority  of 
Protozoa  depart  more  or  less  widely  from  the  primitive  spherical 
form,  for  reasons  which  must  be  considered  in  detail. 

In  the  first  place,  departure  from  a  spherical  form  may  be  merely 
temporary,  the  result  of  vital  activity  producing  altered  conditions 
of  surface-tension.  In  order  that  a  drop  of  fluid  may  assume  a 
spherical  form  as  the  result  of  surface-tension,  its  surface  must  be 

29 


30 


THE  PROTOZOA 


homogeneous — that  is  to  say,  of  similar  nature  in  all  parts  ;  if, 
however,  its  surface  be  heterogeneous,  and  differs  in  different  parts, 
local  inequalities  of  surface-tension  may  be  the  result,  and  then  a 
perfectly  spherical  form  cannot  be  maintained  so  long  as  the  surface 
remains  heterogeneous.  Thus  an  organism,  such  as  an  amoeba,  in 
which  the  protoplasm  is  quite  naked  and  exposed  at  the  surface  of 
the  body,  tends  always  to  have  a  spherical  form  in  the  resting  state  ; 
but  when  it  enters  upon  a  phase  of  vital  activity,  it  may  assume 
various  forms  which  can  be  explained  by  supposing  that  the  surface- 
tension  is  altered  at  one  or  more  regions  of  the  surface  as  the  result 


% 


FIG.  13. — Tlialassicolla  (Thalassopliysa)  pelagica,  Haeckel,  an  example  of  a  species 
of  floating  habit  combined  with  radiate  symmetry  and  spherical  body-form. 
OK,  Central  capsule  ;  EP,  extracapsular  protoplasm  ;  al,  vacuoles  in  the 
calymma  (see  p.  251)  ;  ps.,  pseudopodia.  The  small  dots  in  the  calymma 
represent  "  yellow  cells  "  (p.  252).  After  Lankester,  magnified  25  diameters. 

of  local  changes  in  chemical  constitution,  brought  about  by  the 
vital  activity  of  the  protoplasm  (Rhumbler,  34,  and  p.  200  infra). 
In  consequence,  the  spherical  form  characteristic  of  the  resting 
state  undergoes  modification  in  various  ways  when  the  organism 
becomes  active.  In  floating  forms  the  sphere  throws  out  radiating 
processes,  so-called  "  pseudopodia,"  in  all  directions  (Figs.  3,  13). 
In  creeping  species  the  body  assumes  the  indefinite  and  constantly 
changing  form,  with  pseudopodia  extruded  in  every  direction,  Avhich 
is  characteristic  of  the  amceba  (Fig.  2),  and  hence  commonly  termed 
"  amoeboid.'  In  all  such  cases,  when  the  animal  passes  into  a 


THE  ORGANIZATION  OF  THE  PROTOZOA  31 

resting,  inactive  condition,  or  when  the  vital  activity  is  temporarily 
inhibited  by  some  shock  or  stimulus,  such  as  an  electric  current 
suddenly  turned  on,  physical  forces  reassert  then:  sway,  and  under 
the  influence  of  surface-tension  the  pseudopodia  are  retracted,  and 
the  body  rounds  itself  off  and  returns  to  the  spherical  form. 

Apart,  however,  from  temporarj'  and  variable  departures  from 
the  primary  and  fundamental  spherical  form,  many  unicellular 
organisms  exhibit  a  constant  body-form  which  is  often  widely 
different  from  the  sphere,  and  which  is  characteristic  of  particular 
species,  or  for  the  corresponding  stages  in  the  life-history  of  a 
given  species,  and  varies  only  within  the  narrowest  limits,  if  at  all. 

The  problem  of  form-production  in  Protozoa,  like  all  other  bio- 
logical problems,  may  be  considered  from  two  points  of  view.  In 
the  first  place,  there  is  the  question  why  a  particular  species  has 
such  and  such  a  form.  The  answer  to  this  question  must  be  sought 
in  the  habits  and  mode  of  life  of  the  species  and  its  relation  to  the 
environment.  In  general  it  may  be  said  that  each  species  pos- 
sesses, or  tends  to  possess,  the  body-form  best  adapted  to  its  par- 
ticular mode  of  life,  though  it  is  not  always  easy  to  trace  the 
correlation  of  form  and  habit  in  special  cases.  A  broad  distinction 
may  be  drawn,  however,  between  species  which  move  freely  in 
their  environment  and  those  which  are  fixed  and  sessile  in  habit. 
In  freely-moving  species,  again,  a  further  distinction  can  be  drawn 
betwreen  those  which  float  or  s\vim  in  the  medium,  and  those  which 
creep  on  a  firm  substratum.  Free-swimming  species  tend  to  the 
form  of  an  ovoid,  more  or  less  elongated,  with  the  longitudinal  axis 
lying  in  the  direction  of  forward  movement  (Fig.  14).  Creeping 
forms  tend  to  be  more  or  less  flattened,  and  spread,  as  it  were,  upon 
the  substratum,  leading  in  extreme  cases  to  the  differentiation  of  a 
ventral  surface,  in  contact  with  the  substratum,  from  a  dorsal 
surface  on  the  opposite  side.  Sedentary  forms  tend  to  be  more  or 
less  vasiform,  often  with  the  point  of  attachment  drawn  out  into  a 
stalk  or  peduncle  of  greater  or  less  length.  A  frequent  peculiarity 
of  the  body-form  in  Protozoa,  whether  fixed  or  free,  is  the  tendency 
to  a  more  or  less  pronounced  spiral  twist.  Bilateral  symmetry,  on 
the  other  hand,  is  a  comparatively  rare  phenomenon  in  these 
organisms  ;  examples  are  found  among  the  Flagellata — e.g.,  Lamblia 
intestinalis  (Fig.  117). 

The  second  question  which  arises  is,  Given  a  particular  specific 
form,  how  is  the  form  developed  and  maintained,  on  physiological 
or  mechanical  principles  ?  To  this  question  the  answer  must  be 
sought  in  the  structure  of  the  individual,  and  more  especially  in 
the  formation  and  possession  of  special  structural  elements,  more 
or  less  rigid  in  nature,  which  determine  the  form  and  support  the 
soft  body.  Such  structures  may  be  external  to  the  body,  in  the- 


32 


THE  PROTOZOA 


form  of  cuticular  productions  or  envelopes  of  various  kinds,  or 
internal,  in  the  form  of  an  axis  or  framework.  Both  these  types 
of  form-determining  or  skeletal  elements,  as  they  may  be  termed 
broadly,  may  be  present  together  in  a  given  organism. 

1.  Cuticular  and  Exoskeletal  Structures. — In  the  Sarcodina  gener- 
alty,  and  in  a  few  examples  of  the  Mastigophora  and  Sporozoa,  the 
body-protoplasm  is  quite  naked  at  the  surface,  as  already  stated, 
and  not  covered  by  any  cuticle  or  firm  covering.  With  these 
exceptions,  the  bodies  of  Protozoa  are  clothed  by  a  firm  cortical 


/ 


c.v. 


14. — Prorodon  teres.  N,  Macronucleus  ;  n,  micronucleus  ;  o,  mouth  ;  ces.t 
oesophagus  surrounded  by  rod-apparatus  (p.  433)  ;  f.v.,  food  vacuoles  ;  c.v., 
contractile  vacuole  surrounded  by  feeding-vacuoles ;  al.,  alveolar  layer ; 
st,  meridional  rows  of  cilia  ;  a.,  anal  pore.  After  Schewiakoff,  magnified  660 
diameters. 

layer,  which  is  produced  either  as  a  differentiation  of,  or  secretion 
by,  the  most  superficial  layer  of  the  protoplasmic  body,  and  which 
receives  various  names  in  different  cases. 

The  very  first  beginnings  of  a  cortical  layer  are  seen  in  some 
species  of  arncebse,  such  as  Amoeba  verrucosa — species  in  which  the 
protoplasm,  extremely  viscid  and  slow-flowing,  forms  a  delicate 
investing  pellicle  at  the  surface.  In  these  cases  the  pellicle  is  so 
thin  that  it  does  not  hinder  the  amoeboid  movement  appreciably 
(Fig.  23).  A  further  advance  is  seen  in  some  of  the  Flagellata, 


THE  ORGANIZATION  OF  THE  PROTOZOA 


33 


where  a  thin  cuticle  is  present  which  permits  changes  in  •  shape, 
caused  by  the  contractility  of  the  enclosed  protoplasmic  body. 
Such  forms  are  not  amoeboid,  but  exhibit  rhythmical  changes  of 
form  produced  by  contractions  of  the  superficial  body-layer  in  a 
manner  somewhat  recalling  peristaltic  movement,  and  are  com- 
monly said  to  be  metabolic  (Fig.  15) ;  and 
since  such  movements  are  characteristic 
of  some  species  of  the  genus  Euglena, 
they  are  sometimes  called  euglenoid. 

In  most  cases,  however,  in  which  a 
cuticle  or  firm  cortex  is  present,  a  definite 
and  characteristic  body-form  is  main- 
tained, subject  only  to  such  changes  as 
may  result  from  curvatures  of  the  body, 
or  temporary  shortening  of  its  axis  in  a 
particular  direction,  brought  about  by 
the  contractility  of  the  living  body.  An 
envelope  of  this  kind,  which  may  vary  in 
consistence  from  a  thin,  flexible  cuticle 
to  a  rigid  inflexible  cuirass,  or  "  lorica," 
inhibits  completely  the  natural  tendency 
of  the  fluid  protoplasmic  body  to  round 
itself  off — a  tendency,  however,  which 
frequently  reasserts  itself  during  resting 
phases  of  the  organism,  when  the  cortex 
may  be  softened  or  absorbed.  Hence  it 
is  very  common  to  find  that  the  resting 
phases  of  Protozoa  revert  to  the  primi- 
tive spherical  form,  whatever  the  shape 
characteristic  of  the  organism  in  an 
active  state. 

A  close-fitting  cortex  or  cuticle  which 
is  essentially  a  part  of  the  body  itself 
must  be  distinguished  cleaiiy  from  struc- 
tures built  up  by  the  organism  externally 
to  the  body  to  afford  shelter  or  support. 
Such  a  structure  is  termed  variously  a 
"shell,"  "test,"  or  "house."  The 
formation  of  protective  shells,  into  which 
the  body  can  be  completely  retracted, 

and  from  which  it  can  emerge  to  a  greater  or  less  extent,  is  of 
extremely  common  occurrence  amongst  the  naked-bodied  Sarcodina. 
The  forms  of  these  shells,  their  structure  and  mode  of  formation, 
exhibit  an  almost  infinite  variety,  and  can  only  be  described  here  in 
a  quite  general  manner. 

3 


FIG.  15. — Astasia  tenax,  two 
individuals  showing  the 
changes  of  form  due  to 
metabolic  movement,  oss., 
(Esophagus  ;  c.r.,  reservoir 
of  the  contractile,  vacuole  ; 
.A".,  nucleus.  After  Stein. 


34 


THE  PROTOZOA 


As  regards  material,  the  shells  may  be  composed  of  elements 
secreted  by  the  organism  ("  autophya."  Haeckel),  as  in  Hyalosphenia 
(Fig.  16,  B),  or  of  foreign  particles  taken  up  by  the  animal  from  its 
surroundings  ("  xeriophya  "),  as  in  Difflugia  (Fig.  16,  A).  Skeletal 
elements  secreted  by  the  organism  may  be  of  organic  or  inorganic 
nature.  In  the  former  case  they  are  probably  chitinous  in  most 
cases,  or  composed  of  a  substance  allied  to  chitin  ;  in  the  latter  they 
are  either  calcareous  or  siliceous.  A  good  example  of  the  formation 
of  a  shell  is  seen  in  Euglypha  (Fig.  59),  where  the  chitinous  plates 
composing  it  are  formed  first  of  all  in  the  interior  of  the  proto- 
plasmic body,  and  pass  to  the  surface  to  build  up  the  shell.  When 
the  shell  is  built  up  of  foreign  particles,  the  material  employed  may 
vary  greatly,  and  consists  generally  of  particles  of  sand,  grit,  etc., 


FIG.  16. — Examples  of  shells  or  houses  formed  by  Protozoa.  A,  Diffluqia  spiralis, 
which  forms  a  house  built  up  of  foreign  bodies  ;  B,  Hyalosphenia  cuneata,  in 
which  the  house  is  built  up  of  plates  secreted  by  the  animal  itself  (compare 
also  Euglypha,  Fig.  59).  Both  these  species  belong  to  the  order  Arncebsea  ; 
the  pseudopodia  (ps.)  are  seen  streaming  out  of  the  mouth  of  the  shell.  After 
Leidy  ;  A  magnified  250,  B  500  diameters. 

taken  up  at  hazard  from  the  environment.  Such  shells  are  de- 
scribed technically  as  "  arenaceous."  In  the  case  of  Difflugia, 
Verworn  (36)  was  able  to  cause  it  to  build  up  its  test  of  various 
materials,  such  as  particles  of  coloured  glass  or  other  substances, 
when  these  were  supplied  to  it  exclusively.  Many  species  of 
Foraminifera,  however,  form  their  tests  exclusively  of  particular 
materials  under  natural  conditions.  Thus,  in  the  genus  Haliphy- 
sema  (Fig.  17)  the  test  is  formed  of  sponge-spicules  ;  in  Technitella 
thompsoni  the  calcareous  plates  of  echinoderms  are  selected  ;  and 
other  instances  could  be  cited  in  which  the  organism  selects  habitually 
for  its  shell  certain  materials  from  a  varied  environment  in  which 
the  particular  materials  required  may  be  far  from  common  in 
occurrence  relatively  to  other  particles  apparently  equally  suitable 
(see  especially  Heron- Allen  and  Earlancl).  Verworn  (36)  found  that 


THE  ORGANIZATION  OF  THE  PROTOZOA 


35 


in  the  case  of  Difflugia  the  foreign  particles  used  are  taken  up  by  the 
pseudopodia  during  the  process  of  being  retracted  ;  the  surface  of 
the  pseudopodiuni  then  becomes  wrinkled,  and  particles  of  debris 
are  caught  in  these  wrinkles,  and  so  drawn  into  the  interior  of  the 
protoplasmic  body,  in  which  they  are  stored  up  in  the  fundus  of 
the  shell,  like  the  plates  in  Euglypha,  and  are  utilized  in  the  growth 
of  the  shell,  or  in  repairing  damages  to  it,  or  in  building  a  new  shell 
when  the  animal  reproduces  itself  by  division. 


FIG.  17. — Haliphysema  tumanowiczii,  a  forarninifer  which  builds  up  its  house  out 
of  sponge-spicules.  A,  part  of  the  protoplasm  stained  to  show  the  nuclei  (n.)  ; 
B,  a  living  specimen  with  expanded  pseudopodia  (p.).  After  Lankester  (11). 

The  simplest  architectural  type  of  shell  or  test  is  a  simple  spherical  or 
oval  capsule,  usually  with  a  large  aperture  at  one  pole  through  which  the 
protoplasm  is  able  to" creep  out  in  order  to  capture  food  or  perform  the  function 
of  locomotion  (Fig.  16).  The  wall  of  the  test  may  be  imperforate,  or  may 
have  fine  pores  through  which  also  the  protoplasm  can  stream  out.  With 
continued  growth  of  the  organism,  the  original  shell  may  become  too  small 
for  its  requirements.  Then  the  organism  may  reproduce  itself  by  fission. 


36  THE  PROTOZOA 

and  the  daughter-individual  forms  a  new  shell  for  itself.  In  many  cases  the 
shell  formed  by  the  daughter  is  larger  than  that  of  the  parent ;  for  instance, 
in  Centropyxis  aculeata  and  other  species,  in  which  the  young  individuals 
multiply  by  fission,  and  each  time  they  do  so,  the  new  shell  formed  is  larger 
than  the  old  one,  until  the  full  size  of  the  adult  individual  is  reached 
(Schaudinn,  131),  after  which  point  the  new  shell  formed  after  the  process 
of  fission  is  of  the  same  size  in  both  the  parent  and  the  daughter-individual. 
In  such  cases  the  shell  is  always  a  single  chamber,  and  is  described  technically 
as  "  monothalamous." 

In  other  cases,  however,  the  organism  does  not  multiply  by  fission  when 
it  has  outgrown  its  first  shell,  but  forms  a  new  shell  of  larger  size  which  is  in 
continuity  with  its  first  shell ;  the  protoplasmic  body  now  occupies  both  the 
chambers  of  the  shell  formed  in  this  way.  With  further  growth  more  chambers 
are  formed,  giving  rise  to  a  complex  "  polythalamous  "  shell  composed  of 
many  chambers  all  occupied  by  the  protoplasmic  body  (p.  232,  infra).  For  a 
detailed  study  of  the  developmental  mechanics  of  shell-formation,  see 
Ehumbler  (35). 

2.  Internal  Skeletal  Structures. — In  many  cases  in  which  the  proto- 
plasmic body  is  naked  at  the  surface,  or  bears  only  an  extremely 
thin  cuticle,  a  definite  body-form  may  be  maintained  by  means  of 
internal  supporting  fibrils  or  other  similar  structures  (Koltzoff, 
30,  31).  In  some  cases  such  structures  may  be  of  temporary  nature. 
A  beautiful  example  of  this  is  seen  in  the  delicate  organic  axes 
formed  in  the  pseudopodia  of  Heliozoa  (Fig.  22),  in  the  form  of 
slender  needle-like  rods  secreted  by  the  protoplasm  to  stiffen  the 
pseudopodia,  and  absorbed  again  when  the  pseudopodia  are  re- 
tracted. In  other  cases,  supporting  structures  of  organic  nature 
may  be  permanent  constituents  of  the  protoplasmic  body  ;  such  are 
the  axial  rods,  or  "  axostyles,"  found  in  many  flagellates,  such  as 
Trichomonas  (Fig.  5,  ax.),  Lophomonas  (Fig.  45),  etc.,  slender  flexible 
rods  of  organic  substance  which  form  a  supporting  axis  for  the  body. 
Previous  to  division  the  axostyle  is  absorbed,  and  new  axostyles 
are  formed  in  the  daughter-individuals.  The  axostyles  are  stated 
to  arise  from  a  centrodesrnose  (p.  103,  infra)  formed  in  the  process 
of  division  of  the  blepharoplast  (Dobell,  236)  or  of  the  centriole  of 
the  nucleus  (Hartmann  and  Chagas,  62)  ;  the  centrodesrnose  per- 
sists after  division  is  complete,  and  its  two  halves  become  the 
axostyles  of  the  two  daughter-individuals.  In  TricJiomonas  eberthi, 
however,  Martin  and  Robertson  (348)  find  that  the  axostyles  arise 
after  division  quite  independently  of  the  centrodesmoses  or  other 
nuclear  structures.  In  Octomitus  (Fig.  116)  two  axostyles  are  present. 

From  supporting  structures  of  organic  nature,  such  as  the 
axostyles  or  the  organic  axes  of  the  pseudopodia  mentioned  above, 
it  is  not  difficult  to  derive  the  more  rigid  and  permanent  elements 
known  as  "  spicules,"  in  which  the  organic  basis  becomes  indurated 
by  deposits  of  inorganic  mineral  substance.  In  some  cases  spicules 
may  perhaps  consist  entirely  of  mineral  substance  deposited 
directly  within  the  living  substance  without  .any  organic  basis.  In 


THE  ORGANIZATION  OF  THE  PROTOZOA 


37 


either  case  the  spicules  grow  by  accretion — that  is  to  say,  by  deposi- 
tion of  fresh  layers  of  inorganic  substance  upon  that  already  laid 
down — and  if  such  accretion  takes  place  at  one  end  of  a  rod-shaped 
spicule,  it  may  have  the  result  that  the  opposite  extremity  of  the 
spicule  is  pushed  outwards  by  the  continued  growth,  with  the  result 
that  the  oldest  portion  of  the  spicule  projects  freely  far  beyond  the 
limits  of  the  body. 

As    regards    material,  spicules  are  usually  either  calcareous  or 
siliceous — in  the  first  case  generally  carbonate  of  lime,  in  the  second 


. x% :•. w- |l I TF'( •<!•  i :!J^/^fM:/ ^ ; 

^%iiii         :$M 

•  -z 


>|MrC  ~^^L 

?Q^'' ;^,:''iv-^^ 


FIG.  18. — Jcani/iocysizs  chcetophora,  a  Heliozoon  with  a  skeleton  of  slender  radiating 
siliceous  spicules,  each  forked  at  the  distal  end.  In  the  interior  of  the  body 
are  seen  numerous  symbiotic  algae  (dark)  and  non-contractile  vacuoles  (clear)  ; 
one  vacuole  of  larger  size  is  seen,  probably  the  contractile  vacuole.  sp.,  sp., 
Spicules  ;  ps.,  ps.,  pseudopodia.  After  Leidy,  magnified  750  diameters. 

case  amorphous  silica.  In  the  family  Acanthometridce  among  the 
Radiolaria  the  spicules  are  formed  of  a  substance  which  was  thought 
to  be  of  organic  nature,  and  was  named  "  acanthin,"  but  which 
has  been  found  to  consist  of  strontium  sulphate. 

As  regards  their  form  and  relation  to  the  body,  the  spicules  in 
the  simplest  cases  are  rod-shaped  or  needle-like  elements  disposed 
radially  or  tangentially.  A  simple  type  of  spicular  skeleton  is  seen 
in  Acantliocystis  (Fig.  18),  in  which  elongated  siliceous  rods,  fre- 


38 


THE  PROTOZOA 


^^\\l  1 1////,//, 

^\\\!i  //V//'"/ 

mm  // 


/  ////ill     '  \\   '••    V    . 

'     /     /     /      /    /  /    M     :    VV      •        \ 


% 


\       *      \  \        !''/•'/        /       V\ 

X  \  v^\\\;  I  ////-', -'/\ 

xv        '*          <v       \    X     \  ''     '      \'{''!~~?~  NC-,  '     , '        .-'    VV 

V  ^    ^   -  \\l  '  £••'!!•'/<$-. '    .'    -\\  ,- 
-      ~-    ^.    ••  \\  \\ -'<< ! '  /  /  .  +   -      -    \\' 
%     " "          «      ''' "      ' 


•f>-:\:^.,,^- 


FIG.  19. — Clathndina  elegans,  a  Heliozoon  with  a  lattice-like  skeleton,  attached  by 
a  stalk.  Two  individuals  are  seen,  the  younger  with  its  stalk  attached  to  the 
head  of  the  older  ;  in  the  younger  the  lattice-work  is  still  very  delicate.  Both 
individuals  are  sending  out  numerous  radiating  pseudopod'ia,  very  delicate 
and  slender.  After  Leidy,  magnified  750  diameters. 


THE  ORGANIZATION  OF  THE  PROTOZOA  39 

quently  branched  at  their  distal  ends,  are  arranged  like  radii  of  the 
spherical  body,  projecting  freely  for  some  distance  from  the  surface. 
In  other  cases  the  spicules  may  be  disposed  tangentially  to  the  body, 
as  in  the  family  Collidce  amongst  the  Radiolaria,  and  in  other  forms 
belonging  to  this  order.     From  a  simple  type  of  skeleton  composed 
of  separate  spicules,  more  complicated  types  of  skeletons  are  de- 
rived by  fusion  of  the  spicules  to  form  a  connected  framework. 
The  commonest  type  of  this  is  a  fusion  of   tangentially-disposed 
spicules  to  form  a  lattice- work  ;    an  example  of   this  is  seen  in 
Claihrulina  (Fig.  19),  in  which  a  lattice-like  skeleton  is  formed  at 
the  surface  of  the  body,  standing  off  from  it  like  a  shell.     Skeletons 
of  this  type  are  especially  characteristic  of  the  Radiolaria,  a  group 
in  which  the  architecture  of  the  skeleton  may  reach  a  very  high 
degree  of  complication  and  exhibits  endless  variety.     The  lattice- 
like  framework,  made  up  of  tangentially-arranged  spicules  united 
together,  may  be  further  strengthened  by  radially-disposed  beams. 
As  the  animal  grows,  it  may  outgrow  the  fra,mework  first  laid  down, 
and  another  lattice-work  is  formed  concentric  with  the  first,  and 
connected  with  it  by  radial  beams ;  later  on  a  third  and  a  fourth 
such  framework  is  formed,  as  the  organism  continues  to  grow  in 
size.     Skeletons  formed  in  this  way  may  be  "  homaxon  ':  — that  is  to 
say,  built  up  on  the  axes  of  a  sphere  ;  or  "  monaxon."  with  one 
principal  axis  ;  or  may  follow  various  plans  of  symmetry,  or  may  be 
asymmetrical  (p.  250,  infra). 

Bibliography. — For  references,  see  p.  477. 


CHAPTER  IV 

THE  ORGANIZATION  OF  THE  PROTOZOA  (Conlinued)- 
THE  PROTOPLASMIC  BODY 

THE  substance  composing  the  bodies  of  Protozoa  was  termed 
originally  sarcode  by  Dujardin  ;  but  after  it  had  been  shown  to  be 
identical  in  nature  with  the  living  substance  of  the  cells  of  animals 
and  plants,  the  same  term  was  employed  umVersally  for  both,  and 
the  word  protoplasm,  coined  by  von  Mohl  to  designate  the  living 
substance  of  plant-cells,  supplanted  the  older  term  sarcode,  which 
has  now  quite  diopped  out  of  current  use. 

It  would  be  impossible  within  the  limits  of  the  present  work  to 
discuss  in  detail  the  various  theories  that  have  been  put  forward 
with  regard  to  the  nature  and  constitution  of  protoplasm  ;  they 
can  only  be  summarized  in  brief  outline  here.  Protoplasm,  when 
seen  under  the  microscope  with  powers  of  moderate  strength, 
presents  itself  as  a  viscid,  semi-fluid  substance,  sometimes  clear  and 
hyaline  in  special  regions,  but  always  showing,  throughout  at  least 
the  greater  part  of  its  substance,  numerous  granulations,  which 
vary  greatly  in  size,  from  relatively  coarse  grains  to  those  of  the 
minutest  size  visible  with  the  power  of  the  microscope  used.  The 
most  important  of  these  granulations  are  the  so-called  "chromatin- 
grains,"  which  are  discussed  fully  in  Chapter  VI.  ;  in  this  chapter 
only  non-chromatinic  granules  are  dealt  with.  The  coarser  proto- 
plasmic grains  may  be  present  in  greater  or  less  quantitj^,  or  may 
be  entirely  absent ;  they  are  to  be  regarded  for  the  most  part  as 
so-called  metaplastic  bodies — that  is  to  say,  as  stages  in,  or  by- 
products of,  the  upward  or  downward  metabolism  of  the  organism. 
On  the  other  hand,  the  minute,  ultimate  granules,  or  "  microsomes," 
are  never  absent,  except  over  limited  areas,  in  any  sample  of  proto- 
plasm. It  is  on  the  constant  presence  of  granules  that  the  so-called 
granular  theory  of  protoplasm,  especially  connected  with  the  name 
of  Altmann,  has  been  founded.  On  this  view,  each  minute  granule 
is  regarded  as  an  elementary  organism,  or  "  bioblast,"  capable  in 
itself  of  all  vital  functions,  and  equivalent  to  a  single  free-living 
bacterium,  just  as  a  single  cell  of  a  Metazoan  body  may  be  compared 
with  a  single  Protozoan  organism.  Protoplasm,  on  this  view,  is  re- 

40 


THE  ORGANIZATION  OF  THE  PROTOZOA  41 

garded  as  a  colony  of  bioblasts,  imbedded  in  a  fluid  matrix,  com- 
parable in  a  general  way  to  a  zooglcea-colony  of  bacteria. 

A  special  and  important  class  of  metaplastic  granules  are  the  so-called 
"  deutoplasmic  "  bodies,  consisting  of  reserve  food-materials  stored  up  in 
the  protoplasmic  substance.  Examples  of  such  are  the  yolk-granules  of  ova, 
the  paraglycogen-grains  of  gregarines,  the  plastinoid  bodies  of  coccidia, 
starch-grains  in  holophytic  forms,  etc. 

Amongst  the  granulations  of  the  protoplasm,  special  mention  must  be 
made  of  the  bodies  known  generally  as  chondriosomes  and  mitochondria,  but  also 
by  a  variety  of  other  names  (cytomicrosomes,  bioblasts,  spherules  or  sphero- 
plasts,  and.  collectively,  ergastoplasm).  The  chondriosomes  are  not  to  be 
classed  with  the  temporary,  metaplastic  inclusions,  but  are  permanent  ele- 
ments of  the  cell-protoplasm.  The  chondriosomes  of  Protozoa  have  recently 
been  the  subject  of  detailed  study  by  Faure-Fremiet  (38'5).  In  the  living 
condition  they  are  small  transparent  bodies,  feebly  retractile,  and  of  a  pale 
grey  tint.  In  shape  they  are  generally  spherical,  and  vary  from  0'5  p.  to 
1'5  p.  in  diameter.  In  some  cases  the  chondriosome  appears  homogeneous  in 
structure  ;  in  others  it  presents  the  appearance  of  a  vacuole  with  fluid  con- 
tents and  a  denser  peripheral  layer.  In  contact  with  water  or  with  weak 
alkalis  they  swell  up  immediately.  When  the  nucleus  (in  Infusoria  the 
micronucleus)  divides,  the  chondriosomes  also  divide  simultaneously,  and  the 
daughter-chondriosomes  are  sorted  out  between  the  two  daughter- cells; 
they  have,  however,  no  direct  relation  with  the  nuclear  apparatus.  In  the- 
process  of  division  each  chondriosome  becomes  first  rod-like,  then  durnb-bell- 
shaped,  and  is  finally  constricted  directly  into  two  halves. 

A  purely  chemical  definition  of  the  chondriosomes,  according  to  Faure- 
Fremiet.  cannot  be  given.  They  exhibit  the  reactions  of  a  fatty  acid,  and 
can  be  considered  as  combinations  of  fatty  acids  or  of  phosphates  of  albumin. 
The  physiological  function  of  the  chondriosomes  is  not  clear,  but  Faure- 
Fremiet  considers  that  they  "  play  an  important  part  in  the  life  and  evolu- 
tion of  the  sexual  cell,"  in  Protozoa  or  Metazoa.  and  are  active  in  the  elabora- 
tion of  deutoplasmic  substances  of  fatty  nature,  into  which  they  may  be- 
transformed  directly. 

It  has  been  shown,  however,  that  the  minute  granules  of  proto- 
plasm do  not  lie  isolated  from  one  another,  suspended  freely  in  a 
matrix,  but  are  seen  in  the  microscopic  image  to  be  connected  with 
one  another  by  fine  lines  or  darker  streaks,  the  whole  forming  a 
delicate  network,  at  the  nodes  of  which  the  granules  are  lodged. 
In  some  cases  the  granule  itself  is  perhaps  only  an  optical  effect 
produced  by  a  node  of  the  network.  On  these  appearances  has 
been  founded  the  so-called  reticular  theory  of  protoplasm,  connected 
especially  with  the  names  of  Heitzmann,  Schafer,  and  others.  On 
this  view  protoplasm  has  been  regarded  as  composed  of  an  exceed- 
ingly fine  reticulum,  a  network  or  feltwork  ramifying  in  all  planes, 
bearing  the  granulations  at  its  nodal  points,  and  bathed  throughout  by 
a  fluid,  more  or  less  watery  sap,  or  enchylema.  The  fibrillar  theory  of 
Flemming  may  be  regarded  as  a  modification  of  the  reticular  theory. 

Against  the  reticular  theory  of  protoplasm,  it  may  be  urged  that 
it  leads  to  physical  difficulties,  in  view  of  the  generally  fluid  nature- 
of  protoplasm.  For  the  reticulum  must  itself  be  either  of  a  fluid 
or  a  solid  nature  ;  if  fluid,  it  presents  the  condition  of  one  fluid 


42  THE  PROTOZOA 

suspended  in  the  form  of  a  network  in  another  fluid  with  which  it 
does  not  mix — a  condition  which  could  not  exist  for  more  than  an 
instant  of  time,  since  the  fluid  reticulum  must  break  up  immediately 
into  minute  droplets.  If,  on  the  other  hand,  the  reticulum  is  of 
rigid  consistence,  the  protoplasm  as  a  whole  could  not  be  fluid, 
any  more  than  a  sponge  soaked  in  water  could  behave  as  a  fluid 
mass  in  the  aggregate.  The  difficulty  can,  however,  be  overcome 
by  supposing  the  apparent  reticulum  to  be  the  optical  expression, 
not  of  a  fine  network  of  fibrils,  but  of  delicate  lamellas  limiting 
minute  closed  chambers,  or  alveoli.  Then  the  fine  line  seen  with  the 
microscope  joining  any  two  adjacent  nodal  points  Avould  be  the 
optical  section  of  the  wall  or  lamella  separating  two  contiguous 
alveoli,  and  protoplasm  as  a  whole  would  possess  a  honeycombed 
structure  comparable  to  that  of  a  fine  foam  or  lather — the  fluid 
lamellae  of  the  foam  represented  by  the  apparent  reticulum  of  the 
protoplasm,  and  the  air-contents  of  the  individual  bubbles  repre- 
sented by  the  enchylema.  Or,  to  express  the  state  of  things  in  a 
different  manner,  protoplasm  could  be  regarded  as  an  emulsion  of 
very  fine  structure,  composed  of  two  fluids  not  miscible  with  one 
another — namely,  the  more  fluid  enchylema,  which  is  suspended 
in  the  form  of  minute  droplets  in  the  more  viscid  substance  forming 
the  alveolar  framework.  This  is  the  so-called  alveolar  theory, 
especially  connected  with  the  name  of  Biitschli ;  by  this  conception 
of  protoplasmic  structure,  not  only  are  the  necessary  physical  con- 
ditions satisfied,  but  an  explanation  is  given  for  many  peculiarities 
of  protoplasmic  bodies,  such  as  the  radiate  arrangement  of  the 
meshes  of  the  reticulum  commonly  observed  either  at  the  surface  of 
the  body  or  around  solid  or  fluid  bodies  contained  in  the  proto- 
plasm, and  so  forth. 

The  various  theories  that  have  been  mentioned  all  assume  tacitly 
that  protoplasm  is  monomorphic — that  is  to  say,  that  it  possesses 
one  fundamental  type  of  minute  structure.  Fischer,  on  the  other 
hand,  seeks  to  unite  all  the  different  theories  by  supposing  that 
protoplasm  is  a  polymorphic  substance — that  is  to  say,  one  that 
may  exhibit  a  diversity  of  structure  at  different  times  and  under 
different  conditions,  as  the  result  of  changes  produced  by  its  inherent 
vital  activity.  Thus,  he  supposes  that  a  given  mass  of  protoplasm 
may  be  at  one  time  homogeneous,  and  at  another  time  granular, 
reticular,  fibrillar,  or  alveolar,  as  the  result  of  a  process  of  ' '  vital 
precipitation,"  and  that  by  reabsorption  of  the  structural  elements 
it  may  return  to  a  homogeneous  condition.  Faure-Fremiet  (38  and 
38'5)  also  regards  protoplasm  as  a  homogeneous  fluid,  which  is  pre- 
cipitated by  reagents,  and  which  normally  contains,  in  suspension, 
a  certain  number  of  granulations,  some  temporary,  others  per- 
manent in  nature  ;  compare  also  Degen  (154). 


THE  ORGANIZATION  OF  THE  PROTOZOA  43 

Those  investigators  of  the  Protozoa  who  have  expressed  an 
opinion  on  the  subject  have  been  for  the  most  part  in  favour  of  the 
alveolar  theory  of  protoplasm,  since  it  was  first  propounded  by  its 
author,  Biitschli  (see  especially  Rhumbler).  Protozoa  as  a  rule 
are  very  favourable  objects  in  which  to  study  the  foam-like  structure 
of  the  protoplasm  (compare  Schaudinn,  130,  p.  188).  But  what- 
ever view  be  held  as  to  the  ultimate  structure  of  protoplasm,  its 
essentially  fluid  nature  is  very  apparent  in  these  organisms,  and  is 
a  point  upon  which  it  is  very  important  to  be  clear.  The  fluid 
condition  of  the  living  substance  is  manifested  directly  by  the 
streaming  movements  to  be  observed  in  it,  and  indirectly  by  a 
number  of  phenomena,  such  as  the  tendency,  already  mentioned, 
of  the  body  to  round  itself  off  when  at  rest,  and  the  tendency  of  all 
vacuoles  to  assume  a  spherical  form.  A  vacuole  is  a  drop  of  fluid 
suspended  in  the  protoplasmic  body,  and  may  be  regarded  as 
formed  by  the  bursting  and  running  together  of  many  minute 
alveoli,  just  as  a  large  bubble  in  a  foam  may  arise  by  the  union  of 
many  smaller  ones  ;  or  by  the  gradual  enlargement  of  a  single 
alveolus  by  diffusion  of  fluid  into  it  from  neighbouring  alveoli,  until 
it  attains  proportions  relatively  gigantic.  Vacuoles  assume  uni- 
formly spherical  contours,  except  when  they  are  deformed  by 
mutual  pressure  from  crowding  together  or  from  other  causes.  In 
some  cases  the  protoplasm  rna}^  be  so  full  of  coarse  vacuoles  that  it 
exhibits  an  obvious  frothy  structure,  which  must  by  no  means  be 
confounded  with  the  ultimate  alveolar  structure  of  the  protoplasm, 
a  structure  \vhich  is  exceedingly  delicate,  only  to  be  observed  Avith 
high  powers  of  the  microscope  and  with  careful  attention  to  all 
details  of  microscopic  technique.  Examples  of  vacuolated  bodies 
are  seen  especially  in  Heliozoa — e.g..  Actinosphcerium  (Fig.  3). 

The  statement,  however,  that  protoplasm  generally  is  of  fluid 
nature  admits  of  its  exhibiting  many  degrees  of  fluidity,  and  some 
samples  of  protoplasm  are  far  more  viscid  than  others.  This  is 
true  both  of  different  species  of  organisms,  of  the  same  species  at 
different  phases  of  its  development,  and  of  different  parts  of  the 
same  organism.  In  some  cases  portions  of  the  protoplasm  may  be 
stiffened  to  a  degree  that  perhaps  oversteps  the  ill-defined  boundary 
between  the  liquid  and  solid  states  of  matter.  In  a  great  many 
Protozoa,  perhaps  the  majority  of  them,  the  protoplasm  of  the 
body  is  divisible,  more  or  less  distinctly,  into  two  regions — 
namely  : 

1.  An  external  or  cortical  zone,  termed  ectoplasm  or  ectosarc  ;  in 
appearance  and  consistence  typically  clear,  hyaline,  more  refringent, 
finely  granular  or  without  visible  granulations,  and  of  more  viscid 
nature  ;  in  function  protective,  kinetic,  excretory,  and  sensory. 

2.  An  internal  or  medullary  region,  the  endoplasm  or  endosarc  ; 


44  THE  PROTOZOA 

opaque,  less  refringent  and  coarsely  granular  ;  the  seat  of  trophic 
and  reproductive  functions. 

These  two  zones  of  the  protoplasmic  body  are,  in  the  more  primi- 
tive forms,  differentiations  of  the  protoplasm  more  or  less  tem- 
porary and  transient  in  nature.  For  instance,  in  an  amoeba  which 
is  in  active  movement,  fluid  endoplasm  is  constantly  flowing  along 
the  axes  of  the  pseudopodia  towards  their  tips,  where  it  comes  into 
contact  with  the  surrounding  medium,  the  water  or  other  fluid  in 
which  the  amoeba  lives.  Under  the  influence  of  the  medium  the 
endoplasm  is  converted  into  ectoplasm,  becomes  of  stiffer,  less  fluid 
consistence,  and  loses  its  coarse  granulations.  At  the  same  time, 
at  the  hinder  end  of  the  amoeba,  ectoplasm  is  continually  passing 
into  the  interior  of  the  body,  where  it  becomes  liquefied  and  granular 
in  structure,  and  is  converted  into  endoplasm  (Rhumbler,  34). 

In  Protozoa,  however,  which  do  not  exhibit  amoeboid  movement, 
the  ectoplasm  and  endoplasm  may  be  two  independent  layers,  well 
defined  and  perfectly  separate  the  one  from  the  other.  The  ecto- 
plasm is  the  seat  of  those  functions  which  are  connected  with  the 
relation  of  the  organism  to  the  outer  world,  to  the  environment 
in  which  it  lives  ;  the  endoplasm,  on  the  other  hand,  is  concerned 
specially  with  the  internal  affairs,  so  to  speak,  of  the  protoplasmic 
body.  In  the  following  two  chapters  the  various  organs  of  the 
Protozoa  will  be  considered  under  the  headings  of  the  layer  from 
which  they  are  formed,  and  according  to  the  functions  they  perform. 


Bibliography. — For  references,  see  p.  477. 


CHAPTER  V 

THE  ORGANIZATION  OF  THE  PROTOZOA  (Continued)— 
DIFFERENTIATIONS  OF  THE  ECTOPLASM  AND  ENDOPLASM 

A.  Ectoplasmic  Organs. 

THE  various  structures  and  organs  produced  from  the  ectoplasm 
are  best  classified  by  the  functions  they  subserve,  under  the  headings 
of  protective,  kinetic  and  locomotor,  excretory,  and  sensory 
mechanisms. 

1.  The  protective  function  of  the  ectoplasm  is  often  seen  in 
organisms  in  which  no  cuticle  or  envelope  is  present.  It  has  been 
observed,  for  instance,  that  the  species  of  Myxosporidia  that 
inhabit  the  gall-bladders  or  urinary  bladders  of  their  hosts  resist 
the  effects  of  the  medium  in  which  they  live  so  long  as  their  ecto- 
plasm is  intact,  but  succumb  if  it  be  injured. 

In  most  Protozoa  other  than  those  belonging  to  the  class  Sarco- 
dina,  however,  a  special  protective  envelope  or  cortex  is  present  at 
the  surface  of  the  body,  and  such  forms  are  commonly  said  to  be 
corticate.  A  cuticle  may  be  formed  in  various  ways,  distinguished 
by  the  use  of  different  terms.  It  may  represent  the  entire  ecto- 
plasm, modified  in  its  entirety  to  form  an  envelope,  as  in  the  peri- 
plast  of  the  Flagellata  ;  it  may  represent  a  transformation  or  modi- 
fication of  only  the  most  superficial  layer  of  the  ectoplasm,  as  in 
the  pellicle  of  the  Infusoria  and  of  some  amoeba? — for  instance, 
Amoeba  vermcosa,  the  epicyte  of  the  gregarines,  etc.  ;  or  it  may  arise 
as  a  secreted  layer  deposited  at  the  surface  of  the  ectoplasm,  and  not 
derived  from  a  modification  of  the  substance  of  the  ectoplasm  itself, 
in  which  case  it  is  termed  a  "  cell- membrane." 

Whatever  its  mode  of  origin,  the  cuticle  may  be  developed  to  a 
very  variable  degree,  from  the  thinnest  possible  membrane,  some- 
times very  difficult  to  discover,  to  a  thick  and  tough  investment 
which  may  be  termed  a  "  cuirass  "  or  "  lorica  "  (:'  Panzer  "),'  when 
it  is  formed  by  thickening  of  a  pellicle  ;  or  a  "  house  "  or  "  shell," 
\vhon  it  is  a  greatly  thickened  cell -membrane  standing  off  from  the 
body.  In  many  cases  the  cuticle  undergoes  local  thickenings  to 
form  spikes  or  hooks,  which  may  serve  as  organs  of  attachment, 
as  in  the  epimerite  of  gregarines  (Fig.  14-2). 

45 


40  THE  PROTOZOA 

In  addition  to  the  passive  protection  afforded  by  a  cuticle,  organs 
of  active  defence  may  be  present  in  the  ectoplasm  in  the  form  of 
bodies  kno\vn  as  trichocysts,  found  commonly  in  many  ciliate  In- 
fusoria (p.  447,  Fig.  187)  ;  they  are  little  oval  or  spindle-shaped 
bodies  which  on  suitable  stimulation  are  converted  explosively  into 
a  stiff  thread  which  is  shot  out  from  the  surface  of  the  body.  (For 
the  nematocyst-like  organs  known  as  "  polar  capsules,"  in  Myxo- 
sporidia  and  allied  organisms,  see  p.  399,  infra.} 

2.  The  ectoplasm  is  shown  to  be  the  seat  of  movement  both  by 
the  fact  that  motile  organs  arise  from  it  and  by  the  frequent 
presence  in  it  of  special  contractile  mechanisms.  The  motile 
organs  which  are  found  in  the  Protozoa  are  pseudopodia,  flagella,  cilia 
with  their  various  modifications,  and  undulating  membranes  ;  any 
of  these  structures  may  subserve  the  function  of  food  capture  in 
addition  to,  or  instead  of,  that  of  locomotion.  These  organs  will 
now  be  described  in  order,  after  which  contractile  mechanisms  will 
be  dealt  with. 

(1)  Pseudopodia  are  organs  of  temporary  nature,  extruded  from 
the  protoplasm  when  required,  and  retracted  wrhen  no  longer  needed. 
They  can  be  formed,  probably,  in  all  cases  in  which  the  body 
protoplasm  is  naked,  or  limited  only  by  a  cuticle  not  of  sufficient 
thickness  to  inhibit  the  movements  of  the  underlying  protoplasm. 
They  arise  simply  as  an  eruption  of  the  protoplasm  at  some  point 
at  the  surface  of  the  body,  forming  an  outgrowth  or  process  which 
varies  greatly  in  different  cases  as  regards  size,  length,  width,  com- 
position, and  activity. 

Pseudopodia  always  arise  in  the  first  instance  from  the  ectoplasm, 
and  may  consist  throughout  of  this  layer  alone,  in  which  case  they 
are  relatively  stiff er  and  more  rigid  ;  or  a  core  of  endoplasm  may 
flow  into  the  pseudopodium  when  it  has  grown  to  a  certain  length, 
in  which  case  the  pseudopodium  is  more  fluid  and  flexible.  The 
formation  of  a  pseudopodium  is  best  studied  in  a  common  amoeba, 
such  as  Amoeba  proteus  (Fig.  2)  or  A.  Umax  (Fig.  20)  ;  it  is  then  seen 
to  arise  as  a  protrusion  of  the  ectoplasm,  forming  a  shallow  promi- 
nence at  the  surface  of  the  body.  The  prominence  continues  to 
grow  out  from  the  body,  and  is  at  first  hyaline,  transparent,  and 
free  from  granulations,  since  it  consists  of  ectoplasm  alone.  In 
some  cases  the  pseudopodium  may  grow  to  a  relatively  very  large 
size,  and  still  consist  of  clear  ectoplasm  alone,  as  in  Entamceba 
histolytica  (Fig.  90),  a  form  rather  exceptional  in  this  respect ;  more 
usually,  so  soon  as  the  budding  pseudopodium  has  reached  a  certain 
not  very  great  size,  a  core  of  granular  endoplasm  flows  into  it  and 
forms  the  axial  part  of  the  pseudopodium.  It  is  then  easier  to  study 
the  formation  of  the  pseudopodium,  since  the  granules  in  the  endo- 
plasm permit  the  characteristic  flowing  movements  and  currents  to 


THE  ORGANIZATION  OF  THE  PROTOZOA  47 

be  followed.  In  the  growing  pseudopodium  a  strong  current  can 
be  observed  flowing  down  the  axis  to  the  tip,  and  there  spreading 
out  and  breaking  up  into  weaker  currents  which  turn  round  and 
flow  backwards  along  the  surface  of  the  pseudopodium.  In  amoebae 
with  a  very  viscid  surface  layer  the  back-currents  are  very  feeble, 
ceasing  a  short  way  from,  the  tip  of  the  pseudopodium,  and  often 
scarcely  discernible,  or  even  absent  altogether  ;  in  species  with  a 
fluid  ectoplasm,  however,  the  back  -  currents  are  distinctly  seen, 
and  may  even  pass  back  and  bend  round  again  to  join  the  forward 
axial  current,  as  described  by  Rhumbler  (34)  in  Amoeba  blattce. 

While  the  extrusion  of  the  pseudopodium  is  an  active  process, 
the  retraction  requires  nothing  but  the  action  of  purely  physical 
forces  of  surface-tension  to  explain  it.  The  protoplasm  then  flows 
back  into  the  body  of  the  animal,  and  may  present  some  character- 
istic appearances  in  doing  so.  If  one  .surface  is  in  contact  with  the 
substratum  on  which  the  animal  is  creeping,  the  adhesion  of  the 
pseudopodium  often  causes  the  tip  to  be  drawn  out  into  slender 
processes  like  spikes  or  hairs.  At  the  same  time  the  surface  of  the 

FIG.  20. — Diagram  to  show  the  protoplasmic  currents  in  a  limax- 
amoeba  which  is  moving  forward  in  the  direction  indicated  by 
the  large  arrow  on  the  left.  The  smaller  arrows  indicate  the 
direction,  and  their  length  the  intensity,  of  the  currents  in 
different  parts  of  the  body.  A  forwardly-directed  "  fountain 
current  "  starts  from  near  the  hinder  end,  and  passes  along 
the  axis  of  the  body  to  the  extremity  anterior  in  movement ; 
there  it  turns  outwards  and  passes  back  along  the  sides  of  the 
body,  diminishing  rapidly  in  intensity,  and  finally  dying  out  in 
the  regions  where  the  two  dots  are  placed.  After  Rhumbler 
(34). 

pseudopodium  may  present  a  wrinkled  appearance,  as  the  viscid 
ectoplasm  shrinks  in  consequence  of  the  rapid  withdrawal  of  the 
fluid  endoplasm. 

The  pseudopodia  of  different  species  of  organisms,  or  even  of 
the  same  species  at  different  periods  of  the  life-cycle,  vary  greatly 
in  form,  appearance,  and  structural  characters,  and  the  more  im- 
portant variations  require  a  special  terminology.  In  the  first 
place,  the  pseudopodia  may  be  broad  and  thick  relatively  to  their 
length,  as  in  Amoeba  proteus  (Fig.  2)  ;  they  are  then  termed  "  lobose  " 
("  lobopodia  "),  and  usually  have  a  core  of  endoplasm.  A  typical 
lobose  pseudopodium  is,  in  fact,  nothing  more  than  an  outgrowth 
of  the  body-protoplasm  as  a  Avhole.  In  the  most  extreme  cases  of 
this  type,  the  whole  body  flows  forward  in  one  direction,  forming, 
as  it  were,  a  single  pseudopodium.  Such  a  mode  of  progression  is 
characteristic  of  Amoeba  Umax  (Fig.  20)  and  other  similar  forms, 
in  which  the  body  glides  forward  like  a  slug  as  the  animal  creeps 
over  substratum  ;  the  end  which  is  anterior  in  movement  is  rounded, 


48  THE  PROTOZOA 

while  the  posterior  end  commonly  becomes  drawn  out  into  processes 
similar  to  those  seen  in  a  pseudopodium  in  process  of  retraction. 
In  other  forms,  such  as  A.  proteus  (Fig.  2),  the  pseudopodia  are  sent 
out  on  all  sides  and  balance  each  other,  in  which  case  there  is  very 
little  translation  of  the  body  as  a  whole,  and  the  pseudopodia  serve 
chiefly  for  food-capture.  If,  however,  the  outflow  of  the  pseudo- 
podia is  strongest  on  one  side  of  the  body,  the  organism  moves  in 
that  direction  as  a  whole,  and  the  larger,  more  strongly  developed 
pseudopodia  counteract  and  overcome  the  pull  exerted  by  those 
that  are  weaker.  It  will  be  readily  understood,  therefore,  that  the 
most  rapid  powers  of  progression  are  possessed  by  the  slug-like 
amoebae,  in  which  a  single  pseudopodium  drags  the  whole  body  along 
without  opposition  from  others. 

Rhumbler  (34)  has  drawn  attention  to  the  existence  of  two 
modes  of  progression  exerted  by  amoebae  of  the  lobose  type.  In  the 
more  fluid  species  which  creep  upon  a  substratum  to  which  they 
adhere  more  or  less  firmly,  like  Amoeba  proteus,  the  animal  pro- 
gresses by  a  flowing  movement,  such  as  has  been  described  :  this  is 
the  commonest  type  of  amoeboid  locomotion.  On  the  other  hand, 
in  species  of  the  type  of  A.  verrucosa  and  A.  terricola  the  very 
slightly  fluid  body  is  limited  by  a  thin  pellicle,  and  does  not  adhere 
to  the  substratum. ;  then  progression  is  effected  by  '  rolling  ': 
movement.  The  animal  throws  out  a  number  of  pseudopodia  on 
one  side,  which  cause  it  ultimately  to  overbalance  and  roll  over  to 
that  side  ;  by  continued  repetition  of  this  procedure,  a  slow  progres- 
sion in  a  particular  direction  is  effected.  At  other  times,  however, 
A.  verrucosa  may  flow  along  like  other  amoebae. 

Contrasting  with  the  lobose  pseudopodia  are  the  slender,  thread- 
like, so-called  "  filose  "  pseudopodia,  formed  entirely  of  ectoplasm. 
Pseudopodia  of  this  type  can  effect  a  slow  creeping  movement,  but 
are  not  very  effective  for  locomotion,  and  serve  for  food-capture 
principally,  or  even  entirely,  as  in  the  radiate  floating  forms 
(Heliozoa  and  Radiolaria)  ;  food  is  entangled  by  them  and  drawn 
into  the  body.  The  filose  pseudopodia  may  radiate  from  the 
body  in  all  directions,  remaining  separate  from  one  another,  or 
they  may  anastomose  t^o  form  networks,  and  are  then  termed 
"  reticulose."  Pseudopodia  of  the  reticulose  type  are  specially 
•characteristic  of  the  Foraminifera  (Fig.  21).  Radiate  pseudopodia 
which  do  not  form  anastomoses,  on  the  other  hand,  characterize 
the  groups  of  the  Heliozoa  and  Radiolaria,  organisms  of  floating 
habit.  As  noted  above,  pseudopodia  of  the  radiate  type  are 
.generally  supported  by  an  axial  rod,  a  secreted  structure  of  firm, 
elastic  nature,  and  are  hence  known  as  axopodia.  The  actual  rod 
reaches  some  way  into  the  endoplasm,  often  to  the  centre  of  the 
bodj-,  as  in  Acanthocystis  (Fig.  18),  Wagnerella  (Fig.  48),  etc.  ;  it 


THE  ORGANIZATION  OF  THE  PROTOZOA 


49 


—sn 


$////  Mill  b  i  v.  \\ 

/.•       •  //     ;-•  '      ':      ?•>.••    :•        V--::  X    \        X 

-  f  >j  /v   f    ?U  i'     fe      \       \ 
//.  ^ 


\        '. 

v\ 

il  \\\ 


a\ 


FIG.  21. — Gromia  om- 
formis,  M.  Schultze 
(=G.  o  voidea, 
Rhumbler),  living 
specimen  with  out- 
stretched pseudo- 
podial  network 
(ps.),  in  which  a 
diatom  (d.),  Navi- 
cula  sp.,  is  en- 
tangled and  will  be 
drawn  into  the 
shell  (sh.).  Other 
diatoms  are  seen 
inside  the  shell,  and 
at  its  fundus 
several  nuclei  are 
seen  as  clear  spheri- 
cal bodies  in  the 
protoplasm.  The 
pseudopodial  net- 
work is  drawn  at 
a  magnification  of 
about  200  linear, 
but  for  want  of 
space  is  repre- 
sented extending 
over  about  one- 
third  of  the  area 
over  which  it  com- 
monly spreads.  A 
part  of  the  pseu- 
dopodial network 
is  reflected  back 
over  the  shell,  and 
streams  out  back- 
wards from  the 
pole  opposite  to 
the  shell  -  mouth. 
After  M.  Schultze. 


/r\ 

• 


i 

i\ 
II  \ 


50 


THE  PROTOZOA 


is  probably  of  endoplasmic  origin,  and  is  pushed  out  from  it  in  a 
centrifugal  direction.  As  it  grows  out,  the  ectoplasm  forms  a 
sheath  over  it,  and  extends  usually  some  way  beyond  it.  When 
the  pseudopodium  is  retracted,  the  axial  rod  is  liquefied  and 
absorbed  by  the  protoplasm. 

Food-capture  is  effected  by  the  pseudopodia  in  various  ways  (see 
p.  189).    In  forms  with  lobose  pseudopodia  they  flow  round  the  body 

to  be  ingested,  enclosing  it 
on  all  sides,  and  finally 
imprisoning  the  prey  in 
a  closed  chamber  of  the 
living  substance,  together 
with  a  drop  of  water  which 
forms  the  food  -  vacuole 
(Fig.  2,  P1,  P2)  in  which 
the  prey  is  digested  (p.  192, 
infra).  A  very  noticeable 
feature  of  pseudopodia  of 
all  kinds  is  their  adhesive- 
ness, due  to  the  secretion 
of  a  slimy  substance  at  the 
surface  of  the  ectoplasm. 
In  Difflugia,  if  the  pseudo- 
podia be  touched  gently 
with  a  glass  rod,  the  slime 
can  be  drawn  out  into 
threads,  like  the  mucus  of 
a  snail  (Rhumbler,  34). 
The  adhesive  power  of  the 
pseudopodia  is  of  service 
both  in  adhering  to  the 
surface  upon  which  they 
creep  and  in  the  capture 
of  their  food. 

The  s 1 o  w  -  f 1 o  w  i  n  g 
amoebae,  such  as  A.  verru- 
cosa,  do  not  as  a  rule  flow 
round  the  body  to  be  in- 
gested, but  draw  it  into  their  interior,  as  if  by  suction.  In  this 
manner^!,  verrucosa  absorbs  and  devours  filamentous  algae  (Fig.  23), 
which  are  "  imported  "  into  the  interior  of  the  body  and  there  coiled 
up  and  digested.  Rhumbler  has  shown  that  this  process  can  be 
imitated  by  drops  of  fluid ;  for  instance,  a  drop  of  chlorof  orm  in  water 
will  draw  in  a  thread  of  shellac  and  coil  it  up  in  its  interior  in  a 
manner  similar  to  the  ingestion  of  an  algal  filament  by  an  amoeba. 


end 


FIG.  22.- — Portion  of  an  Actinosphcerium,  magni- 
fied about  660  linear,  ect.,  Ectoplasm  with 
larger  vacuoles ;  end.,  endoplasrn  with  smaller 
vacuoles  ;  N.,  nucleus;  ps.,  pseudopodia; 
ax.,  delicate  axial  rod  in  the  pseudopodia. 
After  Leidy. 


THE  ORGANIZATION  OF  THE  PROTOZOA 


51 


The  pseudopodia  of  the  filose  type  adhere  firmly  to  organisms 
suitable  for  food  with  which  they  come  in  contact,  and  it  can  be 
observed  that  the  prey  is  both  held  fast  and  killed  by  them,  in- 
dicating that  the  pseudopodia  secrete  some  toxic  substance  in 
addition  to  that  of  an  adhesive  nature.  In  the  reticulose  type, 
diatoms  and  organisms  of  various  kinds  are  entangled  in  the 
pseudopodial  network  (Fig.  21),  and  are  generally  digested  there 
also. 

In  a  few  cases  pseudopodia  exhibit  a  peculiar  form  of  movement 
known  as  nutation.  An  example  of  this  is  seen  in  the  remarkable 
Heliozoon  described  by  Schaudinn  (43)  under  the  name  Camptonema 
nutans  (Fig.  47),  which  possesses  slender  axopodia  in  which  the  axial 


FIG.  23. — Four  stages  in  the  ingestion  of  an  Oscillarian  filament  (/. )  by  Amoeba 
vermcosa.  In  A  the  amoeba  has  crept  along  the  filament ;  in  B  one  end  of 
the  amoeba  is  bending  up,  and  is  about  to  fuse  with  the  rest  of  the  body, 
producing  a  twist  in  the  filament ;  in  0  two  have  been  produced  ;  in  D  a 
considerable  length  of  the  filament  has  been  drawn  into  the  amoeba,  and  is 
twisted  up  into  a  stout  coil.  A,  B,  and  C,  are  drawn  at  intervals  of  quarter 
of  an  hour,  D  several  hours  later.  After  Rhumbler  (34). 

filament  does  not  extend  the  whole  length  of  the  pseudopodium. 
The  pseudopodia  perform  a  slow  rotating  movement,  and  "describe 
the  mantle  of  a  cone,  sometimes  acute,  sometimes  obtuse,  remaining 
stretched  out  straight  for  their  entire  length,  and  bending  only  at  their 
base."  Similar  movements  are  performed  by  the  pseudopodia  of 
TrichospJi cerium  (p.  229)  and  Wagnerella  (p.  246).  In  Camptonema 
the  pseudopodia  also  have  the  power  of  bending  suddenly  when 
brought  in  contact  with  prey,  which  they  capture  like  the  tentacles  of 
a  polyp.  The  bending  takes  place  beyond  the  point  at  which  the 
axial  filament  ceases.  Movements  of  this  kind  are  transitional  to 
those  seen  in  flagella. 

(2)  Flagella  are  vibratile  thread-like  extensions  of  the  protoplasm, 
capable   of   performing    very   complicated    lashing    movements    in 


52 


THE  PROTOZOA 


every  direction.  A  flagellum  consists  of  an  elastic  axial  core 
enclosed  in  a  contractile  sheath  or  envelope  (Fig.  24),  from  the 
extremity  of  which  the  core  protrudes  freely  in  some  cases,  forming 
a  so-called  "end-piece."  The  flagellum  takes  origin  from  a  more 
or  less  deeply-seated  granule,  the  blepharoplast,  or  basal  granule, 
which  will  be  described  in  dealing  with  the  nuclear  apparatus 
(p  82,  infra).  The  elastic  axis,  arising  from  the  blepharoplast, 
can  be  regarded  as  a  form-determining  element  of  encloplasmic 
origin,  the  sheath  as  an  ectoplasmic  motor  substance.  A  flagellum 

is  usually  cylindrical  in  form,  with  the  axial 
filament  central  in  cross-section,  but  may  be 
band-like,  with  the  axial  filament  at  or  near 
one  edge ;  it  is  usually  of  even  thickness 
throughout  its  whole  length,  but  when  the 
axial  filament  is  exposed  to  form  a  terminal 
end  -  piece  the  flagellum  tapers  to  a  fine 
point. 

Like  pseudopodia,  flagella  serve  primarily  for 
locomotion,   and  secondarily  for   food-capture, 
which  is  effected  by  causing  food-particles  to 
impinge  on  some  point  or  aperture  at  the  surface 
of  the  body,  where  they  are  ingested.     In  their 
relation  to  locomotion  two  types  of  flagella  can 
be  distinguished,  termed  by  Lankester  pulsella 
and    tractella    respectively.      A    pulsellum    is 
situated   at    the   end    of    the    body    Avhich   is 
posterior  in  movement — that  is  to  say,  it  is  a 
flagellum  which  by  its  activity  propels  the  body 
forwards.    Flagella  of  this  type  occur  in  Oxyrrhis 
(p.  278)  and  in  the  Choanoflagellata  (p.  271), 
but  are  comparatively  rare  in  the  Protozoa.    In 
the  majority  of  cases  the  flagella  are  tractella — 
that  is  to  say,  their  action  is  such  as  to  drag  the 
body  after  them — hence  they  are  situated  at 
the  end  which  is  anterior  in  progression.     Con- 
sidered generally,  the  movements  performed  by 
tractella  are  of  two  types.     In  some  cases  the  entire  flagellum  is 
thrown,   into    even,    sinuous    undulations,    and    the    body    of    the 
flagellate  progresses  with  a  smooth,  gliding  movement,  which  may 
be   extremely  rapid,   and  is   then  well  expressed  by  the  French 
phrase  "  mouvement  en  fleche  ":    this  type  of  movement  is  well 
seen  in  the  trypanosomes  and  allied  genera,  such  as  Leptomonas, 
etc.     In  most  free-living  flagellates,  however,  the  flagellum  is  held 
out  stiff  and   straight   for   the  proximal   two-thirds   or  so   of  its 
length,  while  the  distal  third  performs  peculiar  whirling  or  pulsating 


FIG.  24.  —  Structure 
of  the  flagellum  of 
Euglena.  ax.,  Axial 
filament ;  c.p.,  con- 
tractile protoplasm 
enveloping  the 
axial  filament ;  e.p., 
end  -  piece  of  the 
flagellum,  consist- 
ing of  the  axial  fila- 
ment exposed  ;  r, 
root  of  the  flagel- 
lum passing  into 
the  body  (compare 
Fig.  84).  After 
Eiitschli  (3). 


THE  ORGANIZATION  OF  THE  PROTOZOA 


53 


cv. 


movements,*  which  drag  the  body  along  in  a  succession  of  more  or 
less  distinct  jerks. 

In  many  flagellated  organisms,  forwardly-directed  flagella  may 
be  combined  with  so-called  "trailing  flagella"  (" Schlepp-geissel "), 
which  are  directed  backwards,  running  along  the  side  of  the  body, 
either  quite  free  (Fig.  25)  or  united  to  the  body 
by  an  undulating  membrane  (Fig.  5).  In  such 
cases  the  trailing  flagellum  is  perhaps  the  chief 
organ  of  propulsion,  acting  as  a  pulsellum,  while 
the  forwardly-directed  flagellum  or  flagella  may 
function  more  as  tactile  organs  or  feelers  than 
as  locomotor  organs.  The  flagellum  may  also 
serve  as  an  organ  of  temporary  attachment  in 
some  cases,  especially  in  parasitic  flagellates  ; 
it  then  often  exhibits  at  its  distal  extremity  a 
distinct  bead-like  swelling  or  enlargement, 
doubtless  of  adhesive  nature.  Such  terminal 
enlargements  are  sometimes  seen,  however,  in 
free-swimming  forms. 

There  are  many  grounds  for  assuming  the  existence 
of  a  gradual  transition  from  flagella  to  pseudopodia, 
and  especially  to  the  slender  axopodia  seen  in 
Heliozoa,  etc.  In  organs  of  each  kind  the  type  of 
structure  is  essentially  similar,  an  axis  of  firm  elastic- 
nature,  which  is  pushed  out  from  the  endoplasm,  in 
many  cases  from  a  basal  granule  of  centrosomic  nature 
(p.  82).  and  is  covered  over  by  a  sheath  of  contractile 
fluid  ectoplasm.  The  difference  between  them  is  one 
of  degree,  the  axopodia  being  relatively  shorter  in 
proportion  to  their  thickness,  and  consequently  less 
flexible,  but  the  nutating  and  bending  movements 
seen  in  axopodia  are  essentially  similar  in  type  to 
those  manifested  by  flagella.  The  Heliozoa  are  con- 
nected with  the  Flagellata  by  transitional  forms  which 
indicate  that  their  pseudopodia  have  arisen  as 
modifications  of  flagella  (p.  248).  Goldschmidt,  who 
discusses  the  whole  question  (41,  pp.  116-122),  de- 
scribes in  a  Cercomonas-like  flagellate  the  shorten- 
ing of  the  flagellum,  and  its  transformation  into 
a  pseudopodium  which  swings  to  and  fro.  A 
flagellum  may  be  considered  as  having  arisen  by 
modification  and  specialization  of  an  axopodiurn, 
and  as  capable  in  many  instances  of  reverting  to 
that  type  of  organ.  (Compare  also  p.  465,  infra.) 

(3)  Cilia  are  slender,  thread-like  extensions  of  the  ectoplasm  which 
differ  from  flagella  mainly  in  three  points  :  they  are  as  a  rule  much 
shorter  relatively  to  the  size  of  the  body;  they  are  present 
usually  in  much  greater  numbers,  and  in  their  most  primitive  type 

*  For  a  detailed  description  and  analysis  of  these  movements,  see  Delage  and 
flerouard  (6),  pp.  305-312. 


FIG.  25.  —  A  n  isonema 
grande,  ventral  view, 
showing  the  "  hetero- 
mastigote  "  arrange- 
ment of  the  flagella. 
a.f.,  Anterior  flagel- 
lum ;  p.f.,  posterior 
trailing  flagellum ; 
8,  oesophagus;  c.v., 
contractile  vacuole 
surrounded  by  a 
number  of  feeding 
vacuoles;  N., 
nucleus ;  an.,  anus 
(cytopyge).  After 
Stein. 


54  THE  PROTOZOA 

i 

of  arrangement  form,  as  it  were,  a  furry  covering  to  the  body ;  and 
their  movements  are  different  from  those  of  flagella.  A  cilium 
performs  simple  regular  movements  of  alternate  contraction  and 
relaxation,  whereby  it  is  first  bent  like  a  bow,  with  a  slight  spiral  twist 
(Schuberg,  44),  and  then  becomes  straightened  out  again  ;  from 
this  it  may  be  inferred  that  the  contractile  substance  is  developed 
mainly  on  one  side  of  the  elastic  axis — on  that  side,  namely,  which 
becomes  concave  during  contraction — instead  of  ensheathing  the 
axis  completely,  as  in  most  flagella.  Then  the  bending  of  the 
cilium  would  be  the  result  of  active  contractility,  acting  against 
the  elasticity  of  the  axis,  which  is  operative  in  causing  the 
cilium  to  straighten  out  again  when  the  contractile  substance  is 
relaxed. 

Cilia  are  usually  implanted  in  rows  on  the  surface  of  the  body, 
and  their  movements  are  co-ordinated  in  such  a  way  that  the  con- 
traction— or,  as  it  may  be  better  termed,  the  pulsation — of  a  given 
cilium  takes  place  slightly  after  the  one  in  front  of  it,  and  before  the 
one  behind  it  (Fig.  26).  On  the  other  hand,  the  neighbouring  cilia 
of  adjacent  rows  pulsate  in  unison  ;  consequently,  when  a  ciliated 


FIG.  26. — Diagram  of  ciliary  movement,  representing  the  successive  phases  of 
contraction  and  expansion  in  a  row  of  cilia.     After  Verworn. 

surface  is  seen  from  above  with  sufficient  magnification,  the  move- 
ments of  the  cilia  produce  an  optical  effect  similar  to  that  seen  in  a 
cornfield  when  the  wind  blowing  across  it  gives  rise  to  an  appearance 
of  waves  following  each  other  in  a  continuous  succession.  When, 
however,  a  row  of  cilia  is  seen  in  side-view,  the  successive  beats  of 
the  cilia  may  produce  the  illusion  of  a  rotating  wheel  ;  hence  the 
origin  of  such  names  as  Rotifer,  Trochophore,  etc.,  applied  to 
Metazoan  organisms  bearing  rings  or  girdles  of  stout  cilia. 

In  spite  of  the  apparent  differences  between  cilia  and  flagella, 
there  is  no  difficulty  in  regarding  cilia  as  derived  ancestrally  from 
flagella  by  a  process  of  modification  and  specialization  in  structure, 
movement,  number,  arrangement,  and  co-ordination.  Like  pseudo- 
podia  and  flagella,  cilia  may  serve  both  for  locomotion  and  food- 
capture.  In  many  cases  the  cilia  specialized  for  these  two  functions 
may  be  sharply  distinct ;  the  food-capturing  cilia,  found  in  connec- 
tion with  the  mouth  and  the  peristomial  region,  are  commonly 
much  longer  than  the  locomotor  cilia,  and  show  the  tendency  to 
form  fusions  presently  to  be  described.  In  sedentary  forms  loco- 
motor  cilia  may  be  absent  in  the  ordinary  state  of  the  animal,  and 
only  developed  temporarily  during  motile  phases.  On  the  other 


THE  ORGANIZATION  OF  THE  PROTOZOA  55 

hand,  in  a  purely  parasitic  form  such  as  Opalina  (p.  439),  in  which 
a  mouth  is  entirely  absent,  only  locomotor  cilia  are  present. 

The  chief  modifications  of  cilia,  apart  from  variations  in  size  and 
function,  are  the  result  of  a  tendency  to  adhere  or  fuse  together  ; 
thus  arise  various  types  of  organs,  of  which  the  most  common  are 
the  cirri,  membranellce,  and  undulating  membranes.  Cirri  are  organs 
resembling  bristles,  formed  by  fusion  of  a  tuft  of  cilia,  just  as  the 
hairs  of  an  ordinary  camel's-hair  paint-brush  adhere  when  moistened 
so  as  to  form  a  flexible  pencil.  In  many  cases  the  cirri  have  frayed- 
out  ends,  in  which  the  component  cilia  are  distinct  from  one 
another  ;  and  reagents  often  cause  a  cirrus  to  break  up  into 
separate  cilia.  Cirri  have  a  locomotor  function,  and  are  especially 
characteristic  of  the  ciliate  Infusoria  which  are  of  creeping  habit 
(order  Hypotricha,  p.  440,  infra).  The  cirri  occur  on  the  ventral 
surface  of  the  body — that  is  to  say,  on  the  side  of  the  body  turned 
towards  the  substratum  on  which  the  organism  creeps,  using  the 
cirri  practically  as  legs. 

Membranellae  are  flapping  or  swinging  membranes  formed  by 
fusion  of  two  or  more  transverse  rows  of  cilia  implanted  side  by 
side,  and  adhering  to  form  a  flat  membrane,  the  free  edge  of  which 
often  has  a  fringed  or  frayed  border,  representing  the  free  ends  of 
the  component  cilia.  Membranellae  occur  usually  in  the  region  of 
the  peristome  in  spiral  rows,  implanted  one  behind  the  other,  and 
each  membranella  performs  simple  movements  of  alternate  flexion  and 
expansion,  comparable  to  those  of  a  single  cilium.  Both  in  structure, 
origin,  and  movements,  the  membranellse  must  be  distinguished 
clearly  from  the  undulating  membranes  presently  to  be  described. 

Undulating  membranes  are  sheet-like  extensions  of  the  ectoplasm, 
which  perform  rippling  movements,  comparable  to  those  of  a  sail 
placed  edgewise  to  the  wind  ;  or,  better  still,  to  the  undulating 
movements  performed  by  the  dorsal  fin  of  a  sea-horse  (Hippocampus) 
or  a  pipe-fish  (Syngnathus)  when  swimming.  The  undulating  mem- 
branes of  Ciliata  consist  simply  of  a  single  row  of  cilia  fused  together. 
Such  membranes  are  found  commonly  in  the  oesophagus  of  In- 
fusoria ;  in  the  vestibule  of  Vorticellids  there  are  two  membranes 
of  this  kind.  In  some  genera,  such  as  Pleuronema  (Fig.  27),  they 
represent  the  principal  food-capturing  organ,  and  reach  a  great 
development.  Pleuronema  swims  about  by  means  of  its  cilia,  and 
comes  to  rest  sooner  or  later  in  a  characteristic  attitude,  with  the 
cilia  projecting  stiffly  from  the  body  ;  the  large  undulating  membrane 
is  then  protruded  from  the  mouth,  and  serves  by  its  movements  to 
waft  food-particles  down  the  oesophagus. 

Undulating  membranes  are  also  of  common  occurrence  in  the 
Flagellata,  where  they  are  of  a  different  type  from  those  of  Ciliata. 
The  undulating  membrane  in  this  class  is  always  found  in  connec- 


56 


THE  PROTOZOA 


tion  with  a  flagellum,  and  is  to  be  regarded  as  a  web  of  the  ecto- 
plasm (periplast)  connecting  the  flagellum  to  the  surface  of  the 
body.  Such  a  condition  may  arise  either  by  attachment  of  a  back- 
wardly-directed  trailing  flagellum  to  the  side  of  the  body,  as  in 
TricJiomonas  (Fig.  5)  and  Trypanoplasma  (Fig.  36),  or  by  the 
shifting  backwards  of  the  point  of  origin  of  an  anterior  flagellum, 
as  is  well  seen  in  the  transition  from  crithidial  to  trypanif orm  phases 
in  the  development  of  trypanosomes  (Fig.  131).  As  a  rule,  only  the 
proximal  portion  of  the  flagellum  is  involved  in  the  formation  of 


n 


FIG.  27. — Pleuronema  chrysalis.  M,  The  undulating  membrane  ;  o,  mouth ; 
N,  macronucleus ;  n,  micronucleus ;  c.v.,  contractile  vacuole  ;  f.v.,  food 
vacuole  ;  a.,  anal  pore.  After  Schewiakoff,  magnified  660  diameters. 

the  undulating  membrane,  and  the  distal  portion  projects  freely 
beyond  it ;  but  in  some  cases  a  distal  free  portion  of  the  flagellum 
may  be  quite  absent,  and  then  flagellum  and  undulating  membrane 
are  co-extensive  (Fig.  12,  J).  Undulating  membranes  in  Flagellata 
appear  to  be  specially  related  to  the  endoparasitic  mode  of  life,  and 
in  free-living  species  they  are  found  rarely,  if  ever  ;  they  may  be 
regarded  as  an  adaptation  to  life  in  a  broth-like  medium,  such  as  the 
intestinal  contents,  or  the  blood  of  a  vertebrate,  containing  many 
suspended  particles  or  corpuscles.  In  such  cases  the  membrane 
may  assist  the  organism  to  force  its  way  between  the  solid  bodies 
suspended  in  the  fluid  medium.  Undulating  membranes  may,  how- 


THE  ORGANIZATION  OF  THE  PROTOZOA  57 

ever,  serve  for  other  functions  than  that  of  locomotion,  in  flagel- 
lates as  well  as  in  ciliates.  In  large,  stout  forms  of  trypanosomes, 
for  example,  the  animal  may  remain  perfectly  still  while  its  mem- 
brane is  rippling  actively,  and  in  that  case  the  function  of  the  mem- 
brane is  probably  to  cause  currents  in  the  fluid  surrounding  the 
body,  and  to  change  and  renew  the  liquid  bathing  the  body-surface. 
In  such  a  case  it  has  been  noted  that  the  undulating  membrane 
may  from  time  to  time  reverse  the  direction  of  its  movements,  the 
waves  running  for  a  time  from  the  hinder  end  forwards,  and  then 
for  a  time  in  the  opposite  direction  (Minchin  and  Woodcock,  42, 
p.  150).  It  is  probable  that  the  undulating  membranes  which  pass 
down  the  vestibule  of  Vorticellids  can  reverse  their  movements  in  a 
similar  manner,  since  this  passage  serves  both  for  passage  of  food- 
particles  to  the  mouth  and  for  the  ejection  of  excreta  from  the  anal 
pore  and  the  contractile  vacuoles. 

The  only  structures  found  in  free-living  Flagellata  which  can  be 
compared  at  all  with  undulating  membranes  are  the  peculiar 
"  collars  "  found  in  the  Choanoflagellata  (Fig.  110),  and  also  in  the 
collar-cells  of  sponges.  Each  collar  is  an  extension  of  the  ecto- 
plasm which  grows  up  from  the  edge  of  a  circular  area  round  the 
insertion  of  the  flagellurn,  forming  a  membrane  like  a  cuff  or  sleeve 
surrounding  the  basal  portion  of  the  flagellum,  but  quite  distinct 
from  the  flagellum  itself,  and  not  formed  in  actual  connection  with 
it  like  the  undulating  membrane  of  a  trypanosome.  The  collar 
differs  further  from  a  true  undulating  membrane  in  not  being 
energetically  motile,  but  only  slowly  protrusible  and  retractile.  It 
has  been  stated,  both  for  Choanoflagellates  and  for  the  collar-cells  of 
sponges,  that  the  collar  is  formed  by  a  spirally-folded  membrane. 
Their  function  appears  to  be  that  of  assisting  in  food-capture  by 
a  sessile,  flagellated  organism. 

(4)  Contractile  mechanisms  in  Protozoa,  when  they  are  visible, 
take  the  form  of  so-called  myonemes,  minute  contractile  fibrils  run- 
ning in  various  directions  in  the  ectoplasm,  like  an  excessively 
minute  system  of  muscle-fibres.  Such  elements  are  not  found  in 
Sarcodina  or  in  the  non-corticate  forms  of  the  other  classes  ;  in 
naked  forms  with  amoeboid  movement  the  ectoplasm,  as  has  been 
pointed  out  above,  is  only  a  temporary  differentiation  of  the  proto- 
plasmic body,  which  can  arise  by  conversion  of  the  eiidoplasm,  and 
which  can  be  changed  back  again  into  endoplasm.  Myonemes  occur 
commonly,  however,  in  those  Flagellata,  Sporozoa,  or  Infusoria, 
which  owe  a  definite  body-form  to  the  presence  of  a  firm  cuticle  or 
cortex,  representing  a  stable  ectoplasm.  The  myonemes  are  often, 
however,  extremely  fine,  and  sometimes  escape  detection  in  cases 
in  which  we  can  infer  their  presence  with  certainty  from  the  move- 
ments or  contractions  of  the  organism  or  of  its  ectoplasm.  As  a 


58 


THE  PROTOZOA 


general  rule  they  are  visible  more  or  less  clearly  in  the  larger,  but 
not  in  the  more  minute,  species.  Thus,  in  trypanosomes,  myonemes 
can  be  made  out  in  large  forms  as  delicate  lines  running  parallel  to 
the  undulating  membrane  (Fig.  28),  but  in  small  species  of  trypano- 
somes it  may  be  impossible  to  discover  them,  although  the  nature 
of  their  movements  may  leave  no  doubt  as  to  the  existence  of  con- 
tractile mechanisms  in  the  ectoplasm.  In  other  cases,  both  motile 
species  possessing  myonemes  and  non-motile  species  lacking  them 
may  occur  within  the  limits  of  a  single  group,  as  in  Gregarines, 
where  the  motile  species  show  a  very  distinct  layer  of  myonemes 

(Fig.  29) ;  while  the  non-motile 
forms  have  a  much  thinner  ecto- 
plasm, represented  practically  by 
the  cuticle  alone,  with  no  trace 
of  myonemes.  In  the  non-motile 
trophozoites  of  the  Coccidia  myo- 


••— :-;;v:.-".-:.:;i'.1.',1^;;;;; ; 

sr.'i-'-*"";:-'-"''''1: 


FIG.  28. — Trypanosoma  percce,  stout 
form  stained  with  iron-hsematoxylin 
to  show  myonemes.  After  Minchin, 
X  2,000. 


FIG.  29. — Gregarina  munieri*  showing 
the  layer  of  myonemes  at  the  surface 
of  the  body,  slightly  diagrammatic. 
After  Schneider. 


nemes  are  similarly  absent.  In  the  ciliate  Infusoria  the  myonemes 
run  parallel  to,  and  beneath,  the  rows  of  cilia,  and  in  species  of 
large  size  and  great  powers  of  contractility,  such  as  Stentor,  the 
myonemes  are  lodged  in  canals  and  show  a  transverse  striation 
(Fig.  186,  /). 

According  to  Schaudinn,  these  motile  mechanisms,  both  flagella 
and  myonemes,  are  derived  from  the  achromatic  spindle  of  a 
dividing  nucleus.  In  the  development  of  a  trypanosome  from  a 
non-flagellated  condition,  he  describes  the  entire  kinetic  apparatus 
as  arising  from  a  nuclear  spindle  consisting  of  two  polar  centro- 
somes  connected  by  a  centrodesmose  (p.  103,  infra),  and  by  mantle 


THE  ORGANIZATION  OF  THE  PROTOZOA  59 

fibres,  but  with  chromosomes  apparently  rudimentary  or  absent. 
Such  a  spindle  is  stated  to  persist  and  to  grow  greatly  in  length, 
one  pole  of  it  finally  projecting  beyond  the  anterior  end  of  the  body. 
The  centrosome  at  the  proximal  pole  of  the  spindle  becomes  the 
blepharoplast  or  basal  granule  of  the  flagellum  ;  the  centrodesmose 
itself  becomes  the  flagellum,  or  at  least  its  axial  elastic  filament ;. 


N 


FIG.  30. — Development  of  the  locomotor  apparatus  of  trypanosomes.  A — F,  De- 
velopment of  Trypanosoma  noctuce :  A,  the  single  nucleus  of  the  "ookinete  " 
is  dividing  into  two  unequal  halves  ;  in  each  half  a  centriole  is  seen,  connected 
with  its  twin  by  a  centrodesmose ;  B,  the  division  of  the  nucleus  complete ; 
the  two  sister-nuclei  still  connected  by  a  centrodesmose  uniting  the  centrioles  r 

C,  the  smaller  nucleus  (n. )  is  dividing  unequally  to  furnish  a  third  nucleus  (h.g. ) ; 

D,  E,  the  third  nucleus  is  dividing  to  furnish  a  proximal  (b.g.1)  and  a  distal 
(b.g.2)  centriole,  while  the  fibrils  of  the  achromatic  spindle  become  the  myo- 
nemes  (my. ) ;  F,  development  of  the  trypanosome— N,  trophonucleus ;  n,  kineto- 
nucleus;  b.q.1,  basal  granule  (true  blepharoplast)  of  the  flagellum.     In  C  the 
pigment  (P)  present  in  the  earlier  stages  is  being  thrown  off.     After  Schau- 
dinn  (132). 

G,  stage  in  the  development  of  the  merozoite  of  Trypanosoma  rotatorium 
into  the  trypanosome-form ;  AT,  trophonucleus,  still  connected  by  a  cen- 
trodesmose with  n,  the  kinetonucleus,  which  has  budded  off  b.g.,  the  basal 
granule  of  the  flagellum.  After  Machado  (409). 

the  distal  centrosome  is  carried  out  on  the  tip  of  the  flagellum  ;  and 
the  mantle  fibres  form  the  myonemes,  stated  in  this  case  to  be  eight 
in  number,  of  the  body,  which  are  continued  on  into  the  contractile 
sheath  of  the  flagellum  (Fig.  30).  However  fascinating  the  views 
put  forward  by  Schaudinn,  with  regard  to  these  points,  may  be,  it 
must  be  stated  that  the  greatest  doubt  attaches  to  the  correctness 


60  THE  PROTOZOA 

of  the  observations  upon  which  they  are  founded,  and  that  they 
lack  confirmation  entirely.* 

3.  Organs  apparently  of  excretory  function  are  present  in  many 
Protozoa  as  the  so-called  "  contractile  vacuoles,"  one  or  more  droplets 
of  clear  liquid  which  make  their  appearance  in  the  ectoplasm,  grow 
to  a  certain  size,  and  then  burst,  emptying  their  contents  to  the 
exterior.  When  the  contractile  vacuole  reaches  its  full  size,  it  often 
bulges  inwards  far  beyond  the  limits  of  the  ectoplasm,  and  hence 
may  appear  to  lie  in  the  endoplasm ;  but  its  first  appearance  is 
always  in  the  ectoplasm,  to  which  it  strictly  belongs. 

In  non-corticate  amoeboid  forms  the  contractile  vacuoles  simply 
empty  themselves  to  the  exterior,  and  the  changing  form  of  the 
body  does  not  permit  of  determining  whether  the  position  of  the 
vacuole  is  a  constant  one.  It  is  common  in  amoebae  for  the  vacuole 
to  be  lodged  in  the  region  of  the  body  Avhich  is  hindmost  in  progres- 
sion ;  but  this  may  be  simply  the  mechanical  consequence  of  the 
streaming  movements  in  the  protoplasm,  whereby  the  vacuole  is 
carried  along  to  the  hinder  end  of  the  body.  In  corticate  forms, 
on  the  other  hand,  the  contractile  vacuoles  are  constant  both  in 
number  and  position,  and  void  their  contents  through  a  definite 
pore  in  the  cuticle,  directly  or  indirectly  ;  in  many  Flagellata  and 
Infusoria,  for  instance,  the  vacuoles  do  not  discharge  directly  to 
the  exterior,  but  into  the  oesophagus  or  into  a  reservoir-vacuole 
communicating  with  the  oesophagus. 

The  growth  of  the  contractile  vacuole  is  caused  by  fluid  draining 
into  it  from  the  body-protoplasm.  In  amoebae  and  forms  of  simple 
structure  no  channels  supplying  the  contractile  vacuole  are  visible, 
and  it  must  be  supposed  to  be  fed  by  a  process  of  diffusion  through 
the  protoplasm  from  all  parts  of  the  body.  In  the  highly-organized 
ciliate  Infusoria,  however,  the  deepest  layer  of  the  ectoplasm  has  a 
loose,  spongy  texture,  and  forms  a  definite  excretory  layer  full  of 
spaces  containing  fluid,  which  drains  into  one  or  more  main  canals 

*  It  must  be  added  further  that,  to  judge  from  the  figures  left  by  Schaudinn 
and  published  on  Plate  xxix.  of  his  collected  works  ("  Fritz  Schaudinn's  Arbei- 
ten,"  Hamburg  and  Leipzig,  1911),  the  statements  cited  above  appear  to  be 
founded  on  preparations  made  by  a  method  of  technique  which  is  recognized 
generally  as  giving  unsound  cytological  results — namely,  the  method  of  dried 
films  stained  by  the  Romanowsky  stain.  Schaudinn's  statements  are  nevertheless 
cited  above  on  account  of  the  numerous  theoretical  discussions  and  speculations 
in  modern  protozoological  and  cytological  literature  of  which  they  have  been  the 
foundation.  For  my  part,  I  disbelieve  entirely  in  the  theory  that  the  flagellum 
represents  a  centrodesmose  between  two  centrosornes  ;  I  regard  it  as  a  simple 
outgrowth  from  a  blepharoplast  of  a  nature  essentially  similar  to  the  axopodium 
of  a  Heliozoon.  It  is  curious  that  no  one  has  as  yet  extended  Schaudinn's  theory 
to  the  axopodia,  the  axial  filament  of  which  should  also  represent  a  centrodesmose, 
if  that  view  is  correct  for  the  axial  filament  of  the  flagellum,  a  view  that  seems 
to  me  quite  unthinkable  from  a  phylogenetic  standpoint.  Is  it  to  be  supposed 
that  the  formation  of  each  pseudopodium  by  a  Heliozoon  represents  a  rudimentary 
mitosis  ? 


THE  ORGANIZATION  OF  THE  PROTOZOA 


Gl 


supplying  the  contractile  vacuole  or  vacuoles.  Thus,  in  Stentor 
(Fig.  8)  the  single  vacuole  is  fed  by  a  canal  running  the  length  of 
the  body,  and  in  Paramecium  (Fig.  185)  the  two  vacuoles  are  each 
surrounded  by  a  number  of  canals  forming  a  star-shaped  figure. 

As  regards  the  function  of  the  contractile  vacuoles,  it  should  be 
noted  in  the  first  place  that  their  contents  are  always  fluid  and 
watery,  and  never  contain  solid  particles  of  any  kind.  The  fluid 
winch  a  contractile  vacuole  drains  from  the  body  is  doubtless 
replaced  by  water  absorbed  from  the  surrounding  medium  by 
diffusion  through  the  superficial  layer  of  the  protoplasm,  or  it 
may  be  through  the  mouth  in  some  cases.  The  contractile  vacuole 
is  generally  regarded  as  the  organ  of 
nitrogenous  excretion,  comparable 
functionally  to  the  urinary  organs  of 
the  Metazoa,  but  it  is  highly  probable 
that  the  liquid  discharged  from  it 
contains  also  the  carbon  dioxide  pro- 
duced by  the  respiratory  process. 
Hence  the  contractile  vacuole  may 
be  regarded  as  both  excretory  and 
respiratory  in  function  (see  also 
p.  197,  infra). 

4.  In  the  majority  of  Protozoa 
there  are  no  organs  for  which  a  defi- 
nite sensory  or  nervous  function  can 
be  claimed,  although  these  organ- 
isms show  by  their  reactions  to  the 
environment  or  to  stimuli  that  they 
possess  sensory  and  psychical  func- 
tions. In  some  cases,  however, 
certain  organs  can  be  asserted  to 
have  a  sensory  function,  exhibited 
in  sensitiveness  either  to  impressions 
of  touch  or  light.  Thus,  in  many  Flagellates  the  flagella  appear  to 
be  tactile  as  well  as  locomotor  in  function,  and  in  Ciliata  tactile 
cilia  occur,  especially  in  the  creeping  hypotrichous  forms. 

Sensitiveness  to  light  is  a  marked  feature  of  many  Protozoa, 
even  of  quite  undifferentiated  forms,  such  as  amoebae.  Rhumbler 
(34)  has  shown  that  many  amoebae  cease  feeding  in  a  strong  light, 
and  even  disgorge  food  that  they  have  taken  in  when  suddenly 
subjected  to  the  intense  illumination  necessary  for  microscopic 
study.  This  characteristic  is,  however,  most  marked  in  the  holo- 
phytic  species,  to  which  light  is  a  necessity  for  their  plant-like 
metabolism.  In  the  holophytic  Flagellates  a  red  pigment-spot,  or 
stigma,  is  found  constantly,  situated  close  to  the  anterior  end  of  the 


FIG.  31. — Pouchetia  cornuta,  one  ot 
the  Dinoflagellata,  to  show  the 
large  stigma  (st.),  in  front  of 
which  is  a  lens  (I.).  After  Schiitt 
(386). 


62  THE  PROTOZOA 

body  (Fig.  4,  st.).  The  belief  that  the  stigma  is  the  seat  of  light- 
perception  receives  support  from  the  fact  that  in  some  cases  it  is 
found  associated  with  lens-like  structures,  which  evidently  serve 
to  concentrate  light  upon  it  and  act  as  dioptric  elements,  as  in 
Pouchetia  (Fig.  31). 

B.  Endoplasmic  Organs. 

The  bulk  of  the  endoplasm  in  proportion  to  that  of  the  whole 
body  varies  greatly  in  different  Protozoa.  In  Flagellata,  for 
example,  the  protoplasmic  body  must  be  considered  as  consisting 
almost  entirely  of  endoplasm,  the  ectoplasm  furnishing  only  the 
delicate  periplast  and  myonemes.  Similarly,  in  motionless  para- 
sitic forms,  such  as  the  Coccidia  or  the  "  ccelomic  "  Gregarines 
(p.  326,  infra),  the  body  within  the  cuticle  is  entirely  endoplasm. 
On  the  other  hand,  in  Ciliata,  in  which  the  ectoplasm  may  give  rise 
to  a  number  of  different  structures,  the  endoplasm  is  often  a  rela- 
tively restricted  region  of  the  body.  In  these  examples  that  have 
been  cited,  the  ectoplasm  and  endoplasm  are  probably  stable 
layers,  and  their  relative  proportions  are  consequently  more  or  less 
constant  for  a  given  phase  of  the  life-history  ;  but  in  amoeboid  forms, 
as  already  pointed  out,  ectoplasm  and  endoplasm  are  interchange- 
able, and  the  amount  of  each  layer  present  in  an  organism  varies 
with  the  extent  of  its  body-surface  ;  that  is  to  say,  the  proportion  of 
ectoplasm  to  endoplasm  is  greatest  when  the  amoeba  is  moving 
actively  and  throwing  out  many  pseudopodia,  and  least  when  it  is 
in  a  resting  condition  and  has  assumed  the  spherical  form. 

As  stated  above,  the  endoplasm  is  a  fluid,  granular  substance, 
which  contains  various  enclosures  connected  with  the  nutritive 
function,  and  also  the  nucleus  or  nuclei.  Hence  it  may  be  re- 
garded as  the  seat  of  trophic  and  reproductive  functions.  The 
nuclear  apparatus  will  be  dealt  with  in  a  separate  chapter,  since  it 
belongs,  strictly  speaking,  neither  to  the  ectoplasm  nor  the  endo- 
plasm, though  commonly  lodged  in  the  latter.  In  this  chapter 
only  the  structural  elements  connected  with  the  function  of  food 
ingestion  and  assimilation  will  be  described. 

The  contents  of  the  endoplasm  vary  greatly,  according  to  the 
mode  of  life  of  the  organism.  In  saprophytic  and  most  parasitic 
forms  no  special  organs  are  found  in  connection  Avith  the  nutritive 
function,  the  food  being  simply  absorbed  in  a  soluble  condition 
at  the  surface  of  the  body,  probably  by  the  aid  of  enzymes  secreted 
by  the  organism,  but  not  by  any  recognizable  organs.  In  holozoic 
and  holophytic  forms,  however,  special  organs,  differing  widely  in 
each  case,  are  present  for  the  assimilation  or  elaboration  of  food. 

1.  In  holozoic  Protozoa  the  organs  of  assimilation  take  the  form 
of  food-vac uoles,  minute  droplets  of  fluid  in  which  the  solid  particl;-- 


THE  ORGANIZATION  OF  THE  PROTOZOA  63 

ingested  as  food  are  suspended  and  gradually  digested.  In  some 
cases,  however,  and  especially  when  the  prey  is  relatively  large, 
no  distinct  fluid  vacuole  can  be  made  out  surrounding  it,  "but  the 
food  appears  to  be  simply  lodged  in  the  endoplasm  itself  ;  the 
vacuole  is  "  virtual."  When  the  digestion  is  completed,  the  in- 
soluble faecal  residues  are  cast  out  of  the  body. 

In  Protozoa  in  which  the  body  consists  of  naked,  non-corticate 
protoplasm,  the  food  is  ingested,  and  the  fsecal  remains  are  expelled, 
at  any  point  on  the  surface  of  the  body.  In  corticate  Protozoa, 
on  the  other  hand,  in  which  the  body  is  limited  by  a  resistant 
envelope  or  cuticle  of  a  certain  strength  and  thickness,  food  can- 
not be  ingested  at  any  point,  but  is  taken  in  through  a  special 
aperture,  a  cell-mouth  or  cytostome.  In  such  cases  the  organs  of 
food-capture  are  either  flagella  or  cilia,  and  by  their  action  the  food 
is  wafted  into  the  mouth.  Primitively  the  mouth  is  a  superficial 
aperture  in  the  cuticle,  opening  into  the  endoplasm  by  means  of  a 
longer  or  shorter  tube,  the  oesophagus  or  cytopharynx.  In  the 
Peritricha  (p.  433),  however,  the  mouth  and  oesophagus  are,  as  it 
were,  carried  into  the  body  at  the  end  of  an  in-sinking  of  the  ecto- 
plasm, which  forms  a  long  tube  or  vestibule,  comparable  in  its 
mode  of  formation  to  the  stomodseum  of  the  Metazoa.  In  any  case 
the  food-vacuoles  are  formed  at  the  bottom  of  the  oesophagus,  in 
the  endoplasm.  The  mode  in  which  the  vacuoles  arise,  and  the 
processes  of  digestion  and  defsecation,  are  discussed  in  a  subsequent 
chapter  (p.  189,  infra). 

2.  In  holophytic  forms  assimilation  is  carried  on  by  cell-organs 
of  the  same  nature  as  those  found  in  the  green  cells  of  ordinary 
plants.  Of  primary  importance  are  the  chromatophores,  or  chromo- 
plasts,  bodies  containing  chlorophyll  or  allied  pigments  by  means  of 
which  the  organism  is  enabled  to  decompose  carbon  dioxide  in  the 
sunlight,  setting  free  the  oxygen  and  utilizing  the  carbon  for  build- 
ing up  the  living  substance.  The  chromatophores  vary  greatly 
as  regards  size,  form,  and  number  present  in  the  cell-body.  Other 
bodies  of  constant  occurrence  are  pyrenoids,  small  glistening  cor- 
puscles which  appear  to  serve  as  centres  for  the  formation  or  storage 
of  starch  or  similar  substances  of  amyloid  nature  produced  in  the 
process  of  anabolism  (see  infra,  p.  188). 

In  any  Protozoa,  whatever  their  mode  of  nutrition,  the  endo- 
plasm contains  usually  various  enclosures,  which  can  be  classed 
generally  as  metaplastic — that  is  to  say,  as  products  of  the  upward 
(anabolic)  or  downward  (catabolic)  metabolism  of  the  living  sub- 
stance. Instances  of  anabolic  products  are  the  grains  of  starch  or  of 
the  allied  substance,  paramylum,  found  in  the  holophytic  forms, 
and  the  reserve  food-materials—fat,  "  paraglycogen,"  and  other 
substances — often  stored  up  in  considerable  quantity  in  prepara- 


64  THE  PROTOZOA 

tion  for  developmental  changes,  especially  in  the  female  gamete, 
in  a  manner  analogous  to  yolk-grains  in  an  ovum.  Instances  of 
bodies  resulting  from  catabolic  activity  are  waste-products  of  various 
kinds  in  the  form  of  granules,  crystals,  pigment-grains,  etc.,  often 
present  in  great  numbers,  and  giving  the  endoplasm  an  opaque  and 
coarsely-granular  appearance.  A  familiar  instance  of  such  waste- 
products  is  seen  in  the  grains  of  melanin-pigment  formed  in  the 
bodies  of  the  malarial  parasites  (Fig.  156)  as  a  result  of  the  absorp- 
tion and  decomposition  of  the  haemoglobin  of  the  red  blood-cor- 
puscle. 

Many  bodies  present  in  the  protoplasm  of  Protozoa  may  be  con- 
sidered as  originally  of  metaplastic  nature  and  origin,  but  as 
utilized  secondarily  for  various  functions.  Such  are  the  oil-drops 
in  the  intracapsular  protoplasm  of  Radiolaria  (p.  251),  which  appear 
to  have  a  hydrostatic  function,  and  also  to  serve  as  reserve  food- 
material  in  the  development.  It  is  also  highly  probable  that  both 
internal  and  external  skeletons  originated  simply  as  excretions  in 
the  first  instance  —  that  is  to  say,  as  waste  -  products  of  the 
metabolism  which  have  been  utilized  for  the  function  of  support, 
and  subsequently  adapted  and  modified  in  accordance  with  the 
special  requirements  of  the  organism. 

Finally,  as  bodies  of  hydrostatic  function,  though  not  to  be 
included  necessarily  under  metaplastic  products,  are  the  peculiar 
gas-vacuoles  of  Arcella,  bubbles  of  gas  which  can  be  secreted, 
absorbed,  and  formed  again,  as  circumstances  may  require,  in  and 
by  the  living  protoplasm. 


BibliograpJiy. — For  references  see  p.  47" 


CHAPTER  VI 

THE  ORGANIZATION  OF  THE  PROTOZOA  (Continued)— THE 

NUCLEAR  APPARATUS— CHRO MATIN,  NUCLEUS, 
CHROMIDIA,  CENTROSOMES,  AND  BLEPHAROPLASTS 

OF  all  the  parts  or  organs  of  the  cell-body,  there  is  none  of  greater 
importance  for  the  life  and  activities  of  the  organism  than  the 
so-called  nucleus,  a  term  which,  understood  literally,  means  simply 
a  kernel  or  central  portion  of  the  body,  and  conveys  110  idea  of  the 
true  nature  of  the  structure  in  question  or  of  its  significance  for  the 
life  of  the  organism. 

The  cell-nucleus,  in  all  its  various  modifications  of  form  and 
structure,  is  essentially  and  primarily  a  collection  of  grains  and 
particles  of  a  peculiar  substance  which  has  received  the  name 
chromatin,  on  account  of  its  characteristic  tendency  to  combine 
with  certain  colouring  matters  and  dyes.  A  nucleus  may  consist, 
perhaps,  in  some  cases  of  little  more  than  a  single  mass  of  chromatin, 
or  of  several  such  masses  clumped  together.  In  most  cases,  how- 
ever, the  chrornatin  is  combined  with  other  substances  which  may 
be  termed  comprehensively  achromatin,  and  which  are  built  up  with 
the  chromatin  in  such  a  way  as  to  produce  a  complicated  nuclear 
structure,  as  will  be  described  in  detail  presently. 

The  chromatin-substance  is  not  necessarily,  however,  concen- 
trated entirely  in  the  nucleus  in  all  cases.  In  many*  Protozoa, 
especially  amongst  the  Sarcodina,  as,  for  example,  Arcella  (Fig.  32), 
Difflugia,  and  many  other  genera,  the  cell-body  contains,  in  addi- 
tion to  one  or  more  nuclei,  extranuclear  granules  of  chromatin, 
termed  ckromidia,*  which  may  be  scattered  in  the  cytoplasm 

*  The  term  "  chromidia/'  in  the  German  form  "  Chromidien,"  was  coined  by 
Hertwig  (66)  to  denote  the  extranuclear  grains  of  chromatin,  and  the  whole  mass 
of  them  in  the  cell-body  was  spoken  of  as  a  "  Chromidialnetz."  Subsequent 
authors,  however,  have  used  the  word  in  its  singular  form,  "  chrornidium,"  in  a 
collective  sense,  to  denote  the  entire  mass  of  chrcmidia  present  in  a  cellular  organ- 
ism, and  not,  as  might  have  been  expected,  to  mean  the  individual  grains  or 
particles  of  chromatin  which  constitute  the  chromidial  mass.  In  order  to  avoid 
confusion,  it  is  proposed  in  this  work  to  use  the  term  chromidiosome  to  denote  the 
smallest  chromatin-particles  of  which  the  chromidial  mass  is  made  up,  and  which 
grow  and  multiply  by  division  like  other  elementary  living  bodies.  It  is  clear, 
however,  that  the  chromidiosomes  of  which  the  cliromidial  mass  scattered  in  the 
cytoplasm  is  built  up  are  in  no  way  different  in  kind  from  the  minutest  granules 
of  chrornatin  contained  in  the  nucleus.  The  term  "  chrornidiosorno  "  must  there- 
fore be  applied  to  the  ultimate,  individual  grain  or  particle  of  chromatin,  alike 
whether  it  be  lodged  inside  or  outside  a  nucleus. 

65  5 


66  THE  PROTOZOA 

throughout  the  cell,  or  may  be  aggregated  in  certain  regions  of 
the  body  to  form  ''  chroniidial  masses  "  or  "  chromidial  nets." 
It  is  even  found  that  in  some  species  a  true  nucleus  may  be  absent 
temporarily  during  some  phases  of  the  life-cycle,  all  the  chroniatin 
being  then  in  the  form  of  chromidia,  from  which  nuclei  arise  by  a 
process  of  condensation  and  organization  of  the  chromatin  in  com- 
bination with  achromatinic  elements.  Such  a  condition  may  be 
regarded  as  a  temporary  reversion  to  a  more  archaic  and  ancestral 
condition,  since,  as  has  been  pointed  out  already  (Chapter  I.),  the 
Protista  of  the  lower  or  bacterial  grade  of  organization  do  not 
possess,  speaking  generally,  a  true  nucleus,  but  only  scattered 
grains  of  chromatin.  Hence  the  chromidial  condition  of  the 
chroniatin  may  be  ranked  as  an  earlier  and  more  primitive  state, 
from  which  the  strictly  cellular  grade  of  organization  has  been 
evolved  by  concentration  of  some  or  all  of  the  chromatin  to  form  a 
nucleus.  In  the  tissue-cells  of  Metazoa,  as  a  general  rule,  and  in 
many  Protozoa,  the  chromatin  is  concentrated  entirely  in  the  nucleus 
or  nuclei,  and  chromidia  do  not  occur. 

Whatever  view  be  taken  as  to  the  primitive  or  secondary  nature 
of  the  chroniidial  condition  (a  question  upon  which  individual 
opinions  may  differ  considerably),  the  following  facts  can  be  stated 
definitely  with  regard  to  the  chromidia.  In  some  cases  the  chromidia 
can  be  observed  to  arise  as  extrusions  of  chromatin  from  the  nucleus, 
which  either  casts  off  a  certain  amount  of  chromatin  into  the  cyto- 
plasm, while  preserving  its  individuality,  or  may  undergo  complete 
fragmentation,  becoming  resolved  entirely  into  chromidia,  and 
ceasing  to  exist  as  a  definite  nucleus.  In  other  cases,  chromidia 
arise  from  pre-existing  chromidia,  by  growth  and  multiplication 
of  the  chromidiosomes,  thus  keeping  up  a  chromidial  mass  or  stock 
which  is  propagated  from  cell  to  cell  through  many  generations, 
independently  of  the  nuclei  present  in  addition  to  them  in  the  cell: 

The  chromidial  mass  itself  may  vary  considerably  in  structure- 
in  different  cases  or  at  different  seasons  ;  the  chromidiosonies  may 
be  arranged  in  clumps,  strands,  or  trabeculee,  on  a  protoplasmic- 
framework,  and  the  mass  is  often  vacuolated  and  contains  substances 
other  than  chromatin.  In  Diffliigia,  Zuelzer  (85)  has  shown  that 
in  the  autumn  the  chromidial  mass  assumes  a  vacuolated  or  alveolar 
structure,  and  in  each  alveolus  grains  are  formed  of  a  carbohydrate 
substance  allied  to  glycogen,  which  functions  as  reserve  food- 
material  for  the  organism  during  the  reproductive  processes  initiated 
at  that  season. 

On  the  other  hand,  as  chromidia  arise  from  nuclei,  so  nuclei  may 
arise  from  chromidia.  In  many  Protozoa,  as,  for  example,  Arcella 
(Fig.  32),  the  formation  of  so-called  "secondary"  nuclei  (which, 
however,  do  not  differ  from  other  nuclei  except  in  their  mode  of 


THE  NUCLEUS 


67 


origin),  by  concentration  of  chromidia  into  a  clump  or  mass  which 
acquires  gradually  the  structure  and  organization  of  a  true  nucleus. 
is  a  frequent  and  normal  occurrence  in  the  life-cycle,  as  will  be 
seen  in  subsequent  chapters.  Those  who  regard  the  chromidial 
condition  as  the  more  primitive  will  see  in  the  formation  of  secondary 
nuclei  from  chromidia  the  ontogenetic  recapitulation  of  the  phylo- 
genetic  origin  of  the  nucleus  as  a  structural  element  of  the  cell-body. 
From  the  foregoing  it  is  seen  that  nuclei,  in  the  Protozoa,  do  not 
necessarily  arise  from  pre-existing  nuclei ;  the  generalization  "  Omnis 
nucleus  e  nucleo,"  though  it  probably  holds  good  universallv  for 
the  cells  of  Metazoa,  cannot  be  maintained  for  Protozoa  if  the  term 
"  nucleus  "  be  taken  in  its  strict  sense.  On  the  other  hand,  there 


FIG.  32. — Arcdla  vulgaris,  to  show  formation  of  secondary  nuclei  from  the  chro- 
midia. A,  Ordinary  type  of  individual,  with  two  nuclei  and  a  ring  of  chromidia  : 
B,  example  in  which  secondary  nuclei  are  being  formed  in  the  chromidial 
ring.  A71,  Primary  nucleus  ;  N2,  secondary  nucleus  in  process  of  formation  ; 
clir.,  chromidial  ring  ;  o,  aperture  of  the  shell.  After  R.  Hertwig  (65). 

is  no  evidence  that  chromatin,  within  or  without  the  nucleus,  can 
ever  arise  de  novo  or  in  any  way  except  from  pre-existing  chromatin, 
the  particles  of  which  grow  and  multiply  as  the  result  of  processes  of 
•assimilation  such  as  constitute  the  most  essential  characteristic 
of  the  living  substance  generally. 

There  is  no  doubt,  however,  that  chromatin  may  itself  give  rise- 
to  other  substances  of  achromatinic  nature,  and  probably  of  simpler 
constitution,  by  a  process  of  breaking  down  of  its  complex  sub- 
stance ;  and  also  that  there  may  be  present  in  the  cell  various 
•substances  very  similar  to  chromatin  in  their  properties  and  charac- 
teristics, representing  stages  in  the  building-up  of  the  complex 
material  of  the  chromatin-substance.  In  one  or  the  other  of  these 
two  ways  it  is  possible  to  account  for  bodies  in  the  cell  known  by 
names,  such  as  "  metachromatinic  grains,"  "  chromatoid 


68  THE  PROTOZOA 

grains,"  and  so  forth — bodies  which  are  often  mistaken  for  true 
chromatin,  but  which  must  be  carefully  distinguished  from  it,  just 
as  metaplastic  bodies  are  to  be  distinguished  from  protoplasm 
Among  such  bodies  must  be  mentioned  more  especially  the  so-called 
"  volutin-grains,"*  which  have  attracted  much  attention  of  recent 
years,  and  which  occur  in  various  bacterial  or  unicellular  organisms. 
The  volutiii-grains  resemble  chromatin  in  showing  affinities  for 
so-called  "  nuclear  stains,"  which  they  hold  more  firmly  than  the 
chromatin  itself,  when  treated  with  reagents  that  extract  the  stain. 
According  to  Reichenow  (78),  volutin  is  a  nucleic  acid  combination 
which  is  to  be  regarded  as  a  special  reserve-material  for  the  forma- 
tion of  the  nucleo-proteins  of  the  chromatin-substance  ;  during 
phases  of  the  life-cycle  in  which  the  chromatin  in  the  nucleus 
increases  in  quantity,  the  volutin  in  the  cytoplasm  diminishes,  and, 
conversely,  when  the  quantity  of  chromatin  is  stationary,  the 
volutin-grains  increase  in  number.  Volutin-grains  are  thus  seen 
to  be  bodies  of  totally  different  nature  from  chromidia,  with  which 
they  are  often  confused  on  account  of  their  similar  appearance  and 
staining  reactions  ;  chromidia  are  formed,  typically,  as  extrusions 
from  the  nucleus  into  the  cytoplasm  ;  volutin-grains,  on  the  other 
hand,  are  formed  in  the  cytoplasm,  and  represent,  as  it  were,  a 
food-substance  which  is  absorbed  by  the  nucleus  in  the  growth  and 
formation  of  the  chromatin.  In  some  cases,  however,  the  meta- 
chromatinic  grains  may  represent  chromidial  extrusions  from  the 
nucleus  which  are  breaking  down  or  being  modified  into  other 
substances  ;  compare,  for  example,  the  extrusion  of  vegetative 
chromidia,  which  degenerate  into  pigment,  from  the  nucleus  of 
ActinospJicerium  during  a  depression-period  (p.  209). 

The  occurrence  in  the  cell-body  of  volutin  and  other  substances 
which  resemble  chromatin  very  closely  may  often  render  extremely 
difficult  the  task  of  identifying  and  distinguishing  the  true  chro- 
matin, especially  when  it  is  not  concentrated  into  a  definite  nucleus, 
but  is  scattered  in  the  cytoplasm  in  the  form  of  chromidial  grains. 
The  test  upon  which  reliance  is  mostjisually  placed  for  the  identi- 
fication of  chromatin  is  its  staining  properties,  and  especially  its 
readiness  for  combining  with  basic  aniline  dyes  and  certain  other 
colouring  matters.  But  this  test  is  extremely  inadequate  and  un- 
reliable ;  on  the  one  hand,  as  has  been  stated  above,  there  are 
substances,  such  as  volutin,  which  are  coloured  by  '  nuclear  '; 
stains  more  intensely  than  the  true  chromatin  itself  ;  on  the  other 
hand,  in  cellular  organisms  which  possess  true  nuclei  containing 
undoubted  chromatin,  the  staining  reactions  of  the  nuclei  may  be 
strikingly  different  in  different  cases.  A  good  example  of  each  of 

*  Tho  name  "  volutin  "  was  coined  by  A.  Meyer  in  1904,  and  is  derived  from  the 
fact  that  the  substance  was  tirst  studied  by  him  in  Spirillum  volutans. 


THE  NUCLEUS 


69 


these  statements  is  furnished  by  the  trypanosomes  parasitic  in 
vertebrate  blood  :  on  the  one  hand,  these  parasites  often  contain 
in  their  cytoplasm  so-called  '''  chromatoid  grains,"  probably  of  the 
nature  of  volutin  (Swellengrebel,  514),  which  stain  in  a  similar 
manner  to  the  nucleus  ;  on  the  other  hand,  the  nuclei  of  the 
parasites  react  to  stains  in  a  manner  very  different  from  the 
nuclei  of  the  blood-cells  amongst  which*  they  live.  In  short,  it 
is  not  possible  to  name  any  stain  or  class  of  stains  which  can  be 
relied  upon  either  to  combine  with  chromatin  alone,  or  to  stain 
chromatin  in  the  same  manner  and  to  the  same  degree,  at  all  times 
and  in  all  cases*  (compare  Fig.  33).  When, 
therefore,  the  adjectives  "  chromatinic  "  and 
"  achromatinic  "  are  used  in  the  course  of 
this  work,  it  must  be  clearly  understood 
that  these  terms  signify  that  the  bodies  or 
substances  to  wrhich  they  are  applied  con- 
sist or  do  not  consist,  as  the  case  may  be, 
of  chrornatiii,  and  not  that  they  stain  or 
do  not  stain  with  certain  dyes. 

As  regards  the  chemical  nature  of  chro- 
matin,  it   is    characterized   by   containing 

protein-substances  more  complex  in  com-  FIG.  33. — Diagram  to  repre- 
position  than  any  other  part  of  the  cell ;  it 
is  not  possible  to  say  defimtely,  however, 
whether  it  is  to  be  regarded  as  a  single 
chemical  substance  or  as  a  combination  or 
mixture  of  several.  Its  most  salient  feature 
is  its  variability ;  judged  by  microchemical 
tests,  no  two  samples  of  chromatin  can  be 
considered  identical  hi  composition,  whether 
from  different  cells  or  even  from  the  same 
cell  at  different  times.  Certain  substances, 
especially  phosphorus-compounds,  are  espe- 
cially characteristic  of  iiucleo-proteins,  but 
it  is  not  possible  at  the  present  time  to 
define  or  identify  chromatin  by  its  chemical 
properties  or  composition. 

All  experience  at  the  present  time  tends  to  show  that  the  final 
test  for  the  identification  of  chromatin  in  the  cell  is  its  relation  to 
the  vital  activities  and  life-history  of  the  organism.  The  term 
"  chromatin "  is  thus  to  be  regarded  as  denoting  a  biological  or 
physiological,  but  not  a  chemico-physical,  unity.  A  given  body 

*  Methyl-green,  acidulated  with  acetic  acid,  has  sometimes  been  indicated  as  a 
most  distinctively  nuclear  stain  ;  but  Hertwig  (64)  has  shown  that  in  the  nuclei 
of  ActinospJicerium  this  stain  colours  the  plastin-framework,  and  not  the 
matin,  and  this  author  casts  doubt  on  the  alleged  value  of  this  stain  as 
for  demonstrating  chromatin  in  the  nucleus. 


sent  in  a  graphic  manneg 
the  action  of  colouring 
matters  that  stain  chrr- 
rnatin.  The  circle  drawn 
with  an  uninterrupted  line 
is  supposed  to  represent 
a  theoretically  perfect 
chromatin  -  stain,  which 
would  stain  chromatin 
always,  and  nothing  else 
but  chromatin ;  the  circles 
drawn  with  interrupted 
lines  represent  the  action 
of  chromatin  stains  actu- 
ally ;  they  will  stain  chro- 
matin as  a  general  rule, 
though  notin  variably,  but 
they  will  also  stain  other 
things  which  are  not  chro- 
matin. 


70  THE  PROTOZOA 

or  grain  in  the  cell  cannot  be  definitely  identified  as  cliromatin,  in 
all  cases,  by  any  chemical  or  physical  test,  but  only  by  its  relation 
to  the  life  and  development  of  the  organism  as  a  whole,  and  more 
especially  to  the  function  of  reproduction  and  the  phenomena  of 
sex,  as  will  be  shown  more  fully  by  means  of  concrete  instances  in 
subsequent  chapters.     The  sum  of  modern  knowledge  with  regard 
to  the  vital   activities   of  living   bodies   and  the  life-histories  of 
organisms,    whether    plants    or    animals,    Protozoa    or    Metazoa, 
indicates  that  the  chromatin  exercises  a  regulative  and  determina- 
tive influence  over  the  functions  and  properties  of  the  cell-body. 
Direct  experimental  proof  of  the  all-importance  of  the  nucleus  for 
the  life  of  the  cell  is  obtained  by  cutting  Protozoa  into  pieces,  some 
containing  portions  of  the  nucleus,  others  consisting  of  cytoplasm 
alone  (p.  210,  infra).     Those  pieces  that  contain  nuclear  substance 
are  able  to  regenerate  the  lost  parts  of  the  body  and  to  perform 
all  the  functions  of  life,  and  in  particular  those  of  assimilation, 
growth,  and  reproduction  ;  those,  on  the  contrary,  that  contain  no 
portion  of  the  nucleus  rapidly  lose  the  power  of  assimilation,  and 
are  unable  to  regenerate  the  body,  to  grow  or  to  reproduce;  and 
though  they  remain  for  a  time  irritable  and  capable  of  movement, 
they  soon  lose  these  properties.     There  are  a  number  of  facts  which 
indicate  that  in  the  physiological  activities  of  the  cell  the  chief 
function  of  the  nucleus  is  the  formation  of  ferments  ;  it  is  therefore 
all-important  in  regulating  the  assimilative  processes  of  the  living 
substance  (p.  194). 

The  conception  of  cliromatin  as  the  directive  and  regulative  centre 
of  the  cell-body  renders  intelligible  a  number  of  phenomena  con- 
nected with  it,  such  as  the  elaborate  mechanisms  which,  as  will  be 
described  in  the  next  chapter,  are  gradually  evolved  and  perfected 
for  the  exact  partition  of  the  chromatin  in  the  reproduction  of 
the  cell  by  division,  and  the  relation  of  chromatin  to  the 
sexual  process.  Further,  the  extremely  variable  nature  of  the 
chromatin-substaiice  becomes  at  once  intelligible  on  this  view  of 
its  relation  to  the  specific  characters  and  properties  of  the  organism  ; 
for  since  every  species  of  living  being — perhaps,  even,  every  in- 
dividual of  the  same  species — differs  to  a  greater  or  less  extent 
from  every  other  :  then,  if  such  differences  are  determined  by  the 
chromatin,  it  follows  that  the  chromatin  must  also  differ  to  a 
corresponding  degree  in  each  case,  and  that  consequently  uni- 
formity of  character  in  different  samples  of  chromatin  cannot  be 
expected  to  occur. 

Hertwig  (67,  92)  considers  that  a  certain  quantitative  relation  of 
nucleus  and  cytoplasm  is  necessary  in  any  cell  for  the  normal 
continuance  of  the  vital  functions.  This  nucleo-cytoplasmic  ratio 
("  Kernplasma-Relation ")  is  subject  to  variations  at  different 


THE  NUCLEUS  71 

periods  of  life-history,  but  is  the  same,  normally,  for  corresponding 
phases  of  the  life  of  the  cell  ;  it  can  be  influenced  by  external  con- 
ditions, such  as  food  and  temperature,  and  also  by  internal  factors, 
undergoing  changes  in  a  regular  manner,  in  harmony  with  changing 
functional  conditions  of  the  cell.     In  cultures  of  a  given  species 
at  a  loAver  temperature,  multiplication  is  slower  and  the  organisms 
grow  larger  and  possess  larger  nuclei ;  with  increase  of  temperature 
the  reverse  takes  place  (compare  p.  206,  infra).     It  has  also  been 
observed  that,  in  long-continued  cultures  of  Protozoa,  periods  of 
active  assimilation  and  multiplication  are  followed  by  periods  of 
depression,  during  which  assimilation  and  reproduction  are  at  a 
standstill,  even  in  the  midst  of  abundant  nutriment  (see  especially 
Calkins,  5).     The  depression-periods  are  characterized  by  an  in- 
crease  of  the  nuclear  substance  relatively  to   the  cytoplasm,   a 
'  hyperchromasy  "  of  the  cell,  which  may  lead  to  the  death  of  the 
individual  unless  compensated  by  the  elimination  and  absorption 
of  part  of  the  nuclear  substance  (p.  209,  infra)  ;  when  the  balance 
has  been  thus  restored,  the  organism  becomes  normal  and  feeds 
and  multiplies  again.     From  this  conception  of  a  definite  relation 
between  the  mass  of  the  nucleus,  or  rather  of  the  chromatin,  and 
that  of  the  cytoplasm,  Hertwig  has  deduced  a  number  of  important 
consequences  to  which  reference  will  be  made  in  subsequent  chapters. 
The  influence  exerted  by  the  chromatin  upon  the  life  of  the 
organism  may  be  manifested  in  two  ways,  which  may  be  termed, 
for  convenience,  actual  and  prospective,  respectively.     In  the  first 
case  it  regulates  the  metabolism  and  functions,  both  trophic  and 
kinetic,  of  the  cell  in  which  it  is  contained,  and  is  then  commonly 
termed  vegetative  chromatin,  or  trophochromatin.     In  the  second  case 
it  may  be  dormant  and  inactive  in  the  cell  that  contains  it,  remaining 
latent,  as  it  were,  until  carried  on  to  future  generations  in  the 
course  of  cell -reproduction  ;  at  a  later  period  the  whole  or  a  part 
of  this  latent  chromatin  may  become  active,  determining  the  nature 
and  properties  of  the  offspring,  and  thus  serving  as  the  vehicle  for 
hereditary  transmission  of  the  characters  of  antecedent  generations. 
Such  temporarily  dormant  chromatin  is  commonly  termed  genera- 
tive chromatin,  or  idiochromatin.     It  is  probable  that  in  all  Protozoa 
the  cell-body  contains  chromatin  both  in  the  active  and  inactive 
state,  the  one  regulating  the  vital  functions  of  the  living  body, 
the  other  remaining  dormant,  in  reserve  for  future  generations. 

The  validuty  of  this  conception,  according  to  which  the  chromatin 
present  in  an  organism  is  regarded  as  being  either  vegetative  or 
generative  in  function,  must  be  tested  by  its  capacity  to  account 
for  the  facts  of  the  development  and  life-cycle  which  will  be  con- 
sidered more  fully  in  subsequent  chapters.  There  are  no  means 
of  recognizing  and  distinguishing  vegetative  and  generative  chro- 


72  THE  PROTOZOA 

matin  except  by  their  respective  relations  to  the  life-cycle,  at  certain 
periods  of  which,  as  will  be  seen,  the  nuclear  apparatus  is  entirely 
reconstituted,  effete  vegetative  chromatin  being  eliminated  from 
the  organism,  either  cast  out  or  absorbed,  and  its  place  taken  by 
reserve  generative  chromatin.  It  is  only  necessary  to  remark  that 
some  authorities  speak  of  vegetative  and  generative  chromatin  as 
if  they  were  two  distinct  kinds  of  substance,  whereas  they  are 
probably  to  be  considered  rather  as  two  phases  or  states  of  one  and 
the  same  chromatin.  Vegetative  chromatin  is  that  which  is  in  a 
state  of  functional  activity,  and  which  thereby  tends  to  become 
exhausted  and  effete  in  its  vital  powers,  exhibiting  in  consequence 
the  phenomena  of  "  senility."  Generative  chromatin,  on  the  con- 
trary, by  remaining  inactive,  conserves  its  "  youth  "  unimpaired, 
and  constitutes  a  reserve  from  which  the  worn-out  vegetative 
chromatin  can  be  replaced.  Generative  chromatin  of  one  genera- 
tion may  become  vegetative  chromatin  in  the  next. 

As  regards  their  distribution  in  the  cell-body,  in  some  cases 
vegetative  and  generative  chromatin  cannot  be  distinguished  by 
the  observer  as  separate  structural  elements,  but  are  mixed  up 
together  in  the  same  nucleus  ;  in  other  cases,  however,  they  occupy 
distinct  situations  in  the  body.  Thus,  in  Sarcodina  it  is  common 
for  the  vegetative  chromatin  to  be  lodged  in  the  principal  nucleus 
or  nuclei,  while  the  generative  chromatin  occurs  in  the  form  of 
chromidia,  as  in  Arcetta  (Fig.  32),  or  vice  versa.  In  the  Infusoria 
there  are  two  kinds  of  nuclei,  which  are  shown  by  their  behaviour 
to  consist,  the  one  of  vegetative,  the  other  of  generative  chromatin. 
Chromidia,  when  present  in  the  cell,  may  also  differ  in  kind,  being 
in  some  cases  extrusions  from  the  nucleus  of  purely  vegetative 
chromatin,  in  process  of  elimination,  while  in  other  cases,  as 
already  mentioned,  the  chromidia,  or  a  part  of  them,  represent 
the  generative  chromatin  (see  p.  150,  infra). 

The  nuclei  of  Protozoa  exhibit  great  variety  of  structure  and 
form  as  compared  with  the  relatively  uniform  structure  of  the 
nuclei  of  Metazoa.     As  stated  already,  the  constituent  substances 
or  structural  elements  in  any  nucleus  may  be  distinguished  broadly 
as  chromatinic  and  achromatinic  :   the  former  consisting  of  the 
chromatin,  the  primary  and  essential  element  never  absent  in  any 
nucleus  ;   the  latter  comprising  various  accessory  structures,   an- 
cillary to  the  chromatin,  and  not  all  of  them  invariably  present 
in  any  given  nucleus.     Amongst  the  principal  achromatinic  con- 
stituents of  nuclei  in  general  must  be  mentioned  the  following  : 
(1)  linin,  occurring  in  the  form  of  a  framework,  which  stains  feebly 
or  not  at  all  by  chromatin-stains,  and  which  presents  the  appear- 
ance of  a  delicate  reticulum  or  network,  the  optical  expression  of 
an  alveolar  structure  ;  (2)  a  fluid  encliylema  or  nuclear  sap,  filling 


THE  NUCLEUS 


73 


the  interstices  of  the  linin-framework  ;  (3)  plastin,  a  substance 
which  has  staining  reactions  different  to  those  of  chromatin,  and 
which  occurs  in  lumps  or  masses  forming  the  ground-substance  of 
the  nucleoli  or  karyosomes  presently  to  be  described.  The  whole 
nucleus  is  commonly  enclosed  in  a  membrane,  but  this  structure  is 
probably  formed  in  different  ways  in  different  cases,  and  may  be 
absent.  In  addition  to  these 
various  constituents,  there  are 
commonly  present  also  in  con- 
nection with  nuclei  bodies  of 
kinetic  nature.  Such  are  the 
centrosomes  or  centrioles,  which 
appear  to  control,  or  at  least 
to  act  as  centres  for,  the  move- 
ments which  the  various  parts 
of  the  nucleus  perform  during 
the  process  of  reproduction  by 
division. 

The  structure  and  appear- 
ance of  nuclei  depend  chiefly 
on  the  manner  in  which  the 
chromatin  is  distributed.  Two 
principal  types  of  structure  may 
be  distinguished  :  in  the  first 
the  chromatin  is  concentrated 
into  a  single  mass  or  grain,  or,  if 
other  grains  are  present  in  the 
nucleus,  they  are  smaller  and 
relatively  insignificant  in  size  ; 
in  the  second  a  number  of 
grains  are  present  which  are 
more  or  less  equal  in  size.  In 
the  condition  with  a  single, 
or  one  greatly  preponderating, 
mass  of  chromatin,  the  nuclear 
space  is  not  as  a  rule  filled  by 
it,  but  presents  the  appear- 


FIG.  34. — Cyclical  vegetative  changes  in  the 
resting  nuclei  of  Trichosphcerium  sieboldi. 

A,  Stage  with  finely-meshed  chromatic 
network  and  large  karyosome  (see  p.  76) ; 

B,  the  meshes  of  the  network  widening, 
the   karyosome    budding  off   blocks   of 
chromatin  into  it ;  C,  the  same  process 
carried  farther  ;  D,  coarse  network  con- 
taining scanty  chromatin  at  the  nodes, 
karyosome  wanting  ;  E  to  G,  the  chro- 
matin   increases    greatly    in     quantity, 
covering  the  linin-framework — in  G  the 
meshes  of   the   network   are    becoming 
finer ;  H,  the  network  has  become  fine- 
meshed  again  ;  /,  a  karyosome  is  being 
formed    by  condensation  of   the   chro- 
matin at  certain  points,  leading  to  the 
condition  of  A  again.     After  Schaudinn, 
X  2,250. 


ance  of  a  vesicle  containing 
the  chromatin-mass  at  or  near  its  centre  ;  consequently  such  nuclei 
are  commonly  termed  "  vesicular  "  in  type,  and  the  chromatinic 
mass  maytbe  termed  generalty,  and  without  further  determination 
of  its  precise  nature,  an  endosome  ("  Binnenkorper  ").  When,  on 
the  other  hand,  the  chrpmatin  is  in  the  form  of  numerous  grains, 
they  are  generally  distributed  more  or  less  evenly  throughout  the 
nuclear  cavity  ;  such  nuclei  are  termed  "granular." 


74 


THE  PROTOZOA 


Every  transition  from  the  one  type  of  structure  to  the  other  may 
be  found  in  the  nuclei  of  Protozoa  ;  in  a  vesicular  nucleus  the  prin- 
cipal mass  of  chromatin  may  break  up  into  smaller  grains  which 
become  distributed  throughout  the  nuclear  cavity  ;  in  a  granular 
nucleus  some  or  all  of  the  grains  of  chromatin  may  be  clumped 
together,  and  become  fused  to  form  a  principal  or  single  mass  of 
chromatin.  Such  changes  may  take  place  during  successive  periods 
of  activity  of  one  and  the  same  nucleus  (Fig.  34).  It  is  usual  to 
speak  of  the  condition  of  the  nucleus  as  "  resting  "  when  it  is  not 
actually  undergoing  the  process  of  reproduction  by  division  ;  but 
it  must  be  borne  in  mind  that,  so  long  as  the  cell  is  in  a  state  of 
physiological  activity  of  any  kind,  the  nucleus  also  shares  in  this 
activity,  and,  strictly  speaking,  cannot  be  said  to  be  resting.  The 
activity  of  the  nucleus  is  expressed  in  continual  changes  in  its 
structure  and  rearrangements  of  its  chromatin-substance  and  other 
constituents.  In  the  gregarine  Porospora  gigantea,  Leger  and 
Duboscq  (72)  have  observed  changes  taking  place  rhythmically  in 


\ 


FIG.  35. — Successive  stages  of  the  karyosome  (see  p.  76)  of  Porospora  gigantea, 
showing  the  transformation  of  a  hollow  into  a  homogeneous  karyosoine  by 
expulsion  of  a  vacuole  of  clear  viscous  fluid  into  the  nuclear  cavity,  where  it 
forms  a  little  mass  of  chromatin  in  front  of  the  rnicropyle.  After  Leger  and 
Duboscq  (72). 

the  living  condition  (Fig.  35)  ;  compare  also  Chagas  (48'5).  Hert- 
wig  (64)  has  shown  that  the  structure  of  the  nucleus  of  Actino- 
sphcerium  can  be  correlated  with  the  functional  activities  of  the 
cell.  Thus  a  condition  with  the  chromatin  all  concentrated  to 
form  a  central  endosorne  is  found  prior  to  division  of  the  nucleus, 
and  is  also  found  when  the  animal  is  being  starved  ;  on  the  other 
hand,  when  it  is  supplied  with  abundant  nutriment  and  is  feeding 
actively,  the  chromatin-grains  spread  over  the  whole  nuclear  space. 
Since,  however,  abundant  food  also  leads  to  frequent  nuclear 
division,  the  condition  with  the  chromatin  concentrated  at  the 
centre  also  occurs  during  active  cell-metabolism,  as  well  as  during 
hunger-periods . 

In  the  simplest  condition  of  the  nucleus  the  grain  or  grains  of 
chromatin  are  lodged  in  a  space  or  vacuole,  containing  a  clear  fluid 
or  nuclear  sap,  but  not  enclosed  by  a  definite  membrane.  Nuclei 
of  this  simple  type  of  structure  are  seen  in  some  of  the  primitive 
forms,  such  as  the  small  amoebae  of  the  Umax-type,  in  which  the 


THE  NUCLEUS  75 

nucleus  consists  of  a  large  mass  of  chromatin  suspended  in  the 
nuclear  sap.  In  some  cases  no  other  structural  elements  can  be 
made  out ;  in  others  the  nuclear  sap  contains  granules  of  peripheral 
chromatin  varying  in  size  from  the  most  minute  and  scarcely 
visible  particles  to  distinct  grains.  For  a  simple  nucleus  of  this 
type  the  term  "  protokaryon  "  has  been  proposed  ;  it  is  just  such 
a  nucleus  as  may  be  imagined  to  have  arisen  by  a  concentration 
of  chromidiosomes  at  one  spot  in  the  cell-body,  and  in  many  cases 
such  nuclei  can  be  seen  to  be  formed  actually  in  this  manner.  The 
kinetonucleus  of  trypanosomes  may  be  considered  as  a  nucleus  of 
this  type  in  which  the  single  mass  of  dense  chromatin  fills  almost 
or  quite  completely  the  space  in  which  it  lies.  In  other  cases  there 
may  be  a  clump  of  chromatin-grains  more  or  less  equal  in  size, 
filling  the  nuclear  cavity,  as  in  the  nucleus  of  hamogregarines. 
When  there  are  numerous  grains  of  chromatin,  those  placed  super- 
ficially may  be  united  to  form  a  limiting  layer  which  may  be  termed 
a  "false"  or  " chromatinic "  membrane,  in  distinction  to  a  true 
nuclear  membrane,  which  is  an  achromatinic  structure.  Even  in 
nuclei  of  the  most  simple  type,  however,  substances  or  structures 
accessory  to  the  chromatin  are  probably  always  present. 

In  the  first  place,  it  is  very  probable  that  the  grain  or  grains  of 
chromatin  do  not  lie  loosely  and  freely  in  the  nuclear  vacuole,  but 
are  suspended  in  it,  in  all  cases,  by  a  delicate  achrornatinic  frame- 
work, presenting  the  appearance  of  a  fine  network  or  reticulurn,  at 
the  nodes  of  which  the  chromatin-grains  are  lodged.  It  is  true  that 
in  many  of  the  minute  and  primitive  forms  no  such  framework  has 
been  made  out,  and  is  believed  by  many  observers  to  be  absent ; 
but  on  that  view  it  is  difficult  to  account  for  the  definite  position 
of  the  chromatin,  its  changes  of  position  during  division,  and  the 
frequent  appearance,  during  this  process,  of  an  achromatinic  spindle, 
phenomena  that  may  be  noted  even  in  the  simplest  cases.  The 
achrornatimc  framework  is  often  very  fine  and  delicate,  and  its 
substance  stains  feebly  or  not  at  all  with  the  colouring  matters 
commonly  employed  in  microscopical  technique  ;  hence  it  is  very 
probable  that  it  has  often  been  overlooked  in  cases  where  it  is 
really  present.  When  there  is  but  a  single  mass  of  chromatin,  or 
one  grain  very  much  larger  than  all  the  others,  the  achromatinic 
reticuluni  presents  the  appearance  of  very  delicate  threads  of 
limn  radiating  from  the  principal  mass  of  chromatin  to  the 
periphery.  When,  on  the  other  hand,  there  are  numerous  grains 
more  or  less  equal  in  size,  the  reticuluni  is  seen  as  fine  lines  passing 
from  each  grain  of  chromatin  to  each  of  the  grains  adjacent  to  it. 
In  all  probability  the  apparent  "  threads  "  of  the  reticulum  are  but 
the  optical  expression  of  the  walls  or  partitions  separating  alveoli, 
and  there  is  no  reason  for  considering  the  achroniatinic  reticulum  or 


76  THE  PROTOZOA 

linin  framework  as  different  in  any  essential  point  from  the 
alveolar  framework  of  the  general  protoplasm,  with  which,  in  nuclei 
that  lack  a  true  membrane,  it  is  perfectly  continuous.  Hertwig  (66) 
regards  the  cytoplasmic  framework  as  achromatinic  substance  in 
intimate  combination  with  chromatin  ;  the  nuclear  framework,  on 
the  other  hand,  as  pure  achromatinic  substance  (linin)  from  which 
the  chromatin  has  become  separated  out  and  organized  into  special 
structures,  independent  of  the  framework  in  which  they  are  lodged. 
Similarly,  the  nuclear  sap  filling  the  nuclear  space  and  the  inter- 
stices of  the  reticulum  must  be  identified  with  the  enchylema  of 
the  body-protoplasm.  As  compared  with  the  alveolar  structure 
of  the  general  protoplasm,  that  of  the  achromatinic  nuclear  frame- 
work is  characterized  chiefly  by  the  larger  size  of  the  alveoli,  and, 
consequently,  the  greater  distinctness  of  the  apparent  reticular 
structure. 

A  true  nuclear  membrane,  when  present,  is  probably  formed  in 
all  cases  from  the  achromatinic  framework.  In  the  nuclei  of  Actino- 
sphcerium,  according  to  Hertwig  (64),  the  membrane  is  a  super- 
ficial condensation  of  the  achromatinic  reticulum.  The  membrane 
may  attain  to  a  considerable  thickness  and  appear  doubly-con- 
toured in  optical  section,  separating  the  nuclear  framework  com- 
pletely from  the  extranuclear  protoplasm ;  but  it  is  always  a  structure 
very  readily  absorbed  and  re-formed,  and  it  appears  to  present 
no  obstacle  to  the  passage  of  substance  from  the  nucleus  into  the 
cytoplasm,  or  vice  versa.  Awerinzew  (47),  on  the  other  hand, 
regards  the  nuclear  membrane  as  a  product  of  the  cytoplasm. 

In  addition  to  the  achromatinic  framework,  plastin  is  commonly,  if 
not  invariably,  present  in  the  form  of  masses  or  bodies  which  receive 
different  names,  according  as  they  consist  of  pure  plastin  or  of 
plastin  impregnated  to  a  greater  or  less  extent  with  chromatin. 
In  the  vesicular  type  of  nucleus,  the  endosome  may  perhaps  consist, 
in  some  cases,  of  pure  chromatin,  but  in  most  cases,  if  not  always, 
it  is  composed  of  a  matrix  or  ground-substance  of  plastin  in  which 
the  chromatin  is  lodged.  An  endosome  of  this  kind  is  termed  a 
karyosome,  or  chromatin-nucleolus  ;  as  a  rule  it  has  the  form  of  a 
rounded  mass,  occupying  the  centre  of  the  nucleus,  sometimes  of 
more  than  one  such  mass,  but  in  a  few  cases  it  may  have  the  form 
of  a  crescent  or  cap  ("  calotte  ")  closely  applied  to  the  nuclear  mem- 
brane. In  the  granular  type  of  nucleus,  on  the  other  hand,  there 
may  be  one  or  more  masses  of  pure  plastin  containing  no  chromatin  ; 
such  a  body  is  termed  a  nudeolus  simply,  or  a  "  plastin-nucleolus." 
In  the  nuclei  of  the  tissue-cells  of  Metazoa,  true  nucleoli  occur 
almost  invariably  ;  in  the  nuclei  of  Protozoa,  however,  pure  plastin- 
nucleoli  are  not  of  common  occurrence,  but  have  been  described 
in  a  few  instances — for  example,  in  the  haemogregarine-nucleus 


THE  NUCLEUS  77 

(Reichenow,  78).  As  a  general  rule  in  the  Protozoa,  the  plastin-sub- 
staiice  is  found  as  the  matrix  of  karyosomes,  but  also  as  that  of 
other  masses  of  chroniatin,  such  as  the  chromosomes  of  the  dividing 
nucleus  (see  next  chapter).  Goldschmidt  (41)  observed  that  the 
formation  of  generative  chromidia  in  Mastigella  (p.  265)  was  pre- 
ceded by  the  extrusion  of  plastin  from  the  nucleus  into  the  cyto- 
plasm, to  serve  as  a  matrix  for  the  chromatin  which  passed  out 
from  the  nucleus  subsequently.  In  Actinosph cerium,  Hertwig  has 
shown  that  a  karyosome  or  chromatin-nucleolus,  present  during 
certain  states  or  phases  of  nuclear  activity,  may  give  off  its  chro  • 
matin-substance  into  the  nuclear  framework  (reticulum),  leaving  the 
plastin-matrix  as  a  body  which  is  then  seen  to  consist  of  a  reticular 
framework  similar  in  structure  to  the  achrornatinic  reticulum  of  the 
nuclear  framework,  but  distinguished  from  it  by  smaller  meshes 
(alveoli)  enclosed  by  thicker  walls,  as  well  as  by  its  different  staining 
properties.  Certain  phases  of  the  development  of  Actinosphcerium 
are  further  characterized  by  the  formation  in  the  nucleus  of 
numerous  small  plastin-iiucleoli,  each  consisting  of  a  single  vesicle 
(alveolus)  of  plastin  containing  nuclear  sap. 

Thus,  a  nucleus  in  its  full  complication  of  structure,  and  apart 
from  the  centrosomic  elements,  to  be  discussed  presently,  consists 
of  the  following  parts  :  (1)  An  achrornatinic  framework  or  nuclear 
reticulum  ;  (2)  a  true  membrane,  formed  from  the  achrornatinic 
framework,  and  separating  the  nuclear  contents  from  the  surround- 
ing cytoplasm  ;  (3)  nuclear  sap,  pervading  the  entire  nuclear  cavity  ; 
(4)  plastin,  in  the  form  of  one  or  more  bodies  or  masses  which  may 
consist  either  of  pure  plastin  (nucleoli)  or  of  plastin  impregnated 
with  chromatin  (karyosomes)  ;  and  (5)  the  chromatin,  which  may 
be  present  either  in  the  form  of  granules  lodged  at  the  nodal  points 
of  the  reticulum,  and  scattered  evenly  or  unevenly  throughout  the 
nuclear  framework,  or  may  be  concentrated  in  a  karyosome,  or 
may  combine  both  these  two  modes  of  distribution  in  various  ways. 
Achromatinic  framework  and  nuclear  sap  may  be  considered  as  a 
part  of  the  general  body-protoplasm,  enclosed  within  the  nuclear 
space,  and  set  apart  from  the  cytoplasm  as  a  special  nucleoplasm ; 
plastin,  on  the  other  hand,  is  probably  to  be  regarded  as  a  product 
derived  from  the  chromatin  itself,  either  as  a  secretion  or  as  a 
modification  of  its  substance,  to  form  a  cement-like  material  or 
matrix  in  which  true  chromatin  is  carried.  The  two  primary  con- 
stituents of  a  nucleus  are  chromatin  and  protoplasmic  framework. 

Nuclei,  whatever  their  structure,  are,  as  a  general  rule,  bodies  of 
spherical  or  ovoid  form  ;  but  in  some  cases,  especially  amongst 
Infusoria,  the  nuclei  exhibit  very  varied  forms  in  different  species. 
The  nucleus  may  then  be  sausage-shaped,  or  in  the  form  of  a  horse- 
shoe, or  resemble  a  string  of  beads  ("  moniliform  "),  or  be  branched 


THE  PROTOZOA 


in  a  complicated  manner.  In  the  remarkable  Acinetan  Dendrosoma 
radians  a  colony  is  formed  by  budding,  which  resembles  super- 
ficially a  hydroid  colony,  each  hydranth  being  represented  by  the 
head  of  an  Acinetan  individual  with  suctorial  tentacles  ;  the 
branched  nucleus  is  continuous  throughout  the  whole  colony,  pass- 
ing uninterruptedly  from  one  individual  to  another. 

Typically  the  cell-body  contains  a  single  nucleus,  but  in  many 
Protozoa  two  or  more  nuclei  occur  constantly.     When  there  are 

more  nuclei  than  one,  they  may  be  all  alike 
and  quite  undifferentiated,  or  they  may  show 
differences  in  size,  structure,  and  function. 
In  many  Sarcodina  multiple  nuclei  without 
~  differentiation  are  found  to  occur  constantly 

in  certain  species  ;  for  instance,  two  in  Amoeba 
binucleata  and  Arcella ;  several,  perhaps  a 
dozen  or  so,  in  Difflucjia  (Fig.  16)  ;  from 
twenty  to  forty  up  to  some  five  hundred  in 
Adinosplicerium  (Fig.  3) ;  so  also  in  Pelomyxa  ; 
and  in  the  large  plasmodia  of  Mycetozoa  many 
thousands  of  nuclei  are  found. 

Differentiation    of    nuclei,  when    it    occurs, 
may  be  related  to  various  causes.     In  trypano- 
36.  —  Tnjpano-  somes  and  allied  forms  two  nuclei  occur  con- 
stantly— a  principal  nucleus,  or  trophonucleus, 
pike   (Esox  Indus),  so  called  because  it   appears   to  regulate  the 

a.fl.,  Anterior  flagel-   general   metabolism   and  trophic  activities  of 
lum;    n,     kinetonu-    °  ,,  -.      ,  ,         7  .  x ,  ,  .   ,     .      . 

cleus;  N,  trophonu-   the  celJ-body ;  and  a  Kinetonudeus,  which  is  in 

cleus;  p.fl.,  posterior  special  relation  to  the  organs  of  movement, 
edff  oTthTTiSt-  nagella,  and  undulating  membrane.  As  a  rule 
ting  membrane,  and  the  kinetonucleus  is  smaller,  in  some  cases  very 
continued  beyond  it  mirmte  and  hag  a  dense  compact  structure, 
as  a  very  snort  tree 
flagellum  posteriorly,  while  the  trophonucleus  has  a  vesicular  struc- 

(478)'  ture ;  Lut  in  other  cases  (TrypanoPlasma^  the 

kinetonudeus  is  the  larger  of  the  two  (Fig.  36). 
A   nuclear   differentiation  of  totally   opposite  character  is   seen 
in  the  Infusoria,  where  two  nuclei  of  different  sizes,  hence  termed 
'  macronucleus  "  and  "  micronucleus,"  are  constantly  present ;  the 
behaviour  of  these  two  nuclei  in  relation  to  sexual  phenomena  and 
reproduction  (vide  p.  153,  infra]  shows  that  the  macronucleus  is 
composed  of  vegetative  chromatin,  while  the  micronucleus  contains 
the  reserve  generative  chromatin.     In  some  cases — for  example,  in 
Myxosporidia  (p.  403) — nuclei  of  different  sizes  occur  in  relation  to 
sexual  differences. 

In  some  Protozoa — the  so-called   "  Monera  "    of  Haeckel — the 
nucleus  has  been  stated  to  be  wanting  entirely  ;  but  this  statement 


FIG. 


THE  NUCLEUS  •  79 

is  probably  based  on  incomplete  or  erroneous  observation,  or  on 
defective  technique.  In  all  Protozoa  that  have  been  examined  in 
recent  times,  at  least  one  nucleus  has  been  found  to  occur  without 
exception,  though  in  some  phases  of  the  development  the  nucleus 
may  temporarily  disappear  and  resolve  itself  into  chromidia. 

There  now  remains  for  consideration  the  question  of  the  centro- 
some, the  centre  of  the  kinetic  activity  of  the  nucleus.  Of  all  the 
questions  connected  with  the  nuclear  apparatus,  those  relating  to 
the  centrosome  are  the  most  difficult  to  handle  in  a  general  manner, 
largely  on  account  of  the  minuteness  of  the  bodies  dealt  with,  and 
the  consequent  difficulty  of  ascertaining  their  structure  and  com- 
position, even  their  presence,  in  many  cases.  Hence,  in  the  litera- 
ture of  the  centrosome,  there  is  found  considerable  confusion  in 
the  terminology,  different  authors  disagreeing  entirely  as  to  the 
precise  structures  to  which  the  name  centrosome  should  be  applied, 
and  opposed  theories,  which  cannot  be  discussed  adequately  in  a 
short  space,  have  been  put  forward  as  to  the  nature  and  origin  of 
the  centrosome. 

As  the  focus  of  the  kinetic  activities  of  the  nucleus,  the  centro- 
some is  most  apparent  and  recognizable  when  the  nucleus  is  in 
process  of  reproduction  by  division,  and  much  less  so  when  the 
nucleus  is  in  the  so-called  "resting  state."  Hence  the  study  of  the 
nucleus  during  the  process  of  division  is  alone  decisive  as  to  the 
presence  of  a  centrosome  in  any  given  case  ;  and  since  in  many 
cases  nuclear  division  appears  to  go  on  without  centrosornes  being 
present,  it  may  be  taken  as  equally  probable  that,  in  all  such  cases 
at  least,  no  centrosome  is  present  in  the  resting  state  of  the  nucleus. 
In  many  cases,  however,  the  presence  of  a  centrosome  in,  or  in 
connection  with,  the  resting  nucleus  can  be  ascertained  clearly  ; 
it  may  then  lie  either  outside  or  inside  the  nucleus. 

When  the  centrosome  lies  outside  the  nucleus,  as  it  usually  does 
in  the  cells  of  Metazoa,  it  is  found  typically  as  a,  minute  grain  or 
pair  of  grains  ("  diplosome  ")  close  beside  the  nuclear  membrane. 
Its  presence  may  be  indicated  by  the  radiate  structure  of  the 
surrounding  protoplasm,  giving  the  appearance  of  a  system  of  rays 
centred  on  the  centrosome  ;  but  such  radiations  are  absent  as  a 
rule  during  the  resting  state  of  the  nucleus,  and  the  appearance  of 
rays  is  often  the  first  sign  of  impending  activity  and  division  of 
the  nucleus.  In  many  cases  the  centrosome  is  found  lying  in  a 
mass  of  clear  protoplasm  termed  archo plasm,  a  substance  which 
differs,  apparently,  from  the  rest  of  the  cytoplasm  only  in  being 
free  from  granulations  of  all  kinds.  Archoplasm  may,  in  short,  be 
regarded  simpty  as  pure  cytoplasm,  and  it  appears  either  perfectly 
homogeneous,  or  traversed  by  striations  winch  radiate  from  the 
centrosome,  through  the  archoplasm,  and  even  beyond  its  limits ; 


80  THE  PROTOZOA 

the  striations  themselves  being  the  optical  expression  of  a  radiate 
arrangement  of  the  protoplasmic  alveoli  (meshes  of  the  "  retic- 
ulum  "),  indicating  lines  of  force  or  tension  centred  in  the  centro- 
some.  In  some  cases  it  is  probable  that  archoplasm  showing 
radiate  striations  may  be  present  without  any  centrosome.  In 
A  ctinosph  cerium  Hertwig  showed  that  rays  were  formed  in  the 
archoplasm  before  a  centrosome  had  been  formed,  and  heralded  its 
appearance. 

When  the  centrosome  lies  within  the  nucleus,  it  is  found  most 
frequently,  in  Protozoa,  within  a  plastin-body  or  karyosome,  a 
position  which  it  may  retain  permanently  during  both  the  resting 
and  dividing  conditions  of  the  nucleus.  The  simple  nuclei  of 
the  protokaryon-type  probably  contain  in  most  cases  a  centro- 
somic  grain  lodged  in  the  karyosome.  In  a  few  cases,  however, 
an  intranuclear  centrosome  occurs  without  a  karyosome,  or  outside 
the  karyosome  if  one  is  present.  On  the  other  hand,  there  are 
many  examples  of  the  occurrence  of  extranuclear  centrosomes  in 
Protozoa  ;  but  these  are  for  the  most  part  cases  in  which  the  centro- 
some is  in  relation,  not  only  to  the  kinetic  functions  of  the  nucleus, 
but  also  to  those  of  other  cell-organs,  as  will  be  described  presently. 
Nuclei  containing  centrosomes  have  been  termed  "  centronuclei  " 
by  Boveri. 

The  centrosome  is  seen,  as  a  general  rule,  under  the  form  of  a 
minute  grain,  or  centriole.     This  is  the  form  in  which  it  occurs 
invariably  when  it  has  an  intranuclear  position,  lodged  within  the 
karyosome.     But  when  it  occurs  outside  the  nucleus,  it  exhibits 
structural  peculiarities  which  may  vary  at  different  periods,  and 
it  often  presents  cyclical  changes  corresponding  to  different  phases 
of  the  activity  of  the  nucleus.     Thus,  in  Actinosphcerium,  Hertwig 
(64)  describes  the  centrosome  at  its  first  appearance  as  a  relatively 
large  body  of  spongy  structure,  formed  at  one  pole  of  the  nucleus  from 
extruded  portions  of  the  achroniatinic  reticulum  (Fig.  37,  A — E). 
At  this  stage,  in  which  the  centrosome  is  termed  a  centrosphere,  it 
lies  in  a  patch  of  archoplasm.  and  is  the  centre  of  a  well-marked 
system  of  radiations.     The  centrosphere  then  gives  rise,  by  con- 
densation of  its  substance,  to  two  centrioles,  or  to  one  which  divides, 
and  at  the  same  time  the  archoplasmic  radiations  become  fainter 
and  disappear  (Fig.  37,  F,  G).     The  centrioles  then  take  part  in 
the  division  of  the  nucleus,  and  when  this  process  is  complete  they 
again  become  spongy  centrospheres,  which  go  through  the  same 
series  of  successive  changes  that  have  already  been  described     Ana- 
logous cyclical  changes  of  the  centrosome  have  also  been  described 
in  other  cases,  and  have  led  to  a  conflict  of  opinion  as  to  whether 
the  term  "  centrosome  "  should  be  applied  to  the  whole  centrosomie 
complex,  as  it  may  be  termed,  or  to  the  centrioles,  of  which  many 


THE  NUCLEUS 


81 


may  be  present.  It  is  simplest  in  theory,  and  probably  correct  in 
fact,  to  regard  the  centriole  as  the  primary,  in  many  cases  the  sole, 
constituent  of  the  centrosome — an  element  which  may  be  capable, 
to  a  greater  or  less  extent,  of  changes  in  size  and  structure,  and 
which  multiplies  by  division.  To  the  primary  centrosome  or 


FIG.  37. — Actinosphcerium  eichhorni :  formation  of  the  centrosome.  ^.Concentra- 
tion of  the  nuclear  reticulum  towards  one  pole  of  the  nucleus,  near  which 
the  cytoplasm  appears  free  from  granulations,  forming  the  archoplasm  ; 
B,  0,  D,  passage  of  a  portion  of  the  nuclear  reticulum  to  the  exterior  to  form 
the  "  spongy  centrosome  "  lying  in  the  archoplasm  ;  E,  spongy  centrosome 
with  striations  passing  from  it  through  the  archoplasm  to  the  nucleus  ; 
F,  G,  the  centrosome  passes  back  again  to  the  vicinity  of  the  nucleus  and 
undergoes  a  reduction  of  substance — the  archoplasm  also  diminishes  tem- 
porarily in  quantity  ;  H,  division  of  the  centrosome.  After  Hertwig  (64). 

centriole  there  may  be  added  adventitious  elements  of  protoplasmic 
or  nuclear  origin,  thus  forming  a  centrosomic  complex  which  may 
attain  a  size  relatively  considerable  in  some  cases. 

So  far  the  centrosome  has  been  discussed  only  in  its  relation  to 

6 


82 


THE  PROTOZOA 


the  kinetic  activities  of  the  nucleus,  a  function  which  may  be  re- 
garded as  its  primary  and  most  characteristic  role.  It  may  act 
also,  however,  as  the  centre  of  other  kinetic  functions  of  the  cell- 
body,  especially  in  relation  to  motile  organs  such  as  flagella  ;  it 
then  appears  as  the  so-called  "  basal  granule,"  from  which  the 
flagella  take  origin.  The  basal  granule  appears  as  a  thickening 
at  the  base  of  the  flagellum.  It  may  be  continued  farther  into 
the  cytoplasm,  or  connected  \vith  the  nucleus,  by  means  of  one 

or  more  root-like  processes  known 
as  the  rliizoplast.  A  centrosome 
which  is  in  relation  to  a  motor 
cell-organ  is  termed  generally  a 
blepharoplast.  The  rhizoplast  may 
have  various  origins  ;  in  some  cases 
it  represents  the  centrodesmose 
(p.  103)  which  connects  the  bleph- 
aroplast with  the  nuclear  centro- 
some, or  the  remains  of  such  a 
connection  ;  in  other  cases  it  repre- 
sents the  remains  of  the  nuclear 
spindle  of  the  previous  nuclear 
division,  as  in  the  swarm-spores  of 
Stemonitis  ftaccida  (Jahn,  69)  and 


FIG.  38. — Mastigina  setosa,  after  Gold- 
schmidt  (41).  n.,  [Nucleus  from  which 
the  long  flagellum  arises  ;  the  body 
is  full  of  diatoms  and  other  food- 
bodies.  The  surface  of  the  body  has  a 
covering  of  short  bristle-like  processes. 


FIG.  39. — Connection  of  the  flagellum 
and  the  nucleus  in  Mastigina  setosa. 
A  and  B,  As  seen  in  the  living 
state  ;  C,  after  fixation  and  staining. 
After  Goldschmidt  (41). 


the  collar-cells  of  Heterocoela  (Robertson,  79)  ;  while  in  some 
instances  it  may  be  formed  by  outgrowth  of  root-like  processes, 
of  no  special  cytological  significance,  from  the  blepharoplast. 

The  relation  of  the  nuclear  to  the  kinetic  apparatus  is  best 
studied  in  the  Flagellata,  where  three  principal  conditions  may  be 
distinguished  as  follows  : 

1 .  The  cell-body  contains  but  a  single  centrosome,  which  functions 
also  as  a  blepharoplast  ;  these  two  names,  then,  denote  two  different 
phases  of  activity  of  one  and  the  same  body,  which  is  a  centr<>- 


THE  NUCLEUS 


83 


n. 


some  when  it  is  active  in  relation  to  the  division  of  the  nucleus, 
and  a  blepharoplast  when  it  is  in  connection  with  flagella  or  other 
motile  organs  during  the  resting  state  of  the  nucleus.  In  this, 
probably  the  most  primitive  state  of  things,  there  are,  further,  two 
different  structural  conditions  found  to  occur  in  different  cases. 
First,  the  centrosome  -  blepharoplast  may  be  within,  or  closely 
attached  to,  the  nucleus  ;  secondly,  it  may  be  quite  independent 
of  the  nucleus,  and  some 
distance  from  it  in  the  cell- 
body,  during  the  resting 
state,  of  the  nucleus.  In 
the  first  case — of  which  an 
example  is  seen  in  Mastigina 
(Figs.  38,  39),  paralleled  by 
collar  -  cells  in  the  Leuco- 
soleniid  type  of  calcareous 
sponges — the  flagellum  ap- 
pears to  arise  directly  from 
the  nucleus ;  in  the  second 
case,  exemplified  by  Mas- 
tigella  (Fig.  40),  and  by 
collar-cells  of  the  Clathrinid 
type,  the  flagellum  takes 
origin  quite  independently 
of  the  resting  nucleus.  In 
both  cases  alike,  the  flagel- 
lum generally  disappears  \  FK,  ±Q.  —  Mastigdla  i-itn-n,  after 
before  division  of  the  nucleus  \  Goldschmidt  (41).  n,  Nucleus, 
-UQ  fi, r  KlArJiflT-rml'Kjf  \  almost  obscured  by  the  mass  of 
begins  ,  blepnaroplas  \  food-bodies  of  various  kinds  in 
becomes  the  centrosome,  j  the  cytoplasm, 
divides,  and  initiates  the 
division  of  the  nucleus  ;  the 
new  flagella  of  the  daughter- 
cells  grow  out  from  the  two 
daughter  -  centrosomes  dur- 
incr  or  after  division  of  the 

O 

nucleus,  and  in  either  case, 

when  the  two  daughter-cells  are  completely  formed,  their  centro- 
somes, as  blepharoplasts,  remain  as  the  basal  granules  from  whicb 
the  flagella  arise. 

2.  The  cell-body  contains  more  than  one  body  of  centrosomic 
nature— namely,  a  definitive  centrosome,  in  relation  to  the  single 
nucleus,  and,  in  addition  to  this,  one  or  more  blepharoplasts  in 
relation  to  motile  organs.     Then,  when  division  of  the  eel! 
place,  one  of  two  things  may  happen. 


84 


THE  PROTOZOA 


In  the  first  place,  the  flagellum  or  flagella  may  disappear,  together 
with  their  blepharoplasts  ;  the  nuclear  centrosome  divides  into 
two,  which  control  the  division  of  the  nucleus  in  the  usual  way,  and 
the  centrosome  of  each  daughter-nucleus  divides  again  into  two, 
one  of  which  is  the  definitive  centrosome,  the  other  the  blepharo- 
plast,  of  the  daughter-cell.  The  new  flagella  may  either  grow  out 
from  the  daughter-centrosomes  before  they  divide,  and  be  carried 
off,  as  it  were,  by  the  product  of  division  which  becomes  the 


FIG.  41. — Stages  in  the  division  of  Spongomonas  splendida,  to  show  different  ways 
in  which  the  daughter-flagella  arise.  Compare  the  stages  of  S.  uvella  (Fig.  42). 
A,  Resting  condition  of  the  cell.  B,  Early  stage  of  mitosis;  the  two  flagella 
of  the  parent  cell  are  in  process  of  absorption,  together  with  their  blepharo- 
plasts. G,  Daughter-flagella  arising  at  the  poles  of  the  nuclear  spindle  ;  the 
flagella  of  the  parent  have  disappeared.  D,  Nucleus  completely  divided  ; 
one  pair  of  daughter-flagella  are  seen  arising  from  the  karyosome  of  a  daughter- 
nucleus,  in  which  the  blepharoplasts  are  still  enclosed  ;  in  the  other  daughter- 
nucleus  the  blepharoplasts  have  become  distinct  and  the  flagella  are  given 
off  from  them.  E,  Similar  stage  ;  the  two  pairs  of  blepharoplasts,  from  which 
the  flagella  arise,  are  quite  independent  of  the  two  daughter-nuclei.  After 
Hartmann  and  Chagas  (62),  magnification  about  2,400  diameters. 

blepharoplast  (Fig.  41,  C,  D,  E  ;  Fig.  42,  C),  or  they  may  not  arise 
from  the  blepharoplasts  until  a  later  period,  after  they  have 
separated  off  from  the  definitive  centrosomes  (Fig.  42,  D,  E,  F). 
The  examples  figured  show  that  these  differences  in  the  origin  of 
the  flagella  may  occur  as  developmental  variations  in  one  and  the 
same  species. 

In  the  second  place,  the  blepharoplasts  and  flagella"may  persist 
throughout  the  division  of  the  cell ;  then  either  the  old  flagellum 
and  blepharoplast  are  retained  by  one  daughter-cell,  while  the  other 


THE  NUCLEUS 


85 


forms  a  new  blepharoplast  from  its  centrosome,  and  subsequently 
a  new  flagellum ;  or  the  blepharoplast  of  the  parent  cell  divides 
independently  to  form  the  blepharoplasts  of  the  daughter-cells 
(Fig.  43).  In  this  last  type,  the  blepharoplast,  though  obviously 
a  body  of  centrosomic  nature,  acquires  a  more  or  less  complete 
independence  of  the  definitive  centrosome,  and  becomes  a  distinct 
cell-organ,  permanent  for  at  least  a  certain  number  of  cell-genera- 
tions ;  it  may  multiply  and  undergo  various  structural  complica- 
tions, to  be  described  presently. 


FIG.  42. — Stages  in  the  division  of  Spongomonas  uvella.     A,  Resting  condition  of 
the  cell ;  two  flagella  arise,  each  from  one  of  a  pair  of  blepharoplasts  (diplo- 
some)  ;  the  nucleus  contains  a  large  karyosorne,  in  which  the  centriole  is 
lodged,  and  a  few  irregular  grains  of  peripheral  chromatin  in  the  nuclear  cavity. 
B,  Early  stage  of  mitosis  ;  an  achromatinic  spindle  is  formed  with  the  centrioles 
at  the  poles,  one  centriole  (on  the  right)  having  already  divided  into  two  ; 
the  chromatin,   both  peripheral  and  central,   has  united  to  form  a  dense 
equatorial  plate  in  which  separate  chromosomes  cannot  be  discerned  ;  the 
flagella  have   disappeared,  together   with  their  blepharoplasts.     G,  Similar 
stage  in  which  the  daughter-flagella  are  growing  out  precociously  from  the 
centrioles,  one  on  the  left,  two  on  the  right.     D,  Later  stage  in  which  the 
equatorial  plate  has  split  into  two  daughter-plates,  but  no  flagella  have  as 
yet  grown  out  from  the  centrioles,  of  which  there  are  two  at  each  pole.     E, 
Division  of  the  nucleus  nearly  complete  ;  no  flagella.     F,  Nucleus  completely 
divided,  daughter-nuclei  in  process  of  reconstruction  ;  from  each  a  pair  of 
blepharoplasts  has  been  budded  off,  still  connected  by  a  centrodesmose  with 
the  centriole  contained  in  the  karyosome  ;  a  pair  of  daughter-flagella  has 
arisen  from  one  pair  of  blepharoplasts,  but  not  as  yet  from  the  other.     After 
Hartmann  and  Chagas  (62),  magnification  about  2,400. 

3.  In  certain  flagellates — for  example,  trypanosomes  and  allied 
forms  ("  Binucleata  ") — the  cell-body  contains  two  nuclei,  as  already 
noted :  a  trophonucleus  and  a  kinetonucleus.  To  what  extent 
these  nuclei  are  provided  with  centrosomes  is  at  present  a  little 
doubtful  ;  probably  this  point  is  one  which  varies  in  different  cases 
(compare  Wenyon,  84).  There  are,  however,  three  chief  possi- 
bilities :  (a)  There  may  be  but  a  single  centrosome,  that  of  the 
kinetonucleus,  which  acts  both  as  blepharoplast  and  division-centre 


FIG.  43. — Stages  in  the  division  of  Polytomdla  agilis.  A,  Resting  condition  of  the 
cell ;  the  four  nagella  arise  from  four  blepharoplasts  which  are  connected 
by  a  rhizoplast  with  the  nucleus  ;  in  the  nucleus  is  seen  a  large  karyosonie, 
which  contains  the  centriole  and  is  surrounded  by  a  peripheral  zone  of 
chromatin-grains  in  a  nuclear  reticuluni.  B,  Early  stage  of  mitosis  ;  the  karyo- 
some  is  dividing  to  form  a  bar  of  chromatin  occupying  the  axis  of  the  achro- 
matinic  spindle,  at  the  equator  of  which  a  plate  of  chromosomes  is  formed 
by  the  peripheral  chromatin  of  the  last  stage.  C,  Later  stage ;  the  karyosonie 
has  divided  completely,  forming  two  masses  at  the  poles  of  the  spindle  con- 
nected by  a  centrodesmose.  D,  The  spindle  has  become  elongated,  and  the 
equatorial  plate  has  split ;  the  centrioles  are  seen  connected  by  the  centro- 
desmose. E,  Division  advancing  ;  the  polar  masses  have  become  cap-shaped, 
and  the  daughter-plates  of  chromosomes  have  fused  into  conical  masses  ; 
centrioles  and  centrodesmose  still  visible.  F,  Division  of  body  beginning. 
G,  Centrodesmose  broken  through,  the  two  daughter-nuclei  separate.  H,  I,  J, 
Division  of  cell  complete,  one  daughter-cell  only  represented,  to  show  the 
reconstitution  of  the  daughter-nucleus  ;  the  polar  cap  becomes  the  karyosonie, 
enclosing  the  centriole  ;  the  conical  mass  formed  in  Stage  E  by  fusion  of  the 
chromosomes  in  the  daughter-plates  becomes  resolved  gradually  into 
chromatin-grains  again,  and  so  forms  the  peripheral  zone  of  the  daughter- 
nucleus  ;  each  daughter-cell  has  two  of  the  four  blepharoplasts  and  flagella 
of  the  parent,  and  the  number  is  doubtless  made  up  to  four  again  by  division 
after  the  daughter-cells  are  set  free.  After  Aragao  (45). 


THE  NUCLEUS  87 

for  the  cell  ;  then,  when  cell-division  takes  place,  the  kinetonucleus 
first  divides,  and  the  two  products  of  its  division  place  themselves 
on  each  side  of  the  trophonucleus  and  act  as  its  centrosomes,  as 
described  by  Franca  and  Athias  (56)*  ;  (b)  the  trophonucleus  may 
have  a  centrosome  of  its  own,  lodged  in  the  karyosome,  in  addition 
to  the  centrosome-blepharoplast  in  connection  with  the  kineto- 
nucleus ;  this  is  probably  the  most  usual  condition  with  two  sub- 
ordinate variations,  according  as  the  centrosome-blepharoplast  is 
lodged  within  the  kinetonucleus,  as  in  Leishmania  tropica  (Wenyon, 
84),  or  is  situated  close  beside  it,  as  in  most  trypanosomes  ;  in  either 
case  the  kinetonucleus  and  trophonucleus  divide  quite  independently 
of  one  another,  as  commonly  seen  ;  (c)  it  is  possible,  but  perhaps 
not  very  probable,  that  in  some  cases  there  may  be  a  blepharoplast 
for  the  flagellum  distinct  from  the  centrosomes  of  the  two  nuclei ; 
such  a  condition,  perhaps,  occurs  in  Trypanoplasma.  In  all  cases 
alike,  division  is  initiated  by  the  centrosome  from  which  the 
flagellum  arises;  next  the  kinetonucleus,  and  lastly  the  tropho- 
nucleus, divide. 

The  various  forms  of  flagellar  insertion  described  in  the  foregoing  para- 
graphs admit  of  a  simple  and  uniform  phylogenetic  explanation.  Starting 
with  a  non-flagellated  organism  in  which  a  simple  protokaryon  contains  a 
single  centriole  (Fig.  44,  (9a),  we  may  suppose  the  flagellum  at  its  first  origin 
to  grow  out  from  the  centriole  in  the  nucleus  (Ob).  No  such  condition  is 
actually  known  amongst  flagellates,  though  it  may  be  compared  to  the  origin 
of  the  axopodia  from  a  central  grain  in  an  Actinophrys-type  of  Heliozoon 
(see  below)  ;  in  the  flagellates  the  centrosome-blepharoplast  always,  ap- 
parently, moves  out  of  the  nucleus,  either  remaining  in  close  proximity  to  it 
(la)  or  becoming  quite  independent  of  it  (lh),  the  two  variations  of  the  first 
type. 

The  second  type  may  be  derived  by  division  of  the  centrosome-blepharo- 
plast to  form  the  definitive  centriole  and  the  blepharoplast ;  the  latter  may 
also  remain  in  close  proximity  to  the  nucleus  (2a)  or  become  quite  independent 
of  it  (2b). 

The  third  type  may  be  supposed  to  arise  from  the  hypothetical  primitive 
condition  (On)  by  supposing  that,  not  the  blepharoplast-centrosome  alone, 
but  the  whole  nucleus,  divides  to  form  two  nuclei  of  unequal  size  and  distinct 
function,  the  trophonucleus  and  kinetonucleus,  each  with  its  own  centriole 
(3%  3b).  The  centriole  of  the  kinetonucleus,  which  is  at  the  same  time  the 
blepharoplast,  may  either  remain  within  the  kinetonucleus  (3b)  or  come  out 
of  it  (3C)  ;  its  relations  to  the  kinetonucleus  are  parallel  to  those  of  the  centro- 
some-blepharoplast to  the  nucleus  in  types  la  and  lb.  Or,  on  the  other  hand, 
the  centrosome-blepharoplast  may  divide  into  a  definitive  kinetonuclear 
centrosome  and  a  true  blepharoplast  (3").  The  condition  with  only  a  single 
centriole  for  both  the  nuclei  may,  if  it  exists,  be  derived  from  3a  or  3b  by 
supposing  that  the  trophonuclear  centrosome  becomes  atrophied. 

When  a  blepharoplast  exists  independently  of  the  nuclear 
apparatus,  it  may  retain  the  form  of  a  single  grain  or  basal  granule 
of  the  flagellum,  when  this  organ  is  single,  or  it  may  multiply  to 

*  The  statements  of  Franca  and  Athias  are  not,  however,  confirmed  by  Lebedefi 
(468),  and  it  may  be  doubted  whether  any  species  of  trypanosome  or  other  "  binu- 
cleate  "  exists  which  has  but  a  siusrle  division-centre  in  the  cell. 


88 


THE  PROTOZOA 


form  two  or  more  grains  when  there  are  numerous  flagella.  Thus, 
in  Lophomonas,  which  shows  the  extreme  of  complication,  there  are 
numerous  basal  granules  corresponding  to  the  tuft  of  flagella 
(Fig.  45).  Each  basal  granule  in  this  case  is  divided  into  a  proximal 


FIG.  44. — Diagrammatic  representation  of  the  possible  phylogenetic  origin  of  the 
different  types  of  flagellar  attachment  in  flagellates.  For  the  sake  of  sim- 
plicity it  is  supposed  that  the  animal  has  but  a  single  flagellum.  O,  Non- 
flagelJated  cell  with  a  centriole  in  the  nucleus  ;  Ob,  in  a  cell  like  the  last  a 
flagellum  arises  from  the  centriole  ;  la,  condition  with  a  flagellum  arising 
close  beside  the  nucleus  ;  lb,  condition  with  the  blepharoplast  quite  separate 
from  the  nucleus  ;  2a,  division  of  the  single  centriole  into  a  definitive  centro- 
some  and  a  blepharoplast,  which  becomes  quite  independent  (2b)  of  the 
nucleus  ;  3a,  division  of  both  nucleus  and  centriole  to  form  distinct  kinetic 
and  trophic  nuclei,  each  with  its  own  centriole  ;  3h,  the  kinetonuclear  centriole 
remains  within  the  nucleus  ;  3C,  the  kinetonuclear  centriole  becomes  distinct 
from  the  nucleus  ;  3d,  condition  with  a  single  centriole  in  the  cell ;  3e,  condition 
with  a  blepharoplast  distinct  from  the  centrioles  of  the^two  nuclei. 

and  a  distal  granule,  and  the  pairs  of  granules  are  arranged  in  a 
ring,  interrupted  at  one  point ;  the  tuft  of  flagella  takes  origin  from 
the  distal  granules  of  the  ring.  When  the  nucleus  divides,  the 
daughter-centrosomes  give  rise  to  new  rings  of  blepharoplasts, 


THE  XUCLEUS 


89 


from  which  daughter-tufts  of  flagella  grow  out ;  the  old  tufts,  with 
their  rings  of  blepharoplasts,  persist  for  some  time  after  the  new 
ones  have  been  formed  (Fig.  45,  C),  but  ultimately  they  degenerate 
and  disappear.  The  ring  of  blepharoplasts  in  Lophomonas  is 


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supported  on  the  edge  of  a  membranous  structure,  or  "  calyx," 
which  in  its  turn  is  surrounded  by  a  peculiar  striated  body,  the 
"  collar  "  of  Grassi,  or  "  parabasal  apparatus  "  of  Janicki  (Fig.  45, 
cl).  Janicki  (71)  has  found  a  corresponding  parabasal  apparatus 
in  other  flagellates,  especially  in  TrichonymphidcB  ;  the  significance 


90  THE  PROTOZOA 

of  this  peculiar  structure  remains  for  the  present  problematical. 
In  the  spores  of  Derbesia,  Davis  ("  Annals  of  Botany,"  xxii., 
pp.  1-20,  plates  i.  and  ii.)  has  described  a  condition  very  similar 
to  that  of  Lopliomonas — namely,  a  double  ring  of  blepharoplasts, 
which,  however,  fuse  together  to  form  a  ring  of  homogeneous 
appearance.  The  blepharoplast-grains  are  given  off  from  the 
nucleus. 

Centrosomic  bodies  may  be  related,  not  only  to  flagella,  but  also 
to  pseudopodia,  especially  in  those  cases  in  which  the  pseudopodia 


FIG.  46. — Actinophrys  sol,  showing  the  axial  filaments  of  the  pseudopodia  centred 
on  the  nucleus.  N,  Nucleus  ;  ps.,  pseudopodia  ;  ax.,  axial  filament ;  c.v., 
contractile  vacuole  ;  f.v.,  food-vacuole.  After  Grenadier. 

have  become  specialized  in  form  and  movement,  as  in  the  Heliozoa. 
In  this  group  the  relationship  of  the  nuclear  apparatus  to  the 
pseudopodia  exhibits  two  types  of  arrangement,  which  are  analo- 
gous to  the  two  arrangements  described  above  in  Mastigina  and 
Mastigella  respectively,  and  which  may  be  explained  by  supposing 
that  in  the  one  case  the  kinetic  centre  lies  within,  in  the  other  case 
without,  the  nucleus  itself.  .  Thus,  in  Actinophrys  (Fig.  46)  the 
numerous  pseudopodia  are  all  centred  on  the  single  nucleus,  in 
which  the  centrosonie  is  contained.  A  variation  of  this  type  is 
described  by  Schaudinn  (43),  in  the  peculiar  multinucleate  form 


THE  NUCLEUS 


91 


Camptonema  nutans,  in  which  a  pseudopodium  arises  directly  from 
each  nucleus  (Fig.  47).*  In  AcantJwcystis  (Fig.  18)  an  example 
is  seen  of  the  second  type,  the  evolution  of  which  can  be  traced 
in  the  actual  development ;  in  the  buds  of  Acanthocystis  a  centriole 
is  contained  in  the  karyosome  of  the  nucleus,  but  during  the  growth 


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of  the  bud  into  the  adult  condition  the  centriole  passes  out  of  the 
nucleus,  and  becomes  the  so-called  "  central  grain  "  of  the  adult, 
a  corpuscle  which  occupies  the  centre  of  the  body,  and  upon  which 

'  In  Actinosphcerium,  however,  there  is  no  relationship  between  the  pseudopodia 
and  the  nuclei.  From  the  researches  of  Hertwig  (64),  it  is  evident  that  in  this 
form  the  centrosomes  are  lost  altogether  during  the  vegetative  life,  and  are  formed 
only  in  certain  phases  of  the  development  (p.  115). 


92  THE  PROTOZOA 

the  axial  filaments  of  the  pseudopodia  are  centred,  while  the  nucleus 
is  displaced  to  one  side  and  becomes  excentric  in  position  ;  when 
the  cell  enters  upon  division,  the  central  grain  becomes  the  centro- 
some  (Fig.  64). 

From  the  condition  seen  in  Acanfkocystis,  it  is  not  difficult  to  explain  the 
state  of  things  which  has  been  described  by  Zuelzer  (86)  in  the  remarkable 
form  Wagner ella  (p.  246).  Here  also  the  buds  formed  possess  each  a  single 
nucleus  containing  a  centriole  ;  in  this  condition  they  may  multiply  by  fission 
with  mitosis,  in  which  the  centriole  functions  as  a  centrosome.  When  the 
buds  develop  into  the  adult  form,  a  centriole  is  extruded  from  the  nucleus 
to  form  the  central  grain.  The  organism  attaches  itself,  and  the  body  becomes 
divided  into  three  regions — head,  stalk,  and  basal  plate  (Fig.  48).  The 
nucleus  travels  down  into  the  basal  plate,  while  the  central  grain  remains 
in  the  head  and  functions  as  the  kinetic  centre  of  the  pseudopodia.  becoming 
very  complicated  in  structure.  It  consists  of  a  centrosome  surrounded  by  a 
sphere,  which  is  perhaps  of  the  nature  of  archoplasm,  but  is  stated  to  be 
rich  in  plastin  ;  when  the  pseudopodia  are  extended  the  sphere  shows  well- 
marked  radial  striations.  From  the  centrosome  minute  granules  are  budded 
off.  which  pass  along  the  striations  of  the  sphere  to  its  surface,  and  from  these 
granules  arise  the  delicate  axial  filaments  of  the  pseudopodia  ;  the  basal 
granules  are  therefore  comparable  to  the  ring  of  blepharoplasts  in  Lophomonas. 
When  the  pseudopodia  are  retracted,  the  basal  granules  lie  within  the  sphere, 
immediately  surrounding  the  centrosome,  and  the  radial  striations  of  the 
sphere  vanish.  The  centrosome  itself  varies  in  structure  at  different  times, 
going  through  cyclical  changes,  but  usually  shows  a  distinct  central  granule  or 
centriole. 

When  Wagnerella  divides  by  fission,  the  central  grain  and  the  nucleus 
divide  independently,  and  the  central  grain  does  not  act  as  a  centrosome 
for  the  dividing  nucleus,  which  contains  its  own  centriole.  In  this  form, 
therefore,  the  central  grain,  though  centrosornic  in  origin  and  nature,  loses 
its  primitive  relation  to  the  division  of  the  nucleus,  and  becomes  specialized 
exclusively  as  a  kinetic  centre  for  the  organs  of  locomotion,  a  course  of  evolu- 
tion perfectly  parallel  to  that  which  has  been  traced  above  for  the  blepharo- 
plasts in  their  relation  to  flagella. 

While  there  can  be  but  little  doubt  as  to  the  centrosornic  nature 
of  the  blepharoplasts  or  basal  granules  of  the  flagella,  and  of  the 
central  grains  on  which  the  pseudopodia  of  the  Heliozoa  are  centred, 
the  true  nature  of  the  basal  grains  of  cilia,  on  the  other  hand,  is 
less  certain.  The  majority  of  those  who  have  studied  them  in 
Ciliata  are  of  opinion  that  they  have  nothing  to  do  with  centro- 
somes  (compare  Maier,  73,  and  Schuberg,  44,  and  see  p.  443,  infra)  ; 
but  there  are  certain  observations  which  indicate  that  the  basal 
granules  of  the  cilia  have  a  connection  with  (Collin,  50),  or  an 
origin  from  (Entz,  53),  the  nuclear  apparatus,  in  which  case  they 
may  be  of  the  same  nature  as  the  multiple  blepharoplasts  of  such 
a  form  as  LopJiomonas.  Hertwig  (66)  considers  that  the  basal 
grains  of  the  cilia  may  be  of  centrosornic  nature,  and  that,  if  they 
have  no  connection  with  the  nucleus,  they  afford  support  for  the 
view  that  centrosomes  can  arise  from  the  cytoplasm  as  well  as 
from  the  nuclear  framework.  In  view  of  the  great  structural 
similarity  between  cilia  and  flagella  in  other  respects,  it  seems 


THE  NUCLEUS 


93 


hardly  likely  that  the  basal  granules  would  be  of  a  different  nature 
in  the  two  cases.  The  whole  question  of  the  nature  of  the  basal 
granules  has  been  discussed  in  a  recent  memoir  by  Erhard  (54). 


fflfl 

m 


FIG.  48. — Wagnerella  borealis,  Mereschk.  A,  Whole  specimen 
seen  under  a  low  magnification:  H.,  head  containing 
the  central  grain  ;  P,  stalk  ;  N.,  nucleus  contained  in 
the  basal  plate  of  attachment.  B,  Enlarged  view  of 
the  head,  after  fixation  and  staining  with  iron-haerna- 
toxylin  :  c.,  cuticle  of  the  stalk ;  ps.,  pseudopodia'; 
ax.,  axial  filaments  of  the  pseudopodia,  each  arising 
from  a  basal  granule  ;  e.g.,  central  grain.  After 
Zuelzer  (86). 

Few  problems  in  cytology  have  been  more  discussed  than  the 
question  of  the  nature  and  origin  of  the  centrosome,  and  three 
opposed  views  have  been  put  forward  which  may  be  termed,  re- 
spectively, the  achromatinic  theory,  the  nucleolo  -  ceiitrosomic 
theory,  and  the  nuclear  theory. 


94 


THE  PROTOZOA 


According  to  the  achroraatinic  theory,  the  centrosome  is  "an 
individualized  portion  of  the  achromatinic  nuclear  substance " 
(Hertwig,  66),  a  kinetic  centre  on  Avhich  the  movements  of  the 
framework  are  focussed.  The  essential  and  primary  constituent 
of  the  centrosome  is  the  centriole,  and  so  long  as  the  centrosome 
remains  intranuclear,  as  in  perhaps  the  majority  of  Protozoa,  it 
consists  of  the  centriole  alone.  When,  however,  the  centrosome 
becomes  extranuclear,  as  in  many  Protozoa  and  almost  universally 


FIG.  49. — Paramceba  eilhardi :  stages  of  the  life-cycle.  A,  Amoeba  in  the  vegetative 
stage:  N.,  nucleus;  n.k.,  "  Nebenkern  "  ;  d.,  ingested  diatom.  B,  0,  D, 
Stages  in  the  multiplication  of  the  encysted  amoeba  ;  in  B  the  Nebenkern 
has  divided  up,  the  nucleus  is  still  undivided  ;  in  C  the  nucleus  has  divided 
up  into  a  number  of  daughter-nuclei,  each  of  which  has  paired  with  a  daughter- 
Nebenkern  ;  in  D  the  body  has  divided  into  a  number  of  daughter-cells,  each 
containing  a  nucleus  and  a  Nebenkern.  E,  A  free-swimming  flagellula,  derived 
from  one  of  the  daughter-cells  in  D,  and  containing  a  nucleus  and  a  Nebenkern. 
F,  G,  H,  I,  Four  stages  of  the  division  of  a  flagellula  ;  in  F  the  Nebenkern  is 
dividing  ;  in  G  the  two  halves  of  the  Nebenkern  have  placed  themselves  on 
each  side  of  the  nucleus,  which  is  preparing  for  division  ;  H,  stage  of  the 
nuclear  spindle  with  the  two  halves  of  the  Nebenkern  at  each  pole  ;  in  /  the 
nuclear  division  is  nearly  complete,  and  the  body  is  beginning  to  divide.  After 
Schaudinn  (81),  all  figures  magnified  about  500  diameters. 

in  the  cells  of  the  higher  animals  and  plants,  accessory  oytoplasmic 
elements  may  be  added  to  the  centriole  to  form  a  centrosomic 
complex.  A  point  still  undecided,  on  the  theory  that  centrosomes 
are  of  achromatinic  origin,  is  whether  or  no  these  bodies  can  be 
formed,  in  some  cases,  in  the  cytoplasm  also,  as  maintained  by 
some  authorities.  On  Hertwig's  view,  mentioned  above,  that  the 
achromatinic  substance  of  the  nucleus  is  identical  in  nature  with  the 
ground-substance  of  the  general  protoplasm,  it  follows  that  material 
for  the  formation  of  the  centrosome  must  be  present  in  the  cy1<> 


THE  NUCLEUS  95 

plasm  no  less  than  in  the  nucleus.  Biitschli  (3)  considers  it  possible 
that  the  centrosome  might  have  been  originally  a  cytoplasmic 
structure,  which  had  nothing  to  do  with  the  nucleus,  but  became 
included  in  it  when  a  nuclear  membrane  was  formed. 

Attention  must  be  drawn  here  to  the  remarkable  genus  Paramceba  (Fig.  49) 
founded  by  Schaudinn  for  the  species  P.  eilhardi  (see  p.  228).  In  this  form 
there  is  present  beside  the  nucleus  a  body  which  was  termed  the  "  Neben- 
kern," consisting  of  a  darkly-staining  middle  piece,  at  each  end  of  which 
is  a  cap  of  clear  substance.  The  Nebenkern  has  generally  been  considered 
to  represent  a  centrosome,  and  Chatton  (49)  has  put  forward  the  suggestion 
that  it  may  correspond  to  a  karyosonie  or  a  portion  of  a  karyosorne  that  has 
passed  out  of  the  nucleus  with  the  centrosome.  Recently,  however,  Janicki 
(71'5)  has  described  two  new  species  of  Paramosba,  and  puts  quite  a  different 
interpretation  upon  the  Nebenkern.  He  regards  the  middle  piece  as  chro- 
matin.  the  clear  caps  as  archoplasmic  masses,  each  of  which  contains  a 
centrosome  ;  and  he  considers  the  entire  structure  "  as  a  second  nucleus, 
as  it  were,  fixed  in  division,  in  which  the  state  of  division  has  become  the 
permanent  form."  He  proposes  to  replace  Schaudinn's  term  "  Nebenkern  " 
by  the  term  "nucleus  secundus, "  and  considers  it  especially  comparable  to 
the  "  sphere  "  of  Noctiluca  (Fig.  65).  Division  of  the  nucleus  and  Nebenkern 
takes  place  quite  independently  of  one  another. 

On  the  nucleolo-centrosomic  theory,  the  whole  karyosorne  with 
the  contained  centriole,  as  found  in  many  Protozoa,  is  compared 
with  the  complex  extranuclear  centrosome  of  the  higher  organisms. 
It  is  clear,  however,  that  the  karyosonie  consists  chiefly  of  plastin 
which  is  impregnated  to  a  greater  or  less  extent  with  chromatin, 
and  in  which  the  centriole  is  imbedded.  As  Chatton  (49)  has 
pointed  out,  the  three  elements  which  compose  the  karyosorne  are 
independent  of  each  other.  When  the  centriole  and  chromatin 
have  left  the  karyosorne,  the  plastin-mass  remaining  behind  is 
homologous  in  every  way  with  the  iiucleolus  of  the  metazoan  cell, 
and  the  only  element  common  to  both  the  karyosonie  of  Protozoa 
and  the  centrosome  of  Metazoa  is  the  centriole. 

The  nuclear  theory  of  the  centrosome  is  associated  especially 
with. the  names  of  Schaudinn  and,  in  more  recent  times,  of  Hart- 
niami  and  Prowazek  (63).  According  to  this  view,  the  centrosome 
represents  a  second  cell-nucleus,  and  every  cell  is  to  be  regarded 
as  primarily  binucleate.  The  starting-point  of  the  evolutionary 
series  would  be  such  a  form  as  Amoeba  binucleata,  which  possesses 
two  similar  and  equivalent  nuclei.  In  the  next  stage  of  evolution 
one  of  the  two  nuclei  became  specialized  more  for  kinetic,  the  other 
for  trophic,  functions  ;  examples  of  this  stage  would  be  furnished 
by  Paramceba  (Fig.  49),  with  its  nucleus  and  "  Xebenkern,"  and  by 
a  trypanosome,  with  its  trophonucleus  and  kinetonucleus,  the 
Nebenkern  of  the  first  and  the  kinetonucleus  of  the  second  repre- 
senting the  kinetic  nucleus.  The  central  grain  of  the  Heliozoa  or 
the  extranuclear  centrosome  of  the  Metazoa  would  represent  the 
final  stage  of  evolution,  namely,  a  kinetic  nucleus  deprived  of  all 


9G  THE  PROTOZOA 

chromatin-elements ;  while  the  cell-nucleus  proper  would  represent 
the  trophic  nucleus  deprived  of  all  kinetic  elements. 

On  the  other  hand,  the  condition  in  amoebae  and  similar  or- 
ganisms, where  the  cell  appears  to  contain  but  a  single  nucleus 
which  includes  the  kinetic  centres,  is  explained  by  supposing  that 
here  the  kinetic  nucleus  is  eiicapsuled  in  the  trophic  nucleus,  and 
is  represented  by  the  karyosome  with  its  centriole  ;  hence  the 
supporters  of  this  theory  term  the  type  of  nucleus  characterized 
by  a  large  karyosome  an  "  amphinucleus  "  or  "  amphikaryon," 
and,  in  their  descriptions  of  such  nuclei,  they  speak  of  the  outer 
nucleus  (peripheral  zone  of  chromatin)  and  the  inner  nucleus 
(karyosome). 

The  reasons  against  homologizing  the  karyosome  and  the  extra- 
nuclear  centrosome  have  been  stated  already.  Against  the  theory 
of  binuclearity  it  may  be  urged  further — First,  that  to  regard  the 
protokaryon-type  of  nucleus  seen  in  the  most  primitive  forms  of 
Sarcodiiia  and  Flagellata  as  a  secondary  condition  is  a  complete 
inversion  of  what  is,  to  all  appearance,  the  natural  series  of  evolu- 
tion of  the  nuclear  apparatus  ;  secondly,  that  the  binucleate  con- 
dition of  trypanosomes  and  allied  forms  is  clearly,  by  comparison 
with  other  Flagellates,  a  specialized  condition  ;  the  trophonucleus 
of  trypanosomes  also  contains  a  karyosome  and  centriole,  and 
would  therefore  be  an  "  amphikaryon,"  on  this  theory  ;  thirdly, 
that  the  binuclear  theory  still  leaves  the  centriole  as  a  kinetic 
centre  of  achromatinic  origin,  which  is  present  in  both  trophonucleus 
and  kinetonucleus  of  trypanosomes,  in  both  nucleus  and  central 
grain  of  Heliozoa  (Wagnerella),  etc.  All  that  the  binuclear  theory 
is  capable  of  explaining  is  the  secondary  elements  of  the  extra- 
nuclear  centrosomic  complex.  That  the  centriole  is  a  body  of 
intranuclear  origin  and  formation  is  shown  clearly  by  its  presence 
in  nuclei  of  the  primitive  karyosomatic  type  which  arise,  not  by 
division  of  pre-existing  nuclei,  but  by  aggregation  and  organization 
of  clumps  of  chromidia.  It  should  be  added  that,  in  its  most  recent 
exposition  by  Hartmann  (61),  the  theory  of  binuclearity  has 
undergone  considerable  modification  and  restriction. 

Having  considered  now  the  structure  and  composition  of  the 
nucleus  in  its  principal  types  and  morphological  variations,  it 
remains  to  attempt  to  establish  a  more  precise  conception  as  to 
what  exactly  is  meant  by  a  nucleus.  It  is  evident,  in  the  first 
place,  that  the  essential  component  of  a  nucleus,  never  absent,  is 
chromatin  ;  but  it  is  equally  clear,  in  the  second  place,  that  a  simple 
mass,  or  several  such  masses,  of  chromatin,  do  not  by  themselves 
constitute  a  nucleus  in  the  true  sense  of  the  word.  The  word  "  chro- 
matin "  connotes  an  essentially  physiological  and  biological  con- 
ception, as  it  were,  of  a  substance,  far  from  uniform  in  its  chemical 


THE  NUCLEUS  97 

nature,  which  has  certain  definite  relations  to  the  life-history  and 
vital  activities  of  the  cell.  The  word  "  nucleus,"  on  the  other  hand, 
as  many  authorities  and  more  recently  Dobell  (52)  have  pointed 
out,  is  essentially  a  morphological  conception,  as  of  a  body,  con- 
tained in  the  cell,  which  exhibits  a  structure  and  organization  of 
a  certain  complexity,  and  in  which  the  essential  constituents,  the 
chromatin-particles,  are  distributed,  lodged,  and  maintained,  in 
the  midst  of  achromatinic  elements  which  exhibit  an  organized 
arrangement,  variable  in  different  species,  but  more  or  less  constant 
in  the  corresponding  phases  of  the  same  species.  If  this  standpoint 
be  accepted,  and  the  nucleus  be  regarded  as  an  essentially  morpho- 
logical conception,  it  seems  to  me  remarkable  that  Dobell,  in 
his  valuable  memoir  on  the  cytology  of  the  bacteria,  should  apply 
the  term  "  nucleus  "  to  a  single  grain  of  chromatin,  or  to  a  collection 
of  such  grains,  and  should  speak  of  a  nucleus  ' '  in  the  form  of 
chroniidia  scattered  through  the  cell,"  or  "  in  the  form  of  a  discrete 
system  of  granules  (chroniidia), "  phrases  which  are  self-contra- 
dictory on  the  principles  that  he  himself  has  laid  down. 

We  are  confronted,  nevertheless,  with  a  considerable  difficulty 
when  we  attempt  to  state  exactly  what  amount  of  organization 
and  structural  complexity  is  essential  to  the  morphological  concep- 
tion of  a  nucleus.  If,  as  is  probable  in  phylogeny,  and  certainly 
occurs  frequently  in  ontogeny  (compare  Fig.  32),  the  nucleus  arises 
from  a  primitive  chromidial  condition  of  scattered,  unorganized 
chromatin,  at  what  point  does  the  mass  cease  to  be  a  chromidiurq 
and  become  a  nucleus  ?  This  is  a  question  very  difficult  to  answer 
at  present,  a  verbal  and  logical  difficulty  such  as  occurs  in  all  cases 
where  a  distinction  has  to  be  drawn  between  two  things  which 
shade  off,  the  one  into  the  other,  by  infinite  gradations,  but  which 
does  not,  nevertheless,  render  such  distinctions  invalid,  any  more 
than  the  gradual  transition  from  spring  to  summer  does  away  with 
the  distinction  between  the  seasons.  Hartmann  and  his  school 
consider  the  possession  of  a  centriole  as  the  criterion  of  a  nucleus 
(see  Nagler,  76)  ;  but  it  cannot  be  considered  as  established,  in 
the  present  state  of  knowledge,  that  all  nuclei  have  centrioles  or 
centrosomes.  All  that  can  be  said  is  that,  as  soon  as  a  mass  or  a 
number  of  particles  of  chromatin  begin  to  concentrate  and  separate 
themselves  from  the  surrounding  protoplasm,  with  formation  of 
distinct  nuclear  sap  and  appearance  of  achromatinic  supporting 
elements,  we  have  the  beginning  at  least  of  that  definite  organiza- 
tion and  structural  complexity  which  is  the  criterion  of  a  nucleus 
as  distinguished  from  a  chromidial  mass. 

In  the  first  chapter  of  this  book  a  distinction  was  drawn  between 
organisms  of  the  "  cellular ':  grade,  with  distinct  nucleus  and 
cytoplasm,  and  those  of  the  "  bacterial  '  grade,  in  which  the 

7 


98  THE  PROTOZOA 

chromatin  does  not  form  a  distinct  nucleus.  In  all  Protozoa  there 
is  a  true  nucleus  in  at  least  the  principal  stages  of  the. life-history, 
and  it  is  obvious  that  the  recognition  of  a  cellular  grade,  charac- 
terized by  the  possession  of  a  true  nucleus,  postulates  that  the  first 
origin  and  evolution  of  the  nucleus  must  be  sought  amongst  those 
organisms  which  have  been  classed,  speaking  broadly,  as  the 
bacterial  grade.  We  may  expect,  therefore,  to  find  in  organisms 
which  stand  on  the  plane  of  morphological  differentiation  which 
characterizes  the  bacteria  the  early  stages  of  the  evolution  of  the 
nucleus  from  the  primitive  chromidial  condition,  and  even  cases 
in  which  the  condition  of  a  true  nucleus  has  been  reached.  The 
matter  cannot  be  discussed  further  here,  where  it  must  suffice  to 
establish  the  existence  of  true  nuclei  in  Protozoa  ;  but  Dobell  (52) 
has  described  an  interesting  series  of  conditions  which  may  be 
regarded  as  stages  in  the  evolution  of  nuclei  amongst  bacterial 
organisms. 

Since  the  possession  of  a  true  nucleus  has  been  regarded  here 
as  the  criterion  of  the  cellular  grade  of  organization,  it  is  necessary 
to  discuss  briefly  the  meaning  and  application  of  the  term  "  cell." 
By  many,  perhaps  most  modern  writers,  the  cell  has  been  regarded 
as  the  elementary  vital  unit,  than  which  there  exists  nothing 
fcimpler  amongst  living  beings.  In  this  sense  the  word  "  cell  "  becomes 
synonymous  with  the  term  "  micro-organism,"  "protist,"  or  any  other 
word  used  to  denote  living  beings  of  the  most  primitive  type  : 
"  tout  ce  qui  vit  riest  que  cellules  "  (Delage  and  Herouard,  6).  The 
word  "  cell  "  was,  however,  applied  originally  to  the  elements  that 
built  up  the  tissues  of  animals  and  plants.  At  first,  as  the  word 
cell  implies,  it  was  used  to  denote  only  the  enclosing  membrane  or 
framework  ;  but  when  it  became  apparent  that  the  membrane  was 
of  secondary  importance,  it  was  transferred  to  the  contained  stuff, 
and  so  came  to  signify  a  structural  element  in  which  the  living 
substance,  protoplasm,  is  differentiated  into  two  distinct  parts- 
nucleus  and  cytoplasm.  If  the  term  "  cell  "  is  not  to  become  so 
vague  and  indefinite  in  its  significance  as  to  be  absolutely  meaning- 
less, it  is  best  to  restrict  its  application  to  living  organisms  which 
have  reached  this  degree  of  differentiation.  Dobell  considers  that 
all  Protista  are  nucleated  organisms  ;  in  the  preceding  paragraphs 
reasons  have  been  advanced  against  accepting  this  proposition  as 
a  statement  of  fact,  and  from  the  point  of  view  of  phylogenetic 
speculation,  I,  at  least,  find  it  difficult  to  believe  that  the  earliest 
form  of  life  could  have  been  an  organism  "in  which  the  living  sub- 
stance was  differentiated  ab  initio  into  distinct  nucleus  and  cyto- 
plasm. 

In  my  opinion  the  cell,  as  defined  above — that  is  to  say,  an 
organism  in  which  the  living  substance,  protoplasm,  has  become 


THE  NUCLEUS  99 

differentiated  into  two  parts,  a  nucleus,  in  the  morphological  sense, 
distinct  from  the  cytoplasm — does  not  represent  the  primary  and 
universal  form  of  the  living  organism  or  unit,  but  is  to  be  con- 
sidered as  a  stage  in  the  evolution  of  living  beings,  a  stage  which 
many  living  beings  have  not  reached.  Thus  a  bacterial  type  of 
organism,  in  which  the  chromatin  is  scattered  through  the  proto- 
plasmic body  in  the  form  of  chromidial  granules,  and  which  there- 
fore does  not  possess  a  true  nucleus,  is  not  to  be  regarded  as  a  cell, 
but  as  representing  a  condition  antecedent  to  the  evolution  of 
the  true  cellular  type  of  structure.  In  all  Protozoa,  on  the  other 
hand,  the  entire  plan  of  the  organization  is  founded  on  the  type  of 
the  cell,  which  is  to  be  regarded  as  the  starting-point  in  the  evolu- 
tion of  the  entire  animal  and  vegetable  kingdoms  (compare  Min- 
chin,  75).  This  point  will  be  discussed  further  in  a  subsequent 
chapter  (p.  464). 


Bibliography. — For  references  see  p.  477. 


CHAPTER  VII 
THE  REPRODUCTION  OF  THE  PROTOZOA 

THE  methods  by  which  reproduction  is  effected  amongst  the 
Protozoa  vary  greatly  in  matters  of  detail,  as  will  be  seen  ;  but  the 
obvious  diversity  in  method  throws  into  greater  relief  the  under- 
lying unity  in  principle.  In  Protozoa,  as  in  Protista  generally, 
reproduction  takes  place  always  by  nieans  of  some  form  of  fission— 
that  is  to  say,  division  or  cleavage  of  the  body  into  two  or  more 
parts,  which  are  set  free  as  the  daughter-individuals.  An  essential 
part  of  the  process  is  the  partition  amongst  the  daughter-individuals 
of  at  least  some  part  of  the  chromatin-substance  possessed  by  the 
parent.  Hence  fission  of  the  cell-body  as  a  whole  is  always  pre- 
ceded by  division  of  the  nucleus ;  and  if  chromidia  are  present,  they 
also  are  divided  amongst  the  products  of  the  fission  of  the  body. 
On  the  other  hand,  division  of  the  nucleus  is  not  necessarily 
followed  at  once  by  division  of  the  body. 

Considering  the  methods  by  which  fission  is  effected  from  a 
general  standpoint,  we  may  distinguish  three  chief  types  of  repro- 
duction, each  of  which  may  show  subordinate  variations  : 

1.  Division  of  the  nucleus,  or,  if  there  are  two  differentiated 
nuclei,  division  of  each  of  them,  is  followed  by  division  of  the  body  ; 
this  is  the  commonest  and  most  typical  mode  of  reproduction, 
known  as  simple  or  binary  fission. 

2.  Division  of  the  nucleus  or  of  each  of  two  differentiated  nuclei 
is  not  followed  immediately  by  corresponding  divisions  of  the  body, 
but  may  be  repeated  several  times,  and  so  give  rise  to  a  multi- 
nucleate  condition  of  the  body,  which  may  be— 

((/)  Temporary,  and  soon  followed  by  cleavage  of  the  body  into 
as  many  daughter-individuals  as  there  are  nuclei  or  pairs  of  dif- 
ferentiated nuclei ;  this  method  is  known  as  multiple  fission  (Fig. , 
127)  ;  or  it  may  be— 

(6)  Permanent,  giving  rise  to  a  multinucleate  body  which  is  termed 
a  plasmodium.  Then  division  of  the  body  may  take  place  at  any 
time  by  cleavage  of  the  body  into  two  or  more  multinucleate 
parts  ;  this  process  is  known,  as  plasmotomy.  Ultimately,  however, 
in  all  cases  a  plasmodium  breaks  up  by  multiple  fission  into  uni- 

100 


THE  REPRODUCTION  OF  THE  PROTOZOA  101 

nucleate  individuals  at  the  end  of  a  longer  or  shorter  vegetative 
existence  during  which  it  may  have  multiplied  frequently  by 
plasmotomy. 

The  process  of  fission  must  now  be  considered  in  more  detail, 
beginning  with — 

1.  Division  of  the  Nucleus. — As  in  the  case  of  the  cell-body  as 
a  whole,  the  division  of  the  nucleus  is  effected  in  various  ways. 
Probably  the  most  primitive  type  is  that  in  which  the  nucleus 
becomes  resolved  into  chromidia,  from  which,  again,  secondary 
daughter-nuclei  are  reconstituted.  This  type  of  division  may  be 
termed  "  chromidial  fragmentation."  It  is  of  comparatively  rare 
occurrence,  but  examples  of  it  are  found  among  Sarcodina  and 
Sporozoa.  In  Ecliinopyxis  two  daughter-nuclei  are  formed  in  this 
way  (Hertwig,  66,  p.  8).  In  other  cases  numerous  daughter-nuclei 
may  arise,  as  in  the  formation  of  the  nuclei  of  the  microgametes 
in  Coccidium  (Fig.  50),  where  the  parent  nucleus  gives  off  into  the 
cytoplasm  a  fine  dust  of  chromidial  particles  wrhich  travel  to  the 
surface  of  the  cell  and  become  concentrated  at  a  number  of  spots 
to  form  the  daughter-nuclei. 

True  nuclear  division,  in  which  the  parent  and  daughter -nuclei 
retain  throughout  the  process  their  individuality  and  distinctness 
from  the  cytoplasm,  must  be  distinguished  clearly  from  the  above- 
mentioned  process  of  chromidial  fragmentation.  In  the  vast 
majority  of  cases  the  nucleus  divides  into  two  halves  by  simple  or 
binary  fission,  which,  as  already  stated,  may  be  repeated  several 
times  before  cell-division  takes  place  ;  but  in  a  few  cases  the  nucleus 
divides  simultaneously  into  a  number  of  portions  by  multiple 
fission. 

In  the  cells  of  Metazoa  true  nuclear  division  alone  occurs,  and 
may  follow  one  or  the  other  of  two  sharply-marked  types,  termed 
comprehensively  direct  and  indirect.  In  direct  division  the  nucleus 
is  constricted  simply  into  two  parts,  without  circumstance  or 
ceremony.  In  indirect  division,  on  the  other  hand,  the  nucleus 
goes  through  a  complicated  series  of  changes,  following  each  other 
in  a  definite  order  and  sequence,  the  whole  process  being  known  as 
karyokinesis  or  mitosis.  In  spite,  however,  of  the  intricate  nature 
of  karyokinetic  division,  and  the  variations  in  matters  of  detail 
that  it  exhibits  in  different  cases,  the  whole  process  is  perfectly 
uniform  in  its  general  plan,  and  admits  of  being  described  without 
difficulty  in  generalized  terms.  Such  a  description  is  found  in 
every  textbook  of  biology  at  the  present  time,  and  need  not  be 
repeated  here  ;  it  will  be  sufficient  to  analyze  briefly  the  more 
important  events  that  take  place. 

In  the  process  of  karyokinesis,  the  achromatinic  elements  of  the 
nucleus  furnish  the  active  mechanisms,  while  the  chromatin-sub- 


102 


THE  PROTOZOA 


stance  appears  to  be  the  passive  subject  of  the  changes  that  are 
effected.  With  the  achromatinic  nuclear  elements,  extranuclear 
cytoplasmic  substances,  such  as  archoplasm,  may  collaborate.  After 


FIG.  50. — Formation  of  microgametes  in  Coccidium  schubergi.  A,  Full-grown 
microgametocyte,  with  finely-granular  cytoplasm  and  large  nucleus  con- 
taining a  conspicuous  karyosome  ;  freed  from  the  host-cell.  B,  The  nuclear 
membrane  has  disappeared,  and  the  chromatin,  in  the  form  of  minute  chro- 
midial  granules,  is  passing  out  into  the  cell.  C,  The  chromidia  have  collected 
at  the  periphery  of  the  body  ;  the  karyosome  is  left  at  the  centre,  and  has 
become  pale  through  loss  of  chromatin-substance.  D,  The  chromidia,  seen 
on  the  surface  of  the  body,  are  collecting  together  into  irregular  streaks  and 
clumps.  E,  The  chromatin -streaks  of  the  preceding  stage  are  collecting 
together  into  patches.  F,  The  patches  of  chromatin  of  the  preceding  stage 
have  become  dense  and  closely  packed.  G,  H,  The  patches  of  chromatin 
take  on  a  definite  form  as  the  future  nuclei  of  the  microgametes.  I,  Two 
flagella  grow  out  from  close  to  each  microgamete-nucleus,  and  by  their 
activity  the  microgametes,  consisting  almost  entirely  of  chromatin,  break 
loose  from  the  body  of  the  gametocyte  and  swim  away.  J,  Three  micro - 
gametes,  more  highly  magnified  ;  in  each,  two  flagella  arise  from  the  thicker 
eaid  ;  one  of  the  flagella  (the  shorter)  becomes  free  at  once,  the  other  (the 
longer)  runs  along  the  body  and  becomes  free  at  the  hinder  end.  n.,  Nucleus, 
k,  karyosome,  of  the  microgametocyte  ;  n' ,  n',  nuclei  of  the  microgametes. 
After  Schaudinn  (99);  A— E  magnified  1,000,  F— I  magnified  1,500, 
J  magnified  2,250. 

disappearance,  as  a  rule,  of  the  nuclear  membrane,  the  achromatinic 
substance,  or  the  combination  of  achromatinic  and  archoplasmic 


THE  REPRODUCTION  OF  THE  PROTOZOA          103 

elements,  assumes  a  characteristic  bipolar  form,  like  a  spindle. 
At  each  pole  of  the  spindle  a  centrosome  or  centriole  is  to  be  found, 
as  a  general  rule.  The  two  centrosomes  have  arisen  by  division  of 
the  originally  single  centrosome,  and  may  remain  for  some  time 
connected  by  a  fibril  or  by  a  system  of  fibrils,  forming  what  is  often 
termed  a  "  central  spindle,"  but  is  better  named  a  centrodesmose.  The 
axis  of  the  achromatinic  spindle  is  formed  by  the  centrodesmose,  if  it 
persists,  and  the  remainder  of  the  spindle  is  constituted  by  the  so- 
called  "  mantle-fibres  "  running  from  pole  to  pole.  The  mantle-fibres 
are  derived  from  the  achromatinic  reticulum  of  the  nucleus  and  the 
archoplasm  ;  they  are  probably  in  most  cases  the  optical  expression 
of  an  arrangement  of  the  protoplasmic  alveoli  in  longitudinal  rows, 
under  the  influence  of  tensions  or  forces  centred  at  the  poles  of  the 
spindle.  Such  an  arrangement  of  the  alveoli  produces  the  optical 
appearance  of  fibrils  connected  by  cross-junctions,  the  apparent 
fibril  being  formed  by  thickened  walls  of  alveoli  in  line  with  one 
another,  while  the  cross-junctions  are  the  transverse  walls  between 
consecutive  alveoli.  On  this  view  the  apparent  fibrils  of  the  achro- 
matinic spindle  are  in  reality  merely  the  indication  of  lines  of  force 
in  the  protoplasmic  framework  ;  but  some  authorities  consider  that 
in  certain  cases  at  least  true  fibrils  are  formed,  which  may  be 
isolated  from  each  other  and  without  cross-connections  (Hertwig, 
64).  The  spindle-fibres,  whether  real  or  apparent,  are  centred  at 
the  poles  of  the  spindle  on  the  centrosomes,  from  which  other 
striations  may  radiate  out  in  all  directions  through  the  archo- 
plasmic  masses  ("  attraction-spheres  "),  and  extend  into  the  sur- 
rounding cytoplasm. 

While  the  achromatinic  spindle-figure  is  in  process  of  formation, 
the  chromatin  of  the  nucleus  has  gone  through  a  series  of  changes 
which  may  differ  in  different  cases,  but  which  result  in  the  forma- 
tion of  a  number  of  masses  of  chromatin  termed  chromosomes.  The 
number,  size,  and  shape,  of  the  chromosomes  vary  greatly  in  dif- 
ferent species,  but  in  Metazoa  these  characters  are  generally  con- 
stant for  the  corresponding  phases  of  the  same  species.  Each 
chromosome,  when  formed,  consists  of  a  great  number  of  minute 
grains  of  chromatin,  chromidiosomes,  cemented  together  in  a  matrix 
or  ground-substance  of  plastin.  The  chromosomes  arrange  them- 
selves at  the  equator  of  the  achromatinic  spindle  in  the  form  of  a 
plate,  hence  termed  the  equatorial  plate.  The  nucleolus  disappears, 
being  absorbed  or  cast  out,  and  does  not  contribute  to  the  karyo- 
kinetic  figure,  but  a  part  at  least  of  its  substance  probably  furnishes 
the  plastin  ground-substance  of  the  chromosomes. 

At  this  phase,  when  the  achromatinic  spindle  is  fully  formed,  with 
the  plate  of  chromosomes  at  its  equator,  the  actual  partition  of  the 
chromatin  between  the  two  future  daughter-nuclei  usually  begins, 


104  THE  PROTOZOA 

though  in  some  cases  it  is  accomplished  at  an  earlier  stage  ;  it  takes 
place  in  one  of  two  ways,  known  respectively  as  equating  and  re- 
ducing division.  In  equating  division  each  chromosome  divides  into 
two  daughter-chromosomes,  a  process  which,  in  the  finished  and 
perfect  karyokinesis  of  the  higher  organisms,  is  effected  by  a  longi- 
tudinal splitting  of  the  chromosome,  and  which  may  be  interpreted 
as  a  simple  division  into  two  of  each  of  the  component  chromidio- 
somes  (compare  Fig.  60).  In  reducing  division,  on  the  other  hand, 
the  individual  chromosomes  do  not  divide,  but  are  sorted  out,  half 
of  them  going  to  one  pole  of  the  spindle,  and  eventually  to  one 
daughter-nucleus,  the  other  half  to  the  other  ;  with  the  result, 
finally,  that  each  daughter-nucleus  has  half  the  number  of  chromo- 
somes possessed  originally  by  the  parent  nucleus.  Equating 
division  is  the  usual  type  of  karyokinesis  seen  in  ordinary  cell- 
multiplication  ;  reducing  division,  on  the  other  hand,  is  seen  only 
in  certain  phases  of  the  maturation  of  the  germ-cells,  as  explained 
in  the  next  chapter. 

In  either  type  of  division,  whether  equating  or  reducing,  the 
equatorial  plate  of  chromosomes  as  a  whole  divides  into  two 
daughter-plates,  which  separate  from  one  another  and  travel  towards 
the  poles  of  the  achromatinic  spindle.  As  the  daughter-plates  move 
away  from  each  other,  an  achromatinic  framework  appears  between 
them,  in  which  a  longitudinal  striation  or  fibrillation  is  seen  in  line 
with,  and  continuing  that  of,  the  achromatinic  spindle.  Hence  the 
achromatinic  spindle  as  a  whole  consists  now  of  the  older  terminal 
portions  passing  from  the  poles  to  the  daughter-plates,  and  a  new" 
median  portion  passing  between  the  two  daughter-plates  ;  the  two 
terminal  portions  constitute  together  what  may  be  termed  conveni- 
ently the  "  attraction-spindle,"  the  median  portion  the  "  separation- 
spindle."  As  the  daughter-plates  travel  further  apart,  the  separa- 
tion-spindle elongates  more  and  more  ;  the  attraction-spindle,  on 
the  other  hand,  becomes  shorter,  usually  to  such  a  degree  that  the 
daughter-plates  are  brought  close  up  to  the  poles  of  the  attraction- 
spindle,  which  consequently  is  obliterated  and  disappears.  When 
full  separation  of  the  daughter-plates  is  attained,  the  separation- 
spindle  breaks  down  and  disappears  gradually,  the  middle  part 
alone  persisting  in  some  cases  ;  the  chromatin  of  the  daughter-plates 
becomes  rearranged  to  form  the  daughter-nuclei,  going  through  a 
series  of  changes  similar  to  those  by  which  the  chromosomes  arose 
from  the  parent-nucleus,  but  in  inverse  order.  A  nuclear  mem- 
brane is  formed  round  each  daughter-nucleus,  and  the  process  is 
complete. 

In  the  Metazoa,  direct  and  karyokinetic  division  stand  out  as  the 
sole  types  of  nuclear  division,  in  sharp  contrast  and  without  inter- 
mediate or  transitional  forms  of  the  process.  In  Protozoa,  011  the 


THE  REPRODUCTION  OF  THE  PROTOZOA           105 

contrary,  every  possible  form  of  nuclear  division  is  found,  from  the 
most  simple  and  direct  to  karyokinesis  as  perfect  as  that  seen  in 
the  Metazoa.  The  nuclear  division-processes  of  Protozoa  are  there- 
fore exceedingly  interesting  as  furnishing  object-lessons  in  the 
gradual  evolution  of  the  mechanism  of  nuclear  division  ;  but  the 
extreme  diversity  in  these  processes  makes  it  very  difficult  to  deal 
with  them  in  the  Protozoa  in  a  general  and  comprehensive  manner 
in  a  short  space  and  without  excessive  detail.  Speaking  generally, 
the  indirect  nuclear  division  seen  in  Protozoa  differs  from  that  of 
the  higher  organisms  in  a  number  of  points  which  indicate  that  it 
stands  on  a  lower  grade  of  evolution.  As  regards  the  achromatiiiic 
elements,  the  nuclear  membrane  is  usually  persistent  throughout 
the  process  of  division,  a  circumstance  which  enables  a  sharp  dis- 
tinction to  be  drawn  between  the  portions  of  the  division-mechanism 
derived  from  the  nuclear  framework  and  the  cytoplasm  respectively. 
In  many  cases  it  is  then  seen  that  the  cytoplasm  does  not  take  any 
share  in  the  process  at  all,  but  that  the  nucleus  divides  in  a  per- 
fectly autonomous  manner,  spindle  and  centrioles  remaining  intra- 
nuclear throughout  the  whole  process.  As  regards  the  chromatin, 
the  chromosomes  when  formed  are  often  irregular  in  form,  size, 
and  number  ;  they  often  appear  imperfectly  separated  from  one 
another  ;  they  are  not  always  arranged  in  a  definite  equatorial  plate, 
but  may  be  scattered  irregularly  along  the  spindle  ;  and  they  do 
not  always  split  in  the  exact  manner  characteristic  of  the  nuclear 
divisions  of  the  higher  organisms,  but  divide  irregularly  and  often 
transversely. 

The  principal  types  of  nuclear  division  in  Protozoa  will  now  be 
described  with  the  aid  of  a  few  selected  examples.  We  may  begin 
with  those  in  which  the  division  of  the  nucleus  is  autonomous, 
without  co-operation  of  cytoplasmic  elements. 

Division  has  often  been  asserted  to  be  direct  in  cases  in  which 
subsequent  research  has  revealed  a  more  elaborate  type ;  never- 
theless, many  typical  cases  of  amitosis  occur  among  Protozoa.  In 
some  nuclei  of  the  vesicular  type,  the  chromatin  appears  to  be 
concentrated  entirely  in  the  karyosome,  wrhich  may  contain  a 
centriole  also,  and  when  the  nucleus  divides  the  karyosome  becomes 
dumb-bell-shaped,  and  is  finally  constricted  into  two  halves,  the 
entire  nucleus  following  suit ;  as  an  example  of  this,  almost  the 
simplest  conceivable  type  of  nuclear  division,  may  be  cited  the 
nuclei  of  the  Microsporidia  and  allied  organisms  (Fig.  173,  p.  416). 

A  type  similar  in  the  main  to  that  just  described,  but  slightly 
more  advanced  in  structural  complication,  is  exemplified  by  the 
division  of  the  nucleus  in  the  schizogony  of  Coccidium  (Fig.  5 1 ,  F — M) ; 
here  there  is  a  peripheral  zone  of  chromatin  and  a  more  distinct 
nuclear  membrane.  After  division  of  the  karyosome,  the  peripheral 


106 


THE  PROTOZOA 


chromatin  is  halved  irregularly ;  no  definite  chromosomes  are 
formed,  but  the  grains  of  peripheral  chromatin  form  clumps  and 
masses  of  various  shapes  and  sizes.  A  definite  achromatinic  spindle 


R      r 

B  c 


- 

'v;'' 


F    I    tf 


••.*~  --^- 


FIG.  51. — Formation  of  the  karyosome  and  division  of  the  nucleus  in  the  schizont 
of  Coccidium  schubergi.  A,  Nucleus  of  the  sporozoite,  with  scattered  grains 
of  chromatin  but  no  karyosome.  B,  C,  D,  Nuclei  of  young  schizonts  in  which 
larger  grains  of  chromatin  collect  together  at  the  centre  to  form  the  karyo- 
some. E,  Nucleus  of  older  schizont  with  complete  karyosome.  F,  Nucleus 
of  full-grown  schizont.  G — M ,  Division  of  the  nucleus  of  the  schizont ; 
the  chromatin  of  the  nucleus  becomes  aggregated  into  larger  clumps  and  the 
karyosome  becomes  dumb-bell-shaped,  with  masses  of  chromatin  at  each 
pole  (G  and  H)  ;  the  two  daughter-karyosomes,  at  first  connected  by  a  fila- 
ment or  centrodesmose,  travel  apart,  taking  the  polar  clumps  of  chromatin 
with  them  (/)  ;  the  centrodesmose  breaks  through  and  disappears,  and  the 
two  daughter-nuclei  travel  apart,  with  formation  of  an  intermediate  body 
on  the  filament  between  them  (/ — L)  ;  finally  the  connecting  filament  breaks 
down  and  the  daughter-nuclei  separate  (M).  kl,  Karyosome ;  k2,  k"1,  daughter- 
karyosomes  ;  i.,  intermediate  body.  After  Schaudinn  (99),  magnified  2,250. 


FIG.  52. — -Direct  division  of  the  nuclei  in  the  oiicyst  of  Coccidium  schubergi.  A,  The 
resting  nucleus ;  B,  G,  D,  clumping  together  of  the  chromatin-granuies 
preparatory  to  division  ;  E,  F,  G,  the  nucleus  elongates  and  becomes  dumb- 
bell-shaped ;  H,  the  nucleus  has  just  divided  into  two  halves.  After 
Schaudinn  (99),  magnified  2,250. 

also  does  not  become  differentiated.  As  the  daughter-karyosomes, 
connected  by  a  centrodesmose,  travel  apart,  half  the  peripheral 
chromatin  follows  one  karyosome,  half  the  other.  This  method  of 


THE  REPRODUCTION  OF  THE  PROTOZOA 


10" 


division  is  a  very  common  one  in  the  nuclei  of  Protozoa,  and  may 
show  a  further  advance  towards  a  true  mitosis  in  that  the  peri- 
pheral chromatin  may  shape  itself  into  more  or  less  definite 
chromosomes,  as  in  Euglena. 

Examples  of  granular  nuclei  which  divide  in  the  direct  method 
are  seen  in  the  division  of  the  nucleus  of  the  oocyst  of 
Coccidium  (Fig.  52)  to  form  the  nuclei 
of  the  sporoblasts  (see  p.  349,  infra)  and 
in  the  corresponding  divisions  of  the  nuclei 
of  hsemogregarines  (Fig.  53).  In  these 
two  cases  the  presence  of  a  centriole  in 
the  nucleus  is  doubtful,  but  is  affirmed 
by  Hartmann  and  Chagas  (89)  for  hsemo- 
gregarines ;  a  true  nuclear  membrane, 


FIG.  .33. — Direct  division  of  the  nucleus  in  the  zygote 
of  H cemogregarina  stepanowi.  J  ,  Degenerating 
male  elements  attached  to  the  zygote;  N.,  divid- 
ing nucleus  of  the  zygote,  two  successive  stages 
(.4  and  JB).  After  Reichenow  (78). 


cv.'- 


however,  appears  to  be  absent,  and  this 
form  of  division  is  not  much  advanced 
beyond  the  condition  of  chrornidial  frag- 
mentation. In  the  macroiiucleus  of 
Infusoria  (Fig.  54),  in  which  a  distinct 
membrane  is  present,  the  division  is  also 
direct,  and  centrioles  are  stated  to  be 
absent  as  a  general  rule  ;  in  some  cases, 
however,  true  centrioles  appear  to  be 
present  (Nagler).  When  centrioles  are 
absent,  the  achromatinic  framework  of 
the  nucleus  appears  to  be  principally  active  in  the  division.  In 
some  cases  the  division  of  the  macroiiucleus  of  Infusoria  is 
not  into  two  equal  halves,  but  may  take  the  form  of  budding 
off  a  smaller  daughter-nucleus  from  the  main  mass.  Remark- 
able instances  of  nuclear  budding  of  this  kind  are  seen  in  the 
Acinetaria,  where  it  is  related  to  the  formation  of  buds  by  the  parent 
individual.  In  some  cases  (Fig.  55),  the  nucleus  may  form  a  con- 


FIG.  54. — -Paramecium  cauda- 
turn  :  division  showing  the 
macronucleus  (N)  dividing 
without  mitosis,  the  micro- 
nucleus  (n)  dividing  mito- 
tically.  c.r.1,  Old,  and  c.v.2, 
new,  contractile  vacuoles. 
After  Biitschli  and  Sche- 
wiakoff,  in  Leuckart  and 
Nitsche's  Zoologische  Wand- 
tafdn,  No.  Ixv. 


108 


THE  PROTOZOA 


siderable  number  of  buds  simultaneously,  each  of  which  becomes 
the  nucleus  of  a  daughter-individual  budded  off  from  the  parent. 

The  simplest  types  of  mitosis  show  but  little  advance  on  the 
processes  of  direct  division  that  have  just  been  described.  Taking 
first  the  vesicular  type  of  nucleus  with  a  large  karyosome  ("  proto- 
karyon  "),  the  first  stage  in  the  process  is  the  division  of  the  karyo- 
sorne,  as  in  Coccidium  ;  its  ceiitriole  divides  first,  then  the  karyo- 
some becomes  constricted  and  divides,  the  two  halves  often  plainly 
connected  by  the  centrodesmose  formed  by  the  division  of  the  cen- 
trioles.  Next  an  achromatinic  spindle  is  formed  between  the  two 
daughter-karyosomes,  and  chromosomes  make  their  appearance, 

derived  partly  (perhaps 
in  some  cases  entirely) 
from  the  peripheral  zone 
of  cliromatin,  partly  from 
the  chromatin  contained 
in  the  karyosome.  A 
good  example  of  this 
mode  of  division  has 
been  described  by  Aragao 
(87)  in  an  amoeba  named 
by  him  A.  diplomifotica 
from  the  fact  that  two 
types  of  mitosis  occur  in 
this  species.  In  the  first 
type  (Fig.  5Q,A—G),  the 
little  rod  -  like  chromo- 
somes are  not  arranged 
in  a  definite  equatorial 


FIG.  55. — Budding  in  Podophrya  gemmipara.     The 
macronucleus  of  the  parent  has  sent  off  a  number 


of  outgrowths,  which  extend  into  the  buds  and    plate,   but  are  scattered 

give  rise  to  the  nuclei  of  the  daughter-individuals     irresularly  aloilS  the 

about  to  be  budded  off.     N1,  Parent-nucleus  ; 

N2,  nuclei  of  buds.  After  Hertwig.  spindle  ;  some  travel  to- 

wards one  pole,  some 

towards  the  other,  and,  after  separation  into  two  groups  in  this 
manner,  the  chromosomes  of  each  group  fuse  together  to  form  an 
apparently  solid  mass  of  chromatin,  representing  the  daughter- 
plates  ;  these  masses  of  chromatin  follow  each  their  respective 
karyosomes  as  they  travel  apart,  and  when  the  nucleus  is  finally 
constricted  into  two  daughter-nuclei,  the  chromatin-masses  break 
up  again  into  their  constituent  chromosomes,  which  become  dis- 
tributed in  the  peripheral  zone  and  karyosome  of  the  daughter- 
nuclei,  where  they  can  be  distinguished  plainly  even  during  the 
resting  state  (Fig.  56,  A). 

In  the  second  type  of  mitosis  seen  in  A.  diplomitotica  (Fig.  56, 
H — K],  the  chromosomes  arrange  themselves  in  a  definite  equatorial 


THE  REPRODUCTION  OF  THE  PROTOZOA 


109 


plate,  which  divides  into  two  equally  definite  daughter-plates  com- 
posed of  distinct  chromosomes  ;  whether  this  division  is  brought 
about  by  splitting  of  the  individual  chromosomes  is  not  clear. 
When  the  nucleus  is  finally  constricted  into  the  two  daughter- 
nuclei,  the  chromosomes  are  at  first  aggregated  close  beside  their 
respective  karyosomes,  but  soon  distribute  themselves  in  the 
manner  alreadv  described. 

«/ 

The  simple  types  of  mitosis  described  in  the  two  foregoing  para- 
graphs are  examples  of  the  so-called  "  promitosis  "   (Nagler,  95) 


FIG.  56. — The  two  methods  of  nuclear  division  in  Anceba  diplomitotica.  A,  Resting 
nucleus  ;  B — G,  first  method  ;  H — K,  seconu  method.  In  F  and  G  only 
one  of  the  two  halves  of  the  nuclear  figure  is  drawn.  After  Aragao  (87). 

seen  commonly  in  nuclei  of  the  protokaryon-type.  The  nuclear 
membrane  in  this  type  is  a  negligible  quantity  ;  it  may  be  scarcely 
or  not  at  all  developed  in  the  resting  nucleus,  and  when  a  distinct 
membrane  is  present  it  may  vanish  entirely  during  the  mitosis,  as 
in  the  form  just  described.  In  any  case,  however,  the  entire  mitosis 
goes  on  within  the  nuclear  space.  The  chromosomes  may  show 
every  possible  condition  in  different  cases,  from  complete  irregu- 
larity in  form,  number,  arrangement,  and  mode  of  division,  to  the 


110 


THE  PROTOZOA 


formation  of  a  definite  equatorial  plate  which  splits  into  two 
daughter-plates.  The  most  striking  and  salient  feat-re  of  this  type 
of  mitosis  is  furnished  by  the  relatively  huge  "  polar  masses,"  con- 
sisting of  the  daughter-karyosomes  with  their  contained  centrioles. 
In  the  division  of  the  nucleus  of  Arcella  (Fig.  57),  however,  the 
karyosome  first  breaks  up  into  fine  grains  of  chromatin,  from  which 
the  polar  masses  and  the  equatorial  plate  are  formed.  The  karyo- 
some, as  has  been  pointed  out  in  the  previous  chapter,  consists  of 
three  distinct  elements — namely,  plastin,  chromatin,  and  centriole 


FIG.  57. — Nuclear  division  in  Arcdla  vulgaris:  karyokinesis  of 
one  of  the  two  principal  nuclei.  A,  Spireme- stage,  resulting 
from  disruption  of  the  karyosome  ;  B — D,  formation  of  an 
equatorial  plate  of  minute  chromosomes  (?)  which  split ; 
E,  anaphase ;  F,  the  two  daughter-nuclei  shortly  after 
division.  After  Swarczewsky  (101),  magnified  2,250. 


—each  independent  of,  and  separable  from,  the 
others.  In  proportion  as  the  karyosome  loses  its 
plastin  and  chromatin  elements,  and  becomes  reduced 
to  the  centriole  alone,  so  the  primitive  promitosis 
will  approach  more  and  more  to  the  type  of  an 
ordinary  mitosis.  Such  a  reduction  of  the  karyo- 
some could  take  place  during  the  mitosis  if,  as 
happens  frequently,  the  whole  of  the  chromatin 
F  contained  in  the  karyosome  passed  out  to  join  the 

peripheral  chromatin  in  forming  the  chromosomes, 
the  plastin-substance  at  the  same  time  furnishing  the  required 
ground-substance  of  the  chromosomes  (Fig.  58).  On  the  other 
hand,  the  karyosome  may  disappear  from  the  resting  nucleus 
also  ;  Chatton  (49)  has  brought  together  a  number  of  instances 
of  nuclei  showing  a  gradual  reduction  of  the  karyosome  in 
different  species,  and  the  evolution  of  a  granular  type  of  nucleus 
in  which  the  chromatin  is  scattered  through  the  achromatinic 
framework,  leaving  the  centriole  free  or  but  slightly  encumbered 
by  other  elements  in  the  nuclear  cavity.  When  a  nucleus  of  this 
type  divides  by  mitosis,  a  most  typical  and  perfect  karyokinetic 


THE  REPRODUCTION  OF  THE  PROTOZOA 


111 


figure  may  be  produced,  as  in  Euglypha  (Figs.  59,  60),  only  differing 
from  that  of  Metazoa  in  that  the  whole  mitosis  takes  place  within 
the  nuclear  membrane,  and  consequently  without  any  co-operation 
of  cytoplasrnic  elements.  Chatton  proposes  for  a  mitosis  of  this 
type  the  term  "  mesomitosis,"  as  distinguished  from  the  more  ad- 
vanced type,  or  "  metamitosis,"  in  which  a  collaboration  of  cyto- 
plasmic  and  nuclear  elements  is  effected,  and  the  entire  karyokinetic 


. 

-<.3j:-?-'-  ?-'l'^\ -v *-t'-..  *C— 
-      ""'—•-   '  •"  X'J 


FIG.  58. — Division  of  Hcematococciis  pluvialis.  A ,  Resting 
condition,  the  nucleus  with  a  conspicuous  karyosome 
and  fine  grains  of  chromatin  in  an  achromatinic  reti- 
culum  ;  B,  C,  preparations  for  nuclear  division,  the 
chromatin  passing  from  the  karyosome  into  the 
nuclear  reticulum  ;  D,  further  stage,  the  karyosome 
in  disruption  and  chromosomes  beginning  to  be 
formed  ;  E,  nuclear  spindle  ;  F,  division  of  the 
nucleus  complete,  the  karyosomes  reconstituted  in 
the  daughter-nuclei,  the  cell-body  beginning  to 
divide ;  G,  division  of  the  cell,  the  daughter-nuclei 
of  the  normal  resting  type.  After  Reichenow 
(97-5). 


figure  lies  free  in  the  cytoplasm  after  disappearance  of  the  nuclear 
membrane.  Before  passing  on,  however,  to  this  more  advanced 
type,  account  must  be  taken  of  the  more  simple  types  of  mitosis 
seen  in  granular  nuclei. 

Instructive  examples  of  the  division  of  nuclei,  in  which  the 
chromatin  is  not  concentrated  into  a  karyosome,  but  distributed 
evenly  throughout  the  achromatinic  framework,  are  seen  in  the  nuclei 


1  12 


THE  PROTOZOA 


FIG.  59. — Division  of  Euglypha  alveclala, 
as  seen  in  the  living  animal. 

A,  Condition  of  the  animal  when  about 
to  divide.  The  protoplasmic  body  shows 

three  zones  :  (1)  At  the  fundus  of  the  shell  is  clear  proto- 
plasm containing  the  nucleus  (N.)  and  the  reserve  shell- 
plates  (s. p.)  ;  (2)  the  middle  region  is  occupied  by  granular 
protoplasm  containing  ingested  food-materials  (/.)  and  the 
contractile  vacuole  (c.v.)  ;  (3)  near  the  mouth  of  the  shell  is  a  zone  of  hyaline 
protoplasm  from  which  the  pseudopodia  (ps.)  are  given  off. 

B,  Early  stage  of  division,  about  twenty  minutes  later  than  A.     The  proto- 
plasm  is   streaming   out    of   the   shell-mouth   to    form   the    body  of  a  daughter- 
individual,  into  which  the  reserve  shell-plates  are  passing  and  arranging  them- 
selves at  its  surface  to  form  a  daughter-shell.     In  the  nucleus  chromosomes  are 
beginning  to  be  formed. 

0,  About  twenty-five  minutes  later  than  B.  The  body  of  the  daughter  and 
its  shell  are  further  advanced  in  formation  ;  in  the  nucleus  of  the  parent  the 
equatorial  plate  is  forming,  and  the  two  centrosomes  are  becoming  visible  on 
the  two  flattened  sides  of  the  nucleus  (the  centrosomes  are  probably  derived  from 
the  division  of  the  karyosome,  no  longer  visible  in  the  nucleus  at  this  stage,  or 
from  a  centriole  contained  in  the  karyosome).  [Continued  at  foot  of  p.  113.] 


THE  REPRODUCTION  OF  THE  PROTOZOA 


113 


FIG.  CO. — Details  of  the  structural  changes  of  the  nucleus  of  Euglypha  alveolata 
during  karyokinesis,  showing  the  formation  of  the  chromosomes.  A, 
Coarsely  -  meshed  condition  of  the  nucleus ;  the  chromatin-granules 
aggregated  at  the  nodes  of  the  reticulum.  B,  Later  stage  ;  the  nucleus 
beginning  to  show  a  fibrous  structure  as  a  result  of  the  irregular  clumps 
of  chromatin-granules  of  the  previous  stage  becoming  arranged  in  linear 
series.  B2,  Some  of  the  fibrils  of  this  stage  more  highly  magnified. 
C,  Later  stage  ;  the  fibrils  have  become  smoother  and  more  parallel  in 
arrangement.  C2,  Fibrils  more  highly  magnified  ;  they  consist,  as  in  the  last 
stage  of  darker  and  lighter  parts  (the  former  chrornatin,  the  latter  probably 
plastin)  ;  between  the  individual  fibrils  are  cross-connections,  more  regular 
in  this  stage  than  in  the  last  (remains  of  the  nuclear  reticulum).  D,  The 
fibrils  have  become  shorter  and  thicker,  and  are  bending  up  to  form  the 
U-shaped  chromosomes.  After  Schewiakoff  (100)  ;  magnification  of  A,  B, 
C,  and  D,  about  1,200  diameters. 

of  ciliate  Infusoria,  such  as  Paramecium.  The  macronucleus  divides 
without  mitosis,  as  stated  already,  but  the  micronucleus  exhibits  a 
primitive  type  of  mitosis  (Fig.  61).  When  division  begins,  the 

FIG.  59 — -continued: 

D,  About  fifteen  minutes  later  than  0.     The  daughter-shr-11  is  now  com- 
pletely formed,  and  the  middle  granular  zone  of  the  parent  is  passing  over 
into  it  ;  the  nucleus  of  the  parent  has  assumed  its  definitive  orientation,  with 
the  centrosomes  at  the  poles  of  an  axis  coincident  with  the  longitudinal  axis 
of  the  animal,  and  the  equatorial  plate  is  definitely  formed. 

E,  About  thirty  minutes  later  than  D.     The  whole  of  the  middle  zone  of 
the  parent  has  passed  over  into  the  daughter-shell  ;  the  flattened  form  of  the 
nucleus  is  changing  into  an  elongated  spindle-form,  and  the  equatorial  plate 
is  splitting  to  form  the  two  daughter- plates. 

F,  About  five  minutes  later  than  E.     The  daughter-plates  have  travelled 
apart,  and  the  division  of  the  nucleus  is  beginning. 

G,  About  five  minutes  later  than  F.     The  division  of  the  nucleus  is  com- 
plete, and  one  daughter-nucleus  has  passed  over  into  the  body  of  the  daughter- 
Euglypha. 

H,  About  twenty-five  minutes  later  than  G  (about  125  minutes  from  the 
beginning).  Some  of  the  protoplasm  of  the  middle  zone  flows  back  into 
the  parent-shell,  and  each  individual  has  its  own  contractile  vacuole  ;  the  two 
daughter-nuclei  are  reconstituted,  and  the  karyosome  has  reappeared  in 
each  ;  pseudopodia  are  being  protruded  from  the  mouths  of  the  shells  ;  the 
division  is  complete,  and  the  animals  are  beginning  to  separate. 

After  Schewiakoff  (100)  ;  magnification  about  470  diameters. 

8 


114 


THE  PROTOZOA 


amount  of  chromatin  increases,  and  the  nucleus  becomes  oval  in 
form.  The  chromatin  forms  a  number  of  chromosomes  shaped  like 
elongated  rods  or  short  threads,  which  arrange  themselves  at  the 
equator.  At  the  same  time  the  achromatinic  framework  shows  a 
longitudinal  fibrillation  or  striation,  the  apparent  fibrilhe  being 
centred  in  thickenings  of  the  achromatinic  framework  which  appear 
at  the  two  poles  of  the  nucleus  within  the  persistent  nuclear  mem- 
brane, hence  termed  the  "  polar  plates."  Centrosomic  grains  are 
stated  to  be  entirely  absent,  and  their  functions  are  performed  by 
the  polar  plates.  The  nucleus  continues  to  elongate,  and  the 
chromosomes  divide  transversely  to  their  long  axis  to  form  the 
daughter-plates,  which  travel  apart ;  as  they  do  so  the  fibril! ated 


FIG.  61. — Stages  in  the  division  of  the  micronucleus  of  Para- 
mecium.     A,  B,  Early  stages  ;  C,  spindle-stage  with  equa- 
torial plate  of   chromosomes  ;    D,    spindle  with   the    two 
daughter-plates ;  E — H,  growth  of  the  separation-spindle 
and  separation  of  the  two  daughter-plates  ;  /,  reconstitu- 
tion  of  the  daughter-nuclei,   which  are  widely  separated, 
but  still  connected  by  the  greatly  elongated  separation- 
spindle,    the  central    part  of  which   shows   a   dilatation   prior  to  its    final 
absorption.     After  Hertwig.     Figs  A — E  are  drawn  on  a  larger  scale  than 
the  other  figures. 

separation-spindle  appears  between  them.  The  nucleus  as  a  whole 
now  becomes  dumb-bell-shaped  ;  the  daughter-plates  are  lodged  in 
the  terminal  swellings,  while  the  rapidly-growing  separation-spindle 
occupies  the  handle  of  the  dumb-bell.  The  daughter-plates  now 
break  up  and  reconstitute  the  daughter-nuclei,  but  the  connecting 
portion  continues  to  elongate  and  to  push  the  daughter-nuclei  apart. 
It  is  clear  that  the  separation  is  effected  by  intrinsic  growth  of  the 
achromatinic  framework  constituting  the  separation-spindle,  which 
is  often  curved  up  into  a  horseshoe-figure,  and  shows  bending  or 
twisting  of  its  fibrils,  as  the  result  of  the  inert  resistance  of  the  sur- 
rounding cytoplasm.  Finally,  however,  a  limit  of  growth  is  attained  ; 
the  daughter-nuclei  become  constricted  off  completely  from  the 
connecting  bond,  which  is  absorbed  and  disappears.  The  nuclear 
membrane  persists  throughout  the  division. 

In  all  the  forms  of  nuclear  division  dealt  with  so  far,  nuclear 
elements  alone  have  been  active  in  the  process.  A  most  instructive 
series,  showing  how  extranuclear  elements  come  to  collaborate  in 


THE  REPRODUCTION  OF  THE  PROTOZOA 


115 


the  mechanism  of  division,  is  furnished  by  some  examples  of  the 
Heliozoa,  and  especially  by  the  nuclear  divisions  of  Actinos-pJi  cerium, 
which  have  been  the  subject  of  extraordinarily  thorough  investiga- 
tion by  Hertwig  (64).  In  this  form  there  are  three  different  modes 
of  karyokinesis,  which,  however,  for  present  purposes  may  be 
classified  under  two  heads  :  karyokinesis  without  and  with  centro- 
somes. In  the  ordinary  nuclear  division  during  the  vegetative  life 
of  the  organism,  and  also  in  the  divisions  by  which  the  primary 

/'•'•^'.'•\-!-:y:-\ 


D 


FIG.  62.  —  •Actinosphcerium  eichhorni  :  stages  of  the  ordinary,  vegetative  nuclear 
division,  without  centrosomes,  of  free-living  individuals  (not  encysted). 
A,  B,  Formation  of  the  chromosomes  within  the  nucleus,  and  of  the  proto- 
plasmic polar  cones  outside  the  nucleus  ;  C,  spindle-stage  with  polar  cones 
(p.c.),  polar  plates  (p.p.),  and  equatorial  plate  of  chromosomes  (e.)>.); 
D,  stage  with  daughter  -  plates  of  chromosomes  which  have  travelled 
towards  the  polar  plates  ;  E  —  G,  division  of  the  nucleus,  reconstitution  of 
the  daughter-nuclei,  and  disappearance  of  the  polar  cones.  After  Hertwig  (64). 

«ysts  divide  into  the  secondary  cysts  (p.  138),  centrosomes  are 
absent,  but  they  are  present  in  the  two  divisions  Avhich  produce 
the  two  reduction  -  nuclei  thrown  off  from  each  secondary 
cyst.  , 

In  the  ordinary  karyokinesis  of  Actinosphcerium  (Fig.  62)  an 
equatorial  plate  is  formed  composed  of  a  large  number  of  small, 
rod-like  chromosomes,  imperfectly  separated  from  one  another, 
which  divide  transversely.  The  spindle  arises  from  the  achromatinic 
framework  of  the  nucleus,  and  terminates  in  two  conspicuous  polar 


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FIG.  03. — Aclinosphcerium  eichhorni:  first  reduction-division,  with  centrosomes 
(the  stages  here  shown  follow  those  of  the  centrosome-forraation  in  Fig.  37). 
A,  Centrosome  with  radiations  in  a  mass  of  archo plasm  at  one  pole  of  the 
nucleus  ;  B,  two  centrosomes  and  archoplasmic  cones,  taking  up  positions 
on  opposite  sides  of  the  nucleus,  in  which  chromosomes  are  beginning  to  appear ;. 
C,  D,  formation  of  the  nuclear  spindle  and  equatorial  plate  of  chromosomes  ; 
E,  division  of  the  equatorial  plate  ;  F,  division  of  the  nucleus  beginning  ; 
G,  H,  division  of  the  nucleus  and  rcconstitution  of  the  daughter-nuclei  ;  one 
daiighter-nucleus  will  degenerate  and  be  rejected  as  a  reduction-nucleus  ; 
the  beginning  of  this  is  seen  in  U ,  where  the  upper  darker  daughter- nucleus 
is  the  one  which  degenerates.  After  Hertwig  (64). 


THE  REPRODUCTION  OF  THE  PROTOZOA  117 

plates  lying  within  the  persistent  membrane.  External  to  the 
membrane  are  two  large  conical  masses  of  archoplasm,  termed  the 
•"  polar  cones."  As  in  the  micronucleus  of  Paramecium,  the  polar 
plates  represent  functionally  the  centrosomes,  towards  which  the 
daughter-plates  travel,  and  division  of  the  nucleus  is  effected  by 
growth  of  the  separation-spindle.  The  archoplasmic  polar  cones 
appear  to  take  little  or  no  part  in  the  mechanics  of  the  division, 
since  their  apices  maintain  their  distance  from  one  another,  and 
the  growth  of  the  separation-spindle  pushes  the  daughter-nuclei 
into  their  substance. 

The  reduction-karyokinesis  is  heralded  by  the  formation  of  a 
centrosome  from  the  nucleus  (Fig.  37  ;  see  p.  80,  supra).  The 
centrosomes  are  at  first  close  to  the  nucleus,  external  to  its  mem- 
brane, but  when  the  karyokinetic  spindle  is  formed  the  centro- 
somes travel  to  the  apices  of  the  cones.  From  the  centrosomes 
radiations  extend  through  the  polar  cones,  continuing  the  direction 
of  the  longitudinal  striations  of  the  intranuclear  spindle,  though 
separated  from  them  by  the  intervening  nuclear  membrane.  During 
the  division  the  apices  of  the  cones  move  apart  to  a  slight  extent, 
but  the  separation  of  the  daughter-nuclei  is  still  mainly  the  work 
of  the  separation-spindle,  which  pushes  them  into  the  polar  cones 
and  brings  them  close  to  the  two  centrosomes  again  ;  hence  the 
activity  of  the  polar  archoplasm  can  be  but  slight.  The  chromo- 
somes in  the  reduction-divisions  are  more  distinctly  separated  from 
each  other  as  the  result,  apparently,  of  a  reduction  in  the  amount  of 
the  plastin  forming  the  ground-substance.  The  nuclear  membrane 
persists  throughout  the  whole  process. 

In  Actinophrys  the  karyokinesis  appears  to  be  of  a  type  similar 
to  that  of  Actinosphcerium,  with  persistent  membrane,  but  with 
more  activity  in  the  extranuclear  archoplasmic  elements.  In 
Acantliocystis  (Fig.  64),  however,  the  nuclear  membrane  disappears 
completely  from  the  karyokinetic  figure,  and  it  is  no  longer  possible, 
in  consequence,  to  distinguish  the  parts  of  the  achromatinic  spindle 
which  are  of  intranuclear  and  extranuclear  origin  respectively. 
Nuclear  and  cytoplasmic  elements  are  in  complete  co-operation,  a 
condition  of  things  which  has  apparently  been  brought  about  and 
rendered  possible  by  the  extrusion  of  the  centrosome  from  the  nucleus 
hi  the  first  instance. 

From  the  foregoing  examples,  it  is  seen  that  amongst  the  Protozoa 
the  material  is  to  be  found  for  illustrating  the  gradual  evolution  of 
the  mechanism  of  karyokinetic  division,  from  the  starting-point  of 
simple  and  direct  division  up  to  the  most  advanced  type  in  which 
a  perfect  karyokinetic  figure  is  formed  by  co-operation  of  nuclear 
and  cytoplasmic  substance.  It  is  not  necessary  to  suppose,  how- 
ever, that  the  course  of  evolution  has  always  been  in  the  direction 


118  THE  PROTOZOA 

of  that  type  of  mitosis  found  in  the  cells  of  Metazoa  ;  it  would  be 
more  reasonable  to  expect  that  in  some  cases  at  least  other  distinct 
types  of  division-mechanisms  would  have  been  evolved  —  side- 

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FIG.  64. — Division  of  Acanthocystis  aculeata.  A,  Resting  state  of  the  animal. 
.A".,  Nucleus  ;  c.,  central  grain  ;  a./.,  axial  filaments  of  the  pseudopodia,  ps.  ; 
sp.,  spicules.  B,  Pseudopodia  withdrawn  ;  nucleus  in  the  spirenie-stage  ; 
central  grain  dividing.  C,  Division  of  the  central  grain  further  advanced  ; 
nucleus  showing  distinct  chromosomes.  D,  Central  grain  completely  divided 
into  centrosomes,  between  which  the  nucleus  is  placed  ;  in  the  nucleus  the 
membrane  is  becoming  dissolved,  the  reticulum  is  becoming  modified  in 
arrangement  to  form  the  achromatinic  spindle  (or  a  part  of  it),  and  the  chromo- 
somes are  taking  up  their  position  in  the  equatorial  plate.  E,  Complete 
nuclear  spindle,  with  centrosomes,  achromatinic  spindle,  and  equatorial  plate. 

F,  Later  stage  with  daughter-plates  and  division  of  the  cell-body  beginning. 

G,  Division  of  the  nucleus  and  of  the  cell-body  nearly  complete.     After 
Schaudinn  (82). 


THE  REPRODUCTION  OF  THE  PROTOZOA 


119 


branches,  as  it  were,  of  the  stem  which  culminates  in  the  Metazoan 
type.  An  example  of  this  is  seen  in  the  peculiar  karyokinesis  of 
Noctiluca  (Fig.  65),  in  which  the  division  is  directed  by  a  large 
"  sphere,"  consisting  of  a  mass  of  archoplasm  containing  the  cen- 
trioles.  The  sphere  divides  and  forms  the  axis  of  the  karyokinetic 
figure,  of  which  the  nuclear  portion  is  placed  asymmetrically  to  one 
side. 

In  considering  this  remarkable  process  of  evolution,  consisting  in 
the  gradual  elaboration  of  a  highly  complicated  mechanism  for 
division  ot  the  nucleus,  the  question  naturally  arises,  What  is  the 
object  of  a  process  so  elaborate  ?  Or,  if  this  method  of  posing  the 
problem  offends  as  being  too  teleological,  we  may  alter  the  phrase- 
ology, and  inquire,  What  is  the  result  of  the  process  ?  The  answer 
is  perfectly  obvious.  The  result  effected  by  equating  karyokinesis 


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FIG.  65. — Stages  in  the  nuclear  division  of  Noctiluca  miliaris.  A,  Early  stage, 
the  "sphere"  (sph.)  beginning  to  divide,  the  nucleus  wrapping  round  it; 
B,  later  stage,  the  sphere  nearly  divided,  the  two  poles  of  the  nuclear  spindle 
in  section  attached  to  the  two  daughter-spheres  ;  C,  section  across  B ;  the 
sphere  contains  a  centriole  (c.),  to  which  the  chromosomes  (chr.)  are  attached 
by  achromatic  fibrils.  After  Calkins  (48). 

in  its  most  perfected  forms  is  an  exact  halving,  both  quantitative 
and  qualitative,  of  the  chromatin-substance  of  the  nucleus — quanti- 
tative, by  division  of  each  chromatin-granule  or  chromidiosome, 
and  the  partition  of  the  division-products  equally  between  the  two 
daughter-cells  ;  qualitative  also,  if  we  suppose  that  different  cliro- 
midiosomes  may  have  different  properties,  and  exert  their  own 
peculiar  influence  on  the  life  and  activities  of  the  cell ;  then,  since 
each  daughter-cell  contains  finally  the  sister-chromidiosomes  of  those 
contained  in  the  sister-cell,  the  qualities  of  its  chromatin  are  the 
exact  counterpart  of  those  of  the  sister-cell  and  also  of  the  original 
parent-cell.  Hence  karyokinesis  may  be  regarded  as  insuring  the 
transmission  to  the  daughter-cells  of  the  distinctive  properties  of 
the  parent-cell,  unimpaired  and  unaltered.  The  whole  process  indi- 
cates clearly  the  immense  importance  of  the  chromatin-substance 


120 


THE  PROTOZOA 


in  the  life  of  the  cell.  It  is  probable,  also,  that  the  elaboration  of 
the  process  of  karyokinetic  division  in  Protista  was  an  indispensable 
antecedent  to  the  evolution  of  multicellular  organisms,  since  for 
the  formation  of  a  tissue  it  is  necessary  that  all  the  cells  which 
build  it  up  should  be  perfectly  similar  in  their  constitution  and 
properties,  and  this  condition  could  only  be  brought  about,  prob- 
ably, by  karyokinetic  division  of  the  nuclei  in  the  process  of  cell- 
multiplication. 

In  the  foregoing  paragraphs  we  have  dealt  only  with  simple 
(binary)  nuclear  division,  but,  as  already  stated,  in  some  cases  the 
nucleus  divides  by  multiple  fission  into  a  number  of  daughter- 
nuclei  simultaneously.  A  simple  instance  of  direct  multiple  division 
of  a  nucleus,  in  which,  apparently,  no  centrioles  are  present,  has 
been  described  by  Lebedew  (93)  in  the  nuclei  of  Trachelocerca 
(Fig.  66  ;  see  also  p.  448).  In  this  form  partitions  are  formed 
within  the  nucleus  between  the  grains  and  masses  of  chromatin, 
and  finally  the  nucleus  becomes  segmented  into  a  mulberry -like  mass 

of     daughter  -  nuclei, 

, » .'.  :••;  T 

•  -V:-xs>c'  .•>••'• -:.: .-  XTT^_         which  separate   from 

one  another. 

In  most  cases,  prob- 
ably, of  multiple 
fission  the  nucleus 
contains  a  centriole, 

:o.    DO.— j our  stages  01    direct  nrainpie   nssiori    in          _,  i-i1pn-111H-n-1-,]pfjt,s,inn 
the  nuclei  of  Trachelocerca  phcenicopterus.      After    and  tne  multiple  US. 
Lebedew  (93).  is  brought  about  in  a 

manner  analogous  to 

the  formation,  of  a  plasmodium  by  multiplication  of  the  nucleus 
in  a  cell  which  remains  undivided — that  is  to  say,  the  centriole 
multiplies  by  fission  a  number  of  times  without  the  nucleus  as 
a  whole  becoming  divided.  Thus,  in  a  nucleus  of  the  simple 
protokaryon  type,  containing  at  first  a  single  karyosonie  and  cen- 
triole, division  of  these  structures  may  take  place  within  the  mem- 
brane without  the  nucleus  as  a  whole  dividing,  so  that  the  nucleus 
contains  finally  two  or  more  karyosomes,  each  containing  a  cen- 
triole. The  karyosomes  are  ultimately  set  free  from  the  nucleus, 
either  by  being  budded  off  singly  from  it,  or  by  the  nucleus  as  a 
whole  breaking  up  ;  then  each  karyosome  becomes  the  foundation 
of  a  new  nucleus.  Division  of  this  type,  which  may  be  termed  a 
multiple  promitosis,  has  been  described  by  Zuelzer  (86)  in  Wag- 
nerella.  In  cases  where  the  division  of  the  nucleus  is  of  the  karyo- 
kinetic type,  repeated  divisions  of  the  centriole  result  in  the  forma- 
tion of  a  complicated  multipolar  mitotic  figure,  leading  to  a  multiple 
division  of  the  nucleus,  as  seen  in  the  divisions  of  the  nuclei  in  the 
male  sporont  of  Aggregata  (Fig.  67),  as  described  by  Moroff  (94). 


ABC 

FIG.  66. — Four  stages  of   direct  multiple  fission   in 


THE  REPRODUCTION  OF  THE  PROTOZOA 


121 


The  presence  of  more  than  one  centriole  in  a  nucleus  has  led 
Hartmann  (60)  to  formulate  the  theory  that  such  nuclei  are  to  be 
regarded  as  "  polyenergid  "  nuclei.*  Hartmann  proposes  to  dis- 
tinguish a  nucleus  with  a  single  centriole  as  a  "  nioiiokaryon  "  from 
a  polyenergid  nucleus  or  '  polykaryon ':  containing  many  cen- 
trioles  ;  he  interprets  many  cases,  in  which  a  nucleus  appears  to 
become  resolved  into  chromidia  from  which  secondary  nuclei  are 
formed,  as  being  really  a  setting  free  of  monokarya  from  a  complex 
polykaryon — an  interpretation  which  certainly  gets  over  the  diffi- 
culty of  the  formation 
of  centrioles  in  second- 
ary nuclei  (see  further, 
p.  255,  infra). 

In  conclusion,  men- 
tion must  be  made 
the  theory  of  cell-divi- 
sion and  of  the  causes 
which  bring  it  about, 
put  forward  by  Hertwig 
(91,  92).  This  theory 
is  based  on  the  sup- 
position, of  which  men- 
tion was  made  in  the 
previous  chapter  (p.  70, 
supra)  —  that  for  the 
normal  performance  of  FIG.  67.— Multiple  nuclear  division  in  the  male 


m:  m  M 


sporont  of  Aggregate  jacquemeti.  The  nucleus,  of 
which  the  outline  has  become  irregular  but  is  still 
visible,  is  surrounded  by  eight  centrioles,  from 
each  of  which  striatious  pass  towards  and  into 
the  nucleus.  After  Moroff  (94),  magnified  750 
linear. 


vital  functions  a  cer- 
tain quantitative  re- 
lation must  be  main- 
tained between  the 
nuclear  substance  and 
the  cytoplasm.  As  a  standard  for  the  proportion  of  nuclear 
mass  and  cytoplasm  ("  Kernplasma-Norm  "),  the  individual  im- 
mediately after  fission  may  be  taken.  Exact  measurements  made 
on  Infusoria  show  that,  while  the  body  grows  continuously  in  size 
from  one  division  to  the  next,  the  nucleus  at  first  diminishes  slightly 

*  The  conception  of  "  energids  "  is  due  to  Sachs,  who  coined  the  term  to  denote 
"  a  single  cell-nucleus  with  the  protoplasm  governed  by  it,  so  that  a  nucleus  and 
the  protoplasm  surrounding  it  are  to  be  conceived  of  as  a  whole,  and  this  whole 
is  an  organic  unity,  both  in>  the  morphological  and  the  physiological  sense." 
Hertwig  (66)  has  criticized  this  conception,  and  has  shown  its  untenability  in  the 
case  of  Protozoa,  which  behave  as  single  individuals  whether  they  possess  one 
nucleus  or  many.  Hartmann,  considering  the  centriole  as  the  criterion  of  in- 
dividuality rather  than  the  nucleus,  has  revived  the  energid  theory  in  the  manner 
described  above.  It  leads  him  to  regard  an  ordinary  Metazoan  karyokinesis  as 
the  division  of  a  polykaryon,  in  which  each  separate  chromosome  represents  a 
distinct  nuclear  element  or  monokaryon — a  conclusion  which  appears  to  lead  rather 
to  a  reductio  ad  absurdum  of  the  theory. 


122  THE  PROTOZOA 

in  size,  and  then  grows  slowly  until  the  next  division-period  is 
reached.  As  a  result  of  the  slow  "  functional  growth  '  of  the 
nucleus,  a  disproportion  between  the  mass  of  the  nuclear  substance 
and  that  of  the  cytoplasm  is  brought  about,  producing  a  condition 
of  tension  between  the  nucleus  and  the  cytoplasm  ("  Kernplasma- 
Spannung  ").  When  the  tension  reaches  a  maximum,  the  nucleus 
acquires  the  power  of  growing  rapidly  at  the  expense  of  the  cyto- 
plasm, and  this  "  division-growth  "  leads  to  the  fission  of  the  cell, 
restoring  the  standard  balance  of  nucleus  and  cytoplasm.  Relative 
increase  of  the  nuclear  substance  retards  the  cell -division,  and 
brings  about  increase  in  the  size  of  the  cell ;  relative  decrease  of  the 
nuclear  mass  has  the  opposite  effect. 

2.  Division  of  the  Cell. — A  distinction  has  been  drawn  above 
between  binary  fission,  or  division  of  the  body  into  two,  and  mul- 
tiple fission  into  many  parts  simultaneously.  The  daughter-indi- 
viduals produced  in  either  case  may  be  similar  to  the  parent-indi- 
vidual in  all  respects  except  size,  or  may  differ  from  it  in  lacking 
more  or  fewer  of  its  characteristic  parts  and  organs,  which  are  then 
formed  after  the  daughter-individuals  are  set  free.  In  extreme 
cases  one  or  more  of  the  daughter-individuals  may  possess,  when 
first  liberated,  no  structure  more  elaborated  than  the  essential 
parts  of  a  cell,  cytoplasm  and  nucleus  or  chromidia  ;  in  such  cases 
the  daughter  is  termed  a  "  bud,"  and  the  process  of  fission  by  which 
it  arises  is  termed  "  budding  "  or  gemmation,  distinguished  further  as 
"simple  gemmation"  when  only  one  bud  is  formed  at  a  time,  and 
;'  multiple  gemmation  "  when  many  arise  simultaneously.  In  many 
cases  of  multiple  gemmation  the  parent- organism  does  not  survive 
the  process,  but  breaks  up  almost  completely  into  buds,  leaving 
only  a  greater  or  less  amount  of  residual  protoplasm,  which  degene- 
ates  and  dies  off  ;  budding  of  this  kind  is  termed  sporulation. 

In  binary  fission,  when  the  organism  is  of  simple  structure,  as  in 
the  case  of  amoebae,  the  division  is  equally  simple.  After  division 
of  the  nucleus,  the  two  daughter-nuclei  travel  apart,  and  the  body 
follows  suit,  by  flowing,  as  it  were,  in  two  opposite  directions, 
forming  two  smaller  individuals  each  with  a  nucleus,  and  con- 
nected at  first  by  a  protoplasmic  bridge,  which  soon  snaps  and  is 
drawn  in.  The  contractile  vacuole,  if  present,  is  taken  over  by 
one  of  the  two  daughter-individuals,  while  the  other  forms  a  new 
vacuole  ;  in  many  cases  the  normal  number  of  contractile  vacuoles 
is  doubled  before  division  begins. 

In  forms  of  more  complicated  structure,  the  division  also  becomes 
a  more  complex  process.  Where  the  body-form  is  definite,  the 
plane  of  cleavage  bears  usually  a  constant  relation  to  it.  Thus,  in 
Ciliata  the  division  of  the  body  takes  place  typically  transversely 
to  its  longitudinal  axis,  except  in  the  order  Peritricha.  In  Flagel- 


THE  REPRODUCTION  OF  THE  PROTOZOA 


123 


vKK&r' 


j 


*S;rc^.^) 


FIG.  68. — Budding  of  Acanfhocystis  aculeata  (compare  Fig.  64,  A).  A,  B,  Division 
of  the  nucleus,  in  which  the  central  grain  takes  no  part ;  C,  extrusion  of  a 
bud ;  D,  three  buds  in  process  of  extrusion,  the  nucleus  of  the  parent  dividing 
again;  E,  free  bud;  F,  flagellula,  and  G,  arnoebula,  produced  from  buds; 
H  and  /,  two  stages  in  the  extrusion  of  a  centriole  from  the  nucleus  of  a  bud 
to  form  the  central  grain  of  the  adult  form.  After  Schaudinn  (82). 


124  THE  PROTOZOA 

lata,  on  the  other  hand,  the  division  of  the  body  is  usually  longi- 
tudinal. In  any  case,  the  two  products  of  fission  may  be  equal  or 
subequal  in  size,  without  perceptible  difference  of  parent  and 
young  ;  or  they  may  be  markedly  unequal,  in  which  case  parent 
and  offspring  can  be  distinguished  clearly. 

The  various  organs  of  the  body  may  be  doubled  before  division  : 
either  by  splitting  or  new  growth  of  one  set ;  or,  if  there  are  many 
organs  of  a  particular  kind  present,  such  as  the  cilia  and  tricho- 
cysts  of  Ciliata,  they  may  be  simply  shared  between  the  two 
daughter-organisms  ;  or,  finally,  any  given  organ  present  in  the 
animal  before  division  may  be  retained  by  one  of  the  two  daughter- 
individuals,  while  the  other  forms  the  organ  in  question  anew  after 
division.  Thus,  in  Ciliata  one  daughter-individual  retains  the  old 
peristome ;  the  other  forms  a  new  one  for  itself.  The  greater  the 
number  of  organs  formed  afresh  in  the  daughter-individual,  the 
more  advanced  is  the  transition  from  ordinary  fission  towards 
budding. 

In  typical  gemmation  small  portions  of  the  parent-organism 
grow  out,  into  which  pass  either  nuclei,  the  products  of  the  division 
of  the  parent-nucleus  (Fig.  68),  or  of  budding  from  the  nucleus  of 
the  parent  (Fig.  55),  or  chromidia,  alone  or  together  with  a  nucleus. 
Such  buds  may  arise  on  the  surface  of  the  parent-body,  or  they 
may  be  cut  off  in  the  interior  of  the  cytoplasm  of  the  parent,  and 
may  remain  for  some  time  within  its  body.  Endogenous  budding 
of  this  kind  is  seen  in  the  Neosporidia  (p.  325),  in  the  Acinetaria, 
where  it  is  combined  with  nuclear  budding,  and  in  Arcella  (Fig.  80) 
and  some  amoebae,  where  it  is  combined  with  formation  of  secondary 
nuclei  from  chromidia. 


Bibliography. — For  references  see  p.  479. 


CHAPTER  VIII 
SYNGAMY  AND  SEX  IN  THE  PROTOZOA 

fiapela, 


Kinrpi  ve/j-ea-ffard,    KuTrpi  dvaroiffiv 

IT  is  a  matter  of  common  knowledge  that  amongst  all  the  higher 
animals  and  plants  the  phenomena  of  sexual  generation  and  sexual 
differentiation  are  of  universal  occurrence.  Reduced  to  its  simplest 
terms,  and  stripped  of  all  secondary  complications,  the  sexual 
process  in  an  ordinary  animal  or  plant  consists  essentially  of  the 
following  series  of  events  :  In  the  multicellular  body  certain  cells 
are  produced  which  may  be  termed  comprehensively  and  universally 
the  gametes.  In  the  two  sexes  the  gametes  exhibit  characteristic 
differences  ;  those  of  the  male  sex,  the  spermatozoa,  are  typically 
minute,  active,  and  produced  in  large  numbers  ;  those  of  the  female 
sex,  the  ova,  are,  on  the  contrary,  relatively  bulky,  inert,  and 
produced  in  far  fewer  numbers.  The  gametes  are  set  free  from  the 
body,  or,  at  least,  from  the  organs  in  which  they  arise,  and  each 
male  gamete,  if  it  finds  a  partner  and  if  circumstances  permit, 
unites  with  a  female  gamete  ;  their  bodies  fuse  completely,  cell 
with  cell  and  nucleus  with  nucleus,  and  the  product  is  a  "  fertilized 
ovum,"  or  zygote,  a  single  cell  which  proceeds  to  multiply  actively 
by  cell-division,  the  final  result  being  a  new  multicellular  individual. 

In  the  Protista  belonging  to  what  has  been  termed  in  the  first 
chapter  of  this  book  the  "  cellular  grade  "  —  that  is  to  say,  in  the 
Protozoa  and  the  unicellular  plants  sexual  phenomena  are  also  of 
widespread,  probably  of  universal,  occurrence,  and  the  process  of 
sexual  union  differs  only  in  unessential  points  from  that  seen  in 
higher  organisms. 

In  the  first  place,  since  the  individual  in  Protozoa  is  a  single  cell, 
the  gametes  themselves  are  also  complete  individuals,  modifica- 
tions merely  of  the  ordinary  individuals  of  the  species  produced  at 
certain  periods  or  phases  of  the  life-cycle. 

Secondly,  the  differentiation  of  male  and  female  gametes  rarely 
attains  to  the  high  degree  seen  in  the  Metazoa,  and  may  be  nil  ; 
the  two  gametes  may  be  perfectly  similar  in  all  perceptible  features 
of  structure  or  constitution,  as,  for  example,  Copromonas  (Fig.  111). 

125 


126  THE  PROTOZOA 

Sexual  union  of  similar  gametes  is  termed  isogamy ;  of  dissimilar, 
anisogamy.  When  the  gametes  are  differentiated,  then  one  gamete 
is  generally  smaller,  more  active,  often  with  highly  developed 
motor  mechanisms,  and  without  reserve  food-material  in  the 
cytoplasm  ;  this  is  the  microgamele,  regarded  as  male.  The  other 
gamete,  on  the  contrary,  exhibits  a  tendency,  more  or  less  pro- 
nounced, to  be  large,  inert,  without  motor  mechanisms  of  any 
kind,  and  to  store  up  reserve  food-material  in  the  cytoplasm — 
the  macrogamete,  regarded  as  female.  The  differentiation  of  the 
gametes  is  seen  to  be  a  speci  alization  of  two  kinds  of  cell-individuals, 
the  one  rich  in  motile  or  kinetic  protoplasm  but  poor  in  trophic 
substance,  the  other  rich  in  trophic  protoplasm  but  poor  in  kinetic 
substance.  In  some  cases  the  sexual  differentiation  may  affect 
also  the  mother-cells  of  the  gametes,  the  gametocytes,  or  may  be 
thrown  back  still  farther  in  the  series  of  generations  preceding 
the  gametes  ;  in  such  cases  a  number  of  successive  generations  of 
yamonts  exhibiting  sexual  differentiation  terminate  in  a  gameto- 
cyte  generation  from  which  the  actual  gametes  arise. 

Thirdly,  in  the  process  of  sexual  union,  or  syngamy,  as  it  may 
be  termed  comprehensively,  the  bodies  of  the  two  gametes  do  not 
always  fuse  completely  ;  in  some  cases  the  two  gametes  come 
together  and  merely  interchange  portions  of  their  nuclear  apparatus, 
remaining  separate  and  retaining  their  distinct  individuality.  The 
nucleus  which  remains  stationary  in  the  one  gamete  then  fuses 
with  the  migratory  nucleus  derived  from  the  other  gamete. 
Examples  of  this  type  of  syngamy  are  seen  in  the  Infusoria  (Fig.  77). 
The  type  of  syngamy  in  which  the  two  gametes  fuse  completely 
is  sometimes  termed  copulation  (or  total  karyogamy) ;  that  in  which 
they  remain  separate  and  exchange  nuclear  material,  is  known  as 
conjugation  (or  partial  karyogamy),  and  the  two  sexual  individuals 
themselves  as  conjugants  (they  should  not,  perhaps,  be  termed 
"  gametes,"  strictly  speaking,  for  reasons  explained  below)  ;  but 
the  term  "  conjugation  "  is  often  used  quite  loosely  for  either  type 
and  lacks  precision. 

These  differences  in  the  sexual  process  between  Protozoa  and 
the  higher  organisms  enable  us  to  give  a  wider  significance,  and 
at  the  same  time  a  more  precise  definition,  to  the  word  "  syngamy." 
However  varied  in  detail,  syngamy  is  essentially  nothing  more 
than  an  intermingling  of  chromatin-substance  derived  from  two 
distinct  cell-individuals.  Plus  ca  change,  plus  c'est  la  meme  chose. 
The  chromatin  that  undergoes  syngamic  union  may  be  in  the 
form  either  of  chromidia  or  of  nuclei  ;  in  the  former  case  the  process 
is  termed  cliromidiogamy ,  in  the  second  karyogamy.  Chromidiogamy. 
/though  probably  the  most  primitive  type,  is  known  to  occur  only 
in  a  few  Sarcodina  (Difflugia,  p.  230  ;  Arcella,  p.  148).  In  the  vast 


SYNGAMY  AND  SEX  IN  THE  PROTOZOA 


127 


majority  of  Protozoa,  as  in  all  known  cases  amongst  Metazoa  and 
plants,  sjaigamy  takes  the  form  of  karyogamy.  The  nuclei  of 
the  gametes  are  termed  pronuclei,  and  the  nucleus  that  results 
from  fusion  of  the  pronuclei  in  the  zygote  is  termed  a  synkaryon. 

In  many  Protozoa  (e.g.  Coccidium,  Fig.  69)  the  fusion  of  the  two  pronuclei 
is  effected  by  means  of  a  peculiar  mechanism  termed  a  "  fertilization- 
spindle."  When  the  two  pronuclei  are  in  contact,  the  female  pronucleus 
first  takes  an  elongated,  fusiform  shape,  having  its  chrornatin-grains  spread 
over  an  achromatinic  framework.  The  chromatin  of  the  male  pronucleus 
is  then  spread  over  the  same  structure.  This  mechanism  has  nothing  to  do 
with  nuclear  division,  but  merely  effects  a  complete  intermingling  of  the 
chromatin  of  the  pronuclei,  after  which  the  synkaryon  assumes  its  normal 
appearance  and  rounded  form.  In  Infusoria  the  two  pronuclei  fuse  in  the 
condition  of  the  karyokinetic  spindle  in  many  cases. 


FIG.  69. — Fertilization  of  Coccidium  schubergi.  A,  Pene- 
tration of  the  macrogamete  by  one  of  five  micro- 
gametes  ;  the  female  pronucleus  has  an  elongated 
form  ;  B,  the  favoured,  microgamete  has  passed  into 
the  interior  of  the  macrogamete,  which  has  secreted  a 
membrane  (oocyst)  at  the  surface  of  the  body,  ex- 
cluding the  other  rnicrogametes  ;  C,  the  female  pro- 
nucleus  has  assumed  an  elongated,  spindle-like  form, 
while  the  male  pronucleus  lies  at  one  pole  of  the 
spindle  in  the  form  of  a  little  mass  of  granules  ;  the 
excluded  rnicrogametes  are  degenerating ;  D,  the  granules  of  the  male  pronucleus 
have  spread  themselves  over  the  spindle-figure  formed  by  the  female  pronucleus ; 
E,  the  fertilization-spindle  seen  in  D  has  rounded  itself  off  to  form  the  synkaryon, 
and  fertilization  is  complete.  $ ,  Microgametes  ;  ?  ,  macrogamete  ;  n$ ,  male 
pronucleus;  n?,  female  pronucleus;  f.s.,  fertilization-spindle;  c,  oocyst  ;  n^ , 
synkaryon.  After  Schaudinn  (99),  magnified  2,250. 

True  syngamy,  as  denned  above,  must  be  distinguished  carefully  from 
certain  other  phenomena  which  are  likely  to  be  confused  with  it  ;  it  must 
not  be  assumed  that  every  fusion  of  cells,  or  even  of  nuclei,  is  necessarily  a 
case  of  syngamy.  In  some  Protozoa  the  mother-cells  of  the  gametes,  the 
ganietocytes,  enter  into  a  more  or  less  close  association  prior  to  the  formation 
of  gametes,  which  are  produced  in  due  course  and  then  perform  the  act  of 
syngamy  in  the  normal  manner.  An  example  of  such  association  is  seen 
in  gregarines  (p.  330),  where  association  between  adult  ganietocytes  is  the 
rule.  Sometimes  the  two  gametocytes  associate  in  the  earliest  stages  of 
their  growth,  as  in  Diplocystis  (Fig.  70,  A),  and  their  bodies  may  then  fuse 
completely  into  one ;  but  their  nuclei  remain  distinct,  as  in  Cystobia 
(Fig.  70,  B),  and  give  rise  in  due  course  to  the  pronuclei  of  distinct  gametes. 
Forms  in  which  precocious  association  of  this  kind  occurs  are  described  as 
being  "  neogamous  "  (Woodcock). 

In  many  cases,  union  of  distinct  individuals  can  be  observed  which  have 
nothing  to  do  with  syngamy,  since  no  fusion  takes  place  of  nuclei,  but  only 


128 


THE  PROTOZOA 


of  cytoplasm.  Such  unions  are  distinguished  as  plastogamy  (or  plasmogamy) 
from  true  syngamy.  Plastogamic  union  may  be  temporary  or  permanent  ; 
in  the  latter  case  it  loads  to  the  formation  of  plasmodia,  as  in  the  Mycetozoa 
(p.  239).  The  significance  of  plastogamy  is  obscure  in  many  cases,  but  in 
some^it  may  perhaps  be  comparable  to  the  association  of  gametes'  already 
described,  and  in  this  way  may  throw  light  on  some  cases  of  so-called 
"  autogamy"  (see  p.  138,  infra). 

A  further  case  of  unions  which  are  not  in  any  way  sexual  in  nature  is  seen 
in  the  remarkable  phenomena  of  agglomeration  exhibited  by  some  Protozoa— 
for  example,  trypanosomes.  In  this  case  the  organisms  adhere  to  each  other 
by  the  posterior  or  aflagellar  end  of  the  body,  apparently  by  means  of  a  sticky 
secretion  formed  by  the  kinetonucleus,  so  that  large  clumps  are  formed 
composed  of  numerous  individuals.  The  phenomena  of  agglomeration  are 
associated  with  conditions  unfavourable  to  the  parasite,  and  appear  to  be 
due  to  the  formation  of  special  substances,  agglutinins,  in  the  blood  of  the 
host.  Similar  phenomena  are  well  known  in  bacteria  as  agglutination,  since 
in  this  case  the  agglutinated  individuals  are  unable  to  separate,  while  in 


A 

FIG.  70. — Precocious  association  and  neogamy  of  gametocytes  in  gregarines. 
A,  Diplacystis  minor,  parasite  of  the  cricket:  m.,  common  membrane  uniting 
the  two  associates  ;  g.,  grains  of  albuminoid  reserve-material.  B,  Cystobia 
Jiolotlmrice,  parasite  of  Holothuria  tubulosa,  showing  the  two  nuclei  in  an 
undivided  body.  A  after  Cuenot,  magnified  about  120  diameters  ;  B  after 
Minchin. 

the  case  of  trypanosomes  that  are  agglomerated  it  is  possible  for  the  indi- 
viduals to  become  free  again  if  the  conditions  are  ameliorated.  In  other 
Protozoa,  also,  phenomena  of  the  nature  of  agglomeration  are  seen  in  de- 
generating forms  (see  p.  209,  infra). 

Certain  aspects  of  syngamy  mast  now  be  discussed  in  more 
detail — namely,  the  relation  of  syngamy  to  the  life-history  as  a 
whole  ;  its  occurrence  in  the  world  of  living  beings  ;  its  significance 
for  the  life-cycle  ;  and  its  effects  on  the  species  and  the  individual. 

1.  Syngamy  in  Relation  to  the  Life-History  of  the  Organism.— 
In  any  living  organism  the  principal  manifestation  of  vital  activity 
is  the  power  of  assimilation,  resulting  in  growth.  As  a  general 
rule,  however,  the  growth  of  an  organism  is  not  indefinite,  but  has 
a  specific  limit ;  an  individual  of  a  given  species  does  not  exceed 
a  certain  size,  which  may  be  variable  to  a  slight  extent,  but  which 
is  fairly  constant  for  normal  individuals  of  the  species  in  question 
under  similar  environmental  conditions.  When  the  limit  is 


SYNGAMY  AND  SEX  IN  THE  PROTOZOA  129 

reached  the  organism  tends  to  reproduce  itself.  In  Protista,  as 
described  in  the  last  chapter,  two  principal  types  of  reproduction 
occur — namely,  simple  or  multiple  fission.  In  either  case  the 
organism  grows  to  its  full  specific  size,  and  then  divides  into  smaller 
individuals  ;  the  greater  the  number  of  daughter-individuals  pro- 
duced at  each  act  of  reproduction,  the  more  minute  those  daughter- 
individuals.  Following  the  act  of  reproduction  comes  a  poriod 
of  growth,  during  which  the  small  forms  grow  up  into  full-sized 
individuals  which  reproduce  themselves  in  their  turn. 

Thus  the  life-history  of  a  Protist  may  be  described  as  an  altarna- 
tion  of  periods  of  growth  and  periods  of  reproduction.  If,  how- 
ever, the  life-history  consists  of  only  these  two  events  in  alternating 
succession,  it  is  an  infinite  series,  not  a  cycle  ;  continuous,  not 
recurrent.  Possibly  such  a  condition,  varied  only  by  states  of 
repose  interrupting  the  vital  activity  of  the  organism,  is  found  in 
Bacteria  and  allied  forms  of  life,  where  true  syngamy  apparently 
does  not  occur.  But  it  is  probable  that  in  all  Protozoa,  as  in  all 
Metazoa  and  plants,  the  life-history  is  a  recurrent  cycle,  of  which 
an  act  of  sjmgamy  may  be  taken  as  the  starting-point ;  this  point 
will  now  be  discussed. 

2.  The  Occurrence  of  Syngamy  in  the  Series  of  Living  Beings. — 
With  regard  to  this  question,  there  are  two  possibilities  ;  first,  that 
syngamy  and  sexuality  constitute  a  fundamental  vital  phenomenon, 
common  to  all  living  things  ;  secondly,  that  it  is  an  acquisition  at 
some  period  or  stage  in  the  evolution  of  organisms,  and  not  a 
primar}^  characteristic  ^  of  living  beings.  The  sex-philosopher 
Weininger*  has  argued  in  favour  of  the  first  of  these  hypotheses, 
and  goes  so  far  as  to  regard  all  protoplasm  as  consisting  primarily 
either  of  arrhenoplasra  (male)  or  thelyplasm  (female),  standing  in 
fundamental  antithesis  to  one  another,  and  combined  in  varying 
proportions  in  a  given  cell  or  sample  of  the  living  substance.  A 
view  essentially  similar  has  been  put  forward  by  Schaudinn,  and 
is  discussed  below. 

It  is  beyond  question  that  sexuality  is  a  universal  attribute  of 
all  living  beings  above  the  rank  of  the  Protista,  whether  animals 
or  plants.  In  Protista,  however,  syngamy  has  not  been  observed 
to  occur  with  certainty  in  the  Bacteria  and  organisms  of  a  similar 
type  of  organization.  It  is  true  that  certain  rearrangements  of 
the  chromatin,  observed  in  some  larger  organisms  of  the  bacterial 
type  at  certain  phases  of  their  life-history,  have  been  compared  to 
sexual  processes,  but  such  an  interpretation  is,  to  say  the  least, 
highly  doubtful.  In  Protozoa,  syngamy  has  been  observed  to 
occur  in  a  vast  number  of  forms,  but  by  no  means  in  all.  In  the 

*  Weininger,  0.,  "  Sex  and  Character,"  chapter  ii.  London :  W.  Heinemann, 
1906. 

9 


130  THE  PROTOZOA 

case  of  those  species  in  which  syngamy  has  not  been  observed, 
there  are  three  abstract  possibilities  :  first,  that  it  does  occur, 
but  has  not  yet  been  seen  ;  secondly,  that  it  is  secondarily  in 
abeyance  ;  thirdly,  that  it  is  primarily  absent — that  is  to  say,  that 
it  has  never  occurred  either  in  the  form  in  question  or  in  its  ancestral 
lineage.  On  the  whole,  the  first  of  these  three  possibilities  is  the 
most  probable,  though  the  second  must,  perhaps,  also  be  taken 
into  account,  as  will  be  shown  later. 

So  far  as  a  generalization  is  possible  or  permissible  in  the  present 
state  of  knowledge,  it  appears  that  sex  and  syngamy  are  phenomena 
of  universal  occurrence  in  all  truly  cellular  organisms,  but  we  have 
no  certain  knowledge  that  they  exist  in  any  organisms  of  the 
bacterial  type  of  organization.  With  the  passage  from  the  bacterial 
to  the  cellular  type  of  structure,  syngamy  became,  apparently,  a 
physiological  necessity  for  the  organism,  and  was  probably  acquired 
once  and  for  all. 

3.  The  Significance  of  Syngamy  in  the  Life-Cycle. — In  order 
to  appreciate  the  part  that  syngamy  plays  in  the  life-histories  of 
organisms  generally,  it  is  necessary  to  compare  briefly  and  in 
general  outline  the  life-cycles  of  Metazoa  and  Protozoa  in  typical 
cases. 

In  the  Metazoa  the  cycle  starts  from  a  single  cell,  the  zygote 
or  fertilized  ovum,  which  multiplies  by  cell-division  in  the  ordinary 
way.  Thus  is  produced  a  multicellular  individual,  composed 
always  of  at  least  two  classes  of  cells — tissue-cells  (histocytes)  and 
germ-cells.  The  histocytes  are  differentiated  in  various  ways, 
related  to  various  functions,  to  form  tissues,  and  so  build  up  the 
soma.  The  germ-cells  are  not  differentiated  for  any  functions  but 
those  of  sex  and  reproduction,  and  occur  primarily  as  a  mass  of 
undifferentiated  cells  constituting  the  gertnen ;  they  are  lodged 
in  the  soma  and  dependent  upon  it — parasitic  upon  it,  so  to  speak 
— but  in  a  sense  distinct  from  it ;  they  draw  their  sustenance  from 
the  soma,  influence  greatly  its  development  and  activities,  but 
contribute  nothing  to  the  work  of  the  cell-commonwealth.  Of 
these  two  portions  of  the  Metazoaii  individual,  the  soma  is  neces- 
sarily mortal,  doomed  inevitably  to  ultimate  senility  and  decay. 
The  cells  of  the  germen,  on  the  other  hand,  are  potentially  im- 
mortal, since  under  favourable  conditions  they  can  separate 
from  the  soma  and  give  rise  in  their  turn  to  a  new  individual  of 
the  species  with  soma  and  germen  complete  again.  This  type  of 
generation  is  always  found  in  every  species,  though  non-sexual 
methods  of  generation  may  also  occur  in  many  cases. 

In  the  life-cycle  of  the  Metazoa,  as  sketched  above  in  its  most 
generalized  form,  two  individualities  must  be  clearly  distinguished, 
the  one  represented  by  the  soma  together  with  the  germen,  crn- 


SYNGAMY  AND  SEX  IN  THE  PROTOZOA  131 

stituting  the  complex  body  of  a  Metazoan  individual ;  the  other 
represented  by  the  single  cells  of  which  both  soma  and  germen 
alike  are  built  up.  The  phrase  "  reproduction,"  whether  sexual 
or  non-sexual,  as  applied  to  the  Metazoa,  refers  only  to  the  complex 
multieellular  body  as  a  whole,  and  not  to  its  constituent  cells, 
which  reproduce  themselves  uninterruptedly  by  fission  during  the 
whole  life-cycle. 

In  the  comparison  of  a  typical  Protozoan  life-cycle  with  that  of 
the  Metazoa,  we  may  start  in  both  cases  alike  from  a  single  cell- 
individual  which  is  the  result  of  an  act  of  svngamv.  In  Protozoa, 

i/O  v 

also,  the  zygote  multiplies,  sooner  or  later,  to  produce  numerous 
cell-individuals  ;  but  in  this  case  the  cells  remain  separate  from 
one  another  and  independent,  so  that  no  multieellular  body  is 
produced,  except  in  the  colony-building  species,  nor  is  there  any 
distinction  of  somatic  and  germinal  cells,  save  in  rare  cases,  such 
as  Volvox  (p.  267).  In  Protozoa  the  phenomena  of  vital  exhaustion, 
so-called  "  senility  "  (Maupas)  or  "  depression  "  (Calkins,  Hertwig), 
appear  to  be  as  inevitable  as  in  the  cells  of  the  Metazoan  body 
(see  pp.  135  and  208.  infra) ;  but  if  the  derangement  of  the  bodily 
functions  and  the  vital  mechanism  has  not  gone  too  far,  the  organism 
is  able  to  recuperate  itself  by  self-regulative  processes,  of  which 
the  most  important  and  most  natural  are  those  involved  in  the 
normal  process  of  syngamy.  Consequently  no  cell  -  individuals 
among  Protozoa  are  doomed  necessarily  and  inevitably  to  decadence 
.and  death,  but  a  1  possess  equally  potential  immortality — that  is 
to  say,  the  capacity  for  infinite  reproduction  by  fission  under  favour- 
able conditions.  The  Metazoan  individual  is  represented  in  the 
Protozoa  only  by  the  entire  life-cycle,  from  one  act  of  sjaigamy  to 
the  next,  and  not  by  any  living  organic  individual. 

In  the  life-cycle  of  a  Protozoon,  as  there  is  only  one  individuality, 
•so  there  is  only  one  method  of  reproduction — that,  namely,  of  the 
•cell,  by  fission  ;  and  it  must  be  made  clear  that  the  reproduction 
of  the  cell-individual  is  not  in  any  special  relation  to  syngamy 
in  Protozoa,  anv  more  than  in  Metazoa. 

\J 

It  has  been  pointed  out  above  that  the  life-history  of  a  Protist 
organism  consists  of  alternate  periods  of  growth  and  reproduction. 
In  those  Protozoa  in  which  syngamy  has  been  observed,  it  is  found 
to  take  place  sometimes  at  the  end  of  a  psriod  of  growth  and  before 
a  period  of  reproduction,  sometimes  at  the  end  of  a  psriocl  of 
reproduction  and  before  a  period  of  growth,  and  sometimes  there 
may  be  a  difference  between  the  two  sexes  of  the  same  species 
in  this  respect.  In  the  first  case,  syngamy  takes  place  between 
fiill-grown  individuals  of  the  species,  as  in  Actinophrys  (Fig.  71)— 
so-called  macrogamy,  which  is  almost  always  isogamous.  In  the 
second  case,  syngamy  is  between  the  smallest  individuals  produced 


132 


THE  PROTOZOA 


by  fission  or  gemmation,  as  in  Foraminifera  (p.  235),  Arcella 
(Fig.  80),  etc. — so-called  microgamy,  which  may  be  isogamous  or 
slightly  anisogamous.  In  the  third  case,  syngamy  is  between  two- 
individuals  showing  the  utmost  disparity  in  size,  a  tiny  micro- 
gamete  and  a  bulky  macrogamete,  as  in  Coccidium  (Figs.  63,  152) ; 
the  result  being  am'sogamy  of  the  most  pronounced  type. 

From  these  facts,  it  is  abundantly  clear  that  sj^nganiy  in  the 
Protista  cannot  be  regarded  as  related  specially  to  reproduction, 
but  as  a  process  affecting  the  life-cycle  as  a  whole,  related  equally 


W5^j<t|^ 


FIG.  71. — Copulation  of  Actinophrys  sol.  A,  Two  associated  free-swimming 
individuals.  B,  The  two  individuals  are  beginning  to  encyst  themselves  ;  their 
nuclei  (N.,  N.)  are  preparing  for  karyokinesis ;  an  outer  gelatinous  envelope  (g) 
is  secreted  round  the  two  gametes,  and  also  round  each  individual  an  inner 
cyst -envelope  (c.),  incomplete  at  the  surface  of  contact.  C,  The  nucleus  of  each 
gamete  is  dividing  by  karyokinesis  (first  polar  spindle,  p.sp.).  D,  Formation 
of  the  polar  bodies  or  reduction-nuclei  (r.n.)  ;  the  reduced  pronuclei  (pn.) 
take  a  central  position  in  the  body  of  the  gamete  ;  the  bodies  of  the  gametes 
are  beginning  to  fuse.  E,  The  pronuclei  are  fusing  ;  the  reduction-nuclei  have 
passed  through  the  wall  of  the  inner  cyst.  F,  The  synkaryon  (sk.)  is  beginning 
to  divide  by  karyokinesis ;  the  degenerating  reduction-nuclei  have  passed  out 
of  the  inner  cyst.  N.,  N.,  Nuclei  of  the  gametes  before  reduction.  After 
Schaudinn,  magnified  about  850. 

to  all  vital  functions  of  the  organism,  and  therefore  only  indirectly 
to  reproduction — that  is  to  say,  only  in  so  far  as  reproduction  may 
result  from  renewed  and  invigorated  vitality.  This  is  equally 
true  of  the  Metazoa,  where,  however,  the  life-cycle  begins  and  ends 
with  the  production  of  a  complex  multicellular  body,  composed 
of  soma  and  germen.  Hence,  in  the  Metazoa  syngamy  is  brought 
into  relation  with  the  production  of  a  higher  individuality,  the 
body,  comparable  to  the  whole  Protozoan  life-cycle,  and  it  is  in 
this  sense  that  the  phrase  "  sexual  reproduction  "  must  be  under- 


SYNGAMY  AND  SEX  IN  THE  PROTOZOA  133 

stood  ;  as  already  pointed  out,  syngamy  has  no  special  relation 
in  Metazoa  to  cell-multiplication.  In  Protozoa  sexual  reproduction 
means  simply  reproduction  following  the  sexual  act ;  but  sex  and 
reproduction  must  be  considered  as  two  things  entirely  distinct. 

The  comparison  instituted  above  between  the  life-cycles  of  the  Protozoa 
and  Metazoa,  according  to  which  an  entire  Protozoan  individual  is  the  mor- 
phological equivalent  of  a  single  constituent  cell  of  a  Metazoan  body,  is  that 
which  I  personally  have  always  held  and  taught.  It  is,  I  believe,  the  pre- 
vailing view  among  zoologists,  and  has  been  enunciated  clearly  by  Calkins  (5). 
It  has,  however,  been  attacked  vigorously  by  Dobell  (110),  who  lays  great 
stress  on  the  physiological  analogy  between  the  single  Protozoon.  as  a  com- 
plete organism,  and  the  entire  Metazoan  body.  On  this  ground  he  expresses 
the  view  that  "  a  protist  is  no  more  homologous  with  one  cell  in  a  metazoon 
than  it  is  homologous  with  one  organ  (e.g.,  the  brain  or  liver)  of  the  latter  "  ; 
he  considers  it  "  incredible  that  anybody  could  advocate  the  view  that  the 
Metazoa  have  arisen  from  aggregated  Protozoa,"  and  he  puts  forward  the 
view  that,  if  the  Metazoa  have  arisen  from  protist  forms,  "  it  is  far  more 
natural  to  suppose  that  they  did  so  by  developing  an  internal  cellular  structure, 
and  not  by  the  aggregation  of  individuals  to  form  a  colony."  Similar  ideas 
have  been  put  forward  also  by  Awerinzew  (890).  From  these  and  other 
•considerations,  Dobell  draws  the  conclusion  that  the  Protista  are  not  to  be 
regarded  as  unicellular,  but  as  "  non-cellular  "  organisms. 

So  far  as  the  word  "  cell "  is  concerned,  I  have  already  expressed  the 
opinion  above  that  by  the  term  should  be  understood  a  certain  stage  in  the 
evolution  of  the  Protista,  and  that  many  protist  organisms  should  not  be 
termed  "  cells,"  but  only  those  which  have  reached  what  may  be  considered 
as  the  truly  cellular  type  of  organization.  I  am  not,  therefore,  concerned 
with  Dobell's  attack  on  his  own  conception  of  the  cell-theory  so  far  as  it 
concerns  Protists  generally,  but  only  in  so  far  as  it  applies  to  the  Protozoa. 

It  is  not  possible  here  to  discuss  in  detail  the  ontogenetic  development  of 
the  Metazoa.  It  must  suffice  to  state  that  in  all  primitive  types  of  embryonic 
development  among  Metazoa  the  cells  which  build  up  the  body  originate 
by  repeated  binary  fission  of  a  single  cell,  the  fertilized  ovum  ;  and  that  the 
only  cases  in  which  the  ovum  breaks  up  into  cells  by  the  development  of  cell- 
limits  internally  are  those  in  which  the  development  is  modified  by  the 
presence  of  yolk,  or  where  there  is  good  reason  to  believe  that  yolk  was 
ancestrally  present  in  the  egg.  For  confirmation  of  these  statements  the 
reader  must  be  referred  to  the  ordinary  textbooks  of  embryology.  I  must 
•content  myself  with  a  single  instance,  that,  namely,  with  which  I  am  best 
acquainted  by  personal  study. 

In  the  development  of  a  simple  Ascon  sponge,  such  as  Clathrina  blanca  or 
other  species  (see  chapter  "  Sponges"  in  Lankester's  "  Treatise  on  Zoology," 
part  ii.,  p.  68),  the  ontogeny  may  be  divided  into  four  phases  or  periods, 
which  indicate  clearly,  in  my  opinion,  the  general  lines  in  the  evolution  of 
the  Metazoa  from  Protozoan  ancestors. 

1.  Starting  with  the  fertilized  ovum,  strictly  homologous  with  a  Protozoan 
zygote,  it  divides  by  repeated  binary  fission  into  a  number  of  cells  (blasto- 
meres),  each  similar  to  the  ovum  in  every  respect  except  size  ;  the  process 
is  in  every  way  comparable  to  the  division  of  a  Protozoan  zygote  into  a 
number  of  individuals  which  remain  connected  to  form  a  colony,  as.   for 
example,  in  many  Phytomonadina. 

2.  Of  the  blastomeres  thus  formed,  a  certain  number,  variable  in  different 
species,  but  relatively  few,  retain  their  original  characteristics,  while  the  rest 
become  differentiated  into  columnar  flagellated  cells  forming  the  wall  of  a 
cavity    (blastoccele).      The    undifferentiated    blastomeres    give    rise    to    the 
archgeocytes.  from  which  ultimately  the  germ-cells  and  gametes  arise.     The 
flagellated  cells  are  the  ancestors  of  the  tissue-cells  (histocytes)  in  the  future 
sponge.     At  this  stage,  in  which  the  embryo  is  hatched  out  as  a  free-swimming 


134  THE  PROTOZOA 

larva,  it  is  perfectly  comparable  to  a  colony  of  flagellates  such  as  Volvox,  in 
which  the-  ordinary  individuals  have  lost  the  power  of  becoming,  or  giving  rise 
to,  gametes,  which  can  only  arise  from  certain  special  individuals. 

3.  The  free-swimming  larva,  composed  mainly  of   flagellated  cells,  with 
tlu:  archseocytes  either  at  the  hinder  pole  or  in  the  internal  cavity,  undergoes 
changes  as  it  swims  about,  which  consist  in  some  of  the  flagellated  cells  losing 
their   flagollum,    becoming  modified   in   structure,    and   migrating  into   the 
interior  of  the  larva  ;  in  this  manner  the  two  germ-layers  are  established,  and 
the  organism  has  then,  so  to  speak,  passed  from  the  condition  of  a  Protozoan 
colony  to  that  of  a  true  Metazoon. 

4.  When  the  germ-layers  are  established,  the  larva  fixes  itself,  and  of  the 
subsequent  development  it  is  sufficient  to  state  that  the  cells  of  the  two 
germ-layers  become  differentiated  into  the  tissues  of  the  adult  sponge,  and 
that  in  the  metamorphosis  of  the  larva  the  cells  undergo  a  complete  rearrange- 
ment, which  shows  clearly  that  every  cell  has  an  individuality  as  distinct 
as  that  of  any  Protozoan  individual,  a  conclusion  fully  borne  out  by  Ihe 
recent  experiments  of  Wilson   and   Huxley  (Phil.  Trans.,  B.,  ccii.,  pp.  165- 
189,  pi.  viii.)  on  the  power  of  regeneration  in  sponges  after  complete  separation 
of  the  cells  from  one  another. 

I  am  unable,  therefore,  to  accept  the  standpoint  of  Dobell  with  regard 
to  the  relations  of  Protozoa  and  Metazoa,  but  consider  that  the  comparison 
of  a  Protozoan  individual  to  a  single  cell  in  a  Metazoan  body  is  fully  justified 
both  morphologically  and  physiologically,  and  is  a  reasonable  phylogenetic 
deduction  from  the  ontogenetic  data.  The  objection  that  there  are  no  animals 
known  which  correspond  to  the  four-cell,  eight-cell,  and  blastula  stages  in 
embiyological  development  misses  the  point  and  is  not  strictly  true  ;  the 
stage  at  which  an  embryo  consists  only  of  four  or  eight  blastorneres  is  the 
homologue  of  a  Protozoan  colony,  and  in  the  Flagellata  species  are  known 
in  which  the  colon}-  consists  only  of  four,  eight,  sixteen,  or  thirty-two  cell- 
individuals  (p.  275).  To  the  query,  "Has  anyone  ever  found  a  metazoon 
which  is  composed  of  nothing  but  coherent  gametes  ?"  it  may  be  replied 
that  in  many  Volvocineas  the  colony  also  consists  only  in  part  of  gamete- 
producing  individuals.  The  theory  that  the  Metazoa  arise  by  cleavage  of  a 
mnltinucleate  plasmodiurn,  equivalent  to  a  single  Protozoan  individual,  has 
often  been  put  forward,  but  has  never  found  support  from  a  general  con- 
sideration of  the  facts  of  Metazoan  embryology.  In  Protozoa  the  plasmodial 
phase  is  always  temporary,  and  ends  sooner  or  later  by  breaking  up  initf 
separate  uninucleate  individuals. 

4.  The  Effects  of  Syngamy — (1)  upon  Hie  Individual,  (2)  upon 
the.  Species.--!.  Of  all  Protozoa,  the  ciliate  Infusoria  are  the 
group  in  which  syngamy  is  most  easily  observed  and  studied — in 
the  first  place  because  in  these  organisms  it  is  readily  distinguished 
from  simple  fission,  which  is  transverse,  while  in  syngamy  the  two 
conjugants  apply  themselves  laterally  to  one  another ;  in  the 
second  place,  owing  to  the  fact  that  the  species  of  Ciliata  are 
practically  monomorphic  (p.  440),  and  can  be  identified  without 
difficulty.  Hence  in  this  group  elaborate  and  exhaustive  experi- 
mental studies  upon  syngamy  and  its  relation  to  the  life-cycle 
have  been  carried  out  by  many  investigators,  more  especially  by 
Maupas,  Hertwig,  Calkins,  and  Woodruff.  The  results  of  these 
investigators  is  briefly  as  follows  :  After  syngamy  the  fertilized 
individuals  appear  vigorous,  feed  actively  and  multiply  actively. 
After  many  generations  of  reproduction  by  fission,  however,  the 
race,  if  kept  in  an  unchanged  environment,  becomes  less  vigorous 


SYNGAMY  AND  SEX  IN  THE  PROTOZOA  135 

and  shows  signs  of  enfeeblement  and  "  senility  "  or  "  depression  " — • 
a  condition  which,  with  continued  isolation,  reaches  such  a  pitch 
that  the  organism  is  unable  to  assimilate,  grow,  or  reproduce,  but 
dies  off  inevitably  unless  conjugation  with  another  individual 
takes  place.  At  a  result  of  syngamy,  the  vigour  of  the  race  is 
renewed,  and  the  organisms  once  more  grow  and  reproduce  them- 
selves actively  until  senility  supervenes  again.  From  these  and 
many  other  facts  it  would  appear  as  if  syngamy  produced  a 
strengthening  or  re-organizing  effect  upon  the  organism,  restoring 
vigour  and  activity  to  vital  functions  that  have  become,  as  it  were, 
worn  out  and  effete. 

One  very  important  discovery  has  resulted  from  the  experi- 
ments of  Calkins  and  Woodruff — namely,  that  the  necessity  for 
syngamy  can  be  greatly  deferred  by  change  of  environment.  A 
strain  which  has  become  senile  and  exhausted  can  be  stimulated 
and  revived  by  a  change  of  food.  Even  this  remedy  appears  to 
have  its  limits,  however,  a  degree  of  exhaustion  being  reached 
sooner  or  later  which  nothing  can  restore  to  its  pristine  vigour. 
The  animals  may  even  reach  a  pitch  of  exhaustion  so  great  that 
they  are  unable  to  conjugate,  but  die  off  in  a  helpless  manner. 
Calkins  explains  such  cases  as  due  to  the  senility  having  affected 
not  only  the  vegetative,  but  also  the  generative  chromatin  ;  pro- 
ducing generative  senility,  which  is  incurable,  instead  of  mere  vege- 
tative senility,  for  which  syngamy  is  a  remedy.  Nevertheless,  the 
fact  that  the  advent  of  senility  and  exhaustion  can  be  deferred  by 
the  stimulation  of  changed  conditions  is  a  very  important  discovery. 
It  must  be  remembered  that  the  Ciliata  are  organisms  of  extremely 
complex  organization,  and  it  is  not  unreasonable  to  suppose  that 
in  such  forms  the  work  thrown  upon  the  vegetative  chromatin  is 
much  heavier,  and  therefore  the  tendency  to  exhaustion  much 
greater,  than  it  would  be  in  an  organism  of  simpler  constitution  ; 
in  such  a  form  the  stimulus  of  change  of  environment  might  defer 
the  advent  of  senility  very  greatly,  perhaps  even  for  an  indefinite 
period  (Woodruff,  141).*  This  suggestion  applies  particularly  to 
parasitic  forms,  in  which  the  organization  is  always  greatly  simpli- 
fied, and  in  which  change  of  environment  from  generation  to 
generation  is  inseparable  from  their  mode  of  life.  It  would  not  be 
surprising,  therefore,  if  syngamy  were  found  to  be  completely  in 
abeyance  in  a  parasitic  form  of  simple  structure. 

It  should  be  noted  here  that  examples  of  syngamy  being  in 
abeyance  are  not  wanting  even  in  higher  organisms.  An  instance 

*  In  his  most  recent  work  on  Paramecium,  Woodruff  (142)  expresses  the  view 
that  "  most,  if  not  all,  normal  individuals  have,  under  suitable  environmental 
conditions,  unlimited  power  of  reproduction  without  conjugation  or  artificial 
stimulation."  Compare  also  Woodruff  and  Baitsell  (143). 


136  THE  PROTOZOA 

is  the  banana-tree.  In  the  wild-banana,  seeds  are  produced  from 
flowers  of  a  normal  type  by  fertilization,  just  as  in  any  other  flower- 
ing plant ;  in  the  cultivated  banana,  however,  the  flowers  are 
.sterile  and  incapable  of  fertilization,  consequently  the  tree  bears 
fruit  which  are  entirely  seedless.  Hence  the  cultivated  banana- 
tree  is  propagated  entirely  by  a  non-sexual  method — namely,  by 
the  production  of  suckers  growing  up  from  the  roots,  and  in  no 
other  way.  Whether  this  complete  abolition  of  sexuality  will  in 
time  lead  to  exhaustion  of  the  cultivated  race  of  banana  remains 
to  be  seen,  but  at  present  there  seem  to  be  no  signs  of  loss  of  vigour 
under  cultivation. 

If  syngamy  can  be  entirely  dispensed  with  in  an  organism  rela- 
tively so  high  in  the  scale  of  life  as  a  flowering  plant,  it  seems 
probable  in  the  highest  degree  that  the  same  may  be  true  in  many 
cases  for  unicellular  organisms  of  simple  structure,  and  especially 
for  those  parasitic  forms  which  live,  like  cultivated  plants,  in  a 
medium  rich  in  nutritive  substances,  and  in  an  environment  which 
is  changed  at  least  once  in  each  developmental  cycle.     Instances 
of  this  are  perhaps  furnished  by  the  various  species  of  pathogenic 
trypanosomes,  strains  of  which  have  been  brought  to  Europe  and 
propagated  for  many  years  from  one  infected  animal  to  another 
by  artificial  inoculation,  without  the  natural  agency  of  an  inverte- 
brate host.     If  it  be  true,  as  is  generally  believed,  that  in  trypano- 
somes syngamy  takes  place  in  the  invertebrate  host,  then  in  the 
long-continued  artificial  propagation  of  pathogenic  trypanosomes 
sexuality  has  been  in  abeyance  for  a  vast  number  of  generations 
without  any  apparent  loss  of  vital  powers.     The  case  of  the  patho- 
genic  trypanosomes   cannot,   however,   be   cited,   in   the   present 
state  of  our  knowledge,  as  an  absolutely  conclusive  example  of 
syngamy  in  abeyance,  since  it  is  by  no  means  certain  that  this 
process    does   not   take   place   in   the    vertebrate  host,  where  its 
occurrence  has  frequently  been  affirmed  (see  p.  305,  infra).     But 
it  is  certain  that  in  trypanosomes  generally,  whether  pathogenic 
or  non-pathogenic,  syngamy  is  a  rare  phenomenon,  since  it  has  not 
yet  been  demonstrated  satisfactorily  in  a  single  instance,  either  in 
the  vertebrate  or  the  invertebrate  host,  in  all  the  many  species 
that  have  been  studied.     It  is  possible  that,  in  these  and  many  other 
forms  of  life,  sexual  processes  may  intervene  only  at  long  intervals 
in  the  life-history,  and  by  no  means  in  ever}^  complete  C3rcle  of 
development  or  alternation  of  hosts.     It  then  becomes  necessary 
to  distinguish   a  developmental  cycle,   consisting   of  a  recurrent 
series  of  similar  form-changes  in  regular  succession,  from  a  complete 
life-cycle  marked  by  the  occurrence  of  an  act  of  syngamy.     In 
such  forms  as  the  parasites  of  malaria,  for  example  (p.  358),  the 
life-cycle  and  the  developmental  cycle  coincide — that  is  to  say, 


SYNGAMY  AND  SEX  IN  THE  PROTOZOA 


137 


syngamy  occurs  once  for  each  complete  cycle  of  development 
with  alternation  of  hosts,  though  it  must  not  be  forgotten 
that  the  development  in  the  vertebrate  host  comprises  a  vast 
and  quite  indefinite  number  of  generations  of  the  parasite.  On 
the  other  hand,  in  such  forms  as  trypanosomes,  a  complete  life- 
cycle,  from  one  act  of  syngamy  to  the  next,  may  comprise,  ap- 
parently, a  great  number  of  developmental  cycles  and  alternations 
of  hosts. 

From  the  foregoing  considerations  it  is  evident  that  syngamy, 
though  usually  a  necessity  for  the  continued  existence  of  uni- 
cellular no  less  than  of 
multicellular  organisms, 
can  be  dispensed  with  for 
a  very  large  number  of 
generations,  perhaps  even 
indefinitely,  in  some  in- 
stances or  under  special 
circumstances.  Two  other 
phenomena  of  apparently 
widespread  occurrence 
point  to  the  same  con- 
clusion— namely,  the  phe- 
nomena of  parthenogenesis 
and  autogamy.  Partheno- 
genesis is  a  mode  of  re- 
production so  common  in 
Metazoa  of  Various  classes  FIG.  72. — Parthenogenesis  of  Plasmodium  vivax. 
that  it  is  unnecessary  to  4,  A  female  gametocyte,  of  which  the  nucleus 

J  is  dividing  into  a  darker  portion  (n1)  and  a 

Cite    instances    of    it    here  ;        lighter  portion  (n-);  B,  the  separation  of  the 

it  may  be  defined  briefly      two  Parts  is  comPlete ;  G>  tlie  darker  nucleus 
, ,  "  has  divided  into  a  number  of  portions  ;  D,  a 

as  tile  power  to  develop  number  of  merozoites  are  formed  from  the 
without  syngamy  possessed  darker  nuclei ;  the  lighter  nucleus  is  abandoned 
•L,.  !•«•  ,•  in  the  residual  protoplasm  (r.p.)  containing 

by  a  sexually-differentiated  the  melanin-piginent.  After  Schaudinn  (130) 
gamete,  which  under  nor- 
mal circumstances  could  do  so  only  after  syngamy  with  a 
gamete  of  the  opposite  sex.  To  this  it  must  be  added  that 
the  gamete  wThich  has  this  power  is  always  the  female  ;  but  this 
limitation  receives  an  explanation  from  the  extreme  reduction 
of  the  body  of  the  male  gamete  and  its  feeble  trophic  powers, 
rendering  it  quite  unfitted  for  independent  reproduction,  rather 
than  from  any  inherent  difference  between  the  two  sexes  in 
relation  to  reproductive  activity.  Parthenogenesis  has  been  de- 
scribed by  Schaudinn  for  the  human  malarial  parasite  (Fig.  72) 
and  in  Trypanosoma  noctuce,  and  by  Prowazek  for  Herpetomonas 
muscce-domesticce ;  none  of  these  cases,  however,  are  entirely  free 


138 


THE  PROTOZOA 


from  doubt,  and  in  any  case  parthenogenesis  seems  to  be  of  much 
rarer  occurrence  among  Protozoa  than  among  Metazoa.* 

Autogamy,  on  the  other  hand,  is  a  phenomenon  which  has  been 
frequently  observed  in  Protozoa,  chiefly,  though  not  exclusively, 
among  parasitic  forms  ;  it  may  be  defined  as  syngamy  in  which  the 
two  gametes,  or  at  least  the  two  pronuclei,  that  undergo  fusion 
are  sister-individuals  derived  by  fission  of  the  same  parent  cell 
or  nucleus.  Hartmann  (116)  has  brought  together  the  many  cases 
of  autogamy  known  to  occur  among  Protozoa  and  other  Protist 
organisms,  and  has  classified  them  under  a  complex  terminology. 
It  is  sufficient  here  to  mention  two  typical  cases,  those,  namely, 

of  Actinosphcerium 
and  Entamceba  coli, 
made  known  by  R-. 
Hertwig  (64)  and 
Schaudinn  (131)  re- 
spectively. 

In  Actinosphcerium 
an  ordinary  indi- 
vidual '  (Fig.  3)  be- 
comes encysted  as 
a  multinucleate 
"  mother -cyst ," 
which  becomes  di- 
vided up  into  a  num- 
ber of  unmucleate 
"  primarj7  cysts," 
after  absorption  of 
about  95  per  cent,  of 


D 


FIG.  73. — Autogamy  in  Entamceba  coli.  A,  The  amoeba 
at  the  beginning  of  encystation  with  a  single  nucleus  ; 
B,  the  nucleus  dividing ;  G,  the  two  daughter-nuclei 
throwing  off  chromidia ;  a  space  has  appeared  be- 
tween them  ;  D,  each  nucleus  has  formed  two  re- 
duction-nuclei, which  are  being  absorbed  ;  E,  a 
resistant  cyst-membrane  has  been  secreted  ;  the 

v  _  i .  -» 


partial  division  in  the  protoplasm  has  disappeared,  the  nuclei  originally 
and  the  two  reduced  nuclei  are  each  dividing  into  -present  Each  T3ri- 
two  ;  F,  each  daughter-nucleus  of  the  two  divisions 

in  the  last  stage  has  fused  with  one  of  the  daughter-  mary  cyst  then  dl- 
nuclei  of  the  other  division  to  form  two  synkarya.  yj^es  completely  into 
After  Hartmann  (116),  drawn  by  him  from  the  de-  J .. 

scription  given  by  Schaudinn  (131).  two    distinct    cells— 

"  secondary     cysts." 

Each  secondary  cyst  then  goes  through  a  process  of  nuclear  re- 
duction (see  below),  after  which  it  is  a  gamete  ;  the  two  gametes 
then  fuse  completely,  cell  and  nucleus,  to  form  the  zygote. 

*  Prowazek  (557)  has  described  in  Herpetomonas  muscce-domesticce  a  process 
interpreted  by  him  as  parthenogenesis  ("  etheogenesis  ")  of  male  individuals,  but 
the  correctness  both  of  his  observations  and  of  his  interpretations  are  open  to 
the  gravest  doubt.  According  to  Flu  (536),  the  objects  to  which  Prowazek  gave 
this  interpretation  are  in  reality  stages  in  the  life-history  of  a  quite  distinct 
organism,  named  by  Flu  Octosporea  muscce-domesticce,  and  now  referred  to  the 
Microsporidia.  It  is  greatly  to  be  deprecated  that  interpretations  of  such  un- 
certain validity  should  be  used,  as  has  been  done,  to  support  general  theories  in 
the  discussion  of  the  problem  of  syngamy. 


SYNGAMY  AND  SEX  IN  THE  PROTOZOA  139 

In  Entamceba  coli  (Fig.  73)  the  process  starts  in  like  manner 
from  a  uninucleate  individual,  the  nucleus  of  which  divides  into 
two,  but  the  cell  divides  incompletely  and  only  temporarily.  Each 
nucleus  then  breaks  up  completely  into  chromidia  and  disappears 
from  view.  Some  of  the  chromidia  are  absorbed,  while  from  others 
a  secondary  nucleus  is  formed  on  each  side  of  the  cell,  so  that  two 
nuclei  reappear  again  in  the  cyst,  but  smaller  than  before  and 
staining  feebly.  Each  secondary  nucleus  now  divides  twice  to 
form  three  nuclei  on  each  side,  two  of  which  degenerate  as  re- 
duction-nuclei, while  the  third  in  each  case  persists  as  a  gamete- 
nucleus.  As  soon  as  the  process  of  reduction  is  complete,  the 
incomplete  separation  of  the  two  cells  disappears,  so  that  the  two 
gamete-nuclei  lie  in  a  single  cell,  which  at  this  stage  forms  a  tough 
cyst.  Now  each  gamete-nucleus  divides  into  two  pronuclei,  those 
of  the  same  pair  being  slightly  different  from  those  of  the  other, 
according  to  Schaudinn  (133).  Then  a  pronucleus  of  each  pair  fuses 
with  a  pronucleus  of  the  other  pair,  so  that  two  synkarya  result. 
At  a  later  stage  each  synkaryon  divides  twice,  and  eight  amoebulae 
are  formed  by  division  of  the  cell  within  the  cyst. 

From  these  two  examples,  it  is  seen  that  autogamy  is  a  process 
of  extreme  inbreeding  as  regards  the  gametes.  In  typical  cases 
of  syngamy  the  two  gametes  must  be  derived  from  two  distinct 
strains,  and  those  of  the  same  strain  will  not  conjugate  ;  Schaudinn 
(131),  for  example,  observed  that  the  gametes  of  Polystomella 
crispa  would  only  copulate  when  a  couple  came  together  in  which 
each  gamete  was  of  distinct  parentage.  In  a  great  number  of 
Protozoa  the  differentiation  of  the  gametes  and  their  mode  of 
formation  makes  it  certain  that  the  couple  which  join  in  syngamy 
are  derived  from  different  parents.  On  the  other  hand,  in  many 
cases  of  autoganr^  that  have  been  described,  it  is  equally  certain 
that  the  conjugating  gametes  and  pronuclei  have  a  common 
parentage,  and  it  is  hardly  possible  to  consider  autogamy  otherwise 
than  as  a  degeneration  of  the  sexual  process,  evolved  in  forms  in 
which  one  feature  of  true  syngamy — namely,  the  mixture  of  distinct 
strains — is,  for  some  reason,  no  longer  a  necessity  ;  we  shall  return 
to  this  point  when  discussing  the  nature  and  origin  of  the  syngamic 
process.  It  is  possible,  moreover,  to  recognize  progressive  stages 
of  the  degeneration,  as  shown  by  the  two  examples  selected.  In 
the  less  advanced  stage  (Actinosphcerium)  the  parent  cell  divides 
into  two  complete  cells,  each  of  which,  after  a  process  of  matura- 
tion, becomes  a  gamete.  In  the  more  advanced  stage  (Entamoeba 
coli},  the  division  of  the  parent-cell  is  checked,  and  only  its  nucleus 
divides,  each  daughter-nucleus  becoming  a  pronucleus  after  reduction. 

The  occurrence  of  autogamy  has  been  asserted  in  a  number  of  cases  which 
are,  to  say  the  least,  extremely  doubtful,  as,  for  example,  the  Myxosporidia 


140  THE  PROTOZOA 

(p.  407)  and  allied  organisms,  where  it  is  far  from  certain  that  the  two  nuclei 
or  cells,  from  which  ultimately  the  pronuclei  or  gametes  arise,  have  a  common 
parentage.  Autogamy  has  recently  become  very  fashionable,  and  there  is 
a  tendency  to  regard  as  such,  not  only  many  cases  which  are  probably  truly 
heterogamous,  but  also  nuclear  fusions  or  appositions  which  are  not  in  any 
way  sexual  (e.g.,  Schilling,  134). 

The  essential  point  to  consider,  in  cases  of  autogamy,  is  whether  there  is 
a  union  of  chromatin  derived  from  distinct  strains — amphimixis — or  from 
a  common  parentage — automixis.  Thus,  it  has  been  pointed  out  above  that 
in  gregarines  two  gametocytes  may  associate,  and  even  fuse  into  one  body, 
but  with  the  nuclei  remaining  distinct  (Fig.  71,  B).  When  gamete-formation 
takes  place  in  a  "  neogamous  "  species  of  this  type,  the  gametes  of  one  sex 
derive  their  pronuclei  from  one  gametocyte-nucleus,  those  of  the  opposite 
sex  from  the  other,  with  subsequent  syngamy  of  a  truly  heterogamous  type. 
If  the  fusion  of  the  gametocytes  were  to  go  farther,  a  plastogamic,  non-sexual 
union  of  the  two  nuclei  might  result,  producing  a  single  nucleus  containing 
chromatin  from  two  distinct  sources  ;  in  that  case,  when  gamete-formation 
took  place,  the  syngamy  would  be.  to  all  intents  and  purposes,  a  typical  case 
of  autogamy,  and  would  certainly  be  so  described  if  it  were  not  known  that 
the  single  gametocyte-nucleus  had  arisen  by  fusion  of  two  distinct  nuclei. 
If,  however,  in  each  couple  of  copulating  gametes,  one  pronucleus  contained 
chromatin  derived  from  one  of  the  two  original  gametocyte-nuclei,  the  other 
pronucleus,  similarly,  chromatin  derived  from  the  other  nucleus,  the  result 
would  be  a  true  amphimixis,  just  as  in  ordinary  heterogamy. 

In  Actinosphcerium,  plastogamic  fusions  of  the  ordinary  vegetative,  multi- 
nucleate  individuals  are  stated  to  be  of  common  occurrence  ;  it  is  therefore 
possible  that  an  individual  which  encysts  may  contain  frequently  nuclei 
from  distinct  sources.  According  to  Brauer,  fusion  of  nuclei  takes  place  in  the 
mother- cyst  to  form  the  nuclei  of  the  primary  cyst.  There  is  therefore  at 
least  a  possibility  that  the  autogamy  of  Actinosplicerium  may  be,  in  some 
cases,  combined  with  amphimixis. 

In  other  cases,  however,  such  as  Entamceba  coli  and  Amoeba  albida  (Fig.  87). 
there  seems  little  reason  to  doubt  that  the  autogamy  is  a  true  automixis. 
Analogous  cases  of  self-fertilization  are  well  known  in  flowering  plants,  where 
they  are  sometimes  the  rule,  sometimes  an  alternative  to  cross-fertilization. 
In  free-living  Ciliata,  also,  syngamy  has  been  observed  between  cousins,  the 
descendants  of  an  ex-conjugant  after  but  four  divisions  (Jennings,  121), 
which  is  not  far  removed  from  automictic  autogamy. 

The  conclusion  put  forward  above,  on  experimental  grounds, 
that  syngamy  has  a  strengthening  or  invigorating  effect  on  the 
cell-organism,  receives  further  support  from  the  many  instances  in 
which  it  is  observed  to  occur  as  a  preliminary  to  the  production 
of  resistant  stages  destined  to  endure  unfavourable  conditions  of 
life.  Thus,  in  free-living  Protozoa  syngamy  occurs  commonly  in 
the  autumn,  previously  to  the  assumption  of  a  resting  condition 
in  which  the  organisms  pass  through  the  winter.  In  Difflugia, 
for  instance,  syngamy  in  the  autumn  is  followed  by  encystment, 
and  the  cysts  remain  dormant  until  the  spring.  This  is  strictly 
comparable  to  the  state  of  things  known  in  many  Metazoa,  such  as 
Rotifers,  Daphnids,  etc.,  where  in  the  summer  soft-shelled  eggs 
are  produced  which  develop  parthenogenetically,  but  in  the  autumn 
hard-shelled  winter-eggs  are  produced  which  require  fertilization. 
In  parasitic  forms,  such  as  Coccidia  and  Gregarines,  syngamy  is 
related  to  the  formation  of  resistant  cysts  which  pass  out  of  the  host 


SYNGAMY  AND  SEX  IN  THE  PROTOZOA  141 

and  endure  the  vicissitudes  of  the  outer  world,  until  taken  up  by 
a  new  host  in  which  the  parasite  is  set  free  from  its  cyst  and  starts 
upon  a  fresh  cycle  of  growth  or  multiplication  without  sjiigarny, 
under  the  most  favourable  conditions  of  nutrition. 

2.  As  regards  the  effects  of  syngamy  upon  the  species,  it  must 
be  pointed  out,  in  the  first  place,  that  a  great  difference  exists 
between  multicellular  and  unicellular  organisms  as  regards  the 
effects  of  external  conditions  of  life  upon  the  sexual  process.  In 
Metazoa  the  germ-cells,  as  already  pointed  out,  are  a  race  of  cells 
apart,  and  are  sheltered  by  their  position  in  the  body  from  the 
direct  effects  of  external  conditions — at  least,  to  a  very  large  extent. 
In  Protozoa,  on  the  other  hand,  there  is  no  special  race  or  strain 
of  germ-cells,  but  any  individual  may  become  a  gamete  or  the 
progenitor  of  gametes,  and  all  alike  are  exposed  to  the  direct 
action  of  the  environment.  If,  now,  Protist  organisms  placed  under 
slightly  different  conditions  of  existence,  tend  to  vary  in  their 
characters  as  a  direct  consequence  of  environmental  influences, 
syngamy  would  check  any  such  tendency,  and  would,  on  the  con- 
trary, tend  to  keep  a  given  species  constant  and  uniform  in  char- 
acter, within  narrow  limits.  Were  there  no  intermingling  of 
distinct  strains,  such  as  syngamy  brings  about,  individuals  of  a 
species  subject  to  different  conditions  of  life  would  tend  to  give 
rise  to  divergent  strains  and  races  ;  syngamy  levels  up  such  diver- 
gencies and  keeps  the  tendency  to  variation  within  the  specific 
limits  (compare  Enriques,  112  and  113;  Pearl,  124).  If  this  sup- 
position be  correct,  it  would  follow  that  no  true  species  could  exist 
until  syngamy  had  been  evolved  ;  and  if  it  be  true  that  no  syngamy 
occurs  in  organisms  of  the  bacterial  type  of  organization,  then  such 
organisms  must  be  regarded  as  having  diverged  under  direct 
environmental  influences  into  distinct  races  and  strains,  but  not 
as  constituting  true  species.  The  '"  species  ':  of  bacteria  would 
then  be  comparable  to  the  races  of  the  domestic  dog,  rather  than 
to  the  natural  species  of  the  genus  Canis.  Not  until  syngamy 
was  acquired  could  true  species  exist  amongst  the  Protista,  a 
condition  which  was  probably  first  attained  after  the  cellular  grade 
of  organization  had  been  evolved. 

The  conclusions  reached  in  the  foregoing  paragraphs  may  be 
summed  up  briefly  as  follows  :  Syngamy  is  a  process  of  inter- 
mingling, in  a  single  cell-individual,  of  chromatin  derived  from  two 
distinct  individuals,  gametes,  which  may  exhibit  differentiation 
into  "  male "  individuals,  characterized  by  preponderance  of 
kinetic  activity,  and  "  female,"  in  which  trophic  activities  are 
more  pronounced.  Syngamy  is  probably  of  universal  occurrence 
in  organisms  of  the  cellular  type  of  organization,  and  from  them 
has  been  inherited  by  the  higher  plants  and  animals,  but  apparently 


142  THE  PROTOZOA 

it  does  not  occur  amongst  organisms  of  the  bacterial  grade.  Syn- 
ganiy  is  related  to  the  life-cycle  as  a  whole,  and  not  specially  to 
cell-reproduction.  In  its  effects  on  the  cell-individual,  syngamy 
appears  to  have  an  invigorating  effect,  renewing  vital  powers  that 
have  become  effete  and  exhausted  ;  but  in  species  that  live  in  very 
favourable  conditions  of  nutrition,  etc.,  whether  such  conditions 
are  due  to  artificial  culture  or  to  natural  causes,  such  as  parasitism, 
syngamy  may  be  deferred  for  a  very  long  time,  and  may  even  be 
completely  in  abeyance,  or  may  degenerate  into  parthenogenesis 
or  autogamy.  In  its  relation  to  the  race,  syngamy  tends  to  level 
down  individual  variations,  and  so  produce  true  species  amongst 
the  Protista. 

Before  proceeding  to  discuss  the  nature  and  probable  origin  of 
the  syiigamic  process,  it  is  necessary  to  take  into  account  a  process 
which  appears  to  be  a  universal  concomitant  of  syngamy — namely, 
the  process  of  nuclear  reduction  in  the  gametes.  In  all  cases  of 
syngamy  that  have  been  carefully  studied,  it  has  been  found  that 
the  gametes  differ  from  the  ordinary  cell-individuals  of  the  species 
in  having  undergone  a  process  of  so-called  "  maturation  "  which  con- 
sists essentially  in  nuclear  reduction — that  is  to  say,  in  a  diminution 
of  the  normal  quantity  of  the  chromatin  by  so-called  "reducing" 
divisions  of  the  nucleus.  Hence  the  proiiuclei  which  undergo 
sjTigamic  fusion  differ  in  their  constitution  from  the  nuclei  of  cells 
not  destined  for  this  process,  and  do  not  multiply,  as  a  rule,  under 
normal  conditions  so  long  as  they  remain  single.  In  some  cases 
among  plants,  however,  the  cells  that  have  undergone  nuclear 
reduction  may  multiply  by  fission  and  produce  a  multicellular 
organism  (gametophyte)  from  which  gametes  ultimately  arise  ;  in 
this  way  is  brought  about  the  well-known  alternation  of  genera- 
tions of  the  ferns  and  flowering  plants.  Since,  moreover,  in  Metazoa, 
ova  that  have  undergone  nuclear  reduction  can  be  stimulated 
artificially  to  start  their  development  without  fertilization,  it  is 
clear  that  the  nuclear  reduction  does  not  in  itself  inhibit  further 
development  or  cell-multiplication. 

True  nuclear  reduction  in  gametes  must  be  distinguished  clearly 
from  the  process  of  elimination  of  effete  or  vegetat  ve  chromatin 
which  precedes  the  formation  of  the  gametes  or  their  nuclei,  probably 
in  every  case.  As  has  been  stated  above  (p.  72),  vegetative  and 
generative  chromatin  may  be  combined  in  the  same  nucleus,  or 
may  occur,  the  one  in  the  form  of  a  nucleus,  the  other  in  the  form 
of  chromidia,  or  may  constitute  two  distinct  nuclei.  When  the 
two  are  combined  in  one  nucleus,  a  necessary  preliminary  to  gamete- 
formation  is  the  purification  of  the  generative  chromatin  of  all 
effete  vegetative  material.  When  the  vegetative  chromatin  is 
already  separate  from  the  generative,  the  latter  alone  takes  a 


SYNGAMY  AND  SEX  IN  THE  PROTOZOA  143 

share  in  syngamic  processes,  and  the  vegetative  chromatin,  whether 
as  chromidia  or  a  nucleus,  disappears  from  the  life-history. 

Nuclear  reduction,  in  the  strict  sense,  concerns  simply  the  nuclei 
composed  of  generative  chromatin,  and  is  a  process  which  results 
in  the  reduction  of  the  chromatin  to  half  the  specific  quantity,  a 
deficiency  made  up  again  to  the  full  amount  by  the  union  of  the 
two  pronuclei  to  form  the  synkaryon.  It  is  therefore  a  process 
which  is  seen  in  its  most  characteristic  form  in  those  cases  where 
it  is  possible  to  gauge  the  amount  of  chromatin  in  the  nucleus 
more  or  less  accurately  by  the  number  of  chromosomes  formed 
during  division. 

In  the  Metazoa,  where  each  species  is  characterized  by  possessing 
a  number  of  chromosomes  which  is  generally  constant  (the  so-called 
"  somatic  number  "),  the  process  of  reduction  appears  to  be  ex- 
tremely uniform  in  its  essential  details  throughout  the  whole  series, 
from  the  Sponges  and  Ccelenterates  up  to  man,  and  admits  of  a 
description  in  general  terms.     The  gametocyte  (oocyte  or  sperrna- 
tocyte),  when  at  the  full  term  of  its  growth,  has  a  large  nucleus 
which  then  goes  through  two  maturative  divisions  in  rapid  succes- 
sion.    When    the    garnetocyte-nucleus    prepares    for    division,    it 
appears  with  half  the  somatic  number  of  chromosomes  ;  but  each 
chromosome  is  in  reality  bivalent,  and  produced  by  the  fusion  or 
close  adherence  of  two  separate  somatic  chromosomes.     In  the 
first  reduction-mitosis,  the  two  adherent  chromosomes  in  each  case 
separate  from  one  another  and  travel  to  opposite  poles  of  the 
spindle  ;   hence  this  division  is  in  reality  a  reducing,  though  it 
simulates    in    some   of    its    features    an    equating,   division.     Im- 
mediately or  very  soon  after  the  two  chromosomes  of  each  pair 
have  separated,  they  split  longitudinally  in  preparation  for  the  next 
mitosis,  which  follows  hard  upon  the  first,  and  in  which  the  two 
sister-chromosomes  of  each  pair  go  to  opposite  poles  of  the  spindle. 
Consequently  the  second  reduction-division  is  in  reality  an  equating 
mitosis,  though  on  account  of  the  precocious  splitting  of  the  chromo- 
somes it  may  simulate  a  reducing  division.     Thus,  to  sum  up  the 
process  briefly,  the  number  of  chromosomes  in  the  germ-cells  is 
reduced  to  half  the  somatic  number  by  two  successive  mitoses, 
the  first  a  reducing,  the  second  an  equating  division.     In  the  male 
sex,  the  spermatocyte  divides  into  four  gamete-cells  of  equal  size, 
the  spermatids,  each  of  which  becomes  a  spermatozoon.     In  the 
female  sex  the  oocyte-di visions  are  veiy  unequal,  producing  the 
ovum,  ripe  for  fertilization,  and  three  minute  sister-cells  of  the 
ovum  which,  as  the  so-called  "  polar  bodies,"  are  cast  off  and  die 
away.     By  syngamy  between  a  ripe  ovum  and  a  spermatozoon, 
each  containing  half  the  somatic  number  of  chromosomes,  the  full 
somatic  number  is  restored. 


144  THE  PROTOZOA 

In  Protozoa  the  chromosomes  are  seldom  so  sharply  defined  as 
in  Metazoa,  and  consequently  it  is  difficult  or  impossible  to  deter- 
mine their  number.  Many  cases  in  which  a  fixed  number  of 
chromosomes  is  alleged  to  occur,  as  in  Trypanosoma  noctuce  (Schau- 
dinn,  132),  cannot  be  accepted  without  question  in  the  present 
state  of  our  knowledge.  On  the  other  hand,  in  all  groups  of  the 
Protozoa,  where  the  sexual  processes  have  been  carefully  studied, 
the  union  of  the  gamete-nuclei  has  been  found  to  be  preceded  in 
a  great  many  cases  by  two  successive  divisions  of  each  nucleus,  with 
one  or  the  other  of  the  following  results  :  either  the  successive 
formation  of  two  reduction-nuclei,*  which  are  cast  out  of  the  cell 
or  absorbed  without  dividing  further,  while  the  third  persists  as 
the  pronucleus  of  the  gamete  ;  or  the  production  of  four  nuclei,  all 
of  which,  or  only  one  of  them,  persist  as  pronuclei.  These  reducing 
divisions  in  Protozoa  suggest  forcibly  a  comparison  with  those  of 
the  Metazoa,  and  from  this  analogy  it  may  be  further  inferred  that 
'in  Protozoa  also  the  chromatin  of  the  conjugating  pronuclei  has 
undergone  a  reduction  to  half  the  specific  quantity  ;  but  it  is 
seldom  possible  to  confirm  this  inference  by  accurate  enumeration 
of  the  chromosomes.  In  the  case  which  has  been  the  most  care- 
fully studied  of  all  others,  that,  namely,  of  ActinospJicerium,  Hertwig 
(64)  found  the  number  of  chromosomes  in  the  first  reduction- 
spindle  to  be  between  120  and  150  ;  in  the  second  reduction-spindle 
the  number  was  about  the  same,  but  the  chromosomes  were  about 
half  the  size  of  those  in  the  first  reduction-spindle.  Moreover,  in 
both  the  reducing  divisions  of  Actinosplicerium  the  chromosomes 
in  the  equatorial  plate  divide  to  form  the  daughter-plates,  as  in 
ordinary  karyokinesis,  whereas  in  the  reducing  divisions  of  Metazoa 
the  individual  chromosomes  are  not  divided,  but  merely  sorted  out. 
Heiico  it  would  appear  that  in  Actino splicer ium,  and  probably  many 
other  Protozoa,  the  reduction  of  the  chromatin  in  the  pronuclei 
is  effected  by  more  direct,  though  perhaps  less  exact,  methods 
than  in  the  highly-perfected  process  seen  in  the  Metazoa. 

Nevertheless,  a  few  cases  are  known  among  Protozoa  in  which 
the  small  number  of  chromosomes  permits  of  their  being  accurately 
counted,  and  in  which  they  are  seen  to  be  reduced  to  half  the  usual 
number  in  the  maturation-divisions  of  the  gametes.  In  Pelomyxa 
the  first  division  reduces  the  chromosomes  from  eight  to  four  ;  the 
second  division,  however,  is  equating,  and  no  further  reduction 
takes  place  (p.  150).  In  some  Infusoria  it  has  been  observed  that 

*  These  reduction-nuclei  are  sometimes  termed  "polar  bodies,"  by  analogy 
with  the  maturative  process  of  the  Metazoan  ovum,  but  the  term  is  to  be  avoided 
in  this  connection,  as  it  places  upon  these  divisions  an  interpretation  which  is  at 
least  highly  doubtful ;  the  polar  bodies  of  Metazoa  are  sister-cells  of  the  ovum  ; 
the  reduction-bodies  in  Protozoa  are  simply  nuclei  which  are  extruded  or  absorbed. 
It  is  certainly  not  justifiable  in  fact,  and  probably  no  more  so  in  theory,  to  regard 
their  formation  as  abortive  cell-division. 


SYNGAMY  AND  SEX  IN  THE  PROTOZOA 


145 


the  first  division  of  the  micronucleus  is  an  equating  division,  the 
second  reducing ;  so  in  Opercularia  (Enriques,  112),  Chilodon 
(Enriques,  113),  Carchesium  (Popoff,  125),  Didinium  (Prandtl,  126), 
and  Anoploplirya  (Fig.  74) ;  in  the  last  named  the  second  division 
of  the  micronucleus  reduces  the  chromosomes  from  six  to  three, 
and  union  of  the  pronuclei  brings  the  number  up  to  six  again.  In 
Carchesium  the  number  of  chromosomes  is  reduced  from  sixteen  to 
eight.  A  similar  reduction-process  has  been  described  by  Mulsow 
(123)  in  gregarines  (p.  335).  Hence  in  these  cases  the  pronuclei 


K 


FIG.  74.- — Behaviour  of  the  micronucleus  during  successive  stages  of  the  con- 
jugation of  Anoplophrya  (Gollinia)  branchiarum.  A,  Micronucleus  of  one 
conjugant  preparing  for  division  ;  B,  later  stage,  with  six  chromosomes  dis- 
tinct ;  0,  nuclear  spindle,  with  an  equatorial  plate  of  sis  chromosomes  ; 

D,  diaster-stage,  with  six  daughter-chromosomes  at  each  pole  of  the  spindle  ; 

E,  later  stage,  with  the  chromosomes  at  each    pole  fused  into  one  mass  ; 

F,  G,  H,  reconstruction  of  the  daughter-nuclei ;   the  remains  of  the  spindle 
between  them  disappears  gradually  ;    /,  the  two  micronuclei  preparing  for 
division  ;   appearance  of  six  chromosomes  in  each  (one  nucleus  is  seen  in 
profile,  the  other  from  one  pole)  ;   J,  diaster-stages,  showing  three  chromo- 
somes at  each  pole  of  the  spindle  (reducing  division) ;    K,  later  stage,  the 
chromosomes  fused  into  masses  of  chromatin  ;  L,  four  granddaughter-micro- 
nuclei  ;   M ,  one  of  them  grows  in  size,  the  other  three  begin  to  degenerate  ; 
A7,  division  of  the  persistent  micronucleus  to  form  the  two  pronuclei ,  '.O,  two 
pronuclei  and  three  degenerating  micronuclei.     After  Collin  (50),  magnification 
about  2,000  diameters. 

have  exactly  half  the  amount  of  chromatin  contained  in  the  ordinary 
nuclei,  just  as  in  the  Metazoa. 

Doflein  (111)  and  Hartmann  (116)  consider  that  a  process  of 
reduction  is  absolutely  essential  to  the  conception  and  definition 
of  syngamy,  and  regard  reduction  as  a  criterion  whereby  true 
syngamic  union  of  gametes  and  pronuclei  can  be  distinguished 
from  plastogamic  and  nuclear  fusions  which  have  nothing  to  do 
with  the  sexual  process.  "  No  fertilization  without  reduction  " 
(Hartmann).  But  it  must  be  acknowledged  that  in  a  great  many 
cases  of  gamete-formation  in  Protozoa  a  reduction  of  the  chromatin- 

10 


146 


THE  PROTOZOA 


substance  of  the  conjugating  pronuclei  cannot  be  deduced  from 
observation,  and  could  only  be  inferred  from  analogy.  In  the 
gamete-formation  of  Coccidium  schubergi,  so  carefully  studied  by 
Schaudinn  (99),  a  large  number  of  male  pronuclei  are  formed 
simultaneously  by  local  condensations  of  chromidia  thrown  off 
from  the  nucleus  of  the  gametocyte,  which  is  left  behind  in  the 
residual  protoplasm,  with  its  conspicuous  karyosome  (Fig.  50)  ; 
in  the  female  gamete,  also,  the  process  of  reduction  appears  to 
consist  of  a  simple  elimination  of  the  karyosome  (Fig.  75),  a  process 
which  could  be  interpreted  more  naturally  as  elimination  of  effete 
vegetative  chromatin  than  as  a  process  of  true  nuclear  reduction. 
In  the  case  of  Coccidium,  as  in  others  that  might  be  cited,  it  must 
either  be  assumed  that  reduction-processes,  in  the  strict  sense  of 


FIG.  75. — Four  stages  in  the  maturation  of  the  female  gametocyte  of  Coccidium 
schubergi.  A,  Full-grown  macrogametocyte  contained  in  the  host-cell  ; 
B,  the  macrogametocyte  is  beginning  to  round  itself  off  and  to  expel  the 
karyosome  from  its  nucleus  ;  C,  the  karyosome  expelled  from  the  nucleus  of 
the  macrogametocyte  has  reached  the  surface  of  the  body  and  broken  up  into 
a  number  of  fragments,  which  lie  scattered  in  the  body  of  the  host-cell  or  are 
extruded  from  it ;  D,  the  macrogametocyte  has  now  become  a  ripe  macro- 
gamete,  having  rounded  itself  off,  eliminated  the  karyosome  from  its  nucleus, 
and  divested  itself  entirely  of  the  host-cell,  n.,  Nucleus  of  the  gametocyte  ; 
k.,  its  kaiyosome  ;  n.',  nucleus  of  the  host-cell ;  k.',  k.',  fragments  of  extruded 
karyosome.  After  Schaudinn  (99),  magnified  1,000. 

the  phrase,  occur  but  have  been  overlooked,  or  that  the  method  of 
reduction  is  one  that  can  only  be  brought  into  line  with  the  typical 
method  by  theoretical  interpretation  founded  on  analogy. 

It  must  therefore  remain  an  open  question,  in  the  present  state- 
of  our  knowledge,  whether  a  process  of  nuclear  reduction  strictly 
comparable  to  the  process  seen  in  Metazoa  is  essential  to  the 
definition  of  true  syngamy,  or  whether  such  a  process  has  not  been 
evolved  and  perfected  gradually  as  a  consequence  of  the  sexual 
process.  It  is  quite  conceivable  that  syngamy  may  have  been 
at  its  first  origin  merely  a  process  of  intermingling  of  chromatin  of 
distinct  cell -individuals  ;  that  in  this  crude  and  primitive  form 
syngamy  would  tend  to  disturb  the  normal  balance  of  nucleus 
and  cytoplasm,  since  it  would  lead  to  quantitative  excess  of  the 


SYNGAMY  AND  SEX  IN  THE  PROTOZOA  147 

nuclear  substance ;   that,   consequently,    by   a   regulative   process 
which   may  primitively  have  followed   the  syngamic  union,   the 
chromatin  of  the  zygote  was  reduced  to  the  normal  quantity  by 
elimination  of  half  of  its  mass  ;  and  that  from  this  hypothetical 
primitive  process  of  regulation  of  the  nucleo-cytoplasmic  balance 
a  process  of  nuclear  reduction  preceding  the  syngamic  act  has  been 
gradually  evolved  until  it  reaches  its  perfection  in  the  form  seen 
in  the  Metazoa.     On  this  view,  it  is  to  be  expected  that  in  Protista 
a  great  diversity  in  the  methods  of  nuclear  reduction  would  occur, 
from  those  of  the  roughest  type  to  others  highly  elaborated  and 
perfected  ;    and    this    expectation    certainly   receives    justification 
from  the  data  of  observation.     Hertwig  (119),  on  the  other  hand, 
compares  the  reducing  divisions  in  the  maturation  of  the  gametes 
to  the  so-called  "  hunger-divisions  "    in  Infusoria,  which  exhibit 
a  great  disproportion  in  the  relative  mass  of  nucleus  and  cytoplasm 
as  the  result  of  starvation  in  artificial  cultures  ;  in  such  forms  the 
body  is  smaller  than  in  forms  from  a  normal  culture,  but  the  nucleus 
is    not    merely    relatively,    but   absolutely,    larger    than    that    of 
a  normal  form.     The  disturbance  in  the  nucleo-cytoplasmic  ratio 
(see  p.  70,  supra)  can  however,  be  regulated  by  reducing  divisions 
of  the  nucleus.    On  the  ground  of  this  comparison,  Hertwig  considers 
that  the  maturative  processes  of  the  gametes  are  to  be  regarded  as 
the  necessary  consequences  of  antecedent  events*  in  the  life-history 
—as  processes  which  in  their  turn  bring  about  syngamy,  and  not 
such  as  have  the  object  of  preparing  the  nuclei  for  fertilization. 

In  order  to  give  a  more  concrete  idea  of  the  processes  of  syngamy 
and  reduction  in  Protozoa,  a  few  typical  examples  will  now  be 
described,  selected  in  order  to  illustrate  the  salient  features  of 
these  processes.  The  most  convenient  method  of  classification 
of  the  examples  chosen  is  to  distinguish  those  cases  in  which  chro- 
niidia  are  present  in  addition  to  nuclei  from  those  in  which  nuclei 
alone  are  present. 

1.  Syngamy  and  Reduction  icitli  Nuclei  and  Chromidia. — In  a 
great  many  Sarcodina,  especially  those  belonging  to  the  orders 
Anicebsea  (p.  218)  and  Foraminifera  (p.  231),  chromidia  may  be 
present  in  the  gamete-forming  individuals  as  a  permanent  con- 
stituent of  the  body-structure.  In  such  cases  the  chromidia 
represent,  wholly  or  in  part,  the  generative  chromatin,  and  give 
rise,  by  formation  of  secondary  nuclei,  to  the  nuclei  of  the  gametes. 
As  an  example  Arcella  may  be  taken,  the  life-cycle  of  which  is 
described  in  a  subsequent  chapter.  In  this  form  two  distinct 
forms  of  syngamy  have  been  described. 

*  It  is,  of  course,  hardly  necessary  to  point  out  that  starvation  is  by  no  means 
the  only  influence  which  can  bring  about  a  disturbance  of  the  nucleo-cytoplasmw 
equilibrium  ;  over-nutrition,  for  example,  may  have  the  same  effect. 


148  THE  PROTOZOA 

(a)  Karyogamy. — The  body  of  an  Arcella  gives  rise  by  multiple 
gemmation  to  a  number  of  arncebulae,  each  containing  a  secondary 
nucleus  derived  from  the  chromidia,  while  the  primary  nuclei  of 
the  parent-form  degenerate    (Fig.  80).     The  number  and  size  of 
the   amoebulae    vary,    however,    in   different   individuals.     In   one 
Arcella  the  number  is  less  and  the  arncebulae  are  larger,  eight  or 
nine  macramcebce  being    produced.     In  another  the  amcebulge  are 
more  numerous  and  smaller,  about  forty  micramcebce  being  formed. 
In  either  case  the  amcebulae  swarm  out  of  the  parent-shell  and  are 
the  gametes.     A   micramoeba  copulates  with  a  macranioeba,   the 
two  fusing  completely  to  form  a  zygote  with  a  synkaryon.     The 
amoeboid  zygote  thus  produced  is  the  starting-point  in  the  growth 
and  development  of  an  Arcella  (Fig.  80,  A). 

In  this  example  the  karyogamy  is  a  case  of  microgamy,  which, 
like  other  such  cases,  precedes  a  period  of  growth  and  follows  a 
period  of  active  reproduction.  It  is  possible  that  the  syngamy 
of  the  gametes  is  preceded  by  reducing  divisions  of  the  nuclei  of 
the  amcebulae,  but  no  such  reduction  has  been  observed  in  Arcella. 
In  Foraminifera  (p.  235),  in  which  the  syngamy  is  perfectly  isog- 
amous,  each  secondary  nucleus  formed  from  the  generative 
chromidia  divides  twice  to  form  the  gamete-nuclei — divisions 
doubtless  to  be  regarded  as  reducing  divisions.  In  Centropyxis, 
according  to  Schaudinn  (131),  amcebulaa,  all  of  the  same  size,  are 
produced  as  in  Arcella,  by  formation  of  secondary  nuclei ;  but  in 
some  broods  each  amcebula  divides  into  four  micramcebae  (micro- 
gametes),  while  in  other  broods  the  amoebulse  remain  undivided  as 
macramcebae  (macrogametes)  ;  copulation  then  takes  place  between 
two  gametes  of  different  size. 

(b)  Chromidiogamy  (Fig.  80,  M — Q).— Two  ordinary  adult  Arcellce 
come  together  and  apply  the  mouths  of  their  shells.     The  proto- 
plasm of  one  individual  flows  over  almost  entirely  into  the  other 
shell,  taking  with  it  both  chromidia  and  primary  nuclei,  only  so 
much  protoplasm  being  left  in  the  one  shell  as  suffices  to  hold  the 
two  shells  together.     The  primary  nuclei  now  degenerate,  and  the 
chromidia  derived  from  each  conjugant  break  up  into  a  fine  dust 
of  chromatin-particles  and  become  intimately  commingled.     When 
this    process   is    complete,    the    protoplasm   with    the    chromidia 
becomes  again  distributed  between  the  two  shells,  and  the  two 
conjugants  separate.     Then  in  each  individual  secondary  nuclei 
are  formed  from  the  chromidia,  and  by  a  process  of  multiple  gem- 
mation a  number  of  uninucleate  amoebulae  are  formed  which  swarm 
out  of  the  shell,  and,  like  the  zygotes  resulting  from  karyogamy, 
become  the  starting-point  of  a  new  Arcella. 

Thus  chromidiogamy  is  here  a  case  of  macrogamy  which,  like 
other  similar  cases,  follows  a  period  of  growth  and  precedes  a 


SYNGAMY  AND  SEX  IN  THE  PROTOZOA 


149 


period  of  active  reproduction.  Chromidiogamy  is  a  rare  but  very 
interesting  form  of  syngamy  which,  from  the  standpoint  of  general 
notions  with  regard  to  the  evolution  of  the  nucleus,  may  be  re- 
garded as  the  most  primitive  type.  It  is  known  to  occur  also  in 
Difflitgia  (Zuelzer,  85),  where  also  copulation  of  swarm-spores  takes 
place  as  an  alternative  method  (p.  230). 

A  case  must  now  be  considered  in  which  the  chromidia  represent 
vegetative,  while  the  nuclei  contain  the  generative,  chromatin. 
An  example  of  this  state  of  things  is  furnished  by  Plasmodiophora 
brassicce,  a  well-known  parasite  of  cabbages,  turnips,  etc.,  in  which 


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D 

FIG.  76. — Gamete-formation  and  syngamy  in  Plasmodiopliora  brassicce.  A,  Normal 
vegetative  nuclei  of  the  myxamcebse  ;  B,  C,  extrusion  of  chromidia  from 
the  nuclei ;  D,  division  of  the  nuclei  by  karyokinesis  (first  reducing  division)  ; 
E,  nuclei  after  reduction  ;  F,  formation  of  gametes  which  are  fusing  in  pairs  ; 
G,  spore  (zygote)  containing  two  nuclei,  one  of  which  is  going  through  a 
further  reduction-division  ;  H,  fusion  of  the  two  pronuclei  within  the  spore  ; 
1,  ripe  spore  with  synkaryon  and  two  centrioles.  After  Prowazek  (127), 
magnified  about  2,250  diameters. 

it  produces  a  disease  known  as  "  fingers  and  toes  "  (Kohlhernie). 
According  to  the  investigations  of  Prowazek  (127)  and  others, 
Plasmodiopliora  goes  through  a  development  which  may  be  briefly 
summarized  as  follows  :  At  the  end  of  the  "  vegetative  "  period  of 
growth  and  multiplication,  there  are  found  within  the  cells  of  the 
infected  plant  a  number  of  "  myxamcebae,"  amoeboid  individuals 
(plasmodia)  each  with  many  nuclei  containing  distinct  karyosomes 
(Fig.  76,  A).  From  the  nuclei  chromidia  are  given  off  into  the  cell, 
and  during  this  process  the  karyosomes  disappear  and  centrosomes 
make  their  appearance  (Fig.  76,  B,  C).  The  chromidia  are  ab- 


150  THE  PROTOZOA 

3orl>ed  and  disappear,  and  the  nuclei  divide  twice  by  karyokinesis 
(Fig.  76,  D),  so  that  their  number  is  quadrupled.  The  myxamceba 
then  undergoes  multiple  fission  into  as  many  cells  as  there  are 
nuclei  in  the  plasmodium  (Fig.  76,  F),  and  each  of  these  cells  is  a 
gamete.  The  gametes  now  conjugate  in  pairs,  and  the  zygotes 
become  encysted  to  form  the  spores.  Within  the  spores  the  nuclei 
of  the  gametes  are  stated  to  undergo  a  further  process  of  reduction 
before  they  fuse  to  form  the  synkaryon  (Fig.  76,  G).  The  syngamy 
in  Plasmodiopliora  is  stated  to  be  a  case  of  autogamy,  but  this 
allegation  assumes  that  the  nuclei  of  the  myxamcebse  are  sister- 
nuclei  derived  all  from  the  division  of  one  original  nucleus  ;  they 
may  equally  well  be  nuclei  of  different  origins  brought  together  by 
plastogamic  fusions. 

The  two  examples  selected,  Arcella  and  PlasmodiopJiora,  show 
that  the  chromidia  may  represent  generative  chromatin  in  one 
case,  vegetative  in  another.  Goldschmidt  (57)  has  proposed  to 
distinguish  these  two  conditions  by  a  special  terminology,  retaining 
the  name  "  chromidia  "  (trophochromidia,  Mesnil,  74)  for  those  which 
are  purely  vegetative,  and  coining  a  new  term,  sporetia  (idio- 
chromidia,  Mesnil)  for  those  of  generative  nature.  It  is  more 
convenient,  however,  to  retain  the  term  "  chromidia "  in  its 
original  significance,  to  denote  simply  extraiiuclear  particles  of 
chromatin,  and  to  qualify  the  term  by  the  adjectives  "  vegetative  " 
and  "  generative  "  when  required  (see  also  Goldschmidt,  41,  p.  130)^ 
The  formation  of  vegetative  chromidia,  which  are  finally  absorbed, 
is  a  common  phenomenon  in  many  Protozoa  ;  it  may  take  place 
as  a  purely  regulative  process,  as  in  Actinosphcerium  during  de- 
pression-periods (p.  208),  when  hypertrophy  of  the  nuclear  apparatus 
is  corrected  by  the  extrusion  from  the  nuclei  of  chromidia,  which 
ultimately  degenerate  and  become  converted  into  masses  of  pig- 
ment, and  as  such  are  eliminated  from  the  protoplasm. 

The  account  given  by  Bott  (103)  of  gamete-formation  in  the  commoni 
Pelomyxa  (Amcebcea  nuda,  p.  227)  describes  a  condition  in  which  chromidia, 
extruded  from  the  nuclei,  are  partly  vegetative,  partly  generative  ;  secondary 
nuclei  are  formed  from  them,  which  later  cast  out  a  portion  of  their  chromatin, 
then  give  rise  to  the  gamete-nuclei.  After  the  secondary  nuclei  have  been 
purified  in  this  way  of  their  vegetative  chromatin,  the  generative  chromatia 
remaining  in  each  of  them  forms  a  karyokinetic  spindle  with  eight  chromo- 
somes, and  a  reducing  division  follows  by  which  each  daughter-nucleus  obtains 
four  chromosomes.  The  "  pronuclei  of  the  first  order,"  resulting  from  t he- 
first  reducing  division,  divide  again,  forming  a  spindle  with  four  chromosomes 
which  split,  so  that  the  "  pronuclei  of  the  second  order  "  have  also  four  chro- 
mosomes. From  the  nuclei  that  have  undergone  reduction  in  this  manner 
the  nuclei  of  the  gametes  arise  in  a  somewhat  remarkable  fashion  :  the  pro- 
nuclei  of  the  second  order  separate  into  two  compact  masses  of  chromatin  ; 
a  vacuole  is  formed  near  them  ;  and  the  chromatin  of  the  two  masses  wanders, 
in  the  form  of  finely- divided  granules,  into  the  vacuolo  to  form  the  definitive- 
pronucleus  of  the  gamete,  which  forms  a  membrane  when  the  process  is- 
complete.  When  formed  the  gametes  wander  out  as  Heliozoon-like  ind; 


SYNGAMY  AND  SEX  IN  THE  PROTOZOA  151 

.viduals,  which  copulate  in  pairs,  and  the  uninucleate  zygote  grows  up  into  the 
uiultinucleate  Pelomyxa. 

The  conception  of  vegetative  and  generative  chromidia  has  not  been 
accepted  universally  or  without  criticism.  Hartmann,  as  pointed  out  above, 
considers  that  many  cases  of  generative  chromidia  are  really  the  result  of  a 
disruption  of  a  polyenergid  nucleus  ;  Awerinzew  (47)  is  of  opinion  that,  while 
all  Protozoa  possess  vegetative  chromidia  at  some  stage  at  least  in  the  life- 
cycle,  generative  chromidia  are  to  be  considered  as  a  new  acquisition,  a  hasten- 
ing of  the  process  of  the  formation  of  numerous  gamete-nuclei ;  Dobell  (51) 
puts  forward  a  similar  view  with  regard  to  generative  chromidia.  With 
regard  to  the  latter  criticism,  it  may  be  pointed  out  that  nuclei  may  become 
resolved  into  chromidia  in  order  to  undergo  simple  binary  fission.  With 
regard  to  Hartmann's  view,  there  is  at  present,  at  least,  little  evidence  that 
it  is  an  adequate  explanation  of  the  many  cases  of  formation  of  secondary 
generative  nuclei  from  chromidia  known  amongst  the  Sarcodina.  The  ques- 
tion is  discussed  further  below  (p.  255). 

2.  Syncjamy  and  Reduction  with  Nuclei  only. — A  very  simple 
example  is  furnished  by  the  common  Actinophrys  sol  (Fig.  71),  as 
described  by  Schaudinn  (129).  Conjugation  takes  place  between 
two  adult  forms  (macrogarny),  which  come  together  and  become 
enclosed  in  a  common  cyst.  The  nucleus  of  each  individual  then 
divides  by  karyokinesis,  and  one  nucleus  of  the  pair  thus  produced 
is  expelled  from  the  body  and  undergoes  degeneration  as  a  reduction 
nucleus.  The  persistent  nucleus  of  each  individual  then  repeats 
the  process  and  forms  a  second  reduction-nucleus.  The  nucleus 
now  remaining  in  each  cell  is  the  definitive  pronucleus.  The  two 
gametes  now  copulate,  their  pronuclei  fusing  to  form  the  synkaryon, 
after  which  the  synkaryon  divides  by  karyokinesis  and  the  zygote 
divides  into  two  individuals  which  later  escape  from  the  cyst  and 
resume  the  free-living  vegetative  life.  The  course  of  syngamy  in 
Actinophrys  is  exactly  similar  to  that  performed  by  the  two 
"  secondary  cysts  "  derived  from  division  of  a  "  primary  cyst  "  in 
Actinosphcerium  (see  p.  138,  supra}.  In  both  cases  alike  the  nucleus 
of  the  conjugants  may  be  supposed  to  contain  both  vegetative 
and  generative  chromatin  mixed  together.  It  is  possible  that  the 
vegetative  chromatin  is  extruded  from  the  nucleus  in  the  form  of 
chromidia  prior  to  the  reducing  divisions,  but  no  elimination  of 
vegetative  substance  has  been  described. 

The  last  example  of  syngamy  in  Protozoa  that  need  be  con- 
sidered specially  at  this  point  is  that  of  the  Infusoria,  which  have 
been  the  subject  of  numerous  investigations.  These  organisms 
present  the  highest  degree  of  specialization  of  the  body-structure 
and  elaboration  of  the  nuclear  apparatus  found  in  any  Protozoa. 
Their  syngarnic  processes  vary  in  detail  to  some  extent  in  different 
cases  (see  p.  448),  but  the  whole  process  is  essentially  as  follows 
(Fig.  77)  :  Two  individuals  come  together  and  adhere,  placing 
themselves  side  by  side.  The  two  conjugants  may  be  similar  in 
visible  constitution,  or  may  differ  to  a  greater  or  less  extent,  and 


152 


THE  PROTOZOA 


FIG.  77. — Diagram  showing  the  successive  stages  of  conjugation  in  Infusoria. 
A,  The  two  conjugants  attached,  each  with  a  macronucleus  (N)  and  a  micro- 
nucleus  (n)  ;  B,  C,  the  micronucleus  of  each  conjugant  dividing ;  D,  each 
conjugant  has  two  micronuclei  which  are  beginning  to  divide  again  ;  E,  each 
conjugant  has  four  micronuclei  ;  the  niacronuclei  are  beginning  to  become 
irregular  in  form  ;  in  later  stages  they  degenerate,  break  up,  and  are  absorbed  ; 
F,  three  of  the  four  micronuclei  of  each  conjugant  are  degenerating  and 
being  absorbed  ;  the  fourth  is  dividing  ;  G,  one  half  of  each  dividing  micro- 
nucleus  of  the  preceding  stage  has  travelled  over  into  the  other  conjugant 
as  the  migratory  pronucleus  ;  H,  I,  fusion  of  the  stationary  pronucleus  of  each 
conjugant  with  the  migratory  pronucleus  derived  from  the  other  conjugant 
to  form  the  synkaryon  (S.) ;  J ,  the  two  conjugants  now  separate  ;  in  each 
ex-con jugant  the  synkaryon  (S.)  divides  ;  the  old  macronuclei  are  now  almost 
completely  absorbed  ;  K,  L,  the  synkaryon  has  divided  into  two  nuclei,  one 
of  which  grows  large  and  becomes  the  new  macronucleus,  the  other  remains 
small  and  becomes  the  new  micronucleus,  of  each  ex-conjugant.  After  Delage 
and  Herouard. 


SYNGAMY  AND  SEX  IN  THE  PROTOZOA  153 

are  sometimes  markedly  different  in  size  (Doflein,  111).  The 
greatest  amount  of  differentiation  is  seen  in  the  order  Peritricha 
(p.  448),  where  microconjugants  and  macroconjugants  can  be  dis- 
tinguished. Each  conjugant  has  a  microiiucleus  and  a  macro- 
nucleus.  The  macronucleus  begins  to  degenerate,  and  finally  dis- 
appears completely.  The  microiiucleus,  on  the  other  hand,  en- 
larges and  divides  by  a  simple  form  of  karyokinesis  (see  p.  114, 
supra).  The  division  of  the  microiiucleus  is  repeated  twice  as 
a  rule,  but  sometimes  three  times,  and,  as  stated  above,  in  one  of 
these  divisions  the  number  of  chromosomes  is  halved  in  a  great 
mairy,  possibly  in  all,  cases.  Of  the  four  (or  eight)  micronuclei 
thus  formed,  all  but  one  represent  reduction-nuclei  which  are 
absorbed  and  disappear.  The  persistent  microiiucleus  then  divides 
by  equating  division  into  two  pronuclei,  which  may  be  distinguished 
as  migratory  and  stationary,  respectively  ;  they  sometimes  exhibit 
distinct  structural  differentiation.  At  this  juncture  the  cuticle 
of  each  conjugant  is  absorbed  at  the  point  of  contact,  and  the 
migratory  pronucleus  of  each  conjugant  passes  over  into  the 
protoplasm  of  the  other  and  fuses  with  its  stationary  pronucleus. 
The  gap  in  the  cuticle  is  now  repaired  and  the  two  individuals 
separate,  each  ''  ex-conjugant  "  having  a  synkaryon  constituted 
by  a  fusion  of  one-eighth  (or  one-sixteenth)  of  its  own  original 
micronucleus  with  the  same  fraction  of  the  microiiucleus  of  the 
other  partner.  The  synkaryon  grows  and  divides  into  two  nuclei, 
one  of  which  grows  and  becomes  the  macronucleus,  while  the  other 
remains  small  and  becomes  the  micronucleus,  of  the  ex-coiijugant, 
which  thereby  becomes  indistinguishable  from  an  ordinary  in- 
dividual of  the  species,  and  proceeds  to  start  on  a  course  of  vegeta- 
tive growth  and  reproduction  in  the  usual  manner,  until  the  next 
act  of  syngamy  initiates  a  fresh  cycle.  It  has  been  observed  that 
the  two  ex-conjugants  sometimes  differ  markedly  in  their  capacities, 
one  of  them  multiplying  much  faster  than  the  other. 

In  the  syngamy  of  Ciliata  it  is  seen  clearly  that  the  macronucleus 
represents  effete  vegetative  or  "  somatic  "  chromatin,  which  is 
eliminated  bodily  from  the  life-history  of  the  organism,  while  the 
micronucleus  represents  reserve  generative  chromatin  from  which, 
after  reduction,  the  entire  nuclear  apparatus  is  regenerated.  The 
remarkable  feature  in  the  syngamy  of  Infusoria  is  the  manner 
in  which  the  coiijugants  remain  distinct,  and  merely  exchange 
pronuclei  (so-called  "partial  karyogarny ").  Versluys  (137), 
following  Boveri,  derives  this  from  an  ancestral  condition  of  iso- 
gamic  copulation — that  is  to  say,  a  condition  in  which  the  two 
coiijugants  fused  completely  as  gametes,  both  body  and  nucleus, 
after  which  the  zygote  divided  into  two  individuals  ;  on  this  view 
the  final  division  of  the  micronucleus  which  gives  rise  to  the  two 


154  THE  PROTOZOA 

pronuclei  is  to  be  regarded  as  the  equivalent  of  the  division  of 
the  synkaryon  which  took  place  ancestrally  after  syngamy.  While, 
however,  there  is  a  general  agreement  that  partial  karyogamy 
(conjugation)  is  to  be  derived  from  total  karyogamy  (copulation), 
it  is  very  doubtful  if  the  two  conjugants  in  Infusoria  represent 
simple  gametes  ;  it  is  more  probable  that  the  type  of  syngamy 
characteristic  of  Infusoria  is  derived  from  an  ancestral  condition 
in  which  each  conjugant  produced  a  number  of  minute  gametes 
(swarm-spores)  which  copulated  (compare  especially  Popoff,  125, 
and  Hartmann,  116,  and  see  p.  453,  infra).  On  this  view  the 
divisions  of  the  micronucleus  represent  a  primitively  much  larger 
number  of  divisions  which  produced  the  numerous  gametes,  and 
the  conjugants  themselves  are  not  to  be  regarded  as  true  gametes, 
but  rather  as  gametocytes  or  gamonts. 

Having  now  illustrated  by  typical  examples  the  various  forms 
which  the  syngamic  process  takes  in  Protozoa,  we  may  conclude 
this  chapter  by  a  consideration,  necessarily  brief,  of  the  problem 
of  the  significance  and  origin  of  syngamy  and  sex.  This  is  a 
problem  which  has  a  vast  literature,  and  it  is  only  possible  here  to 
indicate  in  outline  some  of  the  theories  that  have  been  put  forward, 
none  of  which  can  claim  to  be  a  complete  solution  of  one  of  the 
profoundest  nrysteries  of  the  living  substance  and  its  activities. 

Considering  first  the  fertilization  of  the  Metazoa,  it  is  evident 
that  the  union  of  the  spermatozoon  with  the  ovum  has  two  prin- 
cipal results.  In  the  first  place  the  spermatozoon  brings  with  it 
a  pronucleus,  the  equivalent  of  that  contained  in  the  ovum,  but 
derived  from  a  distinct  individual,  and  therefore  possessing  different 
hereditary  tendencies  acquired  from  its  own  particular  ancestral 
history.  The  union  of  the  male  and  female  pronuclei  brings  about, 
therefore,  a  process  for  which  Weismann  has  coined  the  term  amphi- 
mixis— that  is  to  say,  a  mingling  of  different  hereditary  tendencies 
in  one  and  the  same  individual.  In  the  second  place  the  spermato- 
zoon produces  a  result  which  may  be  termed  briefly  "  developmental 
stimulus  ':  (Entwicklungserregung) — that  is  to  say,  it  produces 
a  disturbance  in  the  equilibrium  of  the  protoplasmic  body  of  the 
ovum  which  causes  it  to  start  on  a  course  of  cell-division  oft-re- 
peated, a  process  of  cleavage  which  converts  the  unicellular  ovum 
into  the  mass  of  cells  which  supplies  the  material  for  the  building 
up  of  the  multicellular  body.  It  is  very  probable  that  the  develop- 
mental stimulus  is  supplied  by  the  greatly-developed  centrosome 
of  the  spermatozoon,  that  of  the  ovum  having  completely  atrophied, 
apparently,  after  the  completion  of  its  maturative  processes. 

The  introduction  of  a  male  pronucleus — that  is  to  say,  the  process 
of  amphimixis — can  be  effected  only  by  the  spermatozoon.  But 
the  researches  of  Loeb  and  others  have  demonstrated  fully  that  the 


SYNGAMY  AND  SEX  IN  THE  PROTOZOA  155 

spermatozoon  is  not  indispensable  for  supptying  a  developmental 
stimulus  ;  an  unfertilized  ovum  can  be  induced  by  artificial  stimuli 
of  various  kinds  to  start  upon  a  course  of  development  similar  to 
that  initiated,  under  natural  circumstances,  by  fertilization  with 
a  spermatozoon.  Hence,  of  the  two  results  produced  in  the  fertiliza- 
tion of  Metazoa,  amphimixis  alone  would  appear  to  be  that  which  is 
essential  and  peculiar  in  the  process,  and  which  only  fertilization 
can  bring  about. 

From  the  above  considerations,  amphimixis  is  regarded  by  many 
thinkers  as  the  essence  of  syngamy,  a  necessity  for  the  evolution 
of  living  beings  in  that  it  supplies,  by  the  intermingling  of  different 
hereditary  tendencies,  the  conditions  required  for  the  production 
of  "  innate  "  variations  in  organisms  in  which  the  germinal  substance 
is  shielded  from  the  direct  influence  of  external  conditions  by  its 
position  within  a  multicellular  body.  Apart  from  the  question, 
however,  whether  any  such  innate  variations  exist  in  the  Protozoa, 
where  all  cells  alike  are  exposed  equally  to  the  direct  action  of  the 
environment,  the  criticism  has  often  been  made  that  amphimixis 
gives  only  a  teleological  explanation  of  the  sexual  process,  and  as- 
such  cannot  be  invoked  as  a  causal  explanation  of  its  origin.  The 
intermingling  of  distinct  hereditaiy  tendencies,  however  useful  to 
the  organism  or  important  in  the  evolution  of  living  beings  generally, 
cannot  be  regarded  as  the  incentive  to  syngamy  at  its  first  appear- 
ance in  the  Protista.  In  other  words,  amphimixis  must  be  regarded 
as  a  secondary  consequence,  not  as  a  primary  cause,  of  syngamy. 

It  is  necessary,  therefore,  to  seek  some  explanation  for  the 
first  origin  of  syngarny  other  than  the  benefits  which  it  may  confer 
through  amphimixis,  and  it  is  undoubtedly  among  Protist  organisms 
that  the  conditions  under  which  synganiy  first  arose  must  be 
sought.  It  has  been  pointed  out  above  that  syngarny  appears  to 
have  a  strengthening  or  recuperating  effect  upon  the  cell-organism, 
and  upon  such  grounds  has  been  founded  the  theory  of  "  rejuven- 
escence "  (Verjiingung).  According  to  this  theory,  connected 
chiefly  with  the  name  of  Maupas,  the  cell-protoplasm,  after  many 
generations  of  reproduction  by  fission,  tends  to  become  effete  and 
senile  to  an  ever  -  increasing  degree,  a  condition  which,  if  not 
remedied,  ends  in  the  death  of  the  organism  ;  the  natural  remedy 
is  furnished,  however,  by  the  process  of  syngamy,  which  has  the 
effect  of  renewing  the  "  youth  "  of  the  cell  and  starting  it  upon 
a  fresh  series  of  generations,  until  senilhty,  once  more  supervening, 
necessitates  syngamy  again. 

The  rejuvenescence-theory  has  been  criticized  by  many  critics 
who  have  themselves  done  little  more,  in  some  cases,  than  give  a 
more  precise  meaning  to  the  terms  "  youth  '"  and  "  old  age," 
terms  that  certainly  stand  in  need  of  further  explanation,  since 


156  THE  PROTOZOA 

it  can  hardly  be  supposed  that  the  time-factor  alone  can  account 
for  the  exhaustion  or  depression  of  the  vital  faculties.  It  is  gener- 
ally admitted  that  unicellular  organisms,  such  as  the  Protozoa, 
tend,  after  a  greater  or  less  number  of  generations,  to  exhibit  a 
certain  degree  of  exhaustion  in  their  vital  properties,  or,  it  may  be, 
of  derangement  in  their  organization  and  vital  mechanisms.  Hert- 
wig  (164)  is  of  opinion  that  "  the  conditions  of  death  exist  in  the 
living  substance  from  the  beginning,  and  are  a  necessary  conse- 
quence of  its  vital  function  "  —a  generalization  which  may  be 
accepted  for  those  Protista  in  which  the  body  exhibits  the  degree  of 
specialization  and  structural  complication  proper  to  a  true  cell 
(as  the  term  is  understood  in  this  book — see  p.  98)  ;  but  it  is  very 
doubtful  if  it  is  true  also  for  the  simplest  forms  of  life,  such  as  the 
bacteria  and  allied  organisms.  If  it  be  further  admitted  that 
syngamy  is  the  natural  remedy  in  unicellular  organisms  for  a  natural 
disease,  the  problem  before  us  is  to  discover,  if  possible,  the  precise 
nature  of  the  derangements,  and  of  the  method  by  which  the 
remedy  restores  them  to  the  normal  functional  condition. 

At  the  outset,  attention  must  be  drawn  to  a  very  constant  and 
general  preliminary  to  syngamy  in  Protozoa — namely,  the  elimina- 
tion of  a  large  amount  of  chromatin  which  appears  to  have  been 
regulating  the  vital  activities  during  previous  generations  (vegeta- 
tive chromatin),  and  its  replacement  by  chromatin  which  has  been 
inactive  and  lying  in  reserve  (generative  chromatin).  This  process 
is  seen  in  its  most  striking  form  in  the  Ciliata,  where  the  macro- 
nucleus  is  entirely  eliminated  during  the  act  of  syngamy,  and  is 
replaced  in  subsequent  generations  by  a  new  macroiiucleus  derived 
from  the  micronucleus  formed  by  fusion  of  portions  of  the  micro- 
nuclei  of  the  partners  in  syngamy.  Hence  it  might  seem  as 
if  the  chief  result  of  syngamy  was  to  replace  effete  vegetative 
chromatin  by  fresh  generative  substance  which  through  inactivity 
has  retained  its  powers  unimpaired.  But  in  the  first  place  it  must 
be  pointed  out  that,  to  effect  a  replacement  of  this  kind,  the  union 
of  two  individuals  is  not  necessary  ;  it  would  be  sufficient  for  a 
single  individual  to  form  a  new  nucleus  from  its  store  of  generative 
chromatin,  and  to  get  rid  of  its  old,  effete  vegetative  chromatin. 
If  we  regard  the  chromidia  of  Arcella  as  composed  of  generative 
chromatin,  the  buds  produced  by  formation  of  secondary  nuclei 
from  the  chromidia  would  represent  nuclear  regeneration  of  this 
kind.  Secondly,  it  is  open  to  doubt  how  far  the  theory  of  vegeta- 
tive and  generative  chromatin  can  be  applied  throughout  the  whole 
series.  In  such  forms  as  Arcella  the  chromidial  mass,  although  it 
furnishes  the  gamete-nuclei,  is  a  cell-element  in  a  functional  con- 
dition, and  in  the  more  primitive  forms  the  distinction  between 
vegetative  and  generative  chromatin  cannot  be  pressed  so  far  as 


SYNGAMY  AND  SEX  IN  THE  PROTOZOA  157 

in  highly- organized  forms,  such  as  the  Ciliata.  Hertwig  (68)  con- 
siders that  the  separation  of  two  kinds  of  chromatin  is  an  adaptation 
to  particular  conditions  of  life,  evolved  progressively,  and  attaining 
its  greatest  perfection  in  the  Ciliata  ;  whereby  chromatin  which 
has  become  functionally  effete  is  separated  from  that  which  has 
retained  its  constitution. 

According  to  the  view  put  forward  by  Hertwig  (118),  syngamy 
remedies  the  effete  condition  of  the  cell  chiefly  by  regulating  the 
necessary  quantitative  balance  between  the  nucleus  and  the  cyto- 
plasm. Such  regulation  may  be  effected  also  by  internal  re- 
arrangements of  the  nuclear  substance  or  by  plastoganiy,  but  is 
brought  about  most  efficiently  by  syngamy,  since  the  definite  and 
necessary  mutual  relations  between  nucleus  and  cytoplasm  are 
better  maintained  by  "  arrangements  which  prevent  disturbance, 
than  b^y  arrangements  which  compensate  for  disturbances  that 
have  already  set  in."  The  obvious  criticism  of  this  theory  is  that 
it  is  difficult  to  understand  why  an  internal  regulative  process  of 
the  cell  should  require  the  co-operation  of  two  individuals,  and  the 
reason  contained  in  the  sentence  just  quoted  from  Hertwig  scarcely 
seems  an  adequate  explanation. 

The  fact  that  two  cells  participate  in  syngamy  indicates  in  itself 
that  the  necessity  for  syngamy  depends  on  a  loss  of  balance  between 
two  constituents  or  substances  in  the  cell,  and  that  the  union  of 
the  two  gametes  restores  equilibrium.  As  Hertwig  (119)  has 
pointed  out,  the  quantitative  relation  of  nucleus  to  cytoplasm  is 
more  altered  in  the  gametes  of  Metazoa  than  in  any  other  cells, 
and  to  opposite  extremes  in  the  two  sexes  ;  in  the  ovum  the  quantity 
of  cytoplasm  is  enormous  in  proportion  to  the  nucleus,  while  in 
the  spermatozoon  the  exact  reverse  is  the  case.  The  same  argu- 
ment applies  to  a  greater  or  less  degree  in  the  case  of  anisogamous 
gametes  of  Protozoa.  It  would  not,  however,  apply  to  the  many 
cases  of  isogamy  in  Protozoa  where  the  quantitative  relations  of 
nucleus  and  cytoplasm  are  the  same  in  each  gamete  ;  in  such  cases 
union  of  the  gametes  would  leave  the  nucleo-cytoplasmic  relation 
exactly  what  it  was  before. 

A  theory  of  a  different  kind  has  been  put  forward  by  Schaudinn 
(133)  and  his  folloAvers  Prowazek  (128)  and  Hartmann  (116), 
which  is  based  on  the  notion  that  sex  and  sexual  differentiation 
are  primary  characteristics  of  living  matter.  A  normally  function- 
ing cell  is  regarded  as  hermaphrodite,  having  male  and  female 
elements  equally  balanced.  The  differentiation  which  leads  to 
the  formation  of  gametes  arises,  as  Biitschli  originally  suggested, 
from  inequalities  in  the  results  of  cell-division,  which  may  be 
supposed  to  lead  always  to  more  or  less  imperfect  partition  of  the 
qualities  of  the  parent-cell  between  the  daughter-cells.  As  a  result 


158  THE  PROTOZOA 

of  the  defects  in  the  process  of  cell-division,  some  cells  acquire  more 
;'  male  "  properties,  other  more  "  female  "  ;  the  cells  preponder- 
atingly  male  show  greater  kinetic  and  motile  energy,  those  that 
have  more  female  qualities  show  greater  trophic  activity.  With  con- 
tinued cell-division  these  opposite  tendencies  tend  to  accumulate  in 
certain  cells  which  in  consequence  become  altogether  one-sided  in 
their  vital  activities.  Thus  a  want  of  balance  in  the  vital  functions 
is  brought  about,  which  may  reach  such  a  pitch  that  the  organism  is 
unable  to  continue  to  assimilate  and  reproduce,  and  must  die  unless 
the  balance  is  resorted  by  syngamy  with  an  individual  that  has  become 
specialized  in  the  opposite  direction.  By  the  union  of  two  gametes 
differentiated  in  this  manner,  equilibrium  is  restored  and  the  vital 
functions  are  rein  vigor  ated.  No  gametes,  however,  whatever  their 
degree  of  specialization,  are  to  be  considered  as  perfectly  unisexual, 
but  only  relatively  so ;  a  male  gamete  will  always  contain  a  certain 
amount  of  female  substance,  and  a  female  gamete  a  certain  amount 
of  male  substance,  thus  accounting  for  the  possibility  of  partheno- 
genesis. Schaudinn's  theory  of  sex  is  thus  very  similar  to  that 
developed  by  Weiniiiger  on  purely  psychological  grounds. 

Schaudimi,  whose  work  on  Protozoa  must  secure  full  considera- 
tion for  any  statement  of  his  observations,  however  inherently 
improbable  the  facts  or  the  interpretations  based  upon  them  may 
seem,  founded  his  theorj^  chiefly  on  data  alleged  to  have  been 
observed  by  him  in  the  development  of  Trypanosoma  noctuce  (Schau- 
dinn, 132).  According  to  him,  an  "  indifferent  "  ookinete  might 
give  rise  either  to  male  or  female  forms.  In  the  formation  of  males, 
certain  nuclear  elements  were  separated  out  to  become  those  of 
the  daughter-cells,  while  certain  other  nuclear  elements  remained 
behind  and  degenerated  together  with  a  quantity  of  residual 
protoplasm.  In  the  formation  of  females,  the  same  two  sets  of 
nuclear  structures  were  separated  out,  but  those  proper  to  the 
male  sex  degenerated,  while  those  of  the  female  sex,  which  were 
just  those  which  degenerated  in  the  formation  of  males,  in  this 
case  persist  and  become  the  nucleus  of  the  female  gamete.  Thus 
the  indifferent  ookinete  was  supposed  to  be  really  hermaphrodite, 
containing  male  and  female  elements  mixed  together,  and  giving 
rise  to  individuals  of  one  or  the  other  sex  by  persistence  of  one  set 
of  characters  and  atrophy  of  the  other.  It  must  be  noted  here 
that  these  observations  of  Schaudinn's  are  entirely  unconfirmed, 
nothing  similar  having  as  yet  been  found  by  other  investigators, 
either  in  trypanosomes  or  in  any  other  Protozoa  ;  and  further  that, 
even  if  Schaudinn's  observations  be  accepted  as  exact  in  every  detail, 
they  will  not  bear  the  interpretations  which  he  places  upon  them — 
namely,  that  the  small  and  large  forms  produced  as  he  describes 
are  males  and  females,  since,  a.s  he  himself  admits,  they  do  not, 


SYNGAMY  AND  SEX  IN  THE  PROTOZOA  159 

when  developed,  perform  any  act  of  syngamy.  The  alleged 
sexuality  of  the  forms  described  by  Schaudinn  lacks  the  only  de- 
cisive criterion  of  sexual  differentiation — namely,  sexual  behaviour  ; 
and  the  differentiation  exhibited  by  the  two  forms  of  trypanosomes 
described  by  Schaudinn  admits  of  an  entirely  different  and  far  less 
forced  interpretation  (see  p.  176,  infra). 

There  are  two  further  criticisms  that  may  be  made  of  Schaudinn's 
theory.  The  first  concerns  the  alleged  universality  of  sexual 
differences  in  living  matter.  It  must  be  pointed  out  that,  as  stated 
above,  at  the  present  time  we  have  no  evidence  whatever  of  the 
occurrence  of  true  syngamy  in  any  organisms  of  the  bacterial 
grade.  The  processes  that  have  been  interpreted  by  Schaudinn 
as  autogamy  in  certain  bacteria  may  be  much  more  easily  regarded 
as  processes  of  internal  regulation  of  the  chromatin-substance. 
Nowhere  yet  has  the  union  of  two  distinct  gametes  been  observed 
in  any  bacterial  organisms.  The  theory  that  sex  is  a  universal 
characteristic,  and  syngamy  an  elementary  function,  of  living  things, 
does  not  rest  at  the  present  time  on  any  basis  of  established  fact. 

The  second  criticism  is  that  the  terms  "  male  "  and  "  female  ': 
require  definition  and  explanation,  without  which  they  remain 
meaningless,  connoting  merely  unknown,  mystic  properties,  not 
further  analyzable,  of  the  living  substance.  The  characteristic 
feature  exhibited  by  male  cells  is  the  preponderance  of  kinetic 
activity,  and  by  female  cells,  of  trophic  functions,  as  Schaudinn  and 
many  others  have  pointed  out.  Before  Schaudinn,  the  same  idea 
was  expressed  in  different  language  by  Geddes  and  Thomson  (114), 
who  regarded  the  male  sex  as  characterized  by  katabolic,  the 
female  sex  by  anabolic  activities.  It  we  suppose  that  these  two 
manifestations  of  physiological  activity  have  each  a  distinct  material 
basis  in  the  living  cell,  then  it  can  easily  be  imagined  that  the 
imperfections  of  cell-division  may  lead  to  the  production  of  cells 
in  which  one  or  the  other  substance  predominates.  This  is  the 
view  that  Doflein  (7)  has  developed  in  his  very  interesting  critical 
summary  of  the  views  that  have  been  put  forward  upon  the  sexual 
problem.  He  supposes,  further,  that  these  two  different  physio- 
logical qualities  depend  upon  substances  which  have  intense  mutual 
interactions  and  attract  each  other  strongly,  and  that  a  certain 
equilibrium  between  them  is  necessary  for  the  normal  life  of  the 
cell.  When,  therefore,  one  or  the  other  substance  preponderates 
greatly  in  a  cell,  a  functional  derangement  results  ;  but  since  cells 
differentiated  in  opposite  directions  attract  each  other  strongly, 
they  tend  to  unite,  and  by  their  union  to  restore  equilibrium. 

The  question  of  the  sexual  differentiation  of  the  gametes  is  one 
that  will  be  discussed  at  greater  length  in  the  next  chapter.  It  is 
only  necessary  to  point  out  here  that  a  clear  distinction  must  be 


160  THE  PROTOZOA 

drawn  between  intrinsic  differences,  not  necessarily  visible,  and 
structural  or  other  differences  which  are  more  or  less  obvious. 
The  fact  that  gametes  and  pronuclei  tend  to  unite  proves  that  in 
all  cases  there  must  be  intrinsic  differences  between  them  which 
stimulate  them  to  do  so  ;  in  this  sense,  at  least,  we  may  endorse 
fully  the  dictum  of  Her  twig,  that  "  fertilization  depends  on  a 
fusion  of  sexually-differentiated  cell-nuclei."  On  the  other  hand, 
gametes  of  opposite  sexes  exhibit  every  possible  condition  from 
complete  similarity  in  structure  and  appearance  to  the  greatest 
possible  contrast  in  every  feature  of  their  organization.  There 
can  be  no  doubt  that  visible  differentiation  of  the  gametes  is 
largely,  if  not  entirely,  an  adaptation  to  the  functions  that  they 
have  to  perform  ;  and  this  conclusion  is  by  no  means  weakened 
by  the  fact  that  there  are  many  cases  of  isogamy  which  are  un- 
doubtedly  secondary,  in  which  a  more  primitive  and  phylogeneti- 
cally  older  structural  differentiation  has  gradually  become  annulled, 
under  circumstances  in  which  adaptive  differences  in  the  gametes 
are  no  longer  necessary — as,  for  example,  in  gregarines  (p.  173). 

In  Metazoa  it  is  generally  recognized  that  the  two  pronuclei 
that  undergo  fusion  are  perfectly  equivalent,*  and  that  the  dif- 
ferences seen  between  them  in  the  gametes  are  temporary  and,  in 
the  case  of  the  spermatozoon,  an  adaptation  to  circumstances  ;  here 
the  real  differentiation  of  the  gametes  affects  only  cytoplasmic 
characters.  In  Protozoa,  on  the  other  hand,  the  conjugating 
pronuclei  often  exhibit  differences  of  structure  when  the  cells 
themselves  appear  perfectly  similar.  In  the  Infusoria,  for  instance, 
differences  have  been  noted  between  the  migrator}7  and  stationary 
pronuclei ;  how  far  these  differences  may  be  correlated  directty  with 
the  differences  in  their  activities  must  remain  an  open  question. 

In  the  foregoing  paragraphs  we  have  set  forth  and  discussed 
some  of  the  attempts  that  have  been  made  to  solve  the  problem 
of  sex.  It  cannot  be  said  that  a  perfectly  satisfactory  solution 
has  been  attained,  but  at  least  certain  conditions  of  the  problem 
may  be  laid  down.  In  the  first  place,  no  theory  of  sex  is  satis- 
factory which  does  not  explain  why  the  union  of  two  cells  should 
be  necessary  in  syngamy.  In  the  second  place  a  teleological  inter- 
pretation, such  as  amphimixis,  can  only  state  a  secondary  con- 
sequence, not  a  primary  cause,  of  sexual  union ;  but  such  a 
consequence  may  suffice  to  explain  the  retention  and  persistence 
of  sexual  phenomena  after  the  conditions  have  ceased  to  exist  under 
which  they  came  into  existence. 

In  the  simplest  Protista  of  the  bacterial  grade,  it  may  be  supposed, 
either  that  the  living  matter  is  not  differentiated  into  localized 
substances  having  distinct  physiological  qualities,  or  that  in  such 

*  Apart,  that  is  to  say,  from  the  much-discussed  question  of  the  supernumerary 
chromosome. 


SYNGAMY  AND  SEX  IN  THE  PROTOZOA  161 

minute  bodies  reproduction  by  fission  does  not  produce  differentia- 
tion in  the  fission-products.  With  increased  size  such  differences 
may  arise,  at  first  to  a  minor  extent,  and  capable  of  being  adjusted 
by  internal  rearrangements  of  the  living  substance  such  as  have 
been  described  in  the  larger  Bacteria.  Not  until  the  process  of 
natural  evolution  had  gone  so  far  as  to  produce  the  full  complica- 
tion of  structure  seen  in  a  true  cell  would  localized  differences  hi 
the  living  substance  be  brought  about  to  a  sufficient  extent  to 
lead  to  differences  between  the  daughter-cells  produced  by  fission, 
as  a  consequence  of  the  imperfections  of  the  process  of  cell-division. 
The  differences  produced  in  this  way  might  be  changes  in  the 
nucleo-cytoplasmic  balance,  as  Hertwig  supposes,  or  in  the  relative 
proportions  of  substances  exerting  different  physiological  activities, 
as  suggested  by  Biitschli,  Geddes  and  Thomson,  Schaudinn  and 
Doflein,  or  possibly  of  all  these  and  other  changes  yet  unknown. 
In  any  case  it  is  reasonable  to  suppose  that  the  imperfect  character 
of  the  primitive  types  of  cell-division,  described  in  the  last  chapter, 
might  produce  accumulated  material  or  structural  inequalities  in 
the  daughter-cells,  such  as  could  only  be  rectified  by  the  union  of 
two  cells  differentiated  in  opposite  directions,  thus  making  syngamy 
a  necessity  for  the  continued  existence  of  the  species.  This  theory 
explains  the  necessity  for  syngamy  recurring  with  greater  frequency 
in  forms  having  a  high  degree  of  structural  differentiation  than  in 
forms  of  a  primitive  and  simple  type  of  organization. 

With  increasing  perfection  in  the  process  of  the  division  of  the 
cell,  and  especially  of  the  nucleus,  the  primary  cause  of,  or  necessity 
for,  syngamy  might  be  expected  to  disappear  ;  but  at  this  stage  in 
evolution  other  benefits  to  the  species  consequent  on  the  process 
of  amphimixis  might  be  a  sufficient  cause  for  the  retention  of 
a  process  already  well  established.  This  conclusion  appears  to 
receive  some  support  from  the  fact  that  intensive  culture,  whether 
artificial,  or  natural  as  in  parasitism,  seems  to  diminish  the  necessity 
for  syngamy.  It  can  hardly  be  supposed  that  intensive  culture 
can  diminish  consequences  arising  from  defective  cell-division  ;  but 
it  might  conceivably  produce  a  strengthening  effect  equal  to,  and 
capable  of  supplanting,  the  benefits  derived  from^  amphimixis. 
Enriques  (113)  has  stated  that  in  Infusoria  ex-conjugants  may 
proceed  to  conjugation  again,  so  that  between  one  act  of  syngamy 
and  the  next  there  may  not  be  a  single  cell-division  intervening. 
In  this  case  neither  cell-division/f!or  any  consequences  of  cell- 
division  can  be  the  factor  bringingfabout  sexual  union,  but  some  other 
explanation  must  be  sought.  Enriques  considers  that  the  function 
of  syngamy  in  Infusoria  is  to  maintain  the  fixity  of  the  species. 

Bibliography. — For  references  see  p.  479. 


CHAPTER  IX 
POLYMORPHISM  AND  LIFE-CYCLES  OF  THE  PROTOZOA 

A.  POLYMORPHISM. 

ONE  of  the  most  striking  peculiarities  of  living  beings  is  the  infinite 
variety  of  form,  structure,  and  appearance,  which  they  present. 
There  is,  perhaps,  no  living  individual  of  any  kind  which  is  exactly 
similar,   in   all  respects,    to   any   other.     Nevertheless,    the   most 
uncultured  intellect  cannot  fail  to  recognize  that,  in  the  case  of 
all  ordinary,  familiar  plants  and  animals  there  is  a  pronounced 
tendency  to  segregation  into  distinct  kinds  or  species — that  is  to 
:  ay,  natural  groups  of  individuals  which,  though  they  may  vary 
greatly  amongst  themselves,  yet  resemble  one  another  far  more 
than  they  do  the  individuals  of  another  species.     It  is  not  necessary 
to  point  out  that  species  are  not  to  be  regarded  as  permanent  or 
immutable  entities.     It  is  certain   that  a  species   majT  in  course 
of  time  become  modified  so  as  to  acquire  characters  different  from 
those  it  originally  possessed,  thus  giving  rise  to  a  new  species,  or 
that  a  single  parent-species  may  become  split  up  into  a  number  of 
groups  which,  by  a  similar  process  of  modification,  became  so  many 
daughter-species  differing  from  one  another  and  from  the  parent- 
species  to  a  greater  or  less  degree.     The  problem  of  the  origin  of 
species  is  one  that  it  is  not  necessary  to  discuss  here  ;  it  is  sufficient 
to  point  out  that  the  mutability  of  species  often  makes  it  very 
difficult  to  define  or  delimit  a  given  species  exactly,  of  which  a 
striking  example  is  seen  in  the  pathogenic  trypanosomes  of  the 
brucii-  group,  probably    to   be   regarded,    as    pointed    out   above 
(p.  27),  as  instances  of  species  in  an  incipient  or  nascent  condition. 
Some  species  are  sharply  marked  off  from  others,  some  are  much 
less  so,  and  some  are  of  questionable  rank,  regarded  by  one  naturalist 
as  distinct,  by  another  as  mere  races  or  varieties- — a  state  of  things 
perfectly  intelligible  if   existing  species   are  regarded   as   having 
arisen  by  descent,  with  modification,  from  pre-existing  species. 

In  the  Protozoa  the  existence  of  distinct  species  is  just  as  marked 
as  in  the  higher  plants  and  animals,  and  is  universally  recognized. 
As  has  been  pointed  out  in  the  previous  chapter,  it  is  probably 
syngamy  which  is  responsible  for  the  segregation  of  individual 

102 


POLYMORPHISM  AND  LIFE-CYCLES  163 

into  species,  by  blending  the  divergent  characters  that  may  be 
supposed  to  arise  from  the  influence  of  different  conditions  or 
circumstances  of  life.  Thus,  synganiy  in  unicellular  organisms 
appears  to  have  an  effect  which  is  the  opposite,  to  a  large  extent, 
to  that  which  it  produces  in  multicellular  organisms,  in  which  there 
are  special  germ-cells,  sheltered  to  a  greater  or  less  degree  from 
the  direct  influence  of  the  environment,  and  in  which  amphimixis 
appears  rather  to  be  a  means  by  which  variations  arise. 

The  conception  of  a  species  is  by  no  means  incompatible  with  the 
occurrence  of  a  number  of  distinct  forms  in  its  life-history.  Taking 
well-known  instances  from  the  Metazoa,  there  may  be,  in  the  first 
place,  ontogenetic  or  developmental  differences  ;  not  only  may  the 
individuals  of  the  same  species  differ  in  size  at  different  periods  in 
the  development,  but  they  may  differ  so  greatly  in  appearance  and 
structure  that  only  a  knowledge  of  the  life-history  enables  us  to 
assert  that  they  belong  to  the  same  species — as,  for  example,  a 
caterpillar  and  a  butterfly,  or  a  Irydroid  and  a  medusa.  Secondly, 
the  adult  individuals  may  differ  to  an  enormous  extent  in  the  two 
sexes.  Thirdly,  there  may  be  in  many  cases  differences  between 
individuals  of  a  species  related  to  differences  in  the  functions  which 
they  perform,  not  merely  at  successive  phases  in  the  life-history, 
as  in  some  cases  of  ontogenetic  differentiation  already  mentioned, 
but  even  at  corresponding  phases  of  the  life-history — a  phenomenon 
best  seen  in  social  or  colony-forming  organisms,  as  in  the  case  of 
ants  and  termites,  or  in  the  colonies  of  Hydrozoa. 

In  Protozoa,  similarly,  a  given  species  may  show  distinct  phases 
or  forms  at  different  or  corresponding  periods  of  its  life-history  to 
a  greater  or  less  extent.  In  some  species  the  form-changes  are  very 
slight,  and  the  individuals  occur  always  under  a  similar  form  and 
aspect,  at  least  during  the  active  state,  and  are  therefore  recog- 
nizable without  difficulty  as  regards  their  specific  identit}' ;  such 
forms  may  be  termed  monomorphic,  and  as  examples  the  species 
of  ciliate  Infusoria  can  be  cited.  Other  Protozoa,  on  the  other  hand, 
are  extremely  polymorphic — that  is  to  say,  they  occur  under  a 
variety  of  widely-differing  forms  at  different  stages  in  the  life-c}-cle 
or  in  response  to  variations  in  the  conditions  of  life.  Hence  it  is 
often  difficult  or  impossible  to  refer  a  given  form  to  its  proper 
species  without  tracing  out  its  life-history  and  following  its  develop- 
ment step  by  step.  The  unravelling  of  the  complicated  life-cjx-les 
of  Protozoa  is  attended  by  far  greater  difficulties  than  in  Metazoa, 
Miice  one  important  criterion  fails  us  altogether  in  the  Protozoa, 
that,  namely,  of  sexual  maturity.  A  naturalist  has  no  hesitation 
in  pronouncing  a  trochophore  to  be  a  larval  form,  and  a  rotifer  to 
Le  an  adult  organism,  from  the  fact  that  the  former  is  sexually 
immature,  while  the  latter  produces  ripe  generative  cells.  In  the 


104  THE  PROTOZOA 

Protozoa,  however,  there  is  no  visible  criterion  of  any  similar  state 
of  maturity  or  the  opposite  which  might  be  a  guide  in  estimating 
the  significance  of  a  particular  form.  It  is  certain  that  with  in- 
creasing knowledge  man}7  species  of  Protozoa  now  regarded  as 
distinct  will  prove  to  be  developmental  stages  of  others,  as  has 
happened  so  frequently  in  the  case  of  Metazoa. 

The  polymorphism  of  the  Protozoa  may  be  related  directly  or 
indirectly  to  a  variety  of  causes,  which  may  be  grouped  generally 
under  three  headings — life-conditions,  growth  and  development  of 
the  individual,  and  sex. 

1.  Polymorphism  in  Relation  to  the  Conditions  of  Life. — Under 
this  heading  are  included  all  those  cases  where  the  individual  is 
forced  to  adapt  itself  to  inevitable  changes  in  the  environment, 
or  else  succumb  to  their  effects  ;  hence  this  type  of  polymorphism 
may  be  termed  briefly  adaptive.  The  animal  may  adapt  itself  to 
tiuch  changes  in  one  or  the  other  of  two  waj^s  :  passively,  by  passing 
into  a  resting  state,  in  which  vital  activities  are  temporarily  sus- 
pended ;  or  actively,  by  changes  of  form,  structure,  and  function, 
adapted  to  the  changed  conditions. 

Methods  of  passive  adaptation  to  unfavourable  conditions  occur 
probably  in  all  Protozoa — perhaps  it  might  be  said  in  all  Protista, 
so  that  no  species  can  be  said  to  be  absolutely  nionomorphic.  The 
commonest  form  of  such  adaptation  is  the  process  of  encystment, 
whereby  the  organism  protects  itself  by  secreting  a  firm,  resistant 
envelope,  or  cyst,  round  its  body. 

The  first  preliminary  to  encystment  in  Protozoa  is  usually  a 
rounding  off  of  the  body-form.  In  the  case  of  naked  amoeboid 
forms  such  a  change  of  form  follows  naturally,  as  pointed  out 
above,  from  cessation  of  the  locomotor  activity.  It  is,  however, 
also  observed  that  a  similar  change  takes  place  in  corticate  forms, 
a  phenomenon  which  indicates  that  the  cuticle  or  cortex  must  be 
absorbed  or  softened,  and  that  any  internal  form-giving  elements 
must  be  dissolved,  so  that  the  protoplasm  is  free  to  conform  to 
the  natural  plrysical  tendencies  of  a  fluid  body.  In  the  great 
majority  of  cases,  an  individual  in  process  of  encystment  becomes 
perfectly  spherical,  whatever  may  have  been  the  form  of  its  bodv 
in  the  active  state,  but  in  some  cases  the  spherical  form  is  not  fully 
attained,  and  the  body  becomes  ovoid  or  pear-shaped.  During  the 
process  of  rounding  off,  any  food-particles  or  foreign  bodies  contained 
in  the  cytoplasm  are  rejected  or  absorbed,  as  a  rule  ;  the  contractile 
vacuoles,  if  there  be  any,  cease  to  be  formed  and  vanish  ;  and  all 
locomotor  organs,  such  as  cilia,  flagella,  and  of  course  pseudo- 
podia,  are  absorbed  or  cast  off.  At  the  same  time  the  protoplasm 
of  the  organism  becomes  less  fluid  and  more  opaque,  and  usually 
diminishes  appreciably  in  bulk,  probably  through  loss  of  water  ;  it 


POLYMORPHISM  AND  LIFE-CYCLES  165 

thereby  becomes  denser  in  consistence,  but  of  less  specific  gravity. 
Lastly,  the  cj^st-membrane  itself  appears  round  the  body,  if  it 
has  not  already  done  so  ;  it  generally  stands  off  distinctly  from  the 
surface  of  the  body,  and  may  vary  in  nature  in  different  cases, 
from  a  soft,  slimy  or  gelatinous  coat  to  a  firm  membrane  of  variable, 
thickness,  often  exceedingly  tough  and  impervious. 

In  the  encysted  state,  Protozoa  are  able  to  withstand  the  many 
vicissitudes  to  which  they  are  naturally  subject.  They  can  then 
be  dried  up,  frozen,  or  sun-baked  ;  and  since  the  protoplasm  becomes 
much  lighter,  they  can  be  transported  great  distances  by  winds, 
a  fact  which  accounts  for  the  appearance  of  Protozoa  in  infusions 
exposed  to  the  air  in  any  situation — a  peculiarity  from  which  the 
name  Infusoria  is  derived.  In  general  the  function  of  enc}7strnent 
is  to  protect  the  organism  against  unfavourable  conditions  or  violent 
changes  in  the  environment — for  instance,  in  freshwater  forms, 
against  drought  and  climate,  the  cold  of  winter  or  the  heat  of  a 
tropical  summer.  In  parasitic  forms  it  is  an  adaptation  commonly 
connected  with  a  change  from  one  host  to  another. 

In  parasites  two  types  of  cysts  can  be  distinguished.  In  the 
first  place,  full-grown  forms  may  produce  relatively  large,  resistant 
cysts  (Dauerzysten)  of  the  ordinary  type,  almost  invariably 
spherical  or  ovoid  in  form.  In  the  second  place,  the  smallest  forms 
in  the  developmental  cycle,  the  products  of  multiple  fission  or 
"  sporulation,"  may  secrete  round  themselves  tough,  resistant 
envelopes,  within  which  they  may  multiply  further  ;  in  this  case 
the  envelope  is  termed  a  sporocyst,  and  the  entire  body  a  spore.* 

*  The  word  "  spore  "  has  come  to  be  used  in  two  distinct  senses,  as  applied  to 
Protozoa,  thereby  producing  a  regrettable  confusion  and  ambiguity.  The  word 
itself  is  derived  from  the  Greek  criropos,  a  seed,  and  was  applied  by  botanists  to 
those  cases  where  plants  produce  seed-like  bodies  which  are  not  true  seeds  ;  for 
instance,  the  seed  of  an  ordinary  flowering  plant  is  a  complete  embryo,  with  root 
and  shoot  distinct,  encapsuled  in  protective  envelopes,  but  the  "  seed  "  of  a  fern 
is  merely  a  single  cell  enclosed  in  a  protective  membrane.  Consequently  the 
term  "  spore  "  was  used  to  distinguish  the  "  seeds  "  of  ferns,  fungi,  etc.,  from  the 
true  seeds  of  flowering  plants. 

It  was  observed  at  a  very  early  period  that  many  parasitic  Protozoa  produced 
minute  seed-like  bodies,  which  conveyed  the  infection  ;  for  those  of  Mysosporidia 
Johannes  Miiller  coined  the  term  "  psorosperms,"  but  in  general  the  term  "  spore  " 
was  used  for  these  bodies,  and  the  group  in  which  the  production  of  such  spores 
is  a  very  characteristic  feature  was  named  the  Sporozoa. 

With  the  progress  of  further  investigation,  it  was  found  that  in  a  great  many 
cases  the  essential  part  of  the  spore — namely,  the  encapsuled  protoplasmic  body — 
arose  by  a  process  of  multiple  fission,  hence  termed  "  sporulation,"  from  a  larger 
parent-body  ;  consequently  the  term  "  spore  "  has  been  used  by  many  in  a  secon- 
dary sense  to  denote  a  minute  germ  formed  by  multiple  fission,  as  in  the  merozoites 
of  the  malarial  parasites.  It  is  preferable  to  retain  the  word  "  spore  "  in  its 
original  significance  as  a  seed-like  body  contained  in  a  resistant  envelope  or  sporo- 
cyst, and  to  use  the  word  "  germ  "  (equivalent  to  the  German  word  Keim)  for 
the  protoplasmic  body  formed  by  sporulation,  whether  enclosed  in  a  sporocyst  or 
not.  Unfortunately  the  word  "  germ  "  has  become  very  much  misused  in  popular 
language,  and  a  less  ambiguous  term  would  perhaps  be  the  word  gymnospore  for 
naked  germs  not  enclosed  in  a  protective  envelope. 

There  is  no  essential  difference  between  a  cyst  and  a  spore,  except  their  relation 


166  THE  PROTOZOA 

Sporocysts  are  often  simply  rounded  or  oval  bodies,  like  cysts, 
but  in  some  cases  they  exhibit  special  forms,  and  may  be  prolonged 
into  spikes,  tails,  or  processes  of  various  kinds. 

In  many  cases  the  purely  protective  uses  of  the  cyst  may  be 
combined  with  the  performance  of  some  special  function  within  it. 
The  contained  organism  may  remain  merely  in  a  resting  state 
within  the  cyst  (hypnocyst)  ;  or  it  may  utilize  its  leisure  for  the 
digestion  of  large  quantities  of  ingested  food  -  material,  or  for 
carrying  on  processes  of  reproduction  or  syngamy.  As  a  process 
of  similar  nature  to  encystment,  the  formation  of  "  sclerotia  "  in 
the  Mycetozoa  must  be  noted  (see  p.  240,  infra). 

Active  adaptation  to  changed  conditions  is  seen  in  those  forms  in 
which  the  mode  of  life  is  bound  up  with  changes  of  environment 
during  different  periods  of  the  life-history — that  is  to  say,  more 
especially  in  parasitic  forms,  in  which  a  change  of  hosts  is  necessary 
for  the  continuance  of  the  species.  In  such  forms  there  are  in 
general  two  functions  for  which  provision  must  be  made  :  the  first 
is  that  of  multiplying  in  the  host  itself  and  keeping  up  a  stock  of 
the  parasites  in  it ;  the  second  is  that  of  infecting  a  new  host  sooner 
or  later  (see  p.  20,  supra).  In  the  most  primitive  types  of  para- 
sitic Protozoa  there  is  no  differentiation  of  form  or  structure  corre- 
sponding to  these  two  distinct  functions  ;  but  as  a  general  rule 
a  given  parasite  in  a  given  host  exhibits  usually  two  forms  or  series 
of  forms,  which  may  be  termed  "  multiplicative  "  and  "  propagative  " 
respective ly  (Doflein).  Multiplicative  forms  may  be  wanting  in 
some  cases,  as  in  the  Eugregarines,  but  propagative  forms  are 
always  found,  being  an  absolute  necessity  for  the  continuance  of 
the  species. 

As  examples  of  multiplicative  and  propagative  forms,  we  may 
consider  first  species  which  are  parasitic  only  on  a  single  host  in 
the  course  of  the  entire  life-c}^cle.  A  typical  example  is  seen  in 
Coccidium  (p.  342,  Fig.  152),  in  which  adult  forms,  "  schizonts," 
multiply  rapidly  in  the  host  by  a  process  of  multiple  fission,  "  schi- 
zogony,"  a  process  which  takes  place  unaccompanied  by  any  sexual 
phenomena,  and  in  which  no  resistant  cysts  are  formed,  since  they 
are  quite  unnecessary.  Sooner  or  later,  however,  generations  of 
individuals,  "  sporonts,"  appear  which  do  not  multiply  like  the 
schizonts,  but  which,  as  gametocytes,  give  rise  to  the  gametes.  After 
a  process  of  syngamy  the  zygote  forms  a  resistant  cyst  within 

to  a  developmental  cycle  ;  the  "  spores  "  of  Bacteria  are  for  the  most  part  simply 
cysts,  but  are  called  spores  on  account  of  their  small  size. 

In  this  book  the  word  "spore,"  when  not  qualified  by  any  prefix,  will  be  used 
to  denote  a  resistant  seed-like  body  protected  by  a  tough  envelope,  or  sporocyst, 
and  the  production  or  development  of  such  bodies  will  be  termed  "  spore-forma- 
tion." On  the  other  hand,  the  production  of  numerous  small  cells  or  germs  by 
multiple  fission  will  be  termed  "  sporulation." 


POLYMORPHISM  AND  LIFE-CYCLES  167 

which  it  multiplies  to  form  a  number  of  germs,  which  may  or  may 
not  be  enclosed  in  sporocysts,  in  different  species.  Cysts  and  spores 
pass  out  of  the  host,  and  do  not  develop  further  unless  they  are 
devoured  by  a  second  host  of  a  species  in  which  they  are  able  to 
establish  themselves  ;  if  this  event  takes  place,  the  spores  germinate 
in  the  new  host  and  produce  a  fresh  cycle  of  infection,  each  germ 
when  set  free  growing  up  into  a  schizont.  In  this  case  it  is  seen 
that  the  schizonts  represent  the  multiplicative,  the  sporonts  the 
propagative,  phase,  and  that  in  the  latter  resistant  cysts  are  pro- 
duced as  a  protection  against  the  vicissitudes  of  the  outer  world, 
to  which  the  parasite  must  expose  itself  during  this  phase  of  its 
life-history. 

An  example  of  a  parasite  which  infects  two  distinct  species  of 
hosts  in  the  course  of  its  life-history  is  furnished  by  the  malarial 
parasites  (p.  360,  Fig.  156).  In  this  case  there  are  first  of  all 
schizonts  which,  like  those  of  Coccidium,  reproduce  themselves  by 
multiple  fission,  this  part  of  the  life-cycle  being  passed  in  the  blood 
of  a  vertebrate  host.  Later,  sporonts  are  generated  which  under 
normal  circumstances  are  incapable  of  multiplication  in  the  verte- 
brate host,  or,  indeed,  of  any  further  development,  unless  taken  up 
by  another  host,  in  this  case  a  mosquito,  which  takes  them  from 
the  vertebrate  host  by  sucking  its  blood.  In  the  stomach  of  the 
new  host  the  sporonts  behave  in  a  similar  manner  to  those  of 
Coccidium — that  is  to  say,  they  give  rise  as  gametocytes  to  gametes, 
which  by  syngamy  produce  zygotes.  The  zygotes  grow  and  repro- 
duce themselves  by  multiple  fission,  forming  an  enormous  number 
of  minute  germs  or  sporozoites,  which  do  not  develop  further  unless 
they  pass  from  the  mosquito  back  into  the  blood  of  a  suitable 
vertebrate  host,  in  which  they  start  a  fresh  developmental  cycle. 

The  life-cycle  of  the  malarial  parasites  shows  that  a  given  phase 
of  a  parasite  is  only  to  be  regarded  as  multiplicative  or  propagative 
in  relation  to  a  particular  host.  In  the  vertebrate  blood  the 
schizont  is  the  multiplicative,  the  sporont  the  propagative,  phase. 
As  soon,  however,  as  the  sporont  passes  into  the  mosquito,  it  becomes 
there  the  multiplicative  phase  which  gives  rise  ultimately  to  the 
sporozoites,  representing  the  propagative  phase  in  the  mosquito. 
The  sporozoites  in  their  turn,  when  they  reach  the  blood  of  the 
vertebrate,  develop  there  into  schizonts.  Thus  one  and  the  same 
stage  in  the  life-cycle  represents  one  phase  in  one  host  and  another 
in  another,  according  to  circumstances.  It  should  be  noted  further 
that  in  the  life-cycle  of  the  malarial  parasites  resistant  cysts  are 
unnecessary,  since  the  parasite  never  comes  out  into  the  open,  but 
passes  the  whole  of  its  existence  in  one  or  the  other  of  its  two  hosts ; 
consequently  such  cysts  are  not  formed  at  any  stage  of  the  life- 
cycle  in  these  forms. 


168  THE  PROTOZOA 

Another  example  of  a  parasite  with  alternation  of  hosts,  in  which 
the  course  of  events  is  different  from  that  of  the  malarial  parasites, 
is  furnished  by  the  species  of  the  genus  Aggregata  (p.  353).  Here 
the  schizonts  are  parasitic  in  crabs,  and  reproduce  themselves  by 
multiple  fission  without  encystment  to  form  naked  germs,  mero- 
zoites,  which  grow  up  into  schizonts,  and  multiply  again  in  the  same 
way.  If,  however,  the  crab  is  devoured  by  a  Cephalopod,  the 
merozoites  adapt  themselves  to  their  new  surroundings  and  become 
sporonts,  which  produce  gametes.  The  zygotes  form  resistant 
cysts  in  which  they  multiply  to  form  spores  enclosed  in  tough 
sporocysts.  The  resistant  phases  pass  out  of  the  Cephalopod  in  its 
fseces,  and  to  develop  further  they  must  be  devoured  by  a  crab,  in 
which  they  become  schizonts  again.  In  this  case  there  is  no  special 
differentiation  of  propagative  phases  in  the  crab,  but  the  same 
stage  can  serve  both  functions ;  on  the  other  hand,  in  the 
Cephalopod  there  is  no  multiplicative  phase,  but  only  a  propagative 
phase  with  resistant  cysts. 

2.  Polymorphism  in  Relation  to  Growth  and  Development  of  the 
Individual. — In  Protozoa  which  multiply  only  by  equal  binary 
fission,  as,  for  example,  many  Infusoria,  there  is  practically  no 
difference  between  young  and  old  forms  beyond  a  slight  variation 
in  size.  An  individual  feeds,  and  in  consequence  grows  slightly 
be37ond  the  size  characteristic  of  the  species  to  which  it  belongs. 
It  then  divides  by  equal  binary  fission  into  two  individuals  each 
slightly  below  the  specific  size,  and  they  in  their  turn  feed  and  grow 
and  reproduce  themselves  by  fission  in  due  course. 

In  other  cases,  however,  j^oung  and  adult  forms  of  a  species  can 
be  clearly  distinguished,  and  may  differ  in  structure  as  well  as  in 
size.  Beginning  with  reproduction  by  binary  fission,  the  simplest 
case  is  where  the  adult  individual  divides  into  two  unequal  portions, 
so  that  parent  and  daughter  can  be  distinguished,  the  former  not 
appreciably  smaller  than  ordinary  full  -  grown,  individuals,  the 
latter,  however,  very  much  smaller ;  it  may  be  relatively  minute. 
Examples  of  this  type  of  reproduction  are  furnished  by  trypano- 
somes,  a  group  in  which  all  gradations  may  be  found  between  equal 
and  very  unequal  fission  (Fig.  127).  Still  greater  differences 
between  parent  and  young  individuals  are  seen  in  cases  of  gemma- 
tion— that  is  to  say,  where  the  offspring  is  set  free  in  an  undifferen- 
tiated  condition,  and  acquires  after  separation  from  the  parent  the 
characters  of  the  adult,  as  in  Acinetaria. 

The  greatest  differences  between  young  and  old  forms  are  seen, 
as  might  have  been  expected,  in  cases  of  reproduction  by  multiple 
fission  or  gemmation.  In  such  cases  the  young  forms  produced 
often  differ  from  the  adult  in  structure  and  appearance,  as  well  as 
in  size.  An  example  of  multiple  fission  is  furnished  by  the  common 


POLYMORPHISM  AND  LIFE-CYCLES  169 

Trypanosoma  lenisi  of  rats,  in  which  two  types  of  such  fission  are 
seen  :  either  the  multiplication  of  a  small  individual  by  repeated 
binary  fission  to  form  a  "  rosette  "  composed  of  several  daughter- 
individuals  (Fig.  127,  J,  K).  or  the  separation  of  several  small 
daughter-individuals  from  a  large  one  (Fig.  127,  F,  G,  H).  In  both 
cases  the  multiple  fission  is  simply  rapid  and  repeated  binary  fission. 
The  3Toung  individuals  resulting  from  the  fission  are  sometimes 
crithidial  in  type  (p.  294),  and  grow  into  the  adult  trypanosome- 
form. 

In  multiple  gemmation  (sporulation)  the  parent  body  breaks  up 
into  a  number,  sometimes  very  large,  of  small  or  even  very  minute 
individuals,  buds,  or  germs,  usually  given  off  from  a  more  or  less 
considerable  mass  of  residual  protoplasm,  which  degenerates  and 
dies  off.  The  buds  when  set  free  may  become  active  at  once,  or 
they  may  pass  first  into  a  resting  state  to  \vhich  an  active  state 
succeeds  at  a  later  period.  In  the  latter  case  they  may  form 
sporocysts,  and  become  the  spores  already  described.  Within  the 
sporocyst  the  minute  germ  may  multiply  further  by  fission.  In  the 
subclass  Telosporidia  of  the  Sporozoa,  the  contents  of  the  spore 
may  divide  up  in  this  way  to  form  a  variable  number  of  slender 
sickle-shaped  germs,  for  which  Aime  Schneider  coined  the  term 
sporozoites,  a  term  which  has  since  been  frequently  applied  in  senses 
quite  different  to  its  original  meaning. 

An  active  germ  produced  by  sporulation  is  termed  a  swarm-spore, 
or  zoospore,  whether  or  not  the  active  phase  is  preceded  by  a  resting 
spore-stage.  The  swarm-spores  of  Protozoa  may  be  of  various 
types  in  different  cases.  The  swarm-spore  may  be  amoeboid  and 
creep  about  by  the  aid  of  pseudopodia  ;  it  is  then  termed  an 
amozbula  (or  pseudopodiospore).  It  may  be  provided  with  one  or 
more  flagella  as  organs  of  locomotion,  and  is  then  termed  a  flagellula 
(or  flagellispare).  It  may  have  a  coat  of  cilia,  as  in  the  young  stages 
of  Acinetaria,  and  may  then  be  termed  a  ciliospore.  Lastly,  the 
swarm-spore  may  be  without  organs  of  locomotion,  whether  perma- 
nent or  temporary,  and  may  progress  by  twisting  and  wriggling 
movements  of  the  body  as  a  whole,  or  by  gliding  forwards  on  its  long 
axis  in  a  manner  similar  to  the  gliding  movements  of  gregarines  ; 
swarm-spores  of  this  type  are  specially  characteristic  of  the  Telo- 
sporidia amongst  the  Sporozoa,  arising  either  by  sporulation  of  a 
schizont  (merozoites)  or  in  the  process  of  spore-formation  after 
syngamy  (sporozoites),  and  may  be  termed  gregariniform  swarm- 
spores  or  gregarinulce  comprehensively. 

In  some  cases  the  swarm-spore  may  pass  through  more  than  one 
active  phase,  and  exhibit  different  modes  of  locomotion  in  each. 
This  is  well  seen  in  the  Mycetozoa  (p.  239),  where  the  germination 
of  the  spore  produces  an  amcebula,  which  may  acquire  a  flagellum 


170  THE  PROTOZOA 

and  become  a  flagellula  ;  after  a  time  the  flagellula  settles  down  and 
becomes  an  amcebula  again  after  loss  of  the  flagellum. 

A  very  interesting  point,  in  connection  with  the  question  of  young 
and  adult  forms  of  Protozoa,  is  the  occurrence  of  stages  in  the 
development  which  may  be  interpreted  as  recapitulative  in  the 
phylogenetic  sense — that  is  to  say,  as  representing  past  stages  in  the 
evolution  of  the  species,  in  a  manner  comparable  to  the  recapitu- 
lative larval  or  embryonic  stages  in  the  development  of  Metazoa. 
It  is  probable  that  such  recapitulative  stages  are  commoner  in  the 
development  of  Protozoa  than  has  been  generally  supposed  (compare 
Awerinzew,  47).  The  best-known  instance  is  furnished  by  the 
ciliated  larvse  of  Acinetaria  (p.  459),  indicating  that  this  order  is 
descended  from  a  ciliate  ancestor  of  the  order  Peritricha,  a  relation- 
ship fully  confirmed  by  the  similarity  of  their  reproductive  processes 
to  those  of  other  Infusoria.  The  crithidial  phase  that  occurs  so 
constantly  in  the  development  of  trypanosomes  (p.  299)  is  probabty 
to  be  regarded  as  a  recapitulative  form  representing  a  type  of 
structure  antecedent  in  evolution  to  that  of  the  tj^pical  trypanosome- 
form.  The  frequent  occurrence  of  flagellated  swarm-spores  in  the 
development  of  Sarcodina  (Foraminifera,  p.  235  ;  Radio laria,  p.  254) 
probably  has  a  phylogenetic  significance,  as  pointed  out  by  Jiutschli. 
Finally  attention  may  be  drawn  to  the  remarkable  series  of  forms 
in  the  ontogeny  of  Arcella  described  in  the  next  chapter  ;  first  the 
amcebula,  then  the  Nudearia-stage,  followed  by  the  Pseudochlamys- 
stage,  which  grows  finally  into  the  adult  Arcetta-iorro..  In  the  many 
cases  where  young  forms  are  markedly  different  from  the  adult,  it 
may  be  a  difficult  matter,  as  it  often  is  in  the  case  of  Metazoa,  to 
decide  whether  a  given  larval  form  is  to  be  interpreted  as  recapitu- 
lative or  merely  adaptive  ;  but  even  in  cases  where  the  characters 
of  a  larval  form  have  an  obvious  adaptive  importance,  as  in  the 
ciliated  larvas  of  Acinetaria,  atavism  may  be  nevertheless  a  factor 
determining  the  particular  form  taken  by  the  adaptive  characters  in 
question — that  is  to  say,  by  the  organs  of  locomotion  in  the  example 
chosen. 

3.  Polymorphism  in  Relation  to  Sex. — The  phenomena  of  sexual 
differentiation  consist  primarily  of  differences  in  size,  structure,  and 
other  characteristics  between  the  gametes,  the  cells  which  are  con- 
cerned in  the  act  of  syngarny.  Secondarily  such  differences  may 
extend  to  other  cell-individuals,  both  in  the  life-cycle  of  a  Protozoon 
or  in  the  body  of  a  Metazoon.  In  the  previous  chapter  it  has  been 
pointed  out  that,  while  in  Metazoa  the  gametes  at  least  are  sharply 
differentiated  in  all  cases,  in  the  Protozoa  every  condition  is  found 
from  perfect  isogamy  to  a  differentiation  nearly  as  pronounced  as 
that  in  the  Metazoa.  The  question  has  been  discussed  in  the  last 
chapter  whether  or  no  sexual  differentiation  is  to  be  regarded  as 


POLYMORPHISM  AND  LIFE-CYCLES  171 

an  inherent  property  of  all  living  beings,  as  maintained  by  many 
high  authorities. 

Whatever  view  be  held  with  regard  to  the  existence  or  non- 
existence  of  inherent,  intrinsic  sexual  differences  in  living  organisms,. 
it  seems  clear  that  the  apparent  sexual  differentiation  of  the  gametes 
is  largely,  perhaps  purely,  adaptive,  and  furnishes  good  examples 
of  the  principle  of  morphological  differentiation  of  structure  in 
relation  to  physiological  division  of  labour.  One  gamete,  termed 
"  female,"  tends  to  be  bulky  and  inert,  storing  up  reserve- material 
in  greater  or  less  quantity,  a  provision  (sit  venia  verbo  /)  for  future 
requirements  ;  it  is  economical  of  substance,  and  but  few  are 
produced.  The  other  gamete,  termed  "  male,"  develops  in  the 
opposite  direction  in  every  respect ;  it  tends  to  be  small  and  active, 
not  weighted  with  superfluous  material  of  any  kind,  but  with  motor 
mechanisms  strongly  developed  ;  it  is  prodigal  of  substance,  and 
many  are  produced,  but  few  are  favoured  by  destiny.  In  extreme 
cases  the  female  gamete  is  a  relatively  huge,  inert  cell,  incapable 
of  movement,  crammed  with  foodstuffs  ;  the  male  is  excessively 
minute,  and  is  practically  nothing  but  a  nucleus  which  has  its 
constituent  parts  packed  into  the  smallest  possible  space,  and  with 
motor  mechanisms  attached  to  it. 

In  reviewing  the  progressive  differentiation  of  the  gametes  in 
Protozoa,  it  is  convenient  to  treat  separately  those  forms  in  which 
there  is  little  or  no  ontogenetic  differentiation  from  those  in  which 
there  is  a  more  or  less  pronounced  difference  between  the  young 
and  adult  forms.  An  example  of  the  first  type  is  seen  in  Copromonas 
(Fig.  Ill),  in  which  the  gametes  are  ordinary  individuals  of  the 
species,  only  differing  in  that  their  nuclei  have  undergone  a  process 
of  reduction.  Good  examples  of  monomorphic  forms  are  furnished 
also  by  the  Infusoria,  a  group  in  which  a  species  may  be  free-swim- 
ming, or  may  be  more  or  less  permanently  attached  and  sessile  in 
habit. 

In  the  free-swimming  ciliate  Infusoria,  sexual  differences  in  the 
conjugants  are  frequently  not  discernible  ;  if  they  exist,  they  can 
only  be  inferred  from  the  fact  that  syngamy  takes  place,  or  from 
subsequent  behaviour  of  the  individuals  after  conjugation,  as,  for 
instance,  the  fact  observed  by  Calkins,  that  in  Paramecium  one  ex- 
conjugant  multiplies  much  more  rapidly  than  the  other.  In  other 
cases  differences  of  size  more  or  less  pronounced  are  exhibited  by 
the  conjugants  (Doflein,  111).  As  pointed  out  above,  differences 
of  structure  have  also  been  noted  in  some  cases  between  the 
stationary  and  migratory  pronuclei  produced  by  a  conjugant. 
Collin  (50),  however,  was  unable  to  find  the  slightest  morphological 
differentiation  of  the  conjugating  pronuclei  of  Anoplophrya. 

In  the  sedentary  Infusoria,  sexual  differentiation  may  be  as  little 


172 


THE  PROTOZOA 


apparent  as  in  the  free-swimming  species,  as,  for  instance,  in 
Acinetaria,  where  conjugation  can  take  place  between  two  adjacent 
individuals  each  on  its  own  stalk.  But  in  the  Vorticellids  special 
free-swimming  individuals,  microconjugants,  are  developed  which 
are  budded  off  from  a  sedentary  individual,  and  then  acquire 
cilia,  swim  off,  and  conjugate  with  another  sedentary  individual 

(Fig.  78).  It  seems  obvious  that  this 
state  of  affairs  is  an  adaptation  to  the 
exigencies  of  a  sedentary  life  to  insure  cross- 
fertilization  analogous  to  the  formation  of 
complemental  males  in  the  Cirripedes.  The 
free  -  swimming  microconjugants  of  Vorti- 
cellids are  commonly  termed  "  males,"  but 
it  is  open  to  question  whether,  strictly 
speaking,  they  deserve  that  title. 

It  is  in  species  with  marked  differences 
between  young  and  adult  forms  that  the 
greatest  differentiation  of  the  gametes 
occurs,  though  by  no  means  universally  even 
in  such  forms.  In  polymorphic  species  of 
this  t3rpe,  three  different  conditions  can  be 
distinguished,  to  which  reference  has  been 
made  in  the  previous  chapter. 

FIG.  78.— Vorticella  \micro-        \   Macrogamy — that  is  to  say,  syngainv 
stoma,  Ehrb.    On  the  left    ,     ,  ..,?  .     ,.    .,      ,      /A.          '    •    " 

an    ordinary,  sedentary    between  lull-grown individuals  of  the  species. 

individual  (macroconju-  In  this  type  the  gametes  appear  to  be  always 
gant)  with  two  microcon-  f      ,,      -aimi'lar    QH  far  ns  iq  known  •    PX 

juganta    (m.c.)   attached  Pe  lar'   so  as  1S  Known  >   es> 

to  it,  one  of  which  (to  amples  are  seen  in  Actinophrys  (Fig.  71), 

the  left)  is  in  the  act  of   th    chromidiogamy  of  Arcella  (Fig.  80),  and 

conjugation.       On      the  &        J 

right    is    an    individual    possibly  NoctllUCd  (p.  279). 

with  the  stalk  contracted        £.  Microgamy  —  syngamy    between    the 
and   the   body   enclosed  ,.,./,,  ,  J  . , 

in   a   cyst.   N,    Macro-    youngest  individuals,  products  of  the  rapid 

peristome  multiplication  of  an  adult.  Conjugation  of 
swarm-spores  is  by  far  the  commonest  type 
of  syngamy  in  Protozoa,  and  may  be  re- 
garded as  the  normal  type.  In  this  case  there  is  usually  complete 
isogamy,  as  in  Foraminifera  (p.  235),  sometimes  slight  anisogamy, 
as  in  Radiolaria  (p.  254,  Fig.  108). 

3.  Mixed  microgamy  and  macrogamy— that  is  to  say,  syngamy 
between  a  full-sized  adult  individual  on  the  one  hand  and  a  minute 
individual,  a  swarm-spore,  on  the  other  hand.  This  type  may  be 
regarded  as  derived  from  microgamy  by  progressive,  and  finally 
complete,  inhibition  of  the  divisions  that  produce  the  swarm-spores 
in  one  sex — possibly  also  with  an  enhanced  tendency  to  such  divisions 
in  the  other  sex.  Thus  in  Arcella,  as  described  in  the  previous 


nucleus ;     P, 

and  adoral  ciliary  spiral. 

After  Hickson. 


POLYMORPHISM  AND  LIFE-CYCLES  173 

chapter,  the  niacrauicebae  produced  are  fewer  than  the  micramcebse' 
showing  that  the  tendency  to  division  is  more  restricted  in  the 
former  case  than  in  the  latter.  Again,  in  the  development  of  Centro- 
pyxis,  as  described  by  Schaudinn  (131),  formation  of  gametes  is 
initiated  by  a  process  of  multiple  fission  combined  with  formation 
of  secondary  nuclei  from  chromidia,  as  in  Arcella,  and  in  this  way 
a  number  of  amoebulse  are  produced.  The  amcebulae  from  one 
Centropyxis  remain  undivided,  as  macramcebse,  while  those  pro- 
duced from  another  adult  divide  each  into  four  micramoebae ; 
syngamy  takes  place  later  between  a  niicramceba  and  a  niacrainceba, 
after  each  has  secreted  for  itself  a  shell. 

When  the  inhibition  of  the  gamete-forming  divisions  is  quite 
complete  in  one  sex,  the  result  is  the  most  pronounced  type  of 
anisogamy  occurring  in  Protozoa  ;  and,  conversely,  it  may  be  said 
that  all  cases  of  extreme  anisogamy  in  Protozoa  are  of  this  type. 
In  Metazoa  the  disproportion  in  the  size  of  the  gametes  is  mainly 
due  to  the  relatively  enormous  growth  of  the  gametocyte,  partly 
also  to  the  inequality  of  the  four  cells  produced  by  the  reducing 
divisions,  in  the  female  sex.  In  Protozoa  with  extreme  differen- 
tiation of  gametes,  on  the  other  hand,  such  as  the  Coccidia  and 
Hsemosporidia,  the  gametocytes  do  not  differ  greatly,  sometimes 
not  at  all,  in  size,  though  the  female  gametocyte  may  contain 
more  reserve  food  -  material,  and  consequently  less  protoplasm. 
The  disproportion  of  the  gametes  is  due  almost  entirely  to  the  fact 
that  in  the  female  sex  the  garnetocyte  does  not  divide,  but  becomes 
a  single  niacrogamete,  while  the  male  gametocyte  sporulates  to 
produce  a  larger  or  smaller  number  of  microgametes. 

Very  instructive  in  this  respect  is  the  comparison  of  the  formation 
of  the  gametes  in  the  gregarines  (p.  331)  and  the  coccidia  (p.  346) 
respectively,  two  groups  of  Protozoa  which  are  certainly  closely 
allied  to  one  another.  In  such  a  form  as  Coccidium  (Fig.  152),  the 
gametocytes  remain  separate  one  from  the  other,  and  the  male 
gametocyte  forms  numerous  minute  microgametes  which  swarm 
away  ;  the  female  gametocyte,  on  the  other  hand,  becomes  a  macro- 
gamete  after  going  through  a  process  of  reduction,  and  is  fertilized 
by  a  single  niicrogamete.  In  gregarines,  however,  the  gametocytes 
associate  in  couples,  either  before  or  after  attaining  their  full  size, 
and  become  surrounded  by  a  common  cyst,  within  which  each 
gametocyte  sporulates  to  produce  a  large  number  of  small  gametes. 
The  gametes  of  gregarines  can  be  arranged  in  a  series,  showing 
marked  anisogamy  at  one  end,  complete  isoganiy  at  the  other. 
Thus  in  PterocepMlus  (Fig.  79,  A,  B)  the  gametes  are  very  unequal 
in  size,  and  the  microgametes  are  motile,  the  macrogametes  not  so. 
In  Stijlorliynclms  the  gametes  of  opposite  sexes  are  equal  in  size, 
but  in  one  sex  the  gametes  are  motile,  in  the  other  not  (Fig.  79, 


174 


THE  PROTOZOA 


C,  D).  In  Monocystis  (Fig.  79,  G — L)  the  gametes  differ  slightly  in 
size  in  the  two  sexes,  but  have  no  organs  of  locomotion  in  either 
case.  In  Urospora  (Fig.  79,  E,  F)  the  gametes  are  not  appreciably 
different  in  size,  but  in  those  of  one  sex  the  nuclei  are  slightly 
smaller  than  in  those  of  the  other.  Finally,  in  Gregarina,  Diplodina, 
and  many  other  genera,  no  difference  whatever  is  perceptible 
between  the  two  gametes  that  perform  syngamy.  In  those  gre- 
garines  which  have  dimorphic  gametes,  syngamy  is  always  between 
two  dissimilar  individuals  of  distinct  parentage,  and  it  may  be 
inferred,  therefore,  that  in  all  cases  alike  the  gametes  that  unite  are 
derived  from  distinct  gametocytes. 


H  I 

PIG.  79. — Gametes  of  different  species  of  gregarines.  A,  Male,  B,  female,  gamete 
of  Pterocephalus  (Nina)  gracilis.  G  and  D,  Stylorliynclius  longicollis  :  C,  male 
gamete  ;  D,  male  gamete  attaching  itself  to  a  female.  E,  Male,  F,  female, 
gamete  of  Urospora  lagidis,  showing  differences  in  the  size  of  the  nuclei. 
G — L,  Monocystis  sp.  :  G,  male  gamete  ;  H,  female  ;  /,  union  of  the  two 
gametes,  the  nuclei  still  separate  ;  J,  the  two  nuclei  fusing  ;  K,  the  zygote 
becoming  elongated  ;  L,  the  zygote  has  taken  the  form  of  the  spore,  and  in 
the  synkaryon  a  centrosome  has  appeared,  preparatory  to  division.  A  and 
B  after  Leger  and  Duboscq  ;  0  and  D  after  Leger  ;  E — L  after  Brasil. 

From  a  comparison  of  the  life-cj^cles  of  the  Coccidia  and  the 
Gregarines  respectively  (see  p.  354,  infra),  it  is  highly  probable  that 
in  the  common  ancestor  of  the  two  groups  the  gametocytes  were 
separate,  as  in  Coccidium,  and  each  produced  numerous  gametes, 
as  in  Gregarines.  Since  the  gametes  had  to  find  each  other,  by  a 
process  of  adaptation,  those  of  one  sex  became  smaller  and  more 
motile  (microga metes),  while  those  of  the  other  sex  were  more  bulky 
and  inert  (niacrogametes). 

In  the  course  of  their  evolution  from  this  primitive  ancestral 
type,  the  Coccidia,  with  some  exceptions  presently  to  be  noted, 
retained  the  habit  of  the  gametocytes,  remaining  separate,  and  the 
specialization  of  the  gametes  became  greatly  increased,  as  an  adap- 


POLYMORPHISM  AND  LIFE-CYCLES  175 

tation  to  this  condition,  the  female  gametocj'te  ceasing  to  divide 
and  becoming  a  single  macrogamete,  while  the  male  gametocyte 
produced  a  swarm  of  minute,  motile  microgarnetes.  Only  in  a 
few  Coccidia,  exemplified  by  the  genus  Adelea  (Fig.  154),  did  the 
gametocytes  acquire  the  habit  of  association  before  forming  gametes, 
a  habit  which  led  in  this  case  to  a  reduction  of  the  number  of  micro- 
gametes  produced  to  four,  of  which  one  fertilizes  the  macrogamete, 
while  the  other  three  perish.  It  is  clear  that  the  formation  of 
microga metes  in  close  proximity  to  the  macrogamete  increases 
vastly  the  chance  of  the  gametes  finding  each  other,  and  renders 
unnecessary  the  production  of  a  swarm  of  microga  metes. 

In  the  gregarines,  on  the  other  hand,  the  ganietocytes  acquired 
the  habit  of  associating  and  forming  their  gametes  in  a  common 
cyst.  Under  these  circumstances  it  becomes  a  certaint}'  that  a 
gamete  of  either  sex  will  find  a  partner  if  the  gametes  of  each  sex 
are  in  equal  numbers.  Consequently  there  is  seen  in  gregarines  a 
progressive  tendency,  illustrated  by  the  examples  cited  above,  to 
disappearance  of  those  characters  of  the  gametes  which  are  an 
adaptation  to  the  necessity  of  the  sexes  coming  together,  culminating 
in  production  of  gametes  of  opposite  sexes  which  are  perfectly 
similar.  On  this  view  the  isogamy  seen  in  many  gregarines  is  a 
secondary  condition  brought  about  by  the  gradual  obliteration  of 
adaptive  differences  between  the  gametes  of  opposite  sexes,  under 
circumstances  which  render  such  differences  unnecessary. 

The  comparison  of  the  gamete-formation  in  different  species  of  gregarines 
furnishes  an  instance  of  a  progressive  levelling-down  of  structural  differentia- 
tion of  gametes,  under  conditions  in  which  no  such  differentiation  is  required, 
until  an  anisogamy  undoubtedly  primitive  has  been  reduced  secondarily  to  a 
perfect  isogamy.  This  has  led  to  the  view  expressed  in  many  quarters,  that 
anisogarny  is  in  all  cases  a  primitive,  isogamy  a  secondary,  condition.  The 
case  of  the  gregarines  is  by  no  means  adequate,  however,  to  support  so 
sweeping  a  generalization  ;  the  only  conclusion  that  can  be  drawn  from  it  is 
that  adaptive  differences  tend  to  disappear  when  the  conditions  to  which  they 
are  an  adaptation  no  longer  exist ;  and  the  very  fact  that  the  obvious  structural 
differentiation  between  the  gametes  vanishes  in  such  a  case  is  of  itself  a  proof 
that  such  differentiation  is  not  the  expression  of  intrinsic  constitutional 
differences  between  the  gametes,  for  such  differences  could  not  be  annihilated 
merely  by  changed  conditions  of  environment. 

There  can  be  no  doubt  that  anisogamy  in  the  form  of  visible  structural 
differences  between  the  gametes  of  opposite  sexes  must  have  been  acquired 
very  early  by  gametes  as  an  adaptation  to  their  functions.  On  the  other 
hand,  it  is  highly  improbable,  to  say  the  least,  that  the  earliest  gametes, 
when  the  sexual  process  was  first  invented,  so  to  speak,  were  structurally 
differentiated.  It  must,  of  course,  be  postulated  that  the  gametes  possess 
^.K.-h  intrinsic  constitutional  differences  as  would  account  for  their  behaviour— 
that  is  to  say.  their  mutual  attraction  and  union  ;  and  in  this  sense  anisogamy 
may  be  considered  as  a  universal  and  primitive  phenomenon.  But  the  number 
of  cases  in  which  gametes  are  perfectly  isogamous,  as  regards  visible  struc- 
tural or  other  differences,  is  a  sufficient  proof  that  purely  constitutional 
anisogamy  does  not  necessarily  express  itself  in  perceptible  differentiation 
of  the  gametes. 


176  THE  PROTOZOA 

So  far  only  primary  sexual  differences — that  is  to  say,  those 
between  the  actual  gametes — have  been  discussed  ;  but,  as  has  been 
stated  above,  the  sexual  differentiation  may  be  thrown  back,  as  it 
were,  into  generations  preceding  the  gametes.  Thus,  it  is  by  no 
means  uncommon,  especially  in  Coccidia  and  Hsemosporidia,  for 
the  gametocytes  to  be  clearly  distinguishable  according  to  sex,  the 
female  gametocyte  having  the  cytoplasm  loaded  with  reserve  food- 
material,  and  usually  with  a  smaller  nucleus,  while  the  male  gameto- 
cyte has  the  cytoplasm  clear  and  free  from  inclusions,  and  the 
nucleus  is  relatively  large.  In  Adelea  the  male  gametocyte  is 
very  much  smaller  than  the  female  (Fig.  154).  In  Cydospora 
caryolytica,  parasitic  in  the  mole,  the  sexual  differentiation  is  carried 
back  through  generations  antecedent  to  the  gametocytes,  and, 
according  to  Schaudinn  (147),  male  and  female  merozoites  can  be 
distinguished. 

The  various  types  of  polymorphism  that  have  been  discussed  in 
this  chapter  may  be  classified  as  follows  : 

1.  Adaptive  polymorphism. 

(1)  Passive. 

(2)  Active. 

2.  Ontogenetic  polymorphism. 

(1)  In  size  alone. 

(2)  In  structure  also. 

(a)  Recapitulative. 

(b)  Adaptive. 

3.  Sexual  polymorphism. 

(1)  Primary  (of  gametes). 

(2)  Secondary. 

(a)  Of  gametocytes  alone. 

(b)  Of  other  generations  also. 

In  the  task  of  unravelling  the  complicated  life-cycles  of  Protozoa, 
it  is  of  the  greatest  importance  to  distinguish  clearly  the  significance 
of  the  various  forms  that  are  seen,  and  there  can  be  no  doubt  that 
failure  to  do  so  has  often  been  a  source  of  error.  With  some  writers 
it  is  an  obsession  to  ascribe  all  differences  to  sex,  and  to  interpret, 
for  instance,  in  the  development  of  trypanosomes,  all  bulky  forms 
as  females,  and  all  slender,  active  forms  as  males,  quite  regardless 
of  the  behaviour  of  the  forms  thus  designated.  It  is  far  more 
probable  that  in  the  majority,  at  least,  of  such  cases  the  bulky 
forms  are  related  to  the  multiplicative,  the  slender,  active  forms  to 
the  propagative  function,  respectively,  and  that  the  differences 
between  them  have  no  relation  whatever  to  sexual  functions,  either 
in  the  forms  themselves  or  in  their  descendants. 


POLYMORPHISM  AND  LIFE-CYCLES  177 


B.  LIFE-CYCLES. 

In  the  foregoing  section  the  various  forms  have  been  described 
under  which  one  and  the  same  species  of  Protozoon  may  occur  in 
the  course  of  its  life-history,  and  in  response  to  the  conditions  of  its 
particular  mode  of  life.  In  some  species  it  has  been  seen  that  the 
changes  of  form  and  structure  are  so  slight  that  the  species  are 
practically  monomorphic,  in  the  sense  that  they  can  be  identified 
without  difficulty  in  any  active  phase  of  life  ;  no  species  is  absolutely 
monomorphic,  since,  in  addition  to  resting  states,  differences  in  size 
due  to  growth,  at  least,  will  always  be  found.  Other  species,  on 
the  other  hand,  are  polymorphic  to  such  an  extent  that  their  specific 
identity  in  different  phases  can  only  be  determined  by  tracing  their 
development  in  a  continuous  sequence  ;  and  in  extreme  cases  of 
polymorphism  the  life-history  becomes  a  varied  pageant  of  dis- 
similar forms  succeeding  each  other  in  more  or  less  regular  order, 
determined  largely,  if  not  entirely,  by  the  conditions  of  the  environs 
ment.  In  a  former  chapter  the  distinction  has  been  drawn  between 
a  developmental  cycle,  consisting  of  a  recurrent  series  of  different 
forms,  and  the  complete  life-cycle,  consisting  of  the  whole  series 
of  forms  or  phases  which  appear  between  one  act  of  synganry  and 
the  next.  The  complete  life-cycle  may  comprise  many  develop- 
mental cycles. 

As  a  concrete  example  of  a  life-cycle  comprising  a  great  number  of 
different  forms,  and  in  which  also  the  development  may  follow  more 
than  one  course,  the  life-cycle  of  Arce.Ua  vulgaris  may  be  selected 
(Fig.  80).  The  life-history  of  this  form  has  now  been  made  known 
in  detail  by  the  combined  labours  of  many  investigators,  amongst 
whom  Hertwig  (65),  Elpatiewsky  (144),  Swarczewsky  (101),  and 
Khainsky  (145),  must  be  specially  mentioned. 

The  form  which  may  be  taken  as  the  starting-point  of  the  life- 
cycle  is  a  minute,  amoeba-like  form,  with  a  single  nucleus  (Fig.  80,  A). 
The  amcebula,  when  set  free,  feeds,  grows,  and  becomes  after  a 
time  spherical  in  form  with  radiate  pseudopodia  (Fig.  80,  B)  ;  in 
this  stage  it  resembles  a  species  of  the  genus  Nudearia.  After  a  time 
the  Nudearia-ioTm  secretes  a  shell,  and  now  resembles  an  example 
of  the  genus  Pseudochlamys  (Fig.  80,  C).  With  further  growth, 
chromidia  are  given  off  from  the  nucleus  into  the  cytoplasm,  the 
nucleus  divides  into  two,  and  the  animal  thus  assumes  gradually  the 
characters  of  the  adult  Arcetta  (Fig.  32  ;  Fig.  80,  D).  It  has  a 
chitinous  shell,  circular  in  outline,  flattened  in  profile-view,  and 
slightly  concave  on  the  under-side,  in  the  centre  of  which  is  a  large 
circular  aperture  through  which  the  pseudopodia  stream  out.  The 
body-protoplasm  contains  two  nuclei  situated  approximately  at 

12 


178 


THE  PROTOZOA 


FIG.  80. — Combined  diagram  to  show  the  different  methods  of  reproduction  and 

synganiy  in  the  life-cycle  of  Arcella. 

A- — D,  The  four  stages  in  the  ontogeny :  A,  the  arncebula  ;  B,  the  Nudearia-ioTm  ;  % 
C,  the  Pseudochlamys-iorm  ;  D,  the  adult  Arcella. 

D — G,  Stages  in  the  vegetative  reproduction  by  fission  :  E,  the  protoplasm 
beginning  to  stream  out  of  the  shell  of  the  parent-individual ;  F,  division  of  the 
nuclei  of  the  parent,  and  formation  of  the  shell  of  the  daughter ;  G,  migration 
ui  the  daughter-nuclei  into  the  daughter-individual  and  completion  of  the  division. 

[Continued  at  foot  of  p.  179. 


POLYMORPHISM  AND  LIFE-CYCLES  179 

the  opposite  ends  of  a  diameter  of  the  circular  body,  and  an  irregular 
ring  of  chromidia  forming  a  dense  chromidial  net.  Under  certain 
conditions  Arcella  becomes  encysted,  forming  a  spherical  cyst 
with  a  tough  impervious  membrane  within  the  shell,  closing  the 
mouth  of  it. 

The  adult  Arcella  reproduces  itself  by  a  variety  of  methods, 
which,  however,  may  be  reduced  to  two  principal  types  :  binary 
fission,  producing  daughter-individuals  (Arcellce)  of  approximately 
equal  size ;  and  gemmation,  producing  small  amcebulee  such  as  have 
been  described  above  as  the  starting-point  of  the  ontogeny.  The 
production  of  the  anioebulas  may  or  may  not  be  in  relation  to 
syngamy,  which,  when  it  occurs,  may  be  of  one  or  the  other  of  two 
distinct  types — karyogamy  between  amcebulee,  or  chromidiogamy 
between  adult  Arcellce. 

Binary  fission  (Fig.  80,  D — G)  is  the  ordinary  type  of  reproduction 
during  the  "  vegetative  "'  life  in  the  summer  months,  when  the 
animal  is  actively  feeding,  growing,  and  reproducing  itself.  In 
the  process  of  binary  fission,  the  two  nuclei  divide  by  a  form,  of 
karyo  kinesis  (Fig.  57,  p.  110).  A  quantity  of  the  body-protoplasm 
streams  out  through  the  mouth  of  the  shell,  together  with  some  of 
the  chromidia,  and  one  of  the  two  daughter-nuclei  of  each  pair  also 
passes  out  of  the  shell.  The  daughter-^ rce^a  thus  formed  secretes 
for  itself  a  new  shell,  and  separates  from  the  parent-individual, 
which  retains  the  old  shell.  Thus  in  binary  fission  both  nuclei  and 
chromidia  take  part,  the  former  dividing  by  mitosis,  while  the  latter 
are  subjected  to  a  roughly  equal  partition. 

The  ordinary  binucleate  form  of  Arcella  may  become  multi- 
Pic.  80 — continued: 

All  the  figures  below  the  level  of  D  represent  reproduction  by  gemmation  : 
those  to  the  left  are  reproductive  processes  not  combined  with  syngamy  ; 
those  on  the  right  show  the  methods  of  syngamy. 

H,  Formation  of  secondary  nuclei  and  buds  which  are-  liberated  singly 
from  the  parent  as  arncebulae  (a.). 

I,  P^apid  bud-formation,  leading  to  almost  the  whole  protoplasm  of  the 
parent  being  used  up  to  form  them. 

J,  Bud-formation  external  to  the  shell ;  the  protoplasm  has  streamed  out, 
leaving  only  a  small  residual  portion,  containing  the  primary  nuclei,  in  the 
shell ;  the  extruded  protoplasm  producing  buds  with  formation  of  secondary 
nuclei. 

K,  L,  Formation  of  gametes  and  karyogamy  :  K,  formation  of  rnacrarnrebae 
(  ?  )  ;  L,  formation  of  micramcebse  ( $  ) ;  the  gametes  (  ?  and  $  )  pass  out  of 
the  shell  and  copulate  (?)  to  produce  the  zygote  or  amcebula  (a.). 

M — Q,  Chromidiogamy  :  M ,  two  Arcellce  coming  together  ;  N,  the  proto- 
plasm, with  the  chromidia  and  degenerating  primary  nuclei,  of  the  one  passes 
•over  into  the  shell  of  the  other  ;  0,  after  intermingling  of  the  chromidia,  the 
protoplasm  becomes  equally  distributed  between  the  two  shells  ;  P,  the 
chromidia  give  rise  to  secondary  nuclei  ;  Q,  buds  (amcebulse,  a.)  aro  formed 
and  liberated. 

Other  letters  :  n.,  nucleus  ;  n.1,  primary  nucleus  ;  n.~,  secondary  nucleus ; 
chr.,  chromidia  ;  sh.,  shell ;  o,  mouth  of  slu-ll  ;  a.,  amcebulse. 
Modified  from  a  diagram  by  Swarczewsky. 


180  THE  PROTOZOA 

nucleate  by  formation  of  secondary  nuclei  from  the  chromidia,  as 
described  above  (Fig.  32,  p.  67).  The  secondary  nuclei  are  entirely 
distinct  in  their  origin  from  the  primary  nuclei,  which  degenerate 
when  the  secondary  nuclei  are  formed.  A  multinucleate  Arcella 
may  reproduce  itself  by  binary  fission  after  division  of  each  secon- 
dary nucleus  by  karyokinesis  ;  of  each  pair  of  secondary  daughter- 
nuclei,  one  goes  to  one  d&ughter-Arcella,  the  other  to  the  other,  so 
that  each  daughter  -Arcella  has  the  same  number  of  nuclei  exactly 
(Hertwig,  65). 

Gemmation  takes  place  in  multinucleate  forms  containing  a 
number  of  secondary  nuclei.  A  portion  of  the  body-protoplasm 
becomes  centred  round  each  secondary  nucleus,  and  thus  a  small 
cell  is  formed,  which  becomes  amoeboid,  quits  the  parent-body,  and 
cither  grows  directly  into  an  adult  Arcella  by  the  successive  stages 
described  above,  or  before  doing  so  performs  an  act  of  syngamy. 

Gemmation,  as  above  described,  takes  place  in  three  different 
ways,  as  follows  : 

1.  The  buds  are  formed  one  at  a  time,  and  the  parent-individual 
persists    and    continues    to    reproduce  itself    (simple    gemmation, 
Fig.  80,  H). 

2.  The  whole  body  of  the  Arcella  breaks  up  into  numerous  buds 
which  swarm  out  of  the  shell,  leaving  behind  in  it  the  two  primary 
nuclei,  with  a  small  quantity  of  residual  protoplasm.     The  parent- 
individual  then  dies  off,  apparently,  but  it  is  possible  that  it  may  in 
some  cases  regenerate  the  body  again.     This  process  of  multiple 
gemmation  differs  only  from  the  simple  gemmation  described  in  the 
previous  paragraph  in  being,  as  it  were,  greatly  intensified,  taking 
place  with  such  rapidity  as  to  use  up  almost  the  entire  protoplasm 
at  once  (Fig.  80,  /). 

3.  The  protoplasm  of  the  Arcella,  with  the  chromidia,  streams 
out  of  the  shell,  leaving  in  it  only  the  degenerating  primary  nuclei. 
Outside  the  shell  the  amoeboid  body  forms  secondary  nuclei,  and 
breaks  up  by  multiple  fission  into  a  number  of  amoebulse.      This 
process  differs  from  that  described  in  the  foregoing  paragraph  only  in 
taking  place  outside  the  shell  (Fig.  80,  J). 

As  already  stated,  the  amoebulge  formed  by  multiple  gemmation 
may  either  be  agametes,  which  develop  directly  into  the  adult  form, 
or  gametes,  which  first  go  through  a  process  of  syngamy  which  has 
been  described  in  the  previous  chapter  (Fig.  80,  K,  L).  Both 
agametes  and  gametes  arise  in  the  same  manner  ;  the  gametes, 
however,  show  sexual  differentiation  as  regards  size.  The  zygote 
is  an  amcebula  which  develops  into  the  adult  form  in  the  same  way 
as  an  agamete.  In  addition  to  syngamy  (karyogamy)  between 
amcebulae,  chromidiogamy  between  adult  Arcellce  also  occurs,  as 
already  described  ;  the  result  in  this  case  also  is  the  formation  of  a 


POLYMORPHISM  AND  LIFE-CYCLES  181 

number  of  amoebulae  which  develop  into  the  adult  in  the  usual  way 
(Fig.  80,  M—Q). 

Arcella  thus  furnishes  a  surprising  example  of  diversity  both  in 
the  courses  taken  by  the  development  and  in  the  methods  of 
syngamy.  We  may  now  consider  some  further  complications  of 
the  life-cycle,  which  in  other  Protozoa  takes  usually  a  more  definite 
and  stereotyped  course,  less  liable  to  the  variations  in  one  and  the 
same  species  seen  in  Arcella. 

One  of  the  commonest  complications  introduced  into  the  life- 
cycles  of  Protozoa  is  the  differentiation  of  sexual  and  non-sexual 
cycles.  In  the  account  given  above  of  the  life-cycle  of  Arcella,  it 
has  been  seen  that  an  adult  may  produce  amoebulse  which  as 
agametes  can  grow  up  directly  into  the  adult  form  without  syngamy, 
or  which  as  gametes  copulate  before  developing  further.  The 
adult  Arcellce,  however,  do  not,  so  far  as  is  known,  exhibit  any 
differentiation  in  relation  to  these  developmental  differences,  the 
form  that  produces  gametes  being  perfectly  similar  to  that  which 
produces  agametes.  But  in  other  cases  there  may  be  two  distinct 
forms  of  the  adult  individuals  :  the  one,  known  as  the  sporont  or 
gamont,  which  gives  rise  to  gametes  ;  the  other,  termed  the  schizont  or 
agamont,  which  produces  agametes.*  In  this  way  an  alternation  of 
generations  is  brought  about  in  which  the  life-cycle  as  a  whole 
becomes  a  combination  of  two  distinct  types  of  developmental  cycle 
—one  known  as  schizogony,  in  which  no  sexual  processes  occur  ; 
the  other  as  sporogony,  in  which  at  one  stage  gamete-formation  is 
followed  by  synganry. 

An  example  of  alternation  of  generations  in  a  free-living  form  is 
seen  in  the  life-cycle  of  Trichosphcerium  (Fig.  81),  as  described  by 
Schaudinn  (146).  The  adult  phase  is  a  relatively  large  amoeboid 
form,  approximately  spherical  in  contour,  and  having  the  body 
surrounded  by  a  gelatinous  envelope  in  which  at  intervals  there  are 
apertures  through  which  the  lobose  pseudopodia  are  extruded  ;  the 

*  The  word  "  sporont  "  was  a  modification  suggested  by  Butschli  for  the  term 
"  sporadin,"  originally  coined  by  Aime  Schneider  to  denote  the  adult  spore- 
forming  phase  in  the  cephaline  Gregarines  (p.  339),  and  to  distinguish  it  from  the 
earlier  phase  which  still  bears  the  epimerite,  known  as  a  cephalont  ("  cephalin," 
Schneider).  Since  the  production  of  resistant  spores  in  Gregarines  and  allied 
orders,  such  as  the  Coccidia,  is  accompanied  by  sexual  phenomena,  the  word 
"  sporont  "  has  undergone  both  an  extension  and  a  change  in  its  original  meaning, 
and  has  corne  to  be  used  to  denote  a  gamete-producing  form.  In  his  memoir  on 
Trichosphcerium,  Schaudinn  used  the  word  "  sporont  "  in  this  sense,  and  coined 
the  term  schizont  to  denote  the  agamete-producing  form,  and  further  coined  the 
words  "schizogony"  and  "  sporogony "  to  denote  the  non-sexual  and  sexual 
cycles  respectively.  Since  the  word  "  sporont  "  in  the  secondary  meaning  thereby 
given  to  it  has  reference  solely  to  the  occurrence  of  syngamy  and  not  to  the  forma- 
tion of  resistant  spores,  and  since  these  two  processes  are  not  always,  though 
frequently,  combined  in  the  same  series  of  generations,  it  would  perhaps  be  better 
to  replace  the  terms  "  schizont  "  and  "  sporont  "  by  "  agamont  "  and  "  gamont  " 
respectively,  were  it  not  that  this  leads  to  the  substitution  of  the  extremely  cacopho- 
nous words  "agamogony  "  and  "gamogonj^"  for  "schizogony"  and  "sporogony." 


182 


THE  PROTOZOA 


FIG.  81. — General  life-cycle  of  Trichosphcerium  sieboldi,  as  an  example  of  dimor- 
phism in  the  adult  condition  combined  with  alternation  of  generations. 
A,  Schizont  or  non-sexual  form,  distinguished  by  the  possession  of  rod-like 
bodies  in  the  envelope  (compare  F)  ;  this  form  may  multiply  by  simple  or 
multiple  fission  (plasmotomy)  in  a  "  vegetative  "  manner,  or'by  the  process 
of  sporulation  (schizogony)  seen  in  B  and  G,  in  order  to  give  rise  to  the  gamete- 
producing  form  ;  B,  division  of  the  body  of  the  schizont  into  as  many  cells 
("  sporogonia  ")  as  there  are  nuclei  ;  G,  rupture  of  the  envelope  and  escape 
of  the  sporogonia  as  active  amoebulae,  each  of  which  forms  an  envelope  for 

[Contimied  at  foot  of  p.  183. 


POLYMORPHISM  AND  LIFE-CYCLES  183 

protoplasmic  body  is  a  multinucleate  plasmodium.  There  are  two 
forms  of  the  adult — the  schizonts  (agamonts),  which  are  dis- 
tinguished by  the  presence  of  rod-like  spicules  in  the  envelope 
(Fig.  81,  A) ;  and  the  sporonts  (gamonts),  which  have  no  spicules 
(Fig.  81,  F).  The  schizonts  reproduce  themselves  either  in  the 
free  state  or  after  encystment.  In  the  free  state  the  reproduction 
is  by  simple  or  multiple  plasniotoniy — that  is  to  say,  by  division  of 
the  plasmodium  into  two  or  more  portions.  In  the  encysted  con- 
dition the  schizonts  divide  by  multiple  fission  into  as  many  daughter- 
cells  as  there  are  nuclei  in  the  plasmodium  (Fig.  81,  B),  and  each 
daughter-cell  is  set  free  as  an  amoebula  (agamete),  which  may  either 
grow  up  into  a  sporont,  or  into  a  schizont  which  repeats  the  process 
of  multiplication  by  schizogony. 

The  sporont  may  reproduce  itself  in  the  free  state  in  the  same 
manner  as  the  schizont,  byplasmotonry,  or  it  may  become  encysted, 
and  then  it  multiplies  in  a  manner  totally  different  from  that  seen 
in  the  corresponding  phase  of  the  schizont.  The  nuclei  of  the 
encysted  sporont  multiply  rapidly  by  karyokinesis  (Fig.  81,  G)  until 
there  are  a  very  large  number  of  minute  nuclei ;  very  probably  the 
final  divisions  in  this  process  of  multiplication  are  reducing  divisions. 
The  protoplasmic  body  then  becomes  divided  up  into  as  many 
minute  cells  as  there  are  nuclei,  and  each  of  the  daughter-cells 
acquires  two  flagella,  and  is  set  free  as  a  flagellula  or  gamete 
(Fig.  81 ,  H).  The  gametes,  which  are  not  differentiated  in  any  way, 
copulate  with  those  derived  from  another  sporont,  and  lose  their 
flagella  (Fig.  81,  / — -L)  ;  the  zygote  is  a  small  amoebula  which  grows 
up  into  a  schizont  (Fig.  81,  L,  M,  N,  A). 

An  alternation  of  generations  similar  to  that  of  Trichosphcerium 
occurs  also  in  the  Fora minif era  (p.  234).  Here  the  schizont  contains 
numerous  nuclei,  which  multiply  by  fission  as  the  animal  grows,  and 
also  chromidia  ;  it  reproduces  itself  by  a  process  of  multiple  fission, 
breaking  up  into  a  number  of  amoebulae  (agametes),  each  with  a 
nucleus  and  chroniidia.  The  amcebulse  creep  out  of  the  old  shell, 
which  is  abandoned,  and  each  amoebula  secretes  a  shell  for  itself, 

FIG.  81  continue!  : 

itself  and  grows,  with  multiplication  of  the  nuclei  (D  and  E)  into  the  gamete- 
producing  form  or  sporont  (F),  similar  in  general  structure  to  the  schizont  (A), 
but  without  rods  in  the  envelope  ;  the  sporont  may  also  multiply  in  a  vegeta- 
tive manner  by  simple  or  multiple  fission,  or  it  may  form  gametes  in  the 
manner  seen  in  G  and  H  ;  G,  active  multiplication  of  the  nuclei  of  the  sporont 
to  form  a  great  number  of  very  small  nuclei,  after  which  the  body  divides 
up  into  as  many  minute  cells  as  there  are  nuclei  ;  these  cells  are  the  gametes, 
and  each  gamete  acquires  two  flagella  ;  H,  rupture  of  the  envelope  to  set  free 
the  gametes,  which  swarm  out  and  conjugate  ;  /,  conjugation  of  two  gametes, 
more  highly  magnified  ;  ./,  after  fusion  of  the  bodies  of  the  gametes  the 
flagella  are  thrown  off  ;  K,  fusion  of  the  two  pronuclei  ;  L,  complete  zygote, 
which  forms  an  envelope  and  grows,  with  multiplication  of  the  nuclei  (M,  N) 
into  the  schizont  (^4),  which  was  taken  as  a  starting-point  of  the  life-cycle. 
After  Schaudinn  (146). 


184  THE  PROTOZOA 

and  groAvs  up  either  into  a  sporont  or  into  a  schizont  again.  The 
sporont  possesses  only  a  single  large  nucleus,  the  primary  nucleus 
originally  present  in  the  amoebula,  and  a  great  number  of  chromidia. 
When  the  sporont  enters  upon  the  reproductive  phase,  the  primary 
nucleus  degenerates,  and  an  immense  number  of  secondary  nuclei 
are  formed  from  the  chromidia.  Then  the  protoplasmic  body  divides 
up  to  form  as  many  cells  as  there  are  secondary  nuclei.  The  cells 
thus  produced  are  the  gametocytes,  each  of  which  divides  by  mitosis 
to  form  four  small  cells,  the  gametes,  which  acquire  flagella,  swim 
off,  and  copulate  with  gametes  produced  from  another  sporont ; 
there  appear,  however,  to  be  no  differences  exhibited  by  the  gametes 
of  opposite  sexes.  The  zjrgote  forms  a  shell  and  grows  into  a 
sporont.  Since  the  zygote  is  very  much  smaller  than  the  amcebula 
produced  by  schizogony,  the  shell  formed  by  it  is  also  smaller.  This 
shell  is  later  the  initial  chamber  of  the  polythalamous  adult,  and 
thus  leads  to  a  dimorphism  in  the  adult  shells,  so-called  ' '  micro- 
sphseric  "  and  "  megalosphaeric  '"  forms  (p.  235) — a  dimorphism 
related,  in  this  case,  not  to  the  manner  in  which  the  adult  individuals 
reproduce  themselves,  but  to  the  manner  in  which  they  have  been 
reproduced. 

In  free-living  forms  the  alternation  of  generations  is  related  to 
external  conditions  of  the  environment,  as,  for  example,  seasonal 
changes  ;  the  sexual  generation  may  appear  in  the  autumn,  while 
the  non-sexual  generations  are  found  in  the  spring  and  summer. 
In  parasitic  forms,  on  the  other  hand,  alternation  of  generations  is 
of  common  occurrence  in  relation  to  a  change  of  hosts.  Thus,  in 
the  life-cycle  of  the  Coccidia  (Fig.  152),  described  above,  the  multi- 
plicative phases  reproduce  non-sexually  by  schizogony,  as  the  so- 
called  "  endogenous  cycle  "  ;  the  propagative  phases  are  preceded 
by  gamete-formation,  leading  to  spore-formation,  the  so-called 
"  exogenous  cycle."  In  Hsemosporidia,  such  as  the  malarial  parasites, 
for  example  (Fig.  156),  the  alternation  of  generations  is  related  to 
an  alternation  of  hosts  ;  the  non-sexual,  schizogonous  generations 
take  their  course  in  the  blood  of  the  vertebrate  host,  in  which  the 
gamonts  are  produced,  but  do  not  develop  further  unless  taken  up 
by  the  invertebrate  host,  in  which  alone  gametes  are  formed  and 
sporogony  takes  place. 

The  phrase  "  alternation  of  generations  "  must  not  be  construed 
into  meaning  that  the  sexual  and  non-sexual  generations  succeed 
each  other  in  a  regular  alternation.  On  the  contrary,  such  regular 
alternation,  if  it  occurs  at  all,  is  rare,  and  as  a  rule  a  single  sexual 
generation  is  followed  by  several,  or  it  may  be  by  an  immense 
number,  of  non-sexual  generations  before  the  sexual  cycle  recurs. 
The  malarial  parasite  can  multiply  non-sexually  in  the  blood  for 
many  years  without  dying  out ;  and  if  propagated  artificially  from  one 


POLYMORPHISM  AND  LIFE-CYCLES  185 

vertebrate  host  to  another,  it  is  probable  that  it  could  dispense  alto- 
gether with  the  sexual  cycle,  which  occurs  only  in  the  invertebrate 
host,  so  far  as  is  known.  In  the  suborder  Eugregarinse  of  the 
Gregarinoidea  an  opposite  condition  occurs,  since  these  forms 
possess  only  the  sexual  cycle,  sporogony,  and  there  is  no  non-sexual 
schizogony.  Whether  this  condition  is  to  be  regarded  as  a  primitive 
state  of  things,  or  whether  the  Eugregarines  are  to  be  regarded  as 
having  dispensed  with  the  non-sexual  process  of  schizogony  seen 
in  the  allied  suborder  Schizogregarinae,  must  remain  an  open 
question. 

A  further  caution  is  also  necessary  with  regard  to  the  alternation 
of  generations  in  Protozoa.  From  the  known  facts  of  the  malarial 
life-cycle,  in  which  an  alternation  of  sexual  and  non-sexual  cycles 
is  correlated  with  an  alternation  of  hosts,  it  has  often  been  assumed, 
implicitly  or  explicitly,  that  a  similar  alternation  of  sexual  and  non- 
sexual  cycles  must  occur  in  other  cases  where  there  is  an  alternation 
of  hosts,  as  in  the  case  of  trypanosomes,  and  in  particular  that  the 
sexual  cycle  must  occur  in  the  invertebrate  host.  This  assumption 
is  by  no  means  justified,  however,  and  has  been  the  cause  of  much 
unsound  or  unwarranted  interpretation  of  the  facts,  especially  as 
regards  the  significance  of  the  various  forms  of  trypanosomes, 
which  are  continually  ascribed  to  sexual  differentiation  on  no  other 
ground  than  the  bare  fact  of  form-differentiation,  as  pointed  out  in 
the  previous  chapters.  Up  to  the  present  there  is  not  a  single  case 
in  which  sexual  phenomena  in  trypanosomes  have  been  described 
in  a  perfectly  satisfactory  manner,  free  from  all  doubt ;  and,  on  the 
other  hand,  it  has  been  asserted  that  the  synganiy  occurs  in  the 
vertebrate  host  in  these  parasites  (Ottolenghi,  492). 


Bibliography. — For  references  see  p.  480. 


CHAPTER  X 
THE  GENERAL  PHYSIOLOGY  OF  THE  PROTOZOA 

THE  Protozoa,  as  has  been  seen  in  the  previous  chapters,  exhibit  a 
wide  range  of  structural  differentiation,  fro  informs  which  exemplify 
a  cell  reduced  to  its  simplest  essential  parts,  nucleus  and  cytoplasm, 
to  others  in  which  the  cytoplasmic  elements  give  rise  in  different 
parts  of  the  body  to  a  great  variety  of  structures  and  organs,  each 
subservient  to  some  special  function.  In  the  Protozoa  of  simplest 
structure,  therefore,  the  study  of  the  physiological  activities  of  the 
organism  coincides,  more  or  less,  with  that  of  the  elementary 
properties  of  the  living  substance,  protoplasm,  its  peculiar  powers 
of  metabolism  and  transmutation  of  energy  ;  while  in  Protozoa  of 
complicated  organization  the  mechanism  and  mode  of  action  of  the 
various  cell-organs  must  be  considered  in  relation  to  their  structure, 
so  far  as  it  can  be  made  out. 

It  is  not  possible  to  discuss  adequately,  in  the  limited  space  of  a 
chapter,  the  intricate  problems,  for  the  most  part  still  very  obscure, 
of  the  vital  mechanisms  of  elementary  organisms.  The  matter  can 
only  be  dealt  with  here  on  broad  general  lines,  and  those  desirous 
of  studying  the  subject  further  must  consult  the  references  given  to 
special  works  or  memoirs.*  On  the  other  hand,  the  special  functions 
and  mechanisms  of  the  various  cell-organs  ("  organelte")  have  been 
considered  in  describing  the  structure  of  the  organs  themselves. 
In  this  chapter,  therefore,  it  is  intended  rather  to  fill  the  gaps  left 
in  previous  chapters  ;  and  the  physiological  problems  presented  by 
the  Protozoa  will  be  sketched  in  brief  outline  under  the  following 
headings  :  (1)  Nutrition  and  Assimilation  ;  (2)  Respiration  ;  (3)  Secre- 
tion and  Excretion  ;  (4)  Transmutation  of  Energy  ;  (5)  Reactions  to 
Stimuli  and  to  Changes  of  Medium  or  Environment ;  (6)  Degenera- 
tion and  Regeneration. 

*  For  works  dealing  with  the  physiology  of  Protozoa  in  a  general  way  the  student 
should  consult  especially  Verworn,  "  Allgemeine  Physiologie,"  Jena,  1907  (a  trans- 
lation of  the  second  German  edition,  under  the  title  "  General  Physiology,"  was 
published  by  Macmillan,  1899)  ;  Prowazek,  "  Einfiihrung  in  die  Physiologie  der 
Einzelligen,"  Leipzig  (Teubner),  1910  ;  the  chapter  on  the  general  physiology  of 
the  Protozoa  in  Donein's  "  Lehrbuch  der  Protozoenkunde  "  ;  and  the  excellent 
summary  of  methods  and  results  of  physiological  investigations  upon  Protozoa 
given  by  Putter  in  Tigerstedt's  "  Handbuch  der  Physiologischen  Methodik." 

186 


THE  GENERAL  PHYSIOLOGY  OF  THE  PROTOZOA     187 

] .  Nutrition  and  Assimilation. — Living  organisms,  considered 
generally,  exhibit  a  great  variety  of  methods  of  nutrition,  which 
may  be  classified  into  two  main  groups  ;  bearing  in  mind,  however, 
that  in  all  classifications  of  living  beings,  or  of  their  vital  properties, 
any  groups  or  classes  that  can  be  distinguished  are  always  connected 
by  gradual  and  imperceptible  transitions,  and  that  consequently 
forms  will  present  themselves  which,  owing  either  to  their  transi- 
tional nature  or  to  the  imperfect  state  of  our  knowledge  concerning 
them,  can  only  be  assigned  to  one  or  the  other  group  in  a  manner 
as  arbitrary  as  the  statement  that  the  21st  of  June  is  the  first  day 
of  summer — a  difficulty  which  in  no  way  invalidates  the  distinction 
between  spring  and  summer. 

In  the  first  place,  many  organisms  can  build  up  the  complex 
protein-substances,  of  which  the  living  protoplasm  is  composed, 
from  simpler  chemical  materials.  Of  this  type  there  are  found 
among  Protozoa,  as  already  stated,  two  types  of  nutrition  :  first,  the 
holophytic,  or  plant-like,  in  which  the  organism  is  able,  by  means  of 
special  cell-organs,  to  utilize  the  energy  of  the  sunlight  in  order  to 
synthesize  its  body-substance  from  the  simplest  chemical  materials, 
such  as  water,  carbon  dioxide,  and  mineral  salts,  through  a  series 
of  substances  in  an  ascending  scale  of  chemical  complexity ; 
*  secondly,  the  saprophytic  type,  in  which  the  body  contains  no  visible 
organs  subserving  the  function  of  nutrition,  but  the  organism  is 
able  to  build  up  its  protoplasm  from  food- materials  consisting  of 
organic  substances  in  solution  which  are  far  less  complex  chemically 
than  the  body-proteins. 

In  the  second  place,  many  organisms  cannot  build  up  their  body- 
substance  from  materials  of  simpler  chemical  constitution,  but  are 
entirely  dependent  on  a  supply  of  protein-substance  ready-made, 
which  they  obtain  either  by  ingesting  and  digesting  other  living 
organisms  in  the  holozoic  method,  or  by  living  as  parasites  at  the 
expense  of  other  creatures.  These  two  methods  graduate  into  one 
another,  since  many  parasites  simply  devour  portions  of  the  bodies 
of  their  hosts  in  a  holozoic  manner,  but  the  majority  of  parasites 
absorb  fluid  nutriment  from  their  hosts  in  an  osmotic  manner ; 
hence  it  is  convenient  to  distinguish  holozoic  and  osmotic  parasites. 

Considering  these  various  methods  of  nutrition,  it  is  seen  that, 
from  the  point  of  view  of  the  nature  of  the  food,  those  which  ingest 
solid  food-particles  (holozoic  forms)  can  be  distinguished  from  those 
which  absorb  their  food  in  a  diffused  or  dissolved  condition  (holo- 
phytic and  saprophytic  forms  and  osmotic  parasites).  From  the 
point  of  view  of  the  structure  of  the  organism,  those  which  possess 
special  organs  of  nutrition  (holozoic  and  holophytic  forms)  can  be 
distinguished  from  those  which  possess  none  (saprophytic  forms  and 
osmotic  parasites). 


188  THE  PROTOZOA 

(a)  Holophytic  Nutrition. — The  characteristic  of  this  type  of 
nutrition  is  that  the  organism  contains  special  pigments  by  means 
of  which  it  is  able  to  decompose  C02  in  the  sunlight,  setting  free 
the  oxygen  and  retaining  the  carbon,  which  is  built  up  in  union 
Avith  other  elements  derived  from  water  and  mineral  inorganic  salts. 
The  pigments,  termed  comprehensively  chromophyll,  are  contained 
in  bodies  termed  "  chromatophores,"  which  occur  in  diverse  forms 
and  varying  numbers  in  different  species,  and  which  multiply  by 
division  when  the  cell  divides.  The  chromoplryll-pigments  are  of 
various  tints  —  yellow,  brown,  green,  blue-green,  etc. --but  the 
commonest  tint  is  the  green  chlorophyll,  similar  to  that  character- 
istic of  plant-cells.  A  blood-red  pigment,  termed  hcematochrome, 
occurs  in  some  flagellates — e.g.,  Hcematococcus  ;  it  appears  to  be  a 
modification  of  chlorophyll  produced  under  certain  conditions  (see 
Reichenow,  97 -5). 

For  the  details  of  the  complicated  process  of  the  sjnithesis  of 
•chemical  substances  in  the  holophytic  mode  of  nutrition,  the  student 
is  referred  to  botanical  textbooks  dealing  with  plant-physiology. 
There  appears  to  be  no  essential  difference  between  the  assimilative 
processes  of  holophytic  Protozoa  and  of  ordinary  plant-cells.  A 
characteristic  product  of  holophytic  nutrition  is  seen  in  the  forma- 
tion of  amyloid  substances,  the  most  important  of  which  are  starch 
(amylum),  and  an  allied  substance  known  as  "  paramylum,"  which 
differs  from  starch  in  some  of  its  reactions,  notably  in  that  it  is  not 
coloured  blue  with  iodine.  Paramylum  is  of  more  frequent  occur- 
rence in  Protozoa  than  true  starch.  The  amyloid  substances  occur  in 
characteristic  masses  in  the  cytoplasm  (see  especially  Biitschli,  153). 

The  chromatophores  of  Protozoa  contain  usually  smah1  refringent 
bodies  termed  pyrenoids,  which  also  multiply  by  division.  The 
pyrenoids  are  often  surrounded  by  a  coat  or  envelope  of  paramylum, 
and  appear  to  be  the  centres  of  the  production  of  amyloid  substance. 

Many  flagellates  with  green  chromatophores  combine  holophytic  with 
saprophytic  nutrition.  Examples  of  such  "  mixotrophic  "  forms  are  seen 
in  the  genus  Euglena  (Zumstein,  223),  the  species  of  which  flourish  best  in 
A  medium  containing  organic  substances,  and  cannot  maintain  themselves 
in  pure  water.  Euglena  viridis  was  shown  by  Khawkine  to  be  able  to  live 
for  a  considerable  period  in  the  dark  in  media  containing  organic  substances, 
but  did  not  lose  its  green  colour  and  did  not  multiply.  E.  gracilis,  on  the 
other  hand,  in  Zumstein's  experiments,  lost  its  green  colour  and  passed  into 
an  Astasia-like  phase  in  the  dark,  or  even  in  the  light  when  placed  in  solutions 
very  rich  in  organic  substances,  nourishing  itself  as  a  saprophyte.  When  the 
Astasia-iorm.  was  exposed  to  the  light,  in  solutions  containing  a  small  amount 
•of  organic  matter,  it  became  green  again  and  passed  back  into  the  Euglena- 
phase.  The  degree  to  which  the  species  of  Euglena  can  adapt  themselves 
lo  a  purely  saprophytic  life  would  appear  to  vary  in  different  cases.  In  the 
•colourless  forms  the  chromatophores  lose  their  chlorophyll,  and  remain  as 
colourless  leucoplasts. 

The  combination  of  holozoic  and  holophytic  nutrition  has  been  noted 
above  (p.  15). 


THE  GENERAL  PHYSIOLOGY  OF  THE  PROTOZOA     189 

(6)  Holozoic  Nutrition. — In  this  type  of  assimilation  three  series 
of  events  must  be  distinguished,  each  of  which  may  be  effected  by 
means  of  special  organs  :  the  capture  and  ingestion  of  the  prey  ;  its 
digestion  ;  and  lastly  the  rejection  from  the  body  of  the  non- 
nutritive  residue  (defsecation). 

The  methods  of  food-capture  and  ingestion  have  been  dealt  with 
above  in  a  general  way.  As  regards  food  -  capture,  methods  of 
prehension  by  means  of  pseudopodia,  or  by  special  adhesive  organs, 
such  as  the  suctorial  and  raptorial  tentacles  of  Acinetaria  (p.  457), 
the  tongue  of  Didinium  (p.  442),  etc.,  must  be  distinguished  from 
methods  whereby  the  food  is  wafted  towards  the  body  in  currents 
produced  by  special  vibratile  organs  such  as  flagella  and  cilia.  As 
regards  ingestion  of  food,  a  distinction  is  imposed  by  the  nature  of 
the  outer  surface  of  the  body-protoplasm,  whether  naked  or  invested 
by  a  firm  cortex  or  cuticle. 

In  naked  forms  the  food  is  ingested  at  any  point,  by  methods 
which  vary  in  different  forms.     In  Amoeba  proteus  the  hinder  end 
of  the  body  is  most  active  in  ingestion ;  in  Actinosph  cerium  all  points 
on  the  surface  are  equally  active.     Rhumbler  (204)  distinguishes 
four  methods  of  food-ingestion  in  anicebse  :  (1)  By  "  import,"  when 
the  food  is  drawn  into  the  protoplasmic  body  as  soon  as  it  conies 
into  contact  with  it,  and  with  scarcely  any  movements  on  the  part 
of  the  amoeba  (Fig.  23)  ;  (2)  by  flowing  round,  "  circumfluence,"  in 
which  the  protoplasm,  as  soon  as  it  comes  into  contact  with  the 
food-particle,  flows  round  it  on  all  sides  and  engulfs  it ;   (3)  by 
"  circumvallation,"  when  the  amoeba,  while  still  at  some  distance 
from  the  object,  sends  out  pseudopodia  which  flow  towards  each 
side  of  the  prey,  and  ultimately  meet  round  it  and  surround  it  com- 
pletely, without  ever  having  been  in  actual  contact  with  it ;  (4)  by 
"  invagination,"  in  which  the  amoeba  touches  and  adheres  to  the 
object,  and  the  portion  of  the  ectoplasm  in  contact  with  it  is 
invaginated  into  the  endoplasm  like  a  tube,  the  walls  of  which 
become  liquefied  and  fused  together,  so  that  the  food-particle  is, 
as  it  were,  sucked  into  the  endoplasm  (Fig.  82).     Of  these  various 
methods,  the  process  of  circumvallation  is  most  suggestive  of  a 
conscious  and  purposeful   act  on   the  part,  of  the  amoeba  ;  but  a 
remarkable  parallel  to  it  is  seen  in  the  penetration  of  Lankesterella 
into  a  red  blood-corpuscle,  as  described  by  Neresheimer  (see  p.  378, 
infra).     In  this  case,  as  soon  as  the  parasite  conies  within  a  certain 
distance  of  the  corpuscle,  the  latter  opens  its  arms,  as  it  were,  to 
the   parasite,    and  engulfs   it  in   a   manner    very   similar    to  the 
ingestion  of  food  by  circumvallation  on  the  part  of  an  amoeba. 
In  both  cases  the  object  that  is  ingested  must  give  off  some  substance 
which  exerts  at  a  certain  distance  an  effect  on  the  protoplasm  of 
the  cell  which  ingests  it. 


190 


THE  PROTOZOA 


According  to  Rhumbler  (204),  with  a  more  fluid  condition  of  the 
ectoplasm,  the  food  is  ingested  by  import  or  circumfluence ;  when 
the  ectoplasm  is  stiffened  to  a  membrane-like  consistence,  the 
ingestion  is  effected  by  circumvallation  or  invagination.  Rhumbler 
maintains  that  all  known  methods  of  food-ingestion  by  amcebse,  as 
well  as  their  movements,  can  be  explained  mechanically  by  differ- 
ences of  surface-tension  in  colloidal  limiting  membranes,  and  can 
be  imitated  artificially  in  substances  that  are  not  living. 


D 


FiG.j82. — Ingestion  of  a  food-particle  by  "  invagination  "  in  Amoeba  terricola. 
A — E,  Five  stages  of  the  process,  semi-diagrammatic  ;  F,  diagrammatic 
figure  to  show  the  direction  of  the  currents  on  the  surface  of  the  body  of  the 
amoeba  during  the  process  of  ingestion.  After  Grosse-Allermann  (245). 

In  corticate  forms  the  ingestion  of  food  is  limited  to  one  or  more 
special  openings  or  organs,  in  which  a  direct  communication  is 
established  between  the  fluid  endoplasm  and  the  surrounding 
medium,  as  in  the  cytostomes  of  Flagellata  and  Ciliata  and  the 
suctorial  tentacles  of  Acinetaria. 

The  digestion  of  the  food  is  effected  within  the  protoplasmic  body, 
and  as  a  rule  the  prey  is  taken  bodily  into  the  cytoplasm  ;  but 
the  Acinetaria  have  the  power,  not  fully  explained,  of  sucking  out 


THE  GENERAL  PHYSIOLOGY  OF  THE  PROTOZOA     191 

the  body-substance  of  their  prey,  probably  by  the  aid  of  secreted 
ferments.     Together  with  the  food  a  certain  amount  of  water  is 
ingested,   forming   a   drop   or  food-vacuole   in  which    the   actual 
digestion  takes  place.     The  quantity  of  water  ingested  with  the 
food  varies  considerably,  and,  speaking  generally,  is  inversely  pro- 
portional to  the  size  of  the  object  that  is  devoured  ;  that  is  to  say, 
small  food-particles,  such  as  bacteria,  lie  as  a  rule  in  a  very  distinct 
vacuole,  but  large  bodies,  such  as  diatoms,  usually  appear  as  if 
imbedded  in  the  cytoplasm,  with  no  liquid  vacuole  visible  around 
them.     Amoebae  not   infrequently  devour  organisms  larger  than 
themselves,  so  that  the  cj^toplasm  of  the  amoeba  appears  like  a 
thin  skin  or  envelope  over  the  surface  of  the  prey.     According  to 
Greenwood  (161),  Amoeba  proteus  takes  in   but  little  fluid  when  it 
ingests  quiescent  solid  matter,  such  as  starch-grains  or  yeast-cells, 
but  when  actively- moving  prey  is  dealt  with  an  area  of  water  not 
inconsiderable  surrounds   it ;   on   the  other  hand,   non-nutritious 
particles  are  not  surrounded  by  fluid  when  they  He  in  the  eiidoplasm. 
In  forms  in  which  food  is  ingested  through  a  cytostome,  as  in 
Ciliata,  the  food-particles,  usually  of  small  size,  are  wafted  down 
the  oesophagus  and  collect  at  its  proximal  blind  end,  where  a  depres- 
sion arises  in  the  endoplasm,  which  gradually  deepens,  and  finally 
closes  over  and  separates  from  the  oesophagus  as  a  closed  vacuole 
containing   the  food.     According  to  Nirenstein    (181),    the  food- 
vacuole  is  detached  from  the  oesophagus  by  suction  of  the  endoplasm, 
like  a  process  of  swallowing  ("  Schlingvorgang  ").     The  vacuole  is 
at  first  immured  in  a  thin  layer  of  less  fluid  protoplasm,  doubtless 
as  the  effect  of  contact  with  water  (see  p.  44) ;  consequently  the 
vacuole  is  not  at  first  circular,   but  often  spindle-shaped  in  its 
contours  ;  it  soon,  however,  assumes  a  spherical  form,  indicating 
that  its  protoplasmic  envelope  has  become  liquefied. 

In  cases  where  actively- motile  organisms  are  devoured — as,  for 
example,  flagellates  by  amoebae — the  prey  can  often  be  seen  to  per- 
form violent  movements  within  the  vacuole  ;  but  soon  the  move- 
ments become  feebler  and  cease  entirely.  Bacteria  ingested  by 
Paramecium  become  immobile  about  thirty  seconds  after  the 
vacuole  has  become  detached  from  the  oesophagus.  In  many  cases, 
however,  the  prey  is  killed  when  seized  by  the  pseudopodia,  and 
before  being  ingested,  as  in  Heliozoa  and  Eoraminifera.  After  the 
prey  is  killed  it  is  slowly  digested  within  the  food-vacuole. 

During  the  process  of  digestion  the  food-vacuole  may  perform 
definite  migrations  within  the  body  of  the  animal.  In  amoebae  the 
vacuoles  are  carried  about  by  the  currents  of  the  protoplasm, 
without,  however,  pursuing  any  definite  course,  and  they  tend  to 
become  aggregated  in  the  hinder  end  of  the  body,  when  the  animal 
is  moving  in  a  definite  direction.  In  the  Infusoria,  on  the  other 


192  THE  PROTOZOA 

hand,  the  endoplasm  shows  a  constant  rotating  movement,  known 
as  "  cyclosis."  In  Paramecium  the  vacuoles  are  carried  round  by 
the  current  of  the  cyclosis,  and  each  vacuole  may  either  do  a  short 
course  or  a  long  course  ;  the  short  course  is  simply  round  the 
nucleus,  keeping  close  to  it,  while  the  long  course  travels  the  whole 
length  of  the  body,  up  one  side  and  down  the  other.  As  a  rule  a 
vacuole  goes  a  short  course  two  or  three  times,  and  then  does  a 
long  course  (Xirenstein,  181).  The  path  of  the  vacuole  varies, 
according  to  the  nature  of  the  contents  ;  but  the  tendency  is  to 
keep  them  in  the  region  posterior  to  the  nucleus,  where  the  contents 
are  either  cast  out  through  the  anal  pore,  or  the  vacuole  circulates 
again  in  the  cyclosis.  In  Carchesium  the  food- vacuoles,  when 
formed  at  the  base  of  the  oesophagus,  pass  down  to  one  end  of 
the  horseshoe-shaped  nucleus,  and  then  glide  close  along  its  concave 
margin,  passing  round  and  up  to  the  opposite  end  of  the  horseshoe 
into  the  region  near  the  upper  end  of  the  vestibule,  from  whence  the 
vacuole  is  finally  emptied  through  an  anal  pore  into  the  vestibule 
itself  (Greenwood,  162). 

The  process  of  digestion  within  the  food- vacuole  has  been  studied 
by  a  number  of  investigators,  amongst  whom  Le  Dantec,  Greenwood 
(162),  Metschnikoff  (180),  Metalnikoff  (179),  Nirenstein  (181),  and 
Khainsky  (170'5),  must  be  specially  mentioned.  Their  results  are 
not  always  in  agreement,  indicating  that  the  process  of  digestion 
is  not  always  the  same  in  different  cases,  even  in  the  food- vacuoles. 
of  one  and  the  same  species.  According  to  Nirenstein  (181),  the 
food-vacuoles  of  Infusoria  exhibit  changes  which  can  be  divided 
nto  two  periods  :  in  the  first  the  vacuole  shows  an  acid  reaction, 
and  the  ingested  organisms  are  killed  ;  in  the  second  the  vacuole 
has  an  alkaline  reaction,  and  the  albumens  are  digested.  According 
to  Khainsky  (17O5),  however,  the  reaction  of  the  food-vacuoles  of 
Paramecium  is  acid  during  the  entire  period  of  the  proteolytic 
process,  and  only  becomes  neutral  and  finally  alkaline  when  the 
solution  of  the  food-substance  is  at  an  end. 

In  the  first  or  acid  period,  according  to  Nirenstein  (181),  the 
ingested  food-particles — e.g.,  bacteria— after  being  rendered  im- 
mobile, are  clumped  together,  enveloped  in  a  turbid  substance 
which  makes  their  outlines  indistinct.  The  reaction  of  the  vacuole 
is  strongly  acid,  due  to  the  presence  of  mineral  acid  in  the  vacuole. 
During  this  period,  which  lasts  from  four  to  six  minutes,  the  vacuole 
diminishes  in  size,  till  it  is  not  more  than  one-third  of  its  original  size. 
When  the  vacuole  was  first  formed,  its  wall  was  surrounded  by  a 
number  of  granules  which  stain  very  distinctly  with  neutral-red  ; 
these  granules  pass  suddenly  into  the  interior  of  the  vacuole  after 
it  has  become  diminished  considerably  in  size.  Nirenstein  regards 
the  red -staining  granules  as  bearers  of  a  tryptic  ferment. 


THE  GENERAL  PHYSIOLOGY  OF  THE  PROTOZOA     193 

In  the  second  or  alkaline  period  the  vacuole  enlarges  rapidly  to 
more  than  its  original  volume.  The  red  colour  produced  by  staining 
with  neutral-red  disappears.  The  clumped  food- mass  breaks  up  into 
smaller  particles  again.  From  the  red-staining  granules  of  the  first 
period  deeply-staining  spheres  arise,  homogeneous,  refractile,  and 
apparently  fluid  (Nirenstein,  181).  According  to  Khainsky  (170'5), 
the  grains  or  droplets  which  are  formed  gather  at  the  surface  and 
pass  out  into  the  endoplasm  ;  they  represent  the  first  products  of 
the  assimilatory  process  in  the  vacuole,  and  their  further  chemical 
transformation  takes  place  in  the  endoplasm  itself  (compare  the 
refringent  bodies  formed  in  the  process  of  digestion  in  acinetans, 
p.  458) .  According  to  Nirenstein,  however,  the  spheres  become  smaller 
and  smaller,  being  reduced  to  tiny  grains  which  vanish  completely, 
dissolved  in  the  vacuole-contents.  The  vacuole  now  diminishes  in 
size  a  second  time,  and  passes  to  the  anal  region,  where  it  fuses  with 
other  similar  vacuoles,  and  is  finally  rejected  from  the  anal  pore. 

In  other  cases,  however,  no  acid  reaction  has  been  demonstrated 
in  the  vacuoles  at  any  time,  as,  for  example,  in  Actinosphcerium — a 
peculiarity  which  is  perhaps  to  be  correlated  with  the  fact  that  in 
this  form  the  prey  is  killed  when  seized  by  the  pseudopoclia.  It  may 
be  supposed  that  the  processes  which,  in  Infusoria,  etc.,  go  on  during 
the  first  or  acid  period  of  the  food-vacuole,  take  place  in  Actino- 
sphcerium and  some  other  forms  before  the  vacuole  is  formed,  in 
which  case  the  vacuole  itself  shows  only  the  second  or  alkaline  phase 
of  the  digestion. 

According  to  Greenwood  and  Saunders  (163),  any  ingested  particles  excite 
the  secretion  of  acid,  but  the  true  digestive  vacuole  is  only  formed  under  the 
stimulus  supplied  by  nutritive  matter.  Metalnikoff  (179),  however,  found 
that  in  the  same  individual  some  of  the  food- vacuoles  are  first  acid  and  then 
alkaline,  while  others  are  alkaline  throughout  in  their  reactions,  and  others 
again,  but  rarely,  show  an  acid  reaction  throughout  ;  he  concludes  that  the 
living  cell  has  the  capacity  of  adapting  itself  to  the  food  supplied,  and  of 
altering  the  properties  of  its  digestive  juices  in  accordance  with  its  require- 
ments. The  process  is  perhaps  comparable  to  the  manner  in  which  the  blood- 
cells  produce  different  anti-bodies  when  brought  into  contact  with  different 
pathogenic  organisms  or  toxins. 

The  variety  of  ferments  that  have  been  isolated  from  different 
Protozoa  also  indicates  that  the  digestion  takes  a  different  course 
in  different  cases.  In  the  plasmodia  of  Mycetozoa,  a  peptic  ferment, 
which  when  acidulated  dissolves  fibrin,  has  been  isolated ;  but  since 
the  protoplasm  of  the  plasmodium  has  a  distinctly  alkaline  reaction, 
it  was  thought  by  some  that  the  ferment  must  be  without  function. 
Metschnikoff  (180)  showed,  however,  that  the  food- vacuoles  formed 
in  the  plasmodium  had  a  strongly  acid  reaction,  in  contrast  to  the 
protoplasm,  and  thus  demonstrated  the  function  of  the  peptic 
ferment  in  the  digestion.  In  other  cases  tryptic  ferments  have  been 
isolated  ("  amcebodiastase,"  etc.). 

13 


194  THE  PROTOZOA 

Some  doubt  has  existed  as  to  the  power  possessed  by  Protozoa 
of  digesting  fats,  and,  according  to  Staniewicz  (208),  no  digestion 
of  fat  takes  place  in  Infusoria.  According  to  the  recent  investiga- 
tions of  Nirenstein  (182),  however,  Paramecia  under  natural  con- 
ditions contain  fat  in  more  or  less  considerable  quantities.  By 
choice  of  suitable  food,  the  quantity  of  fat  in  the  endoplasm  can  be 
increased  greatly.  The  fat-granules  serve  as  reserve-nutriment, 
and  disappear  under  starvation.  Paramecia  which  have  lost  their 
fat  in  this  way,  if  then  fed  with  milk,  oil-emulsion,  or  yolk  of  egg 
rubbed  up  in  water,  show  in  a  few  hours  the  endoplasm  full  of  fat- 
granules  ;  if  fed  with  starch  or  particles  of  egg-albumen,  the  same 
result  is  obtained,  but  not  to  anything  like  the  same  extent. 
Experiments  on  fatty  substances  ingested  by  the  animals  showed 
that  the  fat  remains  unaltered  during  the  first  (acid)  period  of  the 
digestion  in  the  food-vacuole,  and  is  digested  during  the  second 
(alkaline)  period.  Feeding  with  fatty  acid  and  glycerine  also  leads 
to  storage  of  fat  in  the  endoplasm.  If  fed  with  oil-globules  stained 
with  Soudan  III.,  unstained  oil-globules  appear  in  the  endoplasm, 
Nirenstein  concludes  from  his  observations  that  the  fat  is  broken 
up  into  its  soluble  components  in  the  vacuole,  and  synthesized  again 
to  neutral  fat  in  the  endoplasm. 

The  indigestible  residues  of  the  food  are  ejected  from  the  body 
either  at  any  point  on  the  surface,  in  amoeboid  forms,  or  through  a 
definite  aperture,  in  corticate  forms.  A  great  accumulation  of 
fgecal  matter  may  take  place  in  some  cases,  as  in  the  "  stercome  ': 
of  Foraminifera  (p.  233),  of  which  the  animal  purges  itself 
periodically. 

(c)  Saprophytic  and  Parasitic  Nutrition.  • — •  In  this  type  the 
organism  absorbs  its  nourishment  by  diffusion  through  the  surface 
of  the  body  without  the  aid  of  any  visible  organs  or  structural 
differentiations  of  any  kind.  Practically  nothing  is  known  of  the 
mechanism  by  which  this  is  effected  or  of  the  chemical  processes 
involved,  but  it  is  probable  that  enzymes  secreted  by  the  organism 
reduce  the  nutritive  particles  to  a  soluble  form  prior  to  absorption. 
There  is  reason  to  believe  that  the  nucleus  is  specially  concerned 
in  the  production  of  enzymes,  and  in  many  species,  parasitic  or 
otherwise,  the  behaviour  of  the  nucleus  indicates  a  relationship 
between  it  and  the  process  of  absorption  of  food-substance.  In 
Carchesium,  as  already  stated,  the  path  along  which  the  food- 
vacuoles  travel  runs  close  along  the  inner  edge  of  the  horseshoe-shaped 
macronucleus  (Greenwood,  162)  ;  in  Euplotes,  similarly,  the  large 
macronucleus  encloses  an  area  containing  all  the  food-vacuoles 
(Fig.  182).  According  to  Wallengren  (214),  the  reactions  of  the 
food-vacuoles  of  Paramecium  change  as  they  pass  the  nucleus,  and 
the  function  of  the  cyclosis  in  the  endoplasm  is  to  bring  the  food- 


THE  GENERAL  PHYSIOLOGY  OF  THE  PROTOZOA     195 

vacuoles  near,  and  under  the  influence  of,  the  nucleus.  In  the 
coccidian  parasite  Caryotropha  (p.  352),  the  nucleus  of  the  parasite 
is  connected  by  a  kind  of  protoplasmic  canal  with  the  nucleus  of  the 
host-cell  (Siedlecki,  653).  In  the  astomatous  Ciliata  (p.  451)  a 
diffuse  nucleus  is  very  commonly  found,  probably  in  relation  to 
absorption  of  nutriment  by  the  osmotic  method. 

The  process  of  nutrition  in  Protozoa  may  lead  in  some  cases, 
not  to  growth  of  the  protoplasmic  body  directly,  but  to  the  produc- 
tion and  storage  of  reserve  food-substances,  which  are  precipitated 
in  the  cytoplasm,  and  are  utilized  at  a  later  period  for  rapid  growth 
during  reproductive  phases.  The  reserve- materials  deposited  in 
this  way  vary  considerably  in  nature  in  different  cases.  Examples 
are  the  paramylum-grains  of  many  flagellates  ;  the  paraglycogen- 
grains  of  gregarines  and  ciliates,  similar  in  nature  to  glycogen,  but 
with  certain  distinctive  reactions  ;  the  plastinoid  granules  of 
coccidia  (p.  346)  ;  and  other  similar  substances.  In  Radiolaria  oil- 
globules  and  albumen  -  spheres  occur.  An  important  substance, 
acting  apparently  as  reserve- material  for  the  growth  of  the  nucleus, 
is  volutin  (p.  68). 

The  effects  of  starvation  oil  Protozoa  have  been  studied  by  a  number  of 
investigators,  most  recently  by  Lipska  (173),  who  gives  a  complete  bibliog- 
raphy and  resume  of  previous  work  on  the  subject.  Lipska  found  that 
Paramecium  died  after  five  to  seven  days,  a  much  shorter  period  than  allowed 
by  Wallengren  (214)  and  others,  indicating  that  Lipska' s  methods  were  more 
•drastic  and  sources  of  food  were  more  thoroughly  excluded  in  her  experiments. 
In  the  first  period  of  starvation  the  reserves  in  the  endoplasin  are  used  up, 
.first,  the  food-vacuoles  and  their  contents,  then  the  smaller  eiidoplasmic 
granules.  After  the  fourth  day  the  animal  becomes  deformed.  Its  dimensions 
.diminish  progressively,  and  death  supervenes  when  it  has  lost  half  its  initial 
volume.  The  ectoplasm  with  its  cilia  and  trichocysts  undergo  no  change, 
-but  the  endoplasm  loses  its  food-vacuoles  and  a  part  of  its  crystals,  and 
becomes  very  transparent.  The  macronucleus  becomes  enlarged  and  breaks 
up  into  two  halves.  The  micronucleus  undergoes  no  change  of  any  kind. 
Death  is  preceded  by  a  progressive  enfeeblenient  of  all  functions,  such  as 
movements  of  the  cilia  and  pulsation  of  the  contractile  vacuoles.  According 
to  Wallengren,  the  reactions  of  the  Paramecium  (geotaxis,  thermotaxis, 
galvanotaxis)  remain  normal  to  the  last.  Wallengren  described  an  excessive 
vacuolation.  of  the  endoplasm  as  the  result  of  starvation  ;  but  according  to 
Lipska  this  phenomenon  is  not  due  to  starvation,  but  to  the  chemical  action 
•of  ammoniacal  products  generated  by  bacteria  present  in  the  infusions,  and 
does  not  occur  if  they  are  excluded.  Other  observers  noted  the  occurrence 
•of  numerous  conjugations  during  the  first  few  days  of  starvation,  but  Lipska 
was  unable  to  confirm  this  ;  in  her  experiments,  however,  the  number  of 
Paramecia  placed  in  each  tube  was  small,  not  more  than  ten.  Paramecia 
containing  symbiotic  algas  were  more  resistant  to  starvation  than  those 
without  them. 

2.  Respiration. — By  respiration  in  its  widest  sense  must  be  under- 
stood all  processes  in  the  organism  whereby  the  potential  energy 
stored  up  in  chemical  compounds  of  high  complexity  is  set  free  to 
furnish  the  energy  required  by  the  organism  for  its  vital  activities. 
'This  object  may  be  effected  in  two  ways-- -b}"  processes  of  oxidation, 


196  THE  PROTOZOA 

or  by  the  splitting  up  of  complex  chemical  substances  ;  the  result 
in  either  case  is  the  production  of  energy  in  various  forms  and  of 
simple  chemical  substances,  such  as  water  and  carbon  dioxide 
(compare  Barratt,  148).  For  the  processes  of  oxidation  the 
organism  may  either  absorb  free  molecular  oxygen  from  its  environ- 
ment, or  may  produce  it  by  internal  molecular  changes  of  substances 
contained  in  its  own  body,  as  in  anaerobic  organisms  living  in  a 
medium  in  which  free  oxygen  is  lacking. 

Many  free-living  Protozoa  require  oxygen,  and  are  visibly  and 
rapidly  affected  by  the  lack  of  it,  especially  in  their  powers  of 
movement.  No  special  organs  of  respiration  are  found  in  any 
Protozoa,  being  unnecessary  in  animals  of  such  small  bulk,  and  in 
which,  consequently,  the  surface  of  the  body  is  considerable  in 
proportion  to  the  mass.  The  contractile  vacuoles,  when  present, 
are  doubtless  a  means  of  eliminating  carbon  dioxide,  together  with 
other  waste  products,  from  the  body.  It  must  be  supposed,  there- 
fore, that  as  a  general  rule  oxygen  is  taken  up  from  the  surrounding 
water  by  the  protoplasm,  of  which  the  limiting  membranes  are 
freely  permeable,  and  that  the  carbon  dioxide  is  given  off  in  a 
similar  manner.  The  experiments  of  Verworn  (211)  on  Spirostomum 
show  that  the  respiratory  processes  take  place  in  the  cytoplasm, 
independently  of  the  nucleus,  which  takes  no  share  in  respiration. 

On  the  other  hand,  many  sapropelic  (p.  14)  and  parasitic  forms 
inhabit  media  lacking  in  free  oxygen,  and  are  anaerobic  ;  in  such 
forms  the  respiratory  processes  of  the  protoplasm  can  only  take  place 
by  intramolecular  changes,  in  which  the  stored-up  reserve- materials- 
are  probably  split  up  to  supply  the  required  oxygen. 

The  experiments  of  Putter  (201)  on  a  number  of  species  of  Ciliata.  both, 
free-living  and  parasitic,  showed  that,  when  these  animals  were  placed  in 
an  anaerobic  environment,  different  individuals  of  the  same  species  reacted 
very  differently  to  the  conditions,  some  dying  very  rapidly,  others  being 
quue  unaffected  for  a  long  time.  It  was  shown  further  that  this  difference 
was  related  to  the  amount  of  reserve-materials  present  in  the  body  (proteins 
and  glycogen),  which  can  be  observed  to  vary  greatly  in  different  individuals 
from  the  same  culture.  If  Paramecia  were  first  starved  for  some  days  and 
then  placed  in  anaerobic  conditions,  they  succumbed  much  more  rapidly 
than  normal  individuals.  Moreover,  under  anaerobic  conditions  the  reserve- 
materials  were  used  up  much  more  rapidly  than  under  normal  conditions, 
and  without  resulting  in  increased  production  of  energy.  Opalina,  when 
placed  in  a  culture-medium  to  which  albumen  was  added  by  boiling  up  dried 
white  of  egg  in  salt-solution,  was  able  to  make  use  of  the  energy  of  the  albumen 
without  the  help  of  free  oxygen,  and  so  to  live  for  a  much  longer  time.  The 
ciliates  were  found  to  succumb  much  more  rapidly  to  the  effects  of  anaerobic 
conditions  in  smaller  than  in  larger  quantities  of  water,  as  the  result  of  auto- 
intoxication in  consequence  of  the  defective  excretion  of  the  products  of 
anaerobic  metabolism.  Spirostomum  was  found  to  be  more  affected  by 
anaerobic  conditions  in  small  quantities  of  water  than  Paramecium.  The 
differences  between  the  two  forms  is  to  be  ascribed  to  the  system  of  the 
contractile  vacuoles,  which  is  far  more  efficient  in  Paramecium  than  in 
Spirostomum  ;  the  contractile  vacuoles  tend  to  remove  from  the  body  the 


THE  GENERAL  PHYSIOLOGY  OF  THE  PROTOZOA     197 

products  of  metabolism,  a  primary  necessity  of  anaerobic  life.  The  question 
of  size  is  also  a  factor,  since  deleterious  substances  may  diffuse  from  the 
.surface  of  the  body,  and  in  a  small  body  the  surface  is  greater  in  proportion 
than  in  a  larger  one.  Consequently  the  conditions  are  more  favourable  for 
a,  smaller  species,  such  as  Paramecium,  than  for  a  large  form,  such  as 
JSpirostomum. 

Excess  of  oxygen  was  found  by  Putter  (198)  to  have  an  injurious  effect 
on  Spirostomum,  affecting,  however,  only  the  cytoplasm,  and  not  the  nucleus, 
in  the  first  instance. 

On  the  current  view  that  the  symbiotic  vegetable  organisms  present  in 
many  Protozoa  aid  in  the  respiratory  processes  by  absorbing  the  carbon 
dioxide,  breaking  it  up,  and  setting  free  the  oxygen,  the  experiments  of 
Lipska  (173)  on  a  culture  of  Paramecia  which  contained  green  algae  (Proto- 
•coccacese)  in  their  endoplasm  are  of  considerable  interest.  In  two  glass 
vessels  of  equal  size  there  were  placed,  in  the  one  Paramecia  with,  in  the  other 
without,  the  algse  in  their  body.  Hydrogen  was  circulated  through  the  vessels 
to  drive  out  the  air,  after  which  they  were  hermetically  sealed  and  exposed 
to  the  same  conditions  of  light  and  temperature.  After  fifty  hours  the 
vessels  were  opened.  The  Paramecia  without  algae  were  dead,  but  those 
containing  algae  were  still  alive,  though  feeble  in  their  movements,  and  they 
revived  'completely  in  about  twenty-four  hours  after  air  had  access  to  them. 
In  another  experiment  two  batches  of  Paramecia  were  kept  in  the  dark  ; 
after  eight  days  those  without  algse  were  dead,  while  those  containing  algae 
were  perfectly  normal.  Old  cultures  of  Paramecia  containing  algae  snowed 
no  conjugation  ;  Lipska  explains  this  as  due  to  the  influence  of  the  algae, 
since,  by  setting  free  oxygen,  they  prevent  the  development  of  anaerobic 
bacteria  which  produce  substances  toxic  to  the  Infusoria. 

According  to  Popoff  (185),  the  depression-periods  of  Protozoa  (p.  208)  are 
partly  due  to  derangements  of  the  respiratory  processes  and  to  accumulation 
of  products  of  metabolism  in  the  cell. 

3.  Excretion  and  Secretion. — The  waste  substances  excreted  from 
the  protoplasm  may  be  either  soluble  or  insoluble  in  nature.  If 
soluble,  they  may  either  pass  out  of  the  protoplasmic  body  by 
diffusion  from  the  surface,  or  may  be  removed  by  the  agency  of  the 
contractile  vacuoles. 

Contractile  vacuoles  are  of  common  occurrence  in  free-living  fresh-water 
Protozoa,  but  are  usually  wanting  in  marine  forms,  or,  if  they  occur  in  them, 
they  pulsate  very  slowly.  They  are  generally  absent  also  in  entozoic  and 
parasitic  Protozoa,  but  are  found,  however,  in  some  internal  parasites — for 
example,  in  all  Anoplophryince  (p.  452  ;  Cepede,  831). 

Some  authors  (e.g.,  Degen,  154)  have  described  an  investing  membrane 
to  the  contractile  vacuole,  but  it  is  practically  certain  that  no  such  membrane 
exists,  and  that  the  vacuole  is  simply  a  drop  of  watery  fluid  lodged  in,  and 
bounded  by,  the  more  viscid  protoplasm,  without  any  special  structural 
differentiation  (compare  Khainsky.  17O5).  The  contractile  vacuoles  were 
believed  at  one  time  to  empty  themselves  internally,  and  to  function  simply 
as  circulatory  organs  ;  but  in  all  cases  in  which  they  have  been  studied  care- 
fully, it  has  been  proved  that  they  empty  themselves  to  the  exterior  (compare 
Jennings,  167,  Khainsky,  170'5). 

The  effect  of  changes  of  temperature  is  noted  below  (p.  206).  Increased 
pressure  makes  the  pulse  slower  (Khainsky,  17O5).  Degen  (154),  experi- 
menting with  Glaucoma  colpidiiim,  found  that  oxygen  produced  at  first  an 
increase  in  the  frequency  of  the  pulse,  which  soon  became  normal  again 
Hydrogen  and  carbon  dioxide  diminished  the  frequency  and  caused  a  dilata- 
tion of  the  vacuole  ;  both  these  gases  were  lethal  in  their  effect,  especially 
carbon  dioxide.  Isotonic  solutions  of  neutral  salts  had  a  retarding  effect. 


198  THE  PROTOZOA 

Substances  that  precipitate  albumens  have  a  retarding  effect  combined  with 
dilatation  of  the  vacuole.  Degen,  following  Hartog,  regards  the  vacuole  as 
primarily  a  mode  of  compensation  for  the  tendency  of  the  protoplasm  to  take 
up  water  by  imbibition,  a  tendency  checked  or  inhibited  by  changes  in  the 
tonicity  of  the  medium.  Thus  Zuelzer  (222)  found  that  Am&ba  verrucosa, 
if  transferred  gradually  from  fresh  water  to  sea- water,  lost  its  contractile 
vacuoles  ;  at  the  same  time  its  protoplasm  shrank  and  altered  in  character, 
and  the  nucleus  acquired  a  different  structure  and  appearance.  When  re- 
stored to  fresh  water,  the  contractile  vacuoles  reappeared,  and  the  nucleus 
and  cytoplasm  became  of  normal  character.  These  experiments  indicate 
that  the  formation  of  the  contractile  vacuoles  depends  011  differences  in  the 
tonicity  of  the  protoplasm  and  the  surrounding  medium  ;  they  also  raise  the 
suspicion  that  many  species  of  marine  Protozoa  may  be  only  different  forms., 
due  to  change  of  medium,  of  fresh-water  species,  or  vice  versa. 
For  the  excretory  vacuole-system  of  Opalina,  see  p.  447. 

Insoluble  excretion-masses  are  often  formed  in  great  quantity  in 
the  bodies  of  Protozoa.  Such  substances  take  the  form  of  crystals 
or  grains  of  various  kinds,  and  often  of  pigment.  An  example  of 
such  a  substance  is  the  melanin-pigment  of  the  hsemamoebse  (p.  359), 
which  appears  to  be  a  derivative  of  the  haemoglobin  of  the  infected 
blood-corpuscle.  Pigment  may  arise  also  by  degeneration  of 
superfluous  chromatin  extruded  from  the  nucleus,  as  in  Actino- 
sphcerium  (p.  209),  or  by  degeneration  of  nuclei,  as  in  abnormal 
oocysts  of  Cydospora  caryolytica  (p.  364). 

The  cytoplasm  of  Paramecium  contains  crystals  which  have  been  studied 
by  Schewiakoff  (206),  who  finds  that  they  consist  of  calcium  phosphate,  either 
Ca3(P04)2  or  Ca2Ho(P04)2.  When  the  Paramecia  were  starved,  the  crystals 
disappeared  completely  in  one  or  two  days  ;  if  then  the  Paramecia  were 
supplied  with  food  again,  the  crystals  reappeared.  Schewiakoff  was  never 
able  to  observe  that  the  crystals  were  ejected  from  the  anus  but  they  were 
seen  to  collect  round  the  contractile  vacuole.  He  is  of  opinion  that  the 
insoluble  phosphate  is  dissolved  in  the  enchylema.  or  is  converted  into  the 
soluble  form  CaH4(P04)2,  and  then  eliminated  by  the  contractile  vacuole. 

Insoluble  excretion-masses  may  be  simply  extruded  from  the 
body,  a  process  which  commonly  takes  place  at  certain  crises,  as, 
for  example,  prior  to  encystment.  Or,  on  the  other  hand,  they 
may  remain  in  the  protoplasm,  and  are  finally  abandoned  in  the 
residual  masses  left  over  during  reproductive  phases,  as  seen  com- 
monly in  the  sporulation  of  various  types  —  for  example,  the 
hsemamcebae  already  cited  and  other  Sporozoa.  In  such  cases  the 
young  individuals  are  formed  of  protoplasm  free  from  the  coarse 
excretion-granules,  and  the  body  of  the  parent,  so  much  as  is  left 
of  it,  dies  off  and  disintegrates.  In  some  cases,  however,  the  young 
individuals  formed  contain  enclosures  derived  from  the  parent-body, 
as,  for  example,  the  crystal-bearing  swarm-spores  of  Radiolaria 
(p.  254)  ;  but  in  such  cases  the  enclosure  is  probably  of  the  nature  of 
reserve-material. 

Secretion,  more  or  less  rapid,  of  various  substances  can  be 
observed  without  difficulty  in  various  Protozoa.  Examples  are  the 


THE  GENERAL  PHYSIOLOGY  OF  THE  PROTOZOA     199 

spicules  and  various  skeletal  structures  ;  the  shells,  houses,  etc.  ; 
adhesive  substances  or  stalks  in  sedentary  forms,  as,  for  example, 
the  non-contractile  stalks  of  many  VorticeUids  (p.  441)  ;  and  the 
cysts  or  envelopes  secreted  round  the  body,  such  as  the  sporocysts, 
etc.     The  pseudopodia  of  many  Amcebaea,  such  as  Dlfflugia,  are 
covered  by  a  sticky  slime  which  enables  the  animal  to  adhere  to 
surfaces  over  which  it  creeps,  and  which  can  be  drawn  out  by 
contact  with  a  glass  rod  into  threads,  like  the  mucus  of  a  snail 
(Rhumbler,  34).     In  Foraminifera  and  Heliozoa  the  pseudopodia 
appear  to  secrete  a  substance  which  holds  the  prey  fast,  and  at  the 
same  time  kills  it,   as  already  mentioned.     Some  Protozoa — for 
example,  gregarines — leave  a  trail  of  mucilaginous  substance  behind 
them  as  they  move  forwards,  and  by  some  authors  this  s  wlion 
has  been  regarded  as  the  mechanism  by  which  locomotion  is  effected 
(p.    327).     Internal   secretions   in   connection   with   the   digestive 
function  have  been  mentioned  in  a  previous  section.     Arcella  has 
the  power  of  secreting  gas-bubbles  in  its  protoplasm  for  hydrostatic 
purposes  (compare  also  the  Radiolaria,  p.  252). 

4.  Transformation  o!  Energy — (a)  Movement.— The  different  motile 
organs  of  Protozoa  have  been  described  above.  Considered  from  a 
morphological  standpoint,  the  protoplasmic  body  may  exhibit,  in 
the  first  place,  no  specially  differentiated  organs  of  movement, 
which  then  takes  the  form  of  currents  and  displacements  in  the  fluid 
protoplasm  itself,  manifested  externally  in  the  form  of  pseudopodial 
processes  or  flowing  movements  of  the  entire  body,  internally  as 
streaming  movements  in  the  protoplasm.  Secondly,  there  may  be 
special  organs  of  movement,  either  external,  in  the  form  of  vibratile 
organs,  such  as  cilia,  flagella,  or  undulating  membranes  ;  or  internal, 
in  the  form  of  contractile  fibrils  or  myonemes. 

Different  as  pseudopodia  may  appear  at  first  sight  from  vibratile 
organs,  such  as  cilia  or  flagella,  there  is  nevertheless  a  very  gradual 
transition  from  the  one  type  to  the  other  (see  p.  53,  supra).     Of 
pseudopodia  there  are  two  chief  types  of  structure — the  lobopodia, 
in  which  a  fluid  core  of  endoplasm  is  enveloped  by  a  superficial  layer 
of  stiffer  ectoplasm  ;  and  the  axopodia,  in  which,  on  the  contrary,  a 
secreted  axis  of  rigid  or  elastic  nature  is  covered  by  a  more  fluid  layer 
of  protoplasm.      The  axopodia  are  connected  by  transitions  both 
of  structure  and  movement  with  organs  of  the  vibratile  type.     In 
both  flagella  and  cilia  the  structure  consists  of  a  firmer  elastic  axis 
covered  over  by  a  more  fluid  superficial  layer  (pp.  52,  54)  ;  many 
axopodia  exhibit  swinging,  nutating,  or  bending  movements  differ- 
ing only  in  degree  from  those  of  flagella  (p.  51).     There  are  grounds 
for  believing  the  one  type  of  organ  to  have  been  derived  phylo- 
genetically  from  the  other. 

The  streaming  movements  of  protoplasm  have  been  the  subject 


200  THE  PROTOZOA 

of  much  investigation  and  discussion.  The  older  view,  which 
ascribed  them  to  contractility  and  assumed  a  complicated  structure 
in  the  protoplasm,  has  now  been  superseded  generally  by  the  theory 
connected  more  especially  with  the  names  of  Quincke,  Berthold, 
Biitschli  (37),  and  Rhumbler  (34,  35,  40,  etc.),  according  to  which 
differences  of  surface-tension  are  regarded  as  the  efficient  cause  of 
the  streaming  movements  of  the  pseudopodia  and  the  protoplasm. 
The  living  substance  is  in  a  state  of  continual  chemical  change  in 
every  part ;  such  changes  are  sufficient  to  account,  in  one  way  or 
another,  for  the  origin  of  local  differences  in  the  physical  nature 
(adhesion)  of  the  surface  of  the  body  in  contact  with  the  surrounding 
medium,  or  of  internal  protoplasmic  surfaces  in  contact  with 
vacuoles  or  cavities  filled  with  fluid  ;  and  the  resulting  differences  in 
surface-tension  cause  flowing  movements  both  in  the  protoplasm 
and  in  the  fluid  with  which  it  is  in  contact.  The  relation  of  such 
currents  to  the  movements  of  pseudopodia  has  been  discussed  above 
(p.  47).  Similar  movements  have  been  imitated  artificially  by 
Biitschli  and  Rhumbler  in  a  manner  which  can  leave  no  doubt  that 
the  physical  analog}?'  is  a  reasonable  interpretation  of  the  mechanism 
of  amoeboid  movement. 

The  close  structural  similarity  between  flagella  and  cilia  on  the 
one  hand,  and  the  axopodia  on  the  other,  makes  it  highly  probable, 
to  say  the  least,  that  the  same  explanation  of  the  movement  applies 
to  both.  The  axis  of  the  vibratile  organ  is  commonly  regarded  as 
a  firm,  elastic,  form-determining  structure  ;  the  more  fluid  sheath 
as  the  seat  of  the  motile  activity.  Chemical  differences  set  up  in 
the  limiting  membrane,  causing  differences  in  the  surface-tension  of 
the  sheath  along  certain  lines,  have  been  supposed  to  be  responsible 
for  a  deformation  of  the  sheath,  bending  the  axis  and  the  whole 
organ  with  it ;  with  equalization  and  disappearance  of  such  differ- 
ences, the  elastic  axis  straightens  itself  again.  How  such  chemical 
differences  are  set  up  remains  to  be  explained  ;  possibly  they  origi- 
nate in  chemical  changes  taking  place  explosively  in  the  basal 
apparatus  of  the  vibratile  organs ;  in  any  case  it  is  clear  that,  as  com- 
pared with  pseudopodia,  they  act  with  extreme  rapidity,  and,  further, 
that  they  are  localized  on  the  surface  of  the  flagellum  or  cilium. 
From  the  movements  of  these  organs,  the  contraction  appears  to  run 
a  spiral  course  as  a  general  rule — at  least  in  cilia  (p.  54)  ;  flagella, 
however,  appear  to  be  capable  of  various  kinds  of  movements  (p.  52). 

According  to  Prowazek  (192),  the  flagellum  of  a  trypanosome  only  retains 
its  motility  so  long  as  it  remains  in  connection  with  the  kinetonucleus.  Wer- 
bitzki  (526),  however,  has  succeeded  in  producing  strains  of  trypanosomes 
without  kinetonuclei,  and  with  apparently  no  resulting  loss  of  motility.  It 
has  been  observed  frequently  that  detached  cilia  or  flagella  continue  to 
contract,  for  a  time  at  least ;  and  Schuberg  (44)  denies  that  the  basal  granules 
of  the  cilia  function  as  centres  of  kinetic  activity. 


THE  GENERAL  PHYSIOLOGY  OF  THE  PROTOZOA     201 

With  regard  to  the  contractility  of  the  myonemes,  no  detailed  explanation 
can  be  offered  at  present.  Biitschli  (37)  has  shown  the  possibility  of  explaining 
the  contractile  mechanism  of  such  structures  by  differences  in  surface-tension 
arising  between  the  walls  and  the  contents  of  protoplasmic  alveoli  which 
are  disposed  with  a  definite  arrangement. 

(b)  Other  Forms  of  Energy. — Light-production  or  phosphorescence 
is  a  common  phenomenon  in  marine  Protozoa,  a  property  expressed 
in  such  names  as  Noctiluca  (p.  279)  and  Pyrodinium  (p.  278).  The 
magnificent  phosphorescent  effects  often  seen  at  night,  especially 
in  warmer  seas,  is  to  be  referred  chiefly  to  swarms  of  Protozoa. 
The  source  of  the  luminosity  appears  to  reside  in  small  globules  of 
fat  or  oil,  and  is  probably  the  result  of  oxidation.  It  is  easy  to 
observe  that  the  production  of  light  is  stimulated  by  agitating  or 
stirring  the  water.  For  a  general  discussion  of  luminosity  in  living 
organisms,  see  Putter  (200). 

From  the  analogy  of  the  known  facts  in  the  physiology  of  animal 
and  plants,  it  may  be  inferred  that  in  Protozoa  also  the  vital 
activities  are  accompanied  by  the  production  of  heat  and  by 
electrical  changes  ;  but  no  exact  determinations  of  such  changes 
have  been  made. 

5.  Reactions  to  Stimuli  and  Environment. — It  can  easily  be 
observed  that  Protozoa  react  in  a  definite  manner  to  stimuli,  and 
behave  in  a  particular  way  under  certain  conditions.  In  most 
cases,  however,  these  responses  to  external  conditions  must  be 
regarded  as  fundamental  properties  of  the  living  protoplasm,  and 
not  as  functions  of  specially  differentiated  organs  of  the  body. 
This  is  well  seen,  for  example,  in  amceba3,  some  species  of  which  are 
very  sensitive  to  light,  and  cease  feeding  when  exposed  to  the 
bright  illumination  of  the  stage  of  the  microscope  (Rhumbler,  34). 
In  Arcella  the  nuclear  division  is  stated  to  take  place  only  at  night, 
between  1  and  5  a.m.  (Khainsky,  145).  In  such  cases,  however, 
there  is  nothing  which  can  be  identified  as  a  special  light-perceiving 
organ. 

In  other  cases  Protozoa  may  possess  organs  which  must  be  regarded 
as  sensory  in  nature.  Pseudopodia  appear  to  possess  in  many  cases 
a  tactile  or  sensory  function  to  a  marked  degree,  and  sometimes  to 
be  specialized  for  such  functions,  as,  for  example,  the  anterior 
pseudopodia  of  some  Myxosporidia,  such  as  Leptotheca  agilis 
(Fig.  165).  The  same  is  true  to  a  much  greater  degree  of  flagella 
and  cilia  ;  anteriorly- directed  flagella  are  perhaps  always  sensory  in 
function,  especially  when  they  are  not  the  sole  means  of  locomotion, 
as  in  such  forms  as  Rhizomastigina  (p.  268)  or  Bodonidce.  (p.  270) ; 
and  in  many  Ciliata  stiff  tactile  bristles  occur  (p.  446).  In  many 
flagellates  organs  are  found  which  appear  to  be  specialty  sensitive 
to  light,  in  the  form  of  pigment-spots  or  stigmata,  which  are 
described  further  below. 


202  THE  PROTOZOA 

The  occurrence  of  a  conducting  nervous  apparatus  is  more 
doubtful ;  it  has  been  affirmed  for  Stentor  by  Neresheimer  (p.  446), 
but  is  not  confirmed  by  other  observers.  It  can  at  least  be  asserted 
that  in  the  more  highly  organized  Ciliata  a  stimulus  may  lead  to- 
sudden  movements  in  which  different  sets  of  contractile  structures 
take  a  concerted  part. 

The  reactions  of  Protozoa  to  stimuli  have  been  the  subject  of  a 
great  deal  of  experimental  research  by  many  investigators,  amongst 
whom  Verworn,  Loeb,  Jennings  (165),  and  Putter  (199),  deserve 
special  mention.  The  results  of  these  investigations  can  only  be 
summarized  briefly  here.  The  various  reactions  are  classified  in  the 
first  instance,  according  to  the  nature  of  the  stimulus,  by  the  use  of 
a  terminology  in  which  each  principal  category  is  denoted  by  a 
word  terminating  in  taxis,  or  in  adjectival  form — tactic.  Thus  we 
can  distinguish — (a)  Chemotaxis,  or  reactions  to  chemical  stimuli ; 
(5)  Phototaxis,  or  reactions  to  light ;  (c)  Thermotaxis,  or  reactions 
to  heat  or  cold  ;  (d)  Barotaxis,  or  reactions  to  mechanical  stimuli ; 
and  (e)  Galvanotaxis,  or  reactions  to  electrical  stimuli.  A  given 
Protozoon  may  be  quite  unaffected  by  a  particular  stimulus  ;  or,  on 
the  other  hand,  it  may  be  affected  by  it  in  such  a  way  that  it  tends 
to  move  towards  the  source  of  the  stimulus  (positive  taxis)  or  away 
from  it  (negative  taxis).  The  result  depends,  in  many  cases,  on 
the  intensity  of  the  stimulus  applied  ;  thus,  a  Euglena  will  move 
towards  a  moderate  light  (positive  phototaxis),  but  away  from  a 
too  intense  illumination  (negative  phototaxis).  In  each  case  an 
optimum  condition  exists,  in  which  the  positive  taxis  reaches  its 
maximum. 

In  such  experiments  the  Ciliata  are  the  objects  of  choice,  on 
account  of  the  definite  polarity  of  their  movements  as  compared 
with  forms  less  highly  organized,  such  as  amoeba.  In  the  Ciliata 
a  negative  taxis  results  in  an  "  avoiding  reaction "  (Schreck- 
bewegung),  in  which  the  animal  shrinks  back  with  reversal  of  the 
ciliary  movements,  "  turning  towards  a  structurally-defined  side, 
followed  by  a  movement  forward  "  (Jennings).  Repeated  experi- 
ments have  shown  that  the  forms  taken  by  the  avoiding  movements 
do  not  depend  on  the  nature  of  the  stimulus,  but  on  the  organization 
of  the  animal  itself,  and  are  always  the  same  for  a  given  species. 
An  Oxytricha,  for  example,  turns  always  to  the  right,  whatever  the 
direction  from  which  the  stimulus  comes.  The  movement  is  deter- 
mined automatically  by  the  structure  of  the  body.  "  The  same 
symptom  can  be  called  forth  by  the  most  diverse  stimuli  "  (Piitter, 
199). 

The  various  taxes  may  now  be  considered  briefly  : 

(a)  Chemotaxis  and  Effects  of  Environment. — This  category  in- 
cludes reactions  to  liquids  or  gases  diffused  in  the  water ;  reactions 


THE  GENERAL  PHYSIOLOGY  OF  THE  PROTOZOA     203 

to  gases  may  be  considered  as  equivalent  to  a  sense  of  smell  in 
higher  organisms  (osmotaxis). 

It  has  been  shown  by  many  experiments  that  a  given  species  is 
attracted  towards  certain  chemical  substances,  repelled  by  others. 
Thus,  Paramecium  is  attracted  towards  weak  acids,  but  repelled  by 
them  in  greater  concentration.  If  a  drop  of  acid  of  suitable  strength 
is  placed  in  the  midst  of  a  number  of  Paramecia  distributed  evenly 
in  the  water  under  a  cover-slip  on  a  slide,  they  tend  to  gather  round 
the  drop.  As  the  drop  diffuses  in  the  surrounding  water,  the 
Paramecia  arrange  themselves  in  a  ring  in  the  region  of  optimum 
concentration.  If,  however,  the  drop  of  fluid  employed  is  of  a 
strength  which  represents  the  optimum  of  chemotaxis  for  the  species,. 


FIG.  83. — Diagram  showing  the  course  taken  by  a  Paramecium  which  has  entered 
a  drop  of  "fluid  to  which  it  is  positively  che  mo  tactic.  The  forward  movements 
of  the  Paramecium  are  indicated  by  arrows  ;  its  backward  movements  by 
dotted  lines  ;  the  outline  of  the  drop  of  fluid  by  a  circle.  Each  time  the 
Paramecium,  in  its  forward  movement,  reaches  the  confines  of  the  drop,  it 
conies  into  contact  with  fluid  which  is  less  positively  chemotactic  than  the  drop 
into  which  it  has  entered  ;  it  then  shrinks  backward  (avoiding  reaction),  after 
which  it  moves  forward  again  with  the  same  result  every  time  it  reaches  the 
edge  of  the  drop.  After  Lang  (10). 

the  Paramecia  gather  within  it,  and  in  such  a  case  the  position  taken 
up  by  each  Paramecium  depends  on  the  avoiding  reaction  made  by 
it  when  it  conies  in  contact  with  a  less  attractive  medium.  Thus, 
if  a  Paramecium,  swimming  in  a  straight  line,  enters  a  drop  of  fluid 
which  is  positively  chemotactic  to  it,  when  it  has  crossed  the  drop 
to  its  opposite  boundary  it  conies  to  the  region  where  it  meets  with 
fluid  which  is  less  chemotactic  to  it ;  it  then  shrinks  back  with  an 
avoiding  movement ;  after  a  time  it  again  moves  forward,  and  comes 
again  into  the  negatively  chemotactic  region,  with  the  same  result 
as  before.  Thus  its  movements  are  as  if  caught  in  a  trap  (Fig.  83), 
in  which  it  is  held  by  the  automatic  movements  called  forth  by  ih& 
difference  between  the  more  and  the  less  chemotactic  fluids,  until 


204  THE  PROTOZOA 

the  differences  slowly  disappear  by  the  diffusion  of  the  one  liquid 
into  the  other. 

Chemotaxis  is  a  phenomenon  which  is  obviously  of  the  greatest 
importance  in  the  natural  life  of  the  organism.  It  comes  into  play  in 
the  search  for  food  and  in  sexual  attraction,  for  example.  It  has  long 
been  known  that  certain  Protozoa  are  attracted  towards  food- 
substances,  especially  those  species  which  feed  more  or  less 
exclusively  upon  certain  particular  foods.  Plasmodia  of  Mycetozoa, 
for  example,  "scent"  their  food  from  a  considerable  distance,  and 
move  towards  it. 

Rhumbler  (34,  204)  has  studied  the  ingestion  of  food  by  amoebae,  and  lias 
made  a  number  of  experiments  on  the  manner  in  which  drops  of  fluid  take  up 
or  cast  out  solid  particles.  Thus,  a  drop  of  chloroform  suspended  in  water 
draws  into  its  interior  a  glass  splinter  coated  with  shellac  when  brought  into 
contact  with  it ;  after  a  time  the  coating  of  shellac  is  dissolved  in  the  chloro- 
form, and  the  glass  splinter  is  then  ejected  from  the  drop.  This  experiment 
furnishes  data  for  a  mechanical  explanation  of  the  ingestion  of  food  and 
ejection  of  faecal  matter  ;  and  it  might  be  expected  that  amoebae  in  Nature 
would  ingest  mechanically,  and  as  it  were  helplessly,  many  substances  of  a 
useless  kind  with  which  they  are  brought  into  contact.  This  may  occur 
experimentally  when  amcebse  are  brought  into  contact  with  substances  of 
no  nutritive  value  ;  Rhumbler  observed  an  amoeba  which  ingested  carmine- 
particles  until  it  died.  In  Nature,  however,  there  can  be  no  doubt  that 
amoebae  exercise  a  certain  choice  or  selection  in  the  food  they  ingest,  doubtless 
as  the  effect  of  rhemotactic  reactions  (compare  Jennings,  168).  In  the 
Ciliata,  however,  tnere  appears  to  be  no  selection  of  the  food-particles  wafted 
down  the  oesophagus  except  as  regards  their  size  (compare  Greenwood,  162). 
Purely  mechanical  reactions,  on  the  other  hand,  may  possibly  explain  the 
apparent  selection  which  many  Protozoa  exhibit  in  building  up  houses  of  cer- 
tain special  materials  (p.  34). 

Chemotactic  reactions  to  particular  substances  must  play  a  large  part 
in  determining  the  migrations  of  certain  parasitic  Protozoa  towards  particular 
organs  of  the  body  in  which  they  are  parasitic,  in  so  far  as  such  migrations 
are  not  purely  passive  on  the  part  of  the  parasite,  or  determined  to  some  extent 
by  rheotaxis  (see  below). 

The  attraction  of  gametes  to  one  another  can  hardly  be  effected  by  any- 
thing but  chemotaxis.  It  is  well  known  that  the  antherozoids  of  the  fern- 
prothallus  are  positively  chemotactic  to  malic  acid,  which  is  secreted  by  the 
oogonium.  In  Coccidium  schubergi,  Schauclinn  (99)  observed  that  the  macro- 
gamete,  as  soon  as  it  had  expelled  its  karyosome,  but  not  before,  became 
attractive  to  the  microgamete. 

The  effects  of  drugs  and  reagents  on  the  activities  of  the  Protozoa  is  a 
field  of  investigation  which  cannot  be  dealt  with  in  detail  here.  Some 
reagents  have  a  quickening  effect  on  the  movements,  others  the  contrary. 
Narcotics,  on  the  other  hand,  such  as  alcohol,  ether,  etc.,  may  at  first  have 
a  stimulating,  later  a  deleterious,  action  on  the  vital  activity.  Minute  doses 
of  alcohol,  according  to  Woodruff  (216),  diminish  the  rate  of  division  at  one 
period,  augment  it  at  another,  of  the  life-cycle,  but  in  the  latter  case  the  rate 
is  not  continuous,  but  decreases  again  ;  increase  in  the  amount  of  alcohol 
will,  however,  again  cause  a  more  rapid  cell-division  for  a  limited  period. 
Thyroid  extract  is  stated  to  have  an  attractive  effect  on  Paramecium,  and  also 
increases  its  capacity  for  reproduction  (Nowikoff,  183).  For  the  effects  of 
other  drugs  and  poisons,  see  Giemsa  and  Prowazek  (159),  and  Prowazek 
(191,  192,  and  195).  In  the  same  culture  different  individuals  often  exhibit 
•different  powers  of  resistance  to  the  effects  of  reagents. 


THE  GENERAL  PHYSIOLOGY  OF  THE  PROTOZOA     205 


(6)  Phototaxis  and  Effects  of  Light  and  Other  Rays. — Many  Pro- 
tozoa appear  quite  indifferent  to  light — at  least  of  ordinary  intensity ; 
others  show  a  very  decided  reaction,  as  already  mentioned,  either 
negative  or  positive.  Thus  many  amoebae,  Pdomyxa,  etc.,  are 
negatively  phototactic,  and  pass  at  once  into  a  condition  of  rest 
and  inactivity  when  exposed  to  light.  According  to  Mast  (176),  a 
sudden  increase  in  the  intensity  of  the  illumination  inhibits  move- 
ment in  Amoeba  proteits ;  but  if  the  illumination  remains  constant,, 
movement  begins  again  in  a  few  moments. 
If  the  illumination  is  very  gradually  in- 
creased, it  produces  no  response.  In 
strong  light  Amoeba  proteus  orientates 
itself,  producing  pseudopodia  only  on  the 
less  illuminated  side. 

Many  flagellates,  on  the  other  hand, 
especially  the  holophytic  forms  such  as 
Dinoflagellates,  Phytornastigina,  Eugle- 
noids,  etc.,  show  the  opposite  reaction, 
moving  towards  the  light  or  becoming 
active  when  exposed  to  it,  and  passing 
into  a  resting  state  in  the  dark.  The 
positive  phototaxis  of  the  holophytic  FIG.  84. 
Protozoa  has  an  obvious  bionomical  sig- 
nificance, since  the  holophytic  nutrition 
can  only  proceed  in  the  presence  of  light. 


A,  Anterior  end  of 
Euglena  viridis.  ft.,  Flagel- 
lum ;  ces.,  oesophagus  ;  bl., 
thickening  (blepharoplast  ?) 
on  one  of  the  two  roots  of  the 
flagellum  ;  st.,  stigma  ;  rh, 
the  two  roots  of  the  flagellum 
passing  through  the  reservoir 
(R)  of  the  contractile  vacuoles, 
two  to  be  attached  to  its 
opposite  side.  B,  Stigma  in 
surface  view,  highly  magni- 
fied, showing  the  pigment- 
grains  imbedded  in  a  proto- 
plasmic basis.  After  Wager 
(213). 


In  the  majority  of  holophytic  flagellates  the 
phototactic  reaction  is  associated  with  the 
possession  of  a  special  organ,  the  stigma  or 
"eye-spot."  The  stigma  of  Euglena  consists 
of  a  protoplasmic  ground-substance  forming  a 
fine  network,  in  which  is  embedded  pigment 
in  the  form  of  drop-like  bodies.  The  pigment 
granules  are  brightly  refractile,  with  a  distinct 
outline,  and  form  a  single  layer.  In  some  cases 
the  granules  are  spherical  and  all  of  the  same 

size  ;  in  others  they  are  more  irregular  in  form  and  of  different  sizes.  The 
pigment  appears  to  be  a  derivative  of  chlorophyll.  The  stigma  is  in  close 
contact  with  a  well-marked  thickening  on  one  of  the  two  branches  into 
which  the  flagellum  bifurcates  at  its  base.  Wager  (213)  suggests  that  this 
thickening  (blepharoplast  ?)  is  a  specialized  sensitive  organ  which  is  stimulated 
by  the  light-absorbing  pigment-spot,  the  stigma,  and  that  in  this  way  the 
reaction  of  Euglena  to  light  is  determined.  Euglena  swims  towards  a  moderate 
light,  but  away  from  strong  sunlight.  If  kept  in  bright  sunlight  it  comes  to 
rest,  rounds  itself  off,  and  ultimately  becomes  encysted. 

The  blue  and  violet  parts  of  the  spectrum  exert  the  strongest  stimulus 
on  flagellates.  In  the  case  of  Amoeba  profess.  Mast  (176)  found  the  blue  rays 
nearly  as  efficient  as  white  light  in  causing  reactions,  but  violet,  green,  yellow, 
and  red,  to  be  but  slightly  active.  Paramecium  and  some  other  Protozoa  are 
stated  to  react  only  to  the  ultra-violet  rays. 

The  effect  of  radium-rays  upon  various  Protozoa  has  been  investigated 
by  Zuelzer  (221).  Some  species  are  more  affected  by  them  than  others; 


206  THE  PROTOZOA 

Amoeba  Umax,  for  example,  was  very  resistant  to  the  rays,  while  other  Protozoa 
were  very  soon  injured  by  them.  In  all  cases  long  exposure  to  the  rays  was 
fatal.  The  first  effect  of  the  rays  was  generally  to  quicken  the  movements ; 
the  next  was  an  injurious  action.  The  rays  appear  to  act  more  particularly 
upon  the  nucleus  in  the  first  instance,  with  subsequent  gradual  deleterious 
•effects  upon  the  cytoplasm. 

In  experiments  on  the  effect  of  Rontgen-rays  on  Paramecium  and  Volvoy; 
.{Joseph  and  Prowazek,  169),  these  forms  were  found  to  exhibit  a  negative 
taxis,  collecting  in  ten  to  fifteen  minutes  in  a  part  not  exposed  to  the  rays. 
Exposure  of  Paramecium  to  the  rays  caused  the  pulse  of  the  contractile 
vacuoles  to  become  slower  to  a  marked  degree  as  a  rule,  but  individual 
variations  were  observed  in  this  reaction,  the  effect  being  inconsiderable  in 
some  cases  ;  and  the  animals  gradually  regain  the  normal  pulse.  Infra  vitam 
staining  of  the  nucleus  of  Paramecium  exposed  to  the  rays  gave  a  result  similar 
to  that  obtained  by  staining  Paramecia  fatigued  by  being  shaken  evenly  and 
continuously  for  two  hours.  Long-continued  action  of  the  rays  killed  the 
organisms. 

(c)  Thermotaxis  and  Effects  of  Temperature. — For  a  given  species 
•of  the  Protozoa  there  is  an  optimum  temperature  at  which  its  vital 
activity  is  at  its  highest  pitch,  and  above  which  the  activity  is 
diminished  until  it  reaches  a  point  at  which  the  vitality  is  impaired 
and  the  animal  is  finally  killed.  A  temperature,  however,  at  which 
the  animal  succumbs  sooner  or  later  may  at  first  have  a  quickening 
effect  upon  the  vital  functions.  Thus,  many  experiments  have 
shown  that  a  rise  of  temperature  increases  greatly  the  rapidity  and 
frequency  of  the  pulsations  of  the  contractile  vacuoles  ;  and  in  the 
case  of  Glaucoma  colpidium  Degen  (154)  found  that,  although  the 
animal  was  killed  by  a  temperature  above  30°  C.,  the  maximum 
frequency  of  the  pulsations  was  produced  temporarily  by  a  tempera- 
ture of  34°  C.,  above  which  the  frequency  was  rapidly  diminished 
(compare  also  Khainsky,  170  "5). 

The  optimum  temperature  may,  however,  be  different  at  different 
stages  in  the  life-cycle,  as  in  parasitic  Protozoa  which  infest  a  warm- 
blooded and  a  cold-blooded  host  alternately  ;  in  such  cases  a  change 
of  temperature  may  perhaps  be  a  factor  in  bringing  about  develop- 
mental changes.  In  free-living  Protozoa  the  phases  of  the  life-cj^cle 
are  often  related  to  seasonal  changes,  and  are  probably  induced 
largely  by  conditions  of  temperature. 

Experimentally  it  has  been  shown  that  Protozoa  tend  to  move  towards 
regions  of  more  favourable  temperature,  and  away  from  those  less  favourable. 
Khainsky  (170'5)  found  that  rise  of  temperature  produced  a  quickening  of 
the  digestive  processes  in  Paramecium,  very  marked  at  24°  C.  or  above.  At 
30°  C.  and  above  Paramecium  takes  up  scarcely  any  more  food  ;  the  contents 
of  the  food-vacuoles,  which  continue  to  be  formed,  then  consist  almost  entirely 
of  water. 

The  effects  of  temperature  on  the  development  in  cultures  are  very  marked. 
Popoff  studied  the  growth  of  Frontonia  leucas  in  cultures  kept  at  14°  C.  and 
25°  C.  respectively  ;  at  the  lower  temperature  the  animals  divide  once  in 
about  eighty  or  ninety  hours,  in  the  warmer  culture  once  in  about  seventeen 
hours  ;  in  the  cold  both  the  nucleus  and  the  body  grow  to  a  size  absolutely 
larger  than  in  the  warmth,  but  in  the  former  case  the  nucleus  is  about  Jj, 
in  the  latter  about  J4,  the  bulk  of  the  whole  body  (Hertwig,  92).  In  the  case 


THE  GENERAL  PHYSIOLOGY  OF  THE  PROTOZOA  207 

of  Actinosphcerium,  the  experiments  of  Smith  (207),  Mackinnon  (174),  and 
Boissevain  (151),  show  that  increased  temperature  hastens  on  encystment, 
and  causes  fewer  and  larger  cysts  to  be  formed  in  which  the  nuclei  are  larger 
but  poorer  in  chromatin  ;  while  at  lower  temperatures  the  encystment  is 
retarded,  and  finally  inhibited  altogether,  and  the  cysts  produced  are  smaller 
and  more  numerous,  with  nuclei  smaller  than  the  normal  but  rich  in  chromatin. 

(d)  Barotaxis  and  Effects  of  Mechanical  Stimuli. — This  category 
includes  Geotaxis,  or  reactions  to  gravity  ;  Thigrnotaxis,  or  reactions 
to  the  mechanical  contacts  of  hard  surfaces  ;  and  Rheotaxis,  or 
reactions  to  the  pressure  of  currents  in  the  surrounding  medium. 
The  influence  of  gravity  is  seen  in  the  manner  in  which  many 
Protozoa,  when  placed  in  a  vessel,  seek  of  their  own  accord  the 
bottom  in  some  cases,  the  surface-film  in  others.  The  plasmodia  of 
Mycetozoa  exhibit  often  a  well-marked  rheotaxis,  and  move  in  the 
opposite  direction  to  currents  of  water.  It  has  been  suggested  that 
a  similar  rheotaxis  may  explain  the  passage  of  blood-parasites  from 
the  invertebrate  to  the  vertebrate  host  during  the  act  of  blood- 
sucking ;  but  it  is  probable  that  such  migrations  are  purely  passive, 
so  far  as  the  parasites  are  concerned. 

Contact-stimuli  acting  from  one  side  often  have  a  marked  effect 
on  the  movements  of  Protozoa.  An  amoeba  tends  to  adhere  to,  and 
spread  itself  over,  a  firm  surface  with  which  it  comes  in  contact. 
The  movements  of  Ciliata  often  cease  when  they  come  in  contact 
with  a  firm  substance,  and  the  animal  remains  still ;  Piitter  (197) 
has  shown  that  the  contact-stimulus  may  be  sufficient  to  prevent 
o,  Paramecium  from  reacting  to  thermal  or  electric  stimuli,  which 
would  otherwise  produce  a  marked  effect  upon  its  movements. 

Under  effects  of  mechanical  stimuli  must  be  included  those  brought  about 
by  changes  in  the  tonicity  of  the  surrounding  medium.  Such  effects  have 
already  been  discussed  above  as  regards  their  action  on  the  contractile 
vacuoles.  For  the  remarkable  experiments  of  Verworn  on-  the  change  in 
body-form  and  in  the  nature  of  the  pseudopodia  exhibited  by  amcebse  under 
the  action  of  different  media,  see  p.  217,  infra.  Free-living  Protozoa  are 
probably  seldom  if  ever  subject  to  such  changes,  though  they  might  well 
occur  in  the  environment  of  marine  forms  living  near  the  upper  limit  of  the 
tide-marks,  in  rock-pools,  or  other  places  where  the  tonicity  of  the  medium 
might  be  lowered  temporarily  by  influx  of  fresh  water,  as  the  result  of  rain 
or  other  natural  causes.  On  the  other  hand,  parasitic  forms,  and  especially 
those  which  pass  from  one  host  to  the  other,  may  be  subject  to  rapid  changes 
of  tonicity  in  their  environment.  In  this  connection  special  interest  attaches 
to  the  experiments  of  Robertson  (503)  on  fish-trypanosomes  ;  it  was  found 
that  in  undiluted  blood  or  in  blood  diluted  with  isotonic  solutions  the 
trypanosomes  underwent  no  change  in  vitro,  but  that  when  the  blood  was 
diluted  with  water  the  trypanosomes  multiplied  by  division,  and  went  through 
changes  similar  to  the  first  stages  of  the  natural  development  in  the  leech. 
It  was  concluded,  therefore,  that  the  principal  stimulus  which  initiates  the 
developmental  changes  in  the  organism  was  a  lowering  of  the  osmotic  tension, 
with  consequent  absorption  of  water  by  the  protoplasm.  Neumann  (677) 
also  found  that  the  "  exflagellation  "  of  the  Proteosoma- parasite  of  birds  was 
greatly  furthered  by  addition  to  the  blood  of  not  more  than  one-fifth  of  its 
volume  of  water. 


208  THE  PROTOZOA 

(e)  Galvanotaxis  and  Effects  of  Electrical  Stimuli. — Protozoa 
placed  in  an  electric  field — that  is  to  say,  in  a  drop  of  water  between 
the  two  poles  of  a  battery  under  a  cover-glass  on  a  slide — -are 
affected  to  a  marked  degree,  but  with  opposite  results  in  different 
species.  Opalina  places  itself  parallel  to  the  direction  of  the  current, 
with  its  anterior  end  towards  the  anode.  With  a  current  of 
moderate  intensity  it  swims  towards  the  anode  ;  but  with  a  stronger 
current  the  speed  at  which  the  animal  moves  is  diminished,  and 
with  still  more  increased  strength  of  current  it  is  carried  passively 
towards  the  kathode,  with  its  hinder  end  forward,  as  the  result  of 
kataphoric  action  (Wallengren,  215).  Chilomonas  behaves  in  a 
similar  manner.  Paramecium  and  Colpidium,  on  the  other  hand, 
move  towards  the  kathode.  Spirostomum  with  a  moderate 
current  also  moves  towards  the  kathode,  but  with  stronger  currents 
it  first  contracts  its  myonemes  spasmodically,  and  then  takes  up 
a  position  transverse  to  the  direction  of  the  current,  and  remains 
still. 

According  to  Wallengren  (215),  the  apparently  different  galvano- 
tactic  phenomena  exhibited  by  different  ciliates  admits  of  a  uniform 
explanation,  by  a  combination  of  two  effects.  In  the  first  place, 
in  the  half  of  the  body  turned  towards  the  kathode  the  expansion- 
phase  of  the  ciliary  movement  is  stimulated  ;  in  the  anodic  half  of  the 
body,  the  contraction-phase  is  stimulated.  In  the  second  place,  the 
turning  movements  of  the  ciliates  are  determined  mechanically 
(compare  the  "  avoiding  reactions  "  mentioned  above),  and  may  be 
effected  either  by  the  expansion  or  by  the  contraction  of  certain 
cilia.  Consequently,  if  the  turning  movements  are  effected  by 
beats  of  expansion,  the  animal  places  itself  automatically  in  a  posi- 
tion in  which  it  moves  towards  the  anode  ;  if  beats  of  contraction 
are  effective  in  the  turning  movement,  it  moves  towards  the 
kathode.  According  to  Statkewitsch  (209),  the  galvanotactic  re- 
action is  one  which  overcomes  chemo tactic  stimuli,  and  leads  the 
animals  irresistibly  into  toxic  media  in  which  they  are  killed. 

6.  Degeneration  and  Regeneration. — The  fact  that  under  certain 
conditions  Protozoa  undergo  a  process  of  physiological  degenera- 
tion, which  may  end  in  death,  has  been  observed  frequently  by  all 
those  who  have  kept  cultures  of  Protozoa  under  observation  for 
a  long  time.  It  has  been  pointed  out  in  a  previous  chapter  (p.  135) 
that  the  life-cycles  of  Protozoa  exhibit  depression-periods  (Calkins) 
which  are  characterized  chiefly  by  cessation  of  feeding,  metabolism, 
growth,  and  reproduction,  together  with  increase  in  the  size  of  the 
nucleus,  and  tendency  to  deposition  of  grains  of  fat  or  other  sub- 
stances in  the  protoplasm,  giving  the  body  a  characteristic  dark- 
grey  appearance.  Such  periods  recur  regularly  and  apparently 
normally  in  the  life-cycles  both  of  Protozoan  and  Metazoan  cells 


THE  GENERAL  PHYSIOLOGY  OF  THE  PROTOZOA     209 

(Popoff,  184)  ;  they  may  also  be  induced  artificially  in  various 
ways  by  unfavourable  conditions,  such  as  overfeeding  or  starvation, 
changes  of  temperature,  or  treatment  with  reagents  (compare 
Smith,  207;  Popoff,  186  ;  Boissevain,  151). 

A  state  of  depression  may  be  regulated  naturally  by  conjuga- 
tion, or  by  restoration  of  the  nucleo-cytoplasmic  balance  through 
•a  process  of  self-regulation  on  the  part  of  the  organism.  The 
regulative  processes  consist  of  absorption  of  a  large  part  of  the 
superfluous  chromatin,  so  as  to  restore  the  normal  quantitative 
relation  of  the  nucleus  and  cytoplasm.  On  the  other  hand,  the 
depression  may  lead  to  complete  degeneration  of  the  organism 
without  possibility  of  recovery,  and  death  ensues  by  a  process  of 
disruption  of  the  protoplasm  into  granules — so-called  "granular 
disruption  "  (korniger  Zerfall).  Some  examples  are  given  below  : 

Actinosphcerium  can  be  brought  into  a  condition  of  depression  either  by 
starvation  or  overfeeding  (Hertwig,  164).  In  the  depressed  state  a  great 
quantity  of  chromatin  is  extruded  from  the  nuclei  in  the  form  of  chromidia 
which  degenerate  into  pigment,  so  that  the  animal  during  a  depression-period 
has  a  characteristic  brownish  tint,  more  or  less  pronounced  in  proportion 
to  the  degree  of  depression.  In  extreme  cases  the  protoplasm  is  bereft  of  its 
nuclei,  and  becomes  incapable  of  continuing  to  live.  The  nuclei  may  become 
entirely  resolved  into  chromidia  ;  or  some  of  the  nuclei  grow  to  a  relatively 
gigantic  size  and  are  cast  out,  while  other  nuclei  break  up  ;  or  the  entire 
medullary  layer  surrounding  the  enlarged  nuclei  may  be  thrown  off.  The 
pseudopodia  may  disappear  altogether  or  become  deformed  in  various  ways, 
the  difference  between  cortical  and  medullary  substance  may  be  annulled 
or  abnormally  increased,  and  the  metabolism  may  be  modified,  all  these 
changes  being  in  relation  to  nuclear  alterations. 

In  Opalina,  according  to  Dobell  (155),  physiological  degeneration  can  be 
induced  by  starvation  of  its  host,  the  frog.  The  degenerating  Opalines  lose 
their  cilia  and  become  irregular  in  form  ;  peculiar  refringent  eosinophile 
globules  appear  in  the  cytoplasm  ;  the  nuclei  undergo  increase  in  size  and 
modification  in  structure,  give  off  chromatin,  and  undergo  irregular  fusions  ; 
and  the  body  divides  irregularly,  sometimes  producing  buds  which  contain 
no  nucleus.  Ultimately  the  Opalince  disintegrate. 

Prandtl  (187)  has  described  the  degeneration  of  Amoeba  proteus.  The 
nucleus  increases  in  size  and  becomes  hyperchromatinic.  Chromidia  are 
extruded  into  the  cytoplasm,  and  may  there  degenerate,  with  formation  of 
numerous  small  crystals.  The  chromatin  in  the  nucleus  also  degenerates 
to  form  a  mass  of  brown  pigment,  which  is  extruded  en  bloc  into  the  cyto- 
plasm, or  forms  a  ring  of  fine  granules  round  the  nucleus.  The  pigment  may 
also  spread  through  the  whole  cytoplasm,  giving  it  a  brownish  tinge.  Finally 
the  nucleus  breaks  up  and  disappears  altogether.  Degenerating  amoebae  are 
.subject  to  the  attacks  of  parasites.  A  noteworthy  feature  is  the  tendency 
of  the  degenerating  amoebae  to  associate  in  clumps,  and  plastogamic  fusion  of 
two  amcebce  was  observed  by  Prandtl.  The  tendency  to  fusion  may  bo 
compared  with  the  agglomeration  of  trypanosomes,  etc.  (p.  128),  which  is 
common  also  in  degenerating  forms  or  under  unfavourable  conditions.*  It 
is  not  improbable  that  many  of  the  plastogamic  unions  of  Sarcodina  of^en 

*  The  "conjugations"  observed  by  Putter  (201,  p.  582)  in  Opalince  kept 
without  oxygen  must  have  been  also  phenomena  of  the  nature  of  agglomeration, 
since  in  Opalina  syngamy  takes  places  between  special  gametes,  and  not  in  the 
ionn  of  conjugation  of  adult  forms  as  in  other  Ciliata  (p.  4f>3). 

14 


210  THE  PROTOZOA 

described  may  be  phenomena  of  agglomeration  associated  with  a  similar 
condition. 

In  Radiolaria,  Borgert  (152)  describes  fatty  degeneration  affecting  the 
nucleus  as  well  as  the  protoplasm,  both  endoplasm  and  ectoplasm.  The 
nucleus  becomes  converted  entirely  into  a  vesicle  filled  with  a  mass  of  fat- 
globules,  or  into  a  number  of  such  vesicles. 

In  Tocophrya  quadripartita  subjected  to  starvation,  after  the  refringent 
bodies  (p.  458)  have  been  absorbed,  the  nucleus  becomes  modified  in  structure, 
the  tentacles  are  retracted,  active  budding  takes  place,  and  with  the  last  bud 
formed  the  nucleus  disappears  and  the  remaining  protoplasm  dies  away. 

From  a  consideration  of  the  various  examples  of  degeneration 
from  different  causes,  it  appears  that  the  first  part  to  be  affected 
is  always  the  nucleus,  and  that  the  other  derangements  of  the 
structure  and  functions  of  the  body  are  secondary  consequences 
of  an  abnormal  condition  of  the  nucleus. 

The  regeneration  of  lost  parts  of  the  cell-body  of  Protozoa  has 
been  the  subject  of  experiment  by  a  great  number  of  investigators. 
The  methods  employed  have  consisted  mainly  in  mutilating  the 
body  or  cutting  it  up  into  a  number  of  pieces,  in  order  to  find  out 
to  what  extent  the  fragments  possess  the  power  of  regenerating  the 
lost  parts.  The  experiments  have  led  to  one  very  definite  result, 
which  can  be  expressed  briefly  :  no  separate  part  of  the  body  is 
capable  of  continuing  its  vital  activities  indefinitely,  or  of  regenera- 
ting any  of  the  deficiencies  in  the  structure  of  the  body,  if  it  does 
not  contain  the  nucleus  or  a  portion  of  the  nucleus.  Non-nucleated 
fragments  may  continue  to  live  for  a  certain  time  ;  in  the  case  of 
amoeba  such  fragments  may  emit  pseudopodia,  the  contractile 
vacuole  continues  to  pulsate,  and  acts  of  ingestion  or  digestion 
of  food  that  have  begun  may  continue  ;  but  the  power  of  initiating 
the  capture  and  digestion  of  food  ceases,  consequently,  all  growth 
is  at  an  end,  and  sooner  or  later  all  non-nucleate  fragments  or 
enucleated  bodies  die  off.  A  Polystomella  which  possesses  a  nucleus 
can  repair  breakages  to  the  shell  ;  an  individual  deprived  of  its 
nucleus  cannot  do  so  (Verworii).  On  the  other  hand,  an  isolated 
nucleus,  deprived  of  all  protoplasm,  dies  off  ;  but  a  small  quantity 
of  protoplasm  containing  the  nucleus  or  a  part  of  it  is  able  in  some 
eases  to  regenerate  the  whole  body,  and  to  produce  a  complete 
individual  of  small  size. 

la  experiments  on  regeneration  the  Ciliata  are  the  objects  of  choice  ;  their 
complicated  structure  permits  the  regeneration  that  has  taken  place  to  be 
estimated  accurately  ;  their  size  renders  the  mutilation  more  easy  to  perform  ; 
and  the  large  size  and  frequently  extended  form  of  the  nucleus  makes  it 
possible  to  divide  up  this  body  also.  In  recent  experiments  Lewin  (171) 
has  succeeded  in  dividing  Paramecium  into  a  number  of  fragments  ("  mero- 
zoa"),  containing  each  a  portion  of  the  macronucleus.  Only  one  of  the 
merozoa  obtained  in  this  manner  contains  the  micronucleus,  which  is  too- 
minute  tobe  divided  by  a  mechanical  operation.  Except  when  the  Paramecium 
was  in  process  of  division,  only  one  merozoon  recovered  the  normal  body- 
form  and  proceeded  to  divide  ;  and  the  interesting  result  was  obtained  that 


THE  GENERAL  PHYSIOLOGY  OF  THE  PROTOZOA     211 

the  merozoon  which  survived  was  not  necessarily  the  one  which  contained  the 
micronucleus.  Regenerated  individuals  multiplied  for  a  number  of  genera- 
tions, producing  a  culture  of  "  amicronucleate  "  Paramecia.  If,  on  the  other 
hand,  a  Paramecium  in  process  of  division  was  halved,  each  half  regenerated 
the  entire  body  and  was  capable  of  division.  These  experiments  indicate 
that  Paramecium  contains  a  division- centre  independent  of  the  nuclei,  and 
that  its  presence  is  necessary  for  regeneration  of  the  body. 

Prowazek  (189)  observed  occasionally  a  certain  power  of  regeneration  in 
non-nucleated  fragments  of  Stentor,  but  considered  it  possible  that  extra- 
nuclear  chromatin  might  have  been  present.  The  same  author  (190)  ob- 
served abnormal  regeneration,  leading  to  monstrosities  with  three  hinder  ends, 
in  a  culture  of  Stylonychia  mytilus  during  a  depression- period  which  led  finally 
to  the  extinction  of  the  culture.  The  recent  experiments  of  Lewin  (172)  on 
Stylonychia  mytilus  show  that,  in  the  regeneration  which  follows  artificial 
mutilation,  multiplication  of  micronuclei  may  occur,  with  the  result  that  the 
regenerated  individual  may  have  more  micronuclei  than  the  number  typical 
of  the  species  or  race. 


Bibliography. — For  references  see  p.  481. 


CHAPTER  XI 
SYSTEMATIC  REVIEW  OF  THE  PROTOZOA  :  THE  SARCODINA 

As  stated  in  Chapter  I.,  the  Protozoa  are  commonly  divided  into 
four  principal  classes.  Of  these,  two — namely,  the  Sarcodina  and 
Mastigophora— may  be  regarded  as  the  more  primitive  groups, 
comprising  the  main  stock  of  less  specialized  and  typical  forms 
from  which  the  other  two  classes  have  been  evolved.  The  Sporozoa 
are  an  assemblage  of  exclusively  endoparasitic  forms  exhibiting 
clearly  the  modifications  and  adaptations  induced  by,  or  necessary 
for,  their  particular  mode  of  life  ;  and  it  is  practically  certain  that 
the  Sporozoa  are  not  a  homogeneous  class  showing  mutual  affinities 
based  upon  a  common  ancestry,  but  that  one  section  of  the  group 
is  a  specialized  offshoot  of  the  Mastigophora,  the  other  of  the 
Sarcodina,  and  that  the  two  sections  are  united  only  by  characters 
of  convergence  due  to  the  influence  of  a  similar  mode  of  life.  The 
Infusoria,  on  the  other  hand,  are  a  specialized  group  in  which  great 
complexity  of  organization  has  been  attained  ;  they  are  the  highest 
class  of  the  Protozoa,  and  furnish  examples  of  the  most  extreme 
degree  of  structural  differentiation  of  which  a  unicellular  organism 
is  capable. 

While  there  is  but  little  difficulty,  as  a  rule,  in  defining  the  classes 
Sporozoa  and  Infusoria,  or  in  assigning  members  of  these  groups 
to  their  proper  systematic  position,  the  case  is  different,  very  often, 
when  we  have  to  deal  with  the  other  two  classes.  The  verbal 
distinction  between  them  is  based  chiefly  on  the  use  of  the  word 
"  adult  ":  Sarcodina  are  Protozoa  which  have  no  permanent  organs 
of  locomotion  in  the  adult  condition,  but  move  by  means  of  pseudo- 
podia  extruded  from  the  naked  protoplasmic  body  ;  Mastigophora, 
on  the  other  hand,  bear  organs  of  locomotion  in  the  form  of  flagella 
in  the  adult  condition,  whether  the  protoplasmic  body  is  naked 
and  amoeboid  or  corticate  and  of  definite  form.  In  both  classes  the 
youngest  stages  may  be  flagellate  ;  if,  in  an  amoeboid  form,  the 
flagella  are  retained  in  the  adult,  the  organism  is  classed  in  the 
Mastigophora  ;  if  lost;  in  the  Sarcodina. 

The  word  "  adult  "  when  applied  to  the  Metazoa  has  a  meaning 
which  can  be  defined  clearly,  as  a  rule,  by  the  criterion  of  sexual 

212 


THE  SARCODINA  213 

maturity.  In  the  Protozoa  no  such  criterion  is  available,  and  the 
distinction  between  young  and  adult  is  based  on  differences  in  size 
and  growth,  or  on  phases  of  the  life-cycle  selected  in  an  arbitrary 
manner.  In  many  cases  the  distinction  presents  no  difficulty  ;  it 
is  perfectly  easy  to  distinguish  young  from  adult  stages  in  such 
forms  as  the  Foraminifera  and  Radiolaria  among  Sarcodina,  or  the 
genus  Noctiluca  among  Mastigophora.  But  in  other  cases  it  is 
purely  a  matter  of  opinion  which  phase  in  the  life-cycle  is  to  be 
regarded  as  adult.  Such  a  form  as  Pseudospora  has  a  flagellated 
and  an  amoeboid  phase  (Robertson),  and  can  be  placed  in  either 
the  Sarcodina  or  the  Mastigophora  with  perfect  propriety.  The 
amoeba-like  genus  Mastigamc&ba  is  placed  in  the  Mastigophora 
because  the  flagellum  is  retained ;  but  if  any  species  of  this  genus 
were  to  lose  its  flagellum  when  adult,  rigid  adherence  to  verbal 
definitions  would  necessitate  its  being  classed  in  the  Sarcodina. 

The  difficulty  of  separating  and  defining  the  stems  of  the  Sarco- 
dina and  Mastigophora  at  their  root  is  only  to  be  expected  on  the 
theory  of  evolution.  The  two  classes  are  undoubtedly  descended 
from  a  common  ancestral  type,  which  has  become  modified  in 
two  divergent  directions,  giving  rise  to  two  vast  groups  of  organisms 
which  may  differ  from  one  another  very  slightly  or  very  greatly  in 
selected  examples.  The  systematist  may  meet  with  many  obstacles 
when  it  is  required  to  lay  down  verbal  distinctions  between  the  two 
classes,  but  it  is  easy  to  recognize,  in  a  general  way,  two  principal 
morphological  types,  round  which  each  class  is  centred,  and  which 
may  be  realized  to  a  greater  or  less  extent  in  given  cases. 

1.  Sarcodine  Type. — Protozoa  which  grow  to  a  relatively  large 
size  ;  in  the  so-called  "  adult  phase  "  permanent  organs  of  loco- 
motion are  wanting,  and  the  naked  protoplasmic  body  moves  or 
captures  food  by  means  of  pseudopodia  ;  the  young  stages  may  be 
flagellate  or  amoeboid. 

2.  Mastigophoran  Type. — Protozoa  usually  of  minute  size,  seldom 
with   a  large  adult  phase   (as,   for   example,   Noctiluca)  ;   flagella 
retained  throughout  active  life,  only  lost  in  resting  phases  ;  body 
amoeboid  or  corticate. 


THE  SARCODINA. 

The  name  Rhizopoda  is  sometimes  used  for  this  class  but  this 
name  is  only  applicable,  strictly  speaking,  to  the  first  four  orders 
recognized  below,  in  which  the  pseudopodia  are  more  or  less  root- 
like,  and  not  to  the  orders  Heliozoa  and  Radiolaria,  characterized 
by  stiff  radiating  pseudopodia. 

General  Characteristics. — As  stated  above,  the  Sarcodina  are  Pro- 
tozoa for  the  most  part  of  relatively  large  size.  Many  Sarcodina 


214  THE  PROTOZOA 

are  visible  to  the  naked  eye,  and  some  of  the  Radiolaria,  Foramin- 
ifera,  and  Mycetozoa,  attain  to  a  size  that  must  be  considered 
gigantic  for  Protozoa.  The  more  primitive  forms,  on  the  other 
hand,  are  often  very  minute. 

The  body-form  is  of  two  principal  types,  related  to  distinct  habits 
of  life — namely,  the  amoeboid  type,  characteristic  of  forms  that 
creep  on  a  firm  substratum ;  and  the  radiate  type,  seen  in  floating 
forms.  Amoeboid  forms  are  found  aquatic,  semiterrestrial,  and 
parasitic  ;  radiate  forms  are  for  the  most  part  pelagic,  living  floating 
or  suspended  in  large  masses  of  water,  marine  or  fresh-water. 

The  protoplasmic  body  is  in  many  cases  distinctly  differentiated 
into  clear  motile  ectoplasm  and  granular  trophic  endoplasm.  The 
surface  of  the  protoplasm  is  naked,  or  may  be  covered  in  rare  in- 
stances (Amceba  verrucosa,  A.  terricola,  etc.)  by  a  very  thin  pellicle 
which  modifies,  but  does  not  restrain,  the  amoeboid  movements. 
A  resistant  cuticle  or  cell-membrane  investing  the  body  is  not 
formed,  but  an.  external  shell  or  internal  supporting  skeleton  is 
frequently  present. 

The  loconiotor  organs  in  the  adult  are  always  pseudopodia,  which 
may  be  of  various  types — lobose,  filose,  or  reticulose  (Chapter  V., 
p.  46)  ;  they  may  lie  in  one  plane,  as  in  creeping  forms,  or  may  be 
given  off  on  all  sides,  as  in  pelagic  forms.  The  youngest  forms 
(swarm-spores)  may  be  flagellate  or  amoeboid.  In  some  cases  the 
pseudopodia  of  the  young  forms  may  differ  markedly  in  character 
from  those  of  the  adult ;  for  example,  the  adult  Amceba  proteus  has 
fluid  protoplasm  with  thick  lobose  pseudopodia,  but  the  young 
amoebula  produced  from  the  cyst  of  this  species  has  viscid  proto- 
plasm with  sharp,  spiky  pseudopodia  (Scheel). 

The  free-living  Sarcodina  are  almost  without  exception  holozoic, 
capturing  other  organisms  by  means  of  their  pseudopodia,  and 
devouring  them ;  but  the  remarkable  genus  Ghlamydomyxa  (p.  243) 
has  chromatophores,  and  can  live  in  either  a  holozoic  or  holophytic 
manner,  like  some  flagellates  ;  and  the  genus  Paulinella,  allied  to 
Euglypha,  also  possesses  chromatophores.  and  is  capable  of  holo- 
phytic nutrition  (Lauterborn). 

The  nuclear  apparatus  consists  of  one  or  more  nuclei,  in  addition 
to  which  chromidia  may  be  present.  A  single  nucleus  is  charac- 
teristic of  the  majority  of  species,  even  of  many  which  grow  to 
very  large  size,  such  as  many  Radiolaria,  in  which  the  nucleus  also 
attains  to  proportions  relatively  gigantic.  In  other  cases  increase 
in  the  size  of  the  body  is  accompanied  by  multiplication  of  the 
nuclei ;  there  may  be  two  nuclei  constantly,  as  in  Amceba  binucleata 
(Schauclinn),  or  several,  as  in  Difflugia  urceolata,  or  many  hundreds, 
as  in  Actinospkcerium  and  Pelomyxa,  or  even  thousands,  as  in  the 
Mycetozoa.  In  such  forms  the  adult  is  a  plasmodium,  but  the 


THE  SARCODINA  215 

numerous  nuclei  show  110  differentiation  amongst  themselves,  and 
appear  to  be  perfectly  equivalent  both  in  structure  and  function. 
Chromidia  may  be  present  as  a  permanent  cell-constituent  in  many 
Anioebsea,  such  as  Arcella,  Difflugia,  and  the  Foraniinifera  ;  in  other 
cases  they  are  formed  temporarily,  as  extrusions  from  the  nucleus, 
during  certain  phases  of  the  life-cycle,  either  as  a  preliminary  to 
reproduction  or  as  a  regulative  process  under  certain  physiological 
conditions. 

The  reproduction  of  the  Sarcodma  is  effected  either  by  binary 
or  multiple  fission.  Binary  fission  may  be  absent  in  some  of  the 
larger,  more  specialized  forms,  as  in  many  Foraniinifera  and  Raclio- 
laria,  but  in  most  cases  it  is  the  ordinary  "  vegetative  "  method  of 
reproduction  during  the  active  trophic  life  of  the  organism.  In 
plasmodial  forms  it  takes  the  form  of  plasrnotomy  (p.  100).  Mul- 
tiple fission  or  gemmation  (sporulation)  is  in  some  cases  the  sole 
method  of  reproduction  ;  in  other  case  it  is  combined  with  binary 
fission,  and  occurs  only  at  certain  crises  in  the  life-cycle,  in  relation 
to  seasonal  changes,  or  as  a  preliminary  to  syngamy.  In  this  type 
of  reproduction  the  organism,  breaking  up  rapidly  into  a  large— 
often  an  immense — number  of  minute  individuals,  is  necessarily 
put  hors  de  combat  as  soon  as  the  reproduction  begins  ;  hence  it  is 
not  uncommon  for  the  sporulation  to  take  place  within  a  cyst, 
when  a  shell  or  protective  envelope  is  not  present,  as  in  Amceba 
proteus  (Scheel).  The  minute  germs  produced  by  sporulation  may 
be  set  free  at  once  as  swarm-spores  ;  or  they  may  form  a  pro- 
tective envelope  or  sporocyst,  and  be  liberated  as  resistant  spores 
which  are  disseminated  passively,  and  germinate  when  conditions 
are  favourable,  as  in  parasitic  forms  and  in  the  semi-terrestrial 
Mycetozoa. 

The  swarm-spores,  whether  produced  directly  by  sporulation  of 
an  adult  or  indirectly  by  germination  of  a  spore,  may  be  either 
flagellulse  or  amoebulse.  In  many  forms  two  types  of  sporulation 
occur — schizogoiiy  producing  agarnetes,  and  sporogony  producing 
gametes.  The  againetes  may  be  structurally  or  morphologically 
distinguishable  from  the  gametes.  Thus,  in  Foraniinifera  the 
agametes  are  amoebulee,  the  gametes  are  flagellulse.  In  Racliolaria 
both  alike  are  flagellulas,  but  the  agametes  produced  in  schizogoiiy 
—the  "  isospores  "  —are  distinguishable  from  the  gametes  produced 
in  sporogony—  "  aiiisospores." 

In  this  class  syngarny  takes  place  rarely  between  adult  indi- 
viduals ;  but  examples  of  this  are  seen  in  Actinophrys,  where  it  takes 
the  form  of  karyogamy  within  a  cyst  (Fig.  71),  and  in  Arcella  (p.  148) 
and  Difflugia,  where  it  takes  the  form  of  chromidiogamy  between 
free  individuals,  followed  in  Diffliigia  by  encystrnent.  In  the  great 
majority  of  Sarcodina  the  syngamy  is  microgamous,  and  takes  place 


216 


THE  PROTOZOA 


between  swarm-spores,  either  amoebulec  or  flagellulse.  The  microg- 
amy  is  isogamous  or  slightly  anisogamous  ;  macrogamy,  as  in  other 
cases,  is  perfectly  isogamous.  Microgamy  occurs,  as  has  been  seen 
(p.  148),  in  Arcella  in  addition  to  chromidiogamy  ;  and,  according 
to  a  recent  note  of  Zuelzer  (86,  p.  191,  footnote),  syngamy  between 
free  swarm-spores  occurs  in  Diffluyia  also. 

As  regards  the  life-cycle  of  the  Sarcodina,  there  remains  still  so 
much  to  be  discovered  that  to  generalize  is  both  difficult  and 
dangerous.  Even  in  the  commonest  forms,  such  as  Amoeba  proteus, 
the  complete  life-cycle  has  not  been  yet  worked  out.  In  some 


FIG.  85. — Changes  in  the  form  of  an  amoeba  under  the  influence  of  differences 
in  the  surrounding  medium.  A — C,  In  its  natural  medium  (water) :  A, 
contracted  ;  B,  beginning  to  throw  out  pseudopodia  ;  G,  Umax-form.  D — F ', 
Forms  assumed  after  addition  of  potash-solution  :  D,  contracted,  beginning; 
to  throw  out  pseudopodia  ;  E,  F,  radiosa-ioruas.  After  Verworn. 

cases  the  life-cycle  appears  to  be  of  comparatively  simple  type,  and 
the  species  is  monomorphic  or  nearly  so,  as  in  ActinospJt cerium ; 
in  other  cases  there  is  a  well-marked  alternation  of  generations, 
with  dimorphism  in  the  adult  condition,  as  in  Trichosphcerium 
(p.  182),  the  Foraminifera,  etc. 

Classification. — The  Sarcodina  are  subdivided  into  a  number  of 
orders,  the  distinctions  between  which  are  based  principally  on  the 
characters  of  the  pseudopodia  and  of  the  skeleton,  when  present ; 
in  more  highly  differentiated  forms,  such  as  Radiolaria,  the  internal 
structure  of  the  body  is  also  taken  into  account.  In  the  primitive 


THE  SARCODINA  217 

forms  of  simple  structure,  however,  in  which  no  skeleton  is  present, 
the  subdivisions  are  defined  entirely  by  the  characters  of  the  proto- 
plasmic body  and  the  pseudopodia,  which  furnish  distinctions  of 
very  doubtful  validity.  Not  only  may  the  characters  of  the 
pseudopodia  vary  in  different  phases  of  the  life  cycle,  as  already 
stated  in  the  case  of  Amoeba  proteus,  but  even  in  the  same  phase 
under  the  influence  of  different  media.  Thus,  no  two  forms  of 
amoeba  could  appear  more  distinct  at  first  sight  than  the  Umax 
and  radiosa  forms,  originally  regarded  as  distinct  species.  In  the 
limax-iorm.  the  whole  body  flows  forward  as  a  single  pseudopodium, 
gliding  along  like  a  slug  ;  in  the  rad^'osa-form  the  spherical  body 
becomes  star-like,  sending  out  sharp-pointed  pseudopodia  on  all 
sides.  Nevertheless,  Verworn  showed  that  the  one  form  could  be 
changed  into  the  other  by  differences  in  the  medium  (Fig.  85). 
Doflein  (238)  obtained  similar  form-changes  in  Amceba  vespertilio. 
and  showed  that  the  body-form  and  character  of  the  pseudopodia 
were  quite  inadequate  features  for  distinguishing  the  species  of 
amoeba,  depending  as  they  do  upon  the  conditions  of  the  environ- 
ment and  the  nature  of  the  medium.  Compare  also  Gruber  (246) 
on  form- varieties  of  Amceba  proteus. 

In  view  of  the  protean  nature  of  these  organisms,  it  is  not  sur- 
prising that  much  diversity  of  opinion  prevails  as  to  the  arrangement 
of  the  groups  and  the  exact  position  of  some  of  their  members.  It  is 
usual  to  put  a  number  of  primitive  organisms  together  in  a  group 
termed  Proteomyxa,  the  members  of  which  probably  have  more 
affinities  with  various  members  of  other  groups  than  with  one 
another.  On  the  other  hand,  the  more  highly  organized  Sarcodiiia 
are  classified  without  difficulty  into  well-characterized  orders ; 
such  are  the  Foraminifera,  Mycetozoa,  Radiolaria,  and  Heliozoa, 
though  even  in  these  groups  there  are  forms  near  the  border-line  and 
of  doubtful  position. 

The  classification  adopted  here  is  mainly  that  of  Biitschli  (2), 
with  the  addition  of  some  forms  not  included  in  his  great  work,  as 
follows  : 

A.    SUBCLASS     RHIZOPODA.  -  -  Typically     creeping    forms     with 
branched,  root-like  pseudopodia. 

I.  Order  Amcebcea. — Amoeboid  forms  of  simple  structure  ; 
skeleton  lacking  or  in  the  form  of  a  simple  shell. 

1.  Suborder  Eeticulosa  (Proteomyxa). — With  filose 

or  reticulose  pseudopodia,  without  shell. 

2.  Suborder  Lobosa. — With  lobose  pseudopodia. 

(a)  Section  Nuda,  without  shell  or  skeleton, 

(b)  Section  Testacea,  with  shells. 

II.  Order  Foraminifera. — With  reticulose  pseudopodia  and 
shells. 


218  THE  PROTOZOA 

III.  Order  Xenophyophora. — With  skeleton  of  foreign  bodies 

and  a  peculiar  internal  structure. 

IV.  Order  Mycdozoa. — Semi-terrestrial  forms  with  repro- 

duction by  resistant  spores  and  formation  of  plas- 
modia. 

B.  SUBCLASS  ACTINOPODA  (Calkins). — Typically   floating   forms 
with  radiating,  unbranched  pseudopodia. 

V.  Order    Heliozoa. — Principally    fresh-water,    without    a 

;'  central  capsule." 

VI.  Order  Radiolaria. — Exclusively  marine,  with  a  central 
capsule. 

I.  AMCEB/EA. 

1.  Reticulosa. — In  this  suborder  are  comprised  a  number  of 
forms  of  doubtful  affinities,  sometimes  ranked  as  a  distinct  order, 
Proteomyxa.  The  only  positive  character  which  they  have  in 
common  is  the  possession  of  filose  or  reticulose  pseudopodia,  with 
which  is  combined  the  absence  of  a  shell  and  skeleton.  Hence  it 
is  not  surprising  that  the  position  of  many  forms  referred  to  this 
suborder  is  extremely  dubious,  and  some  of  them  are  referred  to 
distinct  orders  by  many  authorities. 

In  general  two  types  of  organisms  are  referred  to  this  suborder : 

(a)  Large  marine  plasmodial  forms  ;  an  example  is  Pontomyxa 
flava,  described  by  Topsent  from  the  Mediterranean  and  British 
Channel.  Pontomyxa  is  a  multimicleate  plasmodium  of  yellow 
colour.  It  sends  out  branching  root-like  pseudopodia,  which  may 
spread  out  and  form  a  network  extending  over  two  or  three  inches 
in  length.  Nothing  is  known  of  its  development  or  life-cycle. 

(6)  Small  forms  with  a  single  nucleus,  marine  or  fresh-water, 
which  reproduce  by  process  of  multiple  fission  forming  swarm- 
spores.  These  forms  have  been  subdivided  into  two  families, 
according  to  the  type  of  swarra-spore  found — Zoosporidce,  pro- 
ducing flagellulse ;  and  Azoosporidce,  producing  amoebulse.  An 
example  of  the  Zoosporidce  is  furnished  by  the  genus  Pseudospora. 
which  preys  upon  algse,  diatoms,  Volvociriese,  etc.  The  adult  phase 
is  amoeboid,  flagellate,  or  even  Heliozooii-like.  It  feeds  on  the  cell- 
substance  and  chlorophyll  of  the  prey,  and  multiplies  by  binary 
fission.  It  can  also  break  up  by  multiple  fission  into  flagellate 
swarm-spores,  with  or  without  previous  encystrnent.  Robertson 
has  observed  syngamy  between  flagellulse  thus  formed,  which  are 
therefore  gametes ;  in  other  cases  the  flagellulse  are  perhaps 
agametes.  As  already  pointed  out  above,  the  position  of  this  form 
amongst  the  Sarcodina  is  doubtful ;  by  many  authorities  it  is 
classified  in  the  Mastigophora. 

An  example  of   the  Azoosporidce  is  furnished  by  Vampyrclla,  a 


THE  SARCODINA 


219 


small  amoeboid  form  which,  like  Pseudospora,  preys  upon  algae 
(Fig.  86),  devouring  the  contents  of  the  cell,  and  multiplying  in  the 
free  state  by  binary  fission.  It  also  encysts  and  breaks  up  within 
the  cyst  by  multiple  fission  to  form  a  number  of  anioebulae,  which 
creep  out  and  grow  up  into  the  adult  form. 

A  large  number  of  other  genera  are  referred  to  the  Reticulosa, 
for  the  most  part  so  little  investigated  as  regards  their  develop- 
ment and  life-history  that  it  is  impossible  to  deal  with  them  com- 
prehensively in  a  brief  space.  For  an  account  of  them,  see  Delage 
and  Herouard  (6,  p.  66),  Hickson  (248),  and  Rhumbler  (288). 

2.  Lobosa. — This  suborder  comprises  a  great  number  of  organisms, 
which  it  is  convenient  to  subdivide  into — (a)  Nuda 


FIG.  86. — Vampyrella  lateritia:  various  forms.  A,  Free  Heliozoon-like  phase  ; 
B,  creeping  amoeboid  phase  ;  C,  amoeboid  form  attached  to  a  Conferva-fila- 
ment ;  D,  a  similar  form  ;  it  has  broken  the  algal  filament  at  a  joint,  and  has 
emptied  one  cell  of  its  contents.  A  and  -B  after  Hoogenraad  ;  0  and  D  after 
Cash  and  Hopkinson. 

with  no  shell;  and  (6)  Testacea  (Thecamoebae,  Thalamophora),  with 
a  shell  or  house. 

General  Characters. — Familiar  examples  of  the  Lobosa  Nuda  are 
furnished  by  the  species  of  the  genus  Amoeba  and  allied  forms.  A 
very  large  number  of  free-living  amoebae  have  been  described  and 
named,  but  it  is  very  doubtful  how  far  they  are  true  species  ;  some 
of  them,  with  pronounced  and  constant  characteristics,  such  as 
Amceba  proteus  (Fig.  2)  and  A.  verrucosa  (Fig.  23),  are  probably 
"  good  "  species  ;  others,  such  as  A.  Umax  and  A.  radiosa,  are 
probably  forms  that  may  occur  as  phases  in  the  development  of 
other  species  of  amoebae  or  of  other  organisms,  such  as  Mycetozoa. 


220  THE  PROTOZOA 

At  the  present  time  the  life-history  has  been  worked  out  satisfac- 
torily in  but  f ew  free-living  amoebae,  but  in  such  protean  organisms 
it  is  quite  unsafe  to  attempt  to  characterize  or  define  a  species 
without  a  knowledge  of  the  whole  life-cycle.  As  regards  the 
familiar  Amoeba  proteus,  for  example,  practically  all  that  is  known  of 
its  life-cycle  is  that  it  encysts  and  multiplies  within  the  cyst  to 
form  a  great  number  of  small  amcebulae,  very  different  in  appear- 
ance from  the  parent-organism  ;  the  amoebulse  creep  out  of  the  cyst, 
and  probably  grow  up  into  the  adult  form  (Scheel).  Calkins 
adduces  arguments  in  favour  of  the  occurrence  of  a  sexual  cycle, 
which  remains  at  present,  however,  purely  conjectural. 

The  majority  of  free-living  amoebae  are  aquatic  in  habitat.  A 
certain  number,  however,  are  semi-terrestrial,  inhabiting  damp 
earth,  moss,  etc.  Such  is  Amoeba  terricola  (vide  Grosse-Allermann). 
The  "  earth-amoebae,"  like  other  terricolous  Protozoa,  probably 
play  a  great  part  in  keeping  down  the  numbers  of  the  bacteria  and 
other  organisms  in  the  soil,  and  thereby  lessening  its  fertility  from 
an  agricultural  standpoint  (compare  Russell  and  Hutchmsoii,  24  ; 
Goodey,  16). 

A  great  many  species  of  amoebae  are  found  living  within  the 
bodies  of  animals  of  all  kinds,  for  the  most  part  in  the  digestive 
tract.  The  entozoic  amoabae  are  commonly  placed  in  a  distinct 
genus,  Entamoeba,  distinguished  from  the  free-living  forms  by  little, 
however,  except  their  habitat  and  the  general  (but  not  invariable) 
absence  of  a  contractile  vacuole.  A  common  example  is  Entamoeba 
blattce,  from  the  intestine  of  the  common  cockroach  ;  others  are 
E.  ranarum  of  the  frog  (Dobell,  236,  237)  ;  E.  muris  of  the  mouse 
(Wenyon)  ;  the  species  parasitic  in  the  human  intestine,  presently 
to  be  mentioned  ;  E.  buccalis  (Prowazek),  from  the  human  mouth  ; 
and  many  others.  Chatton  has  described  a  species,  Amoeba  mu- 
cicola,  ectoparasitic  on  the  gills  of  Labridce,  and  extremely  patho- 
genic to  its  host. 

Life-History. — So  far  as  it  is  possible  to  generalize  from  the  scanty 
data  available  at  present,  the  development  of  many  free-living 
species  of  amoebae  appears  to  be  of  a  type  very  similar  to  that  of 
Arcella,  described  in  a  previous  chapter  (p.  179).  In  the  free  state 
the  organisms  reproduce  themselves  in  two  ways  :  first,  "  vegeta- 
tively,5'  by  simple  binary  fission,  preceded  by  a  division  of  the 
nucleus,  which  varies  in  different  cases  from  a  pro  mitosis  (p.  109) 
of  the  simplest  type  to  very  perfect  mitosis  ;  secondly,  by  forma- 
tion of  chromidia  and  subsequently  of  secondary  nuclei,  round 
which  the  cytoplasm  becomes  concentrated  to  form,  a  number  of 
internal  buds,  destined  to  be  set  free  as  amcebulae,  agametes,  which 
grow  up  into  the  adult  form.  In  addition  to  these  two  methods  of 
reproduction  in  the  free  state,  the  animal  may  become  encysted, 


THE  SARCODINA 


221 


and  produce  within  the  cyst  a  number  of  gametes  in  the  same  manner 
as  the  agametes  already  described,  but  with  the  following  differ- 
ences of  detail :  the  principal  nucleus  degenerates  as  soon  as  the 
chromidia  are  formed  ;  the  number  of  secondary  nuclei  produced  is 
much  larger,  and  the  gametes  are  much  smaller  than  the  agametes  ; 
and  the  cytoplasm  of  the  parent  is  entirely  used  up  in  their  forma- 
tion. The  gametes  are  ultimately  set  free  from  the  cyst  as  amoe- 
bulae,  and  pair  ;  the  zygote  grows  into  the  adult  form  of  the  amoeba. 
Such  a  cycle  has  recently  been  described  by  Popoff  (264)  for  a 
species  named  by  him  Amoeba  minuta  ;  the  gametes  in  this  species 
are  iso gametes,  without  any  sexual  differentiation  as  in  Arcella. 
This  type  of  life-cycle  is  probably  very  common  in  many  amoebae, 


FIG.  87. — Amosba  albida  :  autogamy  in  the  encysted  condition  ;  drawn  in  outline, 
with  nuclear  details  only.  A,  Encysted  amoeba  ;  B,  the  nucleus  of  the 
amoeba  divides  unequally  into  a  larger  vegetative  and  a  smaller  generative 
nucleus  ;  the  vegetative  nucleus,  as  seen  in  the  subsequent  figures,  travels 
to  the  surface  of  the  cyst,  degenerates,  and  disappears  ;  the  generative  nucleus 
gives  rise  to  the  gamete-nuclei ;  G,  incomplete  division  of  the  generative  nucleus ; 
D,  one  half  of  the  generative  nucleus  is  budding  off  two  reduction-nuclei 
(on  the  right)  ;  E,  four  reduction-nuclei  have  been  budded  off,  two  from 
each  pole  of  the  incompletely  divided  generative  nucleus  ;  F,  the  reduced 
generative  nucleus  completes  its  division  ;  the  four  reduction-nuclei  are 
degenerating  ;  G,  the  two  pronuclei  far  apart  yH,  the  two  pronuclei  coming 
together  ;  I,  the  pronuclei  fusing.  After  Nagler  (95). 

with  specific  differences  of  detail  in  different  cases,  of  which  the 
most  important  are,  that  in  some  cases,  probably,  the  nucleus 
divides  to  form  the  gamete-nuclei,  instead  of  becoming  resolved 
into  chromidia,  and  that  autogamy  within  the  cyst  may  occur, 
instead  of  free  gametes  being  formed,  as  A.  albida  (Fig.  87). 
According  to  Nagler  (95),  autogamy  of  this  type  is  characteristic 
of  all  amoebae  of  the  Umax-group  ;  in  such  cases  only  two  gamete- 
nuclei  are  formed  in  the  cyst,  which  after  going  through  reducing 
divisions  fuse  to  form  a  synkaryon.  The  zygote  then  leaves  the 
cyst  and  begins  a  fresh  vegetative  cycle. 

A  different  type  of  life-cycle  is  exemplified  by  that  which  Schepo- 
tieff  has  described  in  the  case  of  a  marine  amoeba  identified  by  him 
as  A.  flava.  In  this  case  also  the  ordinary  vegetative  form  is  a 


222 


THE  PROTOZOA 


uninucleate  amoeba,  which  reproduces  itself  by  binary  fission  of  the- 
ordinary  type  ;  but  large  multinucleate  forms  occur  which  become 
encysted.  Within  the  cyst  the  nuclei  break  up  into  chromidia, 
from  which  a  great  number  of  secondary  nuclei  are  formed.  The 
protoplasm  becomes  concentrated  round  the  secondary  nuclei  to 
form  a  number  of  small  cells,  which  acquire  flagella  and  are  set  free 
from  the  cyst  as  flagellulse,  believed  to  be  gametes  and  to  copulate  ; 
the  zygote  is  at  first  encysted,  but  becomes  free  from  the  cyst,  and 
develops  into  the  uninucleate  amoeba.  The  life-cycle  of  A.  proteus 
is  possibly  of  this  type,  since  in  this  species  also  multinucleate 
amoebse  are  commonly  observed  (see  especially  Stole  ;  compare  also 
Paramceba  (Fig.  49). 


FIG.  88. — Amoeba  diploidea.  A,  The  amoeba  in  the  vegetative  condition,  with 
its  two  nuclei  ;  B — F,  the  sexual  processes  within  the  cyst,  drawn  in  outline 
on  a  reduced  scale  ;  B,  two  amoebse,  each  with  its  two  nuclei,  encysted  together, 
the  nuclei  beginning  to  give  off  chromidia  ;  C,  the  two  nuclei  of  each  amoeba 
fused,  numerous  vegetative  chromidia  in  the  cytoplasm  ;  D,  the  bodies  of 
the  amoebse  fused,  each  synkaryon  beginning  its  reduction-process  ;  E,  the 
synkarya  giving  off  reduction -nuclei  which  are  degenerating  ;  F,  the  reduction- 
process  complete  ;  the  cyst  contains  a  single  amoeba  with  two  nuclei  (syn- 
karya), ready  to  emerge  and  begin  its  vegetative  free  life.  After  Nagler  (95)- 

Metcalf  (257)  describes  "  gernmules  "  budded  from  small  free  arnoabse  of 
the  proteus-type,  each  gemmule  becoming  detached  and  developing  into  a. 
flagellated  gamete  of  a  cercomonad  type.  The  flagellulse  were  observed 
frequently  to  lose  their  flagella  and  become  amoeboid.  Copulation  of  two 
flagellulse  took  place  to  form  an  amoeboid  zygote.  Metcalf' s  observations 
upon  the  syngamy  in  this  case  recall  strongly  the  observations  of  Jalm  (294) 
on  the  sexual  processes  of  Mycetozoa  (p.  242).  It  is  possible  that  the  syngamy 
observed  by  him  did  not  form  a  part  of  the  life-cycle  of  the  amceba,  but  of 
some  other  organism. 

The  sexual  process  described  by  Nagler  (95)  in  Amceba  diploidea  is  of  a, 
remarkable  kind  (Fig.  88).  In  the  ordinary  vegetative  condition  the  amoeba 
possesses  normally  two  nuclei,  which  divide  simultaneously  each  time  the 


THE  SARCODINA  223 

animal  reproduces  itself  by  fission.  The  sexual  process  begins  by  two  such 
amcebse  coming  together  and  surrounding  themselves  with  a  cyst  in  common. 
Within  the  cyst  their  nuclei  first  give  off  vegetative  chromidia,  which  are 
absorbed,  after  which  the  two  nuclei  in  each  separate  amoeba  fuse  together 
to  form  a  single  nucleus,  a  synkaryon.  The  protoplasmic  bodies  of  the  two 
amcebse  now  fuse  completely  into  one,  after  which  each  synkaryon  goes 
through  two  reducing  divisions,  producing  each  two  reduction-nuclei,  of 
which  the  first  may  divide  again,  so  that  there  may  be  in  the  cyst  six  reduction- 
nuclei  altogether,  which  are  gradually  absorbed.  The  two  persistent  synkarya, 
after  undergoing  this  process  of  reduction,  approach  each  other,  but  remai:i 
separate,  and  the  amoeba  is  hatched  out  of  the  cyst  to  begin  its  vegetative 
life  with  two  nuclei  representing  gamete-nuclei  that  have  undergone  reduction 
- — that  is  to  say,  pronuclei — which  remain  separate  and  multiply  by  fission 
throughout  the  vegetative  life,  and  do  not  undergo  syngamic  fusion  until  the 
end  of  it. 

In  Amoeba  binucleata,  described  by  Schaudinn,  the  vegetative  phase  also 
contains  two  similar  nuclei  which  multiply  simultaneously  by  division  each 
time  the  animal  divides  ;  but  in  this  case  the  complete  life-cycle  is  not  known. 

Cwing  to  the  practical  importance  of  the  entozoic  amoebae,  and 
the  attention  that  has  been  directed  to  them  in  consequence,  their 
life-cycles  have  been  more  studied  and  are  better  known  than  those 
of  the  free-living  species.  According  to  Mercier,  Entamceba  blattce 
multiplies  by  binary  fission  in  the  gut  of  its  host,  and  later  becomes 
encysted,  passing  out  of  the  body  of  its  host  in  this  condition. 
Within  the  protective  cyst  it  breaks  up  by  multiple  fission,  follow- 
ing repeated  division  of  the  nucleus,  into  a  number  of  amoebulae, 
which  are  set  free  from  the  cyst  when  it  is  devoured  accidentally 
by  a  new  host.  The  amcebulse  are  gametes  which  copulate  after 
being  set  free,  and  the  zygote  grows  into  the  ordinary  vegetative 
form  of  the  amoeba.  E.  blattce  thus  furnishes  a  very  characteristic 
and  primitive  type  of  the  life-cycle  of  an  entozoic  amoeba,  and  one 
which  differs  only  in  points  of  specific  difference  from  that  of 
Amoeba  minuta,  described  above. 

The  question  of  the  human  entozoic  amoebae  is  at  present  in  a 
somewhat  confused  state.  The  occurrence  of  amoebae  in  the  hinder 
region  of  the  human  digestive  tract,  especially  the  colon,  has  long 
been  known,  and  the  name  Amoeba  coli  was  given  by  Losch  to  such 
organisms  (sjTionym,  Entamceba  hominis,  Casagrandi  and  Barba- 
gallo).  It  is,  however,  certain  that  more  than  one  species  of  amoeba 
occurs  in  the  human  bowel,  and  Losch's  name  must  therefore  be 
restricted  to  one  of  these. 

An  epoch  in  the  study  of  human  entozoic  amoebae  was  marked  by  the 
researches  of  Schaudinn  (131),  who  distinguished  two  species.  The  first,  to 
which  he  restricted  the  name  Entamceba  coli,  occurs  commonly  in  Europe 
and  elsewhere  as  a  harmless  inhabitant  of  the  intestine — that  is  to  say,  like 
E.  blattce  and  many  others,  it  is  not,  under  normal  circumstances  at  least,  a 
parasite  in  any  sense  of  the  word,  but  a  simple  scavenger,  feeding  on  bacterial 
and  other  organisms,  detritus,  etc.,  in  the  colon  and  rectum.  The  second 
species,  to  which  Schaudinn  gave  the  name  E.  histolytica,  *  is,  on  the  contrary, 

c  Liihe  has  proposed  to  place  E.  histolytica  in  a  separate  genus,  Poneramceba 
n.  g.  (Schr.  PJiyzik.  Ges.  Koniysberg,  vol.  xlix.,  p.  421). 


THE  PROTOZOA 


a  parasite  of  a  dangerous  kind,  which  occurs  in  tropical  and  subtropical 
regions,  and  is  the  pathogenic  agent  of  amoebic  dysentery  and  liver-abscess  ; 
it  attacks  and  devours  the  tissues  of  the  host,  destroying  the  wall  of  the 
intestine,  whence  it  penetrates  into  the  blood-vessels  and  is  carried  to  the 
liver,  where  it  establishes  itself  and  gives  rise  to  liver-abscesses.  These  two 
species  of  amcebse  are  distinguishable  by  structural  characters.  E.  coli  has 
.a  relatively  fluid  body,  with  ectoplasm  feebly  developed  and  with  a  fairly 
large  spherical  nucleus  (or  nuclei)  lodged  in  the  endoplasm.  E.  histolytica, 


-TL 


•FiG.  89. — Entamaba  coli.  A  and  B,  Living  amoebae  showing  changes  of  form  and 
vacuolation  in  the  endoplasm  ;  C,  D,  E,  amoebae  showing  different  conditions 
of  the  nucleus  (n.)  ;  F,  a  specimen  with  two  nuclei  preparing  for  fission  ; 
G,  a  specimen  with  eight  nuclei  preparing  for  multiple  fission  ;  H,  an  encysted 
amoeba  containing  eight  nuclei  ;  I,  a  cyst  from  which  young  amoebae 
(al)  are  escaping ;  J ,  K,  young  amoebae  free.  After  Gasagrandi  and 
Barbagallo. 

'•on  the  contrary,  has  a  relatively  viscid  body  with  greatly-developed  ecto- 
plasm, as  is  seen  clearly  in  the  formation  of  pseudopodia,  which  may  consist 
entirely  of  ectoplasm ;  it  is  smaller  than  E.  coli,  and  its  nucleus  has  a  com- 
pressed form,  stains  feebly,  and  is  lodged  in,  or  immediately  below,  the 
superficial  ectoplasmic  layer.  The  life -cycles  of  these  two  species  are  also 
very  different,  as  described  by  Schaudinn. 

E.  coli,  in  the  amoeboid  multiplicative  phase,  reproduces  itself  by  binary 


THE  SARCODINA 


225 


fission  of  the  ordinary  type,  and  also  by  a  process  of  multiple  fission  is 
which  the  nucleus  divides  until  there  are  eight  nuclei  in  the  body ;  the 
characteristic  8-nucleate  plasmodiuni  then  divides  up  into  eight  small 
amcebas,  each  of  which  grows  into  an  ordinary  adult  form.  Hence  it  in 
characteristic  of  E.  coli  to  occur  in  various  sizes,  from  very  small  to  full-grown 
amcebag. 

The  propagative  phase  of  E.  coli  is  initiated  by  the  formation  of  a  gelatinous 
envelope  round  a  full-sized  amoeba  possessing  a  single  nucleus.  The  nucleus 
then  divides  into  two,  and  the  process  of  maturation  and  autogamy  takes  place 
that  has  been  described  on  p.  139,  supra  (Fig.  73).  When  it  is  complete,  a 
tough  resistant  cyst  is  formed  within  the  soft  gelatinous  envelope,  and  each 
of  the  two  synkarya  divides  twice  to  produce  four  nuclei.  Thus  is  formed 
the  8-nucleate  resistant  cyst  which  is  characteristic,  perhaps  diagnostic, 
of  this  species.  Within  the  cyst  no  further  changes  take  place  until  it  is 
swallowed  by  a  new  host ;  then  it 
is  believed  that  the  contents  of  the 
cyst  divide  up  into  eight  uninucleate 
amoebulee.  which  are  set  free  in  the 
colon  and  are  the  starting-point  of 
a  new  infection.  Schaudinn  was 
able  to  infect  himself  by  swallowing 
the  8-nucleate  cysts  of  the  amoeba. 

Prowazek  (A.P.K.,  xxii..  p.  345) 
has  described  a  variety  of  E.  coli 
under  the  name  E.  ivilliamsi. 

E.  Tiistolytica  reproduces  itself  in 
the  amoeboid  phase  by  binary  fission 
and  by  a  process  of  gemmation  iu 
which  the  nucleus  multiplies  by 
division,  and  then  small  amcebuloe, 
each  with  a  single  nucleus,  are 
budded  off  from  the  surface  of  the 
body.  In  the  process  of  gemma- 
tion, however,  the  number  of  nuclei 
in  the  body  is  irregular,  and  not 
definitely  eight,  as  in  E.  coli.  In 
its  propagative  phase  E.  liistolytica 
does  not  form  a  cyst  round  the 
whole  body,  but  its  nucleus  becomes 
resolved  into  chromidia,  which 
collect  in  patches  near  the  surface 
of  the  body.  Little  buds  are  then 
formed  as  outgrowths  of  the  body, 
each  bud  containing  a  clump  of 
chromidia.  Bo'und  each  bud  a 
sporocyst  is  formed  of  so  tough  and 
impervious  a  character  that  no 
further  cytological  study  of  the 
bud  is  possible.  The  resistant  spores  formed  in  this  way  separate  from  the. 
body,  of  which  the  greater  part  remains  as  residual  protoplasm  and  dies  off. 
The  minute  spores  are  the  means  of  infecting  a  new  host,  as  shown  by 
Schaudinn  in  experiments  on  cats,  which  are  particularly  susceptible  to  the 
attacks  of  this  amoeba. 

Schaudinn's  investigations,  of  which  a  brief  summary  has  been  given  in 
the  foregoing  paragraphs,  first  introduced  clear  ideas  into  the  problem  of  the 
human  entozoic  aruoebas.  Many  of  the  works  of  subsequent  investigators 
have  tended,  however,  rather  to  confuse  and  perplex  the  question,  for  various 
reasons.  In  the  first  place,  in  cultures  made  from  human  faeces,  free-living, 
non- parasitic  species  of  amoebae  make  their  appearance,  which  have  passed 
through  the  digestive  tract  in  an  encysted  condition,  and  emerge  from  their 

15 


FIG.  90. — Entamceba  liistolytica.  A,  Young 
specimen;  B,  an  older  specimen  crammed 
with  ingested  blood-corpuscles  ;  C,  D,  E, 
three  figures  of  a  living  arnceba  which 
contains  a  nucleus  and  three  blood - 
corpuscles,  to  show  the  changes  of  form 
and  the  ectoplasrnic  pseudopodia  :  «., 
nucleus  ;  6.c.,  blood-corpuscles.  After 
Jiirgens. 


226  THE  PROTOZOA 

cysts  in  the  cultures  ;*  such  amoeboe,  for  the  most  part  of  the  limax-iypc, 
have  been  confused  with  the  true  entozoic  amoeba,  and  have  given  rise  to 
erroneous  ideas.  Secondly,  it  is  certain  now  that  the  two  species  of  amoebae 
recognized  by  Schaudinn  does  not  exhaust  the  list  of  human  entozoic  amoebae. 
Thirdly,  it  is  possible  that  Schaudinn  did  not  see  the  entire  life-cycle  of  the 
forms  studied  by  him,  or  that  in  some  cases  he  confused  stages  of  different 
species  in  the  same  life-cycle  (compare  Hartmann,  247). 

It  is  still  doubtful  how  many  species  of  entozoic  amcebse  occur  in  man. 
Hartmann  recognizes  two  dysenteric  amcebse,  in  addition  to  the  harmless 
E.  coli :  E.  histolytica,  Schaudinn,  and  E.  tetragena,  Viereck  (synonym,  E. 
africana,  Hartmann).     E.  tetragena  has  been  described  from  various  parts 
of  the  tropics ;  it  differs  from  E.  histolytica  in  its  characters,  and  more  nearly 
resembles  E.  coli,  but  is  distinguished  by  the  formation  of  resistant  cysts 
containing  four  nuclei.      In  addition  to  these  species,  many  others  have 
been  described  by  various  investigators— for  example,  E.  minuta.  Elrnassian, 
which,  according  to  Hartmann,  is  merely  a  variety  of  E.  coli.     A  summary 
of  the  various  amcebse  described  from  the  human  intestine  is  given  by 
Doflein  (7)  and  Fantham  (241).     In  Cochin  China,  Noc  obtained  from  liver- 
abscesses  and  dysenteric  stools  a  small  amoeba  (not  named)  which  in  the 
multiplicative  phase  reproduces  in  two  ways  :  by  binary  fission  of  the  ordinary 
type  ;  and  by  budding  off  small  amcebulae  containing  secondary  nuclei  formed 
from  chromidia.     In  the  propagative  phase  Noc's  amoeba  encysts  and  breaks 
up  into  amcebulse.     Greig  and  Wells,   in  Bombay,  obtained  results  very 
similar  to  those  of  Noc.     In  cultures  from  liver-abscesses  from  Bombay, 
Listen  found  two  distinct  forms  of  amoebae — a  larger  form  containing  a  single 
nucleus  and  numerous  chromidia,  and  a  smaller  form  containing  a  nucleus 
only.     The  larger  amoeba  multiplies  either  by  binary  fission,  with  karyo- 
kinesis  of  the  nucleus  and  partition  of  the  chromidia  ;  or  by  the  formation  of 
endogenous  buds  containing  chromidia  from  which  a  secondary  nucleus  is 
formed,  the  bud  being  finally  set  free  as  a  small  amoeba  with  a  nucleus  and  a 
number  of  chromidia.     The  small  amoeba  multiples  only  by  binary  fission, 
preceded  by  amitotic  division  of  the  nucleus.     Both  large  and  small  amoebae 
form  resting  cysts,  in  which,  however,  they  remain  unchanged,  and  from 
which  they  emerge  when  circumstances  are  favourable.     It  is  evident  that 
much  of  the  life-cycle  of  these  liver-abscess  amoeba?  remains  to  be  worked  out. 
From  the  foregoing  it  is  clear  that,  with  regard  to  the  human  pathogenic 
amcebse,  many  Important  problems  remain  to  be  investigated,  especially  as 
regards    their    specific    distinctions,    distribution,    and    life-history.     Much 
recent  work  has  been  carried  on  by  culture-methods,  with  valuable  results, 
which,  however,  should  be  interpreted  with  caution,  since  it  remains  to  be 
ascertained  whether  the  forms  and  phases  assumed  by  these  organisms  in 
cultures  are  identical  in  character  with  those  which  they  exhibit  under  natural 
conditions  ;  and  until  this  point  has  been  cleared  up  it  is  not  safe  to  describe 
the  characters  of  a  species  of  an  amoeba,  any  more  than  of  a  trypanosome, 
from  cultural  forms  alone. 

With  regard  to  the  life-cycle  of  the  pathogenic  amcebse,  it  is  most  important  to 
discover  what  are  the  phases  of  development  or  conditions  of  life  under  which 
they  occur  outside  the  human  body ;  whether  they  exist  only  in  an  encysted, 
resting  condition,  or  in  an  active  state  also  ;  and,  in  the  latter  case,  whether  as 
free-living  organisms  or  within  some  other  host.  On  general  grounds  it  is  un- 
likely that  an  organism  adapted  to  an  entozoic  life  should  be  capable  also  of 
living  free  in  Nature,  and  it  is  more  probable  that  the  pathogenic  amcebse  out- 
side the  human  body  occur  only  in  the  condition  of  resting  cysts  or  spores,  which 
produce  infection  through  being  accidentally  swallowed  with  food  or  water 
(compare  Walker,  276'5).  In  that  case  unfiltered  water,  uncooked  vegetables 

*  Whether  this  also  applies  to  cultures  made  from  the  pus  of  liver-abscesses, 
as  asserted  by  Whitmore  (279)  and  Hartmann  (247),  may  well  be  doubted  ;  it  is 
rot  easy  to  understand  how  an  encysted  amoeba,  could  be  transported  passively 
from  the  intestine  into  a  liver-abscoss. 


THE  SARCODIXA 


•2-21 


and  herbs,  or  fruit  that  grows  near  the  ground,  are  likely  sources  of  infection  by 
becoming  contaminated  with  the  resting  stage  of  the  amoebae  scattered  on  the 
ground  or  in  manure.  In  this  connection  the  further  question  arises  whether 
the  human  entozoic  amoebae  are  specific  parasites  of  man  or  not,  and  conse- 
quently whether  their  infective  stages  would  be  derived  only  from  human 
faeces,  or  from  the  excreta  of  other  animals  also.  From  general  considerations 
of  parasitism  in  Protozoa,  it  seems  probable  that  the  harmless  E.  coli  is  a 
specific  parasite  of  man,  but  that  the  pathogenic 
forms  are  parasites  of  other  animals  also,  and 
perhaps  only  occasionally  find  their  way  into  the 
.Iranian  body ;  in  which  case  garden-manure  might 
be  a  fruitful  source  of  contamination,  through 
the  medium  of  vegetables  habitually  eaten 
uncooked,  such  as  lettuce,  celery,  etc.  'Xone  of 
these  questions  can  be  answered  decisively  at 
present,  however,  and  there  is  a  wide  field  of  in- 
vestigation open. 

Greig  and  Wells  found  that  in  Bombay  amoebic 
infection  shows  a  marked  seasonal  variation, 
closely  associated  with  variations  in  humidity, 
but  not  corresponding  with  those  of  temperature, 
and  reaching  its  maximum  in  August. 

In  addition  to  the  various  species  of  Am^'ni 
and  of  allied  genera  and  subgenera,  a  number  of 
o:her  genera  are  included  in  the  section  under 
consideration,  for  an  account  of  which  the  reader 
must  be  referred  to  the  larger  treatises ;  but  two 
deserve  special  mention — namely,  the  genera 
Pelomyxa  and  Paramceba. 

The  species  of  Pdomyxa  (Fig.  91)  are  fresh- 
water amcebte  of  large  size  and  "  sapropelic  " 
habit  of  life  (p.  14).  The  body,  which  may  be 
several  millimetres  in  diameter,  is  a  plasmodium 
in  the  adult  condition,  containing  some  hundreds 
of  nuclei ;  it  is  general^  very  opaque,  owing  to 
the  animal  having  the  habit  of  loading  its 
ytoplasm  with  sand  and  debris  of  all  kinds,  in 
addition  to  food  in  the  form  chiefly  of  diatoms. 
The  pseudopoclia  are  of  the  lobose  type,  blunt  and 
rounded,  but  the  animal  may  also  form  slender 
reticulose  pseudopodia  under  certain  conditions 
(Veley).  The  cytoplasm  is  very  vacuolated,  and 
contains  a  number  of  peculiar  refringent  bodies 
("  Glanzkorper ")  of  spherical  form,  with  an 
envelope  in  which  bacterial  organisms  (Cladothrix 
pdomyxce.  Veley)  occur  constantly.  The  bacteria 
multiply  by  fission  in  a  linear  series  in  the  form 
of  jointed  rods,  which  may  branch  ;  as  a  rule 
they  have  five  or  six  joints,  or  less,  but  at 
least  two.  The  refringent  bodies  are  of  albu- 
minous nature  (Veley).  According  to  Gold- 
schmidt  (57),  the  refringent  bodies  arise  from  the 
nuclei  when  they  give  off  chromidia ;  in  this 
process  the  chroinatin  is  given  off  into  the  cytoplasm,  and  the  plas-  m-basis 
of  the  karyosorne  is  left  as  a  spherical  mass  which  becomes  the  refringent 
body.  At  first  the  plastin-sphere  is  surrounded  by  the  remains  of  the  nuclear 
membrane,  which  disappears,  and  the  refringeiit  body  grows  in  size.  Re- 
fringent bodies,  with  their  bacteria,  are  seen  frequently  to  be  ejected  by  the 
animal  during  life.  Bott  (103),  on  the  other  hand,  states  that  the  refringent 
bodies  are  reserve  food-stuff,  their  contents  of  the  nature  of  glycogen.  and 


FIG.  91. — Pelomyxa  pcdus- 
tris :  a  specimen  in  which 
the  body  is  transparent 
owing  to  the  absence  of 
food-particles  and  foreign 
bodies,  showing  the 
vacuolated  cytoplasm 
and  the  numerous  nuclei 
and  refringenfc  bodies  (the 
refi'ingent  bodies  are  for 
the  most  part  larger  thari 
the  nuclei)  in  the  living 
condition.  After  Greeff, 
magnified  60. 


228 


THE  PROTOZOA 


that  they  arise  in  the  cytoplasm  independently  of  the  nuclei ;  but  their 
rejection  by  the  animal  is  more  in  favour  of  the  view  that  they  are  waste- 
products  of  the  metabolism  (Veley).  It  is  not  clear  what  is  the  role  of  the 
bacteria,  whether  they  are  parasites  or  symbionts. 

Pelomyxa  reproduces  itself  by  simple  fission  or  by  formation  of  gametes. 
The  sexual  process,  according  to  Bott,  begins  with  extrusion  of  chrouiatin 
from  the  nuclei  into  the  cytoplasm  to  form  chromidia,  which  may  take  place 
so  actively  that  sometimes  the  nuclei  break  up  altogether.  A  similar  extrusion 
of  chromidia  may  take  place  as  a  purely  regulative  process  under  certain 
conditions,  such  as  starvation  ;  but  the  vegetative  chromidia  formed  in  this- 
way,  and  absorbed  ultimately  in  the  cytoplasm,  must  be  distinguished  from 

generative  chromidia  produced 
as  a  preliminary  to  gamete- 
formation.  From  the  genera- 
tive chromidia  secondary  nuclei 
of  vesicular  structure  arise, 
which,  after  elimination  of 
chrouiatin  followed  by  reduc- 
tion (see  p.  150,  supra), 
become  the  gamete-nuclei.  The 
gametes  arise  as  spherical  in- 
ternal buds,  each  with  a  single 
nucleus,  to  the  number  of  100 
or  more,  and  are  extruded 
when  full}'  formed,  causing" 
the  parent-individual  to  break 
up  completely.  Each  free 
gamete  is  Heliozoon-like,  with 
slender,  radiating  pseudopodia ; 
they  copulate  in  pairs,  and  the 
zygote  grows  into  a  young 
Pelomyxa,  either  directly  or 
after  a  resting  period  in  an 
encysted  condition. 

The  genus  Paramceba  (Fig. 
49)  was  founded  by  Schaudinn 
(81)  for  the  species  P.  eilhardi 
discovered  by  him  in  a  marine 
aquarium  in  Berlin.*  In  the 
adult  stage  the  animal  occurs 
as  an  amoeba,  from  10  to  90  p. 
in  diameter,  of  rather  flattened 
form  and  with  lobose  pseudo- 


N 


^R 


FIG.  92. — Portion  of  a  section  through  the  body 
of  Pelomyxa.  N.,  Nucleus  ;  r.b.,  refringent 
bodies ;  b.,  bacteria  on  the  refringent  bodies  ; 
s.,  sand  and  debris  in  the  protoplasm.  After 
Gould. 


podia.  It  contains  a  single 
nucleus,  and  near  it  a  peculiar 
body,  the  "  Nebenkern "  of 
Schaudinn  (see  p.  95).  In 

this  phase  the  amceba  multiplies  by  binary  fission  accompanied  by 
division  both  of  nucleus  and  Nebenkern.  It  also  becomes  encysted  and 
goes  through  a  process  of  multiple  fission,  which  shows  three  stages  ;  in  the 
lirst  the  Nebenkern  multiplies  by  repeated  division,  the  nucleus  remaining 
unchanged  ;  in  the  second  the  nucleus  divides  repeatedly  to  form  as  many- 
small  nuclei  as  there  are  Nebenkerne  present,  and  each  nucleus  attaches  itself 
to  a  Nebenkern  ;  in  the  third  the  protoplasmic  body  undergoes  radial  super- 
ficial cleavage  into  a  number  of  cells,  each  containing  a  nucleus  and  a  Neben- 
kern, Each  of  the  cells  thus  formed  becomes  a  swarm-spore  with  two  flagella. 

*  The  amceba  from  the  human  intestine  described  by  Craig  under  the  name 
Param&ba  hominis  certainly  does  not  belong  to  this  genus.  See  Dofiein  (7), 
pp.  602,  603. 


THE  SARCODINA  229 

The  swarm-spores  are  liberated  from  the  cyst  and  live  freely,  feeding  and 
multiplying  by  binary  fission,  in  which  the  nucleus  divides  by  mitosis  and  the 
Nebenkern  acts  like  a  centrosome.  After  a  time,  however,  the  swarm-spores 
lose  their  flagella,  and  become  amcebulae  which  develop  into  the  adult  phase. 
Syngamy  was  not  observed,  but  probably  takes  place  between  the  flagellulse. 
Two  new  parasitic  species  of  Paramceba  have  been  described  recently  by 
Janicki  (71-5) ;  see  p.  95. 

To  the  order  Amoebeea  should  be  referred,  probably,  the  parasite  of  the 
Malpighian  tubules  of  the  rat-flea  (Ceratophyllus  fasciatus),  described  by 
Minchin  under  the  name  MalpigJiiella  refringens,  and  the  parasite  of  Ptychodera 
•ninuta,  described  by  Sun  under  the  name  Protoentospora  ptychoderce. 

The  section  Lobosa  Testacea  or  Thecamcebae  contains  a  number 
of  free-living  forms  familiar  to  every  microscopist,  such  as  the 
genera  Difflugia  (Fig.  16),  C entropy xis,  Arcella  (Fig.  32),  etc.  The 
majority  of  these  forms  inhabit  fresh  water,  but  Trichosphcerium 
(Fig.  81)  is  marine.  Their  common  distinctive  feature,  in  addition 
to  the  possession  of  lobose  pseudopodia,  is  the  formation  of  a  shell 
or  house  into  which  they  can  be  withdrawn  entirely.  The  shell  may 
te  secreted  by  the  animal,  and  then  is  chitinous  (Arcella)  or  gelat- 
inous (Trichosphcerium),  or  may  be  made  up  of  various  foreign 
bodies  cemented  together  (Difflugia).  Typically  the  house  has  the 
form  of  a  chamber  with  a  single  large  opening,  through  which  the 
pseudopodia  are  extruded  at  one  pole. 

When  the  animal  multiplies  by  fission,  the  protoplasm  streams 
out  through  the  aperture,  and  forms  a  daughter-shell  external  to 
the  old  one,  after  which  division  of  the  nucleus  takes  place  and  the 
two  sister-individuals  separate.  In  Trichosphcerium,  however,  the 
house  has  the  form  of  a  gelatinous  investment  to  the  body,  with 
several  apertures  through  which  pseudopodia  protrude,  and  when 
the  animal  divides  the  investing  envelope  divides  with  it. 

The  protoplasmic  body  contains  typically  one  nucleus — some- 
times more  than  one — surrounded  by  a  ring  of  chromidia.  In 
Arcella  vulgaris  there  are  constantly  two  primary  nuclei ;  in 
Difflugia  urceolata,  from  ten  to  thirty.  Trichosphcerium  possesses 
many  nuclei,  but  no  chromidia. 

The  life-cycle,  so  far  as  is  known,  is  of  various  types  ;  those  of 
Arcella  and  Trichosphcerium  are  described  above  (p.  177,  Fig.  80, 
and  p.  181,  Fig.  81).  The  latter,  with  an  alternation  of  generations 
combined  with  dimorphism  in  the  adult  condition,  approaches  that 
of  the  Foraminifera  in  character. 

In  the  testaceous  amoebae  the  method  of  division  varies  in  accordance 
with  the  nature  of  the  shell.  In  those  in  which  the  shell  is  soft  and  yielding, 
as,  for  example,  Cocliliopodium  and  Cryptodifflugia,  the  division  is  longitudinal 
—i.e.,  in  a  plane  which  includes  the  axis  passing  through  the  mouth  and 
apex  of  the  shell  (Doflein,  239)  ;  in  Cryptodifflugia  rapid  division  of  this  kind 
may  lead  to  colony-formation.  In  forms  with  a  rigid  shell,  on  the  other  hand, 
such  as  Difflugia,  Arcella,  Centropyxis,  etc.,  the  shell  sets  a  limit  to  the  growth 
of  the  animal,  which,  when  it  has  filled  the  shell,  ceases  to  grow  for  a  while 


230  THE  PROTOZOA 

and  stores  up  reserve-material.  Prior  to  division  a  sudden  and  rapid  growth 
takes  place  at  the  expense  of  the  reserve-material  and  by  absorption  of  water  ; 
as  a  result  the  protoplasm  grows  out  of  the  shell-mouth,  a  daughter-shell  is 
formed,  and  the  animal  divides  transversely  (Fig.  50). 

In  Difflugia  urceolata,  Zuelzer  (85)  has  described  a  process  of  chroniidiogamy. 
Two  animals  come  together  with  the  mouths  of  the  shells  in  contact,  and  the 
entire  contents  of  one  shell  flow  over  into  the  other,  the  empty  shell  being 
cast  off.  The  chromidia  of  the  two  animals  fuse  into  a  single  mass  ;  the 
nuclei,  however,  remain  separate.  Copulation  of  this  kind  is  a  preliminary 
to  encystment,  which  takes  place  in  Nature  at  the  end  of  October  or  the 
beginning  of  November.  Prior  to  encystment  the  pseudopodia  are  retracted. 
alf  foreign  bodies,  food-remains,  excreta,  etc.,  are  cast  out,  and  the  proto- 
plasmic "body  rounds  itself  off  in  the  shell,  and  diminishes  to  about  a  quarter 
of  its  former  volume,  becoming  denser  and  more  refractile.  The  cyst- 
membrane  is  then  secreted  at  the  surface  of  the  body.  The  old  nuclei  are 
gradually  absorbed,  and  new  nuclei  are  formed  from  the  chroniidial  rn; 
The  recbnstitution  of  the  nuclear  apparatus  takes  place  from  January  to 
April ;  in  the  spring  the  cyst  is  dissolved,  and  the  rejuvenated  Difflugia  begins 
to  feed  and  to  enter  upon  a  summer  course  of  vegetative  growth  and  repro- 
duction. In  a  recent  note  (86,  p.  191,  footnote)  Zuelzer  states  that  conjuga- 
tion between  free  gametes  also  occurs  in  this  species. 

'  In  Centropyxis  aculeata,  according  to  Schaudinn  (131 ),  the  ordinary  vegeta- 
tive reproduction  is  by  fission,  the  new  shell  that  is  formed  being  larger  than 
the  old  one,  until  the  maximum  size  is  reached.  Sexual  processes  are 
initiated  by  degeneration  of  the  .primary  nucleus,  which  is  single  in  this 
species.  Then  the  protoplasm  with  tlie  chromidia  creeps  out  of  the  shell 
and  divides  into  a  number  of  amcebulse,  each  containing  chromidia  which 
condense  into  a  single  nucleus.  Some  amcebula?  form  a  shell  at  once  ;  others 
before  doing  so  divide  into  four  smaller  arncebulse,  and  then  form  a  shell. 
The  larger  are  macrogametes,  the  smaller  the  microgametes  :  they  copulate 
and  abandon  their  shells.  The  zygote  forms  a  new  shell,  chromidia  appear, 
and  a  fresh  vegetative  cycle  is  started. 

In  a  species  of  the  genus  Cryptodifflugia  ("  Allogromia")  a  remarkable 
type  of  life-cycle  has  been  described  by  Prandtl  (265);  see  also  Doflein  (7), 
p.  310,  Fig.  283.  In  this  form  also  the  organism,  at  the  time  of  garnet e- 
t'ormat'ion,  quits  its  shell  and  penetrates  into  some  other  Protozoan  organism, 
such  as  Amceba  proteus,  in  the  body  of  which  it  becomes  parasitic  and  goes 
through  the  process  of  gamete-formation.  The  nucleus  breaks  up  into 
chromidia,  from  which  secondary  nuclei  are  formed,  producing  a  multinucleate 
plasmodium  which  multiplies  by  plasmotoniy  until  the  host  is  full  of  them. 
Ultimately  the  plasmodia  break  up  into  uninucleate  cells,  the  gametes,  which 
are  set  free  and  copulate.  The  zygote  becomes  a  flagellated  Bodo-Uke 
organism,  with  two  flagella,  one  directed  forward,  the  other  backward  as  a 
trailing  flagellum  (p.  270,  infra)  ;  it  feeds  and  multiplies  in  this  form  for 
several  generations  in  the  free  state,  but  ultimately  it  loses  its  flagella,  becomes 
amoeboid,  forms  a  shell,  and  develops  into  an  adult  Cryptodifflugia.  Note- 
worthy in  this  development  are  the  alternation  of  generations  between  the 
flagellated  and  the  amceboid  phase,  as  in  Pseudospora  (p.  218),  and  the  para- 
sitism in  the  gamete-forming  phases;  if,  however,  the  Cryptodifflugia  does 
not  succeed  in  finding  a  suitable  host,  the  gamete-formation  may  take  place 
in  the  free  state. 

From  the  life-cycles  and  sexual  processes  of  Arcella,  Difflugia,  Centropyxis, 
etc.,  it  is  seen  that  the  primary  nuclei  of  all  these  forms  are  vegetative  in  nature, 
while  the  chromidia  give  rise  to  the  gamete -nuclei,  and  consist  of,  or  at  least 
contain,  the  generative  chromatin.  The  marine  Tricliosplicerium,  however, 
stands  apart  from  the  fresh-water  genera  in  regard  to  its  structure,  sexual 
processes,  and  life-cycle,  in  all  of  which  it  shows  more  similarity  to  the 
Foraminifera. 


THE  SARCODINA  231 

II.    FORAMINIFERA. 

General  Characters — Shell -Structure. — The  characteristic  features 
of  this  group  are  the  possession  of  reticulose  pseudopodia  and  of  a 
shell  or  test.  The  Forarniriifera  are  typically  creeping  forms, 
moving  slowly,  and  using  their  net-like  pseudopodia  chiefly  for  food- 
capture.  Certain  genera,  however,  such  as  Globigerina,  have  taken 
secondarily  to  a  pelagic  existence,  and  float  on  the  surface  of  the 
ocean,  spreading  their  nets  in  all  directions  around  them.  On 
the  other  hand,  some  forms  have  adopted  a  sedentary  life,  attaching 
themselves  firmly  to  some  object.  An  example  is  seen  in  the  genus 
Haliphysema  (Fig.  17).  once  believed  to  be  a  sponge,  and  in  the 
remarkable  genus  Polytrema  and  allied  forms,  recently  monographed 
by  Hickson  (282) — organisms  which  in  many  cases  have  a  striking 
and  deceptive  resemblance  to  corals. 

The  test  may  be  secreted  by  the  animal  itself,  and  then  is  usually 
either  chitinous  or  calcareous,  rarely  siliceous  or  gelatinous  (Myxo- 
theca]  ;  or  it  may  be  made  up  of  foreign  bodies  cemented  together, 
as  in  Haliphysema  (Fig.  17),  and  is  termed  generally  "  arenaceous," 
but  the  materials  used  may  be  of  various  kinds,  and  the  organism 
sometimes  exhibits  a  remarkable  power  of  selection  (see  p.  34,  supra}. 

The  typical  form  of  the  shell,  as  in  the  Amoebaea  Testacea,  is  a 
chamber  with  a  wide  aperture — sometimes  more  than  one- 
through  which  the  pseudopodia  are  extruded,  as  in  Gromia  (Fig.  21). 
In  addition  to  the  principal  aperture,  the  wall  of  the  shell  may  be 
perforated  by  numerous  fine  pores,  through  which  also  the  protoplasm 
can  stream  out  to  the  exterior.  Hence  the  shells  of  Foraminifera 
are  distinguished  primarily  as  perforate  and  imperforate,  the  former 
with,  the  latter  Avitliout,  fine  pores  in  addition  to  the  principal 
opening. 

Whether  perforate  or  imperforate,  the  shell  remains  a  single 
chamber  in  the  simple  forms,  as  in  the  Arnoebasa  Testacea.  In.  some 
cases,  when  the  animal  reproduces  itself  by  binary  fission,  the  proto- 
plasm streams  out  through  the  principal  aperture  to  give  rise  to 
the  body  of  the  daughter-individual,  which  forms  a  shell  for  itself, 
and,  when  the  division  is  complete,  separates  completely  from  the 
mother,  which  retains  the  old  shell.  Division  of  this  type  is  seen 
in  Euglypha  (Fig.  59).  But  in  many  species,  when  the  animal  out- 
grows its  original  single-chambered  shell,  the  protoplasm  flows  out 
and  forms  another  chamber,  which,  however,  is  not  separated  off 
as  a  distinct  individual,  but  remains  continuous  with  the  old  shell, 
so  that  the  animal,  instead  of  reproducing  itself  by  fission,  remains 
a  single  individual  with  a  two-chambered  shell.  By  further  growth, 
third,  fourth,  . .  .nth  chambers  are  formed  successively,  each  newly- 
formed  chamber  being,  as  a  rule,  slightly  larger  than  that  formed 


232 


THE  PROTOZOA 


just  before.  Hence  a  distinction  must  be  drawn  between  mono- 
thalamous  or  single-chambered  shells  and  polythalamous  shells, 
made  up  of  many  chambers  formed  successively.  In  the  latter 
type  the  new  chambers  may  be  joined  in  various  ways  to  the  old, 


I.Saccammina 


2.Lagena 


3-Nodosaria 


4.Frondicu!aria         6.Clobigerina 


7.  Discorbina 


O.PIanorbulina  10  ll.Nummulires 

FIG.  93. — Shells  of  various  genera  of  Foraminifera.  In  3,  4,  and  5,  a  shows  the 
surface-view,  and  b  a  section  ;  8a  is  a  diagram  of  a  coiled  shell  without  supple- 
mental skeleton  ;  86,  of  a  similar  form  with  supplemental  skeleton  (s.sk.) ; 
10,  of  a  form  with  overlapping  whorls  ;  in  11  a  half  the  shell  is  shown  in  hori- 
zontal section  ;  b  is  a  vertical  section.  In  all  the  figures  a  marks  the  aperture 
of  the  shell ;  1  to  15,  the  successive  chambers,  1  being  always  the  oldest  or 
initial  chamber.  From  Parker  and  Haswell. 

producing  usually  either  a  linear  or  a  spiral  series,  and  the  utmost 
variety  of  shape  and  pattern  results  in  different  species  (Fig.  93). 
Some  polythalamous  species  exhibit  a  peculiar  dimorphism  (Fig.  94) ; 


THE  SARCODINA 


233 


in  some  individuals,  hence  termed  microspheric,  the  initial  chamber  of 
the  shell  is  smaller  than  in  others,  which  are  known  as  megalospheric. 
This  point  will  be  discussed  further  under  the  reproduction. 

It  may  be  noted  that  if,  in  this  order,  a  species  were  to  form  no 
shell,  whether  from  having  secondarily  lost  the  habit  or  as  a  primi- 
tive form  which  had  never  acquired  it,  then  such  a  species  would  be 
classed  in  the  order  Amcebaea  Reticulosa.  It  is  very  probable  that 
many  of  the  large  marine  "  Proteomyxa  "  are  allied  to  the  true 


a 


FIG.  94. — Biloculina  depressa:  transverse  sections  of  (a)  the  megalospheric  form, 
magnified  50  diameters,  and  (6)  the  microspheric  form,  magnified  90  diameters. 
After  Schlurnberger,  from  Lister. 

Foraminifera,  as  forms  either  primitively  or  secondarily  without  a 
test ;  and  Rhumbler  unites  the  Foraminif  era  proper  with  the  naked 
forms  in  the  section  Reticulosa. 

The  body-protoplasm  exhibits  no  marked  distinction  of  ecto- 
plasm and  endoplasm.  Contractile  vacuoles  are  present  in  some 
of  the  fresh- water  genera,  but  are  not  found  in  marine  forms. 
The  protoplasm  contains  metaplastic  bodies  of  various  kinds,  and 
may  become  loaded  with  faecal  matter  in  the  form  of  masses  of 
brown  granules,  termed  by  Schaudinn  the  "  stercome  "  (compare  also 
Awerinzew,  281).  Periodically  a  process  of  defaecation  takes  place, 
whereby  the  protoplasm  is  cleared  of  these  accumulations,  often  as 
a  prelude  to  the  formation  of  a  new  chamber  (Winter,  28).  The 


234 


THE  PROTOZOA 


nuclear  apparatus  varies  in  different  forms,  even  in  the  same  species, 
as  will  be  seen  in  the  description  of  the  reproductive  processes. 

The  marine  Foraminifera,  so  far  as  they  have  been  investigated, 
show  a  well-marked  alternation  of  generations  in  their  life-history, 


St. 


^ST-^r^~7-v» 

•$.  ;^>'A  iA^AsB; .'  ••:•; ^..lu^g. 


FIG.  95. — Polystomella  crispa:  decalcified  specimens  to  show  the  structure  of  the 
two  forms.  A,  The  megalospheric  type  ;  B,  the  microspheric  type  :  6,  the 
central  chambers  of  the  latter  more  highly  magnified;  r.,  retral  processes; 
st,  communications  between  the  chambers.  From  Lister. 

combined  with  dimorphism  in  the  adult  condition.     An  example  is 
Polystomella,   which   has   been   investigated   by  Lister    (285)   and 


THE  SARCODINA  235 

Schaudiim  (131)  ;  their  results  have  been  confirmed  in  the  case  of 
Peneroplis  by  Winter,  who  gives  a  useful  combined  diagram  of  the 
life -history  (28,  p.  16,  text -fig.  A).  The  raicrospheric  form 
(Fig.  95,  B.)  has  many  nuclei,  which  multiply  by  fission  as  the 
animal  grows,  and  which  also  give  off  chromidia  into  the  body- 
protoplasm.  When  reproduction  begins,  the  nuclei  become  resolved 
entirely  into  chromidia,  and  the  protoplasm  streams  out  of  the 
shell,  which  is  abandoned  altogether.  Secondary  nuclei  are  formed 
from  the  chromidia,  and  the  protoplasmic  mass  divides  up  into  a 
swarm  of  about  200  amcebulse  (Fig.  96).  Each  amoebula  contains 
a  nucleus  and  chromidia,  and  secretes  a  single-chambered  shell, 
which  is  the  initial  chamber  of  a  megalospheric  individual.  The 
amcebulse  separate,  and  each  one  feeds,  grows,  forms  new  chambers 
successively,  and  becomes  a  megalospheric  adult.  Thus  the  micro- 
spheric  form  is  seen  to  be  an  agamont  or  schizont,  which  gives  rise 
by  a  process  of  schizogony  or  multiple  fission  to  agametes  (amce- 
bulse). The  megalospheric  form,  when  full  grown,  has  a  single 
large  nucleus  and  numerous  chromidia  (Fig.  95,  A}.  The  nucleus 
is  that  of  the  amoebula  which  was  the  initial  stage  in  the  develop- 
ment of  this  form. ;  as  it  grows  the  nucleus  passes  from  chamber  to 
chamber,  and  at  the  same  time  gives  off  chromidia  into  the  cyto- 
plasm. Finally  the  primary  nucleus  is  resolved  entirely  into 
chromidia,  from  which  a  great  number  of  secondary  nuclei  are 
formed.  Round  each  such  nucleus  the  protoplasm  becomes  con- 
centrated to  form  a  small  cell,  which  may  be  termed  a  gameto- 
i.-yte.  By  two  divisions  of  the  nucleus  and  cell  -  body  of  the 
gametocyte  four  gametes  are  formed,  each  of  which  acquires  two 
flagella,  and  is  set  free  as  a  biflagellate  swarm-spore.  In  Peneroplis, 
however,  the  gametes  have  a  single  flagellum,  and  in  Allogromia 
ovoidea  the  gametes  are  amcebulse  (Swarczewsky).  Gametes  pro- 
duced by  different  individuals  copulate,  losing  their  flagella  in  the 
process,  and  the  zygote  secretes  a  minute  single-chambered  shell, 
and  thus  becomes  the  starting-point  of  the  growth  of  a  micro- 
spheric  individual. 

From  the  foregoing  it  is  seen  that  the  megalospheric  form  is  the  gamont. 
which  by  multiple  fission  produces  the  gauietocytes,  and  ultimately  the 
gametes.  Thus,  if  m.  represents  the  microspheric  form  and  M.  the  megalo- 
spheric, am.  the" amcebulse  (agametes).  and  ft.  the  flagellulas  (gametes),  the 
life-cycle  may  be  represented  thus  : 

m. — am. — M. — (fl.  +  fl.) — m. — am.  .  .  . 

In  some  cases,  however,  the  life-cycle  does  not  present  a  regular  alternation 
of  sexual  and  non-sexual  generations,  but  a  number  of  non-sexual  generations 
may  take  place  before  a  sexual  generation  intervenes  ;  that  is  to  say,  the 
megalospheric  forms  may  produce  agametes  and  other  megalospheric  forms 
again  for  several  generations,  before  gametes  are  produced  and  the  sexual 
processes  occur.  Then  the  life-cycle  may  be  represented  thus  :| 

m. — am. — M. — am. — M. — am.  .  .  ,     M. — (fl.  +  fl.) — m. — am. — M.  .  .  . 


r  /  !  ipf?  * 


^  r;u,as 

._.  V'^V  \'  ''T^^A**-^'^ 


^^e><^W;><  ^^pSBBaSa^ 

..-  .  ,  ^  vi/ja^-i.-^-S-tS^' "-.  •«•-  ir*,x;T*-X/ii  .  ,.;-&  3  A 


FIG.  96. — Stages  in  the  reproduction 
of  the  microspheric  form  of  Poly- 
stomella  crispa.  In  a  the  protoplasm 
is  streaming  out  of  the  shell ;  in  b 
and  c  it  is  becoming  divided  up 
into  amoebulffl  ;  in  d  the  amcebulse, 
having  each  formed  a  single- 
chambered  shell,  are  dispersing 
in  all  directions,  abandoning  the 
empty  shell  of  the  parent.  From 
Lister,  drawn  from  photographs 
of  one  specimen  attached  to  the 
walls  of  a  glass  vessel. 


w 


n  / 

£     i  '      r 


V,  ©         O  0 

&P-  0«^ 

^  Vt^ 

«.       / 


»*-vx  r-Jsif*  ••'  •?-•- 

^^    '•    ^p       ,  f       f    £jv''  A       f>ff 

\  ^/^\jffwr- 


t,s^.^4^tJS^ s*—    J    j 

p-y--^%^*^C^ 
=e>— ©— feO-Cs-^^S^^;^ 


•€^;r«f^    ^ 

^ 


1^ 


!^$\  jT  1 

-/If    V  ^ ' 

•    1  ^e  x 


THE  SARCODINA  23T 

Hence  the  dimorphism  of  the  adults  is  due  to  their  parentage,  and  is  not 
necessarily  related  to  the  manner  in  which  they  reproduce.  A  microspheric 
form  is  produced  sexually,  and  is  always  an  agamont ;  a  megalospheric  form 
is  produced  non-sexually,  and  may  be  either  a  gamont  or  an  agamont. 

Very  little  is  known  of  the  life-cycle  of  the  non-marine  genera.  The  only 
form  of  which  the  cycle  is  known  with  any  approach  to  completeness  is 
Chlamydophrys  stercorea,  the  only  entozoic  member  of  the  order,  which  is- 
found  in  the  faeces  of  various  vertebrates ;  a  second  species,  C.  schaudinni,  is 
distinguished  by  Schiissler  (A.P.K.,  xxii.,  p.  366).  The  adult  form  has  a 
chitinous  single-chambered  shell,  and  its  protoplasm  contains  a  single  nucleus 
and  a  ring  of  chrornidia.  It  reproduces  itself  vegetatively  by  binary  fission, 
and  also  by  multiple  fission  producing  gametes.  In  the  gamete-formation, 
according  to  Schaudinn  (131),  the  nucleus  is  ejected  from  the  shell  together 
with  all  foreign  bodies,  food-particles,  etc.  In  the  shell  is  left  a  small  quantity 
of  protoplasm  containing  the  chromidia,  from  which  about  eight  secondary 
nuclei  are  formed,  and  then  the  protoplasm  concentrates  round  each  nucleus 
and  divides  up  into  as  many  cells,  the  gametes,  each  of  which  becomes  a. 
biflagellate  swarm-spore,  and  is  set  free.  The  gametes  copulate  and  the  zygote 
encysts.  In  order  to  develop  further,  the  cyst  must  be  swallowed  by  a 
suitable  host  and  pass  through  its  digestive  tract.  If  this  happens,  the  cyst 
germinates  in  the  hind-gut,  setting  free  an  amcebula  which  forms  a  shell  and 
becomes  a  young  Chlamydoplirys,  living  as  a  harmless  inhabitant  of  the  hind- 
gut,  and  feeding  on  various  organisms  or  waste  products  occurring  there  ;  but 
according  to  Schaudinn  it  may,  under  circumstances  not  yet  defined  or 
explained,  pass  from  the  digestive  tract  into  the  peritoneal  cavity,  and 
multiply  there  as  an  amoeboid  form  without  a  shell,  thus  giving  rise  to  the 
organism  described  by  Leyden  and  Schaudinn,  from  ascites-fluicl,  under  the 
name  Leydenia  gemmipara. 

The  Foraininifera  as  a  group  comprise  a  vast  number  of  genera 
and  species,  both  recent  and  fossil,  for  an  account  of  which  the 
reader  must  be  referred  to  the  larger  works.  They  are  classified 
by  Lister  (286)  into  ten  orders  (suborders  ?),  containing  in  all  thirty- 
two  families  ;  Rhumbler  (288)  recognizes  ten  families  in  all.  The 
vast  majority  are  marine,  but  some  of  the  simpler  forms,  such  as 
Euglypha,  are  found  in  fresh  water,  and  can  scarcely  be  separated 
from  the  Lobosa  except  by  the  characters  of  their  pseudopodia,  a 
feature  upon  which  great  weight  cannot  be  laid  as  an  indication 
of  affinity.  Until  the  life-histories  of  these  simpler  forms  have  been 
studied,  their  true  systematic  position  must  be  considered  as  some- 
what uncertain.  But  the  affinities  of  such  genera  as  Euglypha 
and  Chlamydophrys  would  seem  to  be  with  the  Lobosa  Testacea, 
rather  than  with  the  Forarninifera. 


III.  XEXOPHYOPHORA. 

This  group  was  founded  by  F.  E.  Schulze  (290)  for  a  number  of 
curious  organisms  of  deep-sea  habitat,  the  zoological  position  of 
which  was  a  matter  of  dispute.  By  Haeckel  they  were  believed 
to  be  sponges  allied  to  Keratosa,  such  as  Spongettiidce,  horny  sponges 
which  load  the  spongiii-fibres  of  the  skeleton  with  foreign  bodies  of 
various  kinds.  Schulze  established  definitely  their  relationship  to- 


238  THE  PROTOZOA 

the  Rhizopoda  by  showing  that  the  soft  body  was  a  plasmodium 
containing  numerous  nuclei  and  chromidia,  and  forming  a 
pseudopodial  network,  but  with  110  cell-differentiation  or  tissue- 
formation. 

The  body  consists  principally  of  a  network  of  hollow  tubes  in 
which  the  plasmodium  is  contained.  The  Avail  of  the  tubes  con- 
sists of  a  hyaline  organic  substance  resembling  spongin.  In  the 
interspaces  between  the  tubes  great  numbers  of  foreign  bodies 
("  xenophya,"  Haecke])  are  deposited,  such  as  sand-grains,  spoiige- 
spicules,  Radiolarian  skeletons,  and  so  forth.  In  one  family 
(Stannomidce)  the  xenophya  are  held  together  by  a  system  of  threads. 
"  linellee,"  in  the  form  of  smooth,  refringent  filaments,  approxi- 
mately cylindrical,  which  pass  from  one  foreign  body  to  another,  and 
are  attached  to  them  by  trumpet-like  expansions  of  their  ends. 
The  substance  of  the  linellse  is  doubly  refractile,  and  allied  to  spongin 
in  its  chemical  nature.  Schulze  compares  them  to  the  capillitium 
of  the  Mycetozoa  (see  p.  241,  infra). 

The  protoplasmic  body  within  the  tubes  contains,  in  addition 
to  nuclei  and  chromidia,  enclosures  of  various  kinds.  Many  tubes, 
distinguished  by  the  darker  colour  of  their  walls,  contain  quantities 
of  brown  masses,  apparently  of  fsecal  nature,  and  comparable  to 
the  stercome  of  the  Foraminifera  (p.  233).  In  other  tubes,  lighter 
in  colour,  there  are  found  small,  oval,  strongly-refractile  granules, 
or  "  granellse,"  which  consist  chiefly  of  barium  sulphate.  Schulze 
terms  the  system  of  stercome-containing  tubes  the  "  stercomarium," 
and  those  that  contain  granellse  the  "  granellarium."  The  tubes 
of  each  system  are  distinguishable  by  their  mode  of  branching,  as 
well  as  by  their  colour  and  contents.  In  the  tubes  of  the  granel- 
larium the  protoplasmic  bodies  are  often  found  to  contain  isolated 
cells  or  groups  of  cells,  each  with  a  single  nucleus,  which  are  prob- 
ably stages  in  the  formation  of  swarm-spores.  Hence  the  sterco- 
marium probably  represents  the  purely  vegetative  part  of  the  body, 
in  which  the  waste  products  of  metabolism  are  deposited,  while  the 
granellarium  is  a  differentiated  region  oj:  the  plasmodium  in  which 
the  reproductive  elements  are  produced. 

Nothing  is  known  of  the  actual  life-cycle  of  these  organisms,  but 
from  the  appearances  already  described,  seen  in  preserved  speci- 
mens, Schulze  conjectures  that  they  reproduce  by  formation  of 
swarm-spores,  much  as  is  known,  to  take  place  in  the  Foram- 
inifera. 

The  affinities  of  the  Xenophyophora  are  seen  to  be  with  the 
Foraminifera.  In  their  habit  of  forming  a  skeleton  of  foreign 
bodies  they  resemble  the  arenaceous  Foraminifera,  in  which,  how- 
ever, the  foreign  bodies  build  up  the  house  which  directly  encloses 
the  soft  body,  while  in  the  Xenophyophora  the  soft  body  is  en- 


THE  SARCODINA 


239 


ctf 


closed  actually  within  the  system  of  tubes.     Nothing  similar  to  the 
linellse  is  known  in  any  Foraminifera. 

For  the  classification  of  the  Xenophyophora  and  their  genera  see 
Schulze  (290). 

IV.  MYCETOZOA. 

The  Mycetozoa  are  a  group  of  semi-terrestrial  Rhizopods  occur- 
ring in  various  situations,  especially  on  dead  wood  or  decaying 
vegetable  matter  of  various  kinds.  Their  most  characteristic 
features  are  the  formation  of  plasmodia,  which  represent  the  adult, 
vegetative  phase  of  the  life-history,  and  their  method  of  repro- 
duction, consisting  in  the  formation  of  resistant  spores  very  similar 
to  those  of  fungi.  The  Mycetozoa  were  originally  classified  amongst 
the  Fungi  as  a  group  under  the  name  Myxomycetes,  but  the  in- 
vestigations of  de  Bary  first  made  clear  their  Rhizopod  affinities. 

The  life-history  of  a  typical  member  of  this  group  exhibits  a 
succession  of  phases,  the  description  of  which  may  conveniently 
begin  with  the  spore.  Each  spore  is 
a  spherical  cell  with  a  single  nucleus, 
enclosed  in  a  tough  protective  envelope 
which  enables  it  to  resist  desiccation. 
It  may  be  dormant  for  a  considerable 

«/ 

period,  and  germinates  when  placed 

in  water.     The  envelope  bursts,  and 

the    contained    cell    creeps    out    as 

an   amcebula  with   a   single  nucleus 

(Fig.  97),  the  so-called  "  myxamoeba." 

After  a  time  the  amcebula  develops 

a  flagellum,  and  becomes  a  flagellula 

or  zoospore  ("  myxo flagellate"),  which 

feeds  and  multiplies  by  fission.     The 

flagellula  (Fig.  98)  retains  its  amceboid 

form,  and  sometimes  also  the  amoeboid  method  of  locomotion,  the 

flagellum  appearing  to  act  as  a  tactile  organ.     It  captures  bacteria 

and  other  organisms  by  means  of  its  pseudopodia,  nourishing  itself 

in   a   holozoic,  perhaps   also    in    a    saprophytic,  manner.     It  also 

may  become  temporarily  encysted. 

The  flagellate  phase  is  succeeded  by  a  second  amoeboid  stage, 
the  flagellum  being  lost.  The  anicebulse  of  this  stage  tend  to  con- 
gregate together  in  certain  spots,  and  the  groups  thus  formed  fuse 
together  (their  nuclei,  however,  remaining  separate)  to  form  the 
plasmodium,  the  dominant  vegetative  stage,  which  feeds  and  grows, 
its  nuclei  multiplying  as  it  does  so,  until  from  the  small  mass  of 
protoplasm  formed  originally  by  the  ainoebulee,  with  relatively  few 
nuclei,  it  becomes  a  sheet  or  network  of  protoplasm,  which  may 


FIQ.  97. — The  hatching  of  a  spore 
of  Fuligo  septica.  a,  Spore ;  b, 
c,  contents  emerging  and  under- 
going am  oaboid  movements  prior 
to  the  assumption  of  the  nagel- 
lula-stage ;  d,  flagellula.  c.v., 
Contractile  vacuole.  After  Lister, 
magnified  1,100. 


240 


THE  PROTOZOA 


be  several  inches  across  and  contain  many  thousands  of  nuclei. 

The  plasmodium  moves  about  in  various  directions,  showing 

exquisite  streaming  movements  of  the  proto- 
plasmic body  (Fig.  99).  The  nature  of  the 
food  varies  in  different  species  ;  the  majority 
feed  on  dead  vegetable  matter,  but  some 
attack  and  devour  living  fungi.  The  mode 
of  nutrition  is  generally  holozoic,  but  in 
some  cases  perhaps  saprophytic.  Contractile 
vacuoles  are  present  in  large  numbers  in 
the  protoplasm,  in  addition  to  the  innumer- 
able nuclei,  which  are  all  similar  and  not 

FIG.    98.  _  Flagellula   of    differentiated  in  any  way.     The  plasmodia 

Stemonitis  fusca,  show-  are  often  brightly  coloured. 
ins  successive  stages  in          ^  ,,     .  ,         ,.   ,.r       ,,          ,  ,. 

the  capture  of  a  bacillus.          From   tlieir  mocle   of   llfe>  tlie   plasmodia 

In  a  it  is  captured  by  are  naturally  liable  to  desiccation,  and  when 

a?ethef  htSTin1:    *is  occurs  the  plasmodium  passes  into  the 
it  is  enclosed  in  a  diges-     sclerotial   condition,  in    which    the    proto- 


a 


an 


anterior     vacuole.     containing   ten   to   twenty   nuclei.     When 
From  Lister,  magnified    moistened,   the  cysts  germinate,   the  con- 

tained masses  of  protoplasm  fuse  together, 

and  so  reconstitute  the  active  plasmodium  again. 

The  plasmodium  represents  the  trophic,  vegetative  phase,  which 

is  succeeded  by  the  reproductive  phase,  apparently  in  response  to 

external  conditions,  such 

as  drought,  but  more  es- 

pecially scarcity  of  food. 

The  reproduction    begins 

by  the    plasmodium    be- 

coming   concentrated    at 

one  or  more  spots,  where 

the     protoplasm     aggre- 

gates     and      grows     up 

into  a  lobe  or  eminence, 

the     beginning     of     the 

sporangium     (Fig.    100), 

the  capsule  in  which  the 

spores    are  found.      The 

sporangium  is  modelled, 

as    it    were    on    the    soft 

protoplasmic     body,    and 

takes     the    form     of     a 

rounded    capsule,   attached    to    the    substratum    by    a    disc-like 

attachment  known  as  the  hypothallus.      Between  the  sporangium 


:  ? 


a  plasmodium  of  Badhamia 
utricularis  expanded  over  a  slide.  From 
Lister,  magnified  8  diameters. 


THE  SARCODINA 


241 


proper  and  the  hypothallus   the   body   may   be  drawn  out  into 

a  stalk. 

The  first  events  in  the  reproductive  process  are  the  formation  of 

the  protective  and  supporting  elements 

of  the  sporangium.      Over  the  surface 

•of  the  lobe  a  membrane  or  envelope  is 

secreted,  the  "  peridium,"  and  in  the 

interior  of   the    protoplasmic    mass   a 

network,  orratherfeltwork,  of  filaments, 

the    "  capillitium,"    is    produced,    of 

similar  nature  to  the  peridium,  and  in 

continuity     with     it ;     peridium     and 

•capillitium  contain  cellulose  or  allied 

substances,  and  the  former  may  contain 

carbonate  of  lime  in  some  species. 

During   the   formation   of   the   pro- 
tective peridium    and   the  supporting 

capillitium     the     protoplasmic     mass 

remains  in   the  plasmodial   condition, 

but  when  the  accessory  structures  are    FIG.  100. — Badhamiautricularis. 

•completely   formed   the    actual   spore- 
formation  begins.     According  to  recent 

investigations,  spore-formation  is  initi- 
ated by  the  degeneration  of  a  certain 

number  of  the  nuclei ;  the  nuclei  that 

persist  then  divide  by  karj^okinesis  simultaneously  throughout  the 

•whole  plasmodium.     The   protoplasm   then   becomes   divided  up, 

directly  or  indirectly,  into  as  many 
masses  as  there  are  nuclei.  The  cells 
thus  produced,  lying  in  the  interstices 
of  the  capillitium,  become  surrounded 
each  with  a  tough  membrane,  and  are 
the  spores  (Fig.  101).  They  are 
liberated  by  bursting  of  the  peridium, 
and  the  hygroscopic  properties  of  the 
capillitium  are  the  cause  of  movements 
in  it  which  assist  in  scattering  the 
spores.  With  the  formation  of  the 


a,  Group  of  sporangia,  magni- 
fied 12  ;  b,  a  cluster  of  spores  ; 
c,  a  single  spore  ;  d,  part  of  the 
capillitium  containing  lime- 
granules  :  b  and  d  magnified 
170.  From  Lister. 


spores  the  life-cycle  has  been  brought 


.Fiu.  101.- — Tricliia  varia :  part  of 
a  section  through  a    sporan- 
gium   after    the    spores    are 
formed  ;  threads  cf  the  capil-      round   to   the    startlllg-poillt    that    was 
litium  are  seen  in  longitudinal    selected.     The  spores  are  scattered  in 

all     directions     by     the     wind,     and 


and  transverse  section.  From 
Lister,  magnified  G50  dia- 
meters. 


germinate  in  favourable  localities. 


The  account  given  above  may  be  taken  as  describing  the  typical  series  of 
•*\rents  in  the  life-history,  which  is  liable  to  considerable  variations  in  particular 

1(5 


242  THE  PROTOZOA 

types.  In  the  subdivision  termed  the  Sorophora  or  Acrasise  there  is  no 
fiagellula-stage  in  the  life-history,  and  the  amcebulse  which  are  produced 
from  the  spores  aggregate  together,  but  form  only  a  pseudo-plasmodium, 
in  which  the  constituent  amcebulse  remain  distinct,  without  fusion  of  their 
protoplasmic  bodies,  each  amosbula  multiplying  independently.  The  details 
of  the  reproductive  process  also  vary  greatly.  In  the  division  known  as 
the  Exosporese,  represented  by  the  genus  Ceratiomyxa,  no  sporangium  is 
formed,  but  the  plasmodium  grows  up  into  antler-like  processes,  sporophores, 
over  the  surface  of  which  the  plasmodium  divides  up  into  a  mosaic  of  cells, 
each  containing  a  single  nucleus  of  the  plasmodium.  Each  cell  becomes- 
a  spore,  which  is  produced  on  the  free  surface  of  the  sporophore,  and  drops 
off  when  ripe.  In  the  Sorophora  the  amoebae  associated  in  the  pseudo- 
plasmodium  are  not  all  destined  to  become  reproductive  individuals  ;  some  of 
them  join  together  to  secrete  a  stalk,  and  develop  no  further ;  others  form 
clusters  ("  sori  ")  of  naked  spores  on  the  stalk. 

The  cytological  details  of  the  life-history  of  the  Mycetozoa  have  been  the 
subject  of  a  series  of  studies  by  Jahn,  who,  however,  in  his  latest  investigations, 
has  come  to  conclusions  different  from  those  at  which  he  arrived  in  his  earlier 
works.  According  to  the  earlier  accounts  given  by  Jahn  and  Kranzlin,  the 
spore -formation  was  preceded  by  a  fusion  of  nuclei  in  pairs  throughout  the- 
sporangium,  a  process  which  was  regarded  as  the  true  sexual  karyogamy, 
and  was  followed  by  reducing  divisions.  According  to  Jahn's  latest  investiga- 
tions (294),  however,  the  nuclear  fusions  observed  in  the  sporangium  take 
place  only  between  degenerating  nuclei,  and  are  to  be  interpreted  as  purely 
vegetative  phenomena  which  have  nothing  to  do  with  the  true  sexual  process,, 
which  is  stated  to  be  as  follows  :  The  nuclear  division  which  immediately 
precedes  spore-formation  is  a  reducing  division,  whereby  the  number  of 
chromosomes  is  reduced  from  sixteen  to  eight.  Consequently  the  nuclei  of 
the  spores,  and  also  the  swarm-spores  produced  from  them,  both  flagellulse- 
and  amcebulse,  have  half  the  full  number  of  chromosomes.  In  Physarum 
didermoides  the  amcebulae  multiply  by  fission,  with  mitoses  showing  eight 
chromosomes.  After  a  certain  number  of  such  divisions,  the  amcebulsa 
copulate  in  pairs  as  gametes.  .The  zygotes  thus  formed  are  the  foundation 
of  the  plasmodia  ;  when  one  zygote  meets  another  it  fuses  with  it,  the  nuclei 
remaining  separate,  and  by  repeated  fusions  of  this  kind  the  plasmodia  are 
formed.  When,  on  the  other  hand,  a  young  plasmodium  or  a  zygote  meets 
an  amcebula  (gamete),  it  devours  and  digests  it.  The  nuclei  of  the  plasmodia 
multiply  by  mitoses  which  show  sixteen  chromosomes. 

In  Ceratiomyxa  the  reduction-division  preceding  spore-formation  is  followed 
by  degeneration  of  one  of  the  two  daughter-nuclei ;  the  other  becomes  the 
nucleus  of  the  spore.  Within  the  spore  the  nucleus  divides  twice,  forming 
four  nuclei,  and  as  soon  as  the  spore  germinates  the  contents  divide  into  four 
amcebulse,  which  adhere  in  the  form  of  a  tetrahedron.  Each  amcebula  has 
eight  chromosomes  in  its  nucleus,  and  divides  into  two  amcebulte,  also  with 
eight  chromosomes.  Each  of  the  amcebulse  develops  a  flagellum  and  swims 
off.  Possibly  in  this  genus  the  syngamy  takes  place  between  flagellulse. 

From  the  investigations  of  Jahn,  it  is  clear  that  the  swarm-spores  of 
Mycetozoa,  like  those  of  other  Sarcodina,  are  the  gametes ;  their  nuclei  have 
undergone  a  process  of  reduction,  and  represent  pronuclei,  which  after  a 
certain  number  of  divisions  give  rise  by  syngamy  to  synkarya,  from  which 
the  nuclei  of  the  vegetative  phase,  the  plasmodium,  takes  origin. 

The  Mycetozoa  are  classified  by  Lister  (297)  as  follows  : 

SUBORDER  I. :  ETJPLASMODIDA  (Myxogastres,  Myxomycetes  sens,  strict.). — 
Mycetozoa  with  a  flagellula- stage  and  a  true  plasmodium  formed  by  plasto- 
gamic  fusion  of  amcebulse.  This  suborder  comprises  forms  with  the  full  life- 
cycle  described  above. 

Section  1.  Endosporece. — Spore-formation  within  a  sporangium.  Examples: 
Badhamia,  Fuligo  (JEtlialiwni),  etc. 

Section  2.  Ectosporece. — Spores  formed  on  the  exposed  surface  of  sporo- 
phores.  Example  :  Ceratiomyxa. 


THE  SARCODINA  243 

SUBORDER  II. :  SOROPHORA  (Acrasise,  Pseudoplasmodida).  -  -  With  no 
flagellate  stage  in  the  life-history ;  the  amcebulse  do  not  fuse  completely  to 
form  a  true  plasmodium  ;  the  spores  are  formed  in  clusters  ("  sori  ").  Here 
belong  various  genera,  for  the  most  part  found  in  dung,  such  as  Dictyostelium 
and  Copromyxct.  Acrasis  occurs  in  beer-yeast. 

In  addition  to  the  typical  Mycetozoa  belonging  to  these  two  suborders, 
there  are  a  number  of  forms  on  the  border-line,  referred  by  some  authorities 
to  the  Mycetozoa,  by  others  to  other  orders,  such  as  the  Proteomyxa.  It 
is  only  possible  to  refer  very  briefly  to  these  genera  here. 

In  the  first  place,  there  are  a  number  of  parasitic  forms,  placed  together 
by  Doflein  in  the  suborder  Phytomyxince,  Schroter.  In  this  suborder  no 
sporangium  is  formed,  the  process  of  spore-formation  being  simplified, 
probably,  in  correlation  with  the  parasitic  mode  of  life.  The  typical  members 
of  this  group  are  parasites  of  plants,  but  some  recently-described  parasites 
of  insects  have  been  assigned  to  Phytomyxince.  The  best  known  example  of 
the  group  is  the  common  Plasmodiophora  brassicce,  which  attacks  the  roots 
of  cabbages  and  other  Cruciferae,  producing  a  disease  known  as  "  Fingers 
and  Toes  "  ("  Kohlhernie  "),  characterized  by  knotty  swellings  on  the  roots. 
Other  genera  parasitic  on  plants  are  Tetramyxa  and  Sorosphcera. 

In  Plasmodiophora  the  spores  germinate  to  produce  flagellulse,  which  are 
liberated  in  water  or  damp  earth,  and  which  in  some  way  penetrate  into  the 
cells  of  the  plant,  and  there  appear  as  the  nayxamcebse  after  loss  of  the  flagel- 
lum.  The  youngest  inyxamcebaj  seen  have  two  nuclei.  They  grow  in  the 
cell-contents  with  multiplication  of  their  nuclei,  and  fuse  with  one  another 
to  form,  plasmodial  masses  which  fill  the  cell  after  absorption  of  its  contents. 

In  a  diseased  plant  a  number  of  cells  are  attacked  by  the  parasite,  and  it  is 
not  certain  whether  the  rnyxanioebse  can  pass  from  one  cell  to  another,  and  so 
spread  the  infection,  or  whether  all  the  infected  cells  are  derived  from  the 
multiplication  of  the  first  cell  infected.  The  second  view,  maintained  by 
Nawaschin,  is  supported  by  Prowazek,  and  also  by  Blomfield  and  Schwartz, 
with  regard  to  the  allied  genus  Sorosphcera. 

When  the  host-cell  is  exhausted,  the  reproductive  phase  begins,  according 
to  Prowazek  (127),  by  the  nuclei  of  the  plasmodium  throwing  out  numerous 
chromidia,  and  becoming  in  consequence  very  indistinct.  In  Sorosphcera  at 
this  stage  (Blomiield  and  Schwartz)  the  nuclei  disappear  altogether,  being 
entirely  resolved  into  chromidia  from  which  secondary  nuclei  are  formed. 
Spore-formation,  preceded  by  sexual  processes,  takes  place  in  the  manner 
described  above  (p.  149,  Fig.  76).  In  Sorosphcera,  Blomfield  and  Schwartz 
found  that,  after  reconstitution  of  the  generative  nuclei,  the  plasmodium 
divides  up  into  uninucleate  cells,  each  of  which  divides  twice  by  karyokinesis  ; 
after  these  divisions  the  cells  become  arranged  as  a  hollow  sphere,  the  "  soro- 
sphere,"  and  each  cell  becomes  a  spore.  No  cell-fusions  or  syngamic  processes 
were  observed. 

As  stated  above,  certain  parasites  of  insects  are  referred  to  this  order 
by  Leger.  Such  are  the  genera  Sporomyxa,  Leger  (295),  Mycetosporidium, 
Leger  and  Hesse,  and  Peltomyces,  Leger  (C.R.A.8.,  cxiix.,  p.  239).  Zoomyxa 
leyeri,  Elrnassian  (637),  parasite  of  the  tench,  is  perhaps  also  to  be  referred 
to  the  Mycetozoa.  The  position  of  these  forms  must,  however,  be  considered 
somewhat  doubtful  at  present.  Chatton  has  thrown  out  the  suggestion 
that  the  affinities  of  Peltomyces  are  rather  with  the  Cnidosporidia  (p.  409), 
through  the  genus  Paramyxa  recently  found  by  him  (761). 

Lastly,  mention  must  be  made  of  the  remarkable  genera  Chlamydomyxa, 
Archer,  and  Labyrinthula,  Cienkowski,  the  affinities  of  which  are  still  obscure. 
By  Lankester  (11)  they  were  ranked  as  an  independent  order  of  the  Sarcodina 
under  the  name  Labyrinthulidea  ;  by  Delage  and  Herouard  (6)  and  others 
they  are  placed  as  a  suborder,  Filoplasmodida,  of  the  Mycetozoa. 

Chlamydomyxa  is  a  fresh-water  genus  occurring  either  free  or  encysted. 
Its  most  remarkable  feature  is  the  possession  of  chrornatophores  which  enable 
it  to  live  in  a  holophytic  manner,  and  consequently  to  assimilate  and  grow 
when  encysted.  On  the  other  hand,  when  free  it  forms  a  network  of  long, 


244  THE  PROTOZOA 

filamentous  pseudopodia,  by  means  of  which  it  is  able  to  digest  food  in  the 
ordinary  holozoic  manner.  The  body  is  a  plasmodium  containing,  in  addition 
to  numerous  nuclei,  chromatophores,  and  peculiar  ''oat-shaped  bodies," 
"spindles,"  or  "physodes,"  stated  to  consist  of  phloroglucin.  The  cyst- 
envelope  consists  of  cellulose,  and  has  a  stratified  structure.  In  addition  to 
reproduction  by  fission  (plasmotomy),  Chlamydomyxa  appears  to  form  flagel- 
late swarm-spores,  possibly  gametes. 

Labyrinthula  occurs  in  marine  and  fresh  water.  In  the  active  state  it  has 
the  form  of  a  network  of  filaments,  1  millimetre  or  so  in  extent,  over  which 
travel  a  great  number  of  "  units,"  each  a  nucleate  cell  or  amcebula,  sometimes 
brightly  coloured.  When  dried,  each  unit  encysts  and  hatches  out  again 
separately.  The  units  multiply  by  fission.  They  were  formally  compared 
erroneously  with  the  "  spindles  "  of  Chlamydomyxa.  Lister  (298)  regards 
Labyrinthula  as  a  colonial  organism  of  which  the  units  remain  in  connection 
by  their  pseudopodia.  He  considers  these  two  genera  as  related  in  one 
direction  to  certain  members  of  the  Foraminifera  (Gromiidce),  in  other  drections 
to  the  Heliozoa  and  the  Proteornyxa. 

V.  HELIOZOA. 

The  Heliozoa  are  characterized,  as  a  group,  by  their  spherical 
form  and  stiff,  radiating  pseudopodia,  whence  their  popular  name 
of  "  sun-animalcules."  As  in  the  case  of  the  'E/adiolaria,  these 
peculiarities  of  form  are  generally  correlated  with  a  floating  habit 
of  life,  though  in  a  few  cases  the  animal  is  sedentary  and  attached 
to  a  firm  support.  In  contrast  with  the  Radiolaria,  a  "central 
capsule"  (p.  250)  is  absent  from  the  body-structure.  A  skeleton 
may  be  present  or  absent.  The  majority  of  species  inhabit  fresh 
water,  but  a  few  are  marine. 

General  Characters. — As  in  other  orders  of  Sarcodina,  a  concise 
statement  of  the  characteristic  features  of  the  group  is  rendered 
difficult  by  the  occurrence  of  border-line  forms,  of  which  the  exact 
position  is  doubtful.  It  is  best,  therefore,  to  consider  first  typical 
forms  of  which  the  position  is  incontrovertible,  and  then  those 
which  link  the  Heliozoa  to  other  groups  of  Protozoa. 

The  body-protoplasm  exhibits  commonly  a  vacuolated,  frothy 
structure,  with  distinct  cortical  and  medullary  regions.  The  cor- 
tical zone,  distinguished  by  vacuoles  of  larger  size,  disposed  in  a 
radiating  manner,  is  regarded  as  ectoplasm  ;  the  medullary  region, 
with  smaller  vacuoles  irregular  in  arrangement,  as  endoplasm  ; 
but  it  is  open  to  doubt  if  these  two  regions  correspond  truly  to  the 
ectoplasm  and  endoplasm  of  an  amoeba.  The  cortex  contains  the 
contractile  vacuoles,  and  gives  off  the  pseudopodia,  which  are 
typically  stiff,  straight,  and  filamentous,  ending  in  a  sharp  point 
and  supported  by  an  axial  organic  rod  (p.  48)  ;  but  in  some  genera 
the  supporting  axis  is  wanting.  In  the  medulla  are  lodged  the 
nuclear  apparatus,  the  food- vacuoles,  and  frequently  also  symbiotic 
organisms,  which  are  probably  in  most  cases  vegetative,  non- 
flagellate  phases  of  holophytic  flagellates  (Chlamy  do  monads). 

As  regards  the  nuclear  apparatus,  there  are  two  types  of  arrange- 


THE  SARCODINA  245 

merit  (compare  p.  90).  In  the  first  or  Actinophrys-type  (Fig.  46) 
the  nucleus  is  central,  and  the  pseudopodia  are  centred  on  it. 
Actinosphcerium  (Fig.  3)  can  be  derived  from  this  type  by  multi- 
plication of  the  nucleus,  originally  single,  until  there  may  be  some 
hundreds  present  in  large  specimens.  The  marine  form  Campto- 
nema  nutans,  Schaudinn,  is  perhaps  also  to  be  referred  to  this  type 
of  structure  ;  it  has  as  many  pseudopodia  as  there  are  nuclei  present, 
each  pseudopodium  arising  directly  from  a  nucleus  (p.  91,  Fig.  47). 

In  the  second  or  Acanthocystis-type  (Figs.  18,  64)  the  centre  of 
the  spherical  body  is  occupied  by  a  "  central  grain  "  (p.  91),  on 
which  the  axial  rays  of  the  pseudopodia  are  centred.  The  nucleus, 
on  the  other  hand,  occupies  an  excentric  position  in  the  body.  In 
this  type  there  is  a  tendency  to  a  sessile  habit  of  life,  the  animal 
being  attached  by  the  surface  of  the  body,  which  may  grow  out 
into  a  stalk,  as  in  Clathrulina  (Fig.  19).  In  the  interesting  marine 
genus  Wagner ella  (Fig.  48),  the  surface  of  attachment  has  become 
drawn  out  in  such  a  way  that  the  body  is  divided  into  three  parts — 
basal  plate,  stalk,  and  head.  The  nucleus  is  situated  in  the  basal 
plate.  The  head  contains  the  central  grain,  from  which  the  pseudo- 
podia radiate.  Thus,  in  this  genus  the  excentric  position  of  the 
nucleus  is  carried  to  an  extreme  ;  it  may  be  regarded  as  having 
grown  out  from  the  body  in  a  lobe  or  prolongation  which  forms  the 
basal  plate  and  stalk,  while  the  original  body  remains  as  the  head 
with  the  central  grain  and  pseudopodia. 

The  skeleton,  when  present,  may  take  various  forms.  It  may 
be  a  simple  gelatinous  investment,  or  may  contain  mineral  (sili- 
ceous) substance  either  in  the  form  of  loose,  radiating  spicules,  as 
in  Acanthocystis,  or  of  a  continuous  lattice-like  investment,  as  in 
Clathrulina.  In  Wagner  ella  the  basal  plate  and  stalk  are  protected 
by  a  tough  yellowish  organic  membrane,  replaced  in  the  head  by 
a  colourless  gelatinous  layer,  and  both  head  and  stalk  are  further 
protected  by  siliceous  spicules,  which  are  formed  in  the  protoplasm 
and  transported  by  protoplasmic  currents  (Zuelzer,  86). 

Life  -  History.  —  Reproduction  in  the  free  vegetative  phase  is 
effected  by  binary  fission  or  gemmation.  Imperfect  binary  fission  may 
lead  to  colony-formation,  as  in  Ehaphidiophrys.  The  sexual  phases 
are  only  known  accurately  in  a  few  cases.  In  Actinophrys,  Schaudinn 
described  copulation  within  a  cyst  (p.  132,  Fig.  71),  with  subse- 
coient  division  of  the  zygote  and  liberation  of  two  individuals  from 
the  cyst.  In  Actinosphcerium  (Hertwig),  encystment  of  a  large 
multinucleate  individual  is  followed  by  degeneration  of  about 
95  per  cent,  of  the  nuclei ;  the  remainder  appear  to  fuse  in  pairs, 
and  the  body  then  divides  into  as  many  cells  as  there  are  nuclei. 
Round  each  cell  a  separate  "  primary  "  cyst  is  secreted  within  the 
gelatinous  "  mother-cyst  "  originally  formed  round  the  whole  mass. 


246  THE  PROTOZOA 

Each  primary  cyst  then  divides  into  two  secondary  cysts,  which 
after  nuclear  reduction  become  the  gametes  and  copulate.  The 
zygote  develops  into  a  young  Actinospkcerium  with  several  nuclei, 
which  emerges  from  the  cyst  and  begins  a  vegetative  life,  but  appears 
to  divide  frequently  at  the  start  into  uiiinucleate,  Actinophrys-'ike 
forms. 

In  other  genera,  on  the  other  hand,  and  especially  in  those  of  the 
Acanthocystis-type  (Acanthocystis.  Clatlirulina,  and  Wagnerella), 
flagellate  swarm  -  spores  are  formed,  which  probably  represent 
gametes,  as  in  many  other  Sarcodina. 

The  life-history  of  Wagnerella  has  recently  been  studied  in  detail  by 
Zuelzer  (86)  ;  her  investigations  reveal  a  diversity  in  its  modes  of  reproduction 
almost  as  great  as  that  seen  in  Arcella,  and  indicate  that  there  is  much  yet 
to  be  discovered  with  regard  to  the  life-cycles  of  other  forms. 

Wagnerella  exhibits,  according  to  Zuelzer,  dimorphism  correlated  with 
alternation  of  generations.  In  June  and  July  stout  forms  are  observed, 
which  are  believed  to  arise  from  the  conjugation  of  gametes ;  they  reproduce 
by  binarj1-  fission,  and  by  a  process  of  schizogony  giving  rise  to  anicebulse 
(agametes).  The  more  usual  form,  on  the  other  hand,  is  smaller  and  more 
slender,  and  multiplies  by  binary  fission,  gemmation,  and  formation  of 
flagellate  swarm-spores.  Hence  this  peculiar  form  reproduces  in  a  variety 
of  ways.  In  the  process  of  binary  fission  the  nucleus  migrates  from  the 
base  up  the  stalk  into  the  head,  and  places  itself  beside  the  central  grain, 
which  divides,  its  two  halves  passing  to  opposite  sides  of  the  nucleus  ;  then 
the  nucleus  follows  suit  and  divides  also.  Divisions  of  the  central  grains, 
and  subsequently  of  the  corresponding  nuclei,  may  be  repeated  until  eight  to 
ten  nuclei  and  as  many  central  grains  are  present.  Each  nuclear  division 
is  followed  by  division  of  the  head,  at  first  incomplete,  so  that  a  condition 
results  resembling  the  colonial  form  Ehaphidiophri/s,  a  number  of  daughter- 
individuals  united  together,  and  each  sending  out  pseudopodia  (Fig.  102,  D). 
After  a  time  the  colony  breaks  up,  the  daughter-individuals  separate,  and 
each  one  fixes  itself  and  grows  into  the  adult  Wagnerella-form. 

Bud-formation  in  Wagnerella  (Fig.  102,  A — C)  is  initiated  by  division 
of  the  karyosome  within  the  nucleus,  which  retains  its  position  in  the  base. 
The  process  is  repeated  until  the  nucleus  contains  a  number  of  karyosomes, 
each  with  a  centriole.  The  nucleus  then  buds  off  one  or  more  small  daughter- 
nuclei,  each  containing  a  single  karyosome.  Sometimes  the  nucleiis  breaks 
up  entirely  into  as  many  daughter-nuclei  as  there  are  karyosomes,  in  which 
case  the  parent-individual  dies  off,  in  a  manner  similar  to  Arcella  (p.  ISO), 
after  liberation  of  the  buds.  Each  daughter-nucleus  migrates  up  the  slalk 
into  the  head,  where  it  becomes  surrounded  by  a  layer  of  protoplasm  to  form 
the  bud,  which  is  set  free  at  first  as  an  amoeboid  body.  Before  or  after  being 
set  free,  the  bud  may  multiply  by  binary  fission  with  mitosis,  in  which  the 
centriole  in  the  karyosome  acts  as  a  centrosome.  Finally  each  amoeboid 
body  develops  into  a  Wagnerella,  and  in  the  process  the  centriole  passes  out 
of  the  nucleus  and  becomes  the  central  grain,  while  the  nucleus  becomes 
displaced  from  the  centre.  In  the  process  of  gemmation  the  central  grain 
of  the  parent-individual  takes  no  share  whatever. 

In  the  formation  of  the  swarm-spores,  minute  secondary  nuclei  arise  from 
chromidia  near  the  principal  nucleus  in  the  base.  Each  secondary  nucleus 
forms  a  centriole  and  divides  by  mitosis  ;  the  division  is  repeated  until  the 
whole  body,  stalk  and  head  as  well  as  base,  is  filled  with  small  nuclei,  while 
the  primary  nucleus  degenerates.  The  body  then  divides  up  into  as  many 
cells  as  there  are  secondary  nuclei,  each  cell  becoming  a  biflagellate  swarm- 
spore  which  is  set  free,  while  the  parent-individual  degenerates.  The  destiny 
of  the  swarm-spores  is  uncertain,  but  they  are  believed  to  be  gametes. 


THE  SARCODINA 


247 


In  the  "  schizogony  "  of  the  stout  forms  the  nucleus  breaks  up  into  a  number 
of  daughter-nuclei,  as  in  gemmation  ;  each  daughter-nucleus  grows,  its  karyo- 
sonie  multiplies  by  fission,  and  it  breaks  up  in  its  turn  into  granddaughter- 
nuclei.  Continued  multiplication  of  the  nuclei  in  this  manner  proceeds 
until  the  body  is  filled  with  vesicular  nuclei ;  it  then  breaks  up  into  as  many 
amcebulse,  which  are  set  free,  leaving  a  residual  body  with  the  central  gr.iin, 
which  degenerates. 


^i-x^J       u- 


FIG.  102. — Wagnerella  borealis,  showing  budding  and  fission.  A,  Specimen  with 
a  single  bud  (6) :  e.g.,  central  grain ;  B,  specimen  with  four  buds  (b) ;  C,  en- 
larged view  of  the  head  of  a  specimen  containing  two  buds  (6)  in  process  of 
extrusion  ;  D,  specimen  in  which  the  head  has  multiplied  by  fission  to  produce 
a  Ehaphidiophrys-li^e  colony  ;  six  individuals  are  seen,  five  of  them  each 
with  nucleus  and  central  grain,  the  sixth  in  process  of  fission,  with  two  nuclei 
and  two  central  grains.  After  Zuelzer  (86). 

The  Heliozoa  are  classified  into  four  suborders  : 
SUBORDER  I. :  APKROTHORACA. — Body  naked  in  the  active  state; 
envelopes,  sometimes  with  siliceous  spicules,  only  formed  during 


248 


THE  PROTOZOA 


encystment.  Examples  :  Actinophrys  (Fig.  46),  Actinosphcerium 
(Fig.  3),  Camptonema  (Fig.  47),  etc. 

SUBORDER  II.  :  CHLAMYDOPHORA. — Body  protected  by  a  soft  gela- 
tinous envelope,  but  without  solid  skeletal  elements.  Example  : 
Astrodisculus. 

SUBORDER  III.  :  CHALAROTHORACA. — Body  invested  by  a  soft 
envelope  containing  isolated  spicules,  usually  siliceous,  sometimes 
chitinous.  Examples  :  Acanthocystis  (Figs.  18,  64,  68),  Wagner ella 
(Figs.  48,  102),  Heterophrys  (Fig.  103). 

SUBORDER  IV. :  DESMOTHORACA. — Body  invested  by  a  continuous, 
lattice-like  skeleton.  Example  :  Clathrulina  (Fig.  19). 


c. 


Fio.  103. — Hderophrys  fockei,  Archer,  c.,  c.,  Contractile  vacuoles  ;  s.,  radial  chiti- 
nous spines  surrounding  the  envelope.  A  nucleus  is  present  in  the  body,  but 
is  not  shown  ;  the  bodies  in  the  protoplasm  represent  zooxanthell*.  From 
Weldon  and  Hickson,  after  Hertwig  and  Lesser. 

A  certain  number  of  genera  must  be  mentioned  which  are  of  doubtful 
position,  referred  by  some  authorities  to  the  Heliozoa,  by  others  to  other 
orders.  Some  of  these  genera  perhaps  do  not  represent  independent,  "  adult ' 
forms,  but  may  be  only  developmental  phases  of  other  genera.  Nudearia, 
classed  by  some  in  the  Aphrothoraca,  by  others  in  the  Proteomyxa,  has  an 
amo?boid  body  and  pseudopodia  without  axes.  As  described  above  (p.  177 
and  Fig.  80),  a  Nuclearia-stage  occurs  in  the  development  of  Arcella. 

Especially  remarkable  are  certain  genera  which  indicate  a  close  relation- 
ship between  Heliozoa  and  Flagellata.  An  account  of  several  such  forms  is 
given  by  Penard  (302),  in  addition  to  which  the  following  may  be  noted : 
Ciliophrys,  Cienkowski,  has  two  phases ;  in  the  one  it  appears  as  a  typical 
Heliozoon  with  stiff  radiating  pseudopodia  ;  in  the  other  it  is  a  typical 
flagellate.  In  the  process  of  transformation  the  Heliozoon-form  retracts  its 
pseudopodia,  its  body  becomes  amo?boid,  and  a  flagellum  grows  out ;  finally 


THE  SARCODINA 


the  animal  becomes  a  pear-shaped  flagellate  swimming  by  means  of  its 
flagellum  (Schewiakoff,  863  ;  CauLlery,  300).  Ciliophrys  thus  recalls  Pseudo- 
spora  in  its  two  phases  (p.  218),  and  there  can  be  little  doubt  that  the  two 
forms  are  closely  allied. 

Dimorplia  nutans,  Gruber  (Fig.  104),  has  radiating  pseudopodia  strengthened 
by  axial  rods,  and  in  addition  a  pair  of  flagella  arising  close  together  at  one  pole 
of  the  body.  Both  flagella  and  pseudopodia  arise  from  a  centrosome  situated 
near  the  flagellated  pole  ;  the  single  nucleus  is  also  excentric  and  placed 
close  beside  the  centrosome.  The  animal  uses  one  of  its  flagella  for  attach- 
ment, while  the  other  remains  free  (Schouteden). 

These  facts  appear  to  indicate  an  origin  for  the  Heliozoa  from  Flagellates 
such  as  those  of  the  genus  Multicilia  (p.  270,  Fig.  113),  in  which  the  body 
bears  radiating' flagella  planted  evenly  over  the  surface;  transformation  of 
the  flagella  into  stiff  pseudopodia  would  produce  the  Heliozoon  -  type  of 
organism.  On  such  a  view  two  peculiarities  of  the  Heliozoan  pseudopodia 
receive  explanation  :  the  power  of  nutation  and  bending  which  they  fre- 


FIG.  104. — Dimorpha  nutans.     After  Schouteden. 

quently  possess  ;  and  their  insertion  on  a  "  central  grain,"  which  would  then 
represent  the  blepharoplast,  pure  and  simple,  of  a  flagellate.  On  this  view 
the  pseudopodia  of  the  Heliozoa  would  appear  to  be  structures  quite  different 
in  nature  from  the  similarly-named  organs  of  Lobosa. 

On  the  other  hand  the  Heliozoa  also  show  affinities  towards  forms  classed 
among  the  Reticulosa  or  "  Proteomyxa, "  as  already  noted  in  the  case  of 
Ciliophrys  and  Pseudospora.  Przesmycki  has  described  a  species,  Endoplirys 
rotatorium,  parasitic  in  Rotifers,  which  he  considers  as  a  connecting-link 
between  Nuclearia  and  Vampyrella.  The  exact  systematic  position  of  such 
genera  must  be  considered  at  present  an  open  question. 

VI.  RADIOLARIA. 

General  Characters. — The  Radiolaria  are  characterized,  speaking 
generally,  by  the  same  type  of  form  and  symmetry  that  is  sa 
marked  a  feature  of  the  Heliozoa,  though  in  many  cases  the  internal 


250 


THE  PROTOZOA 


structure  of  the  body,  and  especially  the  skeleton,  may  depart  more 
or  less  widely  from  the  radiate  symmetry  which  is  to  be  regarded, 
probably,  as  primitive  for  the  group.  Hence  three  principal  types 
of  symmetry  can  be  distinguished  in  these  organisms  :  (1)  Homaxon 
(Figs.  13,  105,  107),  in  which  all  axes  passing  through  the  centre 
are  morphologically  equivalent,  the  symmetry  of  the  sphere ; 
{2)  monaxon  (Fig.  109),  in  which  the  body  has  a  principal  or  vertical 
axis  round  which  it  is  radially  symmetrical,  the  type  of  symmetry  of 
the  cone  ;  (3)  bilaterally  symmetrical  (Fig.  106),  in  which  the  body 


fi 


FIG.  105. — Acanthometra  dastica,  Haeckel.  sp.,  Radiating  spines  of  the  skeleton 
(twenty  in  number,  but  only  twelve  are  seen  in  the  figure)  ;  ps.,  pseudo podia  ; 
c.,  calymma  ;  ex.,  central  capsule  ;  N.,  N.,  nuclei  ;  x,  yellow  cells  ;  my.,  myo- 
phrisks.  After  Butschli,  Leuckart  and  Nitsche's  "  Zoologische  Wandtafeln." 

can  be  divided  along  a  principal  plane  into  equivalent  right  and 
left  halves.  With  further  modification  the  body  may  become 
asymmetrical.  Sedentary  forms  are  not  known  in  this  group,  the 
species  of  which  are  exclusively  marine,  and  occur  on  the  open 
surfaces  of  seas  and  oceans,  reaching  in  many  instances  a  re'atively 
large  size  and  a  very  high  degree  of  structural  differentiation. 

In  the  internal  structure,  the  most  salient  feature  is  the  division 
of  the  body  by  means  of  a  membranous  structure,  termed  the 
central  capsule  (Fig.  13,  CK),  into  a  central  medullary  region  and  a 
peripheral  cortical  zone — hence  distinguished  as  the  intracapsular 


THE  SARCODINA  251 

.and  extracapsular  regions  of  the  body.  The  intracapsular  medulla 
contains  the  nucleus  or  nuclei,  and  is  the  seat  of  reproductive 
processes.  The  extracapsular  cortex  is  the  seat  of  assimilation, 
excretion,  food-capture,  and  of  such  locomotor  processes  as  these 
organisms  are  able  to  perform,  consisting  chiefly  of  rising  or  sinking 
in  the  water  by  means  of  changes  in  a  hydrostatic  apparatus 
presently  to  be  described. 

The  Radiolaria  are  an  exceedingly  abundant  group  represented  by  a  great 
number  of  species  both  at  the  present  time  and  in  past  ages  ;  over  vast 
tracts  of  the  ocean-floor  their  skeletons  are  the  principal,  almost  the  sole 
constituents  of  the  ooze ;  and  the  same  must  have  been  true  in  past  times, 
since  in  many  geological  deposits  the  rocks  are  composed  of  the  same  materials. 
Every  microscopist  is  familiar  with  their  skeletons,  which  on  account  of 
their  beauty  and  variety  of  form  are  favourite  objects  for  microscopic  study 
and  demonstration.  Corresponding  with  the  variety  of  forms  and  species, 
the  internal  structure  shows  a  range  of  variation  and  differentiation  which 
it  is  impossible  to  deal  with  adequately  in  a  short  space  ;  it  must  suffice, 
therefore,  to  describe  here  the  main  structural  peculiarities  of  this  group 
in  a  general  manner,  and  to  indicate  briefly  the  principal  variations  of  structure 
which  are  of  importance  for  the  classification  of  the  group.  For  further 
information  the  reader  must  be  referred  to  the  larger  treatises  and  special 
monographs. 

Structure. — The  central  capsule,  absent  in  rare  cases,  may  be  a 
thin,  delicate  structure,  visible  only  after  treatment  with  reagents, 
or  may  be  fairly  thick.  In  homaxon  forms  it  is  generally  spherical, 
but  may  assume  various  shapes  correlated  with  the  general  body- 
form,  and  even  may  be  lobed  or  branched.  It  is  perforated  by 
openings  which  place  the  intracapsular  protoplasm  in  communica- 
tion with  the  extracapsular  ;  the  openings  may  take  the  form  of 
fine  pores  scattered  evenly  over  the  whole  surface  (Peripylaria)  ;  of 
similar  pores  aggregated  into  localized  patches,  pore-areas  or  pore- 
plates  (Acaiitharia)  ;  of  a  single  pore-plate  at  one  pole  of  an  asym- 
metrical capsule  (Monopylaria,  Fig.  106)  ;  or  of  one  principal  and 
two  lateral  apertures  (Tripylaria). 

The  intracapsular  protoplasm  contains  the  nuclear  apparatus, 
either  one  nucleus  of  very  large  size  or  a  number  of  smaller  nuclei 
(Fig.  105).  In  addition,  various  bodies  of  metaplastic  nature, 
serving  as  reserve-material  for  the  reproductive  processes,  are 
found  in  this  region,  in  the  form  of  fat-globules,  oil-drops,  concre- 
tions, crystals,  etc. 

The  extracapsular  region  consists  of  three  zones,  from  within 
outwards  :  (1)  an  assimilative  layer  or  matrix  immediately  sur- 
rounding the  capsule  ;  (2)  a  vacuolated  layer,  known  as  the  "  cal- 
yrnma,"  hydrostatic  in  function  ;  (3)  a  protoplasmic  layer  from 
which  the  pseudopodia  arise. 

1.  The  assimilative  layer  contains  pigment,  representing  ex- 
cretory substances  and  ingested  food-material  in  the  shape  of  small 


252 


THE  PROTOZOA 


organisms  captured  by  the  pseudopodia  and  passed  into  the  body, 
to  be  digested  in  this  region.  In  the  Tripylaria  an  aggregation  of 
food-material  and  excretory  substances  produces  a  characteristic 
greenish  or  brownish  mass  concentrated  round  the  main  aperture 
of  the  central  capsule,  and  known  as  the  phceodium,  whence  this 
suborder  is  sometimes  known  as  the  Pheeodaria. 

2.  The  calymma  is  composed  for  the  most  part  of  a  great  number 
of  vacuoles  containing  fluid,  the  function  of  which  is  hydrostatic  ; 
the  contents  of  the  vacuoles  are  stated  to  be  water  saturated  with 
carbon  dioxide,  causing  the  animal  to  float  at  the  surface,  and 

enabling  it  to  regulate  its  position 
in  relation  to  conditions  of  environ- 
ment. In  rough  weather  the  vacuoles 
burst  or  are  expelled  from  the  body, 
and  the  animal  sinks  into  deeper  and 
quieter  layers  of  water ;  there  fresh 
vacuoles  are  formed,  enabling  it  to 
return  again  to  the  surface  if  the 
conditions  are  favourable.  Contractile 
vacuoles  of  the  ordinary  type  are  not 
present. 

In  addition  to  the  vacuoles,  the 
calymma  contains  numerous  "  yellow 
cells,"  generally  regarded  as  sym- 
biotic organisms  of  vegetable  nature, 


jfc— ! 


CC 5 


FIG.  106.  —  Lithocircus  productus, 
Hertwig,  showing  a  bilaterally 
symmetrical  skeleton  consisting 
of  a  simple  siliceous  ring  pro- 
longed into  spicular  processes. 
sk.,  Skeleton  ;  ex.,  central  cap- 
sule;  pf.,  pore-area,  surmounted 
by  a  conical  structure  (c.),  the 
so-called  "  pseudopodial  cone  "  ; 
N.,  nucleus  ;  o.,  oil-globule. 
After  Biitschli,  Leuckart  and 
Nitsche's  "  Zoologische  Wand- 
tefeln." 


and     named      "  zooxanthellse "     or 


"  zoochlorellse,"  according  to  their 
colour.  Absent  in  the  Tripylaria, 
these  yellow  cells  are  found,  as  a 
rule,  in  the  calymma,  but  in 
Acantharia  they  occur  in  the  intra- 
capsular  protoplasm  (Fig.  105,  x). 
The  nature  of  the  yellow  cells  of 
Acantharia  has  been  much  disputed, 
and  many  observers  have  regarded 
them  as  an  integral  part  of  the  organism  itself  ;  this  view  has 
recently  been  revived  by  Moroff  and  Stiasny,  who  bring  forward 
evidence  to  prove  that  the  yellow  cells  of  Acantharia  are  a 
developmental  phase  of  the  organism.  Still  more  recently  this 
view  has  been  extended  by  Stiasny  to  the  colony-forming 
Sphserozoa  in  the  first  place,  and  then  to  Radiolaria  generally. 
The  difficulty  in  the  way  of  such  an  interpretation  which  arises 
from  the  co-existence,  in  Thalassicolla  and  other  genera,  of  yellow 
cells  in  the  calymma,  with  an  undivided  nucleus  in  the  host- 
organism,  is  met  by  supposing  that  in  such  cases  developmental 


THE  SARCODINA  253 

stages  of  other  Radiolarians  have  penetrated  into  the  calymma, 
and  live  there  symbiotically — a  supposition  which  is  certainly  in 
need  of  further  proof  before  it  can  be  accepted. 

3.  The  most  external  layer  of  the  body  is  a  protoplasmic  envelope 
from  which  the  pseudopodia  radiate.  In  Radiolaria,  speaking 
generally,  the  pseudopodia  are  straight,  slender,  and  filamentous, 
composed  of  motile  protoplasm  entirely  ("  myxopodia  ")  ;  but  in 
Acantharia  some  of  the  pseudopodia  are,  like  those  of  Heliozoa, 
axopodia  supported  by  stiff  axial  rods  of  organic  substance,  which 
originate  deep  within  the  central  capsule  and  pass  through  the 
calymma  along  the  axis  of  the  pseudopodium,  but  without  reaching 
as  far  as  its  distal  extremity.  In  some  Acantharia  (Acanthometrida) 
are  found  also  peculiar  modifications  of  the  bases  of  certain  of  the 
pseudopodia  in  the  form  of  groups  of  rod-like  bodies,  "  myonemes  " 
or  "  myophrisks "  (Fig.  105,  my.),  clustered  round  each  of  the 
spicules  of  the  skeleton.  As  their  name  implies,  the  myonemes  are 
contractile  elements  which,  by  their  contraction  or  expansion,  alter 
the  hydrostatic  balance  of  the  organism,  and  enable  it  to  rise  or 
sink  in  the  water.  According  to  Moroff  and  Stiasny,  the  myonemes 
are  formed  in  the  interior  of  the  central  capsule,  and  are  derived 
from  nuclei. 

In  a  certain  number  of  Radiolaria  a  skeleton  is  absent  altogether. 
The  Acantharia  have  a  skeleton  composed  of  a  substance  which 
was  formerly  supposed  to  be  of  organic  nature,  and  was  termed 
acanthin  by  Haeckel,  but  which  consists  of  strontium  sulphate 
-according  to  Butschli  (310).  In  other  Radiolaria  the  skeleton, 
when  present,  is  siliceous.  In  Acantharia  the  skeleton  invades  the 
intracapsular  region,  and  consists  typically  of  a  system  of  twenty 
spines  or  spicules  radiating  from  the  centre  of  the  body  (Fig.  105). 
It  is  a  simple  and  enticing  view  to  regard  such  a  skeleton  as  origin- 
ating phylogenetically  from  a  modification  of  the  axis  of  pseudo- 
podia. Union  of  outgrowths  from  radially-directed  spicules  gives 
rise  to  a  lattice-work  forming  a  spherical  perforated  shell,  and  as 
the  animal  grows  in  size  several  such  concentric  spheres  may  be 
formed,  one  within  the  other,  supported  by  radial  bars  which 
represent  the  original  radiating  spicules  (Fig.  107).  In  Radiolaria 
other  than  Acantharia  the  skeleton  is  usually  entirely  extracapsular, 
and  exhibits  a  variety  of  form  and  structure  which  cannot  be  dis- 
cussed further  here.  In  some  of  the  Tripylara  foreign  bodies  are 
utilized  for  building  up  the  skeleton,  either  to  form  the  basis 
of  spines  secreted  by  the  animal  or  to  construct  a  coat  of  armour 
on  the  exterior  of  the  body  (Borgert). 

Life-History.  —  Reproduction  of  the  Radiolaria  is  effected  in 
some  instances  by  binary  fission — namely,  in  those  forms  in  which 
<a  skeleton  is  lacking  or  consists  of  loose  spicules.  The  nucleus 


254 


THE  PROTOZOA 


divides  by  a  mitosis  remarkable  for  the  vast  number  of  chromo- 
somes, of  which  there  may  be  over  a  thousand,  and  the  apparent 
absence  of  a  centrosome.  The  more  usual  method  of  reproduction, 
however,  is  formation  of  flagellated  swarm-spores  by  a  process  of 
rapid  multiple  fission  within  the  central  capsule.  Two  lands  of 
swarm-spores  are  produced,  which  are  known  respectively  as 
"  isospores  "  and  "  anisospores."  The  isospores  (Fig.  108,  A),  which 
are  probably  agametes,  are  all  similar  in  size  and  appearance,  and 
frequently  contain  a  crystal  in  their  protoplasm,  and  are  hence 
sometimes  termed  "  crystal-spores."  The  anisospores  (Fig.  108, 


SO. 


cc 


1 

FIG.  107. — Actinomma  asteracanthion :  semi-diagrammatic  to  show  the  mode  of 
growth  of  the  skeleton.  S.1,  S.2,  S.3,  Three  concentric  lattice- work  shells, 
connected  by  sp.,  radial  bars  which  are  prolonged  beyond  the  outermost  shell 
as  spikes  ;  N.,  nucleus  ;  ex.,  central  capsule  ;  ps.,  pseudopodia.  After  Biitschli, 
Leuckart  and  Nitsche's  "  Zoologiscbe.  Wandtafeln." 

B,  C],  probably  gametes,  are  of  two  kinds,  smaller  microspores  and 
larger  macrospores  ;  they  differ  in  structure  from  the  isospores,  and 
lack  the  characteristic  crystal.  The  swarm-spores  vary  in  struc- 
ture in  different  species,  but  usually  have  two  flagella.  Isospores 
and  anisospores  are  formed  in  different  individuals,  but  it  is  still  a 
moot  point  whether  an  alternation  of  generations  occurs.  Micro- 
spores  and  macrospores  may  be  formed  in  the  same  individual  in 
some  species  ;  in  others  they  are  produced  by  different  individuals. 
Previous  to  formation  of  the  swarm-spores  the  extracapsular  region 
of  the  body  disintegrates,  and  the  central  capsule  with  its  contents 


THE  SARCODINA  255 

sinks  to  a  considerable  depth.  The  swarm-spores  are  liberated  by 
the  breaking-up  of  the  central  capsule.  The  subsequent  develop- 
ment of  the  swarm-spores  when  set  free  has  not  been  made  out. 

While  the  main  features  of  the  reproductive  process  are  as  stated  above, 
the  cytological  details  of  the  formation  of  the  swarm-spores  is  still  a  matter- 
of  dispute.  The  subject  is  dealt  with  in  the  recent  memoirs  of  Moroff  on  the 
one  -part,  and  Hartmann  and  Hammer,  Hartmann  (60),  and  Huth,  on  the 
other.  The  formation  of  the  anisospores  is  generally  regarded  as  a  breaking- 
up  of  the  primary  nucleus  into  chromidia,  from  a  part  of  which  the  secondary 
nuclei  arise,  which  become  those  of  the  swarm-spores  (compare  Foraminifera). 
But  according  to  Hartmann  and  his  adherents,  the  huge  primary  nuclei  seen 
in  many  Badiolaria  are  polyenergid  nuclei  or  polykarya  (p.  121)  containing 
a  vast  number  of  nuclear  energids  or  rnonokarya,  consisting  each  of  chromatin, 
in  the  form  of  a  twisted  thread  or  so-called  "  chromosome,"  and  a  centriole. 
In  the  gamete-formation  a  great  number  of  such  monokarya  are  set  free 
from  the  primary  nucleus  to  become  the  gamete-nuclei ;  hence  the  so-called 
"  generative  cliromidia  "  set  free  from  the  nucleus  are  interpreted  as  secondary 
nuclei  or  rnonokarya  already  formed  within  the  primary  nucleus.  A  similar 
interpretation  is  given  to  the  mitosis  seen  in  the  process  of  binary  fission  ; 
the  huge  mitotic  figure,  composed  of  more  than  a  thousand  chromosomes, 
is  interpreted  as  being  in  reality  made  up  of  as  many  mitotic  figures  as  there 
are  chromosomes,  since  each  so-called  "  chromosome  "  is  regarded  as  a  single 


FIG.  108. — Swarm-spores  of  Collozoum  inerme.  A,  Crystal-bearing  swarm-spores, 
agametes  ;  B,  0,  swarm-spores  without  crystals,  gametes  ;  B,  microspores 
(microgametes) ;  C,  macrospores  (macrogametes).  After  Hertwig. 

nuclear  energid  or  monokaryon  with  its  own  centriole,  the  whole  number  of 
energids  dividing  independently  but  synchronously  to  form  the  supposed 
mitotic  figure. 

According  to  Moroff  and  Stiasny,  in  Acanihometra  pellucida  a  process  of 
multiplication  is  proceeding  continually  within  the  central  capsule,  until  it 
is  entirely  filled  up  with  cells,  from  which  the  swarm-spores  arise.  In  this 
multiplication,  termed  bj*  the  authors  "  schizogony,"  trophic  nuclei  ("  macro- 
nuclei")  and  generative  nuclei  ("  micronuclei  ")  are  formed.  The  trophic 
nuclei  are  the  "  yellow  cells,"  which  ultimately  degenerate.  Hence  the  Acan- 
tharia  are  considered  not  to  be  single  individuals,  but  colonies  of  animals  which 
have  the  extracapsular  protoplasm,  pseudopodia  and  skeleton  in  common. 

Finally,  attention  must  be  drawn  to  the  peculiar  organisms  found  in  certain 
Radiolaria,  and  regarded  by  some  authorities  as  parasitic  Flagellata  (Silico- 
flagellata,  Borgert),  by  others  as  developmental  stages,  of  the  Badiolaria 
themselves.  See  Delage  and  Herouard  (6,  p.  371). 

The  Radiolaria  are  classified  as  follows  : 

SUBORDER  I. :  PERIPYLARIA  SETT  SPTTMELLARIA. — Central  capsule  spherical, 
perforated  by  evenly-distributed  pores.  Extracapsular  region  well  developed. 
Skeleton  wanting  or  consisting  of  scattered  spicules  or  of  lattice-work  shells, 
developed  in  the  extracapsular  region,  siliceous. 

Legion  1 :  Collodaria. — Skeleton  wanting  or  simple  in  structure  ;  monozoio 
forms.  Five  families.  Examples  :  Thalassicolla  (Fig.  13),  ThalassopJiysa. 

Legion  2 :  Sphcerellaria. — Skeleton  complex,  usually  with  lattice-work 
shell  ;  monozoic,  generally  small.  Four  families. 


256 


THE  PROTOZOA 


Legion  3  :  Sphcerozoa  sen  Polycyttaria. — Colonial  forms  consisting  of 
numerous  individuals  embedded  in  a  common  jelly ;  their  central  capsules 
are  distinct,  but  their  extracapsular  regions  anastomose.  The  colonies  reach 
a  length  of  several  centimetres.  Two  families.  Example  :  Collozoum. 

SUBORDER  II. :  ACANTHARIA.— Skeleton  composed  of  strontium  sulphate, 
typically  in  the  form  of  spicules  radiating  from  the  centre  of  the  body,  within 
the  central  capsule  ;  in  addition  lattice-work  shells  may  be  developed.  Central 
capsule  with  pores  evenly  developed,  or  grouped  in  areas. 

A  number  of  families  are  recognized,  grouped  in  different  ways  by  different 
authorities.  Example  :  Acanthometra  (Fig.  105). 


FIG.  109.  —  Eucyrlidium  cranioides,  Haeckel:  entire  animal  as  seen  in  the  living 
condition.  The  central  capsule  is  hidden  by  the  beehive-shaped  siliceous 
shell  within  which  it  is  lodged.  From  Gamble,  magnified  150. 

SUBORDER  III.  :  MOXOPYLARIA  SEU  NASSELLARIA.  —  Central  capsule  monaxon 
in  form,  with  the  pores  aggregated  at  one  pole  into  a  pore-plate,  and  the 
walls  of  the  pores  thickened  to  form  a  conical  structure  directed  inwards 
into  the  central  capsule.  Several  families.  Examples  :  Lithocircus  (Fig.  106), 
Eucyrtidium  (Fig.  109). 

SUBORDER  IV.  :  TRIPYLARIA  SEU  PH^ODARIA.  —  Central  capsule  with  a 
principal  aperture  (astropyle)  and  two  accessory  apertures  (parapyle).  A 
mass  of  pigment  (phseodium,  p.  252)  surrounds  the  principal  aperture. 
Divided  by  Hacker  into  six  legions  and  numerous  families.  Example  : 
Ardacantha. 


Bibliography.  —  -For  references  see  p.  483. 


CHAPTER  XII 

SYSTEMATIC  REVIEW  OF  THE  PROTOZOA  :  THE 
MASTIGOPHORA 

THE  distinctive  feature  of  the  class  Mastigophora  is  the  possession 
of  one  or  more  flagella  as  organs  of  locomotion  and  food-capture, 
not  merely  during  early  stages  of  development,  but  in  the  active 
phases  of  the  adult  organism  also.  In  other  classes,  as  has  been 
pointed  out  in  a  previous  chapter,  flagella  may  be  present  in  the 
young  stages,  but  are  absent  in  the  adult  phases.  In  the  Masti- 
gophora a  flagellurn  is  a  permanent  feature  of  the  organization, 
though  even  in  this  class  it  may  be  temporarily  lost,  either  in 
active  phases,  when  the  animal  may  become  amoeba-like,  or  in 
resting  phases,  especially  in  parasitic  forms  of  intracellular  habitat. 
The  Mastigophora  are  divided  into  three  subclasses,  of  which 
the  first,  the  Flagellata,  contains  the  more  typical  forms,  and  con- 
stitutes the  nucleus,  so  to  speak,  of  the  class  ;  while  the  two  remain- 
ing subclasses,  the  Dmoflagellata  and  Cystoflagellata,  may  be 
regarded  as  specialized  offshoots  of  the  primitive  flagellate  stem- 
It  is  convenient,  therefore,  to  deal  with  the  Flagellata  in  a  general 
manner  first,  and  then  to  describe  the  special  features  of  the  other 
two  subclasses. 

SUBCLASS  I.  :  FLAGELLATA  (EUFLAGELLATA). 

General  Characters. — The  members  of  this  group  are  for  the  most 
part  of  minute  size,  and  seldom  attain  to  considerable  dimensions  ; 
forms  of  relatively  large  size,  such  as  the  species  of  Euglena  and 
allied  genera,  are  small  as  compared  with  the  larger  species  of  the 
Sarcodina  and  other  classes.  As  a  rule  the  Flagellata  are  free- 
swimming  organisms  ;  a  certain  number,  however,  are  sedentary  in 
habit,  attaching  themselves  to  a  firm  basis,  and  using  their  flagella 
for  food-capture  alone.  There  is  a  great  tendency  to  colony- 
formation  in  this  group.  In  the  process  of  multiplication  by  fission 
of  the  ordinary  type,  separation  between  the  daughter-individuals 
may  be  incomplete,  so  that  they  remain  connected  together,  either 
by  means  of  a  common  envelope,  house,  or  gelatinous  matrix,  or 
by  organic,  protoplasmic  union,  or  in  both  ways.  Repeated  fission 

257  17 


258  THE  PROTOZOA 

of  this  kind  leads  to  the  formation  of  a  colony,  which  may  attain 
to  dimensions  relatively  large,  though  composed  of  individuals 
of  minute  size.  The  colony  may  be  free-swimming  or  fixed,  and 
in  the  latter  case  is  frecuieiitly  arborescent  in  form.  In  many  cases 
the  colonies  of  Flagellata  show  a  differentiation  of  the  constituent 
individuals  into  vegetative  and  generative  individuals — the  former 
not  capable  of  reproduction,  but  purely  trophic  in  function  ;  the 
latter  destined  to  be  set  free,  and  to  produce  new  colonies,  with  or 
without  going  through  a  process  of  syngamy. 

Bionomics. — In  their  modes  of  life  the  Flagellata  exhibit  all  the 
four  types  described  in  Chapter  II.  (p.  13),  different  forms  being 
holozoic,  holophytic,  saprophytic,  or  parasitic  ;  and  one  and  the 
same  form  may  live  in  different  ways  during  different  periods  of  its 
life-history,  according  to  circumstances. 

The  parasitic  flagellates  have  attracted  a  great  deal  of  attention  of  recent 
years,  on  account  of  their  importance  in  causing  disease  in  man  and  animals. 
Ectozoic  parasites  may  occur  in  aquatic  forms,  as  for  example  Costia,  para- 
sitic on  the  skin  of  fishes.  The  entozoic  forms  are  parasitic  for  the  most 
part  in  the  digestive  tract,  or  in  the  blood  and  lymph  of  their  hosts.  Parasitic 
flagellates  are  found  in  the  intestines  of  practically  all  classes  of  the  Metazoa, 
and  especially  in  arthropods  and  vertebrates  ;  those  parasitic  in  blood  and 
lymph  are  found  especially  in  vertebrates,  and  constitute  an  important 
group  commonly  termed  as  a  whole  the  Hsemoflagellates,  to  which  a  special 
•chapter  will  be  devoted.  From  forms  which  were  probably  parasitic  originally 
in  the  blood  have  arisen  secondarily  forms  parasitic  in  cells  which  in  their 
intracellular  phase  lose  their  flagellum  entirely  (Leishmania). 

Many  of  the  intestinal  flagellates,  especially  in  vertebrates,  are  probably 
not  true  parasites  at  all,  but  for  the  most  part  scavengers.  In  any  case  their 
pathogenic  role  appears  to  be  very  limited  ;  but  in  some  cases  a  pathological 
condition  of  the  host  may  be  combined  in  a  suspicious  manner  with  great 
numbers  of  the  parasites  (compare  Bohne  and  Prowazek,  Noc).  It  is  worthy 
of  note  that  in  some  cases  an  intestinal  parasite  may  pass  from  the  intestine 
into  the  blood  or  lyniph  under  pathological  conditions  of  the  host.  This 
condition  suems  to  have  been  noticed  first  by  Danilewsky,  who  described 
cases  of  frogs  and  tortoises  which  had  been  kept  long  in  captivity  and  were 
in  bad  condition,  thin,  and  with  oadematous  swellings  in  the  muscles  and 
transudation  of  lymph  into  the  peritoneal  cavity ;  in  such  animals  there 
were  found  in  the  blood  and  lymph,  especially  in  the  oedemata  and  trans- 
udations.  abundant  flagellates  of  the  genus  Hexamitus  (  =Octomitus.  Fig.  116). 
of  a  species  which  in  normal,  healthy  animals  is  found  only  in  the  intestine. 
A  number  of  similar  cases  have  been  recorded  by  Plimmer  (383,  and  Presi- 
dential Address  to  the  Royal  Microscopical  Society,  1912),  who  found  botli 
Octomitus  and  Trichomonas  in  the  blood  of  various  batrachia  and  reptiles. 
The  conditions  under  which  these  intestinal  parasites  pass  into  the  blood 
appears  to  be  strictly  comparable  to  those  under  which  the  Leydenia-iorw 
of  Chlamydophrys  passes  into  the  ascitic  fluid  (p.  237).  Whether  in  such 
cases  the  migration  of  the  parasite  is  the  cause  of  the  diseased  state  of  the 
host,  or  whether,  as  seems  more  likely,  the  abnormal  condition  of  the  host 
gives  the  parasite  an  opportunity  of  spreading  into  fresh  pastures,  must 
remain  for  the  present  an  open  question  ;  but,  according  to  Plimmer,  the 
presence  of  intestinal  flagellates  in  the  blood-circulation  is  associated  with 
definite  and  recognizable  lesions  of  the  intestinal  wall.  In  any  case,  the 
fact  that  intestinal  flagellates  can'  pass  into  the  blood  is  a  point  which  is 
probably  of  phylogenetic  as  well  as  of  practical  importance  (p.  322). 


THE  MASTIGOPHORA  259 

Structure. — The  body-form  is  of  three  principal  types  :  d)  An 
envelope  or  tough  cortex  may  be  entirely  absent,  and  the  body  is 
then  amoeboid,  as  in  the  Rhizomastigina  (Figs.  38,  40)  ;  (2)  a  thin 
cuticle  may  be  present,  insufficiently  rigid  to  inhibit  changes  of 
body-form  due  to  contractility  of  the  living  substance  (Fig.  15) ; 
(3)  a  thicker  cuticle  necessitates  a  constant  body-form,  which  is 
either  rigid  and  unalterable  or  sinuous  and  permitting  movements 
of  flexion  and  torsion.  In  the  second  type  are  comprised  forms 
termed  commonly  "  metabolic,"  on  account  of  the  changes  of  form 
they  exhibit ;  contractions  of  the  superficial  layer  of  the  body  pass, 
as  it  were,  in  waves  from  the  anterior  to  the  posterior  end  of  the 
body,  in  a  manner  similar  to  the  peristaltic  contractions  of  the 
intestine,  producing  rhythmic  form-changes  in  the  body. 

In  species  in  which  the  cuticle  is  thin  or  absent,  a  constant  body- 
form  may  nevertheless  be  maintained  by  internal  form-giving 
organs,  such  as  the  axostyle  of  Trichomonas  (Fig.  5),  Lophomonas 
(Fig.  45),  etc.  True  internal  skeletons,  however,  do  not  occur.  An 
external  shell  or  house  may  be  present,  enclosing  the  whole  body. 

The  protoplasmic  body  shows,  in  the  amoeboid  forms  such  as 
the  Rhizomastigina  (p.  268),  distinct  ectoplasm  and  encloplasm. 
But  as  a  general  rule  the  thin  ectoplasm  is  converted  into  a  firm 
cuticle,  or  periplast,  enclosing  the  body  and  containing  contractile 
elements — myonemes.  Hence  the  ectoplasm  appears  at  first  sight- 
to  be  absent,  and  the  protoplasmic  body  to  consist  of  endoplasm 
alone.  In  larger  forms  the  myonemes  can  be  made  visible  by 
suitable  treatment  (Fig.  28),  but  as  a  general  rule  in  such  minute 
organisms  the  existence  of  myonemes  or  other  contractile  mechan- 
isms can  only  be  inferred  from  the  movements  of  contractility  or 
flexibility  which  the  body  exhibits. 

The  flagella  may  perform  various  functions  in  different  cases  ; 
they  may  serve  as  organs  of  locomotion  and  of  food-capture,  as 
organs  of  temporary  attachment,  and  as  tactile  organs.  As  stated 
above  (p.  52),  they  may  be  distinguished  by  their  relation  to  the 
progression  of  the  organism,  as  tractella,  anterior,  and  pulsdla, 
posterior  in  movement.  The  flagella  vary  in  number  and  in  arrange- 
ment in  different  species,  and  for  the  different  types  of  the  flagellar 
apparatus  a  number  of  technical  terms  are  in  use  :  monomastigote, 
Avith  a  single  flagellum  (Fig.  38)  ;  isomastigote,  with  two  or  four 
fUgella  of  equal  length  (Fig.  43)  ;  paramastigote,  with  one  long 
principal  flagellum  and  a  short  accessory  flagellum  (Fig.  15)  ; 
.heteroma-stigote,  with  one  or  more  anterior  flagella  directed  forwards. 
and  a  "  trailing  flagellurn "  directed  backAvards  (Figs.  5,  25)  ; 
polymastigote,  with  a  tuft  of  flagella  (Fig.  45)  ;  and  holomastigote, 
Avith  numerous  flagella  scattered  evenly  over  the  body  (Fig.  113). 
Of  these  various  types  of  arrangement,  the  heteromastigote  con- 


260 


THE  PROTOZOA 


dition.  with  a  backwardly-directed  trailing  flagellum  ("  Schlepp- 
geissel  "),  deserves  special  attention,  since  by  attachment  of  the 
trailing  flagellum  to  the  body  an  undulating  membrane  (p.  56) 
may  arise  ;  and  that  it  has  actually  so  arisen  in  some  cases  is 
indicated  by  the  existence  of  pairs  of  similar  forms,  in  which  a 


FIG.  110. — Codonosiga  botrytis.  A,  Young  specimens 
attached  singly  to  the  stalk  of  a  Vorticella ;  B,  colony 
of  six  individuals  on  a  common  stalk  ;  G,  stalked 
individual  which  has  recently  divided  into  two,  pro- 
ducing a  dichotomous  division  of  the  stalk,  c.v., 
Contractile  vacuole.  After  Stein. 


trailing  flagellum,  free  from  the  body,  in  the  one  form  is  represented 
by  the  marginal  flagellum  of  an  undulating  membrane  in  the 
other  —  as,  for  example,  Tricliomastix  and  Trichomonas  (Fig.  5), 
Prowazekia  (Fig.  141),  and  Trypanoplasma  (Fig.  36). 

In  one  group  of  flagellates — hence  known  as  the  Choanoflagollata 


THE  MASTIGOPHORA  261 

or  Craspedomoiiads  (Fig.  110) — a  peculiar  structure  occurs,  known 
as  the  "  collar,"  a  delicate  protoplasmic  tube  or  funnel  which 
arises  along  a  circular  base-line  of  which  the  insertion  of  the  flagellum 
is  the  centre,  and  so  forms  a  cup,  sleeve,  or  collar-like  structure 
surrounding  the  flagellum  for  about  a  third  or  a  half  of  its  length. 
It  is  stated,  both  for  Choanoflagellates  and  for  the  very  similar 
collar-cells  of  sponges,  that  the  collar  is  a  membrane  folded  in  a 
spiral  manner,  its  insertion  running  along  the  body  and  round  the 
base  of  the  flagellum  ;  but  the  spiral  structure  is  not  easy  to  make 
out.  The  Choanoflagellates  are  sedentary  forms  which,  if  set  free 
temporarily  from  their  attachment,  swim  with  the  flagellum 
directed  backwards,  doubtless  the  mechanical  result  of  the  presence 
of  the  collar.  The  function  of  the  collar  is  probably  connected 
with  the  capture  and  absorption  of  food-particles  wafted  towards 
the  body  by  the  flagellum.  The  collar  is  retractile,  but  is  not  capable 
of  active  movements  such  as  are  seen  in  an  undulating  membrane. 

The  organs  of  nutrition  must  be  considered  in  connection  with 
the  four  modes  of  life  already  mentioned. 

(a)  In  holozoic  forms  the  organism  captures  and  ingests  other 
organisms  of  various  kinds.  In  some  forms  the  ingestion  of  food- 
particles  nia}7  take  place  at  any  point  on  the  body-surface  ;  examples 
of  this  are  the  amoeboid  forms,  such  as  Mastigamosba,  which  capture 
their  food  by  means  of  their  pseudopodia,  like  an  amoeba  ;  the  holo- 
mastigote  genus  Multicilia  (Fig.  113)  ;  the  parasitic  LopJiomonas 
.(Fig.  45),  and  possibly  others.  But  in  most  cases  food-particles 
are  ingested  at  the  base  of  the  flagellum,  the  spot  towards  which 
they  are  propelled  by  the  activity  of  the  flagellum  itself.  There 
may,  however,  be  no  special  aperture  for  food-ingestion,  particles 
which  impinge  upon  the  soft  protoplasmic  body  being  simply 
>rbed  directly  with  formation  of  a  food-vacuole.  With  a  more 
advanced  type  of  organization,  a  special  aperture  or  cytostome  for 
the  ingestion  of  food-particles  is  found  at  the  base  of  the  flagellum. 
The  cytostome  may  be  a  simple  aperture  leading  through  the  cuticle 
directly,  or  by  means  of  a  funnel-shaped  depression,  into  the  proto- 
plasmic body,  or  it  may,  in  more  highly  organized  forms,  lead  into 
a  special  tube,  termed  an  "  oesophagus  "  or  "  cytopharyiix,"  which 
receives  the  evacuations  of  the  contractile  vacuoles,  and  serves  for 
excretion  as  well  as  ingestion  (Fig.  84).  In  any  case  the  oesophagus 
ends  blindly  in  the  fluid  endoplasrn.  There  is  no  special  anal  aper- 
ture for  expulsion  of  fa3cal  material,  which  is  expelled  at  any  point 
of  the  body-surface  in  primitive  forms,  or  through  the  oesophagus 
cytostome  in  those  more  highly  organized. 

(6)  In  holophytic  forms  the  organs  of  nutrition  are  those  of  the 
plant-cell  (p.  188) — namely,  chromatophores,  or  corpuscles  contain- 
ing chlorophyll  or  allied  pigments  :  pyreiioids,  small  glistening  bodies 


262  THE  PROTOZOA 

embedded  in  the  chromatophores,  the  centres  of  the  formation  of 
amyloid  substances ;  and  grains  of  amyloid  nature  formed  by  the 
constructive  metabolism  of  the  organism.  It  is  also  common  to 
find  in  the  holophytic  flagellates  a  peculiar  red  spot,  or  stigma, 
placed  near  the  anterior  end  of  the  body,  and  probably  sensitive 
to  light  (p.  205). 

In  general,  two  types  of  holophytic  flagellates  can  be  recognized  : 
first,  forms  in  which,  in  addition  to  the  organs  already  mentioned, 
those  pertaining  to  the  holozoic  mode  of  nutrition  are  also  present ; 
secondly,  those  possessing  only  the  holophytic  apparatus.  The 
first  type  may  be  regarded  as  more  primitive  forms  in  which  the 
holophytic  habit  of  life  has  not  become  so  engrained  as  to  exclude 
any  other  mode  of  nutrition ;  but  a  change  is  still  possible,  and  the 
organism  can  combine  or  vary  the  holophytic  Avith  the  holozoic 
or  saprophytic  method.  In  the  second  type  the  organism  has  be- 
come plant-like,  to  the  complete  exclusion  of  other  methods  of 
nutrition  ;  the  body  is  generally  enclosed  completely  in  a  firm  cellu- 
lose envelope,  allowing  diffusion  of  liquids  and  gases,  but  without 
apertures  through  which  foreign  bodies  can  pass  into  the  interior. 
Such  forms,  if  they  lose  their  flagellum  in  the  adult  state,  are  classed 
as  unicellular  Algse,  and  the  young  flagellated  individuals  are  termed 
"  zoospores."  The  transition  from  holophytic  flagellates  to  plants 
is  a  gradual  one,  and  the  border-line  is  simply  fixed  by  the  characters 
of  the  "  adult,"  and  is  therefore  as  arbitrary  as  that  between  Sar- 
codina  and  Mastigophora  discussed  in  a  previous  chapter. 

(c)  In  saprophytic  and  parasitic  forms  no  special  organs  of  nutri- 
tion are  present,  since  the  food  is  absorbed  in  a  fluid  condition  from 
the  surrounding  medium. 

Contractile  vacuoles  are  commonly  present  in  those  flagellates 
which  inhabit  fresh-water.  In  the  more  primitive  forms  the 
vacuoles  empty  themselves  direct  to  the  exterior.  In  more  highly 
organized  types  the  vacuoles  open  into  the  oesophagus.  In 
Euglena  the  two  contractile  vacuoles  open  into  a  reservoir- vacuole, 
which,  according  to  Wager  (213),  is  in  open  communication  with 
the  oesophagus  (Fig.  84). 

The  nuclear  apparatus  consists,  as  a  rule,  of  a  single  nucleus  of 
vesicular  type,  with  a  distinct  karyosome.  Chroniidia  are  generally 
absent,  but  are  found  in  a  few  cases  (Rhizoniastigina). 

The  relations  of  the  nuclear  apparatus  and  the  flagella  have  been  discussed 
above,  and  are  briefly  as  follows  : 

1.  There  is  a  single  nucleus  with  a  single  centriole,  which  functions  at  the 
same  time  as  centrosome  and  blepharoplast.  Then  either  (a)  the  centriole 
is  within,  or  connected  intimately  with,  the  nucleus,  in  which  case  the  fla- 
gellum appears  to  arise  directly  from  the  nucleus,  as  in  Mastigina  (Fig.  38)  ;  or 
(b)  the  centriole,  and  the  flagellum  it  gives  off,  are  quite  independent  of  the 
nucleus,  as  in  Mastigella  (Fig.  40). 


THE  MASTIGOPHORA  263 

2.  There  is  a  single  nucleus  with  its  centrosome,  and  in  addition  one  or 
more   blepharoplasts  in  relation  to  the  flagellar  apparatus.     Then   (a)   at 
division  the  old  blepharoplasts  and  flagella  are  lost,  and  new  blepharoplasts 
arise  during  or  after  nuclear  division  from  the  centrosomes  ;  or  (6)  the  blepharo- 
plasts and  flagella  persist,  and  the  former  divide  independently  to  form 
daughter-blepharoplasts  from  which  new  flagella  arise  (Fig.  43). 

3.  In  a  certain  number  of  Flagellata,  grouped  provisionally  as  Haemo- 
tiagellates  or  Binucleata  (see  next  chapter),  two  nuclei,  each  probably  possess- 
ing its  own  centrosome,  are  present  :  a  principal  or  trophic  nucleus  and  an 
accessory  or  kinetic  nucleus. 

In  Type  2  the  blepharoplast  attains  to  a  greater  or  less  degree  of  indepen- 
dence of  the  centrosome,  and  divides  independently  of  it  for  many  generations 
of  ordinary  vegetative  reproduction  by  fission.  But  there  are  probably  in 
all  cases  periods  in  the  life-cycle  when  the  entire  nuclear  apparatus  is  reduced 
to  a  single  nucleus  and  centriole,  from  which  the  condition  in  the  adult, 
whatever  it  may  be.  arises.  For  the  so-called  fourth  type  of  Hartrnann  and 
Ohagas  (62),  see  below  (p.  273). 

Reproduction  and  Life-Cycle. — The  commonest  method  of  repro- 
duction is  simple  or  binary  fission  in  the  free  state.  The  products 
of  the  fission  are  of  equal  size,  and  the  division  of  the  body  is  in- 
variably longitudinal  (Senn,  358) — that  is  to  say,  along  an  axis 
continuing  the  direction  of  the  principal  flagellum  or  flagella.  In 
addition  to  this,  the  typical  method  of  reproduction,  other  types  of 
division  occur.  Multiple  fission  in  the  free  active  condition  is 
known  in  some  parasitic  forms,  such  as  Trypanosoma  lewisi  and 
Lophomonas  blattarum  (Janicki,  70).  On  the  other  hand,  fission 
may  sometimes  take  place  in  a  resting,  non-flagellated  condition,  or 
within  a  cyst ;  in  the  first  case  it  is  frequently,  in  the  second 
perhaps  always,  of  a  multiple  type. 

The  occurrence  of  syngamy  in  the  life-cycle  is  a  point  which 
has  been  disputed,  probably  owing  to  the  fact  that  in  forms  of 
simple  structure  it  takes  place  only  at  long  intervals  in  the  life- 
cycle,  or  under  special  conditions.  Moreover,  the  longitudinal 
division  prevalent  in  this  group  makes  it  practically  very  difficult 
to  decide,  except  by  continuous  observation,  whether  two  conjoined 
flagellates  are  individuals  about  to  fuse  in  syngamy  or  to  separate 
after  fission.  In  the  colonial  Phytomonadina,  where  highly-differ- 
entiated gametes  are  found,  the  occurrence  of  syngamy  has  long 
been  known,  but  the  existence  of  sexual  processes  in  other  flagel- 
lates has  been  doubted  by  high  authorities.  In  recent  years,  how- 
ever, it  has  been  observed  in  a  number  of  forms,  and  there  can  be 
no  doubt  of  the  existence  of  sexual  processes  in  flagellates  generally. 
A  summary  of  recent  observations,  with  full  references,  is  given  by 
Dobell  (335,  pp.  109-111).  The  available  data  are  as  yet  insufficient 
to  make  it  possible  to  give  a  connected  account  of  syngamic  pro- 
cesses in  Flagellata  generally,  and  only  a  few  typical  cases  can  be 
dealt  with  here. 

A  simple  type  of  syngamy  has  been  described  in  Copromonas 


264 


THE  PROTOZOA 


subtilis  (Fig.  Ill)  by  Doboll  (335).  In  this  species  the  two  gametes 
appear  perfectly  similar  to  each  other,  and  are  not,  in  fact,  distin- 
guishable in  any  way  from  ordinary  individuals  of  the  species.  Two 
such  individuals  come  together  and  unite  by  their  anterior  or  flagellar 

extremities.     In  one 
gamete  the  flagellum  is 
lost,  and  the  couple  swims 
about  by  means  of  the  re- 
maining one  ;  this  is  the 
only  difference  between 
the  two  gametes  which 
could  be  interpreted  as 
one  of  sex.    While  fusion 
of    the    bodies    is    still 
incomplete,  the  nucleus 
of   each  gamete  divides 
by     a    simple    type    of 
promitosis  (p.  109).    One 
of   each    pair  of   sister- 
nuclei  thus  produced  is 
a       reduction  -  nucleus, 
which  degenerates  ;  the 
other  persists.     The  per- 
sistent nucleus  of   each 
gamete  then   divides   a 
second    time,    but   into 
two  very  unequal  halves; 
the   smaller    nucleus   in 
each  case  degenerates  as 
a     reduction -nucleus, 
while  the  larger  persists 
as  the  pronucleus.     The 
bodies  of  the  gametes  are 


FIG.  111. — Life-cycle  of  Copromonas  subtilis.  A, 
Ordinary  adult  form  ;  B,  C,  D,  "  vegetative  " 
reproduction  by  binary  fission  ;  E—J,  stages  of 
reduction  and  syngamy :  F,  G,  H,  reduction  ; 
/,  J,  fusion  of  the  two  pronuclei  ;  the  zygote 
(/)  may  develop  into  an  ordinary  free-swimming 
individual,  or  (J)  may  retract  its  flagellum  and 
become  encysted  ;  K,  cyst ;  L,  liberation  of  an 
adult  form  from  the  cyst.  After  Dobell  (335). 


now  completely  fused, 
and  the  fusion  of  the 
pronuclei  follows.  The 
zygote  may  become  en- 
cysted at  once,  or  may 
continue  to  live  a  free 
life.  In  the  first  case 


the  fusion  of  the  pro- 
nuclei  takes  place  within  the  cyst,  from  which  it  is  ultimately  set 
free  as  an  ordinary  individual  which  feeds  and  multiplies  vegeta- 
tively.  In  the  second  case  the  zygote  becomes  an  ordinary  free 
individual  at  once,  the  interlude  of  encystment  being  omitted. 


THE  MASTIGOPHORA  265 

The  syngamy  of  Copromonas  is  thus  seen  to  be  a  case  of  perfect 
isogamy,  and  is  probably  to  be  regarded  as  representing  a  very 
primitive  type,  whence  the  more  complex  sexual  processes  of  other 
Flagellata  have  been  evolved — (1)  by  greater  specialization  and 
differentiation  of  the  gametes  in  their  relation  to  other  phases  of 
the  life-cycle  (gamete-formation)  and  to  one  another  (sexual  differ- 
entiation) ;  (2)  by  correlation  of  the  sexual  phases  with  definite 
crises,  to  which  they  become  restricted,  in  the  general  life-cycle. 

In  the  Rhizomastigina  sexual  processes  occur  of  a  type  resembling  those 
found  in  the  Sarcodina  to  such  an  extent  as  to  indicate  that  the  affinities  of 
this  group  is  rather  closer  to  some  of  the  primitive  Rhizopods  than  to  typical 
Flagellata.  The  life-cycle  (Fig.  112)  has  been  worked  out  in  full  detail  in 
Mastigella  vitrea  by  Goldschmidt  (41).  Vegetative  reproduction  in  the  free 
state  is  by  binary  fission  of  the  ordinary  type,  and  occurs  when  food  is  abun- 
dant ;  a  falling-off  in  the  supply  of  nutriment  leads  to  gamete-formation  and 
syngamy.  In  the  earliest  stages  of  the  sexual  generation  a  differentiation 
of  the  individuals  into  macrogametocj^tes  and  rnicrogametocytes  is  to  be 
observed,  though  externally  they  are  similar  to  ordinary  individuals  and 
continue  their  vegetative  life  during  the  early  stages  of  gamete-formation. 
In  the  macrogametocyte,  first  a  quantity  of  nucleolar  substance,  and  then  of 
chromatin,  is  set  free  from  the  nucleus  ;  these  two  substances  unite  to  form 
a  chromidial  mass  from  which  a  number  of  secondary  nuclei  are  formed. 
The  secondary  nuclei  become  scattered  through  the  cytoplasm,  and  each 
becomes  surrounded  by  a  protoplasmic  body.  The  small  cell  thus  formed 
is  a  macrogarnete,  which  goes  through  reducing  divisions.  The  still  active 
macrogametocyte,  which  has  its  cytoplasm  crammed  with  the  small  gametes, 
now  becomes  encysted.  Within  the  cyst  the  gametes  acquire  flagella  and 
become  motile.  At  this  stage  the  original  nucleus  of  the  gametocyte  breaks 
up  and  disappears  rather  suddenly.  Finally  the  cyst -wall  is  ruptured  and  the 
flagellated  gametes  escape. 

The  formation  of  the  microgametes  takes  place  in  a  manner  essentially 
similar  to  that  already  described  for  the  macrogametes,  but  with  a  few 
differences  in  detail.  The  microgametocytes  become  encysted  at  the  very 
beginning  of  the  process ;  then  formation  of  chromidia  begins,  and  as  soon 
as  it  is  completed  the  primary  nucleus  degenerates ;  the  microgametes  have 
no  flagella,  and  are  shot  out  of  the  cyst  when  it  bursts. 

The  free  macrogametes  measure  on  the  average  about  3'6  p.  diameter, 
and  have  a  flagellum  15  to  18  fj.  in  length ;  the  microgametes  are  2'8  p  in 
diameter,  and  have  no  flagellum.  A  niacroganiete  seeks  out  a  rnicrogai 
and  fuses  with  it,  cytoplasm  and  nucleus.  The  zygote  retains  the  flagellum 
of  the  macrogamete,  and  becomes  a  small,  monad-like  individual  which 
multiplies  by  fission  as  such.  After  several  generations  the  monads  cease 
lo  multiply,  and  each  grows  up  into  an  adult  Mastigella.  A  development 
similar  in  the  main  is  described  by  Goldschmidt  for  Mastiyina,  but  some  of 
the  phases  escaped  his  observation. 

Comparing  the  sexual  cycle  of  Masiigdla  (Fig.  112)  with  that  of 
Copromonas  (Fig.  Ill),  the  chief  difference  is  seen  to  be  that  in 
the  former  an  ordinary  individual  does  not  become  a  gamete  directly 
but  a  gametocyte,  which  by  a  process  of  multiple  fission  gives  rise 
to  a  generation  of  minute  swarm-spores,  the  gametes.  In  the  two 
sexes  a  slight  differentiation  of  the  gametes  is  seen.  Further,  in  the 
life-cycle  of  Mastigella  considered  as  a  whole,  there  are  two  forms 
of  individuals,  each  capable  of  multiplying  vegetatively  for  many 


266 


THE  PROTOZOA 


generations — namely,  the  monad  form,  product  of  syngamy,  and 
the  adult,  niastigamoeba-form,  which  ultimately  produces  the 
monad-like  gametes.  Hence  the  life-cycle  in  such  a  type  is  an 
alternation  of  generations  (metagenesis),  which,  as  in  so  many  other 


FIG.  112. — Life-cycle  of  Mastigdla  vitrea,  diagrammatic.  1,  2,  and  3,  Different 
forms  assumed  by  the  adult  "  vegetative  "  type  of  individual ;  3a,  36,  repro- 
duction by  binary  fission;  4 — 10,  gamete  -  formation  ;  a  (in  each  case), 
microgamete-formation,  b,  macrogamete-formation  ;  in  the  former  the  gamont 
becomes  encysted,  and  the  principal  nucleus  degenerates  early  in  the  process ; 
in  the  latter  the  gamont  remains  motile  and  the  principal  nucleus  persists 
to  the  last :  4 — 6,  extrusion  of  chromidia  from  the  nucleus  and  formation 
of  secondary  nuclei  ;  7,  8,  formation  of  the  gametes  round  the  secondary 
nuclei  ;  9,  extrusion  of  the  gametes  ;  10a,  the  small,  non-flagellated  micro- 
gametes  ;  101),  the  larger,  flagellated  macrogametes  ;  11,  copulation  of  the 
gametes  ;  12,  12a,  126,  multiplication  by  binary  fission  of  the  monad-like 
zygote  ;  13,  14,  growth  of  the  monad-form,  after  a  period  of  multiplication, 
into  the  adult  mastigamceba-forrn.  After  Goldschmidt  (41). 

cases  in  the  animal  kingdom,  appears  to  have  come  about  by  mul- 
tiplicative processes  taking  place  in  a  larval  type,  phylogenetically 
older — namely,  the  monad  form,  the  only  form  of  individual  that 


THE  MASTIGOPHORA  267 

occurs  in  the  life-cycle  of  Copromonas.  In  Mastigina,  on  the  other 
hand,  the  monad  form  developed  from  the  zygote  apparently  does 
not  multiply  by  fission,  but  develops  directly  into  the  adult  form — 
perhaps  a  more  primitive  state  of  affairs. 

A  very  instructive  series  is  furnished  by  the  colony-forming 
Phytomonads  of  the  family  Volvocidce.  At  one  end  of  the  series 
are  primitive  types,  such  as  Stephanos phcer a,  where  the  colony  is 
composed  of  eight  monad  individuals,  all  alike,  which  may  be 
agamonts  in  one  colony  or  gamonts  in  another.  Each  agamont 
multiplies  by  fission  to  form  eight  small  cells,  which  remain  con- 
nected together  and  grow  into  full-sized  monads,  thus  giving  rise 
directly  to  new  colonies.  In  the  gamont-colonies  each  gamont 
(garnetocyte)  gives  rise  by  multiple  fission  to  a  large  number  of 
minute  biflagellate  swarm-spores,  the  gametes,  which  are  set  free  and 
copulate.  The  syngamy  is  perfectly  isogarnous.  The  zygote  grows  in 
size,  and  finally  multiplies  to  form  the  eight  monads  of  a  new  colony. 

At  the  other  end  of  the  series  are  the  species  of  the  genus  Volvox, 
in  which  the  colony  is  composed  of  a  great  number  of  individuals, 
which  may  be  of  three  kinds,  not  necessarily  all  present  in  the  same 
colony:  (1)  The  ordinary  "somatic"  monads,  locomotor  and 
trophic  in  function,  which  do  not  reproduce  themselves  in  any  way  ; 
(2)  agamonts,  so-called  "  parthenogoiiidia,"  which  multiply  by 
fission  to  form  daughter-colonies  ;  (3)  gamonts  or  gametocytes, 
which  are  sexually  differentiated  as  "  microgonidia  "  and  "  ruacro- 
gonidia."  The  microgonidia  produce  by  multiple  fission  a  swarm  of 
small  biflagellate  microgametes,  comparable  to  the  gametes  of 
Stephauosphcera.  In  the  macrogoiiidia,  on  the  other  hand,  multi- 
plicative processes  are  in  abeyance,  and  each  becomes  a  single,  ovum- 
like  macrogamete,  which  is  fertilized  by  the  relatively  minute 
rnicrogainete.  Thus,  the  syngamy  in  Volvox  is  anisogarnous  to 
the  highest  degree  ;  and,  as  in  other  cases  among  Protozoa,  this 
condition  appears  to  have  arisen  from  a  primitive  isogamy  in  which, 
in  both  sexes,  the  gametocytes  sporulated  to  produce  a  swarm  of 
minute  gametes,  by  the  process  of  sporulation  becoming  altogether 
suppressed  in  one  sex — namely,  the  female — while  retained  in  its 
primitive  form  in  the  other.  The  colonies  of  Volvox,  with  their 
differentiation  of  individuals,  exhibit  a  condition  transitional  to 
that  of  the  Metazoa.  The  trophic,  non-rep  reductive  individuals, 
taken  as  a  whole,  may  be  compared  to  the  Metazoan  soma,  the  repro- 
ductive individuals  to  the  germen.  In  Pleodorina  calif ornica  dis- 
tinct male,  female,  or  parthenogenetic  colonies  occur  (Chatton),  as 
is  the  case  in  some  species  of  Volvox. 

Classification. — The  Flagellata  are  classified  in  different  ways  by  different 
authors,  and  in  the  present  state  of  our  knowledge  of  the  group  no  system 
can  be  regarded  as  in  any  way  final.  As  in  other  groups  of  Protozoa,  there 


268  THE  PROTOZOA 

arc  a  certain  number  of  well-defined  orders  and  families  characterized  by 
l  he  possession  in  common  of  certain  features  of  organization  which  leave 
no  doubt  as  to  their  taxonomic  homogeneity.  On  the  other  hand,  there  are 
a  large  number  of  primitive  forms  whose  characteristics  are  mainty  of  a 
negative  order,  and  of  which  the  affinities  are  in  consequence  vague  and 
uncertain,  the  systematic  position  debatable.  There  is,  moreover,  frequently 
an  element  of  uncertainty,  in  the  case  of  many  forms,  as  to  whether  they 
represent  truly  specific  adult  forms,  or  merely  developmental  stages  of  some 
other  species  of  the  Flagellata  or  Sarcodina.  Finally  there  are  a  certain 
number  of  species  and  genera  concerning  which  it  is  still  debated  whether 
they  should  be  assigned  to  the  Mastigophora  or  some  other  class  of  Protozoa. 

Hartmann  and  Chagas  (62)  have  proposed  to  utilize  the  relations  of  the 
flagellar  to  the  nuclear  apparatus  for  systematic  classification  of  the  Flagellata, 
as  suggested  also  by  Prowazek  (354).  But,  apart  from  the  fact  that  these 
relations  have  as  yet  been  investigated  in  very  few  flagellates,  and  that  in 
such  minute  objects  the  details  are  very  difficult  to  make  out  and  liable  to 
be  a  subject  of  dispute,  it  may  be  doubted  whether  these  points  of  structure 
are  sufficiently  constant  to  be  of  classificatory  value  in  this  subclass,  since 
they  appear  to  vary  considerably  in  allied  forms.  Thus  in  Copromonas 
subtilis,  according  to  Dobell  (335),  the  blepharoplast  persists  through  division- 
phases,  and  divides  independently  of  the  nucleus  ;  but  in  G.  major,  according 
to  Berliner,  the  old  blepharoplast  and  flagellum  are  lost  at  each  division, 
and  a  new  blepharoplast,  from  which  the  new  flagellum  grows  out,  is  formed 
by  division  of  the  nuclear  centriole  in  each  daughter-individual.  Again,  the 
third  type  of  flagellar  insertion  (p.  263)  is  found  in  the  Trypanosomidce.  allied 
to  the  Cercomonadidce,  and  in  the  trypanoplasms,  which  belong  to  the  family 
Bodonidos,  as  shown  in  the  next  chapter.  Classification  by  these  characters 
is,  therefore,  at  least  premature-,  if  not  fallacious.  Compare  also  Senn  (358). 

The  classification  adopted  here  is  in  the  main  that  of  Doflein  (7),  with 
certain  modifications.  For  convenience  a  number  of  forms  are  put  together 
in  the  Pantastomina,  without,  however,  claiming  that  this  order  is  anything 
more  than  a  cataloguer's  makeshift  for  disposing  of  a  number  of  forms  of 
dubious  position  and  uncertain  affinities. 

ORDER  I.  :  PANTASTOMINA. — Holozoic,  with  no  definite  mouth-opening ; 
food-particles  ingested  at  any  point  on  the  surface  of  the  body. 

Suborder  1  :  Bhizomastigina. — Body  amoeboid  ;  food  captured  and  ingested 
by  means  of  pseudopodia. 

Several  genera,  only  known  as  yet  from  fresh  water,  are  referred  to  this 
very  interesting  group  ;  such  are  Mastigamoeba,  F.  E.  Schulze,  Mastigina, 
Frenzel  (Fig.  38),  and  Mastigella,  Frenzel  (Fig.  40),  distinguished  from  one 
another  by  the  nature  of  their  amoeboid  movement  and  the  characters  of  their 
pseudopodia.  In  appearance  the  species  resemble  amcebte  which  possess  a 
long  and  well-developed  flagellum,  or  in  Dimastigamoeba  two,  in  Trimastig- 
amoeba  (Whitmore,  280)  three  flagella.  Locomotion  and  food-capture  are 
carried  on  for  the  most  part  as  in  an  amoeba,  and  the  flagellum  appears  to 
function  chiefly  as  a  tactile  organ  in  the  adult  mastigamceba- phase  ;  in  the 
young  monad-phase,  on  the  other  hand,  the  flagellum  is  the  sole  organ  of 
locomotion  and  food-capture,  as  in  an  ordinary  flagellate.  The  relation  of 
the  flagellum  to  the  nucleus  is  of  Type  1  described  above  (p.  263),  a  single 
centriole  which  functions  both  as  centrosome  and  blepharoplast ;  in  Mastigina 
and  Mastigamceba  the  flagellum  arises  from  the  nucleus  (Type  la) ;  in  Masti- 
gella the  origin  of  the  flagellum  is  distinct  from  the  nucleus  (Type  16).  The 
life-cj^cle  of  Mastigella  is  described  above  (p.  265).  In  many  points,  especially 
in  the  formation  of  secondary  gamete-nuclei  from  chromidia.  the  develop- 
ment resembles  more  that  of  the  Sarcodina  than  that  of  the  Flagellata,  and 
by  many  authorities  the  affinities  of  the  Rhizomastigina  are  considered  to  be 
rather  with  the  first  of  these  two  classes.  The  mastigamcebfe  certainly  link 
the  true  flagellates  with  the  Proteomyxa  and  Mycetozoa  ;  and  if  the  flagellnm 
were  lost  in  the  adult  phase,  they  would  be  classed  in  the  Sarcodina  without 
hesitation. 


FIG.  113. — A,  Multicilia  lacustris,  after  Lauterborn.  /?.,  Flagella,  one  of  which 
is  curled  up  into  a  loop  ;  ps.,  pseudopodiurn-like  process  ;  N.,  one  of  the 
nuclei  (the  others  are  hidden  by  the  ingested  food-masses)  ;  0.,  ingested 
Ohlamydomonads  ;  c.,  chlorophyll-bodies,  the  remains  of  other  Chlamydo- 
monads  in  process  of  digestion.  B,  Mnlticilia  palustris,  after  Penard.  N.,  The 
single  central  nucleus. 


270  THE  PROTOZOA 

Suborder  2:  Holomastigina. — With  numerous  flagella  radiating  from  a 
spherical  or  approximately  spherical  body. 

This  suborder  contains  the  single  genus  Multicilia,  Cienkowski,  to  which 
several  species,  some  fresh-water,  some  marine,  have  been  referred.  The 
number  of  flagella  varies  in  different  species,  and  their  precise  relation 
to  the  nuclear  apparatus  remains  to  be  made  out.  M.  lacusti  is,  Lauterborn 
{Fig.  113,  A),  is  multinucleate  ;  M .  palustris,  Penard  (Fig.  113,  B),  has  a  single 
nucleus.  The  body  is  not  covered  by  a  cuticle,  and  may  throw  out  pseudo- 
podia,  or  even  become  amoeboid  (Lauterborn).  Nothing  is  known  of  the 
life-cycle,  but  in  M.  lacustris  Lauterborn  observed  reproduction  by  simple 
fission  (plasmotomy  ?).  In  the  present  state  of  our  knowledge  adequate  data 
are  lacking  for  discussion  of  the  affinities  of  this  genus.  Doflein  (7)  regards 
it  as  a  form  lying  at  the  root  of  the  Infusorian  stem,  and  derives  the  most 
primitive  Ciliata  from  a  form  similar  to  Multicilia,  in  which  the  numerous 
flagella  become  specialized  in  structure  and  movement  to  give  rise  to  an  even 
coat  of  cilia ;  Penard  (302),  on  the  other  hand,  considers  Multicilia  allied  to 
the  Heliozoa  (p.  249).  It  is  clear  that  the  genus  is  one  which  would  repay 
further  study. 

ORDER  II. :  PROTOMONADINA. — Flagellates  for  the  most  part  of  small  or 
minute  size  ;  with  a  single  flagellum  ;  or  with  a  principal  and  one  or  two  acces- 
sory flagella  ;  or  with  two  flagella,  one  directed  anteriorly,  the  other  pos- 
teriorly as  a  trailing  flagellum.  Nutrition  holozoic,  saprophytic,  or  parasitic  ; 
in  the  first  case  the  food-particles  are  ingested  at  the  base  of  the  flagellum. 
where  a  definite  mouth-opening  may  be  present  or  absent,  but  without  a 
distinct  oesophagus  in  any  case.  The  contractile  vacuole  is  generally  single, 
if  present,  and  empties  itself  direct  to  the  exterior. 

This  order  comprises  a  vast  assemblage  of  genera  and  species,  subdivided 
by  Doflein  into  eight  families,  one  of  which,  the  Trypanosomidce,  including 
the  important  parasitic  genus  Trypanosoma,  is  discussed  in  detail  in  the  next 
chapter.  The  cuticle  is  generally  thin,  and  the  body  is  often  capable  of 
amceboid  or  metabolic  movements  ;  if  amoeboid,  however,  the  flagellum  is 
the  organ  of  locomotion,  so  long  as  it  is  present,  and  not  the  pseuclopodia. 
The  relations  of  the  flagellum  to  the  nuclear  apparatus  are,  in  general,  of  the 
second  type  (p.  263),  according  to  Hartmann  and  Chagas  (62) — that  is  to  say, 
with  distinct  centrosome  and  blepharoplast  ;  but  it  is  extremely  probable 
that  in  the  simpler  forms  Type  1  occurs  also  (compare  Alexeieff.  327),  and  in 
the  Trypanosomidce  the  distinctive  feature  is  the  possession  of  Type  3,  with 
trophonucleus  and  kinetonucleus,  as  also  in  some  of  the  Bodonidce  (Prowa- 
zelcia).  The  life-cycle  of  the  free-living  forms  is  probably  in  general  of  a 
simple  type,  similar  to  that  described  above  in  Copromonas  (Fig.  Ill)  ;  but 
observations  on  the  sexual  processes  are  at  present  very  scanty. 

For  a  detailed  description  of  the  forms  included  in  this  order  the  reader 
must  be  referred  to  the  larger  treatises,  especially  Biitschli  (2)  and  Senn  (320)  ; 
it  must  suffice  here  to  mention  some  of  the  more  typical  forms.  Cercomonas, 
type  of  the  family  Cercomonadidce  (Fig.  11-i).  has  a  single  flagellum  ;  the  hinder 
end  is  frequentty  drawn  out  into  a  long  tail-like  process,  and  is  capable  of 
change  of  form.  CEcomonas  (Oikomonas)  differs  in  having  the  body  rounded. 

Monas,  type  of  the  family  Monadidce,  has  a  principal  flagellum  and  one 
or  two  accessory  flagella.  Cladomonas  and  Spongomonas  (Figs.  41,  42)  form 
arborescent  colonies  ;  the  constituent  monads  have  two  flagella  of  equal 
size,  both  directed  forwards.  Alexeieff  (327)  considers  that  the  MonadidcK 
should  be  placed  in  the  suborder  Chrysomonadina  (see  below). 

Bodo  (Fig.  115),  type  of  the  family  Bodonidcs,  has  two  flagella,  one  directed 
forwards,  the  other  backwards  as  a  trailing  flagellum  ;  the  species  of  this 
genus  are  free-swimming  and  do  not  form  colonies  ;  they  occur  both  free- 
living  and  parasitic,  for  the  most  part  in  the  digestive  tracts  of  various  animals 
Bodo  lacertce,  from  the  cloaca  of  Lacerta  spp.,  has  been  studied  by  Prowazek 
(354),  who  has  described  a  process  of  autogamy,  but  doubt  has  been  cast  upon 
his  observations  by  Dobell  (336).  Note  also  the  occurrence  of  Bodo-like, 
forms  in  the  development  of  Cryptodifflugia  (p.  230,  supra).  The  flagellate 


THE  MASTIGOPHORA 


271 


FIG.  114. — Cercomonas  crnssicauda,  Dujardin, 
showing  amoeboid  changes  of  form.  After 
Stein. 


recently  described  by  Wenyon  (361)  from  a  culture  of  human  fasces,  and 
referred  by  him  to  the  genus  Cercomonas,  would  appear  rather  to  belong  to 
the  genus  Bodo.  To  the  family  Bodonidce  must  be  referred  also  the  genera 
Prou'azekia  and  Trypanoplasma,  dealt  with  in  greater  detail  in  the  next  chapter. 
Helcomastix,  Senn  (358),  is  to 
be  referred  to  the  Bodonidce  or 
made  the  type  of  a  distinct 
family ;  its  two  flagella  of 
unequal  length  are  both 
directed  backwards  in  move- 
ment. 

Finally,  mention  must  be 
made  of  the  group  of  flagel- 
lates characterized  by  the  pos- 
session of  a  collar  (see  p.  261, 
supra),  and  hence  commonly 
known  as  "  choanoflagel- 
lates  "  or  "  craspedomonads." 
They  are  sedentary  forms, 
attached  by  the  end  of  the 
body  opposite  to  the  flagellum, 
and  may  remain  single,  but 
more  usually  form  colonies 
often  of  considerable  extent 
(Fig.  110).  The  flagellum  is 
used  mainly  for  food-capture, 
in  which  the  collar  also  pro- 
bably plays  an  important 
part ;  but  an  individual  may 
become  detached  from  its 
support,  and  swim  freely,  the 

flagellum  being  then  directed  backwards.  The  systematic  position  of  the 
choanoflagellates  has  been  differently  estimated  by  different  authors ;  by  some 
they  have  been  ranked  as  a  primary  subdivision  of  the  Flagellata,  which  are 
then  divided  as  a  whole  into  Choanoflagellata  and  Lissoflagellata.  the  second 
of  these  divisions  being  used  to  include  all  other  flagellates.  Since,  however. 
the  choanoflagellates  scarcely  differ  from  ordinary  monads 
except  in  the  possession  of  the  characteristic  collar,  a 
specialization  of  the  food-capturing  function  related  to 
a  sedentary  life,  they  are  now  generally  ranked  as  a 
family  of  the  Protomonadiiia,  the  Choanoftagellidce. 

ORDER  III.  :  POLYMASTIGINA. — Flagella  from  three  to 
eight  in  number,  usually  all  more  or  less  equal  in  size  ; 
in  other  points  of  structure  similar  to  the  last -mentioned 
order.  Two  families,  which  are  sharply  marked  off  from 
one  another,  are  referred  to  this  order. 

1.  Tetramitidce,  with  three  or  more  flagella.  which  all 
arise  at  the  anterior  end  close  together.  The  flagella 
may  all  be  directed  forwards,  or  one  of  them  may  be 
turned  backwards  as  a  trailing  flagellum  ;  in  the  latter 
case  the  trailing  flagellum  may  or  may  not  be  united  to 
the  body  by  an  undulating  membrane. 

The  species  referred  to  this  family  are  for  the  most 
part  parasitic.  Endoparasitic  forms  of  common  occur- 
rence, especially  in  the  digestive  tracts  of  vertebrates, 
are  Trichotnastix,  with  three  anterior  flagella  and  a  free 
trailing  flagellum,  and  Tricliomonas  (Fig.  5),  with  the  same  number  and  arrange- 
ment of  the  flagella,  but  having  the  trailing  flagellum  united  to  the  body  by  an 
undulating  membrane.  These  two  forms  occur  frequently  in  the  same  host, 
and  are  perhaps  to  be  interpreted  as  two  developmental  phases  of  the  same 


A 

FIG.  115. — A,  Bodo 
saltans,  Ehren- 
berg.  B,  Bodo 
gracilis,  Stein. 
After  Stein. 


272 


THE  PROTOZOA 


organism  rather  than  as  distinct  generic  types.  Trichomonas  hominis  is 
entozoic  in  the  human  intestine,  T.  vaginalis  in  the  human  vagina  ;  they 
appear  to  be  harmless  scavengers  rather  than  parasites.  The  encystment 
of  Trichomonas  has  been  the  subject  of  some  controversy.  According  to 
Alexeieff  (326).  the  supposed  cysts  of  Trichomonas  described  by  various 
authors  are  in  reality  independent  vegetable  organisms,  of  the  nature 

of  yeasts.  In  some  species  of  Trichomonas  the 
anterior  flagella  are  four  in  number  (Alexeioif, 
323)  ;  for  such  forms  Parisi  (A.P.K.,  xix., 
p.  232)  has  founded  a  subgenus  Tetratricho- 
monas.  The  genus  Macrostoma,  according  to 
Wenyon  (362),  differs  from  Trichomonas  in 
having  the  undulating  membrane  wedged  in 
a  deep  groove ;  M.  mesnili  occurs  in  the 
human  intestine.  According  to  Alexeieff  (324), 
Macrostoma  is  a  synonym  of  Tetramitus.  Mono- 
cercomonas,  including  a  number  of  common 
intestinal  parasites,  has  four  anterior  flagella 
of  equal  length,  or  two  longer,  two  shorter 
(Alexeieff,  325). 

Costia  necatrix,  also  referred  to  this  family, 
is  ectoparasitic  on  the  skin  of  fishes.  According 
to  Moroff,  it  has  four  flagella  in  two  pairs,  two 
larger  and  two  smaller,  all  of  which  serve  for 
locomotion ;  but  the  larger  pair  are  used  also 
for  fixation,  and  the  smaller  pair  for  wafting 
into  the  mouth  the  food-particles,  which  consist 
chiefly  of  dead  epithelial  cells  torn  away  from 
the  epidermis  (see  also  Neresheimer). 

2.  Octomitidce.* — With  six  or  eight  flagella, 
arranged  in  pairs ;  the  body  is  bilaterally 
symmetrical  in  structure.  Entozoic  forms,  for 
the  most  part  of  intestinal  habitat. 

The  remarkable  bilateral  symmetry  of  the 
species  of  this  family  is  not  merely  an  external 
characteristic  of  the  body,  but  affects  the 
internal  structure  as  well,  and  the  entire 
nuclear  structure  is  doubled,  with  right  and  left 
halves.  Octomitus  (synonym,  Hexamitus ;  see 
Dobell,  236),  with  four  pairs  of  flagella  (Fig.  116), 
includes  a  number  of  entozoic  species — e.g., 
0.  intestinalis,  from  the  cloaca  of  the  frog  and 
other  animals.  Lamblia  intestinalis  (synonym, 
Megastoma  enter icum,  Fig.  117)  is  a  common 
inhabitant  of  the  human  intestine.  It  becomes 
encysted,  and  is  probably  disseminated  in  this 
form.  Within  the  cyst  it  divides  into  two 
(Rodenwaldt).  L.  sanguinis,  described  by 
Gonder  (A.P.K.,  xxi.,  p.  209)  from  the  blood 
of  a  falcon,  is  probably  an  intestinal  parasite 
gone  astray  (vide  p.  258). 
The  order  Polymastigina  differs  little  from  the  Protomonadina  except  in 
the  complication  of  the  flagellar  apparatus,  correlated  probably  with  the 
entozoic  habit.  Hartmann  and  Chaga,s  propose  to  merge  the  Polymastigina 

*  Doflein  terms  this  family  the  Polymasfiyidce,  but  the  name  is  clearly  in- 
admissible, since  the  genus  Polymastix  belongs  to  the  preceding  family,  and  is 
closely  allied  to  Trichomonas,  but  has  six  anterior  flagella  and  no  trailing 
flagellum  (compare  Alexeieff,  325). 


FIG.  116. — Octomitus  dujar- 
dini.  bl.1,  Anterior  blep- 
haroplast,  from  which  the 
first  and  second  flagella  of 
that  side  of  the  body  arise  ; 
bl.2,  second  blepharoplast, 
giving  off  the  flagellum  of 
the  third  pair ;  N.,  left-hand 
nucleus  ;  ax.,  left  axostyle  ; 
U.3,  third  blepharoplast,  at 
the  extremity  of  the  axo- 
style, giving  off  one  of  the 
flagella  of  the  fourth  pair. 
All  the  structures  indicated 
are  paired,  and  the  letters 
indicate  the  member  of  each 
pair  on  the  left  side  of  ths 
body.  After  Dobell  (236). 


THE  MASTIGOPHORA 


273 


in  the  Protomonadina,  and  then  to  divide  the  order  into  two  suborders  ;  the 
tirst,  entitled  the  Monozoa,  would  include  the  Protomonadina  as  constituted 
above,  with  the  exception  of  the  Trypanosomidce  ("  Binucleata  "),  and  with 
the  addition  of  the  Tetramitidce.  The  second  suborder,  Diplozoa,  would  in- 
clude only  the  Octomiiidce.  This  arrangement  certainly  seems  more  natural 
than  that  which  is  usually  adopted,  so  far  as  the  Tetramitidce  and  Octomitidce 
are  concerned. 

ORDER  IV. :  EUGLENOIDINA. — Larger  forms,  with  mouth-aperture  and 
oesophagus  ;  with  a  complex  vacuole- system  opening  into  the  oesophagus  ; 
often  with  holophytic  apparatus,  chromatophores,  stigma,  etc. 

This  order  represents,  so  far  as  structural  complication  of  the  individual 
is  concerned,  the  highest  type  of  organization  among  Flagellata.  The  body 
may  be  metabolic,  or  of  definite  contours,  with  thick  cuticle.  The  free-living 


FIG.  117. — Lamblia  intestinalis.  A,  Ventral  view  ;  B,  side  view.  N.,  One  of  the 
two  nuclei ;  ax.,  axostyles ;  ft.1,  fl.2,  fl.3,  fl.*,  the  four  pairs  of  flagella  ;  s.,  sucker- 
like  depressed  area  on  the  ventral  surface  ;  x,  bodies  of  unknown  function. 
After  Wenyon  (277). 

forms  are  either  holozoic  or  saprophytic,  if  colourless,  or  holophytic  if  pro- 
vided with  chromatophores,  in  which  case  they  may  be  capable  of  nourishing 
themselves  by  more  than  one  method.  The  flagellum  may  be  single,  or  there 
may  be  a  second  flagellum,  usually  smaller  than  the  principal  flagellum, 
and  sometimes  directed  backwards  as  a  trailing  flagellum.  The  attachment 
of  the  flagellum  is  of  the  second  type  (p.  263),  with  blepharoplast  distinct 
from  the  centrosome.  According  to  Hartmann  and  Chagas  (62),  in  Peranema 
trichophorum  the  centrosome  first  divides  to  furnish  a  blepharoplast,  and 
the  latter,  having  become  completely  independent  of  the  nucleus,  divides 
into  two,  a  distal  blepharoplast  or  basal  granule  of  the  flagellum,  connected 
by  a  rhizoplast  (centrodesmose)  with  the  proximal  blepharoplast  or  anchoring 
granule.  The  authors  consider  that  this  should  be  regarded  as  a  fourth  type 

18 


274 


THE  PROTOZOA 


of  flagellar  insertion,  characteristic  of  this  order  ;  but  it  is  simplest  to  regard 
it  merely  as  a  secondary  complication  of  the  second  type,  and  one  which  is 
not  universal  in  this  order,  since  in  Copromonas  subtilis  the  blepharoplast 
remains  undivided,  so  that  this  species  shows  a  flagellar  attachment  strictly 
of  the  second  type.  In  Euglena,  according  to  Wager  (213),  the  flagellum 
passes  through  the  oesophagus  and  becomes  attached  to  the  wall  of  the 
reservoir-vacuole  by  a  bifurcate  base.  On  one  of  the  branches  is  a  distinct 
thickening  in  close  contact  with  the  stigma  (p.  205).  The  thickening  is  prob- 
ably the  blepharoplast,  and  the  two  branches  represent  the  rhizoplast. 

The  sexual  processes  of  the  Euglenoidina  are  but  little  known,  and  Copro- 
monas is  the  only  genus  in  which  the  complete  life-cycle  has  been  worked  out  ; 
in  this  species  it  is  of  a  simple  type  (p.  264,  Fig.  111). 

The  order  comprises  three  families.  The  first,  Euglenidce,  contains  forms 
provided  with  cliromatophores,  holophytic,  saprophytic,  and  parasitic 
(Haswell)  in  habit.  Examples:  Euglena  (Fig.  4),  Pliacus  (Fig.  118).  The 
second  family,  Astasiidce,  contains  the  genus  Astasia  (Fig.  15),  colourless 

and  saprophytic  or  parasitic.  The  third  family,  Per- 
anemidce,  contains  numerous  genera  without  chro- 
matophores.  holozoic  or  saprophytic.  Examples : 
Peranema,  Copromonas  (Fig.  111).  Tho  subfamilies 
Heteronemince  and  Anisonemince  are  heteromastigote. 
Example  :  Anisonema  (Fig.  25). 

ORDER  V. :  CHROMOMONADINA. — Small  forms,  with- 
out oesophagus  or  vacuole-system,  with  delicate  cuticle 
and  one  or  two  flagella  ;  their  characteristic  feature  is 
the  possession,  usually,  of  one  or  two  conspicuous 
cliromatophores,  green,  yellow,  or  brownish,  in  colour. 
The  nutrition,  for  the  most  part  holophytic,  may 
be  also  holozoic  or  saprophytic.  Divided  into  two 
suborders. 

Suborder  1 :  Chrysomonadina. — With  one  or  two 
flagella  and  one  or  two  yellowish-brown  chroma- 
tophores  ;  body  often  amoeboid  or  metabolic  ;  colony- 
formation  frequent ;  nutrition  holozoic  and  holophytic. 
Three  families.  Examples  :  Chrysamosba,  Chromulina, 
Dinobryon,  etc.  According  to  Scherfl'el,  Chrysamceba 
is  the  amoeboid,  non-flagellated  phase  of  Chromulina  ; 
compare  also  Lauterborn  (345'5).  To  this  suborder 
must  be  referred  also  the  Coccolithophoridce.  marine 
flagellates  which  secrete  the  calcareous  shells  known  as 
coccoliths  (vide  Lohmann). 
Suborder  2  :  Cryptomonadina. — Small  forms  with  one  or  two  flagella,  colour- 
less, or  with  chromatophores  ranging  in  colour  from  yellowish-brown  to  olive- 
green  or  blue-green.  Holophytic  or  saprophytic,  not  holozoic.  Examples  : 
Chilomonas,  colourless  ;  Cryptomonas,  some  species  of  which  are  symbiotic  in 
Sarcodina  (p.  15).  Doflein  refers  the  Silicoflagellata  to  this  order  (p.  255). 

ORDER  VI. :  PHYTOMONADINA  SETT  PHYTOFLAGELLATA. — Completely  and 
exclusively  holophytic,  with  cellulose  envelope  and  without  mouth-aperture. 

This  order  comprises  the  most  plant-like  flagellates,  to  all  intents  and 
purposes  unicellular  algae  which  retain  throughout  life  their  flagellar  apparatus 
and  their  motility.  The  individual  is  generally  small,  and  the  body  is,  except 
in  one  family,  of  definite  form  and  enveloped  in  a  rigid  cellulose  envelope 
which  may  stand  off  from  the  body,  and  is  perforated  by  pores  through  which 
the  flagella  pass  out  to  the  exterior.  The  flagella  are  usually  two  in  number, 
sometimes  four,  of  equal  size.  The  cytoplasm  generally  contains  a  large 
green  chromatophore  and  a  red  stigma.  The  flagellar  insertion,  according 
to  Hartmann  and  Chagas,  is  of  the  second  type,  as  in  Protomonadina.  The 
reproduction  may  take  the  form  of  multiple  fission  within  the  body-envelope 
to  form  numerous  swarm-spores,  which  when  set  free  may  be  gametes  or 
agametes.  Colony-formation  is  frequent  in  this  order  (p.  257). 


FIG.  118.  —  Phacus 
triqueter.  ces.,  (Eso- 
phagus;  c.v.,  con- 
tractile vacuole  ;  st., 
stigma ;  AT.,  nucleus. 
After  Stein. 


THE  MASTIGOPHORA 


275 


Three  families  are  recognized.  The  first,  represented  by  the  genus  Pyra- 
mimonas,  contains  primitive  forms  in  which  the  body  is  metabolic  and  the 
cellulose  envelope  is  absent.  The  second  family,  Chlamydomonadidce,  com- 
prises non-colonial  forms  such  as  CJdamydomanas,  Hcematococcus,  etc.  Nephro- 


B 

FIG.  119. — Gonium  pectorale:  colony  of  sixteen  individuals,  each  with  two  flagella. 
A,  In  surface  view  ;  B,  in  side  view.  N.,  Nuclei  ;  c.v.,  contractile  vacuoles  ; 
st.,  stigmata.  After  Stein. 

selmis,  referred  by  Senn  (358)  to  this  family,  has  two  flagella,  on  which  it 
creeps  like  a  Bodo.  The  third  family,  Volvocidce,  comprises  colony-forming 
species  in  which  the  individual  is  similar  in  structure  to  the  Chlamydomonads, 
and  the  colony  is  composed  of  individuals  ranging  in  number  from  four,  eight, 


276  THE  PROTOZOA 

sixteen,  or  thirty-two,  up  to  many  thousands.  Examples  are  Oonium 
(Fig.  119),  Stephanosphcera,  Volvox,  etc. 

In  addition  to  the  six  orders  of  flagellates  enumerated  above,  there  remain 
some  peculiar  parasitic  forms,  the  systematic  position  of  which  is  extremely 
doubtful.  Such  are  the  family  Lophomonadidce,  represented  by  Lophomonas 
blattarum,  a  common  parasite  of  the  end-gut  of  the  cockroach  and  other 
Orthoptera,  and  the  Trichonymphidce.  including  the  genus  Trichonympha  and 
allied  forms,  parasitic  in  the  end-gut  of  termites  of  various  species. 

Lophomonas  blattarum,  which  has  recently  been  studied  by  Janicki  (70), 
bears  a  tuft  of  flagella  arising  at  the  anterior  pole  of  the  body  from  a  double 
ring,  or  rather  horseshoe,  of  blepharoplasts,  situated  at  the  edge  of  a  funnel- 
shaped  or  cup-like  structure,  the  calyx,  which  is  prolonged  into  an  axostyle 
(Fig.  45).  The  nucleus  lies  within  the  calyx,  which  is  surrounded  in  its  turn 
by  a  peculiar  thickening  or  support,  termed  the  "collar,"  consisting  of  free, 
radially-disposed  rods  crowded  together  to  form  an  aureole-like  figure,  approxi- 
mately spherical.  The  nutrition  is  holozoic,  and  food-particles  are  ingested 
at  any  point  on  the  body-surface,  as  in  the  Pantastomina.  Multiplication 
takes  place  by  binary  or  multiple  fission  in  the  free  state  ;  and  division  of  the 
nucleus  up  to  eight  within  a  cyst  has  been  observed,  but  the  entire  life-cycle 
has  not  been  worked  out.  Associated  with  L.  blattarum,  another  form, 
L.  striata,  occurs,  but  it  is  doubtful  if  this  is  a  distinct  species,  or  a  phase  or 
condition  of  L.  blattarum. 

The  group  or  family  Trichonymplndce  comprises  a  number  of  peculiar 
parasites  found  in  the  digestive  tract  of  various  species  of  Termitidce  ;  such 
are  the  genera  Joenia,  Lophophora,  Calonympha,  Devescovina,  etc.,  and  finally 
the  genus  Trichonympha,  from  which  the  family  takes  its  name.  The  chief 
peculiarity  of  these  forms  is  the  possession  of  numerous  flagella,  which  may 
be  disposed  in  tufts  at  the  anterior  end  of  the  body,  in  a  manner  similar  to 
Lophomonas  (which  by  some  authorities  is  included  in  this  family),  or  may 
be  distributed  over  the  whole  body,  like  a  coat  of  cilia,  as  in  the  genera 
Trichonympha,  Dinenymplia,  etc. 

According  to  Hartmann,  Trichonympha  hertivigi  occurs  under  two  forms, 
which  he  believes  to  represent  male  and  female  gamonts.  They  multiply 
by  binary  fission,  and  also  by  a  process  of  sporulation  to  produce  swarm- 
spores  which  are  believed  to  be  gametes.  Dinenympha  also  exhibits  sexual 
dimorphism,  according  to  Comes  (333). 

From  Janicki's  investigations,  there  can  be  no  doubt  that  Lophomonas  is  a 
true  flagellate,  possibly  allied  to  Trichomonas,  possibly,  however,  to  the  Pan- 
tastomina. The  genus  Joenia,  parasitic  in  Calotermes  flavicollis,  was  thought 
by  its  discoverer,  Grassi,  to  connect  Lophomonas  and  Trichonympha  ;  the 
recently-described  genus  Lophophora  (Comes,  332)  also  has  points  of  resem- 
blance to  Lophomonas,  but  is  remarkable  for  the  presence  of  undulating  mem- 
branes running  the  length  of  the  body.  By  some  authorities,  however,  the 
Trichonymphidce  have  been  placed  with  the  Ciliata,  while  Hartmann  considers 
that  they  should  rank  as  an  independent  class  of  the  Protozoa. 

SUBCLASS  II.  :  DINOFLAGELLATA  SEU  PERIDINIALES. 

The  characteristic  feature  of  this  subclass  is  the  possession  of 
two  flagella,  which  arise  close  together  about  the  middle  of  the 
body.  One  flagellum  (Fig.  120,  e)  runs  longitudinally  backwards 
as  a  trailing  flagellum  ;  the  other  (Fig.  120,  d)  runs  transversely 
round  the  body.  It  is  further  characteristic  of  this  group  for  the 
cuticle  to  be  greatly  thickened,  forming  a  tough  cuirass,  or  lorica, 
investing  the  body.  The  two  flagella  are  usually  lodged  in  grooves 
in  the  cuirass,  the  longitudinal  flagellum  in  a  longitudinal  groove 
or  sulcus,  the  transverse  flagellum  in  a  circular  groove,  or  annulus. 


THE  MASTIGOPHORA 


277 


a, 


The  transverse  flagellum  executes  undulating  movements  whicti 
were  formerly  mistaken  for  those  of  a  ring  of  cilia  ;  hence  the  name 
Cilioflagellata  formerly  applied  to  this  group. 

The  cuirass,  composed  of  cellulose  or  an  allied  substance,  is  in  its 
typical  form  a  perfectly  rigid  structure,  and  is 
often  prol  mged  into  spikes  and  processes  which 
cause  the  body  as  a  whole  to  assume  strange  or 
even  monstrous  forms  (Fig.  121).  Detailed 
studies  on  the  skeleton  have  been  published  by 
Kofoid  in  a  series  of  memoirs  (374-383).  The 
nutrition  is  for  the  most  part  holophytic,  but 
in  some  species  ingestion  of  solid  food  has  been 
observed.  A  great  many  parasitic  forms  have 
been  made  known  of  recent  years  (Chatton, 
366-369  ;  Caullery,  364)  ;  these  are  for  the  most 
part  forms  which,  in  the  vegetative,  parasitic 
phase  are  inert  bodies  with  no  sign  of  locomotor 
organs,  often  fixed  and  pedunculate  when  ecto- 
parasitic  ;  but  in  their  reproductive  phases 
they  betray  their  affinities  by  the  formation 
of  numerous  flagellated  swarm-spores  exhibiting 
the  typical  Dino flagellate  structure. 

The  pelagic  species  generally  possess  chroma- 
tophores,  and  frequently  a  red  stigma,  which  in 
some  genera — Pouchetia  (Fig.  31),  Erythropsis — is  modified  into  an 
eye-like  organ.   The  deep-sea  forms,  on  the  other  hand,  are  colourless. 

In  many  Dinoflagellates  a  peculiar  system  of  vacuoles  is  found  (Fig.  122), 
consisting  of  two  sacs  containing  watery  fluid,  each  of  which  empties  itself 

to  the  exterior  by  its  own  duct.  They  differ  from 
ordinary  contractile  vacuoles  in  possessing  a  dis- 
tinct envelope  and  in  not  performing  rhythmical 
contractions,  and  have  hence  been  given  the 
special  name  of  "  pusules  "  (Schiitt).  One  of  these 
organs,  termed  the  "collecting-pusule,"  consists  of 
a  reservoir-vacuole  surrounded  by  a  ring  of  smaller 
vacuoles  which  emptv  themselves  into  it ;  the 
other,  termed  the  "  sack-pusule,"  is  a  large  cavity 
which  takes  up  a  great  part  of  the  interior  of  the 
cuirass.  The  function  of  these  organs  is  probably 
hydrostatic. 

The  commonest  method  of  reproduction  is 
binary  fission  in  the  transverse  plane  of  the  body, 
in  which  each  daughter-individual  receives  a  half 
of  the  cuirass  of  the  parent  and  regenerates  the 
half  that  is  wanting.  Fission  rapidly  repeated  may 
lead  to  the  formation  of  chains  of  individuals.  In 

other  cases  multiple  fission  within  the  cuirass  has  been  observed,  leading  to  the 
formation  of  swarm-spores  which  are  possibly  gametes  ;  but  little  is  known  of 
the  sexual  processes  of  these  organisms. 

The  Dinoflagellates  are  an  exceedingly  abundant  and  widespread  group, 


FIG.  120.  —  Glenodi- 
niiim  cinctum, 
Ehrenberg.  a, 
Amyloid  granules  ; 
b,  stigma  ;  c,  chro- 
matophores;  d, 
flagellum  of  the 
transverse  groove  ; 
e,  flagellum  of  the 
vertical  groove  ;  v., 
vacuole.  From 
Lankester. 


FIG.  121. — Ceratocorys 
horrida:  cuirass.  After 
Stein,  from  Lankester. 


278 


THE  PROTOZOA 


highly  differentiated  as  regards  forms  and  species.  The  vast  majority  are 
pelagic  in  habit,  and  constitute  an  important  element  of  the  plancton-fauna, 
both  marine,  and  fresh-water.  A  certain  number  of  species  are  adapted  to 

parasitic  life.      They  are  divided  into    two 
orders. 

ORDER  I.  :  ADINIDA  (Prorocentracese). — 
Primitive  forms  in  which  the  typical  peculi- 
arities of  Dinoflagellate  organization  are  not 
fully  developed.  The  body-envelope  consists 
of  a  bivalve  shell  without  furrows.  The  two 
fiagella  emerge  through  an  aperture  between 
the  two  valves,  and  one  flagellum  projects 
freely  into  the  water,  while  the  other  twists 
round  it  at  the  base.  Example :  Prorocentmm. 
ORDER  II.  :  DINIFERA. — With  the  typical 
characters  of  the  subclass,  as  described  above. 
Families:  (1)  Gymnodinidce,  without  a  well- 
developed  cuirass — example  :  Qymnodinium  ; 
the  marine  genus  Oxyrrkis  (Fig.  123)  is  referred 
to  this  family  by  Senn  (358) ;  it  is  holozoic 
in  habit.  (2)  Peridinidce,  with  a  well-developed 
cuirass  made  up  of  definite  plates— examples : 
Glenodinium  (Fig.  120),  Ceratium,  Ceratocorys 
(Fig.  121),  Peridinium,  etc.  ;  Pyrodinium 
(Plate,  385)  is  remarkable  for  its  intense  phos- 
phorescence ;  at  the  hinder  pole,  between  the 
chromatophores,  the  cytoplasm  contains  a  body, 
the  "  Nebenkorper  "  of  Plate,  surrounded  by 
numerous  oil-drops,  which  are  perhaps  the 
seat  of  the  luminosity.  (3)  Dinopliysidce, 
oceanic  species  with  the  cuirass  divided  by  a 
sagittal  suture,  often  of  extraordinary  form — 
example  :  Dinophysis,  etc.  (4)  Blastodinidce, 

a  family  created  by  Chatton  (366.  367)  for  certain  parasitic  forms  ;  such 
are  Blastodinium,  an  internal  parasite  of  various  copepods,  and  Apodinium 
mycctoides,  an  ectoparasite  of  appendicularians  (Fritillaria).  The  parasitic, 
vegetative  form,  without  organs  of  locomotion, 
gives  rise  by  periodic  segmentation  of  mother- 
cells  to  successive  generations  of  swarm-spores, 
which  in  their  structure  resemble  Gymnodinium. 


FIG.  122. — Peridinium  diver- 
gens  :  ventral  view  showing 
the  vacuole-system.  c.p., 
The  collecting-pusule  sur- 
rounded by  a  rosette  of  still 
smaller  pusules  which  open 
into  it ;  s.p.,  the  large  sac- 
pusule,  or  reservoir ;  both 
opening  into  the  fundus  (/.), 
from  which  both  the  trans- 
verse flagellum  (t,),  lying  in 
the  annulus  (a.),  and  the 
longitudinal  flagellum  (I.), 
arise.  After  Schiitt,  from 
Lankester. 


N 


SUBCLASS  III. :  CYSTOFLAGELLATA  SEU 
RHYNCHOFLAGELLATA  . 

This  group  comprises  a  small  number  of 
forms  all  marine  and  pelagic  in  habitat. 
Their  chief  peculiarity  is  that,  like  KO 
many  other  pelagic  organisms  of  all  classes, 
the  body  is  inflated,  as  it  were,  Avith 
watery  gelatinous  substance,  so  that  it 
attains  to  a  size  which  far  exceeds  the 
actual  bulk  of  the  living  substance  con- 


eoe. 


FIG.  123. — OxyrrMs  marina, 
Duj.  P.,  Peristome  ;  N., 
nucleus;  f.v.,  food- 
vacuoles  ;  ex.,  excretory 
mass  about  to  be  ejected. 
After  Blochmann,  from 
Senn  (slightly  modified)  j 
magnification  1,000. 


tained    in    it.      In    consequence    of    the 

secondary  increase  in  size,  the  powers  of  locomotion  are  feeble,  and 

these  organisms  float  more  or  less  helplessly  on  the  surface  of  the  sea. 


THE  MASTIGOPHORA  279 

The  best  known  form  is  the  common  Nociiluca  miliaris  of  our  coasts.  The 
adult  Noctiluca  is  about  the  size  of  an  ordinary  pin's  head  (1  to  1'5  millimetres 
in  diameter).  The  spherical  body  consists  chiefly  of  jelly,  with  at  one  pole 
a  superficial  concentration  of  the  protoplasm  containing  the  nuclei  and  giving 
off  the  locomotor  organs.  From  this  central  mass  of  protoplasm  strands  extend 
in  an  irregular  network  through  the  whole  body,  which  is  limited  by  a  thin 
pellicle.  The  central  protoplasm  bears  the  so-called  "  peristome,"  a  deep  groove 
containing  the  mouth-aperture  near  one  end.  The  mouth  is  bordered  by  pro- 
jections known  as  the  "  tooth  "  and  the  "  lip,"  and  near  it  arise  two  motile 
organs — a  small  flagellum,  and  a  large  tentacle-like  process  which  shows  a 
transversely  striated  structure  and  performs  twisting  and  lashing  movements. 
The  tentacle  is  sometimes  named  the  "  flagellum,"  and  the  true  flagellum 
the  "  cilium  "  ;  the  former  probably  serves  as  the  organ  of  locomotion,  the  latter 
for  food-capture.  The  nutrition  is  holozoic. 

Noctiluca  reproduces  itself  by  binary  fission,  and  also  by  multiple  fission 
producing  a  brood  of  small  flagellate  swarm-spores.  The  formation  of  the  latter 
has  been  stated  to  be  preceded  by  isogamous  conjugation  of  the  adults,  but 
the  matter  is  open  to  doubt,  and  it  is  possible  that  the  swarm-spores  them- 
selves represent  the  gametes.  Other  genera  of  Cystoflagellata  are  Leptodiscus 
and  Craspedotetta  (Kofoid,  373),  both  remarkable  for  their  superficial  resem- 
!  ilance  to  medusae.  No  tentacle  like  that  of  Noctiluca  is  present  in  either  of  these 
forms,  and  locomotion  is  effected  by  rhythmic  contractions  of  the  disc-like 
body. 

BibliograpJiy. — For  references  see  p.  486. 


CHAPTER  XIII 
THE  H^BMOFLAGELLATES  AND  ALLIED  FORMS 

General  Characters  and  Principal  Types. — Under  the  term  "Hsemo- 
flagellates  "  are  grouped  together  a  number  of  forms  of  which  the 
characteristic,  though  by  no  means  invariable,  habit  is  alternating 
parasitism  in  the  blood  of  a  vertebrate  and  in  the  digestive  tract 
of  a  blood-sucking  invertebrate  host.  The  group  must  be  regarded, 
however,  as  one  founded  on  practical  convenience  rather  than  on 
natural  affinity — as  a  method  of  classification  comparable  to  that 
of  the  gardener  rather  than  of  the  botanist.  The  existence  of  a 
parasitic  habit  common  to  a  number  of  different  forms  is  in  itself 
no  proof  of  genetic  affinity  or  community  of  descent,  and  it  is  highly 
probable  that  more  than  one  line  of  ancestry  has  contributed, 
through  divergent  adaptation,  to  the  composition  of  the  group 
Haemoflagellates.  The  name  itself  has,  moreover,  lost  much  of  its 
significance,  since  closely  allied  to  the  forms  parasitic  in  blood,  and 
inseparable  from  them  in  a  natural  scheme  of  classification,  are 
other  forms  parasitic  only  in  invertebrates,  or  even  free-living. 

The  chief  morphological  characteristic  of  the  Hsemo flagellates  is 
the  possession  of  two  nuclei,  a  trophonucleus  and  a  kinetonucleus, 
and  the  relation  of  the  locomotor  to  the  nuclear  apparatus  is  of  the 
third  type  distinguished  in  the  preceding  chapter  (p.  263)  ;  on  this 
account  they  are  ranked  by  Hartmann  and  Jollos  (390)  as  a  distinct 
order  of  the  Flagellata  termed  the  Binucleata. 

The  Haemo flagellates  as  a  group  comprise  a  number  of  forms 
which  represent  in  some  cases  distinct  generic  types,  in  others 
merely  developmental  phases  alternating  with  other  forms  in  the 
life-cycles  of  particular  species.  The  following  six  generic  names 
represent  the  more  important  of  these  types  : 

1.  Trypanosoma  (Fig.  126,  etc.),  with  a  single  flagellum  which 
arises  near  the  kinetonucleus,  at  the  extremity  of  the  body  which  is 
posterior  in  progression,  and  runs  forward  as  the  marginal  flagellum 
of  an  undulating  membrane.  At  the  anterior  end  of  the  body  the 
flagellum  is  usually  continued  as  a  free  flagellum,  but  in  some  cases 
it  ends  with  the  undulating  membrane.  A  vast  number  of  species 
parasitic  in  the  blood  of  vertebrates  and  in  the  digestive  tract  of 

280 


: 


THE  ILEMOFLAGELLATES  AND  ALLIED  FORMS    281 

invertebrates  alternately  are  comprised  in  this  genus.  Trypano- 
some-forms  also  occur  as  developmental  phases  in  the  life-cycle  of 
species  parasitic  solely  in  the  digestive  tracts  of  insects. 

2.  Trypanoplasma  (Figs.  36,  134),  with  two  flagella  arranged  in 
a  heteromastigote  manner,  and  with  the  posterior  trailing  flagellum 
united  to  the  body  by  an  undulating  membrane  for  the  greater  part 
of  its  length.     A  number  of  species  are  known,  which  by  their  dis- 
tribution fall  into  three  sections  :  (1)  Species  parasitic  in  the  blood 
of  fresh- water  fishes,  with  alternating  parasitism  in  the  digestive 
tract  of  leeches  ;  (2)  species  parasitic  in  the  digestive  tract  of  marine 
fishes  ;  (3)  species  parasitic  in  various  invertebrates. 

3.  Crithidia  (Fig.  135),  with  a  single  flagellum  which  arises  near 
the  kinetoiiucleus,  at  about  the  middle  of  the  body,  in  front  of  or 
close  beside  the  trophonucleus,  and  runs  along  the  pointed  anterior 
end  of  the  body  to  form  the  marginal  flagellum  of   a  relatively 
short,   often    rudimentary,  undulating   membrane,   beyond   which 
it  is  continued  as  a  free  flagellum.     As  an.  independent  genus  this 
type  comprises  species  parasitic  in  the  digestive  tracts  of  various 
insects  ;  but  the  majority  of  the  so-called  species  of  Crithidia  are 
merely  phases  in  the  developmental  cycle  of  trypanosomes. 

4.  Leptomonas   (Herpetomonas —  Figs.    124,    136),   with   a  single 
flagellum  arising  at  the  anterior  end  of  the  body,  and  with  no  trace 
of   an  undulating  membrane.      As   an  independent  generic   type 
this  form  occurs  as  a  parasite  of  invertebrates,  chiefly  insects  ; 
secondarily  also  in  the  latex  of  plants  (Euphorbiacese).     It  occurs 
also  as  a  developmental  form  of  the  next  genus  in  the  invertebrate 
host  or  in  cultures. 

5.  Leishmania  (Fig.  138),  with  an  oval  body  containing  a  tropho- 
nucleus and  kinetoiiucleus,  but  with  no  flagellum.     As  a  generic 
type  this  form,  is  an  intracellular  parasite  of  a  vertebrate  host, 
multiplying  there  by  fission  and  developing  into  a  typical  Lepto- 
monas-ioim.    On  the  other  hand,  as  a  developmental  phase  this  form 
represents  simply  a  non-flagellated,  resting  stage  which  may  occur 
in  the  life-cycle  of  either  Trypanosoma,  Crithidia,  or  Leptomonas. 

6.  Prowazekia  (Fig.  141),  with  two  flagella  arranged  in  the  hetero- 
mastigote manner,   as  in   Trypanoplasma,   but  with   the  trailing 
flagellum  quite  free  from  the  body,  without  an  undulating  mem- 
brane.    Prowazekia  is  therefore  quite  similar  in  its  morphology  to 
Bodo,  with  which  it  was  formerly  confused,  if,  indeed,  it  is  really 
distinct,  and  it  differs  from  Bodo  only  in  the  possession  of  a  kineto- 
nucleus.     Several  species  are  described,  free-living  or  intestinal  in 
habitat. 

Considering  the  above  six  types  as  a  whole  from  a  morphological 
standpoint,  it  is  seen  that  there  are  two  types  of  structure  amongst 
them — the  cercomonad  or  rnonornastigote  type,  represented  by 


282 


THE  PROTOZOA 


Mr— - 


Trypanosoma,  Crithidia,  and  Leptomonas,  of  which  Leishmania  may 
be  regarded  as  the  resting,  non-flagellated  phase  ;  and  the  bodonid 
or  heteromastigote  type  with  two  flagella,  seen  in  Trypanoplasma 
and  Proivazekia.  We  shall  return  to  this  point  in  considering  the 
affinities  of  the  group  as  a  whole  and  of  its  constituent  genera. 

The  six  types  enumerated  above  are  given  with  the  nomenclature  tmd 
definitions  most  commonly  accepted,  but  it  is  necessary  to  state  that  the 
application  and  significance  of  the  names  Crithidia,  Leptomonas,  and  Herpeto- 

monas,  are  much  disputed  and  are  far  from 
being  settled.  The  type  of  the  genus  Herpeto- 
monas of  Saville  Kent  is  a  species  found  in 
the  digestive  tract  of  house-flies,  H.  muscce- 
domesticce  (Fig.  124).  According  to  Prowazek 
(557),  this  form  possesses  normally  two 
flagella,  which  are  connected  together  by  a 
membrane  ;  according  to  Patton  (551)  and 
many  others,  the  biflagellate  condition  is  due 
to  precocious  division  of  the  normally  single 
fiagellum  as  a  preparation  for  division  of  the 
body  (compare  Strickland,  558  ;  Wenyon,  84). 
Those  who  follow  Prowazek  in  regarding  the 
biflagellate  condition  of  Herpetomonas  as  its 
normal  adult  form  employ  the  older  genus 
Leptomonas  of  Saville  Kent*  for  forms  with  a 
single  flagellum(Chatton,Roubaud,  Prowazek). 
The  main  source  of  the  confusion  in  the  nomen- 
clature arises  from  the  uncertainty  which  st  ill 
exists  in  many  cases  as  to  whether  a  given  form 
or  structural  type  is  to  be  regarded  as  an  in- 
dependent specific  or  generic  type,  or  as  a 
developmental  phase  of  another  species.  This 
applies  especially  to  the  genus  Crithidia, 
founded  by  Leger  (543)  for  a  species,  C. 
fasciculata,  from  the  intestine  of  Anopheles 
maculipennis,  and  defined  as  a  small  uniflagel- 
late  form  shaped  like  a  grain  of  barley  (Greek, 
npidrj).  Such  forms,  however,  occur  as 
developmental  forms  of  trypanosomes  or  of 
leptomonads,  and  it  is  extremely  probable  that 
the  species  on  which  Leger  founded  his  genus 
was  simply  a  phase  of  this  kind,  which  Wood- 
cock (527)  has  proposed  to  call  the  "  trypano- 
monad "  phase,  in  the  development  of  a 
trypanosome.  On  this  ground  Dunkerly 
(535),  who  has  recently  discussed  the  whole 
question,  considers  that  the  name  Crithidia 

cannot  be  used  as  a  generic  name  at  all,  but  must  be  merged  in  Leptomonas, 
the  name  that  should  be  used  for  all  the  uniflagellate  parasites  of  insect-guts ; 
while  Herpetomonas  should  either  become  a  synonym  of  Leptomonas,  or  should 
be  used  solely  for  Prowazek's  biflagellate  type,  if  that  prove  to  be  a  distinct 
generic  type.  On  the  other  hand,  Leger  and  Duboscq  (646,  p.  232,  footnote) 
consider  that  Crithidia  should  be  retained,  and  Leptomonas  ranked  as  a 

*  The  genus  Leptomonas  was  founded  by  Saville  Kent,  ''Manual  of  Infusoria," 
vol.  i.,  p.  243,  for  L.  'biltscUii,  parasite  of  the  nematode  worm  Trilobus  gracilis  ; 
the  genus  Herpetomonas  was  founded  on  p.  245  of  the  same  work  for  //.  muscce- 
domesticce  and  H.  lewisi  (  =  Trypanosoma  lewisi).  Leptomonas  is  therefore  techni- 
cally the  older  genus. 


B 


FIG.  124. — Herpetomonas 
muscce-domesticce  (Burnett). 
A,  Motile  individual  with 
two  flagella  ;  B,  cyst :  n., 
nucleus  ;  II .,  kinetonucleus. 
After  Prowazek. 


THE  HJEMOFLAGELLATES  AND  ALLIED  FORMS    283 

synonym  of  it.  The  question  has  given  rise  to  a  controversy  which  has  been 
carried  on  by  some  of  the  participants  in  an  acrimonious  and  even  unseemly 
manner,  and  which  it  would  be  unprofitable  to  discuss  further  here,  since 
the  question  is  one  which  must  be  decided  ultimately  by  facts,  and  not  by 
personal  opinions  or  tastes. 

The  various  forms  comprised  in  the  Haemo  flagellates  may  now 
be  considered  in  detail,  beginning  with  the  most  important  type. 

I.  THE  GENUS  TRYPANOSOMA. 

Occurrence. — Trypanosomes  were  first  discovered  as  blood- 
parasites  of  cold-blooded  vertebrates — fishes  and  batrachia  ;  the 
type-species  of  the  genus  Trypanosoma  is  T.  rotatorium  (synonyms, 
T.  sancjuinis,  Undulina  ranarum)  of  the  frog  (Sana  esculenta). 
Trypanosomes  are  now  known,  however,  to  occur  commonly  as 
blood-parasites  in  all  classes  of  vertebrates.  In  a  wild  state  many 
species  of  mammals,  birds,  and  other  vertebrate  animals,  are  often 
found  to  harbour  trypanosomes  in  their  blood,  though  frequently 
in  such  scanty  numbers  as  to  render  the  detection  of  the  parasites 
extremely  difficult.  It  may  be  almost  impossible  in  some  cases  to 
find  trypanosomes  in  the  blood  of  an  animal  by  direct  microscopic 
examination,  owing  to  their  great  scarcity  ;  but  in  such  cases  an 
artificial  culture  made  from  the  blood  may  reveal  the  presence  of  the 
parasites,  since  in  a  few  days  the  trypanosomes  originally  present 
in  small  numbers  in  the  blood  multiply,  under  favourable  conditions, 
to  produce  a  swarm  of  flagellates.  The  cultural  forms  are  quite 
different,  as  a  rule,  from  the  blood-forms  which  gave  rise  to  them, 
and  appear  generally  as  crithidial  or  trypanomonad  types  ;  thus, 
cultures  furnish  evidence  of  the  existence  of  a  trypanosome  in  a 
given  host,  but  give  no  indication  whatever  of  the  type  of  parasite 
actually  present  in  the  blood. 

In  some  cases  the  trypanosomes  appear  to  be  present  in  the 
peripheral  circulation  of  the  vertebrate  host  only  at  certain  periods, 
and  at  other  times  they  are  only  to  be  found  in  the  internal  organs 
or  tissues  of  the  host,  such  as  the  spleen,  bone-marrow,  liver,  lungs, 
etc.  The  trypanosome  of  Athene  noctua — T.  noctuce,  for  example — 
is  to  be  found  during  the  winter  only  in  the  bone-marrow  of  its  host, 
and  appears  in  the  peripheral  circulation  during  the  summer  months, 
and  then  most  abundantly  in  the  night-time  (Minchin  and  Wood- 
cock, 42).  Hence,  for  various  reasons,  it  may  often  be  extremely 
difficult  to  decide  whether  a  given  animal  is  infected  with  trypano- 
somes or  not ;  and  in  recent  years  trypanosomes  have  been  dis- 
covered in  animals  in  which  their  presence  was  previously  quite 
unsuspected — for  instance,  in  calves  (Crawley,  Carini,  423,  Stockman ; 
see  also  Bulletin  of  the  Sleeping  Sickness  Bureau,  No.  29,  p.  320), 
and  in  sheep  (Woodcock,  527,  p.  713,  footnote). 


V^:v-'^;^C 
Wt^SS^ 


FIG.  125. — Trypanosoma  mega,  from  the  blood 
of  African  frogs,     fl.*-,  Marginal  flagellum  of 
the  undulating  membrane ;  ft.2,  free  flagellum  ; 
m.,  myoneme-striations  (it  is  doubtful  whether 
the  granular  streaks  or  the  clear  interspaces 
correspond  exactly  to  the  actual  myonemes); 
n,    kinetonucleus ;   N,   space  in    which 
the  trophonucleus  lies,  but,  not   being 
stained,    it    is    not    clearly   defined   in 
the  preparation.    After  Minchin,  magni- 
fied 2,000;  compare  Figs.  11  and  12  at 
the  same  magnification. 


THE  H.EMOFLAGELLATES  AND  ALLIED  FORMS     285 

Effects  on    the  Host. — The   trypanosomes  found   infesting   wild 
animals  in  Nature  are,  as  a  rule,  quite  specific  to  a  particular  host, 
and,  so  far  as  can  be  observed,  perfectly  harmless  to  it.     If  the 
relations  between  host  and  parasite  had  always  been  of  this  type 
in  all  cases,  our  knowledge  of  trypanosomes  would  be  in  a  much 
more  backward  state  even  than  it  is.     Of  recent  years  a  vast 
amount  of  attention  has  been  attracted  to  these  parasites  owing  to 
the  diseases  of  man  and  animals  caused  by  certain  species  of  trypano- 
somes,   and   hence   termed   comprehensively    "  trypanosomiases." 
The  greater  number  of  these  pathogenic  species  belong,  from  the 
structural  point  of  view,  to  a  type  which  may  be  called  the  brucii- 
type  (Fig.  12) ;  such  are  T.  brucii,  cause  of  tsetse-fly  disease  ;  T.  gam- 
biense,  of  sleeping  sickness  ;  T.  evansi,  of  surra  ;  T.  equiperdum,  of 
dourine  ;    and  many  others.     The   structural   similarity   of   these 
species  renders  their  identification  a  matter  of  extreme  difficulty. 
Of  a  slightly  different  type  is  T.  equinum,  of  "  mal  de  caderas  "  in 
South  America,  with  a  very  minute  kinetonucleus  ;  but  the  recently- 
described  T.  hippicum  of  "  murrina  "  (Darling,  428)  appears  to  be 
a  typical  member  of  the  &mcn'-group.     T.  theileri,  on  the  other 
hand,  from  cattle,  is  very  distinct  in  size  and  appearance  from  the 
members  of  the  brucii-gioup.     Finally,  T.  cruzi,  the  cause  of  human 
trypanosomiasis  in   Brazil,   stands   apart  from  all  the  others  in 
peculiarities  of  reproduction  and  development,  which  have  led  to 
its  being  ranked  in  a  distinct  subgenus,  Schizotrypanum. 

The  problem  of  the  pathogenic  trypanosomes  has  been  touched 
upon  in  Chapter  II.  From  a  survey  of  trypanosomes  in  general,  it 
is  clear  that  the  normal  type  of  these  parasites  is  one  which  is  specific 
to  one  or  to  a  limited  number  of  species  of  hosts,  to  which  it  is  quite 
harmless.  The  pathogenic  species  are  to  be  regarded  as  aberrant 
forms  not  yet  adapted  to  their  hosts,  as  an  instance  of  a  disharmony 
in  Nature.  They  are  species  which  have  probably  established 
themselves  but  recently  in  the  hosts  to  which  they  are  pathogenic. 
As  contrasted  with  the  natural,  non-pathogenic  forms,  their  most 
striking  peculiarities  are  that  they  are  not  specific  to  one  host,  but 
can  flourish  in  a  great  number  of  different  species  of  hosts,  and  that 
in  susceptible  animals  their  power  of  multiplication  has  no  limit. 
T.  brucii,  so  deadly  to  many  domestic  animals,  is  known  to  occur 
also  as  a  natural  parasite  of  wild  animals,  to  which  it  is  harmless. 

Structure. — The  constitution  of  the  trypanosome-body  is  of  a 
very  uniform  type  in  its  general  traits,  though  subject  to  great 
variation  in  different  cases  as  regards  size,  form,  and  minor  details 
of  structure.  The  body  is  typically  long  and  sinuous,  with  the 
anterior  end  tapering  gradually  to  a  fine  point,  while  the  posterior 
extremity  is  usually  broader,  and  tapers  more  abruptly,  or  ends 
bluntly  ;  but  in  different  forms,  even  of  the  same  species,  there  may 


28G  THE  PROTOZOA 

be  great  variation,  from  long,  slender  to  short,  stumpy  types,  and 
in  some  cases  the  posterior  end  is  also  greatly  draAvn  out  and  attenu- 
ated. The  principal  nucleus  or  trophonucleus  is  usually  situated 
near  the  middle  of  the  body.  The  kinetonucleus  is  almost  invariably 
behind  the  trophonucleus,*  sometimes  close  behind  it,  but  more 
usually  near  the  posterior  extremity,  separated  from  the  tropho- 
nucleus by  about  half  the  length  of  the  body. 

The  flagellurn  arises  from  a  centriole  (blepharoplast)  which  is  in 
•connection  with  the  kinetonucleus.  In  the  more  primitive  type  of 
arrangement  the  blepharoplast  is  lodged  within  the  kinetonucleus 
itself,  and  then  the  flagellum  appears  to  arise  from  the  kineto- 
nucleus directly  (Wenyon,  84).  In  most  cases,  however,  the 
blepharoplast  is  situated  close  beside,  and  usually  in  front  of,  the 
kinetonucleus,  connected  with  it  by  a  delicate  rhizoplast.  When 
the  blepharoplast  is  distinct  from  the  kinetonucleus,  it  is  at  present 
an  open  question  whether  the  kinetonucleus  contains  a  centriole 
of  its  own,  in  addition  to  the  blepharoplast,  or  whether  the  blepharo- 
plast represents  a  centriole  which  belongs  to  the  kinetonucleus,  but 
has  migrated  to  the  exterior  of  this  body. 

Passing  from  the  blepharoplast  to  the  surface  of  the  body,  the 
fiagellum  forms  the  free  border  of  the  undulating  membrane,  which 
runs  forward  from  the  vicinity  of  the  kinetonucleus  to  the  extreme 
.anterior  end  of  the  body  as  a  fin-like  ridge  or  fold  of  the  periplast, 
of  variable  width  (c/.  Fig.  126).     The  flagellum  may  in  some  cases 
end  with  the  undulating  membrane  at  the  anterior  end  of  the  body, 
but  more  usually  it  is  prolonged  forward  beyond  this  point,  so  that 
a  free  portion  of  variable  length  is  to  be  distinguished  from  the  mar- 
ginal portion  contained  in  the  undulating  membrane.     The  sinuous 
body,  the  undulating  membrane,  and  the  flagellum,  are  alike  in  a 
state  of  incessant  movement  during  life,  and  in  larger  forms  con- 
tractile myonemes  are  clearly  visible  in  the  periplast  of  the  body 
(Fig.  28,  p.  58)  ;  in  the  more  minute  individuals  the  presence  of  such 
•elements  must  be  inferred  from  their  movements,  but  cannot  always 
be  demonstrated  optically. 

The  movements  of  a  trypanosome,  speaking  generally,  are  of  two  types  : 
travelling  movements,  when  it  progresses  with  the  free  flagellum  forwards, 
sometimes  very  fast,  shooting  across  the  field  of  the  microscope  in  a  straight 
line  (mouvement  en  fleche),  sometimes,  on  the  other  hand,  pushing  its  way 
.slowly  through  the  blood-corpuscles,  with  the  flagellum  directed  either  forwards 
or  backwards  in  movement ;  and  wriggling  movements,  when  the  animal 
•writhes  incessantly  in  serpentine  contortions  with  little  or  no  displacement 

*  The  only  known  exceptions  are  furnished  by  certain  forms  of  the  recently- 
described  T.  rhodesiense  (vide  Stephens  and  Fantham),  and  by  some  of  the  small 
forms  seen  during  the  multiplication  of  T.  lewisi  (Fig.  127,  L).  It  is  needless  to 
point  out  that  the  statement  made  above  applies  to  the  typical  trypanosome-forra 
as  found  in  the  vertebrate  blood,  and  not  to  the  developmental  forms  through  which 
they  pass  in  the  invertebrate  host  (crithidial  and  other  types). 


THE  H^EMOFLAGELLATES  AND  ALLIED  FORMS     287 


from  a  given  spot.  Many  trypanosomes,  especially  the  large  stout  forms, 
are  very  sluggish  in  their  movements,  and  show  but  little  power  of  progression. 
At  the  opposite  extreme,  in  this  respect,  is  the  African  parasite  of  cattle,  well 
named  by  Ziemann  T.  vivax,  which,  according  to  Bruce  and  his  collaborators 
(411,  iii.),  "  dashes  across  the  field  of  the  microscope  with  such  rapidity  that 
it  is  impossible  to  follow  its  movements,  cyclone-like  leaving  a  clear  path,  the 
corpuscles  in  its  track  having  been  flung  on  either  side.  If  it  remains  at  the 
same  spot  for  a  time,  as  it  sometimes  does,  it  has  an  appearance  of  great 
energy  and  power,  throwing  the  surrounding  red  blood- corpuscles  about  in 
wild  confusion." 

In  the  foregoing  paragraphs  the  terms  "  anterior  "  and  "  posterior,"  as 
applied  to  the  trypanosome-body,  have  been  used  strictly  with  reference  to 
its  mode  of  progression.  It  is  pointed  out  below,  in  the  comparison 
with  other  types  such  as  Trypanoplasma  and  Crithidia,  that  the  extremity 


FIG.  126. — A,  Trypanosoma  tincce  of  the  tench  ;  note  the  very  broad  undulating 
membrane  in  this  species ;  B,  C,  T.  percce  of  the  perch,  slender  and  stout 
forms.  After  Minchin,  x  2,000. 

of  the  body  which  is  anterior,  in  the  strictly  morphological  sense,  in  one 
species,  may  conceivably  be  posterior  in  another  case.  Hence  some  writers 
avoid  the  use  of  the  words  "  anterior  "  and  "  posterior,"  and  substitute  for 
them  "  flagellar  "  and  "  aflagellar  "  respectively,  to  denote  the  two  poles  of 
the  body.  There  is  as  yet,  however,  no  concrete  evidence  for  regarding  the 
flagellar  extremity  as  morphologically  posterior  in  any  known  species  of 
trypanosome. 

The  undulating  membrane  is  to  be  regarded  as  a  fold  of  the  periplast  or 
ectoplasm,  into  which  the  granular  endoplasm  may  extend  a  short  way  in 
some  cases  ;  it  arises  from  the  body  along  a  line  which  is  sometimes  spoken  of 
as  "  dorsal,"  an  unnecessary  refinement  of  terms.  The  free  edge  of  the 
membrane,  with  its  marginal  flagellum,  can  be  shown  by  direct  measurements 
to  exceed  considerably  in  length  that  portion  of  the  body  to  which  it  is  at- 
tached ;  consequently  its  free  edge  is  thrown  into  folds  or  pleats  more  or  less 
marked.  In  preparations,  trypanosomes  are  seen  to  lie,  speaking  generally, 


288  THE  PROTOZOA 

in  one  of  the  three  ways  ;  a  certain  number  show  the  body  extended  nearly 
in  a  straight  line,  with  the  free  edge  of  the  membrane  much  pleated,  but  as  a 
rule  the  body  is  curved,  and  then  either  with  one  principal  bend,  like  a  C,  or 
with  several  S-like  serpentine  bends.  In  either  case  the  undulating  membrane 
is  seen  almost  invariably  to  run  on  the  convex  side  of  each  curve.  In  C-like 
forms  (Fig.  125,  ^4)  the  membrane  runs  evenly  along  the  outside  of  the  principal 
curve,  and  the  myonemes  parallel  to  it.  In  S-like  forms  (Fig.  125,  B)  the 
membrane  is  often  seen  distinctly  to  be  spirally  twisted  round  the  body,  the 
myonemes  also  exhibiting  the  same  twist.  In  life  the  undulating  membrane 
performs,  as  its  name  implies,  movements  like  those  of  a  sail  flapping  in  the 
wind.  Wave-like  undulations  run  along  it  from  one  end  to  the  other,  but  not 
always  in  the  same  direction  ;  it  has  been  observed  that  reversals  of  the  move- 
ments may  take  place,  the  waves  first  running  in  one  direction  for  a  time, 
and  then  suddenly  undergoing  a  change  and  running  in  the  opposite  direction 
(Minchin  and  Woodcock,  42). 

Much  confusion  exists  in  the  nomenclature  of  the  parts  of  the  trypanosome- 
bodj%  more  especially  with  regard  to  the  small  body  for  which  Woodcock's 
term  "  kinetonucleus  "  ("  Geisselkern  ")  is  here  used — a  confusion  due  to 
differences  of  cytological  interpretation.  While  it  has  never  been  doubted 
that  the  larger  body  (N.)  is  a  true  nucleus,  various  views  have  been  held 
with  regard  to  the  smaller  body  (n.),  which,  summarized  briefly,  are  as 
follows  :  The  older  writers  regarded  it  merely  as  an  organ  of  the  periplast 
from  which  the  flagellum  arose.  Stassano  and  Bradford  and  Plimmer  re- 
garded n.  as  a  body  of  nuclear  nature,  and  termed  it  the  "  micronucleus," 
comparing  it  with  the  similarly-named  body  of  Infusoria.  Laveran  and 
Mesni!  (464,  391),  on  the  other  hand,  regarded  n.  as  the  "  centrosome,"  the 
name  by  which  it  is  generally  known  in  France.  Schaudinn  (132)  emphasized 
strongly  its  nuclear  nature,  and  stated  that  n.  was  not  a  centrosome,  but 
nevertheless  used  for  it  the  term  "  blepharoplast,"  by  which  it  is  still  generally 
known  in  Germany,  although  a  true  blepharoplast  is  a  body  of  centrosomic 
nature.  Moore  and  Breinl  (484)  reverted  to  the  centrosomic  view,  and  termed 
n.  the  "  extranuclear  centrosome,"  believing  that  it  arose  by  division  of  the 
intranuclear  centrosome  contained  in  the  principal  nucleus  (N.).  Hartmann 
and  Prowazek  (63),  on  the  basis  of  their  nuclear  theory  of  the  centrosome  (see 
Chapter  VI.,  p.  95),  regarded  n.  as  a  body  both  of  nuclear  and  centrosomic 
nature,  using  for  it  the  term  "  blepharoplast  "  ;  so  also  Rosenbusch.  Finally, 
Doflein  (7),  who  is  not  convinced  of  its  truly  nuclear  nature,  continues  to 
employ  for  n.  the  term  "  blepharoplast."  With  these  many  conflicting  views 
with  regard  to  the  nature  of  n.,  the  basal  granule  has  been  either  ignored  or 
overlooked,  or  considered  as  a  mere  "  end-bead  "  of  no  particular  importance, 
or  ranked  as  a  centriole,  as  it  doubtless  is.  The  nomenclature  used  here  is 
based  on  the  general  theory  that  a  centrosome,  or  its  equivalent,  a  blepharo- 
plast, is  an  achromatinic  body  of  nuclear  origin,  but  not  equivalent  to  an  entire 
nucleus,  and  on  the  conviction  that  n.  is  a  true  nucleus,  and  therefore  is  not 
to  be  regarded  either  as  a  centrosome  or  a  blepharoplast.  For  a  fuller  dis- 
cussion of  these  points,  see  Robertson  and  Minchin  (80). 

The  trophonucleus  of  a  trypanosome  is  typically  a  vesicular  nucleus  con- 
taining a  karyosome  in  which  is  lodged  a  centriole.  The  karyosome  varies 
in  size  in  different  species,  and  is  sometimes  double  or  multiple  ;  in  T.  qranu- 
losum  the  smallest  forms  have  a  single  karyosome  which  buds  off  others  as 
the  animal  increases  in  size  (Minchin,  478).  By  the  method  which  is  most  in 
vogue,  however,  for  making  permanent  preparations  of  trypanosomes — 
namely,  the  various  modifications  of  the  Romanowsky-stain — this  structure 
is  seldom  to  be  made  out,  and  the  trophonucleus  appears  generally  as  an 
evenly-stained  mass  or  as  a  dense  clump  of  stained  granules.  It  contains 
a  centriole,  difficult  to  make  out  in  the  resting  condition,  owing  to  its  being 
embedded  in  the  substance  of  the  nucleus.  The  kinetonucleus  consists 
mainly  of  a  mass  of  plastin  impregnated  with  chromatin,  staining  very 
deeply,  rounded,  oval,  or  even  rod-like  in  shape.  According  to  Rosenbusch, 
the  chromatinic  mass  of  the  kinetonucleus  is  to  be  regarded  as  representing 


THE  H^MOFLAGELLATES  AND  ALLIED  FORMS     289 

a  karyosome,  and  it  is  surrounded  by  a  space,  sometimes  purely  virtual, 
which  represents  the  nuclear  vacuole,  bordered  by  a  delicate  nuclear  mem- 
brane, on  or  close  to  which  the  basal  granule  of  the  flagellum  is  lodged. 

In  some  species  of  the  brucii-group,  an  axial  filament,  apparently  a  sup- 
porting structure  of  the  nature  of  an  axostyle,  has  been  described  (cf.  Swel- 
lengrebel,  514).  The  system  of  fibrils,  however,  with  which  Prowazek 
decorates  the  trypanosome-body  are  probably  artefacts  (cf.  Minchin,  479). 

Many  trypanosomes  contain  granules  in  their  cytoplasm  which  stain 
similarly  to  cliromatin,  so-called  "  chromatoid  grains."  According  to  Swel- 
lengrebel  (514),  they  are  of  the  nature  of  volutin  (p.  68,  supra). 

The  division  of  a  trypanosome  is  initiated,  as  a  rule,  by  the  division  of  the 
blepharoplast  or  basal  granule  of  the  flagellum,  and  following  close  on  this 
a  reduplication  of  the  flagellum  takes  place,  the  exact  method  of  which  is 
disputed.  In  some  cases  the  old  flagellum  appears  to  split  ;  in  others  the 
parent-flagellum  remains  unaltered,  and  a  daughter-flagellum  grows  out 
from  the  daughter-blepharoplast.  It  is  asserted  by  some  that  in  all  cases 
the  new  flagellum  really  arises  as  an  independent  outgrowth  of  a  blepharoplast, 
and  that  the  splitting  of  the  old  flagellum  is  only  apparent,  and  due  to  the 
daughter-flagellum  growing  out  at  first  in  its  sheath,  from  which  it  separates 
later  (cf.  Wenyon,  84).  The  division  of  the  kinetonucleus  follows  hard 
on  that  of  the  blepharoplast,  and  next,  as  a  rule,  the  trophonucleus  divides. 
When  the  division  of  flagellum  and  nuclei  is  complete  the  body  divides,  begin- 
ning to  do  so  at  the  flagellar  end  ;  the  two  sister-trypanosomes  are  often 
connected  for  a  time  by  the  posterior  extremities. 

The  division  of  the  kinetonucleus  is  a  simple  constriction  into  two  ;  that  of 
the  trophonucleus  is  of  a  simple  type,  in  which  first  the  centriole  and  then  the 
karyosome  divides.  The  two  daughter-karyosomes  travel  apart,  and  the 
nucleus  follows  suit.  The  two  daughter-nuclei  sometimes  remain  connected 
for  a  time  by  a  long  centrodesmose,  which  is  finally  severed.  Such,  at  least, 
is  the  mode  of  division  of  the  two  nuclei  as  it  has  presented  itself  to  the  majority 
of  investigators,  and  the  nuclear  division  of  trypanosomes  is  to  be  regarded 
as  amitotic,  or  at  least  not  further  advanced  towards  mitosis  than  that  of 
Coccidium  described  above  (p.  106,  Fig.  51).  According  to  Rosenbusch, 
however,  the  division  of  the  nuclei,  both  trophic  and  kinetic,  takes  place  by 
true  mitosis.  This  author  is  in  advance  of  his  contemporaries  upon  this 
point,  and  his  statements  require  independent  confirmation  before  they  can 
be  accepted  unreservedly,  since  in  objects  of  such  minuteness,  requiring 
delicate  and  elaborate  technique,  imagination  may  all  too  readily  outrun 
perception. 

Life-History. — The  transmission  of  trypanosomes  from  the  blood 
of  one  vertebrate  host  to  another  is  effected,  probably  for  every 
species  of  these  parasites,  by  the  agency  of  a  blood-sucking  inverte- 
brate of  some  kind.  When  the  host  is  a  terrestrial  vertebrate,  the 
transmitting  agent  is  generally  an  insect,  such  as  a  mosquito  or 
some  biting  fly  or  bug,  or  an  ectoparasite  of  the  host,  such  as  a 
flea,  louse,  or  possibly  a  tick  in  some  cases  ;  the  trypanosomes  of 
aquatic  vertebrates,  on  the  other  hand,  are  transmitted  by  leeches 
in  all  cases  that  have  been  investigated.  In  addition  to  inoculative 
transmission  (p.  24)  of  this  kind,  trypanosomes  may  pass  directly 
from  one  vertebrate  host  to  another  during  coitus  ;  this  is  known  to 
occur  in  the  case  of  the  parasite  of  "  dourine  "  in  horses  (T.  equi- 
perdum),  and  has  been  suspected,  but  not  proved,  to  take  place  in 
other  cases  also.  It  is  also  possible  for  the  vertebrate  to  become 
infected  by  devouring  animals  containing  living  trypanosomes, 

19 


290  THE  PROTOZOA 

whether  it  be  the  blood-sucking  invertebrate,  or  possibly  the  flesh 
or  organs  of  another  vertebrate  infected  with  trypanosomes. 

Two  methods  of  inoculative  transmission  of  trypanosomes  have 
been  distinguished  ;  in  the  one,  known  as  the  "  direct "  or  "  mechan- 
ical" method,  the  parasites  merely  become  contained  in  or  adhere  to 
the  proboscis  of  the  blood-sucking  intermediary  when  it  sucks  blood 
from  an  infected  animal ;  and  when  it  feeds  a  second  time  the  try- 
panosomes pass  directly,  and  without  having  undergone  any  change 
or  development,  into  the  second  host ;  in  the  other,  known  as  the 
"  indirect  "  or  "  cyclical"  method,  the  trypanosomes,  when  taken  up 
by  the  blood-sucking  invertebrate,  go  through  a  developmental  cycle 
in  it,  at  the  end  of  which,  but  not  before,  they  are  "  ripe  "  for  inocu- 
lation into  a  suitable  vertebrate  host.  Comparing  natural  with 
artificial  processes  of  infection,  in  the  direct  method  the  blood- 
sucking invertebrate  may  be  said  to  play  the  role  merely  of  an 
injection-syringe,  but  in  the  indirect  method  it  acts  also  as  a  culture- 
medium,  in  which  the  parasite  passes  through  various  phases  and 
assumes  forms  quite  different  from  those  occurring  in  vertebrate 
blood.  Patton  (393)  has  put  forward  the  viewr  that  transmission 
is  always  by  the  direct  method,  and  that  the  crithidial  and  other 
forms  found  in  the  blood-sucking  invertebrate  are  parasites  of  the 
invertebrate  alone,  and  have  110  connection  with  the  trypanosomes 
found  in  vertebrates  ;  but  the  number  of  cases  in  which  it  has 
now  been  shown  clearly  that  trypanosomes  go  through  a  definite 
cycle  in  the  invertebrate  host  disproves  Patton's  contention,  and 
renders  it  unnecessary  to  discuss  it  further.  It  is  rather  the 
direct  method  that  stands  in  need  of  further  demonstration  ;  though 
undeniably  possible  as  a  laboratory-experiment,  it  may  be  doubted 
if  it  ever  really  occurs  in  Nature,  and  in  any  case  it  is  probably  to 
be  regarded  as  a  purely  accidental  rather  than  a  normal  occurrence. 

It  has  been  frequently  asserted  or  assumed  that  trypanosomes 
can  pass  from  parent  to  offspring,  by  so-called  "  hereditary  trans- 
mission," in  the  invertebrate  host,  but  convincing  proof  of  this  state- 
ment is  as  yet  lacking  entirely.  Attempts  to  prove  hereditary  trans- 
mission by  direct  experiment  have  given,  for  the  most  part,  negative 
results,  and  the  observation  so  frequently  made,  that  leeches,  tsetse- 
flies,  fleas,  mosquitoes,  etc.,  bred  from  the  egg  and  not  exposed 
to  infection,  are  entirely  free  from  parasitic  flagellates,  affords  cumu- 
lative evidence  against  the  existence  of  any  such  method  of  trans- 
mission (c/.  Kleiiie  and  Taute,  459).  Brumpt  (419),  however,  asserts 
that  T.  inopinatum  is  transmitted  hereditarily  from  parent  to  off- 
spring of  the  leech  Helobdella  algira.  According  to  Porter  (554), 
"  Crithidia  "  melophagia  of  the  sheep-ked  is  also  transmitted  from 
parent  to  offspring  in  this  insect ;  and  if,  as  is  extremely  probable, 
the  flagellate  in  question  is  the  developmental  phase  of  the  trypano- 


THE  H^MOFLAGELLATES  AND  ALLIED  FORMS    291 

some  of  the  sheep,  it  would  furnish  another  instance  of  hereditary 
transmission.  Hence  this  mode  of  transmission  must,  apparently, 
be  reckoned  with  in  some  instances,  though  it  is  evidently  an  ex- 
tremely rare  phenomenon  in  trypanosomes  generally. 

Just  as  a  given  species  of  trypanosome  is,  in  Nature,  capable  of 
maintaining  itself  only  in  a  particular  species,  or  limited  group  of 
species,  of  vertebrate  hosts,  so  it  may  be  said,  as  a  general  rule, 
that  in  transmission  by  the  cyclical  method  the  parasites  are 
specific  in  the  same  way  to  certain  invertebrate  hosts,  in  which 
alone  they  are  able  to  go  through  their  full  natural  cycle.  Amongst 
the  many  blood-sucking  invertebrates  which  may  prey  upon  the 
vertebrate,  we  may  distinguish  "  right "  and  "  wrong  "  hosts  ;  in 
the  right  host  or  hosts  the  parasite  establishes  itself  more  or  less 
easily,  and  passes  through  a  full  and  complete  developmental 
cycle  ;  in  the  wrong  host  it  either  dies  out  immediately  or  goes 
through  only  a  part  of  its  cycle.  The  distinction  between  right 
and  wrong  hosts  must  not,  however,  be  taken  in  an  absolute  sense, 
but  as  implying  only  that,  amongst  many  possible  hosts,  there  is 
one  at  least  to  which  the  parasites  have  become  better  adapted 
than  to  any  other  ;  but  the  trypanosomes  may  sometimes  succeed 
in  maintaining  themselves  in  other  than  the  right  host  sufficiently 
long  to  pass  back  again  into  the  vertebrate.  Thus,  in  the  case  of 
the  rat-trypanosome  (T.  lewisi)  the  right  host  is  a  rat-flea  (Cerato- 
phyllus  fasciatus,  or  possibly  other  species)  ;  but  it  may  persist  in 
the  rat-louse  (Hcematopinus  spinulosus),  and  even  pass  from  it, 
though  rarely,  back  into  the  rat  again. 

The  following  are  a  few  well-established  examples,  in  addition 
to  that  of  T.  lewisi  already  cited,  of  trypanosomes  and  their  right 
hosts.  Many  pathogenic  species  of  trypanosomes  in  Africa  are 
transmitted  by  tsetse-flies — e.g.,  T.  gambiense  and  T.  vivax  by 
Glossina  palpalis,  T.  brucii  by  G.  morsitans,*  etc.  The  recently- 
described  T.  cruzi  of  Brazil  Avas  discovered  in  its  invertebrate  host, 
a  blood-sucking  hemipterous  insect,  Conorliinus  megistus,  before  it 
was  found  in  the  blood  of  human  beings.  The  trypanosomes  of 
certain  fresh-water  fishes  —  namely,  goldfish,  perch,  etc. --pass 
through  their  developmental  cycle  in  the  leech  Hemiclepsis  mar- 
ginata  (Robertson,  503).  T.  mice  of  skates  and  rays  develops  in 
the  leech  Pontobdella  muricata  (Robertson,  500,  502).  The  trypano- 
some of  African  crocodiles,  T.  grayi,  develops  in  the  tsetse-fly 
Glossina  palpalis  (Kleine,  458  ;  Kleine  and  Taute,  459),  and  stages 
in  its  life-cycle  have  consequently  been  confused  with  those  of 
T.  gambiense  in  the  same  fly.  The  trypanosomes  of  birds  are  prob- 
ably transmitted  for  the  most  part  by  mosquitoes,  but  the  details  of 

*  According  to  Taute,  G.  morsitans  can  act  as  a  true  host  for  T.  gambien.se,  and, 
•conversely,  according  to  Fischer,  G.  palpalis  can  do  the  same  for  T.  brucii. 


292  THE  PROTOZOA 

their  transmission  have  not  yet  been  worked  out  in  a  satisfactory  or 
conclusive  manner. 

It  must  be  considered  for  the  present  an  open  question  whether  true  try- 
panosomes  occur  as  parasites  of  an  invertebrate  host  exclusively  ;  the  answer 
to  the  question  will  depend  on  the  significance  given  to  the  expression  "  true 
trypanosome."  It  is  now  practically  certain  that  many  leptomonads  have  a 
trypaniform  phase  in  their  development  (see  p.  314,  infra),  so-called  "  lepto- 
trypanosomes."  In  Drosopliila  confusa,  a  non-biting,  muscid  fly,  Chatton 
and  Alilaire  (compare  also  Chatton  and  Leger)  found  in  the  Malpighian  tubules 
a  trypaniform  type  of  flagellate  which  they  consider  as  a  "  eutrypanosome," 
as  a  species  of  Trypanosoma  distinct  from  the  Leptomonas  occurring  in  the 
gut  of  the  same  fly  (Fig.  137).  Wenyon  (84)  also  found  similar  forms  in  the 
Malpighian  tubules  of  house-flies  in  Bagdad,  and  considered  that  they  might 
belong  to  the  cycle  of  the  Leptomonas  (Herpetomonas)  in  the  same  host.  In 
both  cases  the  phase  in  the  Malpighian  tubules  is  a  little  stumpy  trypanosome- 
like  form,  very  similar  in  its  characters  to  T.  nanum.  The  fact  that  these 
"  eutrypanosomes  "  are  so  far  known  only  to  occur  in  flies  which  are  infected 
also  by  a  species  of  Leptomonas  indicates  that,  like  the  "  leptotrypanosomes," 
they  are  merely  a  phase  in  the  cycle  of  the  Leptomonas. 

From  the  foregoing  it  is  seen  that  the  complete  life-cycle  of  a 
trypanosome  is  an  alternation  of  generations  corresponding  to  an 
alternation  of  hosts.  One  part  of  the  cycle  is  passed  in  the  blood  of 
a  vertebrate,  in  which  the  predominant  form  is  the  trypanosome- 
type  of  flagellate  ;  the  second  part  is  passed  in  the  digestive  tract 
of  an  invertebrate,  and  here  the  predominant  form  is  the  crithidial 
or  trypanomonad  type.  We  may  consider  the  life-history,  therefore, 
under  these  two  principal  phases  : 

1.  As  a  type  of  the  life-cycle  in  the  vertebrate  host,  that  of  the 
common  rat-trypanosome  may  be  taken.  After  infection,  natural 
or  artificial,  of  the  rat,  the  trypanosomes  make  their  appearance 
in  the  blood  about  the  fifth,  sixth,  or  seventh  day.  What  the  para- 
sites have  been  doing  during  this  time,  the  so-called  "  incubation- 
period  "  in  the  rat,  cannot  as  yet  be  stated  definitely  ;  it  may  be 
that  the  relatively  few  trypanosomes  inoculated  by  the  flea  or 
syringe  have  merely  been  multiplying  steadily,  in  the  manner 
presently  to  be  described,  until  they  become  sufficiently  numerous 
in  the  blood  to  be  detected  by  microscopic  examination  ;  there  may, 
on  the  other  hand,  be  phases  of  the  parasite  as  yet  unknown  during 
this  period,  and,  according  to  recent  statements  (Carini,  422),  a 
process  of  schizogony  takes  place  in  the  lung  similar  to  that  dis- 
covered by  Chagas  in  Schizotrypanum  cruzi  (see  below). 

When  the  trypanosomes  first  appear  in  the  blood,  their  most 
striking  peculiarity  is  the  extraordinary  diversity  in  type  which  they 
exhibit.  Besides  "  ordinary  "  individuals  of  the  normal  dimensions 
of  the  "  adult  "  form,  there  are  others  smaller  or  larger,  the  extremes 
of  size  being  relatively  huge  in  one  direction,  very  minute  in  the 
other.  These  differences  of  size  are  due  to  the  fact  that  the  try- 
panosomes are  multiplying  actively,  the  large  forms  being  those 


.*.**•. 


K 


FIG  127.- — -Various  forms  of  multiplication  in  Trypanosoma  lewisi  from  the  blood 
of  the  rat.  A,  Trypanosome  of  the  ordinary  type  ;  B,  small  form  resulting 
from  division  ;  0,  stage  in  equal  binary  fission  ;  the  nuclei  have  divided  and 
two  flagella  are  present,  but  division  of  the  body  is  beginning,  and  is  indicated 
by  a  lighter  streak  down  the  middle  of  the  body  ;  D,  final  stage  of  binary 
fission,  which  is  complete  except  for  a  bridge  of  protoplasm,  much  drawn 
out,  connecting  the  hinder  ends  of  the  two  sister-trypanosomes  ;  E,  form 
with  hinder  end  drawn  out  (longocaudense  type),  the  result  of  binary  fission 
as  seen  in  the  last  figure  ;  F,  unequal  binary  fission  of  a  large  trypanosome  ; 
0,  H,  continued  fission  of  the  same  type ;  in  G  a  parent  and  three  daughter- 
individuals,  in  H  a  parent  and  seven  daughter-individuals,  can  be  distin- 
guished ;  the  parent-individual  in  each  case  is  marked  by  the  possession  of 
a  flagellum  of  the  full  normal  length,  while  the  daughter-individuals,  formed 
by  successive  divisions,  have  flagella  varying  in  length  ;  /,  a  small  form, 
similar  to  B,  but  with  the  kinetonucleus  in  front  of  the  trophonucleus  ;  J, 
binary  fission  of  a  form  similar  to  /  ,•  K,  further  division  of  a  similar  form 
producing  a  rosette  of  seven  individuals  still  connected  together.  From 
preparations  made  by  Dr.  J.  D.  Thomson  ;  magnified  2,000  diameters. 


294  THE  PROTOZOA 

which  are  about  to  reproduce  themselves  by  some  form  of  fission, 
while  the  small  forms  are  those  which  have  resulted  from  a  recent 
act  of  reproduction. 

The  multiplication  of  T.  lewisi  in  the  rat's  blood  takes  various  forms- 
(Fig.  127).  In  some  cases  a  trypanosome  divides  by  equal  binary  fission 
(C,  D),  but  this  is  comparatively  rare.  More  usually  the  fission  is  markedly 
unequal,  and  of  a  multiple  type.  Small  daughter-forms  are  split  off  from 
large  parent-individuals,  and  usually  many  at  a  time;  the  nucleus  of  the  parent- 
form  divides  several  times,  and  subsequently  the  body  divides  into  as  many 
portions  as  there  are  nuclei,  thus  producing  rosette-like  forms  (Fig.  127, 
F,  G,  H)  in  which  the  original  parent  can  usually  be  distinguished  by  its  long 
flagellum  from  the  small  daughter-individuals  with  their  flagella  growing 
out.  The  small  forms  are  sometimes  set  free  with  a  crithidial  type  of  struc- 
ture, the  kinetonucleus  in  front  of  the  trophonucleus  (Fig.  127,  L),  and  these 
immature  forms  may  proceed  to  reproduce  themselves  rapidly  again  by 
either  binary  or  multiple  fission,  in  the  latter  case  forming  rosettes  in  which 
no  large  parent-form  can  be  distinguished  (Fig.  127,  K). 

A  curious  type  of  trypanosome  found  during  the  multiplication-period  of 
T.  lewisi  is  a  form  with  the  posterior  end  prolonged  to  a  great  length,  so 
that  it  almost  resembles  a  second  flagellum  (Fig.  127,  E),  and  has  sometimes 
been  mistaken  for  such.  This  form  has  been  described  by  Lingard  as  a  dis- 
tinct species  under  the  name  T.  longocaudense.  These  forms  appear  to  arise 
by  binary  fission  (Fig.  127,  J>)  ;  they  are  of  constant  occurrence  and  very 
numerous  at  a  certain  stage  of  the  multiplication-period. 

The  multiplication  of  T.  lewisi  in  the  rat's  blood  is  most  active 
from  the  eighth  to  the  tenth  day  after  infection,  after  which  it  is 
on  the  decline  and  gradually  ceases.     The  relative  number  of  forms 
of  ordinary  size  increases  steadily,  while  those  of  unusual  dimen- 
sions, whether  great  or  small,  become  continually  scarcer,  until 
about  the  twelfth  or  thirteenth  day  the  trypanosomes,  now  usually 
present  in  vast  numbers  in  the  blood,   are  of  uniform  size  and 
appearance,  exhibiting,  apart  from  occasional  abnormalities,  indi- 
vidual variations  only  of  a  comparatively  slight  character  ;  and  all 
multiplication  has  ceased  entirely,  never  to  recommence  in  the 
same  host.     The  trypanosomes  swarm  in  the  blood  of  the  rat  for 
a  certain  time,  which  varies  in  different  cases,  but  is  usually  one 
or  two  months.     The  infection  of  the  rat  is  sometimes  spoken  of  as 
"  acute  "  when  the  trypanosomes  are  multiplying,  and  as  "  chronic  " 
when  multiplication  has   ceased,   not,  however,   very   well-chosen 
terms,  since  the  trypanosomes  soon  begin  to  diminish  in  number, 
and  finally  disappear  altogether  ;  sometimes  the  diminution  is  very 
gradual  and  slow,  sometime?  it  takes  place  with  great  rapidity.     In 
either  case  the  rat  gets  rid  of  its  infection  entirely  sooner  or  later, 
without  having  suffered,   apparently,   any  marked   inconvenience 
from  it,*  and  is  then  immune  against  a  fresh  infection  with  this 
species  of  trypanosome. 

*  Instances  are  on  record  of  lethal  epizootics  of  rats  ascribed  to  T.  lewisi ;  but 
the  proof  that  this  parasite  was  really  the  cause  of  the  disease  is  lacking.  Under 
normal  circumstances  rats  show  no  perceptible  pathological  symptoms  whatever 


THE  ILEMOFLAGELLATES  AND  ALLIED  FORMS    295 

A  type  of  development  in  the  vertebrate  host  contrasting  in  many  points 
with  that  described  in  the  foregoing  paragraphs  is  seen  in  T.  cruzi  (Fig.  128), 
the  cause  of  human  trypanosomiasis  in  Brazil.  In  this  case  the  ordinary  or 
adult  forms  of  the  trypanosome  found  in  the  general  circulation  do  not 
multiply  there  ;  but  the  investigations  of  Chagas  and  of  Hartmann  have 
made  known  two  types  of  multiplication  which  take  place  in  the  internal 
organs  of  the  body. 

The  first  type  of  multiplication  proceeds  in  the  capillaries  of  the  lung 
(Fig.  128,  b — e).  An  adult  trypanosome  loses  its  flagellum,  and  in  some  cases 
its  kinetonucleus  also  ;  its  body  then  becomes  rounded  off  into  an  oval  mass  ; 
the  trophonucleus,  and  also  the  kinetonucleus,  if  present,  multiply  by  suc- 
cessive divisions  to  form  eight  nuclei  of  each  kind  ;  and  finally  the  body 
divides  within  its  own  periplast  into  eight  minute  daughter-individuals,  so- 
called  "merozoites."  The  merozoites  are  stated  to  exhibit  a  dimorphism 


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Flo.  128. — Phases  of  T.  (Schizotrypanuiri)  cruzi  in  vertebrate  blood,  a,  The  two 
forms  of  the  adult  trypanosome,  "  male  "  (upper)  and  "  female  "  (lower),  from 
human  blood  ;  b,  preparations  for  schizogony  ;  c,  schizont  ;  d,  division  of  the 
nucleus  of  the  schizont  ;  e,  division  of  the  schizont  into  eight  merozoites  ; 
f,  merozoite  in  a  blood-corpuscle  ;  g,  intracorpuscular  phase  in  late  stage 
of  growth  ;  h,  similar  phase  escaping  from  a  corpuscle,  the  flagellum  not  yet 
formed  ;  i,  similar  phase,  the  flagellum  in  process  of  formation.  Stages 
b — e  are  found  in  the  lung,  the  others  in  the  peripheral  blood.  After 
Chagas  (425). 

which  Chagas  regards  as  sexual ;  those  produced  by  trypanosomes  which 
retained  their  kinetonucleus  have  both  trophic  and  kinetic  nuclei  and  a 
rudiment  of  a  flagellum  (male  forms)  ;  those  derived  from  trypanosomes  which 
lost  both  flagellum  and  kinetonucleus  have  only  a  trophonucleus  (female 
forms)  ;  in  the  latter  case  the  single  nucleus  divides  into  two  unequal  parts, 
of  which  the  smaller  becomes  the  new  kinetonucleus,  and  a  flagellum  is 
formed  subsequently.  In  either  case  the  merozoites  penetrate  into  blood- 

f  rom  even  the  most  swarming  infection  with  T.  lewisi  (for  the  action  of  the  "  ren- 
forces  "  strains  see  p.  28).  Those  who  study  habitually  the  lethal  species  of 
trypanosomes  often  display  a  natural  bias,  not  in  the  least  justified,  to  assume 
that  a  similar  virulence  is  an  inseparable  attribute  of  all  other  species  of  these 
parasites.  If  that  were  so,  it  would  be  necessary  to  consider  practically  every 
specimen  of  pike,  bream,  perch,  or  tench,  hi  the  Norfolk  Broads,  for  instance,  to  be 
in  a  diseased  condition. 


296  THE  PROTOZOA 

corpuscles,  and  so  pass  into  the  general  circulation.  Within  the  corpuscle 
they  grow  into  the  adult  form,  which  is  finally  set  free  from  the  corpuscle  as 
a  trypanosome  of  normal  structure.  The  adult  trypanosome  (Fig.  128,  a), 
swimming  freely  in  the  blood-plasma,  may  either  be  taken  up  by  the  inverte- 
brate host  in  which  it  develops,  or  may  repeat  the  process  of  multiplication 
by  schizogony. 

The  second  type  of  multiplication  was  first  described  by  Hartmann  from 
hyportrophied  endothelial  cells  of  the  lung  ;  Chagas  (426)  has  since  found  it 
in  the  tissues  of  the  body,  more  especially  in  the  cardiac  muscle,  central  nervous 
system,  and  striped  muscle.  In  this  type  the  parasite  is  intracellular,  and  has 
the  appearance  and  structure  of  a  Leishmania  (cf.  Fig.  138),  a  rounded 
body  containing  a  trophonucleus  and  a  kinetonucleus,  but  no  flagellum  or 
undulating  membrane. 

On  account  of  its  power  of  multiplication  by  schizogony,  Chagas  has  made 
T.  cruzi  the  type  of  a  special  genus,  Schizotrypanum ;  the  type  of  multiplication 
observed  in  the  lung-capillaries  is  not  essentially  different,  however,  from  that 
of  T.  leioisi  in  the  blood,  except  for  its  alleged  sexual  dimorphism  ;  and,  accord- 
ing to  Carini  (424),  similar  processes  of  schizogony  occur  in  other  trypanosomes. 
The  intracellular  multiplication  in  the  tissues,  however,  recalls  strongly  that 
of  the  parasite  of  kala-azar  (see  p.  316,  infra).  Schizotrypanum  thus  forms 
an  important  link  between  a  typical  blood-trypanosome,  such  as  T.  lewisi, 
and  a  tissue-parasite,  such  as  the  species  of  Leishmania,  in  which  the  free 
trypanosome-phase  no  longer  exists,  apparently. 

Chagas  considers  the  multiplication  of  Schizotrypanum  cruzi  in  the  tissues  as 
non-sexual,  and  serving  to  increase  the  number  of  parasites  in  the  host,  but  that 
which  takes  place  in  the  lung- capillaries  as  a  process  of  gametogony  whereby 
the  sexually  differentiated  adult  forms  are  produced.  His  grounds  for  this 
interpretation  are,  first,  that  in  human  blood  the  adult  trypanosomes  exhibit 
a  dimorphism  rarely  found  in  guinea-pigs  infected  artificially,  in  which  also 
schizogony  in  the  lung  is  seldom  observed  ;  secondly,  that  the  invertebrate 
-host,  Conorhinus,  is  always  rendered  infective  if  fed  directly  on  infected 
human  blood,  but  very  rarely  becomes  infective  if  fed  on  guinea-pigs,  even 
when  these  animals  show  an  intense  infection.  He  suggests  that  the  greater 
resistance  of  the  human  organism  to  the  parasite  stimulates  the  production 
of  sexual  forms  which  the  trypanosome  may  cease  to  produce  in  a  less  resistant 
host. 

In  the  more  familiar  pathogenic  species,  such  as  T.  brucii,  T.  gambiense, 
etc.,  the  development  in  the  vertebrate  host  takes  the  form  mainly  of  continued 
multiplication  by  binary  fission  simply.  Reproduction  of  this  kind  may  pro- 
ceed until  the  trypanosomes  swarm  in  the  blood  ;  or,  on  the  contrary,  the 
trypanosomes  may  be  at  all  times  relatively  few  in  number,  even  when 
fatal  to  their  host.  T.  brucii,  for  example,  may  produce  in  different  hosts 
an  acute  or  a  chronic  form  of  disease  ;  in  the  latter  case  the  infected  animal 
may  live  a  long  time,  and  the  parasite  exhibits  very  limited  powers  of  multi- 
plication. The  behaviour  of  the  parasite  in  the  natural  hosts  to  which  it  is 
harmless  has  not  been  studied. 

In  many  pathogenic  species,  periods  of  multiplicative  activity,  during 
which  the  trypanosomes  are  abundant,  alternate  with  periods  during  which 
the  parasites  pass  into  a  resting  condition  in  the  internal  organs,  and  become 
scarce  or  disappear  in  the  general  circulation.  In  this  phase  they  are  alleged 
to  lose  their  flagellum,  diminish  in  size,  and  become  small,  rounded  "  latent 
bodies,"  which,  according  to  Moore  and  Breinl  (484),  have  only  a  single  nucleus  ; 
but  according  to  Fantham  they  are  Leishmania-like,  with  distinct  tropho- 
nucleus and  kinetonucleus.  From  resting  stages  of  this  kind  the  active 
trypanosomes  are  developed  again.  Laveran  (462),  however,  denies  that  there 
is  a  non- flagellated  stage  of  development  in  the  vertebrate  host,  and  considers 
that  the  elements  described  as  "latent  bodies"  represent  involution-stages  of 
the  parasites — that  is  to  say,  forms  which  have  become  deformed  in  structure 
owing  to  unfavourable  conditions,  but  not  to  such  an  extent  as  to  be  incapable 
of  recovery  if  the  conditions  improve. 


THE  ILEMOFLAGELLATES  AND  ALLIED  FORMS     297 

In  the  vast  majority  of  trypanosomes  in  their  natural  hosts,  such  as  birds, 
fishes,  etc.,  the  mode  of  multiplication  and  the  developmental  cycle  remains 
a  mystery,  although  the  sizes  of  the  individual  trypanosomes  and  their  numbers 
are  observed  to  van-  at  different  times  in  the  same  host.  Considerable  light 
has  been  thrown  upon  this  question  by  the  recent  investigations  of  Machado 
upon  the  multiplication  of  Trypaiwsoma  rotatorhtm  of  frogs,  a  species  re- 
markable for  the  polymorphism  it  exhibits.  The  results  obtained  by  Machado 
may  be  summarized  briefly  as  follows :  Trypanosomes  of  any  size  may  divide 
by  binary  fission  when  free  in  the  blood  (supposed  "  non-sexual"  reproduction). 
On  the  other  hand,  trypanosomes  of  large  size  may  become  rounded,  flattened, 
leaf-like  forms,  losing  their  flagellum  ;  such  forms  undergo  a  process  of 
schizogony  in  the  internal  organs,  chiefly  in  the  liver  or  kidneys,  sometimes  in 
the  spleen,  sometimes  even  in  the  circulating  blood.  The  kinetonucleus 
approaches  the  trophonucleus,  and  may  (1)  remain  distinct  from  it,  so-called 
"  male  "  type  ;  or  (2)  may  pass  into  the  trophonucleus,  in  which  the  karyo- 
some  breaks  up  to  form  a  small  secondary  karyosome  ;  the  kiiietonuclear 
karyosome  then  fuses  with,  or  becomes  closely  adherent  to,  the  secondary 
trophonuclear  karyosome — so-called  "  female  "  type.  A  multiplication  of 
the  nuclei  then  takes  place  :  in  the  "  male  "  type  by  independent  divisions 
of  the  kinetonucleus  and  trophonucleus ;  in  the  "  female  "  type  by  divisions 
of  the  single  mass  formed  by  fusion  of  the  kiiietonuclear  and  trophonuclear 
karyosomes,  followed  by  budding  off  of  small  nuclei  from  the  originally 
single  nucleus.  Thus  the  body  of  the  rounded-off  trypanosome  becomes 
rilled,  within  its  periplast,  with  nuclei  varying  in  number  from  five  to  seven- 
teen ;  then  round  each  nucleus  ("  female  ")  or  each  pair  of  dissimilar  nuclei 
("  male  ")  the  protoplasm  becomes  condensed  to  form  as  many  merozoites, 
which  are  finally  set  free  by  rupture  of  the  periplast.  The  merozoites  of 
"  male  "  type  develop  a  flagellum  ;  in  those  of  "  female  "  type  the  single 
nucleus  divides  into  two  nuclei  of  unequal  size,  a  larger  trophonucleus  and  a 
smaller  kinetonucleus,  and  from  the  latter  a  basal  granule  is  budded  off 
from  which  the  flagellum  grows  out  (Fig.(,  30,  G).  In  either  case  the  mero- 
zoites (which  may  divide  further  after  being  liberated  from  the  parent  body) 
become,  transformed  finally  into  the  smallest  forms  of  trypanosomes.  which 
then  grow  up  into  the  larger  forms  found  in  the  blood.  Machado' s  observa- 
tions of  fact,  apart  from  his  theoretical  interpretations,  explain  the  many 
different  forms  found  in  the  frog's  blood,  which  have  recently  been  studied 
in  detail  by  Lebedew  ;  compare  also  Mathis  and  Leger. 

In  other  cases  there  may  be  three  well-marked  types  of  form — long  and 
slender,  short  and  stumpy,  and  intermediate  or  indifferent  forms,  as  in 
T.  gambiense  (Fig.  12 ;  cf.  Minchin,  477,  Kindle,  450,  Bruce,  405)  ;  or  there 
may  be  every  gradation  in  size  from  small  to  large  forms,  as  in  T.  granulosum 
of  the  eel  (Fig.  129) ;  or,  finally,  the  trypanosomes  may  be  practically  uniform 
in  size  and  structure,  as  in  T.  lewisi  after  the  multiplication-period,  T.  vivax, 
etc.  A  satisfactory  explanation  of  the  polymorphism  has  not  been  found 
in  all  cases ;  the  various  forms  may  be  in  some  instances  stages  of  growth 
related  to  multiplication,  as  in  T.  lewisi  during  the  multiplication-period  ;  in 
other  cases  the  polymorphism — for  example,  of  T.  gambiense — may  be  sexual 
differentiation  which  is  related  to  the  subsequent  development  in  the  in- 
vertebrate host ;  a  third  possibility  is  that  in  some  cases  the  propagative 
forms,  destined  for  multiplication  in  the  invertebrate  host,  are  differentiated 
from  the  other  forms  found  in  the  vertebrate  host,  as  in  T.  noctuce  (Minchin 
and  Woodcock,  42).  Different  explanations  must  probably  be  sought  in 
different  cases. 

2.  The  cycle  in  the  invertebrate  host  always  takes  place  entirely 
or  mainly  in  the  digestive  tract,  though  the  extent  to  which  this 
region  is  invaded  varies  greatly.  In  the  development  of  T.  lewisi 
in  the  flea  the  parasites  pass  down  as  far  as  the  rectum,  and  there 


298 


THE  PROTOZOA 


undergo  the  principal  phase  of  their  cycle.  In  the  development  of 
the  trypanosomes  of  fresh-water  fish  in  the  leech  Hemiclepsis,  the 
parasites  do  not  pass  farther  back  than  the  crop  (Robertson,  503). 
Finally,  in  the  many  species  of  pathogenic  trypanosomes  which  are 
transmitted  by  tsetse-flies  of  various  species,  two  types  of  develop- 
mental cycle  can  be  distinguished  :  in  the  one,  the  parasite  invades 


FIG.    129. — Trypanosoma  granulosum  of  the  common  eel :   four  different    sizes, 
probably  stages  of  growth.     After  Minchin  (478),   x  2,000. 

the  whole  alimentary  canal  of  the  fly  ;  in  the  other  it  undergoes  the 
greater  part  of  its  development  in  the  proboscis  and  pharynx  alone. 
The  details  of  the  developmental  cycle  in  the  invertebrate  host 
are  very  inadequately  known,  and  have  only  been  studied  in  a 
very  few  instances.  As  a  rule  the  characteristic  form  of  this 
part  of  the  life-history  is  a  crithidial  or  trypanomonad  type,  repre- 


THE  H.EMOFLAGELLATES  AND  ALLIED  FORMS     299 

senting  the  principal  multiplicative  phase  in  the  invertebrate  host ; 
it  is  a  form  in  which  the  kinetonucleus  is  placed  in  front  of,  or  close 
beside,  the  trophonucleus,  and  in  which,  consequently,  the  undu- 
lating membrane  is  confined  to  the  anterior  region  of  the  body* 
and  may  be  quite  rudimentary.  As  a  rule  the  body  of  the  trypano- 
monad  is  shorter,  stiffer,  more  pear-shaped,  than  in  the  typical  try- 
panosome-form  ;  no  longer  sinuous  and  flexible,  it  is  held  straight 
and  rigid  in  progression,  which  is  effected  almost  entirely  by  the 
flagellum.  In  many  cases,  however,  the  free  flagellum  is  very  short, 
and  used  to  attach  the  organism  to  the  lining  of  the  digestive  tract. 
Besides  the  trypanomonad  form,  the  developmental  cycle  may  also 
include  many  other  types  of  form,  and  often  exhibits  a  degree  of 
polymorphism  which  is  most  bewildering,  and  compared  to  which 
the  diversity  of  form  seen  in  the  vertebrate  host  is  but  slight. 

Taking  the  development  of  T.  lewisi  in  the  rat-flea  as  a  typical 
example,  the  parasites  when  taken  up  by  the  flea  pass  with  the 
ingested  blood  into  the  stomach  (mid-gut)  of  the  insect.     In  this 
part  they  multiply  actively  in  a  peculiar  manner,  not  as  yet  de- 
scribed in  the  case  of  any  other  trypanosome  in  its  invertebrate  host 
(Fig.  130)  ;  they  penetrate  into  the  cells  of  the  epithelium,  and  in 
that  situation  they  grow  to  a  very  large  size,  retaining  their  flagellum 
and  undulating  membrane,  and  exhibiting  active  metabolic  changes 
in  the  form  of  the  body,  which  in  early  stages  of  the  growth  is 
doubled  on  itself  in  the  hinder  region,  thus  becoming  pear-shaped 
or  like  a  tadpole  in  form,  but  later  is  more  block-like  or  rounded. 
During  growth  the  nuclei  multiply,  and  the  body  when  full-grown 
approaches  a  spherical  form,  and  becomes  divided  up  within  its 
own  periplast  into  a  number  of  daughter-individuals,  which  writhe 
and  twist  over  each  other  like  a  bunch  of  eels  within  the  thin  envelope 
enclosing  them.     When  this  stage  is  reached,  the  flagellum,  which 
hitherto  had  been  performing  active  movements  and  causing  the 
organism  to  rotate  irregularly  within  the  cell,  disappears  altogether, 
and  the  metabolic  movements  cease  ;   the  body  becomes  almost 
perfectly  spherical,  and  consists  of  the  periplast-envelope   within 
which   a   number   of   daughter-trypanosomes   are   wriggling    very 
actively  ;  the  envelope  becomes  more  and  more  tense,  and  finally 
bursts  with  explosive  suddenness,  setting  free  the  flagellates,  usually 
about  eight  in  number,  within  the  host-cell.     The  products  of  this 
method  of  multiplication  are  full-sized  trypanosomes,  complete  in 
their  structure,  and  differing  but  slightly  in  their  characters  from 
those  found  in  the  blood  of  the  rat.     They  escape  from  the  host-cell 
into  the  lumen  of  the  stomach. 

To  the  intracellular  multiplicative  phase  in  the  stomach  a 
crithidial  phase  in  the  rectum  succeeds  (Fig.  131).  In  the  fully- 
established  condition  the  rectal  phase  consists  of  small  pear-shaped 


300 


THE  PROTOZOA 


forms  with  the  flagellum  very  short,  in  some  cases  projecting 
scarcely  at  all  from  the  body  at  its  pointed  end.  These  forms  are 
found  attached  by  means  of  their  flagella,  often  in  vast  numbers, 
to  the  wall  of  the  rectum,  sometimes  also  in  the  intestinal  or  pyloric 
region ;  they  multiply  by  binary  fission,  and  form  a  stock,  as  it  were, 
of  the  parasites,  which  persists  for  a  long  time  in  the  flea — probably, 
under  favourable  conditions,  for  the  whole  life  of  the  insect.  Experi- 
ments have  shown  that  a  flea  once  rendered  infective  to  rats  can 


FIG.  130. — Trypanosoma  lewisi:  developmental  phases  from  the  stomach  of  the 
rat-flea.  0,  Ordinary  form  from  the  blood  of  the  rat  ;  A — F,  intracellular 
stages  :  A,  a  trypanosome  curled  on  itself  ;  B,  similar  form  in  which  the  body 
has  become  rounded  ;  C,  multiplication  beginning,  division  of  kinetonucleus 
and  trophonucleus,  daughter-flagellum  growing  out  ;  D,  further  stage — three 
nuclei  of  each  kind,  two  short  daughter-flagella,  and  a  long  parent-ilagellum 
wrapped  round  the  body  ;  E,  six  nuclei  of  each  kind,  five  daughter- flagella, 
parent- flagellum  wrapped  round  the  body  ;  F,  eight  nuclei  of  each  kind,  the 
daughter-flagella  running  parallel  with  the  parent-flagellum  ;  G,  the  type  of 
trypanosome  resulting  from  the  process  of  multiplication  seen  in  the  fore- 
going figures  ;  this  is  the  form  which  passes  down  the  intestine  into  the  rectum. 
Magnified  2,000. 

N.B. — The  drawings  in  this  figure  and  in  Fig.  131  are  made  from  prepara- 
tions fixed  wet  with  Schaudinn's  fluid  and  stained  with  iron-haematoxylin  ; 
in  such  preparations  the  trypanosomes  always  appear  appreciably  smaller 
than  in  films  stained  with  the  Romanowsky-stain  (see  Minchin,  479)  ;  con- 
sequently these  figures,  though  drawn  to  the  same  magnification  as  Figs.  11, 
127,  etc.,  are  on  a  slightly  smaller  scale  ;  compare  the  trypanosome  drawn  in 
0  with  those  in  Figs.  11,  A,  and  127,  A. 

remain  so  for  at  least  three  months,  without  being  reinfected. 
From  the  rectal  stock  trypaniform  individuals  arise  by  a  process  of 
modification  of  the  crithidial  forms,  in  which  the  flagellum  grows 
in  length,  the  anterior  portion  of  the  body  becomes  more  drawn  out, 
the  kinetonucleus  migrates  backwards  behind  the  trophonucleus, 
taking  with  it  the  origin  of  the  flagellum,  and  an  undulating  mem- 


THE  H^EMOFLAGELLATES  AND  ALLIED  FORMS    301 


brane  running  the  length  of  the  body  is  established.  The  trypani- 
form  individuals  thus  formed  are  of  small  size  and  broad,  stumpy 
form  ;  they  represent  the  propagative  phase  which  passes  from  the 
flea  back  into  the  rat.  From  the  rectum  they  pass  forwards  into 
the  stomach,  and  from  the  stomach  they  appear  to  be  regurgitated 
into  the  rat's  blood  when  the  flea  feeds. 

Experiments  show  that  the  flea  becomes  infective  to  the  rat  in 
about  six  days  after  it  first  took  up  the  trypanosomes  from  an 
infected  rat.  The  intracellular  phase  is  at  the  height  of  its  develop- 
ment about  twenty-four  hours  after  the  flea  takes  up  the  trypano- 
somes ;  the  rectal  phase  begins  to  be  established  towards  the  end  of 


A 


FIG.  131. — Trypanosoma  lewisi:  developmental  phases  from  the  rectum  of  the  rat- 
flea.  A,  Early  rectal  form  ;  B,  crithidial  form  attached  to  wall  of  rectum  ; 
C,  D,  division  of  crithidial  form  ;  E,  clump  of  crithidial  forms  detached  from 
wall  of  rectum,  hanging  together  by  their  flagella,  one  of  them  beginning  to 
divide  ;  F,  0,  H,  crithidial  forms  without  free  flagella  ;  /,  rounded  form 
without  flagellum  ;  J,  K,  L,  M,  series  of  forms  transitional  from  the  crithidial 
to  the  final  trypaniform  type  ;  N,  the  last  stage  in  the  flea.  Magnified  2,000. 

the  first  or  beginning  of  the  second  day  ;  and  the  stumpy,  trypani- 
form, propagative  phase  is  developed  in  the  rectum  towards  the  end 
of  the  fifth  day. 

The  account  of  the  development  of  T.  lewisi  in  the  flea  given  in  the  fore- 
going paragraphs  is  based  upon  investigations,  some  of  them  as  yet  unpub- 
lished, carried  on  in  conjunction  with  Dr.  J.  D.  Thomson  by  the  author 
(480-482).  Some  of  the  phases  of  the  parasite  have  also  been  described  by 
Swellengrebel  and  Strickland  (517).  A  number  of  investigators — namely, 
Prowazek  (497),  Breinl  and  Hindle,  Baldrey  (396),  Rodenwaldt,  and  others — 
have  studied  the  development  of  this  trypanosome  in  the  rat-louse  (Hcemato- 
pinus  spinulosus).  Experiments  have  shown  that  this  insect  is  also  capable 
of  transmitting  the  trypanosome  from  rat  to  rat,  but  only,  to  judge  from  the 


302 


THE  PROTOZOA 


published  results,  in  rare  instances,  in  striking  contrast  with  the  ease  with 
which  the  transmission  is  effected  by  the  rat-flea.  The  rat-louse  may  be 
regarded,  therefore,  as  a  host  in  which  the  trypanosome  establishes  itself 
only  exceptionally,  and  by  no  means'  as  the  host  to  which  it  is  best  adapted. 
Crithidial  and  other  forms  have  been  seen  in  the  louse,  but  the  intracellular 
phase  has  not  been  observed,  and  it  is  probable  that  most  of  the  forms  de- 
scribed from  this  host  are  degenerating  forms  maintaining  a  feeble  and  pre- 
carious existence  under  adverse  conditions,  and  destined  to  die  off  and  dis- 
appear sooner  or  later. 

The  developmental  cycle  of  Schizotrypanum  cruzi  in  the  bug  Conorhinus 
megistus  has  been  described  by  Chagas,*  and  is  briefly  as  follows  (Fig.  132) : 


J 

FIG.  132.  —  Phases  of  Schizotrypqnum  cruzi  in  the  bug  Conorhinus  megistus. 
a,  b,  and  c,  Forms  transitional  from  the  ordinary  trypanosomes  to  the  rounded 
forms  ;  d,  clump  of  rounded  forms  ;  e  and  /,  change  of  rounded  into  crithidial 
forms  ;  g  and  h,  crithidial  forms  ;  i,  trypaniform  type  from  the  salivary 
glands  ;  j,  encapsuled  form  from  the  intestine.  After  Chagas  (425). 

The  trypanosomes  taken  up  by  the  bug  into  its  stomach  change  in  about 
six  hours  ;  they  lose  their  flagellum  and  contract  into  rounded,  Leishmania- 
like  forms,  which  multiply  actively  by  fission.  After  a  time  multiplication 
ceases,  and  the  rounded  forms  become  pear-shaped,  develop  a  flagellum  at 
the  pointed  end,  and  change  into  typical  crithidial  forms  which  pass  on  into 
the  intestine,  and  there  multiply  by  fission.  In  this  way  the  characteristic 
condition  of  the  infected  bug  is  produced,  with  the  intestine  containing  a 
swarm  of  trypanomonad  individuals  multiplying  actively.  The  final  stage 
in  the  insect  is  a  small  trypaniform  type  which  is  found  in  the  body- cavity 
and  salivary  glands,  whence  it  doubtless  passes  into  a  vertebrate  host  again. 

*  A  critical  summary  and  review  of  the  memoir  of  Chagas  is  given  by  Minchin 
in  Nature,  vol.  Ixxxiv.,  pp.  142-144  (August  10,  1910),  with  three  text-figures. 


THE  H^MOFLAGELLATES  AND  ALLIED  FORMS     303 

The  three  principal  phases  in  the  development  of  T.  cruzi  in  the  bug  may  be 
compared,  without  difficulty,  with  those  of  T.  lewisi  in  the  flea,  though 
differing  in  minor  details  ;  in  both  cases  an  early  multiplicative  phase  in  the 
stomach  is  followed  by  a  crithidial  phase,  also  multiplicative  and  constituting 
the  principal  stock  of  the  parasite,  in  the  hinder  part  of  the  digestive  tract ; 
to  this  succeeds  a  propagative  trypaniform  phase,  which  in  the  case  of  T.  lewisi 
passes  forwards  to  the  stomach,  but  which  in  the  case  of  T.  cruzi  appears  to 
pass  through  the  wall  of  the  alimentary  canal  into  the  body-cavity,  and  so 
into  the  salivary  glands.  Other  developmental  forms  have  been  described 
by  Chagas,  but  their  relation  to  the  cycle  of  the  parasite,  if  indeed  they  really 
belong  to  it,  is  not  clear. 

The  developmental  cycle  of  the  trypanosomes  of  fresh- water  fishes  in  the 
leech  Hemiclepsis  marginata  (Robertson,  503)  begins  also  by  active  multi- 
plication in  the  crop  about  six  to  nine  hours  after  the  flagellates  have  been 
ingested.  The  trypanosomes  divide  by  repeated  binary  fission  of  unequal 
type,  budding  off  small  individuals  which  are  crithidial  in  type  and  multiply 
in  their  turn.  In  a  few  days  the  crop  is  populated  by  a  swarm  of  trypano- 
rnonad  forms  of  various  sizes,  multiplying  actively.  Towards  the  end  of  the 
•digestion,  the  propagative  phase  begins  to  appear  in  the  form  of  long,  slender 
trypaniform  individuals  which  arise  directly  from  the  crithidial  forms,  and 
pass  forwards  in  great  numbers  from  the  crop  into  the  proboscis-sheath, 
whence  they  are  inoculated  by  the  leech  into  a  fresh  host.  A  certain  number 
of  the  crithidial  forms  remain  behind  in  the  crop,  however,  where  during 
hunger- periods  they  may  pass  into  a  resting  Leishmania-iorm  ;  when  the 
•crop  is  again  filled  with  fresh  blood,  these  forms  begin  to  multiply  again, 
repopulating  the  crop  with  crithidial  forms,  from  which  a  fresh  batch  of 
trypaniform  propagative  individuals  arise  towards  the  end  of  digestion 
again. 

In  the  development  of  T.  raice  in  the  leech  Pontobdetta  muricata  (Robertson, 
500,  502),  the  ingested  trypanosomes  multiply  in  the  crop  in  a  similar  manner 
by  unequal  binary  fission,  budding  off  small  individuals  which,  however,  are 
rounded  and  leishrnanial  in  type,  and  which  pass  down  from  the  crop  into  the 
intestine,  where  they  develop  a  flagelluni,  become  crithidial  in  type,  and 
multiply  actively.  During  hunger-  periods  they  become  leishmanial,  resting 
forms  which  persist  when  all  other  forms  have  succumbed  and  died  out,  becom- 
ing crithidial  again  when  the  supply  of  food  is  renewed.  From  the  crithidial 
forms  arise  the  long,  slender  trypaniform  individuals  of  the  propagative  phase, 
which  pass  forward  into  the  proboscis  to  be  inoculated  into  the  fish.  The 
development  of  T.  vitiates,  from  the  blood  of  the  Ceylon  tortoise,  Emyda  vittata, 
in  the  leech  GlossipJionia  sp.,  is  of  a  similar  type,  but  takes  place  almost  entirely 
in  the  crop  (Robertson,  501). 

The  development  of  T.  gambiense  in  the  tsetse-fly,  Glossina  palpalis,  so  far 
as  it  has  been  described  by  Kleine  (457),  Kleine  and  Taute  (459),  and  Bruce 
and  his  collaborators  (415),  presents  some  peculiar  features  not  quite  intelli- 
gible at  present.  The  whole  development  takes  a  long  time,  about  eighteen 
to  twenty- five  days  or  more,  a  fact  which,  together  with  the  low  percentage 
of  flies  which  become  infected,  accounts  for  the  existence  of  a  developmental 
cycle  having  been  missed  by  so  many  investigators,  until  it  was  first  dis- 
covered by  Kleine.  From  five  to  seven  days  after  the  infection  of  the  fly  the 
trypanosomes  disappear  or  become  scarce  in  its  digestive  tract,  indicating, 
possibly,  an  intracellular  stage  yet  to  be  discovered.  Later,  in  a  small 
percentage  of  the  flies,  the  trypanosomes  reappear  in  the  digestive  tract  in 
enormous  numbers.  The  flagellates  at  this  stage  vary  greatly  in  size,  form, 
and  appearance,  but  crithidial  forms  are  stated  to  be  very  rare,  a  feature 
in  which  the  development  contrasts  with  the  usual  type  seen  in  other  trypano- 
somes. Finally  an  invasion  of  the  salivary  glands  takes  place,  though  in  what 
way  it  is  brought  about  is  not  clear  ;  short,  stumpy  trypaniform  individuals 
are  found  in  the  glands,  which  represent  the  ripe,  propagative  phase  destined 
to  be  inoculated  into  the  vertebrate  host.  These  ripe  forms  first  make  their 
appearance,  according  to  Kleine,  in  the  intestine. 


304  THE  PROTOZOA 

In  many  species  of  trypanosomes  transmitted  by  tsetse-flies,  a  peculiar 
mode  of  development  occurs,  as  already  stated,  in  the  proboscis,  termed 
by  Roubaud,  who  discovered  it,  a  culture  d'attente.  The  trypanosomes 
taken  up  from  the  vertebrate  change  very  rapidly  into  trypanomonad 
("leptomonad,"  Roubaud)  forms,  with  the  kinetonucleus  far  forward,  and 
attach  themselves  by  the  tip  of  the  flagellum  to  the  wall  of  the  proboscis-tube. 
In  this  situation  they  multiply  in  the  salivary  fluid  by  binary  fission,  until 
great  numbers  are  present.  In  some  cases  this  culture  in  the  proboscis  appears 
to  be  the  sole  form  of  developmental  cycle  in  the  fly,  as,  for  example  in 
T.  cazalboui  (Roubaud,  506,  Bouffard),  T.  vivax  (Bruce,  411,  iii.)  ;  this  type 
is  termed  by  Roubaud  evolution  par  fixation  directe.  In  other  species 
(T.  dimorphon,  T.  pecaudi)  the  parasite  multiplies  first  in  the  digestive  tract 
of  the  fly,  and  then  spreads  forward  into  the  proboscis — evolution  par  fixation 
indirecte  of  Roubaud  ;  in  this  case,  however,  the  possibility  does  not  seem 
to  be  excluded  that  the  forms  seen  in  the  digestive  tract  may  have  belonged 
to  the  developmental  cycle  of  a  distinct  trypanosome.  Development  of  this 
kind  has  only  been  observed  in  tsetse-flies. 

According"  to  Bouffard,  T.  cazalboui  can  be  transmitted  mechanically  by 
Stomoxys,  but  goes  through  its  developmental  cycle  only  in  the  proboscis  of 
Glossina  palpnlis  ;  Stomoxys  may  therefore  cause  epidemics  of  the  disease 
("souma"),  but  endemic  areas  are  always  in  regions  where  G.  palpalis 
occurs.  The  tsetse-fly  is  not  infective,  until  six  days  after  first  feeding  on  an 
infected  animal,  and  it  then  remains  infective  permanently,  or  at  least  for  the 
greater  part  of  its  existence.  Hence  the  proboscis- cycle  is  a  rapid  develop- 
ment, comparable,  as  regards  the  time  it  requires,  to  that  of  T.  lewisi  in  the 
flea  rather  than  to  that  of  other  trypanosomes  in  the  digestive  tract  of  the 

tsetse. 

Finally,*  mention  must  be  made  of  the  cysts  of  T.  grayi,  described  by 
Minchm"(476),  occurring  in  the  hind-gut  of  Glossina  palpalis.  The  cysts  result 
from  the  encystment  of  a  crithidial  form,  and  are  very  similar  to  the  cysts  of 
Herpetomonas,  described  by  Prowazek  (Fig.  124),  from  the  hind-gut  of  the 
house-fly ;  their  mode  of  formation  indicates  that  they  are  destined  to  pass 
out  of  the  rectum  to  the  exterior  with  the  faeces,  and  Minchin  has  suggested 
that  a  contaminative  method  of  spreading  the  infection  may  occur  in  addition 
to  the  usual  inoculative  method.  The  possibility  must  be  reckoned  with, 
however,  that  the  cysts  in  question  may  be  part  of  the  cycle  of  a  distinct 
flagellate  parasite,  perhaps  peculiar  to  the  fly  alone,  and  may  not  belong  at  all 
to  the  life-cycle  of  T.  grayi,  which  has  now  been  shown  to  be  the  developmental 
form  of  the  trypanosome  of  the  crocodile  (cf.  Cystotrypanosoma,  Roubaud, 
557-5).  According  to  Kleine  and  Taute,  trypanosomes,  not  encysted,  may 
be  found  in  the  faeces  of  infected  tsetses. 

Apart  from  the  somewhat  aberrant  development  of  the  members 
of  the  &wcu-group,  which  require  further  elucidation,  the  cycle 
of  a  trypanosome  in  the  invertebrate  host  appears  to  consist  typically 
of  three  principal  phases  :  (1)  An  initial  multiplicative  phase,  which 
may  be  trypaniform,  as  in  T.  leivisi,  or  Leishmania  -  like,  as  in 
T.  cruzi,  or  may  take  the  form  of  unequal  division  of  large  trypani- 
form individuals  to  produce  either  small  crithidial  forms  directly, 
as  in  fish-trypanosomes  in  the  leech  Hemiclepsis,  or  rounded 
Leishmania-iorms,  which  later  become  crithidial,  as  in  T.  raice 
and  T.  vittacet ;  to  this  initial  phase  succeeds  (2)  a  crithidial  phase, 
which  may  pass  farther  down  the  alimentary  canal,  and  which  in  any 
case  multiplies  by  fission  and  constitutes  the  principal  stock  of  the 

*  The  development  described  by  Schaudinn  (132)  for  T.  noctiite  is  dea]t  with  in 
a  subsequent  chapter  (p.  390). 


THE  H^MOFLAGELLATES  AND  ALLIED  FORMS     305 

parasite,  keeping  up  the  infection  of  the  invertebrate  host.  In 
hunger-periods  the  flagellates  may  persist  as  simple,  rounded, 
Leishmania-like  forms.  Sooner  or  later  many,  it  may  be  the  greater 
number,  but  not  all,  of  the  crithidial  forms  become  modified  into  the 
trypaniform  individuals,  which  represent  (3)  the  propagative  phase 
of  the  parasite,  and  pass  forwards  to  be  inoculated  into  the  verte- 
brate host.  Those  crithidial  forms  which  do  not  become  trans- 
formed into  the  propagative  individuals  remain  to  multiply  and 
replenish  the  stock. 

A  very  much  debated  question  in  this  development  is  that  relating  to  the 
occurrence  of  sexual  phases  and  synganiy,  which,  purely  on  the  analogy 
of  the  malarial  parasites,  are  assumed  almost  universally  to  occur  in  the 
invertebrate  host.  Not  in  a  single  instance  as  yet,  however,  has  the  sexual 
act  been  proved  satisfactorily  to  take  place  in  the  development  of  trypano- 
somes.  The  fertilization  described  by  Schaudinn  (132)  in  "  T.  noctuce"  is 
the  well-known  conjugation  of  H alter idium,  which  can  be  observed  without 
difficulty  ;  and  though  Schaudinn  described  so-called  "  male  "  and  "  female  " 
types  of  trypanosomes  in  the  mosquito,  he  expressly  stated  that  they  did  not 
and  could  not  conjugate.  The  process  of  syngamy  described  by  Prowazek 
(497)  for  T.  lewisi  in  the  rat-louse,  though  "  confirmed  "  by  Baldrey  (396), 
Gonder  (445'5),  and  Rodenwaldt,  is  almost  certainly  the  agglomeration  of 
degenerating  forms  (Swellengrebel,  516  ;  compare  Reichenow,  78,  p.  268). 
Less  biassed  investigators,  who  have  studied  the  developmental  cycle  of 
trypanosomes  with  great  care,  such  as  Chagas,  Robertson,  and  others,  have 
been  quite  unable  to  observe  sexual  processes  of  any  kind.  The  liability  to 
error  in  the  interpretation  of  observations  is  greatly  increased,  first  by  the 
fact  that  trypanosomes  divide  longitudinally  and  often  unequally,  secondly 
by  the  phenomena  of  agglomeration  (p.  128),  which  occur  readily  under  un- 
favourable conditions.  Consequently  the  adhesion  together  of  two  trypano- 
somes may  be  due  to  quite  other  causes  than  sexual  affinity.  In  some  cases 
the  alleged  occurrence  of  syngamy  has  been  based  merely  on  the  fact  that 
non- flagellated  forms  have  been  seen,  which,  on  the  analogy  of  the  malarial 
parasites  (p.  382),  are  termed  "  ookinetes  "  and  interpreted  as  zygotes. 

It  is  certainly  remarkable,  in  view  of  the  paucity  of  data,  that  so  many 
investigators,  following  Schaudinn's  lead,  should  persist  in  ascribing  all  form- 
differentiation  in  trypanosomes  to  sex,  and  should  be  unable,  apparently,  to 
conceive  of  any  other  cause  of  polymorphism  in  parasites  which  have  to  adapt 
themselves,  in  the  course  of  their  life-cycle,  to  a  great  diversity  of  conditions 
(compare  also  Doflein,  430).  It  must  be  emphasized  that  the  only  true 
criterion  of  sexual  polymorphism  is  sexual  behaviour,  and  until  that  has  been 
established  it  is  premature  to  speak  of  sexual  differentiation. 

Some  investigators  have  upheld  the  unfashionable  view  that  the  syngamy  of 
trypanosomes  occurs  in  the  vertebrate  host ;  so  Bradford  and  Plimmer,  and 
more  recently  Ottolenghi,  who  has  described  in  T.  brucii,  T.  equinum, 
T.  gambiense,  and  T.  equiperdum,  the  following  process  of  sexual  conjugation  : 
Two  trypanosomes  of  very  different  size  and  appearance  attach  themselves 
to  one  another  by  their  hinder  ends.  One,  regarded  as  the  microgamete,  is 
more  slender,  and  contains  one  trophonucleus  or  a  larger  nucleus  of  this  kind 
and  two  smaller  (reduction-nuclei)  ;  the  other,  the  macrogamete,  is  much 
larger,  and  contains  also  a  larger  nucleus  near  the  kinetonucleus  and  two  or 
more  other  nuclei  in  process  of  degeneration.  The  macrogamete  also  has 
usually  three,  sometimes  two  or  four,  flagella  and  undulating  membranes. 
After  the  two  gametes  have  united  by  their  hinder  ends,  a  small  nucleus  is 
budded  off  from  the  principal  nucleus  of  the  microgamete,  passes  over  into  the 
body  of  the  macrogamete,  and  fuses  with  its  principal  nucleus.  Subsequently 
the  microgamete  appears  to  degenerate,  and  the  fertilized  macrogamete  to 

20 


306  THE  PROTOZOA 

divide  up  into  trypanosomes  of  the  ordinary  type.  Those  who  consider  that 
syngamy  can  only  occur  in  the  invertebrate  host  will  doubtless  regard  the 
process  described  by  Ottolenghi  as  phenomena  of  agglomeration  and  de- 
generation. In  the  present  state  of  our  knowledge,  however,  it  is  best  to  keep 
an  open  mind  on  this  question,  and  to  await  further  investigations. 

In  T.  gambiense,  Moore  and  Brcinl  (484)  have  described  a  process  of  fusion 
between  the  kinetonucleus  and  trophonucleus  in  the  formation  of  the  "  latent 
bodies,"  and  have  interpreted  this  as  a  sexual  process,  a  suggestion  hardly 
to  be  taken  seriously.  A  similar  process  alleged  to  occur  in  the  multiplication- 
forms  of  T.  leivisi  has  been  interpreted  by  Schilling  as  the  inevitable  autogamy. 

All  that  can  be  said  at  present,  with  regard  to  sexual  processes  in  trypano- 
somes, is  that,  on  the  analogy  of  other  Protozoa  generally,  syngamy  may  be 
expected  to  occur  in  some  part  of  the  life- cycle.  It  remains,  however,  for 
further  research  to  establish  definitely  the  conditions  under  which  syngamy 
takes  place,  and  the  nature  of  the  process  in  these  organisms  ;  nor  can  it  be 
considered  as  sound  reasoning,  in  the  absence  of  concrete  observations,  to  at- 
tempt to  limit  the  possible  occurrence  of  syngamy,  or  to  infer  the  exact  form 
it  takes,  either  by  analogies  more  or  less  far-fetched  with  one  or  another 
group  of  Protozoa,  or  by  the  mere  existence  of  form-differentiation,  and  still 
less  by  the  arbitrary  interpretation  of  certain  forms  as  zygotes  or  ookinetes. 

A  very  variable  feature. in  the  development  of  trypanosomes  is  the  sus- 
ceptibility of  the  invertebrate  host.  In  the  case  of  T.  lewisi,  only  about 
20  per  cent.,  approximately,  of  the  fleas  fed  experimentally  on  infected  rats 
become  infective  in  their  turn,  and  in  the  case  of  tsetse-flies  and  pathogenic 
trypanosomes  the  percentage  is  much  smaller.  There  are  also  grounds  for 
suspecting  that  a  certain  condition  or  phase  of  the  trypanosome  in  the  blood 
of  the  vertebrate  is  sometimes  necessary  for  establishing  the  developmental 
cycle  in  the  invertebrate  ;  compare  the  observations  and  conclusions  of  Chagas 
with  regard  to  Schizotrypaniim  cruzi,  mentioned  above  (p.  296).  In  Trypano- 
soma  noct-uce  the  summer  form  which  appears  in  the  blood  is  of  a  type  distinct 
from  the  winter  forms  found  in  the  bone-marrow  (Minchin  and  Woodcock,  42). 
On  the  other  hand,  in  the  case  of  the  trypanosomes  of  fresh- water  fishes,  Robert- 
son (503)  found  that  every  leech  became  infected  that  was  fed  on  an  infected 
fish  ;  so  that  the  simplest  method  of  determining  whether  a  fish  was  infected 
was  to  feed  a  newly- hatched  Hemiclepsis  on  it. 

A  question  often  discussed  is  whether  trypanosomes  in  any  part  of  their 
development  may  pass  through  "  ultramicroscopic  "  stages.  Schaudinn  (132) 
expressed  the  opinion  that  some  stages  of  trypanosomes  investigated  by  him 
were  small  enough  to  pass  through  bacterial  filters  ;  though  he  did  not  put 
this  suggestion  to  an  experimental  test,  it  is  often  quoted  as  a  proved  fact.* 
Moore  and  Breinl  (484)  also  asserted,  without  experimental  data,  that  infected 
blood  remained  infective  after  filtration.  On  the  other  hand,  attempts  by 
Bruce  and  Bateman  to  obtain  experimental  verification  of  these  statements 
gave  negative  results  (compare  also  Report  XI.,  p.  122,  of  the  Sleeping  Sickness 
Commission). 

Recently  it  has  been  asserted  by  Fry  that  T.  brucii  can  throw  off  granules 
which,  when  liberated,  possess  a  certain  motility  of  their  own  in  the  blood  ; 
this  process  is  regarded  as  "  essentially  of  a  vital  and  not  a  degenerative 
nature."  That  a  trypanosome  or  any  other  living  cell  might  excrete  grains 
which  when  set  free  could  exhibit  movements  due  to  molecular  or  other 
causes  is  highly  probable  ;  but  that  such  grains  represent  a  stage  in  the  life- 
history  of  a  trypanosome  is  far  from  being  so  ;  nor  can  analogy  with  spiro- 
chsetes  be  considered  as  a  legitimate  argument  in  favour  of  any  such  con- 
clusion. 

There  remains  for  consideration  the  development  which  trypanosomes 
undergo  in  artificial  cultures,  in  which  they  exhibit  a  series  of  forms  quite 
different  from  those  seen  in  the  blood  of  the  vertebrate,  and  so  far  resembling 
the  cycle  in  the  invertebrate  host  in  that  the  predominant  phase  is  a  crithidial 

*  It  is  doubtful  whether  the  forms  of  which  Schaudinn  made  this  statement  were 
really  trypanosomes  or  spirochactes. 


THE  H/EMOFLAGELLATES  AND  ALLIED  FORMS     307 


or  trypanomonad  type  of  flagellate.  Until  the  cultural  development  of  a 
trypanosome  has  been  compared  in  detail  with  its  natural  development  in 
the  invertebrate  host,  it  is  impossible  to  estimate  precisely  the  bearing  of  the 
cultural  series  of  stages  from  the  point  of  view  of  the  physiology  and  mor- 
phology of  the  parasite.  The  only  investigator  who  has  attempted  this  is 
Chagas  (425),  who  found  in  cultures  of  Schizotrypanum  cruzi  the  same  three 
principal  phases — namely,  rounded,  crithidial,  and  trypaniform — that  occur 
in  the  natural  cycle,  and  in  the  same  order  of  sequence.  At  present,  therefore, 
it  would  be  unprofitable  to  discuss  in  detail  the  series  of  forms  occurring 
in  artificial  cultures,  and  it  must  suffice  to  refer  the  reader  for  further  infor- 
mation to  the  principal  works  on  the  subject,  narnelv,  those  of  Novy  and 
McNeal  (489),  Bouet,  Franya  (438,  443),  Rosenbusch,  Thomson  (525),  Wood- 
cock (527),  Lebedew,  and  Doflein  (431).  As  already  pointed  out  above,  the 
cultural  method  is  often  of  the  greatest  practical  value  in  determining  whether, 
in  a  given  case,  an  animal  is  infected  with  trypanosomes  or  not. 

Lebedew  has  described  what  he  believes  to  be  syngamv  in  the  cultural 
phases  of  T.  rotator  ium  ;  compare  also  the  account  of  Leishmania  below 
(p.  319). 

The  genus  Trypanosoma  comprises  a  vast  number  of  species, 
parasitic  in  the  blood  of  animals  throughout  the  vertebrate  series  ; 
and  several  attempts  have  been  made  to  subdivide  and  classify 


E 


FIG.  133. — Endotrypanum  sckaudinni  from  the  blood  of  Cholcepus  didactylus. 
A — E,  Various  forms  of  the  intracorpuscular  parasite  ;  F,  trypanosome 
from  the  blood  of  the  same  host.  After  Mcsnil  and  Brimont,  magnified  about 
1,500  diameters. 

this  comprehensive  genus  into  smaller  groups.  Such  attempts 
have  either  taken  the  course  of  splitting  off  particular  forms,  char- 
acterized by  some  special  peculiarity,  from  the  main  group,  or  of 
subdividing  the  group  as  a  whole  on  some  principle  of  morphology 
or  development.  An  example  of  the  first  method  is  the  foundation 
by  Chagas  (425)  of  the  genus  Schizotrypanum,  as  already  mentioned, 
for  T.  cruzi,  011  the  ground  that  it  multiplies  by  schizogony  and 
possesses  intracorpuscular  phases.  The  genus  Endotrypanum  was 
proposed  by  Mesnil  and  Brimont  for  a  peculiar  form  which  was 
discovered  by  them  within  the  red  blood-corpuscles  of  a  sloth 
(Cholcepus  didactylus),  and  which  is  very  probably  an  intracorpus- 
cular phase  of  a  trypanosome  found  free  in  the  blood-plasma  of 
the  same  host.  The  life-cycle  of  Endotrypanum  is  not  yet  known. 
Ohagas  considers  it  not  improbable  that  it  should  be  placed  in  the 


208  THE  PROTOZOA 

same  genus  as  T.  cruzi,  in  which  case  the  name  Endotrypanum  has 
the  priority  over  Schizotrypanum.  In  the  present  state  of  know- 
ledge, data  are  lacking  for  deciding  how  far  it  is  possible  to  employ 
either  multiplication  by  schizogony  or  an  intracorpuscular  habitat 
as  characters  for  defining  genera  of  trypanosomes.  An  intra- 
corpuscular habitat  is  probably  commoner  in  trypanosomes  than 
has  usually  been  supposed.  It  has  been  described  quite  recently 
by  Buchanan  in  T.  brucii. 

Attempts  to  subdivide  the  genus  Trypanosoma  as  a  whole  have 
been  based  on  the  possibility  that  the  trypanosome-type  of  structure 
may  have  had  two  distinct  phylogenetic  origins,  one  through 
Leptomonas  and  Crithidia  from  a  cerconionad  ancestor,  the  other 
through  Trypanoplasma  from  a  heteromastigote  or  Bodonid  type. 
The  trypanosome-form  might  be  imagined  to  have  arisen  from 
either  of  these  two  types.  It  could  be  derived  from  a  form  like 
Trypanoplasma  by  loss  of  the  free  anterior  flagellum,  in  which 
case  the  flagellum  of  a  trypanosome  is  to  be  regarded  as  posterior  ; 
on  the  other  hand,  if,  in  a  form,  like  Leptomonas,  the  kinetonucleus 
and  with  it  the  origin  of  the  flagellum,  be  shifted  backwards  to  the 
neighbourhood  of  the  trophonucleus,  and  if  at  the  same  time  the 
flagellum  runs  forwards  along  the  body  connected  to  it  by  an  un- 
dulating membrane,  a  Crithidia-like  form  results,  from  which,  by 
still  further  displacement  backwards  of  the  kinetonucleus  and 
flagellum  to  near  the  posterior  end  of  the  body,  a  trypanosome- 
form  is  produced  in  which  the  single  flagellum  is  to  be  regarded  as 
anterior.  It  is  therefore  conceivable  that  the  trypanosome-form 
may  comprise  two  morphological  types,  structurally  indistinguish- 
able, but  entirely  different  in  origin,  and  opposite  in  morphological 
orientation  of  the  body. 

From  this  point  of  view,  Woodcock  (395)  subdivided  trypano- 
somes into  two  genera  :  Trypanomorpha,  with  cercomonad  ancestry 
and  flagellum  morphologically  anterior  ;  and  Trypanosoma,  in  a 
restricted  sense,  with  heteromastigote  ancestry  and  flagellum 
morphologically  posterior.  The  genus  Trypanomorpha  included 
only  one  species,  T.  noctuce  of  Athene  noctua  ;  all  other  species  of 
trypanosornes  were  left  in  the  genus  Trypanosoma  sens,  strict. 
Liihe  put  forward  a  classification  based  on  similar  conceptions  with 
different  interpretations,  and  proposed  three  genera  of  trypano- 
somes :  Hcematomonas  (Mitrophanow)  for  the  trypanosomes  of  fresh- 
water fishes  believed  to  have  a  heteromastigote  ancestry  ;  Trypano- 
zoon  for  the  trypanosomes  of  mammals,  such  as  T.  lewisi,  T.  brucii, 
etc.,  regarded  as  having  a  cercomonad  ancestry  and  an  anterior 
flagelluni ;  and  Trypanosoma  sens,  strict,  for  the  trypanosomes  of 
frogs  and  reptiles.  T.  noctitce,  on  the  other  hand,  he  regarded,  in 
agreement  with  Schaudhm  (see  p.  390,  infra),  merely  as  a  develop- 


THE  ILEMOFLAGELLATES  AND  ALLIED  FORMS     309 

mental  stage  of  Hcemoproteu-s.  Although,  however,  it  is  quite 
possible  that  some  trypanosomes  may  have  a  heteromastigote 
ancestry,  all  the  developmental  facts  hitherto  discovered  indicate 
a  cercomonad  ancestry  with  a  single  anterior  flagellum,  and  there 
is  no  concrete  evidence  of  a  heteromastigote  origin  for  any  species 
that  has  been  studied  up  to  the  present.  Trypanoplasms,  so  far 
as  they  have  been  studied,  preserve  their  biflagellate,  heteromastigote 
type  of  structure  throughout  their  development  in  all  active  phases, 
and  never  pass  through  a  trypaniform  or  crithidial  phase.  Try- 
panosomes, on  the  other  hand,  show  constantly  a  crithidial  phase 
in  the  invertebrate  host,  but  have  not  been  observed  in  any  case 
to  be  heteromastigote  or  even  biflagellate,  except  temporarily  during 
division,  in  any  phase  of  the  life-history.  Consequently,  attempts 
to  subdivide  trypanosomes  on  a  morphological  or  phylogenetic 
basis  must  be  regarded  at  present  as  premature  (compare  also 
Laveran,  461). 


II.  THE  GENUS  TRYPANOPLASMA. 

The  peculiar  distribution  and  occurrence  of  the  species  of  this 
genus  has  been  pointed  out  above.  Originally  founded  for  forms 
parasitic  in  the  blood  of  fishes,  it  now  comprises  a  somewhat 
heterogeneous  collection  of  species,  some  of  which  were  formerly 
referred  to  other  genera  of  Flagellates.  Of  recent  years,  the 
number  of  species  known  to  be  parasitic  in  invertebrate  hosts  has 
increased,  and  is  increasing  rapidly.  Such  are  T.  ("  Trypano- 
phis  ")  grobbeni,  found  in  the  gastro  vascular  system  of  Siphonophora 
(Kej^sselitz,  453)  ;  T.  ("  Bodo  ")  helicis,  from  the  receptaculumseininis 
of  Helix  pomatia  and  other  snails  (Friedrich)  ;  T.  dendrocodi,  from 
the  digestive  tract  of  Dendroccelum  lacteum  (Fantham  and  Porter, 
P.Z.S.,  1910,  p.  670)  ;  T.  vaginalis,  from  the  female  genital  organs 
of  leeches  (Hesse,  C.E.A.S.,  cli.,  p.  504)  ;  and  T.  (jryllotalpce,  from 
the  end-gut  of  Gryllotalpa  vulgaris  (Hamburger).  These  examples 
show  that  the  genus,  as  at  present  defined,  is  of  widespread  occur- 
rence. It  may  be  doubted,  however,  if  the  various  species  described 
should  all  be  placed  together. 

The  species  of  Trypano plasma  parasitic  in  blood  are  only  known 
as  yet  from,  fresh-water  fishes  ;*  they  have  an  alternation  of  hosts, 
being  transmitted  by  leeches.  The  life-history  of  the  intestinal 
trypanoplasms  has  not  been  investigated,  but  in  all  probability  they 
have  but  a  single  host,  which  acquires  the  infection  by  swallowing 
accidentally  their  cysts  or  other  resting  stages  passed  out  from  a 

*  The  "  Trypanoplasma  "  stated  by  Bruce  and  his  colleagues  (412,  pp.  495,  496) 
to  occur  in  the  blood  of  birds  and  in  the  digestive  tract  of  tsetse-flies  was  in  reality 
a  Leucocytozoon. 


310 


THE  PROTOZOA 


former  host.  T.  helicis,  according  to  Friedrich,  passes  from  one 
snail  to  another  mechanically  in  the  spermatophores  during  coitus. 
The  following  account  refers  mainly  to  the  blood-inhabiting  species  : 
The  body  of  a  trypanoplasm  is  relatively  broader  and  shorter, 
less  sinuous  and  serpentine,  than  that  of  a  trypanosome,  and  is 
at  the  same  time  softer  and  more  plastic,  being  limited  by  an 
extremely  thin  periplast.  The  contractile,  often  slightly  metabolic, 
body  yields  readily  to  pressure,  and  exhibits  in  consequence 
passive  form-changes  when  moving  among  blood-corpuscles  or 


B 


FIG.  134. — A,  Trypanoplasma  abramidis  from  the  blood  of  the  bream  ;  B  and  C, 
T.  keyssditzi  from  the  blood  of  the  tench  :  B,  small  ordinary  form  ;  G,  large 
form.  After  Minchin,  magnified  2,000. 

other  solid  particles.  The  principal  structural  feature  is  the 
possession  of  two  flagella,  which  arise  close  together  at  the  anterior 
extremity  from  a  pair  of  blepharoplasts  or  diplosome,  or  from  a 
single  basal  granule  (Martin).  One  flagellum  projects  freely  for- 
wards ;  the  other  turns  more  or  less  abruptly  backwards,  and  passes 
down  the  side  of  the  body  at  the  edge  of  an  undulating  membrane 
to  the  hinder  end,  beyond  which  it  projects  freely  backwards  to 
a  variable  extent  in  different  species.  In  T.  gryllofalpce  the  un- 


THE  H.^MOFLAGELLATES  AND  ALLIED  FORMS     311 

dulating  membrane  only  extends  along  two-thirds  of  the  length  of 
the  body,  after  which  the  posterior  flagelluin  becomes  free.  The 
kinetonucleus,  situated  at  the  extreme  anterior  end  of  the  body, 
is  relatively  very  large,  usually  exceeding  the  trophonucleus  in 
size,  and  is  sometimes  constricted  into  two  or  three  portions,  but 
is  generally  a  compact  mass  which  stains  deeply  in  preparations. 
In  T .  helicis.  according  to  Jollos,  it  is  prolonged  backwards  into 
fibrils,  usually  two  in  number,  which  extend  some  way  down  the 
body,  and  are  probably  comparable  to  an  axostyle.  The  tropho- 
nucleus has  a  vesicular  structure  with  a  conspicuous  karyosome.  Its 
position  in  the  body  varies,  being  in  some  species  close  behind  the 
kinetonucleus,  in  others  near  the  middle  of  the  body.  It  often 
appears  to  be  lodged  completely  in  the  undulating  membrane,  which 
in  this  genus  is  often  very  broad  and  less  sharply  defined  than  in  a 
trypanosome,  appearing  as  the  border  of  a  flattened  body.  The 
cytoplasm  frequently  contains  numerous  "  chromatoid  grains." 

Trypanoplasnis  in  the  blood  of  fishes  often  exhibit  marked 
polymorphism,  with  two  extremes  of  size,  small  and  large  (Fig.  134, 
B,  C).  According  to  Keysselitz  (454),  the  large  forms  are  the 
gametes  which  conjugate  in  the  leech,  and  are  distinguishable  as 
male  and  female  forms,  but  the  statement  requires  confirmation. 
From  the  investigations  of  Robertson  (503)  on  the  development, 
it  appears  more  probable  that  the  large  forms  are  simply  full-grown 
individuals,  ripe  for  multiplication  by  fission.  Unfortunately, 
next  to  nothing  is  known  of  the  reproduction  of  the  parasites  in 
the  vertebrate  host,  though  it  has  been  observed  that  their  numbers 
are  subject  to  considerable  fluctuations,  and  that  a  fish  showing 
at  one  time  a  very  scanty  infection  of  the  blood  may  have  a 
i4  relapse,"  and  appear  later  well  infected.  Keysselitz  accuses 
these  parasites  of  pathogenic  properties,  but  this  charge  is  founded 
on  observations  on  fish  in  captivity,  in  which  weakened  powers  of 
resistance  may  lead  to  abnormal  activities  on  the  part  of  the  parasite 
(compare  also  Neresheimer) . 

The  development  of  blood  -  trypanoplasms  in  the  invertebrate 
host,  which  is  in  all  known  cases  some  species  of  leech,  appears  to  be 
of  a  comparatively  simple  type  as  compared  with  that  of  trypano- 
somes,  and  consists  of  little  more  than  rapid  multiplication  by 
binary  fission  to  produce  a  swarm  of  relatively  small  trypano- 
plasms, some  of  which,  more  slender  and  elongate  in  form,  pass 
forwards  into  the  proboscis,  and  are  inoculated  by  the  leech  into 
a  fish.  Conspicuous  in  this  development,  as  compared  with  that 
of  trypaiiosomes,  is  the  entire  absence  of  any  uniflagellate  forms, 
crithidial  or  other.  So  long  as  a  trypaiioplasm  is  in  an  active  state, 
it  is  invariably  biflagellate.  Resting  forms  without  a  locomotor 
apparatus  may  occur.  In  T.  helicis,  Friedrich  describes  winter 


312 


THE  PROTOZOA 


forms  with  a  single  nucleus,  which  is  in  some   cases   the   tropho- 
nucleus,  in  others  the  kinetonucleus. 

The  accounts  given  of  the  process  of  division  are  somewhat  conflicting. 
According  to  Martin,  division  of  T.  congeri  is  initiated  by  the  division  of  the 
single  basal  granule  of  the  flagella,  followed  by  splitting  of  each  flagellum 
longitudinally.  Next  the  trophonucleus  divides  amitotically,  the  karyosome 
becoming  first  drawn  out  into  a  band,  after  which  the  nucleus  as  a  whole  is 
constricted  into  two.  Lastly  the  kinetonucleus  becomes  elongated,  and 
divides  simply  by  a  transverse  constriction  into  two  pieces.  Jollos,  however, 
following  Rosenbusch's  statements  for  trypanosomes,  affirms  that  the  division 
of  both  nuclei  is  mitotic  in  T.  helicis.  Alexeieff,  on  the  other  hand,  denies 
that  the  kinetonucleus  of  Trypanoplasma  is  a  nucleus  at  all.  This  author  also 
describes  a  series  of  chromatinic  blocks  at  the  base  of  the  undulating  membrane 
of  T.  intestinalis,  similar  to  those  seen  in  Trichomonas  (compare  Fig.  5). 

Keysselitz  (454)  has  described  syngamy  in  the  development  of  T.  "  borreli  " 
in  the  leech  Piscicola,  but  the  description  and  figures  are  unconvincing,  and  the 
matter  requires  reinvestigation.  No  other  investigators  have  found  sexual 
processes  of  any  kind  in  trypanoplasms. 


III.  THE  GENUS  CRITHIDIA. 

The  distinctive  structural  feature  of  Crithidia  (Fig.  135,  A)  is 
the  relatively  short  undulating  membrane  which,  with  the  single 
flagellum,  arises  in  the  middle  of  the  body  from  the  vicinity  of  a 

kinetonucleus  situated  beside,  or  in  front  of, 
the  trophonucleus.  The  form  of  the  body  varies 
from  a  relatively  long,  slender  type  to  the  short, 
"  barley-grain  "  form  from  which  the  name  of 
the  genus  is  derived. 

As  already  pointed  out,  the  application  of 
the  name  Crithidia  as  the  denomination  of  a 
genus  is  involved  in  considerable  confusion 
and  perplexity  —  partly  because  the  distinctive 
morphological  characters  shade  off  by  imper- 
ceptible gradations  into  those  of  trypanosomes 
on  the  one  hand,  and  leptomonads  on  the  other, 
|3ut  gti^  more  Because  a  certain  number  of  the 
'  species  of  Crithidia  "  are  unquestionably  de- 

tergestinus.    A,  Or-     velopmental  stages  either  of  trypanosomes  or 
dinary  motile  mm-      n  •     Ii  j 

vidual;  B,  0,  young    leptomonads,  and  others  are  justly  suspected 

forms,  with  flagel-     of  being  so.      In  the  present  state  of  know- 
lum  short  or  rudi-      •,    -,  ..      .  f  ,1 

mentary.     After    lec^ge'    jt    1S     safest    to     presume     that     any 

Leger.  "  Crithidia  "    from    the    digestive    tract    of    a 

blood-sucking  insect  is  a  stage  of  a  trypano- 
some  from  the  blood  of  a  vertebrate,  until  the  contrary  has  been 
clearly  established.  At  the  same  time  the  possibility  must  always 
be  taken  into  account  that  a  blood-sucking  invertebrate  may 
harbour  flagellate  parasites  peculiar  to  itself  in  addition  to  those 


FIG.  135.  —  -Cnthidta 
mmuta,  Leger,  trom 
the  gut  of  Tabanus 


THE  H^MOFLAGELLATES  AND  ALLIED  FORMS     313 

which  it  takes  up  in  vertebrate  blood,  and  that  in  this  way  stages 
of  the  life-cycle  of  two  or  more  distinct  parasites  may  be  confused 
together.  Up  to  the  present,  however,  no  blood-sucking  insect  has 
been  proved  satisfactorily  to  harbour  flagellate  parasites  not  derived 
from  vertebrate  blood. 

After  deducting  doubtful  species  of  Crithidia,  there  remains  a 
residue  which  appears  to  comprise  genuine,  independent  species, 
parasites  of  the  digestive  tract  of  insects.  As  examples  of  such 
species  may  be  cited  C.  campanulata,  recorded  from,  the  digestive 
tract  of  Chironomus  plumosus  (Leger,  A.P.K.,  ii.  1903,  p.  180), 
from  that  of  the  larva  of  .Ptychoptera  (Leger  and  Duboscq)  and 
of  caddis-worms  (Mackinnon,  547)  ;  C.  gerridis,  from  Gerris  spp. 
(Patton,  550  ;  Porter,  555)  ;  and  possibly  others.  The  life-cycle 
of  C.  gerridis  has  been  investigated  by  Patton  and  Porter.  The 
parasite  appears  under  two  principal  phases  :  an  active,  flagellate 
phase,  which  grows  to  a  large  size,  and  multiplies  by  fission, 
sometimes  very  actively,  forming  rosettes  ;  and  a  resting,  non- 
flagellate  Leishmania  -  form.  The  flagellate  forms  may  be  free 
in  the  digestive  tract,  or  may  attach  themselves  to  the  lining 
epithelium  of  the  gut  by  their  flagella.  The  noil- flagellate  forms 
are  found  in  the  crop,  where  they  grow  into  the  adult  phase, 
and  in  the  rectum,  where  they  become  encysted.  The  flagellate 
phase  is  found  throughout  the  digestive  tract  and  in  the  ovaries, 
but  has  not  been  observed  to  pass  into  the  ova.  The  encysted 
forms  pass  out  of  the  rectum,  and  infect  new  hosts  by  the 
contaminative  method. 

IV.  THE  GENUS  LEPTOMONAS  (HERPETOMONAS). 

The  genus  Leptomonas  comprises  typical  intestinal  parasites 
of  insects,  especially  Diptera  and,  above  all,  Muscidce.  Several 
species  are  also  known  in  Hemiptera.  They  are  in  most  cases 
parasites  of  the  insect  alone,  having  no  alternate  host,  and  infection 
is  brought  about  by  the  contaminative  method,  so  far  as  is  known, 
cysts  dropped  by  one  host  being  accidentally  devoured  by  another. 
But  some  species  are  found  as  parasites  of  the  latex  of  Euphor- 
biacese,  and  in  this  case  an  alternation  of  hosts  occurs.  The  para- 
sites are  taken  up  from  the  plants  by  bugs  (Hemiptera)  which 
suck  their  juices,  and  by  the  agency  of  the  bugs  the  flagellates 
are  inoculated  into  other  plants  again  (Lafoiit ;  Bouet  and  Roubaud, 
530  ;  Franca,  537,  538).  There  can  be  little  doubt  that  in  this  case 
the  bug  is  the  primary,  the  plant  the  secondary  host.  The  plants, 
or  the  parts  of  them  that  are  infected  by  the  Leptomonas,  suffer 
considerably.  The  term  "  flagellosis  "  has  been  proposed  for  the 
disease. 


314 


THE  PROTOZOA 


The  distinctive  structural  features  of  this  genus  are  the  possession 
of  a  single  flagellum,  arising  from  close  beside  a  kinetonucleus 
which  is  placed  far  forwards  in  the  body,  and  the  entire  absence 
of  an  undulating  membrane  (Fig.  136,  B  ;  Fig.  137,  d).  As  already 
stated  above,  however,  the  application  of  the  names  Leptomonas 
and  Herpetomonas  is  much  disputed,  and  the  morphological  defini- 
tion of  the  genera  in  question  is  attended  with  considerable  diffi- 
culties, chiefly  owing  to  the  fact  that  in  one  and  the  same  host  a 
great  variety  of  forms  may  occur,  with  regard  to  which  it  is  not 
possible,  in  the  present  condition  of  knowledge,  to  state  with  cer- 
tainty whether  they  represent  distinct  species  of  flagellates,  refer- 
able even  to  distinct  genera,  occurring  fortuitously  in  the  same 
host,  or  whether  they  are  all  merely  developmental  phases  of  the 
same  species.  The  following  are  the  principal  forms  which  may 


F  G 

FIG.  136. — Leptomonas  jaculum,  Leger,  from  the  intestine  of  Nepa  cinerea.  A,  B, 
Monad  forms  ;  G,  division  of  a  monad  form  ;  D,  monad  form  with  short 
flagellum  ;  E,  F,  G,  gregarine-like  forms :  E,  in  division,  F.  attached  to  an 
epithelial  cell  by  the  rudimentary  flagella,  which  resemble  the  rostra  of  gre- 
garine  sporozoites.  After  Leger. 

occur  together  in  the  same  host  :  (1)  Large,  biflagellate  individuals 
(Fig.  124,  A),  often  with  a  distinct  pair  of  rhizoplasts  connected 
with  the  two  flagella,  the  type  to  which,  according  to  one  set  of 
opinions,  the  name  Herpetomonas  should  be  restricted,  but  which 
on  another  view  represents  merely  an  early  stage  in  binary  fission, 
with  a  daughter- flagellum  precociously  formed.;  (2)  smaller  flagel- 
lates with  a  single  flagellum  (Fig.  136,  B  ;  Fig.  137,  d),  the  type  for 
which  the  name  Leptomonas  is  employed  by  those  who  regard  the 
true  Herpetomonas  as  typically  biflagellate,  while  by  those  who  hold 
the  contrary  view  the  two  genera  are  ranked  as  synonyms  ;  (3)  cri- 
thidial  forms  (Fig.  137,  g)  ;  (4)  trypaniform  flagellates  (Fig.  137,  j.  k}, 
with  the  kinetonucleus  at  the  posterior  end,  and  the  flagellum 
running  the  whole  length  of  the  body  with  a  more  or  less  distinct 
undulating  membrane — the  "  leptotrypanosoines  "  of  Chatton.  In 


THE  H^MOFLAGELLATES  AND  ALLIED  FORMS     315 


addition  to  these  four  types  of  active  flagellates,  there  may  occur 
also  noil- flagellated  individuals  or  with  the  flagellum  rudimentary — 
namely,  (5)  long  "  gregariiiiform  "  individuals  (Fig.  136,  E — G  ; 
Fig.  137,  q)  and  (6)  oval  or  rounded  Leishmania-iorms.  The  latter 
may  become  encysted  and  function  as  the  propagative  stages.  If 
the  four  active  forms  are  all  distinct  species,  one  and  the  same  host 
may  have  intestinal  flagellates  belonging  to  four  different  genera ; 
if  they  are  all  phases  in  the  development  of  one  species,  it  becomes- 
a  subtle  point  for  discussion  which  of  the  four  forms  is  to  be  regarded 
as  the  "  adult  "  generic  type. 


n. 


FIG.  137. — Flagellates  from  the  digestive  tract  and  Malpighian  tubules  of  Dro- 
sophila  confusa.  a,  b,  c,  Trypanosoma  drosophilce,  three  forms,  from  the 
Malpighian  tubules;  d—  q,  various  forms  of  Leptomonas  drosophilce  from 
the  intestine  :  d,  e,  f,  leptomonad  forms  ;  g,  crithidial  form  ;  h,  i,  transitional 
forms  from  the  preceding  to  j,  k,  the  leptotrypanosome-forms  ;  m,  n,  small 
crithidial  ("  barley-grain  ")  forms  ;  o,  p,  forms  transitional  from  the  preceding 
to  q,  gregariniform  individuals  attached  to  the  epithelium  by  a  rudimentary 
flagellum,  the  middle  one  of  the  three  in  process  of  division.  After  Chatton 
and  Leger  (533). 

Not  in  every  case,  however,  does  such  complexity  of  form  occur  in  the 
same  host.  The  development  of  a  typical  leptomonad,  such  as  L.  (H.)  jaculum 
of  Nepa  cinerea,  as  described  by  Porter  (556),  is  of  a  comparatively  simple 
type,  like  that  of  Crithidia  gerridis  described  above.  Non-flagellated  Leish- 
marif'a-like  individuals  give  rise  to  flagellates  of  the  true  leptomonad  type, 
which  multiply  by  fission  ;  these  in  their  turn  pass  into  a  non-flagellated 
condition  in  the  hind-gut,  there  becoming  encysted  and  being  cast  out  with  the 
faeces  to  infect  new  hosts.  Prowazek  (557)  has  described  in  H.  muscce-domes- 
ticce  an  extraordinary  complication  of  male  and  female  types — autogamy, 
parthenogenesis  of  female  forms,  and  "  etheogenesis  "  of  male  forms  ;  none 
of  these  statements  can  be  accepted  as  even  probable  until  the  weighty  super- 
structure of  theoretical  interpretation  is  supported  by  a  more  substantial 
foundation  of  observed  facts.  Many  of  the  stages  described  by  Prowazek, 
especially  his  so-called  "etheogenesis,"  represent  stages  in  the  development  of 
distinct  parasitic  organisms  not  belonging  to  the  group  Flagellata  ;  compare 
Flu,  Dunkerly. 


316 


THE  PROTOZOA 


V.  THE  GENUS  LEISHMANIA. 

This  genus  was  founded  by  Ross  to  include  two  human  parasites  : 
the  so-called  Leishman-Donovan  bodies,  cause  of  the  disease 
known  in  India  as  "Kala-azar"  ;  and  Wright's  bodies  (L.  tropica), 
cause  of  boils  known  by  various  local  names,  but  termed  compre- 
hensively "  Oriental  sore."  To  these  a  third  species — namely, 
L.  infantum — has  been  added  by  Nicolle  (570),  causing  a  disease  in 
children  in  Tunis,  Algeria,  and  Italy,  and  found  also  in  dogs,  which 
are  regarded  by  Nicolle  as  the  primary  host  of  the  parasite  and  the 
source  of  the  infection  in  human  beings.  In  all  cases  the  type  of 
parasite  found  in  the  vertebrate  host  is  very  uniform  (Fig.  138)— 
.small  bodies,  usually  rounded  or  oval,  contained  within  cells  and 


138.  —  Leishmania  donovani  in  cells.  A,  A  macrophage  ;  B  and  C,  endothelial 
cells  containing  the  parasites  (p.)  ;  n.,  nucleus  of  the  infected  cell.  After 
Christophers. 


multiplying  by  fission  (Fig.  139).  Each  parasite  possesses  two 
distinct  nuclear  bodies,  which  the  development  shows  to  be  a  tropho- 
nucleus  and  a  kinetonucleus  respectively.  The  cells  which  harbour 
the  parasite  are  mainly,  if  not  exclusively,  of  two  classes  —  namely, 
leucocytes  and  endothelial  cells  ;  the  latter  become  greatly  hyper- 
trophied,  forming  the  so-called  "macrophages  "  (Fig.  138,  A),  which 
may  contain  150  to  200  parasites  at  a  time.  L.  donovani  was 
believed  originally  to  occur  also  in  red  blood-corpuscles,  and  was 
first  described  as  a  species  of  the  genus  Piroplasma  (p.  379).  The 
balance  of  evidence,  however,  is  against  their  occurrence  in  the 
hsematids.  If  set  free  by  the  disintegration  of  their  host-cell,  they 


THE  ILEMOFLAGELLATES  AND  ALLIED  FORMS     317 

are  probably  taken  up  by  leucocytes,  and  in  them  they  may  be 
carried  into  the  general  circulation. 

Although  the  diseases  caused  by  these  parasites  are  termed 
comprehensively  "'  leishmanioses,"  they  are  not  all  of  one  type. 
L.  donovani  produces  a  systemic  disease,  very  deadly  in  its  effects, 
and  the  parasite  is  found  in  immense  numbers  in  the  spleen,  bone- 
marrow,  liver,  etc.  L.  infantum  is  similar  in  its  effects.  L.  tropica, 
on  the  other  hand,  produces  a  purely  local  infection,  manifested 
in  the  form  of  one  or  more  boils  on  the  skin,  each  of  which,  accord- 
ing to  Wenyon  (84),  represents  either  a  single  infection  by  the 
insect,  as  yet  not  known  with  certainty,  which  transmits  the 
disease,  or  a  secondary  infection  by  a  house-fly  or  by  the  in- 
dividual himself  from  another  boil  on  the  skin.  The  infection  by 
L.  tropica  has  an  incubation-period  of  about  two  months.  The 
disease  lasts  from  twelve  to  eighteen  months,  and  one  attack,  after 
it  is  healed  spontaneously,  confers  absolute  immunity  for  the 
rest  of  the  patient's  life.  Corresponding  with  these  differences  in 


A  B  C  D  E 

PIG.  139. — Leishmania  donovani.  A,  Three  parasites  in  the  ordinary  condition, 
each  showing  a  larger  trophonucleus  and  a  smaller  kinetonucleus  ;  B,  C,  D, 
stages  of  binary  fission  ;  E,  multiple  fission  into  three  parts.  After  Chris- 
tophers. 

the  effects  produced  by  the  parasites,  there  are  also  slight  structural 
differences  to  be  made  out  in  them.  L.  donovani  (Fig.  138)  is  very 
uniform  in  shape,  being  rounded  or  ovoid  ;  L.  tropica  (Fig.  140), 
on  the  other  hand,  shows  more  variety  of  form,  with  every  transition 
from  elongated,  narrow  forms  with  one  end  pointed  to  the  typical 
oval  body  (Row,  Wenyon). 

No  other  stage  than  that  described  above  is  known  from  the 
human  body  ;  but  it  was  first  discovered  by  Rogers  (576)  for 
L.  donovani,  and  subsequently  confirmed  by  other  investigators 
for  this  and  other  species,  that  in  artificial  cultures  the  parasite 
develops  into  a  typical  leptornonad  form  (Fig.  140).  The  Leish- 
mania-foims  in  the  cultures  grow  considerably  in  size,  and  at  the 
same  time  multiply  by  fission.  The  relatively  large  rounded  forms 
become  pear-shaped,  and  a  flagellum  is  developed  at  the  blunt  end 
of  the  body ;  finally  the  organism  assumes  the  typical  elongated  form 
of  a  leptornonad,  with  a  long  flagellum  arising  close  beside  the  kine- 
tonucleus, which  is  situated  near  the  anterior  end  of  the  body. 
Leishman  and  Statham  have  described  a  further  stage  in  the 


318 


THE  PROTOZOA 


development  in  which  slender,  so-called  "  spirillar  "  forms  are  split 
off  from  the  large  leptomonad  forms. 

There  can  be  little  doubt  but  that  the  cultural  development  observed  in 
all  the  species  of  Leishmania  represents  the  natural  development  which  t  he 
parasite  goes  through  in  some  invertebrate  host.  As  regards,  first,  L.  dono- 
vani,  arguments  have  been  brought  forward  incriminating  the  bed-bug  as  the 


FiO.  140. — Leishmania  tropica.  A,  Parasites  from  the  sore,  showing  different 
forms  ;  B  and  C,  development  in  cultures  :  B,  parasites  growing  and  multi- 
plying prior  to  the  formation  of  the  flagellum  ;  C,  adult  flagellated  leptomonad 
forms,  with  a  couple  probably  the  result  of  binary  fission  ;  D,  adult  leptomonad 
form  ;  E,  similar  form  with  the  kinetonucleus  dividing  ;  F,  G,  stout  forms, 
two  stages  of  division  ;  note  the  flagella  arising  direct  from  the  kinetonuclei, 
which  are  connected  by  a  centrodesmose,  indicating  that  the  centriole  is  con- 
tained within  the  kinetonucleus  (compare  p.  87).  A — C,  after  Row,  from 
preparations  stained  by  the  Romanowsky  method,  magnified  2,000  :  D — G, 
after  Wenyon  (84),  from  preparations  stained  with  iron-hsematoxylin  after 
wet  fixation. 

transmitting  agent,  and  Patton  (573)  has  found  that  the  parasite  goes  through 
the  same  stages  of  development  in  the  digestive  tract  of  the  bug  (Cimex  rotun- 
datus)  as  in  the  artificial  cultures  ;  but  Donovan  believes  the  true  intermediate 
host  in  Madras  to  be  another  species  of  bug,  Conorhinus  rubrifasciatus,  and 
Wenyon  (84)  considers  that  the  development  in  the  bug  obtained  by  Patton 
is,  like  the  development  in  artificial  cultures,  only  an  imitation  of  the  develop- 
ment in  the  true  host,  and  not  a  proof  of  transmission  by  the  bug.  Basile 


THE  H^MOFLAGELLATES  AND  ALLIED  FORMS    319 

claims  to  have  transmitted  L.  infantum  by  fleas.  In  the  case  of  L.  tropica, 
Wenyon  points  out  that  the  sores  occur  almost  invariably  on  parts  of  the 
person  not  covered  or  protected  by  clothing,  a  fact  which  is  strongly  against 
the  infection  being  effected  by  fleas,  bugs,  or  ticks,  and  indicates  that  the 
invertebrate  host  is  some  biting  fly,  probably  either  a  species  of  mosquito  or 
a  sand-fly  ( Phlebotomy s).  Experimental  evidence  of  transmission,  however, 
is  as  yet  lacking. 

It  is  clear  from  the  development  that  the  species  of  Leislimania  are  non- 
flagellated  phases  of  a  true  leptomonad,  and  it  has  been  proposed  by  Rogers 
to  abolish  the  genus  Leislimania,  and  to  place  the  parasites  in  question  in  the 
genus  Herpetomonas.  The  life-cycle  of  a  Leishmania  is,  however,  so  different 
from  that  of  a  typical  Herpetomonas  (Leptomonas),  which  is  parasitic  solely 
in  the  digestive  tract  of  an  insect,  that  the  genus  Leishmania  may  well  be 
allowed  to  stand. 

So  long  as  the  development  is  only  known  from  artificial  cultures,  the 
significance  of  the  "  spirillar  "  forms  of  Leishman  cannot  be  determined. 
Assuming  that  they  are  not  merely  degenerative  forms,  they  may  possibly 
represent  the  propagative  stage  in  which  the  invertebrate  host  'inoculates 
the  parasite  back  into  the  vertebrate  ;  the  fact  that  L.  donovani  causes  a  sys- 
temic disease  rather  suggests  that  the  initial  phase  in  the  vertebrate  may  be 
a  flagellated  form  which  is  carried  all  over  the  body  in  the  circulation,  and 
from  which  the  typical  Leishmania-pha.se  is  developed.  Another  possible 
explanation  of  the  spirillar  forms  is  that  they  may  be  gametes,  perhaps  of 
male  sex  ;  but  there  is  no  evidence  in  support  of  this  interpretation  either 
from  observation  or  analogy,  since  sexual  phenomena  in  leptomonads  have 
not  been  observed.  Marzinowsky  claims,  however,  to  have  observed  copula- 
tion of  male  and  female  gametes  in  cultures  of  L.  tropica. 

Darling  has  described  under  the  name  Histoplasma  capsulatum  an  organism 
causing  a  disease  in  human  beings,  and  believed  to  be  allied  to  Leishmania. 
It  is  stated  to  develop  flagellated  phases  in  lung-smears.  For  Toxoplasma, 
referred  by  some  to  a  position  near  Leishmania,  see  p.  387.  "  Leucocytozoon  " 
piroplasmoides,  found  in  epizootic  lymphangitis  of  horses  in  Senegal  (Thiroux 
and  Teppaz),  is  possibly  a  Leishmania,  but  only  a  single  mass  of  chrornatin 
appears  to  be  present  in  the  body,  and  no  flagellated  forms  were  obtained 
in  cultures ;  possibly,  therefore,  its  proper  systematic  position  is  near  Toxo- 
plasma. 

VI.  THE  GENUS  PKOWAZEKIA. 

This  genus  was  created  by  Hartmann  and  Chagas  (62)  for  P.  cruzi,  a  species 
discovered  in  a  culture  from  human  faeces  on  an  agar-plate  in  Brazil.  Two 
other  species  have  also  been  described  from  human  fa3ces — namely,  P.  wein- 
bergi,  Mathis  and  Leger  (Fig.  141,  A  and  B),  and  P.  asiatica,  Whitmore. 
It  would  appear,  therefore,  that  several  species  (or  possibly  a  single  species)  of 
this  genus  occur  in  various  parts  of  the  world  in  human  faeces.  Martini  considers 
P.  cruzi  to  be  a  cause  of  human  diarrhcea  and  intestinal  catarrh  in  China. 
Nagler  has  described  a  species  P.  parva  (Fig.  141,  C),  which  is  free-living,  and 
Dunkerly  has  found  a  Prowazelcia  in  the  gut  of  the  house-fly.  The  form  which 
Walker  has  described  under  the  name  "  Trypanoplasma  ranee  "  very  possibly 
should  be  referred  to  Prowazelcia ;  it  was  obtained  from  cultures  of  the 
intestinal  contents  of  the  frog. 

In  its  structure,  Prowazekia  resembles  the  genus  Bodo  in  the  heteromastigote 
arrangement  of  the  flagella,  and  in  its  nuclear  apparatus  it  resembles  Trypano- 
plasma, with  trophonucleus  and  kinetonucleus.  It  differs  structurally  from 
Trypanoplasma  only  in  the  fact  that  the  backwardly-directed  flagellum  is  free 
from  the  body,  not  united  to  it  by  an  undulating  membrane  ;  it  bears,  in  fact, 
the  same  structural  relation  to  this  genus  that  Trichomastix  has  to  Trichomonas. 
Alexeieff  (388)  denies  that  the  genus  is  distinct  from  Bodo,  and  considers  that 
the  name  Prowazekia  should  be  cancelled  ;  he  identifies  P.  cruzi  with  B.  edar, 
Klebs,  and  P.  parva  with  B.  saltans,  Ehrenberg. 


320 


THE  PROTOZOA 


Affinities  and  Phytogeny  of  the  Hcemo flagellates. — Two  opposite 
views  have  been  held  with  regard  to  the  origin  of  the  Flagellates  para- 
sitic in  blood  and  their  allies  :  First,  that  they  have  a  double  origin 
along  two  distinct  lines  of  descent,  some  being  derived  from  hetero- 
mastigote,  the  others  from  cercomonad  ancestors  (Woodcock, 
Doflein,  Semi)  ;  secondly,  that  the  Hsemo flagellates  are  closely 
allied  to  certain  forms  hitherto  classed  as  Hsemosporidia  (p.  388), 
and  form  with  them  a  homogeneous  group  or  order  of  the  Flagellata, 
the  so-called  Binucleata  (Hartmann). 

The  question  of  the  Haemosporidia  will  be  discussed  below 
(p.  389).  It  is  sufficient  here  to  deal  with  the  Hcemo  flagellates  alone. 
From  the  general  survey  of  the  "  forms  "  or  "  genera  "  dealt  with 
in  this  chapter,  it  is  very  evident  that  Trypanosoma,  Crithidia, 
Leptomonas  (Herpetomonas),  and  Leishmania,  are  very  closely 


FIG.    141. — A  and  B,   Prowazekia  weiribergi,  Mathis  and  Leger  (473),   magnified 
2,400  ;  C,  Prowazekia  parva,  Nagler  (585),  magnified  about  2,250. 

related  to  one  another.  Structurally  the  first  three  types  shade 
off  insensibly  into  one  another,  the  dividing  line  between  Trypano- 
soma and  Crithidia,  or  between  Crithidia  and  Leptomonas,  being 
quite  arbitrary,  and  far  less  definite  in  reality  than  it  appears  when 
reduced  to  words  ;  while  Leishmania  is  a  resting  non-flagellated 
phase  of  any  of  the  three.  Developmeiitally  the  four  types,  or  any 
two  of  them,  may  occur  as  phases  in  the  life-history  of  a  single 
species,  so  that  the  selection  of  a  given  form  as  the  "  adult  "  in- 
dividual, by  means  of  which  the  generic  name  is  to  be  determined, 
is  also,  in  many  cases,  quite  arbitrary.  Phylogeiietically  an  evolu- 
tionary series  can  be  recognized  beginning  with  Leptomonas,  and 
passing  through  Crithidia  to  Trypanosoma,  of  which  the  central 
feature  is  the  gradual  development  of  an  undulating  membrane, 
which  finally  runs  the  whole  length  of  a  more  or  less  sinuous  and 


THE  H^EMOFLAGELLATES  AND  ALLIED  FORMS     321 

serpentine  body,  probably  as  an  adaptation  to  life  and  movement 
in  a  broth-like  medium,  containing  numerous  suspended  bodies, 
such  as  occurs  in  the  gut  of  an  insect,  especially  a  blood-sucking 
insect,  or  in  the  blood-fluid  of  a  vertebrate.  Leishmania,  on  the 
other  hand,  represents  an  offshoot  from  the  main  stem  in  which  the 
resting,  non-flagellated  phase  has  become  the  most  prominent  stage 
in  at  least  one  part  of  the  life-cycle. 

On  the  other  hand,  the  Hserno flagellates  of  the  biflagellate  type, 
Trypanoplasma  and  Prowazekia,  stand  sharply  apart  from  the 
uniflagellate  genera.  The  orientation  of  the  body,  and  of  the  undu- 
lating membrane,  when  present,  in  particular,  is  entirely  different  in 
the  two  types.  The  development  in  the  invertebrate  host  of  Trypano- 
plasma and  Trypanosoma,  respectively,  are  quite  distinct  in  type, 
neither  form  passing  through  any  stages  which  suggest  the  slightest 
affinity  with  the  other.  The  only  feature  common  to  the  two  types 
is  the  possession  of  a  kinetonucleus  in  addition  to  the  principal 
nucleus,  and  it  is  questionable  to  what  extent  this  structure  can 
be  relied  upon  to  indicate  affinity.  The  large  kinetonucleus  of 
Trypanoplasma  is  very  different  in  appearance  from  that  of  the 
uniflagellate  genera  ;  and,  according  to  Alexeieff  (324),  it  is  a  struc- 
ture of  quite  a  different  order  from  the  cytological  point  of  view. 
Finally  it  should  be  remarked  that  it  is  only  in  the  biflagellate 
genera  that  parasitism  in  the  gut  of  vertebrates  is  known  to  occur. 

With  regard  to  the  origin  of  the  forms  parasitic  in  blood,  two 
theories  have  been  put  forward.  Leger  (545)  and  Brumpt  (389) 
have  upheld  the  view  that  they  were  originally  parasites  of  the 
digestive  tracts  of  invertebrates,  as  many  allied  forms  still  are  ; 
that  in  many  cases  their  invertebrate  hosts  acquired  the  blood- 
sucking habit,  whereby  the  intestinal  flagellates  became  accus- 
tomed and  adapted  to  life  in  blood  ;  and  that,  finally,  forms  so 
adapted  passed  from  the  invertebrate  host  into  the  blood  of  the 
vertebrate  itself.  Minchm  (476),  on  the  other  hand,  suggested 
that  possibly  the  ancestral  forms  may  have  been  parasites  of  the 
digestive  tract  of  vertebrate  hosts,  and  may  have  passed  from  the 
digestive  tract  into  the  blood,  whence  they  were  taken  up  by  blood- 
sucking invertebrates  and  transmitted  to  fresh  hosts,  acquiring 
finally  the  power  of  being  parasitic  upon,  and  establishing  themselves 
in,  the  invertebrate  host. 

It  must  be  admitted  that  all  evidence  which  has  accumulated 
of  recent  years  is  in  favour  of  the  view  of  Leger  and  Brumpt.  so 
far  as  the  uniflagellate  forms  are  concerned.  The  types  denoted 
by  the  generic  names  Leptomonas,  Criihidia,  and  Trypanosoma, 
form  a  perfect  evolutionary  series,  beginning  with  monogeiietic 
parasites  of  invertebrates  and  culminating  in  digenetic  blood- 
parasites.  From  the  same  stem  other  forms  of  parasitism  are  seen 

21 


322  THE  PROTOZOA 

to  arise  in  other  directions,  as  in  the  digenetic  flagellate  parasites 
of  Euphorbiacese. 

The  biflagellate  genus  Trypanoplasma,  on  the  other  hand,  com- 
prises species  which,  like  those  of  Prowazekia,  appear  to  have  been 
primarily  parasites  of  the  vertebrate  digestive  tract,  and  which 
in  some  cases  have  established  themselves  in  the  blood  and  have 
acquired  an  alternation  of  hosts  (they  can  hardly  be  said  to  have 
an  alternation  of  generations),  having  become  parasitic  in  an  inter- 
mediate host,  always,  so  far  as  is  known,  a  leech,  in  which  they 
pass  through  a  simple  type  of  development,  consisting  of  little  more 
than  simple  multiplication  by  fission.  Their  structure  indicates 
affinities  with  heterornastigote  types  such  as  Bodo  and  Trichomonas, 
common  intestinal  parasites,  rather  than  with  uniflagellate  forms. 

The  suggestion  is,  therefore,  that  the  flagellates  parasitic  in  the 
blood  of  vertebrates  have  two  distinct  lines  of  ancestry  :  the  one 
from  heterornastigote  forms  such  as  Bodo  and  Trichomonas,  origin- 
ally parasitic  in  the  gut  of  the  vertebrate  and  culminating  in  the 
genus  Trypanoplasma  ;  the  other  derived  from  uniflagellate  cer- 
comonad  ancestors  originally  parasitic  in  the  digestive  tracts  of 
invertebrates,  and  culminating  in  the  genus  Trypanosoma  (compare 
also  Senn,  358).  It  must  be  emphasized  strongly,  however,  that 
any  such  conclusions  are  of  a  tentative  nature,  and  can  have  no 
finality,  but  are  liable  to  modification  with  every  increase  of  know- 
ledge concerning  these  organisms. 

Bibliography. — For  references  see  p.  488. 


CHAPTER  XIV 
THE  SPOROZOA  :  I.  THE  GREGARINES  AND  COCCIDIA 

UNDER  the  common  denomination  Sporozoa  are  grouped  together 
a  great  number  of  parasitic  organisms  extremely  varied  in  form, 
structure,  habitat,  and  life-history,  but  of  which  the  most  general 
though  not  invariable  characteristic  is  that  the  propagation  of  the 
parasite  from  one  host  to  another  is  effected  by  means  of  spores, 
in  the  primary  sense  of  the  word  (see  p.  165,  footnote) — that  is  to 
say,  resistant  seed-like  bodies  within  which  one  or  more  parasitic 
germs  are  protected  by  a  firm  envelope  or  capsule,  whereby  they  are 
enabled  to  resist  the  vicissitudes  of  the  outer  world  until  they  pass, 
in  one  way  or  another,  into  the  body  of  a  suitable  host ;  when  this 
end  is  attained,  the  spore  germinates — that  is  to  say,  the  contained 
organisms  are  set  free  and  a  fresh  infection  is  started. 

It  is  very  obvious  that  propagation  by  means  of  resistant  spores 
is  a  character  very  inadequate  for  diagnosing  an  extensive  group 
of  Protozoa.  In  the  first  place,  many  organisms,  parasitic 
or  free-living,  which  are  not  included  in  the  class  Sporozoa,  are 
propagated  by  means  of  resistant  spores.  In  the  second  place, 
many  forms  included  in  the  Sporozoa  do  not  produce  resistant  spores, 
being  propagated  by  methods  which  render  any  such  phase  un- 
necessary. The  class  therefore  ceases  to  be  amenable  to  strict 
verbal  definitions,  and  it  is  not  surprising  that  the  limits 
assigned  to  it  have  varied  at  different  times,  and  are  even  now 
debated.  The  class  Sporozoa  was  originally  founded  by  Leuckart 
to  comprise  two  closely  allied  orders — the  Gregarines  and  the 
Coccidia.  To  this  nucleus  other  groups  were  added,  in  particular 
the  various  forms  termed  vaguely  "  psorosperms  "* — a  word 
coined  originally  by  Johannes  Miiller  to  denote  the  spores  of  the 
Myxosporidia,  but  soon  extended  to  other  parasitic  organisms. 
Thus  "  Sporozoa "  and  "  psorosperms "  became  practically 
synonymous  terms,  and  the  class  to  which  these  names  were 
applied  became  a  most  heterogeneous  assemblage  of  organisms 

*  From  the  Greek  ^cipa,  mange,  and  <nrep/j.a,  a  seed,  on  account  of  the 
sores  and  ulcers  of  the  skin  of  fishes  produced  by  Myxosporidia,  and  the  resemblance 
of  their  spores  to  little  seeds. 

323 


324  THE  PROTOZOA 

having  nothing  in  common  except  the  parasitic  habit  and  the 
adaptations  arising  from  it,  more  especially  the  propagation  by 
spores. 

The  modern  tendency  is  rather  to  split  up  this  vast  assemblage 
into  smaller  groups,  and  to  abolish  the  Sporozoa  as  a  primary 
subdivision  of  the  Protozoa.  It  is  practically  certain,  at  least,  that 
the  two  main  subclasses  into  Avhich  it  is  alwaj^s  divided  are  per- 
fectly distinct  in  their  origin.  The  class  Sporozoa  is  retained  here 
solely  in  deference  to  custom  and  convenience,  and  without  preju- 
dice to  the  affinities  and  systematic  position  of  its  constituents, 
a  question  which  will  be  discussed  when  the  group  as  a  whole  has 
been  surveyed. 

The  life-cycle  of  a  Sporozooii  may  be  started  conveniently  from 
the  minute  germ  or  sporozoite  which  escapes  from  the  spore,  or 
from  the  corresponding  stage  when  spores  are  not  formed.  The 
sporozoite  may  have  one  of  two  forms  :  it  may  be  an  amoebula, 
a  minute  amoeboid  organism  ;  or  it  may  be  of  definite  form,  a  little 
rod-like  or  sickle-shaped  animalcule  ("  falciform  body,"  ''  Sichel- 
keim  ")  wnich  is  capable  of  twisting  or  bending  movements,  but 
retains  its  body-form,  and  progresses  by  gliding  forwards  ;  for  this 
second  type  of  sporozoite  the  term  "  gregarinula  "  has  been  proposed 
in  a  previous  chapter  (p.  169). 

The  sporozoite,  whatever  its  form,  is  liberated  in  the  body  of 
the  new  host,  and  begins  at  once  its  parasitic  career  ;  it  nourishes 
itself  and  grows,  often  to  a  relatively  huge  size,  at  the  expense  of 
the  host.  This  phase  of  the  life-history  is  termed  the  "  trophic 
phase,"  and  the  parasite  itself  during  this  phase  a  tropJiozoite, 
by  which  term  is  understood  a  parasite  that  is  actually  absorbing 
nourishment  from  the  host.  The  trophozoite  may  be  lodged  within 
cells  (cytozoic),  or  in  tissues  of  the  body  amongst  the  cells  (histo- 
zoic),  or  in  some  cavity  of  the  body  in  which  it  either  lies  free  or 
is  attached  to  the  wall  (ccelozoic).  Whatever  their  habitat,  the 
trophozoites  of  Sporozoa  never  exhibit  any  organs  or  mechanisms 
for  the  ingestioii  or  digestion  of  food,  but  absorb  their  nutriment 
in  all  cases  in  the  fluid  state,  by  osmosis  through  the  surface  of 
the  body,  from  the  substance  of  the  host ;  if  pseudopodia  or  flagella 
are  possessed  by  these  parasites,  they  are  never  used  for  food- 
capture,  except  in  so  far  as  pseudopodia,  by  increasing  the  surface 
of  the  body,  may  augment  its  absorptive  powers. 

The  parasite  may  exhibit  multiplicative  phases  in  which  it 
reproduces  itself  actively,  so  that  there  may  be  many  generations 
of  trophozoites  within  one  and  the  same  host,  which  may  thus  be 
quite  overrun  by  swarms  of  the  parasites.  Multiplication  of  this 
kind,  which  is  non-sexual,  is  known  as  schizogony  ;  the  trophozoites 
which  multiply  in  this  manner  are  termed  schizonts  ;  and  the  minute 


THE  GREGARINES  AND  COCCIDIA  325 

daughter- individuals,  products  of  schizogony,  are  termed  mero- 
zoites,  to  distinguish  them  from  sporozoites  which  they  may  resemble 
closely.  Sooner  or  later,  however,  the  propagative  phase,  destined 
to  infect  new  hosts,  makes  its  appearance  ;  so-called  sporonts  (see 
p.  330,  infra)  multiply  by  sporogony,  which  is  combined  with 
sexual  phases,  to  produce  the  sporozoites.  The  life-cycle  of  the 
parasite  may  be  passed  entirely  in  one  host,  or  there  may  be  an 
alternation  of  hosts  of  different  species,  with  a  distinct  series  of 
phases  of  the  parasite  in  each.  When  there  is  but  a  single  species 
of  host,  the  method  of  infection  of  new  hosts  is  usually  contamina- 
tive  (p.  24),  by  means  of  resistant  spores  and  cysts  ;  when  there  is 
an  alternation  of  hosts,  the  infection  may  be  inoculative  (p.  23), 
without  resistant  phases,  as  in  malarial  parasites,  or  contamina- 
tive,  •with  resistant  phases,  as  in  Aggregate,  (p.  353). 

Whether  the  life-cycle  be  of  simple  or  complex  type,  it  ends 
with  the  production  of  sporozoites,  bringing  it  back  to  the  starting- 
point  again  ;  and  in  the  vast  majority  of  cases  the  sporozoites  are 
enclosed,  one  or  more  together,  in  tough  sporocysts  to  form  the 
characteristic  resistant  spores.  As  a  rule  each  spore  arises  from 
a  single  spore-mother-cell  or  sporoblast. 

The  Sporozoa  fall  naturally  into  two  subclasses,  which  have 
received  various  names,  according  as  one  or  another  of  their  char- 
acteristic features  has  been  considered  diagnostic.  It  is  best  to 
define  each  subclass  by  a  number  of  characteristics,  since  none  by 
itself  is  sufficiently  distinctive. 

In  the  first  subclass  the  trophic  and  reproductive  phases  are 
typically  distinct— that  is  to  say,  the  animal  becomes  full-grown, 
and  ceases  to  grow  further,  before  reproduction  begins,  hence 
Telosporidia  (Schaudimi)  ;  reproduction  takes  place  usually  by 
a  process  of  multiple  fission  in  which  the  daughter-individuals  are 
budded  or  split  off  on  the  outer  surface  of  the  parent-body, 
hence  Ectosporea  (Metchnikoff)  ;  and  the  germs  or  sporozoites 
produced  are  gregarinulse,  hence  Rhabdogenise  (Delage  and 
Herouard). 

In  the  second  subclass  the  trophic  and  reproductive  phases 
usually  overlap— that  is  to  say,  the  still-growing  or  even  quite 
young  trophozoite  may  begin  to  form  spores,  hence  Neosporidia 
(Schaudinn)  ;  the  spore-mother-cells  are  formed  by  a  process  of 
internal  gemmation,  being  cut  off  within  the  cytoplasm  of  the 
parent,  hence  Endosporea  (Metchnikoff)!;  and  the  sporozoites 
produced  are  amoebulse,  hence  Amcebogeniae  (Delage  and 
Herouard). 

Of  the  three  contrasted  characters  by  which  the  two  subclasses 
are  distinguished,  the  most  absolutely  diagnostic  is  probably  the 
form  of  the  sporozoite.  The  names  Telosporidia  and  Neosporidia 


326  THE  PROTOZOA 

are,  however,  in  more  common  use  than  the  other  names  of  the 
subclasses  given  above.* 

The  subclass  Telosporidia,   as  mentioned   above,   includes  the 
three  orders  Gregarinoidea,  Coccidiidea,  and  Hsemosporidia. 


ORDER  I. — GREGARINOIDEA. 

The  chief  characteristics  of  this  order  are— First,  that  the  tropho- 
zoites  are  parasites  of  epithelial  cells  in  the  earlier  stages  of  their 
growth,  but  in  later  stages  they  become  entirely  free  from  the  cells, 
and  lie  in  cavities  of  the  body  ;  their  most  frequent  habitat  is  the 
digestive  tract,  but  sometimes  they  are  found  in  the  body-cavity  or 
the  hsemoccele.  The  full-grown  trophozoite  is  of  relatively  large  size 
and  definite  form,  with  a  thick  cuticle  as  a  rule.  In  addition  to 
these  characters,  the  reproduction  and  spore-formation,  presently 
to  be  described,  are  quite  distinctive  in  type,  the  most  diagnostic 
feature  being  that  each  spore  is  the  product  of  a  single  zygote. 

The  Gregarines  are  an  extremely  abundant  order  of  the  Sporozoa, 
highly  differentiated  in  structure,  and  comprising  a  great  number 
of  species  classified  into  genera  and  families.     They  occur  most 
commonly  as  parasites  of  the  digestive  tract  or  body-cavity  of 
insects,  but  also  as  parasites  of  other  classes,  such  as  Echinoderms 
and  Annelids  ;  in  Molluscs  they  are  comparatively  rare,  and,  though 
they  occur  commonly  in  Prochordata  (Ascidians),  they  are  not 
known  from  any  class  of  Vertebrata  in  the  strict  sense  of  the  word. 
In  the  early  phases  of  development,  during  which  the  tropho- 
zoite is  a  cell-parasite,  it  may  be  entirely  enclosed  in  the  cell,  or 
only  attached  to  it  by  one  extremity  of  the  more  or  less  elongated 
body.     In  the  latter  case  the  sporozoite  may  have  the  anterior 
end  of  the  body  modified  into  a  definite  rostrum,  by  which  it  attaches 
itself  to  the  host-cell,  and  from  which  is  developed  a  definite  organ 
of  attachment,  termed  an  epimerite  (Fig.  142,  ep.),  often  of  com- 
plicated structure,  and  provided  with  hooks  and  other  appendages. 
When  the  cytozoic  phase  is  past  and  the  host-cell  is  exhausted,  the 
parasite  drops  off,  shedding  its  epimerite  as  a  rule.     In  the  earlier 
phase,  in  which  an  epimerite  is  present,  the  parasite  was  termed 
by  Aime  Schneider  a  cephalont   ("  cephalin  "),   and  in  the  later 
phase  a  sporont  ("  sporadin  "),  the  original  use  of  this  term,  now 
applied  in  a  wider  sense  to  denote  in  this  and  other  orders  of  Sporozoa 
those  individuals  about  to  proceed  to  spore-formation.     The  body 
of  the  Gregarine-sporont  always  contains  a  single  nucleus,  but  may 
be  divided  into   partitions  or  septa  formed  as  ingrowths  of  the 
ectoplasm,  and  is  then  said  to  be  "  septate "  or  "  polycystid.'" 

*  The  subclass  Rhabdogenia,  as  instituted  by  Delage  and  Herouard,  included 
the  Sarcosporidia,  which,  however,  are  almost  certainly  true  Amosbogenise. 


THE  GREGARINES  AND  COCCIDIA 


327 


As  a  rule,  in  such  cases  there  is  but  a  single  septum,  which  divides 
the  body  into  two  parts  termed  respectively  protomerite  and  deuto- 
merite (Figs.  7,  142)  ;  but  in  the  curious  genus  Tceniocystis  (Leger, 
616)  there  are  a  number  of  septa, 
giving    the    parasite    a    superficial 
resemblance  to  a  segmented  worm. 

The  body  of  a  gregarine  consists 
typically  of  distinct  ectoplasm  and  endo- 
plasm.  The  ectoplasm  may  be  further 
differentiated  into  three  layers :  an  ex- 
ternal cuticle  or  epicyte,  a  middle  layer 
or  sarcocyte,  and  a  deeper  contractile 
layer  or  myocyte  containing  myonemes 
(Fig.  29,  p.  58).  The  epimerite,  with 
its  hooks  and  processes,  is  derived  from 
the  epicyte  ;  the  septa,  if  present,  from 
the  sarcocyte.  The  endoplasrn  is  usually 
extremely  granular,  and  contains  great 
quantities  of  stored-up  food  material  in 
reserve  for  the  reproductive  processes  ; 
chief  amongst  these  substances  are  para- 
glycogen  -  spherules,  extremely  charac- 
teristic of  these  parasites. 

A  remarkable  feature  of  gregarines  is 
the  power  possessed,  by  many  species,  of 
gliding  forward,  often  at  a  great  pace, 
without  any  visible  organs  of  locomotion. 
Two  explanations  have  been  given  of 
these  movements:  (1)  by  Schewiakoff, 
that  they  are  due  to  extrusion  of 
gelatinous  fibres  from  the  hinder  end  of 
the  body,  secreted  between  the  epicyte 
and  sarcocyte  ;  (2)  by  Crawley.  that  the 
movements  are  produced  by  contrac- 
tions of  the  niyonernes  which  are  only 
present  in  motile  forms.  In  motionless 
forms  the  ectoplasm  is  very  thin,  and 
consists  of  epicyte  alone. 

The  nucleus  of  a  gregarine  is  usually 
very  large,  spherical,  and  vesicular  in 
type,  with  one  or  more  distinct  karyo- 
somes.  It  is  typically  single,  except  in 
the  cases  of  precocious  association  men- 
tioned below— exceptions,  however,  which 
are  only  apparent,  since  in  such  cases 
the  gregarine  represents  in  reality  two 
individuals  fused  into  one.  In  the 
septate  forms  the  nucleus  lies  in  the 

deutomerite  normally.  In  Pterocephalus  (Nina),  however,  a  second  nucleus, 
which  appears  to  be  of  transitory  nature  and  to  take  no  share  in  the  repro- 
ductive processes,  has  been  discovered  in  the  protomerite  (Leger  and  Duboscq, 
621).  The  nucleus-like  body  observed  by  Siedlecki  in  Lankesteria  ascidice, 
and  by  Wenyon  (84)  in  L.  culicis,  occurring  at  the  point  of  contact  of  the  two 
associated  sporonts  in  the  cyst,  is  perhaps  a  body  of  similar  nature.  The 
nucleus  of  Callyntrochlamys  phronimce  is  remarkable  for  being  surrounded 
by  a  halo  composed  of  radiating  processes,  each  a  thin  tubular  evagination 


FIG.   142. — Examples  of  gregarines 
in    the    "  cephalont  "    condition. 

A,  Actinocephalus    oligacanthus ; 

B,  Stylorhynchus  longicollis.     ep., 
Epimerite  ;  pr.,  protomerite  ;  d., 
deutomerite.     After  Schneider. 


328  THE  PROTOZOA 

of  the  nuclear  membrane  (Dogicl,  605)  ;  as  a  rule  the  surface  of  the  nucleus 
is  perfectly  smooth. 

Chromidia  arc  stated  to  occur  in  the  cytoplasm  of  some  gregarines  (compare 
Kuschakewitsch).  According  to  Comes,  they  are  scarce  in  normal  individuals, 
but  become  abundant  with  over-nutrition  ;  since  he  states,  however,  that 
they  arise  in  the  cytoplasm,  it  is  possible  that  they  represent  grains  of  the 
nature  of  volutin  rather  than  true  chromidia.  According  to  Drzewecki, 
however,  the  nucleus  of  Monocystids  may,  during  the  early  growth  of  the 
trophozoite,  break  up  into  chromidia  and  be  re-formed  again,  or  may  throw 
out  vegetative  chromidia  which  are  absorbed  in  the  cytoplasm  ;  Kuschake- 
witsch, however,  regards  this  as  a  degenerative  process. 

Drzewecki  affirms  that  Stomatopliora  (Monocystis)  coronata,  from  the  vesiculae 
seminales  of  Pheretima  sp.,  possesses  a  mouth-opening  in  a  peristome,  and  an 
anal  aperture,  and  takes  up  solid  food  in  the  form  of  the  spermatozoa  of  its 
host.  If  so  it  is  quite  unique,  not  only  among  gregarines,  but  among  Sporozoa 
generally.  The  ingested  spermatozoa  are  stated  to  be  taken  up  and  digested 
by  the  nucleolus  (karyosome).  According  to  Hesse,  the  supposed  mouth  and 
peristome  are  parts  of  a  sucker-like  organ  of  attachment.  The  alleged 
nucleolar  digestion  is  perhaps  a  misinterpretation  of  the  extrusion  of  chroma- 
tinic  particles  from  the  karyosome. 

The  Gregarines  are  subdivided  at  the  present  time  into  two 
suborders  characterized  by  differences  in  the  life-cycle.  In  the 
first  suborder,  known  as  the  Eugregarinae,  the  parasite  has  no 
multiplicative  phase,  but  the  tropliozoites  proceed  always  as 
sporonts  to  the  propagative  phase  by  a  method  of  reproduction 
(sporogony)  which  is  combined  with  sexual  processes,  and  leads 
to  the  formation  of  resistant  spores.  In  the  second  suborder,  the 
Schizogregarmse,  the  trophozoites  which  arise  from  the  sporozoites 
become  schizonts  which  multiply  for  several  generations  non-sexually, 
by  schizogony,  before  a  generation  of  sporonts  (gamonts  or  gameto- 
cytes)  is  produced  which  proceed  to  reproduce  themselves  by  sexual 
sporogony.  Stated  briefly,  the  Eugregarinae  have  only  a  propaga- 
tive phase,  sporogony,  in  their  life-cycle  ;  the  Schizogregarinae  have 
both  a  multiplicative  phase,  schizogony,  and  sporogony.  The 
sporogony  is  of  essentially  the  same  'type  in  both  orders.  It  is 
simplest,  therefore,  first  to  describe  the  life-cycle  of  a  eugregarine, 
and  then  to  deal  with  the  multiplicative  phases  of  the  schizogre- 
garine.  The  complete  life-cycle  of  a  eugregarine  may  be  divided 
into  eight  phases. 

1.  The  sporozoites  are  liberated  from  the  spores  in  the  digestive 
tract  of  the  host  in  all  cases  known,  and  usually  proceed  at  once  to 
attach   themselves   to,  or  penetrate  into,   the  cells   of   the  lining 
epithelium  of  the  gut ;  but  in  a  few  cases  the  sporozoites  pass  through 
the  wall  of  the   gut  into  other  organs,  as  does,  for  example,  the 
common  Monocystis  of  the  earthworm,  which  penetrates  into  the 
vesicula  seminalis,  and  finally  into  sperm-cells. 

2.  In  the  early  cytozoic    phase  the  trophozoite  may  be  con- 
tained completely  within  a  cell  (Fig.  143,  A,  B,)  or  merely  attached 
to  it ;    the  former  condition,  speaking  generally,  is  characteristic 


THE  GREGARINES  AND  COCCIDIA 


329 


of  the  Acephalina,  the  latter  of  the  Cephalina.  In  either  case, 
the  first  effect  of  the  parasite  is  to  produce  a  hypertrophy,  often 
very  great,  of  the  cell  attacked  (Fig.  143,  B]  ;  later,  however,  the 
cell  atrophies,  dies,  and  shrivels  up  (Fig.  143,  C). 

(a)  In  the  Acephalina  the  intracellular  parasite  is  set  free  from 
the  cell  by  its  dissolution,  and,  if  lodged  in  the  epithelium  of  the 
gut,  may  pass  out  of  the  epithelium  either  on  its  inner  side,  into  the 
lumen  of  the  gut  again,  or  on  its  outer  side,  into  the  bloodvessels 
or  body-cavity. 

(6)  In  the  Cephalina  the  relation  of  the  parasite  to  the  host- 


:£Vvr  .  •  -:.  (;'•-'•••' ^!"SJ^«C  v-    ••   ,  -      •*  .    •  • 


SS-.  I  t  •»*fj5  -,  -;-'     . 

SjLLl--i'A*|.''.lVj  fit] 

^BSll'-  i   *•         ,-    ,NJ.,.'1    ".      ;     1  -E      ./ 

•i 


SiJ 

I 

X( 

d' 


^~^f-^^'-   .  -•  ^^i--*-.  •  .^^      ^>  _  — .^ 


^S 


A  B 

FIG.    143. — Lankesteria  ascidia,    parasite   of   Ciona   intestinalis. 

A,  Young  intracellular  stages  in  the  intestinal  epithelium ; 

B,  older  intracellular  stage  ;    G,   extracellular  trophozoite 
attached  by  a  process  of  the  anterior  end  of  the  body  to 
a  withered  epithelial  cell,    ep.,  Normal  epithelial  cell  ;  ep. '', 
hypertrophied  epithelial  cell  containing  (G.  )the  young  grega- 
rine  ;  n.,  nucleus  of  normal  cell ;  n/,  nucleus  of  infected  cell. 
After  Siedlecki,  magnified  750. 


cell  varies  greatly,  and  has  been  studied  in  detail  by  Leger  and 
Duboscq  (618  and  620).  The  sporozoite  may  merely  prick  the 
surface  of  an  epithelial  cell  with  its  rostrum  (e.g.,  Pterocephalus) , 
or  may  dip  a  short  stretch  of  its  anterior  end  into  the  cell  (e.g., 
Pyxinia),  or  may  penetrate  so  far  that  the  nuclear  region  of  the 
parasite  is  within  the  cell  (e.g.,Stylorhynchus),  or,  finally,  may  become 
completely  intracellular  (e.g.,  Stenophora) .  Ultimately,  in  all  cases, 
the  chief  mass  of  the  body  of  the  gregarine  projects  from,  or  grows  out 
of,  the  host-cell  into  the  cavity  of  the  digestive  tract,  and  becomes 
the  protomerite  and  deutomerite  in  septate  forms  ;  the  attached 


330  THE  PROTOZOA 

portion  of  the  body  develops  into  an  epimerite  which  may  acquire 
a  large  size  and  a  complicated  structure.  Originally  attached  to 
one  cell,  which  it  destroys,  the  epimerite  may  acquire  a  secondary 
attachment  to  other  cells  of  the  epithelium,  which  in  this  case  are 
not  injured  by  it,  as  in  Pterocephalus .  Ultimately  the  epimerite 
breaks  off,  and  the  body  of  the  sporont  drops  into  the  cavity  of 
the  digestive  tract.  In  some  cases  (Pyxinia)  the  early  attached 
stages  may  free  themselves  from  the  epithelium  several  times, 
and  attach  themselves  again. 

3.  When   liberated   from   the   host-cell,    the  trophozoite   grows 
into  the  adult  sporont,  which,  as  its  future  history  shows,  is  a  gamont 
or  gametocyte.     A  remarkable  feature  of  gregarines  at  this  stage 
is  the  tendency  to  associate  together  (Fig.  7),  a  habit  from  which 
the  name  Gregarina  is  itself  derived.     In  some  cases  quite  a  number 
of  individuals  may  adhere  to  one  another  in  strings  ;  such  associa- 
tions, known  as  "  syzygies,"  are,  however,  of  a  temporary  nature, 
passing  flirtations,  as  it  were,  which  have  no  significance  for  the 
life-cycle  or  development.     On  the  other  hand,  a  true  association 
of  individuals  destined  to  form  gametes  always,  apparently,  occurs 
at  one  time  or  another  in  the  life  of  the  sporont.     In  the  majority 
of  cases,  however,  the  sexual  association  does  not  take  place  till 
the  end  of  the  trophic  phase,  when  the  sporont  is  full-grown  and 
ripe  for  reproduction.     But  in  a  number  of  instances  the  associa- 
tion  takes  place  early  in  the  trophic  phase,  between  quite  young 
free  trophozoites  ;  and  "  neogamous  "  association  of  this  kind  may 
lead  to  almost  complete  fusion  of  the  bodies  of  the  two  individuals, 
only  their  nuclei  remaining  separate,  thus  producing  the  appear-- 
ance  of  a  binucleate  trophozoite  (Fig.  70,  p.  128). 

In  general,  the  two  trophozoites  which  associate  are  perfectly 
similar  in  appearance,  and  exhibit  no  differentiation  ;  this  is  so 
in  all  cases  where  they  pair  side  by  side.  In  some  cases  where 
there  is  an  early  association  end  to  end — that  is  to  say,  where  one 
sporont  attaches  itself  by  its  protomerite  to  the  deutomerite  of 
another  (Fig.  7,  p.  9),  as  is  common  in  polycystid  forms — the  two 
sporonts  may  be  differentiated  one  from  the  other.  In  Didy- 
mophyes,  for  instance,  the  protomerite  of  the  posterior  individual 
disappears  ;  in  Ganymedes  the  two  sporonts  are  held  together  by 
a  ball-and-socket  joint  (Huxley).  It  is  not  known  whether  these 
differences  stand  in  any  constant  relation  to  the  sex  of  the  sporonts. 
In  StylorJiynchus  the  two  partners  attach  themselves  to  one  another 
by  their  anterior  extremities  (Leger,  614). 

4.  As  soon  as  growth  is  completed,  the  reproductive  phases  are 
initiated  by  the  formation  of  a  common  cyst  round  the  two  asso- 
ciated sporonts,  which  together  form  a  spherical  mass  (Fig.  144,  a). 
The  parasite  is  now  quite  independent  of  its  host ;  it  is,  in  fact,  a 


THE  GREGARINES  AND  COCCIDIA 


331 


parasite  no  longer,  and  may  now  be  ejected  with  the  faeces.  The 
nucleus  of  each  sporont  then  divides  by  repeated  binary  fission 
(Fig.  144,  b)  into  a  large  number  of  nuclei,  which  place  themselves 
at  the  surface  of  the  body  (Fig.  144,  c). 

A  question  much  debated  with  regard  to  the  life-history  of  gregarines  is 
whether  a  single  sporont  can  encyst  by  itself,  without  association  with  another, 
and  then  proceed  to  the  formation  of  spores.  It  has  been  asserted  frequently 
that  this  can  occur,  and  the  suggestion  has  been  put  forward  that  the  differences 
in  the  size  of  the  spore  observed  in  some  species  may  be  correlated  with  double 
or  solitary  encystment.  Schellack  (630)  has  discussed  the  question  in  detail, 
and  is  of  opinion  that  in  septate  eugregarines  solitary  encystment  either  does 


f 


FIG.  144. — Schematic  figures  of  syngamy  and  spore-formation  in  gregarines. 
a,  Union  of  two  sporonts  in  a  common  cyst  ;  b,  various  stages  of  nuclear 
division  in  each  sporont  ;  c,  formation  of  gametids  beginning  ("  pearl-stage  ") ; 

d,  stages  in  the  copulation  of  the  gametes  :  in  the  left  upper  quadrant  of  the 
figure,  separate  gametes  are  seen  ;  in  the  left  lower  quadrant  the  gametes  are 
uniting  in  pairs  ;  the  right  lower  quadrant  shows  fusion  of  the  pronuclei  ; 
and  in  the  right  upper  quadrant  complete  zygotes  (sporoblasts)  are  seen  ; 

e,  stages  in  the  division  of  the  nuclei  of  the  sporoblasts,  which  assume  an 
oval  form  ;  a  different  stage  is  seen  in  each  quadrant,  eight  nuclei  being 
present  in  the  final  stage  ;  /,  cyst  with  ripe  spores,  each  containing  eight 
sporozoites  ;  two  spores  are  seen  in  cross-section.     Modified  after  Calkins  and 
Siedlecki. 

not  occur,  or  leads  to  nothing  if  it  does,  but  that  amongst  the  Acephalina  and 
schizogregarines  it  can  take  place  ;  a  clear  case  has  been  described  by  Leger 
in  Litlwcystis  schneideri,  parasite  of  Echinocardium ;  and  in  Monocystis 
pareudrili  solitary  encystment  leading  to  spore-formation  is  described  by 
Cognetti  de  Martiis.  In  some  species  cysts  containing  three  sporonts  have 
been  seen  ;  Woodcock  also  found  a  specimen  of  Cystobia  irregular  is  with  three 
nuclei.  With  regard  to  the  differences  in  the  size  of  the  spores,  the  possi- 
bility has  to  be  taken  into  account  that  in  some  cases  they  may  be  developed 
parthenogenetically — that  is  to  say,  the  gametids  may  each  become  a  sporo- 
blast  directly,  without  copulation  with  another. 


332 


THE  PROTOZOA 


The  first  division  of  the  nucleus  of  the  sporont  has  given  rise  to  considerable 
•discussion  and  has  been  the  object  of  much  study.  In  the  resting  state  the 
sporont-nucleus  is  a  body  of  relatively  huge  size,  but  the  first  spindle  formed 
in  the  sporont  is,  like  all  the  subsequent  mitoses,  a  minute  structure.  Some 
authors  have  believed  that  the  sporont  contains  two  nuclei,  comparable  to 
those  of  Infusoria — namely,  a  very  large  macronucleus  of  purely  vegetative 
nature,  which  takes  no  part  in  the  subsequent  development ;  and  a  minute 
micronucleus  of  generative  nature,  from  which  the  first  and  subsequent 


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t^-:*-^'!v^>V^a^*8f:®^v'>'-;'€u:'v;  i^*>--^" 
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m 


FIG.  145. — Stages  in  the  formation  of  a  generative  nucleus  ("  micronucleus  ") 
from  the  primary  nucleus  of  Pterocephalus  (Nina)  gracUis.  A,  Primary 
nucleus  showing  the  first  appearance  of  the  micronucleus  in  a  clear  space  ; 
B,  disruption  of  the  primary  nucleus  ;  appearance  of  the  micronucleus  in  the 
form  of  a  few  chromosomes  in  the  centre  of  a  little  island  of  nuclear  substance  ; 
G,  further  stage  in  the  formation  of  the  micronucleus  ;  D,  micronucleus  com- 
plete with  the  first  centrosome  ;  the  remainder  of  the  primary  nucleus  in  process 
of  absorption.  After  Leger  and  Duboscq  (621)  ;  A  magnified  800,  B,  G,  D, 
1,000,  diameters. 

mitoses  arise.  Recent  researches,  however — more  especially  those  of  Schnitzler 
on  Oregarina  ovata,  Schellack  (629)  on  Echinomera  hispida,  Leger  and  Duboscq 
(621)  on  Pterocephalus,  Robinson  on  Kalpidorhynchus ,  Duke  on  Metamera, 
and  especially  Mulsow  (123)  on  Monocystis  rostrata — leave  no  doubt  but  that 
the  sporont  contains  a  single  large  nucleus,  which  consists  chiefly  of  vegetative 
chromatin  and  other  substances,  but  contains  also  the  generative  cliromatin, 
relatively  minute  in  quantity  in  proportion  to  the  whole  bulk  of  the  nucleus. 


THE  GREGARINES  AND  COCCIDIA 


333 


The  generative  chroruatin  may  organize  itself  into  a  definite  secondary  nucleus 
("  micro  nucleus  ")  during  the  break-up  of  the  sporont- nucleus,  as  in  Ptero- 
cepludus  (Fig.  145) ;  or  the  first  spindle  arises  within  the  sporont -nucleus 
before  it  breaks  up,  as  in  G.  ovata  (Fig.  146) ;  or  a  number  of  distinct  chromo- 
somes are  formed  in  the  sporont-nucleus  during  the  process  of  its  disintegration, 
which  pass  to  the  exterior  of  the  nucleus  and  form  the  equatorial  plate  of  a 
spindle  of  which  the  achroniatinic  elements  appear  to  arise  chiefly  outside  the 
nucleus,  as  in  Monocystis  rostrata.  In  either  case  the  first  spindle  consists 
only  of  the  generative  chromatin  ;  the  remainder  of  the  original  sporont-nucleus 
is  disintegrated  and  absorbed,  or  is  left  over  in  the  residual  protoplasm  of  the 
cyst.  The  statement  of  Kuschakewitsch,  to  the  effect  that  the  primary 
nucleus  of  the  sporont  may  break  up  into  a  mass  of  chromidia,  from  which 
a  number  of  secondary  (generative)  nuclei  are  re-formed,  has  not  received 
confirmation  in  any  quarter.  { 

The  mitoses  in  the  sporont  are  remarkable,  in  most  cases,  for  the  very 
distinct  centrosonies  (Fig.  147),  which  appear  at  the  side  of  the  nucleus  before 


<^m^^K^m 
P%ppgj : 


' 

,V\i^,;  ;.    .-- 

:o--        •          7^ 


FIG.  146. — Two  stages  in  the  formation  of  the  first  division-spindle  of  Gregarina 
ovata,  showing  its  origin  from  a  very  small  part  of  the  primary  nucleus.  In 
A  the  spindle  is  seen  within  the  primary  nucleus  ;  in  B  the  spindle  is  becoming 
free  from  it  at  one  point,  after  which  the  remainder  of  the  primary  nucleus 
degenerates.  After  Schnitzler  ;  magnification  850  diameters. 

division  begins  as  a  grain  or  a  pair  of  grains  placed  at  the  apex  of  a  "cone 
of  attraction"  ;  in  Monocystis  rostrata,  however,  centrosonies  appear  to  be 
absent.  The  number  of  chromosomes  in  the  equatorial  plate  is  usually  four  ; 
but  in  Monocystis  rostrata  the  number  appears  to  be  eight,  and  in  Pterocepkalus 
and  the  allied  genus  Echinomera  there  are  five  chromosomes,  four  of  ordinary 
size  and  one  large  unpaired  chromosome.  Unlike  the  unpaired  chromosome 
of  Metazoa,  that  of  the  gregarines  is  present  in  both  sexes  ;  it  gives  rise,  during 
the  reconstitution  of  the  daughter  nucleus,  to  the  karyosome  ;  and  the  karyo- 
sorne  is  eliminated  from  the  nuclear  spindle  at  the  subsequent  mitosis. 
The  significance  of  the  unpaired  chromosome  is  far  from  clear,  and  requires 
further  elucidation. 

5.  Each  of  the  nuclei  of  the  preceding  stage  grows  out  from  the 
surface  of  the  body  surrounded  by  a  small  quantity  of  protoplasm, 
and  thus  a  great  number  of  small  cells  are  budded  off  over  the 


334 


THE  PROTOZOA 


whole  body  of  each  sporont.  The  small  clear  cells  produced  stud 
the  opaque  body  of  the  sporont  like  pearls  ;  hence  this  stage  is  often 
spoken  of  as  the  "  pearl-stage  "  (perlage,  etc.).  The  remainder  of 
the  body  of  the  sporont  is  left  over  as  residual  protoplasm,  which 
may  contain  nuclei,  but  which  takes  no  further  direct  share  in  the 
development.  The  cells  that  are  produced  are  known  as  the  "primary 


,  - 


ft: 


,  v*-  •.-' ''-'.'  '•  -.. 

-••>••-.!;  ---,"-  'I''-?'!, i**. 

.jvy^,7--';-,  .AV---'.'.-^^-;: 


H 


K 


FIG.  147. — Stages  of  nuclear  division  in  the  cyst  of  Pterocephalus  (Nina)  gracilis. 
A,  Resting  nucleus  with  a  centrosome  at  one  pole  ;  B,  division  of  the  centro- 
some  ;  G,  D,  formation  of  the  nuclear  spindle  and  equatorial  plate  ;  ejection 
of  the  karyosome ;  E,  nuclear  spindle,  with  the  unpaired  chromosome  on  the 
left,  also  the  remains  of  the  karyosome  ;  F,  diaster-stage,  with  the  unpaired 
chromosome  stretching  across,  the  karyosome  on  the  left  ;  the  centrosomes 
have  each  divided  again  ;  G,  H,  later  stages  of  division  ;  /,  J,  K,  reconstruction 
of  the  daughter-nucleus  ;  the  unpaired  chromosome  forms  the  karyosome. 
After  Leger  and  Duboscq  (621) ;  magnification  of  the  figures,  1,200  diameters. 

sporoblasts,"  but  a  better  name  for  them  is  the  gametids,  since  each 
one  is  destined  to  become  a  gamete.  The  amount  of  transforma- 
tion which  a  gametid  undergoes  in  becoming  a  gamete  may  be 
very  considerable,  or  it  may  be  practically  nil.  In  some  cases  the 
male  gamete  develops  a  special  structure,  while  the  female  remains 


THE  GREGARINES  AND  COCC1DIA  335 

unmodified  ;  in  other  cases  both  male  and  female  remain  in  the 
undifferentiated  condition  of  the  gametid.  For  an  account  of  the 
gametes  of  gregarines,  see  above  (Fig.  79,  p.  174). 

Reduction  has  been  described  in  several  cases  in  the  formation  of  the 
gametids.  In  the  genus  Gregarina  the  nucleus  of  the  gametid  divides  twice 
to  form  two  reduction-nuclei  (Leger  and  Duboscq,  621);  Paehler  and 
Schnitzler  have  also  described  a  reduction-division  in  the  gametids  of  Gre- 
garina ovata.  In  Monocystis  rostrata,  on  the  other  hand,  the  reduction  takes 
place,  according  to  Mulsow  (123),  in  the  last  nuclear  division  in  the  sporont- 
body,  prior  to  the  budding  off  of  the  gametids.  In  this  case  the  ordinary 
number  of  chromosomes  is  eight,  as  seen  in  all  the  divisions  of  the  nuclei ; 
in  the  final  division  the  eight  chromosomes  associate  to  form  four  pairs,  those 
of  each  pair  being  in  close  contact,  but  not  fused ;  in  the  mitosis  that  follows 
one  chromosome  of  each  pair  goes  to  each  pole  of  the  spindle,  thus  reducing 
the  number  of  chromosomes  in  each  gametid-nucleus  from  eight  to  four. 

6.  When   the   gametes   are   ripe,    they   copulate   in   pairs,    and 
probably  in  every  case  the  gametes  of  each  pair  are  of  distinct 
parentage.     This  is  certainly  the  case  when  the  gametes  show  any 
trace  of  sexual  differentiation,  since  those  of  one  sex  can  be  seen 
to  arise  from  one  sporont,  and  of  the  other  sex  from  the  other. 
In  many  cases  the  two  sporonts  are  separated  from  one  another 
by  a  partition  dividing  the  cyst  into  two  chambers,  in  one  of  which 
the  male  gametes  are  formed,  in  the  other  the  female  ;  when  the 
gametes  are  ripe,  the  partition  breaks  down  and  pairing  of  the  sexes 
takes  place. 

7.  The  zygote  becomes  oval  or  spindle-shaped,  and  a  membrane 
is  secreted  at  its  surface  to  form  the  sporocyst,  which  becomes 
an  exceedingly  tough  and  impervious  envelope,  and  is  generally 
composed  of  two  layers — epispore  and  endospore.    Within  the  sporo- 
cyst the  nucleus  (synkaryon)  divides  usually  three  times  to  form 
eight  nuclei,  and  then  the  protoplasm  of  the  sporoblast  divides  up 
into  as  many  slender,   sickle-shaped  sporozoites,  leaving  over  a 
small  quantity  of  residual  protoplasm.     The  sporozoites  are  usually 
arranged  longitudinally  in  the  spore,  with  the  residual  protoplasm 
at  the  centre.     The  number  of  sporozoites  in  the  spore  is  almost 
invariably  eight ;  exceptions  to  this  rule  are  only  known  amongst 
the  schizogregarines. 

The  spores  of  gregarines  differ  enormously  in  different  species 
in  form  and  appearance,  and  often  have  the  sporocyst  prolonged 
into  tails,  spines,  or  processes  of  various  kinds.  Various  mechanisms 
may  be  developed  for  liberating  the  spores  from  the  cyst;  for 
instance,  in  the  genus  Gregarina  (Clepsydrina)  the  cyst  is  provided 
with  sporoducts,  and  the  residual  protoplasm  derived  from  the 
sporonts  swells  up  when  the  spores  are  ripe,  and  forces  them  out 
through  the  sporoducts  in  long  strings. 

8.  The  ripe  spore  with  its  contained  sporozoites  passes  out  of 


336  THE  PROTOZOA 

the  body  to  the  exterior.  Usually  it  passes  out  per  anum  with  the 
faeces,  but  Avlien  the  spores  are  formed  in  some  internal  organ  of 
the  body,  as  in  the  Monocystis  of  the  earthworm,  it  may  be  necessary 
for  the  host  to  be  eaten  by  some  other  animal,  which  then  scatters 
the  spores  broadcast  in  its  faeces.  In  all  cases,  so  far  as  is  known, 
the  new  host  is  infected  by  the  casual  or  contaminative  method, 
and  in  its  digestive  tract  the  spores  germinate  and  liberate  the 
sporozoites.  In  the  case  of  Cystobia  minchinii,  parasite  of  Cucu- 
maria,  it  is  extremely  probable  that  the  host  acquires  the  infection 
by  taking  up  the  spores  per  anum  into  its  respiratory  trees,  where 
the  spores  germinate  (Woodcock). 

The  schizogony  characteristic  of  the  schizogregarines  takes 
place  during  either  the  second  or  third  of  the  phases  described  in 
the  foregoing  paragraphs,  in  trophozoites  derived  from  the  sporo- 
zoites by  growth,  and  it  takes  various  forms  which  cannot  be 
described  in  general  terms  ;  a  few  examples  must  suffice. 

1.  Selenidium  caulleryi  (Fig.  148) :  The   sporozoite  penetrates  into  a  cell 
of  the  intestinal  epithelium,  and  grows  to  a  large  size,  remaining  uninucleate. 
When  full-grown,  the  intracellular  parasite  gives  rise  by  a  process  of  multiple- 
fission  to  a  great  number  of  motile  merozoites  which  penetrate  into  epithelial 
cells,  grow,  and  finally  become  free  sporonts.     The  schizogony  of  Merogre- 
garina  amaroucii  (Porter)  is  of  a  similar  type,  but  fewer  merozoites  are  produced 
by  the  schizont. 

2.  In  Schizocystis  gregarinoides  (Fig.  149)  the  sporozoite  attaches  itself  by 
its  rostrum  to  an  epithelial  cell,  and  as  it  grows  in  size  its  nuclei  multiply  ; 
it  finally  becomes  a  multinucleate  schizont  of  very  large  size,  which  may  be 
either  vermiform,  and  is  then  attached  by  an  anterior  sucker-like  organ  to 
the  epithelium,  or  massive  in  form,  and  quite  free.     When  full-grown,  its- 
body  divides  up  into  as  many  small  merozoites  as  there  are  nuclei.     The 
merozoites  may  probably  repeat  this  development  and  multiply  by  schizogony 
again  ;  or  a  merozoite  may  grow,  without  multiplication  of  its  nucleus,  into  a 
sporont,   which  proceeds  to  sporogony  of    a  typical  kind.     In  Schizocystis 
sipunculi  (Dogiel,  603)  the  schizont  has  a  principal  nucleus  near  its  anterior 
end,  and  forms  a  number  of  secondary  nuclei  near  the  hinder  end  of  the  body, 
apparently  from  chromidia  given  off  from  the  principal  nucleus,  which  loses 
its    chromatin.      Bound  the  secondary  nuclei  protoplasm  aggregates,   and 
finally  about  150  to  200  merozoites  are  formed,  lodged  in  a  cavity  in  the  cyto- 
plasm of  the  schizont.     The  principal  nucleus  and  the  maternal  body  of  the 
schizont  now  degenerate,  and  the  merozoites  are  set  free. 

3.  In  Porospora  gigantea  of  the  lobster,  the  largest  gregarine  known,  the 
full-grown  individuals  round  themselves  off,  become  encysted  singly,  and  divide 
up  to  form  an  immense  number  of  so-called  "  gyrnnospores  "  (Fig.  150),  each  of 
which  consists  of  a  cluster  of  merozoites  grouped  round  a  central  mass  of 
residual  protoplasm.     The  subsequent  development  and  the  sporogony  are 
unknown ;  the  schizogony  was  formerly  mistaken  for  the  sporogony  (Leger  and 
Duboscq,  621). 

In  the  species  Porospora  legeri,  recently  described  by  Beauchamp  (592) 
from  the  crab  Eripliia  spinifrons,  a  similar  process  of  schizogony  is  recorded  ; 
but  in  this  case  an  associated  couple  or  syz}Tgy  of  two  trophozoites  becomes 
encysted  together,  to  undergo  a  similar  process  of  non  sexual  multiplication. 
The  association  is  one  of  two  septate  trophozoites  closely  attached,  with  loss 
of  the  protornerite  in  the  posterior  individual,  as  inDidymophyes  ;  the  subse- 
quent development  and  sporogony  are  unknown.  Leger  and  Duboscq  (622 ) 


THE  GREGARINES  AND  COCCIDIA 


337 


have  described  recently  a  number  of  new  species  of  Porospora  from  various 
Crustacea  ;  they  suggest  that  the  genus  Porospora  represents  the  schizogony, 
the  genus  Cephaloidophora  the  sporogony,  of  the  same  cycle. 

4.  In  the  peculiar  genus  Ophryocystis  (Fig.  151),  parasitic  in  theMalpighian 


; 


FIG.  148. — Sdenidmm  caulleryi.  A,  Full-grown  intracellular  schizont,  X  850  ; 
B,  stage  in  the  multiplication  of  the  nuclei  of  the  schizont,  x  1,200;  C,  schi- 
zogony complete,  showing  the  merozoites,  X  1,000;  D,  young  sporont  embedded 
in  an  epithelial  cell,  X  700  ;  E,  free,  adult  sporont,  x  700.  After  Brasil  (596). 

tubules  of  certain  beetles  (Tenebrionidce,  Curculionidce,  etc.).  and  formerly 
regarded  as  a  distinct  order  of  Sporozoa.  the  Amrebosporidia,  a  double 
schizogony  takes  place  ;  there  are  first  of  all  multinucleate  schizonts  which  can 

22 


338 


THE  PROTOZOA 


reproduce  their  like  for  many  generations,  but  which  finally  produce  mero- 
zoites  which  grow  up  into  paucinu  cleat  e  schizonts,  and  these  produce  mero- 
zoites  which  grow  up  into  sporonts.  The  sporogony  of  this  genus  is  also 
peculiar.  Two  sporonts  associate,  and  the  nucleus  of  each  sporont  divides 
into  three  ;  the  body  of  each  sporont  then  divides  into  a  smaller  cell  with  one 
nucleus  and  a  larger  cell  with  two  nuclei ;  the  small  cell  is  a  gamete,  which  is 


FIG.  149. — General  diagram  of  the  life-cycle  of  Schizocystis  gregarionides,  after 
Leger  (617,  ii.).  A,  Sporozoite  escaping  from  the  spore  ;  B,  G,  D,  E.  growth 
of  the  sporozoite  into  the  multinucleate  schizont,  of  which  there  are  two 
types:  the  vermiform  schizont  (a),  which  attaches  itself  to  the  epithelium  by 
its  anterior  end,  and  the  massive  schizont  (b),  which  lies  free  in  the  gut  of  the 
host;  F,  division  of  the  schizont  into  a  number  of  merozoites,  which  may 
either  grow  into  schizonts  again  (G1,  G2),  or  may  grow  into  sporonts  (G3)  ; 
H,  young  sporonts  ;  /,  association  of  two  full-grown  sporonts  ;  J ,  formation  of  a 
common  cyst  by  two  associated  sporonts  ;  K,  division  of  the  nuclei  in  the 
sporonts  ;  L,  formation  of  the  gametes  by  the  sporonts  ;  II,  copulation  of  the 
gametes  ;  A',  each  zygote  becomes  a  sporoblast  and  forms  a  spore. 


enveloped  by  the  larger  binucleate  cell.     The  two  gametes  copulate,  and 
the  zygote  becomes  a  single  spore  with  the  usual  eight  sporozoites ;  the  two 
binucleate  envelope-cells  form  a  protective  envelope  to  the  spore  during  its 
development,  and  die  off  when  it  is  ripe  (Leger,  617,  i.). 
(For  Schaudinnella  see  p.  355.) 


THE  GREGARINES  AND  COCCIDIA  339 

The  Gregarinoidea  are  classified  as  follows  : 

Suborder  I. — Eugregarince  (without  Schizogony}. 

Tribe  1  :  Acephalina. — Without  an  epimerite  and  non-septate  ; 
typically,  though  by  no  means  invariably,  "  ccelomic  "  parasites. 
Example  :  Monocystis,  with  several  species  parasitic  in  the  vesiculse 
seminales  of  earthworms,  and  many  allied  genera  and  species  ; 
see  especially  Hesse.  Also  many  other  genera  parasitic  in  various 
hosts — echinoderms,  ascidians,  arthropods,  etc. 

Tribe  2  :  CepJialina. — With  an  epimerite  in  the  early  stages,  at 
least,  of  the  trophic  phase  ;  in  one  family,  Doliocystidce,  non-septate, 
but  all  others  septate,  with  protomerite  and 
deutomerite,  or  with  many  segments  (Tcenio- 
•cystis,  Metamera).  Typically  parasites  of  the 
digestive  tract,  most  common  in  insects. 

This  tribe  comprises  a  great  number  of 
families,   genera,  and   species  ;    see  Minchin     FIG.     150.  —  "  Gymno- 

(589).     The    type-genus    Gregarina    (Clepsy-        spore"   of   Porospora 

,  gigantea,  consisting  of 

dnna)  comprises  many  common  species,  such        a   number  of    sporo- 

as   G.  ovata  of   the  earwig,  G.  blattarum  of        zoites  arranged  radi- 

,-v  7  7          £    j_i  i  ally    round    a    central 

the  cockroach,  G.  polymorpha  of  the  meal-        residual    mass    which 

worm   (Fig.    7,  p.    9),    etc.      Other   well-known          contains  a  chromatinic 

•species  sae—Pterocephalus  (Nina)  nobilis,  from        ^ubo'scf  (62l)fg< 
the    centipede     (Scolopendra     spp.)  ;    Stylo- 

rhynckus  longicollis  (Fig.  142),  from  the  cellar-beetle,  Blaps  mortisaga, 
and  many  others.  The  family  Doliocystidce  contains  species  parasitic 
in  marine  Annelids. 

Suborder  II. — Schizogregarince  (ivith  /Schizogony). 

Various  methods  of  classifying  the  Schizogregarines  have  been 
proposed.  Leger  and  Duboscq  (645)  divide  them  into  Monospora, 
which  produce  a  single  spore  in  the  sporogonic  cycle  (example  : 
Ophryocystis) ;  and  Polyspora,  which  produce  many  spores.  Fantham 
proposes  to  divide  them  into  Endoschiza,  in  which  the  schizogony 
takes  place  in  the  intracellular  phase,  as  in  Selenidium  and  Ecto- 
^chiza,  in  which  the  schizont  is  a  free  trophozoite,  as  in  Ophryo- 
cystis and  Schizocystis  ;  the  aberrant  genus  Siedleckia  is  probably 
to  be  referred  here  also  (see  Dogiel,  606).  The  present  state  of 
knowledge  is  hardly  ripe,  however,  for  a  comprehensive  classifica- 
tion of  the  schizogregarines,  and  it  may  well  be  doubted  whether 
they  are  to  be  considered  as  a  homogeneous  and  natural  suborder  ; 
some  of  the  families  of  the  Schizogregarinae  appear  to  be  more 
closely  allied  to  particular  families  of  Eugregarinas  than  to  one 
another.  Leger  (617,  ii.)  points  out  that  the  family  Schizocystidce 
shows  close  affinities  with  the  eugregarine  family  Actinocephalidce. 


340 


THE  PROTOZOA 


Pfeffer  asserts  that  the  young  intracellular  stages  of  the  mealworm- 
gregarine  multiply  by  fission  Porospora,  with  its  remarkable 
schizogony,  is  apparently  a  septate  cephaline  gregarine  of  the 


FIG.  151. — Diagram  of  the  life-cycle  of  Opliryocystis,  after  Leger  (617,  i.).  A,  The 
spore  setting  free  sporozoites  ;  B,  the  sporozoite  attached  by  its  rostrum  to 
the  epithelium  of  the  Malpighian  tubule  ;  C,  multiplication  of  the  nucleus 
of  the  sporozoite,  and  growth  to  form  D,  the  multinucleate  or  "  mycetoid  " 
schizont  ;  E,  division  of  the  multinucleate  schizont  into  a  number  of  mero- 
zoites  (F),  each  of  which  may  become  a  multinucleate  schizont  again,  or 
(G,  H)  may  become  a  paucinucleate  or  "  gregarinoid  "  schizont  ;  H,  division 
of  the  paucinucleate  schizont  to  form  young  sporonts  (/,  J) ;  K,  association 
of  two  sporonts  ;  L,  formation  of  a  common  cyst  round  the  associated  sporonts, 
and  division  of  their  nuclei  ;  M,  formation  of  three  nuclei  in  each  sporont ; 
N,  separation  of  a  gamete  (g.)  within  the  body  of  each  sporont,  while  the 
rest  of  the  body,  with  two  nuclei,  becomes  an  envelope-cell ;  0,  the  two  gametes 
have  fused  to  form  the  zygote  (2.)  or  sporo blast  ;  P,  the  sporo blast  has  as- 
sumed the  form  of  the  spore,  and  its  nuclei  have  divided  into  four ;  ultimately 
eight  nuclei  and  as  many  sporozoites  are  formed. 

ordinary  type.  A  character  such  as  the  possession  of  the  power 
of  multiplication  by  schizogony  is  clearly  one  of  great  adaptive 
importance  in  the  life-history  of  a  parasitic  organism,  and  therefore 


THE  GREGARINES  AND  COCCIDIA  341 

not  likely  to  be  of  classificatory  value.  The  classification  of  the 
future  will  probably  be  one  which  divides  all  gregarines  into  Cepha- 
lina  and  Acephalina,  and  distributes  the  schizogregarines  amongst 
these  two  divisions. 

At  present  the  following  families  of  schizogregarines  are  recog- 
nized :  Ophryocystidcs,  Schizocystidce ,  Selenidiidce,  Merogregarinidce, 
and  Porosporidce.  For  the  family  Aggregatidce  see  p.  353. 


ORDER  II. — COCCIDIA. 

The  chief  characteristics  of  the  Coccidia  are  that,  with  very  few 
exceptions,  the  parasites  are  of  intracellular  habitat  during  the 
trophic  phase,  and  that  a  number  of  spores  or  sporozoites  are 
produced  within  a  cyst,  all  of  which  are  the  offspring  of  a  single 
zygote.  Further,  there  is  always  an  alternation  of  generations, 
non-sexual  multiplicative  schizogony  alternating  with  sexual 
propagative  sporogony.  As  a  general  rule  the  entire  life-cycle  is 
confined  to  a  single  host,  but  in  one  family  (Aggregatidce)  an  alterna- 
tion of  hosts  occurs,  corresponding  with  the  alternation  of  genera- 
tions ;  that  is  to  say,  the  schizogony  takes  place  in  one  host,  the 
sporogony  in  another. 

Coccidia  are  found  as  parasites  of  various  groups  of  the  animal 
kingdom.  In  contrast  to  gregarines,  they  are  found  sparingly  in 
Insects,  and,  indeed,  in  Arthropods  generally  with  the  exception 
of  Myriopods  ;  but  they  occur  commonly  in  Molluscs,  and  especially 
in  Vertebrates  of  all  classes.  They  are  found  also  in  Annelids,  but 
not  abundantly,  and  in  Flat- Worms  (Turbellaria)  and  Nemertines. 
A  parasite  of  the  gregarine  Cystobia  chiridotce  has  been  identified 
by  Dogiel  (602)  as  a  coccidian,  and  given  the  name  Hyalosphcera 
gregarinicola. 

The  intracellular  trophozoite  is  typically  a  motionless  body, 
spherical,  ovoid,  or  bean-shaped,  often  with  a  considerable  resem- 
blance to  an  ovum  ;  hence  these  parasites  were  formerly  spoken  of 
as  egg-like  psorosperms  ("  eiformige  Psorospermien "),  and  the 
same  idea  is  expressed  in  such  a  name  as  Coccidium  oviforme,  given 
by  Leuckart  to  the  familiar  parasite  of  the  rabbit  now  generally 
known  as  C.  cuniculi  (or  C.  stiedce).  The  same  deceptive  resemblance 
extends  to  the  propagative  phases,  and  the  eggs  of  parasitic  worms 
have  before  now  been  mistaken  for  coccidian  cysts,  or  vice  versa. 

The  infection  of  the  host  takes  place  in  every  case,  so  far  as  is 
known  at  present,  by  the  casual  or  contaminative  method.  Resis- 
tant spores  or  cysts  of  the  parasite  are  swallowed  accidentally  with 
the  food,  and  germinate  in  the  digestive  tract.  The  sporozoites 
escape  and  are  actively  motile  ;  in  the  majority  of  cases  they  pene- 
trate into  cells  of  the  intestinal  epithelium,  but  they  may  under- 


342 


THE  PROTOZOA 


n 


FIG.  152. — Life-cycle  of  Coccidium  schubergi.  A — E,  Schizogony  ;  F — /,  gametog- 
ony  ;  K,  L,  syngamy  ;  L — 0,  sporogony.  A,  Sporozoite  liberated  from 
the  spore  ;  B,  three  epithelial  cells  to  show  three  stages  of  the  parasite-  ;  in 
the  first  (to  the  left)  a  sporozoite  (or  merozoite)  is  seen  in  the  act  of  pene- 

\flontinued  at  foot  of  p.  343. 


THE  GREGARINES  AND  COCCIDIA  343 

take  more  extensive  migrations,  and  find  their  way  into  some  other 
organ  of  the  body,  of  which  they  are  specific  parasites,  such  as  the 
liver,  fat-body  of  insects,  genital  organs,  kidneys,  and  so  forth. 
When  they  have  reached  the  cell,  of  whatever  tissue  it  may  be, 
which  is  their  destination,  they  penetrate  as  a  rule  into  the  cyto- 
plasm, and  come  to  rest  there,  but  in  some  cases  they  are  intra- 
nuclear parasites.  The  trophozoite  grows  slowly  at  the  expense 
of  the  host-cell,  which  is  at  first  greatly  hypertrophied  as  a  rule, 
but  is  ultimately  destroyed  ;  and  when  full-sized  the  parasite 
enters  upon  the  multiplicative  phase  as  a  schizoiit.  After  several 
generations  of  schizogony,  a  generation  of  trophozoites  is  produced 
ultimately,  which  become  sexually  -  differentiated  sporonts  and 
proceed  to  sporogony. 

The  great  power  of  endogenous  multiplication  possessed  by  these 
parasites  renders  them  often  pathogenic,  or  even  lethal,  to  their 
hosts,  in  contrast  to  the  usually  quite  harmless  gregarines.  As  a 
rule,  however,  the  production  of  a  pathological  condition  in  the  host 
reacts  on  the  parasite,  and  stimulates,  apparently,  the  development 
of  propagative  phases,  which,  by  passing  out  of  the  host,  purge  it 
of  the  infection.  In  this  way  the  disease—  ;'  coccidiosis,"  as  it  is 
termed  generally — may  cure  itself,  and  the  host  recuperates  its 
health,  but  without  acquiring  immunity  against  reinfection. 

As  a  typical  coccidian  life-cycle  may  be  taken  that  of  Coccidium 
schubergi  (Fig.  152),  from  the  common  centipede,  Lithobius  forficatus, 
described  by  Schaudiim  (99)  in  a  classical  memoir.  The  complete 
life-history  may  be  divided  into  eight  phases,  which  are  described 

FIG.  52  continued  : 

trating  the  cell  ;  the  other  two  cells  contain  parasites  (p.)  in  different  stages 
of  growth  (schizonts) :  n.,  nucleus  of  the  host-cell  ;  0,  D,  multiplication 
of  the  nuclei  of  the  full-grown  schizont;  E,  the  schizont  has  divided 
into  a  number  of  merozoites  (mz.)  implanted  on  a  mass  of  residual  proto- 
plasm ;  the  merozoites,  when  set  free,  may  either  penetrate  into  epithelial 
cells  and  become  schizonts  again,  as  indicated  by  the  long  arrow,  or  may 
develop  into  sporonts  (gametocytes)  ;  F,  epithelial  cell  containing  two  young 
sporonts,  the  one  male  ( $  ),  with  fine  granules,  the  other  female  ( ?  ),  with 
coarse  plastinoid  granules  in  its  cytoplasm  :  G  $  ,  full-grown  male  sporont  ; 
G  $  ,  full-grown  female  sporont :  k. ,  its  karyosorne :  H  $  ,  male  sporont  with  nuclei 
divided  up  ;  the  remains  of  the  karyosome  are  seen  at  the  centre  of  the  body  ; 
//  V  ,  female  sporont  which  has  expelled  the  karyosome  :  k.2,  fragments  of  the 
karyosome  in  the  host-cell  ;  /  $ ,  ripe  male  gametes  round  the  residual  mass 
of  the  body  of  the  sporont  ;  /  ?  ,  female  gamete  ripe  for  fertilization,  throwing 
out  on  one  side  a  cone  of  reception  towards  the  male  gametes  ( $  )  swarming 
round  it  ;  J,  fertilized  zygote  which  has  surrounded  itself  by  an  oocyst  (ooc. )  ; 
inside  the  body  the  female  pronucleus  (  ?  )  has  taken  the  form  of  a  spindle, 
at  one  pole  of  which  is  seen  the  chromatin  of  the  male  pronucleus  ( $  *) ; 
outside  the  oocyst  is  seen  a  clump  of  degenerating  male  gametes  (  $  2)  ;  K,  the 
fertilization-spindle  complete,  with  male  and  female  chromatin  spread  over 
it  ;  L,  synkaryon  dividing  ;  M,  the  synkaryon  has  divided  into  four  ;  N,  four 
sporoblasts  are  formed,  each  of  which  has  surrounded  itself  with  a  sporocyst, 
lying  in  a  mass  of  residual  protoplasm  (cystal  residuum)  ;  0,  ripe  oocyst 
containing  four  spores,  each  enclosing  two  sporozoites  and  a  small  quantity 
of  residual  protoplasm  (sporal  residuum).  After  Schaudinn  (99). 


344  THE  PROTOZOA 

in  the  sequel,  together  with  a  brief  summary  of  the  chief  variations 
M  Inch  each  phase  may  exhibit  in  other  coccidia. 

1.  The  sporozoites,  liberated  in  the  digestive  tract,  are  small 
gregarinula3  which   move  by  gliding  movements,   and    penetrate 
into    epithelial    cells    by   means    of    their    pointed    anterior    end 
(Fig.  152,  A,B). 

2.  In  the  cytoplasm  of  the  cell  they  grow  into  the  large  rounded 
schizonts,  distinguished  by  the  absence  of  reserve  food-materials  in 
their  cytoplasm,  and  by  the  large  vesicular  nucleus  with  a  karyosome 
(Fig.  152,  B). 

In  a  few  rare  instances — namely,  Coccidium  mitrarium,  Lav.  et  Mesn., 
Cryptosporidium  muris,  Tyzzer,  and  the  recently-described  Sclenococcidium 
intermedium  (see  p.  351,  infra),  the  trophozoite  is  free  as  in  gregarines.  In 
Barroussia  spiralis,  from  Cerebratulus  sp.,  the  schizont  during  its  early  phases 
of  growth  is  vermiform  and  spirally  twisted,  but  becomes  rounded  off  when 
full  grown  (Awerinzew,  47).  In  the  intranuclear  parasite  of  the  mole,  Cydo- 
spora  caryolytica,  the  schizonts  are  stated  by  Schaudinn  (147)  to  be  sexually 
differentiated,  as  also  the  merozoites  towhich  they  give  rise.  In  the  case  of  Adelea 
ovala,  however,  a  sexual  differentiation  of  the  schizonts  alleged  by  Siedlecki 
(Fig.  153)  is  stated  by  Schellack  and  Reichenow  to  be  due  to  a  confusion  of  two 
distinct  species ;  the  supposed  microschizonts,  giving  rise  to  microgametocytes,  of 
Siedlecki,  are  stated  to  be  in  reality  the  schizonts  of  Barroussia  alpina,  Leger, 
while  Siedlecki's  macroschizonts  alone  represent  the  true  schizonts  of  Adelea 
ovata ;  compare  also  Debaisieux.  Chagas,  however,  describes  in  Adelea 
hartmanni  (Chagasia  hartmanni,  Leger,  644)  distinct  male  and  female  genera- 
tions, microschizonts  and  macroschizonts,  multiplying  by  microschizogony 
and  inacroschizogony  respectively. 

3.  In  the  full  -  grown  schizont  (agamont)  the  nucleus  divides 
repeatedly  by  binary  fission  (Fig.  51,  p.  106  ;  Fig.  152,  C,  D,  E) 
until  a  variable  number  of  nuclei,  about  thirty  or  forty  as  a  rule, 
are  produced.  The  body  of  the  schizont  then  divides  into  as  many 
segments  as  there  are  nuclei,  leaving  a  certain  quantity  of  residual 
protoplasm,  and  each  segment  becomes  a  merozoite  ("  schizozoite," 
Leger) . 

The  schizogony  takes  place  without  any  formation  of  resistant  membranes 
by  the  parasite,  but  the  remains  of  the  host-cell  may  furnish  an  envelope  or 
cytocyst  within  which  the  multiplication  of  the  parasite  proceeds.  As  a  general 
rule  the  merozoites  produced  are  arranged  like  a  barrel  round  the  residual 
protoplasm  (Fig.  153,  F),  forming  a  so-called  corps  en  barillet.  In  Caryo- 
tropha  a  double  process  of  schizogony  occurs,  recalling  somewhat  that  of 
Porospora  ;  the  schizont  divides  into  a  number  of  cells,  "  schizontocytes  "  or 
"  cytomeres,"  each  of  which  divides  in  its  turn  into  a  cluster  of  merozoites 
arranged  in  a  corps  en  barillet. 

The  nuclear  multiplication  in  the  schizont  is  not  always  effected  by  simple 
binary  fission,  as  in  Coccidium  schubergi.  In  Adelea  ovata  binary  or  multiple 
fission  of  the  nucleus  occurs  (Jollos).  First  the  centriole  contained  in  the 
karyosome,  and  then  the  karyosome  itself,  divides  into  two  ;  the  whole  nucleus 
may  then  divide  into  two  also,  or  the  division  of  the  karyosome  may  be  re- 
peated several  times,  until  the  nucleus  contains  a  number  of  karyosomes. 
In  the  later  nuclear  divisions  the  karyosome  becomes  very  small,  consisting 
of  little  more  than  the  bare  centriole,  while  the  peripheral  chromatin  increases 


THE  GREGARINES  AND  COCCIDIA 


345 


greatly  in  amount,  forming  the  characteristic  star-shaped  figures  that  have  so 
often  been  depicted.  According  to  Schellack  and  Reichenow,  however,  Jollos' 
observations  relate  to  Barroussia  alpina,  and  not  to  Adelea  ovata,  and  his  state- 
ments with  regard  to  cytological  details  are  criticized,  and  contradicted  in 
part,  by  these  authors  and  also  by  Debaisieux.  In  Caryotropha,  the  nucleus 


(-.,,; V     :>:'::-:-.  ^o.;..^*--    -.$ 

ii^-^Btfii 

j ' •')" 


v- 


FIG.  153. — Schizogony  of  Adelea  ovata.  A — C,  Multiplication  of  a  female  schizont 
to  produce  a  cluster  of  merozoites  (C)  in  which  the  nucleus  has  no  karyosome  ; 
D — F,  multiplication  of  male  schizont  to  produce  a  corps  en  barillet  (F) 
of  merozoites,  in  each  of  which  the  nucleus  has  a  conspicuous  karyosome 
placed  at  one  end  of  the  nucleus.  (According  to  Schellack  and  Reichenow, 
however,  the  figures  A — C  alone  represent  the  schizogony  of  Adelea  ovata, 
and  the  figures  D — F  represent  that  of  a  distinct  species,  Barroussia  alpina.) 
After  Siedlecki. 

of  the  schizont  resolves  itself  into  a  mass  of  chromidia,  which  is  then  constricted 
simply  into  two  masses,  then  again  into  two.  and  so  on  (Siedlecki,  653). 

Non-sexual  multiplication  has  long  been  known  to  occur  in  Coccidia,  but 
the  schizogonous  generation  was  regarded  formerly  as  a  distinct  genus  and 


346  THE  PROTOZOA 

species  from  the  propagative,  spore-producing  phase,  and  was  given  the 
generic  name  Eimeria,  with  type  E.  falci/ormis  of  the  mouse.  When  the  true 
connection  between  the  two  forms  was  discovered,  Eimeria  became  a  synonym 
of  Coccidium,  or  of  whatever  the  generic  name  of  the  sporont  might  be  (e.g., 
Eimeria  nepcc.  from  Nepa  cinerea,  =Barroussia  ornata).  The  nomenclature- 
purists  have,  however,  sought  to  abolish  the  generic  name  Coccidium,  and  to 
replace  it  by  Eimeria,  on  the  ground  of  priority — a  procedure  which,  in  my 
opinion,  is  contrary  to  public  policy,  and  should  not  be  followed,  anything  in 
the  law  of  priority  notwithstanding. 

4.  The  merozoites  (agametes),  the  daughter-individuals  produced 
by  schizogony,  are  set  free  from  the  remains  of  the  host-cell  (cyto- 
cyst).     Each  merozoite  is  very  similar  to  a  sporozoite  in  form, 
structure,  and  movements,  differing  only  in  minor  points  of  detail ; 
for  instance,  in  C.  schubergi  the  nucleus  of  the  merozoite  has  a  distinct 
karyosorne,  wanting  in  that  of  the  sporozoite.     The  merozoites 
penetrate  into  epithelial  cells,  and  become  trophozoites  which  may 
develop  in  one  or  the  other  of  two  ways — (1)  into  schizonts  again, 
repeating   the   schizogony   already   described ;    (2)    into    sporonts 
(gamonts),  destined  to  produce  gametes  and  resistant  propagative 
phases. 

5.  The  growth  of  the  sporonts  is  slower  than  that  of  the  schizonts, 
and  differs  in  the  two  sexes  ;  in  the  male  sporont  (Fig.  152,  G  $ ) 
the  cytoplasm  remains  clear,  free  from  enclosures,  but  in  the  female 
(Fig.  152,  G  ?  )  it  becomes  crowded  with  reserve  nutriment,  stored 
up  as  a  provision  for  the  reproductive  phases,  in  the  form  chiefly 
of  so-called  "  plastinoid  spherules." 

In  C.  schubergi  the  female  sporonts  differ  also  from  the  spherical  male  form 
in  being  bean-shaped,  but  this  is  a  specific  peculiarity.  In  some  species  the 
female  sporonts  are  very  much  larger  than  the  male,  as  in  Adelea  ovata 
(Fig.  154),  Orcheobius  herpobdellce,  etc.  In  the  last-named  species,  parasitic  in 
the  testis  of  the  leech  Herpobdella  alomaria,  the  trophozoites  which  become 
schizonts  are  parasitic  in  the  cytophores ;  but  the  merozoites  destined  to  become 
sporonts  are  quite  motionless,  and  lie  free  in  the  lymph,  whence  they  are 
taken  up  passively  by  the  lymphocytes,  often  several  by  one  such  cell.  In  the 
lymphocytes  they  associate  in  couples,  a  male  and  a  female  sporont  together, 
and  the  female  sporonts  grow  into  long,  monocystid-like  bodies  (Kunze). 

6.  When  full-grown,  the  sporonts  proceed  to  gamete-formation: 
(a)  In  the  male  sporonts  (Fig.  50,  p.  102  ;  Fig.  152,  H  J ,  /  (?)  the 

nucleus  gives  off  chromidia  into  the  cytoplasm,  and  the  chromidia 
collect  at  the  surface  of  the  body  ;  the  old  nucleus,  now  much  poorer 
in  chromatin,  and  with  its  karyosome  still  distinct,  remains  in  the 
centre  of  the  body.  The  chromidia  become  condensed  and  con- 
centrated into  patches  to  form  secondary  nuclei,  which  finally  take 
shape  as  elongated  compact  bodies  consisting  of  dense  chromatin  ; 
each  such  nucleus,  together  with  an  almost  imperceptible  quantity 
of  cytoplasm,  forms  the  body  of  a  male  gamete  (microgamete),  and  is 
set  free,  while  the  greater  part  of  the  body  of  the  sporont,  together 
with  its  old  nucleus,  degenerates  and  dies  off  as  residual  protoplasm. 


THE  GREGARINES  AND  COCCIDIA 


347 


(6)  The  body  of  the  female  sporont  rounds  itself  off  and  bursts 
the  host-cell.  At  the  same  time  the  karyosome  is  expelled  from 
the  nucleus  (Fig.  75,  p.  146 ;  Fig.  152,  £?,#?).  It  is  then  ripe 
for  fertilization  as  a  complete  and  mature  macrogamete. 

The  process  of  gamete -formation  varies  considerably  in  its  details  in  other 
coccidia,  though  similar  in  all  essential  points  to  that  of  C.  schubergi.  The 
most  important  difference  is  that  in  many  coccidia — as,  for  instance,  in  Adelea 


FIG.  154. — Adelea  ovata:  association  of  sporonts  and  gamete-formation.  A,  The 
two  sporonts  associated  ;  in  the  male  ( $  )  the  nucleus  beginning  to  sbreak 
up  into  chromidia  ;  B,  the  nucleus  of  the  male  sporont  resolved  into  cliro- 
midia  ;  C,  formation  of  four  secondary  nuclei  from  the  chromidia  ;  D,  in  the 
male  gametocyte  four  microgametes  are  formed  from  the  four  secondary 
nuclei  of  the  previous  stage  ;  in  the  female  gamete  the  nucleus  has  taken  the 
form  of  a  fertilization-spindle.  After  Dobell. 

ovata  (Fig.  154) — the  two  sporonts  do  not  remain  separate,  as  in  C.  schubergi, 
but  associate  in  pairs ;  a  small  male  sporont  (gametocyte)  attaches  itself  to 
the  larger  female  form,  and  the  gametes  are  then  produced.  In  correlation 
with  this  habit,  a  great  reduction  in  the  number  of  the  male  gametes  takes 
place,  four  only  being  produced.  In  Adelea  (Chagasia)  hartmanni,  Chagas 
states  that  two  or  even  four  microgametocytes  attach  themselves  to  the 
female  gametocyte ;  Dobell  also  figures  attachment  of  two  male  sporonts 
in  A.  ovata. 


348  THE  PROTOZOA 

The  maturation  of  the  female  gamete  does  not  necessarily  take  the  form  of 
expulsion  of  the  karyosomo ;  on  the  contrary,  the  karyosome  may  be  retained 
throughout  the  development.  In  the  macrogamete  of  Cydospora  caryolytica 
the  nucleus  divides  twice  to  form  two  reduction-nuclei,  which  are  cast  off, 
and  a  third  nucleus  which  persists  as  the  pronucleus.  A  similar  reduction- 
process  has  been  described  by  Chagas  in  Adelea  harlmanni.  In  Adelea  ovata, 
according  to  Jollos,  a  reducing  division  occurs  in  the  female  gametocyte  before 
association  with  the  male  takes  place  ;  this  is  denied,  however,  by  Schellack 
and  Reichenow  and  by  Debaisieux. 

In  Caryotropha  the  male  sporont  does  not  divide  at  once  into  microgametes, 
but  first  into  a  number  of  microgametocytes,  each  of  which  then  produces 
microgametes.  The  process  of  gamete-formation  is  thus  seen  to  be  exactly 
parallel  to  the  schizogony,  in  which  the  schizont  first  divides  into  cytomeres, 
which  in  their  turn  produce  merozoites.  It  is  obvious  that  in  coccidia,  as  in 
Protozoa  generally,  schizogony  and  gametogenesis  are  strictly  homologous 
processes ;  the  only  difference,  primarily,  is  in  the  nature  and  destiny  of  the 
swarm-spores  produced  in  each  case,  merozoites  or  gametes.  This  comparison 
accentuates  the  fact,  which  will  be  discussed  further  below,  that  in  the  coccidia 
multiple  reproduction  to  produce  gametes  is  entirely  in  abeyance  in  the 
female  sex. 

7.  The  fully-formed  microgamete  (Fig.  50,  p.  102)  is  a  minute, 
slender,  serpentine  organism,  the  body  of  which  consists  almost 
entirely  of  chromatin  ;  the  cytoplasm  is  represented  by  the  two 
flagella,  which  arise  close  together  at  one  end  of  the  body.  One 
flagellum  is  entirely  free,  the  other  runs  along  the  body  to  the  hinder 
end,  from  which  it  is  continued  freely  ;  thus  the  structure  of  the 
male  gamete  recalls  that  of  a  trypanoplasm  in  the  heterornastigote 
arrangement  of  the  flagella. 

The  male  gametes  swarm  round  the  inert  female  gamete,  and  one 
of  them  penetrates  into  it  and  fertilizes  it.  As  soon  as  the  entrance 
of  a  microgamete  is  effected,  the  macrogamete  secretes  a  tough 
membrane,  the  oocyst,  at  the  surface  of  the  body,  preventing  the 
penetration  of  any  other  microgametes.  A  fertilization-spindle 
(Fig.  69,  p.  127  ;  Fig.  152,  J,  K)  is  then  formed  in  the  zygote.  The 
female  pronucleus  becomes  spread  out  into  a  fusiform  figure  con- 
sisting of  grains  of  chromatin  on  an  achromatiiiic  framework.  When 
the  spindle  is  complete,  the  male  pronucleus  breaks  up  into  granules 
of  chromatin  which  spread  over  the  spindle,  and  are  thus  com- 
mingled intimately  with  the  chromatin  of  the  female  pronucleus. 
When  this  has  taken  place,  the  spindle  contracts  to  form  the  rounded 
synkaryon,  and  the  syngamy  is  complete. 

The  structure  of  the  microgamete  varies  in  different  species.  In  some 
cases  (Adelea,  Klossia,  Legerella,  Barroussia  spiralis)  flagella  are  wanting, 
and  the  microgamete  is  a  slender,  spirochsete-like  organism,  consisting  entirely, 
so  far  as  can  be  seen,  of  chromatin,  but  actively  motile.  When  fiagella  are 
present,  they  are  usually  two  in  number.  In  Orcheobius  herpobdellce,  Bar- 
roussia (Minchinia)  caudata,  and  some  other  species,  the  microgamete  ter- 
minates anteriorly  in  a  point  or  rostrum,  close  behind  which  two  flagella  are 
given  off,  and  are  directed  obliquely  backwards,  quite  free  from  the  body. 
In  Aggregata,  Moroff  (94)  describes  the  microgametes  as  long  and  slender, 
with  a  nucleus  of  peculiar  form,  sometimes  greatly  drawn  out,  and  with 


THE  GREGARINES  AND  COCCIDIA  349 

two  flagella,  both  arising  at  the  anterior  end  and  directed  forwards.  In 
Coccidium  rouxi,  Elmassian  describes  two  forms  of  microgametes  differing 
greatly  in  size. 

In  forms  in  which  the  sporonts  associate,  as  in  Addea  and  Orcheobius,  one 
of  the  four  microgametes  produced  penetrates  the  macrogamete;  the  other 
three  die  off.  In  some  species — e.g.,  Coccidium  proprium  of  the  newt — the 
oocyst  is  formed  prior  to  fertilization,  and  the  male  gamete  enters  through  a 
minute  aperture  or  micropyle,  which  is  closed  as  soon  as  one  has  entered. 
In  Cyclospora  caryolytica,  however,  numerous  microgametes  penetrate  into 
the  macrogamete,  but  only  one  of  them  furnishes  a  male  pronucleus.  which 
copulates  with  the  female  pronucleus  ;  the  remaining  male  nuclei  are  absorbed. 

A  fertilization-spindle  appears  always  to  be  formed  in  the  process  of 
syngamy,  but  may  differ  considerably  in  appearance  from  that  seen  in 
C.  schubergi ;  compare  Kunze's  description  of  the  fertilization  of  Orcheobius 
herpobdellce. 

8.  The  zygote  is  enclosed,  as  stated  above,  in  an  oocyst 
(Fig.  152,  J)  secreted  at  its  surface  as  a  membrane  delicate  at  first, 
but  very  soon  becoming  thickened  to  a  tough  impervious  capsule, 
in  which  the  parasite  can  pass  out  of  the  body  of  the  host  and  brave 
the  vicissitudes  of  the  outer  world.  The  synkaryon  divides  in  the 
genus  Coccidium  into  four  nuclei  (Fig.  52,  p.  106),  and  the  body 
of  the  zygote  then  divides  into  as  many  sporoblasts,  each  with  a 
single  nucleus,  leaving  over  a  certain  amount  of  residual  protoplasm 
("  cystal  residuum").  Each  sporoblast  secretes  a  sporocyst  at 
its  surface  (Fig.  152,  N),  and  within  the  envelope  the  sporoblast- 
micleus  divides  into  two,  after  which  the  cytoplasm  segments  round 
each  nucleus  to  form  two  sporozoites  (Fig.  152,  0),  leaving  a  small 
amount  cf  residual  protoplasm  ("  sporal  residuum ").  These 
residua  are  slowly  absorbed.  When  sporogony  is  complete,  there- 
fore, the  tough  oocyst  contains  four  spores,  each  consisting  of  a 
tough  sporocyst  containing  two  sporozoites.  In  order  to  develop 
further,  the  cyst  must  be  swallowed  by  a  new  host,  in  the  digestive 
tract  of  which  the  oocyst  dissolves,  and  the  spores  split  open,  libera- 
ting the  sporozoites. 

In  other  species  of  coccidia  the  details  of  the  spore -formation  may  vary 
enormously  as  compared  with  the  example  described.  The  contents  of  the 
oocyst  may  divide  into  only  two,  or  into  a  very  large  number  of  sporoblasts. 
In  the  genus  Caryospora  (Leger,  644)  and  Cryptosporidium  (Tyzzer).  the 
oocyst  does  not  divide  into  sporoblasts,  but  gives  rise  to  a  single  spore,  contain- 
ing eight  sporozoites  in  Caryospora,  four  in  Cryptosporidium.  In  Paracoccidium 
prevoti  sporocysts  are  formed  in  the  oocyst.  but  absorbed  again,  so  that  the 
sporozoites  finally  lie  free  in  the  oocyst,  as  in  the  genus  Legerella,  in  which  no 
sporocysts  are  formed  at  all,  but  the  body  of  the  zygote  divides  directly  into 
sporozoites.  With  these  exceptions,  resistant  spores  are  always  formed,  in 
numbers  varying  from  two  to  some  thirty  or  so  in  different  genera. 

The  spore  may  contain  one.  two,  three,  four,  or  n  sporozoites,  and 
said  to  be  monozoic,  dizoic,  trizoic,  tetrazoic,  or  polyzoic  ;  it  is  rarely  octozoic, 
as  in  gregarines,  but  Caryospora  is  so.     In  Caryotropha  mesnilii  the  spore 
contains  twelve,  in  Angeiocystis  audouinice  about  thirty  sporozoites  (Brasi 
597).     In  contrast  also  with  gregarines,  the  spores  of  coccidia  are  generally 
smooth,  round,  or  ovoid  bodies,  but  in  a  few  cases  (e.g.,  Minchinia  chitonis) 
bear  tails  or  spikes. 


;!50 


THE  PROTOZOA 


FIG.   155. — For  description  see.  foot  oj  opposite  page. 


THE  GREGARINES  AND  COCCIDIA  351 

The  germination  of  the  spore  takes  place  always,  apparently,  in  the  digestive 
tract  of  the  specific  host,  and  there  alone  ;  it  may  be  in  some  special  part  of 
it,  as  in  C.  cuniculi,  the  spores  of  which,  according  to  Metzner.  germinate  in 
pancreatic,  but  not  in  gastric,  juice. 

The  remarkable  form  Selenococcidium  intermedium  (Fig.  155),  parasitic 
in  the  intestine  of  the  lobster,  described  by  Legcr  and  Duboscq  (646),  differs 
from  all  other  known  coccidia  in  the  character  of  its  trophozoites  and  its 
schizogony.  The  trophozoites  are  vermiform,  nematode-like  organisms, 
extremely  active  in  their  movements,  and  frequently  coiling  themselves  up 
and  wriggling  like  worms  (Fig.  155,  A — D).  The  anterior  end  of  the  body  is 
blunt,  the  posterior  pointed ;  the  surface  of  the  body  contains  myonemes 
running  spirally,  visible  in  the  living  state  at  the  anterior  end  as  oblique 
striations.  The  youngest  trophozoites  have  a  single  nucleus,  but  as  they 
grow  the  nuclei  multiply,  until  in  the  full-grown  organism  there  are  eight. 
The  trophozoite  is  now  a  schizont,  and  penetrates  into  an  epithelial  cell  of  the 
intestine  in  order  to  multiply  by  schizogony.  The  vermiform  body  rolls  up 
within  the  cell  into  a  compact  oval  mass  (Fig.  155,  E),  and  then  each  of  its 
eight  nuclei  grows  out  into  a  tongue-like  cytoplasmic  process.  In  this  way 
eight  merozoites  are  formed  round  a  central  residual  mass.  The  merozoites 
are  set  free  as  the  uninucleate  trophozoites  (Fig.  155.  F,  G).  This  "  in- 
different" type  of  schizogony  may  continue  for  several  generations,  until  a 
final  generation  appears  in  which  the  schizonts  are  sexually  differentiated ; 
smaller,  slender  trophozoites  with  eight  nuclei  give  rise  to  eight  merozoites 
which  grow  into  male  sporonts,  and  larger,  stouter  forms  with  four  nuclei 
produce  four  merozoites  which  become  female  sporonts. 

The  male  sporonts  (gametocytes)  arise  from  verniicules  with  clear  cytoplasm, 
which  penetrate  into  an  epithelial  cell  and  roll  up  into  an  ovoid  mass 
(Fig.  155.  H) ;  they  may  do  this  when  they  have  but  a  single  nucleus,  but 
usually  not  until  the  nuclei  have  increased  to  eight.  In  the  compact,  intra- 
cellular  gametocyte  the  nuclei  multiply  rapidly  in  a  manner  similar  to  that 
described  above  for  the  schizont  of  Adelea,  by  binary  or  multiple  tission 
following  division  of  the  karyosorne.  In  later  stages  of  multiplication  the 
karyosomes  become  very  small,  and  the  peripheral  chrornatin  of  the  nuclei 
increases  greatly,  so  that  they  have  the  appearance  of  patches  of  granules 
(Fig.  155,  /).  When  the  multiplication  is  complete,  each  such  patch  of  granules 
forms  the  dense,  comma-shaped  nucleus  of  a  microgamete  (Fig.  155,  J).  An 
enormous  number  of  microgametes  arise  from  each  gametocyte,  but  the 
structure  of  the  free  microgametes  has  not  been  made  out. 

The  female  gametocytes  arise  from  stout  vermicules  which  penetrate  into 
a  cell  and  become  rounded  off,  the  nucleus  remaining  single  all  the  time 
(Fig.  155,  K,  L,  M).  The  oval  gametocyte  grows,  and  its  cytoplasm  becomes 
full  of  chromatoid  grains.  When  full-grown  it  appears  to  go  through  a  process 
of  maturation,  in  which,  as  in  Adelea,  the  karyosome  divides  into  two,  and  one 
half  is  expelled.  The  full  details  of  the  fertilization  have  not  been  made 
out,  but  macrogametes  have  been  seen  with  the  nucleus  placed  superficially, 
and  with  a  small  corpuscle,  apparently  a  microgamete,  adherent  to  the  body 
(Fig.  155,  N).  After  fertilization  the  zygote  becomes  spherical  and  surrounds 

FIG.  155. — Selenococcidium  intermedium:  various  phases  in  the  life-cycle.  A,  B, 
C,  D,  Vermicules  with  one,  two,  five,  and  eight  nuclei  respectively  ;  E,  vermi- 
cule  rolling  up  prior  to  schizogony  ;  F,  schizogony  nearly  complete  ;  eight 
pear-shaped  merozoites,  each  with  a  single  nucleus,  budded  off  from  a  mass 
of  residual  protoplasm  to  which  they  are  still  attached  by  long  stalks ;  G, 
schizogony  complete  ;  eight  uninucleate  vermicules  rolled  up  together  ;  H,  I,  J , 
formation  of  microgametes  :  H,  the  nuclei  of  the  microgametocyte  at  an  early 
stage  of  division  ;  /,  later  stage  :  J,  formation  of  a  great  number  of  comma- 
shaped  microgametes  ;  K,  L,  vcrmicule  rolling  up  to  become  a  macrogameto- 
cyte  ;  M,  fully-formed  macrogametocyte,  its  cytoplasm  full  of  patches  of 
chromatoid  granules  that  stain  deeply  with  iron-hsematoxylin  ;  N,  macro- 
gamete  at  the  moment  of  fertilization  ;  0,  oiicyst  with  very  numerous  chroma- 
toid grains.  After  Leger  and  Duboscq  (G46). 


352  THE  PROTOZOA 

itself  by  a  tough  oocyst  (Fig.  155,  0)  ;  in  this  stage  it  is  expelled  from  the 
body  with  the  faeces.  The  subsequent  development  of  the  oocyst,  spore- 
formation,  etc.,  are  not  known. 

From  these  data  it  is  sufficiently  clear  that  Selenococcidium  is  perfectly 
gregarino-like  in  its  trophic  phase  and  in  its  schizogony  ;  the  trophozoites  are 
free  vermicides  which  multiply  just  as  in  Schizocystis.  The  parasite  only 
penetrates  into  a  cell  when  it  enters  upon  reproductive  phases.  On  the  other 
hand,  the  sporogony,  so  far  as  it  is  known,  and  especially  the  sexual  processes, 
are  entirely  coccidian  in  typo.  Selenococcidium  links  the  gregarines  and 
coccidia  in  a  striking  and  convincing  manner,  as  will  be  discussed  further 
below. 

Classification. — The  Coccidia  have  been  classified  in  various  ways  at  different 
times,  as  increased  knowledge  of  these  organisms  has  shown  older  schemes 
to  be  artificial  or  unnatural.  The  following  classification  is  in  the  main  that 
of  Liihe  (392),  with  certain  modifications.  Some  genera  have  not,  however, 
been  investigated  sufficiently  to  make  their  systematic  position  certain. 

Suborder  I.  :  Prococcidia. 

Trophozoites  free,  vermiform,  motile  ;  schizogony  similar  in  type  to  that 
of  Schizogregarines.  The  only  genus  known  at  present  is  Selenococcidium. 
The  genus  Siedleckia  should  perhaps  be  placed  here,  perhaps  in  the  Schizo- 
gregarines near  Schizocystis  ;  its  sporogony  is  as  yet  unknown. 

Suborder  II.  :  Eiicoccidia. 

Trophozoites  typically  intracellular,  motionless,  oviform,  rarely  free  or 
vermiform  ;  schizogony  of  coccidian  type. 

SECTION  A. — Forms  in  which  the  sporonts  do  not  associate  prior  to  gamete- 
formation,  and  numerous  microgametes  are  produced  : 

Family  1  :  Coccidiidce  (Eimeridce). — The  schizogony  is  of  a  simple  type, 
as  described  in  C.  schubergi.  Examples  :  Coccidium  (Eimeria)  and  allied 
genera  ;  Barroussia  (Barrouxia),  with  type  B.  ornata,  from  the  gut  of  Nepa 
cinerea;  Cyclospora,  including  C.  caryolytica,  from  the  intestine  of  the  mole; 
and  other  genera.  Cryptosporidium  muris,  from  the  gastric  glands  of  the 
mouse,  has  free  trophozoites  and  produces  a  single  tetrazoic  spore. 

Family  2  :  Caryotrophidce. — With  double  multiple  fission  in  the  schizogony. 
Example  :  Caryotroplia  mesnilii,  parasite  of  the  Annelid  Polymnia  nebulosa 
(Siedlecki,  653).  Klossiella  muris,*  from  the  kidney  of  the  mouse,  should 
perhaps  be  referred  to  this  family,  possibly  also  Merocystis  kathcc  (Dakin). 

SECTION  B. — Forms  in  which  the  sporonts  (gametocytes)  associate  prior 
to  gamete-formation,  and  the  number  of  male  gametes  is  reduced  to  four  : 

Family  3  :  Addeidce. — With  sporocysts.  Examples  :  Adelea,  with  several 
species,  of  which  the  best  known  is  A.  ovata,  parasite  of  the  intestine  of 
Lillwbius  ;  Klossia,  with  type  K.  helicina,  from  the  kidneys  of  Helix  spp.  ; 
Orcheobius  herpobdellce,  from  the  testis  of  the  leech  Herpobdella  (Kunze)  ; 
and  Caryospora  simplex,  from  the  intestine  of  Vipera  aspis,  in  which  the 
contents  of  the  oocyst  form  a  single  octozoic  spore  (Leger,  644).  Minchinia 
chitonis,  from  the  liver  of  Chiton  and  Patella  spp.,  should  perhaps  be  referred 
to  this  family,  but  the  gamete-formation  is  not  yet  known. 

Family  4 :  Legerellidce. — Without  sporocysts.  Example :  Legerella  nova, 
parasite  of  the  Malpighian  tubes  of  Glomeris. 

A  classification  similar  in  the  main  to  the  above  has  been  put  forward  by 
Leger  (644),  who  terms  Section  A  the  Eimeridea,  Section  B  the  Adeleidea. 

*  My  friend  Dr.  A.  C.  Stevenson,  of  the  Pathological  Department,  University 
College,  who  has  studied  Klossiella,  informs  me  that  he  considers  it  possible  that 
it  may  represent  a  stage  of  H cemogregarina  musculi  (p.  377). 


THE  GREGARINES  AND  COCCIDIA  353 

Leger  proceeds  to  divide  the  two  sections  further  by  the  number  of  sporozoites 
produced  in  the  oocyst,  but  we  venture  to  doubt  if  this  is  a  method  of  classi- 
fication which  is  natural.  In  the  section  Adeleidea,  Leger  includes  the  haerno- 
gregarines  as  a  family,  Hcemogregarinidce,  characterized  by  producing  one 
octozoic  spore ;  but  this  is  true  only  of  two  species,  so  far  as  is  known  at 
present,  and  certainly  not  of  many  others  (see  p.  378,  infra). 

There  remains  for  mention  the  family  Aggregatidoe,  comprising  certain 
organisms,  generally  regarded  as  coccidia,  parasitic  upon  Cephalopods  of 
various  genera  (Sepia,  Eledone,  Octopus,  etc.).  These  parasites  fall  into 
numerous  species,  of  which  Moroff  (94)  enumerates  twenty-one,  but  they 
are  comprised  in  a  single  genus  which  has  gone  through  many  vicissitudes  of 
nomenclature,  having  figured  at  different  times  under  the  names  Benedenia, 
Legeria,  Legerina,  and  Eucoccidium  ;  but  when  it  had,  apparently,  settled 
down  under  the  last  of  these  names,  it  was  discovered  that  the  schizogony, 
formerly  supposed  to  be  absent  in  this  genus  of  parasites,  occurs  in  a  distinct 
host — namely,  a  crab — where  it  had  been  seen  by  Frenzel  and  named  by  him 
Aggregate  ;  this  name  stands,  therefore,  as  the  "  correct  "  name  of  this  genus 
of  parasites. 

Not  less  debatable  than  the  name  of  these  parasites  is  their  systematic 
position.  While,  up  to  a  comparatively  recent  tune,  their  schizogonous 
phases  in  crabs  had  been  regarded  as  those  of  coelomic  gregarines,  their 
sporogonous  cycle  in  Cephalopods  was  accepted  as  that  of  a  coccidian. 
Siedlecki  (652)  investigated  the  sexual  phases,  and  found  a  type  of  sporogony 
quite  in  accordance  with  that  of  coccidia— namely,  sporouts  (gametocytes) 
separated  from  one  another,  the  male  gametocyte  producing  a  great  number 
of  microgametes,  one  of  which  fertilized  a  niacrogamete,  with  subsequent 
division  of  the  zygote  to  form  a  number  of  sporoblasts  and  spores. 

Recently,  however,  Moroff  published  a  note  in  which  he  maintained  that  the 
fertilization  was  of  a  type  quite  different  from  that  described  by  Siedlecki. 
He  asserted  that  the  inacrogametocyte  gave  rise  before,  not  after,  fertilization 
to  a  number  of  sporoblasts,  and  that  the  sporoblasts  in  question  were  the  true 
macrogametes,  each  of  which,  after  being  fertilized,  gave  rise  to  a  single 
spore.  In  other  words,  Moroff  described  the  fertilization  as  being  of  the 
gregarine-type,  and  not  that  characteristic  of  coccidia.  Consequently  these 
organisms  have  been  classified  by  Fantham  and  by  Leger  and  Duboscq  (645) 
amongst  the  schizogregarines. 

In  his  latest  work,  however,  Moroff  (94)  acknowledges  that  the  proofs  of 
the  process  of  fertilization  alleged  by  him  are  inadequate  to  establish  the 
point  at  issue,  and  that  further  investigations  are  necessary ;  he  is  no  longer 
prepared  to  insist  on  the  gregarine-nature  of  these  organisms.  Until,  there- 
fore, the  question  has  been  settled  by  fresh  observations,  the  account  of  the 
sporogony  and  sexual  phases  given  by  Siedlecki  must  stand.  These  parasites 
may  be  regarded  as  a  distinct  family  of  the  coccidia,  the  Aggregatidoe, 
characterized  by  an  alternation  of  hosts  corresponding  to  an  alternation  of 
generations.  The  life-cycle  in  its  general  outline  is  as  follows:  The  spores 
are  produced  in  the  bodies  of  Cephalopods  ;  the  dead  bodies  of  the  Cephalopods, 
killed  in  various  ways  (by  porpoises,  for  example),  are  eaten  by  crabs,  which 
thus  infect  themselves ;  the  spores  germinate  in  the  intestine  of  the  crab  and 
liberate  the  sporozoites,  which  traverse  the  wall  of  the  intestine  and  come  to 
rest  in  the  subepithelial  connective-tissue  layer.  There  the  parasite  grows 
to  a  large  size,  forming  a  cyst  which  bulges  into  the  body-cavity,  and  repro- 
duces itself  by  schizogony,  a  process  which  has  been  studied  exhaustively  by 
Leger  and  Duboscq  (645).  The  final  result  is  a  vast  number  of  merozoites. 
If  now  the  crab  be  eaten  and  digested  by  a  Cephalopod,  the  merozoites  resist 
the  digestive  juices  and  establish  themselves  in  their  new  host. 

The  cycle  in  the  Cephalopods  has  been  studied  by  Moroff.  The  merozoites 
grow  into  sporonts  or  gametocytes  which  are  not  sexually  differentiated,  but 
waen  their  growth  is  complete  sexual  differences  are  seen  in  the  mode  of 
gunete-formation.  Whatever  the  method  of  fertilization,  a  number  of 
sporoblasts  are  formed  from  which  the  spores  arise ;  each  spore  has  a  tough 

23 


354  THE  PROTOZOA 

sporocyst,  and  contains,  in  different  species,  from  three  to  twenty-four 
sporozoites.  The  various  species  of  Aggregaia  appear  to  be  specific  to  par- 
ticular hosts,  whether  crabs  or  cephalopods. 

If  the  Aggregatidce  are  coccidia,  they  differ  from  other  coccidia  in  having 
an  alternation  of  hosts,  and  in  the  absence  of  an  oocyst  formed  round  the 
zygotc.  If,  on  the  other  hand,  they  are  gregarines,  they  differ  from  all  other 
known  gregarines  (with  the  exception  of  the  doubtful  form  Scliaudinndla. 
see  p.  355,  infra),  not  only  in  the  alternation  of  hosts,  but  also  in  the  fact 
that  the  gametocytes  remain  separate  and  produce  gametes  without  previous 
association.  If  the  view  put  forward  by  Moroff  is  the  true  one,  they  are  to 
be  regarded  rather  as  forms  derived  from  the  ancestral  form  of  gregarines  and 
coccidia  (see  below),  before  the  habit  of  association  of  gametocytes,  so  charac- 
teristic of  gregarines,  had  been  acquired. 

Comparison  of  the  Life-Cycles  of  Coccidia  and  Gregarines. — It  is  seen  that  a 
typical  coccidian,  such  as  Coccidium  schubergi,  differs  from  a  typical  gregarine 
mainly  in  the  following  points :  (1)  The  trophozoites  are  intracellular  ;  (2)  the 
gametocytes  are  more  or  less  widely  separated  from  one  another  at  the  time 
they  produce  gametes ;  (3)  the  female  gametccyte  does  not  divide  into  a 
number  of  gametes,  but  remains  undivided  to  form  a  single  macrogamete, 
disproportionately  large  as  compared  with  the  male  gametes ;  (4)  the  zygote 
undergoes  a  process  of  division,  with  the  result  that  all  the  spores  produced 
within  the  cyst  are  the  offspring  of  a  single  zygote,  while  in  gregarines  the 
cyst  contains  many  zygotes  and  each  zygote  gives  rise  to  a  single  spore. 

When,  however,  the  coccidia  are  considered  as  a  whole,  it  is  seen  at  once 
that  the  first  two  points  do  not  furnish  absolute  distinctions;  in  Selenococ- 
ddium  the  trophozoites  are  motile  and  extracellular,  and  in  Adeleidce  the  game- 
tocytes associate  together.  There  remains  only  the  sporogony  which  stands 
out  as  the  distinctive  feature  of  each  group.  It  is  by  no  means  difficult  to 
understand,  however,  the  manner  in  which  the  two  types  of  sporogony, 
different  as  they  may  appear,  could  have  arisen  from  a  common  source. 

The  common  ancestral  form,  from  which  the  two  groups  arose  by  divergent 
evolution  and  adaptation  to  different  modes  of  parasitism,  may  be  supposed 
to  have  been  a  parasitic  organism  in  which  the  trophozoites  that  grew  into 
gametocytes  were  separated  from  one  another,  as  in  coccidia,  and  consequently, 
when  full-grown,  produced  their  gametes  separately  ;  and  each  gametocyte 
produced  a  number  of  gametes  which  differed  only  slightly  from,  one  another, 
as  in  gregarines. 

From  such  a  form  the  coccidia  arose  by  the  acquisition  of  an  intracellular 
habitat  on  the  part  of  the  trophozoites,  whereby  the  gametocytes  remained 
more  or  less  widely  separated  when  they  produced  gametes.  As  a  result  of 
this  condition  the  gametes  have  to  seek  each  other  out,  and  may  easily  miss 
one  another ;  consequently  there  was  a  tendency  to  greater  specialization  of 
the  gametes.  The  male  gametes  became  very  small  and  very  motile,  and  were 
produced  in  large  numbers.  The  female  gametocyte,  on  the  other  hand,  no 
longer  divided  up  into  a  number  of  gametes,  but  became  a  single  large  macro- 
gamete.  As  soon,  however,  as  fertilization  is  effected,  the  suppressed  divisions 
of  the  female  gametocyte  take  place  in  the  zygote,  which  divides  into  the 
sporoblasts  produced  formerly  by  the  division  of  the  gametocyte. 

The  gregarine  -type,  on  the  other  hand,  arose  from  the  ancestral  form  by 
the  trophozoites  which  grow  into  sporonts  being  free  and  motile  in  the  later 
stages  of  their  growth  ;  consequently,  gametocytes  of  different  sexes  were  able 
to  come  together  and  produce  their  gametes  m  close  proximity,  and  finally 
to  associate  intimately  and  produce  their  gametes  within  a  common  cyst. 
In  such  a  condition  it  was  impossible  that  the  gametes  should  miss  one 
another  ;  consequently  there  was  no  tendency  to  increased  specialization  of 
the  gametes,  but,  on  the  contrary,  a  tendency  for  the  gametes  to  lose  even 
1  lie  slight  degree  of  specialization  inherited  from  the  ancestral  form,  with  the 
result  that  a  more  or  less  perfect  isogamy  was  developed  ;  and  instead  of  the 
microgametes  being  produced  in  excess,  the  numbers  of  each  kind  of  gamete 
produced  arc  approximately  equal. 


THE  GREGARINES  AND  COCCIDIA  355 

It  follows,  from  the  course  of  evolution  sketched  in  the  foregoing  paragraphs, 
that  in  both  gregarines  and  coccidia  the  cyst  is  to  be  regarded  as  a  secondary 
acquisition.  In  the  ancestral  form  there  were  simply  scattered  zygotes 
from  which  the  spore  with  its  contained  sporozoites  arose  ;  the  spore  may,  in 
fact,  be  regarded  as  representing  the  primary  form  of  the  encysted  parasite, 
comparable  to  an  encysted  zygote  of  the  Flagellata.  It  is  indeed  obvious 
that  the  cyst  of  gregarines  and  coccidia  respectively  are  quite  different 
things.  In  gregarines  the  cyst  is  formed  round  the  two  associated  gameto- 
cytes — it  is  a  "  copularium,"  asLeger  has  termed  it ;  in  coccidia  the  cyst  is 
a  protective  membrane  formed  round  the  zygote,  immediately  after  fertiliza- 
tion. In  the  genus  Legerella  among  coccidia,  however,  the  cyst  is  the  sole 
protective  membrane  formed  to  enclose  the  sporozoites,  no  sporocysts  being 
produced,  a  condition  which  is  of  interest,  since  it  leads  on  to  that  found 
in  the  Haemosporidia. 

In  both  coccidia  and  gregarines  secondary  departures  from  the  primary 
type  of  the  life-cycle  occur.  In  coccidia  the  gametocytes  of  certain  forms 
(Adeleidce)  have  acquired  the  habit  of  association  prior  to  gamete-formation  ; 
this  has  not  led,  however,  to  a  development  in  the  direction  of  isogamy,  as 
in  gregarines,  but  merely  to  a  reduction  in  the  number  of  male  gametes  formed. 
In  some  gregarines,  on  the  other  hand,  notably  in  those  forms  of  "  ccelomic  " 
habitat,  or  parasitic  in  the  haemoccele,  the  sporonts  in  the  later  stages  of  growth 
are  inert  and  motionless  ;  this  condition  has  led  to  neogamous  association 
of  young  sporonts  Avhile  still  motile  and  capable  of  coming  together  proprio 
moiu. 

Here  mention  must  be  made  of  the  remarkable  form  Schaudinnella  de- 
scribed by  Nusbaum  (624),  parasitic  in  the  gut  of  an  oligochsete  worm.  The 
full-grown  trophozoites  of  Schaudinnella  are  gregarine-like,  and  may  be  either 
free  in  the  lumen  of  the  gut  or  attached  to  the  epithelium  by  an  epimerite  ; 
the  body  is  non-septate.  Temporary  associations  (syzygies)  may  be  formed 
which  have  nothing  to  do  with  sexual  conjugation,  since  the  associates  part 
again  and  produce  gametes  separately  and  independently.  The  full-gro  wn 
sporonts  are  distinguishable  as  male  and  female  forms.  The  female  sporonts 
divide  up  into  eight  or  ten  spherical  cells,  the  niacrogarnetes.  The  male 
sporonts  divide  up  into  a  great  number  of  minute  spindle-shaped  elements, 
the  rnicrogarnetes.  Copulation  takes  place  between  a  microgamete  and  a 
macrogamete.  The  zygote  may  become  encysted  and  cast  out  with  the 
fgeces,  or  may  penetrate  into  the  wall  of  the  intestine.  In  the  first  manner 
infection  of  new  hosts  is  brought  about ;  in  the  second,  multiplication  of  the 
parasite  in  the  same  host.  The  zygotes  in  the  wall  of  the  intestine  grow  in 
size,  and  divide  each  into  a  number  of  sporozoites. 

Some  doubt  may  be  felt  as  to  whether  the  life-history  of  Schaudinnella  has 
been  interpreted  correctly  throughout ;  it  is  unusual  for  endogenous  multi- 
plication to  be  preceded  by  sexual  processes,  and  the  development  requires 
further  examination.  If,  however,  the  account  of  the  gamete-formation  be 
correct,  Schaudinnella  is  a  form  which  in  this  respect  stands  very  near  to  the 
hypothetical  ancestral  form  of  gregarines  and  coccidia. 

"There  can  be  no  doubt  that  the  gregarines  and  coccidia  are  closely  allied 
in  every  respect,  and  that  the  two  groups  are  distinguished  by  points  of 
difference  which  can  be  referred  quite  simply  to  adaptation  to  slightly  different 
habits  in  their  parasitic  life. 


Bibliography. — For  references  see  p.  494. 


CHAPTER  XV 
THE  SPOROZOA:  II.  THE   H.ffiMOSPORIDIA 

IN  the  order  Hsemosporidia  are  comprised  a  number  of  organisms 
characterized  by  the  following  peculiarities  :  They  are  parasites  of 
the  blood-corpuscles,  red  or  white,  of  vertebrates  during  a  part  of 
the  life-cycle  ;  like  the  Coccidia,  they  exhibit  an  alternation  of 
generations,  non-sexual  schizogony  and  sexual  sporogony  ;  and,  in 
all  cases  thoroughly  investigated  up  to  the  present,  the  alternation 
of  generations  corresponds  to  an  alternation  of  hosts,  the  schizogony 
taking  place  in  the  blood  or  internal  organs  of  a  vertebrate,  the 
sporogony  in  the  digestive  tract  or  other  organs  of  an  invertebrate  * 
lastly,  resistant  spores  are  not,  as  a  rule,  produced  in  this  order, 
being  rendered  unnecessary  by  the  fact  that  the  parasite  is  never, 
so  to  speak,  in  the  open,  but  always  sheltered  within  the  body  of 
one  or  the  other  of  its  two  hosts  during  its  entire  life-cycle. 

The  Hremosporidia,  as  the  name  is  generally  understood,  are  a 
group  which  comprises  a  number  of  forms  differing  considerably 
amongst  themselves.  Some  of  the  types  referred  at  present  to 
this  order  will,  perhaps,  when  thoroughly  investigated,  be  removed 
from  the  order  altogether.  The  existence  of  these  dubious  forms 
renders  the  precise  limits  of  the  group  uncertain  and  ill-defined. 
All  that  can  be  said  at  present  is  that  the  order  contains  a  nucleus 
of  true  Haemosporidia  presenting  very  obvious  and  close  affinities 
with  the  Coccidia,  and,  in  addition  to  such  forms,  certain  others, 
the  true  affinities  of  which  remain  to  be  determined,  but  which  can 
be  ranked  provisionally  in  the  group. 

Under  these  circumstances,  the  occasion  is  not  yet  ripe  for  treating 
the  group  in  a  comprehensive  manner,  as  has  been  done  with 
Gregarines  and  Coccidia.  The  difficulty  of  dealing  with  these 
blood-parasites  is  enhanced  by  the  fact  that  there  is  perhaps  no 
group  in  the  animal  kingdom  in  which  the  nomenclature-purist  has 
wrought  such  havoc  as  in  the  Heemosporidia.  Matters  have  reached 
such  a  pitch  that  in  some  cases  the  popular  names  of  certain  forms 
are  more  distinctive  than  their  strictly  scientific  appellations,  so 
that  the  very  raison  d'etre  of  a  scientific  terminology  has  been 
stultified. 

356 


THE  H^MOSPORIDIA  357 

In  the  sequel,  therefore,  the  Hsemosporidia  will  be  discussed 
under  five  principal  types,  each  of  which  comprises  several  forms. 
So  far  as  possible,  the  "  correct  "  names  of  these  forms  will  be 
stated.  Finally  an  attempt  will  be  made  to  discuss  the  position 
and  affinities  of  the  group  as  a  whole.  The  following  is  a  summary 
of  the  distinctive  characters  of  the  types  in  question  : 

1.  The  Hcemamoeba-Type. — The  trophozoites  of  the  schizogonous 
cycle  occur  within  red  blood-corpuscles,  and  are  amoeboid  ;  they 
produce  a  characteristic  pigment,  termed  "  melanin."     When  the 
blood  is  drawn  and  cooled  down  on  a  slide,  the  male  sporonts,  if 
present,  form  filamentous  male  gametes  resembling  flagella,  and 
are  consequently  said  to   "  exflagellate."     The  invertebrate  host, 
so  far  as  is  known,  is  a  mosquito. 

2.  The'Halteridium-Type. — The  intracorpuscular  trophozoite  is  a 
characteristic  halter-shaped  parasite  of  red  blood-corpuscles',  which 
is  amoeboid,  and  which,  like  the  last,  produces  melanin-pigment, 
and  "  exflagellates  "  on  the  slide.     Only  known  from  the  blood  of 
birds  ;  the  invertebrate  host,  so  far  as  is  known,  is  a  Hippoboscid  fly. 

3.  The  Leucocytozoon-Type. — The  full-grown  sporonts  are  found 
within  white  blood-cells,  which  are  greatly  altered  by  the  parasite. 
They  are  not  amoeboid,  and  do  not  produce  pigment,  but  they 
"  exflagellate  "  when  the  blood  is  drawn.     Only  known  in  birds  ; 
the  invertebrate  host  is  unknown. 

4.  The  Hcemogregarine-Type. — Parasites  usually  of  red  blood-cor- 
puscles, sometimes  of  white  ;  they  are  not  amoeboid,  do  not  produce 
pigment,  and  do  not  "  exflagellate."     They  occur  throughout  the 
whole  vertebrate  series,  but  are  most  abundant  in  cold-blooded 
vertebrates.     Those  of  fishes,   amphibia,  and  reptiles,  are  trans- 
mitted generally  by  leeches  ;  those  of  mammals  and  some  reptiles 
apparently  by  ectoparasitic  Arthropods. 

5.  The  Piroplasma -Type. — Parasites  of  red   blood  -  corpuscles, 
amoeboid  or  of  definite  form  ;    they  do  not  produce  pigment  and 
do  not  "exflagellate";  generally  very  minute.     They  are  known 
only  in  mammals,  and  the  invertebrate  host  is  always  a  tick. 

These  five  types  will  now  be  considered  in  more  detail. 

1.  The  Hcemamcebce. — The  characteristic  form  of  parasite  in  this 
section  is  a  minute,  amoeba-like  organism  contained  within  a  red 
blood-corpuscle  ;  as  it  grows  it  gradually  exhausts  and  destroys  the 
corpuscle,  and  at  the  same  time  produces  the  characteristic  melanin- 
pigment.  Such  are  the  well-known  malarial  parasites  of  mammals 
and  birds.  Unfortunately,  the  accepted  rules  of  nomenclature 
render  it  obligatory  to  use  the  generic  name  Plasmodium  for  these 
parasites,  a  most  unsuitable  name,  since  they  are  not  plasmodia 
in  any  phase  except  very  temporarily,  when  they  are  sporulating. 
They  may,  however,  be  termed  familiarly  "  hsemamcebae,"  pro- 


358  THE  PROTOZOA 

vided  the  word  be  not  written  in  italics  or  with  an  initial  capital 
letter  ;  anything  is  better  than  to  speak  of  them  as  "  plasmodia." 

In  human  beings  three  distinct  species  at  least  of  hsemamoebse 
are  recognized — namely,  the  parasites  of  tertian,  quartan,  and 
pernicious  or  tropical  malaria,  now  generally  named  Plasmodium 
vivax,  P.  malarice,  and  P.  falciparum,  respectively  ;  the  last-named 
is  distinguished  from  the  other  two  by  the  sporonts  being  crescent- 
shaped,  and  was  put  formerly  in  a  distinct  genus,  Laverania,  which 
has  been  abolished .  Hsemamoebse  similar  to  those  causing  malaria 
in  man  have  been  described  from  other  mammals — for  example, 
monkeys,  several  species  ;  bats  ;  and  squirrels.  The  human 
malarial  parasites  go  through  their  sporogony  in  mosquitoes  of  the 
subfamily  Anophelinse  ;  the  life-cycle  of  those  of-  other  mammals 
has  not  been  yet  fully  investigated. 

In  bftds  haemamoebse  are  of  very  common  occurrence.  For 
these  Labbe  created  the  genus  Proteosoma,  a  name  still  in  use 
unofficially  as  a  distinctive  appellation  ;  but  the  correct  name  of 
the  avian  malarial  parasites,  commonly  assumed  to  belong  all  to 
one  species,  is  variously  stated  to  be  Plasmodium  prcecox  or  P.  re- 
lictum.  In  contrast  with  the  human  malarial  parasites,  those  of 
birds  are  transmitted  by  mosquitoes  of  the  subfamily  Culicinse. 

Lastly,  parasites  are  known,  from  certain  reptiles,  which  are 
intracorpuscular  in  habitat,  amoeboid  in  form,  and  produce  pig- 
ment. Hence  they  appear  to  be  genuine  hsemamcebee,  but  they 
do  not  exflagellate  when  the  blood  is  drawn,*  and  very  little  is 
known  of  their  life-cycle.  By  some  authorities  these  reptilian 
forms  are  referred  also  to  the  genus  Plasmodium,  but  it  is  best 
for  the  present  to  maintain  the  genus  Hcemocystidium,  Castel- 
lani  and  Willey,  for  these  reptilian  forms.  Examples  are  //.  metsch- 
nikovi  (Simond),  from  an  Indian  tortoise,  Trionyx  indicus  ;  H. 
simondi,  Castellani  and  Willey,  from  a  Ceylon  gecko,  Hemidactylus 
leschcnaulti ;  and  various  other  species. 

Since  the  transmission  of  the  malarial  parasites  by  mosquitoes 
was  first  discovered  by  Ross  in  his  experiments  on  the  Proteosoma- 
parasite  of  birds,  the  development  of  human  malarial  parasites 
has  been  studied  in  full  detail  by  numerous  investigators,  amongst 
whom  Grassi  and  Schaudimi  (130)  must  be  specially  mentioned. 
Consequently  the  life-cycle  of  these  parasites  is  better  known  than 
that  of  almost  any  other  Protozoa,  and  is  now  to  be  found  described 
in  every  textbook.  It  will  be  sufficient,  therefore,  to  describe  the 
life-cycle  of  the  species  parasitic  in  human  beings  in  brief  outline, 
as  typical  of  this  class  of  parasites  (Fig.  156). 

*  Aragao  and  Neiva  have  observed  in  Plasmodium  (Hcemocystidium)  diploylo.ssi 
that,  in  the  male  gametocytes  on  the  slide,  violent  streaming  movements  occur, 
such  as  are  the  prelude,  in  other  htemamoebae,  to  exflagellatioii  ;  but  formation  of 
gametes  was  not  seen. 


THE  MLAXOSPORIDIA  359 

The  sporozoites  introduced  into  the  blood  by  the  proboscis  of 
a  mosquito  are  minute  active  organisms  of  slender  form  (Fig.  156, 
XIX.).  Each  sporozoite  attacks  a  red  blood-corpuscle  and  pene- 
trates into  it.  Within  the  corpuscle  it  becomes  a  small,  amoeboid 
trophozoite,  which  grows  at  the  expense  of  the  corpuscle  (Fig.  156, 
I. — V.).  A  characteristic  feature  of  the  young  trophozoite  is  the 
possession  of  a  large  space — probably  a  vacuole — in  the  body, 
which  gives  the  parasite  an  appearance  which  has  been  compared 
to  a  signet-ring.  As  the  parasite  grows,  this  space  disappears  and 
the  body  becomes  compact.  The  characteristic  pigment  is  formed 
within  the  body  of  the  parasite  at  an  early  stage  of  its  growth, 
and  as  it  increases  in  size  the  pigment-grains  become  more  numerous. 
When  the  parasite  is  full-grown  it  is  a  schizont,  and  proceeds  to 
multiply  by  schizogony  (Fig.  156,  6 — 10).  The  body  becomes 
rounded  by  cessation  of  the  amoeboid  movement,  and  the  nucleus, 
hitherto  single,  multiplies  by  repeated  division.  Then  as  many 
small  daughter-individuals  (merozoites)  as  there  are  nuclei  are 
budded  off  round  the  whole  periphery  of  the  schizont,  leaving  at 
the  centre  a  small  quantity  of  residual  protoplasm  containing  the 
pigment-grains  ;  this  is  the  characteristic  rosette-stage,  or  corps 
en  rosace.  The  corpuscle  now  disintegrates,  setting  free  the 
morozoites. 

The  three  species  of  human  malarial  parasites  are  distinguished  by  differ- 
ences in  their  amoeboid  activity,  their  effects  on  the  corpuscles,  the  number 
of  merozoites  produced,  and  other  points,  but  more  especially  by  the  time 
required  for  a  complete  schizogonous  generation.  Thus,  in  Plasmodium  vivax 
the  growth  and  multiplication  of  the  schizont  requires  about  forty-eight 
hours  ;  in  P.  malarice,  seventy-two  hours ;  in  P.  falciparum,  twenty- four 
hours  or  an  irregular  time.  The  attacks  of  fever  produced  by  the  parasites 
occur  when  the  rosettes  are  breaking  up  and  setting  free  the  merozoites, 
probably  because  the  disintegration  of  the  body  of  the  parasite  sets  free 
toxic  substances  contained  in  it.  Hence  in  the  tertian  ague  caused  by 
P.  vivax  the  fever  returns  every  third  day  ;  in  quartan  ague  of  P.  malarice, 
every  fourth  day  ;  while  P.  falciparum  causes  irregular  or  quotidian  fevers, 
more  or  less  continuous. 

The  schizogony  of  the  tertian  and  quartan  parasites  proceeds  in  the 
peripheral  blood,  but  that  of  the  pernicious  parasite  takes  place  more 
generally  in  the  internal  organs.  The  amceboid  trophozoites  present  them- 
selves under  the  most  varied  forms  in  the  corpuscles  ;  especialy  noteworthy 
in  the  quartan  parasite  is  the  occurrence  of  haemogregarine-like  forms 
(Billet,  664). 

There  is  some  doubt  as  to  whether  the  trophozoites  are  in  all  cases  within, 
or  merely  attached  to,  the  corpuscles.  Schaudinn  (130)  held  at  first  the  view 
that  in  all  cases  the  parasites  were  intracellular,  and  that  appearances  tending 
to  prove  the  contrary  were  the  result  of  alterations  due  to  manipulation  in 
making  preparations.  It  is  nevertheless  maintained  by  many  authors  that 
some  stages,  at  least,  of  the  parasites  are  attached  to  the  corpuscles  ;  Halber- 
staedter  and  Prowazek,  for  example,  believe  that  in  P.  pithed  the  trophozoites 
which  develop  into  female  sporonts  are  extracellular,  whilst  those  which 
become  schizonts  are  intracellular. 

Different  species  of  hsemamcebte  differ  also  in  the  effects  they  produce  on 


360 


THE  PROTOZOA 


Y 


Vllb. 


TO. 


FIG.  156. — Life-cycle  of  a  malarial  parasite :  combined  diagram  (the  figures  are 
not  in  all  cases  from  the  same  species,  and  some  of  them  are  schematic). 
All  the  figures  above  the  dotted  line  represent  stages  passed  in  human  blood  ; 
those  below  are  the  stages  that  are  found  in  the  mosquito. 

I- — V.  and  6 — 10,  Schizogony  of  the  tertian  parasite,  Plasmodium  vivax,  after 
Schaudinn  (130),  magnified  about  1,500  diameters.  I.,  Youngest  intracor- 
puscular  stage,  which  has  arisen  either  from  a  sporozoite  (XIX.)  or  a  merozoite" 
(10)  that  has  penetrated  into,  or  is  attached  to,  the  corpuscle  (represented 
by  a  circular  outline).  II. — IV.,  Further  stages  of  the  growth  of  the  para- 
site ;  a  vacuole  is  formed  in  its  body  which  gives  it  the  characteristic  "  signet- 
ring  "  appearance  (IV.).  V.  and  6,  Later  stages  of  growth;  the  vacuole 

[Continued  at  foot  of  p.  361. 


THE  H^MOSPORIDIA  361 

the  corpuscles.  An  effect  commonly  seen  is  the  so-called  "  stippling " 
{Tiipfelung)  of  the  corpuscles,  which  exhibit  a  dotted  appearance  (Schiiffner's 
dots). 

The  nierozoites,  when  set  free,  penetrate  into  other  corpuscles, 
and  become  in  their  turn  trophozoites,  which  may  either  grow 
into  schizonts  again  and  repeat  the  process  of  multiplication  by 
schizogony,  or  may  grow  into  sporonts.  As  in  Coccidia.  a  number 
of  generations  of  schizogony  succeed  each  other  before  sporonts 
are  produced.  At  first  the  parasites  are  not  sufficiently  numerous 
to  be  perceptible  in  the  blood  or  to  evoke  febrile  symptoms,  and 
during  this,  the  so-called  "  incubation-period,"  schizogony  alone 
occurs,  in  all  probability  ;  but  when  the  numbers  of  the  parasite 
are  sufficient  to  affect  the  health  of  the  host,  the  reaction  of  the 
host  against  the  parasite  probably  stimulates  the  production  of 
the  propagative  phases.  The  trophozoites  which  grow  into  sporonts 

PIG.  156  continued  : 

disappears  ;  in  6  the  parasite  is  full-grown  and  its  nucleus  is  beginning  to 
divide.  7,  8,  Progress  of  the  nuclear  divisions,  complete  in  8.  9,  Division 
of  the  body  of  the  parasite  to  form  the  merozoites  ;  the  blood-corpuscle 
beginning  to  degenerate.  10,  The  parasite  has  divided  up  into  sixteen  mero- 
zoites, leaving  the  pigment-grains  in  a  small  quantity  of  residual  protoplasm  ; 
the  corpuscle  has  completely  disappeared  and  the  merozoites  are  set  free* 

VI.,  Vila.,  VII&.,  Formation  of  the  gametocytes  of  pernicious  malaria 
(Plasmodium  falciparum)  ;  the  gametocytes  arise  from  the  intracorpuscular 
parasites  by  a  series  of  stages  similar  to  those  represented  in  II. — V.,  but 
without  a  vacuole  in  the  body.  In  P.  falciparum  the  ripe  gametocytes  have 
the  form  of  crescents,  as  shown,  but  in  the  tertian  and  quartan  parasites  the 
gametocytes  are  simply  rounded,  as  Villa,  and  VIII6.  Vila.,  Male  crescent 
with  larger  nucleus  and  scattered  pigment  ;  VII&.,  female  crescent,  with  a 
smaller  nucleus  and  the  pigment  more  concentrated  round  it.  (N.B. — Vila, 
and  VII6.  are  drawn  on  too  small  a  scale  ;  the  crescent  should  be  as  large 
as  XIII.) 

VIII. — XIII.,  Stages  of  the  sexual  generation  of  the  tertian  parasite  in 
the  stomach  of  the  mosquito,  after  Schaudinn.  a,  Male  forms;  b,  female 
forms.  (In  pernicious  malaria  the  crescents  round  themselves  off,  become 
free  from  the  corpuscle,  and  assume  forms  similar  to  VIII.  a  and  b.)  VIII., 
Rounded  -  off  parasites  free  from  the  corpuscle.  IX.,  Gamete-forma- 
tion ;  in  a  the  nucleus  is  divided  into  eight ;  in  b  the  nucleus  has  passed  to 
the  surface  of  the  body.  X.,  Further  stage  ;  in  a  the  body  of  the  gametocyte 
is  throwing  off  the  long  slender  microgametes,  one  of  which  is  represented 
free  ;  in  b  the  nucleus  is  dividing  to  throw  off  a  reduction-nucleus.  XL, 
Process  of  syngamy  ;  a  male  gamete  is  seen  penetrating  the  body  of  a  female 
gamete.  XII.,  Zygote  shortly  after  fertilization  ;  the  body  is  growing  out 
and  becoming  vermiform,  with  the  synkaryon  at  the  hinder  end  ;  male  and 
female  chrornatin  still  distinct  ;  near  the  zygote  is  seen  a  clump  of  degenerating 
microgametes.  XIII.,  Motile  ookinete  formed  from  the  zygote  ;  the  syn- 
karyon, with  male  and  female  chromatin  still  distinct,  is  seen  near  the  middle 
of  the  body  ;  the  pigment- grains  are  at  the  hinder  end  of  the  body,  whence 
they  are  soon  rejected. 

XIV.— XVIII.,  Sporogony:  diagrammatic.  The  ookinete  (XIII.)  pene- 
trates the  stomach-wall  and  becomes  encysted  (XIV.);  its  nuclei  multiply 
(XV.),  and  it  forms  a  number  of  sporoblasts  so  called  (XVI.)  ;  in  each  sporo- 
blast  the  nucleus  divides  to  form  a  great  number  of  small  nuclei,  which  grow 
out  in  tongue-like  processes  from  the  surface  to  form  the  sporozoites  (XVII.)  ; 
the  ripe  cyst  contains  great  numbers  of  sporozoites  with  a  certain  amount  of 
residual  protoplasm  ;  the  sporozoites  when  set  free  (XIX.)  pass  into  the 
salivary  glands,  and  thence  through  the  proboscis  into  the  blood  of  the 
vertebrate  again. 


362  THE  PROTOZOA 

have,  according  to  Schaudinn  (130),  no  signet-ring  stage  in  their 
development,  but  are  of  compact  form,  and  grow  more  slowly  than 
the  trophozoites  which  become  schizonts.  The  sporonts  are  of 
two  types,  male  and  female  (Fig.  156,  Villa.,  VIII&.)  ;  the  male 
forms  have  a  large  nucleus  and  lightly-staining,  clearer  cytoplasm  ; 
the  female  forms  have  a  smaller  nucleus  and  more  deeply  staining 
cytoplasm.  In  the  tertian  and  quartan  parasites  the  sporonts  are 
distinguishable  from  the  schizonts  by  their  greater  size  and  more 
abundant  pigment  in  larger  grains.  In  the  parasite  of  pernicious 
malaria,  the  sporonts  are  further  characterized  by  their  sausage- 
like  form  (Fig.  156,  Vila.,  VII&.),  and.  are  thereby  easily  dis- 
tinguishable from  the  rounded  schizonts. 

The  sporonts  only  undergo  further  change  if  taken  up  by  a  mos- 
quito of  a  species  capable  of  acting  as  the  specific  host  of  the  para- 
site. When  human  blood  containing  various  stages  of  the  parasite 
is  ingested  by  a  culicine  mosquito,  all  stages  of  the  parasite  are 
digested  with  the  blood  ;  but  if  taken  up  by  an  anopheline,  the  ripe 
sporonts  resist  the  action  of  the  digestive  juices  of  the  mosquito, 
and  develop  further  in  its  stomach,  while  all  other  stages  succumb. 
The  sporonts  burst  the  corpuscle  in  which  they  are  contained,  and 
round  themselves  off.  In  the  male  sporont  the  nucleus  undergoes 
rapid  fragmentation  into  some  four  or  six  nuclei  (Fig.  156.  IXa.), 
leaving  a  residual  karyosome  at  the  centre  of  the  body,  as  in 
Coccidium  (Schaudinn,  99).  The  daughter-nuclei  place  themselves 
at  the  surface  of  the  body,  and  grow  out  with  explosive  suddenness 
into  fine  filaments  of  chromatin,  en  sheathed  in  a  scarcely  perceptible 
layer  of  cytoplasm  (Fig.  156,  Xa.).  Each  such  filament  is  a  micro- 
gamete,  of  slender,  spirochsete-like  form,  without  flagella,  but 
endowed  with  powers  of  active  movement.  The  microgametes 
lash  about  violently,  often  dragging  the  body  of  the  sporont  after 
them,  and  presenting  a  superficial  resemblance  to  flagella,  which, 
indeed,  they  were  formerly  thought  to  be  ;  hence  the  process  of 
microgamete-formation,  which  can  be  observed  without  difficulty 
in  freshly-drawn  blood,  was  thought  to  represent  a  flagellated 
'  Polymitus  "  stage  of  the  parasite,  and  was  termed  "  exflagella- 
tion."  The  microgametes  by  their  movements  finally  become 
detached,  and  swim  awray  from  the  body  of  the  sporont,  which 
perishes  as  residual  protoplasm. 

In  the  female  sporont  the  nucleus  divides  to  give  off  a  reduction- 
nucleus  (Fig.  156,  X6.)  ;  it  is  then  ripe  for  fertilization  by  a  niicro- 
gamete  (Fig.  156,  XI.),  which  penetrates  the  body  and  fuses  with 
the  female  pronucleus.  The  zygote  then  changes  from  a  rounded 
form  inio  an  elongated  vermicule,  termed  an  "  ookinete  "  (Fig.  156, 
XII.,  XIII.),  which  moves  by  gliding  movements,  like  a  gregarine. 
The  ookinete  bores  its  way  through  the  lining  epithelium  of  the 


THE  ILEMOSPORIDIA  363 

gnat's  stomach,  and  comes  to  rest  in  the  subepithelial  tissue  ;  here 
it  rounds  itself  off  and  forms  an  oocyst  (Fig.  156,  XIV.),  becoming 
surrounded  by  a  delicate  membrane,  which  is  not,  however,  of  a 
tough  and  impervious  naturelike  a  coccidiaii  oocyst,  since  the  parasite 
continues  to  absorb  nutriment  and  to  grow  in  size,  bulging  out  the 
stomach-wall  towards  the  body-cavity.  As  it  grows,  the  originally 
single  nucleus  of  the  zygote  multiplies  by  binary  fission,  and  the 
cytoplasm  becomes  concentrated  round  each  nucleus  to  form  a 
"  sporoblast,"  so  called  (Fig.  156,  XV.,  XVI.).  In  each  sporoblast 
the  nucleus  divides  repeatedly,  and  then  the  surface  of  the  sporo- 
blast grows  out  into  slender  tongue-like  processes,  each  carrying 
out  one  of  the  nuclei  in  it  (Fig.  156.  XVII.).  Thus  a  vast  number 
of  minute  sporozoites  are  formed  by  a  process  of  multiplication 
recalling  that  seen  in  the  schizogony  of  Aggregata  or  Porospora. 
Finally  the  cyst  contains  some  hundreds,  or  even  thousands,  of 
sporozoites,  together  with  a  certain  amount  of  residual  protoplasm, 
in  which  the  melanin-pigment  of  the  macrogamete  is  contained 
(Fig.  156,  XVIII.).  The  ripe  cysts  burst  and  scatter  their  contents 
in  the  body-cavity  (hseniocoele)  of  the  mosquito  ;  the  sporozoites 
pass  by  means  of  the  blood-currents  to  the  salivary  glands,  in 
which  they  collect  in  vast  numbers.  The  mosquito  is  now  infective  ; 
at  its  next  feed,  which  is  usually  the  fourth,  counting  as  the  first 
that  by  which  it  first  took  up  the  parasites  in  the  infected  blood, 
the  tiny  sporozoites  pass  with  the  salivary  secretion  down  the 
proboscis  into  the  blood  of  the  man  on  whom  the  mosquite  feeds, 
and  so  produce  a  new  infection. 

A  disputed  point  in  the  life-cycle  is  the  manner  in  which  relapses  are  brought 
about  in  malarious  persons  ;  as  is  well  known,  persons  who  have  had  malaria 
may  have  fresh  attacks  of  the  disease  under  conditions  which  preclude  infec- 
tion by  mosquitoes,  and  leave  no  doubt  but  that  the  parasite  has  been  present 
in  the  body  in  a  latent  or  inconspicuous  condition,  and  has  for  some  reason 
reacquired^the  power  of  multiplication  until  its  presence  becomes  perceptible 
again.  Two  views  have  been  put  forward  to  explain  relapses.  According 
to  Schaudinn  (130),  in  the  healthy  intervals  all  forms  of  the  parasite  have 
died  off  except  the  female  sporonts,  which  are  the  most  resistant  forms  of  the 
parasite,  and  maintain  their  existence  in  a  resting  state  ;  when,  however,  the 
conditions  occur,  whatever  they  may  be,  which  favour  a  relapse,  the  female 
sporonts  multiply  parthenogenetically  (Fig.  72,  p.  137),  and  produce  a  brood 
of  merozoites  which  are  the  starting-point  of  a  fresh  series  of  schizogonous 
generations.  Ross,  on  the  other  hand,  believes  that  in  the  healthy  intervals 
the  number  of  parasites  in  the  blood  merely  falls  below  that  sufficient  to  pro- 
duce febrile  symptoms,  and  that  a  relapse  is  brought  about  simply  by  an 
increase  in  the  numbers  of  the  parasites  present. 

The  number  of  cysts  formed  in  the  stomach  of  the  mosquito  may  be  very 
large,  500  or  more  ;  and  the  cysts  themselves  vary  in  size  considerably,  some 
developing  only  a  few  hundreds  of  sporozoites,  while  in  others  they  are  to  be 
counted  in  thousands.  Even  in  mosquitoes  of  a  species  susceptible  generally 
to  a  particular  species  of  malarial  parasite,  however,  the  sporonts  do  not 
succeed  in  every  case  in  passing  through  their  sexual  stages  and  developing 
normally  (compare  Darling,  669).  In  many  cases  also  the  cysts  degenerate 


364  THE  PROTOZOA 

and  form  masses  of  pigment,  the  so-called  "  black  spores  "  of  Ross.  Similar 
degeneration-phenomena  have  been  observed  by  Schauclinn  (147)  in  the 
oocysts  of  Cyclospora  caryolytica,  and  may  be  compared  to  the  transformation 
of  chromidia  into  pigment  in  the  degeneration  of  Actinosphcerium  in  cultures 
(p.  209). 

The  "  exflagellation,"  or  formation  of  microgametes,  which  takes  place, 
under  normal  circumstances,  in  the  stomach  of  the  mosquito,  can  be  seen  also 
in  blood  freshly  drawn  and  examined  on  a  slide,  if  ripe  sporonts  are  present. 
The  process  is  greatly  furthered  by  lowering  the  density  of  the  blood — for 
example,  by  adding  to  it  not  more  than  one- fifth  of  its  volume  of  ordinary 
water,  or  by  simply  breathing  on  the  blood  when  drawn  (compare  Neumann, 
€77). 

It  is  curious  that,  while  so  many  experimenters  have  established  absolutely 
beyond  all  doubt  the  transmission  of  hsemamcebse  by  mosquitoes,  those  of  man 
by  anophelines,  and  those  of  birds  by  culicines,  no  experiments  seem  to  have 
been  performed  to  determine  how  long  a  mosquito,  once  infected,  remains 
infective  without  being  reinfected.  In  other  cases  of  similar  transmission, 
such  as  that  of  trypanosomes,  yellow  fever,  etc.,  it  is  known  that  the  inverte- 
brate host,  once  rendered  infective,  remains  so  for  a  very  long  time,  probably 
for  the  rest  of  its  life.  In  the  case  of  malarial  parasites  this  point  remains  to 
be  tested  experimentally. 

The  haemamcebse  of  Primates  have  been  studied  by  a  number  of  investigators, 
and  several  species  distinguished  :  Plasmodium  kochi  (Laveran)  from  the  chim- 
panzee and  various  African  monkeys  ;  P.  pithed  from  the  orang-outang,  and 
P.  inui  from  Macacus  spp.  (Halberstaedter  and  Prowazek,  Mathis  and  Leger, 
473) ;  P.  cynomolgi  from  Macacus  cynomolgus  (Mayer,  A.P.K.,  xii.,  p.  314) ; 
and  P.  brasilianum  from  the  ouakari,  Brachyurus  calvus  (Berenberg-Gossler). 
The  schizogony  appears  to  be  generally  similar  to  that  of  the  species  parasitic 
in  man  ;  ring-stages  occur,  and  the  multiplication  is  in  some  cases  similar 
to  the  tertian,  in  other  cases  to  the  quartan  parasite.  Binucleate  trophozoites 
are  of  common  occurrence,  and  binary  fission  also  occurs  (Flu,  A.P.K.,  xii., 
p.  323).  A  striking  feature  of  monkey- malaria  is  the  comparative  rarity 
of  multiplicative  phases,  which  may  be  in  relation  to  the  fact  that  these 
parasites  cause  no  appreciable  symptoms  of  disease  in  their  hosts  ;  in  both 
respects  they  are  comparable  to  non-pathogenic  trypanosomes.  Transmission 
is  probably  effected  by  anopheline  mosquitoes  (Mayer). 

In  bats  two  distinct  forms  of  intracorpuscular  parasites  have  been  described 
under  distinct  generic  names  :  PolycJiromophihis,  from  Vespertilio  and  Miniop- 
terus  spp.,  and  Achromaticus,  from  Vesperugo  spp.  These  two  genera  are 
distinguished  by  the  fact  that  Polychromophilus  produces  melanin -pigment, 
and  Achromaticus  does  not.  Polychromophilus  is  apparently  an  ordinary 
haemamceba  which  should  be  included  in  the  genus  Plasmodium.  Achro- 
maticus, on  the  other  hand,  appears,  from  the  recent  investigation  of  Yakimoff 
and  others  (753),  to  be  a  true  piroplasm  (see  below). 

Plasmodium  vassali  from  squirrels  has  ring-like  young  trophozoites,  and 
its  schizogony  takes  place  by  binary  or  multiple  fission,  more  commonly  the 
former  (Vassal)  ;  some  forms  of  the  parasite  figured  resemble  Piroplasma. 

The  life-history  of  the  Proteosoma- parasite  of  birds  has  been  studied  in 
detail  by  Neumann  ;  the  principal  phases  of  the  parasite  are  essentially  similar 
to  those  of  the  hsemamcebse  parasitic  in  man.  Experimenting  with  canaries, 
Neumann  transmitted  the  infection  by  means  of  Stegomyia  fasciata,  but  this 
mosquito  was  found  to  be  less  efficient  as  a  host  for  Proteosoma  than  the 
species  of  Culep.  Of  Stegomyia  only  11  '4  per  cent,  developed  ripe  cysts,  as 
against  85  per  cent,  of  Culex  ;  the  development  of  the  parasite  is  accomplished 
in  nine  to  eleven  days  in  Culex,  in  thirteen  to  fifteen  days  in  Stegomyia  ;  and 
a  far  smaller  number  of  the  parasites  succeed  in  developing  in  Stegomyia,  in 
which  the  maximum  number  of  cysts  seen  in  the  stomach  of  any  mosquito 
was  thirty-six,  while  in  Culex  much  larger  numbers,  500  to  1,000,  are  recorded. 

But  little  is  known  of  the  life-cycle  of  the  reptilian  hsemamcebse  of  the 
genus  Hcemocystidium.  Aragao  and  Neiva  have  described  schizogony  of  the 


THE  H^EMOSPORIDIA  365 

ordinary  multiple  type,  taking  place  in  the  blood- corpuscles,  in  H.  tropiduri 
and  H.  diploglossi.  According  to  Dobell,  however,  the  schizogony  of 
H.  simondi  consists  simply  of  binary  fission  as  a  rule,  sometimes  of  division 
into  four.  The  male  and  female  ganietocytes,  sharply  differentiated  by  their 
staining  properties  in  this  as  in  other  species,  are  stated  also  to  have  the 
nucleus  divided  into  two  when  mature  ;  Woodcock  (687),  however,  disputes 
the  correctness  of  Dobell's  interpretations.  In  no  case  as  yet  is  the  inverte- 
brate host  of  any  Hcemocystidium  known. 

2.  The  Halteridia. — The  characteristic  form  of  parasite  in  this 
section,  only  known  to  occur  in  the  blood  of  birds,  is  an  organism 
which  is  found  within  the  nucleated  red  corpuscle,  and  which  does 
not  displace  the  nucleus  of  the  corpuscle,  but  grows  round  it  into  a 
halter-like  form,  whence  the  name  Halteridium  given  to  it  by 
Labbe.  Hence  the  parasite  is  easily  distinguished  from  Proteosoma, 
which  is  more  compact  in  form,  and  which  displaces  the  nucleus  of 
the  corpuscle.  Halteridium  is  amoeboid,  but  the  form-changes 
are  generally  slight ;  it  produces  the  characteristic  melanin-pigment 
in  abundance  ;  and  when  the  blood  is  drawn,  "  exflagellation  "  of 
the  ripe  male  sporonts  takes  place  very  readily.  Not  merely  the 
gamete-formation,  but  the  subsequent  fertilization  and  the  for- 
mation of  the  ookinete,  can  be  observed  on  the  slide.  It  is  in  this 
form  that  Macallum  first  followed  out  the  whole  process,  and  so 
made  clear  the  true  significance  of  the  "  Polymitus  "  stage  in  the 
malarial  parasites. 

The  correct  generic  name  for  the  Halteridium-pa,Ta,site  is  believed 
to  be  Hcemoproteus.  Labbe  considered  the  halteridia  of  different 
birds  to  be  all  one  species,  to  which  he  restricted  the  specific  name 
danilewskyi  (Grassi  and  Feletti).  By  other  naturalists  several 
species  have  been  distinguished  and  named  after  the  birds  in  which 
they  occur,  as  H.  noctuce  of  the  little  owl,  H.  columbce  of  pigeons, 
etc.  The  halteridia  of  different  birds  show  considerable  differences 
in  form,  structure,  and  appearance,  and  there  can  be  no  doubt  that 
there  are  many  species  of  these  parasites  ;  but  it  by  no  means 
follows  that  a  given  species  is  restricted  to  a  particular  host.  It  is 
probable  that  in  some  cases  one  and  the  same  species  may  be 
capable  of  infecting  several  species  of  avian  hosts.  The  Sergent 
brothers  were  unable,  however,  to  infect  canaries  with  H.  columbce 
of  pigeons. 

The  life-cycle  of  these  parasites  has  been  the  subject  of  con- 
flicting statements.  We  shall  consider  first  the  type  of  develop- 
ment made  known  by  the  Sergent  brothers  (686)  in  part,  and  more 
fully  by  Aragao  (Fig.  157).  The  development  described  by  Schau- 
dinn  (132),  to  which  the  utmost  doubt  attaches,  will  be  dealt  with 
later  (p.  390). 

The  invertebrate  host  of  H.  columbce  is  a  biting  fly  of  the  genus 
Lynchia,  of  the  dipterous  family  Hippoboscidce.  These  flies,  though 


366 


THE  PROTOZOA 


FIG.  157. — For  description  see  foot  of  opposite  page. 


THE  H.EMOSPORLDIA  367 

provided  with  wings  (some  genera  of  this  family,  such  as  Melophagus, 
the  common  sheep-ked,  are  wingless),  are  extremely  louse-like  in 
appearance,  and  creep  in  the  plumage  of  birds  ;  they  attack  nest- 
lings as  well  as  adults — a  fact  which  explains  the  appearance  of  the 
infection  in  pigeons  before  they  have  left  the  nest. 

When  blood  containing  the  parasites  is  taken  up  by  a  Lynchia, 
the  ripe  gametocytes  burst  the  corpuscles  in  which  they  are  con- 
tained, round  themselves  off,  and  form  gametes,  in  the  manner 
already  described  for  haemamcebee,  in  the  stomach  of  the  fly 
(Fig.  157,  D,  E).  Fertilization  then  takes  place,  and  ookinetes  are 
formed  (Fig.  157,  F — J).  Practically  the  only  difference  from  the 
hseniamoebae  is  that  the  ookinetes  get  rid  of  their  melanin-pigment, 
which  is  cast  off  in  a  small  bead  of  protoplasm  at  the  hinder  end. 

The  ookinete  grows  considerably  larger  than  the  full-grown 
halteridia  of  the  blood.  The  development  of  the  parasite  does  not 
proceed  further,  apparently,  than  this  stage  in  the  fly,  and  it  is  the 
ookinete  which  is  inoculated  back  into  the  bird's  blood  by  the 
Lynchia. 

At  this  point  there  is  a  gap  in  the  development  which  it  remains 
for  further  observations  to  fill  up.  Thirteen  or  fourteen  days  after 
the  actual  infection  by  the  fly  the  parasite  makes  its  first  recorded 
appearance  in  the  pigeon,  within,  a  leucocyte  which  is  adherent  to 
the  wall  of  a  blood-capillary,  so  that  possibly  the  previous  develop- 
ment of  the  parasite  has  taken  place  in  an  endothelial  cell  (Aragao). 
The  parasite  has  the  form  of  a  small  round  body  contained  in  the 
cytoplasm  of  a  leucocyte  (Fig.  156,  K)  ;  it  has  a  single  nucleus  of 

FIG.  157. — Developmental  cycle  of  Hcemoproteus  columbce,  after  Aragao  (683). 
A,  Youngest  halteridia  in  the  blood-corpuscles:  a,  female;  b,  male;  B,  C, 
growth  of  the  gametocytes,  female  (a)  and  male  (b)  ;  D,  gamete-formation  : 
a,  reducing  division  in  the  female  gametocyte ;  b,  division  of  the  nucleus  of 
the  male;  E,  ripe  gametes:  a,  female;  b,  male  ("  Polymitus  "  stage);  F, 
copulation  of  male  and  female  gametes  ;  G,  the  zygote  beginning  to  assume 
the  ookinete-form  ;  //,  the  oiJkinete  with  pigment  in  the  body  ;  /,  the  pigment 
passing  to  the  hinder  end  of  the  body  ;  J,  the  ookinete  after  it  has  got  rid  of 
the  pigment. 

K,  Youngest  stage  in  the  leucocyte  in  the  lung  of  the  pigeon  ;  L,  the  pre- 
ceding stage  has  divided  into  a  number  of  small  individuals,  each  with  one 
nucleus,  and  the  leucocyte  has  increased  in  size  ;  M,  the  individuals  of  the 
last  stage  have  grown  in  size  and  become  multinucleate  ;  the  leucocyte  still 
further  enlarged  ;  N,  further  advance  on  the  last  ;  O,  the  greatly  hypertrophied 
leucocyte  contains  a  number  of  multinucleate  masses  ;  P,  Q,  further  multi- 
plication of  the  nuclei  ;  the  leucocyte  beginning  to  break  down  ;  R,  the  multi- 
nucleate  masses  become  divided  into  a  vast  number  of  small  uninucleate 
individuals,  which  are  set  free  from  the  leucocyte  by  its  disintegration,  and 
which  penetrate  into  blood-corpuscles  and  there  become  the  youngest  halteri- 
dia, as  in  A. 

The  stages  D — J  are  passed  through  in  the  fly  (Lynchia),  the^  stages  K—0 
in  the  pigeon.  Between  J,  the  last  stage  seen  in  the  fly,  and  K,  the  earliest 
stage  yet  found  in  the  pigeon,  is  a  gap  which  it  remains  for  further  investigation 
to  fill. 

The  stages  H — J  are  drawn  rather  too  small  in  proportion  to  those  pre- 
ceding. 


368  THE  PROTOZOA 

irregular  form,  often  seen  in  process  of  division.  The  parasite 
grows,  its  nucleus  multiplies,  and  it  divides  into  a  number  of  small 
bodies,  twelve  to  fifteen  in  number,  each  with  one  nucleus 
(Fig.  156,  L).  During  this  process  the  leucocyte  also  increases 
in  size.  Each  of  the  small  bodies  produced  by  division  grows 
rapidly  in  its  turn,  and  its  nucleus  divides  repeatedly  to  produce  a 
very  large  number  of  nuclei,  which  become  arranged  in  clumps 
resembling  the  sporoblasts  of  a  malarial  parasite  (Fig.  156,  M — 0). 
Finally  each  mass  becomes  divided  up  into  a  great  number  of 
minute  "  merozoites  "  of  irregular  form  (Fig.  156,  P — R).  During 
this  process  the  leucocyte  first  becomes  greatly  hypertrophied,  and 
finally  breaks  down  altogether,  setting  free  the  merozoites,  which 
pass  into  the  blood  and  attack  the  blood-corpuscles,  into  which  they 
penetrate  and  become  the  young  halteridia  (Fig.  156,  A).  The 
development  in  the  lung  that  has  been  described  takes  about 
twelve  days,  so  that  the  youngest  parasites  make  their  appearance 
in  the  circulating  blood  about  the  twenty-sixth  day  after  infection 
by  the  fly. 

In  the  blood  -  corpuscles  the  youngest  halteridia  are  minute 
bodies  with  a  single  nucleus,  which  grow  into  the  adult  form,  and 
become  male  or  female  gametocytes,  readily  distinguishable  by  the 
characters  of  the  cytoplasm,  which  is  darker  in  the  female,  and  of 
the  nucleus,  which  is  larger  in  the  male  (Fig.  156,  B,  C).  No  multi- 
plication takes  place  in  the  red  corpuscle  :  the  sole  multiplicative 
stage  known  with  certainty  is  that  in  the  lung.  Consequently,  in 
the  pigeon  the  infection  dies  out  after  a  time,  unless  re-infections 
take  place,  and  the  degree  to  which  parasites  abound  in  the  blood  is 
related  directly  to  the  number  of  infected  flies  fed  on  the  bird.  This 
may  not  be  equally  true,  however,  of  other  species  of  these  parasites. 

From  Aragao's  account  it  would  appear  that  in  H.  columbce  only  male  and 
female  halteridia  (sporonts)  occur.  In  other  species,  however,  indifferent 
forms  occur  also,  which,  it  may  be  supposed,  are  destined  as  schizonts  to 
repeat  the  process  of  schizogony,  and  so  to  maintain  the  infection  in  the 
bird,  like  the  schizonts  of  the  malarial  parasites.  Anschutz  has  described 
in  H.  oryzivorce  (of  Padda  oryzivora]  a  process  of  schizogony  taking  place  in 
the  circulating  blood. 

The  development  of  the  halteridia  in  the  leucocytes  may  be  considered, 
probably,  as  equivalent  to  the  schizogony  of  the  malarial  parasites.  On  this 
interpretation  the  missing  part  of  the  development  is  that  which  corresponds 
to  the  sporogony  of  the  malarial  parasite,  and  which  in  this  case  is  either 
suppressed  entirely  ("  aposporogony,"  Aragao),  or  takes  place  in  the  verte- 
brate host,  in  some  manner  yet  to  be  described,  instead  of  in  the  invertebrate. 
The  absence  of  sporogony,  and  of  any  but  the  sexual  phases,  in  the  Lynchia, 
doubtless  explains  the  short  duration  of  the  infectivity  of  the  fly ;  according 
to  Aragao,  if  the  flies  are  fed  for  three  days  011  clean  pigeons,  they  cease  to  be 
infective.  Some  of  the  stages  in  the  lung  show  a  certain  resemblance  to  the 
sporogony  of  the  malarial  parasites,  especially  the  formation  of  sporoblast- 
like  masses,  which,  however,  are  probably  more  comparable  to  the  schizonto- 
cytes  of  Caryotropha  than  to  true  sporoblasts. 


THE  H^MOSPORIDIA 


369 


Labbe  described  for  halteridium  a  process  of  multiplication  in  the  red 
corpuscle  which  has  never  been  confirmed.  He  stated  that  the  nucleus  of 
the  parasite  divided  into  a  number  of  small  nuclei  placed  at  the  two  ends  of 
the  halter-shaped  body,  which  then  divided  up  into  two  bunches  of  small 
merozoites.  It  is,  of  course,  possible  that  the  development  may  differ 
in  different  species.  But  it  is  more  probable  that  the  supposed  nuclei  at 
the  ends  of  the  body  are  merely  metachromatinic  grains,  possibly  the 
"  alkaliphilous  "  granules  described  by  Mayer  (685,  p.  23-4). 

3.  The  Leucocytozoa. — The  true  leucocytozoa — that  is  to  say, 
the  species  of  the  genus  Leucocijtozoon  of  Danilewsky — are  only 
known  to  occur  in  the  blood  of  birds,  as  stated  above  ;  they  must  be 


FIG.  158. — Leucocytozoon  ziemanni  from  the  blood  of  the  Little  Owl,  Athene  noctua. 
A,  Male,  B,  female,  0,  young  form.  N.,  N.,  nucleus  of  the  parasite  ;  N1,  N1, 
nucleus  of  the  host -cell.  Original ;  magnification  2,000. 

distinguished  clearly  from  the  pseudo-leucocytozoa  of  mammals, 
which  are  in  reality  hsemogregarines,  and  will  be  dealt  with  as  such 
below.  The  leucocytozoa  of  birds  are  found  in  the  blood  as  bodies 
usually  elongated  and  spindle-shaped,  sometimes,  however,  rounded 
in  form,  which  represent  each  a  gametocyte,  male  or  female,  con- 
tained in  its  host-cell  (Fig.  158).  The  exact  composition  of  these 
bodies  is,  however,  a  little  doubtful ;  it  is  not  quite  certain  where 
the  host-cell  ends  and  the  parasite  begins.  The  centre  of  the  body 

24 


370  THE  PROTOZOA 

is  occupied  by  an  oval,  compact  mass  of  cytoplasm  containing  a 
nucleus.  By  some  this  mass  is  regarded  as  the  whole  parasite,  by 
others  as  its  endoplasmic  region  alone.  In  the  female  forms  the 
cytoplasm  is  dense  and  stains  deeply,  and  the  nucleus  is  relatively 
small,  with  a  distinct  karyosome  sometimes  placed  eccentrically. 
In  the  male  forms  the  cytoplasm  is  paler,  and  the  much  larger 
nucleus  stains  feebly,  with  a  diffuse  granular  structure  and  with- 
out a  conspicuous  karyosome.  Stretched  along  one  side  of  the 
body  of  the  parasite  is  the  nucleus  of  the  host-cell,  compressed, 
usually  more  or  less  drawn  out,  and  staining  deeply.  The  surface 
of  the  body  is  covered  by  a  thin  membrane,  which  is  prolonged 
usually  into  two  horn-like  processes  at  the  two  poles  of  the  body. 
It  is  doubtful  whether  these  two  processes  consist  solely  of  the 
substance  of  the  host-cell,  or  whether  they  contain  ectoplasmic 
extensions  of  the  parasite  also.  In  any  case  it  is  certain  that  the 
parasite  modifies  the  host-cell  in  a  singular  manner.  It  is  also 
disputed  whether  the  host-cell  itself  is  an  erythroblast  or  a  mono- 
nuclear  leucocyte.  Most  recent  investigators,  however,  incline 
to  the  latter  view  ;  but  Keysselitz  and  Mayer  (A.P.K.,  xvi.,  p.  237) 
state  that  the  host-cell  is  an  erythroblast.  No  melanin-pigment  is 
formed. 

The  young  forms  of  the  parasite  are  compact,  rounded,  or 
haemogregariiie-like,  contained  in  white  cells  with  a  large  nucleus, 
and  without  the  horn-like  processes  characteristic  of  the  adult. 
Faiitharn  (689)  has  described  in  L.  lovati  of  the  grouse  multiplica- 
tion by  schizogony  taking  place  in  the  spleen.  The  schizonts  pro- 
duce a  number  of  merozoites  which  escape  into  the  blood,  and 
doubtless  give  rise  to  the  young  forms  of  the  leucocytozoa.  The 
periodicity  of  the  sexual  forms  in  the  blood  observed  by  Mathis 
and  Leger  (473)  depends,  probably,  on  successive  schrzogonous 
generations  occurring  in  the  internal  organs,  such  as  Fantham  has 
described. 

The  method  of  transmission  and  the  invertebrate  host  are  as  yet 
unknown.  If  blood  containing  the  parasites  in  the  condition  of 
ripe  gametocytes  be  drawn,  the  sexual  phases  and  fertilization  can 
be  studied  without  difficulty  on  the  slide.  The  female  gametocytes 
round  themselves  off,  losing  their  spindle-like  form,  and  burst  their 
envelope.  The  male  gametocytes  contract  themselves  into  two  or 
three  rounded  masses,  which  give  off  about  eight  thread-like 
microgametes  altogether,  in  a  manner  similar  to  the  "  exflagel- 
lation  "  of  the  malarial  parasites.  The  microgametes  become  de- 
tached and  fertilize  a  female. 

Schaudinn  (132)  gave  an  account  of  the  development  of  these  parasites 
which  cannot  be  accepted  as  correct.  According  to  him,  L.  ziemanni  of 
Athene  noctua  is  in  reality  the  resting  stage  of  a  large  trypanosome,  which 


THE  ILEMOSPORIDIA  371 

when  full-grown  attaches  itself  to  an  erythroblast  and  develops  into  the 
leucocytozoon,  losing  its  locomotor  apparatus.  The  large  trypanosomes  in 
question  were  supposed  to  be  the  sexual,  propagative  phases,  male  and 
female,  of  a  very  minute  spirochsete-like  trypanosome,  which  represented  the 
indifferent,  multiplicative  form  of  the  parasite.  The  existence,  however,  of 
young  forms  of  the  leucocytozoon,  no  less  than  the  schizogony  discovered  by 
Fantham,  disprove  entirely  any  such  origin  from  trypanosomes. 

In  correspondence  with  his  ideas  upon  the  nature  and  orgin  of  leucocytozoa, 
Schaudinn  regarded  the  nucleus  of  the  female  forms  (Fig.  158,  B)  as  con- 
sisting of  a  trophonucleus  with  a  kinetonucleus  ("  blepharoplast ")  close 
beside  it ;  while  the  nucleus  of  the  male  leucocytozoon  (Fig.  158,  A)  was  sup- 
posed to  consist  of  a  cluster  of  small  trophonuclei,  each  with  a  small  kiueto- 
nucleus  beside  it,  precocious  division  of  the  two  nuclei  of  the  "  male  trypano- 
some "  being  supposed  to  have  produced  a  number  of  couples  of  nuclei  in  readi- 
ness for  gamete-formation.  These  cytological  interpretations  cannot  be  upheld. 
There  is  nothing  in  the  structure  of  the  nucleus  of  the  male  leucocytozoon  to 
support  the  notion  that  it  is  not  a  single  large  nucleus,  and  the  "  blepharo- 
plast "  of  the  female  form  appears  to  be  simply  the  karyosome,  eccentric  in 
position. 

Schaudinn  also  described  what  he  believed  to  be  the  development  of 
Leucocytozoon  (or,  as  he  named  it,  Spirocliceta)  ziemanni  in  Culex  pipiens. 
According  to  his  account,  the  ookinete  became  an  elongated,  worm-like  body 
which  divided  up  to  produce  an  immense  number  of  spirochsetes,  or  very 
slender  trypanosomes.  The  spirochsetes  were  stated  to  find  their  way  into  the 
Malpighian  tubules,  where  they  multiplied  and  occurred  in  vast  numbers. 
The  spirochsetes,  inoculated  by  the  mosquito  into  the  blood  of  the  owl,  there 
became  the  "  indifferent  form  of  the  leucocytozoon." 

The  statements  of  Schaudinn  with  regard  to  the  development  of  Leucocyto- 
zoon have  received  no  confirmation,  in  spite  of  the  efforts  of  the  Sergent 
brothers  to  find  experimental  proof  for  them.  These  investigators  were 
unable  to  obtain  any  development  of  the  leucocytozoon  in  Culex,  or  to 
transmit  the  parasite  from  owl  to  owl  by  the  agency  of  mosquitoes.  They 
found,  however,  that  mosquitoes  were  commonly  infected  with  spirochaetes 
in  the  Malpighian  tubules,  but  injection  of  these  spirocheetes  into  the  owl 
produced  no  infection  with  Leucocytozoon,  and  there  can  be  no  doubt  that 
the  spirochsetes  in  question  were  true  spirochsetes,  not  connected  in  any  way 
with  either  trypanosomes  or  leucocytozoa.  Mayer  (685)  obtained  only 
ookinetes,  apparently  similar  to  those  of  halteridium,  but  non-pigmented 
and  slightly  larger,  in  mosquitoes  fed  on  owls  infected  with  leucocytozoa,  and 
observed  no  sign  whatever  of  nuclear  multiplication  in  the  ookinetes  ;  Wood- 
cock's unpublished  results  were  practically  the  same  as  those  of  Mayer. 
Mathis  and  Leger(473)  obtained  no  development  of  L.  sabrazesi  in  mosquitoes, 
bugs,  and  leeches,  fed  on  well-infected  fowls,  nor  could  they  bring  about 
transmission  by  means  of  mosquitoes. 

4.  The  Hcemogregarines. — Parasites  of  this  type  have  been 
found  in  the  blood  of  all  classes  of  vertebrates,  and  are  especially 
common  in  cold-blooded  animals,  such  as  fishes  and  reptiles. 
Until  quite  recently,  haemogregarines  were  not  known  to  occur  in 
birds  ;  but  Aragao  (692)  has  described  a  number  of  species  para- 
sitic in  the  leucocytes  of  various  species  of  birds  in  Brazil.  It  is 
a  curious  anomaly  of  the  distribution  of  these  parasites  that, 
while  common  in  marine  fishes,  they  are  not  known  in  fresh- 
water fish,  with  the  sole  exception  of  the  eel.  While  in  other 
classes  they  are  parasitic  in  the  red  corpuscles,  in  mammals  they  are 
parasitic  in  either  the  red  or  the  white  corpuscles,  but  more  com- 


372  THE  PROTOZOA 

monly  in  the  latter  as  the  so-called  "  leucocytozoa,"  not  to  be  con- 
fused with  the  true  leucocytozoa  dealt  with  in  the  last  section. 

Haemogregarines  present  themselves  usually  as  more  or  less 
elongated  parasites  of  quite  definite  form,  sausage-shaped  or  worni- 
like,  not  amoeboid,  lying  within  the  blood-corpuscle.  The  middle 
of  the  body  is  occupied  by  a  conspicuous  nucleus,  and  there  are 
often  numerous  metachromatinic  grains  in  addition,  but  no  melanin- 
pigment  is  produced.  The  parasite  may  be  liberated  from  the 
corpuscle  as  a  free  vermicule,  the  resemblance  of  which  to  a  small 
gregarine  is  accentuated  by  its  active  gliding  movements  ;  liberation 
of  the  vermicules  may  often  be  seen  when  the  blood  is  drawn,  but 
no  "  exflagellation  "  ever  occurs,  since,  as  will  be  seen  when  the 
development  is  described,  the  microgametes  are  formed  in  a  manner 
totally  different  from  that  characteristic  of  the  hsemamoebse. 

In  many  hsemogregarines  the  body  of  the  parasite,  when  lodged 
within  the  blood-corpuscle,  is  enclosed  in  a  distinct  capsule  or  mem- 
brane, which  may  be  of  considerable  thickness,  and  often  stains 
deeply.  When  the  parasite  is  liberated  from  the  corpuscle,  the 
capsule  may  be  left  behind  as  a  conspicuous  enclosure  of  the  cor- 
puscle, which  has  puzzled  some  observers,  and  has  even  been 
described  as  a  distinct  form  of  parasite  (compare  Sambon  and 
Seligmann).  In  H.  bicapsulata  the  capsule  is  thickened  at  the  two 
©extremities  of  the  sausage-shaped  body  to  form  two  caps,  plainly 
visible  in  the  living  condition,  and  staining  a  bright  red  colour  in 
preparations  made  with  the  Romanowsky-stain  (Franca,  712). 

Different  species  of  hsemogregarines  differ  considerably  in  their 
appearance  and  size  relatively  to  the  blood-corpuscle  in  which  they 
are  lodged,  and  distinct  genera  have  been  founded  on  these  differ- 
ences ;  but  as  yet  the  complete  life-cycle  is  known  in  so  few  cases 
that  it  is  not  possible  at  present  to  draw  up  a  classification  of  these 
parasites  that  can  have  any  pretence  to  be  natural. 

The  following  are  the  principal  genera  that  have  been  suggested  for  these 
parasites.  Lankesterella  (Drepanidium)  is  of  very  small  size,  the  full-grown 
vermicule  being  not  more  than  two-thirds  of  the  length  of  the  blood- corpuscle  ; 
type,  L.  ranarum  (minima),  parasitic  in  the  blood- corpuscles  of  the  frog. 
In  Karyolysus  the  parasite  is  about  the  same  length  as  the  corpuscle,  or 
slightly  shorter ;  the  generic  name  is  derived  from  the  action  of  the  parasite 
on  the  nucleus  of  the  host-cell,  which  is  often  broken  up  and  "  karyolysed," 
though  not  invariably.  This  form  of  parasite  is  especially  common  in  Reptilia 
Squarnata,  lizards  and  snakes  ;  type,  K.  lacertarum.  In  the  genus  Hcemo- 
gregarina  (sens,  strict.)  the  full-grown  vermicule  is  much  longer  than  the 
corpuscle,  within  which  it  is  doubled  on  itself  in  the  form  of  the  letter  U, 
with  the  nucleus  situated  at  the  bend ;  type,  H.  stepanou-i  of  European  water- 
tortoises,  Emys  lutaria  and  Cistudo  europcea.  Finally  there  are  the  "  leuco- 
cytozoa "  of  mammals,  for  which  the  generic  names  Hepatozoon,  Miller,  and 
Leucocytogregarina,  Porter,  have  been  proposed ;  if  it  becomes  necessary  to 
separate  them  from  the  genus  Hcemogregarina,  Miller's  name  has  the  priority, 
as  Wenyon  (690)  has  pointed  out.  The  fact,  however,  of  parasitism  in  a  white 


THE  ILEMOSPORIDIA  373 

corpuscle,  instead  of  a  red,  does  not  of  itself  supply  adequate  grounds  for  a 
generic,  or  even  for  a  specific,  distinction,  since  in  some  species — for  example, 
H.  agamce — the  parasites  may  occur  either  in  white  or  red  corpuscles  (Laveran 
and  Pettit).  For  the  present,  therefore,  these  leucocytozoa,  so  called,  may 
remain  in  the  genus Hcemogregar ina,  until  greater  knowledge  of  the  life-histories 
of  hsemogregarines  makes  possible  a  natural  classification  of  these  organisms. 
A  hsemogregarine  of  leucocytic  habitat  has  been  described  also  from  a  frog 
by  Carini  (Rev.  Soc.  Sci.,  Sao  Paulo,  1907,  p.  121). 

As  a  type  of  the  life-cycle  of  the  hfemogregarines  may  be  taken 
H.  stepanowi  (Fig.  159),  which  has  been  studied  by  Reichenow  (78). 
The  chief  points  in  this  author's  account  of  the  life-history  are  con- 
firmed in  essential  details,  but  with  specific  variations,  by  that 
given  by  Robertson  (725)  for  the  life-cycle  of  H.  nicorice.*  In  both 
cases  the  developmental  cycle  in  the  tortoise  comprises  two  forms 
of  schizogony,  the  one  producing  schizonts,  the  other  sporonts  ; 
and  the  invertebrate  host  is  a  leech. 

(1)  The  sporozoite  penetrates  into  a  blood-corpuscle,  and  grows 
into  a  long  vermicule,  which  is  at  first  doubled  on  itself  (Fig.  159,  F). 
The  two  limbs  of  the  U-shaped  body  within  the  corpuscle  fuse 
together  to  produce  a  bean-shaped  parasite — the  macroschizont. 

(2)  The  macroschizont  of  H.  stepanowi,  remaining  within  the 
blood-corpuscle,  goes  through  its  schizogony  in  the  bone-marrow 
of  the  tortoise,  producing  some  thirteen  to  twenty -four  macromero- 
zoites  (Fig.  159,  B,  C).  The  number  produced  is  larger  in  the  earlier 
stages  of  the  infection  than  in  older  infections  (Fig.  159,  D — H}. 
In  H.  nicorice,  however,  the  macroschizont  is  set  free  in  a  capillary 
of  the  lung,  and  there  produces  about  seventy  macromerozoites. 

In  the  account  of  the  schizogony  given  by  Reichenow,  the  significance  of  the 
recurved  vermicules  is  not  clear.  In  drawn  blood  they  can  be  observed  to 
be  set  free  from  the  blood-corpuscles,  and  then,  as  free  vermicules,  to 
exhibit  active  powers  of  movement,  which  indicate  the  existence  of  some  sort 
of  locomotor  apparatus,  probably  of  myonemes.  According  to  Reichenow, 
however,  liberation  from  the  corpuscle  never  occurs  normally  within  the 
body  of  the  tortoise,  but  the  recurved  vermicule  remains  within  the  blood- 
corpuscle  in  which  it  has  grown  up,  and  its  two  limbs  fuse  to  form  the  body 
of  the  bean-shaped  macroschizont.  If  that  is  so,  it  is  difficult  to  xmderstand 
why  the  motile  vermicule  is  ever  developed.  One  is  inclined  to  suspect  that 
it  becomes  free  from  the  corpuscle  in  which  it  has  developed,  and  as  a  "  schizo- 
kinete  "  (Minchin  and  Woodcock,  483)  finds  it  way  as  a  motile  vermicule 
to  the  bone-marrow  (or  lung  in  H.  nicorice),  where  it  penetrates  another 
corpuscle  (or  remains  free  in  a  capillary  vessel,  H.  nicorice)  and  becomes  the 
macroschizont. 

(3)  The   macromerozoites    produced    penetrate   into    blood-cor- 
puscles, and  may  (a)  repeat  the  development  already  described,  and 
become  macroschizonts  again  ;  or  they  may  (b)  develop  into  micro- 
schizonts,    which    produce    micromerozoites    in    small    numbers, 

*  Nothing  in  the  work  of  these  authors  confirms  in  any  way  the  peculiar  account 
of  the  life-history  of  H.  stepanowi  given  by  Hahn,  whose  work  is  criticized  by 
Reichenow. 


374 


THE  PROTOZOA 


FIG.  159. — Life-cycle  of  Hcemogregarina  stepanoivi.  The  figures  to  the  right  of 
the  dotted  line  represent  the  phases  in  the  blood  of  the  tortoise  ;  those  to  the 
left,  the  phases  in  the  leech.  [Continued  at  foot  of  p.  375. 


THE  H^MOSPORIDIA  375 

destined  to  grow  into  gametocytes  (Fig.  159,  J — L).  In  H.  stepanowi 
the  microschizoiit  sporulates  in  the  bone-marrow  or  in  the  circu- 
lating blood,  and  produces  six  micromerozoites.  In  H.  nicorice 
it  sporulates  only  in  the  circulating  blood,  and  produces  six  to 
eight  micromerozoites. 

(4)  The  micromerozoites  penetrate  into  a  blood-corpuscle,  and 
may  (a)  repeat  the  rnicroschizogony,  or  (6)  develop  into  sporonts 
(gametocytes). 

(5)  The  sporonts  (Fig.  159,  Jf1,  If2)  are  sexually  differentiated. 
They  represent  the  end  of  the  development  in  the  tortoise,  and  can 
only  develop  further  in  a  leech.     H.  stepanowi  develops  in  Placob- 
della  catenigera  (=Hcementeria  costata),  H.  nicorice  in  Ozobranchus 
shipley i. 

(6)  When  the  leech  sucks  the  blood  of  an  infected  tortoise,  it 
may  take  up  every  stage  of  the  parasite  into  its  stomach,  where, 
however,  all  stages  are  digested  except  the  sporonts,  which  resist 
digestion  and  pass  on  into  the  intestine.      There  they  associate  in 
couples,  male  and  female  together.     The  male  sporont  produces 
four  microgametes,  and  one  of  the  four  penetrates  the  macrogamete 
and  fertilizes  it  (Fig.  159,  N—  E). 

(1)  The  zygote  forms  an  oocyst  with  a  thin  membrane,  and 
divides  within  it  into  eight  sporozoites  (Fig.  159,  S — U),  which 
pass  into  the  blood-spaces  and  collect  in  the  dorsal  blood-vessel  of 
the  leech.  Hovr  they  pass  from  thence  into  the  tortoise  is 
uncertain. 

The  existence  of  two  types  of  schizogony — macrocysts  producing  macro- 
merozoites,  and  microcysts  producing  micromerozoites — in  the  cycle  of  the  same 
species  of  hfemogregarine,  has  long  been  known,  but  without  the  significance 
of  this  fact  being  understood. 

While  the  life- history  described  above  is  very  probably  typical  of  the  haemo- 
gregarines  of  aquatic  cold-blooded  vertebrates,  where  the  intermediate  host 
is  a  leech,  that  of  terrestrial  animals,  so  far  as  it  is  known,  is  of  a  somewhat 

FIG.  159  continued  : 

A,  Sporozoite  ;  B,  C,  early  schizogony,  in  which  a  large  number  of  mero- 
zoites  are  produced ;  D,  merozoite  penetrating  a  blood-corpuscle ;  E — H, 
later  schizogony,  in  which  few  merozoites  are  produced  ;  in  F  the  recurved 
vermicule  within  the  corpuscle  is  seen  ;  /,  free  merozoite  about  to  penetrate 
a  corpuscle  and  recapitulate  the  stages  D — H ,  or  to  initiate  the  next  phase  ; 
J,  K,  the  stages  of  the  final  schizogonous  generation  which  produces  the 
gametocytes  ;  L1,  L2,  sexually-differentiated  merozoites  of  the  final  generation, 
which  grow  up  into  male  (If1)  or  female  (M 2)  gametocytes  respectively  ;  these 
are  the  stages  which  develop  in  the  leech  when  taken  up  by  it. 

N,  Association  of  male  and  female  gametocytes  in  the  gut  of  the  leech  ; 
0,  formation  of  four  male  gametes  by  the  male  gametocyte  ;  P,  one  of  the 
male  gametes  has  penetrated  into  the  body  of  the  female  gamete,  and  the 
two  pronuclei  are  undergoing  fusion,  with  formation  of  a  fertilization-spindle  ; 
Q,  zygote  with  synkaryon  and  the  degenerating  remains  of  the  male  gameto- 
cyte attached  to  it,  which  is  seen  also  in  the  next  four  stages  ;  R,  8,  T,  succes- 
sive divisions  of  the  synkaryon  ;  U,  ripe  cy^t  containing  eight  sporozoites, 
residual  protoplasm,  and  the  remains  of  the  male  gametes. 

After  Reichenow  (78),  modified  in  arrangement. 


376  THE  PROTOZOA 

different  type.  In  these  cases  the  invertebrate  host  appears  to  be  always 
an  ectoparasitic  arthropod.  The  only  life-cycle  of  such  forms  which  has  been 
described  completely  is  that  of  the  parasite  of  the  leucocytes  of  rats,  which 
has  been  described  by  Miller  under  the  name  Hepatozoon  perniciosum.  This 
parasite  appears  to  be  identical  with  that  named  by  Balfour  (694)  Leucocyto- 
zoon  muris  and  by  Adie  L.  ratti ;  its  correct  name,  therefore,  is  Hcemogregarina 
(Hepatozoon)  muris.  According  to  Miller,  this  parasite  causes  lethal  epidemics 
amongst  tame  rats,  but  in  London  it  occurs  commonly  in  the  blood  of  wild 
sewer-rats,  and  appears  to  be  quite  harmless  to  them.  It  is  a  parasite  of  world- 
wide distribution,  apparently,  having  been  recorded  from  rats  in  the  Punjaub 
(Adie),  Khartoum  (Balfour),  North  America  (Miller),  Brazil  (Carini),  and  various 
other  parts  of  the  world  (see  Franca  and  Pinto,  A.I.B.C.P.,  iii.,  p.  207). 

The  life-cycle  of  H.  muris,  according  to  Miller,  is  in  the  main  as  follows: 
The  sporozoites  are  liberated  in  the  intestine  of  the  rat,  and  pass  through  the 
wall  of  the  gut  into  the  blood-stream  ;  they  may  be  found  in  the  circulation 
twenty-four  hours  after  infection.  Ultimately  the  sporozoites  reach  the 
liver  and  penetrate  into  liver-cells  ;  in  this  situation  they  grow  into  schizonts, 
which  when  full-grown  sporulate  to  produce  some  twelve  to  twenty,  usually 
about  sixteen,  merozoites.  The  merozoites  may  penetrate  into  liver-cells 
again  and  repeat  the  schizogony,  or  they  may  pass  out  into  the  capillaries 
of  the  liver ;  in  the  latter  event  they  are  taken  up  by  leucocytes,  doubtless 
as  an  act  of  phagocytosis.  The  merozoites  are  able,  however,  to  resist  any 
digestive  action  of  the  leucocytes  ;  they  become  encapsuled  in  the  leucocytes, 
and  in  this  state  they  are  carried  into  the  general  circulation.  They  do  not 
increase  in  size  in  the  leucocytes,  and  their  further  development,  so  far  as  the 
rat  is  concerned,  is  at  an  end.  Hence  the  "  leucocytozoon  "  of  the  rat  is  an 
encapsuled  merozoite  of  a  hremogregarine  which,  strictly  speaking,  is  a  para- 
site of  the  rat's  liver,  and  not  of  the  blood  at  all ;  in  the  leucocytes  its  role  is 
one  merely  of  passive  resistance.  These  merozoites  represent  at  the  same  time 
the  sporonts,  the  propagative  phase  which  develops  further  in  the  inverte- 
brate host,  in  this  case  a  rat-mite,  Lcelaps  ecliidninus,  which  sucks  the  rat's 
blood,  and  so  takes  up  the  parasite  into  its  stomach. 

In  the  stomach  of  the  mite  the  haemogregarines  are  set  free  as  motile  vermi- 
cules  which  associate  in  couples.  According  to  Miller,  this  association  is  a 
true  copulation  of  two  gametes  which  fuse  into  a  zygote  ;  from  the  analogy 
of  the  life-cycle  described  above,  it  is  more  likely  that  some  stages  have  been 
overlooked,  and  that  the  verniicules  are  gametocytes  which  associate,  with 
subsequent  production  of  gametes  by  the  male  and  fertilization  of  the  female 
by  a  microgamete. 

The  zygote,  however  formed,  becomes  a  motile  ookinete  which  passes 
through  the  wall  of  the  gut  into  the  body-cavity  of  the  mite,  and  there  forms 
an  oocyst  which,  like  that  of  the  malarial  parasites,  has  a  thin  wall,  permitting 
the  parasite  to  absorb  nourishment  from  the  surrounding  tissues  and  to  grow 
to  a  large  size.  When  full-grown,  the  contents  of  the  oocyst  divide  up  into  a 
large  number  of  sporoblasts,  each  of  which  becomes  surrounded  by  a  delicate 
sporocyst.  The  contents  of  the  spore  divide  up  into  some  twelve  to  twenty 
sporozoites,  and  then  the  development  of  the  parasite  is  at  an  end  <so  far  as 
the  mite  is  concerned.  The  cyst  and  spores  are  the  propagative  phase,  and 
in  order  that  they  may  develop  the  mite  must  be  eaten  by  a  rat ;  if  this  occurs, 
the  sporozoites  are  liberated  in  the  stomach  and  the  cycle  is  complete. 

In  the  case  of  other  mammalian  haemogregarines,  fragments  of  the  develop- 
ment are  known  which  indicate  a  life-cycle  similar  in  the  main  to  that  of 
H.  muris,  allowing  for  specific  differences.  Forms  parasitic  in  the  red  blood- 
corpuscles  are  H.  gerbilli  of  Gerbillus  indicus  (Christophers,  699)  ;  H.  balfouri 
(jaculi)  of  the  jerboa  (Balfour,  693) ;  and  the  three  species  recently  described 
by  Welsh  and  others  (Journ.  Path.  Bact.,  xiv.)  from  marsupials,  one  of  which 
(H.  peramelis)  is  remarkable  for  having  been  found  only  in  the  free,  extra- 
corpuscular  condition.  The  schizogony  of  H.  gerbiUi  has  not  been  described, 
but  that  of  H.  jaciili  takes  place  in  the  liver,  and  is  of  two  types,  producing 
in  the  one  case  a  large  number  of  small  merozoites,  in  the  other  a  small 


THE  ILEMOSPORIDIA  377 

number  of  large  merozoites  (compare  H.  cam's,  below).  In  both  H.  gerbilli 
and  H.  jaculi  free  vermicules  occur,  and  are  set  free  readily  in  vitro  ;  those  of 
H.  gerbilli  are  recurved  when  contained  in  the  blood-corpuscle.  Stages  of 
the  development  of  H.  gerbilli  were  found  in  a  louse,  Hcematopinus  stephensi  ; 
first  free  vermicules  in  the  stomach  and  intestine,  later  large  cysts  in  the 
body-cavity  containing  a  great  number  of  spores,  each  of  which  encloses 
six  to  eight  sporozoites.  It  seems  impossible  that  the  parasites  encysted  in 
the  body- cavity  of  the  louse  should  get  back  into  the  gerbille  in  any  other 
way  than  that  of  being  eaten  by  the  gerbille.  Christophers  found  that,  though 
the  sporozoites  were  liberated  in  the  intestinal  juice  of  the  gerbille,  they  soon 
•died  in  it,  but  that  in  the  blood- plasma  of  the  gerbille  they  became  extremely 
active  ;  this  observation  may  perhaps  be  interpreted  as  indicating  that  the 
spores  germinate  in  the  intestine,  and  the  sporozoites,  when  liberated,  pass  at 
once  through  the  wall  of  the  intestine  into  the  blood- circulation. 

The  crithidial  forms  seen  by  Balfour  in  Pulex  deopatrce  can  have  no  connec- 
tion whatever  with  the  haemogregarine  of  the  jerboa  ;  the  flea  is  probably  not 
the  right  host  for  this  parasite. 

A  number  of  leucocytic  gregarines  have  been  described  from  various  mam- 
mals, amongst  which  may  be  mentioned  H.  canis  (Christophers,  700),  H. 
funambuli  (Patton,  721),  and  H.  musculi  (Porter).  The  life-cycle  of  H.  canis 
has  been  described  by  Wenyon  (84).  The  schizogony  takes  place  in  the  bone- 
marrow  and  the  spleen  of  the  dog,  and  is  of  two  distinct  types.  In  the  one 
case  the  schizont  divides  into  a  small  number  of  merozoites,  usually  three, 
•of  large  size.  In  the  second  case  the  schizogony  results  in  the  production  of 
a  large  number  of  small  merozoites.  The  larger  merozoites  grow  up  into 
schizonts  again  ;  the  small  merozoites  pass  into  the  blood,  are  taken  up  by 
the  leucocytes,  and  become  the  garnetocytes,  as  in  H.  muris.  The  sporogony 
takes  place  in  the  tick,  Ehipicephalus  sanguineus,  and  is  similar  throughout 
to  that  of  H.  muris.  The  sexual  phases  were  not  observed  by  Wenyon,  but 
according  to  Christophers  (701)  the  vermicules  become  free  in  the  stomach, 
and  penetrate  the  epithelial  cells,  in  which  they  multiply  by  fission  to  form 
gametes  ;  probably  this  applies  to  the  male  sex  alone.  The  next  stage  is  an 
oocyst  in  the  tissues  of  the  tick.  The  oocyst  grows  in  size,  its  nuclei  multiply, 
some  thirty  to  fifty  uninucleate  sporoblasts  are  formed,  and  each  secretes 
a  sporocyst  and  becomes  a  spore  containing  on  the  average  sixteen  sporozoites. 
The  oocyst-wall  dissolves,  and  the  ripe  spores  are  set  free  in  the  body  of  the  tick. 
Wenyon  considers  it  possible  that  the  dog  acquires  the  infection  by  eating 
infected  ticks. 

Free  vermicules  of  H.  funambuli  were  seen  in  a  louse  by  Patton,  and  a  similar 
observation  was  made  for  H.  musculi  by  Porter.  H.  musculi  also  reproduces 
by  schizogony  in  the  bone-marrow  of  its  host. 

The  hsemogregarines  of  birds  described  by  Aragao  (692)  appear  to  be  very 
similar  to  those  parasitic  in  the  leucocytes  of  mammals.  The  schizogony 
takes  place  in  the  epithelial  cells  of  the  gut  or  in  the  cells  of  the  liver,  lung,  or 
bone-marrow ;  it  results  in  the  formation  of  a  number  of  small,  comma- 
shaped  merozoites,  which  escape  from  the  cell  and  are  taken  up  by  the  mono- 
nuclear  leucocytes.  They  do  not,  however,  remain  in  a  resting  phase  in  the 
leucocytes,  but  grow  within  them  to  a  fair  size.  When  set  free  from  the 
leucocyte,  they  perform  active  movements.  The  intermediate  host  and  the 
mode  of  transmission  remain,  however,  to  be  discovered. 

The  schizogony  of  hsemogregarines  parasitic  in  snakes  has  been  studied 
by  Sambon  and  Seligmann,  Hartmann  and  Chagas  (89),  and  Laveran  and 
Pettit  (716).  It  takes  place  in  the  capillaries  of  the  liver  and  lung  or  in  the 
bone-marrow.  The  parasite  becomes  free  from  the  corpuscle  in  the  capillary, 
and  grows  to  a  large  size.  In  H.  sebai  the  number  of  merozoites  formed 
varies  from  two  or  four  to  over  thirty,  but  is  more  often  from  four  to  eight. 
The  merozoites  are  larger  when  a  smaller  number  is  produced.  Possibly  the 
variation  is  related  to  the  age  of  the  infection,  as  in  H.  stepanowi,  or  to  the  destiny 
•of  the  merozoites,  whether  to  become  schizonts  or  gametocytes,  as  in  H.  canis. 
The  sporogony  of  the  hasrnogregarines  of  terrestrial  reptiles  is  practically 


378  THE  PROTOZOA 

unknown  in  its  details,  but  the  transmission  appears  to  be  effected  by  ticks  ; 
so  Karyolyms  lacertarum  by  Ixodes  ricinus  (Schaudinn,  A.P.K.,  ii.,  p.  339, 
footnote),  H.  mauritanica  by  Hyalomma  cegyptium  (Laveran  and  Pettit, 
718),  and  the  hpemogregarines  of  snakes  (Flu,  707). 

The  minute  "  drepanidia  "  of  frogs  and  newts  appear  to  stand  rather  apart 
from  the  true  hcemogregarines  ;  beyond  the  fact  that  they  multiply  by 
schizogony  in  the  red  blood-corpuscles,  but  little  is  known  of  their  develop- 
ment. According  to  Hintze,  Lankesterella  ranarum  has  no  invertebrate  host, 
but  passes  from  the  blood  into  the  wall  of  the  intestine,  where  it  forms  re- 
sistant cysts  like  a  coccidian  parasite.  The  cysts  were  believed  to  pass  out 
of  the  frog  with  the  fseces  and  infect  other  frogs  by  the  direct  contaminative 
method.  It  is,  however,  very  doubtful  if  the  cysts  described  by  Hintze  really 
belong  to  the  cycle  of  the  Lankesterella  ;  from  other  observations  it  is  possible 
that  the  drepanidia  are  not  hsemogregarines  at  all,  but  stages  in  the  life-cycle 
of  a  trypanosome  (compare  Billet,  696).  According  to  Franca  (709),  "  Dacty- 
losoma  "  splendens  of  the  frog  produces  LeisJimania-like  merozoites,  with 
distinct  kinetonuclei  (compare  also  Seitz).  Until  further  researches  have 
been  undertaken,  the  position  of  the  drepanidia  must  remain  uncertain. 

Neresheimer  (720)  has  described  the  penetration  of  the  red  blood- corpuscles 
of  frogs  by  Lankesterella  sp.,  a  process  in  which  remarkable  phenomena  are 
exhibited.  When  a  Lankesterella,  in  approaching  a  blood- corpuscle,  is  within 
a  distance  from  the  corpuscle  about  equal  to  the  length  of  the  parasite,  the 
edge  of  the  corpuscle  turned  towards  the  parasite  shows  distinct  amoeboid 
movements.  As  the  parasite  comes  still  nearer,  two  long  processes  are 
thrown  out  by  the  corpuscle,  forming  a  deep  bay,  into  which  the  parasite  enters ; 
as  soon  as  it  does  so,  the  two  processes  approach  each  other,  fuse  and  engulf 
the  parasite,  just  as  an  amoeba  ingests  its  prey.  The  parasite,  after  this  point 
is  reached,  appears  to  be  drawn  into  the  corpuscle  without  further  exertion 
on  its  part ;  the  protoplasm  of  the  corpuscle  closes  up  behind  it,  and  the 
corpuscle  regains  its  normal  smooth  contour,  with  the  parasite  lying  within 
it.  The  whole  process  of  penetration  takes  one  or  two  minutes.  Neresheimer 
compares  the  activity  of  the  corpuscle  to  the  "  cone  of  reception  "  formed 
by  an  ovum  when  approached  by  a  spermatozoon. 

From  the  foregoing  account  of  the  life-cycles  of  hfemogregarines,  it  is  seen 
that  the  sporogoiiy  varies  greatly,  from  the  production  of  eight  sporozoites 
in  the  ob'cyst  of  H.  stepanoivi  and  H.  nicorice,  to  the  condition  of  H.  cam's, 
H.  muris,  and  H.  gerbiJU,  in  which  a  large  number  of  spores  are  formed  with  a 
variable  number  of  sporozoites.  It  is  impossible,  therefore,  to  accept  as 
adequate  the  diagnosis  given  by  Leger  (644)  of  the  "  Hcemogregarinidce  "  as 
producing  a  single  octozoic  spore  (see  p.  353,  supra). 

5.  The  Piroplasms. — The  parasites  of  this  type  are  minute 
organisms,  capable  of  amoeboid  movement,  but  generally  of  a 
definite  form,  which  is  usually  pear-shaped  or  rod-like.  They  are 
contained,  sometimes  as  many  as  a  dozen  or  more  together,  within 
a  mammalian  red  blood-corpuscle.  They  produce  no  pigment,  but 
destroy  the  corpuscle  in  which  they  are  contained,  and  set  free  the 
haemoglobin,  which  is  then  excreted  by  the  kidneys  of  the  host.  In 
consequence  of  this,  the  diseases  produced  by  these  parasites, 
termed  generally  "  piroplasnioses  "  (or  "  babesioses  "),  are  of  a  very 
characteristic  type,  the  most  striking  symptoms  being  an  enormous 
destruction  of  blood-corpuscles  and  a  red  coloration  of  the  urine 
by  haemoglobin  (haemoglobinuria).  From  this  peculiarity  are 
derived  popular  names,  such  as  '  redwater,"  etc.,  applied  to 
diseases  caused  by  piroplasms. 


THE  MMOSPORIDIA 

The  best-known  member  of  this  group  of  organisms  is  a  parasite 
of  the  blood  of  cattle  (Fig.  160),  which  has  been  most  unfortunate 
in  its  nomenclature,  and  has  appeared  under  a  variety  of  generic 
names  (Hcematococcus,  Pyrosoma,  Apiosoma,  Piroplasma),  but  of 
which  the  correct  name  is  probably  Babesia  bovis  (or  bigemina). 
The  typical  form  of  this  parasite  is  a  pear-shaped  body  within  the 
blood-corpuscle.  It  multiplies  by  binary  fission,  and  is  often 
double  in  consequence — whence  the  specific  name  bigemina. 

Many  other  species  are  now  known,  parasites  of  domestic  animals  in 
various  parts  of  the  world,  and  of  recent  years  a  number  of  species  hav& 
been  made  known  from  wild  animals,  but  our  knowledge  of  piroplasms 
in  a  natural  state  is  not  very  extensive.  No  species  is  known  with 
certainty  to  be  parasitic  upon  human  beings,  but  a  disease  known 
as  "  spotted  fever  of  the  Rocky  Mountains  "  has  been  stated  to  be 
caused  by  Piroplasma  hominis,  and  it  is  possible  that  the  organisms 


FIG.  160. — Piroplasma  bigeminum  (Babesia  bovis)  in  the  blood-corpuscles  of  the 
ox.  a,  b,  Youngest  forms;  c — /,  binary  fission;  g — /,  various  forms  of 
the  twin  parasites  ;  k,  I,  doubly-infected  corpuscles.  After  Laveran  and 
Nicolle. 

described  from  the  blood  of  yellow  fever  patients  by  Seideliii  (757), 
and  named  by  him  Paraplasma  ftavigenum,  may  be  allied  to 
the  piroplasms. 

The  investigations  upon  these  organisms  carried  on  during  the 
last  few  years  have  led  to  their  being  divided  up  into  a  number  of 
genera  based  on  differences  of  form  and  structure.  The  following 
enumeration  of  the  genera  of  "  Piroplasmidse  "  may  serve  at  the 
same  time  to  indicate  the  structural  varieties  exhibited  by  these 
parasites  (compare  Fraii9a,  736). 

(1)  Piroplasma,  Patton  (Babesia,  Starcovici). — Pear-shaped  forms, 
dividing  by  a  process  of  gemmation — hence  commonly  found  in 
pairs  in  the  corpuscle.     Species  are  known  from  oxen,  sheep,  horses 
(P.  caballi  of  "  biliary  fever  "),  dogs,  monkeys,  rats,  and  various 
wild  animals. 

(2)  Theileria,  Bettencourt,  Franga  and  Borges. — Bacilliform  or 
rod-shaped   parasites    arranged    in    a    characteristic    figure   of    a 


380  THE  PROTOZOA 

cross.*  T.  parva  is  the  parasite  of  "  East  Coast  fever  "  of  cattle  in 
Africa.  Other  species  have  been  described  from  the  fallow-deer  and 
from  Cephalolophus  grimmi. 

(3)  Nicollia,  Nuttall. — Oval  or  pear-shaped  parasites  with  peculiar 
iiuclear  structure  (see  below),  and  with  quadruple  division,  pro- 
ducing a  figure  at  first  like  a  fan,  then  like  a  four-leaved  clover. 
One    species,    N.    quadrigemina,    from    the    gondi,    Ctenodactylus 
(Nicolle,  746). 

(4)  Nuttallia,  Franca. — Parasites  oval  or  pear-shaped  (not  rod- 
shaped)  ;   multiplication-forms  like   a   cross.     N.   equi,    of   equine 
piroplasmosis  ;  N.  herpestidis,  of  a  mongoose  (Herpestes  ichneumon). 

(5)  Smithia,  Fran§a. — Pear-shaped  forms,  occupying  the  whole 
diameter  of  the  corpuscle,  not  in  pairs  ;  quadruple  multiplication 
in  the  figure  of  a  cross.     S.  microti  from  Microtus  arvalis. 

Future  research  will,  no  doubt,  determine  the  value  of  these 
generic  distinctions,  some  of  which  seem  to  rest  upon  a  somewhat 
slender  foundation. 

As  is  evident  from  the  foregoing  classification,  the  form  of  the  para- 
site varies  considerably  in  different  species,  and  even  in  the  same 
species.  In  many  cases  the  body  may  show  amoeboid  changes  of 
shape,  and  may  throw  out  long  pseudopodial  processes.  The  two 
principal  types  of  form  of  the  full-grown  parasite  are  the  pear- 
shaped  and  the  bacillary  forms  ;  but  the  smaller  parasites  may  be 
ring-like,  with  the  nucleus  excentric,  and  placed  near  the  margin 
of  the  body  in  some  cases.  The  relation  of  these  forms  to  one 
another,  and  their  significance  in  the  life-cycle,  are  not  clear,  but  the 
annular  forms  appear  to  be  young  stages  of  either  the  pear-shaped 
•or  bacillary  forms.  Kinoshita  claims  to  be  able  to  distinguish 
indifferent  (schizonts)  from  sexually-differentiated  forms  (sporonts) 
(compare  Theileria,  p.  382,  infra}. 

The  minute  structure  of  the  body  is  very  simple,  since  the  cyto- 
plasm has  as  a  rule  no  enclosures  except  the  nucleus,  which  is 
.single.  In  some  cases,  however,  the  cytoplasm  may  be  vacuolated 
to  some  extent,  and  in  the  ring-like  forms  has  a  large  central 
vacuole.  The  nucleus  itself  appears  to  be  of  a  simple  type  of 

*  A  confusion  has  arisen  between  two  parasites  very  similar  as  regards  the 
appearances  they  present  in  the  blood,  but  differing  in  every  other  respect — namely, 
Theileria  parva,  the  true  parasite  of  "  East  Coast  fever  "  of  cattle,  and  Babesia 
(Piroplasma)  mutans,  also  found  in  cattle.  In  both  parasites  alike  the  charac- 
teristic cross-forms  appear  in  the  blood.  In  Theileria  parva,  however,  the  cross- 
forms  are  an  aggregation  of  four  distinct  gametocytes  (see  p.  382,  infra)  which 
have  invaded  the  same  corpuscles,  while  in  Babesia  mutans  the  cross-forms  are 
produced  by  quadruple  fission  of  an  ordinary  multiplicative  individual ;  this 
•difference  has  the  consequence  that,  since  the  gametocytes  of  T.  parva  are  not 
capable  of  further  development  in  the  blood  of  the  ox,  direct  inoculation  of  blood 
from  an  infected  to  a  healthy  ox  does  not  produce  an  infection  in  the  latter,  as 
happens  always  when  a  healthy  ox  is  inoculated  with  blood  containing  Babesia 
mutans.  The  diagnosis  of  the  genus  Theileria  given  by  Franca  would  appear  to 
apply  to  B.  mutans  rather  than  to  T.  parva.  See  especially  Gonder  (739). 


THE  ILEMOSPORIDIA  381 

structure,  a  compact  mass  of  chromatin  or  karyosome  contained 
in  a  vacuole-like  space — in  other  words,  a  protokaryon  of  the  simplest 
type  (compare  Breinl  and  Kindle,  730).  The  remarkable  form 
Nicollia  quadrigemina  has  an  oval  nucleus  at  the  blunt  end  of  the 
body,  with  two  karyosomes,  a  larger  one  placed  close  to  the  surface, 
and  a  smaller  one  nearly  at  the  centre  of  the  pear-shaped  body 
(Nicolle,  746). 

With  the  unreliable  method  so  much  in  vogue  until  quite  recently,  of 
making  preparations  by  drying  blood-smears  and  staining  them  with  the 
Ronianowsky  stain,  the  nucleus  may  show  various  appearances  about  which 
much  has  been  written,  and  which  cannot  be  interpreted  with  certainty  until 
they  have  been  examined  by  better  cytological  methods.  In  such  prepara- 
tions the  appearance  is  usually  presented  of  a  deeply-stained  karyosome 
lying  at  the  edge  of,  or  near  to,  a  diffuse,  more  or  less  irregular  chroniatin- 
mass  ;  or  the  nucleus  as  a  whole  may  appear  as  an  evenly-stained  mass  lying 
usually  at  one  end  of  the  body  in  bacillary  forms,  or  near  the  rounded  ex- 
tremity in  the  pear-shaped  forms.  In  other  cases,  in  addition  to  the  principal 
clironiatinic  mass,  some  specimens  may  exhibit  a  grain  or  dot,  which  from  its 
staining  reactions  appears  to  be  chromatin.  Many  efforts  have  been  made 
to  establish  on  this  slender  basis  a  theory  of  nuclear  dimorphism  for  piro- 
plasms,  and  to  interpret  the  second  grain  as  a  kinetonucleus  ;  but  it  bears  no 
resemblance  to  any  such  body  in  its  structural  and  cytological  relations,  and  is 
inconstant  in  its  occurrence,  being  entirely  absent  as  a  general  rule. 

A  question  much  discussed  is  that  of  the  occurrence  of  flagellated  forms  of 
piroplasms  in  the  blood  of  the  vertebrate  host.  In  a  few  rare  cases,  in  parasites 
preserved  by  the  defective  method  mentioned  in  the  last  paragraph,  irregular 
streaks  of  substance  similar  to  chromatin  in  its  staining  properties  have  been 
seen  extending  from  the  karyosome  even  some  way  be3Tond  the  body  of  the 
parasite  (Fantham,  735;  Kinoshita,  741),  and  these  appearances  have  been 
interpreted  as  flagella  ;  but  the  published  figures  of  these  structures  do  not 
in  the  least  favour  any  such  interpretation.  Kinoshita  suggests  that  the 
"  flagella  "  figured  by  him  may  represent  formation  of  microgametes.  Of 
more  value  are  the  observations  of  Nuttall  and  Graham-Smith  (748)  on  the 
living  parasites.  They  observed  that  a  pear-shaped  parasite,  when  free  in 
the  blood- plasma,  is  capable  of  moving  very  rapidly,  with  the  blunt  end 
forwards,  while  the  posterior  pointed  end  exhibits  active  vibrations  which  they 
compare  to  those  of  a  fish's  tail.  In  some  cases  the  hinder  end  was  observed 
to  be  prolonged  into  a  flagellum-like  process.  The  authors  cited  explain  the 
absence  of  flagellated  forms  in  permanent  blood- preparations  by  supposing  that 
the  flagellum  becomes  retracted  when  preserved ;  if  so,  it  is  a  structure  of  a 
very  different  kind  to  a  true  flagellum,  such  as  that  of  a  trypanosome,  and  its 
relations  to  the  progression  of  the  parasite  also  differ. 

Breinl  and  Hindle  (730)  have  figured  biflagellate  organisms  from  the  blood 
of  dogs  dying  from  piroplasrnosis.  The  flagellates  in  question  were  of  transi- 
tory appearance,  and  were  only  found  in  the  blood  of  the  dog  the  day  before 
its  death.  The  authors  interpret  these  forms  as  a  phase  of  the  piroplasni ; 
but  a  consideration  of  the  figures  given,  and  of  the  circumstances  under  which 
the  flagellates  were  found,  leave  hardly  any  doubt  but  that  the  forms  seen 
were  intestinal  flagellates,  Bodo  or  Prowazekia  sp.,  which,  in  the  pathological 
condition  of  the  host,  had  passed  into  the  blood  (see  p.  258). 

The  development  of  the  parasite  in  the  vertebrate  host  appears 
to  consist  solely  of  multiplication  by  fission  (Figs.  160,  161),  usually 
either  binary  or  quadruple,  within  the  corpuscle ;  though  the 
presence  of  the  annular  forms,  apparently  representing  young 


382  THE  PROTOZOA 

individuals,  would  seem  to  indicate  the  existence  of  some  form  of 
schizogony,  yet  to  be  discovered,  in  the  tissues  or  internal  organs 
of  the  body.  When  the  parasite  or  parasites  have  destroyed  the 
corpuscle  in  which  they  are  lodged,  they  are  set  free  in  the  blood- 
plasma  and  penetrate  other  red  corpuscles. 

Theileria  parva  stands  apart  from  other  piroplasms  in  its  developmental 
cycle  in  the  vertebrate  host.  According  to  Gonder  (738,  740),  the  minute 
sporozoites  injected  by  the  tick  collect  in  the  spleen  and  lymphatic  glands, 
where  they  penetrate  into  lymphocytes,  in  which  they  grow  rapidly.  The 
originally  single  nucleus  divides  repeatedly,  and  large  multinucleate  plasmo- 
dial  masses  are  formed  which  finally  divide  up  into  as  many  minute  mero- 
zoites,  "  agamonts,"  as  there  are  nuclei ;  the  process  recalls  strongly  the 
schizogony  of  Hcemoproteus  columbce  (Fig.  157,  K — R),  and  leads  to  the  break- 
up of  the  lymphocyte.  The  first  schizogonous  generation  may  be  repeated 
several  times,  but  at  last  a  generation  of  "  garnonts  "  is  produced,  which 
•are  distinguished  from  the  agamonts  by  characteristic  differences  in  the 
nuclear  structure.  The  gamonts  multiply  by  a  process  of  schizogony,  the 
final  or  "  gamogenous  "  generation,  ending  in  the  production  of  gametocytes, 
minute  parasites  which  do  not  multiply  further,  but  penetrate  into  the  red 
blood-corpuscles,  where  they  grow  into  adult  gametocytes  of  two  kinds — male 
gametocytes,  which  are  long,  slender,  "  bacillary  "  forms ;  and  female  gameto- 
cytes, which  are  plump,  rounded,  or  pear-shaped  forms.  The  gametocytes 
can  only  develop  further  in  the  tick  Ehipicephalus  (see  below). 

The  forms  found  in  the  red  corpuscles  in  the  peripheral  blood  are  either 
gamonts  or  gametocytes,  incapable  of  developing  beyond  the  latter  stage 
except  in  the  tick ;  this  explains  a  peculiarity  of  this  parasite,  namely,  that 
inoculation  of  infected  blood  into  a  healthy  animal  does  not  produce  an 
infection. 

The  position  of  the  genus  Achromaticus,  founded  by  Dionisi  for  A.  vesperu- 
ginis,  parasitic  in  the  blood  of  bats  of  the  genus  Vesperugo,  is  still  doubtful. 
It  occurs  under  a  number  of  different  forms,  some  free  in  the  blood-plasma ; 
others,  more  common,  within  the  corpuscles.  The  free  forms  are  rounded  or 
spindle-shaped  ;  the  intracorpuscular  parasites  may  be  also  of  these  two 
forms,  but  are  more  often  pear-shaped.  Within  the  corpuscles  the  rounded 
and  pear-shaped  forms  divide  into  two  or  four  by  a  process  of  schizogony. 
According  to  Gonder  (737),  the  parasite  has  a  double  nucleus  in  all  stages, 
but  this  is  not  confirmed  by  Yakirnoff  and  Co.  (753),  who  regard  the  parasite 
as  a  true  Piroplasma.  Neumann  (745)  states  that  in  the  bat-mite  (Pteroptus 
vespertilionis)  the  parasites  undergo  a  transformation  into  flagellated  organisms, 
and  considers  Achromaticus  allied  to  trypanosomes.  It  is  not  improbable 
that  stages  of  Achromaticus,  both  in  the  vertebrate  and  invertebrate  hosts, 
have  been  confused  with  stages  of  the  trypanosome  found  in  the  blood  of  the 
same  vertebrate  hosts. 

The  process  of  division  in  Piroplasma  canis  (Fig.  161)  has  been  studied  in 
great  detail  by  Nuttall  and  Graham-Smith  (748),  and  by  Christophers  (732). 
The  small  rounded  forms  divide  by  simple  binary  fission  of  the  ordinary  type. 
In  the  larger  forms  the  division  takes  place  in  a  peculiar  manner,  more  akin 
to  gemmation  than  to  ordinary  fission.  Before  division  the  parasites  become 
amoeboid  and  irregular  in  form,  and  the  nucleus  has  the  form  of  a  compact 
mass.  The  nucleus  then  sends  out  two  buds  which  grow  towards  the  surface 
of  the  body,  and  at  this  point  two  protoplasmic  buds  grow  out  into  which 
the  nuclear  buds  pass.  The  buds  increase  in  size  until  they  become  two  pear- 
shaped  piroplasms,  joined  at  their  pointed  ends  by  the  continually-diminishing 
remains  of  the  body  of  the  original  parent-individual.  The  connecting  mass 
dwindles  to  a  mere  point,  and  finally  the  two  daughter-individuals  separate. 
A  modification  of  this  method  leads  to  the  quadruple  fission  producing  four 
buds  and  four  daughter-individuals,  as  in  Babesia  mutans. 


THE  H^MOSPORIDIA 


383 


The  piriform  parasites  escape  from  the  corpuscle  when  it  is  exhausted, 
and  approach  other  corpuscles,  moving  with  considerable  rapidity.  The 
parasite  attacks  the  corpuscle  with  its  blunt  extremity  foremost,  and  "  rapidly 
indents  its  surface.  Then  violent  movement  of  the  thin  end  of  the  parasite 
occurs,  and  the  side  of  the  corpuscle  becomes  greatly  distorted. .  .  .  Gradually 
the  parasite  sinks  more  deeply  into  the  corpuscle,  and  finally  disappears  within 
it,  when  the  movements  of  the  corpuscle  cease  and  it  resumes  its  rounded 
shape  "  (Nuttall  and  Graham-Smith,  748,  vi.,  p.  235  ;  compare  the  penetra- 
tion of  blood- corpuscles  by  Lankesterella  described  above).  Only  piriform  or 
long  parasites  enter  corpuscles,  never  the  round  forms  ;  but  immediately  after 
its  entry  into  the  corpuscle  the  parasite  becomes  rounded.  If  rounded  para- 
sites are  set  free  from  a  corpuscle  by  its  rupture,  they  die  off,  as  do  also  the 
pear-shaped  forms  if  they  do  not  succeed  in  penetrating  into  a  corpuscle. 


FIG.  161. — Diagrams  showing  the  mode  of  division  of  Piroplasma  canis  in  the 
blood-corpuscle.  A,  Parasite  about  to  divide  ;  B,  the  nucleus  budding  off  a 
smaller  mass  ;  C,  the  nuclear  bud  has  grown  out  into  a  forked  strand  ;  D,  the 
forked  ends  of  the  strand  are  growing  out  into  protoplasmic  buds  ;  E,  F,  G, 
growth  of  the  buds  at  the  expense  of  the  main  body  ;  H,  I,  J,  final  stages  of 
the  division  of  the  body.  After  Nuttall  and  Graham-Smith. 

A  peculiar  parasite,  perhaps  allied  to  the  true  piroplasms,  is  Anaplasma 
marginale,  which  occurs  in  the  blood  of  cattle,  and  causes  a  disease  charac- 
terized by  destruction  of  the  red  corpuscles  and  production  of  high  fever, 
leading  to  a  degeneration  of  the  large  parenchymatous  organs.  The  parasite 
occurs  within  the  red  corpuscles,  and  is  described  as  consisting  solely  of 
chromatinic  substance,  without  a  cytoplasmic  body;  hence  the  parasites 
were  formerly  described  as  "  marginal  points."  The  parasite  has  the  form 
of  a  round  or  oval  coccus-like  body  which  multiplies  by  simple  fission.  It  is 
transmitted  by  a  tick,  Rhipicephalus  decoloratus.  See  especially  Theiler  (752). 

The  transmission  of  piroplasms  was  first  discovered  by  the 
American  investigators  Smith  and  Kilborne,  who  in  a  classical 


384  THE  PROTOZOA 

memoir  showed  that  the  parasite  of  Texas  cattle-fever  (Babesia 
bovis  or  bigemina)  was  transmitted  from  sick  to  healthy  oxen  by 
the  agency  of  ticks.  The  method  of  transmission  is  of  a  peculiar 
type,  which  finds  its  explanation  in  the  habits  and  life-history  of 
ticks.  These  arachnids  have  typically  three  stages  in  their  life- 
history — (1)  the  minute  six-legged  larva  hatched  from  the  egg, 
which,  after  growing  to  its  full  size,  sheds  its  skin  and  appears  as. 
(2)  the  nymph,  eight-legged,  but  sexually  immature  ;  the  nymph 
after  another  moult  becomes  (3)  the  adult  tick,  sexually  mature  and 
with  four  pairs  of  legs.  In  each  of  these  three  stages  of  the  life- 
history  the  tick  feeds,  as  a  rule,  but  once.  Consequently,  if  the 
parasites  are  taken  up  by  the  tick  at  one  stage  of  its  existence,  they 
cannot  be  reinoculated  into  another  host  until  a  later  stage  of  the 
tick.  Smith  and  Kilborne  found  that  the  parasites  taken  up  by  the 
adult  female  ticks  passed  through  their  ova  into  the  next  generation 
of  the  ectoparasites,  so  that  the  minute  larval  ticks,  progeny  of  an 
infected  mother,  were  the  infective  agents  which  spread  the  disease 
amongst  the  cattle. 

Subsequent  investigations  have  confirmed  and  extended  the  dis- 
covery made  by  Smith  and  Kilborne,  and  in  every  case  the  in- 
vertebrate host  of  any  species  of  piroplasm  appears  to  be  a  tick. 
In  P.  bovis  (bigeminum)  the  parasites  develop  only  if  taken  up  by 
an  adult  female  tick  (Koch),  but  this  is  not  so  in  other  cases.  The 
parasites  may  be  taken  up  by  the  tick  at  various  stages,  and  returned 
to  the  vertebrate  host  at  a  later  one  ;  for  instance,  by  the  larva  and 
returned  by  the  nymph,  or  by  the  nymph  and  returned  by  the  adult, 
or  by  the  adult  and  returned  by  the  larva  of  the  next  generation. 

Although  the  transmission  of  piroplasms  by  ticks  is  well  established,  the 
developmental  cycle  of  the  parasite  in  the  tick  is  known  only  in  a  fragmentary 
and  incomplete  manner.  The  most  complete  accounts  are  those  given  by 
Christophers  (732)  for  Piroplasma  canis,  and  Koch  (743)  for  P.  bovis,  whose 
observations  supplement  each  other,  since  Koch  studied  chiefly  the  earlier 
stages,  while  Christophers'  investigations  appear  to  be  more  complete  for 
later  phases  of  development.  Stages  in  the  tick  are  also  described  by 
Dschunkowsky  and  Luhs  (734),  but  in  a  disconnected  manner,  and  observa- 
tions on  the  development  in  cultures  have  been  published  by  Kleine  (742) 
and  by  Nuttall  and  Graham-Smith  (750).  Accounts  differ  chiefly  as  to  the 
events  at  the  beginning  of  the  development.  So  far  as  it  is  possible  to  make 
a  connected  story  out  of  the  published  observations,  the  development  in  the 
tick  appears  to  comprise  six  principal  phases : 

1.  The  piroplasms  taken  up  in  the  blood  pass  into  the  stomach  of  the 
tick,  and  there  the  pear-shaped  forms  are  set  free  from  the  corpuscles, 
these  forms  alone  being  capable  of  further  development.  After 
about  twelve  to  eighteen  hours  they  become  amoeboid,  sending  out  in  all 
directions  slender,  stiff,  sharply- pointed  pseudopodia  which  are  slowly  re- 
tracted and  emitted  again.  Usually  the  pseudopodia  are  given  off  chiefly 
from  the  thicker  end  of  the  pear-shaped  body,  but  in  some  cases  the  form  is 
spherical  and  the  appearance  of  the  parasite  strikingly  Heliozoon-like  (Fig.  162, 
A—C).  The  nucleus  of  the  parasite  divides  into  two  parts— a  larger  mass, 


THE  H/EMOSPORIDIA 


385 


staining  more  deeply,  on  which  the  pseudopodia  are  centred ;  and  a  smaller, 
paler  body  placed  more  excentrically.  In  the  pear-shaped  forms  the  large, 
dark  nucleus  is  placed  at  the  blunt  end,  the  small,  pale  body  near  the  pointed 
end.  Forms  similar  to  these  have  been  obtained  in^cultures,  and  evidently 


jglp— * 


^^V 


H 


FIG.  162. — Stages  in  the  development  of  Piroplasma  in  the  tick.  A — 0,  Amoeboid 
forms  (gametes  ?) :  A,  pear-shaped,  with  the  pseudopodia  given  off  at  the 
thicker  end  of  the  body  ;  B,  C,  spherical  or  Heliozoon-like,  with  the  pseudo- 
podia radiating  out  on  all  sides  ;  D — F,  fusion  of  the  gametes  (?)  ;  0,  result 
of  fusion  (?)  ;  H — J,  globular  bodies  (zygotes  ?) ;  K — M,  motile  vermicules 
(ookinetes  ?).  A — J  after  Koch  (P.  bovis)  ;  K — M,  after  Christophers 
(P.  cam's).  _j 

represent  the  first  stages  of  the  development;  but  they  appear  to^havejbeen 
missed  by  Christophers,  unless  it  is  to  be  assumed  that  these  forms  occur  in 
P.  bovis,  and  not  hi  P.  canis.  i 

The  star-like  forms  would  appear  to  represent  the  gametes  ;  they  congregate 

25 


386  THE  PROTOZOA 

in  clusters,  and  according  to  Koch  they  fuse  in  pairs  (Fig.  162,  D — G) ; 
cytological  details  of  the  syngamy,  if  such  it  be,  are  lacking  (but  compare 
Theileria,  infra). 

2.  The  stellate  stage  is  succeeded  by  a  spherical  stage,  very  possibly  repre- 
senting the  zygote.     This  body  grows  in  size,  but  its  development,  as  de- 
scribed by  Koch,  is  difficult  to  understand,  and  requires  further  elucidation. 
The  final  result  is  a  globular  mass  with  a  single  nucleus,  found  in  great  numbers 
on  the  third  day,  according  to  Koch  (Fig.  162,  J).     Whether  these  bodies  have 
arisen  by  division  of  the  zygote,  or  represent  simply  the  zygotes,  is  not  clear, 
but  the  latter  alternative  seems  the  more  probable. 

3.  The  globular  stage  is  succeeded  by  a  club-like  or  retort-shaped  stage. 
According  to  Christophers,  whose  account  of  the  life-cycle  appears  to  begin 
at  this  stage,  a  split  appears  in  the  globular  body,  whereby  a  portion  contain- 
ing the  nucleus  is  divided  off  incompletely  from  a  portion  which  has  no 
nucleus.     Tho  non-nucleated  portion  then  swings  round  and  forms  the  tail- 
piece of  the  complete  club-shaped  body,  which  has  a  single  nucleus  at  the 
swollen  extremity.     The  club-shaped  bodies  appear  to  represent  the  ookinetes 
(Fig.  162,  K — M).     They  are  motile  and  gregarine-like,  and  in  some  cases 
have  an  organ  resembling  an  epimerite,  regarded  by  Christophers  as  a  boring 
organ,  at  the  anterior  extremity.     Their  size  is  about  four  times  that  of  the 
piroplasrns  in  the  blood. 

4.  The  club-shaped  bodies  pass  from  the  gut  of  the  tick  into  the  ovary 
and  oviduct,  and  penetrate  into  the  ova.     There  they  become  again  globular 
in  form,  and  are  found  in  the  yolk  of  the  egg,  and  later  in  the  cells  of  the 
embryo  developed  from  the  egg.     When,  however,  the  parasites  have  been 
taken  up  by  a  nymph,  as  may  happen  in  P.  canis,  the  globular  bodies  are 
found  in  the  tissue-cells  of  the  body.     This  globular  stage,  termed  "  zygote  " 
by  Christophers,  very  probably  corresponds  to  the  oocyst  of  the  ha?marncebae. 

5.  The  globular  body  of  the  previous  stage  divides  up  by  multiple  fission 
into  a  number  of  "  sporoblasts,"  which  do  not  remain  aggregated  together, 
but  scatter  themselves  through  the  tissues  of  the  tick,  larva,  nymph,  or  adult, 
as  the  case  may  be. 

6.  The  sporoblasts  divide  in  their  turn  into  a  great  number  of  sporozoites, 
small  bodies  with  a  single  nucleus  similar  in  appearance  to  the  piroplasms  in 
the  blood.     The  sporozoites  collect  in  vast  numbers  in  the  salivary  glands 
of  the  tick,  and  pass  into  the  vertebrate  when  next  the  tick  feeds.     According 
to  Goncler,  ticks  infected  with  Theileria  parva  purge  their  salivary  glands  com- 
pletely of  the  parasites  when  they  feed,  and  are  only  infective  for  a  single  meal. 

The  development  of  Theileria  parva  in  the  tick  has  been  described  by 
Gonder  (740).  Within  an  hour  after  passing  into  the  stomach  of  the  tick 
the  parasites  become  free  from  the  corpuscles.  The  immature  gametocytes 
die  off,  but  the  adult  forms  proceed  to  gamete -formation.  The  free  parasites 
are  at  first  rounded  off,  but  soon  send  out  processes  and  become  aniceboid. 
The  male  gametocytes  send  out  a  single  process,  and  creep  about  actively 
like  a  limax-amceba  ;  their  nucleus  goes  through  an  unequal  division,  after 
which  the  gametocyte  becomes  a  gamete.  The  female  gametes,  which  are 
inactive,  go  through  a  similar  reduction-process.  Pairing  of  two  gametes 
and  fusion  of  the  cytoplasmic  bodies  takes  place,  but  before  the  nuclei  fuse 
each  nucleus  goes  through  a  second  reduction-division.  After  copulation  of 
the  nuclei  the  zygote  becomes  an  active  ookinete,  first  retort -shaped  and  then 
gregariniform,  which  penetrates  into  the  salivary  glands,  and  there  goes 
through  a  multiplicative  process,  very  similar  to  that  of  Halteridium  in  the 
lung  of  the  pigeon  (cf.  Fig.  157),  producing  a  swarm  of  sporozoites  which  are 
inocu  ated  into  the  vertebrate  host  by  the  tick.  Thus  in  Theileria  also 
there  is  no  flagellated  stage  at  any  part  of  the  life-cycle — a  fact  which  does 
not,  however,  prevent  Gonder  from  seeing  "  blepharoplasts,"  and  even  crith- 
idial  forms  on  every  possible  occasion  ;  he  seems  to  consider  nuclear  reduction 
and  blepharoplast-formation  as  the  same  thing.  It  is  a  pity  that  the  effect 
of  such  excellent  work  should  be  marred  by  so  much  theoretical  bias.  Aber 
wie  die  Alien  sungen  .  .  .  ! 


THE  M;MOSPORIDIA  337 

From  the  foregoing  it  is  seen  that  the  development  of  piroplasms 
appears  to  be  of  a  type  essentially  similar  to  that  of  the  hsem- 
amcebae  and  haemogregarines.  In  the  present  fragmentary  state  of 
our  knowledge,  however,  it  would  be  premature  to  generalize  con- 
cerning the  development  of  these  forms.  The  most  noteworthy 
feature  of  the  development  is  the  entire  absence  of  flagellated  forms 
from  the  life-cycle.  The  alleged  flagellate  forms  of  P.  canis  in 
the  dog's  blood  described  by  Breinl  and  Hindle  have  been  dealt 
with  above ;  it  only  remains  to  be  mentioned  that  Miyajima 
obtained  trypanosomes  in  cultures  of  the  blood  of  calves  suffering 
from  piroplasmosis,  an  observation  which  led  to  the  discovery  of  a 
trypanosome  in  calves  not  previously  known  to  exist  (see  p.  283). 

Doubtful  Genera  of  Hcemosporidia. — A  certain  number  of  blood- 
parasites  have  been  described  which  at  present  are  not  sufficiently 
well  known  to  make  it  possible  to  assign  to  them  a  definite  systematic 
position.  When  more  thoroughly  investigated,  many  of  them  may 
turn  out  to  belong  to  other  groups  than  the  Hsemosporidia  ;  it  is 
even  possible  that  some  of  these  bodies  are  not  parasites  at  all,  but 
merely  some  forms  of  cell-enclosures. 

The  genus  Toxoplasma  was  founded  by  Nicolle  and  Manceaux  (754)  for 
T.  gondii,  a  parasite  of  the  gondi  (Ctenodactylus  gondii) ;  other  species  have 
since  been  described — namely,  T.  cuniculi,  Carini,  from  the  rabbit,  T.  canis, 
Mello,  from  the  dog,  and  T.  talpce,  Prowazek,  from  the  mole.  The  organisms 
in  question  are  parasites  of  the  white  blood- corpuscles,  and  occur  most 
abundantly  in  the  spleen  or  liver,  causing  a  disease  which  is  frequently  fatal. 
The  parasite  is  a  crescent-shaped  body,  with  one  end  thicker  than  the  other, 
.and  containing  a  single  nucleus  ;  they  multiply  by  binary  or  multiple  fission. 
Nicolle  and  Manceaux  regarded  them  as  allied  to  Leishmania,  but  their 
resemblance  to  this  genus  appears  to  be  purely  superficial,  since  in  Toxoplasma 
no  kinetonucleus  is  present,  and  in  cultures  no  flagellated  stage  is  developed. 

Elleipsisoma  thomsoni  is  the  name  given  by  Franca  (441)  to  a  parasite  of 
the  blood  of  moles  discovered  by  Thomson  (524).  It  occurs  as  an  amoeboid 
intracorpuscular  parasite  with  a  single  nucleus  situated  at  the  margin  of  the 
body,  which  contains  no  melanin-pigment.  Multiplication  takes  place  ex- 
clusively in  the  lung,  and  is  by  binary  or  multiple  fission,  according  to  Franga  ; 
the  young  forms  are  either  vermiform,  with  the  nucleus  drawn  out,  or  oval, 
with  a  compact  nucleus  ;  they  penetrate  into  the  corpuscles  and  grow  there. 
Franga  considers  this  form  to  be  allied  to  Tovoplasma. 

The  name  Toddia  bufonis  is  given  by  Franga  (440)  to  certain  bodies  in  the 
red  blood-corpuscles  of  batrachia,  first  described  by  Todd.  The  earliest  stage 
in  the  corpuscle  is  a  small  globule  of  chromatin  ;  Franga  believes  that  the 
parasite  when  it  penetrates  the  corpuscle  is  reduced  to  its  nucleus  alone,  and 
that  it  gradually  forms  a  cytoplasmic  body  which  becomes  substituted  for 
that  of  the  corpuscle.  As  the  cytoplasmic  body  is  formed,  crystals  appear 
in  it,  one  large  crystal  or  as  many  as  three  smaller  ones.  Finally  the  corpuscle 
is  seen  with  a  slightly  hypertrophied  nucleus  pushed  to  one  side,  and  its  contents 
consisting  chiefly  of  substance  which  stains  intensely  blue  with  the  Roman- 
owsky  stain,  in  which  are  the  crystals  and  the  nucleus  of  the  parasite,  no\v 
3  to  3'5  fj.  in  diameter.  No  multiplication-stages  have  been  observed. 

Globidium  multifidum  is  the  name  given  by  Neumann  (488)  to  a  parasite 
of  the  red  blood-corpuscles  of  Gobius  minutus  and  Arnoglossus  grohmanni.  It 
was  met  with  in  the  form  of  a  cluster  of  some  thirty  to  sixty  merozoite-like 
bodies,  each  2'5  n  in  length  by  1'5  ^  in  breadth  ;  similar  bodies  were  seen  in 


388  THE  PROTOZOA 

blood-corpuscles  singly,  but  their  growth  and  multiplication  were  not  ob- 
served. The  parasite  appears  to  develop  in  red  corpuscles,  which  it  finally 
fills  completely,  breaking  up  the  nucleus  ;  no  pigment  is  formed.  The  youngest 
forms  show  sometimes  a  grain  near  the  nucleus,  possibly  a  kinetonucleus. 
With  the  bodies  desciibed  by  Neumann  may  be  compared  those  observed 
by  Mathis  and  Leger  (473,  pp.  417-419,  Plate  XIII.,  Figs.  12-16)  in  a  fish, 
Clarias  macrocephalus  ;  possibly  they  have  some  connection  with  the  trypano- 
some  found  in  the  same  host. 

Imrnanoplasma  scyllii,  Neumann  (488),  is  a  parasite  of  the  red  blood- 
corpuscles  of  Scyllium  canicula.  It  grows  to  a  size  of  30  by  2  0  ,  and  in  life 
is  feebly  amoeboid.  Its  protoplasm  stains  very  deep  blue  by  the  Romanowsky 
stain,  and  its  nucleus  appears  usually  as  if  separate  from  the  rest  of  the  body 
of  the  parasite,  lying  apparently  free  from  it  in  the  blood- corpuscle.  Some 
forms  of  the  parasite  have  paler  protoplasm  with  a  larger  nucleus,  others 
darker  protoplasm  with  a  smaller  nucleus  ;  the  two  forms  are  possibly  male 
and  female.  No  pigment  is  produced.  The  development  of  the  parasite 
remains  at  present  unknown. 

Finally  mention  must  be  made  of  the  so-called  "  Kurloff-Demel  bodies," 
found  in  the  leucocytes  of  the  guinea-pig.  According  to  Patella  (755)  they 
are  true  "  leucocytozoa,"  but  according  to  Mathis  and  Leger  (473)  they  are 
not  of  parasitic  nature.  A  memoir  will  be  published  shortly  by  Dr.  E.  H.  Ross, 
however,  in  which  it  will  be  shown  that  the  Kurloff- bodies  are  true  parasites, 
representing,  apparently,  a  stage  of  a  motile  organism,  probably  a  spirochsete, 
found  free  in  the  blood.  The  author  proposes  for  this  parasite  the  name 
Lymphocytozoon  cobayce. 

Affinities  of  the  Hcemosporidia. — TAVO  opposed  and  conflicting 
theories  with  regard  to  the  systematic  position  of  the  Hsemosporidia 
hold  the  field  at  the  present  time. 

1.  The  older   and  more  generally   accepted    view  is   that  the 
Haemosporidia  are  closely  allied  to  the  Coccidia,  sufficiently  so, 
in  fact,  to  be  classed  with  them  in  a  single  order.     Thus,  Doflein. 
divides  the  Telosporidia  into  two  orders,  the  Gregarinoidea  and 
the  Coccidiomorpha,  the  latter  comprising  two  subdivisions,  Coc- 
cidia and  Hsemosporidia  ;  while  Mesnil  placed  the  Haemosporidia, 
together  with  the   genus  Legerella,  amongst   the  Coccidia   in  an 
order  Asporocystea,   characterized   by  the  absence  of  sporocysts 
in  the  oocyst,  a  character  that  cannot  be  utilized  in  this  manner 
now  that  some  hsernogregarines  have  been  shown  to  form  sporocysts. 

2.  Hartmann  and  others  (e.g.,   Awerinzew)  maintain    that   the 
Haemosporidia  should  be  removed  altogether  from  the  Sporozoa, 
and  should  be  classed,  together  with  the  Haenioflagellates,  as  an 
order  of  the  Flagellata,  for  which   the  name  Binucleata  is   pro- 
posed, since  the  chief  structural  feature  common  to  all  members  of 
the  order  is  supposed  to  be  the  possession  of  two  differentiated 
nuclei,  a  kinetonucleus  and  a  trophonucleus,  distinct  from  each 
other. 

It  must  be  clearly  understood  that  the  theory  of  the  Binucleata,  as  pro- 
pounded by  Hartmann  and  his  school,  is  not  merely  one  of  a  general  relation- 
ship between  Hsemosporidia  and  Flagellata.  This  wider  point  of  view  will 
be  discussed  when  the  affinities  of  the  Telosporidia  as  a  whole  are  considered. 
The  question  at  present  under  discussion  is  whether  the  Hsemosporidia,  more 


THE  H^MOSPORIDIA  389 

than  the  other  Telosporidia,  are  allied  specially  to  the  Haemoflagellates,  more 
so  than  to  other  Flagellata  ;  whether,  in  short,  the  Htemosporidia  should 
be  removed  from  the  Telosporidia  altogether,  and  should  be  classified,  together 
with  the  H?enioflagellates,  in  one  natural  order,  family,  or  other  systematic 
category.  In  dealing  with  the  Haemoflagellates  in  a  previous  chapter,  cause 
was  shown  for  believing  them  'to  have  two  distinct  lines  of  ancestry,  the  one 
from  a  Cercomonad,  the  other  from  a  Bodonid  type  of  Flagellate  ;  in  that 
case  it  is  the  Cercomonad  section — that  is  to  say,  the  trypanosomes  and  their 
allies — to  which  the  Ha?mosporidia  must  be  considered  to  be  specially  related 
on  the  theory  now  to  be  discussed. 

Leger  and  Duboscq  (646),  recognizing  distinct  Bodonid  and  Cercomonad 
stems  in  the  Hsemoflagellates,  derive  the  Gregarines,  Coccidia,  and  Haemo- 
gregarines,  from  the  Bodonid  stem  (trypanoplasms),  the  Haeniamoabse  and 
Piroplasms  from  the  Cercomonad  (trypanosome)  type. 

The  close  relationship  of  the  Haeinosporidia  and  the  Coccidia 
seems  at  first  sight  so  obvious,  from  a  general  consideration  of  the 
life-histories  of  typical  members  of  each  group,  that  any  theory 
to  the  contrary  must  justify  itself  by  convincing  and  cogent  argu- 
ments. The  chief  grounds  upon  which  affinities  between  Haemo- 
sporidia  and  Heemo flagellates  are  alleged  are  found,  when  analyzed, 
to  be  of  three  kinds — namely  :  first,. developmental  data  ;  secondly, 
structural — that  is  to  say,  mainly  cytological — peculiarities  ; 
thirdly,  resemblances  between  certain  forms  which  appear  to  be 
sufficiently  close  to  link  the  two  groups  together  by  a  series  of  gradual 
transitions.  The  evidences  of  affinity  between  Hsemosporidia  and 
Hsemoflagellates  based  on  these  three  classes  of  facts  must  be 
considered  separately. 

1.  Developmental  Data. — Beginning  with  the  first  of  the  five  types  of 
Hsemosporidia  which  have  been  recognized  above — namely,  the  haernamcebaa 
or  malarial  parasites,  it  is  very  evident,  as  Schaudinn  (658)  first  pointed  out, 
that  their  life-cycle  resembles  in  the  closest  manner  that  of  the  Coccidia. 
With  one  exception,  every  phase  in  the  life-cycle  of  a  malarial  parasite  has  a 
corresponding  phase  in  that  of  a  coccidian,  and  the  same  terminology  can  be 
used  throughout  for  describing  the  stages  of  the  development ;  the  one  ex- 
ception to  this  statement — the  only  phase  that  requires  a  special  name — is 
the  ookinete-stage  of  the  malarial  parasites,  which  is  not  known  to  occur 
in  any  coccidian.  It  is  clear,  however,  that  the  points  in  which  the  life- 
cycles  differ  from  one  another  in  the  two  cases  are  such  as  can  be  correlated 
with  the  differences  in  the  mode  of  parasitism — that  is  to  say,  with  the  fact 
that  in  Coccidia,  speaking  generally,  there  is  a  single  host,  and  the  mode  of 
infection  is  contaminative,  while  in  the  hsemamoebte  there  are  two  hosts, 
and  the  vertebrate  is  infected  by  the  inoculative  method.  Corresponding 
with  this  difference,  the  zygote  in  the  Coccidia  prepares  at  once  for  leaving 
the  body  of  the  host  and  passing  out  into  the  open,  and  protects  itself  by  a 
firm  envelope  ;  while  that  of  the  hsemamcebse,  produced  in  the  body  of  an 
intermediate  host,  does  not  encyst  itself,  but  is  actively  parasitic,  continuing 
to  absorb  nourishment  from  the  host  and  to  grow.  Further,  in  the  hsemarncebae 
the  parasite  is  always  in  the  body  of  one  or  the  other  of  its  two  hosts,  and 
consequently  tough,  impervious  cysts  and  spores  like  those  of  Coccidia  are 
superfluous  and  are  never  formed  ;  the  oo'cyst  is  a  thin  membrane  through 
which  soluble  foodstuffs  can  diffuse,  and  sporocysts  are  not  secreted,  as  is  the 
case  also  in  some  Coccidia.  The  adaptive  significance  of  these  differences 
is  so  obvious  that  it  does  not  require  further  elucidation  or  discussion. 

The  development  of  the  halteridium-type,  as  described  by  Aragao,  can  be 


390  THE  PROTOZOA 

derived  without  difficulty  from  that  of  the  hsmamcebae  ;  and,  in  spite  of 
the  hiatus  in  what  is  known  of  the  life-cycle,  there  is  no  difficulty  in  comparing 
and  homologizing  the  phases  of  Hccmoproteus  columbce  with  those  of  a  malarial 
parasite,  and  consequently  with  those  of  a  coccidian.  The  development  of 
Lmcocytozoon  requires  investigation,  but  the  little  that  is  known— namely,  the 
schizogony,  sexual  phases,  and  ookinete -formation — is  entirely  of  the 
ha^mamceba-type. 

More  striking  than  in  any  other  type  of  the  Hsernosporidia  are  th-  coccidian 
features  of  the  harnogregarines.  In  such  a  form  as  H.  stepanowi  the  life-cycle 
is  seen  to  exhibit  not  merely  a  general  similarity  to  that  of  the  Coccidia,  but 
even  a  special  resemblance  to  particular  forms.  The  mode  of  gamete-forma- 
tion is  that  which  characterizes  the  family  Adeleidce  among  Coccidia,  and  the 
many  developmental  similarities  between  H.  stepanowi  and  the  only  known 
coccidian  parasite  of  a  leech,  Orcheobhis  herpoMdlce,  have  led  Reichenow 
to  derive  them  from  a  common  form.  In  many  ha-mogregarines,  apparently, 
the  parasite  obtains  an  entry  into  the  vertebrate  host,  not  by  the  inoculative 
method,  but  by  the  contaminative,  through  the  vertebrate  devouring  the 
invertebrate  host.  In  such  cases  (H.  rmiris,  H.  gerbilli)  the  characteristic 
coccidian  sporocysts  reappear  in  the  sporogony.  It  is  not  necessary,  however, 
to  dilate  further  on  the  coccidian  affinities  of  the  hsemogregarines,  since  they 
are  recognized  by  Hartmann  and  his  school,  and  the  latest  revisions  of  the 
order  Binucleata  do  not  comprise  the  liEemogregarines,  which  are  left  in  the 
Telosporidia. 

As  regards  the  piroplasms,  it  is  perhaps  unsafe  to  generalize  in  the  present 
fragmentary  state  of  our  knowledge  of  the  life-cycle,  and  in  particular  of  the 
sexual  phases  ;  but  so  far  as  it  is  known,  the  phases  of  the  development  appear 
to  correspond  closely  with  those  of  the  typical  Heemcsporidia.  But  at  least 
it  can  be  said  that  the  development  of  piroplasms  does  not  afford  the  slightest 
support  to  the  view  that  they  are  in  any  way  allied  to  Hsemoflagellates  ; 
indeed,  it  can  be  affirmed,  on  the  contrary,  that,  of  all  the  forms  included  in 
the  Hfemosporidia,  the  piroplasms  exhibit  the  least  indications  of  flagellate 
affinity. 

From  a  general  consideration  of  the  life-cycles  of  the  typical  Haemosporidia, 
such  as  the  haemamcebse  and  hsemogregarines,  and  omitting  doubtful  forms, 
it  is  very  clear  that  what  may  be  called  the  nucleus  of  the  group  bears  a  close 
and  unmistakable  resemblance  to  the  Coccidia.  One  section,  comprising  the 
hfemamcebte,  halteridia,  and  leucocytozoa  of  birds,  are  to  be  derived  from  an 
ancestor  which  formed  gametes  after  the  manner  of  Coccidivm,  and  in  these 
types  the  phenomena  of  "  exflagellation  "  can  be  observed  readily.  In  the 
other  section,  comprising  at  least  the  heemogregarines,  gamete-formation  is 
of  the  type  of  that  seen  in  Adeleidce,  and  does  not  take  place  until  the  garneto- 
cytes  have  associated  ;  consequently  exflagellation  in  vitro  does  not  occur^ 
but  coupling  of  the  sporonts,  as  in  gregarines,  has  often  been  described,  but 
wrongly  interpreted  as  copulation  (cf.  Sambon  and  Seligmann). 

In  the  face  of  such  profound  homologies  with  Coccidia,  what  are  the  argu- 
ments from  the  developmental  cycle  in  favour  of  a  contrary  opinion  ?  The 
case  for  the  alleged  HEemoflagellate  affinities  of  the  Haemosporidia  rests  on 
the  famous  memoir  of  Schaudinn  (132)  on  the  blood-parasites  of  the  Little  Owl, 
a  work  which  must  now  be  considered  briefly. 

The  Little  Owl  (Athene  noctua)  harbours  the  full  number  of  known  avian 
blood-parasites — namely:  (1)  a  proteosoma  ;  (2)  a  halteridium  ;  (3)  a  small 
form  of  trypanosome  ;  (4)  a  large  form  of  trypanosome  ;  (5)  a  leucocytozoon  : 
(6)  a  spirocheete. 

According  to  Schaudinn,  these  six  forms  belong  to  the  life-cycle  of  three 
species  of  parasites.  First,  the  proteosoma  (1)  is  a  distinct  form,  not  related 
to  any  of  the  others.  Secondly,  the  halteridium  ( 2)  and  the  small  trypanosome 
(3)  are  alleged  to  be  two  phases  of  the  same  parasite.  Thirdly,  the  large 
trypanosome  (4),  the  leucocytozoon  (5),  and  the  spirochiete  (6),  are  supposed 
to  represent  different  phases  of  one  and  the  same  life-cycle. 

The  halteridium  (Hcemoproteus  noctuce)  was  stated  by  Schaudinn  to  be  the 


THE  ILEMOSPORIDIA  391 

resting  intracorpuscular  diurnal  phase  of  a  trypanosome  which  at  night 
developed  a  locomotor  apparatus,  became  free  from  the  blood- corpuscle,  and 
swam  freely  in  the  plasma  ;  in  the  morning  the  trypanosome  penetrated  into 
a  corpuscle,  lost  its  locomotor  apparatus  again,  and  became  a  halteridium. 
Male,  female  and  indifferent  forms  were  distinguished.  The  smallest  in- 
different forms  went  through  a  six-day  development  and  growth,  in  the 
corpuscle  as  a  halteridium  by  day,  free  in  the  plasma,  as  a  trypanosome  by 
night,  until  full  grown  ;  then  they  multiplied  rapidly  by  repeated  fission  to 
produce  trypanosomes  of  the  smallest  size.  These  young  forms  might  grow 
up  into  indifferent  forms  in  their  turn,  or  might  become  male  or  female  forms  ; 
in  the  latter  event  their  development  was  slower,  and  in  its  later  stages  the 
parasite  lost  the  power  of  forming  a  locomotor  apparatus  or  of  leaving  the 
corpuscle.  Thus  arose  the  adult  male  and  female  halteridia,  which,  in  order 
to  continue  their  development,  required  to  be  taken  up  by  a  gnat,  Culev 
pipiens.  In  the  stomach  of  the  gnat  the  parasites  formed  gametes  which 
copulated  and  produced  zygotes  in  the  well-known  manner.  Each  ookinete, 
according  to  Schaudinn,  formed  a  locomotor  apparatus  (see  Fig.  30,  p.  59)  and 
either  became  a  trypanosome  which  might  be  of  female  or  indifferent  type, 
or  gave  rise  to  several  trypanosomes  in  the  male  sex.  The  trypanosomes 
of  each  type  multiplied  in  the  digestive  tract  of  the  gnat  to  produce  a  swarm 
of  trimorphic  individuals,  but  no  further  copulation  of  the  male  and  female 
forms  occurred  or  could  occur  (Schaudinn,  132,  p.  401).  Ultimately,  after 
complicated  migrations,  the  trypanosomes  were  inoculated  by  the  gnat  into 
the  owl  again  ;  the  male  and  indifferent  forms  passed  through  the  proboscis, 
but  the  female  forms  were  too  bulky  to  do  so,  and,  as  the  male  forms  were 
stated  to  die  off  in  the  blood,  there  was  effective  inoculation  of  indifferent 
forms  only,  which  start  on  the  cycle  of  development  already  described. 

These  remarkable  statements,  the  origin  and  significance  of  which  have 
been,  for  the  last  seven  years,  a  veritable  riddle  of  the  sphinx,  have  met  with 
general  scepticism  except  from  a  few  devoted  partisans,  who  have  been 
striving  continually  to  find  corroborative  evidence  for  Schauclinn's  theories, 
in  spite  of  the  mass  of  evidence  to  the  contrary  that  has  been  steadily  accu- 
mulating. Recently  Mayer  (685)  has  affirmed  that  in  owl's  blood  containing 
only  halteridia,  kept  under  observation  in  hanging  drops  under  the  micro- 
scope, trypanosomes  make  their  appearance  which  could  only  have  come 
there  by  transformation  of  halteridia.  These  experiments  are  supposed  to 
prove  conclusively  one  part,  at  least,  of  Schaudinn's  statements — namely, 
that  the  halteridia  are  merely  intracorpuscular  stages  of  trypanosomes. 

Against  Schaudinn's  views,  on  the  other  hand,  two  principal  objections, 
out  of  many,  may  be  urged  : 

First,  that  the  development  of  Hcemoproteus  columbce,  as  made  known  by 
the  Sergent  brothers  and  by  Aragao,  is  of  a  totally  different  type  to  that 
described  by  Schaudinn. ;  it  comprises  no  trypanosome-phases  at  any  point 
of  the  life-cycle,  and  the  invertebrate  host  is  not  a  gnat,  but  a  biting  fly  of  an 
altogether  different  kind.  To  meet  this  objection,  Mayer  proposes  to  restrict 
the  name  Hcemoproteus  to  forms  which  develop  after  the  manner  of  H.  columbce, 
and  to  revive  the  name  Halteridium  (in  italics  and  with  an  initial  capital 
letter)  for  parasites  that,  on  the  Schaudinnian  theory,  are  really  trypanosomes. 

Secondly,  that  the  small  trypanosomes  of  Athene  noctua  are  connected 
by  every  possible  transitional  form  with  the  largest  found  in  the  same  bird, 
and  there  is  every  reason  to  suppose  that  in  this  case,  as  in  other  birds  or 
vertebrates  of  all  classes,  they  are  all  merely  forms  of  one  polymorphic  try- 
panosome (Minchin  and  Woodcock,  42). 

It  may  be  added  that  the  whole  mystery  receives  a  complete  solution  on  a 
simple  supposition — namely,  that  the  trypanosome  of  the  Little  Owl,  like  other 
known  species  of  trypanosomes  (see  p.  308),  has  intracorpuscular  forms 
which  have  been  confused  with  the  true  halterida  ;  on  such  an  assumption, 
so  eminent  an  investigator  as  Schaudinn  can  be  acquitted  of  having  made 
what  would  appear  at  first  sight  to  be  a  gross  error  of  observation,  and  Mayer's 
observations  are  easily  explained.  Mayer  seems,  in  fact,  to  have  figured 


392  THE  PROTOZOA 

such  forms  on  his  Plate  XXII.,  Figs.  2-4 — small  intracorpuscular  forms,  more 
or  less  Leishmania-like,  ivithout  pigment,  and  with,  apparently,  distinct  tro- 
phonucleus  and  kinetonucleus. 

It  is  not  necessary  to  deal  with  Schaudinn's  statements  concerning  Leuco- 
cytozoon  further  than  has  been  done  above  (p.  370).  It  is  now  as  certain  as 
anything  can  ever  be  in  such  matters  that  Leucocytozoon  has  nothing  whatever 
to  do  with  either  trypanosomes  or  spirochsetes.  The  six  forms  of  biood- 
parasites  of  the  Little  Owl  may  be  regarded  as  belonging  to  five  species, 
namely:  A  proteosoma  (1),  a  halteridium  (2),  a  trypanosome  (3  and  4),  a 
leucocytozoon  (5),  and  a  spirochaete  (6).  Of  these  five,  it  is  probable  that  only 
the  proteosoma,  the  trypanosome,  and  possibly  the  spirochsete,  can  develop 
in,  and  be  transmitted  by,  a  gnat ;  the  halteridium  and  the  leucocytozoon 
require,  probably,  quite  different  intermediate  hosts.  If,  therefore,  a  Culex 
were  fed  on  an  owl  containing  in  its  blood  halteridia  and  leucocytozoa  abun- 
dantly, and  trypanosomes  and  spirochsetes  in  scanty  numbers,  the  first  two 
parasites  might  be  expected  to  die  out  after  the  ookinete-stage,  while  the 
trypanosomes,  and  possibly  the  spirochsetes,  would  multiply,  and  thus  produce 
very  easily  the  impression  that  they  were  derived  from  the  intracorpuscular 
parasites. 

Even  less  cogent  for  the  theory  of  Haemoflagellate  affinities  than  the  argu- 
ments deduced  from  the  development  of  Hsemosporidia  are  those  based  on 
the  development  of  Haemoflagellates.  Thus  the  schizogony  of  Schizotry- 
panum  discovered  by  Chagas  has  been  compared  to  that  of  a  malarial  parasite, 
and  has  been  adduced  seriously  as  an  additional  proof  of  the  alleged  affinities 
between  trypanosomes  and  haemamceba?.  But  "  schizogony  :' — that  is,  repro- 
duction by  simple  or  multiple  fission  without  concomitant  sexual  phenomena, 
—occurs  throughout  the  whole  range  of  the  Protozoa,  and  affords  no  proof 
whatever  of  genetic  affinities.  Those  who  bring  forward  such  an  argument 
must  surely  have  forgotten  that  the  word  "  schizogony "  was  originally 
coined  by  Schaudinn  for  the  non-sexual  multiplication  of  Trichospharium 
sieboldi,  a  marine  Rhizopod  (p.  181). 

2.  Cytological  Data. — The  theory  of  the  Hsemoflagellate  affinities  of  the 
Hsemosporidia  has  led  to  the  most  laborious  and  painstaking  efforts  to  discover 
in  the  body  of  each  and  every  Hsemosporidian  parasite,  in  at  least  some  of 
its  phases,  a  second  nucleus,  the  homologue  of  the  kinetonucleus  ;  and  any 
little  granule,  however  minute,  that  can  be  coloured  like  chromatin  is  pro- 
claimed triumphantly  to  be  the  inevitable  kinetonucleus,  or  any  streak  of 
similar  staining  properties  to  be  a  flagellum. 

Consider  first  by  itself  the  case  of  a  cell  in  which,  in  addition  to  the  nucleus, 
there  is  seen  a  grain  which,  by  some  particular  dye,  is  stained  in  a  manner 
similar,  or  nearly  so,  to  the  chromatin  of  the  nucleus.  This  is  not  by  itself 
a  decisive  proof  that  the  grain  in  question  is  chromatin,  since,  as  pointed  out 
above,  other  grains  may  take  up  so-called  "  chromatin-stains  "  ;  the  body 
in  question  may  therefore  be  chromatin  or  some  other  substance.  If  it  be 
chromatin,  it  may  be  a  chromidial  granule  extruded  from  the  nucleus  ;  or  it 
may  be  a  body  of  the  nature  of  a  karyosome,  situated  close  to  the  edge  of  the 
nucleus,  or  possibly,  in  some  cases,  where  the  nucleus  has  no  limiting  mem- 
brane, a  little  way  from  the  main  mass  of  the  nucleus  ;  or  it  may  be  a  true 
kinetonucleus.  If  it  be  not  chromatin,  it  may  be  a  centrosome  or  blepharo- 
plast ;  or  a  grain  of  metachromatinic  substance,  such  as  volutin  ;  or,  lastly,  some 
other  kind  of  metaplastic  body.  There  are  therefore  many  possible  alterna- 
tives before  a  grain  that  stains  like  chromatin  can  be  identified  definitely  as 
being  a  kinetonucleus  and  nothing  else. 

What  are  the  criteria  by  which  a  grain  that  stains  like  chromatin  can  be 
identified  as  a  kinetonucleus,  to  the  exclusion  of  other  possible  interpretations 
of  its  nature  ?  In  the  first  place,  according  to  modern  views  (see  p.  288, 
supra,  and  compare  especially  Rosenbusch,  505),  a  kinetonucleus  is  not  a 
simple  granule,  mass  or  lump  of  chromatin,  but  it  is  a  true  nucleus  with 
centriole,  karyosome,  and  a  nuclear  cavity,  actual  or  virtual,  containing 
nuclear  sap  at  least,  if  not  peripheral  chromatin  also.  Secondly,  a  kineto- 


THE  H^MOSPORIDIA  393 

nucleus  when  present  is  a  permanent  cell-element  which,  like  the  principal 
nucleus,  divides  when  the  cell  divides,  and  is  propagated  by  fission  equally 
with  the  cell  itself.  Thirdly,  and  this  is  the  most  important  criterion  of  all, 
the  kinetonucleus  is  in  relation  with  a  flagellum  during  at  least  some  phases 
of  the  development,  though  for  a  time  the  locomotor  apparatus  may  be 
temporarily  absent,  its  existence  indicated  only  by  the  kinetonucleus  during 
resting  phases. 

The  smaller  chromatinic  body  of  Leislimania  may  be  cited  as  an  example  of 
a  body  which  fulfils  these  conditions,  and  which  can  be  identified  unhesita- 
tingly as  a  true  kinetonucleus,  homologous  in  every  way  with  that  of  a  try- 
panosome.  But  with  the  alleged  kinetonuclei  of  Hasmosporidia  the  matter 
stands  quite  otherwise.  It  is  not  possible  to  discuss  fully  here  every  separate 
instance,  but  a  few  typical  examples  of  such  bodies  may  be  dealt  with 
briefly. 

In  female  halteridia  and  leucocytozoa  (Fig.  158),  a  large  grain  is  seen  by 
the  side  of  the  nucleus,  and  often  interpreted  as  a  kinetonucleus.  Until  this 
body  has  been  shown  conclusively  to  be  related  in  some  phase  of  the  life- 
history  to  a  flagellum,  it  is  far  simpler  to  regard  it  as  a  karyosome  which, 
like  that  of  the  merozoites  of  Adelea  (Fig.  153,  F),  is  excentric,  or  possibly 
extranuclear  in  position ;  assuming,  that  is,  that  the  body  in  question  is  a 
true  chromatinic  nuclear  element. 

In  the  merozoites  of  Proteosoma,  Hartmann  (675)  has  discovered  a  flagelluni- 
like  process  at  the  anterior  end,  arising  from  a  grain  which  he  regards  as  a 
kinetonucleus  ("  blepharoplast "  in  the  German  use  of  the  term),  thus  con- 
firming certain  obiter  dicta  of  Schaudinn  (132,  p.  436)  with  regard  to  the  mero- 
zoites and  sporozoites  of  the  tertian  parasite.  It  may  be  pointed  out  that  the 
rostrum  of  the  sporozoites  of  Gregarines  appears  to  be  a  perfectly  similar 
structure,  which  very  possibly  represents  a  rudimentary  flagellum  arising 
from  a  true  blepharoplast  of  centrosomic  nature.  Hartniann's  discovery  is 
therefore  more  proof  of  the  affinities  of  proteosoma  with  other  Telosporidia 
than  with  Haemoflagellates. 

The  supposed  kinetonuclei  of  piroplasms  have  been  mentioned  above  ;  the 
entire  absence  (pace  Hartmann)  of  flagellated  stages  throughout  the  life- 
cycle  make  it  impossible  to  accept  any  such  interpretation  of  the  nature  of 
these  granules  so  highly  inconstant  in  their  occurrence. 

Lastly  it  should  be  mentioned  that  Schaudinn,  and  recently  Hartmann, 
have  maintained  that  the  microgametes  of  halteridia  and  other  Hsemosporidia 
have  the  structure  of  a  trypanosome.  Inasmuch  as  Schaudinn  also  pointed 
out  the  great  structural  similarity  between  trypanosomes  and  spermatozoa, 
this  point  might  not  count  for  much,  even  if  it  were  true  ;  unless  the  Metazoa 
also  are  to  be  classified  amongst  the  Binucleata,  a  conclusion  which,  indeed, 
seems  to  follow  from  the  nuclear  theory  of  Hartmann  and  Prowazek  (63). 
In  objects  of  such  extreme  minuteness,  however,  statements  ascribing  to  them 
complicated  details  of  structure  must  be  regarded  with  great  scepticism  until 
thoroughly  substantiated.  It  is  a  sufficient  warning  of  the  need  of  caution 
to  bear  in  mind  the  controversy  that  has  raged  over  the  question  of  the  minute 
structure  of  spirochsetes,  with  regard  to  which  Schaudinn  was  obliged  to 
retire  from  the  position  he  took  up  at  first — namely,  that  their  structure  was 
similar  to  that  of  a  trypanosome. 

3.  Possible  Transitional  Forms. — The  parasite  of  kala-azar  was  originally 
described  by  Laveran  under  the  name  Piroplasma  donomni*  in  the  belief  that 
it  was  a  true  piroplasm ;  and  many  writers  have  been  struck  by  the  external 
similarity  of  the  two  parasites,  in  spite  of  the  difficulty  in  finding  in  Piroplas  ma 
a  satisfactory  representative  of  the  constant  and  definite  kinetonucleus  of 
Leishmania.  In  fact  these  two  genera  are  often  cited  as  the  connecting  link 
between  Haemoflagellates  and  Hsemosporidia,  and  are  supposed  to  indicate 
the  course  of  evolution  whereby  serum-parasites  of  the  first  type  became 

*  On  the  other  hand,  the  parasite  of  Oriental  Sore  was  first  described  by  Wright 
under  the  name  Helcosoma  tropicum,  and  referred  to  the  Microsporidia. 


394  THE  PROTOZOA 

cell-parasites  of  the  second  (compare  Leger  and  Duboscq,  646).  However 
enticing  such  a  view  may  seem  when  only  the  forms  parasitic  in  the  verte- 
brate hosts  are  taken  into  consideration,  the  facts  of  the  development  in  the 
invertebrate  hosts  must  dispel  completely  any  notion  of  affinity  between 
the  two  types.  Nothing  could  be  imagined  more  different  than  the  develop- 
ment of  Leishmania,  with  its  typical  leptomonad  forms  (Fig.  140),  and  that 
of  Piroplasma  (Fig.  162),  with  no  flagellated  stages  at  all  in  its  life-cycle.  It 
becomes  evident  at  once  that  any  apparent  resemblance  between  the  two 
genera  is  due  to  convergent  adaptation  induced  by  a  similar  mode  of  parasitism, 
and  that  the  two  forms  are  in  reality  poles  apart,  with  no  more  real  affinity 
than  porpoises  and  fishes,  or  bats  and  birds.  It  is  certainly  not  at  this 
point  that  any  transition  from  one  group  to  the  other  is  to  be  sought.* 

In  the  foregoing  paragraphs  an  attempt  has  been  made  to  sum 
up  the  arguments  for  and  against  the  theory  that  the  ILgemosporidia 
are  to  be  removed  from  the  vicinity  of  the  Coccidia,and  classified 
with  the  trypanosomes  and  allied  forms  in  an  order  of  the  Flagellata. 
When  the  evidence  on  each  side  is  weighed  in  the  balance,  in  one 
scale  must  be  placed  the  complete  similarity  of  the  life-cycles  of 
typical  Coccidia  and  Hsemosporidia,  a  similarity  seen  in  every  phase 
of  the  life-cycle,  and  extending  even  to  minor  developmental 
details  ;  and  in  the  other  scale  certain  cell-granules  of  doubtful 
significance.  It  is  almost  inconceivable  that  more  importance 
should  be  attached  to  cytological  details,  the  genetic  and  classifi- 
catory  value  of  which  is  at  present  quite  uncertain,  than  to  the 
homologies  of  the  life-cycle  as  a  Avhole,  in  estimating  the  affinities 
of  the  orders  of  Protozoa  ;  the  more  so  since  even  in  the  Hsemo- 
flagellates  themselves  the  possession  of  the  binucleate  type  of 
structure  does  not,  apparently,  indicate  a  common  ancestry  for  all 
members  of  the  group. 

The  conclusion  reached  is,  then,  that  the  Ha?mosporidia  as  a 
group,  excluding  doubtful  forms  insufficiently  investigated  at 
present,  are  closely  allied  to  the  Coccidia.  It  is,  indeed,  probable 
that  there  are  two  lines  of  evolution  in  the  group — the  one  repre- 
sented by  the  hseniarnceba?,  halteridia,  and  true  leucocytozoa, 
descended  from  a  Coccidium-like  ancestor  ;  the  other  represented 
by  the  hsemogregarines,  from  an  ancestral  form  similar  to  Adelea 
or  Orcheobius.  Leger  (644)  has  classified  the  hoemogregarines  in 
the  section  Adeleidea  of  the  Coccidia,  and  one  may  regret  that 
the  distinguished  French  naturalist  did  not  go  one  step  farther  and 
place  the  hsemamcebse  in  his  section  Eimeridea  (see  p.  352,  supra}. 

On  the  other  hand,  any  resemblances  which  the  Ha?mosporidia 
exhibit  to  trypanosomes  and  allied  forms  are  due  to  convergent 
adaptation  on  the  part  of  the  Flagellates  themselves,  and  more 
especially  to  the  secondary  acquisition  by  the  latter  of  intracellular 

*  Leger  and  Duboscq  (646),  who  derive  Leishmania  and  Babesia  directly  from 
Crithidia  as  a  common  ancestor,  do  not  seem  to  have  taken  the  development  of 
Babesia  (Piroplasma)  into  consideration  at  all  ;  they  neither  refer  to  it  in  their 
text  nor  cite  any  of  the  relevant  memoirs  in  their  bibliography. 


THE  ILEMOSPORIDIA  395 

parasitism,  and  consequent  temporary  loss  of  the  locomotor 
apparatus.  It  may  well  be,  therefore,  that  some  forms  now 
generally  included  amongst  the  Hsemosporiclia  (e.g.,  possibly  the 
drepanidia)  may  prove,  when  better  known,  to  be  stages  of  Hsemo- 
flagellates,  and  to  have  in  reality  nothing  to  do  with  the  true 
Hsemosporidia. 

Affinities  of  the  Telosporidia  .—F?om  the  foregoing  discussion,  the 
conclusion  has  been  drawn  that  the  Coccidia  and  the  typical 
Harnosporidia  are  closely  allied,  sufficiently  so  to  be  grouped 
together  in  a  single  order,  for  which  the  name  "  Coccidiomorpha  " 
may  be  used.  In  a  former  chapter  (p.  354)  the  relationship  of  the 
Gregarines  and  Coccidia  was  discussed,  and  it  was  pointed  out 
that  there  was  no  difficulty  in  assuming  a  common  ancestral  origin 
for  the  two  groups — a  conclusion  which,  indeed,  has  never  been 
called  in  question.  The  Telosporidia,  taken  as  a  whole,  may  be 
regarded,  therefore,  as  a  homogeneous  and  natural  group,  in  which 
the  close  affinity  existing  between  its  constituent  members  may  be 
regarded  as  indicating  a  common  pliylogenetic  origin.  If  this 
conclusion  be  accepted,  it  remains  to  discuss  the  affinities  of  the 
Telosporidia  as  a  whole  to  other  groups  of  Protozoa.  It  is  not 
unreasonable  to  suppose  that  a  parasitic  group  of  this  kind  has  been 
evolved  from  free-living,  non-parasitic  ancestors,  and  the  question 
to  be  discussed  is  to  which  of  the  groups  of  Protozoa  the  ancestral 
form  of  the  Telosporidia  belonged.  Of  the  three  great  classes  of 
the  Protozoa,  the  Infusoria  may  almost  certainly  be  excluded 
from  consideration  in  regard  to  this  question,  since,  in  view  of  the 
very  specialized  and  definite  features  of  this  group,  there  are  no 
grounds  whatever  for  connecting  them  with  the  Telosporidia. 
There  remain,  therefore,  only  the  Sarcodina  and  Mastigophora  to 
be  considered. 

At  different  times  two  opposed  theories  have  been  put  forward 
with  regard  to  the  affinities  and  ancestry  of  the  Sporozoa.  One 
view  sees  in  them  the  descendants  of  typical  forms  of  Sarcodina, 
such  as  Amoeba  (Awerinzew,  890)  ;  the  other  derives  them  from 
flagellate  ancestors  such  as  are  represented  at  the  present  day  by 
Euglena  or  Astasia.  It  is  no  longer  possible,  however,  to  regard  the 
Sporozoa  as  a  whole  as  a  homogeneous  group,  and  the  two  so-called 
"  subclasses,"  Telosporidia  and  Neosporidia,  must  be  considered 
separately,  each  on  its  own  merits.  The  Neosporidia  are  considered 
at  the  end  of  the  next  chapter.  The  question  here  is  of  the  Telo- 
sporidia alone.  For  this  group  opinion  is  practically  unanimous  at 
the  present  day  in  favour  of  a  flagellate  ancestry,  a  theory  which 
must  be  considered  critically. 

One  of  the  main  arguments  generally  put  forward  for  the  theory 
of  the  flagellate  origin  of  the  Telosporidia  is  the  existence  of  flagel- 


396  THE  PROTOZOA 

lated  stages  in  the  life-history.  In  the  first  place,  the  micro- 
gametes  are  very  often  flagellated,  as  has  been  stated  frequently 
in  the  two  foregoing  chapters.  In  the  second  place,  the  youngest 
stages  in  the  development — the  merozoites  or  sporozoites — exhibit 
structural  features  which  are  either  those  of  a  flagellate  swarm- 
spore  (Hartmann,  675  ;  Schaudinn,  132),  or  can  readily  be  derived 
from  a  flagellula  in  which  the  flagellar  apparatus  has  become  rudi- 
mentary, as  in  the  sporozoites  of  gregarines,  where  the  rostrum  may 
be  interpreted,  with  a  high  degree  of  probability,  as  representing 
a  rudimentary  flagellum.  The  existence  of  flagellated  stages  of 
the  kinds  mentioned  in  the  development  of  the  Telosporidia  is  by 
no  means,  however,  a  cogent  argument  for  a  flagellate  ancestry  for 
the  group,  since  quite  typical  Sarcodina  of  all  orders  exhibit  flagel- 
late swarm-spores  and  gametes.  It  may  be  urged  that  in  the  case 
of  these  types  of  Sarcodina,  also,  the  existence  of  flagellate  stages 
indicates  a  flagellate  ancestry ;  but  such  an  argument  merely 
evades  the  question  at  issue,  which  is  not  whether  the  Telosporidia 
are  derived  from  Flagellata  indirectly  through  Sarcodine  ancestors, 
but  whether  or  not  they  are  descended  directly  from  ancestors 
that  were  typical  Flagellata.  The  existence  of  flagellated  swarm- 
spores  and  of  gametes  representing  a  modification  of  such  swarm- 
spores  is  not  sufficient  of  itself  to  prove  a  flagellate  ancestry  for  the 
Telosporidia. 

Far  more  cogent  arguments  for  the  flagellate  affinities  of  the 
Telosporidia  maybe  drawn  from  the  characters  of  the  adult  forms, 
especially  from  the  gregarine-type  of  body,  elongated  and  ver- 
micular in  character,  and  perfectly  definite  and  constant  in  form, 
which  occurs  in  every  group  of  the  Telosporidia  at  one  point  or 
another  in  the  life-history.  Such  a  type  of  body  can  be  readily 
derived,  as  Butschli  (2)  pointed  out,  from  an  organism  similar  to 
Astasia  or  Eugle.ua,  in  which  the  flagellar  apparatus  has  been  lost, 
and  all  special  organs  of  nutrition,  whether  holozoic  or  holophytic, 
have  disappeared  in  relation  with  the  parasitic  mode  of  life.  On 
the  other  hand,  the  gregarine-type  of  body  cannot  be  derived  from 
the  adult  forms  of  the  Sarcodina,  which  are  typically  amoeboid, 
and  without  any  definite  body-form  other  than  that  imposed  by 
the  physical  nature  of  their  body-substance. 

We  may  therefore  consider  the  ancestral  form  of  the  Telosporidia 
to  have  been  a  flagellate  organism  with  an  elongated  form  of  body, 
with  a  definite  form,  owing  to  the  presence  of  a  cuticle  of  a  certain 
degree  of  thickness  and  toughness,  and  with  a  flagellar  apparatus 
at  the  anterior  end.  Such  a  form  would  have  been  not  unlike  the 
leptomonads  now  found  commonly  as  parasites  of  insect-guts  ; 
but  there  is  no  reason  to  suppose  the  ancestral  form  to  have  had 
a  kinetonucleus  and  the  third  type  of  flagellar  insertion.  Such  a 


THE  ILEMOSPORIDIA  397 

form  probably  used  its  flagellum  for  the  purpose  of  attaching  itself 
to  the  epithelium  of  the  digestive  tract,  as  leptomonads  do  now 
(compare  Figs.  136,  137)  ;  and  from  this  primitive  type  of  attach- 
ment the  epimerite  of  the  gregarines  may  have  been  derived  by 
secretion  of  chitin  round  the  attaching  flagellum,  just  as  the 
primitive  tuft  of  fixing  cilia,  the  "  scopula.''  of  the  primitive 
Vorticellids  appears  to  become  converted  into  the  chitinous  stalks 
of  such  forms  as  Epistylis  (p.  441). 

The   conclusion    drawn   from   these    various    considerations   is, 
therefore,  that  the  Telosporidia  may  be  regarded  as  a  group  de- 
scended from  flagellate  ancestors  modified  in  adaptation  to  a  para- 
sitic mode  of  life  ;  not,  however,  specially  from  flagellates  of  the 
'  binucleate  "  type  of  structure. 

Bibliography. — For  references  see  p.  496. 


CHAPTER  XVI 
THE  SPOROZOA  :  III.  THE  NEOSPORIDIA 

A  TYPICAL  member  of  the  subclass  Neosporidia  is  a  parasite  of 
which  the  life-cycle  is  initiated  by  the  liberation  from  the  spore 
of  one  or  more  amcebulse  within  the  body  of  the  host,  in  the  digestive 
tract  in  all  known  cases.  For  this  initial  amcebula-phase  StempelFs 
term,  planont  (i.e.,  "wanderer"),  may  be  employed  conveniently, 
since  in  no  case  does  it  remain  in  the  lumen  of  the  digestive  tract, 
but  penetrates  into  the  wall  of  the  gut,  and  in  most  cases  migrates 
thence  into  some  organ  or  tissue  of  the  host,  where  it  lives  and 
multiplies  actively,  being  usually  at  this  stage  an  intracellular 
parasite,  in  some  cases,  however,  occurring  free  in  the  blood  or 

lymph. 

The  planont-phase  is  succeeded  typically  by  a  plasmodial  phase, 
which  arises  in  some  cases  by  simple  growth  of  the  amcebula 
(probably  then  a  zygote),  accompanied  by  multiplication  of  its 
nuclei ;  in  other  cases  by  association  together  and  cytoplasmic 
fusion  of  at  least  two  distinct  amoabulee,  of  which  the  nuclei  remain 
separate.  The  plasmodial  stage  is  very  characteristic  of  this  sub- 
class ;  it  represents  the  principal  or  "  adult "  trophic  phase  of  the 
parasite,  and  is  also  the  spore-forming  phase  ;  and,  as  the  name 
Neosporidia  implies,  the  production  of  spores  begins,  as  a  rule, 
when  the  plasmodium  is  still  young,  and  continues  during  its 
growth. 

In  some  cases,  however,  no  plasmodium  is  formed,  but  the 
planont-phase  is  succeeded  by  uninucleate  "  meronts  "  or  schizonts, 
which  multiply  by  fission  and  give  rise  ultimately  to  sporonts  in 
which  spore-formation  sets  a  limit  to  the  growth.  In  such  forms 
the  general  course  of  the  life-cycle  is  not  essentially  different  in 
any  way  from  that  of  a  member  of  the  Telosporiclia,  such  as  Coc- 
cidium.  The  tendency,  therefore,  of  many  Neosporidia  to  form 
spores  during  the  trophic  phase  cannot  be  used  to  frame  a  rigorously- 
exact  definition  of  the  group.  A  more  distinctive  characteristic 
of  the  subclass  is  the  complete  absence  of  flagellated  phases  in 
any  part  of  the  life-cycle,  and  more  especially  the  fact  that 

39S 


THE  NEOSPORIDIA 


.399 


the    sporozoites    are    always,    apparently,   amcebulae,   and   never 
gregarinulee.* 

The  Neosporidia  are  divisible  into  two  sections,  known  re- 
spectively as  the  Cnidosporidia  and  the  Haplosporidia.  The 
Cnidosporidia  are  distinguished  by  the  possession  in  the  spore  of 
peculiar  structures  termed  polar  capsules,  which  are  lacking  in  the 
Haplosporidia. 

A  polar  capsule  (Fig.  163)  is  a  hollow,  pear-shaped  body,  with  a 
tough  envelope,  probably  chitinoid  in  nature.  It  is  situated  at  one 
pole  of  the  spore,  with  its  pointed  end  immediately  below  the 
surface,  in  continuity  with  a  minute  pore  in 
the  sporocyst.  Coiled  up  within  the  capsule 
is  a  delicate  filament,  often  of  great  length, 
probably  of  the  same  nature  as  the  capsule, 
and  continuous  with  it.  Under  suitable  stimu- 
lation the  polar  filament  is  shot  out  through 
the  pore  in  the  sporocyst.  In  their  structure 
the  polar  capsules  resemble  the  nematocysts 
of  the  Ccelentera.  Each  polar  capsule  is 
formed  within  a  capulogenous  cell. 

The  Cnidosporidia  comprise  four  orders— 
the     Myxosporidia,    Actinomyxidia,     Micro- 
sporidia,    and    Sarcosporidia.      The    Haplo- 
sporidia constitute  an  order  apart. 

Order  I.  :  Myxosporidia.  -  -  This  order  is 
characterized  chiefly  by  the  following  points  : 
The  principal  trophic  phase  is  a  multinucleate 
plasmodium  of  relatively  large  size,  resembling 
an  amoeba  in  its  appearance  and  movements. 
The  spores  are  also  relatively  large,  and 
exhibit  typically  a  binary  symmetry,  having 
a  sporocyst  composed  of  two  valves  and 
usually  two  polar  capsules,  sometimes  increased 
in  number  to  four,  rarely  reduced  to  one. 

The  Myxosporidia  comprise  a  great  number  of  genera  and  species, 
parasitic  for  the  most  part  in  cold-blooded  vertebrates,  especially 
fishes,  in  which  they  are  found  very  commonly.  They  are  not  as 
yet  known  as  parasites  of  birds  or  mammals,  but  a  few  species  are 
known  from  invertebrate  hosts. 

Myxosporidia  are  typically  tissue-parasites,  occurring  in  various 
tissues  of  the  body,  by  preference  muscular  or  connective,  but  also 

*  A  possible  exception  to  this  statement  is  furnished  by  the  family  Ccdospor- 
idiidce  of  the  Haplosporidia  (p.  424).  But  the  position  of  all  the  forms  in  this  order 
is  more  or  less  questionable,  and  their  attachment  to  the  typical  Neosporidia  is 
still  probationary. 


FIG.  163.  — Polar  cap- 
sules of  the  spores 
of  Myxosporidia.  a, 
Polar  capsule  with 
the  filament  coiled 
within  it  ;  b,  with  the 
filament  partly  ex- 
truded ;  c,  d,  with  the 
filament  completely 
extruded.  After 
Balbiani. 


400 


THE  PROTOZOA 


p.s. 


:S"\      :*K*?K'  •  -  • 
^4^f^pHo?:v;^ 


~"-'^.'.*i-   '         .  ••  f-i  ••"•--  -vj 


other  classes  of  tissue.  A  few  species  are  known  to  attack  the 
nervous  system — for  instance,  Lentospora  (Myxobolus)  cerebralis, 
cause  of  "  Drehkrankheit  "  in  Salmonidce  (Plehn),  and  Myxobolus 
neurobius  of  trout  (Schuberg  and  Schroder).  In  the  tissue  attacked 
the  parasite  may  be  concentrated  at  one  spot,  so  as  to  form  a  dis- 
tinct cyst  visible  to  the  naked  eye  ;  or  parasite  and  tissue  may  be 
mixed  up  together  in  a  state  of  "  diffuse  infiltration  "  such  that 
microscopic  examination  is  required  to  detect  the  parasite,  and  as 
its  body  becomes  used  up,  to  form  spores,  the  tissue  becomes  in- 
filtrated with  vast  numbers  of  spores  lying  singly  or  in  groups 
between  the  cells. 

In  many  species  of  Myxosporidia,  on  the  other  hand,  the  spore- 
forming  plasmodial  phase  is  found  in 
cavities  of  the  body — not  in  any 
known  instance  in  the  lumen  of  the 
digestive  tract,  but  frequently  in  the 
gall-bladder  or  urinary  bladder  of  the 
host.  In  such  cases  the  parasite 
may  lie  quite  freely  in  the  cavity  it 
inhabits,  or  may  be  attached  by 
its  pseudopodia  to  the  lining  epi- 
thelium ;  in  the  latter  case  the 
attachment  is  purely  mechanical, 
and  does  not  involve  injury  to  the 
epithelial  cells. 

As  might  be  expected,  the  Myxo- 
sporidia parasitic  in  tissues  are 
often  very  deadly  to  their  hosts, 
and  are  sometimes  the  cause  of 
severe  epidemics  among  fishes. 
Those  species,  on  the  other  hand, 
which  inhabit  cavities  with  natural 
means  of  exit  from  the  body  appear  to  be  as  harmless  to  their 
hosts  as  are  the  majority  of  parasitic  Protozoa  in  nature. 

The  adult  trophic  phase  is  usually  a  large  amoeba-like  organism 
with  a  distinct  ectoplasm  and  eiidoplasm.  In  some  species  the 
ectoplasm,  which  appears  to  be  purely  protective  in  function,  ex- 
hibits vertical  striations,  or  is  covered  by  a  fur  of  short,  bristle-like 
processes,  the  nature  and  significance  of  which  are  uncertain — as, 
for  example,  Myxidium  lieberkuhni,  the  common  parasite  of  the 
urinary  bladder  of  the  pike  (Esox  lucius).  The  form  of  the  body 
changes  constantly,  with  extrusion  of  pseudopodia,  which  are 
used  for  locomotion  to  a  limited  extent,  more  often  for  fixation, 
but  never  for  food-capture.  They  may,  however,  by  increasing 
the  body-surface,  increase  also  the  power  of  absorption  of  food- 


>• ec£ 


FIG.  164.  —  Chloromyxum  leydigi, 
parasite  of  the  gall- bladder  of  the 
dogfish,  skate,  etc.  ;  trophozoite 
(plasmodium)  in  an  active  state. 
eel.,  Ectoplasm  ;  end,,  endo plasm  ; 
y.,  yellow  globules  in  the  endo- 
plasm  ;  sp.,  spores,  each  with  four 
polar  capsules.  After  Thelohan, 
from  Minchin,  magnified  525. 


THE  NEOSPORIDIA 


401 


stuffs  b}>-  diffusion,  the  method  by  which  the  organism,  like  other 
sporozoaii  parasites,  obtains  the  required  nourishment.  The  pseu- 
dopodia  vary  in  form  in  different  species,  from  coarsely  lobose 
and  blunt  to  fine  filaments  ending  in  sharp  points.  In  some  species 
the  formation  of  pseudopodia  is  localized  at  one  pole  of  the  body, 
termed  "  anterior,"  and  in  such  cases  a  peculiar  propulsive  pseudo- 
podium  ("  Stemm-pseudopoclium ")  may  be  developed  at  the 
posterior  pole  like  a  tail,  which 
by  its  elongation  pushes  the  body 
forward.* 

The  endoplasm  is  distinguished 
from  the  ectoplasm  by  its  coarsely 
granular  appearance.  In  addition 
to  numerous  nuclei  and  stages  of 
spore-formation,  the  endoplasm 
may  contain  various  metaplastic 
products,  such  as  crystals,  pig- 
ment-grains, fat-globules,  etc.  ; 
but  never  food-vacuoles  or  solid 
ingested  food-particles. 

The  plasmodial  trophozoite 
forms  spores  in  its  endoplasm, 
as  a  rule,  during  the  whole  period 
of  growth,  but  may  also  multiply 
by  plasmotomy.  In  Myxidium 
lieberkuhni,  for  example,  plas- 
motomy proceeds  actively  during 
the  summer  months,  and  leads 
to  the  wall  of  the  pike's  bladder 
being  carpeted  with  the  slimy, 
orange -coloured  plasmodia,  the 
presence  of  which  can  generally 
be  detected  at  a  glance  ;  spore- 
formation,  on  the  other  hand, 
takes  place  almost  exclusively  during  the  colder  months  of  the  year. 

Spore-formation  in  the  Myxosporidia  is  a  somewhat  complicated 
process,  and  is  accompanied  by  sexual  phenomena,  which  are 
commonly  stated  to  be  autogamous,  but  which  are  probably 
nothing  of  the  sort.  There  is  a  slight  difference  between  the 
mode  of  spore-formation  in  the  Disporea,  in  which  each 
trophozoite  produces  but  two  spores,  and  the  Polysporea.  which 
produce  many. 

*  Auerbach  (758,  p.  11)  seeins  to  have  mistaken  altogether  the  significance- of 
Doflein's  "  Stemm-pseudopodium,"  and  applies  the  term  to  the  anterior  pseudo- 
podia,  which  appear  to  be  rather  tactile  in  function  in  such  cases. 

26 


young 
which 


FIG.  165.  —  Leptotheca  agilis : 
plasmodial  trophozoites  in 
the  spore-formation  has  not  begun. 
A,  Individual  moving  forward  by 
means  of  the  "  Stemm-pseudopo- 
dium "  (st.  ps.)  ;  B,  individual  in 
which  only  the  anterior  pseudopodia 
are  developed.  After  Doflein. 


402 


THE  PROTOZOA 


crrv 


FIG.   166. — For  description  nee  fool  of  opposite  page. 


THE  XEOSPORIDIA  403 

An  example  of  the  Disporea  is  Ceratomyxa  drepanopsetta;,  of  which  the 
spore-formation  is  described  by  Awerinzew  (759).  The  trophozoite  has  at 
first  only  two  nuclei,  which  are  considered  by  Awerinzew  to  be  derived, 
''beyond  all  doubt,"  from  division  of  a  single  nucleus;  it  seems  far  more 
probable,  on  the  contrary,  that  the  binucleate  trophozoite  is  to  be  derived 
from  the  association  and  fusion  of  two  distinct  planonts.  In  the  binu- 
cleate trophozoite  each  nucleus  divides  by  karyo kinesis  into  two  nuclei, 
a  larger  and  a  smaller  (Fig.  166,  A).  The  two  smaller  nuclei  are  vegetative, 
the  two  larger  generative,  in  function.  Round  each  of  the  two  generative 
nuclei  the  protoplasm  becomes  concentrated  so  as  to  form  two  cells  which 
lie  embedded  in  the  endoplasm  of  the  trophozoite.  These  two  cells  are  usually 
•of  distinctly  different  sizes,  and  represent  a  microgametocyte  and  a  macro- 
gametocyte  respective!}'.  Each  gametocyte  next  divides  into  two  gametes 
(Fig.  166,  B,  C,  D),  and  in  each  gamete  a  certain  amount  of  chromatin  is 
•extruded  from  the  nucleus,  first  into  the  cytoplasm  of  the  gamete,  and  then 
into  the  endoplasm  of  the  mother-trophozoite.  Then  each  microgamete 
copulates  with  one  of  the  two  rnacrogametes  (Fig.  166,  E,  F).  The  two 
zygotes  thus  formed  represent  the  sporoblasts,  each  of  which  forms  a  spore 
independently  of  the  other. 

Each  sporoblast  divides  into  two  cells,  a  larger  and  a  smaller  (Fig.  166,  G), 
and  the  smaller  divides  again  into  two  (Fig.  166,  H) ;  the  result  is  an  aggregate 
of  three  cells :  a  larger,  which  gives  rise  ultimately  to  the  two  parietal  cells 
which  form  the  valves  of  the  sporocyst,  and  may  be  termed  the  "  sporocyst- 
mother-cell "  ;  and  two  smaller  cells,  one  of  which  is  the  mother-cell  of  the 
two  capsulogenous  cells,  the  other  the  future  sporozoite  or  amcebula.  The 
sporocyst-mother-cell  may  become  temporarily  separate  from  the  capsule- 
mother-cell  and  the  amcebula. 

The  three  cells  of  the  previous  stage  build  up  the  spore  in  the  following 
manner  :  The  sporozoite  grows  in  size,  and  its  nucleus  divides  into  two.  The 
capsule-mother-cell  divides  into  two  capsulogenous  cells,  each  of  which 
forms  a  polar  capsule  in  its  interior.  The  amcebula  and  the  two  capsulogenous 
cells  are  placed  close  together  and  arranged  in  a  definite  manner  (Fig.  166,  7). 
The  sporocyst-mother-cell  divides  into  two  parietal  cells  (Fig.  166,  J),  which 
place  themselves  on  either  side  of  the  cell-complex  composed  of  the  associated 
amcebula  and  capsulogenous  cells  (Fig.  166,  K),  and  each  secretes  one  valve 
of  the  sporocyst  enveloping  the  whole  complex. 

Thus  the  trophozoite  consists  finally  of  an  amoeboid  body  containing  two 

FIG.  166. — Spore-formation  in  Ceratomyxa  drepanopsettce.  A,  Trophozoite  sketched 
in  outline,  showing  in  the  plasmodium  two  generative  nuclei  (g.),  each  sur- 
rounded by  a  cell-body,  and  two  vegetative  nuclei  (v. ),  which  lie  in  the  pro- 
toplasm of  the  body  (left  blank)  ;  note  that  the  generative  cells  are  of  different 
sizes  ;  B,  C,  the  two  generative  cells  have  divided  each  into  two,  so  that 
there  are  now  two  macrogametes  (  $  )  and  two  microgametes  ( $  )  ;  chromatin 
is  being  given  off  from  the  nuclei  of  the  gametes  into  the  cytoplasm  ;  D,  each 
microgamete  is  apposed  to  a  macrogamete  ;  the  chro matin-bodies  given  off 
by  the  gamete-nuclei  are  now  extruded  into  the  plasmodial  body  ;  E,  F. 
stages  in  the  syngamy  between  the  gametes  ;  in  E  the  cell-bodies  are  fused, 
in  F  the  zygotes  (z.)  are  complete  ;  G,  each  zygote  (sporoblast)  has  divided 
into  a  larger  (p)  and  a  smaller  cell ;  H,  the  smaller  cell  in  each  sporoblast 
has  divided  into  two,  the  capsule-mother-cell  (c.m.)  and  the  sporozoite  (am) ; 
the  larger  cell  (p.)  is  the  mother-cell  of  the  parietal  cells  ;  I,  a  single  sporoblast 
showing  the  parietal  mother-cell  (p.)  still  undivided,  the  sporozoite  (am) 
with  its  nucleus  divided  into  two,  and  two  capsulogenous  cells  (e.g.)  derived 
from  division  of  c.m.  in  H  ;  J,  a  trophozoite  showing  the  two  parietal  mother- 
cells  of  H  each  divided  into  two  parietal  cells  (p.')  but  still  separate  from  the 
cell-complex  consisting  of  the  binucleate  sporozoite  (am)  and  the  two  capsu- 
logenous cells  (e.g.)  ;  K,  union  of  all  the  cell-elements  of  the  spore  ;  the  two 
parietal  cells  (p.')  surround  the  cell-complex  (drawn  on  a  smaller  scale  than 
the  last  figure)  ;  L,  spore  nearly  fully  formed  :  n.p.,  nucleus  of  a  parietal 
cell  ;  am,  sporozoite  with  two  nuclei  (n.g.) ;  p.c.,  polar  capsules.  After 
Awerinzew  (759). 


404 


THE  PROTOZOA 


FIG.  167. — Spore-formation  in  Sphceromyxa  sabrazesi.  A,  Propagative  cell  with 
two  nuclei  of  different  sizes  ;  B,  two  such  propagative  cells  undergoing  fusion 
to  form  C,  a  pansporoblast  with  four  nuclei,  two  smaller,  peripheral,  the 
nuclei  of  the  two  envelope-cells,  and  two  larger,  central,  the  nuclei  of  the 
spore-forming  elements  ;  D,  pansporoblast  with  fourteen  nuclei,  eight  peri- 
pheral, six  central ;  two  of  the  latter,  smaller  than  the  others,  represent  redue- 

[Continued  at  foct  of  p.  405, 


THE  NEOSPORIDIA  405 

vegetative  nuclei  and  two  spores.  Each  spore  (Fig.  166,  L)  consists  of  (1)  a 
sporocyst  composed  of  two  valves,  each  secreted  by  a  parietal  cell ;  (2)  two 
polar  capsules,  each  secreted  by  a  capsulogenous  cell ;  (3)  a  binucleate  amcebula, 
the  sporozoite  or  sporoplasm.  When  the  spore  is  fully  formed,  the  cells  which 
form  the  valves  and  polar  capsules  are  used  up  and  degenerate,  remnants 
only  of  their  nuclei  being  visible.  The  spores  represent  the  propagative 
phase,  and  the  trophozoite  with  its  vegetative  nuclei  degenerates. 

The  Myxosporidia  Polysporea  differ  from  the  Disporea  in  that  the  plasrno- 
clium  contains  a  great  number  of  nuclei,  some  of  which  are  purely  vegetative 
in  function,  others  generative  ;  and  the  plasmodium  produces  in  its  interior 
numerous  spores,  which  are  always  formed  in  couples.  This  peculiarity  is 
due  to  the  fact  that  the  two  sporoblasts  arise  from  a  cell-complex  which  is 
termed  a  "  pansporoblast,"  producing  two  sporoblasts  and  two  spores. 

Spore-formation  in  Pol.ysporea  has  been  studied  in  Spliceromyxa  sabrazesi 
(not  labrazesi),  from  the  gall-bladder  of  Hippocampus,  by  Schroder  (767  and  768), 
and  in  Myxobolus  pfeifferi,  a  deadly  tissue-parasite  of  the  barbel,  by  Keysselitz. 
Their  results  are  almost  identical  in  each  case,  except  for  minor  details,  and 
are  in  the  main  as  follows  (Figf.  167,  168). 

The  generative  nuclei  of  the  plasmodium  become  the  centres  of  a  condensed 
patch  of  protoplasm  (Fig.  168,  A),  forming  a  "  propagative  cell  "  (Keysselitz). 
These  cells  may  multiply  with  mitosis  of  the  nuclei  for  a  while,  but  finally 
proceed  to  spore-formation.  The  nucleus  of  a  propagative  cell  divides  into 
two,  a  larger  and  a  smaller,  and  division  of  the  cell  follows  sooner  or  later 
(Fig.  167,  A  ;  Fig.  168,  B,  C).  Two  such  couples  of  cells  become  associated,  and 
the  two  smaller  cells  form  an  envelope  surrounding  the  two  larger  cells,  which 
by  their  association  form  the  pansporoblast  (Fig.  167,  B,  0 ;  Fig.  168,  D).  Hence 
the  pansporoblast  is  from  the  first  a  complex  of  two  distinct  cells,  and  not, 
as  was  formerly  supposed,  a  single  cell.  The  two  cells  of  the  pansporoblast 
may  be  termed  gamonts,  since  they  give  rise  ultimately  to  gametes,  but  not 
to  gametes  alone,  like  the  gametocytes  of  Ceratomyxa.  The  cytoplasm  of 
the  two  gamonts  may  fuse  into  one  mass,  but  the  nuclei  remain  separate  and 
undergo  repeated  divisions,  until  the  pansporoblast  within  its  envelope 
contains  twelve  nuclei,  and  may  consist  of  as  many  separate  cells  (Fig.  167,  D  ; 
Fig.  168,  E).  The  nuclei  or  cells  then  become  arranged  in  a  definite  manner  ; 
eight  of  them  take  up  a  peripheral  position,  four  of  them  place  themselves 
more  centrally  (Fig.  167,  E).  The  four  central  cells  are  the  gametes  ;  their 
nuclei  undergo  reducing  divisions,  and  the  four  cells  then  pair  off  into  two 
couples  ;  in  each  couple  the  cytoplasmic  bodies  of  the  two  cells  fuse  together, 
but  their  nuclei  remain  distinct.  It  is  probable  that  in  each  couple  one 
nucleus  is  descended  from  that  of  one  of  the  two  original  propagative  cells,  the 
other  nucleus  from  that  of  the  other. 

At  this  stage  the  pansporoblast  divides  into  two  masses,  the  sporoblasts 

FIG.  167  continued: 

tion-nuclei  beginning  to  degenerate  ;  the  envelope-nuclei  are  not  represented  ; 
E,  the  pansporoblast  beginning  to  divide  into  two  sporoblasts  ;  within  the 
envelope  are  seen  also  some  small  bodies  of  doubtful  nature  ;  F,  the  two 
sporoblasts  completely  separated,  between  them  two  residual  nuclei ;  each 
sporoblast  has  six  nuclei,  four  peripheral,  two  central ;  at  the  two  extremities 
of  the  sporoblast  the  polar  capsules  are  beginning  to  be  formed  ;  G,  one  of 
the  two  sporoblasts  at  a  later  stage,  showing  two  parietal  cells,  situated 
superficially  ;  two  nuclei  of  the  capsulogenous  cells,  each  near  a  polar  capsule ; 
the  two  germinal  nuclei  close  together  at  the  centre ;  and  a  residual  nucleus 
attached  to  the  surface  ;  //,  /,  further  stages  in  the  development  of  the 
sporoblast  ;  J,  pansporoblast  with  two  spores  almost  fully  formed,  and  the 
two  residual  nuclei  ;  each  spore  has  a  polar  capsule  (p.c.)  at  each  end,  and  near  it 
a  nucleus  of  the  capsulogenous  cell  (n.c.)  ;  two  large  parietal  nuclei  (n.p.),  in 
process  of  degeneration  ;  and  two  germinal  nuclei  (n.g.)  ;  K,  L,  M,  fully- 
formed  spores  ;  in  K  and  M  the  two  germinal  nuclei  are  still  separate,  in 
L  they  have  undergone  fusion  ;  in  M  the  two  polar  filaments  are  extruded. 
After  Schroder  (767  and  768). 


406 


THE  PROTOZOA 


each  containing  six  nuclei — namely,  four  peripheral  and  two  central 
(Fig.  167,  F  ;  Fig.  168,  F).  The  reduction-nuclei  are  left  out  in  the  cold, 
and  die  off.  From  each  sporoblast  a  spore  is  formed  in  the  following  way 
(Fig.  167,  G — J  ;  Fig.  168,  (?) :  Of  the  four  peripheral  cells,  two  are  parietal  cells 
which  give  rise  to  the  two  valves  of  the  sporocyst,  the  other  two  as  capsu- 
logenous  cells  produce  the  two  polar  capsules  ;  the  two  central  nuclei  with  the 
mass  of  protoplasm  in  which  they  lie  become  the  amcebula  or  sporozoite  of 
the  spore.  The  sporozoite  is  thus  at  first  binucleate,  but  when  the  spore 
is  fully  formed  its  two  nuclei  fuse  into  one.  There  can  be  no  doubt  that  this 
fusion  represents  a  karyogamy,  and  that  the  single  nucleus  is  a  synkaryon. 
The  cells  which  form  the  valves  of  the  sporocyst  and  polar  capsules  degenerate 
when  the  spore  is  completely  formed. 


H 


FIG.  168. — Spore-formation  in  Myxobolus  pfeifferi.  A,  Propagative  cell  from  the 
plasmodium  ;  B,  division  of  the  propagative  cell  into  two  unequal  halves  ; 
C,  the  smaller  cell  of  the  preceding  stage  applies  itself  as  a  flattened  envelope- 
cell  to  the  larger  ;  D,  a  mass  formed  by  union  of  two  couples  of  cells  similar 
to  those  of  the  preceding  stage — the  pansporoblast  ;  E,  pansporoblast  with 
fourteen  nuclei,  two  representing  the  envelope-cells,  and  twelve  arisen  by 
division  of  the  two  larger  cells  of  the  preceding  stage  ;  F,  the  pansporoblast 
divided  into  the  two  envelope-cells  and  two  masses,  sporoblasts,  each  con- 
taining six  nuclei,  which  are  arranging  themselves  so  that  two  nuclei  are 
more  central,  four  more  peripheral  in  position  ;  G,  spore  in  process  of  forma- 
tion ;  the  sporocyst  is  formed  by  two  parietal  cells  (p.) ;  at  the  upper  pole  are 
the  two  polar  capsules  (p.c.)  in  their  capsulogenous  cells  ;  and  the  lower  part 
of  the  spore  is  occupied  by  the  binucleate  amoebula  (am.) ;  H,  ripe  spore  ; 
in  the  amoebula  the  two  nuclei  have  fused  into  one  ;  lettering  as  in  the  last. 
After  Keysselitz. 

Mercier  (765'5),  on  the  other  hand,  who  has  also  studied  the  spore-formation 
of  Myxobolns  pfeifferi,  differs  from  Keysselitz  in  his  account,  more  especially 
with  regard  to  the  sexual  processes.  He  affirms  that  the  plasmodium  contains 
four  zones:  (1)  A  peripheral  zone,  without  nuclei  or  spores;  (2)  a  zone  of 
nuclei,  all  similar  amongst  themselves,  which  multiply  by  mitosis  ;  (3)  a  zone 
containing  nuclei  of  different  sizes  and  early  stages  of  spore-formation  ;  and 
(4)  a  central  region  containing  ripe  spores.  In  the  third  zone  differentiation 
of  microgametes  and  macrogametes  takes  place.  The  gametes  copulate,  and 
the  zygote  is  a  pansporoblast.  Its  nucleus  (synkaryon)  divides  to  form 
fourteen  nuclei,  two  of  which  are  rejected,  while  from  the  remaining  twelve 
arise  two  sporoblasts,  each  with  six  nuclei,  and  finally  two  spores. 


THE  NEOSPORIDIA  407 

According  to  Awerinzew  (760),  in  Myxidium  sp.  a  propagative  cell  may 
give  rise  sometimes  to  a  single  spore,  as  in  Ceratomyxa,  in  other  cases  to  three 
spores  ;  this  must  doubtless  be  interpreted  to  mean  that  a  propagative 
cell  may  become  a  sporoblast  without  entering  into  association  with  another 
propagative  cell,  and  that  in  other  cases  three  propagative  cells  may  form 
an  association  ;  these  variations  present  an  analogy  with  the  solitary  encyst- 
ment  or  triple  associations  of  gregarines  (p.  331). 

The  process  of  syngamy  in  these  parasites  has  been  described  as  being  a 
process  of  autogamy,  but  whether  it  is  so  or  not  depends  entirely  upon  the 
manner  in  which  the  plasmodium  arises  ;  if  a  single,  uninucleate  amoebula 
becomes  a  plasmodium  by  growth  accompanied  by  nuclear  multiplication, 
then  the  sexual  process  is  a  case  of  autogamy ;  but  if,  as  is  more  likely,  two 
or  more  distinct  amcebulse  become  associated  to  form  a  plasmodium,  then 
the  two  nuclei  of  the  gametocytes  in  Disporea,  of  the  "  pansporo blast "  of 
Polysporea,  may  well  be  of  distinct  parentage,  and  in  that  case  the  sexual 
process  is  not  autogamous. 

Comparing  the  different  modes  of  spore-formation,  it  is  seen  that 
in  all  cases  alike  the  spore  arises  from  a  sporoblast  which  divides 
into  several  cells  :  two  to  form  the  sporocyst,  which  consists  of  two 
distinct  valves  meeting  in  a  suture,  and  thus  defining  a  sutural 
plane  in  the  spore  ;  two  (or  four  in  Chloromyxidce)  to  form  the 
polar  capsules  ;  and  a  fifth  to  furnish  the  binucleate  sporozoite. 
The  spores  of  Myxosporidia  have,  as  has  been  seen,  a  complex 
structure,  and  are  highly  characteristic  bodies — the  original  psoro- 
sperrns  of  Johannes  Miiller.  In  minor  details  of  form,  and  structure 
they  vary  enormously  in  different  species.  The  greatest  diameter 
of  the  spore  may  lie  in  the  sutural  plane,  as  in  Polysporea  generally, 
or  in  a  plane  at  right  angles  to  it,  as  in  Disporea  (Fig.  169).  The 
sporocyst  may  be  prolonged  into  tails  and  processes  of  various 
kinds  ;  the  polar  capsules  may  be  close  together  at  one  pole  of  the 
spore,  or  at  opposite  poles.  In  all  cases,  so  far  as  is  known,  the 
spores  germinate  in  the  intestine  of  the  new  host,  which  becomes 
infected  casually  by  taking  in  the  spores  with  its  food.  Other 
methods  of  infection  have  been  imagined,  but  have  never  been 
demonstrated  experimentally. 

The  most  complete  account  of  the  germination  of  the  spore  and  of  the  early 
development  of  the  parasite  in  its  new  host  is  that  given  by  Auerbach  (758) 
for  Myxidium  bergense,  parasite  of  the  gall-bladder  of  Gadus  virens.  The 
spores  from  the  gall-bladder  pass  through  the  rectum  to  the  exterior.  To 
develop  further,  they  must  be  taken  up  by  the  new  host,  in  the  stomach  of 
which,  however,  the  spores  undergo  very  little  change  ;  the  sporozoite  rounds 
itself  off,  and  in  some  cases  its  nuclei  copulate,  in  others  they  remain  apart. 
From  the  stomach  the  spores  pass  into  the  duodenum,  and  as  soon  as  they 
are  acted  upon  by  the  bile  the  polar  filaments  are  extruded,  the  valves  of  the 
sporocyst  split  apart,  and  the  amoeboid  sporozoite  creeps  out.  When  the 
amcebula  becomes  free,  its  two  nuclei  fuse  into  one  if  they  have  not  done  so 
already. 

The  free  amoebula  wanders  actively  up  the  bile-duct,  and  penetrates  into  a 
cell  of  the  lining  epithelium.     Within  the  cell  the  nucleus  of  the  parasite 
undergoes  a  change,  becoming  looser  in  texture.     The  amoebula  leaves 
cell  and  becomes  free  in  the  bile  again,  where  it  multiplies  by  fission,  ^producing 
in  this  way  very  numerous  amoebulse,  which  may  occur  singly  or  in  clumps. 


408  THE  PROTOZOA 

The  amoebulse  next  associate  in  couples.  In  each  couple  the  cytoplasm  of 
the  associates  undergoes  partial  fusion.  In  one  associate  the  loosely-textured 
nucleus  remains  unaltered ;  in  the  other  the  nucleus  divides  by  mitosis,  and 
one  of  the  two  daughter-nuclei,  with  a  small  quantity  of  the  cytoplasm,  is 
cast  off.  The  bodies  of  the  two  associates  now  fuse  completely  into  a  single 
mass  containing  two  nuclei,  a  large  and  a  small.  The  larger  nucleus  represents 
the  unaltered  nucleus  of  one  of  the  two  original  associates  ;  the  smaller 
nucleus  is  the  reduced  nucleus  of  the  other  associate. 

The  binucleate  stage  formed  by  the  association  of  two  arncebulsc  (planonts) 
is  the  foundation  of  the  plasmodium.  The  two  nuclei  remain  separate  and 
multiply  independently,  maintaining  their  difference  in  size.  Hence  the 
young  plasmodia  consist  of  nuclei  of  two  sizes,  small  and  large  ;  and  this 
difference  in  size,  which  has  often  been  noted  in  the  plasmodia  of  other 
species,  is  due,  according  to  Auerbach,  to  the  fact  that  the  smaller  nuclei  are 
derived  from  a  nucleus  which  has  undergone  reduction,  while  the  larger  nuclei 
are  derived  from  one  which  has  not  done  so. 

So  far  as  it  is  possible  to  generalize  from  the  few  recorded  observa- 
tions and  experiments,  the  germination  of  the  Myxosporidian  spore 
probably  takes  place  always  in  the  digestive  tract  of  the  new  host. 
The  first  act  in  the  process  is  the  rounding  off  of  the  amoeboid 
sporozoite  ;  next  the  polar  capsules  are  discharged,  the  function  of 
these  organs  being,  apparently,  that  of  fixing  the  spore  to  the  wall 
of  the  gut.  Then  the  two  valves  of  the  sporocyst  separate,  and 
the  amcebula  creeps  out ;  its  two  nuclei  copulate  to  form  the  syn- 
karyon,  if  they  have  not  done  so  already.  In  this  way  the  planont- 
phase  arises  from  the  sporozoite,  and  is  set  free  in  the  digestive 
tract,  whence  it  migrates  to  the  organ  or  tissue  of  which  it  is  a 
specific  parasite.  When  its  destination  is  an  organ  which,  like  the 
gall-bladder,  is  in  open  communication  with  the  gut,  the  migration 
may  be  comparatively  simple  and  direct ;  but  in  the  majority  of 
cases  the  journey  to  be  accomplished  is  a  complicated  one.  It  is 
probably  safe  to  assume  that  in  most  cases  the  planont  passes 
through  the  wall  of  the  gut  into  the  channels  of  the  blood  or  lymph, 
and  by  this  route  arrives  ultimately  at  its  destination.  In  the 
organ  or  tissue  which  the  parasite  attacks,  the  planont  probably 
passes  through  a  period  of  cell-parasitism  and  proliferation  by 
binary  fission  ;  ultimately  the  plasmodial  phase  is  initiated  by 
association  of  two  planonts,  of  which  the  bodies  fuse,  but  the  nuclei 
remain  separate.  Growth  of  the  body  with  independent  multipli- 
cation of  its  nuclei  to  four  (Disporea)  or  many  (Polysporea)  produces 
the  spore-forming  plasmodium  characteristic  of  the  order. 

The  Myxosporidia  are  classified  as  follows  : 

SUBORDER  I. :  DISPOREA. — Only  two  spores  formed  in  the  plasmodium. 
The  greatest  diameter  of  the  spore  is  at  right  angles  to  the  sutural  plane 
(Fig.  169). 

One  family,  Ceratomyxidce,  with  two  genera  :  Ceratomyxa,  with  several 
species  parasitic  in  the  gall-bladders  of  fishes  ;  Leptotheca  (Fig.  165),  in- 
cluding several  species  from  gall-bladders  of  fishes,  but  L.  ranarum  occurs 
in  the  kidneys  of  frogs  (Rana  spp.). 


THE  NEOSPORIDIA  409 

SUBORDER  II. :  POLYSPOREA. — Numerous  spores  formed  in  the  plasmodium. 
The  greatest  diameter  of  the  spore  lies  in  the  sutural  plane. 

Three  families  :  (1)  Myxobolidce,  with  two  polar  capsules  (sometimes  reduced 
to  one),  and  with  a  peculiar  vacuole,  which  stains  with  iodine,  in  the  amcebula. 
Typically  tissue -parasites  of  fishes  ;  principal  genera  Myxobolus,  with  round 
or  oval  spores,  and  Henneguya,  with  tail-like  processes  to  the  spore. 

(2)  Myxidiidce  ;  spores  with  two  polar  capsules,  no  iodinophilous  vacuole  ; 
typically    "free"    (i.e.,    ccelozoic)    parasites.     Principal    genus    Myxidium, 
with  the  polar  capsules  at  opposite  poles  of  the  spore  ;  M.  lieberkiihni,  the 
common  parasite  of  the  pike. 

(3)  Chloromyxidce,  with  four  polar  capsules  ;  the  best  known  species  is 
Chloromyxum  leydigi  (Fig.  164),  from  the  gall-bladder  of  various  Elasmobranch 
fishes. 

To  the  typical  Myxosporidia  enumerated  in  the  above  summary  must  be 
added  two  genera  recentty  described : 

Coccomyxa  morovi  (Leger  and  Hesse,  765),  from  the  gall-bladder  of  the 
sardine  ;  the  plasmodium  has  only  two  nuclei,  a  large  and  a  small,  and  forms 
a  single  spore  with  two  valves  and  two  parietal  cells,  one  polar  capsule,  and 
an  amcebula  with  two  nuclei.  This  form  seems  to  be  transitional  between 
Myxosporidia  and  Microsporidia,  and  should  perhaps  form  the  type  of  a  third 
suborder,  the  Monosporea. 

Paramyxa  paradoxa  (Chatton,  761),  a  parasite  of  the  intestine  of  a  pelagic 
Annelid  larva  ;  the  multiplicative  amcebula  stage  is  succeeded  by  a  plasmodial 


FIG.  169. — Spore  of  Ceratomyxa  sphcerulosa.  p.c.,  Polar  capsules  ;  sp.p.,  sporo- 
plasm  ;  s.,  suture  of  the  sporocyst  ;  x,  "  irregular,  pale  masses  of  undetermined 
origin."  After  Thelohan,  magnified  750. 

stage  with  two  nuclei  of  unequal  size,  which  multiply  by  fission.  Finally 
the  plasmodium  produces  four  spores,  each  with  a  single  parietal  cell  and  no 
polar  capsule.  Chatton.  is  of  opinion  that  this  species  is  the  type  of  a  new 
order  of  Cnidosporidia,  to  be  named  Paramyxidia. 

Order  II. :  Actinomyxidia. — The  members  of  this  group  are 
only  known,  up  to  the  present,  as  parasites  of  oligochsete  worms, 
fresh-water  or  marine.  They  were  discovered  originally  by  Stole, 
who  found,  in  the  intestinal  epithelium  of  different  species  of  Tubi- 
ficidce,  the  spores  of  three  genera  of  these  parasites,  named  by  him 
Synactinomyxon,  Hexactinomyxon,  and  Triactinomyxon,  respectively. 
The  nature  and  affinities  of  these  organisms  remained  for  some  time 
doubtful ;  but  the  investigations  of  Caullery  and  Mesnil  (769)  on 
Splicer actinomyxon  stolci,  a  species  found  by  them  in  the  coelome  of 
several  species  of  Tubificidce,  established  indisputably  the  position 
of  these  parasites  amongst  the  Cnidosporidia.  Their  distinctive 
features  are — first,  that  the  plasmodial  stage  is  represented  only  by 
a  binucleate  amoebula,  which  is  the  spore-forming  phase  ;  secondly, 
that  the  spore  is  of  very  large  size  and  exhibits  a  ternary  symmetry, 
with  three  valves  and  three  polar  capsules. 


410 


THE  PROTOZOA 


The  development  of  Sphceractinomyxon  (Fig.  170)  begins  with  a  uninucleate 
amcebula  (Fig.  170,  A),  which  represents  the  planont  phase,  and  doubtless 
multiplies  by  fission,  since  these  parasites,  though  rare  generally,  occur  abun- 


FIG.  170. — Stages  in  the  development  of  Spltcsractinomyxon  stolci.  A,  Amcebula 
with  a  single  nucleus  ;  B,  binuclcate  amcebula  ;  0,  the  two  nuclei  of  the 
preceding  stage  have  each  divided,  and  the  body  is  divided  into  four  cells, 
two  peripheral  envelope-cells  and  two  central  germinal  cells  ;  D,  the  space 
enclosed  by  the  envelope-cells  has  become  greatly  enlarged,  and  the  two 
germinal  cells  have  divided  into  four ;  E,  the  germinal  cells  have  increased  in 
number  by  repeated  division  into  sixteen,  which  as  gametes  are  copulating 
in  eight  pairs  ;  F,  G,  two  stages  in  the  fusion  of  two  gametes  ;  H,  the  zygote 
has  divided  into  two  cells  ;  in  one  of  these  (on  the  left),  which  will  form  the 
germinal  mass  of  the  spore,  the  nucleus  is  at  this  stage  undivided  ;  in  the 
other  (on  the  right),  which  will  form  the  accessory  structures  of  the  spore,  the 
nucleus  has  divided  to  form  six  nuclei  ;  I,  further  stage  of  the  preceding  : 
in  the  germinal  cell  (on  the  left)  the  nucleus  has  divided  into  several  nuclei 
of  unequal  sizes  ;  the  sporal  tissue  (on  the  right)  is  represented  by  six  cells, 
three  peripheral,  the  parietal  cells,  and  three  central,  the  capsulogenous  cells  ; 
J,  ripe  spore,  enclosed  by  a  sporocyst  composed  of  three  valves  meeting  in 
sutures  ;  the  germinal  mass  (g.),  separate  in  the  preceding  stage,  has  migrated 
into  the  interior  of  the  spore,  and  contains  an  immense  number  of  nuclei  ; 
at  the  upper  pole  of  the  spore  are  seen  the  three  polar  capsules  (p.c.).  After 
Caullery  and  Mesnil  (769). 

dantly  in  the  infected  animals.  The  planont  phase  is  succeeded  by  a  binu- 
cleate  stage  (Fig.  170,  B),  the  origin  of  which  is  uncertain,  but  which  most 
probably  arises  from  an  association  and  plastogarnic  fusion  of  two  planonts, 
and  which  represents  the  spore-forming  phase. 


THE  NEOSPORIDIA  411 

The  binucleate  amcebula  is  succeeded  by  a  stage  with  four  cells  (Fig.  170,  C), 
the  result  of  the  division  of  each  nucleus,  with  subsequent  division  of  the 
cytoplasm  of  the  amcebula.  Two  of  the  cells  take  up  a  superficial  position 
and  form  an  envelope  for  the  other  two,  which  are  the  gametocytes.  The 
two  enveloping  cells  do  not  develop  further,  but  the  two  internal  cells  proceed 
to  multiply  by  repeated  division  to  form  sixteen  gametes  (Fig.  170,  D,  E),  eight 
derived  from  each  of  the  gametocytes.  The  gametes  now  copulate  in  pairs, 
those  of  each  couple  being  slightly  different  from  one  another,  chiefly  at? 
regards  the  size  of  their  nuclei.  It  is  very  probable  that  in  each  couple  one 
gamete  is  descended  from  one  of  the  two  original  gametocytes,  the  other 
from  the  other  (Fig.  170,  F,  G).  In  this  way  eight  zygotes  are  formed,  each 
of  which  represents  a  sporoblast  and  proceeds  to  form  a  spore. 

Each  sporoblast  now  divides  into  two  cells,  which  may  be  distinguished 
as  Cell  A  and  Cell  B  respectively.  Cell  A  is  the  mother-cell  of  all  the  accessory 
elements  of  the  spore — namely,  parietal  cells  and  capsulogenous  cells.  Cell  B 
is  the  mother-cell  of  the  germinal  elements.  The  development  of  these  two 
sets  of  elements  proceeds  at  first  quite  independently.  Cell  A  divides  into 
six  cells  (Fig.  170,  H,  I,  right),  three  parietal  cells  which  secrete  the  three 
valves  of  the  sporocyst,  and  three  capsulogenous  cells  which  produce  the 
three  polar  capsules.  Cell  B  is  at  first  a  cell  with  a  single  large  nucleus,  which 
now  begins  to  divide,  and  when  it  does  so  Cell  B  separates  from  the  six  cells 
derived  from  Cell  A  (Fig.  170,  H,  I,  left).  As  a  result  of  the  nuclear  division 
in  Cell  B,  it  becomes  a  large  multinucleate  plasmodium,  the  germinal  mass, 
containing  larger  central  nuclei,  and  smaller  towards  the  periphery.  The 
larger  nuclei  are  perhaps  trophic  in  function,  the  smaller  germinal. 

As  a  result  of  these  changes,  the  body  now  consists  of  two  envelope-cells, 
destined  to  degenerate,  containing  sixteen  cell-masses  ;  eight,  consisting  each 
of  the  six  spore-forming  cells,  which  take  up  a  more  central  position,  and 
eight  multinucleate  germinal  masses,  which  lie  at  the  periphery  of  the  body. 
Each  central  mass  forms  the  sporocyst  and  polar  capsules  of  the  spore,  and 
when  these  parts  are  completely  formed  the  germinal  masses  migrate  bodily 
into  the  spores,  each  germinal  mass  occupying  the  cavity  of  one  of  the  spores 
(Fig.  170,  J).  Within  the  spore  the  germinal  mass  remains  for  a  time  in  the 
condition  of  a  multinucleate  plasmodium,  but  divides  ultimately  into  a  vast 
number  of  uninucleate  sporozoites.  The  spore  germinates,  doubtless,  in  the 
digestive  tract  of  a  new  host,  setting  free  a  swarm  of  amcebulce  which  as- 
planonts  pass  through  the  intestinal  epithelium  and  initiate  a  fresh  develop- 
mental cycle. 

The  spore-formation  in  Actinomyxidia  is  seen  to  agree  in  all 
essential  details  with  that  of  the  Myxosporidia,  and  inasmuch  as 
each  zygote  becomes  a  sporoblast,  and  gives  rise  to  an  entire  spore, 
with  all  its  accessories,  the  process  is  similar  to  that  of  the  Disporea. 
The  chief  points  in  which  the  Actinomyxidia  differ  from  the  Myxo- 
sporidia are  the  absence  of  the  large  trophic  plasmodial  stage,  the 
ternary  symmetry  of  the  spore,  and  the  enormous  number  of  sporo- 
zoites contained  in  the  relatively  huge  spore. 

Order  III. :  Microsporidia. — The  characteristic  feature  of  this 
order  is  furnished  by  the  spores,  which  are  minute  oval  refringent 
bodies  in  which  no  polar  capsule  is  visible  in  the  fresh  condition ;. 
but  Avhen  treated  with  reagents  the  spores  are  seen  to  contain, 
with  one  exception,  a  single  polar  capsule,  from  which,  after  suit- 
able stimulation,  a  polar  filament  of  very  great  length  is  extruded. 
The  existence  of  the  polar  capsule  in  the  Microsporidian  spore  was 
discovered  by  Thelohan,  who  in  consequence  of  this  discovery 


412  THE  PROTOZOA 

united  the  Microsporidia  with  the  Myxosporidia  into  a  single  order 
—the  Myxosporidia  (sensu  latiori) — which  was  divided  by  him  into 
two  suborders  :  Phsenocystes  (=  Myxosporidia  sensu  strictiori)  and 
Cryptocystes  (=  Microsporidia).  This  classification  is  found  in 
many  textbooks  ;  but  in  view  of  the  possession  of  polar  capsules  by 
other  orders  of  the  Cnidosporidia,  it  is  more  convenient  to  maintain 
the  old  order  Microsporidia  of  Balbiani. 

The  Microsporidia  first  attained  an  unenviable  notoriety  through 
the  ravages  caused  by  Nosema  bombycis,  the  cause  of  "  pebrine,"  or 
silkworm-disease  ;  hence  the  spores  are  often  spoken  of  as  "  pebrine- 
corpuscles."  The  silkworm-disease  was  investigated  by  Pasteur, 
who  found  that  the  silkworms  acquired  the  infection  in  two  ways  : 
first,  by  the  coiitaminati ve  method,  by  eating  leaves  contaminated  by 
the  faeces  of  other  infected  caterpillars,  and  thus  infecting  themselves 
with  the  spores  of  the  parasite  byway  of  the  digestive  tract ;  secondly, 
by  the  so-called  "hereditary"  method — that  is  to  say,  through 
the  parasite  penetrating  into  the  ovaries  and  eggs  of  the  female 
silkworm-moth,  and,  in  the  form  of  spores,  remaining  dormant  in 
the  egg  through  its  embryonic  development  until  the  hatching  of 
the  caterpillar,  which  in  this  way  is  born  infected  with  the  disease. 

In  contrast  with  the  Myxosporidia,  the  Microsporidia  are  chiefly 
parasites  of  arthropods,  especially  insects,  and  are  comparatively 
scarce  in  fishes,  from  which,  however,  a  few  species  are  known — 
•e.g.,  Glugea  stephani  of  the  flounder,  G.  anomala  of  the  stickleback, 
•etc.  TAVO  species  are  known  which  are  parasitic  in  gregarines. 
No  species  of  Microsporidia  are  known  as  yet  from  warm-blooded 
vertebrates,  though  their  occurrence  in  such  hosts  has  often  been 
alleged  erroneously ;  for  instance,  Leishmania  tropica  (p.  316>,  para- 
site of  Oriental  Sore,  was  referred  originally  to  the  Microsporidia 
by  Wright  (581)  under  the  name  Helcosoma  tropicum.  In  addition 
to  Nosema  bombycis  already  mentioned,  other  highly  pathogenic 
species  are  known — Thelohania  contejeani,  cause  of  destructive 
epidemics  amongst  river-crayfishes  in  parts  of  France  ;  and  Nosema 
apis,  cause  of  the  recent  destructive  epidemic  among  hive-bees  in 
England  (vide  Fantham  and  Porter,  P.Z.S.,  1911,  p.  625). 

As  a  general  rule  the  parasites  of  this  order  are  cell-parasites, 
which  multiply  and  form  their  spores  within  cells,  and  the  trophic 
phase  of  the  parasite  is  typically  minute  and  microscopic  in  size. 
Usually  some  particular  tissue  is  attacked,  but  the  pathogenic 
species  owe  their  lethal  powers  to  the  fact  that  they  infest  all  the 
tissues  of  the  body.  In  a  few  cases,  however,  the  parasites  produce 
cysts  of  relatively  large  size,  visible  to  the  naked  eye  in  the  tissues 
of  the  host — as,  for  example,  the  species  of  the  genus  Glugea. 

The  most  marked  effect  of  the  parasites  is  to  produce,  in  many 
cases,  an  extraordinary  hypertrophy  of  the  host-cell,  and  in  par- 


THE  NEOSPORIDIA 


413 


ticular  of  its  nucleus,  which  becomes  of  gigantic  size,  and  multiplies 
by  division,  usually  in  a  direct  and  irregular  manner  (Fig.  171). 
Hypertrophied  nuclei  may  also  come  into  contact  with  one  another, 
and  fuse  into  irregular  masses  ;  and  the  nuclear  hypertrophy  affects 
not  only  the  infected  host-cell,  but  also  neighbouring  cells  (Schuberg). 
According  to  Mercier,  a  species  of  Pleistophora  parasitic  in  the  cells 
of  the  fat-body  of  the  cockroach  stimulates  the  cells  to  multiply, 
with  mitosis  of  the  nuclei,  and  so  form  neoplasial  growths.  These 
facts  are  of  considerable  interest  from  the  point  of  view  of  the 
growth  of  tumours. 


FIG.  171. — Section  of  a  testis-tubule  of  a  barbel  infected  by  Pleistophora  longifilis, 
showing  the  cysts  of  the  parasite  (P.,  P.)  and  the  greatly  hypertrophied  tissue- 
nuclei  (N.,  N.).  After  Schuberg. 

Corresponding  with  the  two  types  of  the  parasite  mentioned  above,  there 
are  two  methods  of  development  to  be  distinguished  in  the  trophic  phase. 
As  an  example  of  the  first,  Nosema  bombycis,  of  which  the  development  has 
recently  been  described  in  full  detail  by  Stempell  (785),  may  be  selected ; 
while  Glugea  anomala  (Stempell,  784)  is  an  example  of  the  second  type. 

The  development  of  Nosema  bombycis  in  the  silkworm  (Fig.  172)  begins 
with  small  uninucleate  amcebulfe,  which  are  found  first  free  in  the  digestive 
tract,  and  later  in  the  lymph-channels  (Fig.  172,  5-8) ;  they  multiply  by 
simple  fission  and  wander  all  over  the  body,  and  are  hence  termed  planonts 
(i.e.,  wanderers)  by  Stempell.  After  a  time  the  planonts  penetrate  into  cells, 
and  there  grow  larger,  assume  a  definite  oval  or  spherical  form,  and 
become  "  meronts "  or  schizonts,  which  multiply  by  binary  or  multiple 
fission  until  they  have  rilled  and  exhausted  the  host-cell  (Fig.  172,  9-13)  ; 
but  they  do  not  pass  into  other  cells.  The  multiplication  of  the  meronts  may 


414 


THE  PROTOZOA 


FIG.  172. — Diagram  of  the  life-cycle  of  Nosema  bombycis.  All  the  stages  to  the  left 
of  the  dotted  line  are  passed  within  a  single  cell,  in  which  the  parasite  goes 
through  its  sporogony  after  active  multiplication  by  schizogony.  1,  2,  Spores 
showing  the  division  of  the  two  nuclei  of  the  sporozoite  ;  3,  4,  germination 
of  the  spore,  showing  first  the  extrusion  of  the  polar  filament,  and  then  the 
escape  of  the  sporozoite,  which  leaves  two  nuclei  behind  in  the  empty  sporo- 
oyst  and  comes  out  with  two  nuclei  ;  5,  uninucleate  planont  ;  6,  multiplication 
of  the  planont  by  fission  ;  7,  8,  planonts,  the  latter  entering  the  host-cell  ! 

[Continued  at  foot  of  p.  415. 


THE  NEOSPORIDIA  415 

be  very  similar  in  its  general  appearance  to  that  of  yeast-organisms,  and 
may  result  in  the  formation  of  chains  of  cells.  When  the  host-cell  is  used  up, 
the  meronts  do  not  multiply  further,  but  produce  a  final  generation  of  uni- 
nucleate  cells  which,  as  sporonts  (Fig.  172,  13),  give  rise  in  this  genus  each 
to  a  single  spore. 

In  the  development  of  a  spore,  the  nucleus  of  the  sporont  (sporoblast) 
buds  off  three  small  nuclei  (Fig.  172,  14),  two  of  which,  as  parietal  nuclei, 
form  the  sporocyst,  while  the  third  is  concerned  with  the  formation  of  the 
single  polar  capsule,  and  the  fourth  or  principal  nucleus  remains  as  the  nucleus 
of  the  amcebula  (Fig.  172,  15).  Doubtless  there  are  divisions  of  the  proto- 
plasm corresponding  to  the  divisions  of  the  nuclei,  but  in  such  minute  bodies 
they  cannot  be  made  out  clearly.  The  sporocyst,  when  formed,  is  a  tough 
capsule,  which,  though  produced  by  two  cells,  does  not  show  any  indications 
of  a  double  composition,  but  appears  to  be  cast  in  one  piece.  In  some  species 
only  a  single  parietal  cell  has  been  seen.  The  spore  as  a  whole  (Fig.  172,  16, 
1,  2,  3)  is  egg-shaped,  with  one  end,  commonly  termed  "  anterior,"  narrower 
than  the  other.  It  contains  two  vacuoles,  one  near  the  anterior,  the  other 
near  the  posterior  end.  The  single  polar  capsule  is  of  relatively  large  size  ; 
situated  axially  in  the  spore,  it  occupies  its  whole  length,  and  contains  a  polar 
filament  of  immense  length,  wound  spirally  in  its  interior.  In  Glugea  anomala 
a  spore  6  p  in  length  may  eject  a  polar  filament  150  n  long  (Stempell,  784)  ; 
while  in  Pleistophora  longifilis  the  filament  may  measure  as  much  as  510  p., 
more  than  forty-one  times  the  length  of  the  spore  (Schuberg).  The  existence 
of  a  polar  capsule  is  denied  by  Schuberg,  who  maintains  that  the  filament 
is  coiled  up  within  the  posterior  vacuole  of  the  spore. 

The  amoebula  occupies  the  middle  region  of  the  spore,  between  the  two 
vacuoles,  and  apparently  separating  them  ;  but  in  reality  it  has  the  form  of  a 
ring  or  girdle,  wrapping  round  the  axial  polar  capsule  and  filament,  and 
placed  slightly  nearer  the  anterior  pole  of  the  spore.  The  amoebula  contains 
at  first  a  single  nucleus,  which,  according  to  Stempell,  divides  into  two  and 
then  into  four.  Schuberg,  however,  maintains  that  the  amoebula,  and  indeed 
the  entire  spore,  contains  but  a  single  nucleus  ;  he  denies  the  existence  of 
parietal  and  capsulogenous  nuclei,  and  in  his  opinion  the  bodies  that  have 
been  interpreted  as  such  are  in  reality  metachromatinic  grains.  Stempell' s 
description  of  the  development  of  the  spore  is,  however,  in  accordance  with 
that  given  by  other  investigators. 

When  the  spore  germinates  in  the  intestine  of  a  new  host,  the  polar  filament 
is  shot  out,  and  the  amcebula  creeps  out  through  a  pore  at  the  anterior  end  ; 
there  would  appear  to  be  at  this  point  a  small  cap  which  closes  the  spore,  and 
which  is  blown  off  by  the  explosion  of  the  polar  capsule  (Fig.  172,  4).  Accord- 
ing to  Stempell,  the  amoebula  emerges  from  the  spore  with  two  nuclei,  leaving 
the  other  two  behind  in  the  sporocyst  as  reduction-nuclei ;  then  the  two  nuclei 
of  the  amoebula  copulate,  in  an  autogamous  manner,  to  form  a  synkaryon, 
and  the  uninucleate  amoebula  that  results  initiates  the  generation  of  planonts. 
It  seems,  however,  not  improbable  that  some  process  of  copulation  with  other 
amcebulfe,  liberated  from  other  spores,  may  occur  at  this  stage,  and  remains 
to  be  described. 

A  life-cycle  similar  in  the  main  to  that  described  for  Nosema  bonibycis, 
with  planonts,  meronts,  and  sporonts,  as  successive  phases,  is  probably 

FIG.  172  continued: 

9 — 13,  multiplication  of  the  meront  (sckizont)  in  ths  cell,  in  two  different 
ways,  the  one  shown  in  the  series  9a,  lOa,  lla,  12a,  13a,  the  other  in  the  series 
96,  106,  116,  126,  12c,  l'2d,  136  :  13,  a  and  6,  young  sporonts  ;  14,  divisions 
of  the  nucleus  of  the  sporont  ;  two  small  nuclei  which  have  been  budded 
off  at  the  lower  end  are  the  future  parietal  nuclei  ;  from  the  principal  nucleus 
the  nucleus  of  the  polar  capsule  is  being  budded  off  ;  15,  16,  formation  of 
the  spore,  with  two  parietal  nuclei,  one  capsulogenous  nucleus  applied  to 
the  polar  capsule,  and  the  nucleus  of  the  sporozoite.  at  first  single  (15),  later 
double  (1C).  After  Stempell  (785),  slightly  modified. 


416 


THE  PROTOZOA 


characteristic  of  Microsporidia  generally.  Its  most  important  variations  are 
exhibited  in  the  mode  of  spore-formation  and  in  the  vegetative  or  multiplicative 
stages.  Only  in  the  genus  Nosema  does  the  sporont  give  rise  to  a  single 
spore.  In  Thelohania  chcrtogastris,  studied  by  Schroder  (781),  for  example, 
the  sporonts  are  distinguished  from  the  meronts  by  being  enclosed  in  a 
delicate  cyst,  within  which  the  sporont  multiplies  by  successive  divisions 
into  eight  uninucleate  sporoblasts  (Fig.  173),  connected  at  first  by  a  central 
mass  of  protoplasm  like  a  rosette  ;  but  as  soon  as  the  sporocyst  is  formed 
the  sporoblasts  become  separate.  The  nucleus  of  each  sporoblast  divides 
until  there  are  five,  two  for  the  amcebula,  one  for  the  polar  capsule,  and  two 
for  the  sporocyst,  and  the  development  is  similar  to  that  of  the  spore  of 
Nosema  bombycis  already  described. 

A  noteworthy  feature  of  many  Microsporidia  is  that  the  spores  formed  are 
of  two  sizes,  rnicrospores  and  macrospores,  which  may  differ  considerably  in 
their  dimensions.  In  Pleistophora  longifilis  the  macrospores  are  12  M  in 
length  by  6  M  in  breadth,  while  the  microspores  are  2  or  3  /*  in  length  and 
broad  in  proportion  (Schuberg).  It  is  very  probable  that  these  differences 
are  related  to  differences  in  sex  of  the  contained  amcebulae,  and  that  the  two 
kinds  of  spores  produce  macrogametes  and  microgametes  respectively. 


H 


FIG.  173. — Stages  in  the  spore-formation  of  Thelohania  chcetogastris.  A,  Uni- 
nucleate sporont  ;  B,  C,  division  of  its  nucleus  into  two  ;  D,  E,  F,  G,  division 
of  the  nucleus  and  body  into  four  ;  H,  division  into  eight  sporoblasts  ;  /,  eight 
sporoblasts,  each  with  the  nucleus  dividing  again  ;  J,  two  sporoblasts  from  a 
clump,  showing  further  divisions  of  the  nuclei  ;  K,  young  spore  showing  two 
parietal  and  three  central  nuclei  (nucleus  of  the  capsulogenous  cell  and  two 
nuclei  of  the  amoebula).  After  Schroder  (781). 

In  Pleistophora  periplanetce,  according  to  Shiwago,  several  planonts 
("  amoeboids  ")  fuse  into  a  plasm odi um ;  their  nuclei  become  resolved  into 
chromidia  which  become  mixed  together — a  process  interpreted  by  Shiwago 
as  chromidiogamy.  From  the  chromidia  secondary  nuclei  are  formed,  which 
become  the  nuclei  of  the  sporonts  ("  daughter-am ceboids  ").  The  sporonts 
become  free  from  the  plasmodium  and  form  spores.  If  this  account  be  con- 
firmed, it  is  clear  that  the  alleged  autogamy  of  the  Microsporidia,  if  it  occurs, 
is  not  necessarily  an  autogamy  without  amphimixis.  In  Thelohania  mcenadis, 
according  to  Perez  (778),  the  nucleus  of  the  sporont  becomes  resolved  into  a 
cloud  of  chromidia,  from  which  the  eight  nuclei  of  the  sporoblasts  are  recon- 
structed. 

The  greatest  difference  in  the  vegetative  phase  from  the  condition  described 
for  Nosema  bombycis  is  seen  in  the  genus  Ohigea,  where  the  multiplication  of 
the  meront  leads  to  the  formation  of  a  multinucleate  plasmodium — a  result 
easily  explained  on  the  supposition  that  the  nucleus  of  the  meront  divides 
repeatedly,  but  the  body  as  a  whole  does  not  do  so.  In  this  way  a  relatively 
large  plasmodial  trophozoite,  comparable  to  that  of  the  Myxosporidia,  is  pro- 


THE  NEOSPORLDIA 


417 


duced,  which  may  form  a  conspicuous  cyst.  From  the  plasmodial  stage 
sporonta  arise  by  separation  of  a  mass  of  protoplasm  round  a  nucleus  within 
the  body  of  the  parasite,  and  thus  distinct  cells  are  formed  lying  in  vacuoles 
in  the  plasmodium.  Such  cells  are  commonly  termed  "  pansporoblasts,"  but 
the  use  of  this  term  is  best  avoided,  since  the-  cells  in  question  are  in  no 
way  equivalent  to  the  pansporoblasts  of  Myxosporidia,  which  are  associa- 
tions of  two  gamonts  ;  but  they  correspond  exactly  to  the  sporonts  of 
Nosema  and  other  genera,  and  proceed  to  the  formation  of  spores  in  the 
manner  that  has  been  described  already,  dividing  first  into  several 
sporoblasts. 

The  plasmodia  of  the  G^ea-type  lead,  as  already  stated,  to  the  forma- 
tion of  conspicuous  cysts,  visible  to  the  naked  eye,  in  the  tissues  of  the 
host ;  but  the  composition  and  nature  of  these  cysts  are  at  present  a  matter 
of  dispute.  According  to  Stempell  (784),  in  Glugea  anomala,  the  body  of  the 
parasite  is  sharply  denned  and  marked  off  from  the  tissues  of  the  host  by  a 
thick  membrane  or  autocyst  ( "  Eigencyst  " )  formed  by  the  parasite  itself 
(Fig.  174,  e).  Within  the  autocyst  is  contained  the  plasmodium,  consisting  of 


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FIG.  174. — Glugea  anomala,  Moniez :  part  of  a  section  of  a  cyst,  e.,  Envelope 
(autocyst) ;  bn,  vegetative  nuclei  ;  sp.,  spores  ;  psp,  sporont  lying  in  a  space 
in  the  protoplasm.  After  Sternpell. 

protoplasm  containing  many  nuclei,  amongst  which  the  most  conspicuous 
are  large — indeed,  relatively  gigantic — vegetative  nuclei,  which  multiply  by 
direct  division.  From  the  vegetative  nuclei  the  minute  nuclei  of  the  sporonts 
are  stated  to  arise,  while  in  other  case  vegetative  nuclei  break  up  and  de- 
generate. 

Schroder  (781)  and  Schuberg,  on  the  other  hand,  maintain  that  the  large 
vegetative  nuclei  of  Stempell  are  in  reality  tissue-nuclei  of  the  host,  greatly 
hypertrophied  and  mixed  up  with  the  plasmodium  of  the  parasite.  Schuberg 
found  that  Pleistophora  longifilis,  from  the  testis  of  the  barbel,  causes  a  hyper- 
trophy, not  only  of  the  host-cell  in  which  it  is  contained,  but  also  of  neigh- 
bouring cells,  the  effect  of  which  is  to  produce  a  sort  of  host-plasmodium,  as 
it  were,  containing  gigantic  host-nuclei  of  irregular  form  (Fig.  171),  amongst 
which  the  sporonts  and  spores  of  the  parasite  are  scattered.  Mrazek  also 
interprets  the  supposed  vegetative  nuclei  of  Myxocystis  as  hypertrophied 
host-nuclei  (see  below).  This  interpretation  of  the  composition  of  the  plas- 
modium greatly  diminishes,  or  even  abolishes,  the  principal  distinction  between 
Glugea  and  the  other  genera  of  Microsporidia.  In  opposition  to  this  view, 

27 


418  THE  PROTOZOA 

Stempcll  (786)  brings  forward  a  number  of  arguments,  the  most  cogent  of 
which  is  the  existence  of  the  autocj'st  separating  the  plasmodium  of  the 
parasite,  containing  the  nuclei  of  disputed  nature,  from  the  tissues  of  the 
host. 

The  most  recent  investigations  of  Awerinzew  and  Fermor  confirm  com- 
pletely Stern  pell's  interpretation  of  the  cysts  of  Glugea  anomala  ;  compare  also 
Weissenberg.  These  authors  find  nuclei  of  various  sizes  in  the  protoplasm  of 
the  cyst,  larger  or  smaller.  The  larger  nuclei  are  found  in  the  outer,  non- 
vacuolated  protoplasmic  layer  of  the  Glugea  ;  they  grow  in  length  and  become 
sausage-shaped,  and  are  ultimately  segmented  into  smaller  nuclei,  which 
may  form  chains  at  their  first  origin,  like  the  meronts  of  Nosema  and  other 
forms.  In  this  way  arise  the  smaller  nuclei,  which  either  become  sporonts, 
or  remain  as  vegetative  nuclei  in  the  protoplasmic  walls  of  the  vacuoles 
containing  the  spores,  where  they  ultimately  degenerate  and  break  up.  The 
sporonts  are  stated  to  arise  in  toto  from  nuclei,  without  visible  participation 
of  the  protoplasm  of  the  cyst ;  they  become  enclosed  separately  in  vacuoles, 
within  which  each  sporont  forms  a  cluster  of  spores.  Thus,  in  older  cysts 
the  central  part  of  the  body  becomes  divided  by  fine  protoplasmic  partitions 
into  a  mass  of  separate  chambers  or  vacuoles,  each  containing  ripe  spores. 
Glugea  anomala  is  to  be  regarded,  therefore,  as  a  colonial  organism,  in  which 
meronts  and  sporonts,  homologous  with  those  of  Nosema,  etc.,  lie  embedded 
in  the  protoplasm  of  their  own  cyst- — the  meronts  in  the  peripheral  zone  of 
growth,  the  sporonts  and  spores  in  the  central  protoplasmic  region  of  the 
cyst. 

Classification. — The  two  types  of  the  trophic  phase  that  have  been  de- 
scribed in  the  foregoing  paragraphs  have  been  utilized  by  Perez  (779)  to  sub- 
divide the  Microsporidia  into  two  suborders,  as  given  below.  Stem  pell 
(785),  on  the  other  hand,  divides  the  group  into  three  families  ;  the  un- 
certainty that  prevails  at  present  with  regard  to  the  exact  structure  of  the 
trophic  phases  in  some  forms  is  a  hindrance  to  finality  in  the  classification 
of  this  order. 

SUBORDER  I. :  SCHIZOGENEA  (seu  Oligosporea). — The  principal  trophic  phase 
is  a  uninucleate  meront  which  multiplies  by  fission,  and  from  which  the  sporont 
finally  arises.  Several  genera,  characterized  by  the  number  of  spores  produced 
by  the  sporont :  One  spore,  Nosema  ;  two  spores,  Perezia  ;  four  spores,  Gurleya  ; 
eight  spores,  Thelohania  ;  sixteen  spores,  Duboscqia  (see  below)  ;  n  spores, 
Pleistophora  ;  but  Stempellia  (Leger  and  Hesse,  775),  for  S.  mutabilis,  parasite 
of  the  fat-body  of  Ephemerid  larvae,  produces  spores  to  the  number  of  eight, 
four,  two,  or  one  indifferently ;  Oclosporea,  the  species  of  which  are  parasitic 
in  Muscidce,  produces  eight  spores  in  one  species,  one  in  another.  These 
anomalies  indicate  that  the  classification  by  the  number  of  spores  produced 
by  the  sporont  is  purely  artificial  (Chatton  and  Krempf).  Telomyxa  glugei- 
Jonnis  (Leger  and  Hesse),  also  from  the  fat-body  of  Ephemerid  larvae,  pro- 
duces eight,  sixteen,  or  n  spores,  and  stands  apart  from  all  other  known 
Microsporidia  in  possessing  two  polar  capsules  in  the  spore. 

SUBORDER  II. :  BLASTOGENEA  (seu  Polysporea). — The  principal  trophic  phase 
is  a  multinucleate  plasmodium  producing  sporonts  by  internal  cleavage  ; 
example  :  Glugea.  To  this  section,  also,  the  peculiar  form  Myxocystis  has 
been  referred,  which  was  discovered  by  Mrazek  in  the  body-cavity  of  Oligo- 
chaetes.  Myxocystis  occurs  in  the  form  of  large  masses  floating  freely  in  the 
body-cavity,  each  mass  remarkable  for  an  envelope  composed  of  a  fur  of 
vertical  filaments,  not  unlike  stiff  cilia,  and  enclosing  nuclei  and  spores  in 
various  stages  of  development.  According  to  the  most  recent  investigations 
of  Mrazek,  however,  each  of  these  masses  represents  in  reality  a  lymphocyte 
containing  numerous  parasites,  which  multiply  and  form  spores,  and  provoke 
a  great  hypertrophy  of  the  host-cell,  accompanied  by  multiplication  of  its 
nucleus.  Hence  the  true  Myxocystis  is  an  intracellular  parasite  referable, 
apparently,  to  the  order  Schizogenea,  and  characterized  chiefly  by  the  peculiar 
form  of  its  spores.  Duboscqia  legeri,  Perez  (780),  from  the  body-cavity  of 
Te.rm.es  lucifugus,  is  perhaps  an  organism  of  similar  nature  ;  it  is  described 


THE  NEOSPORIDIA  419 

as  a  floating  plasmodium  in  which  sporonts  arise,  each  of  which  produces 
sixteen  spores  ;  it  has,  however,  been  referred  by  its  discoverer  to  the  Blasto- 
genea. 

Order  IV. :  Sarcosporidia. — The  parasites  of  this  order  are  con- 
sidered at  present  to  constitute  a  single  genus,  Sarcocystis,  with 
numerous  species.      In  contrast  to  the  three  orders  of  Cnidosporidia 
dealt  with  in  the  foregoing  pages,  the  Sarcosporidia  are  pre-eminently 
parasites  of  the  higher  vertebrates,  more  especially  of  mammals, 
occurring  occasionally,  though  rarely,  in  man  (see  Darling)  ;  but 
they  are  known  also  to  occur  in  avian  and  reptilian  hosts,  though 
sparingly.     On  the  other  hand,  no  Sarcosporidia  are  known  to  be 
parasitic  in  invertebrate  hosts  of  any  kind.      In  their  hosts  the 
Sarcosporidia    are    tissue-parasites,    occurring    principally    in    the 
striped  muscles,  but  occasionally  in  unstriped.     In  a  few  cases  they 
are  found  in  connective  tissue,  but  this  appears  to  be  a  secondary 
condition  in  which  a  parasite  living  first  in  the  muscle-fibres  becomes 
free  from  them  at  a  later  period.      As  a  general  rule  the  Sarco- 
sporidia appear  to  be  harmless  parasites,  which  do  not  make  their 
presence  known  by  any  symptoms  of  disease,  and  can  only  be 
detected  by  post-mortem  examination.     Some  species,  however,  are 
an  exception  to  this  rule,  and  are  extremely  pathogenic  to  their 
host — for  example,  Sarcocystis  muris  of  the  mouse.      The  extent  to 
which  the  health  of  the  host  is  impaired  appears  to  be  directly  pro- 
portional to  the  numbers  of  the  parasite  in  the  body,  and  conse- 
quently   to    the    power   which    a    given  species    may  possess    of 
multiplying    and    overrunning    the    host.     In    most   species   the 
capacity  for  endogenous  multiplication  appears  to  be  extremely 
limited. 

In  spite  of  the  fact  that  Sarcosporidia  are  very  common  parasites 
of  domestic  animals,  and  have  been  found  frequently  in  man,  our 
knowledge  of  their  structure  and  life-history  is  in  a  very  backward 
state.  As  a  rule  Sarcosporidia  present  themselves  as  opaque, 
whitish  bodies,  usually  elongated  and  cylindrical  in  form,  encysted 
in  the  muscle-fibres  of  the  infected  animal,  and  known  commonly 
as  "  Miescher's  tubes."  They  are  distinctly  visible  to  the  naked 
eye,  and  often  very  large.  Sarcocystis  tenella  of  the  sheep  reaches 
a  length  of  16  millimetres,  while  in  the  roebuck  (Cervus  capreolus) 
cysts  of  50  millimetres  in  length  are  recorded.  The  Miescher's 
tube,  when  examined  microscopically,  is  seen  to  be  a  body  of 
complex  structure,  and  consists  chiefly  of  vast  numbers  of  sickle- 
shaped  spores — "  Rainey's  corpuscles  ':  -lying  in  clumps  or  bunches 
contained  in  chambers  separated  off  from  one  another  by  partitions. 
The  whole  organism  is  enclosed  by  a  distinct  envelope,  often  ex- 
hibiting vertical  striations,  and  the  partitions  between  the  chambers 
containing  the  spores  are  continuations  of  the  envelope.  The  exact 


420  THE  PROTOZOA 

structure  of  the  spores  is  still  a  matter  of  dispute,  and  it  is 
possible  that  there  is  more  than  one  kind  of  spore  even  in  the 
same  species  of  parasite.  A  remarkable  feature  of  the  spores— 
in  some  species,  at  least — is  that  they  are  motile  when  set  free  : 
for  example,  in  S.  muris.  They  are  also  extremely  delicate 
structures,  easily  injured  by  external  media,  in  marked  contrast  to 
the  spores  of  the  other  orders  of  Cnidosporidia.  The  spores  of 
S.  muris,  S.  bertrami  (of  the  horse),  and  S.  tenella,  reproduce  them- 
selves by  division  (Negri,  Fiebiger,  Teichmann).  Finally  it  must 
be  mentioned  that  the  spores  of  Sarcosporidia  contain  a  true  toxin, 
which  was  named  by  Laveran  and  Mesnil  "  sarcocystine."  Its 
properties  have  been  investigated  recently  by  Teichmann  (25)  and 
Teichmann  and  Braun  (26). 

The  natural  mode  of  transmission  of  the  Sarcosporidia  remains 
to  be  discovered.  It  was  found  by  Theobald  Smith  that  mice  could 
be  infected  experimentally  with  S.  muris  by  feeding  them  with  the 
flesh  of  other  infected  mice  ;  but  it  is  extremely  unlikely  that 
cannibalism  is  the  method  whereby  sheep  and  other  ruminants 
become  infected  with  these  parasites.  All  experiments  indicate 
that  the  spores  germinate  in  the  digestive  tract  of  the  new  host ; 
but  the  delicate  nature  of  the  spores  seems  to  preclude  any  possi- 
bility of  the  occurrence  of  ordinary  coiitaminative  infection,  as  in 
other  Cnidosporidia.  In  this  connection  attention  should  be  drawn 
to  the  statement  of  Watson,  that  the  spores  are  to  be  found  in  the 
circulating  blood,  indicating  the  possibility  of  transmission  by  an 
intermediate  host. 

In  spite  of  several  recent  investigations  upon  the  structure  and  develop- 
ment of  the  Sarcosporidia,  the  subject  is  in  a  confused  state,  even  the  structure 
of  the  spores  being  still  disputed.  It  is  therefore  difficult  to  obtain  a  clear 
notion  of  the  course  of  the  life-cycle  in  these  organisms. 

According  to  Laveran  and  Mesnil,  the  spores  of  S.  tenella  (Fig.  175)  are 
sausage-shaped  bodies,  curved,  with  one  end  more  pointed  than  the  other. 
At  the  pointed  end  is  a  striated  structure  representing  a  polar  capsule,  and 
at  the  blunt  end  is  a  nucleus,  while  the  middle  of  the  body  is  occupied  by 
coarse,  deeply-staining,  metachromatinic  grains.  Watson  also  figures  a  large 
nucleus  near  the  blunt  end  of  the  spore,  and  places  the  polar  capsule  at  the 
pointed  end.  Negri  also  describes  the  spores  of  S.  muris  and  S.  bertrami  as 
having  the  nucleus  near  the  blunt  end,  while  the  opposite  extremity  appears 
hyaline  and  homogeneous  for  a  certain  distance.  Betegh,  again,  describes 
a  nucleus  at  the  blunt  end  of  the  spore,  and  one  or  two  "  centrosornes  "  in  the 
middle  region.  Erdnianu  (790),  on  the  other  hand,  places  the  nucleus  in  the 
middle  of  the  body  amongst  the  metachromatinic  grains,  and  describes  it  as 
consisting  of  a  large  dense  karyosome  lodged  in  a  small  vacuole  ;  she  does  not 
seem  to  be  decided,  however,  whether  the  polar  capsule  is  at  the  pointed  or 
the  blunt  end  of  the  spore.  Teichmann  describes  a  large  nucleus  at  the 
blunt  end  of  the  body,  and  is  doubtful  as  to  the  existence  of  a  polar  capsule. 
So  far  as  it  is  possible  to  draw  any  conclusions  from  so  many  contradictory 
statements,  the  clear  description  given  by  Laveran  and  Mesnil  seems  to  be, 
on  the  whole,  confirmed.  But  according  to  Crawley,  the  spores  of  S.  rileyi 
are  binucleate ;  compare  those  of  Gastrocystis  (Fig.  179,  p.  428).  It  is  not 


THE  NEOSPORIDIA  421 

clear  which   part    of  the   spore  contains   the   amcebula  which  is  liberated 
from  it,  as  presently  to  be  described. 

In  addition  to  spores  having  the  complicated  structure  described  for  those 
•of  8.  tenella,  there  appear  to  be  also  spores  of  much  simpler  structure,  as, 
for  example,  in  S.  muris.  Apparently  the  more  complicated  spore  is  propa- 
gative  in  function,  serving  to  infect  new  hosts,  while  the  simpler  form,  which 
should  perhaps  be  regarded  rather  as  a  sporoblast,  as  a  simple  cell  not  differ- 
entiated as  a  spore,  serves  for  spreading  the  infection  in  the  same  host.  The 
occurrence  of  the  simpler  type  of  spore  in  S.  muris  would  account  for  the 
manner  in  which  this  parasite  overruns  its  host,  and  is  usually  lethal  to  it, 
while  S.  tenella,  which  appears  to  produce  chiefly  propagative  spores,  is  a 
harmless  parasite.  How  far  these  suggestions  are  true  must  be  determined 
by  future  investigations. 

The  discovery  made  by  Smith,  mentioned  above,  that  mice  could  be  infected 
with  ,9.  muris  by  feeding  them  with  the  flesh  of  other  infected  mice,  has  been 
confirmed  and  extended  by  other  observers.  According  to  Negre,  the  fseces 
•of  mice  which  have  been  fed  with  infected  muscular  tissue  are  infective  to  other 
mice  if  ingested  by  them  ;  they  possess  this  power  about  fifteen  to  sixty  days 
after  the  mouse  was  fed  with  muscle  containing  Sarcosporidia,  and  retain 
th^ir  infectivity  even  if  kept  dry  in  an  open  bottle  for  a  month,  or  heated  to 
€5°  C.  for  fifteen  minutes.  Negri  was  able  to  infect 
guinea-pigs  with  S.  muris  by  feeding  them  with  the 
flesh  of  infected  mice,  and  found  that  in  the  guinea- 
pig  the  parasite  appeared  with  quite  different  char- 
acters from  those  which  it  presents  in  the  mouse,  so 
that  it  might  be  taken  easily  for  a  distinct  species. 
Darling  also  infected  guinea-pigs  with  S.  muris  in 
the  same  way,  and  points  out  the  resemblance 
between  the  experimental  sarcosporidiosis  of  the 
guinea-pig  and  a  case  of  human  sarcosporidiosis 
observed  by  him;  it  is  suggested  that  the  sarco-  ll9T-  17°'  "  ^pores  of 
sporidia  occasionally  observed  in  the  human  subject  Sarcocyst^  t  >nella 
arc  those  of  some  domestic  animal  undergoing  a  COnditkm ;  5,  after 
ihed  or  abortive  development  in  a  host  that  is  staining  with  iron- 
not  their  usual  one.  Erdmann  also  infected  mice  h£eniatoxylin:  N., 
with  S.  tenella  in  a  similar  manner.  It  is  remarkable  nucleus  ;  c,  striated 
that  parasites  generally  so  harmless  should  be  so  body  (polar capsule?), 
little  specific  to  particular  hosts,  and  the  results  of  After  Laveran  and 
Negri  render  the  value  of  the  characters  used  for  Mesnil. 
distinguishing  species  of  Sarcosporidia  as  doubtful  in 
their  validity  as  the  distinctions  founded  on  their  occurrence  in  certain  hosts. 

According  to  Erdmann  (791),  the  spore  germinates  in  the  intestine  of  the 
new  host,  and  the  first  act  in  the  process  is  the  liberation  from  the  spore  of 
its  toxin,  sarcocystine,  which  causes  the  adjacent  epithelium  of  the  intestine 
to  be  thrown  off.  At  the  same  time  an  amcebula  is  set  free  from  the  spore  ; 
and,  owing  to  the  intestine  being  denuded  of  its  lining  epithelium,  the  amoebula 
is  able  to  penetrate  into  the  lymph-spaces  of  the  submucous  coat  and  establish 
itself  there.  Before  this  happens,  however,  the  metachromatinic  grains  of  the 
spore  disappear,  and  it  is  suggested  that  this  disappearance  is  related  to  the 
secretion  of  the  sarcocystine,  and  that  the  toxin  is  contained  in  the  metachro- 
matinic grains.  If,  however,  a  polar  capsule  be  discharged  during  the  germina- 
tion of  the  spore,  as  in  other  Cnidosporidia,  it  might  well  be  that  the  toxin 
is  contained  in  the  polar  capsule,  and  is  set  free  by  its  discharge,  like  the 
poison  in  the  nematocysts  of  the  Ccelentera.  However  that  may  be,  it  would 
appear  as  if  the  sarcocystine  were  a  weapon,  as  it  were,  the  function  of  which 
is  to  facilitate  the  invasion  of  the  germ,  the  amoabula,  by  destroying  the  lining 
•epithelium  of  the  gut. 

The  liberation  of  the  amcebula  from  the  spore  initiates  the  first  period 
of  the  development,  which  is  passed  in  the  lymph-spaces  of  the  intestine, 
and  which  lasts,  according  to  Erdmann,  some  twenty-eight  to  thirty  days. 


422 


THE  PROTOZOA 


Analogy  with  other  Ncosporidia  would  lead  us  to  identify  this  with  the 
planont- phase,  initiated,  possibly,  by  sexual  processes  between  different 
amcebulse  and  subsequent  active  multiplication.  The  second  period  of 
the  development  begins  with  the  penetration  of  the  amoebula  into  a 
muscle-fibre,  in  which  the  parasite  grows  into  a  Miescher's  tube  and  forms- 
spores. 

,  The  intramuscular  development  of  the  parasite  begins  by  multiplication 
of  the  nuclei  to  about  twelve,  forming  a  plasmodium  (Fig.  176,  A).  This  next 
becomes  divided  up,  in  parasites  about  thirty-three  days  old,  into  separate  cells, 

pansporo blasts  or  sporonts,  whichmultiply 
actively  by  division.  The  form  of  the  para- 
site now  becomes  elongated ;  this  stage 
is  reached  in  from  forty-eight  to  sixty 
clays  (Fig.  176,  B).  At  this  point  the  para- 
site may  disintegrate,  setting  free  the 
sporonts,  or  may  develop  into  a  Miescher's 
tube.  In  the  first  case  the  sporonts 
wander  out  and  establish  themselves  in 
other  muscle-fibres,  where  each  sporont 
initiates  a  fresh  development,  thus  spread- 
ing the  infection  in  the  tissues  of  the  host. 
In  the  second  case  a  membrane  is  secreted 
round  the  body,  which  forms  the  striated 
envelope  prolonged  inwards  to  form  the 
chambers.  The  striated  envelope  of  the 
Miescher's  tube  has  generally  been  com- 
pared to  the  striated  ectoplasm  of  some 
Myxosporidia  —  e.g.,  Myxidium  lieber- 
killmi ;  but  according  to  Fiebiger  it  is 
not  ectoplasm,  but  altered  muscular 
tissue.  The  nuclei  of  the  muscle-fibres 
are  stimulated  by  the  parasite  to  multi- 
plication and  migration.  The  body  then 
consists  of  a  peripheral  zone  of  sporonts, 
multiplying  actively,  and  a  central 
region  in  which  spores  are  differentiated. 
In  the  development  of  the  spore,  the 
sporont  becomes  sausage-shaped,  and 
multiplies  l>y  division.  Finally  the 
sausage-shaped  bodies  become  spores, 
and  are  stated  to  be  at  first  binucleate  ; 
probably  one  nucleus  is  that  of  the 
amoebula,  the  other  that  of  the  capsu- 
logenous  cell,  parietal  cells  being  absent ; 
but  these  statements  are  at  present  hypo- 
thetical and  require  substantiation.  FuDy- 
formed  spores  are  found  in  parasites 
eighty  to  ninety  days  after  the  infection 
of  the  host. 

In  old  infections  the  parasites  may  have 
destroyed  the  muscle-fibre  completely, 
so  that  the  Miescher's  tube  lies  in  the 
connective  tissue.  In  such  forms  the 

centre  of  the  body  may  consist  of  granular  debris,  derived  from  the 
disintegration  of  spores  which  are  past  their  prime  and  have  degenerated. 


B 

1'iG.  176. — Four  stages  in  the  de- 
velopment of  a  "  Miescher's  tube  " 
of  Sarcocystis  muris  in  the  pectoral 
muscles  of  white  rats  infected  ex- 
perimentally. A,  Parasite  25  fj.  in 
length,  fifty  days  after  infection  ; 
the  contents  of  the  body  beginning 
to  divide  into  separate  cells  ;  11, 
parasite  of  the  same  age,  35  fj,  in 
length,  division  of  the  contents 
further  advanced ;  C,  parasite  of 
the  same  age,  60  /*  in  length,  con- 
taining separate  cells  ;  at  the 
centre  the  division  of  a  sporont 
into  two  sickle-shaped  bodies  is 
seen  to  be  taking  place  ;  D,  middle 
portion  of  a  tube  about  450  /J. 
in  length,  seventy  days  after  in- 
fection, showing  two  couples 
of  sickle-shaped  bodies  formed 
by  division  of  a  sporont.  After 
Negri. 


So  far  as  it  is  possible  to  draw  conclusions  in  the  present  state 
of  knowledge,  the  Sarcosporidia  would  appear  to  be  true  Cnido- 
sporidia,  with  spores  which  contain  each  a  single  polar  capsule, 


THE  NEOSPORIDIA  423 

and  from  which  an  amoebula  is  liberated,  as  in  other  Xeosporidia 
(Amcebogenise). 

Order  V.  :  Haplosporidia. — The  distinctive  features  of  this  order 
are  for  the  most  part  of  negative  character,  and,  as  the  name  im- 
plies, the  tendency  is  towards  simplicity  in  structure  and  develop- 
ment. The  spores  are  without  the  polar  capsules  which  are  so 
marked  a  peculiarity  in  the  four  previous  orders,  and  have  the 
form  of  simple  cells,  each  with  a  single  nucleus,  and  with  or  without 
a  sporocyst,  which,  however,  when  present,  is  not  formed  by  distinct 
parietal  cells. 

In  organisms  of  such  simple  structure,  the  absence  of  distinctive 
peculiarities  renders  the  limits  of  the  group  indefinite,  and  the 
affinities  of  its  members  vague  and  undecided,  and  it  is  possible 
that  the  order  Haplosporidia,  as  generally  understood,  is  a  hetero- 
geneous assemblage,  many  members  of  which  present  only  develop- 
mental analogies  to  the  true  Neosporidia — that  is  to  say,  a  simi- 
larity in  the  life-history  which  is  an  adaptation  to  a  similar  mode 
of  life,  and  not  a  true  indication  of  genetic  affinity.  Leger  and 
Duboscq  (646)  point  out  that  the  characters — "  peu  limitatifs  " 
of  the  Haplosporidia  would  suit  Protista  of  the  most  diverse  affini- 
ties, and  scarcely  mark  them  off  from  yeasts  or  Chytridinese.  With 
the  exception  of  the  family  Haplosporidiidce,  they  regard  the  group 
Haplosporidia  as  purely  provisional,  and  comprising  heterogeneous 
forms  with  undecided  affinities. 

The  life-cycle  of  a  typical  Haplosporidian  parasite  is  very  simple. 
The  initial  phase  is  an  amoebula  or  planont,  which  multiplies  by 
fission,  division  of  the  nucleus  being  followed  by  division  of  the 
body  to  form  two  planonts,  which  may  continue  to  divide  for  many 
generations.     From  a  planont  arises  ultimately  a  plasmodial  phase, 
the  result  of  divisions  of  the  nucleus  without  corresponding  divisions 
of  the  body,  which  grows  to  a  relatively  large  size.     The  plasmoclium 
is  the  principal  trophic  phase.     It  may  multiply  by  plasmotomy  or 
by  schizogony,  or  may  proceed  to  spore-formation,  and  then  it 
divides  into  as  many  cells  as  there  are  nuclei.     The  cells  formed  in 
this  way  are  either  sporoblasts,  each  of  which  becomes  a  single 
spore    (Oligosporulea),    or   they    represent    sporonts    ("  pansporo- 
blasts  "),  which  give  rise  each  to  a  cluster  of  spores  (Polysporulea). 
The  spores   are   usually    simple   rounded    bodies   invested    by  a 
more    or    less    distinct     protective    membrane,    which    in    rare 
instances    becomes  a  definite  sporocyst  prolonged  even  into  tails 
or  spikes. 

The  Haplosporidia  were  divided  by  Caullery  and  Mesnil  (802) 
into  three  families.  In  order  to  include  forms  more  recently  dis- 
covered, Ridewood  and  Fantham  have  extended  the  classification, 
and  recognize  two  suborders  : 


424  THE  PROTOZOA 

SUBORDER  I. :  OLIGOSPORULEA.—  The  plasmodium  divides  at  once  into 
sporoblasts,  each  of  which  becomes  a  single  spore. 

_  Family  Haplosporidiidce. — Spores  with  a  double  envelope,  the  outer  some- 
times prolonged  into  tails  or  processes.  Genera :  Haplosporidiiim,  Urospor- 
idium,  and  Anurosporidium ;  all  the  known  species  are  parasitic  in  Annelids. 
Family  Bertramiidce. — Spores  with  a  simple  envelope,  or  with  none. 
Bertramia,  with  several  species  :  B.  capitellce,  parasite  of  the  ccelome  of 
Capitella  capitata  ;  B.  aspcrospora,  a  common  parasite  of  the  body-cavity 
of  Rotifers.  B.  kirkmanni,  described  by  Warren  from  Rotifers  in  Natal, 
is  stated  to  have  several  nuclei  and  a  vacuole  in  the  spore,  and  appears  to 
belong  to  a  distinct  genus. 

In  this  family  the  genus  Iclithyosporidium  is  ranked  provisionally,  as  the 
mode  of  spore-formation  is  unknown  as  yet.  1 '  chthyosporidium  is  a  common 
parasite  of  fishes,  often  lethal  to  an  extreme  degree.  It  occurs  in  the  form 
of  plasmodia,  sometimes  irregular,  sometimes  more  or  less  spherical  in  form, 
scattered  in  varioiio  organs,  but  usually  in  the  muscles  or  the  connective 
tissue  ;  the  plasmodium  contains  numerous  vesicular  nuclei  with  distinct 
karyosonies,  and  may  be  naked  at  the  surface,  or  marked  off  from  the  sur- 
rounding tissues  by  a  membrane  or  envelope,  often  of  considerable  thick- 
ness. The  plasmodia  multiply  actively  by  plasmotomy,  and  an  intense 
infection  is  produced.  Parasites  with  a  single  nucleus  are  also  found,  which 
may  either  represent  the  planont  stage,  or  may  be  derived  from  the  division 
of  a  plasmodium  :  from  them  the  plasmodial  stage  arises  by  multiplication 
of  the  nuclei.  No  other  stage  of  the  parasite  is  known,  and  the  method  of 
transmission  remains  to  be  discovered. 

Bertramia  bit  fonts,  described  by  King  (Proc.  Acad.  Sci.  Philad.,  59,  p.  273), 
is  possibly  a  species  of  J clithyosporidium  or  allied  to  this  genus. 

Family  Ccelosporidiidcc,  for  the  genera  Coelosporidnim,  Mesnil  and  Marchcux 
and  Polycanjum,  Stempell :  All  the  species  known  are  parasites  of  Crustacea 
(Phyllopoda  and  Cladocera).  The  plasmodium  forms  globules  of  fatty 
substance  in  the  interior  ;  it  becomes  encysted  as  a  whole,  and  breaks  up  into 
sporozoite-like  bodies  within  the  cyst. 

Cautterya  mesnili,  Chatton  (803),  parasite  of  the  epithelium  of  the  mid-gut 
of  Daplmia  spp.,  produces,  by  fragmentation  of  the  plasmodium,  spores 
with  resistant  envelopes  containing  each  about  thirty  nuclei.  Chatton 
considers  it  to  be  intermediate  between  the  Haplosporidiidce  and  Calo- 
sporidiidce  ;  possibly  it  should  be  referred  to  the  next  suborder. 

Blastulidium  pcedophthorum,  Perez,  referred  to  this  family,  is,  according 
to  Chatton  (804),  a  Chytridinian.  Coelosporidium  blatcUce,  Crawley,  is 
referred  by  Leger  (C.R.A.S.,  cxlix.,  p.  239)  to  the  genus  Peltomyces  (Myce- 
tozoa,  p.  243). 

SUBORDER  II. :  POLYSPORULEA. — The  plasmodium  divides  into  sporonts, 
each  of  which  produces  a  cluster  of  spores. 

Two  genera,  each  with  a  single  species  :  Neurospcridium  ceplmlodisci,  from 
the  nervous  system  of  Cephalodiscus  nigrescens  (Ridewood  and  Fantham) ; 
and  Ehinosporidium  kinealyi,  from  the  septum  nasi  of  human  beings  in  India 
(Minchin  and  Fantharn  ;  Beattie)  ;  a  case  has  also  been  observed  in  America 
(Wright). 

Ehinosporidium  causes  vascular  pedunculated  growths  or  tumours, 
resembling  raspberries,  in  the  septum  nasi  or  floor  of  the  nose.  In 
sections  of  the  growth,  great  numbers  of  the  parasite  are  found  embedded 
in  the  connective  tissue,  while  the  mature  cysts  may  be  in  the  stratified 
epithelium  (Wright).  The  youngest  parasites  are  rounded  cells  with  a 
single  nucleus  and  a  distinct  envelope  (Beattie).  By  division  of  the 
nucleus  the  parasite  becomes  a  multinucleate  plasmodium,  the  so-called 
"granular  stage,"  often  of  irregular  form,  but  this  may  be  due  to  the  action 
of  the  preserving  reagents.  Older  parasites  are  spherical,  with  the 
envelope  thickened  to  form  a  thick  transparent  cjst,  external  to  which 
a  nucleated  envelope  is  formed  by  cells  of  the  connective  tissue  (Beattie). 
The  contents  of  the  cyst  (Fig.  177,  A)  become  divided  up  into  numerous 


THE  NEOSPORIDIA 


425 


uninucleate  sporcnts  ("  pansporo blasts ")  towards  the  centre  or  at  one 
pole,  while  the  peripheral  zone  or  the  opposite  pole  remains  in  the 
plasmodial  condition.  The  sporonts  grow  in  size,  and  at  the  same  time 
multiply  by  repeated  fission  to  form  a  cluster  of  about  sixteen  spores, 
a  "  spore-morula "  (Fig.  177,  B),  enclosed  by  a  membrane.  Between 
the  spore-morulae  an  indefinite  framework  is  formed  by  the  residual 
protoplasm  in  which  the  sporonts  have  developed  (Beattie).  Hence  the 
full-grown  parasite  exhibits  three  zones,  which  may  be  concentric  or  polar 
in  arrangement :  a  plasmodial  region,  peripheral  or  polar ;  an  intermediate 
zone  of  spore-formation ;  and  a  central  or  polar  region  containing  ripe 
spore-morula?.  The  process  of  spore-formation  continues  until  the  whole 
cyst  is  full  of  spore-morula?.  The  ripe  cysts  burst  and  scatter  their 
contents  in  the  tissues.  It  is  possible  that  spores  set  free  in  this  way 
may  germinate  in  the  tissues  and  give  rise  to  fresh  cysts ;  but  it  is  more 
probable  that  the  spores,  if  they 
•escape  the  phagocytes,  are  dis- 
charged from  the  surface  of  the 
epithelium.  From  the  analogy  of 
other  Neosporidia,  it  is  reasonable 
to  suppose  that  the  youngest  uni- 
nucleate forms  of  the  parasite  are 
the  multiplicative  phase  in  the 
tissues,  and  that  the  spore-morula? 
represent  the  propagative  phase. 
Nothing  is  known,  however,  of  the 
mode  of  transmission  of  the  para- 
site or  of  the  manner  in  which  the 
infection  is  acquired. 

A  parasite  is  described  by 
Laveran  and  Pet  tit  from  Salmo 
irideus,  which  in  the  opinion  of 
the  authors  presents  affinities 
with  Rliinosporidium  and  Neuro- 
•sporidium.  It  causes  a  disease 
jn  the  fish,  termed  in  German 
«'  Taumelkrankheit." 


e 


pz 


FIG.  177.- — Rltinosporidiv.ni  l-incalyi.  A, 
Segment  of  a  section  through  a  cyst : 
e.,  hyaline  envelope  ;  p.z.,  peripheral 
zone  of  pansporoblasts  ;  i.z.,  inter- 
mediate zone  of  pansporoblasts  contain- 
ing a  few  spores;  c.z.,  central  zone  of 
ripe  spore-morulse;  B,  ripe  spore-morula ; 
Mi.,  membrane  ;  sp.,  spores.  After 
Miucllin  and  Fantham. 


In  addition  to  the  more  or  less 
typical  genera  of  Haplosporidia 
mentioned  in  the  foregoing  para- 
graphs, a  number  of  other  forms 
have  been  described,  of  which  the 
affinities  and  systematic  position  re- 
main for  the  present  uncertain.  Such  are  the  "  Serumsporidia  "  of  Pfeiffer,  and 
other  forms,  for  a  review  of  which  the  reader  must  be  referred  to  the  comprehen- 
sive memoir  of  Caullery  and  Mesnil  (802)  or  to  the  original  descriptions.  The 
remarkable  form,  Schewiakovella  schmeili,  however,  presents  peculiarities  which 
deserve  special  mention.  It  is  a  parasite  of  the  body-cavity  of  Cyclops  spp., 
and  was  the  subject  of  detailed  study  by  Schewiakoff.  In  the  active  con- 
dition it  occurs  as  an  amoeba  with  a  single  nucleus  and  a  contractile  vacuole,  or 
as  a  plasmodium  formed  by  fusion  of  such  amoeba?.  Encystment  of  either  the 
amoeba?  or  the  plasmodia  occurs,  and  within  the  cyst  a  number  of  simple, 
uninucleate  spores  are  formed,  which,  although  possessing  a  distinct  envelope, 
multiply  further  by  fission,  with  mitosis  of  the  nucleus.  Germination  of  the 
spores  sets  free  small  amoebula?.  In  many  points  this  form  is  unique  amongst 
the  Spcrozca,  and  should  perhaps  be  classed  rather  with  the  parasitic 
amoeba?. 

Incertce  Sedis. — In  conclusion  a  number  of  forms  must  be  mentioned  which 
have  been  referred  to  the  Keosporidia,  but  of  which  the  position  and  affinities 
;are  quite  doubtful. 


426  THE  PROTOZOA 

Under  the  generic  name  Microklossia,  Krassiltschik  has  described 
certain  cell -parasites  of  caterpillars,  which  appear  to  belong  to  the  Neo- 
sporidia,  though  it  is  not  possible  to  assign  the  genus  to  a  definite  position, 
since  the  structure  of  the  spores  has  not  been  made  out,  and  the  account 
given  of  the  life-cycle  requires  revision.  According  to  Krassiltschik,  the  cycle 
begins  with  non-sexual  schizogony ;  the  nucleus  of  the  schizont  divides  into 
four  or  eight  nuclei,  and  as  many  merozoites  are  produced  within  the  body 
of  the  schizont.  Schizogony  is  succeeded  by  formation  of  "  macronts  "  and 
"  micronts  "  which  give  rise  to  gametes  ;  the  macront  by  a  process  of  fission 
similar  to  the  schizogony  produces  four  to  eight  macrogametes,  while  the 
micront  produces  in  a  similar  way  two,  four,  or  eight,  microgametes.  The 
nucleus  of  the  macrogamete  divides  to  form  two  reduction-nuclei.  The 
microgamete  attaches  itself  to  one  pole  of  the  macrogamete,  and  its  nucleus- 
passes  over  into  the  cytoplasm  of  the  latter  and  fuses  with  the  female  pro- 
nucleus.  In  the  zygote  the  synkaryon  buds  off  daughter-nuclei,  round 
which  the  cytoplasm  of  the  zygote  is  condensed  to  form  internal  buds—  "  pro- 
toblasts."  The  protoblasts  are  set  free,  and  produce  in  their  turn  "  deuto- 
blasts,"  which  are  set  free,  become  amoeba-like,  multiply  in  the  blood  of  the 
insect,  and  infect  the  tissues  and  organs  of  the  host,  especially  the  fat-body 
and  the  wall  of  the  digestive  tract.  In  the  fat-body  the  deutoblasts  produce 
a  generation  of  "  tritoblasts  "  which  multiply  actively  and  spread  amongst 
the  tissue.  From  the  tritoblasts  arise  finally  a  generation  of  "  teloblasts," 
which  divide  each  into  a  rosette  of  small  cells,  the  definitive  sporoblasts, 
round  a  central  residual  mass.  Each  sporoblast  produces  a  spore,  a  smooth, 
strongly  refractile  body,  ellipsoidal  or  egg-shaped,  in  which  no  details  of 
structure  could  be  made  out.  The  spores  appear  to  be  produced  in  the  wall 
of  the  digestive  tract,  whence  they  are  set  free  with  the  faeces.  The  concluding 
phases  suggest  a  Nosema-type,  but  the  earlier  part  of  the  life-cycle,  if  correctly 
described,  appears  to  be  a  type  sui  generis. 

Under  the  name  Lympliocystis  johnstonei,  Woodcock  (824)  described  a 
parasite  of  plaice  and  flounders,  which  forms  conspicuous  cysts  in  the  lymph- 
spaces  of  the  skin  and  mesentery.  Each  cyst  (Fig.  178)  contains  a  single 
parasite,  which  may  attain  1'5  millimetres  in  diameter,  and  shows  a  remarkable- 
structure.  The  body  is  enclosed  by  a  thick,  structureless  membrane,  and 
contains  at  the  centre  a  very  large  nucleus,  irregular  in  shape,  staining  feebly, 
and  containing  a  number  of  karyosomes  in  a  faintly-staining  reticulum. 
Surrounding  the  nucleus  is  a  chromidial  network  forming  a  ring  or  zone  of 
considerable  thickness,  filling  the  greater  part  of  the  cytoplasm  between  the 
nucleus  and  the  envelope.  The  outermost  zone  of  the  chromidial  net  may 
contain  a  series  of  small,  clear  "  spherules." 

According  to  Awerinzew  (815  and  816),  the  youngest  stages  of  Lymplwcystis 
are  minute  cells  with  a  single  nucleus  which  grow  very  rapidly,  and  as  they 
do  so  the  chrornatin  passes  out  of  the  nucleus  to  form  the  chromidial  ring. 
The  spherules  are  masses  of  plastin  which  separate  from  the  chromidial  net. 
From  the  chromidia  secondary  nuclei  are  formed,  round  which  a  portion  of 
the  cytoplasm  is  cut  off  to  form  small  cells,  termed  by  Awerinzew  "  secondary 
amoeboids, "  and  compared  by  him  to  the  sporonts  of  Glugea.  Within  the- 
secondary  amceboids  spores  are  formed,  of  which,  however,  the  structure 
has  not  been  made  out  clearly.  In  teasecl-up  preparations  of  Lympliocystis, 
Awerinzew  found  spores  similar  to  those  of  Henneguya,  and  proposed  to  place 
the  parasite  in  that  genus.  He  has  now  become  doubtful,  however,  whether 
the  Henneguya-spores  belong  to  the  Lympliocystis  or  to  a  distinct  parasite, 
since  he  was  unable  to  demonstrate  a  similar  structure  in  the  spores  found 
in  the  secondary  amoeboids.  Awerinzew  is  of  opinion,  nevertheless,  that 
Lt/mpliocystis  should  be  referred  to  the  Cnidosporidia,  but  this  form  requires 
further  investigation. 

Toxocystis  liomari,  Leger  and  Duboscq  (646),  is  a  parasite  of  the  posterior 
intestinal  caecum  of  lobsters.  In  appearance  it  resembles  a  hsemogregarine,, 
motionless,  with  granular  cytoplasm  and  a  small  karyosomatic  nucleus  at 
the  middle  of  the  body  ;  there  are  also  usually  two,  sometimes  one,  "  para- 


THE  NEOSPORIDIA 


427 


nuclear  bodies,"  round  masses  larger  than  the  nucleus,  and  staining  very  in- 
tensely with  nuclear  stains.  The  parasite  occurs  between  the  basal  membrane 
and  the  epithelium,  or  in  the  epithelial  cells,  or  occasionally  free  in  the  lumen 
of  the  caecum.  Multiplication  appears  to  take  place  by  longitudinal  fission. 
No  other  stages  are  known. 

Gastrocystis  gilruthi,  Chatton  (819),  is  a  parasite  of  sheep  and  goats  dis- 
covered by  Gilruth  in  Australia,  but  of  common  occurrence  in  Europe.  The 
parasite  appears  as  a  cyst,  visible  to  the  naked  eye,  in  the  mucous  membrane 
of  the  stomach.  The  cyst  has  an  envelope  formed  by  a  single  cell  with  a 
large  nucleus  ;  the  envelope  is  concentrically  striated,  and  bears  externally  a 
fur  of  short,  stiff,  bristle-like  processes,  recalling  the  covering  of  Myxidium 
lieberkiihni,  Myxocystis,  and  Sarcosporidia.  The  younger  cysts  contain  a 
plasmodium  with  a  vast  number 
of  nuclei,  some  of  them  in  groups 
of  two,  three,  four,  and  so  on  up 
to  a  large  number,  which  are  then 
arranged  in  a  single  layer  en- 
closing a  blastula-like  sphere  or 
blastophore.  The  blastophore 
becomes  separated  off  from  the 
interstitial  protoplasm  of  the 
plasmodium,  and  each  nucleus 
grows  out  from  the  surface  in  a 
tongue-like  process  to  form  a 
cluster  of  sporozoite-like  bodies 
or  germs  in  a  manner  very 
similar  to  the  sporulation  of  a 
malarial  parasite  or  of  Porospora 
or  Aggregata.  The  ripe  cyst  is 
full  of  an  enormous  number  of 
these  germs  (Fig.  179),  each  of 

which  is  a  fusiform  bodv,  about 

G.    1  tS.—  Lympliocystis   johnstonei :    section 

through  one  of  the  parasites  lying  in  the 
mesentery.  N.,  The  large  nucleus  of  the 
parasite  ;  chr.,  the  ring  of  chroniidia  :  l.s., 
lymph  -  space  ;  I.,  layer  of  lymphocytes 
adherent  to  the  parasite.  After  Woodcock 
(824),  magnified  45  diameters. 


10  /J.  in   length,  with  one  end 

pointed  and  terminating  in    a 

rostrum,     the     other    blunter. 

Near     the     blunt     end     is      a 

large    nucleus,    and    at    about 

the  middle  of   the    body    is    a 

deeply-staining  mass  resembling 

a   separate   karyosome    or  a  kinetonucleus.     The    surface    of    the   germ   is 

clothed  by  a  delicate  pellicle.      The  germs  are  set  free  from  the  cyst  by 

dehiscence. 

The  affinities  of  Gastrocystis  remain  for  the  present  quite  uncertain. 
Negre  reports  the  occurrence  of  a  similar  cyst  in  the  duodenum  of  a  mouse 
of  which  the  faeces  infected  other  mice  with  sarcosporidiosis  (see  p.  421), 
and  suggests  that  Gastrocystis  may  be  a  stage  in  the  development  of 
Sarcosporidia. 

Pansporella  perplexa,  Chatton  (818),  is  a  parasite  of  the  intestine  of  Daphnia 
spp..  occurring  in  the  form  of  amoeboid  bodies,  reaching  80  P.  in  diameter, 
adherent,  but  not  permanently  attached,  to  the  epithelium  of  the  intestinal 
wall.  The  amceboid  movement  may  be  active,  but  does  not  serve  for  food- 
capture,  since  nutrition  is  effected  by  the  osmotic  method.  The  cytoplasm 
is  divided  into  l^aline  ectoplasm  and  granular  endoplasm  containing  a  single 
large  nucleus  in  which  the  karyosome  has  the  form  of  one  or  two  caps  adherent 
to  the  nuclear  membrane.  The  amceboid  phase  does  not  multiply  by  fission, 
but  becomes  encysted,  and  then  the  nucleus  divides  repeatedly  until  a  large 
number  of  small  nuclei  are  present.  The  body  then  becomes  divided  into  a 
number  of  spores,  each  containing  eight  nuclei,  of  which  sis  degenerate, 
so  that  the  ripe  spore  is  binucleate.  Germination  of  the  spore  sets  free  a 
binucleate  amcebula  which  divides,  apparently,  into  two,  each  of  which  has- 


428  THE  PROTOZOA 

a  single  nucleus  and  grows  up  into  the  adult  amoeba-liko  phase.  Sexual  phe- 
nomena have  not  been  observed,  though  their  occurrence  is  indicated  by  the 
•development  described.  Chatton  considers  that  the  parasite  has  resemblances 
to  Amcebsea,  Mycetozoa,  and  Sporozoa. 

Chytridiopsis,  Schneider. — Leger  and  Duboscq  (823)  describe  several  species 
parasitic  in  the  intestine  of  insects,  and  have  followed  out  the  development  of 
C.  socius.  The  youngest  form  is  a  minute  amcebula  which  penetrates  into 
an  epithelial  cell,  and  grows,  with  multiplication  of  its  nuclei,  to  form  a 
plasmodium  or  schizont,  which  then  divides  up  to  form  a  mass  of  uninucleate 
"  schizozoites,"  each  one  at  first  crescent-shaped,  then  amoeboid.  The 
schizozoites  are  set  free  in  the  intestine,  and  penetrate  other  cells  ;  they  either 
•grow  into  schizonts,  which  repeat  the  process  of  schizogony,  or  into  gameto- 
cytes.  Certain  schizozoites  grow  within  the  cells  without  multiplication 
of  the  nuclei  till  they  attain  a  diameter  of  about  10  /".  ;  then  the  nucleus  divides 
rapidly,  and  a  number  of  microgametes  are  formed.  Other  schizozoites  become 
inacrogametes,  which  are  about  8  M  in  diameter  and  appear  to  be  fertilized 
each  by  a  microgamete.  The  nucleus  of  the  zygote  divides  into  a  great 

number  of  nuclei,  three  or  four  of  which  travel  to  the 
surface  of  the  spherical  body  and  form  a  cyst- 
envelope  ;  the  remaining  nuclei  retain  their  central 
position,  and  the  body  of  the  zygote  divides  into  uni- 
nucleate spores.  In  this  way  resistant  cysts  are  formed 
containing  a  large  number  of  spores,  each  containing 
a  single  nucleus  and  a  vacuole.  The  cysts  are  cast  out 
of  the  body  and  infect  new  hosts. 

Leger  and  Duboscq  consider  that  Chytridiopsis  may 
be  allied  to  the  Microsporidia  ;  but  having  found  no 
polar  filament  in  the  spore,  they  prefer  to  regard  it  as 
FIG.  179. — Spores  of     having  affinities  with  Mycetozoa.* 

Gastrocystis   gilru-         The   genera   Amosbidium   and  Siedleclcia    were    held 

thi.  After  Chatton     formerly  to  constitute  a  distinct  order  of  the  Sporozoa, 

(819).  which  was  named  the  Exosporidia.      Amoebidium  has 

been  shown  clearly  by  Chatton  (817)  to  be  an  organism 

of  the  nature  of  a  fungus  ;  while  Siedleckia  is  now  generally  referred  to  the 
schizogregarines,  as  suggested  by  Minchin  (589) ;  see  Dogiel  (606).  Compare 
also  Capillus  intestinalis,  Granata,  parasite  of  the  intestine  of  Millepedes. 

Affinities  of  the  Neosporidia. — It  is  sufficiently  apparent,  from  the 
structure  and  development  of  typical  examples  of  any  order  of  this 
subclass,  that  their  affinities  are  wholly  with  the  Sarcodina.  In  the 
case  of  many  of  the  more  primitive  forms,  it  is  an  open  question 
whether  they  should  be  classed  in  the  Neosporidia  or  in  one  of  the 
orders  of  the  Sarcodina.  Comparing  them  with  the  Telosporidia, 
it  is  seen  that  the  two  characteristics  of  that  subclass  which  indi- 
cate affinities  with  the  Flagellata  are  absent  altogether  in  the 
Neosporidia — namely,  the  possession  of  flagellated  swarm-spores  or 
gametes,  and  the  definite,  gregarine-like  body-form  of  the  adults. 
No  flagellated  stages  are  known  to  occur  at  any  period  of  the  life- 
history  in  any  member  of  the  Neosporidia,  and  the  body-form  of 
the  adult  in  this  group  is  typically  that  of  an  amoeba.  Many  of  the 
Myxosporidia  might  almost  be  regarded  as  parasitic  amoebse  with 
a  peculiar  type  of  reproduction.  Even  more  remarkable  is  the 

*  It  is  not  clear  on  what  grounds  Schepotieff  (269,  p.  51G)  considers  Chytridiopsis 
to  be  a  Flagellate. 


THE  NEOSPORIDIA  429 

regularity  with  which  the  sporozoite  in  the  Neosporidia  has  the  form 
of  an  amcebula,  as  contrasted  with  the  equally-constant  gregarinula- 
form  of  the  Telosporidian  sporozoite.  The  characters  implied  in 
the  terms  Amcebogenise  and  Rhabdogenise  appear  to  be  more 
diagnostic  of  the  two  groups  than  any  other.  There  can  be  little 
doubt,  therefore,  that  the  union  of  the  Telosporidia  and  Neosporidia 
in  one  class — the  Sporozoa — is  a  quite  artificial  arrangement,  and 
that  the  two  subclasses  in  question  show  distinct  affinities,  and  are 
descended  from  distinct  ancestral  forms — the  Telosporidia  from 
Flagellata,  the  Neosporidia  from  Sarcodina. 

BibliograpJty •. — For  references  see  p.  449. 


CHAPTER  XVII 
THE    INFUSORIA 

"THE  term  Infusoria  had  originally  a  much  wider  application  than 
at  present,  being  used  to  denote  the  various  microscopic  animalcules 
which  make  their  appearance  in  infusions  exposed  to  the  air.  Hence 
the  Infusoria  included  any  Protozoa,  and  even  organisms  distinct 
from  them,  such  as  Rotifers.  Just  as  the  word  "  insect  "  has  been 
restricted  in  its  zoological  application  to  a  single  class — the  Insecta 
Hexapoda — so  the  term  Infusoria  has  become  narroAved  down  to 
denote  the  Infusoria  Ciliata  and  Suctoria,  which  constitute,  taken 
together,  one  of  the  most  definite  and  sharply-marked  classes  of  the 
Protozoa,  characterized  by  two  principal  structural  features  :  first, 
the  possession  of  cilia  during  the  whole  or  a  part  of  their  active  life  ; 
secondly,  the  differentiation  of  the  nuclear  apparatus  into  a  vegeta- 
tive macro  nucleus  and  a  generative  micronucleus  (p.  153). 

The  Infusoria  fall  naturally  into  two  subclasses  :  the  Ciliata 
proper,  in  which  the  cilia  are  retained  throughout  life  ;  and  the 
Acinetaria  or  Suctoria,  in  which  cilia  are  present  only  during 
the  early  or  larval  phases  of  the  life-history,  and  are  lost  in  the 
adult  organism,  which  is  of  sedentary  habit,  and  in  which  food- 
capture  is  effected  by  special  organs — suctorial  tentacles. 

SUBCLASS  I. — CILIATA. 

The  Ciliata,  the  most  abundant  and  familiar  of  microscopic  forms 
of  life,  may  be  considered  in  a  sense  the  highest  of  the  Protozoa, 
since  in  110  other  class  does  the  cell-body  attain  to  so  great  a  com- 
plication of  parts  and  organs  or  to  so  high  a  degree  of  structural 
differentiation.  Not  even  in  the  Metazoa  are  single  cells  to  be 
found  of  such  visibly  complicated  structure,  since  in  the  Metazoa 
the  cell  is  specialized  usually  for  one  particular  function  of  a  living 
body,  while  in  the  Ciliata  the  single  cell  performs  all  the  functions 
of  life.  Moreover,  the  differentiation  of  the  nuclear  apparatus  into 
.generative  and  vegetative  portions  may  be  considered  analogous 
with,  and  parallel  to,  the  differentiation  of  gernien  and  soma  in  the 
Metazoa  ;  and  Lewin  (172)  regards  the  micronucleus  as  living  inde- 

430 


THE  INFUSORIA 


431 


H 
iW. 


pendently  during  the  asexual  cycle,  with  the  cell  as  its  environment. 
In  contrast  to  the  extreme  elaboration  in  the  structure  of  the  indi- 
vidual, the  life-cycle  as  a  whole  is  generally  of 
a  simple  type,  and  the  majority  of  the  free- 
living  species  are  practically  monomorphic  ; 
but  some  of  the  parasitic  forms  show  a 
succession  of  form-changes  in  their  life-cycle. 

Habits,  Mode    of   Life.— The   majority  of 
Ciliata  are  free-living  aquatic  forms,  marine 
or  fresh-water,  probably  without  exception 
holozoic  in  the  mode  of  nutrition  ;    but  a 
great  number  of  parasitic  forms  are  known. 
A  ciliate,  whatever  its  mode  of  life,  may  be 
free  or  sedentary.     The  free  forms  may  be 
of  swimming  or  creeping  habit,  using  their 
cilia  in  the  one  case  to  move  freely  through 
the  water  or  to  glide  along  firm  surfaces,  in 
the  other  to  creep  over  solid  objects  or  on 
the  surface  film  of  the  water.     The  sedentary 
forms  may  be  attached  temporarily  or  more 
or  less  permanently  to  some  object,  which  is 
often  the  body  of  some  larger  animal.    Para- 
sitic forms  may  be,  as  in  other  cases,  epizoic 
or  entozoic  ;  but  the  word  "  parasitic  "  must 
be  taken  in  a  wide  sense,  since  many  Ciliata 
living  in  or  upon  other  organisms  are  not 
parasitic   in   the   strict   sense  of  the  word, 
though  many  truly  parasitic  forms  occur. 

Body-Form. — Correlated  with  the  diversity 
in    the    habit    of    life,    the   body-form    and 
external    structure   show    many    variations. 
The  primitive  type  of  ciliate  may  be  con-      /= 
sidered  to   be  an  ovoid,  gooseberry-shaped      '*" 
organism  with  a  principal  axis  parallel  to  the 
direction  of  movement,  consequently  with  an 

FIG.  180. — Spirosiomum  ambiguum,  one  of  the  largest 
free-living  Ciliata,  reaching  a  length  of  3  millimetres 
consequently  a  favourable  object  for  physiological 
experiments.  AT,  Macronucleus,  greatly  elongated, 
in  shape  like  a  string  of  beads  or  sausages  (so-called 
"  moniliform  "  type)  ;  o,  mouth  at  the  hinder  end  of 
the  elongated  peristome  ;  c.v.,  contractile  vacuole, 
supplied  by  a  very  long  feeding-canal  (f.c.) ;  the 
rnicronucleus  is  not  shown.  After  Stein. 

anterior  and  a  posterior  pole  (Fig.  14,  p.  32).     The  mouth  is  terminal 
at  the  anterior  pole.    The  cilia  clothe  the  whole  body  evenly,  being 


•-o 


432 


THE  PROTOZOA 


arranged  in  meridional  rows  running  from  the  anterior  to  the 
posterior  pole,  and  are  of  equal  length  in  all  parts  of  the  body. 
An  ideally-simple  type  of  this  kind  is  very  nearly  realized  in  some 
of  the  primitive  forms,  but  as  a  rule  is  modified  in  various  ways. 

In  the  first  place,  the  mouth  does  not  remain  anterior,  but  is 
shifted  to  the  side  of  the  body,  as  far  as,  or  even  farther  than,  half- 
way to  the  posterior  pole  (Fig.  181)  ;  consequently  the  rows  of 
cilia  become  displaced  from  their  primitively  meridional  arrange- 
ment, and  tend  to  run  obliquely  round  the  body.  Secondly,  a 
differentiation  is  set  up  between  the  general  coat  of  cilia  clothing 
the  body  and  locomotor  in  function,  and  special  cilia  near  or  around 
the  mouth,  which  are  usually  much  longer  than  the  others,  and 
modified  in  various  ways  in  connection  with  the  function  of  food- 
capture.  The  mouth  itself  becomes  surrounded  by  a  special  area 

termed  the  "  peristorne,"  in 
which  are  found  the  special 
food-capturing  cilia. 

In  forms  of  creeping  habit 
the  form  becomes  still  more 
modified.  The  body  becomes 
flattened,  and  a  ventral  sur- 
face, turned  towards  the 
substratum  and  bearing  the 
mouth  and  peristome,  is 
distinguished  from  the  oppo- 
site or  dorsal  surface.  Even 
more  marked  are  the  adapta- 
tions of  the  coat  of  cilia  to 
this  mode  of  life  (Fig.  182). 
The  locomotor  cilia  become 

restricted  to  the  ventral  surface,  and  those  on  the  dorsal  side  either 
tend  to  disappear  altogether  or  persist  with  a  purely  tactile  function. 
The  cilia  of  the  ventral  surface  tend  to  form  tufts  which  fuse  into 
cirri  (p.  55),  with  which  the  animal  creeps  as  if  on  legs. 

Sedentary  forms  may  be  attached  temporarily  by  means  of  special 
cilia  or  adhesive  organs,  or  more  or  less  permanently  by  a  portion 
of  the  body-surface  on  the  side  opposite  to  the  mouth.  In  such 
forms  (Fig.  183)  the  general  coating  of  cilia  may  be  retained,  or 
may  disappear  entirely,  only  the  peristomial  cilia  persisting  ;  but 
locomotor  cilia  may  be  developed  temporarily,  enabling  the  animal 
to  become  detached  from  one  spot,  and  to  swim  away  and  attach 
itself  again  elsewhere.  In  sedentary  forms  the  point  of  attachment 
may  be  drawn  out  into  a  stalk,  which  may  be  of  great  length  rela- 
tively, and  may  be  a  secreted  structure  or  a  portion  of  the  body 
drawn  out.  In  the  second  case  the  stalk  may  contain  highly-per- 


B  C 

FIG.  181. — Diagram  illustrating  the  shifting 
of  the  mouth,  and  the  consequent  displace- 
ment of  the  rows  of  cilia,  in  Ciliata,  from  a 
form  in  which  the  mouth  is  at  the  anterior 
pole  and  the  rows  of  cilia  run  a  meridional 
course  ( A),  to  a  form  in  which  the  mouth  is 
shifted  to  the  side  of  the  body  (C).  After 
Delage  and  Herouard. 


THE  INFUSORIA 


433 


fected  contractile  mechanisms,  enabling  the  animal  to  stretch  out 
a  long  way  from  the  base  of  attachment,  or  to  retract  itself  close  to 
it.  Sedentary  forms  may  also  secrete  round  themselves  a  protec- 
tive sheath  or  tube. 

Structure  of  the  Body. —The  mouth,  or  cytoslome,  is  an  aperture 
leading  into  a  longer  or  shorter  oesophagus,  or  cytopharynx,  which 
ends  blindly  in  the  endoplasm.  The  indigestible  remains  of  the 
food  are  cast  out  through  a  pore  in  the  cuticle— a  cell-anus,  or 
cytopyge,  which,  though  a  permanent  structure,  is  usually  only 
visible  at  the  moment  of  defalcation  ;  but  in  some  cases  there  is  a 
distinct  anal  tube  leading  to  an  anal  pore,  visible  at  all  times.  In 
the  Gymnostomata  (see  p.  439,  infra)  the  mouth  can  be  closed  or 
opened  by  a  system  of  rods  contained  in  the  wall  of  the  oesophagus 
(Fig.  184),  which  contains  no  vibratile  apparatus  ;  but  in  all  other 

ilk 


--n 


r^ 


ev. 


~~~--cr/t 


A  BC 

FIG.  182. — A  and  B,  Euplotes  patella :  A,  ventral  view ;  B,  dorsal  view  ;  G,  Euplotes 
harpa.  In  all  the  figures  :  N,  macronucleus  ;  n,  micronucleus  ;  c.v.,  contractile 
vacuole ;  crh,  cirri  ;  p.m.,  peristomial  mernbranellae  ;  F,  area  containing  food- 
vacuoles  enclosed  by  the  macronucleus.  After  Stein,  the  micronucleus  added 
from  original  preparations. 

Ciliata  the  mouth  (if  present)  is  permanently  open,  and  the  oeso- 
phagus has  no  rod-apparatus,  but  contains  one  or  more  undulating 
membranes.  In  the  orders  Heterotricha,  Hypotricha,  and  Peritricha 
(see  pp.  439,  440,  infra),  the  peristome  contains  a  spiral  zone  of 
cilia  modified  in  various  ways,  leading  to  the  mouth,  and  continuous 
with  the  undulating  membrane  in  the  oesophagus.  In  the  two  first 
of  these  orders  the  cilia  in  the  adoral  zone  are  generally  fused  in 
transverse  rows  to  form  membranellse.  In  the  Peritricha  the  adoral 
zone  is  composed  of  two  parallel  undulating  membranes,  and  in 
this  order  the  mouth,  together  with  the  anus  and  the  contractile 
vacuoles,  are  sunk  into  a  funnel-shaped  or  tubular  depression  called 
the  "vestibule"  (Fig.  183,  V-).  The  two  undulating  membranes,  after 
describing  a  spiral  which  varies  from  one  and  a  quarter  to  five  com- 

28 


434 


THE  PROTOZOA 


^^•^^fc^ 


FIG.  183. — Campanula  unibdlaria.  p.g.,  Peristomial  groove  in  which  runs  the 
adoral  spiral  zone  of  cilia,  which  in  this  species  takes  4£  turns  ;  p.r.,  peri- 
stomial  ridges  between  the  peristomial  grooves  ;  a.sp.,  the  two  undulating 
membranes,  each  made  up  of  three  rows  of  cilia  fused,  which  compose  the 
adoral  spiral,  seen  in  optical  section  ;  the  two  undulating  membranes  pass 
down  into  the  vestibule  (V.),  and  run  down  inside  it  spirally  as  far  as  its 
termination  at  in.,  which  represents  the  true  mouth,  leading  into  the  short 
cytopharynx  or  oesophagus  (ces.)  ;  n,  inicronucleus ;  rN,  macronucleus  ; 
c.pl.,  cortical  ectoplasm,  thick  at  the  base  of  the  body,  thin  at  the  sides  ; 
st.c.,  "  collar  "  of  the  stalk  ;  st.,  stalk  ;  gr.,  granules  in  the  endoplasm  which 
stain  red  with  neutral  red  in  the  living  condition  ;  f.v.,  food-vacuoles  ;  c.v., 
contractile  vacuole  opening  by  two  canals  into  the  vestibule.  After 
Schroder  (864). 


THE  INFUSORIA 


435 


plete  turns,  pass  down  into  the  vestibule,  at  the  bottom  of  which 
as  the  mouth,  leading  into  a  short  oesophagus  (Fig.  183,  m,  ess.).  The 
vestibule,  into  which  the  fseces  and  the  excretions  of  the  contractile 
vacuoles  are  evacuated,  forms  a  sort  of  cloaca,  combining,  as  it 
were,  the  functions  of  a  stomodseum  and  a  proctodaeum. 

The  body  of  a  ciliate  Infusorian  is  composed  of  ectoplasm  and 
•endoplasm,  the  first  of  these  two  regions  being  highly  differentiated 
and  complex  in  structure.  The  surface  of  the  entire  body  is  clothed 
"by  a  pellicle  (Fig.  185,  p.) — the  most  superficial  differentiation  of  the 
ectoplasm — usually  in  the  form  of  a  thin,  delicate  membrane,  which 
is  sometimes,  however,  greatly  thickened  to  form  a  cuirass  or 
lorica.  In  addition  to  the  mouth  and  anal  pore  already  men- 
tioned, the  pellicle  is  perforated 
l»y  the  openings  of  the  contractile 
vacuoles,  one  or  more  in  number. 
The  cilia  also  pass  through  the 
pellicle. 

Beneath   the  pellicle  the  ecto- 
plasm,  in   its   full    development, 
may   be    differentiated    into   four 
layers,  which,  however,  are  not  all 
of  them  invariably  present.     The 
most  external  layer  of  the  ecto- 
plasm is  the  so-called  alveolar  layer 
(Fig.    185,  al.),   consisting  of  the 
outermost  stratum  of  the  alveoli 
•of    the   protoplasmic   framework, 
which  take  a  regular  arrangement, 
the     walls     between     contiguous 
alveoli    being   disposed    vertically 
to   the   pellicle,    thus   giving    the 
appearance  of   a  radially-striated 
layer.     Within  the  alveolar  layer 
is  found  commonly  a  protoplasmic  zone  containing  small,  spindle- 
shaped  bodies — the  so-called  trichocysts  (Fig.  185,  tm.) — from  which  a 
long,  stiff  thread  is  discharged  upon  suitable  stimulation.   Within  the 
trichocyst-layer  comes  a  contractile   layer,  containing   myonemes 
which  run  primitively  beneath,  or  parallel  to,  the  rows  of  cilia  at 
the  surface.     The  cilia  themselves  take  origin  from  basal  granules 
placed  externally  to,  or  between,  the  myonemes,  and  pass  to  the 
exterior   between   the   alveoli   of   the   alveolar   layer.     The   most 
internal  stratum  of  the  ectoplasm  is  a  spongy  protoplasmic   zone 
traversed  by  irregular  spaces  and  channels  containing  fluid,  and 
representing  an  excretory  layer.     The  liquid  from  this  region  drains 
into  the  contractile  vacuole  or  vacuoles.      The  smaller   channels 


FIG.  184. — Chilodon  cucullulus.  o, 
Mouth  ;  ph.,  pharynx  surrounded 
by  a  supporting  apparatus  of  rods ; 
N,  macronucleus  ;  c.v.,  c.v.,  con- 
tractile vacuoles  ;  an.,  anus,  tem- 
porarily visible  during  the  extrusion 
of  faecal  matter  (ex.).  After  Stein. 


cv- 


N 


P 


F&E  X  /MV8  >'  .'•  4^; ••;  'vs  /s^s1 

mffiW/m&^& 

v-y,S{ '?-,  /: ••/  \£-J%'(Ty&:£'  ^'-'^  •'•'••* 


. . 

" 


r&&&iW>  i  •"^•?-  v^-', 

^i:"I;4^^ 


FIG.  185. — Paramecium  caudatum:  semi-diagramrnatic  figure  to  show  the  structure. 
P.,  peristomial  groove  ;  o,  mouth  ;  as.,  oesophagus,  containing  an  undulating 
membrane  (a.m.)  ;f.v.',  food-vacuole  forming  at  the  base  of  the  cesophagus  ; 
f.v.,  f.v.,  other  food-vacuoles  circulating  in  the  endoplasm  ;  c.v.,  c.v.,  the  two 
contractile  vacuoles,  showing  a  different  condition  in  each,  the  upper  one  full 
and  ready  to  empty  itself,  the  lower  one  beginning  to  fill  after  a  contraction  ; 
ex.,  excretory  crystals  in  the  endoplasm  ;  N,  macronucleus  ;  n,  micronucleus  ; 
tm.,  trichocyats ;  al.,  alveolar  layer;  p.,  pellicle.  After  Lang  (10),  slightly 
modified. 


THE  INFUSORIA  437 

•unite  usually  into  more  or  less  conspicuous  main  ducts — so-called 
"  feeding-canals "  —which  empty  themselves  into  a  contractile 
"vacuole. 

The  arrangement  of  the  contractile  vacuoles  and  canals  varies 
•considerably  in  different  species.  Thus,  in  Stentor  (Fig.  8)  there  is 
a  single  contractile  vacuole,  with  a  feeding-canal  running  the  length 
•of  the  body  ;  so  also  in  Spirostomum  (Fig.  180,  f.c.).  In  Paramecium 
(Fig.  185)  there  are  two  contractile  vacuoles  near  each  end  of  the 
body.  The  vacuole  contracts  suddenly,  diminishing  to  a  tiny 
globule,  and  then  some  six  or  eight  feeding-canals  make  their 
appearance,  arranged  round  the  vacuole  in  a  star-like  figure,  but 
at  first  distinct  from  the  central  vacuole.  The  inner  ends  of  the 
feeding-canals  gradually  swell,  and,  after  reaching  a  certain  size, 
burst  through  and  empty  themselves  into  the  central  vacuole,  which 
•grows  slowly  to  its  full  size,  and  as  it  does  so  the  feeding-canals 
disappear  by  degrees  from  view.  When  the  vacuole  has  reached 
its  full  size,  it  empties  itself  to  the  exterior,  and  the  process  begins 
again.  The  contractile  vacuole  itself  may  be  considered  as  a  cen- 
tralized portion  of  the  canal-system,  and  though  when  full  it 
bulges  into  the  endoplasm,  it  belongs  strictly  to  the  ectoplasm. 

The  endoplasm  is  the  seat  of  nutrition,  and  also,  as  containing 
the  nuclear  apparatus,  of  reproductive  processes.  It  is  of  fluid 
consistence,  and  exhibits  streaming  movements,  termed  "  cyclosis  " 
—that  is  to  say,  currents  of  protoplasm  which  flow  round  constantly 
in  one  direction,  as  if  the  endoplasm  was  being  stirred  round  and 
round.  The  endoplasm  contains  enclosures  of  various  kinds,  chief 
amongst  which  are  the  food- vacuoles,  containing  ingested  food- 
particles  in  process  of  digestion.  The  food- vacuoles  are  formed  at 
the  base  of  the  oesophagus,  down  which  food-particles  are  wafted 
by  the  action  of  the  adoral  cilia  and  membranes.  When  full-sized, 
the  food- vacuole  becomes  detached  from  the  end  of  the  oesophagus, 
like  a  soap-bubble  from  a  pipe,  and  passes  round  the  body  in  the 
currents  of  the  endoplasm,  the  indigestible  faecal  residue  being 
expelled  finally  from  the  anal  pore  (p.  433,  supra).  In  addition  to 
food-vacuoles,  the  endoplasm  contains  various  metaplastic  grains, 
excretory  granules,  "  spheroplasts "  (see  p.  448),  and  sometimes 
symbiotic  algee. 

The  nuclei  are  typically  two  in  number — a  large,  conspicuous 
macronucleus,  staining  deeply  ;  and  a  microiiucleus  of  much  smaller 
size,  often  very  inconspicuous,  and  difficult  to  stain.  In  primitive 
forms  the  macronucleus  is  a  compact  bocty,  and  the  microiiucleus 
appears  as  a  small  refringeiit  globule  close  beside  it,  often  lodged 
in  a  depression  of  the  surface  of  the  macronucleus  (Fig.  185,  N,  n). 
But  the  nuclei  show  very  great  variation  in  form,  number,  and 
appearance.  The  macronucleus  may  be  drawn  out  into  the  shape 


438  THE  PROTOZOA 

of  a  sausage  or  of  a  horseshoe,  as  in  Vorticellids  (Fig.  183,  N),  or 
exhibit  the  form  of  a  string  of  beads,  as  in  Stentor  (Fig.  8)  and 
Spirostomum  (Fig.  180)  ;  or  there  may  be  two  macro  nuclei  con- 
nected by  a  delicate  filament,  with  a  micronucleus  beside  each,  as 
in  Stylonychia  ;  or,  finally,  the  macronucleus  may  be  broken  up 
to  form  a  diffuse  network  or  a  great  number  of  small  nuclei.  The 
micronucleus  may  be  single  or  multiple,  but  does  not  vary  in  form 
to  any  marked  extent. 

Life-History. — Reproduction  takes  the  form  of  binary  fission, 
usually  in  the  free  state ;  but  some  species  become  encysted  prior  to 
division,  and  then  divide  into  two,  four,  eight,  or  a  large  number 
of  small  individuals  within  the  cyst.  Binary  fission  in  the  free 
state  is,  with  few  exceptions,  transverse  to  the  long  axis  of  the 
body  ;  but  in  the  fixed,  sedentary  forms  the  fission  is  usually  in  the 
vertical  plane,  or  slightly  oblique  to  it,  and  often  takes  the  form  of 
very  unequal  fission  or  budding.  In  some  of  the  entozoic  species 
of  Astoniata  (p.  439),  repeated  transverse  division  of  the  body 
without  complete  separation  of  the  daughter-individuals  from  one 
another  leads  to  the  formation  of  chains  of  individuals,  of  which 
the  most  anterior  may  be  larger  than  the  others. 

As  in  other  Protozoa,  colonies  may  be  formed  in  Ciliata  as  the 
result  of  imperfect  separation  of  sister-individuals  produced  by 
fission.  This  is  especially  common  in  the  sedentary  Peritrichar 
leading  usually  to  the  formation  of  arborescent  growths  ;  but  some- 
times the  colony  takes  other  forms,  as,  for  example,  in  Ophrydium, 
where  it  consists  of  a  great  number  of  individuals  embedded  in  a 
common  mass  of  jelly  which  floats  freely. 

Encystment  is  related  in  various  ways  to  the  life-conditions  of 
the  Ciliata.  Most  frequently  it  appears  to  take  place  as  a  protec- 
tion against  desiccation  in  free-living  forms,  or  as  an  adaptation 
to  a  change  of  hosts  in  parasitic  forms.  But  in  some  cases  it  is 
related  to  the  digestion  of  food,  in  others  to  reproductive  processes. 
In  some  species  it  is  stated  to  take  place  if  the  supply  of  food  fails, 
and  it  can  be  induced  artificially  in  various  ways. 

The  process  of  syngamy  has  been  described  above  (p.  152,  Fig.  77). 
Summarized,  it  consists  essentially  of  the  following  processes  ;  some 
exceptions  are  described  below  : 

1.  Degeneration  and  ultimate  absorption  of  the  macronucleus  of 
each  conjugant. 

2.  Reducing  divisions  of  the  micronucleus  to  form  four  micro- 
nuclei,  three  of  which  are  absorbed. 

3.  Division  of  the  single  remaining  micronucleus  into  two  pro-, 
nuclei,  one  stationary,  the  other  migratory. 

4.  Passage  of  the  migratory  pronucleus  of  each  conjugant  across 
into  the  body  of  the  other  conjugant,  where  it  fuses  with  the 
stationary  pronucleus. 


THE  INFUSORIA  439 

5.  Separation  of  the  conjugants  ;  division  of  the  synkaryon  to 
form  a  new  micronucleus  and  macronucleus. 

Classification. — The  Ciliata  are  divisible  into  two  sections,  which 
comprise  in  all  four  orders  : 

Section  A, — Aspirigera. 

Without  a  spiral  zone  of  adoral  cilia  or  membranellse. 

ORDER  I.  :  HOLOTRICHA. — Cilia  of  approximately  even  length  all  over 
the  body,  forming  a  continuous,  evenly-distributed  coat  in  more  primitive 
forms,  arranged  in  bands  or  restricted  to  special  regions  in  more  specialized 
forms. 

Suborder  1  :  Astomata. — Mouthless  forms  of  parasitic  habit.  Opalina, 
Anoplophrya,  Discoplirya,  etc.  (see  p.  451). 

Suborder  2:  Gymnostomata. — Mouth  a  simple  pore,  near  or  at  the  anterior 
pole  of  the  body,  leading  into  a  simple,  usually  straight  oesophagus  without 
cilia  or  undulating  membranes,  often  with  a  rod-apparatus  by  which  the  mouth 
is  closed  and  opened  for  food-ingestion. 

Classified  in  various   ways ;   three  families  recognized   by  Doflein   (7) : 

(1)  Enchelidce,  including  Holophrya,  Prorodon  (Fig.  14),  Coleps,  Didinium, 
etc.  ;  BuetscJilia,  parasitic  in  the  rumen  of  ruminants.     To  the  family  Enche- 
lidce must  be  referred,  apparently,  the  remarkable  form  described  by  Meunier 
under  the  name  Gymnozoum  viviparum,  which  is  stated  to  have  the  following 
characteristics  :  The  surface  of  the  body  bears  no  cilia,  which  appear  to  be 
wanting  altogether  in  this  form  ;  the  mouth-opening  is  at  one  extremity  of 
the  ovoid  body,  and  contains  an  extrusible  proboscis,  used  for  the  capture 
of  prey  (see  p.  442) ;  the  micronucleus  is  contained  within  the  macronucleus  ; 
reproduction  is  by  transverse  fission,  and  also  by  internal  budding,  producing 
embryos  which  may  produce  in  their  turn  other  embryos  in  a  similar  manner 
before  being  liberated  from  the  parent  body,  from  which  they  are  set  free  by 
dehiscence.     (2)  Trachelidce,  including  Tmchelius,  Trachelocerca,  Amphileptus, 
Lionotus,  Loxodes,  Dileptus,  etc.     (3)  Chlamydodontidce,  including  Chilodon 
(Fig.   184),  Nassula,  etc.     (4)  F attingeriidce  (Chatton,  83T5):   Fcettingeria, 
Perikaryon. 

Suborder  3  :  Hymenostomata. — Mouth  usually  at  the  side  of  the  body  and  at 
the  bottom  of  a  peristoniial  depression,  leading  into  a  short  oesophagus  never 
supported  by  a  rod-apparatus,  but  containing  an  undulating  membrane  ; 
consequently  not  capable  of  being  closed,  but  permanently  open.  _ 

Families:  (1)  Chili feridce :  Leucophrys,  Glaucoma,  Frontonia,  Colpoda, 
etc.  (2)  Parameddce  :  Paramedum  (Fig.  185),  etc.  (3)  Pleuronemidce  : 
Pleuronema  (Fig.  27),  etc.  (4)  Isotrichidce  :  Isotricha,  parasitic  in  the  rumen 
of  ruminants  ;  "and  other  families.  (5)  Microthoracidce :  Microthorax,  Con- 
chophrys  (Chatton.  831  '5). 

Section  B. — Spirigera. 

With  a  conspicuous  spiral  zone  of  larger  cilia  or  vibratile  membranes  leading 
to  the  mouth  ;  oesophagus  as  in  Hymenostomata. 

ORDER  II.  :  HETEROTRICHA.— Generally  of  swimming  habit,  sometimes 
sedentary. 

Suborder  1  :  Polytriclia. — Body  covered  with  an  even  coat  of  cilia. 

Principal  families:    (1)  Plagiotomidce ;  example:  Spirostomum  (Fig.  180). 

(2)  Bursaridce;    examples:    Bursaria ;   Nyctotherus    (Fig.   9),  with    species 
entozoic   in  various   animals;    Balantidium,  also  entozoic.     (3)  Stentoridce; 
example:  Stentor  (Fig.  8).     (4)  Tintinnidce  (compare  Entz,  53);  examples: 
Tintinnus,  etc. 

Suborder  2  :  Oligotriclia.—  Body-cilia  greatly  reduced  or  absent. 

Families:  (1)  Haltendce ;  example:  Halteria.  (2)  Ophryoscoleddce,  with 
numerous  genera  parasitic  in  the  stomachs  of  ruminants;  examples:  Ento- 
dinium,  Ophryoscolex,  Cyclopostliium. 


440  THE  PROTOZOA 

ORDER  III. :  HYPOTRICHA. — Ciliata  typically  of  creeping  habit ;  the  body 
flattened,  with  dorsal  and  ventral  surfaces,  the  ciliation  highly  modified 
and  specialized,  usually  with  cirri  on  the  ventral  surface. 

Principal  families :  ( 1 )  Peritromidos,  with  cilia  on  the  ventral  surface  ; 
example  :  Peritromus.  (2)  Oxytrichidce,  with  cirri ;  examples :  Oxytricha,  Uro- 
styla,  Stylonychia.  (3)  Euplotidce  ;  example  :  Euplotes  (Fig.  182). 

ORDER  IV.  :  PERITRICHA. — Typically  of  sedentary  habit,  the  locomotor 
cilia  reduced  to  a  single  ring  or  absent  temporarily  or  permanently ;  the 
adoral  spiral  runs  down  into  a  deep  depression,  the  vestibule,  into  which 
open  the  anus  and  contractile  vacuoles,  and  at  the  base  of  which  is  the  mouth, 
leading  into  the  oesophagus. 

Suborder  1  :  Scaiotricha. — The  adoral  zone  describes  a  left-handed  spiral. 

Two  families:  (1)  Spirochonidce  :  Spirochona,  ectozoic  on  the  gill-plates 
of  Gammarus  pulex,  has  a  non-contractile  body  which  bears  at  the  upper 
extremity  a  spirally-folded  membranous  funnel,  on  the  inner  side  of  which 
is  a  zone  of  cilia.  Allied  genera  are  Kentrochona  and  Kenirochonopsis,  both 
ectozoic  on  the  gill-plates  of  Nebalia.  (2)  LicnopJioridce  ;  example  :  Licnophora, 
ectozoic  on  various  marine  animals  (one  species  entozoic  in  the  respiratory 
trees  of  Holothurians)  ;  attachment  by  a  sucker-like  disc. 

Suborder  2  :  Dexiotricha. — The  adoral  zone  describes  a  right-handed  spiral. 

Family :  Vorticellidce,  with  three  subfamilies  :  (a)  Urceolarince,  unstalked, 
attached  temporarily  by  a  sucker  or  disc,  surrounded  by  a  persistent  zone 
of  locomotor  cilia;  examples:  Trichodina,  Cyclochce.ta.  (b)  Lagenophryince  ; 
example :  Lagenophrys.  (c)  Vorticellince,  with  numerous  genera  :  Vorticella, 
Carchesium,  Zoothamnium,  etc.,  with  contractile  stalks  ;  Epistylis,  Opercu- 
laria,  Campanella  (Fig.  183),  Ophrydium,  etc.,  with  non-contractile  stalks ; 
Cothurnia,  Vaginicola,  with  sheaths  ;  Scypliidia,  free-swimming. 

The  entozoic  Ciliata  exhibit  two  different  methods  of  nutrition  :  first,  the 
holozpic  method,  in  which  the  animals  ingest  solid  food-particles,  like  the 
free-living  species,  and  possess  in  consequence  a  distinct  mouth  and  contain 
food-vacuoles  in  their  interior;  secondly,  the  osmotic  method,  seen  in  the 
astomatous  forms,  which  absorb  fluid  nutriment  by  diffusion  from  their  host, 
and  in  which  a  mouth  is  rudimentary  or  absent  and  food-vacuoles  are  not 
found.  The  Ciliata  of  the  astomatous  type  represent  the  truly  parasitic 
forms,  a  familiar  example  of  which  is  the  genus  Opalina,  with  species  parasitic 
in  the  common  frog  and  other  vertebrates.  Common  entozoic  genera  of  the 
holozoic  type  are  Balantidium  and  Nyctoiherus,  found  in  the  digestive  tracts 
of  various  animals  ;  such  forms  are  perhaps  for  the  most  part  scavengers  ; 
according  to  Comes  (A.P.K.,  xv.,  p.  54),  Balantidium  nourishes  itself  exclu- 
sively on  red  blood-corpuscles,  which  are  set  free  in  the  intestine  from  wounds 
caused  by  other  parasites,  especially  Trematodes.  Species  which  inhabit 
the  human  intestine  are  Balantidium  coli,  B.  minutum,  and  Nyctothems  faba. 

On  the  other  hand,  ciliates  may  crop  up  in  cultures  of  human  f  a?ces,  which, 
like  the  amoebae  and  flagellates  found  there,  are  not  to  be  regarded  as  in- 
habitants of  the  human  intestine,  but  as  free-living  forms  which  have  passed 
through  the  digestive  tract  in  an  encysted  condition  without  being  destroyed, 
and  germinate  when  set  free  from  the  gut.  An  example  is  Cliilodon  dentatus 
(uncinatus),  described  by  Guiart  from  human  faeces  ;  possibly  also  the  ciliates 
described  by  Martini  (850)  in  a  case  of  dysentery. 

The  free-living  Ciliata  exhibit,  as  a  rule,  great  uniformity  of  character 
in  the  active  state,  occurring  constantly  in  one  specific  form  which  only 
varies  slightly  in  size  under  natural  conditions ;  they  are,  in  fact,  as  nearly 
as  possible  monomorphic.  Some  of  the  parasitic  forms  exhibit,  how- 
ever, a  well-marked  recurring  cycle  of  forms  in  relation  to  the  special 
necessities  of  their  mode  of  life,  as  is  described  below  (p.  450).  In  some 
free-living  forms  also  different  forms  occur  in  the  same  species.  The  small 
free-swimming  conjugants  (gametes,  so  called)  of  the  sedentary  Vorticellids 
have  been  noted  above  (p.  172).  In  Leucophrys  patula,  a  free-swimming 
species,  large  and  small  individuals  occur;  but,  according  to  Prowazek(861),' 


THE  INFUSORIA  441 

/ 

this  dimorphism  has  no  relation  to  sex,  but  only  to  differences  in  the  sur- 
rounding medium ;  he  states  that  by  the  addition  of  quinine  ( 1  :  80,000)  to  a 
•culture  of  the  small  forms  he  was  able  to  bring  about  the  appearance  of  the 
large  forms. 

The  body  of  a  ciliate  is  often  prolonged  into  processes,  spikes,  etc.,  giving 
the  animal  a  curious  appearance.  The  most  bizarre  forms  are  found  amongst 
the  species  entozoic  in  the  digestive  tracts  of  ruminants,  such  as  Ophryosco'ex, 
Entodinium,  etc.  ;  but  some  free-living  species  also  exhibit  peculiarities  of 
•external  form.  Actinobolus  radians  (Holotricha)  has  the  body  covered  with 
tentacle-like  processes,  each  bearing  a  trichocyst  at  the  extremity.  Legendrea 
loyezce  (Faure-Fremiet),  allied  to  Prorodon,  bears  on  the  left  side  of  the  body 
about  twenty  digitiform  processes  of  variable  length,  flexible  but  not  motile  ; 
•each  process  is  composed  of  clear  protoplasm  enveloped  by  the  pellicle,  and 
at  its  slightly  dilated  extremity  is  lodged  a  bundle  of  trichocysts.  Hastatella 
radians  is  a  free-swimming  Vorticellid  which  bears  two  circlets  of  pointed 
"  fulcra,"  or  spines,  one  circlet  on  the  external  border  of  the  peristome,  the 
other  about  the  middle  of  the  body  (Collin). 

The  pellicle  may  be  greatly  thickened  to  form  a  lorica,  as  in  Coleps,  where  it 
is  composed  of  a  series  of  plates ;  or  may  be  decorated  with  warts  or  sculpt urings 
of  various  kinds,  formed  as  local  thickenings,  as  in  some  species  ofVorticella,  etc. 
The  body  is  often  enveloped  in  a  protective  sheath  or  envelope  secreted 
by  the  animal,  especially  in  sedentary  forms.  The  animal  may  then  be  capable 
of  protruding  its  body  from  the  sheath,  and  retracting  itself  back  again  into 
it,  and  when  retracted  the  aperture  of  the  sheath  may  be  closed  by  a  special 
lid,  or  operculum.  In  the  Tintinnidce,  some  species  of  which  are  free-swimming, 
others  sedentary,  the  body  secretes  a  shell  or  house,  to  which  foreign  bodies 
may  be  added,  derived  for  the  most  part  from  the  faecal  pellets  of  the  animal 
itself  ;  the  structure  of  these  shells  has  been  studied  in  detail  by  Entz  (53). 

The  sedentary  habit  of  life  occurs  in  species  of  all  orders,  though  especially 
characteristic  of  Peritricha.  The  mechanism  of  fixation  varies  greatly  in 
different  cases.  Stentor  attaches  itself  by  cilia,  and  also  by  pseudopodial 
processes  thrown  out  from  the  point  of  fixation,  and  from  this  type  is  to  be 
derived  that  of  the  Tintinnidce  (Faure-Fremiet,  836). 

The  hypotrichous  genus  Ancystropodium  (Oxytricliidce)  swims  freely  or 
attaches  itself  by  its  posterior  cirri ;  the  body  is  then  drawn  out  at  the  hinder 
end  into  a  long  stalk  (Faure-Fremiet,  837).  Trachelius  ovum  possesses  a 
conspicuous,  sucker-like  organ  by  means  of  which  it  attaches  itself  to  the 
stalks  of  Epistylis-colomes,  in  order  to  devour  the  members,  of  the  colony 
(Hamburger,  841). 

In  the  Peritricha  the  attachment  may  be  permanent  or  temporary ;  in  the 
latter  case  the  animal  fixes  itself  by  a  sucker-like  organ  of  the  aboral  pole. 
In  Trichodina  the  adhesive  organ  is  surrounded  by  a  ring  of  cilia  ;  in  Cydo- 
chceta  there  is  an  additional  circlet  of  stiff  bristles  ;  in  Licnopliora  the  disc  of 
attachment  is  in  the  form  of  a  cup  surrounded  by  four  concentric  ciliary 
membranes  (Stevens,  872)  ;  these  three  genera,  and  others  with  similar  modes 
of  attachment,  are  ectozoic  forms,  attaching  themselves  to  the  skin  of  various 
aquatic  animals.  Faure-Fremiet  (834)  has  traced  the  evolution  of  the  per- 
manently fixed  Vorticellid  type  from  temporary  fixation  by  an  aboral  sucker. 
As  a  starting-point  is  taken  Hemispeira  aster  ice,  which  attaches  itself  to  the 
gills  of  Asterias  by  a  bundle  of  fixative  cilia.  In  Scyphidia  fixation  is  by  a  cup- 
like  sucker  containing  a  circular  brush  of  rod-like  processes,  equivalent, 
apparently,  to  the  fixative  cilia  of  Hemispeira.  For  this  brush-like  organ 
the  term  "  scopula  "  is  proposed;  the  cilia  in  it  have  lost  their  motilityand 
secrete  a  terminal  chitinous  knob.  Epistylis  fixes  itself  in  a  similar  way  by 
means  of  a  scopula,  of  which  each  rod  forms  a  secretion  of  albuminoid  nature 
(Schroder,  865),  which  grows  continually,  forming  a  bundle  of  delicate  tubes 
composing  the  stem,  and  ensheathed  by  an  outer  covering  secreted  by  a 
rim  round  the  scopula  ;  the  stem  that  results  is  a  non-contractile  structure 
representing  a  secretion  of  the  body,  and  not  a  prolongation  of  the  body 
itself.  The  contractile  stalk  of  Vorticella,  Carchesium,  etc.,  arises  by  an  out- 


442  THE  PROTOZOA 

growth  of  the  central  part  of  the  scopula  on  a  prolongation  of  the  body- 
substance,  leaving  a  peripheral  ring  of  scopular  rods  surrounding  a  central 
protoplasmic  cord,  which  furnishes  the  contractile  muscular  stalk. 

The  mouth  and  cytopharynx,  whether  capable  of  being  closed,  as  in  the 
Gymnostomata,  or  permanently  open,  as  in  other  forms,  constitute  together 
a  conspicuous  organ  in  the  holozoic  Ciliata,  sometimes  showing  remarkable 
adaptations  to  special  modes  of  feeding.  In  the  gymnostomatous  genus- 
Didinium,  the  cytopharynx  contains  a  peculiar  tongue-like  organ,  a  prolonga- 
tion of  the  endoplasm,  which  shows  a  longitudinal  striation  due  to  the  presence- 
of  fine  rods —  "  trichites."  The  tongue  ot  Didinium  is  used  for  capturing  prey, 
consisting  chiefly  of  Paramecium  and  other  Ciliata,  and  the  manner  in  which 
it  is  used  recalls  the  tongue  of  a  chameleon.  If  the  Didinium  comes  into 
contact  with  its  prey,  the  tongue  is  shot  out  by  a  violent  contraction  of  the 
pharynx,  and  adheres  to  the  victim,  which,  according  to  Thon,  is  killed  in- 
stantly ;  but  according  to  Mast  larger  Ciliata  sometimes  escape,  and  in  doing 
so  may  break  off  and  carry  away  the  tongue  of  the  Didinium.  A  Paramecium 
when  thus  attacked  emits  a  cloud  of  trichocysts,  but  none  are  discharged  by 
the  Didinium.  The  prey  when  mastered  is  drawn  into  the  endoplasm  by  the 
retraction  of  the  tongue.  The  recently-described  genera  Proboscidium  and 
Gymnozoum  (Meunier)  possess  similar  organs.  The  hymenostomatous  genus 
Pleuronema  and  allied  forms  are  remarkable  for  the  huge  size  of  the  un- 
dulating membrane  (Fig.  27).  The  animal,  after  swimming  freely  for  a  time,, 
comes  to  rest,  with  its  body-cilia  sticking  out  stiff  and  straight ;  the  undulating 
membrane  is  then  protruded  from  the  mouth,  and  by  its  active  movements- 
serves  to  waft  food-particles  into  the  pharynx. 

The  peristome,  or  region  round  the  mouth,  exhibits  a  wide  range  of  special 
adaptations  in  relation  to  the  function  of  food-capture,  as  is  apparent  from 
the  classification  given  above.  Absent  or  scarcely  developed,  as  a  rule,  in 
the  Gymnostomata,  in  the  Hymenostomata  it  has  the  form,  usually,  of  a 
simple  groove  leading  to  the  mouth  (Fig.  185,  P.) ;  in  the  Spirigera,  on  the  other 
hand,  it  is  generally  disc-like,  bearing  the  adoral  zone  which  terminates  in 
the  mouth  ;  the  extreme  type  of  complication  is  seen  in  the  Peritricha,  where 
the  peristomial  disc  can  be  contracted  completely  over  the  mouth  by  means 
of  circular  myonemes  situated  in  the  margin  of  the  disc  like  a  sphincter 
(see  below),  while  a  central  funnel-shaped  portion  is  prolonged  inwards,  with 
the  mouth  at  its  extremity  to  form  the  vestibule,  in  a  manner  analogous  to 
the  stomodeeum  of  the  Metazoa.  The  adoral  ciliary  spiral  may  consist  simply 
of  longer  cilia,  more  powerful  than  those  of  the  general  body-covering,  the 
most  primitive  condition ;  or  of  transversely-planted,  comb-like  mem- 
branellae  or  "  pectinellse,"  the  usual  arrangement  in  Heterotricha  and  Hypo- 
tricha  ;  or  of  a  pair  of  undulating  membranes  running  parallel  to  one  another 
in  the  spiral,  as  in  Peritricha.  These  various  structures,  seen  in  optical  section 
in  the  living  state,  have  often  produced  erroneous  impressions  of  bristles, 
cirri,  etc.  The  adoral  spiral  varies  greatly  in  extent,  and  the  peristomial 
region  shows  numerous  modifications  which  cannot  be  described  or  sum- 
marized briefly  ;  the  reader  must  be  referred  to  the  beautiful  descriptions  of 
Schroder  (864-867),  amongst  recent  witers.  In  the  remarkable  peritrichous 
form  Opercularia  (Cochlearia)  faurei,  the  adoral  spiral  takes  five  complete 
turns,  running  like  a  screw  round  a  sort  of  retractile  proboscis  (Collin,  832). 

The  ciliary  apparatus  and  its  modifications  (Fig.  186)  have  been  the  subject 
of  much  minute  and  detailed  study ;  among  recent  investigators  must  be 
mentioned  especially  Maier  (73)  and  Schuberg  (44).  The  body-cilia  run  in 
rows  with  a  meridional,  spiral,  or  other  arrangement ;  they  arise  in  depressions 
of  the  body-surface  which  have  usually  the  form  of  furrows,  but  in  some 
cases  (Paramecium,  Frontonia]  each  cilium  arises  from  the  centre  of  a  small 
depressed  area  of  the  surface.  In  Paramecium  the  areas  are  for  the  most 
part  hexagonal  in  form,  but  in  places  they  are  rhombic  (cf.  Khainsky,  170'5). 
The  points  of  the  trichocysts  are  situated  in  the  angles  of  the  polygons,  and 
also  in  the  broader  edges  between  the  areas  in  each  row. 

Each  cilium  takes  origin  from  a  basal  granule  situated  at  the  level  of  the 


THE  INFUSORIA  443 

rnyonernes,  or  just  external  to  this  level,  below  the  alveolar  layer  (Fig.  186, 
B,  D) ;  the  cilium  passes  outwards  in  the  edges  of  the  alveoli — that  is  to  say, 
along  the  lines  in  which  the  walls  of  contiguous  alveoli  touch  at  their  corners — 
and  pierces  the  pellicle  to  pass  to  the  exterior.  In  Anoploplirya,  Collin  (50) 
describes  root-like  fibrils  which  pass  inwards  through  the  endoplasm,  and 
are  inserted  on  the  membrane  of  the  macronucleus.  Khainsky  (170'5)  also 
describes  fibrils  passing  inwards  from  the  basal  granules  of  the  cilia  of  Para- 
mecium.  In  the  remarkable  form  Pycnothrix  monocystoides,  which  possesses 
an  ectoplasm  of  great  thickness  and  distinctness,  there  are,  according  to 
Schubotz  (868),  two  layers  of  basal  granules,  one  more  superficial,  the  other 
deeper.  Each  granule  of  the  outer  layer  gives  off  a  cilium  on  its  outer  side, 
and  on  its  inner  side  a  fibril  connecting  it  to  a  granule  of  the  deeper  layer,, 
from  which,  again,  a  fibril  passes  inwards  and  becomes  directly  continuous 
with  a  myoneme. 

The  free  cilium  shows,  according  to  Schuberg  (44),  a  distal  "  end-piece,"' 
which  stains  more  lightly  and  is  of  finer  calibre,  and  a  basal,  thicker,  and 
darkly-staining  portion  (Fig.  186,  A]  ;  the  basal  portion  is  of  even  thickness, 
and  is  about  double  the  length  of  the  distal  end-piece,  which  tapers  to  a  fine 
point.  Motile  cilia  are  not  stiff,  but  change  their  form  by  bending  in  a  heli- 
coid  spiral,  or  in  a  portion  of  such  a  spiral,  like  the  flagella  of  the  Flagellata 
and  of  spermatozoa.  Cast-off  cilia  often  coil  up  at  their  proximal  end  into  a 
fine  loop. 

A  cilium  is  composed  of  two  different  parts — an  elastic  axial  filament  of 
firm  consistence  covered  by  a  sheath  of  more  fluid  contractile  substance. 
According  to  Khainsky  (ITO'o),  the  sheath  of  the  cilium  is  in  continuity  with 
the  substance  of  the  pellicle.  The  end-piece  represents  the  axis  exposed  and 
continued  beyond  the  sheath.  The  axis  is  compared  by  Schuberg  to  that  of 
the  axopodia  (p.  48),  and  is  the  form-determining  element  for  the  fluid 
sheath.  Cilia  perform  active  movements  even  when  separated  from  their 
basal  granules,  which  are  not  to  be  regarded,  in  Schuberg's  opinion,  as  kinetic 
centres  ;  the  movements  caused  by  the  fluid  envelope  are  probably  due  to 
alterations  in  surface-tension  (p.  200,  supra). 

The  basal  granules  of  the  cilia  are  not  regarded  by  Maier  or  Schuberg  as 
centrosomic  in  nature.  Maier  considers  that  they  probably  arise  as  cytoplasmic 
bodies  at  the  surface  of  the  cell,  and  are  to  be  interpreted  as  special  thicken- 
ings at  the  roots  of  the  cilia  ;  Khainsky  (170'5)  takes  a  similar  view.  In  this 
connection,  however,  attention  should  be  drawn  to  the  observations  of 
Entz  (53),  who  finds  that  in  the  division  of  Tintinnidce  the  new  peristome 
arises  in  the  interior  of  the  cytoplasmic  body  as  a  split  or  cavity,  and  that 
the  basal  granules  appear  first,  the  pectinellse  later ;  the  basal  granules  are 
stated  to  be  formed  in  connection  with  the  nuclear  apparatus,  and  their 
substance  to  be  formed  either  from  the  macronucleus  or  micronucleus.  The 
connection  between  the  basal  granules  and  the  macronucleus  described  by 
Collin  (50)  would  seem  also  to  indicate  a  nuclear  origin  for  them.  The 
question  of  their  centrosomic  nature  must  remain,  therefore,  open  for  the 
present.  According  to  Schuberg,  the  basal  granules  of  each  row  of  cilia  are 
connected  with  one  another  by  a  fine  longitudinal  fibril. 

The  typical  motile  cilia  described  above  become  modified  in  various 
wa\'s,  chiefly  by  fusion  of  separate  cilia  to  form  more  complex  structures. 
The  stiff,  tactile  bristles  have  precisely  the  same  structure  and  mode  of 
insertion  as  the  ordinary  cilia  (Fig.  186,  H,  i.e.),  and  in  this  case  the  change 
is  purely  one  of  function  or  substance  rather  than  of  perceptible  cytological 
structure.  The  undulating  membranes  found  in  the  pharynx  of  the  Hymeno- 
stomata  are  formed  by  fusion  or  adhesion  of  a  single  row  of  cilia,  of  which 
the  basal  granules  are  ranged  in  a  series  to  form  a  "  basal  rim  "  (Basalsaum) 
from  which  the  membrane  takes  origin  (Fig.  186,  E,  u.m.).  According  to 
Schuberg,  the  fibrils  of  which  the  membranes,  membranellse,  etc.,  are  made 
up  correspond,  not  to  a  whole  cilium,  but  to  its  axial  portion  alone.  Some- 
times, however,  more  than  one  row  of  cilia  contribute  to  the  formation  of 
an  undulating  membrane  ;  the  two  membranes  which  compose  the  adoral 


-•& 


444 


THE  PROTOZOA 


B 


\ 


m    jnr. 

^j?-^^^'   sTn.r 


\ 
i       \ 


FIG.  186. — Details  of  the  structure  of  the  ciliary  and  contractile  apparatus  of 
Ciliata.  A,  Two  isolated  cilia  of  Stentor  cceruleus,  showing  the  deeply-stained 
proximal  portion,  of  even  thickness  throughout,  and  the  lighter  distal  portion, 
tapering  to  a  point  ;  magnified  2,250  diameters  ;  B,  section  through  the  surface 
of  the  body  of  Prorodon  teres,  showing  the  cilia  arising  from  basal  granules 
(b.g.),  situated  above  canals  (c.m.),  at  the  base  of  which  run  the  myonemes  (m.), 
seen  in  transverse  section  ;  G,  section  through  the  mouth  of  Prorodon  teres 
(Fig.  14),  showing  the  rod-apparatus  (R.),  each  rod  with  two  myonemes 
(m.r.,  m.r.1)  ;  N.,  nucleus  ;  D,  section  of  the  body-surface  of  Paramecium 
caudatum,  showing  the  cilia  arising  from  basal  grains :  T.,  trichocysts  ;  f.v., 
food-vacuole  ;  E,  section  through  the  mouth  and  oesophagus  of  Paramecium 
caudatum,  showing  the  undulating  membrane  (u.m.)  in  the  oesophagus : 
other  letters  as  in  D  ;  F,  section  through  the  adoral  zone  of  Nyctotherus 
cordiformis,  showing  the  membranellse  (ml.)  cut  across,  each  composed  of  two 
cilia  arising  from  a  pair  of  basal  granules  ;  G,  section  of  the  adoral  zone  of 
Stentor  niger,  showing  a  membranella  (ml. ),  composed  of  fused  cilia  arising 

[Continued  at  foot  of  p.  445. 


THE  INFUSORIA  445 

spiral  of  Vorticellids  are  formed  each  by  the  concrescence  of  three  rows  of 
cilia  (Fig.  186,  K,  u.m.) ;  in  Glaucoma  scintillans  there  is  a  "  pororal  "  mem- 
brane built  up  of  five  rows,  an  "  endoral  "  membrane  of  ten  rows  of  fused  cilia 
(Maier,  73). 

The  membranellse  of  the  adoral  zone  are  formed  each  by  the  concrescence- 
of  two  transverse  rows  of  cilia  (Fig.  186,  6,  ml.).  In  some  genera  (Stentor, 
Spirostomum)  the  basal  rim  of  each  membranella  is  continued  down  into  the 
endoplasm  in  the  form  of  a  fibrillar  plate,  triangular  in  form,  with  the  apex 
continued  into  a  terminal  filament,  which  is  attached  at  its  proximal  ex- 
tremity to  a  fibril  running  longitudinally,  parallel  to  the  row  of  membranelljc. 
The  nature  of  this  basal  fibril  has  been  much  discussed ;  it  has  been  regarded' 
as  a  nervous  element,  co-cordinating  the  movements  of  the  membranellse  ; 
Maier,  on  the  other  hand,  regards  the  basal  lamella  and  its  terminal  filament  as- 
serving  for  the  firmer  attachment  of  the  membranellae,  and  considers  the- 
basal  fibril  to  be  a  contractile  element ;  Schroder  states  that  the  basal  fibril 
is  really  a  broad  band,  and  believes  its  function  to  be  purely  mechanical ; 
Schuberg  rejects  the  nervous  theory  of  the  basal  system  of  the  adoral  zone  of 
Stentor,  but  comes  only  to  negative  conclusions  with  regard  to  its  function. 

The  cirri  of  the  Hypotricha  are  formed  by  concrescence  of  a  tuft  of  cilia, 
arising  from  a  number  of  basal  granules  which  are  arranged  to  form  a  basal 
plate  (Fig.  186,  H,  C.).  The  posterior  ciliary  ring  of  Vorticellids  is  composed 
of  "  niembranulse  "  (Maier),  each  formed  by  concrescence  of  a  single  row  of 
cilia,  three  in  each  row.  The  two  circlets  of  Didinium  are  also  membranulfe 
(Thon). 

Closely  connected  with  the  bases  of  the  cilia  in  position,  and  with  the 
ciliary  apparatus  in  their  general  arrangement,  are  the  myonemes.  The  most 
superficial  study  of  the  Ciliata  suffices  to  convince  the  observer  that  these 
animals  have  in  many  cases  an  extremely  efficient  contractile  system.  Such 
forms  as  Stentor,  Vorticella,  etc.,  contract  with  such  lightning  rapidity  that 
it  is  almost  impossible  to  kill  and  preserve  them  expanded  ;  the  spasmodic 
action  of  their  contractile  organs  contrasts  sharply  with  the  slow  contractility 
of  lower  Metazoa,  such  as  polyps.  Trachelocerca,  according  to  Lebedew  (93), 
contracts  in  an  instant  to  one-twelfth  of  its  length  when  expanded. 

In  their  primitive  arrangement  the  myonemes  run  parallel  to  the  rows  of 
cilia,  immediately  beneath  the  basal  granules  or  close  beside  them  (Fig.  186, 
B,  m.}.  In  Stentor  the  myonemes  are  broad  and  band-like,  and  composed  of 
alternating  light  and  dark  portions  (Fig.  186,  J) ;  they  are  lodged  in  canals 
below  the  alveolar  layer,  running  in  the  intervals  between  the  "  ribs  "  or 
pigmented  strips  of  the  body-surface  ;  the  rows  of  cilia  run  above  each 
myoneme-canal,  slightly  to  the  side  of  it  (Fig.  186,  7).  The  myonemes  run 
the  length  of  the  body,  from  the  foot  to  the  adoral  zone  of  membranellse. 
At  the  extremity  of  the  foot  they  bend  inwards  and  form  a  cone  or  "  foot- 

FIG.  186  continued  : 

from  a  number  of  basal  granules  in  a  row  forming  the  basal  rim  (b.r.) ;  below 
the  basal  rim  is  the  basal  lamella  (b.L),  continued  at  its  apex  into  the  end- 
fibril  (c.f.),  which  passes  down  to  the  basal  fibril  (&./.),  seen  cut  in  transverse 
section  :  Z,  zoochlorellse  ;  H,  part  of  a  section  of  the  body  of  Stylonychia 
histrio,  showing  two  tactile  cilia  (t.c.)  on  the  dorsal  surface,  and  on  the  ventral 
surface  two  cirri  (C.),  each  composed  of  a  fused  tuft  of  cilia  arising  from  a  basal 
plate  of  granules  ;  /,  section  of  the  body-surface  of  Stentor  coeruleus,  showing 
the  longitudinal  myonemes  (l.m.)  lodged  in  canals  (c.m.)  between  the  pig- 
mented "  ribs  "  (p.)  of  the  outer  surface  ;  J,  one  of  the  longitudinal  myonemes 
of  Stentor  in  surface  view,  showing  the  alternating  light  and  dark  portions  ; 
K,  detail  from  a  longitudinal  section  of  Epistylis  plicatilis,  showing  the  two 
undulating  membranes  (u.m.)  of  the  peristome  in  transverse  section,  each 
composed  of  three  fused  cilia  arising  from  three  basal  granules  (b.g.)  fused 
together  ;  from  each  basal  plate  arises  a  fibril ;  the  two  fibrils  join  and  become 
continuous  with  one  of  the  longitudinal  myonemes  running  down  the  body 
to  the  stalk. 

A   after   Schuberg   (44)  ;    B — H  after  Maier   (73)  ;    /,    J,  after   Schroder 
(867)  ;  K  after  Schroder  (865). 


446  THE  PROTOZOA 

plate."  At  the  upper  end  of  the  body  fine  continuations  of  the  longitudinal 
myonemes  can  be  traced  to  the  adoral  zone,  ending  in  the  basal  rims  of  the 
smembranellae  (Schroder,  867). 

Stentor  may  be  taken  as  a  type  showing  the  contractile  system  highly 
developed  in  functional  efficiency,  but  more  or  less  primitive  in  arrangement. 
Canals  lodging  the  myonemes  are  not  present  universally,  even  in  highly 
contractile  forms ;  they  are  absent,  according  to  Lebedew  (93),  in  Trachelo- 
cerca,  but  they  are  figured  by  Maier  (73)  in  Prorodon  teres  (Fig.  186,  B).  In  their 
general  form  the  myonemes  are  simple  fibrillee,  often  beaded  when  contracted. 

In  the  more  specialized  forms  the  contractile  system  acquires  a  more  com- 
plicated arrangement.  In  Campanella,  Schroder  (864)  describes  five  systems 
of  myonemes  :  (1)  Annular  myonemes  of  the  basal  part  of  the  body;  (2)  longi- 
tudinal myonemes  of  the  outer  body- wall,  doubtless  representing  the  primitive 
system  (Fig.  186,  K)  ;  (3)  annular  myonemes  forming  the  sphincter-like 
muscle  of  the  margin  of  the  peristome  ;  (4)  a  spiral  myoneme  running  under 
the  adoral  spiral,  and  continued  down  the  wall  of  the  vestibule  ;  (5)  a  series 
•of  re  tractor- myonemes  of  the  peristomial  disc.  In  Epistylis  plicatilis,  on  the 
other  hand,  Schroder  (865)  found  only  three  systems :  The  longitudinal 
myomenes  (2),  the  annular  peristomial  myonemes  (3),  and  the  vestibular 
myoneme  (4).  To  these  systems  found  in  the  Vorticellids  with  non-con- 
tractile stalks  must  be  added,  in  the  genera  Vorticella,  Carchesium,  etc.,  the 
powerful  stalk-muscle  ("  spasmoneme  ")  formed  by  the  union  of  the  longi- 
tudinal myonemes  (Schroder,  866).  In  Vorticella  monilata  fine  connections 
run  from  the  hinder  ciliary  ring  upwards  and  downwards  to  the  longitudinal 
myonemes  when  the  cilia  are  developed,  but  disappear  when  these  cilia  dis- 
appear. In  Licnophora,  according  to  Stevens,  the  fibril  that  runs  under  the 
adoral  spiral  is  continued  down  to  the  disc  or  cup  of  attachment  and  ramifies 
in  its  walls. 

In  the  aberrant  form  Pycnothrix  monocystoides,  Schubotz  describes  a  re- 
markable development  of  the  myonemes  in  the  form  of  a  dense  plexus  of 
fibrils  at  the  inner  limit  of  the  ectoplasm.  The  fibrils  are  connected  with  the 
basal  granules  of  the  cilia,  and  run  in  two  directions,  forming  a  deeper  layer 
of  circular  myonemes  and  a  more  superficial  layer  of  longitudinal  myonemes. 

The  question  has  been  much  discussed  whether  the  contractile  system, 
often  so  highly  developed,  is  accompanied  by  any  conducting  elements  of 
nervous  nature.  That  many  ciliates  react  with  extreme  rapidity  to  stimuli 
has  been  noted  above,  and  that  their  movements  are  co-ordinated  is  suffi- 
ciently apparent.  Neresheimer  (856)  describes  in  Stentor  filaments  believed 
to  be  of  nervous  nature,  neuronemes  which  take  origin  from  the  foot  and 
run  about  halfway  up  the  body,  at  which  point  each  neuroneme  either  ends 
in  a  bulbous  swelling  or  becomes  thinner  and  disappears.  The  neuronemes 
are  situated  externally  to  the  myonemes,  and  run  parallel  to  them.  By 
experiments  with  various  drugs,  Neresheimer  tried  to  prove  the  existence 
in  Stentor  of  true  nervous  elements,  as  compared  with  Paramecium  and  other 
forms  in  which  neuronemes  were  not  found,  and  concluded  that  the  elements 
described  by  him  were  truly  nervous  in  nature.  Schroder  (867)  casts  doubt 
on  the  existence  of  neuronemes  and  criticizes  Neresheimer's  technique. 
Lebedew  (93),  however,  describes  fibrils,  possibly  nervous  in  nature,  running 
parallel  to  the  myonemes  in  Trachelocerca. 

For  the  present  the  existence  of  nervous  elements  in  Ciliata  must  remain 
doubtful.  But  of  the  sensory  function  of  the  cilia  there  can  be  hardly  any 
doubt,  and  the  fact  that  their  basal  granules  are  always  in  close  proximity 
to  the  myonemes  is  extremely  significant.  Such  a  direct  contact  between  the 
sensory  and  contractile  mechanisms  may  render  conducting  elements  of 
nervous  nature  unnecessary,  except  for  purposes  of  co-ordination  of  move- 
ments. In  some  cilia,  as  already  stated,  the  motile  function  is  lost,  and  only 
the  sensory  function  remains.  The  genus  Mycterothriys  (Tr  ichor  Jiynchus]  is 
characterized  by  a  rostrum  bearing  a  number  of  stiff,  tactile  cilia  (Faure- 
Fremiet,  839).  In  some  cases,  however,  sensory  organs  occur  which  appear 
not  to  be  derived  from  cilia,  as,  for  example,  the  tentacle-like  or  club-shaped 


THE  INFUSORIA 


447 


organs,  probably  tactile,  between  the  membranellaj  of  the  adoral  spiral  of 
Tintinmdce  (Schweyer). 

The  nature  and  mechanism  of  the  peculiar  trichocysts  remains  to  be  ex- 
plained. The  trichocyst  in  the  unexploded  state  is  a  spindle-shaped  body 
with  a  fine,  hair-like  process  at  its  outer  end  which  reaches  to  the  pellicle 
(Fig.  186,  D,  T.).  The  exploded  trichocyst  tapers  gradually  to  a  sharp  point 
at  its  proximal  end  ;  distally  it  shows  a  cap-like  swelling  (Fig.  187,  D— G). 
According  to  Khainsky  (170'5)  the  trichocyst  consists  of  two  portions :  a  distal 
or  outer  part  which  stains  deeply,  and  a  proximal  or  inner  part  which  stains 
a  lighter  colour  (Fig.  187,  A — C). 
The  unexploded  trichocyst  consists 
entirely  or  almost  entirely  of  the 
darker  substance  ;  in  the  process  of 
explosion  the  dark  substance  is  con- 
verted into  the  light,  so  that  in  the 
exploded  trichocyst  only  a  small 
portion  of  the  dark  substance 
remains  to  form  the  distal  cap. 
The  notion,  recently  upheld  by 
Mitrophanow  (855),  that  the  tricho- 
cyst consists  of  viscid  fluid  con- 
tained in  a  cavity  in  the  ectoplasm, 
whence  it  is  expelled  by  a  sudden 
contraction  of  the  ectoplasm,  and 
stiffens  to  a  solid  thread  under  the 
action  of  the  watery  medium, 
cannot  be  maintained  (Schuberg, 
44)  ;  nor  does  there  seem  to  be 
any  ground  for  comparing  it  to  a 
Coelenterate  nematocyst  or  to  a 
polar  capsule  of  a  Cnidosporidian 
spore.  According  to  Mitrophanow, 
the  substance  of  the  trichocysts 
appears  first  near  the  nucleus  in 
the  endoplasrn  as  small  grains  which 


B 


FIG.  187. — Trichocysts  of  Infusoria. 
A — E,  Stages  in  the  explosion  of  the 
trichocysts  of  Paramecium  caudatum, 
showing  the  manner  in  which  the  tricho- 
cyst grows  in  length,  with  conversion  of 
a  darkly-staining  substance  into  a  lighter 
material ;  the  fully-exploded  trichocysts 
are  seen  in  D  and  E.  After  Khainsky 
(170-5).  F,  G,  Exploded  trichocysts 
of  Frontonia  leucas.  After  Schuberg, 
magnified  1,500  diameters. 


C          D         E  <3 

pass  out  into  the  ectoplasm.  Tricho- 
cysts do  not  occur  in  any  Peritricha, 
but  in  one  species,  Epistylis  umbel- 
laria,  large  oval  nematocysts  occur, 
arranged  in  pairs — a  phenomenon 
unique  amongst  the  Ciliata. 

The  contractile  vacuoles  open  to 
the  exterior  as  a  general  rule,  but 
in  the  Peritricha,  as  already  stated, 
they  open  into  the  vestibule  ;  in 
this  order  there  is  usuallj7  a  reservoir- 
vacuole  into  which  one  or  two  con- 
tractile vacuoles  empty  themselves,  and  which  in  its  turn  voids  its 
contents  into  the  vestibule.  In  Campanctta,  however,  there  is  no  reservoir- 
vacuole,.  and  the  single  contractile  vacuole  opens  by  two  canals  into  the 
vestibule  (Schroder,  804).  In  Opalina  there  are  no  contractile  vacuoles, 
and  in  some  species  (e.g.,  0.  ranarum)  no  excretory  organs  are  to  be  found  ; 
but  in  other  species  the  endoplasm  contains  an  axial  series  of  more  or  less 
irregular  vacuoles,  opening  one  into  the  other  and  to  the  exterior  by  a  poro  at 
the  posterior  end  of  the  body.  These  vacuoles  are  sometimes  in  close  relation 
with  the  nuclei,  often  enveloping  them  to  form  a  perinuclear  space  (Metcalf, 
852).  In  Pycnothrix  monocystoides  the  endoplasm  is  traversed  by  a  branched 
system  of  excretory  canals,  which  unite  into  a  single  efferent  duct  opening  at 
the  surface  of  the  body  near  the  posterior  end  by  a  pore  ;  the  duct  is  ciliated. 
and  is  homologized  by  Schubotz  with  the  C3'topyge,  which  in  Nyctotherus  is 


448  THE  PROTOZOA 

also  ciliated.  These  excretory  systems  of  Opalina  and  Pycnothrix  differ  in> 
being  endoplasmic  from  the  ordinary  contractile  vacuoles,  which  are  always 
formed  in  the  ectoplasm. 

The  endoplasm  of  the  Ciliata  may  contain  enclosures  of  various  kinds : 
food-vacuoles ;  metaplastic  bodies  in  the  form  of  excretory  grains,  crystals,, 
pigment-grains,  etc.  ;  zoochlorellae,  and  occasionally  parasites  of  one  kind  or 
another,  etc.  Special  attention  has  been  drawn  by  Faure-Fremiet  (38 '5  and 
835)  to  the  bodies  termed  by  him  spheroplasts,  and  considered  by  him  to  be 
homologous  with  the  mitochondria  (p.  41).  The  bodies  in  question  are 
small  spherules,  which  multiply  by  fission  when  the  cell-body  divides  ;  they 
are  permanent  cell-organs  to  the  same  extent  as  the  nuclear  apparatus,  of 
which,  however,  they  are  entirely  independent. 

As  pointed  out  above,  the  form  of  the  macronucleus  and  the  number  of 
nuclei  vary  greatly  in  different  species.  The  cases  will  be  considered  below 
in  which  the  micronucleus  appears  to  be  wanting  (Opalina),  or  is  contained! 
in  the  macronucleus  in  the  ordinary  condition  of  the  body  (Trachelocerca, 
Ichthyophthirius).  As  a  rule  the  macronucleus  has  a  finely  granular  appear- 
ance, with  the  chromatin  distributed  evenly  over  the  nuclear  framework ,-. 
but  in  a  few  cases  it  has  a  distinctly  vesicular  structure,  with  a  large  karyo- 
some,  as  in  Loxodes  (Joseph,  Kasanzeff),  Chilodon  (Nagler,  96),  etc.  The 
macronucleus  divides  by  binary  fission  of  a  simple  and  direct  type  (Fig.  54). 
The  micronucleus,  on  the  other  hand,  divides  by  mitosis  (Fig.  61).  In 
Trachelocerca,  a  form  which  may  possess  one  or  many  nuclei  (but  no  separate 
micronuclei),  Lebedew  (93)  describes  a  peculiar  mode  of  multiplication  of  the 
nuclei,  which  divide  by  multiple  fission  to  form  a  niorula-like  body  consisting 
of  a  mass  of  small  nuclei  which  separate  from  one  another  (Fig.  66).  In 
Loxodes,  another  form  in  which  the  number  of  nuclei  varies  greatly  in  different 
specimens,  the  macronuclei  do  not  divide,  but  only  the  micronuclei  do 
so,  and  the  macronuclei  arise  by  growth  and  modification  of  the  micro- 
nuclei  (Kasanzeff).  In  many  cases  in  which  the  macronucleus  is  of  the 
elongated  moniliforni  type,  or  in  which  the  body  in  the  ordinary  state  contains 
two  or  more  niacronuclei,  they  come  together  to  form  a  single  compact 
macronucleus  prior  to  division  ;  but  in  other  similar  cases  this  does  not  occur, 
and  when  the  body  divides  the  nuclei  are  distributed  irregularly  between  the 
two  daughter-individuals,  as  in  Trachelocerca,  Opalina,  etc.  The  distributed 
form  of  nucleus  is  especially  characteristic  of  the  astomatous  parasitic  forms, 
and  in  the  opinion  of  Pierantoni  (A.P.K.,  xvi.,  p.  99)  is  correlated  with  nutri- 
tion by  the  osmotic  method. 

The  micronucleus  is  less  variable  in  form  or  number,  as  a  general  rule, 
than  the  macronucleus,  but  is  not  infrequently  multiple,  especially  when  there 
is  more  than  one  macronucleus  ;  but  in  Trachelius  ovum  a  single  large  macro- 
nucleus  is  combined  with  thirteen  micronuclei  (Hamburger,  841). 

The  conjugation  of  the  Ciliata  conforms,  as  a  general  rule,  in  its  main 
outlines  to  the  scheme  sketched  out  above  (Fig.  77),  but  some  important 
variations  must  be  noted.  In  the  first  place,  the  conjugation  is  often  pre- 
ceded by  active  division  of  the  animals,  so  that  the  conjugants*  are  much 
smaller  than  the  ordinary  individuals  of  the  species.  When  the  two  conju- 
gants come  together,  the  micronucleus  of  each  usually  divides  into  four,  but 
sometimes  into  eight,  as  in  both  conjugants  of  Euplotes  and  the  microconju- 
gant  of  Peritricha  ;  in  either  case,  however,  only  one  micronucleus  persists, 
and  furnishes  the  two  pronuclei. 

The  Peritricha  exhibit  in  their  conjugation  certain  peculiarities  which  are 
clearly  of  a  secondary  nature  and  correlated  with  their  sedentary  habit. 
Certain  individuals  divide  two  or  three  times  successively  to  produce  four  or 
eight  microconjugants  ("  microgametes  ")  which  acquire  a  ring  of  locomotor 

*  It  is  preferable  not  to  speak  of  two  conjugating  Infusoria  as  gametes,  since 
it  is  very  doubtful  if  they  correspond  to  the  gametes  in  the  other  classes  of  Protozoa. 
It  is  on  the  whole  more  probable  that  the  conjugants  correspond  rather  with 
gamonts  or  gametocytes,  which  originally  produced  a  number  of  gametes,  reduced 
now  to  two,  represented  in  each  conjuganfc  by  the  two  pronuclei. 


THE  INFUSORIA  449 

cilia  and  swim  off.  Each  microconjugant  attaches  itself  to  a  macroconjugant 
— that  is  to  say,  to  an  ordinary  sedentary  individual  ;  each  of  the  conjugants 
has  a  single  micronucleus  and  macronucleus,  but  as  soon  as  they  become 
associated  the  changes  preparatory  to  syngamy  begin.  In  the  microconjugant 
the  micronucleus  divides  three  times  to  produce  eight  micronuclei.0  In 
Carchesiwm  the  first  of  these  divisions  is  an  equating  division  ;  the  second 
reduces  the  number  of  chromosomes  from  sixteen  to  eight ;  and  the  third 
division  is  again  an  equating  division  (Popoff,  125).  Meanwhile  the  macro- 
nucleus  is  in  process  of  degeneration,  and  is  breaking  up  into  fragments. 
Of  the  eight  micronuclei,  seven  degenerate,  one  persists  and  divides  into  two 
pronuclei.  In  the  macroconjugant,  meanwhile,  similar  events  are  taking 
place,  but  the  micronucleus  only  divides  twice,  first  by  a  reducing,  then  by  an 
equating  division,  to  produce  four  micronuclei,  of  which  three  degenerate, 
while  the  fourth  persists  and  divides  into  the  two  pronuclei. 

Of  the  two  pronuclei  now  present  in  each  conjugant,  one  degenerates  in 
each  case  ;  the  persistent  pronucleus  of  the  microconjugant  passes  over  into 
the  macroconjugant  and  copulates  with  its  persistent  pronucleus.  The  frag- 
ments of  the  macronucleus  also  pass  over  into  the  macroconjugant,  but  are 
there  absorbed  slowly.  The  body  of  the  microconjugant  then  falls  off  and  dies ; 
only  the  macroconjugant  is  fertilized. 

Variations  of  minor  importance  are  seen  in  the  behaviour  of  the  synkaryon 
of  the  exconjugant  after  fusion  of  the  pronuclei  has  taken  place.  For  example, 
in  Paramecium  bursaria  the  synkaryon  divides  to  form  four  nuclei,  two  of 
which  become  macronuclei,  whereupon  the  exconjugant  divides  into  two 
ordinary  individuals  (Hamburger,  842)  ;  in  Licnophora  the  synkaryon  divides 
into  eight,  which  become  a  micronucleus  and  a  macronuclear  chain  of  seven 
segments  (Stevens,  872)  :  in  Carchesium  the  synkaryon  divides  also  into  eight 
to  furnish  a  micronucleus  and  seven  separate  macronuclei,  but  the  micro- 
nucleus  then  divides  six  times,  with  subsequent  divisions  of  the  body  and 
sorting  out  of  the  macronuclei,  until  seven  individuals,  each  with  a  single 
micronucleus  and  macronucleus,  are  produced  (Popoff,  125) ;  in  Anoplophrya 
the  synkaryon  divides  into  four  nuclei,  two  of  which  degenerate,  the  remaining 
two  becoming  a  micronucleus  and  a  macronucleus  respectively.  The  method 
of  nuclear  reconstruction  may  vary  even  in  the  same  species,  as  shown  by 
Prandtl  (126)  in  the  case  of  Didinium. 

The  most  important  deviations  from  the  usual  scheme  of  conjugation  are 
seen  in  those  forms  in  which  there  is  no  separate  micronucleus  in  the  ordinary 
condition.  The  cases  of  Opalina  and  Ichthyophthirius,  parasitic  forms  and 
therefore  open  to  the  charge  of  degeneration,  are  dealt  with  below.  In 
Trachelocerca  plioeni  copter  us,  a  free-living  species,  conjugation  has  been 
described  by  Lebedew  (93)  between  individuals  containing  many  nuclei  all 
similar  in  appearance,  each  with  a  large  karyosome.  Prior  to  conjugation 
the  chroniatin  passes  out  of  the  karyosome  into  the  nuclear  cavity  of  each 
nucleus  (Fig.  188,  A,  B),  which  then  divides  into  four.  The  chromatin  forms 
a  compact  mass  at  one  pole  of  each  nucleus.  During  conjugation  these  masses 
of  chromatin  pass  out  of  the  nuclei,  and  lie  free  in  the  cytoplasm  between 
them  (Fig.  188,  C — (?)  ;  each  such  mass  is  now  to  be  regarded  as  a  micro- 
nucleus  and  lies  in  a  clear  area,  finally  becoming  a  vesicular  nucleus  with  a 
distinct  alveolar  structure ;  the  old  nuclei  can  now  be  considered  as  macro- 
nuclei.  All  the  nuclei  now  collect  in  a  mass  near  the  middle  of  the  body. 
The  macronuclei  ultimately  degenerate  ;  the  micronuclei  multiply  by  fission, 
but  ultimately,  according  to  Lebedew,  they  all  degenerate  with  the  exception 
of  one  in  each  conjugant  ;  the  persistent  micronucleus  divides  into  two  pro- 
nuclei  which  conjugate  in  the  usual  way  ;  unfortunately,  the  author's  observa- 
tions contain  so  many  gaps  that  this  statement  cannot  be  considered  estab- 
lished so  decisively  as  could  be  desired.  The  exconjugants  contain  each  a 
single  synkaryon  which  divides  by  successive  divisions  into  a  number  of  nuclei 
not  differentiated  into  micronuclei  and  macronuclei. 

The  case  of  Trachelocerca,  as  it  is  described,  furnishes  an  important  clue 
to  understanding  the  origin  of  the  heterokaryote  condition  of  Infusoria  from 

29 


450 


THE  PROTOZOA 


that  found  in  other  Protozoa.  In  this  case,  during  the  ordinary  vegetative 
condition,  the  generative  chromatin  representing  the  rnicronucleus  of  other 
Infusoria,  and  the  vegetative  chromatin  representing  the  macronucleus,  are 
contained  in  one  and  the  same  nucleus,  and  become  separate  only  when 
syngamy  is  about  to  take  place.  The  first  sign  of  the  separation  is  the  forma- 
tion of  chromidia  from  the  karyosome  within  the  nucleus,  resulting  in  the 
formation  of  a  secondary  nucleus  which  becomes  separate  and  which  behaves 
exactly  as  an  ordinary  micronucleus  ;  thus  indicating  a  clear  homology  between 
the  micronuclei  of  Infusoria  and  the  secondary  generative  nuclei  of  Sarcodina. 
The  production  of  numerous  micronuclei  in  the  conjugation  of  Trachelocerca 


FIG.  188. — Formation  of  micronuclei  in  Trachelocerca  phcenicopterus.  A,  B,  A 
nucleus  has  divided  into  two,  and  from  the  karyosome  (k. )  of  each  daughter- 
nucleus  masses  of  chromatin  are  being  given  off  into  the  nuclear  cavity  ; 
C,  D,  the  two  nuclei  of  the  preceding  stages  have  divided  again,  to  form  a 
group  of  four,  and  the  chromatin-rnasses  (n)  have  acquired  a  compact  struc- 
ture and  are  passing  out  of  the  nuclei  to  form  the  micronuclei  ;  in  C  crystals 
are  seen  in  the  cavities  of  the  old  nuclei,  probably  a  sign  of  degeneration  ; 
E,  F,  two  groups  of  nuclei,  both  from  the  same  specimen  ;  the  micronuclei 
given  off  from  the  old  nuclei  become  surrounded  by  a  vacuole  (n'  in  F),  and 
then  acquire  an  alveolar  structure  (n'  in  E)  ;  G,  portion  of  a  preparation  of 
the  body  of  a  conjugant,  the  wavy  contour  on  the  right  being  the  surface  of 
the  body  which  is  in  contact  with  the  other  conjugant  ;  numerous  micronuclei 
(n)  are  seen,  and  also  macronuclei,  some  of  which  still  appear  normal  (N), 
others  degenerating  (N').  After  Lebedew  (93). 

is  noteworthy,  and  would  appear  to  favour  the  theory  (see  p.  154)  that  primi- 
tively numerous  gametes  (swarm-spores)  were  produced  in  the  conjugation 
of  Infusoria. 

Examples  of  a  complicated  life  cycle  are  to  be  found  in  Ciliata  chiefly, 
perhaps  solely,  among  parasitic  forms.  As  an  example  may  be  taken  Ich- 
thyophthirius  miiUifiliis,  a  parasite  of  the  skin  of  various  species  of  fresh-water 
fishes.  In  aquaria,  where,  owing  to  the  limited  space,  the  parasites,  if  present, 
find  their  way  to  the  fish  very  easily,  and  where,  consequently,  a  fish  becomes 
infected  with  vast  numbers  of  the  ciliates,  the  parasites  are  usually  lethal  to 
the  host,  and  cause  its  death,  according  to  Buschkiel,  in  about  fourteen  daj's. 
In  Nature,  on  the  other  hand,  "  ichthyophthiriasis  "  is  seldom  observed,  prob- 


THE  INFUSORIA  451 

ably  owing  to  the  fact  that  under  natural  conditions  only  a  very  small  propor- 
tion of  the  young  parasites  succeed  in  establishing  themselves  on  a  fish,  and 
consequently  the  infections  produced  are  so  slight  that  they  are  overlooked, 
and  the  fish  is  unharmed. 

The  life-cycle  of  Ichthyophtliirius  is  as  follows :  The  youngest  parasites 
hatched  out  from  a  cyst  are  very  small,  and  have  a  macronucleus  and  a  micro- 
nucleus.  They  seek  out  a  fish  and  bore  into  its  epidermic,  attaching  them- 
selves by  one  end  of  the  club-shaped  body  and  rotating  actively,  with  tho 
result  that  epithelial  cells  are  displaced,  and  either  cast  off  into  the  water  or 
form  a  ring-like  wall  round  the  parasite.  In  this  way  the  infusorian  works 
its  way  gradually  into  the  deeper  laj'ers  of  the  epidermis,  which  closes  over  it, 
so  that  the  parasite  lies  finally  in  a  closed  hollow  space  in  the  epidermis.  In 
this  position  it  grows  in  size,  and  at  a  certain  point  the  niicronucleus  disappears, 
passing  into  the  macronucleus  to  form  a  nucleolus-like  body  within  it.  The 
parasite  appears  to  the  naked  eye  as  a  little  white  spot  on  the  skin,  occurring 
on  any  part  of  the  body-surface  or  on  the  gills.  It  retains  its  cilia,  and  can  be 
seen  rotating  within  the  cavity  in  which  it  lies. 

The  full-grown  Ichthyophthirius  may  reach  1  millimetre  in  diameter,  but  is 
usually  less,  about  0'75  millimetre.  When  full-grown  the  ciliate  breaks  out 
of  the  cavity  in  the  epidermis  and  sinks  to  the  bottom,  attaching  itself  to  the 
ground  or  to  water-weeds,  and  becomes  encysted.  Within  the  cyst  it  multi- 
plies by  binary  fission  repeated  eight  times,  producing  256  small  ciliates  ; 
sometimes  this  multiplication  takes  place  without  encystment.  During  this 
process  of  multiplication  the  micronucleus  reappears,  being  extruded  from 
the  macronucleus  of  each  individual  when  not  less  than  four  are  present  in 
the  cyst  ;  but  the  exact  period  at  which  the  micronuclei  appear  varies  in 
different  cases.  In  addition  to  the  micronucleus,  one  or  two  other  extrusions 
from  the  macronucleus  take  place  (Buschkiel)  ;  but  whether  these  represent 
•other  micronuclei  or  expelled  vegetative  chro matin  is  not  clear ;  in  any  case 
they  degenerate  and  disappear.  When  the  micronucleus  makes  its  appearance, 
it  divides  by  mitosis  at  each  division  of  the  cell-body,  as  in  ordinary  Ciliata, 
while  the  macronucleus  divides  in  the  usual  way  by  direct  division. 

When  the  full  number  of  tiny  ciliates  is  formed,  each  with  a  macro- 
nucleus  and  micronucleus,  sexual  phenomena  occur,  but  the  events  that 
take  place  are  described  differently  by  different  investigators.  According  to 
Neresheiiner  (858),  in  each  individual  the  micronucleus  divides  twice,  and 
three  of  the  four  micronuclei  produced  degenerate  ;  the  fourth  then  divides 
again.  The  reduction-process  is,  therefore,  according  to  this  account,  similar 
to  that  of  other  Ciliata,  and  the  organism  appears  to  be  ready  for  conjugation, 
with  two  pronuclei ;  but  Neresheimer  was  unable  to  observe  conjugation  taking 
place  either  in  the  cyst  or  after  the  organisms  have  become  free  ;  he  observed, 
however,  sometimes  two  micronuclei,  sometimes  one,  both  in  free  forms  and 
in  those  attached  to  the  fish,  and  from  this  it  was  inferred  that  the  two  pro- 
nuclei  fuse  autogamously,  leaving  the  possibility  open,  however,  that  heter- 
ogamous  conjugation  might  sometimes  occur.  According  to  Buschkiel,  on 
the  other  hand,  the  micronucleus  of  each  individual  divides  twice,  and,  of  the 
four  thus  produced,  two  degenerate,  and  the  remaining  two  fuse  autoga- 
•mously  while  still  within  the  cyst. 

The  little  ciliates  are  set  free  from  the  cyst,  and  seek  out  a  new  host  in  their 
turn.  From  the  time  that  the  full-grown  parasite  leaves  the  fish  to  the  time 
that  the  brood  is  liberated  from  the  cyst  is,  according  to  Buschkiel,  about 
twenty  hours,  more  or  less.  If  an  infected  aquarium  be  kept  empty  of  fish 
for  sixty  hours,  it  becomes  disinfected,  since  the  parasites  ail  die  off  if  they 
cannot  attach  themselves  to  a  fish  very  soon  after  they  are  hatched  out. 

The  entozoic  Ciliata,  in  which  adaptation  to  a  purely  parasitic  life  has  led 
to  the  degeneration  of  the  apparatus  of  a  holozoic  mode  of  nutrition — that  is 
to  say,  of  the  mouth,  peristome,  and  accessory  cilia — are  sometimes  classified 
as  an  order,  Astomata,  of  the  Holotricha  ;  but  there  can  be  little  doubt  this 
group,  like  others  founded  on  negative  characters,  is  a  heterogeneous  collection 
of  forms  in  which  the  characters  they  possess  in  common  are  due  to  convergent 


452  THE  PROTOZOA 

adaptation  to  their  mode  of  life  (c/.  Leger  and  Duboscq,  848).  The  best- 
known  genera  are  Anoploplirya,  a  typical  ciliate  with  micronucleus  and 
macronucleus  and  with  a  rudimentary  cytostomo,  constituting  with  Hopli- 
tophrya,  Herpetophrya  Discophrya,  etc.,  the  group  Anoplophryince  ;  Chromidina 
and  Opalinopsis,  parasitic  in  Cephalopods,  are  probably  allied  to  the  fore- 
going (c/.  Dobell,  833).  The  species  of  Opalina,  constituting  the  group 
Opalinince,  are  parasitic  in  frogs  and  various  cold-blooded  vertebrates ; 
their  nuclei  vary  in  number  in  different  species  from  two  to  an  indefinitely 
large  number,  but  are  all  similar  and  without  differentiation  into  micronuclei 
and  macronuclei  at  any  period  of  the  life-cycle.  Cepede  has  monographed 
the  section  Anoplophryince,  and  has  described  a  number  of  new  genera  and 
species,  distributed  amongst  eleven  families.  The  Astomata  are  internal 
parasites  of  their  hosts,  especially  of  the  digestive  tract.  Protophrya  ovicola 
occurs  in  the  brood-sac  of  the  mollusc  Littorina  rudis,  and  is  parasitic  upon 
its  eggs,  causing  their  disintegration  (Kofoid). 

The  remarkable  form  Pycnothrix  monocystoides,  from  the  gut  of  Hyrax 
capensis,  described  by  Schubotz,  deserves  special  mention.  It  reaches  a  length 
of  3 '2  millimetres,  and  contains  parasitic  nematodes.  The  animal  itself  has 
a  great  superficial  resemblance  to  a  nematode  or  to  a  monocystid  gregarine  ; 
it  has  a  very  thick  and  distinct  ectoplasm,  covered  by  an  even  coat  of  short 
cilia,  and  with  two  longitudinal  grooves  which  Schubotz  regards  as  equivalent 
to  the  peristomial  grooves  of  other  Ciliata.  Each  groove  contains  a  series  of 
pouch-like  depressions,  which  open  down  into  the  endoplasm,  and  are  provided 
with  special  tracts  of  myonemes.  Schubotz  regards  these  pouches  as  a  series- 
of  cytostomes,  but  no  food-particles  or  vacuoles  are  found  in  the  endoplasm  ; 
the  interpretation,  therefore,  of  these  openings  as  cytostomes  can  only  be 
taken  in  a  phylogenetic  sense  ;  actually  they  appear  to  represent  perforations 
of  the  tough  ectoplasm  which  may  facilitate  absorption  of  food  by  the  osmotic 
method.  For  the  cilia,  myonemes  and  excretory  system  of  this  form  see 
above  (pp.  443,  446  447)  ;  the  micronucleus  and  macronucleus  are  each 
single  and  of  the  ordinary  type.  Pycnothrix  stands  at  present  quite 
isolated. 

The  species  of  the  genus  Opalina  differ  in  certain  peculiarities  of  structure 
and  life-history  from  all  other  ciliates.  The  life-history  of  the  common 
species  of  Opalina  parasitic  in  the  rectum  of  the  frog  has  been  studied  by 
Metcalf  (853)  and  Neresheimer  (857),  whosx-  accounts  agree  as  regards  the 
general  life-cycle,  but  differ  in  some  cytological  details. 

Opalina  ranarum  multiplies  in  a  vegetative  manner  during  the  summer 
and  autumn  months,  but  in  the  spring  a  special  propagative  cycle  occurs  in 
relation  to  change  of  hosts  and  is  followed  by  sexual  processes. 

The  vegetative  reproduction  increases  the  numbers  of  the  parasite  in  the 
host ;  it  consists  of  two  processes,  multiplication  of  the  nuclei  and  division 
of  the  body,  which  go  on  independently.  The  animal  contains  a  great  many 
nuclei,  and  when  it  reaches  a  certain  size  the  body  divides  either  longi- 
tudinally or  transversely  to  produce  two  daughter-individuals,  each  of  which 
grows  again  to  the  full  size.  The  multiplication  of  the  nuclei  is  effected  by 
a  simple  mitosis,  similar  to  that  of  the  micronucleus  of  other  Infusoria,  and 
without  centrosomes. 

In  the  spring  the  parasites  divide  rapidly  and  repeatedly,  without  growing 
to  full  size  between  the  divisions,  so  that  they  become  continually  smaller  in 
size.  A  few  individuals,  however,  do  not  undergo  this  process  of  rapid 
fission,  but  remain  of  the  ordinary  type,  forming  a  stock  which  persists  and 
carries  on  the  infection  in  the  frog,  while  those  which  divide  up  are  destined 
to  pass  out  of  it.  At  the  beginning  of  the  process  of  rapid  division,  the  nuclei 
extrude  chromidia,  some  of  which  are  absorbed,  while  from  the  remainder 
secondary  nuclei  are  formed  (Neresheimer).  Finally  the  old  nuclei  are 
absorbed.  The  secondary  nuclei  also  multiply  by  mitosis ;  and,  according 
to  Metcalf,  in  the  later  mitoses  preceding  encystinent  the  number  of  chromo- 
somes is  reduced  to  one-half  the  ordinary  number  (in  O.  intestinalis  from  eight 
to  four,  in  0.  caudata  from  six  to  three).  The  result  of  the  repeated  division 


THE  INFUSORIA  453 

is  to  produce  small  individuals  containing,  as  a  rule,  from  three  to  six  secondary 
nuclei.  Such  individuals  become  encysted  (infection-cysts),  and  pass  out  of 
the  frog  in  the  fseces.  The  animal  at  first  fills  the  cyst  completely  and  shows 
no  cilia,  but  after  a  time  the  body  shrinks  within  the  cyst,  and  the  animal  is 
then  seen  to  have  a  ciliary  covering. 

The  fasces  of  the  frogs  are  readily  devoured  by  tadpoles,  which  thus  become 
infected  with  cj'sts.  In  the  gut  of  the  tadpole  the  Opalina  emerges  from  its 
cyst.  It  at  once  divides  up  into  uninucleate  individuals,  the  gametes, 
elongated  club-shaped  forms  with  a  sparse  coat  of  cilia  over  the  flattened 
body.  Under  unfavourable  circumstances  the  gametes  undergo  agglomera- 
tion in  rosettes,  adhering  by  their  pointed  ends  (Neresheimer).  Under 
normal  circumstances  they  copulate  in  pairs  as  isogametes,  according  to 
Neresheimer,  in  O.  ranarum  ;  butMetcalf  describes  smaller  uninucleate  micro- 
gametes  and  larger  macrogametes  with  one  or  two  nuclei,  in  other  species  ; 
the  male  pronucleus  then  fuses  with  one  of  the  two  nuclei  of  the  macrogamete. 
The  zygote  of  0.  ranarum,  with  the  two  pronuclei  still  separate,  rounds  itself 
off  and  becomes  encysted  ( copulation- cyst)  ;  within  the  cyst  the  two  pronuclei, 
which  have  passed  into  a  spindle-stage,  undergo  fusion.  The  zygote  emerges' 
from  the  cyst  with  a  synkaryon,  and  it  becomes  an  adult  Opalina. 

Neresheimer  considers  that  the  life-cycle  of  Opalina  proves  that  its  affinities 
are  with  Flagellata  rather  than  with  Infusoria.  In  deciding  this  question, 
it  must  be  considered,  in  the  first  place,  whether  in  such  a  form  the  life-cycle, 
or  the  structural  features  of  the  body,  are  most  likely  to  indicate  affinity — 
that  is  to  say,  least  likely  to  exhibit  secondary  peculiarities  due  to  adaptation. 
Opalina  is  a  parasitic  form,  and  its  life-cycle  shows  very  obviously  a  direct 
daptation,  of  a  type  very  common  in  parasitic  Protozoa,  to  its  mode  of  life  ; 
multiplicative  reproduction  increasing  its  numbers  within  the  host,  and  prop- 
agative  reproduction,  combined  with  sexual  phenomena,  leading  to  the 
infection  of  new  hosts.  On  the  other  hand,  its  minute  structure  is  that  typical 
of  Ciliata,  a  character  hardly  likely  to  be  due  to  the  influence  of  parasitism, 
as  Popoff  (125)  has  well  pointed  out. 

The  chief  difference  between  Opalina  and  other  Ciliata,  which  requires 
special  consideration,  is  the  fact  that  the  animal  contains  but  one  kind  of 
nucleus.  This,  however,  is  a  character  known  in  other  genera  of  Ciliata 
also — e.g.,  Trachelocerca,  Iclitliyoplitliirius.  There  can  be  but  little  doubt 
that  the  "  heterokaryote  "  condition  of  the  Infusoria,  with  distinct  generative 
and  vegetative  nuclei,  must  have  been  derived  phylogenetically  from  a  condi- 
tion in  which,  as  in  other  Protozoa,  the  two  kinds  of  chrornatin  were  contained 
in  one  and  the  same  nucleus ;  and  to  find  this  condition  still  retained  in  some 
Infusoria  would  not  be  remarkable.  In  such  forms  it  is  to  be  expected  that 
prior  to  gamete-formation  the  vegetative  chro matin,  equivalent  to  the 
macronucleus,  would  be  expelled,  and  the  pronuclei  would  be  formed  from 
generative  chromatin. 

There  is  nothing,  therefore,  to  be  said  against  the  view  of  Popoff,  that 
Opalina  shows  the  most  primitive  type  of  gamete-formation  known  at  present 
amongst  the  Ciliata.  Its  nuclei  contain  generative  and  vegetative  chromatin 
combined,  and  in  preparation  for  syngamy  nuclei  are  formed  which  are  purely 
generative,  out  of  chromidia  expelled  from  the  primary  nuclei.  The  forma- 
tion of  uninucleate  gametes  which  copulate  (total  karyogamy)  has  been  re- 
garded by  almost  all  those  who  have  theorized  on  the  subject  as  being  probably 
the  most  primitive  type  of  syngamy  from  which  the  conjugation  (partial 
karyogamy)  of  the  Ciliata  has  been  derived  (p.  154). 

In  Trachelocerca  (p.  450)  the  gamont  produces  in  a  similar  manner  a  number 
of  generative  nuclei  (micronuclei)  prior  to  the  syngamic  process  ;  but  here, 
as  in  Ciliata  generally,  the  gamont  no  longer  divides  into  a  number  of  gametes  ; 
only  one  micronucleus  in  each  gamont  persists  to  form  the  two  pronuclei,  and 
the  usual  process  of  partial  karyogamy  takes  place.  These  considerations 
indicate  that  the  mononiorphic  character  of  the  Infusorian  life-cycle  is  a 
secondary  feature  ;  as  the  structural  complication  of  the  body  has  increased, 
so  the  tendency  to  divide  up  into  relatively  minute  swarm-spores  has  been 


454 


THE  PROTOZOA 


suppressed,  and  has  been  replaced  by  the  peculiar  type  of  syngamy  charac- 
teristic of  the  group. 

The  question  of  the  exact  systematic  position  of  Opalina  cannot  be  decided 
until  more  is  known  of  the  life-cycles  of  other  parasitic  Ciliata  ;  but  at  present 
there  do  not  seem  to  be  any  cogent  reasons  for  removing  this  genus  from  the 
Ciliata. 

Affinities  of  the  Ciliata. — A  typical  ciliate,  such  as  Paramecium,  with  its 
even  coat  of  fine  cilia,  its  heterokaryote  nuclear  apparatus,  and  its  peculiar 
type  of  syngamy  with  partial  karyogamy,  stands  apart  and  apparently 
isolated  from  the  typical  members  of  other  classes  of  the  Protozoa.  Never- 
theless, even  within  the  limits  of  the  class  Ciliata, 
examples  are  to  be  found  in  which  the  heterokaryote 
condition  is  not  developed,  or  only  appears  prior 
to  syngamy  in  the  form  of  a  separation  of  generative 
from  vegetative  chromatin  (Trachelocerca,  Opalina), 
and  in  which  the  syngamy  takes  the  form  of  total 
karyogamy  between  minute  gametes,  swarm-spores 
(Opalina).  Such  cases,  while  they  minimize  the  gap 
between  Ciliata  and  other  Protozoa,  do  not  bring  the 
ciliates  nearer  to  any  particular  class,  since  a  similar 
type  of  syngamy  and  of  preparations  for  it  may  occur 
either  in  Sarcodina  or  Mastigophora. 

As  the  most  distinctive  feature  of  the  Ciliata  there 

remains  that  which  is 
implied  in  the  name- 
that  is  to  say,  the  posses- 
sion of  cilia.  As  has  been, 
pointed  out  above,  how- 
ever, a  cilium  is  similar 
to  a  flagellum  in  every 
essential  point  of  structure 
and  function.  There  can 
be  no  doubt  that  the 
ciliary  covering  represents 
a  large  number  of  flagella 
specialized  in  respect  to 
size,  number,  arrange- 
ment, and  co-ordination. 
It  has  been  mentioned 
above  that  some  flagel- 
lates, such  as  the  Tricho- 
nymphidce  and  allied 
forms,  are  regarded  by 
some  authorities  as  transi- 
tional from  the  Flagellata 
to  the  Ciliata.  It  is  per- 
haps improbable,  how- 
ever, that  the  transition 
from  the  one  group  to 


e.v. 


FIG.  189. — A,  Monomastix  ciliatus :  ft.,  flagellum  ; 
o,  mouth  ;  N,  macronucleus  ;  n,  micronucleus  ; 
c.v.,  contractile  vacuole  ;  a.,  anus,  near  which  opens 
the  efferent  canal  of  the  contractile  vacuole.  After 
Roux,  magnified  1,000.  B,  Maupasia  paradoxa  : 
as.,  oesophagus ;  other  letters  as  in  A.  After 
Schewiakoff,  magnified  1,300. 


the  other  should  have  been 
through  endoparasitic  forms  ;  and  it  is  on  the  whole  more  likely  that  free- 
living  forms,  such  as  the  holomastigote  genus  Multicilia,  are  the  nearest 
representatives  of  the  earlier  ancestral  forms  of  the  Ciliata. 

Two  interesting  forms  have  been  described  which  combine  in  some  respects 
the  characters  of  both  Flagellata  and  Ciliata. 

Maupasia  paradoxa  (Fig.  189,  B)  is  described  by  its  discoverer,  Schewiakoff 
(863),  as  having  the  body  metabolic,  with  cilia  in  the  anterior  part  of  the 
body,  and  the  remainder  covered  with  long  flagella.  At  the  hinder  end  of  the 
body  is  a  longer  flagellum  implanted  close  beside  the  aperture  of  the  efferent 
duct  of  the  contractile  vacuole.  The  mouth-opening,  on  the  ventral  side  of 


THE  INFUSORIA  455 

the  body,  leads  into  a  short  oesophagus.  The  nucleus  is  single,  without  a 
micronucleus.  Schewiakoff  makes  Maupasia  the  type  of  a  distinct  order  of 
the  Ciliata — the  Mastigotricha. 

Monomastix  ciliatus  (Fig.  189,  A),  described  by  Roux  (862),  and  referred  by 
him  also  to  the  Mastigotricha,  has  an  even  coat  of  cilia  all  over  the  body,  and 
possesses  two  macronuclei,  near  each  of  which  is  a  micronucleus  ;  its  most 
remarkable  feature  is  the  possession  of  a  long  flagelluni  implanted  at  the 
anterior  end  of  the  body  close  to  the  mouth. 

From  these  various  considerations,  it  seems  highly  probable  that  the  Ciliata 
are  descended  from  flagellate  ancestors  ;  but  it  is  not  possible  at  present  to 
indicate  with  any  approach  to  exactness  the  line  of  descent. 


SUBCLASS  II. — ACINETARIA  (Suctoria,  Tentaculifera). 

The  Acinetaria  are  distinguished  from  the  Ciliata  by  the  posses- 
sion of  the  following  characters  in  combination  :  The  adult  organism 
is  of  sedentary  habit,  and  has  no  cilia,  though  the  youngest  stage 
in  the  life-history  is  typically  a  free-swimming  ciliated  organism  ; 
there  is  no  mouth,  but  both  the  capture  and  ingestion  of  food  is 
effected  by  means  of  special  organs  peculiar  to  this  subclass,  and 
known  as  tentacles. 

An  acinetan  may  be  attached  to  various  objects,  and  is  frequently 
epizoic.  Some  species  attach  themselves  indifferently  to  a  living 
or  a  lifeless  object ;  others  are  constantly  epizoic,  and  occur  always 
attached  to  some  particular  animal,  frequently  to  a  particular 
organ  of  it.  Very  few  species,  however,  are  truly  parasitic  in  the 
adult  condition  ;  on  the  other  hand,  many  species  are  parasitic  in 
the  early  larval  stages  of  their  life-history,  and  frequently  so  within 
the  bodies  of  Ciliata  (Fig.  192).  The  marine  genus  Ophryodendron, 
however,  is  a  true  ectoparasite  of  hydroids,  according  to  Martin, 
and  contains  nematocysts  derived  from  its  hosts.  In  this  case  the 
parasitism  is  correlated  with  a  peculiar  dimorphism  of  "  proboscidi- 
form  "  and  "  vermiform  "  individuals,  the  former  possessing  a  tuft 
of  tentacles  on  a  proboscis-like  process,  the  latter  being  without 
tentacles  altogether.  The  vermiform  individuals  are  budded  from 
the  proboscidiform,  and  either  form  can  produce  ciliated  buds, 
which  develop  into  proboscidiform  individuals  again  ;  but  the 
vermiform  type  does  not  grow  into  the  proboscidiform.  In  Den- 
drosomides  paguri,  however,  Collin  (881)  finds  that  similar  vermi- 
form individuals  become  transformed  into  the  tentacle-bearing 
form.  In  Rhabdophrya  trimorpha,  ectozoic  on  a  Copepod  (Cletodes 
longicaudatus),  there  are  three  forms  of  individuals — namely,  in 
addition  to  tentaculated  and  vermiform  specimens,  peculiar  "  unci- 
forni  "  individuals,  which  are  also  without  tentacles  (Chatton  and 
Collin,  876). 

The  form  of  the  body  varies  greatly,  but  may  be  said  to  be 
typically  vase-like,  with  or  without  a  stalk  or  peduncle.  In  sessile 
forms  the  body  is  attached  by  a  broad  base  to  the  substratum.  In 


456 


THE  PROTOZOA 


stalked  forms  the  body  is  raised  up  from  the  point  of  attachment 
on  a  straight,  non-contractile  stalk  of  secreted  substance,  similar  to 
that  of  many  Vorticellids,  and  the  animal  as  a  whole  may  resemble 
in  its  general  contours  an  Epistylis  or  other  Vorticellid  (Figs.  10, 
190).  Collin  (877)  finds  that  the  stalk  consists  of  a  sheath,  a  cor- 
tical layer  thickest  at  the  base,  and  a  medullary  substance  stratified 
longitudinally  to  the  longitudinal  axis.  The  base  of  the  stalk  rests 
on  a  cushion  of  secreted  substance — the  portion  which  is  first 
formed,  and  which  is  produced  by  a  special  organ  of  the  larva 
comparable  to  the  scopula  (p.  441)  of  the  Vorticellids. 

The  body  is  often  protected  by  a  secreted  house  or  theca,  con- 


FIG.  190. — A,  Podophrya  mollis ;  B,  Tocoplirya  quadripartite,  two  specimens 
attached  to  the  stalk  of  Epistylis  plicatilis  ;  C,  Podophrya  fixa,  two  specimens 
conjugating.  After  Saville  Kent. 

tinuous  with  the  stalk  in  the  pedunculate  forms.  In  AstropJirya 
arenaria  the  house  is  built  up  of  foreign  particles  of  various  sizes 
(Aweriiizew).  As  in  the  attached  ciliates,  colonies  may  be  formed 
of  considerable  size  and  extent,  and  of  various  forms.  The  non- 
pedunculate  genus  Dendrosoma  produces  spreading  colonies,  which 
bear  a  considerable  resemblance  to  a  polyp-colony. 

The  characteristic  tentacles  are  stiff  protoplasmic  processes  con- 
sisting of  a  parietal  layer  of  ectoplasm  in  the  form  of  a  tube  en- 
closing a  canal  containing  fluid.  The  apex  of  the  tentacle  usually 
terminates  in  a  sucker-like  knob  ;  suctorial  tentacles  ("  Saugten- 


THE  INFUSORIA 


457 


takel  ")  of  this  type  are  always  present.  In  the  genus  Ephclota 
there  are  present  in  addition  prehensile  tentacles  ("  Greiftentakel  "), 
which  end  in  a  fine  point.  The  exterior  of  the  tentacle  is  clothed 
by  a  delicate  pellicle,  continuous  with  that  of  the  body,  and  forming 
in  the  suctorial  tentacles  a  sheath  or  tube,  from  the  end  of  which 
the  sucker  protrudes.  The  tentacles  are  slowly  retractile.  When 
expanded  they  appear  homogeneous  ;  but  in  the  process  of  retrac- 
tion they  exhibit  a  spiral  marking,  due  apparently  to  creases  and 
folds  in  the  pellicle,  and  not  to  be  interpreted  as"  indicating  the 
presence  of  myonemes.  The  tentacles  are  used  for  the  capture  of 
prey,  which  consists  chiefly  of  ciliates.  As  soon  as  the  sucker-like 
extremity  of  a  tentacle  touches  a  ciliate  it  is  held  fast ;  the  substance 
of  the  prey  is  then 
slowly  absorbed  by  the 
tentacle,  and  passes  as 
a  stream  of  granules 
down  the  axis  of  the 
tentacle.  During  this 
process  the  ciliate  re- 
mains alive,  with  cilia 
moving  and  contractile 
vacuoles  pulsating,  until 
about  half  its  substance 
is  absorbed  (Filipjev). 

In  the  genus  Bhyn- 
cheta  there  is  but  a 
single  tentacle  of  great 
length  ;  in  Urnula  (Fig. 
191),  one  or  two.  Other 
genera  bear  usually 
many  tentacles,  which 
may  be  distributed 
evenly  over  the  body- 
surface,  or,  more  commonly,  occur  in  special  regions  of  the  body 
or  are  distributed  in  tufts  and  patches.  In  Dendrocometes  the 
tentacles  occur  in  bunches  borne  on  branches  or  arm-like  processes 
of  the  body- wall. 

Ishikawa  describes  in  the  larger  prehensile  tentacles  of  Eplielota  buetschliana 
a  system  of  filaments,  consisting  of  fine  threads  running  parallel  to  one 
another  in  pairs  and  continued  into  the  body  as  far  as  its  base.  The  filaments 
stain  deeply  with  iron-hsematoxylin.  According  to  Collin  (877),  each  such  pair 
of  filaments  is  in  reality  the  optical  section  of  a  fine  tube.  A  suctorial  tentacle, 
according  to  Collin,  represents  a  deep  invagination  of  the  ectoplasm,  opening 
at  its  innermost  end  into  the  endoplasm  like  the  cytopharynx  of  a  ciliate. 
The  prehensile  tentacles,  on  the  other  hand,  are  special  formations  of  a 
different  kind,  simple  evaginations  of  the  bodj'-wall,  pseudopodial  in  natuiv, 
and  containing  from  one  to  three  axial  filaments,  the  number  increasing  with 
the  age  of  the  tentacle. 


FIG.  191. —  Urnula  epistylidis,  epizoic  on  Dendro- 
soma  radians.  A,  B,  Individuals  with  one  or  two 
tentacles  respectively  ;  C,  formation  of  a  bud 
(g)  ;  D,  the  same  seen  in  transverse  section 
passing  through  the  bud  and  the  macronucleus 
of  the  parent  ;  E,  free-swimming  larva  ;  F,  en- 
larged view  of  the  single  tentacle,  showing  the 
spiral  striation.  After  Hickson  and  Wads- 
worth  (886). 


458  THE  PROTOZOA 

When  a  ciliate — for  example,  a  Paramecium — is  captured  by  the  tentacle,, 
its  protoplasm  streams  down  the  tentacle  to  form  a  mass  in  the  endoplasm 
of  the  acinetan.  Before  the  process  of  suction  is  complete  the  mass  breaks; 
up  into  smaller  masses,  and  these  again  into  still  smaller  ones,  which  are 
carried  away  by  the  cyclosis  of  the  endoplasm,  and  other  masses  of  snvill 
size  continue  to  be  formed  at  the  base  of  the  tentacle.  Round  each  of  thcso 
food-masses  a  fluid  vacuole  is  formed,  in  which  the  ingested  protoplasm  is 
for  the  most  part  dissolved,  becoming  reduced  to  a  few  granulations.  The- 
vacuole  then  gives  off  fluid  and  diminishes  in  size,  and  the  contents  are  con- 
centrated to  form  a  refractile  body.  Three  kinds  of  such  retractile  bodies  are 
formed  :  so-called  "colourless  bodies"  which  stain  feebly  with  nuclear  stains, 
and  are  derived  from  the  protoplasm  of  the  prey ;  "  tinctin-bodies,"  staining 
deeply,  and  originating,  as  described  by  Martin,  from  the  chromatin  of  the- 
prey  ;  and  others,  found  in  some  acinetans,  derived  from  the  chlorophyll  of 
green  ciliates  and  algal  spores  devoured  by  the  animal.  If  a  Tocoplirya  be 
starved,  the  ref  ringent  bodies  are  slowly  absorbed,  and  the  protoplasm  becomes 
quite  clear  (Filipjev).  Hence  the  refringent  bodies  that  arise  from  the  diges- 
tive vacuoles  represent  reserve-material ;  there  appears  to  be  no  defaecation 
of  indigestible  residues. 

The  nature  and  origin  of  the  tentacles  of  acinetans  have  been  much  dis- 
cussed, and  some  authors  have  sought  to  derive  them  from  cirri  or  cilia. 
Schuberg  (44)  points  out,  however,  that  the  structure  of  the  tentacles  is  quite 
the  opposite  of  that  of  the  cilia  ;  in  a  cilium  the  axial  portion  is  of  firm  con- 
sistence, the  superficial  layer  is  fluid,  while  in  a  tentacle  the  axis  is  fluid  and 
the  superficial  sheath  is  of  firm  texture.  Collin  (877)  considers  that  the  pre- 
hensile tentacles  are  modifications  or  adaptations  of  a  pseuclopodium-like 
process  ;  on  the  other  hand,  he  regards  the  suctorial  tentacles  as  organs  of 
quite  a  different  kind,  more  like  the  cytostome  of  a  ciliate  than  anything 
else  ;  they  may  be  considered  each  as  a  cytostome  which  has  grown  out  from 
the  body  on  a  slender  process  or  stalk  (compare  also  Hickson,  826). 

In  correlation  with  their  sedentary  habits,  the  organization  of  the 
Acinetaria  is  greatly  simplified  as  compared  with  the  Ciliata,  and 
the  remarkable  structural  and  functional  differentiation  of  the 
ectoplasm  seen  in  the  Ciliata  is  wanting  altogether  in  Acinetaria, 
in  which  the  ectoplasm  is  relatively  a  feebly-developed  layer.  Con- 
tractile vacuoles  are  usually  present,  one  or  more  in  number.  As 
in  Ciliata,  the  macronucleus  exhibits  a  great  variety  of  forms.  One 
of  the  most  remarkable  is  seen  in  the  colonial  form  Dendrosoma, 
where  the  macronucleus  is  branched  to  the  same  degree  as  the 
colony,  throughout  which  it  extends  continuously. 

The  methods  of  reproduction  are  more  varied,  and  exhibit  a 
greater  specialization,  in  the  Acinetaria  than  in  the  Ciliata.  Simple 
binary  fission  in  the  adult  condition  is  rare  in  acinetans.  Collin  (881 ) , 
however,  has  observed  division  into  two  or  four  within  a  cyst  in 
Podophrya  fixa.  The  fission  usually  takes  the  form  of  bud-forma- 
tion. The  buds  may  be  formed  either  on  the  exterior  of  the  body 
or  in  the  interior  in  special  brood-cavities,  and  they  may  be  pro- 
duced in  either  case  singly  and  successively  or  in  batches  or  relays 
of  several  at  a  time.  The  bud  is  usually  a  simple  outgrowth  of  the 
cytoplasm  containing  a  prolongation  budded  off  from  the  macro- 
nucleus,  and  one  of  the  daughter-nuclei  derived  from  a  division  of 
the  micronucleus.  At  first  a  simple  cell  without  structural  differ- 


THE  INFUSORIA 


459 


entiation,  the  bud  is  set  free  with  a  complete  or  partial  coat  of 
cilia  as  a  free-swimming  "  embryo,"  "  larva,"  "  swarm-spore " 
(Schwarmer),  or  "  gemmula."  The  larva  often  becomes  parasitic 
within  the  body  of  another  Infusorian  (Fig.  192),  multiplying  there 
by  binary  fission.  Finally  it  becomes  free  again,  swims  away, 
attaches  itself  in  a  suitable  locality,  and  develops  into  the  adult 
form. 

The  ciliated  larvae  of  acinetans  exhibit  various  types  of  ciliation, 
commonly  classed  as  peritrichous  (Fig.  193,  A,  B),  holotrichous 
(Fig.  191,  E),  and  hypotrichous.  Coffin  (882)  has  studied  recently 
the  morphology  of  the  different  types  of  larvse. 


FIG.  192. — A  and  B,  Stylonychia  mytilus  infested  by  parasitic  Acinetans.  N,  N, 
Macronuclei  of  the  Stylonychia  ;  P,  parasitic  Acinetan  embryo  from  which 
arise  small  ciliated  larvae  (c.e)  which  swim  off  and  develop  into  the  adult 
free-living  Acinetan.  After  Stein. 

The  most  primitive  and  commonest  larval  type  of  larva  amongst  the 
Acinetaria  is  very  similar  to  a  free-swimming  stage  of  a  Vorticellid.  It  has 
a  principal  axis  round  which  the  body  is  radially  symmetrical,  with  an  upper 
pole  (posterior  in  movement)  bearing  a  rudimentary  adoral  zone,  and  a  lower 
(anterior)  pole  bearing  a  mass  of  secretion  or  a  sucker,  indicating  the  future 
point  of  fixation  and  representing  the  scopula  of  the  Vorticellid  ;  the  body  is 
surrounded  by  several  rings  of  cilia  forming  a  zone  more  or  less  equatorial 
in  position.  Such  a  form,  while  retaining  its  radiate  symmetry,  may  become 
either  lengthened  or  shortened  to  a  remarkable  degree  in  the  direction  of  the 
principal  axis  ;  in  the  elongated  forms  the  rings  of  cilia  may  increase  in 
number  until  they  cover  the  whole  body,  thus  producing  the  holotrichous 
type.  On  the  other  hand,  the  body  may  become  elongated  in  the  morpho- 
logically transverse  plane,  and  acquire  a  bilateral  symmetry,  with  a  dorsal 
surface  representing  the  primitive  upper  pole  and  bearing  the  rudimentary 
adoral  zone,  and  a  ventral  surface,  with  the  sucker  in  the  middle  of  it,  repre- 
senting the  primitive  lower  pole  ;  secondary  anterior  and  posterior  extremities 
are  now  distinguishable  in  relation  to  progression,  but  representing  opposite 


460 


THE  PROTOZOA 


;points  of  the  primitive  transverse  plane.  In  such  a  type  the  zones  of  cilia 
run  obliquely  along  the  sides  of  the  body,  or  may  be  confined  to  the  ventral 
surface,  where  they  run  a  more  or  less  elliptical  course  round  the  sucker, 
thus  producing  the  hypotrichous  type  seen  in  Ephelota  gemmipara  and  in  the 
persistent  larval  form  Hypocoma  acinetarum.  Examples  of  holotrichous 
larvae  are  seen  in  Tocophrya  limbata  and  Urnula  epistylidis  (Hickson  and 
Wadsworth,  886).  In  all  cases  the  principal  or  dorsiventral  axis  of  the  larva 
becomes  the  principal  axis  of  the  adult ;  in  the  process  of  budding,  however, 
the  principal  axis  of  the  bud  arises  at  right  angles  to  that  of  the  parent,  accord- 
ing to  Collin ;  Filipjev,  however,  does  not  confirm  this  for  Tocophrya  quadri- 
partita. 

The  remarkable  form  Tachyblaston  described  by  Martin  lives  in  the  adult 
condition  attached  to  the  stalk  of  Ephelota;  it  produces  buds  each  with  a 
single  tentacle,  which  creep  up  the  stalk  of  the  Ephelota  and  penetrate  into 
the  body,  becoming  parasitic  in  it  and  multiplying  by  fission  to  produce 
ciliated  larvae,  which  in  their  turn  swim  out,  attach  themselves  to  the  stalk 
of  the  Ephelota,  and  become  adult  forms. 

The  conjugation  of  the  Acinetaria  conforms  in  general  to  the 
type  of  the  process  seen  in  Ciliata,  as  regards  cytological  details. 
Conjugation  may  take  place  between  two  individuals  fixed  near 


FIG.  193. — Free-swimming  larva  of  Dendrosoma  radians.  A,  Side  view  ;  B,  viewed 
from  above  ;  C,  older  larva  with  the  first  rudiments  of  the  tentacles  beginning 
to  appear.  After  Hickson  and  Wadsworth  (886). 


together  (Fig.  190,  G)  ;  then  a  lobe  or  outgrowth  may  be  formed 
from  one  individual,  which  meets  a  similar  outgrowth  from  the 
other,  thus  establishing  contact.  On  the  other  hand,  as  in  Peri- 
tricha,  conjugation  may  take  place  between  a  fixed,  ordinary  indi- 
vidual and  a  free-swimming  bud  or  larva  liberated  from  another 
adult  individual  (Martin  ;  Collin,  879).  In  Dendrocometes  the 
macronuclei  come  into  contact  during  conjugation,  but  separate 
again  (Hickson  and  Wadsworth). 

Classification. — The  Acinetaria    are    divisible    into    eight    families    (cf. 
Doflein,  7). 

1.  Hypocomidce,  for  the  single,  somewhat  aberrant  genus  Hypocoma,  which 
is  free-swimming,  ciliated  on  one  surface,  and  with  a  single  suctorial  tentacle — 
possibly  a  persistent  larval  form  (see  Collin,  877). 

2.  Urnulidce. — With  or  without  a  house,  with  one  or  few  tentacles.     Rhyn- 
cheta,  Urnula  (Fig.  191). 

3.  Metacinetidce. — With  a  stalked  house  opening  at  the  upper  end  for  the 
exit  of  the  tentacles.     Metacineta. 


THE  INFUSORIA  461 

4.  Podophryidce. — Stalked  or  sessile,  with  no    house  and  with  numerous 
tentacles.     Sphcerophrya,  Podophrya  (Fig.  190),  Ephelota. 

5.  Acinetidce. — Stalked  or  sessile,  with  a  house  of  simple  form  and  wide 
aperture,  and  with  numerous  tentacles,  all  knobbed.     Tocophrya  (Fig.  190), 
Acineta  (Fig.  10). 

6.  Dendrosomidce   (Trichophryidce). — Sessile,    without   a   house ;   tentacles 
knobbed,  arranged  in  tufts  or  branches.     Trichophrya,  Dendrosoma,  Lernceo- 
phrya  (Perez),  Bhabdophrya  (Chatton  and  Collin),  Astrophrya  (Awerinzow). 

7.  Dendrocometidce. — Flat  forms  with  numerous  branched  arms  on  the  ends 
of  which  the  suckers  occur.     Dendrocometes. 

8.  Opliryodendridce. — Marine  stalked  forms  with  numerous  short  tentacles 
concentrated  on  proboscis-like  processes.     Vermiform  individuals  also  occur 
(p.  455).     Ophryodendron. 

Affinities  of  the  Acinetaria. — The  presence  of  cilia  in  the  young  stages,  the 
possession  of  distinct  vegetative  macronuclei  and  generative  micronuclei,  and 
the  process  of  conjugation,  similar  in  all  essential  details  to  that  of  the  Ciliata, 
can  leave  no  doubt  as  to  the  position  of  the  Acinetaria  in  the  class  Infusoria, 
and  their  affinities  with  the  Ciliata.  Collin,  in  a  series  of  interesting  studies, 
has  drawn  attention  to  many  points  indicating  a  close  relationship  between 
Acinetaria  and  Vorticellids,  more  especially  the  structural  homologies  between 
the  larvoe  of  the  one  and  the  free-swimming  stages  of  the  other  group  ;  for 
example,  the  peritrichous  arrangement  of  the  cilia,  the  rudimentary  adoral  zone 
at  the  posterior  pole,  and  the  fixation  by  means  of  a  scopula-like  organ  at  the 
anterior  pole,  points  especially  well  seen  in  the  larva  of  Tocophyra  cyclopum. 


Bibliography. — For  references  see  p.  502. 


CHAPTER  XVIII 

AFFINITIES  AND  CLASSIFICATION  OF  THE  MAIN 
SUBDIVISIONS— DOUBTFUL  GROUPS 

TJST  the  foregoing  chapters  the  Protozoa  have  been  dealt  with 
systematically,  grouped  in  a  somewhat  conservative  manner  under 
the  four  old-established  and  generally-recognized  classes.  At  the 
same  time  it  has  been  pointed  out  that  one  class  at  least — namely, 
the  exclusively-parasitic  Sporozoa — comprises  two  subclasses  which 
are  quite  distinct  from  one  another,  and  are  descended,  in  all 
probability,  from  ancestors  differing  greatly  in  characters  and 
affinities.  And  in  the  case  of  the  three  remaining  classes,  con- 
sisting mainly  of  free-living,  non-parasitic  forms,  two  which  exhibit 
more  primitive  characters — namely,  the  Sarcodina  and  Mastigophora 
—are  connected  with  one  another  by  transitional  forms  which 
render  the  distinction  between  them  very  arbitrary  (p.  213)  ;  while 
the  third,  the  highly-specialized  Infusoria,  are  linked  closely  by 
structural  characters  and  by  transitional  forms  to  the  Mastigophora. 
Many  authorities  oil  the  Protozoa  have  put  forward  schemes  of 
classification  which  are  intended  to  express  the  affinities  and  inter- 
relationships of  the  chief  groups  in  a  clearer  and  more  satisfactory 
manner  than  the  fourfold  classification  generally  recognized.  The 
systems  proposed  have  taken  the  form  either  of  subdividing  the 
Protozoa  into  more  than  four  classes  or  of  uniting  the  recognized 
subdivisions  into  a  smaller  number  of  categories. 

Holleston  and  Jackson  (15)  divide  the  Protozoa  as  a  whole  into  three  groups : 
(1)  the  Rhizopoda  (=Sarcodina) ;  (2)  the  Endoparasita  (=Sporozoa);  and 
(3)  the  Plegepoda,  "  referring  to  their  mode  of  progression  by  means  of  a 
rapidly  -  repeated  stroke  (wXrjyi])  of  vibratile  processes,"  to  comprise  the 
Mastigophora  and  Infusoria. 

Doflein  (891)  recognizes  two  principal  stems  in  the  Protozoan  phylum: 
(1)  the  Plasmodroma,  to  include  the  Sarcodina,  Mastigophora,  and  Sporozoa, 
organisms  that  make  use  of  locomotor  organs  which  represent  true  pseudo- 
podia,  or  their  derivatives  or  modifications ;  and  (2)  the  Ciliophora,  comprising 
the  Ciliata  and  Suctoria,  in  which  the  locomotor  organellse  are  cilia.  The 
obvious  criticism  of  this  scheme  is  that,  whatever  opinion  may  be  held  as  to 
the  desirability  of  drawing  a  line  between  the  Infusoria,  so  highly  specialized  in 
many  respects,  and  other  Protozoa,  the  distinctive  character  chosen  is  not  a 
happy  one,  since  whatever  may  be  predicated  of  flagella  as  derivatives  of  pseu- 
dopodia  applies,  apparently,  with  equal  force  to  cilia. 

462 


CLASSIFICATION  OF  THE  MAIN  SUBDIVISIONS     463 

Hartmann  (892)  recognizes  six  classes  of  the  Protozoa  :  Class  I.,  the  Sarco- 
•dina,  including  four  subclasses — namely,  Rhizopoda,  Heliozoa,  Radiolaria, 
.and  Mycetozoa  ;  Class  II.,  the  Cnidosporidia,  including  Microsporidia,  Sarco- 
sporidia,  Myxosporidia,  and  Actinomyxidia  ;  Class  III.,  the  Mastigophora, 
including  the  Rhizomastigina,  Protomonadina,  Binucleata,  Chromomonadina, 
Euglenoidea,  and  Phytomonadina,  the  order  Binucleata  including  the  Ha-nio- 
flagellates  and  the  Htemosporidia  with  the  exception  of  the  hsemogregarines  ; 
•Class  IV.,  the  Telosporidia,  including  the  gregarines,  coccidia,  and  hsemo- 
gregarines  ;  Class  V.,  the  Trichonymphida  ;  Class  VI.,  the  Infusoria.  With 
regard  to  this  classification,  the  order  Binucleata  has  been  dealt  with  at 
length  above  ;  it  only  remains  to  say  that  the  isolated  position  given  to  the 
Trichonymphida  appears  to  express  the  defective  state  of  knowledge  con- 
cerning the  affinities  of  these  peculiar  parasites,  rather  than  their  true  taxo- 
momic  importance. 

A  number  of  radical  changes  in  the  classification  of  the  Protozoa  are  pro- 
posed by  Awerinzew  (890).  With  Hartmann  he  unites  the  Haemoflagellates 
and  Hsernosporidia  in  an  order  Binucleata  to  be  placed  in  the  Flagellata. 
The  class  Sporozoa  is  to  be  entirely  abolished.  The  order  Arncebina 
(Anicebsea)  is  removed  by  him  entirely  from  the  Sarcodina,  which  will  then 
comprise  only  the  Foraminifera  and  some  Heliozoa.  The  Amoebinaare  to  be 
put  with  the  Flagellata  as  the  Amoeboflagellata,  a  group  from  which  all  other 
Protozoa  are  supposed  to  have  arisen,  and  from  which  the  Amcebina  branch 
•off  in  one  direction,  the  Flagellata  and  Dinonagehata  in  another.  The  gre- 
.garines  are  believed  by  Awerinzew  to  be  connected  on  the  one  side  with  the 
Amoebina,  on  the  other  with  the  Coccidia.  In  the  Xeosporiclia,  the  Sarco- 
•sporidia  are  regarded  as  allied  to  Flagellata  ;  the  Myxosporidia,  Microsporidia, 
and  Actinomyxidia,  are  considered  not  to  be  Protozoa  at  all ;  the  Haplo- 
sporidia  are  to  be  placed  provisionally  as  an  independent  group  taking  origin 
from  Amcebina.  For  the  Infusoria,  it  is  suggested  that  thejrtake  origin  from 
•amceboflagellate  ancestors  rather  than  from  true  Flagellata. 

The  object  of  what  is  termed  a  natural  as  opposed  to  an  artificial 
system  of  classification  is  to  endeavour  to  express  by  the  arrange- 
ment of  the  groups  the  affinities  of  the  living  organisms  concerned, 
and  more  especially  the  genetic  relationships  of  one  to  another  on 
the  theory  of  evolution — that  is  to  say,  on  the  assumption  or  belief 
that  forms  now  existing  are  descended  from  older  ancestral  forms, 
and  that  any  two  existing  forms  are  descended  from  a  common 
ancestral  form  more  or  less  remote,  according  as  the  two  existing 
forms  in  question  have  diverged  more  or  less  widely  from  one  another. 
The  foundation  of  a  natural  classification  is  therefore  the  phylogeny 
of  the  groups  dealt  with — that  is  to  say,  their  pedigrees  and  lines 
of  descent,  so  far  as  they  can  be  traced.  Phylogeny  must,  however, 
always  be  a  matter  of  speculation,  and  to  a  large  extent  of  personal 
opinion,  rather  than  of  direct  observation.  It  is  only  possible  to 
infer  from  the  study  of  existing  species  what  the  ancestral  forms 
may  have  been  like,  since  it  is  unnecessary  to  point  out  that  no 
form  can  be  the  ancestor  of  another  species  existing  at  the  same 
time.  The  most  that  can  be  said  of  two  co-existing  species  is 
that  one  of  them  may  be  believed  to  have  diverged  much  less  in 
its  characters  from  the  common  ancestral  form  than  the  other. 
When,  therefore,  a  given  form  is  said  to  have  an  amcebic  or  a  cer- 
comonad  ancestry,  it  is  not  intended  to  imply  by  that  statement 


464  THE  PROTOZOA 

that  the  ancestor  was  Amoeba  proteus  or  Cercomonas  crassicauda,. 
but  only  that  it  was  a  form  such  that,  if  it  existed  at  the  present 
day,  it  would  be  referred  by  its  characters  to  the  genus  Amoeba  or 
Cercomonas,  as  the  case  might  be. 

The  data  for  drawing  phylogenetic  conclusions  in  Protozoa  con- 
sist entirely  of  comparisons  between  the  structure  and  life-history 
of  the  various  existing  forms.  Palaeontology  gives  no  assistance, 
since  only  skeletons  are  preserved  as  fossils.  All  that  can  be 
learned  from  the  geological  record  is  that  the  differentiation  of  the 
main  groups  must  have  taken  place  at  an  immeasurably  remote 
period  of  the  earth's  history,  since  skeletons  of  Foraminifera  and 
Radiolaria — groups  of  which  the  structure  and  life-history  indicate 
a  long  pedigree — are  found  in  the  earliest  fossiliferous  strata.  It  is 
little  wonder,  therefore,  that  the  phylogeny  of  the  Protozoa  is  a 
subject  on  which  the  most  opposite  opinions  are  held,  as  is  apparent 
from  the  classificatory  systems  cited  above.  There  can  be  no 
finality  in  a  phylogenetic  theory,  nor,  consequently,  in  any  scheme 
of  classification  put  forward.  Both  the  one  and  the  other  express 
merely  the  state  of  current  knowledge,  and  may  be  expected  to 
undergo  modification  as  knowledge  advances. 

It  is  impossible  to  discuss  here  at  length  the  phylogeny  and 
classification  of  the  Protozoa,  and  only  a  few  guiding  principles 
can  be  put  forward.  From  a  general  survey  of  the  phylum,  it  may 
be  claimed  first  of  all  that  the  Protozoa  constitute  a  compact  group 
with  definite  characters,  not  a  mere  receptacle  into  which  can  be 
put  anything  and  everything  of  microscopic  dimensions  which  is 
not  a  bacterium,  a  fungus,  or  a  parasitic  worm,  as  some  writers 
seem  to  think.  Common  to  all  Protozoa  in  at  least  the  principal 
stages  of  the  life-cycle  is  the  differentiation  of  the  body  into  distinct 
nucleus  and  cytoplasm — that  is  to  say,  the  possession  of  that  type 
of  organization  to  which  I  have  proposed  to  restrict  the  application 
of  the  term  cell.  Doubtless  there  are,  or  have  been,  transitions 
from  this  type  to  the  simpler  grade  of  organization  characteristic 
of  the  bacteria  and  allied  organisms,  but  such  transitions  must  be 
sought  for  outside  the  phylum  Protozoa. 

The  essential  unity  and  homogeneity  underlying  the  innumerable 
differentiations  of  form  and  structure  in  the  Protozoa  may  be  taken 
to  mean  that  the  phylum  as  a  whole  is  descended  from  a  common 
ancestral  form,  and  the  first  problem  is,  then,  to  attempt  to  form 
some  notion  of  what  the  ancestor  was  like.  In  dealing  with  the 
more  specialized  forms,  such  as  those  constituting  the  Infusoria  or 
the  two  principal  subdivisions  of  the  Sporozoa,  it  has  been  pointed 
out  that  each  group  appears  to  be  derived  either  from  flagellate  or 
sarcodine  ancestors.  In  reviewing  the  Mastigophora  and  Sarcodina, 
it  was  further  pointed  out  that,  greatly  as  the  typical  representa- 


CLASSIFICATION  OF  THE  MAIN  SUBDIVISIONS     465 

tives  of  the  two  classes  may  differ,  there  are  forms  of  which  the 
systematic  position  is  quite  arbitrary.  In  such  a  form  as  Pseudo- 
spora,  it  becomes  almost  purely  a  matter  of  opinion  or  taste  which 
phase  of  the  life-cycle  is  to  be  regarded  as  the  "  adult "  form 
determining  the  class  in  which  the  genus  is  to  be  placed. 

Thus,  all  paths  of  evolution  in  Protozoa  appear  to  lead  back- 
wards to  one  or  the  other  of  the  two  forms  that  occur  so  frequently 
in  the  actual  development  as  the  earliest  phases — the  amcebula 
and  the  flagellula.  Most  of  those  who  have  speculated  on  the 
phylogeny  of  the  Protozoa  have,  consequently,  regarded  the  an- 
cestral form  of  the  phylum  as  one  combining  amoeboid  and  flagellate 
characters.  Biitschli  (2)  considered  that  the  Rhizomastigina  re- 
present more  nearly  than  any  other  existing  group  the  primitive 
type  of  Protozoon.  Since  then,  however,  the  life-cycle  of  the 
mastigamcebse  has  been  studied,  and  it  is  seen  that  the  adult 
amoeboid  form  is  preceded  in  development  by  a  simpler  monad 
form  (p.  266,  Fig.  112),  which  makes  it  very  doubtful  if  the  niastig- 
aniceba  itself  can  be  taken  as  a  primitive  type.  Awerinzew  (890) 
also  regards  an  "  amceboflagellate  "  type  as  the  primitive  stock 
of  Protozoa,  which  gave  rise  to  all  existing  groups,  and  became 
differentiated  into  the  Amcebina  on  the  one  hand,  the  Flagellata 
on  the  other. 

If  an  organism  possesses  two  kinds  of  locomotor  organs — pseudo- 
podia  and  flagella — it  is  reasonable  to  suppose  that  a  still  more 
primitive  and  ancestral  form  would  have  possessed  only  one  of 
these  two  kinds  of  organs.  It  has  been  seen  that  there  is  a  gradual 
transition  from  pseudopodia  to  flagella,  the  intermediate  type  of 
organ  being  a  pseudopodium  (axopodium)  with  a  firm,  rigid,  or 
elastic  secreted  axis.  The  question  then  arises,  Which  end  of  the 
series  is  to  be  put  first,  the  flagellum  or  the  pseudopodium  ?  Inas- 
much as  flagella  are  found  commonly  in  bacteria,  it  might  be  argued 
that  they  represent  the  most  primitive  type  of  locomotor  organella, 
and  that  a  simple  flagellate  monad  would  represent  most  nearly  the 
ancestral  type  of  organization  in  Protozoa.  Then  it  must  be  sup- 
posed that  the  formation  of  pseudopodia  is  a  secondary  character, 
acquired  by  the  ancestral  form,  and  the  pseudopodia  themselves 
would  represent  either  simple  outgrowths  of  the  naked  body  (lobo- 
podia)  or  modifications  of  flagella  (axopodia). 

Having  regard,  however,  to  the  manner  in  which  flagella  them- 
selves arise — as  simple  outgrowths  from  the  body — and  to  the  fact 
that  their  structure  and  mode  of  action  are  apparently  of  a  much 
more  specialized  type  than  those  of  pseudopodia,  the  conclusion 
seems  irresistible  that  pseudopodia  preceded  flagella  in  evolution. 
We  may,  then,  regard  as  the  most  ancestral  type  in  the  Protozoa 
a  minute  amcebula-form,  in  structure  a  true  cell,  with  nucleus  and 

30 


466  THE  PROTOZOA 

cytoplasm  distinct,  which  moved  by  means  of  pseudopodia  ;  but 
it  must  be  supposed  that  some  of  the  pseudopodia  very  soon  under- 
went modifications  which  resulted  in  the  acquisition  of  true  flagella, 
and  thus  arose  at  a  very  early  stage  of  evolution  the  flagellula  or 
monad-form.  In  all  probability  these  earliest  monads  were  forms 
with  an  amoeboid  body,  most  nearly  represented  at  the  present 
day  by  such  forms  as  Cercomonas  (Fig.  114)  or  the  flagellulse  of 
Mycetozoa  (Fig.  98).  From  such  forms  arose  the  Sarcodina  and 
their  derivatives  (Neosporidia)  by  loss  of  flagella  and  specialization 
of  the  amoeboid  form  in  the  adult,  and  the  Mastigophora  and  their 
derivatives  (Telosporidia,  Infusoria)  by  specialization  of  the  flagellar 
apparatus  combined  with  the  acquisition  of  a  cortex  and  loss  of 
amoeboid  movement. 

If  the  foregoing  phylogenetic  speculations  be  accepted,  it  is  clear 
that  in  a  natural  classification  of  the  Protozoa  the  Sporozoa  must 
be  abolished  as  a  class,  and  the  two  groups  comprised  in  them 
must  either  be  raised  to  the  rank  of  independent  classes  or  dis- 
tributed amongst  the  others — the  Telosporidia  placed  near  the 
Mastigophora,  the  Neosporidia  near  the  Sarcodina.  The  primary 
subdivision  of  the  Protozoa,  if  it  is  to  represent  the  first  branching 
of  the  ancestral  stem,  should  be  one  which  places  on  one  side  the 
Mastigophora,  Telosporidia  (better  Rhabdogenise),  and  Infusoria, 
on  the  other  the  Sarcodina  and  Neosporidia  (better  Amcebogeiiise). 
Beyond  this  point  it  is  scarcely  profitable  at  the  present  time  to  push 
phylogenetic  speculations  farther. 

In  conclusion,  two  groups  of  organisms  require  brief  mention — 
the  Spirochsetes  and  the  Chlamydozoa — since  by  many  authorities 
they  have  been  referred  to  a  position  in  or  near  the  Protozoa. 

THE  SPIROCHJETES. 

Under  the  name  "  spirochsetes  "  are  grouped  a  number  of  or- 
ganisms, free-living  or  parasitic,  with  flexible  bodies  of  slender, 
thread-like  form,  concerning  the  nature  and  systematic  position  of 
which  a  great  deal  of  confusion  has  existed  of  recent  years,  due 
chiefly  to  conflicting  statements  with  regard  to  the  facts  of  their 
structure  and  methods  of  reproduction.  The  group  comprises  five 
principal  types,  regarded  each  as  of  generic  rank  : 

1.  Spirochceta  sens,  strict.,  a  name  given  by  Ehrenberg  in   1833 
to  a  relatively  large,  free-living  form,  S.  plicatilis.     Other  species 
of  the  genus  have  been  described.     For  a  full  account,  see  Zuelzer 
(904). 

2.  Cristispira,  a  name  proposed  by  Gross  (897)  for  a  number  of 
species  parasitic  in  the  digestive  tract  or  crystalline  style  of  Lamelli- 
branch  molluscs,  and  characterized  by  the  possession  of  a  crest  or 


CLASSIFICATION  OF  THE  MAIN  SUBDIVISIONS    467 

ridge,  commonly  but  wrongly  termed  an  "  undulating  membrane," 
running  the  length  of  the  body.  The  type  of  the  genus  is  C.  bal- 
bianii,  originally  named  by  Certes  Trypanosoma  balbianii,  from  the 
crystalline  style  of  the  oyster. 

3.  Saprospira,    Gross    (898),   for  free-living,   saprophytic   forms 
.similar  in  structure  to  Cristispira,  but  without  the  crest. 

4.  Spiroschaudinnia,   the  name   proposed   by   Sambon  for  the 
many  species  of  minute  spirochsetes  parasitic  in  the  blood  of  verte- 
brates   and    in    various    invertebrates.      Such    are   S.    recurrentis 
(—  obermeieri),    parasite    of    human    relapsing   fever;    S.    duttoni, 
parasite  of  African  relapsing  fever  ;  S.  gallinarum  of  fowls  ;  S. 
anserina  of  geese  ;  and  numerous  other  species  from  various  hosts. 
In  structure  the  body  of  these  species  appears  to  be  little,  if  any- 
thing, more  than  a  flexible  thread  of  cliro matin  ;  but  the  develop- 
ment indicates  rather  that,  as  in  the  genus  Cristispira,  the  interior  of 
the  body  is  divided  into  minute  segments  or  chambers.    The  species 
parasitic  in  blood  are  transmitted  by  the  agency  of  blood-sucking 
arthropods.     S.  duttoni,  for  example,  is  transmitted  by  a  tick— 
Orniihodoros  moubata — which  lives  in  the  mud-floors  of  huts  or  in 
the  soil  in  spots  where  caravans  camp  habitually.     The  spirochsetes 
are  taken  up  from  human  blood  by  the  adult  ticks,  and  pass  through 
the  egg  into  the  next  generation  of  nymphs,*  which  transmit  the 
infection  to  human  beings. 

5.  Treponema,  the  name  proposed  by  Schaudimi  for  T.  pallidum, 
the  spirochsete  of  syphilis  discovered  by  him.     A  second  species — 
T.  pertenue,  the  parasite  of  yaws  (frambcesia) — is  also  recognized. 
Structurally  this  type  is  very  similar  to  the  last. 

Some  authors — for  instance,  Gross  (899)  and  Dobell  (895) — consider  that 
there  is  "  no  valid  reason  for  drawing  a  generic  distinction  between  Treponema 
pallidum  and  such  forms  as  '  Spirochceta '  recurrentis,  etc."  Gross  combines 
Types  4  and  5  under  the  name  Spironema  proposed  by  Vuillemin;  but 
since  this  name  is  preoccupied,  Dobell  places  them  together  in  Schaudinn's 
genus  Treponema. 

The  forms  parasitic  in  the  blood  of  human  beings  and  other  vertebrates 
Avere  generally  regarded  as  Bacteria  of  the  genus  Spirillum,  or  at  least  of  the 
section  Spirillacea,  until  quite  recent  years,  and  the  diseases  caused  by  them 
were  spoken  of  as  spirilloses.  The  chief  points  of  difference  between  the 
spirilla  of  relapsing  fevers  and  those  of  the  ordinary  type  were  the  flexibility 
of  the  body  in  the  former  and  the  failure  to  grow  them  in  cultures.  The  con- 
fusion prevailing  at  present  originated  with  Schaudinn's  famous  memoir  on 
the  blood- parasites  of  the  Little  Owl  (132).  While,  on  the  one  hand,  it  is  to 
Schaudinn's  credit  to  have  recognized  the  affinities  of  the  parasitic  "  spirilla  " 
to  Ehrenberg's  free-living  genus  Spirochceta  he  was,  on  the  other  hand,  misled 
by  the  superficial  resemblance  between  spirochsetes  and  certain  small,  slender 
forms  of  trypanosomes,  which  again  he  connected,  quite  erroneously,  with 
the  life-cycle  of  Leucocytozoon  (see  p.  370).  Schaudinn  therefore  regarded 
the  spirochaetes  as  Protozoa  allied  to  trypanosomes,  and  endeavoured  to 
prove  a  similar  type  of  organization  in  both  classes  of  organisms :  a  nuclear 

*  The  six-legged  larval  stage  is  suppressed — that  is  to  say,  passed  through  ii> 
the  egg — in  this  species  of  tick. 


468  THE  PROTOZOA 

apparatus  with  kinetonucleus  and  trophonucleus,  and  a  locomotor  apparatus 
\\iih  flagellum  and  undulating  membrane.  Schaudinn  further  constructed 
a  hypothetical  form  of  "  Urhsemoflagellat  "  connecting  the  spirochsete  and 
trypanosome  type  of  organization  ;  he  put  forward  the  suggestion  (903)  that 
"  as  the  general  structural  plan  of  a  trypanosome  (nuclear  and  locomotor 
apparatus)  may  be  found  realized  in  various  groups  of  Protozoa  as  a  transitory 
developmental  condition  (comparable  somewhat  to  the  gastrula-condition 
in  the  Metazoa),  so  also  the  spirochsete  may  crop  up  occasionally  as  a  morpho- 
logical type  in  the  development  of  Protozoa,  and  as  a  developmental  stage 
may  indicate  to  us  phylogenetic  relations." 

Schaudinn  lived  long  enough,  fortunately,  to  retract  many  of  his  state- 
ments with  regard  to  the  structure  of  spirochsetes,  and  acknowledged  that  the 
trypanosome-type  of  structure  was  not  to  be  made  out  in  the  minute  parasitic 
spirochsetes.  Nevertheless,  since  his  time  the  investigators  of  these  organisms 
have  been  divided  into  two  camps — those  who  hold  fast  to  Schaudinn's  theory 
of  the  spirochsetes  as  Protozoa,  and  those  who  class  them  with  Bacteria, 
respectively ;  it  being  generally  assumed,  for  some  unknown  reason,  that  if; 
they  are  not  Protozoa  they  must  be  Bacteria,  or  vice  versa.  A  third  set  of 
authorities  compromise  by  placing  the  spirochfetes  in  an  intermediate  position- 
between  the  two  groups. 

In  considering  the  question  of  the  affinities  of  the  spirochsetes,  attention 
has  been  directed  not  only  to  their  structure,  but  also  to  their  life-history ; 
and  a  hot  controversy  has  raged  with  regard  to  their  mode  of  fission,  whether 
it  takes  place  longitudinally,  as  in  a  trypanosome,  or  transversely,  as  in  a 
bacterium.  Investigators  contradict  each  other  flatly  with  regard  to  this 
point ;  but  from  the  most  recent  investigations  it  seems  probable,  at  least, 
that  the  division  is  always  transverse,  and  that  the  appearance  of  longitudinal 
division  is  due  to  the  peculiar  method  of  "  incurvation  "  described  by  Gross 
(Fig.  194).  A  spirochaete  about  to  divide  grows  greatly  in  length,  and  one 
end  of  the  body  doubles  back  on  itself,  continuing  to  do  so  until  the  recurved 
limb  of  the  body  is  of  the  same  length  as  the  remainder  ;  the  two  halves  twist 
round  each  other  and  produce  an  appearance  which  may  be  mistaken  easily 
for  longitudinal  fission  ;  but  the  actual  division  of  the  body  takes  place  at  the 
point  where  it  is  bent  over,  and  is  transverse. 

With  regard  to  the  development,  nothing  has  been  found  in  the  least  con- 
firmatory of  Schaudinn's  statements  with  regard  to  "  Spirochata  ziemanni" 
with  the  sole  exception  of  the  statements  of  Krzysztalowicz  and  Siedlecki  (901), 
who  profess  to  have  seen  trypanosome-stages  in  the  development  of  Treponema 
paJlidum  ;  but  their  statements  are  entirely  unconfirmed  by  other  investi- 
gators. Of  a  very  opposite  type  are  the  statements  of  Leishman  (902)  with 
regard  to  the  development  of  S.  duttoni  in  the  tick.  The  spirochaete  appears 
to  break  up  into  minute  masses  of  chromatin,  "  coccoid  granules,"  in  the 
ova  and  tissue-cells  of  the  tick.  The  coccoid  granules  appear  to  develop  into 
spirochsetes  again. 

The  observations  of  Leishman  have  recently  been  fully  confirmed  by  the  in- 
vestigations on  the  development  of  Spiroschaudinnia  gallinarum  published  by 
Hinclle  (900),  who  gives  a  useful  diagram  of  the  entire  life-history.  Bosanquet 
(894)  also  observed  the  formation  of  coccoid  bodies  in  Cristispira  anodontce 
by  the  segmentation  of  the  elongated  body  into  a  number  of  coccoid  bodies 
like  a  string  of  beads.  A  development  of  this  type  suggests  very  strongly 
affinities  with  bacteria,  but  none  whatever  with  Protozoa  of  any  class.  The 
coccoid  grains  may  be  compared  with  the  spore-formation  in  bacteria,  and 
with  that  described  by  Gross  (898)  in  Saprospira  grandis.  In  all  cases,  through- 
out the  series  of  living  beings,  wherever  an  organism  exhibits  in  its  fully- 
developed  "  adult "  stage  peculiarities  of  a  special  kind,  it  is  above  all  to 
the  early  developmental  forms  that  the  naturalist  turns  for  indications  of  the 
true  affinities  of  the  organism  in  question. 

Recently  the  structure  of  spirochsetes  has  been  studied  carefully  by  Gross 
(897,  898),  Zuelzer  (904),  and  Dobell  (895),  by  means  of  proper  cytological 
methods  of  technique.  The  results  show  a  complete  difference  in  every 


CLASSIFICATION  OF  THE  MAIN  SUBDIVISIONS    469 

respect  between  spirochsetes  and  trypanosomes  and  other  flagellates.  Tn  the 
words  of  DobelL  "  the  nuclear  and  cytoplasmic  structures  are  wholly  different  ; 
a  trypanosome  has  a  flagellum,  a  spirochsete  has  none  ;  the  crista  is  not  an 
undulating  membrane  ;  the  cell-membranes  are  not  similar  ;  and,  moreover, 
the  method  of  division  is  quite  different  in  the  two  organisms." 

Doflein  (7)  places  the  spirochpetes  as  a  group  named  the  Pro- 
flagellata,  supposed  to  be  transitional  from  bacteria  to  flagellates. 
Zuelzer  (904)  takes  a  similar  view,  rejecting,  however,  any  affinity 
between  spirochsetes  and  Hartmann's  "  Binucleata."  Awerinzew 
(890)  puts  forward  the  remarkable  suggestion  that  the  Flagellata 
"  pass  on  into  different  Binucleata,  and  end  with  the  Spirochceta 


FIG.  194. — Stages  in  the  division  of  Cristispira  pectinis.  A,  B,  Two  successive 
stages  of  the  incurvation  ;  0,  incurvation  complete  ;  D,  division  of  the  body 
at  the  point  where  it  is  bent  back  ;  E,  F,  separation  of  the  two  daughter- 
spirochgetes.  After  Gross  (897). 

{sic)"  from  which  it  would  appear  that  he  regards  the  spirochsetes 
as  the  last  product  of  the  line  of  evolution  that  produced  the 
trypanosomes  and  allied  forms. 

For  the  various  reasons  that  have  been  set  forth  above,  it  appears 
impossible  to  include  the  spirochsetes  any  longer  in  the  Protozoa. 
Do  bell  regards  them  as  "an  independent  group  of  unicellular 
organisms  which  show  very  little  affinity  to  any  other  group." 
Gross,  on  the  other  hand,  considers  that  the  Spironemacea — i.e., 
the  genera  Cristispira,  Saprospira,  and  Spironema,  in  the  sense  in 
which  this  genus  is  understood  by  him  (see  above) — form  a  family 
which  can  be  ranked  in  the  bacteria,  but  which  is  related  to  the 
Cyanophyceae,  especially  the  Oscillatorise. 


470  THE  PROTOZOA 

THE   CHLAMYDOZOA. 

The  name  Chlamydozoa  of  Prowazek  (Strongyloplasmata,  Lip- 
schiitz)  was  proposed  in  order  to  include  in  the  first  place  a  class  of 
highly  problematic  organisms  believed  to  be  the  causes  of  certain 
diseases  of  man  or  animals.  It  is  not  yet  certain  exactly  what 
diseases  are  to  be  referred  to  Chlamydozoa.  According  to  Hart- 
maim  (909),  undoubted  chlamydozoal  diseases  are  vaccinia  and 
variola,  trachoma,  and  molluscum  contagiosuni,  amongst  human 
beings,  and  in  birds  epithelioma  contagiosum  and  diphtheria. 
Further  diseases  probably  attributable  to  Chlamydozoa  are  hydro- 
phobia, scarlet  fever,  measles,  foot-and-mouth  disease  of  animals, 
and  "  Gelbsucht  "  of  silkworms.  In  all  these  diseases  the  virus  has 
certain  common  properties,  while  exhibiting  specific  peculiarities 
in  each  case.  It  can  pass  through  ordinary  bacterial  filters  without 
losing  its  virulence,  and  it  produces  characteristic  reaction-products 
or  cell-inclusions  in  the  infected  cell. 

In  order  to  understand  why  these  organisms  should  be  men- 
tioned in  a  book  dealing  with  Protozoa,  the  subject  is  best  dealt 
with  in  an  historical  manner.  The  advances  in  the  knowledge  of 
the  diseases  mentioned  may  be  summarized  briefly  in  four  principal 
stages  : 

1 .  Various  investigators  at  different  times  have  made  known  the 
existence  of  peculiar  cell-inclusions  in  the  infected  cells  in  a  certain 
class  of  diseases,  inclusions  which  have  been  known  by  the  names 
of  their  discoverers — for  instance,  in  trachoma  (Prowazek's  bodies), 
vaccinia    (Guarnieri's    bodies),    scarlet   fever    (Mallory's    bodies), 
hydrophobia  (Negri's  bodies),  etc. 

2.  By  many  investigators  the  characteristic  cell-inclusions  were 
identified  as  the  actual  parasitic  organisms  causing  the  disease. 
They  received  zoological  names,  were  referred  to  a  definite  position 
in  the  ranks  of  the  Protozoa,  and  attempts  were  made  to  work  out 
and  construct  a  developmental  cycle  for  them.     The  supposed 
parasites  of  molluscum  contagiosum  were  referred  to  the  coccidia  ; 
those  of  vaccinia  and  variola  were  given  the  name  Cytoryctes  ;  of 
hydrophobia,  Neuroryctes  ;  of  scarlet  fever,  Cydasterium. 

Calkins  (908)  studied  in  great  detail  the  cell-inclusions  of  vaccine 
and  smallpox,  and  described  a  complete  developmental  cycle,  in  its 
main  outlines  as  follows  :  The  primary  infection  is  brought  about, 
probably,  at  some  spot  on  the  mucous  membrane  of  the  respiratory 
or  buccal  passages  by  air-borne  germs  (spores).  After  active  pro- 
liferation at  the  seat  of  the  primary  infection,  the  parasites  are 
carried  to  all  parts  of  the  body  in  the  circulation,  probably  during 
the  initial  fever.  These  two  early  phases  are  hypothetical.  The 
third  phase  is  the  appearance  of  the  parasites  in  the  cells  of  the 


CLASSIFICATION  OF  THE  MAIN  SUBDIVISIONS    471 

stratified  epithelium  of  the  epidermis.  In  this  situation  they  run 
through  two  cycles— the  one  cytoplasmic,  the  other  intranuclear. 
The  first  is  the  vaccine-cycle,  and  is  the  only  part  of  the  develop- 
ment  of  which  the  harmless  vaccine-organism  is  capable  ;  the 
variola-organism,  however,  after  passing  through  a  vaccine-cycle 
proceeds  to  the  extremely  pathogenic  intranuclear  cycle. 

The  vaccine-cycle,  according  to  Calkins,  begins  with  the  appear- 
ance of  "  gemmules  "  in  the  cytoplasm  of  the  cells  affected.  Each 
gemmule  is  a  minute  grain  of  chromatin  without  cytoplasm  of  its 
own  at  first,  but  as  it  grows  a  cytoplasmic  body  is  formed.  When 
full-grown,  the  parasite  sporulates  by  fragmentation  of  its  nucleus 
into  a  great  number  of  grains,  which,  as  gemmules,  pass  into  other 
cells  and  repeat  the  development  already  described.  Several 
generations  of  this  type  may  succeed  each  other  before  giving  rise 
to  the  next  type. 

The  intranuclear  variola-cycle  begins  in  the  same  way  with 
gemmules,  which,  however,  penetrate  into  the  nucleus,  and  develop 
a  cytoplasmic  body.  According  to  Calkins,  they  become  sexually 
differentiated,  and  produce  gametes  which  conjugate.  The  final 
result  is  the  production  of  numerous  spores,  which  are  probably  the 
means  of  spreading  the  infection. 

Calkins  referred  Cytoryctes  to  the  Microsporidia.  Now,  however, 
he  inclines  to  the  opinion  that  the  genus  should  be  placed  amongst 
the  Rhizopods  (4). 

Negri  (910)  also  describes  a  developmental  cycle  for  Neuroryctes 
hydrophobia,  which  he  regards  as  a  true  Protozooii,  and  which 
Calkins  refers  also  to  the  Rhizopoda.  Siegel  (914)  describes  under 
the  name  Cytorhyctes  organisms  of  a  type  perfectly  different  from 
those  described  by  Calkins.  He  distinguishes  four  species — Cyto- 
rhyctes vaccinice  of  vaccine  and  smallpox,  C.  luis  of  syphilis,  G.  scarla- 
tince  of  scarlet  fever,  and  C.  aphtkarum  of  foot-and-mouth  disease. 

3.  The  parasitic  life-cycles  described  by  Calkins  and  others  have 
been  criticized  by  a  number  of  investigators,  who  have  maintained 
that  the  bodies  in  question  are  not  Protozoa,  nor  even  independent 
living  organisms  at  all,  but  merely  degeneration-products  of  the  cell 
itself,  provoked  by  a  virus  yet  to  be  found.  Thus,  with  regard  to 
Guarnieri's  bodies  (Cytoryctes)  of  vaccine,  it  is  maintained  by  Foa, 
Prowazek,  and  others,  that  they  consist  of  nucleolar  substance 
(plastin)  extruded  from  the  nucleus  ;  that  they  have  no  definite 
developmental  cycle  ;  and  that  infection  can  be  produced  by  lymph 
in  which  Guarnieri's  bodies  have  been  destroyed,  or  by  tissue  in 
which  they  are  not  present.  With  regard  to  the  Negri  bodies, 
Acton  and  Harvey  (906)  come  to  the  same  conclusions,  and  state 
that  similar  nucleolar  extrusions  can  be  brought  about  also  by 
other  stimuli  than  the  rabies- virus. 


472  THE  PROTOZOA 

4.  The  foregoing  sceptical  phase  has  been  succeeded  by  the  positive 
belief  that  the  true  parasitic  organism  in  these  diseases  consists  of 
certain  minute  bodies — the  Chlamydozoa  or  strongyloplasms.* 

The  chief  characteristics  of  the  Chlamydozoa,  according  to 
Prowazek  and  Lipschiitz  (913),  are,  first,  their  minute  size,  smaller 
than  any  bacteria  hitherto  known,  enabling  them  to  pass  the 
ordinary  bacterial  filters  ;  secondly,  that  they  develop  within  cells, 
in  the  cytoplasm  or  nucleus,  and  produce  characteristic  reaction- 
products  and  enclosures  of  the  cell  (their  position  within  the  cell 
is  not  the  result  of  phagocytosis)  ;  thirdly,  that  they  pass  through 
a  series  of  developmental  stages,  and  are  specially  characterized  by 
their  mode  of  division,  which  is  not  a  simple  process  of  splitting, 
as  in  bacteria,  but  is  effected  with  formation  of  a  dumb-bell-shaped 
figure,  as  in  the  division  of  a  centriole.  Two  dots  are  seen  con- 
nected by  a  fine  line  like  a  ceiitrodesmose,  which  becomes  drawn  out 
until  it  snaps  across  the  middle,  and  its  two  halves  are  then  re- 
tracted into  the  body.  Chlamydozoa  have  not  yet  been  grown 
successfully  in  cultures,  but  infections  can  be  produced  with  pure 
colloid-filtrates,  free  from  bacteria,  but  containing  the  minute 
bodies  themselves.  They  are  characteristically  parasites  of  epi- 
blastic  cells  and  tissues. 

As  an  example  of  the  development  of  a  chlamydozoon  may  be 
taken  that  of  the  vaccine- virus,  which,  according  to  Prowazek  (913) 
and  Hartrnami  (909),  is  briefly  as  follows  : 

1.  The  infection  begins  and  ends  with  numerous  "  elementary 
corpuscles  "  (gemmules  of  Calkins  ?),  which  occur  both  within  and 
amongst  the  cells .  They  are  very  minute,  and  can  pass  bacterial  filters. 

2.  Within  the  cells  the  elementary  corpuscles  grow  into   the 
larger  "  initial  bodies." 

3.  The  infected  cell  extrudes  nucleolar  substance — plastin — from 
its  nucleus,  which  envelops  the  parasites  as  in  a  mantle  (hence  the 
name  Chlamydozoa,  from  x^a/^'«,  a  mantle),  thus  producing  in  the 
case  of  vaccine  the  characteristic  Guarnieri's  bodies,  in  which  the 
parasites    multiply.     It    is    this    mantle    of    nucleolar    substance, 
apparently,  which  represents  the  "  cytoplasm  "  of  Cytoryctes,  as 
described  by  Calkins. 

The  name  Chlamydozoa,  as  denoting  a  class  of  microscopic  organisms,  must 
on  no  account  be  confused  with  the  names  Cytoryctes,  Neuroryctes,  etc.,  which 
represent  the  generic  names  of  the  supposed  parasites  of  variola  and  rabies  re- 
spectively. To  those  who  regard  Cytoryctes,  etc.,  as  true  organisms,  the  Chlamydo- 
zoa are  merely  chrornidia  or  dots  of  chromatin  in  the  body  of  the  parasite  ;  to 
those  who  believe  in  the  Chlamydozoa  as  complete  organisms,  Cytoryctes,  etc., 
are  cell-inclusions  or  degeneration-products  of  the  nucleus.  The  conceptions 
implied  in  the  words  Chlamydozoa  and  Cytoryctes  respectively  are  antagonistic 
and  mutually  destructive  ;  if  the  one  is  a  reality,  the  other  is  non-existent.  It  is 
altogether  incorrect  to  speak  of  Cytoryctes,  Neuroryctes,  etc.,  as  genera  of  Chlamy- 
dozoa. 


CLASSIFICATION  OF  THE  MAIN  SUBDIVISIONS    473 

4.  Finally,  the  Guarnieri's  body  breaks  up,  and  the  cell  becomes 
full  of  initial  corpuscles,  which  divide  up  in  their  turn  into  numerous 
elementary  corpuscles,  and  the  cycle  is  complete. 

An  interesting  problem,  from  both  the  medical  and  biological  points  of 
view,  is  that  of  the  relation  of  the  organism  of  vaccinia  (cow-pox)  to  that  of 
variola  (small-pox).  It  is  well  known  that  an  inoculation  with  vaccine-lymph 
(vaccination)  produces  a  transitory  local  disturbance  which  confers  partial 
immunity  against  infection  with  variola.  It  does  not  seem  to  be  quite  clear 
whether  the  organisms  of  vaccinia  and  variola  are  to  be  regarded  as  two 
distinct  species  or  as  two  phases  or  conditions  of  the  same  species  of  or- 
ganism ;  the  latter  is  the  view  of  Calkins,  as  stated  above.  Manson  has 
suggested  (Brit.  Med.  Journ.,  1905,  ii.,  p.  1263)  that  the  relationship  between 
the  organisms  of  vaccinia  and  variola  may  be  similar  to  that  between 
Leislimania  tropica,  of  Oriental  Sore,  and  L.  donovani,  of  Kala-azar.  No 
evidence  has  been  brought  forward  as  yet,  however,  to  show  that  an  infection 
with  Oriental  Sore  confers  any  immunity  against  Kala-azar. 

The  Chlamydozoa  have  been  most  studied  in  those  cases  where 
their  power  of  producing  disease  has  forced  them  upon  the  atten- 
tion of  medical  investigators,  but  it  is  not  to  be  supposed  that  as  a 
group  of  organisms  they  occur  solely  as  parasites  of  higher  animals. 
It  is  probable  that  they  are  of  widespread  occurrence,  and  that  the 
peculiar  nuclear  parasite  of  Amoeba,  known  as  Nucleophaga,  Dan- 
geard,  for  instance,  should  be  referred  to  the  Chlamydozoa  (com- 
pare Schepotieff,  269),  and  perhaps  also  the  similar  parasite  of 
Paramecium  described  by  Calkins  under  the  name  Caryoryctes, 
No  Chlamydozoa  are  known,  however,  to  occur  as  free-living,  non- 
parasitic  organisms,  but  this  circumstance  may  be  due  to  their 
extreme  minuteness  ;  the  species  known  owe  their  detection  to  the 
disturbances  they'  cause  in  their  hosts.  Finally,  it  must  be  men- 
tioned that  the  parasitic  theory  of  cancer,  sometimes  thought  to  be 
long  since  defunct,  has  been  revived  recently  by  Awerinzew  (907), 
who  is  of  opinion  that  cancer  is  caused  by  intranuclear  parasites  of 
the  nature  of  Chlamydozoa. 

Such,  briefly  summarized,  is  the  present  position  of  the  problem. 
Future  research  must  decide  the  truth  or  falsity  of  one  or  the 
other  of  the  solutions  that  have  been  advocated.  It  only  remains 
to  discuss  briefly  the  nature  of  the  Chlamydozoa,  if  the  interpreta- 
tion of  Prowazek  and  his  adherents  be  accepted.  According  to 
Prowazek  and  Lipschiitz  (913),  the  Chlamydozoa  belong  neither  to 
the  Bacteria  nor  to  the  Protozoa.  Hartmann  (909),  however,  seems 
to  consider  that  their  development  and  their  characteristic  mode  of 
division  are  Protozoan  characteristics.  The  "  development,"  how- 
ever, seems  to  consist  of  little,  if  anything,  more  than  growth  in  size. 
As  "elementary  corpuscles"  they  are  smaller,  as  "initial  bodies" 
larger.  The  dumb-bell-shaped  figure  seen  in  division  may  mean 


474  THE  PROTOZOA 

simply  that  their  substance  is  of  a  viscid  or  semifluid  nature,  and 
that  their  bodies  are  not  limited  by  a  membrane  ;  consequently, 
when  the  two  halves  travel  apart  in  the  process  of  division,  the 
substance  of  the  body  is  drawn  out  into  a  connecting  thread  until 
its  surface  tension  overcomes  its  cohesion.  On  the  other  hand, 
they  exhibit  nothing  of  cell-structure  or  of  any  other  characteristics 
which  indicate  any  affinity  to  the  Protozoa.  Their  type  of  organiza- 
tion seems  to  be  the  simplest  possible  in  a  living  body — a  mere 
grain  of  chromatin  without  cytoplasm,  and  without  a  membrane 
or  envelope  of  any  kind.  In  the  latter  respect  they  appear  to  be 
of  a  simpler  type  of  organization  than  any  bacterium,  and  perhaps 
represent  more  nearly  than  any  other  known  organism  the  simplest 
possible  form  of  living  being. 

Bibliography. — For  references  see  p.  504. 


Ite  domum,  saturce,  venit  Hesperus,  ite  capellce. 


BIBLIOGRAPHY 

The  references  to  literature  are  numbered  consecutively,  but  are  grouped  according 

to  the  chapters. 
An  asterisk  (*)  attached  to  a  reference  indicates  that  the  ivork  in  question  contains 

full  references  to  the  previous  literature  of  the  subject. 
Memoirs  in  which  only  new  species  are  described  are  not  cited,  unless  there  is  some 

special  reason  for  doing  so.     All  new  species  are  recorded  in  the  "  Zoological 

Record"  published  annually  by  the  Zoological  Society  of  London  ;  the  last  volume 

published  up  to  date  is  that  for  1910  ,•  the  volume  for  1911  will  appear  towards 

the  end  of  1912. 
The  titles  of  the  subject-matter  of  articles  are  in  many  cases  not  given  verbatim,  but 

in  abbreviated  form. 
The  abbreviations  employed  for  the  titles  of  periodicals  are  given  below.     (In  other 

cases  the  titles  of  periodicals  are  abbreviated  in  a  manner  which  does  not  require 

special  explanation.) 

A.I.C.P.  Archives  do  Institute  Bacteriologico  Camara  Pestana  (Lisbon). 

A. I. P.  Annales  de  1'Institut  Pasteur  (Paris). 

A.K.G.A.  Arbeiten  aus  dem  kaiserlichen  Gesundheitsamte  (Berlin). 

A.P.K.  Archiv  fiir  Protistenkunde  (Jena). 

A.S.T.H.  Archiv  fiir  Schiffs-  und  Tropenhygiene  (Leipzig). 

A.T.M.P.  Annals  of  Tropical  Medicine  and  Parasitology  (Liverpool). 

A.Z.E.  Archives  de  Zoologie  experimentale  et  generale  (Paris). 

B.A.S.C.  Bulletin  Internationale  de  I'Acadeniie  des  Sciences  a  Cracovie. 

B.B.  Biological  Bulletin  (Woods  Holl,  Mass.). 

B.C.  Biologiscb.es  Centralblatt  (Leipzig). 

B.I.P.  Bulletin  de  1'Institut  Pasteur  (Paris). 

B.S.P.E.  —  de  la  Societe  de  Pathologic  Exotique  (Paris). 

B.S.Z.F.  —  de  la  Societe  Zoologique  de  France  (Paris). 

C.B.B.P.K.  Centralblatt   fiir   Bakteriologie,    Parasitenkunde   und   Infectiona- 

krankheiten  (Jena). 

C.R.A.S.  Comptes-rendus  hebdoniadaires  des  Seances  de  1'Academie    des 

Sciences  (Paris). 

C.R.S.B.  -  des  Seances  et  Memoires  de  la  Societe  de  Biologic  (Paris). 

J.E.M.  Journal  of  Experimental  Medicine  (Baltimore). 

J.E.Z.  —  of  Experimental  Zoology  (Baltimore). 

J.H.  —  of  Hygiene  (Cambridge). 

J.L.S.  —  of  the  Linnean  Society  :  Zoology  (London). 

M.I.O.C.  Memorias  do  Institute  Oswaldo  Cruz  (Rio  de  Janeiro). 

P.R.S.  Proceedings  of  the  Royal  Society  of  London. 

Py.  Parasitology  (Cambridge). 

P.Z.S.  Proceedings  of  the  Zoological  Society  of  London. 

Q.J.M.S.  Quarterly  Journal  of  Microscopical  Science  (London). 

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Z.H.        -  fiir  Hygiene  und  Infectionskrankheiten  (Leipzig). 

Z.w.Z.  —  fiir  wissenschaftliche  Zoologie  (Leipzig). 

475 


476  THE  PROTOZOA 

CHAPTER  I 

General  Works  on  Protozoa. 

(I)  BRTTMPT,  E.  (1910).     Precis  de  Parasitologie.     Paris  :  Masson  et  Cie. 

*(2)  BUTSCHLI,  0.  (1882-1889).     Protozoa.     Bronn's  Klassen  und  Ordnungen  die 
Thier-Reichs,  I. 

(3)  (1910).     Vorlesungcn      iiber      vergleichcnde      Anatomie,       1.     Leipzig  : 

W.  Engelmann. 

(4)  CALKINS,  G.  N.  (1901).     The  Protozoa.     New  York  :  Macmillan  and  Co. 

*(5)  (1909).     Protozoology.     New  York  and  Philadelphia  :  Lea  and  Fiebiger. 

*(6)  DELAGE,  Y.,  and  HEROUARD,  E.   (1896).     Traite  de  Zoologie  Concrete,  I. 

Paris  :  Schleicher  Freres. 

*(7)  DOFLEIN,  F.  (1911).     Lehrbuch  der  Protozoenkunde.     Third  edition.     Jena: 
Gustav  Fischer. 

(8)  HARTOG,  M.  (1906).     Protozoa.     Cambridge  Natural  History,  vol.  i.     London: 

Macmillan  and  Co. 

(9)  KEKT,  W.  S.   (1880-1882).     A  Manual  of  the  Infusoria.     London  :  David 

Bogue. 

*(10)  LANG,  A.  (1901).     Lehrbuch  der  vergleichenden  Anatomie  der  wirbellosen 
Thiere,  2te  Auflage.     Jena  :  Gustav  Fischer. 

(II)  LANKESTER,    E.    R.     (1891).     Protozoa.     Encyclopaedia    Britannica,    ninth 

edition  ;  reprinted  in  Zoological  Articles.     London  :  A.  and  C.  Black. 

(12)  (1903  and    1909).     A  Treatise   on   Zoology.     Part   I.,    Fascs.    1   and   2. 

London  :  A.  and  C.  Black. 

(13)  MINCHIN,  E.  A.   (1907).     Protozoa.     Allbutt  and  Rolleston  :  A  System  of 

Medicine,  vol.  ii.,  part  ii.,  p.  9. 

(14)  PROWAZEK,  S.  V.,  and  others  (1911).     Handbuch  der  Pathogenen  Protozoen. 

Leipzig  :  J.  A.  Barth.     Lief.  1  and  2. 

(15)  ROLLESTON,  G.,  and  JACKSON,  W.  H.  (1888).     Forms  of  Animal  Life.     Second 

edition.     Oxford  :  Clarendon  Press. 


CHAPTER  II 

In  addition  to  the  general  works  cited  under  the  previous  chapter,  see  especially  : 

(16)  GOODEY,  T.  (1911).     A  Contribution  to  our  Knowledge  of  the  Protozoa  of 

the  Soil.     P.R.S.  (B.),  Ixxxiv.,  p.  165. 

(17)  LATJTERBORN,  R.  (1901).     Die  "  sapropelische  "  Lebewelt.     Z. A.,  xxiv.,  p.  50. 

(18)  LAVERAN,  A.,  and  MESNIL,  F.  (1899).     De  la  Sarcocystine,  toxine  des  Sarco- 

sporidies.     C.E.S.B.,  Ii.,  p.  311. 

(19)  --  and  PETTIT,  A.  (1911).     Les  trypanotoxines.     B.S.P.E.,  iv.,  p.  42. 

(20)  MESNIL,  F.  (1905).     L'Heredite  dans  les  Maladies  a  Protozoaires.     B.I. P., 

in.,  p.  401. 

(21)  MINCHIN,    E.    A.    (1910).     Phenomena    of    Parasitism    amongst    Protozoa. 

Journ.  Quekett  Microscop.  Club  (2),  xi.,  p.  1. 

(22)  ROUDSKY,    D.    (1910).     Le   Trypanosoma  lewisi   Kent   renforce.     C.R.S.B., 

Ixix.,  p.  384. 

(23)  —  (1911).     La  possibilite  de  rendre  le   Trypanosoma  lewisi  virulent  pour 

d'autres  rongeurs  que  le  rat.  O.R.A.S.,  clii.,  p.  56.  (See  also  Bulletin  of 
the  Sleeping  Sickness  Bureau,  vol.  iii.,  pp.  81  and  265,  for  further  references 
on  this  subject.) 

(24)  RUSSELL,   E.  J.,  and  HUTCHINSON,   H.   B.   (1909).     The  Effect  of  Partial 

Sterilization  of  Soil  on  the  Production  of  Plant  Food.  Journ.  Agric.  Sci., 
iii.,  p.  111. 

(25)  TEICHMANN,  E.  (1910).     Das  Gift  der  Sarcosporidien.     A.P.K.,  xx.,  p.  97. 

(26)  --  and  BRAUN,  H.  ( 1911).    Ein  Protozoentoxin  (Sarcosporidiotoxin).    A.P.K., 

xxii.,  p.  351. 
»(27)  WENDELSTADT  and  FELLMER,  T.   (1910).     Einwirkung  von  Kaltbliiterpas- 

sagen  auf  Nagana-  und  Lewisi-Trypanosomen.     Zeitschr.  f.  Immunitdts- 

forsclmng,  v.,  p.  337. 
•(28)  WINTER,  P.  W.  (1907).     Untersuchung  iiber  Peneroplis  pertusus  (Forskal). 

A.P.K.,  x.(  p.  1. 


BIBLIOGRAPHY  477 


CHAPTER  III 

In  addition  to  the  general  works  cited  under  Chapter  L,  see  especially  : 

(29)  HERON-ALLEN,  E.,  and  EARLAND,  A.  (1909).     A  New  Species  of  Technitella. 

Journ.  Quekett  Microsc.  Club  (2),  x.,  p.  403. 

(30)  KOLTZOFF,  N.  K.   (1903).     Fornibestinimende  elastische  Gebilde  in  Zellen. 

B.C.,  xxiii.,  p.  680. 

(31)  —  (1906).     Die  Gestalt  der  Zelle.     Arch.  mikr.  Anat.,  Ixvii.,  p.  364. 

(32)  PROWAZEK,  S.  v.  (1908).     Biologie  der  Zellen,  I.     B.C.,  xxviii.,  p.  782. 

(33)  -  -  (1909).     Theorie  der  Cytomorphe.     Z.A.,  xxxiv.,  p.  712. 

(34)  RHTTJIBLER,  L.  (1898).     Physikalische  Analyse  von  Lebenserscheinungen  der 

Zelle,  I.     Arch.  Entwicklungsmech.,  vii.,  p.  103. 

(35)  —  (1902).     Die  Doppelschalen  von  Orbitolites.     A.P.K.,  L,  p.  193. 

(36)  VERWORN,  M.  (1888).     Biologische  Protisten-Studien.     Z.w.Z.,  xlvi.,  p.  455. 

CHAPTER  IV 

In  addition  to  Nos.  34  and  35,  see  : 
*(37)  BUTSCHIJ,  0.  (1894).     Microscopic  Foams  and  Protoplasm.     (Translation 

by  E.  A.  Minchin.)     London  :  A.  and  C.  Black. 
(38)  FATJRE'-FREMIET,  E.  (1908).     La  Structure  des  Matieres  Vivantes.     B.S.Z.F., 

xxxiii.,  p.  104. 
*(38'5)  —  (1910).     Les  Mitochondries  des  Protozoaires  et  des  Cellules  sexuelles. 

Arch.  d'Anat.  Microsc.,  xi.,  p.  457. 
*(39)  FISCHER,  A.  (1899).     Fixirung,  Farbung  und  Bau  des  Protoplasmas.     Jena  : 

Gustav  Fischer. 

(40)  PvHTTMBLER,  L.  (1902).     Der  Aggregatzustand  und  die  physikalischen  Beson- 

derheiten  des  lebenden  Zellinhalts.     Z.a.P.,  ii.,  p.  183. 

CHAPTER  V 

In  addition  to  the  references  cited  above  for  Chapters  I.  and  III.,  and  those 
cited  below  for  Chapter  X.,  see  : 

(41)  GOLDSCHMIDT,   R.    (1907).     Lebensgeschichte  der  Mastigamoben.     A.P.K., 

Suppl.  L,  p.  83. 

(42)  MINCHIN,  E.  A.,  and  WOODCOCK,  H.  M.  (1911).     The  Trypanosome  of  the 

Little  Owl  (Athene  noctua).     Q.J.M.S.,  Ivii.,  p.  141. 

(43)  SCHATJDINN,  F.  (1894).     Gamptonema  nutans.     S.B.A.B.,  lii.,  p.  1227.     Re- 

printed, Schaudinn's  Arbeiten,  1911,  p.  50. 

(44)  SCHTJBERG,  A.  (1905).     Cilien  und  Trichocysten  einiger  Infusorien.     A.P.K., 

vi.,  p.  61. 

CHAPTER  VI 

In  addition  to  the  works  cited  here,  see  also  the  bibliographical  references  for 
Chapter  VII. 
(45)~ARAGAO,  H.  DE  B.  (1910).     Ueber  Polytomella  agilis.     M.I.O.C.,  ii.,  p.  42. 

(46)  AWERINZEW,  S.  (1907).     Struktur  des  Protoplasma  und  des  Kerns  von  Amoeba 

proteus  (Pall.).     Z.A.,  xxxii.,  p.  45. 

(47)  —  (1909).     Entwicklungsgeschichte    von    Coccidien    aus    dem    Darme    von 

Cerebratulus  sp.  (Barrouxia  spiralis).     A.P.K.,  xviii.,  p.  11. 

(48)  CALKINS,  G.  N.  (1903).     The  Protozoan  Nucleus.     A.P.K.,  ii.,  p.  213. 
(48'5)  CHAGAS,  C.   (1911).     Die  zyklischen  Variationen  des  Caryosoms  bei  zwei 

Arten  parasitischer  Ciliaten.     M.I.O.G.,  iii.,  p.  136. 
*(49)  CHATTON,  E.  (1910).     La  structure  du  Noyau  et  la  Mitose  chez  les  Amcebiens. 

A.Z.E.  (5),  v.,  p.  267. 
(50)  COLLIN,    B.    (1909).     La    Conjugaison    d'Anoplophrya    branchiarum    (Stein) 

(A.  circulans,  Balbiani).     A.Z.E.  (5),  i.,  p.  345. 
*(51)  DOBELL,    C.    C.    (1909).     Chromidia    and    the    Binuclearity    Hypothesis. 

Q.J.M.S.,  liii.,  p.  279. 


478  THE  PROTOZOA 

*(52)  DOBELL,  C.  C.  (1911).      Contributions  to  the  Cytology  of  the  Bacteria. 
Q.J.M.S.,  Ivi.,  p.  395.     "  Autorreferat  "  in  A.P.K.,  xxiv.,  p.  84. 

(53)  ENTZ,  G.  (1909).     Organisation  und  Biologic  der  Tintinniden.     A.P.K.,  xv., 

p.  93. 

(54)  ERHARD,  H.  (1911).     Die  Henneguy-Lenhosseksche  Theorie.     Ergebn.  Anat. 

Entwick.,  xix.  (second  half),  p.  893. 

(55)  FAURE-FREMIET,  E.  (1910).     Appareil  nucleaire,  Chromidies,  Mitochondries. 

A.P.K.,  xxi.,  p.  186. 

(56)  FRANCA,  C.,  and  ATHIAS,  M.  (1907).     Les  Trypanosomes  des  Amphibiens,  II. 

Le  Trypanosoma  rotatorium  de  Hyla  arborea.     A.I.G.P.,  i.,  p.  289. 
•(57)  GOLDSCHMIDT,  R.  (1904).     Die  Chromidien  der  Protozoen.     A.P.K.,  v.,  p-  126. 

(58)  —  and  POPOFF,  M.  (1907).     Die  Karyokinese  der  Protozoen  und  der  Chromi- 

dialapparat  der  Protozoen-  und  Metazoenzelle.     A.P.K.,  viii.,  p.  321. 

(59)  GTJILLERMOND,  A.  (1910).    Corpuscules  metachromatiques  ou  Grains  de  Volu- 

tine.     A.P.K.,  xix.,  p.  289. 

(60)  HARTMANN,  M.  (1909).     Polyenergide  Kerne.     B.C.,  xxix.,  pp.  481  and  491. 

(61)  —  (1911).     Die  Konstitution  der  Protistenkerne.     Jena  :  Gustav  Fischer. 

(62)  --  and  CHAGAS,  C.  (1910).     Flagellatenstudien.     M.I.O.C.,  ii.,  p.  64. 

(63)  —  and  PROWAZEK,  S.  v.  (1907).     Blepharoplast,  Caryosom  und  Centrosom. 

A.P.K.,  x.,  p.  306. 

(64)  HERTWIG,  R.  (1898).     Kerntheilung,  Richtungskorperbildung  und  Befruch- 

tung  von  Actinosphcerium  Eichhorni.      Abhandl.   bayer.   AJcad.   (II.   Cl.), 
xix.,  p.  631. 

(65)  —  (1899).     Encystierung  und  Kernvermehrung  bei  Arcella  vulgaris.     Kup- 

ffer's  Festschrift,  p.  567. 

(66)  —  (1902).     Die  Protozoen  und  die  Zelltheorie.     A.P.K.,  i.,  p.  1. 

•(67)  --  (1903).     Das  Wechselverhaltnis  von  Kern  und  Protoplasma.     8.B.G.M.P., 
xviii.,  p.  77. 

(68)  —  (1907).     Der  Chromidialapparat  und  der  Dualismus  der  Kernsubstanzen. 

Ibid.,  xxiii.,  p.  19. 

(69)  JAHN,  E.  (1904).     Kernteilung  und  Geisselbildung  bei  den  Schwarmern  von 

Stemonitis  ftaccida.     Ber.  Deutsch.  Bot.  Ges.,  xxii.,  p.  84. 

(70)  JANICKI,    C.    (1910).     Parasitische   Flagellaten,    I.     Lophomonas   blattarum, 

L.  striata.     Z.w.Z.,  xcv.,  p.  243. 

(71)  —  (1911).     Der     Parabasalapparat     bei     parasitischen     Flagellaten.     B.C., 

xxxi.,  p.  321. 

(71'5)  —  (1912).     Parasitische    Arten    der    Gattung    Paramaba.      Verh.    Natur- 
forsch.  Ges.  Basel,  xxiii. 

(72)  LEGER,  L.,  and  DUBOSCQ,  0.  (1911).     Deux  Gregarines  des  Crustacea.    A.Z.E. 

(5),  vi.,  "  Notes  et  Revue,"  p.  lix. 

(73)  MAIER,  H.  N.  (1903).     Der  feinere  Bau  der  Wimperapparate  der  Infusorien. 

A.P.K.,  ii.,  p.  73. 

(74)  MESNIL,  F.  (1905).     Chromidies  et  Questions  connexes.     B.I. P.,  iii.,  p.  313. 

(75)  MINCHIN,  E.  A.  (1911).     Some  Problems  of  Evolution  in  the  Simplest  Forms 

of  Life.     Journ.  Quekett  Microsc.  Club  (2),  xi.,  p.  165. 

(76)  NAGLER,  K.  (1911).     Protozoen  aus  einem  Almtiimpel,  I.     Arnosba  hartmanni, 

n.  sp.     Anhang  :  Zur  Centriolfrage.     A.P.K.,  xxii,  p.  56. 

77)  POPOFF,  M.  (1909).     Die  Zellgrosse,  ihre  Fixierung  und  Vererbung.     Arch. 
Zellforschung,  iii.,  p.  124. 

(78)  REICHENOW,  E.   (1910).     Hcemogregarina  stepanowi.     Die  Entwicklungsge- 

schichte  einer  Hamogregarine.     A.P.K.,  xx.,  p.  251. 

(79)  ROBERTSON,  M.  (1911).     The  Division  of  the  Collar-Cells  of  the  Calcarea 

Heteroccela.     Q.J.M.S.,  Ivii.,  p.  129. 

(80)  --  and  MINCHIN,  E.  A.  (1910).     The  Division  of  the  Collar-Cells  of  Clathrina 

coriacea.     Q.J.M.S.,  lv.,  p.  611. 

(81)  SCHAUDINN,  F.  (1896).    Der  Zeugungskreis  von  Paramceba  eilhardi.    S.B.A.B., 

p.  31.     Reprinted,  Schaudinn's  Arbeiten,  1911,  p.  115. 

(82)  --  (1896).     Das  Centralkorn  der  Heliozoen.     V.D.Z.G.,  vi.,  p.  113.     (With 

discussion  by  Lauterborn  and  Biitschli.) 

(83)  SIEDLECKI,  M.  (1905).     Die  Bedeutung  des  Karyosoms.     B. A.S.C.,  p.  559. 

(84)  WENYON,  C.  M.  (1911).     Oriental  Sore  in  Baghdad,  together  with  Observa- 

tions on  a  Grogarine  in  Stegomyia  fasciata,  the  Hsemogregarines  of  Dogs, 
and  the  Flagellates  of  House  Flies.     Py.,  iv.,  p.  273. 

(85)  ZTJEI.ZER,  M.  (1904).     Difflugia  urceolata.     A.P.K.,  iv.,  p.  240. 
<86)  --  (1909).     Wagnerdla  borealis.     A.P.K.,  xvii.,  p.  135. 


BIBLIOGRAPHY  479 

CHAPTER  VII 

In  addition  to  the  works  cited  here,  see  also  Nos.  45,  48,  49,  50,  56,  58,  60,  62, 
•64,  66,  69,  70,  71,  71'5,  78,  79,  80,  81,  82,  and  86  above. 

(87)  ARAGAO,  H.  DE  B.  (1904).     Amoeba  diplomitotica.     M.I.O.C.,  i.,  p.  33. 

(88)  AWERINZEW,  S.  (1904).     Teilung  von  Amoeba  proteus.     Z.A.,  xxvii.,  p.  399. 

(89)  HARTMANN,  M.,  and  CHAGAS,  C.  (1910).     Sehlangenhainogregarinen.     A.P.K., 

xx.,  p.  351. 
(90) (1910).     Die  Kernteilung  von  Amoeba  hyalina.     M.I.O.G.,  ii.,  p.  159. 

(91)  HERTWIG,  R.  (1903).     Korrelation  von  Zell-  und  Kerngrosse.     B.C.,  xxiii., 

pp.  49  and  108. 

(92)  —  (1908).     Neue  Probleme  der  Zellenlehre.     Arch.  f.  Zellforschung.  i.,  p.  1. 

(93)  LEBEDEW,  W.  (1908).     Trachelocerca  phcenicopterus.     A.P.K.,  xiii.,  p.  70. 

(94)  MOROFF,  T.  (1908).     Die  bei  den  Cephalopoden  vorkommenden  Aggregata- 

Arten.     A.P.K.,  xi.,  p.  1. 

(95)  NAGLER,    K.    (1909).     Entwicklungsgeschichtliche    Studien    iiber    Amoben. 

A.P.K.,  xv.,  p.  1. 

<96)  —  (1911).     Caryosom   und    Centriol   beim   Teilungsvorgang   von    Chilodon 
uncinatus.     A.P.K.,  xxiv.,  p.  142. 

(97)  PROWAZEK,   S.   v.   (1903).     Die   Kernteilung  des   Entosiphon.     A.P.K.,   ii., 

p.  325. 
(97'5)  REICHENOW,  E.  (1909).     Hcematococcus  pluvialis.     A.K.G.A.,  xxxiii.,  p.  1. 

(98)  SCHAUDINN,  F.  (1894).     Kerntheilung  mit  nachfolgender  Korpertheilung  bei 

Amoeba  crystalligera.     S.B.A.B.,   1894,  p.   1029.     Reprinted,  Schaudinn's 
Arbeiten,  1911,  p.  95. 

499)  —  (1900).     Der  Generationswech.se!  bei  Coccidien.     Zool.  Jahrbucher  (Abth. 
f.  Anat.),  xiii.,  p.  197.     Schaudinn's  Arleiten,  1911,  p.  208. 

(100)  SCHEWIAKOFF,  W.  (1887).     Die  karyokinetische  Kerntheilung  der  Euglypha 

alveolata.     Morph.  Jahrbuch,  xiii.,  p.  193 

(101)  SWARCZEWSKY,  B.    (1908).     Die   Fortpflanzungserscheinungen   bei   Arcella 

vulgaris.     A.P.K.,  xii.,  p.  173. 

CHAPTER  VIII 

In  addition  to  the  works  cited  here,  see  also  Nos.  41,  47,  50,  51,  57,  64,  67,  68, 
74,  75,  81,  85,  92,  93,  99,  and  101. 

(102)  BAITSELL,    G.   A.  (1911).     Conjugation  of  Closely  Related  Individuals  of 

Stylonychia.     Proc.  Soc.  Exper.  Biol.  Med.,  viii.,  p.  122. 

(103)  BOTT,  M.  (1907).     Fortpflanzung  von  Pelomyxa.     A.P.K.,  viii.,  p.  120. 

(104)  CALKINS,    G.   N.    (1904).     Studies  on   the   Life-History   of   Protozoa,    IV. 

J.E.Z.,i.,  p.  423. 

(105)  —  (1906).     The  Protozoan  Life-Cycle.     B.B.,  xi.,  p.  229. 

,(106)  —  and   CTTLL,    S.    W.    (1907).     The   Conjugation   of   Paramecium   aurdia 
(caudatum).     A.P.K.,  x.,  p.  375. 

(107)  DANGEARD,  P.  A.  (1911).     La  Conjugaison  des  Infusoires  cilies.     G.R.A.S., 

clii.,  p.  1032. 

(108)  —  (1911).     La  Fecondation  des  Infusoires  cilies.     C.R.A.S.,  clii.,  p.  1703. 

(109)  DEHORNE,  A.  (1911).     Permutation  nucleaire  dans  la  Conjugaison  de  Col- 

pidium  colpoda.     C.R.A.S.,  clii.,  p.  1354. 

(110)  DOBELL,   C.   C.    (1911).     The   Principles  of  Protistology.     A.P.K.,   xxiii., 

p.  269. 

(111)  DOFLEIN,  F.  (1907).     Die  Konjugation  der  Infusorien.     S.B.G.M.P.,  xxiii., 

p.  107. 

(112)  ENRIQUES,  P.  (1907).     La  Coniugazione  e  il  Differenziamento  sessuale  negli 

Infusori.     A.P.K.,  ix.,  p.  195. 

(113)  —  (1908).     Die  Conjugation  und  sexuelle  Differenzierung  der  Infusorien. 

A.P.K.,  xii.,  p.  213. 

(114)  GEDDES,  P.,  and  THOMSON,  J.  A.  (1901).     The  Evolution  of  Sex.     Revised 

edition.     London. 

(115)  HAMBURGER,  C.   (1908).     Die  Conjugation  von  Stentor  coeruleus.      Z.w.Z., 

xc.,  p.  423. 

(116)  HARTMANN,  M.  (1909).     Autogamie  bei  Protisten.     A.P.K.,  xiv.,  p.  264. 


480  THE  PROTOZOA 

(117)  HARTOG,  M.  (1910).     Apropos  of  Dr.  Hartmann's  "  Autogamie  bei  Proto- 

zoen."     A.P.K.,  xviii.,  p.  111. 

(118)  HERTWIG,  R.  (1902).     Wesen  und  Bedeutung  der  Befruchtung.     Sitzber.  k. 

Akad.  Wiss.  Munchcn.,  xxxii.,  p.  57. 

(119)  —  (1905).     Das  Problem  der  sexuellen  Differenzierung.      V.D.Z.G.,   1905, 

p.  186. 

(120)  HICKSON,  S.  J.  (1910).     The  Origin  of  Sex.     Ann.  Eep.  Trans.  Manchester 

Microsc.  Soc.,  1909,  p.  34. 

(121)  JENNINGS,  H.  S.   (1910).     What  Conditions  induce  Conjugation  in  Para- 

mecium  ?    J.E.Z.,  ix.,  p.  279. 

(122)  MAUPAS,    E.    (1889).     Le  Rajeunissement  karyogamique    chez    les    Cilies. 

A.Z.E.,  (2)  vii.,  p.  149. 

(123)  MULSOW,  K.  (1911).     Fortpflanzungserscheinungen  bei  Monocystis  rostrata. 

A.P.K.,  xxii.,  p.  20. 

(124)  PEAKL,  R.   (1907).     A  Biometrical  Study  of  Conjugation  in  Paramecium. 

Biometrika,  v.,  p.  213. 

(125)  POPOFF,  M.   (1908).     Die  Gametenbildung  und  die  Conjugation  von  Car- 

chesium  polypinum.     Z.w.Z.,  Ixxxix.,  p.  478. 

(126)  PKANDTL,  H.  (1906).     Die  Konjugation  von  Didinium  nasutum.     A.P.K., 

vii.,  p.  229. 

(127)  PROWAZEK,   S.   v.   (1905).     Der  Erreger  der   Kohlhernie,   Plasmodiophora 

brassicce.     A.K.G.A.,  xxii.,  p.  396. 

(128)  --  (1907).     Die  Sexualitat  bei  den  Protisten.     A.P.K.,  ix.,  p.  22. 

(129)  SCHAUDINN,  F.  (1896).     Copulation  von  Actinophrys.     S.B.A.B.,  p.  83. 

(130)  —  (1902).     Krankheitserregende  Protozoen,  II.     Plasmodium  vivax. 

A.K.G.A.,  xix.,  p.  169. 

(131)  -  -  (1903).     Die  Fortpflanzung  einiger  Rhizopoden.     A.K.G.A.,  xix.,  p.  547- 

(132)  --  (1904).     Generations-  und  Wirtswechsel   bei  Trypanosoma  und  Spiro- 

chcete.     A.K.G.A.,  xx.,  p.  387.     Reprinted,  with  "  Nachtrag,"  in  Fritz- 
Schaudinn's  Arbeiten,  1911. 

(133)  --  (1905).     Die  Befruchtung  bei  Protozoen.      V.D.Z.G.,  xv.,  p.  16. 

(134)  SCHILLING,  C.  (1910).     Autogamie  bei  Trypanosoma  lewisi.     A.P.K.,  xix., 

p.  119. 

(135)  STEMPELL,  W.  (1906).     Die  neuere  Protozoenforschung  und  die  Zellenlehre. 

S.  B.  Med.-naturwiss.  Ges.  Miinster  i.  W.,  June  13. 

(136)  STEVENS,  N.  M.   (1910).     The  Chromosomes  and  Conjugation  in  Boveria 

subcylindrica,  var.  concliarum.     A.P.K.,  xx.,  p.  126. 

(137)  VERSLUYS,  J.  (1906).     Die  Konjugation  der  Infusorien.     B.C.,  xxvi.,  p.  46. 

(138)  WOODRUFF,  L.  L.  (1905).     Life-History  of  Hypotrichous  Infusoria.     J.E.Z., 

ii.,  p.  585. 

(139)  --  (1908).     Life-Cycle  of  Paramecium.     Amer.  Nat.,  xlii.,  p.  520. 

(140)  --  (1909).     Further  Studies  on  the  Life-Cycle  of  Paramecium.     B.B.,  xvii.,. 

p.  287. 

(141)  —  (1911).     Two    Thousand    Generations    of    Paramecium.     A.P.K.,    xxi., 

p.  263. 

(142)  —  (1911).     The    Adaptation    of    Paramcecia    to    Different    Environments. 

B.B.,  xxii.,  p.  60. 

(143)  —  and  BAITSELL,  G.  A.  (1911).     Rhythms  in  the  Reproductive  Activity  of 

Infusoria.     J.E.Z.,  xi.,  p.  339. 

CHAPTER  IX 

In  addition  to  the  works  cited  here,  see  also  Nos.  41,  65,  78,  85,  86,  99,  101, 
130,  and  131. 

(144)  ELPATIEWSKY,  W.   (1907).     Fortpflanzung  von  Arcella  vulgaris.     A.P.K., 

x.,  p.  441. 

(145)  KHAINSKY,  A.  (1910).     Uber  Arcellen.     A.P.K.,  xxi.,  p.  165. 

(146)  SCHATJDINN,  F.  (1899).    Der  Generationswechsel  von  Trichosphcerium  sieboldi. 

Anhang.  Abhandl.  Preuss.  Akad.  Wiss. 

(147)  --  (1902).     Cydospora  caryolytica.     A.K.G.A.,  xviii.,  p.  378.     Reprint  in 

Fritz  Schaudinn's  Arbeiten,  1911,  p.  318. 


BIBLIOGRAPHY  481 

CHAPTER  X 

In  addition  to  the  works  cited  below,  see  also  34,  35,  36,  37,  40,  and  237. 

(148)  BARRATT,  J.  0.  W.  (1905).     Die  Kohlensaureproduktion  von  Paramecium 

aurelia.     Z.a.P.,  v.,  p.  66. 

(149)  —  (1905).     Der  Einfluss  der  Konzentration  auf  die  Cheinotaxis.     Z.a.P 

v.,  p.  73. 

(150)  BASS,  C.  C.  (1911).     A  New  Conception  of  Immunity  :  its  Application  to 

the  cultivation  of  Protozoa  and  Bacteria.     Journ.  Amer.  Med    Assoc 
Ivii.,  p.  1534. 

(151)  BOISSEVAIN,   M.    (1908).     Kernverhaltnisse   von   Actinosphcerium  eichhorni 

bei  fortgesetzter  Kultur.     A.P.K.,  xiii.,  p.  167. 

(152)  BORGERT,   A.    (1909).     Erscheinungen  fettiger  Degeneration   bei  tripyleen 

Radiolarien.     A.P.K.,  xvi.,  p.  1. 

(152'5)  BOVARD,  J.  F.  (1907).     Structure  and  Movements  of  Condylostoma  patens. 
Univ.  California  Publ.,  iii.,  p.  343. 

(153)  BUTSCHLI,  0.  (1906).     Zur  Kenntnis  des  Paramylons.     A.P.K.,  vii.,  p.  197. 

(154)  DEGEN,  A.  (1905).     Die  kontraktile  Vacuole  und  die  Wabenstruktur  des 

Protoplasmas.     Bot.  Zeitung,  Ixiii.,  p.  163. 

(155)  DOBELL,  C.  C.  (1907).     Physiological  Degeneration  in  Opalina.     Q.J.M.S,, 

li.,  p.  633. 

(156)  ERDMANN,   R.   (1910).     Depression  und  facultative  Apogamie  bei  Amoeba 

diploidea.     Hertivig's  Festschrift,  i.,  p.  323. 

(157)  GARBOWSKI,  L.   (1907).     Gestaltsveranderung  und  Plasmoptyse.     A.P.K., 

ix.,  p.  53. 

(158)  GIEJISA,  G.  (1911).     FixierungundFarbungderProtozoen.     Vide  Prowazek 

(14),  p.  7. 

(159)  -  -  and  PROWAZEK,  S.  v.  (1908).     Wirkung  des  Chinins  auf  die  Protistenzelle. 

A.S.T.H.,  xii.,  Beiheft  5,  p.  188. 

(160)  GREELEY,  A.  W.  (1902).     Artificial  Production  of  Spores  in  Monas  by  a 

Reduction   of  the   Temperature.       Univ.    Chicago   Decennial   Publ.,    x., 
p.  73. 

(161)  GREENWOOD,  M.  (1886-1887).     Digestive  Processes  of  some  Rhizopods,  I. 

Journ.  Physiol.,  vii.,  p.  253.     II.,  ibid.,  viii.,  p.  263. 

(162)  —  (1894).     Constitution  and  Formation  of  "  Food-Vacuoles  "  in  Infusoria, 

etc.     Phil.  Trans.  (B),  clxxxv.,  p.  355. 

(163)  -  -  and  SAUNDERS,  E.  R.  (1894).     The  Role  of  Acid  in  Protozoan  Digestion. 

Journ.  Physiol.,  xvi.,  p.  441. 

(164)  HERTWIG,    R.    (1904).     Physiologische    Degeneration    bei    Actinosphcerium 

eichhorni.     Haeckel's  Festschrift  (Jena,  G.  Fischer),  p.  301. 

*(165)  JENNINGS,    H.    S.    (1904).       The    Behaviour   of   the    Lower    Organisms. 
Washington  :  Carnegie  Institute. 

(166)  -  -  (1904).     The  Behaviour  of  Paramecium.     Journ.  Comp.  Neurology,  xiv., 

p.  441 ;  Contr.  Zool.  Lab.  University  of  Philadelphia,  xi.,  1905. 

(167)  —  (1904).     The   External   Discharge   of   the   Contractile   Vacuole.     Z.A., 

xxvii.,  p.  656. 

(168)  —  (1904).     Physical  Imitations  of  the  Activities  of  Amoeba.     Amer.  Natural., 

xxxviii.,  p.  625. 

(169)  JOSEPH,  H.,  and  PROWAZEK,  S.  v.  (1902).      Die  Einwirkung  von  Rontgen- 

Strahlen  auf  einige  Organismen.     Z.a.P.,  i.,  p.  142. 

(170)  KANITZ,  A.  (1907).    Der  Einfluss  der  Temperatur  auf  pulsierenden  Vakuolen 

der  Infusorien.     B.C.,  xxvii.,  p.  11. 

(170-5)  KHAINSKY,  A.   (1910).     Morphologic  und  Physiologic  einiger  Infusorien 
(Paramecium  caiidatum).     A.P.K.,  xxi.,  p.  1. 

(171)  LEWIN,  K.  R.  (1910).     Nuclear  Relations  of  Paramecium  caudatiim  during 

the  Asexual  Period.     Proc.  Cambridge  Phil.  Soc.,  xvi.,  p.  39. 

(172)  --  (1911).     Behaviour   of   the    Infusorian    Micronucleus   in    Regeneration. 

P.B.S.,  Ixxxiv.,  p.  332. 

(173)  LIPSKA,  I.  (1910).     L'Influence  de  1'Inanition  chez  Paramecium  caudatum. 

Rev.  Suisse  Zool.,  xviii.,  p.  591. 

(174)  MACKINNON,   D.   (1908).     Encystation  of  Actinosphcerium  eichhorni  under 

Different  Temperatures.     Q.J.M.S.,  Hi.,  p.  407. 

(175)  McLENDON,  J.  F.  (1909).     Protozoan  Studies.     J.E.Z.,  vi.,  p.  265. 

(176)  MAST,  S.  0.  (1910).     Reactions  of  Amoaba  to  Light.     J.E.Z.,  ix.,  p.  265. 

31 


482  THE  PROTOZOA 

(177)  MESNIL,  F.,  arid  MOUTON,  H.  (1903).     Une  Diastase  Proteolytique  Extraite 

dcs  Infusoircs  Cilies.     G.R.8.B.,  lv.,  p.  1016. 
(17S) (1903).     L' Action  Antiproteolytique  Comparee  des  Diverses  Serums 

sur  1'Amibodiastase  etc.     G.R.8.B.,  lv.,  p.  1018. 

(179)  METALNIKOFF,    S.    (1903).     Die   intracellulare    Verdauung.     Bull.    Ac.    St. 

Petersbourg,  xix.,  p.  187. 

(180)  METSCHNIKOFF,  E.  (1889).     La  Digestion  Intracellulaire.     A. I. P.,  iii.,  p.  25. 

(181)  NIRENSTEIN,  E.  (1905).     Ernahrungsphysiologie  der  Protisten.     Z.a.P.,  v., 

p.  434. 

(182)  --  (1910).     Fettverdauung   und   Fettspeicherung   bei   Infusorien.     Z.a.P., 

x.,  p.  137. 

(183)  NOWIKOFF,  M.  (1908).     Die  Wirkung  des  Schilddriisenextrakts  auf  Ciliaten. 

A.P.K.,  xi.,  p.  309. 

(184)  POPOFF,  M.  (1907).    Depression  der  Protozoenzelle  und  der  Geschlechtszellen 

der  Metazoen.     A.P.K.,  Suppl.,  i.,  p.  43. 

(185)  --  (1909).     Der  Einfluss  chemischer  Reagentien  auf  der  Funktionszustand 

der  Zelle.     S.B.G.M.P.,  xxv.,  p.  55. 

{186)  --  (1909).     Einige    Ursachen    der    physiologiscken    Depression    der    Zelle. 
Arch.  Zellforschung,  iv.,  p.  1. 

(187)  PRANDTL,  H.  (1907).     Die  physiologische  Degeneration  der  Amoeba  proteus. 

A.P.K.,  viii.,  p.  281. 

(188)  PROWAZEK,   S.    v.    (1903).      Studien    zur    Biologie   der  Zelle.      Z.a.P.,   ii., 

p.  385. 

<189)  --  (1903).     Regeneration  und  Biologie  der  Protozoen.     A.P.K.,  iii.,  p.  44. 
.(190)  --  (1903).     Degenerative  Hyperregeneration  bei  den  Protozoen.     A.P.K., 

iii.,  p.  60. 

{191)  --  (1908).     Das  Lecithin.     B.C.,  xxviii.,  p.  382. 
{192)  --  (1908).     Einfluss  von  Saurelosungen  niedrigster  Konzentration  auf  die 

Zell-  und  Kernteilung.     Arch.  Entwicklungsmech. ,  xxv.,  p.  643. 
(193)  --  (1909).     Biologie  der  Zellen.     II.  Zelltod  und  Strukturspannung.     B.C., 

xxix.,  p.  291. 
{194)  -  -  (1910).     Die  Physiologic  der  Einzelligen.     Leipzig  :  Teubner. 

(195)  --  (1910).     Giftwirkung  und  Protozoenplasrna.     A.P.K.,  xviii.,  p.  221. 

(196)  --  (1910).     Biologie  der  Protozoen,  V.     A.P.K.,  xx.,  p.  201. 

(197)  PUTTER,    A.    (1900).     Thigmotaxis    bei    Protisten.     Arch.    Anal.    Physiol., 

Physiol.  AM.,  Suppl.  Band,  p.  243. 

(198)  --  (1903).     Die  Wirkung  erhohter  Sauerstoffspanmmg  auf  die  lebendige 

Substanz.     Z.a.P.,  iii.,  p.  363. 

(199)  -  -  (1903).     Reizbeantwortung  der  ciliaten  Infusorien.     Z.a.P.,  iv.,  p.  406. 

(200)  -  -  (1905).     Leuchtende  Organismen.     Z.a.P.,  v.,  Referate,  p.  17. 

(201)  -  -  (1905).     Die  Atmung  der  Protozoen.     Z.a.P.,  v.,  p.  566. 

(202)  —  (1908).     Vergleichende  Physiologie  des  Stoffwechsels.     Abh.  k.  Ges.  W iss. 

Goltingen  (n.F.),  vi.,  p.  1. 

*(202)  --  (1908).     Erforschung  des  Lebens  der  Protisten.     Tigerstedt,  Handbuch 
der  physiologischen  Methodik. 

(203)  RHTJMBLER,    L.     (1905).     Die    Oberflachenkrafte    der    Amoben.     Z.io.Z., 

Ixxxiii.,  p.  1. 

(204)  -  -  (1910).     Die  verschiedenen  Nahrungsaufnahmen  bei  Amoben  als  Folge 

verschiedener  Colloidalzustande  ihrer  Oberflachen.     Arch.  Entwicklungs- 
mech., xxx.,  p.  194. 

(205)  ROESLE,  E.  (1902).     Die  Reaction  einiger  Infusorien  auf  einzelne  Induk- 

tionsschlage.     Z.a.P.,  ii.,  p.  139. 

(206)  SCHEWIAKOFF,  W.  (1893).     Die  Natur  der  sogennanten  Excretkorner  der 

Infusorien.     Z.w.Z.,  Ivii.,  p.  32. 

(207)  SMITH,  G.  (1903).     Actinosphcerium  eichhorni  :  A  Biometrical  Study  in  the 

Mass  Relations  of  Nucleus  and  Cytoplasm.     Biometrika,  ii.,  p.  241. 

(208)  STANIEWICZ,  W.   (1910).     La  Digestion  de  la  Graisse  dans  les  Infusoires 

Cilies.     B.A.8.C.,  p.  199. 

(209)  STATKEWITSCH,  P.  (1905).     Galvanotropismus  uud  Gal vano taxis  der  Ciliata. 

Z.a.P.,  v.,  p.  511. 

(210)  -  -  (1904).     Zur  Methodik  der  biologischen  Untersuchungen  iiber  die  Pro- 

tisten.    A.P.K.,  v.,  p.  17. 

(211)  VERWORN,  M.  (1904).     Die  Localisation  der  Atmung  in  der  Zelle.     Denkschr. 

Ges.  Jena,  xi.,  p.  561. 

(212)  --  (1907).     Allgemeine  Physiologie.     Jena.     Fourth  edition. 


BIBLIOGRAPHY  483 

{213)  WAGER,   H.   (1900).     On  the  Eyespot  and  Flagelluni  of  Euglena  viridis. 
J.L.8.,  xxvii.,  p.  463. 

(214)  WALLENGREN,  H.   (1902).     Inanitionserscheinungen  der  Zelle.     Z.a.P.,  i., 

p.  67. 

(215)  -  -  (1902).     Zur  Kenntnis  der  Galvanotaxis.     Z.a.P.,  ii.,  p.  341. 

(216)  WOODRUFF,  L.  L.  (1908).     Effects  of  Alcohol  on  the  Life-Cycle  of  Infusoria. 

B.B.,  xv.,  p.  85. 

(217)  —  (1911).     The  Effect  of    Excretion  Products  of  Paramecium  on  its  Rate 

of  Reproduction.     J.E.Z.,  x.,  p.  559. 

(218)  --  and  BAITSELL,  G.  A.  (1911).     The  Reproduction  of  Paramecium  aurelia 

in  a  "  Constant  "  Culture  Medium  of  Beef  Extract.     J.E.M.,  xi.,  p.  135. 

(21 9)  -        -  (1911).     The  Temperature  Coefficient  of  the  Rate  of  Reproduction 

of  Paramecium  aurelia.     Amer.  Journ.  Physiol.,  xxix.,  p.  147. 
.(220)  -  -  and  BUNZEL,  H.  H.  (1909).     The  Relative  Toxicity  of  Various  Salts  and 
Acids  towards  Paramecium.     Amer.  Journ.  Physiol.,  xxv.,  p.  190. 

(221)  ZUELZER,  M.  (1905).     Die  Einwirkung  der  Radiumstrahlen  auf  Protozoen. 

A.P.K.,  v.,  p.  358. 

(222)  -  -  (1907).      Der   Einfluss   des   Meerwassers   auf   die   pulsierende    Vacuole. 

S.B.G.B.,  p.  90. 

(223)  ZUMSTEIX,  H.  (1899).     Morphologic  und  Physiologic  der  Ettglena  gracilis. 

Pringsheim's  Jahrbiicher  f.  K'i-s-y.  Botanik,  xxxiv.,  p.  419. 


CHAPTER  XI 

SARCODTXA 

(a)  General  Works. 

<224)  CASH,  J.,  and  HOPKINSON,  J.  (1905,  1909).     The  British  Freshwater  Rhizo- 
poda  and  Heliozoa.     London,  Kay  Society,  vol.  i.  (1905)  and  ii.  (1909). 

(225)  HARTOG,  M.  (1910).     Rhizopoda.     Encyclop.  Brit.,  eleventh  edition,  xxiii., 

p.  244. 

(226)  LEIDY,  J.  (1879).     Freshwater  Rhizopods  of  North  America.     Rep.   U.S. 

Geol.  Survey,  xii. 

(b)  AmcEbsea. 

See  also  Nos.  32,  34,  36,  46,  49,  65,  71-5,  76,  81,  85,  87,  88,  90,  95,  98,  101, 
103,  131,  144-146,  156,  161,  168,  176,  178,  187,  203,  204,  222. 

(227)  ALEXEIEFF,    A.    (1911).      La    Division    nucleaire   et   I'Enkystement   chez 

quelques  Arnibes,  I.-III.     C.R.S.B.,  Ixx.,  pp.  455,  534,  588. 

(228)  AWERINZEW,  S.  (1907).     Die  Struktur  des  Protoplasma  und  des  Kerns  von 

Amceba  proteus.     Z.A.,  xxxii.,  p.  45. 
^229)  —  (1906).     Die  Struktur  und  die  chemische  Zusammensetzung  der  Gehause 

bei  den  Siisswasserrhizopoden.     A.P.K.,  viii.,  p.  95. 

(230)--  (1906).     Zur  Kenntnis  der  Siisswasserrhizopoden.     A.P.K.,  viii.,  p.  112. 
(231)  CALKINS,  G.  N.  (1904).     Evidences  of  a  Sexual  Cycle  in  Amceba  proteus. 

A.P.K.,  v.,  p.  1. 
<232)  -  -  (1907).     Fertilization  of  Amceba  proteus.     B.B.,  xiii.,  p.  219. 

(233)  CASAGRANDI,    0.,    and    BARBAGALLO,    P.    (1897).     Entamceba   nominis,    s. 

Amceba  coli.     Ann.  Igiene  Sperimental.,  vii.,  p.  103. 

(234)  CHATTON,    E.    (1910).      Protozoaires  parasites  des   Branchies  des   Labres  : 

Amoeba  mucicola,  Trichodina  labrorum.     A.Z.E.  (5),  v.,  p.  239. 
•(235)  CRAIG,  C.  F.  (1908).     The  Amcebse  in  the  Intestine  of  Man.     Journ.  />//«/. 
Diseases,  v.,  p.  324. 

(236)  DOBELL,    C.    C.    (1909).     The    Intestinal    Protozoa    of   Frogs    and    Toads. 

Q.J.M.S.,  liii.,  p.  201. 

(237)  —  (1909).     Physiological  Degeneration  and  Death  in  Entamceba  ranarum. 

Q.J.M.S.,  liii.,  p.  711. 

(238)  DOFLEIN,  F.  (1907).     Araobenstudien.     A.P.K.,  Suppl.  i.,  p.  250. 

(239)  —  (1907).     Der     Teilungsvorgang      bei     den      Siisswasserthalamophoren. 

S.B.G.M.P.,  xxiii. 

,(240)  FANTHAM,  H.  B.  (1910).     The  Protozoa  Parasitic  in  the  Red  Grouse,  etc, 
P.Z.8.,  1910,  p.  692. 


484  THE  PROTOZOA 

(241)  FANTHAM,  H.  B.  (19]  1).     The  Amoebae  Parasitic  in  the  Human  Intestine. 

A.T.M.P.,  v.,  p.  111. 

(242)  GAUDICHEAU,  A.  (1908).     Formation  de  Corps  spmllaire  dans  une  Culture 

d'Amibe  (Entamceba  phagocytoides).     C.E.S.B.,  Ixiv.,  p.  493. 

(243)  GOTJLD,  L.  J.  (1894).     The  Minute  Structure  of  Pdomyxa  palustris.    Q.J.M.S. 

xxxvi.,  p.  295. 

(244)  GEEIG,  E.  D.  W.,  and  WELLS,  R.  T.  (1911).     Dysentery  and  Liver  Abscess 

in  Bombay.     S.M.I.,  47. 

(24.">)  GROSSE-ALLERMANN,  W.  (1909).     Amceba  terricola.     A.P.K.,  xvii.,  p.  203. 
(°46)  GRUBER,    K.     (1911).     Eigenartige    Korperformen    von    Amceba    proteus. 

A.P.K.,  xxiii.,  p.  253. 
*(247)  HARTMANN,   M.   (1911).     Die  Dysenterie-Amoben.     Vide  PROWAZEK  (14), 

p.  50. 

(248)  HICKSON,  S.  J.  (1909).     The  Proteomyxa.     Lankester's  Treatise  on  Zoology, 

i.,  fasc.  1. 

(249)  --  (1909).     TheLobosa.     Ibid. 

(250)  HOOGENRAAD,  H.  R.  (1907).      Vampyrella  lateritia.     A.P.K.,  viii.,  p.  21(J. 

(251)  --  (1907).     Hyalodiscus  rubicundus.     A.P.K.,  ix.,  p.  84. 

(252)  JiiRGENS    (1902).     Die    Darmanioben    und    die    Amobenenteritis      Verb'ff. 

Militdr-Sanitdtswesens,  xx.,  p.  110. 

(253)  LISTON    W.    G.,   and   MARTIN,    C.    H.    (1911).     Pathogenic   Amoebae  from 

Bombay.     Q.J.M.S.,  Ivii.,  p.  107. 

(254)  McCARRisoN,  R.  (1909).      Amcebce  in  Intestines  of  Persons  suffering  from 

Goitre  in  Gilgit.     Q.J.M.S.,  liii.,  p.  723. 

(255)  MARTIN,  C.  H.  (1911).     Nuclear  Division  of  the  Large  Amceba  from  Liver 

Abscess.     Q.J.M.S.,  Ivii.,  p.  279. 

(256)  MERCIER,  L.   (1910).     L'Aniibe  de  la  Blatte  (Entamceba  blattce).     A.P.K., 

xx.,  p.  143. 

(257)  METCALF,  M.  M.  (1910).     Studies  upon  Amceba.     J.E.Z.,  ix.,  p.  301. 

(258)  MINCHIN,  E.  A.  (1910).      Parasites  observed  in  the  Rat-Flea  (Ceratophyttus 

fasciatus).     Hertwirfs  Festschrift,  i.,  p.  289. 

(259)  MUSGRAVE,  W.  E.,  and  CLEGG,  M.  T.  (1904).     Amcebas  :  their  Cultivation 

and  Etiologic   Significance.      Manila,   Dept.   of  the  Interior,   Bureau  of 
Govt.  Laboratories,  Biol.  Lab.,  xviii. 

(260)  NEBESHEIMER,    E.    (1905).     Vegetative    Kernveriinderungen    bei    Amceba 

dofleini.     A.P.K.,  vi.,  p.  147. 

(261)  Noc,  F.  (1909).     La  Dysenteric  amibienne  en  Cochinchine.      A. I. P.,  xxiii., 

p.  177. 

(262)  PENARD,  E.  (1902).     Faune  Rhizopodique  du  Bassin  du  Leman.     Geneva  : 

Kundig. 

(263)  -  -  (1905).     Les  Amibes  a  Pellicule.     A.P.K.,  vi.,  p.  175. 

(264)  POPOFF,   M.    (1911).      Der   Entwicklungscyclus   von   Amceba  minuta,   etc. 

A.P.K.,  xxii.,  p.  197. 

(265)  PRANDTL,  H.  (1907).     Der  Entwicklungskreis  von  Attogromia  sp.     A.P.K., 

ix.,  p.  1. 

(266)  ROBERTSON,  M.  (1905).     Pseudospora  volvocis.     Q.J.M.S.,  xlix.,  p.  213. 

(267)  SCHATJDINN,  F.  (1895).     Teilung  von  Amceba  binucleata.     8.B.G.B.,   1895, 

p.  130.     Reprinted,  Schaudinn's  Arbeiten,  1911,  p.  101. 

(268)  SCHEEL,    C.    (1899).     Fortpflanzung    der    Amoben.     Kupffer's    Festschrift, 

p.  569. 

(269)  SCHEPOTIEFF,    A.    (1910).     Arnobenstudien.     Zool.    Jahrb-ilcher    (Anat.    u. 

Ontog.),  xxix.,  p.  485. 

(270)  SCHUBOTZ,  H.  (1905).     Amceba  blattce  und  Amaba  proteus.    A.P.K.,  vi.,  p.  1. 

(271)  STOLC,    A.    (1906).     Plasmodiogonie,    eine   Vermehrungsart  der  niedersten 

Protozoen.     Arch.  Entwicklungsmech.,  xxi.,  p.  111. 

(272)  SUN,  A.  (1910).     Uber  einen  Parasiten  aus  der  Korperhohle  von  Ptychodera 

minuta.     A.P.K.,  xx.,  p.  132. 

(274)  TOPSENT,  E.  (1893).     Pontomyxa  flava.     A.Z.E.  (3),  i.,  p.  385. 

(275)  VAHLKAMPF,  E.  (1905).     Biologie  und  Entwicklungsgeschichte  von  Amceba 

Umax.     A.P.K.,  v.,  p.  167. 

(276)  VELEY,  L.  J.  (nee  GOULD)  (1905).     Pdomyxa  palustris.     J.L.S.,  xxix.,  p.  374. 
(276-5)  WALKER,  E.  L.  (1911).     Amoeba?  in  the  Manila  water-supply,  etc.    Philip- 
pine Journ.  Sci.,  vi.  (B),  p.  259. 

(277)  WENYON,    C.   M.    (1907).     Protozoa   in   the   Intestine   of   Mies.     A.P.K., 

Suppl.,  i.,  p.  169. 


BIBLIOGRAPHY  485 

(278)  WERNER,  H.  (1911).     Entamceba  coli.     Vide  PROWAZEK  (14),  p.  67. 

(279)  WHITMORE,  E.  (1911).     Parasitare  und  freilebende  Amoben  aus  Manila  und 

Saigon.     A.P.K.,  xxiii.,  p.  71. 

(280)  -  -  (1911).     Kulturamoben  aus  Manila.     Ibid.,  p.  81. 

(c)  Foramiaifera. 
See  also  Nos.  28,  29,  35,  100,  and  131. 

(281)  AWERINZEW,  S.  (1910).     Gromia  dujardini.     Z.A.,  xxxv.,  p.  425. 

(282)  HICKSON,  S.  J.  (1911).     Polytrema  and  some  Allied  Genera.     Trans.  Linn. 

Soc.  London  (2),  xiv.,  p.  443. 

(283)  LATJTERBORN,  R.  (1895).     Paulinella  cliromatopliora.     Z.w.Z.,  lix.,  p.  537. 

(284)  LEYDEN,  E.v.,  and  SCHATTDINN.F.  (1896).     Leydenia  gemmipara.     8.B.A.B., 

p.  951. 

(285)  LISTER,  J.  J.  (1895).     Life-History  of  the  Foraminifera.     Phil.  Trans.  (B), 

clxxxvi.,  p.  401. 

(286)  —  (1903).     The  Foraminifera.     Lankester's  Treatise  on  Zoology,  i.,  fasc.  2, 

p.  47. 

(287)  -  -  (1906).     Life-History   of   the   Foraminifera.     Pres.    Address   Zool.    Sec. 

Brit.  Assoc.,  York,  1906. 

(288)  RHTJMBLER,    L.    (1903).     Systematische    Zusammenstellung    der    recenten 

Reticulosa.     A.P.K.,  iii.,  p.  181. 
(288-5)  SWARCZEWSKY,  B.  (1909).     Allogromia  ovoidea.     A.P.K.,  xiv.,  p.  396. 

(d)  Xenophyophora. 

(289)  ANON.  (1909).     The  Xenophyophoridae,  F.  E.  Schultze  (sic).     Lankester's 

Treatise  on  Zoology,  i.,  fasc.  1,  p.  284. 

(290)  SCHTJLZE,  F.  E.  (1905).     Die  Xenophyophoren.      Wiss.  Ergebn.  Expedition 

"  Valdivia,"  xi. 

(291)  --  (1906).     Die  Xenophyophoren  der  Siboga-Expedition.      U itkomst.  Siboga, 

iv.  bis. 

(e)  Mycetozoa. 
See  also  Nos.  69  and  127. 

(292)  BLOMFIELD,  J.  E.,  and  SCHWARTZ,  E.  J.  (1910).     The  Tumours  on  Veronica 

Chamcedrys  caused  by  Sorosphcera  Veronicas.     Ann.  Botany,  xxiv.,  p.  35. 

(293)  JAHN,    E.    (1908).     Myxornycetenstudien.     7.    Ceratiomyxa.     Ber.   Deutscli. 

Bot.  Ges.,  xxvia.,  p.  342. 

(294)  --  (1911).     Myxomycetenstudien.     8.  Der  Sexualakt.     Ibid.,  xxix.,  p.  231. 

(295)  LE'GER,  L.  (1908).     Sporomyxa  scauri.     A.P.K.,  xii.,  p.  109. 

(296)  --  and  HESSE,  E.  (1905).     Un  Parasite  des  Otiorhynques  (Mycetosporidium). 

C.B.S.B.,  Iviii.,  p.  92. 

(297)  LISTER,   J.   J.   (1909).     The  Mycetozoa.     Lankester's  Treatise  on  Zoology, 

i.,  fasc.  1,  p.  37. 

(298)  -  -  (1909).     Chlamydomyxa  and  Labyrinthula.     Ibid.,  p.  274. 

(299)  MARCHAND,  E.  F.  L.  (1910).     Le  Plasmodiophora  brassicce.     C.R. A.S.,  cl., 

p.  1348. 

(f)  Heliozoa. 
See  .also  Nos.  43,  64,  66,  82,  86,  129,  151,  161,  164,  174,  and  207. 

(300)  CATJLLERY,  M.   (1910).     Un  Protozoaire  Marin  du  Gejire  Ciliophrys  Cien- 

kowsky  (C.  marina,  n.  sp.).     C.R.  Assoc.  Franc.  Sci.,  Lille,  1909,  p.  708. 

(301)  HARTOG,    M.    (1910).     Heliozoa.     Encyclop.    Brit.,   eleventh   edition,    xiii., 

p.  232. 

(302)  PENARD,  E.  (1903).     Quelques  Protistes  Voisins  des  Heliozoaires  ou  des 

Flagelles.     A.P.K.,  ii.,  p.  283. 

(303)  -  -  (1904).     Les  Heliozoaires  d'Eau  Douce.     Geneva  :  Henry  Kiindig. 

(304)  PRZESJIYCKI,  A.  M.  (1901).     Parasitische  Protozoen  aus  dem  inneren  der 

Rotatorien.     B.A.S.C.,  1901,  p.  358. 
*(305)  SCHAUDINN,  F.  (1896).     Heliozoa.     Das  Tierreich,,  Berlin,  1896. 

(306)  SCHOUTEDEN,  H.  (1907).     Quelques  Flagelles.     A.P.K.,  ix.,  p.  108. 

(307)  WELDON,  W.  F.  R.,  and  HICKSON,  S.  J.  (1909).     The  Heliozoa.     Lankester's 

Treatise  on  Zoology,  i.,  fasc.  1,  p.  14. 


4S6  THE  PROTOZOA 

(g)  Radiolaria. 
See  also  No.  152. 

(308)  BORGEKT,     A.     (1911).     Fremdkorperskelete     bei     tripyleen     Radiolarien- 

A.P.K.,  xxiii.,  p.  125. 

(309)  BRANDT,  K.  (1902).     Die  Colliden.     A.P.K.,  i.,  p.  59. 

(310)  BUTSCHLI,  0.  (1906).     Die  chemische  Natur  der  Skeletsubstanz  der  Acan- 

tharia.     Z.A.,  xxx.,  p.  784. 

(311)  GAMBLE,  F.  W.  (1909).     The  Radiolaria.     Lankester's  Treatise  on  Zoology, 

i.,  fasc.  1,  p.  94. 

(312)  HARTMANK,  M.,  and  HAMMER,  E.  (1909).     Die  Fortpflanzung  vori  Radio- 

larien.    8.B.G.B.,  1909,  p.  228. 

(313)  HARTOG,  M.  (1910).     Radiolaria.     Encydop.  Brit.,  eleventh  edition,  xxii., 

p.  802. 

(314)  HUTU,  W.  (1911).     Fortpflanzung  von  Thalassicolla.     S.B.G.B.,  1911,  p.  1. 

(315)  MOROFF,    T.     (1910).     Vegetative    und    reproduktive    Erscheinungen    bei 

Thalassicolla.     Hertwig's  Festschrift,  i.,  p.  73. 

(316)  —  and  STIASNY,  G.   (1909).     Bau  und  Entwicklung  von     Acanthometron 

pellucidum.     A.P.K.,  xvi.,  p.  209. 

(317)  SCOTT,  R.  (1911).     On  Traquairia.     Ann.  Botany,  xxv.,  p.  459. 

(818)  STIASNY,    G.    (1910).     Die   Beziehung  der  sog.,    "  gelben   Zellen  "   zu  deii 
kolonie-bildenden  Radiolarien.     A.P.K.,  xix.,  p.  144. 


CHAPTER  XII 

MASTIGOPHORA 

(a)  General  Works. 

(319)  HARTOG,  M.  (1910).     Flagellata.     Encydop.  Brit.,  eleventh  edition,  x.,  p.  44. 
*(320)  SENN,  G.  (1900).     Flagellata.     Engler  and  Prantl,  "  Die  natilrlichen  Pflan- 
zenfamilien,"  I.  Toil,  1.  Abth.,  a,  p.  93. 

(321)  WILLEY,  A.,  and  HICKSON,  S.  J.  (1909).     The  Mastigophora.     LanJcester's 

Treatise  on  Zoology,  i.,  fasc.  1,  p.  154. 

(b)  Flagellata. 
See  also  Nos.  41,  45,  62,  70,  71,  97,  97-5,  153,  160,  213,  223,  236,  and  277. 

(322)  ALEXEIEFF,  A.  (1909).     Les  Flagelles  Parasites  de  1'Intestin  des  Batraciens 

Indigenes.     C.R.S.B.,  Ixvii.,  p.  199. 

(323)  —  (1909).     Trichomonas  a  Quatre  Flagelles  Anterieurs.     C.E.S.B.,  Ixvii., 

p.  712. 

(324)  —  (1910).     Les  Flagelles   Intestinaux  des   Poissons   Marins.     A.Z.E.    (5), 

vi.,  Notes  et  Revue,  p.  i. 

(325)  -  -  (1911).     Notes  sur  les  Flagelles.     Ibid.,  p.  491. 

(326)  -  -  (1911).     ;'  Kystes  de  Trichomonas  intestinalis."     C.E.S.B.,  Ixxi.,  p.  296. 

(327)  —  (1911).     La  Position  des  Monadides  dans  la  Systematique  des  Flagelles, 

etc.     B.S.Z.F.,  xxxvi.,  p.  96. 

(328)  BENSEN,  W.  (1909).     Trichomonas  intestinalis  und  vaninalis  des  Menschen. 

A.P.K.,  xviii.,  p.  115. 

(329)  BERLINER,  E.  (J909).     Flagellaten-Studien.     A.P.K.,  xv.,  p.  297. 

(330)  BOHNE,  A.,  and  PROWAZEK,  S.'  v.  (1908).     Zur  Frage  der  Flagellateiidysen- 

terie.     A.P.K.,  xii.,  p.  1. 

(331)  CHATTON,  E.  (1911).     Pleodorina  cali/ornica  a  Banyuls-sur-Mer.     Bull.  Sci. 

Franc.  Belg.  (7),  xliv.,  p.  309. 

(:532)  COMES,   S.   (1910).     Lophophora  vacuolata.     Boll.   Ace.   Gioen.   Catania  (2), 
xiii.,  p.  11. 

(333)  -  -  (1910).     A  Proposito  del  Dimorfisrno  sessuale  riscontrato  in  Dinenympha 

gracilis.     Ibid.,  p.  20. 

(334)  DANILEWSKY,  W.  B.  (1886).     Une  Monade  (Hexamitus),  Parasite  du  Sang. 

Arch.  Slav.  Biol.,  i.,  p.  85. 

(335)  DOBELL,  C.  C.  (1908).     Structure  and  Life-History  of  Copromonas  suUilis. 

Q.J.M.S.,  lii.,  p.  75. 


BIBLIOGRAPHY  487 

(336)  DOBELL,  C.  C.  (1908).  The"  Autogamy  "of  Bodolacertce.  B.C.,  xxviii.,  p.  548, 

(337)  FOA,  A.   (1905).     Due  nuovi  Flagellati  parassiti  (Calonympha  grassii  and 

Devescovina  striata).     Rend.  Ace.  Lincei,  xiv.  (2),  p.  542. 

(338)  GRASSI,  B.,  and  FOA,  A.  (1904).     Processo  di  Divisione  delle  Joenie  e  Forme 

affini.     Ibid.,  xiii.  (ii.),  p.  241. 

(339)  HAASE,  G.  (1910).     Euglena  sanguined.     A.P.K.,  xx.,  p.  47. 

(340)  HAMBURGER,  C.   (1905).     Dunaliella  salina  und  eine  Amobe  aus  Salinen- 

wasser  von  Cagliari.     A.P.K.,  vi.,  p.  111. 

(341)  —  (1911).     Euglena  ehrenbergii,   insbesondere  die   Korperhiille.      Sitz-ber. 

Heidelberg.  Ak.  Wiss.,  1911. 

(342)  HARTMANN,    M.    (1910).     Bau    und    Entwicldung    der    Trichonymphiden 

(Trichonymplia  hertivigi).     Hertwitfs  Festschrift,  L,  p.  349. 

(343)  HASWELL,  W.  A.  (1907).     Parasitic  Euglente.     Z.A.,  xxxi.,  p.  296. 

(344)  KEYSSELITZ,  G.  (1908).     Studien  iiber  Protozoen.     A.P.K.,  xi.,  p.  334. 

(345)  LATJTERBORN,    R.    (1895).     Eine    Siisswasserart    der    Gattung    Multicilia 

(M.  lacustris).     Z.w.Z.,  lx.,  p.  236. 
(345'5)  --  (1911).     Pseudopodien  bei  Chrysopyxis.     Z.A.,  xxxviii.,  p.  46. 

(346)  LIEBETANZ,  E.  (1910).     Die  parasitische  Protozoen  des  Wiederkauermagens. 

A.P.K.,  xix.,  p.  19. 

(347)  LOHMANN,  H.  (1902).     Die  Coccolithophoridse.     A.P.K.,  I,  p.  89. 

(348)  MARTIN,  C.  H.,  and  ROBERTSON,  M.  (1911).     Csscal  Parasites  of  Fowls,  etc. 

Q.J.M.S.,  Ivii.,  p.  53. 

(349)  MOROFF,  T.  (1903).     Einige  Flagellaten.     A.P.K.,  iii.,  p.  69. 

(350)  NERESHEIMER,  E.  (1911).     Costia  necatrix.     Vide  PROWAZEK  (14),  p.  98. 

(351)  Noc,  F.  (1909).     Le  Cycle  evolutif  de  Lamblia  intestlnalis.      B.S.P.E.,  ii., 

p.  93. 

(352)  PASCHER,  A.  (1910).     Chrysomonaden  aus  dem  Hirschberger  Grossteiche. 

Leipzig  :  Werner  Klinkhardt. 

(353)  PLIMMER,  H.  G.  (1909).     Report  on  Deaths  at  the  Zoological  Gardens  during 

1908.     P.Z.S.,  1909,  p.  125. 

(354)  PROWAZEK,  S.  v.  (1903).     Flagellatenstudien.     A.P.K.,  ii.,  p.  195. 

(355)  -  -  (1904).     Einige  parasitische  Flagellaten.     A.K.G.A.,  xxi.,  p.  1. 

(356)  RODENWALDT,    E.    (1911).     Trichomonas,    Lamblia.     Vide  PROWAZEK  (14), 

p.  78. 

(357)  SCHERFFEL,  A.  (1911).     Die  Chrysomonadineen.     A.P.K.,  xxii.,  p.  299. 

(358)  SENN,  G.  (1911).     Oxyrrhis,  Nephroselmis  und  einige  Euflagellaten.     Z.w.Z., 

xcvii.,  p.  605. 

(359)  STEIN,  F.  (1878,  1883).    Der  Organismus  der  Infusionsthiere.    III.    Leipzig: 

Wilhelm  Engelmann. 

(360)  STEVENSON,   A.   C.    (1911).      The   Protozoa   parasitic  in   Bufo  regularis  in 

Khartoum.     Rep.  Wellcome  Lab.  Khartoum,  iv.,  p.  359. 

(361)  WENYON,  C.  M.  (1910).     A  Flagellate  of  the  Genus  Oercomonas.     Q.J.N.S., 

Iv.,  p.  241. 

(362)  --  (1910).     Macrostoma  mesnili  from  the  Human  Intestine.     Py.,  iii.,  p.  210. 

(c)  Dinoflagellata  and  Cystoflagellata. 

(363)  BORGERT,  A.  (1910).     Kern-  und  Zellteilung  bei  marinen  Ceratiiim-Arten. 

A.P.K.,  xx.,  p.  1. 

(364)  CAULLERY,  M.  (1910).     Ellobiopsis  chattoni,  Parasite  de  Calanus  helgolandicus 

Bull.  Sci.  Franc.  Belg.  (1),  xliv.,  p.  201. 

(365)  COTJTIERE,    H.    (1911).      Les    Ellobiopsis    des    Crevettes    bathypelagiques. 

C.R.A.S.,  clii.,  p.  409. 

(366)  CHATTON,  E.  (1906).     Les  Blastodinides.     C.R.A.S.,  cxliii.,  p.  981. 

(367)  --  (1907).     Nouvel  Aper§u  sur  les  Blastodinides  (Apodinium  mycetoides). 

C.R.A.S.,  cxliv.,  p.  282. 

(368)  —  (1910).      Sur  1'Existence  de  Dinoflagelles  parasites  coelomiques.      Les 

Syndinium  chez  les  Copepodes  pelagiques.     G.R.A.S.,  cli.,  p.  654. 

(369)  —  (1910).       Paradinium     poucheti,     Flagelle     parasite     d'Acartia     clausi. 

C.R.S.B.,  Ixix.,  p.  341. 

(370)  DOGIEL,  V.  (1906).     Die  Peridinien.     Mitth.  Zool.  Stat.  Neapel,  xviii.,  p.  1. 

(371)  DUBOSCQ,  0.,  and  COLLIN,  B.  (1910).      La  Reproduction  sexuee  d'un  Pro- 

tiste  parasite  des  Tintinnides.     G.R.A.S.,  cli.,  p.  340. 

(372)  JOLLOS,  V.  (1910).     Dinoflagellatenstudien.     A.P.K.,  xix.,  p.  178. 

(373)  KOFOID,  C.  A.  (1905).     Craspedotella,  a  New  Genus  of  the  Cystoflagellata. 

Bull.  Mus.  Harvard,  xlvi.,  p.  163. 


488  THE  PROTOZOA 

(374)  KOFOID,  C.  A.  (1906).     Asymmetry  in  Triposolenia.     Univ.  California  Publ. 

Zool.,  iii.,  p.  127. 

(375)  --  (1906).     Structure  of  Gonyaulax  triacantha.     Z.A.,  xxx.,  p.  102. 

(376)  -  -  (1907).     Structure  and  Systematic  Position  of  Polykrikos.     Ibid.,  xxxi., 

p.  291. 

(377)  -  -  (1907).     The  Plates  of  Ceratium.     Ibid.,  xxxii.,  p.  177. 

(378)  —  (1908).     Exuviation,  Autotomy,  and  Regeneration,  in  Ceratium.     Univ. 

California  Publ.  Zool.,  iv.,  p.  345. 

(379)  --  (1909).     On  Peridinium  steini.     A.P.K.,  xvi.,  p.  25. 

(380)  -  -  (1909).     Morphology  of  the  Skeleton  of  Podolampas.     Ibid.,  p.  48. 

(381)  --  (1909).     Mutations  in  Ceratium.     Bull.  Mus.  Harvard,  Iii.,  p.  211. 

(382)  --  (1910).     A  Revision  of  the  Genus  Ceratocorys.      Univ.  California  Publ. 

Zool.,  vi.,  p.  177. 

(383)  —  (1910).     Forms  of  Asymmetry  of  the  Dinoflagellates.     Proc.  Internal. 

Cotif/r.  Zool.,  vii. 

(384)  KtiSTER,  E.  (1908).     Eine  kultivierbare  Peridinee.     A.P.K.,  xi.,  p.  351. 

(385)  PLATE,  L.  (1906).     Pyrodinium  bahamense.     A.P.K.,  vii.,  p.  411. 

(386)  ScutfTT,    F.    (1895)v     Die    Peridineen    der    Plankton-Expedition.     Ergebn. 

Plankton-Exped.,  iv. 

(387)  STEIN,  F.   (1883).     Der  Organismus  der  Infusorien.  III.   (ii.)  Die  Natur- 

geschichte  der  Arthrodelen  Flagellaten.     Leipzig  :  W.  Engelmann. 


CHAPTER  XIII 
H^EMOFLAGELLATES 

(a)  General  Works. 

See  also  the  Bulletin  of  the   Sleeping  Sickness  Bureau,  London,  for  abstracts 
and  reviews  of  literature. 

(388)  ALEXEIEFF,  A.   (1911).     La  Structure  des  "  Binucleates  "  de  Hartmann. 

C.R.S.B.,  Ixix.,  p.  532. 

(389)  BRUMPT,  E.  (1908).     L'Origine  des  Hemoflagelles  du  Sang  des  Vertebres. 

C.B.S.B.,  Ixiv.,  p.  1046. 

(390)  HARTMANN,  M.,  and  JOLLOS,  V.  (1910).     Die  Flagellatenorclnung  "  Binu- 

cleata."     A.P.K.,  six.,  p.  81. 

*(391)  LAVERAN,  A.,  MESNIL,  F.,  and  NABARRO,  D.  (1907).  Trypanosomes  and 
Trypanosomiases.  London  :  Bailliere,  Tindall  and  Cox. 

*(392)  LtiHE,  M.  (1906).  Die  im  Blute  schmarotzenden  Protozoen.  Mense's 
Handbuch  der  Tropenkrankheiten,  iii.,  p.  69. 

*(393)  PATTON,  W.  S.  (1909).  Our  Present  Knowledge  of  the  Hasnioflagellates 
and  Allied  Forms.  Py.,  ii.,  p.  91. 

*(394)  THIMM,  C.  A.  (1909).  Bibliography  of  Trypanosomiasis.  London  :  Sleep- 
ing Sickness  Bureau. 

*(395)  WOODCOCK,  H.  M.  (1909).  The  Haemofiagellates  and  Allied  Forms.  Lan- 
kester's  Treatise  on  Zoology,  i.,  fasc.  1,  p.  193. 

(b)  Trypanosoma  and  Trypanoplasma. 

See  also  Nos.  19,  22,  23,  27,  42,  56,  132,  134,  686,  and  696. 

(396)  BALDREY,  F.  S.  H.  (1909).     Die  Entwicklung  von  Trypanosoma  lewisi  in  der 

Rattenlaus  Hatinatopimi.s  spinulosus.     A.P.K.,  xv.,  p.  326. 

(397)  -  -  (1911).    Evolution  of  T.  evansi  through  the  Fly :  Tabanus  and  Stomoxys. 

Journ.  Trap.   [7eterin.  Sci.,  vi.,  p.  271. 

(398)  Bosc,  F.  J.  (1904).    La  Structure  etl'Appareil  Nucleaire  des  Trvpanosomes. 

A.P.K.,  v.,  p.  40. 

(399)  BOTJET,  G.  (1906).    Culture  du  Trypanosome  de  la  Grenouille  (T.  rotatorium). 

A.I. P.,  xx.,  p.  564. 

(400)  --  and    ROUBATJD,    E.    (1910).     Transmission   des   Trypanosomes   par  les 

Glossincs,  1.  and  II.     A.I. P.,  xxiv.,  p.  658.     III.,  B.8.P.E.,  iii.,  p.  599. 
IV.,  Ibid.,  p.  722. 

(401)  BOUFFARD,  G.  (1910).      Glossina  palpalis  et  T.  Cazilboui.      A.I. P.,  xxiv., 

p.  276. 


BIBLIOGRAPHY  489 

<402)  BRADFORD,  J.  R.,  and  PLIMMER,  H.  G.  (1902).     The   T.   brucii  found  in 
Nagana,  or  Tse-tse  Fly  Disease.     Q.J.M.S.,  xlv.,  p.  449. 

(403)  BREINL,  A.,  and  HINDLE,  E.  (1910).     Life-History  of  T.  lewisi  in  the  Rat- 

Louse.     A.T.M.P.,  iii.,  p.  553. 

(404)  BRUCE,    D.    (1911).      Morphology    of    T.    evansi.      P.E.S.    (B),    Ixxxiv., 

p.  181. 

(405)  --  (1911).     Morphology  of  T.  gambiense.     Ibid.,  p.  327. 

(406)  —  and  BATEMAN,  H.  R.  (1908).    Have  Trypanosomes  an  Ultramicroscopical 

Stage  in  their  Life-History  ?     (No  .')     P.E.S.,  (B),  Ixxx.,  p.  394. 
{407)  —  HAMERTON,    A.    E.,    BATEMAN,    H.    R.,    and    MACKIE,   F.    P.    (1909). 
T.  ingens,  n.  sp.     P.E.S.  (B),  Ixxxi.,  p.  323. 

(408)  — •  -  (1909).     Development  of  T.  gambiense  in   Glossina  palpalis. 

Ibid.,  p.  405. 

(409)  -  -  (1909).     A   Trypanosome    in   the    African    Elephant.     Ibid., 

p.  414. 

(410)  -  -  (1910).     Development    of    Trypanosomes    in     Tsetse    Flies. 

Ibid.,  Ixxxii.,  p.  368. 

(411)  —  -  (1910,  1911).     Trypanosome  Diseases  of  Domestic  Animals  in 

Uganda,  I-V.     Ibid.,  Ixxxii.,  p.  468  ;  Ixxxiii.,  pp.  1,  15,  176,  and  180. 

(412)  -  -  (1910).     The     Natural    Food     of     Glossina    palpalis.     Ibid., 

Ixxxii.,  p.  490. 

(413)  —  -  (1910).     Mechanical  Transmission  of  Sleeping  Sickness  by  the 

Tsetse  Fly.     Ibid.,  p.  498. 

(414)  —  -  (1911).       Experiments   to    Ascertain  if  T.   gambiense  during 

its  Development   within   Glossina   palpalis  is  Infective.     Ibid.,  Ixxxiii., 
p.  345. 

(415)  —  -  (1911).     Further  Researches  on  the  Development  of  T.  gam- 

biense in  Glossina  palpalis.     Ibid.,  p.  513. 

(416)  —  -  and   BRUCE   (LADY)    (1911).     T.  gallinarum.     Rep.    Sleeping 

Sickness  Oomm.,  xi.,  No.  32,  p.  170. 

(417)  —  -  (1911).     A  Trypanosome  found  in  the  Blood  of  a  Crocodile. 

Ibid.,  No.  36,  p.  184. 

(418)  BRUMPT,  E.  (1906).     Le  Mode  de  Transmission  des  Trypanosomes  et  des 

Trypanoplasmes  par  les  Hirudinees.     C.R.S.B.,  Ixi.,  p.  77. 

(419)  —  (1907).     L'Heredite  des  Infections  a  Trypanosomes  et  a  Trypanoplasmes 

chez  les  Hntes  intermediaires.     Ibid.,  Ixiii.,  p.  176. 

(420)  BUCHANAN,    G.    (1911).      Developmental  Forms  of  T.  brucei  (pecaudi)  in 

the  Internal  Organs  of  the  Gerbil.     P.E.S.  (B),  Ixxxiv.,  p.  161. 

(421)  CARINI,    A.    (1910).     Stades   Endoglobulaires   des  Trypanosomes.     A.I. P., 

xxiv.,  p.  143. 

(422)  --  (1910).     Formas  de  Eschizogonia  do  T.  lewisi.     Soc.  de  Med.  e  Cir.  de 

Sao  Paulo,  August  16,  1910  (quoted  from  B.I. P.,  ix.,  p.  937). 

(423)  --  (1911).     Presence    de    Trypanosomes  chez  les   bovides,    a   Sao   Paulo. 

B.S.P.E.,  iv.,  p.  191. 

(424)  --  (1911).     Schizogonien  bei  Trypanosomen.     A.P.K.,  xxiv.,  p.  80. 

(425)  CHAGAS,  C.  (1909).     Eine  neue  Trypanosorniasis  des  Menschen.     M.I.O  C  , 

i.,  p.  159. 

(426)  —  (1911).     Le    Cycle  de  "  Schizotrypanum   cruzi"    chez  1'Homme  et  les 

Animaux  de  Laboratoire.     B.S.P.E.,  iv.,  p.  467. 

(427)  CRAWLEY,  H.  (1910).     T.  americanum  from  the  Blood  of  American  Cattle. 

Journ.  Comp.  Path.  Therap.,  xxiii.,  p.  17. 

(428)  DARLING,  S.  T,  (1911).     Murrina.     Journ.  Infect.  Diseases,  viii.,  p.  467. 

(429)  —  (1911).     Mode  of  Infection  and  Methods  of  Controlling  an  Outbreak  of 

Equine  Trypanosoniiasis  in  the  Panama  Canal  Zone.     Py.,  iv.,  p.  83. 

(430)  DOFLEIN,  F.  (1909).     Problem  der  Protistenkunde.     I.  Die  Trypanosomen. 

Jena :  G.  Fischer. 

(431)  —  (1910).     Experimented  Studien  iiber  die  Trypanosomen  des  Frosches. 

A.P.K.,  xix.,  p.  207. 

(432)  DUTTON,  J.  E.,  TODD,  J.  L.,  and  TOBEY,  E.  N.  (1906,  1907).     Certain  Para- 

sitic   Protozoa    observed    in    Africa.      Part    L,    Liverpool    Trop.    Med. 
Memoirs,  xx.,  p.  87.     Part  II.,  A.T.M.P.,  i.,  p.  287. 

(433)  ELDERS,     C.     (1909).      Trypanosorniasis    beim     Menschen     auf     Sumatra. 

C.B.B.P.K.  (I  Abth.  Orig.),  liii.,  p.  42. 

(434)  FANTHAM,    H.    B.    (1911).     Life-History    of    T.    gambiense   and   T.  rhode- 

siense  as  seen  in  Rats  and  Guinea-pigs.     P.E.S.  (B),  Ixxxiii.,  p.  212. 


490  THE  PROTOZOA 

(435)  FISCHEK,  W.  (1911).     Zur  Kenntnis  der  Trypanosomen.     Z.H.,  Ixx.,  p.  93. 

(436)  FRANCA.  C.  (1908).     La  Biologic  cles  Trypanosomes.     A.I.C.P.,  ii.,  p.  43. 

(437)  —  (1908).     Le  Cycle  Evolutif  des  Trypanosomes  de  la  Grenouille.     Ibid., 

p.  89. 

(438)  -  -  (1908).     Le  Trypanosome  de  1'Anguille  (T.  gramtlosum).     Ibid.,  p.  113. 
(i:;'.M      -  (1910).     Un  Trypanosome  du  Lerot  (T.  elyomis).     Ibid.,  iii.,  p.  41. 

(440)  —  (1911).     Hematozoaires  de  la  Guinee  Portuguaise.     Ibid.,  pp.  201,  229. 

(441)  —  (1911).     Les  Hematozoaires  des  Taupes.     Ibid.,  p.  271. 

(442)  —  (1911).     Relation  autogenetique  entre  les  grands  et  les  petits  Trypano- 

somes de  la  Grenouille.     C.R.8.B.,  Ixx.,  p.  978. 

(443)  --  (1911).     La  Transformation   "in  vitro"  des    Formes  crithidiennes  de 

"  T.  rotatorium  "  en  Formes  trypanosomiques.     B.S.P.E.,  iv.,  p.  534. 

(444)  FRIEDRICH  L.  (1909).     Bau  und  Naturgeschichte  des  Trypanoplasma  helicis. 

A.P.K.,  xiv.,  p.  363. 

(445)  FRY,  W.  B.  (1911).     The  Extrusion  of  Granules  by  Trypanosomes.     P.K.8. 

(B),  Ixxxiv.,  p.  79. 

(445-5)  GONDER     R.     (1911).      Arzneifeste     Mikroorganisrnen.      I.     T.    lewisi. 
O.B.B.P.K.  (I  Abth.  Orig.),  Ixi.,  p.  102. 

(446)  HAMBURGER,  C.  (1911).     Einige  parasitische  Flagellaten.      Verh.  Heidelberg. 

NaturMst.-Med.  Ver.  (n.  F.),  xi.,  p.  211. 

(447)  HARTMANN,  M.  (1910).     Eine  weitere  Art  der  Schizogonie  bei  Schizotrypanum 

cruzi.     A.P.K.,  xx.,  p.  361. 

(448)  HINDLE,  E.  (1909).     Life-History  of  T.  dimorplion.     Univ.  California  Publ. 

Zool.,  vi.,  p.  127. 

(449)  -  -  (1910).     Degeneration  Phenomena  of  T.  gambiense.     Py.,  iii.,  p.  423. 

(450)  —  (1910).     A  Biometric  Study  of  T.  gambiense.     Ibid.,  p.  455. 

(451)  —  (1911).     The  Passage  of  T.  gambiense  through  Mucous  Membranes  and 

Skin.     Ibid.,  iv.,  p.  25. 

(452)  JOLLOS     V.    (1910).     Bau   und    Vermehrung   von    Trypanoplasma   helicis. 

A.P.K.,  xxi.,  p.  103. 

(453)  KEYSSELITZ,  G.  (1904).     Trypanophi-i  grobbeni.     A.P.K.,  iii.,  p.  367. 

(454)  —  (1906).     Generations-    und    Wirtswechsel    von    Trypanoplasma    borrdi. 

A.P.K.,  vii.,  p.  1. 

(455)  —  (1907).     Die  undulierende  Membran  bei  Trypanosomen  und  Spirochaten. 

A.P.K.,  x.,  p.  127. 

(456)  —  and  MAYER,  M.  (1908).     Die  Entwicldung   von    T.    brucei  in  Glossina 

fusca.     A.S.T.H.,  xii.,  p.  532. 

(457)  KLEINE,    F.    (1909).     Positive    Infectionsversuche    mit    T.    brucei    dureh 

Glossina  palpalis.  Deutsch.  Med.  Wochenschr.,  xxxv.,  p.  469.  Die 
Entwicldung  von  Trypanosomen  in  Glossinen.  Ibid.,  p.  924.  Die 
Aetiologie  der  Schlafkrankheit.  Ibid.,  p.  1257.  Tsetsefliegen  und  Try- 
panosomen. Ibid.,  p.  1956. 

(458)  -  -  (1910).     Trypanosomenbefunde  am  Tanganyika.     Ibid.,  xxxvi.,  p.  1400. 

(459)  --  and  TATTTE,  M.  (1911).     Erganzungen  zu  unseren  Trypanosornenstudien. 

A.K.G.A.,  xxxi.,  p.  321.     Reprinted  as  "  Trypansomenstudien." 

(460)  KOCH,  R,,  BECK,  M.,  and  KLEINE,  F.  (1909).     Die  Tatigkeit  der  zur  Erfor- 

schung  der  Schlafkrankheit  im  Jahre  1906-07  nach  Ostafrika  entsandten 
Kommission.  A.K.G.A.,  xxxi.,  p.  1. 

(461)  LAVERAN,  A.  (1911).     Identification  et  Classification  des  Trypanosomes  dea 

MammiftJres.     A. I. P.,  xxv.,  p.  497. 

(462)  -  -  (1911).     Les  Trypanosomes,  ont-ils  des  Formes  latentes  chez  leurs  Hutes 

vertebres  ?     C.R.A.S.,  cliii.,  p.  649. 

(464)  --  and  MESNIL,  F.   (1902).     Des  Trypanosomes  des  Poissons.     A.P.K.,  i., 

p.  475. 

(465)  --  and  PETTIT,  A.  (1910).     Des  Trypanosomes  du  Mulct  et  du  Campagnol 

(T.  grosi  et  T.  microti).     C.B.S.B.,  Ixviii.,  p.  571. 

(466)  -        -  (1910).     Le  Trypanosome  du  Lerot  (Myoxus  nitela)  et  la  Puce  qui 

parait  le  propager  (T.  blanchardi).     Ibid.,  p.  950. 

(467)  LEBAILLY,  C.  (1906).     Les  Hematozoaires  parasites  des  Teleosteens  marins. 

Arch.  Parasitol.,  x.,  p.  348. 

(468)  LEBEDEFF,  W.  (1910).     T.  rotatorium,  Gruby.    Hertwig's  Festschrift,  i.,  p.  397. 

(469)  MACHADO,    A.    (1911).     Zytologische    Untersuchungen   iiber  T.  rotatorium, 

Gruby.     M.I.O.C.,  iii.,  p.  108. 

(470)  MANTEUFEL    (1909).     Studien    iiber    die    Trypanosomiasis    der    Ratten. 

A.K.G.A.,  xxxiii.,  p.  46. 


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(498)  —  (1909).     Kritische  Bemerkungen  zum  Trypanosomenproblem.    A.S.T.H., 

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(499)  ROBERTSON,    M.    (1906).     Certain    Blood-inhabiting    Protozoa.     Proc.    R. 

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(I  Abth.  Orig.),  lii.,  p.  30. 


492  THE  PROTOZOA 

(505)  ROSENBUSCH,  F.  (1909).     Trypanosomen-studien.     A.P.K.,  xv.,  p.  263. 

(506)  ROUBAUD,  E.  (1909).     Les  Trypanosomes  pathogenes  et  la  Glossina  palpalis. 

Rapport  de  la  Mission  d'Etudes  de  la  Maladie  du  Sommeil  au  Congo  Fran- 
rais  (Paris,  Masson  et  Cie.),  p.  511. 

(507)  —  (1910).     Phenomenes  morphologiques  du  Developpement  des  Trypano- 

somes chez  les  Glossines.     G.R.A.S.,  cli.,  p.  1156. 

(508)  STASSANO,  H.  (1901 ).     La  Fonction  et  Relation  du  petit  Noyau  des  Trypano- 

somes.    C.R.S.B.,  liii.,  p.  468. 

(509)  STEPHENS,  J.  W.  W.,  and  FANTHAM,  H.  B.  (1911).     Peculiar  Morphology  of 

a  Trypanosome  from  a  Case  of  Sleeping  Sickness  (T.  rhodesiense).     P.R.S. 
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(510)  STOCKMAN,   S.   (1910).     A  Trypanosome  of  British  Cattle.     Journ.   Cornp. 

Pathol.  Therapeut.,  xxiii.,  p.  189. 

(511)  STRICKLAND,  C.  (1911).     Mechanism  of  Transmission  of  T.  lewisi  by  the  Rat- 

Flea.     Brit.  Med.  Journ.,  1911,  p.  1049. 

(512)  --  and  SWELLENGREBEL,  N.  H.  (1910).     On  T.  lewisi  and  its  Relation  to 

Certain  Arthropoda.     Py.,  iii.,  p.  436. 

(513)  STUHLMANN,  F.  (1907).     Die  Tsetsefliegen  (Glossina  fusca  und  Gl.  tachinoides). 

A.K.G.A.,  xxvi.,  p.  301. 

(514)  SWELLENGREBEL,  N.  H.  (1909).     Bau   und   Zellteilung  von    T.  gambiense 

und  T.  equinum.     Tijdsclir.  Ned.  Dierk.  Ver.  (2),  xi.,  p.  80. 

(515)  —  (1910).     Fixation  and  Staining  of  T.  lewisi.     Py.,  iii.,  p.  226. 

(516)  —  (1910).     Normal  and  Abnormal  Morphology  of  T.  leivisi.     Ibid,  p.  459. 

(517)  --  and  STRICKLAND,  C.  (1910).     The  Development  of  T.  lewisi  outside  the 

Vertebrate  Host.     Ibid.,  p.  360. 

(518)  —     -  (1911).     Remarks  on   Dr.    Swingle's   Paper,  "The  Transmission   of 

T.  lewisi  by  Rat-Fleas,"  etc.     Ibid.,  iv.,  p.  105. 

(519)  SWINGLE,  L.  D.  (1907).     On  T.  lewisi.      Trans.  Amer.  Micr.  Soc.,  xxvii., 

p.  111. 

(520)  --  (1911).     Transmission  of  T.  leivisi  by  Rat-Fleas.     Three  New  Herpeto- 

monads.     Journ.  Infect.  Diseases,  viii.,  p.  125. 

(521)  TAUTE,   M.   (1911).     Die  Beziehungen  der  Glossina  morsitans  zur  Schlaf- 

krankheit.     Z.H.,  Ixix.,  p.  553. 

(522)  THIROUX,  A.  (1905).     T.  paddce.     A.I.P.,  xix.,  p.  65. 

(523)  --  (1905).     T.  duttoni.     Ibid.,  p.  564. 

(524)  THOMSON,  J.  D.  (1906).     Blood-Parasites  of  the  Mole.     J.H.,  vi.,  p.  574. 

(525)  -  -  (1908).     Cultivation  of  the  Trypanosome  found  in  the  Blood  of  the  Gold- 

fish.    Ibid.,  viii.,  p.  75. 

(526)  WERBITZKI,  F.  W.  (1910).     Blepharoplastlose  Trypanosornen.     C.B.B.F.K. 

(I  Abth.  Orig.),  liii.,  p.  303.     (See  also  Bulletin  of  the  Sleeping  Sickness 
Bureau,  vol.  iii.,  pp.  221,  313,  and  458,  for  further  references.) 

(527)  WOODCOCK,  H.  M.  (1910).     On  Certain  Parasites  of  the  Chaffinch  (Fringilla 

codebs)  and  the  Redpoll  (Linota  rufescens).     Q.J.M.S.,  Iv.,  p.  641. 

(528)  YAKIMOFF,   W.   L.,   KOHL- YAKIMOFF,   N.,   and   KORSSAK,   D.   W.    (1910). 

T.  korssafci  of  Mus  agrarius,  Piroplasmoses  of  Mus  agrarius,  Reindeer, 
Yak,  and  Bears.     C.B.B.P.K.  (1  Abth.  Orig.),  Iv.,  p.  370. 

(529)  ZUPITZA,    M.     (1909).     Die    Vogel-    und    Fischtrypanosomen    Kameruns. 

A.S.T.H.,  xiii.,  Beiheft  3,  p.  101. 

(c)  Crithidia,  Leptomonas,  Herpetomonas,  etc. 
See  also  No.  84. 

(530)  BOUET,  G.,  and  ROTJBATJD,  E.  (1911).     La  Presence  au  Dahomey  et  Trans- 

mission du  Leptomonas  davidi.     C.R.S.B.,  Ixx.,  p.  55. 

(531)  CHATTON,  E.  (1909).     Un  Trypanosomide  nouveau  d'une  Nycteribie,  et  les 

Relations    des    Formes     Trypanosoma,    Herpetomonas,    Leptomonas    et 
Crithidia.     C.R.S.B.,  Ixvii.,  p.  42. 

(532)  -  -  and  ALILAIRE,  E.  (1908).     Coexistence  d'un  Leptomonas  et  d'un  Trypano- 

soma chez  un  Muscide   non  vulnerant,   Drosopliila  confusa.     C.R.8.B., 
Ixiv.,  p.  1004. 

(533)  —  and  LEGER,  A.  (1911).     Eutrypanosomes,  Leptomonas  et  Leptotrypano- 

somes  chez  Drosophila  confusa  (Muscide).     C.R.S.B.,  Ixx.,  p.  34. 

(534)  -        -  (1911).     Quelques  Leptomonas  de  Museides  et  leurs  Leptotrypano- 

somes.     Ibid.,  p.  120. 

(535)  DUNKERLY,  J.  S.  (1911).     Life-History  of  Lept.  muscce-domesticce.     Q.J.M.S., 

Ivi.,  p.  645. 


BIBLIOGRAPHY  493 

(536)  FLTJ,  P.  C.  (1911).     Die  im  Darm  der  Stubenfliege  vorkommenden  proto- 

zoaren  Gebilde.     G.B.B.P.K.  (I  Abth.  Orig.),  Ivii.,  p.  522. 

(537)  FRANCA,  C.  (1911).    L'Existence  en  Portugal  de  Lept.  davidi  dans  le  Latex  de 

Euphorbia  peplus  et  E.  segetalis.     B.S.P.E.,  iv.,  p.  532. 

(538)  -  -  (1911).     Notes  sur  Lept.  davidi.     Ibid.,  p.  669. 

(539)  GEORGEWITCH,  J.  (1909).    Le  developpement  de  Crithidia  simulice.    C.E.S.B., 

Ixvii.,  p.  517. 

(540)  LAFONT,  A.  (1910).     La  Presence  d'un  Leptomonas  .  .  .  dans  le  Latex  de 

Trois  Euphorbiacees.     A. I. P.,  xxiv.,  p.  205. 

(541)  —  (1911).     La  Transmission  du  Lept.  davidi  des  Euphorbes  par  un  Hemip- 

tere.     C.R.S.B.,  Ixx.,  p.  58. 

(542)  LEGER,  L.  (1902).     La  Structure  et  Multiplication  des  Flagelles  du  Genre 

Herpetomonas  Kent.     C.R.A.S.,  cxxxiv.,  p.  781. 

(543)  —  (1902).     Un  Flagelle  Parasite  de  V  Anopheles  maculipennis.     C.E.S.B., 

liv.,  p.  354. 

(544)  —  (1904).     Un  nouveau  Flagelle,  Parasite  des  Tabanides.     C.E.8.B.,  Ivii., 

p.  613. 

(545)  —  (1904).     Les  Affinites  de  V Herpetomonas  subulata  et  la  Phylogenie  des 

Trypanosomes.     G.R.S.B.,  Ivii.,  p.  615. 

(546)  -  -  and  DUBOSCQ,  0.  (1909).     Parasites  de  1'Intestin  d'une  Larve  de  Ptychop- 

tera.     Bull.  Acad.  Belgique,  No.  8,  p.  885. 

(547)  MACKINNON,  D.  L.  (1910).    New  Parasites  from  Trichoptera.    Pi/.,  iii.,  p.  245. 

(548)  -  -  (1910).     Herpetomonads  from  Dung-Flies.     Ibid.,  p.  255. 

(549)  -  -  (1911).     More  Protozoan  Parasites  from  Trichoptera.     Ibid.,  iv.,  p.  28. 

(550)  PATTON,  W.  S.   (1908).     Life-Cycle  of  a  Species  of  Crithidia  parasitic  in 

Gerris  fossarum.     A.P.K.,  xii.,  p.  131. 

(551)  —  (1908).     Herp.  lygcei.     A.P.K.,  xiii.,  p.  1. 

(552)  —  (1909).     Life-Cycle  of  a  Species  of  Crithidia  parasitic  in  Tabanus  hilarius 

and  Tabanus  sp.     A.P.K.,  xv.,  p.  333. 

(553)  —  (1910).     Infection  of  the  Madras  Bazaar  Fly  with  Herp.  muscce-domesticas. 

B.S.P.E.,  iii.,  p.  264. 

(554)  PORTER,  A.  (1910).     Crithidia  melophagia.    Q.J.M.S.,  Iv.,  p.  189. 

(555)  —  (1909).     Crithidia  gerridis.     Pi/.,  ii.,  p.  348. 

(556)  -  -  (1909).     Life-Cycle  of  Herp.  jaculum.     Ibid.,  p.  367. 

(557)  PROWAZEK,  S.  v.  (1904).     Die  Entwicklung  von  Herpetomonas.     A.K.G.A., 

xx.,  p.  440. 

(557'5)  RotTBAtrD,    E.  (1911).      Cystotrypanosoma  intestinalis.      C.R.S.B.,   Ixxi., 
p.  306. 

(558)  STRICKLAND,  C.  (1911).     A  Herpetomonas  parasitic  in  the  common  Green- 

bottle  Fly,  Lucilia  sp.     Ptj.,  iv.,  p.  222. 

(559)  SWELLENGREBEL,     N.    H.     (1911).     Morphology    of     Herpetomonas    and 

Crithidia,  etc.     Ibid.,  p.  108. 

(560)  WERNER,    H.    (1908).     Eine   eingeisselige   Flagellatenform   im    Darm   der 

Stubenfliege.     A.P.K.,  xiii.,  p.  19. 

(d)  Leishmania,  etc. 

See  also  No.  84.     For  references  to  literature  and  critical  summaries  and  reviews, 
see  Kala  Azar  Bulletin  (Royal  Society,  London). 

(561)  BASILE,  C.  (1910).     Leishmaniosi  del  Cane  e  1'Ospite  intermedio  del  Kala- 

Azar  infantile.     Rend.  Ace.  Lincei  (5),  xix.  (2),  p.  523. 

(562)  --  (1911).     Trasmissione  delle  Leishmaniosi.     Ibid.  (5),  xx.  (1),  p.  50. 

(563)  —  (1911).     Leishmaniosi  e  suo  Modo  di  Trasmissione.     Ibid.  (5),  xx.  (2), 

p.  72. 

(564)  —  LACAVA,  F.,  and  VISENTINI,  A.  (1911).     L'  Identita  delle  Leishmaniosi. 

Ibid.,  p.  150. 

(565)  DARLING,  S.  T.  (1909).     Histoplasma  capsulatum  and  the  Lesions  of  Histo- 

plasmosis.     J.E.M.,  xi.,  p.  515. 

(566)  DONOVAN,  C.  (1909).     Kala-Azar  in  Madras.     Bombay  Medical    Congress, 

February  24,  1909. 

(567)  LEISHMAN,  W.  B.,  and  STATHAM,  J.  C.  B.  (1905).      Development  of  the 

Leishman  Body  in  Cultivation.     Journ.  R.  A.  Med.  Corps,  iv.,  p.  321. 

(568)  MARSHALL,   W.   E.   (1911).     Pathological  Report,   Kala-Azar  Commission. 

Rep.  Wellcome  Lab.,  iv.,  p.  157. 

(569)  MARZINOWSKY,  E.  J.  (1909).     Cultures  de  Leishmania  tropica.     B.S.P.E., 

ii.,  p.  591. 


494  THE  PKOTOZOA 

(570)  NICOLLE,  C.  (1909).     Le  Kala-Azar  infantile.     A. I. P.,  xxiii.,  p.  361. 

(571)  —  and  COMTE,  C.  (1908).     Origine  canine  du  Kala-Azar.     C.R.A.S.,  cxlvi., 

p.  789. 

(572)  Now,  F.  G.  (1909).     Leishmania  infantum.     B.S.P.E.,  ii.,  p.  385. 

(573)  PATTOK,  W.  S.  (1908).     The  Leishman-Donovan  Parasite  in  Cimex  rotun- 

datus.     S.M.I.,  xxxi. 

(574)  —  (1908).     Inoculation  of  Dogs  with  the  Parasite  of  Kala-Azar  (Herpeto- 

monas  [Leishmania}  donovani).     Py.,  i.,  p.  311. 

(575)  --  (1909).     The  Parasite  of  Kala-Azar  and  Allied  Organisms.     Trans.  Soc. 

Trap.  Med.  Hygiene,  ii.,  p.  113. 

(576)  ROGERS,  L.  (1904).     Trypanosomes  from  the  Spleen  Protozoic  Parasites  of 

Cachexial  Fevers  and  Kala-Azar.     Q.J.H.S.,  xlviii.,  p.  367. 
(577)--  (1907).      The    Milroy    Lectures   on    Kala-Azar.       Brit.    Med.    Jo-urn., 

February  23,  March  2  and  9. 

578)  Row,  R.  (1909).     Development  of  the  Parasite  of  Oriental  Sore  in  Cultures. 
Q.J.M.S.,  liii.,  p.  747. 

(579)  THIROUX,  A.,  and  TEPPAZ,  L.  (1909).      La  Lymphangite  epizootique  des 

Equides  au  Senegal.     A. I. P.,  xxiii.,  p.  420. 

(580)  VISENTINI,  A.  (1910).     La  Morfologia  ed  il  Ciclo  di  Sviluppo  della  Leishmania. 

Istituto  d.  Clin.  Med.  d.  R.  Univ.  Roma. 

(581)  WEIGHT,  J.  H.  (1903).     Protozoa  in  Tropical  Ulcer  ("  Delhi  Sore  ").    Journ. 

Med.  Research,  x.  (n.s.  v.),  p.  472. 

(e)  Prowazekia. 

(582)  ALEXEIEFF,  A.  (1911).     La  Morphologic  et  la  Division  de  Bodo  caudatus. 

G.R.S.B.,  Ixx.,  p.  130. 

{582-5)  DTJNKERLY,  J.S.  (191:2).     Thelohania  and  Prowazekia  in  Anthomyid  Flies. 
C.B.B.P.K.  (I  Abth.  Orig.),  Ixii.,  p.  136. 

(583)  HARTMANN,    M.    (1911).      Die    Flagellatenordnung    Binudeata    und    die 

Gattung  Prowazekia.     A.P.K.,  xxii.,  p.  141. 

(584)  MARTINI,   E.   (1910).     Pr.   cruzi  und  ihre  Beziehungen  zur  Atiologie  von 

ansteckenden  Darmkrankheiten  zu  Tsingtau.     Z.H.,  Ixvii.,  p.  275. 

(585)  NAEGLER,  K.  (1910).     Pr.  parva.     A.P.K.,  xxi.,  p.  111. 

(586)  WALKER,  E.  L.  (1910).     Trypanoplasma  ranee.     Journ.  Med,  Research,  xxiii., 

(n.s.  XVIIL),  p.  391. 

(587)  WHITMORE,  E.  R.  (1911).     Pr.  asiatica.     A.P.K.,  xxii.,  p.  370. 


CHAPTER  XIV 
SPOROZOA— TELOSPORIDIA 

(a)  General  Works. 

*(588)  HAGENMULLER    (1899).     Bibliotheca    Sporozoologica.     Ann.    Mus.    Nat. 

Hist.  Marseille  (2),  i. 
*(589)  MINCHIN,  E.  A.  (1903).     The  Sporozoa.     A  Treatise  on  Zoology  (Lankester) 

(London,  A.  and  C.  Black),  p.  150. 

(590)  WOODCOCK,   H.  M.   (1910).     Sporozoa.     Encyclop.  Brit.,  eleventh  edition, 

xxv.,  p.  734.  Coccidia.  Ibid.,  vi.,  p.  615.  Gregarines.  Ibid.,  xii., 
p.  555.  Hremosporidia.  Ibid.,  xii.,  p.  806.  Endospora.  Ibid.,  ix. 
p.  383. 

(b)  Gregarines. 
See  also  Nos.  72,  84,  and  123. 

(591)  AWERINZEW,  S.  (1909).     Die  Vorgange  der  Schizogonie  bei  Gregarinen  aus 

dem  Darm  von  Amphiporus  sp.     A.P.K.,  xvi.,  p.  71. 

(592)  BEATJCHAMP,  P.  de  (1910).     Une  Gregarine  nouvelle  du  Genre  Porospora. 

C.R.A.S.,  cli.,  p.  997. 

(593)  BERNDT,  A.  (1902).     Die  im  Darme  der  Larve  von  Tenebrio  molitor  lebendcn 

Gregarinen.     A.P.K.,  i.,  p.  375. 

(594)  BRASIL,     L.     (1905).     La    Reproduction    des    Gregarines    monocystidees. 

A.Z.E.  (4),  iii.,  p.  17. 


BIBLIOGRAPHY  495 

(595)  BEASIL,     L.     (1905).      La    Reproduction    des    Gregarines    monocvstidees 

A.Z.E.  (4),  iv.,  p.  69. 

(596)  —  (1907).     La  Schizogonie  et  la  Croissance  des  Gametocytes  chez  Selenidium 

caulleryi.     A.P.K.,  viii.,  p.  370. 

(597)  —  (1909).     Documents   sur   quelques   Sporozoaires   d'Annelides.     A.P  K 

xvi.,  p.  107. 

(598)  COGNETTI  DE  MAETiis,  L.  (1911).     Le  Monocistidee  e  loro  Fenomeni  ripro- 

duttivi.     A.P.K.,  xxiii.,  p.  205. 

(599)  COMES,    S.    (1907).     Der   Chromidialapparat  der  Gregarinen.     A.P  K     x 

p.  416. 

(600)  CBAWLEY,  H.  (1905).     Movements  of  Gregarines.     Proc.  Acad.  Philadelphia 

Ivii.,  p.  89. 

(601)  CUNNINGHAM,  J.  T.  (1907).     Kalpidorliynclius  arenicolce.    A.P.K.,  x.,  p.  199. 

(602)  DOGIEL,  V.  (1906).     Cystobia  chiridotce.     A.  P.K.,  vii.,  p.  106. 

(603)  -  -  (1907).     Schizocystis  sipunculi.     A.P.K.,  viii.,  p.  203. 

(604)  --  (1909).     Die  Sporocysten  der  Colom-Monocystidese.    A.P.K.,  xvi.,  p.  194. 

(605)  —  (1910).     Callynthrochlamys  phronimce.     A.P.K.,  xx.,  p.  60. 

(606)  -  -  (1910).     Einige  neue  Catenata.     Z.w.Z.,  xciv.,  p.  400. 

(607)  DEZEWECKI,  W.  (1903,  1907).     Vegetative  Vorgange  im  Kern  und  Plasma 

der  Gregarinen  des  Regemvurmhodens.     A. P. K.,  in.,  p.  107.     \\.Stomatci- 
phora  coronata.     Ibid.,  x.,  p.  216. 

(608)  DUKE,  H.  L.  (1910).     Metamera  schubergi.     Q.J.M.S.,  Iv.,  p.  261. 

(609)  FANTHAM,  H.  B.  (1908).     The  Schizogregarines.     P,/.,  L,  p.  369. 

(610)  HALL,  M.  C.  (1907).     A  Study  of  some  Gregarines,  with  especial  Reference  to 

Hirmocystis  rigida.     Stud.  Zool.  Lab.  Univ.  Nebraska,  vii.,  p.  149. 

(611)  HESSE,   E.   (1909).     Les  Monocystidees  des  Oligochetes.     A.Z.E.  (5),   iii., 

p.  27. 

(611 -5)  HOFFMANN,  R.  (1908).     Fortpflanzungserscheinungen  von  Monocystideen 
des  Lumbricus  agricola.     A.P.K.,  xiii.,  p.  139. 

(612)  HUXLEY,  J.  S.  (1910).     Ganymedes  anaspidis,  Q.J.M.S.,  Iv.,  p.  155. 

(613)  KUSCHAKEWITSCH,  S.  (1907).     Vorgange  bei  den  Gregariuen  des  Mehlwurm- 

darms.     A.P.K.,  Suppl.  L,  p.  202. 

(614)  LEGEE,  L.  (1904).     La  Reproduction  sexuee  chez  les  StylorJiynchus.    A.P.K., 

iii.,  p.  303. 

(615)  -  -  (1904).     Sporozoaires  Parasites  de  YEmbia  Solieri.     Ibid.,  p.  358. 

(616)  —  (1906).     Tceniocystis  mira.     A.P.K.,  vii.,  p.  307. 

(617)  —  (1907,   1909).     Les    Schizogregarines   des   Tracheates  :    I.  Ophryocystis. 

A.P.K.,  viii.,  p.  159.     II.  Schizocystis.     Ibid.,  xviii.,  p.  83. 

(618)  —  and  DUBOSCQ,  0.  (1902).     Les  Gregarines  et  1'Epithelium  intestinal  chez 

les  Tracheates.     Arch.  Parasitol.,  vi.,  p.  377. 

(619)  —  —  (1903).     Le  Developpement  des  Gregarines  Stylorhynchides  et  Steno- 

phorides.     A.Z.E.  (4),  i.,  Notes  et  Revue,  p.  Ixxxix. 
(620) (1904).     Les   Gregarines  et  1'Epithelium  intestinal  des  Tracheates. 

A.P.K.,  iv.,  p.  335. 

(621) (1909).     La  Sexualite  chez  les  Gregarines.     A.P.K.,  xvii.,  p.  19. 

(622) (1911).     Deux  nouvelles  Especes  de  Gregarines  appartenant  au  Genre 

Porospora.     Ann.  Univ.  Grenoble,  xxiii., p.  401. 
*(623)  LUHE,  M.  (1904).     Die  Sporozoiten,  die  Wachstumsperiode  und  die  ausge- 

bildeten  Gregarinen.     A.P.K.,  iv.,  p.  88. 

(624)  NUSBAUM,  J.  (1903).     Fortpflanzung  einer  Gregarine — Schaudinella  henlece. 

Z.w.Z. ,  lxxv.,p.  281. 

(625)  PAEHLER,  F.  (1904).     Die  Morphologic,  Fortpflanzung  und  Entwicklung  von 

Gregarina  ovata.     A.P.K.,  iv.,  p.  64. 

(626)  PFEFFEE,  E.   (1910).     Die  Gregarinen  im  Darm  der  Larve  von  Tenebrio 

molitor.     A.P.K.,  xix.,  p.  107. 

(627)  POETER,  A.  (1909).     Merogregarina  amaroucii.     A.P.K.,  xv.,  p.  228. 

(628)  ROBINSON,  M.  (1910).     On  the  Reproduction  of  Kalpidorhynchus  arenicolce, 

Q.J.H.S.,  liv.,  p.  565. 

(629)  SCHELLACK,  C.  (1907).    Die  Entwicklung  und  Fortpflanzung  von  Echinomera 

hispida.     A.P.K.,  ix.,  p.  297. 

(630)  -  -  (1908).     Die  solitare  Encystierung  bei  Gregarinen.     Z.A.,  xxxii.,  p.  597. 

(631)  SCHNITZLEE,  H.  (1905).     Die  Fortpflanzung  von  Clepsidrina  ovata.    A.P.K., 

vi.,  p.  309. 

(632)  WOODCOCK,  H.  M.  (1906).     Life-Cycle  of  "  Cystobia  "  ir-regularis.     Q.J.M.S. 

1.,  p.  1. 


496  THE  PROTOZOA 

(c)  Coccidia. 

See  also  Nos.  47,  83,  94,  99,  and  147. 

*(633)  BLANCHARD,  R.  (1900).     Les  Coccidies  et  leur  Role  pathogene.     Causeries 
Sci.  Soc.  Zool.  France,  p.  133. 

(634)  CHAGAS,  C.  (1910).     Adelea  hartmanni.     M.I.O.C.,  ii.,  p.  168. 

(635)  DAKIN,  W.  J.  (1911).     Merocystis  kathce.     A.P.K.,  xxii.,  p.  145. 

(635'"))  DEBAISIEUX,  P.  (1911).    Recherches  sur  les  Coccidies.    La  Cellule,  xxvii., 
pp.  89  and  257. 

(636)  DOBELL,  C.  C.  (1907).     Life-History  of  Adelea  ovata.     P.E.S.  (B.),  Ixxix., 

p.  155. 

(637)  ELMASSIAN,  M.  (1909).     Coccidium  rouxi,  Zoomyxa  legeri.     A.Z.E.  (5),  ii.,. 

p.  229. 

(638)  FANTHAM,  H.  B.  (1910).     Eimeria  (Coccidium)  avium.     P.Z.S.,  1910,  p.  672. 

(639)  -  -  (1910).     Avian  Coceidiosis.     Ibid.,  p.  708. 

(640)  HADLEY,  P.  B.  (1911).     Eimeria  avium.     A.P.K.,  xxii.,  p.  7. 

(641)  JOLLOS,    V.    (1909).     Multiple   Teilung   und    Reduktion   bei   Adelea   ovata. 

A.P.K.,  xv.,  p.  249. 

(642)  KUNZE,  W.  (1907).     Orclieobius  herpobdellce.     A.P.K.,  ix.,  p.  382. 

(643)  LAVEEAN,  A.,  and  PETTIT,  A.  (1910).     Une  Coccidie  de  Agama  colonorum. 

(Cocc.  agamce).     G.R.8.B.,  Ixviii.,  p.  161. 

(644)  LEGER,  L.  (1911).     Caryospora  simplex,  et  la  Classification  des  Coccidies. 

A.P.K.,  xxii.,  p.  71.  * 

(645)  —  and   DUBOSCQ,  0.   (1908).     L'Evolution    schizogonique    de    V Aggregate 

(Eucoccidium)  eberthi.     A.P.K.,  xii.,  p.  44. 

(646)  -        -   (1910).     Selenococcidium  intermedium.     A.Z.E.  (5),  v.,  p.  187. 

(647)  METZNER,  R.  (1903).     Coccidium  cuniculi.     A.P.K.,  ii.,  p.  13. 

(648)  MOEOFF,  T.  (1906).     Adelea  zonula.     A.P.K.,  viii.,  p.  17. 

(649)  --  and  FIEBIGEE,  J.  (1905).     Eimeria  subepithelialis.     A.P.K.,  vi.,  p.  166. 

(650)  PEEEZ,  C.  (1903).     Le  Cycle  evolutif  de  1' Adelea  mesnili.     A.P.K.,  ii.,  p.  1. 

(651)  SCHELLACK,   C.,   and  REICHENOW,  E.  (1910).     Lithobius-Coccidien.     Z.A., 

xxxvi.,  p.  380. 

(652)  SIEDLECKI,  M.  (189S).     La  Coccidie  de  la  Seiche.     A.I.P.,  xii.,  p.  799. 
(653)--  (1907).     Caryotropha  mesnilii.     B.A.S.C.,  1907,  p.  453. 

(654)  STEVENSON,  A.  C.  (1911).     Coccidiosis  of  the  Intestine  of  the  Goat.     Rep. 

Wellcome  Lab.  Khartoum,  iv.,  p.  355. 

(655)  TYZZEE,    E.    E.    (1910).     Cryptosporidium   muris  of  the   Common   Mouse. 

Journ.  Med.  Research,  xxiii.  (n.s.  XVIII.),  p.  487. 

(656)  WOODCOCK,  H.  M.  (1904).     On  Klossiella  muris.     Q.J.M.S.,  xlviii.,  p.  153. 


CHAPTER  XV 

H^EMOSPORIDIA 

(a)  General  Works. 

*(657)  LAVERAN,  A.  (1905).     Haernocytozoa.     B.I.P.,  iii.,  p.  809. 
*(658)  SCHAUDINN,  F.  (1899).     Der  Generationswechsel  der  Coccidien  und  Hsemo- 
sporidien.     Zool.  Centralbl.,  vi.,  p.  765. 

(659)  WASIELEWSKI  (1908).     Studien  und  Mikrophotogramme  zur  Kenntnisse  der 

pathogenen     Protozoen.     II.  Untersuchungen     iiber     Blutschmarotzer. 
Leipzig  :  Barth. 

(b)  Hsemamcebse. 
See  also  Nos.  130  and  686. 

(660)  AEAGAO,  H.   DE  B.,  and    NEIVA,   A.    (1909).      Intraglobular   Parasites  of 

Lizards.  PL  diploglossi  and  PI.  tropiduri.     M.I.O.C.,  i.,  p.  44. 

(661)  BEEENBEEG-GOSSLEE,    H.    v.    (1909').     Naturgeschichte    der    Malariaplas- 

modien.     A.P.K.,  xvi.,  p.  245. 

(662)  BERTRAND,  D.  M.   (1911).      Les  Parasites  endoglobulaires  pigmentes  des 

Vertebres.     Paris  :  Jouve  et  Cie. 

(663)  BILLET,  A.  (1905).      Une  Forme  particuliere  de  I'Heniatozoaire  du  Palu- 

disme  decrite  par  MM.  Ed.  et  Et.  Sergent.     C.R.S.B.,  Iviii.,  p.  720. 

(664)  -  -  (1906).     La  Forme  hemogregarinienne  du  Parasite  de  la  Fievre  quarte. 

C.R.S.B.,  Ix.,  p.  891. 


BIBLIOGRAPHY  497 

(665)  BILLET,    A.    (1906).     Diagnose   differentielle    des    Formes    annulaires    de3 

Hernatozqaires  du  Paludisme.     C.R.S.B.,  Ixi.,  p.  754. 

(666)  —  (1910).     Evolution  chez  le  mGme  Sujct  du  Paludisine  tierce  primaire  en 

Paludisme  tierce  secondaire.     B.S.P.E.,  iii.,  p.  187. 

(667)  CARDAMATIS,  J.  P.  (1909).     Le  Paludisme  des  Oiseaux  en  Gr£ce.     Etude  du 

Parasite  de  Danilewsky.     C.B.B.P.K.  (I  Abth.  Orig.),  Hi.,  p.  351. 

(668)  CASTELLANI,  A.,  and  WILLEY,  A.   (1904).     Hsematozoa  of  Vertebrates  in 

Ce3'lon.     Spolia  Zeylanica,  ii.,  p.  78. 

(669)  DARLING,   S.  T.   (1910).     Transmission  and  Prevention  of  Malaria  in  the 

Panama  Canal  Zone.     A.T.M.P.,  iv.,  p.  179. 

(670)  DOBELL,  C.  C.  (1910).     Life-History  of  Hcemocystidium  simondi.     Hertwig's 

Festschrift,  i.,  p.  123. 

(671)  FLTT,  P.  C.  (1908).     Affenmalaria.     A.P.K.,  xii.,  p.  323. 

(672)  GILRTJTH,  J.  J.,  SWEET,  G.,  and  DODD,  S.  (1910).     Proteosoma  li^iurce  and 

Hcemogregarina  megalocystis.     Proc.  Roy.  Soc.  Victoria  (n.s.),  xxiii.,  p.  321. 

(673)  GRASSI,  B.  (1901).     Die  Malaria,  Studien  eines  Zoologen.     Jena  :  Gustav 

Fischer. 

(674)  HALBERSTAEDTER,  L.,  and  PROWAZEK,  S.  v.  (1907).     Die  Malariaparasiten 

der  Affen.     A.K.G.A.,  xxvi.,  p.  37. 

(675)  HARTMANN,   M.   (1907).     Das  System  der  Protozoen.   Zugleich  vorlaufige 

Mitteilung  iiber  Proteosoma.     A.P.K.,  x.,  p.  139. 

(676)  MAYER,  M.  (1908).     Malariaparasiten  bei  Affen.     A.P.K.,  xii.,  p.  314. 

(677)  NEUMANN,  B.   0.  (1908).     Die  Ubertragung  von  Plasmodium  prcecox  auf 

Kanarienvogel  durchStegomyiafasciata.     A.P.K.,  xiii.,  p.  23. 

(678)  Boss,  B.  (1910).     The  Prevention  of  Malaria.     London  :  John  Murray. 

(679)  SERGENT,  ET.,  and  SERGENT,  ED.  (1910).     L'Immunite  dans  le  Paludisme 

des  Oiseaux,  etc.     O.R.A.S.,  cli.,  p.  407. 

(680)  THIROTTX,  A.  (1906).     Des  Relations  de  la  Fifevre  tropicale  avec  la  Quarte  et 

la  Tierce.     A.I. P.,  xx.,  pp.  766  and  869. 

(681)  VASSAL,  J.  J.  (1907).     L'Hematozoaire  de  1'Ecureil  (Hcemamceba  vassali). 

A.I. P.,  xxi.,  p.  851. 

(c)  Halteridia. 
See  also  No.  132. 

(682)  ANSCHUTZ,  G.  (1910).     Uebertragungsversuche  von  Hcemoproteus  oryzivorce 

uiid  Trypanosoma  paddce.     G.B.B.P.K.  (I  Abth.  Orig.),  liv.,  p.  328. 

(683)  ARAGAO,  H.  DE  B.  (1908).     Der  Eritwicklungsgang  und  die  Ubertragung  von 

Hcemoproteus  columbas.     A.P.K.,  xii.,  p.  154. 

(684)  MAYER,  M.   (1910).     Die  Entwicklung  von  Halteridium.     A.S.T.H.,  xiv., 

p.  197. 

(685)  —  (1911).     Ein  Halteridium  und  Leucocytozoon  des  Waldkauzes.     A.P.K., 

xxi.,  p.  232. 

(685'5)  MINCHIN,    E.   A.    (1910).     Report  on    Blood-Parasites  collected   by  the 
Commission.     Rep.  Sleeping  Sickness  Comm.,  x.,  p.  73. 

(686)  SERGENT,  ED.,  and  SERGENT,  ET.  (1907).     Les  Hematozoaires  d'Oiseaux. 

A.I. P.,  xxi.,  p.  251. 

(687)  WOODCOCK,  H.  M.  (1911).     An  Unusual  Condition  in  Halteridium.     Z.A., 

xxxviii.,  p.  465. 

(d)  Leucocytozoa  (Vera). 
See  also  Nos.  132,  473,  and  686. 

(688)  BERESTNEFF,    N.    (1904).     Das   Leucocytozoon   Danilewskyi.     A.P.K.,    iii., 

p.  376. 

(689)  FANTHAM,  H.  B.  (1910).     Parasitic  Protozoa  of  the  Red  Grouse.     P.Z.S., 

1910,  p.  692. 

(690)  WENYON,  C.  M.  (1910).     On  the  Genus  Leucocytozoon.     Py.,  iii.,  p.  63. 

(e)  Hsemogregarines. 
See  also  Nos.  78,  84,  and  89. 

(691)  ADIE,  J.  B.  (1906).     "  Leucocytozoon  "  ratti.     Journ.  Trop.  Med.,  ix.,  p.  325. 

(692)  ARAGAO,   H.   DE  B.   (1911).     Hamogregarinen  von  Vogeln.     M.I.O.C.,  iii. 

p.  54. 

(693)  BALFOITR,  A.  (1906).     //.  balfouri.     Rep.  Wellcome  Lab.  Khartoum,  ii.,  p.  96. 

(694)  —  (1906).     "  Leucocytozoon"  muris.     Ibid.,  p.  110. 

32 


498  THE  PROTOZOA 

(695)  BERESTNEFF,  N.  (1003).     Einc  neue  Blutparasiten  der  indischen  Frosche. 

A.P.K.,  ii.,  p.  343. 

(696)  BILLET,  A.  (1904).     Trypanosoma  inopinatum  ct  Drepanidium.     C.R.8.B., 

Ivii.,  p.  161. 

(697)  BOTJET     G.    (1909).     Hemogregarines    de    1'Afrique    occidentale    fran9aise. 

C.E.S.B.,  Ixvi.,  p.  741. 

(698)  CARINI,  A.  (1910).     "  H.  muris."     Rev.  Soc.  Sci.  Sao  Paulo,  v. 

(699)  CHRISTOPHERS,  S.  R.  (1905).     H.  gerbilli.     S.M.I.,  18. 
(7<Ht)  --  (1906).     Leucocytozoon  canis.     S.M.I.,  26. 

(701)  --  (1907).     Leucocytozoon  canis  in  the  Tick.     S.M.I.,  28. 

(703)  DANILEWSKY,   B.    (1886).     Les   Hematozoaires  des   Lezards.     Arch.   Slav. 

Bid.,  i.,  p.  364. 

(704)  --  (1887).     Les  Hematozoaires  des  Tortues.     Ibid.,  iii.,  pp.  33  and  370. 

(705)  --  (1889).     La  Parasitologie  comparee  du  Sang.     I.  Nouvelles  Recherches 

sur  les  Hematozoaires  du  Sang  des   Oiseaux.     II.  Recherches  sur  les 
Hematozoaires  des  Tortues.     Kharkoff. 

(706)  FANTHAM,  H.  B.  (1905).     Lankesterella  tritonis.     Z.A.,  xxix.,  p.  257. 

(707)  FLTJ,   P.   C.  (1909).     Hamogregarinen  im  Blute  Surinamischer  Schlangen. 

A.P.K.,  xviii.,  p.  190. 

(708)  FRANCA,    C.    (1908).     Une   Hemogregarine   de  1'Anguille    (H.   bettencourti). 

A.I.C.P.,  ii.,  p.  109. 

(709)  --  (1908).     H.  splendens  (Labbe).     Ibid.,  p.  123. 

(710)  --  (1909).     Hemogregarines  de  Lacerta  ocellata.     Ibid.,  p.  339. 

(711)  --  (1910).     Parasites    endocellulaires    du    Psammodromus   algirus.      Ibid., 

iii.,  p.  1. 

(712)  --  (1910).     Hemogregarines  de  Lacerta  muralis.     Ibid.,  p.  21. 

(713)  HAHN,  C.  W.  (1909).     H.  stepanowi  in  the  Blood  of  Turtles.     A.P.K.,  xvii., 

p.  307. 
{714)  KOIDZUMI,  M.  (1910).     H.  sp.  in  Clemmys  japonicus.    A.P.K.,  xviii.,  p.  260. 

(715)  LAVERAN,  A.,  and  PETTIT,   A.   (1909).     Les  Hemogregarines  de  quelques 

Sauriens  d'Afrique.     B,S.P.E.,  ii.,  p.  506. 

(716)  --  —  (1910).     Les    Formes    de    Multiplication    endogene    de    H.     sebai. 

C.R.A.S.,  cli.,  p.  182. 

(717)  -        -  (1910).     H.  agamce.     C.R.S.B.,  Ixviii.,  p.  744. 

(718)  -        -  (1910).     Le  Role  d'Hyalomma  Mgyptium  L.  dans  la  Propagation  de 

H.  maurita.nica.     C.-R.  Assoc.  France  (Lille),  p.  723. 

(719)  MILLER,  W.  W.  (1909).     Hepatozoon  perniciosum  and  its  Sexual  Cycle  in 

the  Intermediate  Host,  a  Mite  (Lelaps  echidninus).     Hygienic  Laboratory 
Bulletin,  No.  46  (June,  1908). 

(720)  NERESHELMER,  E.  (1909).     Das  Eindringen  von  Lankesterella  spec,  in  die 

Froschblutkorperchen.     A.P.K.,  xvi.,  p.  187. 

(721)  PATTON,  W.  S.  (1906).     On  a  Parasite  found  in  the  Blood  of  Palm  Squirrels. 

S.M.I.,  24. 

(722)  -  -  (1908).     The  Hsemogregarines  of  Mammals  and  Reptiles.     Py.,  i.,  p.  319. 

(723)  PORTER,  A.  (1908).     Leucocytozoon  musculi.     P.Z.S.,  1908,  p.  703. 

(724)  PROWAZEK,  S.  v.  (1907).     Ueber  Hamogregarinen.     A.K.G.A.,  xxvi.,  p.  32. 

(725)  ROBERTSON,  M.  (1910).     Life-Cycle  of  H.  nicorice.     Q.J.M.S.,  lv.,  p.  741. 

(726)  SAMBON,  L.  W.,and  SELIGMANN,  C.  G.  (1907).     Ha?mogregarines  of  Snakes. 

Trans.  Pathol.  Soc.  London,  Iviii.,  p.  310. 

(727)  SEITZ    (1910).     Dio    Hartmannsche    Binukleaten.     C.B.B.P.K.    (I.    Abth. 

Orig.),  Ivi.,  p.  308. 

(!)  Piroplasms. 
See  also  No.  528. 

(728)  BETTENCOURT,    A.,    FRANCA,    C.,    and    BORGES,    I.    (1907).     Piroplasmose 

bacillifornie  chez  le  Daim.     A.I.C.P.,  i.,  p.  341. 

(729)  BOWHILL,  T.  (1905).     Equine  Piroplasmosis,  or  "  Biliary  Fever."     J.H.,v., 

p.  7. 

(730)  BREINL,  A.,  and  HINDLE,  E.  (1908).     Morphology,  etc.,  of  Piroplasma  canis. 

A.T.M.P.,  ii.,  p.  233. 

(731)  BRUCE,  D.,  HAMERTON,  A.  E.,  BATEMAN,  H.  R.,  and  MACKIE,  F.  P.  (1910). 

Amakebe  :  a  Disease  of  Calves  in  Uganda.     P.R.S.  (B.),  Ixxxii.,  p.  256. 
*(732)  CHRISTOPHERS,  S.  R.  (1907).      P.  canis  and  its  Life-Cycle  in  the  Tick. 

S.M.I.,  29. 
(733)  DSCHXTNKOWSKY,  E.,  and  LUHS,  J.  (1909).     Protozoenkrankheiten  des  Blutes 

des  Haustiere  in  Transkaukasien.     Ber.  IX,  Int.  Tierarztl.  Kongr.  Haag 


BIBLIOGRAPHY  499 

{734)  DSCHUNKOWSKY,  E.,  and  Lrns,  J.  (1909).  Entwickelungsformen  von 
Piroplasmen  in  Zccken.  Ibid. 

(735)  FAXTHAM,  H.  B.  (1907).     The  Cbromatin-Masses  of  P.  bigemiimm  (Babesia 

bovis.     Q.J.M.S.,  li.,  p.  297. 

(736)  FRANCA,   C.    (1910).     La   Classification  des  Piroplasmes  et  Description  de 

deux  Formes.     A.I.O.P.,  iii.,  p.  11. 

(737)  GONDER,  R.  (1906).     Achromaticus  vesperuginis.     A.K.G.A.,  xxiv.,  p.  220. 

(738)  —  (1910).     Die  Entwicklung  von  Theileria  parva.     A.P.K.,  xxi.,  p.  143. 

(739)  —  (1911).     Tli.  parva  und  Babesia  mutans  Kiistenfieberparasit  und  Pseudo- 

kiistenfieberparasit.     Ibid.,  p.  222. 

(740)  -  -  (1911).     Die  Entwicklung  von  Th.  parva.     II.     A.P.K.,  xxii.,  p.  170. 

(741)  KIKOSHITA,  K.  (1907).     Babesia  canis.  '  A.P.K.,  viii.,  p.  294. 

(742)  KLEINE,     F.     K.     (1906).     Kultivierungsversuch    der    Hundepiroplasrnen. 

Z.H.,  liv.,  p.  10. 
{743)  KOCH,  R.  (1906).     Entwicklungsgeschickte  der  Piroplasmen.     Ibid.,  p.  1. 

(744)  MAYER,  M.  (1910).     Das  ostafrikanische  Kiistenfieber  der  Kinder.    A.8.T.H. 

xiv.,  Beiheft  7,  p.  307. 

(745)  NEUMANN,    R.    0.    (1910).     Die    Blufparasiten    von    Vesperugo.     A.P.K., 

xviii.,  p.  1. 

(746)  NICOLLE,  G.  (1907).     Une  Piroplasmose  nouvelle  d'un  Rongeur.     C.E.S.B., 

Ixiii.,  p.  213. 

(747)  NTJTTALL,  G.  H.  F.,  and  FANTHAM,  H.B.  (1910).     Theileria  parva.     Py., 

iii.,  p.  117. 

*(74S)  --  and  GRAHAM-SMITH,  G.  S.  (1906,  1907).  Canine  Piroplasmosis  V.  and 
VI.  J.H.,  vi.,  p.  585  ;  vii.,  p.  232. 

(749)  —      -  (1908).     Multiplication  of  Piro  plasma  bovis,  P.  pithed  in  the  circu- 

lating Blood  compared  with  that  of  P.  canis.     Py.,  i.,  p.  134. 

(750)  -        -  (1908).     Development  of  P.  canis  in  Cultures.     Ibid.,  p.  243. 

(751)  SMITH,  T.,  and  KILBORNE,  F.  L.  (1893).      Southern  Cattle  Fever.      U.S. 

Dept.  of  Agriculture,  Eighth  and  Ninth  Reports  Bureau  Animal  Industry, 

1891,  1892,  p.  77. 
{752)  THEILEE,    A.    (1910).     Texasfieber,    Rotwasser   mid    Gallenkrankrieit    der 

Rinder.     Zeitschr.  /.  InfektionskranJcheiten  der  Haustiere,  viii.,  p.  39. 
{753)  YAKIMOFF,  W.  L.,   STOLNIKOFF,  W.  J.,   and  KOHL-YAKIMOFF,  N.   (1911). 

L.  Achromaticus  vesperujinus.     A.P.K.,  xxiv.,  p.  60. 

(g)  Incertas  Sedis. 

(754)  NICOLLE,  C.,  and  MANCEATJX,  L.  (1909).  Un  Protozoaire  nouveau  du  Goudi. 
G.E.A.S.,  cxlviii.,  p.  369. 

{755)  PATELLA,  V.  (1910).  Corps  de  Kurloff-Demel  dans  quelques  Mononucleaires 
du  Sang  des  Cobayes.  La  Glnese  Endothiliale  des  Leucocytes  Mono- 
nucleaires du  Sang  (Siena,  Imprimerie  St.  Bernardin),  p.  211. 

(756)  SEIDELIN,    H.    (1911).     Protozoon-like   Bodies   in   Yellow-Fever   Patients. 

Journ.  Pathol.  Bacterial.,  xv.,  p.  282. 

(757)  —  (1911).     Etiology  of  Yellow  Fever.      Yellow  Fever  Bureau  Bulletin,  i., 

p.  229. 

CHAPTER  XVI 

SPOROZOA— NEOSPORIDIA 
A.  CNIDOSPORIDIA 

(a)  General  Works. 
*(758)  AUEEBACH,  M.  (1910).     Die  Cnidosporidien.     Leipzig  :  Werner  Klinkhardt. 

(b)  Myxosporidia. 

(759)  AVTEEINZEW,  S.  (1909).     Die  Spore nbildung  bei  Ceratomyxa  drepanopsettce. 

A.P.K.,  xiv.,  p.  72. 

(760)  -  -  (1911).     Sporenbildung  bei  Myxidium  sp.  aus  der  Gallenblase  von  Coitus 

scorpius.     A.P.K.,  xxiii.,  p.  199. 

(761)  CHATTON,  E.  (1911).     Paramyxa  paradoxa.     G.R.A.S.,  clii.,  p.  631. 

(762)  DOFLEIN,   F.   (1898).     ilyxosporidien.     Zool.  Jalirbuclicr  (Abth.  f.  Anal.  u. 

Ontoy.},  xi.,  p.  281 


500  THE  PROTOZOA 

(763)  KEYSSELITZ,  G.  (1908).     Die  Entwicklung  von  Myxobolus  pfeifferi,  I.  and  II- 
A.P.K.,  xi.,  p.  252. 

(704)  LEGEK,  L.,  and  HESSE,  E.   (1906).     La  Paroi  sporale  des  Myxosporidies. 

C.B.A.S.,  cxlii.,  p.  720. 

(765)  -        -  (1907).     Coccomyxa  morovi.     C.R.A.S.,  cxlv.,  p.  85. 

(765'5)  MERCIER,  L.  (1910).      La  sexualite  chcz  les  Myxosporidies  et  chez  les 
Microsporidies.     Acad.  Roy.  Belgique,  Mem.  Svo.  (2),  ii.,  No..  6. 

(766)  PLEHN,  M.   (1904).     Die  Drehkrankheit  der  Salmoniden  (Lentospora  cere- 

bralis).     A.P.K.,  v.,  p.  145. 

(767)  SCHRODER,      0.      (1907).       Entwicklungsgesckichte     der     Myxosporidien. 

Sphceromyxa  labrazesi  (sabrazesi).     A.P.K.,  ix.,  p.  359. 

(705)  —  (1910).     Die  Anlage  der  Sporocyste  (Pansporoblasten)  bei  Sphoeromyxa 

sabrazesi.     A.P.K.,  xix.,  p.  1. 

(c)  Actinomyxidia. 

(769)  CATTLLERY,  M.,  and  MESNIL,  F.  (1905).     Splioeractinomyxon  stolci.     A.P.K., 

vi.,  p.  272. 

(d)  Microsporidia. 

(770)  AWERINZEW,  S.,  and  FERMOR,  K.  (1911).     Die  Sporenbildung  bei  Glugea 

anomala.     A.P.K.,  xxiii.,  p.  1. 

(771)  CHATTON,  E.,  and  KREMPF,  A.  (1911).     Les  Protistes  du  genre  Octosporea. 

B.S.Z.F.,  xxxvi.,  p.  172. 

(772)  HESSE,   E.    (1904).     Le   Developpernent   de   Thelohania  legeri.     C.E.S.B., 

Ivii.,  p.  571. 

(773)  __  (1905).     Myxocystis  mrazeki.     C.R.S.B.,  Iviii.,  p.  12. 

(774)  LEGER,    L.,    and   DUBOSCQ,    0.    (1909).     Perezia  lankesterice.     A.Z.E.    (5), 

i.,  Notes  et  Revue,  p.  Ixxix. 

(775)  --  and    HESSE,     E.     (1910).      Cnidosporidies    des    Larves    d'Ephemeres. 

C.B.A.S.,cl.,p.4(ll. 

(776)  MERCIER,  L.  (1908).     Neoplasie  du  Tissu  Adipeux  chez  les  Blattes  Parasitees 

par  une  Microsporidie.     A.P.K.,  xi.,  p.  372. 

(777)  MRAZEK,  A.  (1910).     Auffassung  der  Myxocystiden.     A.P.K.,  xviii.,  p.  245. 

(778)  PEREZ,    C.     (1904).       Une    Microsporidie    parasite    du    Carcinus    mcenas. 

C.R.S.B.,  Ivii.,  p.  214. 

(779)  -  -  (1905).     Microsporidies   Parasites   des   Crabes   d'Arcachon.     Bull.  Stat. 

Biol.  Arcachon,  viii. 

(780)  -  -  (1908).     Duboscqia  legeri.     C.E.S.B.,  Ixv.,  p.  631. 

(781)  SCHRODER,  0.  (1909).     Thelohania  chcetogastris.     A.P.K.,  xiv.,  p.  119. 

(782)  SCHUBERG,  A.  (1910).     Microsporidien  aus  dem  Hoden  der  Barbe.    A.K.G.A., 

xxxiii.,  p.  401. 

(783)  SHIWAGO,    P.    (1909).     Vermekrung    bei    Pleistophora    periplanetce.     Z.A., 

xxxiv.,  p.  647. 

(784)  STEMPELL,  W.  (1904).     Nosema  anomalum.     A.P.K.,  iv.,  p.  1. 

(785)  --  (1909).     Nosema  bombycis.     A.P.K.,  xvi.,  p.  281. 

(786)  -  -  (1910).     Morpkologie  der  Microsporidien.     Z.A.,  xxxv.,  p.  801. 

(787)  WEISSENBERG,    R.    (1911).     Einige    Mikrosporidien    aus   Fiscken    (Nosema 

lophii,  Glugea  anomala,  Gl.  Hertwigii).     S.B.G.B.,  p.  344. 

(787-5)  WOODCOCK,  H.M.  (1904).     On  Myxosporidia  in  Flatfisk.     Trans.  Liverpool 
Biol.  Soc.,  xviii.,  p.  126. 

(e)  Sarcosporidia. 
See  also  Nos.  18,  25,  and  26. 

(788)  BETEGH,  L.  v.  (1909).     Entwicklungsgange  der  Sarcosporidien.    O.B.B.P.K. 

(I  Abtk.  Orig.),  Hi.,  p.  566. 

[788'5)  CRAWLEY,  H.  (1911).     Sarcocystis  rileyi.     Proc.  Acad.  Philadelphia,  1911, 
p.  457. 

(789)  DARLING,  S.  T.  (1910).     Experimental  Sarcosporidiosis  in  tke  Guinea-Pig. 

J.E.M.,  xii.,  p.  19. 

(790)  ERDMANN,    R.    (1910).     Kern   und    metackromatiscke    Korper   bei    Sarko- 

sporidien.     A.P.K.,  xx.,  p.  239. 

(791)  -  -  (1910).     Sarcocystis  muris  in  der  Muskulatur.     S.B.G.B.,  p.  377. 

(792)  FIEBIGER,    J.    (1910).      Sarkosporidien.      Verh.    Zool.-Bot.    Ges.    Wien,   Ix., 

p.  (73). 


BIBLIOGRAPHY  501 

(793)  LAVERAN,  A.,  and  MESNIL,  F.  (1899).     La  Morphologic  des  Sarcosporiclies. 

O.B.S.B.,  II,  p.  245. 

(794)  NEGRE,  L.   (1910).     Le  Stade  intestinal  de  la  Sarcosporidie  de  la  Souris. 

C.B.S.B.,  Ixviii.,  p.  997. 

(795)  NEGRI,  A.   (1908,   1910).      Ueber  Sarkosporidien,   I.  and  II.      C.B.B.P.K. 

(I  Abth.  Orig.),  xlvii.,  pp.  56  and  612  ;  III.,  Ibid.,  lv.,  p.  373. 

(797)  TEICHMANN,  E.  (1911).     Die  Teilungen  der  Keime  in  der  Cyste  von  Sarco- 

cystis  tenella.     A.P.K.,  xxii.,  p.  239. 

(798)  VUILLEMIN,  P.  (1902).     Sarcocystis  tenella.     C.R.A.S.,  cxxxiv.,  p.  1152. 

(799)  WATSON,    E.    A.    (1909).     Sarcosporidiosis  :  Its    Association    with    Loco- 

Disease,  etc.     Journ.  Comp.  Pathol.  Therapeut.,  xxii.,  p.  1. 

B.  HAPLOSPORIDIA. 

(800)  BEATTIE,  J.  M.  (1906).     Rhinosporidium  kinealyi.     Journ.  Pathol.  Bacterial., 

xi.,  p.  270. 

(801)  CAULLERY,  M.,  and  CHAPPELLIER,  A.  (1906).     Anurosporidium  pelseneeri. 

C.R.S.B.,  lx.,  p.  325. 

(802)  --  and  MESNIL,  F.  (1905).     Les  Haplosporidies.     A.Z.E.  (4),  iv.,  p.  101. 

(803)  CHATTON,  E.  (1907).     Caullerya  mesnili.     C.R.S.B.,  Ixii.,  p.  529. 

(804)  -  -  (1908).     Blastulidium  pasdopkthorum.     C.R.S.B.,  Ixiv.,  p.  34. 

(805)  CRAWLEY,  H.  (1905).     Ocdosporidium  blatellas.      Proc.  Acad.  Philadelphia, 

Ivii.,  p.  158. 

(806)  KING,  H.  D.  (1907).     P.ertmmia  lujonis.     Ibid.,  lix.,  p.  273. 

(807)  LAVERAN,  A.,  and  PETTIT,  A.  (1910).     Une  Epizootie  des  Truites.     G.R.A.S., 

cli.,  p.  421. 

(808)  MINCHIN,  E.  A.,  and  FANTHAM,  H.  B.   (1905).     Rhinosporidium  kinealyi. 

Q.J.M.S.,  xlix.,  p.  521. 

(809)  RIDEWOOD,  W.  G.,  and  FANTHAM,  H.  B.  (1907).     Neurosporidium  cephalo- 

disci.     Q.J.M.S.,  li.,  p.  81. 

(810)  ROBERTSON,  M.  (1908).     A  Haplosporidian  of  the  Genus  Ichthyosporidium. 

Proc.  R.  Pliys.  Soc.  Edinburgh,  xvii.,  p.  175. 

(811)  —  (1909).     An    Ichthyosporidian  causing  Disease   in    Sea-Trout.     P.Z.S., 

1909  p.  399. 

(812)  STEMPELL,  W.  (1903).     Die  Gattimg  Polycaryum.     A.P.K.,  ii.,  p.  349. 

(813)  WARREN,  E.  (1906).     Bertramia  kirktnanni.     Ann.  Natal.  Govt.  M  us.,  i.,  p.  7, 

(814)  WRIGHT,    J.    (1907).     Rhinosporidium   kinealyi.     New    York   Jled.   Journ., 

December  21. 

C.  INCERTJE  SEDIS. 

(815)  AWERLNZEW,  S.  (1909).     Lymphocyslis  johnstonei.     A.P.K.,  xiv.,  p.  335. 

(816)  —  (1911).     Die     Entwicklungsgeschichte     von     Lymphocystis    johnstonei. 

A.P.K.,  xxii.,  p.  179. 

(817)  CHATTON,  E.  (1906).      La  Biologie,  etc.,  des  Amcebidium.     A.Z.E.  (4),  v., 

Notes  et  Revue,  p.  xvii. 

(818)  --  (1907).     Pansporella  perplexa.     O.R.S.B.,  Ixii.,  p.  42. 

(819)  -  -  (1910).     Gastrocystis  gilruthi.     A.Z.E.  (5),  v.,  Notes  et  Revue,  p.  cxiv. 

(820)  GILRUTH,  J.  A.  (1910).     Gastrocystis  gilruthi.     Proc.  Roy.  Soc.  Victoria  (n.s.), 

xxiii.,  p.  19. 

(821)  GRANATA,  L.  (1908).     Capillus  intestinalis.     Biologica,  ii.,  p.  1. 

(822)  KRASSILSTSCHIK,   J.   M.   (1909).     Neue   Sporozoen  bei  Insekten.     A.P.K., 

xiv.,  p.  1. 

(823)  LE'GER,   L.,  and  DUBOSCQ,  0.   (1909).     Les   Chytridiopsis.     A.Z.E.  (5),  i. 

Notes  et  Revue,  p.  ix. 

(824)  WOODCOCK,    H.    M.    (1904).     Lymphocystis  johnstonei.     Trans.    Biol.   Soc. 

Liverpool,  xviii.,  p.  143. 


502  THE  PROTOZOA 

CHAPTER  XVII 
INFUSORIA 

(a)  General  Works. 

(Sj.->)  HAETOG,    M.    (1910).     Infusoria.     Encydop.    Brit.,    eleventh   edition,    xiv., 
" 


.  .. 

*(826)  HICKSUX,  S.  (1903).     The  Infusoria.     A   Treatise  on  Zoology  (Lankester) 
(London  :  A.  and  C.  Black),  p.  301. 

(b)  Ciliata. 

See  also,  Nos.  16,  32,  33,  38-5,  44,  50,  53,  73,  93,  96,  102,  104,  106-109,  111-113- 
115  121  122,  124-126,  136-143,  148,  149,  155,  162,  165-167,  170-173,  177,  181-183' 
197-199/201,  205,  206,  208,  209,  211,  214-220,  and  346. 

(827)  BEATJCHAMP,    P.    DE,    and    COLLIN,    B.    (1910).      Sur    Hastatella   radians. 

A.Z.E.  (5),  v.,  Notes  et  Revue,  p.  xxviii. 

(828)  BTTSCHKIEL,  A.  L.  (1911).     Ichthyophthirius  mtdtifiliis.     A.P.K.,  xxi.,  p.  61. 

(829)  CAULLERY,  M.,  and  MESNIL,  F.  (1903).     La  Structure  nucleaire  d'un  Infu- 

soire  Parasite  des  Actinies  (Fcettingeria  actiniarum).     C.R.8.B.,  lv.,  p.  806. 

(830)  --  (1907).     L'Appareil  nucleaire  d'un  Infusoire  (Ehizocaryum  concavum). 

C.R.Ass.  Franc.     Reims. 

(831)  CEPEDE,  C.  (1910).     Les  Infusoires  astomes.     A.Z.E.  (5),  iii.,  p.  341. 
(831'5)  CHATTON,    E.   (1911).      Perlkaryon  ciSticola   and    Conchophrys   davidoffi. 

A.Z.E.  (5),  viii.,  Notes  et  Revue,  p.  viii. 

(832)  COLLIN,    B.    (1909).     Deux    Formes    nouvelles    d'Infusoires    Discotriches. 

A.Z.E.  (5),  ii.  Notes  et  Revue,  p.  xxi. 

(833)  J  OBELL,  C.  C.  (1909).     Infusoria  parasitic  in  Cephalopoda.     Q.J.M.S.,  liii., 

p.  183. 

(834)  i  AT7EE-FEEMIET,    E.    (1905).     L'Appareil    fixateur    chez    les    Vorticdlidce. 

A.P.K.,  vi.,  p.  207. 

(835)  —  (1907).     Mitochondries    et    Spheroplastes    chez    les    Infusoires    cilies. 

C.E.S.B.,  Ixii.,  p.  523. 

(836)  —  (1908).     Tintinnidium  inquilinum.     A.P.K.,  xi.,  p.  225. 

(837)  --  (1908).     L'  Ancystropodium  maupasi.     A.P.K.,  xiii.,  p.  121. 

(838)  -  -  (1909).     Le  Macronucleus  des  Infusoires  cilies.     B.S.Z.F.,  xxxiv.,  p.  55. 

(839)  --  (1910).     Le  Mijcterotlirix  tuamotuensis.     A.P.K.,  xx.,  p.  223. 

(840)  GONDER,  R.  (1905).     Kernverhiiltnisse  bei  den  in  Cephalopoden  schmarot- 

zenden  Infusorien.     A.P.K.,  v.,  p.  240. 

(841)  HAMBURGER,  C.  (1903).     Traclidius  ovum.     A.P.K.,  ii.,  p.  445. 

(842)--  (1904).     Die  Konjugation  von  Param  cecium'bursaria.     A.P.K.,  iv.,  p.199. 

(843)  --  and    BTTDDENBROCK,  v.  (1911).     Nordische   Ciliata  mit  A\isschluss  der 

Tintinnoidea.     Brandt  and  Apstein,  Nordisches  Plankton. 

(844)  JOSEPH    (1907).      Kernverhiiltnisse    von    Loxodes   rostrum.     A.P.K.,    viii., 

p.  344. 

(845)  KASANZEFF,  W.  (1910).     Loxodes  rostrum.     A.P.K.,  xx.,  p.  79. 

(846)  KIERNIK,  E.  (1909).     Chilodon  hexastichus.     B.A.S.G.,  p.  75. 

(847)  KOFOID,    C.    A.    (1903).     Protophrya   ovicola.     Mark   Anniversary    Volume, 

p.  111. 

(848)  LEGER,   L.,   and  DUBOSCQ,    0.  (1904).      Les  Astomata  representent-ils  un 

Groupe  naturel  ?     A.Z.E.  (4),  ii.,  Notes  et  Revue,  p.  xcviii. 

(849)  -        -  (1904).     Les.  Infusoires  endoparasites.     A.Z.E.  (4),  ii.,  p.  337. 

(850)  MARTINI  (1910).     Uber  einen   bei  amobenruhrahnlichen  Dysenterien   vor- 

kommenden  Ciliateii.     Z.H.,  Ixvii.,  p.  387. 

(851)  MAST,  S.  0.  (1909).     The  Reactions  of  Didinium  nasutum.     B.B.,  xvi.,  p.  91. 
(851-5)  MAUPAS,  E.  (1888).     La  Multiplication  des  Infusoires  cilies.      A.Z.E.  (2), 

vi.,  p.  165. 

(852)  METCALF,  M.  M.  (1907)  .     Excretory  Organs  of  Opalina.     A.P.K.,  x.,  pp.  183, 

365. 

(853)  -  -  (1909).     Opalina  :  Its  Anatomy,  etc.     A.P.K.,  xiii.,  p.  195. 

(854)  MEUNIER,   A.    (1910).     Microplankton  des   Mers  de   Barents  et  de   Kara. 

Due  d'Orleans,  Campagne  Arctique  de  1907.     Brussels. 


BIBLIOGRAPHY  503 

(855)  MiTRorHANOW,  P.  (1905).     La  Structure,  etc.,  des  Trichocystes  des  Para- 

meeies.     A.P.K.,  v.,  p.  78. 

(856)  NERESHEIMER,  E.  R.  (1903).     Die  Hohe  histologischer  Differenzierung  bei 

heterotrichen  Cilia,ten.     A.P.K.,  ii.,  p.  305. 

(857)  NERESHEIMER,    E.    (1907).     Die    Fortpflanzung    der    Opalinen.     A.P.K., 

Suppl.  i.,  p.  1. 

(858)  —  (1908).     Fortpflanzung  eines  parasitischen   Infusors   (Ichthyophthiriiis), 

8.B.G.M.P.,  xxiii. 

(859)  PROWAZEK,  S.  v.  (1904).     Der  Encystierungvorgang  bei  Dileptus.     A.P.K., 

iii.,  p.  64. 

(860)  -  -  (1909).     Conjugation  von  Lionotus.     Z.A.,  xxxiv.,  p.  626. 

(861)--  (1909).     Formdimorphismus  bei  Ciliaten  Inf usorien.     H.I.O.C.,  i.,  p.  105. 

(862)  Rcrox,  J.  (1899).  Quelques  Infusoires  cilies  des  Environs  de  Geneve.     Rev. 

Suisse  Zool.,  vi.,  p.  557. 

(863)  SCHEWIAKOFF,  W.  (1893).     Die  geographische  Verbreitung  der  Susswasser- 

Protozoen.     Mem.  Acad.  Imp.  St.-Petersbourg  (vii.),  xli. 

(864)  SCHRODER,  0.  (1906).     Campanella  umbellaria.     A.P.K.,  vii.,  p.  75. 

(865)  —  (1906).     Epistylis  plicatilis.     Ibid.,  p.  173. 

(866)  —  (1906).      Vorticella  monilata.     Ibid.,  p.  395. 

(867)  -  -  (1906).     Stentor  cceruleus  und  St.  rceselii.     A.P.K.,  viii.,  p.  1. 

(868)  SCHUBOTZ,  H.  (1908).     Pycnothrix  monocystoides.     Denkschr.  Ges.  Jena,  xiii.. 

p.  1. 

(869)  SCHWEYER,    A.    (1909).      Tintimiodeenweichkorper,    etc.      A.P.K.,    xviii., 

p.  134. 

(870)  SIEDLECKI,  M.  (1902).     ISHerpetophrya  astoma.     B.A.S.C.,  p.  356. 

(871)  STEIN,  F.  v.  (1859,  1867).      Der  Organismus  der  Infusionthiere  :  I.  Hypo- 

tricha  ;  II.  Heterotricha.     Leipzig  :  W.  Engelmann. 

(872)  STEVENS,  N.  M.  (1904).     On  Licnophora  and  Boveria.     A.P.K.,  iii.,  p.  1. 

(873)  THON,  K.  (1905).     Bau  von  Didinium  nasutum.     A.P.K.,  v.,  p.  281. 

(874)  WALKER,   E.   L.   (1909).      Sporulation  in  the  Parasitic    Ciliata.      A.P.K., 

xvii.,  p.  297. 

(c)  Aciaetaria. 

(875)  AWERINZEW,  S.  (1904).     Astroplirya  arenaria.     Z.A.,  xxvii.,  p.  425. 

(876)  CHATTON,   E.,   and    COLLIN,    B.    (1910).      Un  Acinetien   commensal   d'ua 

Copepode,   Rhabdophnja   trimorpha.     A.Z.E.    (5),    v.,    Notes   et   Revue, 
p.  cxxxviii. 

(877)  COLLIN,   B.   (1907).     Sur  quelques  Acinetiens.     A.Z.E.    (4),  vii.,    Notes  et 

Revue,  p.  xciii. 

(878)  —  (1908).     Sur  Tolcophrya  cydopum.     A.Z.E.   (4),   viii.,   Notes  et  Revue, 

p.  xxxiii. 

(879)  —  (1909).     La  Conjugaison  genimiforme   chez  les   Acinetiens.     C.R.A.S., 

cxlviii.,  p.  1416. 

(880)  —  (1909).     Les  Formes  hypertrophiques  et  la  Croissance  degenerative  chez 

quelques  Acinetiens.     C.R.A.S.,  cxlix.,  p.  742. 

(881)  —  (1909).     Sur  deux  Acinetiens.     Ibid.,  p.  1407. 

(882)  -  -  (1909).     La  Symetrie,  etc.,  des  Embryons  d'Acinetiens.     A.Z.E.  (5),  ii., 

Notes  et  Revue,  p.  xxxiv. 

(883)  FILIPJEV,  J.  (1910).     Tocoplirya  quadripartita.     A.P.K.,  xxi.,  p.  117. 

(884)  HARTOG,  M.  (1902).     Notes  on  Suctoria.     A.P.K.,  i.,  p.  372. 

(885)  HICKSON,  S.  J.,  and  WADSWORTH,  J.  T.  (1902).     Dendrocometes  paradoxus. 

Q.J.M.S.,  xlv.,  p.  325. 

(886)  -        -  (1909).     Dendrosoma  radians.     Q.J.M.S.,  liv.,  p.  141. 

(887)  ISHIKAWA,    C.    (1897).     Eine  in   Misaki  vorkommende   Art   von   Ephelota. 

Journ.  Coll.  Sci.  Tokyo,  x.,  p.  119. 

(888)  MARTIN,  C.  H.  (1909).     On  Acinetaria.     Parts  I.  and  II.     Q.J.H.S.,  lin., 

p.  351.     Part  III.     Ibid.,  p.  629. 

(889)  PEREZ,  C.  (1903).     Lernceophrya  capitata.     C.R.S.B.,  lv.,  p.  98. 


504  THE  PROTOZOA 


CHAPTER  XVIII 

(a)  Classification. 

(890)  AWEEINZEW,  S.  (1910).     Die  Stellung  im  System  und  die  Klassifizierung  der 

Protozoen.     E.G.,  xxx.,  p.  465. 

(891)  DOFLEIN,  F.  (1902).     Das  System  der  Protozoen.     A.P.K.,  i.,  p.  169. 

(892)  HARTMANN,  M.  (1911).     Das  System  der  Protozoen.     Vide  Prowazek  (14), 

p.  41 ;  and  No.  675. 

(b)  Spirochsetes. 

*(S93)  BOSANQUET,    W.    C.    (1911).     Spirochsetes.     Philadelphia    and    London  : 
W.  B.  Saunders  Company. 

(894)  --  (1911).     Sp.  anodontce  Keysselitz.     Q.J.M.S.,  Ivi.,  p.  387. 

(895)  DOBELL,  C.  C.  (1911).     On  Cristispira  veneris  and  the  Classification  of  Spiro- 

chaates.     Q.J.M.S.,  Ivi.,  p.  507. 

(896)  FANTHAM,  H.  B.  (1911).     Life-Cycle  of  Spirochsetes.     A.T.M.P.,  \.,  p.  479. 

(897)  GROSS,  J.  (1910).     Cristispira  nov.  gen.     Mitt.  zool.  Stat.  Neapel,  xx.,  p.  41. 

(898)  --  (1911).     Freilebende  Spironemaceen.     Ibid.,  p.  188. 

(899)  —  (1911).     Nomenclatur  der  Sp.  pallida.     A.P.K.,  xxiv.,  p.  109. 

(900)  KINDLE,  E.  (1912).     Life-Cycle  of  Sp.  gallinarum.     Py.,  iv.,  p.  463. 

(901)  KRZYSZTALOWICZ,  F.,  and 'SIEDLECKI,  M.  .(1905).     La  Structure,  etc.,  de 

Sp.  pallida.     B.A.S.O.,  p.  713. 

(902)  LEISHMAN,  W.  B.  (1910).     Mechanism  of  Infection  in  Tick  Fever  and  Heredi- 

tary Transmission  of  Sp.  duttoni  in  the  Tick.     Trans.  Soc.  Trap.  Med. 
Hyg.,  iii.,  p.  77. 

(903)  SCHAUDINN,    F.    (1905).     Sp.   pallida.     Deutsch.   Med.    Wochenschr.,  xxxi., 

p.  1665. 

(904)  ZUELZER,  M.  (1911).     Sp.  plicatilis.     A.P.K.,  xxiv.,  p.  1. 

(c)  Chlamydozoa. 

(906)  ACTON,  H.  W.,  and  HARVEY,  W.  F.  (1911).     Negri  Bodies.     Py.,  iv.,  p.  255. 

(907)  AWERINZEW,  S.  (1910).     Die  Krebsgeschwiilste.     C.B.B.P.K.,  Ivi.  (I  Abth. 

Orig.),  p.  506. 

(908)  CALKINS,  G.N.  (1904).     Cytoryctes  variolas,,  Guarnieri.     J  own.  Med.  Research 

(Special  Variola  Number),  xi.,  p.  136. 

(909)  HARTMANN,    M.     (1910).     Chlamyclozoen.      C.B.B.P.K.     (I    Abth.    Ref.), 

xlvii.,  Beiheft,  p.  94. 

(910)  NEGRI,  A.  (1909).     Die  Morphologic  und  der  Entwicklungszyklus  des  Para- 

siten  der  Tollwut.     Z.H.,  etc.,  Ixiii.,  p.  421. 

(911)  PROWAZEK,  S.  v.  (1907).     Chlamydozoa.     A.P.K.,  x.,  p.  336. 

/912)  —  and  ARAGAO,   H.   DE  B.   (1909).     Variola-Untersuchungen.     M.I.O.C., 
i.,  p.  147. 

(913)  —  LiPSCHtJTZ,  B.,  and  Others  (1911).     Chlamydozoa,  etc.      Vide  Prowazek 

(14). 

(914)  SIEGEL,  J.  (1905).     Die  Atiologie  der  Pocken  und  der  Maul-  und  Klauen- 

seuche  :  des  Scharlachs  :  der  Syphilis.     Abhandl.  k.  preuss  Akad.  Wise. 
(Anhang.) 


INDEX  TO  TECHNICAL  TERMS  AND 
ZOOLOGICAL  NAMES 


The  numerals  printed  in  heavier  black  type  refer  to  pages  on  which  the  meaning 
of  the  word  or  the  systematic  position  of  a  genus,  family,  or  order  are  fully  explained. 


ACANTHARIA,  251,  256 

Acanthin,  37,  253 

Acanthocystis,  37,  48,  91,  245,  248 

—  aculeata,    117,    118    (Fig.    64),     123 

(Fig.  68) 

—  chcetophora,  37  (Fig.  18) 
Acanthometra,  256 

—  elastica,  250  (Fig.  105) 

—  pellucida,  255 
Acanthojnetrida},  37 
Acephalina,  339 
Achromaticus,  364,  382 

—  vesperuginis,  382 
Achromatin,  65 
Acineta,  461 

-  grandis,  11  (Fig.  10) 

—  papillifera,  16 
Acinetaria,  430,  455 
Acinetida},  461 
Acrasiee,  243 
Acrasis,  243 
Actinobolus  radians,  441 
Actinocephalidai,  339 

Actinocephalus  oligacanthus,  327  (Fig.  142) 
Actinomma  asteracanthion,  254  (Fig.  107) 
Aetinomyxidia,  409 

Actinophrys,  117,  215,  245,  248 

—  sol,  90  (Fig.  46),  132  (Fig.  71),  151 
Actinopoda,  218 
Actinosphcerium,    43,    50    (Fig.    22),    68, 

74,  77,  78,  80,  91,  138,  144,  150,  193, 
198,  207,  209,  214,  216,  245,  248 

—  eichhorni,  7  (Fig.  3),  81  (Fig.  37),  115 

(Fig.  62),  116  (Fig.  63) 
Adaptive  polymorphism,  164 
Adelea,  175,  176,  348,  352,  393 

—  hartmanni,  344,  347,  348 

—  ovata,  344,  345   (Fig.   153),  346,  347 

(Fig.  154),  352 
Adeleidco,  352,  354,  355 
Adeleidea,  352,  394 
Adinida,  278 
Adoral  spiral,  442 
Adult,  212 
^EthaUurn,  242 
Aflagellar,  287 
Agametes,  180, 181 
Agamogony,  181 
Agamont,  181 

Agglomeration,  128,  209,  305 
Agglutination,  128 
Agglutinin,  128 
Aggregata,  23,  168,  325,  348,  353 

—  jacquemeti,  121  (Fig.  67) 
AggregatidcB,  353 


Alcohol,  effects  of,  204 
Allogromia,  230 

-  ovoidea,  235 

Alternation  of  generations,  181 
Alveolar  layer,  435 

Alveoli,  42 
Amicronucleate,  211 
Amitosis,  105 
Amoeba,  219 

—  albida,  221  (Fig.  87) 

-  binucleata,  78,  95,  214,  223 

—  diploidea,  222  (Fig.  88) 

-  diplomHotica,  108,  109  (Fig.  56) 

-  flava,  221 

-  Umax,  46,  47  (Fig.  20),  206,  217,  219 

-  minuta,  221,  223 

—  mucicola,  220 

—  proteus,  6  (Fig.  2),  47,  191,  205,  209, 

215,  216,  217,  219,  220,  222, 230 

-  radiosa,  217,  219 

-  terricola,  48,  190  (Fig.  82),  214,  220 

—  verrucosa,  32,  45,  48,  50,  51  (Fig.  23), 

198,  214,  219 

-  vespertilio,  217 

Amoaha,  form-changes,  216  (Fig.  85) 
Amcebsea,  217 
Amcebidium,  428 
Amoebodiastase,  193 
Amceboflagellata,  463 
Amcebogenice,  325,  466 
Amoeboid,  30 
Amoebula,  169 
Amphikaryon,  96 
Amphilephis,  439 
Amphimixis,  150,  154 
Amphinucleus,  96 
Amylum,  188 
Anaerobic,  196 
Anaplasma  marginale,  383 
Ancystropodium,  441 
Angeiocystis  audouinice,  349 
Anisogamy,  126,  132,  175 
Anisonema,  274 

—  grande,  53  (Fig.  25) 
Anisonemina},  274 
Anisosporo,  215,  254 
Annulus,  276 
Anophelinse,  358 

Anoplophrya,  171,  439,  443,  449,  452 

—  branchiarum  (reduction),  145  (Fig.  74) 
Anoplophryince,  197,  452 
Anurosporidium,  424 
Aphrothoraca,  247 

Apiosoma,  379 
Apodinium,  278 


505 


f>06 


THE  PROTOZOA 


Aposporoprony,  368 

Arcellit.  (il,  (!.•),  72,  78,  120,  MS,  173,  199, 
201,  215,  21(i,  229 

-  vulijuri*,  (i7   (Fitr.  :'.2),  110  (Fig.  57), 

177,  178  (Fig.  SO) 
Archreocyles,  133 
Archoplasm,  79,  10:? 
Arenaceous,  34,  231 
Asporocystoa,  388 
Aspirigora,  439 
Arrlienoplasm,  129 
Artificial  classification,  463 
Assimilation,  187 
Association,  127,  330 
Astasia,  274 

-  tenax,  33  (Fig.  15) 
Astasiidco,  274 
Astomata,  438,  439,  451 
AstrodisculuK,  248 
Astrophrya,  461 

—  arenaria,  456 
Athene  noctua,  390 
Attraction-sphere,  103 
Attraction-spindle,  104 
Aulacantha,  256 
Autocyst,  417 
Autogamy,  138,  306 
Automixis,  140 
Autopliya,  34 
Avoiding  reaction,  202 
Axopodium,  48,  53,  60,  87,  199,  465 
Axostyle,  36,  259,  289,  311 
Azoosporidre,  218 

Babesia,  357,  379,  394 

—  bovis  (bifjemina),  379,  384 

—  mutans,  380,  382 
Babesioses,  378 
Bacteria,  5,  98 
Badhamia,  242 

—  utricularis,  240  (Fig.  99),  241  (Fig.  100) 
Balantidium,  439,  440 

-  coli,  440 

-  minutum,  440 
Banana-tree,  136 
Barroussia,  352 

—  alpina,  344,  345  (Fig.  153) 

—  caudata,  348 

—  ornata,  346,  352 

-  spiralis,  344,  348 
Barotaxis,  202,  207 

Basal  granule,  82,  92,  200,  443 

—  rim,  443 
Benedenia,  353 
Bertramia,  424 

-  asperospora,  424 

—  bufonis,  424 

—  capitellcs,  424 

—  kirkmanni,  424 
Bertramiida},  424 
Bilateral  symmetry,  31,  250 
Biloculina  depressa  shells,  233  (Fig.  94) 
Binary  fission,  100 

Binuclearity,  96 
Binucloata,  85,  280,  388 
Bioblast,  40,  41 
Bionomics,  15 
Black  spores,  364 
Blastoccelo,  133 
lihtslodinido),  278 
Blasfodinium,  278 
Blastogenea,  418 


Blastomere,  133 

IHiixtiilit/iiii/i  jxcdophthorum,  424 

Blopharoplast,  52,  59,  82,  262,  286,  288, 

289 
Bodo,270,  281,  319 

-  edax,  319 

-  gracilis,  271  (Fig.  115) 

—  lacertai,  270 

-  salterns,  271  (Fig.  115),  319 
Bodonidcc,  268,  270 
Body-form,  29 

Bud,  122 
Buetschlia,  439 
Bursar  ia,  439 
Bursarida',  439 

Callyntroclilamys  phronimco,  327 

Calonympha,  276 

Calymma,  251,252 

Calyx, 89 

CampaneUa,  440,  446,  447 

-  umbellaria,  434  (Fig.  183) 
Camptoncma,  51,  248 

-  nutans,  91  (Fig.  47) 
Cancer,  473 
Capillitiurn,  241 
Capilhis  inteslinalis,  428 
Capsulogenous  cell,  399,  403 
Carchesium,  145,  192,  194,  440,  441,  449 
Caryoryctes,  473 

Caryospora,  349,  352 

-  simplex,  352 

Caryotropha,  195,  344,  348,  352 
• —  mesnilii,  349,  352 
Caryotrophidcc,  352 
Caullerya,  424 

—  mesnili,  424 
Cell,  1,  98,  464 
Cell-anus,  433 
Cell-division,  121 
Cell -membrane,  45 
Cell-mouth,  63 
Cell-theory,  133 
Central  capsule,  250 

-  grain,  91 

-  spindle,  103 
Centriole,  73,  80,  97,  262 
Centrodesmose,  36,  58,  59,  82, 103 
Centropyxis,  148,  173,  229 

-  nculeata,  36,  230 
Centrosome,  58,  59,  73,  79,  262,  288 
Centrosphere,  80 

Cephalina,  339 
Ccphaloidophora,  337 
Cephalont,  181,326 
Ceratiomyxa,  242 
Ceratium,  278 
Ceratocorys,  278 

-  horrida,  277  (Fig.  121) 
Ceratomyxa,  408 

-  drepanopsetlai,  402  (Fig.  166),  403 

-  spltcerulosa,  409 
Cer atomy xidcc,  408 
Ceratophylhis  fasciatus,  291 
Cercomonadidcc,  268,  270 
Cercomonas,  270,  271 

-  crassicauda,  271  (Fig.  114) 
CJiagasia  hartmanni,  344,  347 
Chalaiothoraca,  248 
Chemotaxis,  202 
ChiliferidcB,  439 

CMlodon,  145,  439,  448 


INDEX 


507 


Chilodon  cucullulus,  435  (Fig.  184) 

—  dentatus,  440 
Chilomonas,  208,  274 
Chlamydodontidcc,  439 
Chlamydomonadidce,  275 
Chlamydomonas,  275 
CMamydomyxa,  214,  243,  244 
Chlarnydophora,  248 
Chlamydophrys,  237 

—  schaudinni,  237 

—  stercorca,  17,  237 
Chlarnydozoa,  470 
Chloromyxidce,  407,  409 
Chloromyxum ,  409 

—  Jeydic/i,  400  (Fig.  1G4),  409 
Chlorophyll,  13,  63,  188,  261 
Choanoflagellata,  261,  271 
ChoanoflagelluLoB,  271 
Chondriosome,  41 
Chromatin,  65,  69 
Chromatoid  grains,  67,  289,  311 
Chromatophore,  13,  63,  188,  261 
Chromidia,  6,  65,  97, 150,  215,  328 
Chromidial  fragmentation,  101 
Chromidina,  452 
Chromidiogamy,  126,  416 
Chromidiosome,  65,  103 
Chromomonadina.  274 
Chromophyll,  188 
Chromoplast,  13,  63 
Chromosome,  103 
Chromulina,  274 

—  flamcans,  15 
Chrysamceba,  274 
Chrysonionadina,  14,  274 
Chytridiopsis,  428 

-  socius,  428 

Ciliary  apparatus,  442,  444  (Fig.  186) 

Ciliata,  430,  432  (Fig.  181) 

Cilioflagellata,  277 

Ciliophora,  462 

Ciliophrys,  248 

Ciliospore,  169 

Cilram,  12,  53,  92,  199,  200,  442,  454 

Circumfluence,  189 

Circumvallation,  189 

Cirrus,  55,  445 

Cladomonas,  270 

Cladothrix  •pclomyxce,  227 

Classification,  462 

Clathrulina,  39,  245,  248 

-  elegans,  38  (Fig.  19) 
Clcpsydrina,  335,  339 
Cnidosporidia,  399 
Coccidia,  341,  389 
CoccidiidcK,  352 
Coccidioidcs  immitis,  17 
Coccidiomorpha,  388,  395 
Coccidiosis,  343 

Coccidium,  101,  166,  173,  174,  346,  352 

-  cuniculi,  341,  351 

—  mitrarium,  344 

—  oviforme,  341 

—  rouxi,  349 

—  schubcrgi,  102  (Fig.  50),  106  (Figs. 

51,  52),  127  (Fig.  69),  146  (Fig.  75), 
204,  342  (Fig.  152),  353,  354 

-  stiedce,  341 
Coccoid  bodies,  468 
Coccolith,  274 
Coccolithophoridcc,  274 
Coccomyxa,  409 


Coccomyxa  morori,  400 
Cochlearia  faurei,  442 
Cochliopodium,  229 
Codonosiga  botrytis,  260  (Fig.  110 
Ccelosporidiidcc,  399,  424 
Ccelosporidium,  424 

-  blatellce,  424 
Ccelozoic,  324 
Coleps,  439,  441 
Collar,  57,  89,261 
Collecting-pusule,  277 
Collodagia,  255 
CoUozoum,  256 
Colpidium,  208 
Colpoda,  439 
Conclwplirys,  439 
Conjugant,  126,  448 
Conjugation,  126,  448 
ConorMnus  megistus,  291,  302 
Contact-stimulus,  207 

Contractile  vacuole,  60,   196,   197,   262, 
437,447 

-  system,  445,  446 
Contractility,  200,  201 
Copromonas,  171,  274 

-  major,  268 

—  suMlis,  264  (Fig.  Ill),  268 
Copromyxa,  243 
Copularium,  355 
Copulation,  126 

Corps  en  barillet,  344 
Cortex,  45 
Cortical  layer,  32 
Corticate,  45 
Costia,  258,  272 

-  necatrix,  16,  272 
Cothurnia,  440 
Craspedomonads,  261,  271 
Craspedotella,  279 
Cristispira,  466,  469 

—  anodontcB,  468 

-  balbianii,  467 

—  pectinis,  469  (Fig.  194) 

Crithidia,  281,   2S2.-287,  308,  312,  320, 
321 

-  campanulata,  313 

-  gerridis,  313 

-  melophagia,  290 

-  minula,  312  (Fig.  135) 
Cryptocystes,  412 
Cryptodifflugia,  229,  230 
Crypt omonadina,  15,  274 
Cryptomonas,  274 

- — •  schaudinni,  15 
Cryptosporidium,  349,  352 

—  muris,  344,  352 
Crystal-spores,  254 
Cuirass,  33,  45,  276 
Culicinse,  358 
Culture  d'attente,  304 
Cuticle,  45 
Cyclasterium,  470 
Cyclical  transmission  ,290 
Cyclochceta,  440,  441 
Cycloposthium,  439 
Cyclosis,  192,  194   43 
Cyclospora,  352 

-  caryolitica,  176    198,   344,  348,  349, 

352 

Cyst,  154 

Cystal  residuum,  349 
Cystobia  chiridota}   341 


508 


THE  PROTOZOA 


Cystobia  Jiolothiirim,  128  (Fig.  70) 

-  innjiilarift,  3:>  I 

-  minchinii,  336 
Cystollagellata,  257,  278 
Cystotrypanosoma,  304 
Cytocyst,  344 

( 'ytomcro,  344 
Cytomicrosomo,  41 
Cytopharynx,  63,  261, 433,  442 
Cytoplasm,  6,  7,  99 
Cytopyge,  433 
Cytorhyctes,  471 

—  apJitJiartim,  471 

—  luis,  471 

—  scarlatinas,  471 

-  vaccince,  471 
Cytoryctes,  470,  471 

Cytostome,  63,  190, 191,  261,  433,  452 
Cytozoic,  324 

Daclylosoma  splendcns,  378 
Defalcation,  233 
Degeneration,  208 
Dendrocometcs,  457,  460,  461 
Dendrocometidce,  461 
Dendrosoma,  456,  458,  461 

-  radians,  78,  460  (Fig.  193) 
Dendrosojnidfc,  461 
Dendrosomides  paguri,  455 
Depression,  131,  135,  197,  208 
Derbesia,  90 
Desmothoraca,  248 
Deutoblast,  426 
Deutomerite,  327 
Deutoplasmic,  41 
Derescovina,  276 
Dexiotricha,  440 
Dictyosteliwm,2A& 
Didinium,  145,  439,  442,  449 
Didymopliycs,  330 

Difflwjia,  34,  35,  50,  65,  66,  78,  126,  140, 
149,  199,  215,  216,229 

—  spiralis,  34  (Fig.  16) 

-  urceolata,  214,  229,  230 
Diffuse  infiltration,  400 
Digestion,  192 
Dileptus,  439 
Dimastigamceba,  268 
Dimorpha,  249 

—  nittans,  249  (Fig.  104) 
Dinenympha,  276 
Dinifera,  278 
Dinobryon,  274 
Dinoflagellata,  257,  276 
Dinophysidcv,  278 
Dinophysis,  278 
Diphtheria,  470 

Diplocystis  minor,  128  (Fig.  70) 
Diplodina,  174 

Diplosome,  79 
Diplozoa,  273 
Direct  division,  101 
Direct  transmission,  290 
Discophrya,  439 
Discorbina,  232  (Fig.  93,  vii) 
Disporoa,  408 
Dizoic,  349 
DoliocystidcB,  339 
Dourine,  26,  285,  289 
Drehkrankhoit,  400 
Drepanidia,  395 
Drepanidium,  372 


Duboscqia,  418 

-  legeri,  418 

Earth-amoebae,  220 
Echinomera,  333 
Echinopyxis,  101 
Ectoplasm,  43,  45,  435 
Ectosarc,  43 
Ectoschiza,  339 
Eetosporea,  325 
Eimeria,  346,  352 

-  falciformis,  346 

-  nepcc,  346 
Eimerida},  352 
Eimeridea,  352,  394 
Electrical  stimuli,  effects  of,  208 
Elementary  corpuscles,  472 
Elleipsisoma,  387 

-  thorn soni,  387 
EncJiclida,  439 
Enchylema,  41,  72 
Encyst  ment,  164 
Endogenous  budding,  124 

-  cycle,  184 
Endoparasita,  462 
Endophrys  rotatorium,  249 
Endoplasm,  43,  62,  437 
Endoral  membrane,  445 
Eudosarc,  43 
Endoschiza,  339 
Endosome,  73 
Endospore,  335 
Endosporea?,  242,  325 
Endotrypanum,  307 

-  schaudinni,  307  (Fig.  133) 
End-piece,  443 

Energid,  121 
Entamceba,  220 

-  africana,  226 

-  blattcB,  47,  220,  223 

-  buccalis,  220 

—  coli,  18,  138  (Fig.  73),  139,  223,  224 

(Fig.  89),  225 

-  histolytica,    18,    46,    223,    224,    225 

(Fig.  90) 

—  minuta,  226 

—  muris,  220 

—  ranarum,  220 

-  tetragena,  226 

-  williamsi,  225 
Entodinium,  439,  441 
Entozoic,  16 

Enzymes.     See  Ferments 
Ephclota,  457,461 

—  buctschliana,  457 

—  gemmipara,  460 
Epicyte,  45,  327 
Epimerite.  45.  326 
Epispore,  335 
Epistylis,  440,  441 

-  plicatilis,  444  (Fig.  186,  K),  446 

—  umbellaria,  447 
Epithelioma  contagiosum,  470 
Epizoic,  16 

Equating  division,  104 
Equatorial  plate,  103 
Ergastoplasm,  41 
Erythropsis,  277 
Etheogenesis.  138,  315 
Eucoccidia,  352 
Eucoccidium,  353 
Eucyrtidium,  256 


INDEX 


509 


Eucyritidium  cranioides,  256  (Fig.  109) 

Euflagellata,  257 

Euglena,  14,  33,  52  (Fig.  24),  107,  202,  274 

—  gracilis,  188 

—  spirogyra,  8  (Fig.  4) 

—  viridis,  1SS,  205  (Fig.  84) 
Euglenidcc,  274 
Euglenoid  movement,  33 
Euglenoidina,  273 
Euglypha,  34,  35,  214,  237 

—  alveolata,    111,     112    (Fig.    59),     113 

(Fig.  60) 

Eugregarina?,  32 S,  339 
Euplasinodida,  242 
Euplotes,  194,440,448 

—  harpa,  433  (Fig.  182) 

—  patella,  433  (Fig.  182) 
Euplotidm,  440 
Eutrypanosome,  292 
Ex-conjugaut,  153 
Excretion,  197 
Excretory  canals,  447 
Exflagellatiou,  357,  382,  364,  365,  390 
Exogenous  cycle,  184 

Eye-spot,  205 

Falciform  body,  324 

Fat,  194 

Fatty  degeneration,  210 

Feeding  canals,  437 

Female  sex,  159 

Ferments,  193,  194 

Fertilization-spindle,  127,  348 

Filoplasmodida,  243 

Filose,  48 

Fission,  100 

Fixation,  441 

Flagellar,  287 

Flagellata,  82,  257 

Flagellispore,  169 

Flagellosis,  313 

Flagellula,  169 

Flagellum,  6,  51,  199,  200,  289,  454,  465 

Fcettingeria,  439 

Fcettingeriidcc,  439 

Food-vacuole,  50,  62,  191,  194,  437 

Foot-and-mouth  disease,  470 

Foraminifera,  217,  231 

Form-production,  31 

Franibo3sia,  467 

Frondicularia,  232  (Fig.  93,  iv.) 

Frontonia,  439,  442 

—  leucas,  206,  447  (Fig.  187) 
Fulcra,  441 

Fuligo,  242 

—  septica,  239  (Fig.  97) 

Galvanotaxis,  202,  208 

Gamete,  125,  448 

Gametid,  334 

Gametocyte,  126 

Gamogony,  181 

Gamont,  126,  181 

Ganymedes,  330 

Gas-vacuole,  64 

Gastrocystis  gilruthi,  427,  428  (Fig.  179) 

Gemmation,  122 

Gemmula,  459 

Gemmule,  471 

Generative  chrotuatin,  71 

Geotaxis,  207 

Germ,  165 


Germ-cells,  130 
Germen,  130 

Germinativo  infection,  24 
Glaucoma,  439 

-  colpidium,  197,  206 

-  scintillans,  445 
Glenodinium,  278 

—  cinctum,  277  (Fig.  120) 
Globidium,  387 

—  multifidum,  387 
Globigerina,  231,  232  (Fig.  93,  vi. 
Glossina  morsitans,  291 

-  palpalis,  291,  303,  304 
Glugca,  412,  417,418 

-  anomala,  411,  415,  417  (Fig.  174),  41& 

-  stephani,  412 
Gonium,  276 

-  pectorale,  275  (Fig.  119) 
Granclke,  238 
Granellarium,  238 
Gregarina,  174,  335,  339 

—  blattarum,  339 

-  munieri,  58  (Fig.  29) 

-  ovata,  332,  333  (Fig.  146),  335,  339 

—  polymorpha,  9  (Fig.  7),  339 
Gregarines,  sporogony,  331  (Fig.  144) 
Gregariniform  phases,  315 
Gregarinoidea,  326 

Gregarinula,  169,  324 
Gromia,  231 

—  oviformis,  49  (Fig.  21) 
Guarnieri's  bodies,  470 
Gurleya,  418 
Gymnamo3bee,  219 
GymnodinidcB,  278 
Gymnodinium,  278 
Gyniuospore,  165 
Gyrnnostornata,  439,  442 
Gymnozoum,  439,  -142 

—  viviparum,  439 

Hfleruamcebte,  357,  389 
Hseinatochronie,  188 
Hcematococcus,  188,  275,  379 

-  pluvialis,  111  (Fig.  58) 
Hatmatomonas,  308 
Hccmatopinus  spinulosus,  291,  301 
Hczmocystidium,  358,  364 

—  diploglossi,  358,  365 

—  metschnikovi,  358 

—  simondi,  358,  365 

—  tropiduri,  365 
Hsemoflagellates,  258,  280 
Hcemogregarina,  372 

—  agamcB,  373 

—  balfouri,  376 

-  bicapsulata,  372 

—  canis,  377 

-  funambuli,  377 

-  gerbilli,  376,  377,  390 

—  jaculi,  376 

—  muris,  23,  376,  390 

—  musculi,  352,  377 

-  nicoritc,  373,  375 

-  peramelis,  376 

-  sebai,  377 

—  stepanowi,    107    (Fig.    53),   372,   373,. 

374  (Fig.  159),  375,  390 
Hseuiogregarines,  357,  371,  390 
HcBmogregariniidce,  378 
Hcemoproteus,  365,  391 

-  columbce,  365,  366  (Fig.  157),  390,  391 


510 


THE  PROTOZOA 


II  mnoprotcus  danilcwskyi,  365 

-  noctucc,  365,  390 

-  oryzivorcD,  368 
ll.-i'tnosporidia,  356 
llnliiihusema,  35,231 

-  tumanowiczii,  35  (Fig.  17) 
Hatteria,  439 

HaUcridw,  439 
llalteridia,  389,  391 
Halteridium,  357,  365,  391 
Haplosporidia,  399,  423 
Haplosporidiidcc,  423,  424 
Haplosporidium,  424 
Hastatclla  radians,  441 
Hclcosoma  tropicum,  393,  412 
Hcliozoa,  90,  218,244 
Hcmiclepsis  maryinata,  291,  298,  303 
Hemispeira  asterice,  441 
Henneguya,  409,  426 
Hepaiozoon,  372 
—  muris,  376 

-  pcrniciosum,  376 
Hereditary  transmission,  24,  290 
Herpelomonas,  281,  282,  292,  313,  319, 

320 

-  muscco-domesticce,      137,      138,      282 

(Fig.  124),  315 
Herpetophrya,  452 
Heterokaryote,  449,  453 
Heteromastigoto,  259 
HelcronemincB,  274 
Heterophrys,  248 

-  fockei,  248  (Fig.  103) 
Heterotricha,  433 
Hcxactinomyxon,  409 
llcjcamitus,  258,272 
Hist  ocytes,  130   133 
Hixtoplasma,  319 

-  capsulatum,  319 
Histozoic,  324 
Holomastigina,  270 
Holomastigote,  259 
Holophrya,  439 
Holophytic,  13,  187,  188,  261 
Holotricha,  439 
Holotrichous  larvae,  459 
Holozoic,  8,13,  187,  261 
Homaxon,  39,  250 
Hoplitophrya,  452 

House,  33,  45 

HyalosphcBra  grcgarinicola,  341 

Hyalosphenia,  34 

-  cuneata,  34  (Fig.  16) 
Hydrophobia,  470 
Hyruenostoruata,  439,  442 
Hyperchromasy,  71 
Hypnocyst,  166 
Hypocoma,  460 

-  acinetarum,  460 
HypocomidcB,  460 
Hypothallus,  240 
Hypotricha,  433,  440 
Hypotrichous  larvae,  459,  460 

Ichthyophthiriasis,  450 
Jrlitlii/ophthirius,  448,  453 

-  iiiiiUiJiliis,  16,  21,  450,  451 
/ 1 •!,  Hi  i/osporidiuin,  424 
Idiochro  matin,  71 
Idiochromidia,  150 
Immanoplasma,  388 


Imporforatc,  231 
Import,  189 

Incubation-period,  292,  361 
Incurvation,  468 
Indirect  division,  101 
-  transmission,  290 

Infusoria,  2, 12,  152  (Fig.  77),  153,  430 
Ingestion,  204 
Initial  body,  472 
Intestinal  flagellates,  258 
Invagination,  189 
Involution  stages,  296 
Isogamy,  126,  175 
Isomastigoto,  259 
Isosporo,  215,  254 
Isotricha,  439 
IsotrichidcB,  439 

•Jcenia,  276 

Kala-azar,  316 
Kalpidorliynchus,  332 
Karyogamy,  126 
Karyokinesis,  101,  119 
Karyolysus,  372 

-  lacertarum,  372,  37S 
Karyosome,  76,  288 
Kataphoric  action,  208 
Kentrochona,  440 
Kentrochonopsis,  440 
Kinetouucleus,  78,  85,  200,  2SG,  288,  289, 

392 
Klossia,  348,  352 

-  lielicina,  352 
Klossiella,  352 

-  muris,  352 
Kurloff-Dernel  bodies,  388 

Ldbyrinthula,  243,  244 
Labyrinthulidea,  243 
Lagena,  232  (Fig.  93,  ii.) 
LagenophryincB,  440 
LagenopJvrys,  440 
Lamblia,  272 

-  intestinalis,  31,  272,  273  (Fig.  117) 
—  sanguinis,  272 
Lankesterella,  189,  372,  378 

-  ranarum,  372,  378 

Lankestcria  ascidicB,  327,  329  (Fig.  143) 

-  culicis,  327 
Latent  bodies,  296 
Laverania,  358 
Legendrea  loyescc,  441 
Legcrella,  348,  349,  352,  355,  388 

-  nova,  352 
Legercllidco,  352 
Legeria,  353 
Legerina,  353 

Leishmania,    258,   281,   316,,   320,   321, 
393,394 

-  donovani,   316   (Fig.    138),   317    (Fig. 

139),  473 

-  infantum,  316,  317 

-  tropica,  87,  316,  317,  318  (Fig.  140), 

412,  473 
Lcntospora  cerebralis,  400 
Leptodiscus,  279 
Leptomonas,  52,  281,  282,  292,  308,  313, 

319, 320,  321 
liutschlii,  282 

jaculum,  314  (Fig.  136),  315 
LeptotJieca,  408 


INDEX 


511 


Leptotheca  agilis,  201,  401  (Fig.  165) 

—  ranarum,  408 
Leptotrypanosome,  292,  314 
Lernaiophrya,  461 

Lethal,  19 

Leucocytogregarina,  372 
Leucocytozoa,  372 
Leucocytozoon,  357,  369,  390,  392 

-  lovati,  370 

—  muris,  376 

—  piroplasmoides,  319 

—  ratti,  376 

—  sabrazcsi,  371 

—  siemanni,  369  (Fig.  158),  370,  371 
Leucophrys,  439 

-  patula,  440 
Leucoplasts,  1SS 
Leydenia  gemmipara,  237 
LlcnopTiora,  440,  441,  446,  449 
Licnophorido),  440 

Life -cycle,  129,  130 
Light-perception,  201 
Light-prod\iction,  201 
Linellfe,  238 
Linin,  72 
Lionotus,  439 
Lithocircus,  256 

-  productus,  252  (Fig.  106) 
Lithocystis  schneidcri,  331 
Lobopodia,  47,  199 
Lobosa,  217,  219 

-  testacea,  229 
Lobose,  47 
Lophomonadidcc,  276 
Lophomonas,  36,  88,  261,  276 

-  blattarum,  17,  18,  89  (Fig.  45),  263, 

276 

—  striata,  276 
Lophophora,  276 
Lorica,  33,  45,  276,  441 
Loxodes,  439,  448 
Luminosity,  201 
Lymphocystis,  426 

—  johnstonei,  426,  427  (Fig.  178) 
Lymphocytozoon,  388 

-  cobayce,  388 
LyncMa,  365 

Macramceba,  148 
Macroconjugant,  153,  449 
Macrogamete,  126 
Macrogamy,  131,  151,  172 
Macrogonidirc,  267 
Macromerozoitc,  373 
Macront,  426 

Macronucleus,  78,  107,  430,  437,  448,  458 
Macroschizogouy,  344 
Macroschizont,  344,  373 
Macrosporcs,  254,  255,  416 
Macrostoma,  272 

-  mesnili,  272 
Mai  de  caderas,  285 
Malaria,  358,  359 
Male  sex,  159 
Mallory's  bodies,  470 
MalpigJiiella  refringcns,  229 
Mantle-fibres,  103 
Mastigcemceba,  213,  261,  268 
MastigeUa,  77,  268 

-  vitrea,  83  (Fig.  40),  265,  266  (Fig.  112) 
Mastirjina,  265,  267,  268 

-  setose,  82  (Figs.  38,  39) 


Mastigophora,  12,  257 
Mastigotricha,  455 
Maturation,  142 
JIaitpasia,  454 

-  paradoxa,  454  (Fig.  189,  B) 
Measles,  470 

Mechanical  stimuli,  effects  of,  207 
Mechanical  transmission,  290 
Megalosphceric,  184,  233 
Meyastoma,  272 

-  cntcricum,  272,  273  (Fig.  117) 
Melanin,  64,  198,  357 
Membrane  (nuclear),  76 
Menabranelke,  55,  443,  445 
Membranulse,  445 
Merocystis,  352 

-  kathai,  352 

Merogregarina  amaroucii,  336 
MerogregarinidcB,  341 
Meront,  398,  413 
Merozoite,  169,  325 
Merozoon,  210 
Mesomitosis,  111 
Metabolic,  33 

Metachromatmic  grains,  67,  420,  421 
Metacineta,  460 

Metadnetidce,  460 

Metagenesis,  266 

Metamera,  332,  339 

Motamitosis,  111 

Metaplastic,  40,  63 

Metazoa,  2 

Micramoeba,  148 

Microconjugant,  153,  172,  448 

Microgamete,  126,  448 

Microgamy,  132,  172 

Microgonidia,  267 

Microklossia,  426 

Microrncrozoite,  373 

Micront,  426 

Micronucleus,  78,  113,  114  (Fig.  61),  288, 

332,  333,  430,  437, 448 
Microschizont,  344,  373 
Microsome,  40 
Microspheric,  184,  233 
Microspore,  254,  255,  416 
Microsporidia,  411 
Microlhoracidce,  439 
Microthorax,  439 
Miescher's  tubes,  419,  422 
Minchinia,  352 

-  caudata,  348 

-  chitonis,  349,  352 
Mitochondria,  41,  448 
Mitosis,  101 
Mixotrophic,  188 
Molluscum  coutagiosum,  17,  470 
Monad,  466 

Monadidcc,  270 

Monas,  270 

Monaxon,  39,  250 

Monera,  78 

Monilif  orm,  77 

Monocercomonas,  272 

Monocystis,  23,  174  (Fig.  79),  328,  336, 

339 
—  coronata,  328 

-  pareudrili,  331 

-  rostrata,  332,  333,  335 
'  Monokaryon,  121,  255 

Monomastigote,  259 
Monomastix,  455 


512 


THE  PROTOZOA 


Monomastix  ciliatus,  454  (Fig.  189,  A), 

455 

Monomorphic  species,  163 
Monopylaria,  251,  256 
Monospora,  339 
Mouosporea,  409 
Monothalamous,  36,  232 
Monozoa,  273 
Monozoic,  349 
Mothor-cyst,  138 
Movement,  199 
Movements  of  gregarines,  327 
Multicilia,  249,  261,  270,  454 

-  lacustris,  269  (Fig.  113),  270 

-  iinlustris,  269  (Fig.  113),  270 
Multiple  fission,  100,  120 

^'•imnation,  122 

-  promitosis,  120 
Multiplicative  phase,  20, 166 
Multipolar  mitosis,  120 
Murrina,  285 
Mycotosporidium,  243 
Mycetozoa,  218,  239,  268 
Mycterothrix,  446 
Myocyte,  327 

Myonemes,  57,  201,  253,  259,  286,  445 
Myophrisks,  253 
Myxamoeba,  239 
MyxidiidcB,  409 
Myxidium,  409 

-  bergense,  407 

-  lieberkuhni,  400,  401,  409 

-  sp.,  406 

Myxdbolidce,  22,  23,  409 
Myxobolus,  409 

-  cerebralis,  400 

-  neurobius,  400 

-  Pfeiffcri,  405,  406  (Fig.  168) 
Myxocystis,  417,  418 
Myxoflagellate,  239 
Myxogastres,  242 
Myxomycetes,  239,  242 
Myxopodia,  253 
Myxosporidia,  399 
Myxotheca,  231 

Nagana,  19 

Narcotics,  effects  of,  204 
Nassellaria,  256 
Nassula,  439 

Natural  c1  assification,  463 
Nebenkcrn,  95 
Nebenkorper,  278 
Negri's  bodies,  470 
Nemato  yst,  447 
Neogamous,  127,  330 
Neosporidia,  325,  398,  466 
Nephroselmis,  275 
Nervous  system,  446 
Neuroneinos,  446 
Neuroryctes,  470 

—  hydrophobice,  471 
Neurosporidium,  424 

—  cephalodisci,  424 
Nicollia,  380 

-  quadrigemina,  380,  381 
Nina.     See  Pteroccpltalus 
Noctiluca,2Ql,  213,279 

—  miliaris,  119  (Fig.  65),  279 
Nodosaria,  232  (Fig.  93,  3) 
Nosema,  418 

-  apis,  412 


Nosema  bombycis,  24,  411,  413,  414  (Fig. 

172) 
Nuclear  membrane,  76 

-  sap,  72 
Nuclearia,  248 
Nuclearia-siskge,  177 
Nucleo-cytoplasmic  ratio,  70 
Nucleolo-centrosome,  95 
Nucleolus,  76,  103 
Nucleophaga,  473 
Nucleus,  6,  7,  65,  96 

—  secundus,  95 
Nuda,  217,219 
Nummulites,  232  (Fig.  93,  11) 
Nutation,  51 

Nutrition,  187 
Nutlallia,  380 

—  equi,  380 

-  herpestidis,  380 
Nyctotherus,  439,  440,  447 

—  cordiformis,    10    (Fig.    9),    444    (Fig. 

186,  F) 

—  faba,  440 

Octomitidco,  272 
Octomitus,  36,  258,  272 

-  dujardini,  272  (Fig.  116) 
Octosporca,  418 

-  muscat  domesticco,  138 
Octozoic,  349 
CEcomonas,  270 
(Esophagus,  261,  433 
Oikomonas,  270 
Oligosporea,  418 
Oligosporulea,  424 
Oligotricha,  439 
Oocyst,  348 

Ob'cyte,  143 
Ookinete,  305,  362 

Opalina,    196,    198,   208,   209,  439,    440, 
447,  448,  452,  454 

—  caudata,  452 

—  intestinalis,  452 

-  ranarum,  447,  452,  453 
Opalinince,  452 
Opalinopsis,  452 
Opercularia,  145,  440 

-  faurei,  442 
Operculum,  441 
Ophrydium,  438,  440 
Ophryocystidce,  341 
Ophryocystis,  337,  339 
Orcheobius,  352 
Ophryodendridce,  461 
Ophryodcndron,  455,  461 
Ophryoscolecidcv,  439 
OpJiryoscolex,  439,  441 

Orcheobius  JierpobdellcB,  346,  348,  349,  352 

Organella,  1 

Oriental  sore,  316 

Osmotaxis,  203 

Ovum,  125 

Oxyrrhis,  52,  278 

-  marina,  278  (Fig.  123) 
Oxytricha,  202,  440 
Oxytrichidcv,  440 

Pansporclla  pcrpJexa,  427 
Pansporoblast,  405,  417,  423 
Pantastomina,  268 
Parabasal  apparatus,  89 
Paracoccidium  prevoti,  349 


INDEX 


513 


Paraglycogen,  41,  63,  195,  327 

Paramastigote,  259 

Paramecidce,  439 

Paramerium,  61,  114  (Fig.  61),  171,  191, 
192,  194,  196,  197,  198,  203  (Fig.  83), 
205, 206, 208,  210,  437,  439,  442,  443 

—  bursaria,  449 

—  caudatum,    107    (Fig.    53),    436    (Fig. 

185),  444  (Fig.  186,  D,  E),  447  (Fig. 
187) 
Paramceba,  228 

—  eilhardi,  94  (Fig.  49),  95,  228 

—  hominis,  228 
Paramylum,  63,  188,  195 
Paramyxa,  243,  409 

—  paradoxa,  409 
Paramyxidia,  409 
Paraplasmaflavigenum,  379 
Parasite,  8,  14 

Parietal  cell,  403 
Parthenogenesis,  137 
Parthenogonidia,  267 
Partial  karyogamy,  126,  153,  453 
Pathogenic,  19 

—  amoebae,  226 
Paulinella,  214 
Pearl-stage,  334 
Pebrine,  24,  411 
Pectinellse,  442 
Peduncle,  31 
Pellicle,  32,  45,  435 

Pelomyxa,  78,  144,  150,  205,  214,  227 

—  palustris,  227  (Fig.  91) 
Peltomyces,  243 
Peneroplis,  15,  235 
Peranema,  274 

—  trichophorum,  273 
Peranemidce,  274 
Perczia,  418 
Perforate,  231 
Peridiniales,  276 
Peridinidce,  278 
Peridinium,  278 

—  divergens,  278  (Fig.  122) 
Peridium,  241 
Perikaryon,  439 
Periplast,  45,  259 
Peripylaria,  251,  255 
Peristome,  433,  442 

Peritricha,  433,  438,  440,  441,  442,  448 

Peritrichous  larvae,  459 

Peritromido},  440 

Peritromus,  440 

Pernicious  malaria,  358' 

Peroral  membrane,  445 

Phacus,  274 

—  triqueter,  274  (Fig.  118). 
Phaenocystes,  412 
Phseodaria,  256 
PhfEodiuna,  252 
Phosphorescence,  201,  278 
Phototaxis,  202,  205 
Phylogeny,  463 
Physarum  didermoides,  242 
Physodes,  244 
Phytoflagellata,  274 
Phytomonadina,  274 
PhytomyxincB,  243 
Piroplasma,  24,  357,  379,  393,  394 

—  Mgeminum    (bovis),    379    (Fig.    160), 

384,  385  (Fig.  162) 

—  caballi,  379 


Piroplasma  cams,    382,    383  (Fig.   161), 
384,  385  (Fig.  162),  387 

-  donovani,  393 

-  hominis,  379 
Piroplasmoees,  378 
Piroplasms,  378,  390 
PlagiotomidcG,  439 
Planout,  398,  408,  413, 423 
Planorbulina,  232  (Fig.  93,  9) 
Plasmodiophora,  243 

-  brassicce,  149  (Fig.  76),  243 
Plasmodium,  100,  128,  240,  398,  423 
Plasmodium,  357 

—  brasilianum,  364 

—  cynomolgi,  364 

—  diploglossi,  358 

—  falciparum,  358,  359,  360  (Fig.  156) 

—  inui,  364 

—  kochi,  364 

—  malar  ice,  358,  359 

—  pithed,  359,  364 

—  prmcor,  358 

—  relictum,  358 

—  vivax,   137    (Fig.    72),   358,   359,   360 

(Fig.  156) 

—  vassali,  364 
Plasmodioma,  462 
Plasmogamy,  128 
Plasmotomy,  100 
Plastin,  73,  103 

Plastinoid  granules,  41,  195,  346 
Plastogamj ,  128,  209 
Plegepoda,  462 
Pleistophora,  418 

-  longiftlis,  413  (Fig.  171),  415,  416- 
- —  periplanetcB,  416 

-  species,  413 
Pleodorina  californica,  267 
Pleuronema,  55,  439,  442 

—  chrysalis,  56  (Fig.  27) 
Pleuronemidcv,  439 
Podophrya,  461 

-  flxa,  456  (Fig.  190,  C),  458 

—  gemmipara,  108  (Fig.  55) 

—  mollis,  456  (Fig.  190,  A) 
Podophryidcc,  461 

Polar  bodies,  143 

-  capsule,  399  (Fig.  163) 

—  cones,  117 

-  filament,  399 

—  masses,  110 

-  plates,  117 
Polycaryum,  424 
Polychromoptiilus,  364 
Polycystid,  326 
Polycyttaria,  256 
Polyeuergid  nuclei,  121,  151,  255 
Polykaryon,  121,  255 
Polymastigido),  272 
Polymastigina,  271 
Polymastigoto,  259 
Polymastix,  272 

Polymoiphism,  162,  163,  297,  311 
Polyspora,  339 

Polysporea,  409,  418 
Polysporulea,  424 
Polystomella,  210 

-  crispa,  139,  234  (Fig.  95),  235, 

(Fig.  96) 

Polythalamous,  36,  232 
Polytomella  ar/ilis,  86  (Fig.  43) 
Polytrema,  231 


514 


THE  PROTOZOA 


Polytricha,  439 
Polyzoic,  349 
Ponerama-.ba,  224 
Pontobdclla  muricata,  291,  303 
Pontomyxa  flava,  218 
Porospora,  337,  340 

-  f/!Y/<m<ea,74(Fig.35),336,339(Fig.  150) 
—  leycri,  336 
PorosporidcB,  341 
Pouchdia,  62 

-  cornuta,  61  (Fig.  31) 
Prehensile  tentacle,  457 
Proboscidiform  individuals,  455 
Proboscidium,  442 
Prococcidia,  352 
Proflagollata,  469 
Promitosis,  109 
Pronucleus,  127 
Propagative  cell,  405 

-  phase,  21, 166 
Propulsive  psoudopodium,  401 
Prorocentracese,  276 
Prorocentrum,  278 
Prorodon,  439 

-  teres,  32  (Fig.  14),  444  (Fig.  186,  B, 

C),  446 

Proteomyxa,  217,  268 
Proteosoma,  358,  364,  365,  393 
Protista,  4,  5 
Protoblast,  426 
Protococcacese,  15 
Protoentospora  plychoderce,  229 
Protokaryon,  75,  87,  108 
Protomerito,  327 
Protomonadina,  270 
Prolophrya,  452 

—  ovicola,  452 
Protophyta,  8 
Protoplasm,  29,  40 
Protozoa,  2,  10,  464 
Prowazek's  bodies,  470 

Prowazckia,  260,  271,  281,  319,  321,  322 

-  asiatica,  319 

-  cruzi,  319 

-  parva,  319,  320  (Fig.  141) 

—  weinbergi,  319,  320  (Fig.  141) 
Pseudochlamys-st&ge,  170,  177 
Pseudoplasmodida,  243 
Pseudoplasmodium,  242 
Pseudopodiospore,  169 
Psoudopodium,  30,  46,  90,  199,  214,  400, 

465 

Pseudospora,  213,  218,  249 
Psorosporni,  165,  323 
Ptcrocephalns,  173,  327,  329,  330,  339 

-  gracilis,  174  (Fig.  79),  332  (Fig.  145), 

334  (Fig.  147) 

-  nobilis,  339 
Pulsellum,  52,  259 
Pusule,  277 
Pycnothrix,  452 

-  monocystoidcs,  443,  446,  447,  452 
Pyramimonas,  275 

Pyrenoid,  63, 188,  261 
Pyrodinium,  201,278 
Pyrosoma,  379 
Pyxinia,  329,  330 

Quartan  malaria,  358,  359 

Radiolaria,  218,  249 
Radium-rays,  effects  of,  205 


Rainey's  corpuscles,  419 
Reactions  of  protozoa,  201 
Recapitulative  forms,  170 
Reducing  division,  104 
Reduction,  142,  145,  335 
Reduction-nuclei,  144 
Redwator,  378 
Regeneration,  208,  210 
Rejuvenescence,  155 
Relapse  (malarial),  363 
Reserve-materials,  195,  196 
Reservoir-vacuole,  262 
Respiration,  195 
Reticulosa,  217,218 
Reticuloee,  48 
Reticulum  (nuclear),  75,  103 

-  (protoplasmic),  41 
Rhabdogenise,  325,  466 
Rhabdophrya,  461 

-  trimorpha,  455 
Rhaphidiophrys,  245 
Rheotaxis,  207 
Rhinosporidium,  424 

-  kinealyi,  424,  425  (Fig.  177) 
Rhizomastigina,  265,  268,  465 
Rhizoplast,  82 
Rhizopoda,  213,  217 
Rhyncheta,  457,460 
Rhynchoflagellata,  278 
Right  hosts,  291 
Rod-apparatus,  433,  439 
Rontgen-rays,  effects  of,  206 
Rostrum,  326 

Saccamina,  232  (Fig.  93,  1) 

Sack-pusule,  277 

Sapropelic,  14 

Saprophytic,  S,  14,  187,  194,  262 

Saprospira,  467,  469 

-  gland  is,  468 
Saprozoic,  14 
Sarcocystine,  20,  420,  421 
Sarcocystis,  20,  419 

—  bertrami,  420 

—  muris,  419,  420,  421,  422  (Fig.  176) 

—  rileyi,  420 

—  tenella,  419,  420,  421  (Fig.  175) 
Sarcocyte,  327 

Sarcode,  40 
Sarcodina,  11,  213 
Sarcosporidia;  20,  419 
Scaiotricha,  440 
Scarlet  fever,  470 
Schaudinnella,  355 
Schewiakovella  schmeili,  425 
Schizocysiidce,  339,  341 
Schizocystis,  339 

-  oregarinoidcs,  336,  338  (Fig.  149) 
Schizogenea,  418 

Schizogony,  166,  324,  392 
Schizogregarinse,  328,  339 
Schizokinete,  373 
Schizont,  166,  181,  324 
Schizontocyte,  344 
Schizotrypanum,  285,  307,  392 

-  cruzi,    28,   295    (Fig.    128),    296,    302 

(Fig.  132),  307 
Schizozoite,  344,  428 
Sclerothmi,  166,  240 
Scopula,  441,  456,  459 
Scyphidia,  440,  441 
Secondary  nuclei,  66 


INDEX 


515 


Secretion,  197,  198 
SelenidiidcB,  341 
Selenidium,  339 

-  caulleryi,  336,  337  (Fig.  148) 
Selenococcidium,  352,  354 

-  intermedium,  344,  350  (Fig.  155),  351 
Senility,  131,  135,  155 

Sensory  organs,  201,  446 

Separation-spindle,  104 

Septate,  326 

Serumsporidia,  425 

Sex, 154 

Sexual  differentiation,  160,  170,  176 

—  phases  of  trypanosomes,  305 
Shell,  33,  45,  232  (Fig.  93) 
Siedleckia,  339,  352 
Silicoflagellata,  274 
Sleeping  sickness,  26 
Smithia,  380 

-  microti,  380 
Soma,  130 

Somatic  number,  143 
Sorophora,  243 
Sorosphwra,  243 
Sorus,  242 
Souma,  304 
Spasmoneme,  446 
Species,  141, 162 
Spermatocyte,  143 
Spermatozoon,  125 
Sphceractinomyxon,  409 

-  stolci,  409,  410  (Fig.  170) 
SphaDrellaria,  255 

Sphccromyxa    sabrazcsi,    404    (Fig     167), 

405 

Sphcvrophrya,  461 
Sphterozoa,  256 
Sphere,  95 
Spheroplast,  41,  448 
Spicule,  36 

Spindle  (nuclear),  103 
Spirigera,  442 
Spirillacea,  467 
Spirillar  forms,  319 
Spirillum,  467 
Spirochceta,  466 

—  plicatilis,  466 

-  ziemanni,  371,  468 
Spirochsetes,  466 
Spirochona,  440 
Spirochonidce,  440 
Spiroloculina,  232  (Fig.  93,  5) 
Spironema,  467,  469 
Spironemacea,  469 
Spiroschaudinnia,  467 

—  anserina,  467 

—  duttoni,  467,  468 

—  gallinarum,  467 

—  obermeieri,  467 

—  recurrentis,  467 

Spirostomum,  196, 197,  203,  438,  439,  445 

—  ambiguum,  431  (Fig.  180) 
Spongomonas,  270 

—  splendida,  84  (Fig.  41) 

—  uvella,  85  (Fig.  42) 
Sporal  residuum,  349 
Sporangium,  240,  241 
Spo^e,  165, 166,  323 
Spore -format  ion,  166 
Sporetia,  150 
Sporoblast,  325 
Sporocyst,  165 


Sporocyst-mother-cell,  403 
Sporoduct,  335 
Sporogony,  181,  325 
Sporomyxa,  243 
Sporont,  166, 181,  325,  326 
Sporophore,  242 
Sporoplasm,  405 
Sporozoa,  12,  323,  462,  466 
Sporozoite,  169,  324 
Sporulation,  122, 165,  166 
Spumellaria,  255 
Stannomidce,  238 
Starvation,  195,  210 
StemonUis  flaccida,  82 

-  fusca,  240  (Fig.  98) 
Stemm-pseudopodium,  401 
Stempellia,  418 

—  mutabilis,  418 
Stenophora,  329 

Stentor,  61,  202,  211,  437,  438,  439,  441, 
445, 446 

-  cceruleus,  444  (Fig.  186,  A,  I) 

—  niger  444  (Fig.  186,  O) 

-  roeselii,  10  (Fig.  8) 
Stentoridw,  439 
Stephanosphcera,  267,  276 
Stercomarium,  238 
Stercome,  194,  233 
Stigma,  61,  205,  262 
Stomatophora  coronata,  328 
Streaming  movements,  199 
Strongyloplasmata,  470 
Stylonychia,  438,  440 

-  histrio,  444  (Fig.  186,  H) 

-  mytilus,  211,  459  (Fig.  192) 
Stylorhynchus,  173,  329,  330,  339 

-  longicollis,    174    (Fig.    79),    327    (Fig. 
142),  339 

Suctoria,  455 

Suctorial  tentacle,  190,  456 
Sulcus,  276 
Surface-tension,  200 
Surra,  26 

Swarm-spore,  169,  396 
Symbiosis,  15 
Symbiotic  algee,  197 
Synactinomyxon,  409 
Syngamy,  126,  438 
Synkaryon,  127 
Syphilis,  467 
Syzygy,  330 

Tachyblaston,  460 
Tactic,  202 
Tactile  bristles,  443 

-  organs,  201 
Tceniocystis,  327,  339 
Taxis,  202 

Technitella  thompsoni,  34 
Teloblast,  426 
Telomyxa,  418 

-  glugeiformis,  418 
Telosporidia,  325,  395,  466 
Temperature,  effects  of,  206 
Tentaculifera,  455 
Tertian  malaria,  358,  359 
Test,  33 

Testacea,  217,  219 
Tetramyxa,  243 
Tetratrichomonas,  272 
Tetrazoic,  349 
Thalamophora,  219 


516 


THE  PROTOZOA 


'J'hiilassicolla,  255 

liHiitiirii,  30  (Fig.  13) 
TlinlassopJiysa,  255 
Thocamrclw,  219,  229 
TlK'ili'i-iit,  379 

litu-ra,  380,  382,  386 
Thelohania,  418 

-  chcelogasiris,  416  (Fig.  173) 

—  contejeani,  412 

-  mtenadis,  416 
Tholyplasm,  129 
Thermotaxis,  202,  206 
Thigmotaxis,  207 

Thyroid  extract,  effects  of,  204 
Tinctin-body,  458 
Tintinnidm,  439,  441,  443,  447 
Tocophrya,  461 

-  cyclopum,  461 

—  limbata,  460 

—  quadripartita,  210,  456  (Fig.  190,  B) 

460 
Toddia,  387 

—  bufonis,  387 
Tolerant,  21 
Tonicity,  effects  of,  207 
Total  karyogamy,  126,  453 
Toxocystis  homari,  426 
Toxoplasma,  319,  387 

—  canis,  387 

—  cuniculi,  387 

—  gondii,  387 

—  talpm,  387 
Trachelidce,  439 
Trachelius,  439 

—  OUMWI,  441,  448 
Trachelocerca,  439,  448,  453 

-  phcenicopterus,  120  (Fig.  66),  449,  450 

(Fig.  188) 
Trachoma,  470 
Tractellum,  52,  259 
Trailing  flagellum,  53,  260 
Transmission  of  trypanosomes,  289 
Transmutation  of  energy,  199 
Treponema,  467 

—  pallidum,  467,  468 

-  pertenue,  467 
Triactinomyxon,  409 
Trichiavaria,  241  (Fig.  101) 
Trichites,  442 

Trichocyst,  46,  435,  447  (Fig.  187) 
Trichodina,  440,  441 
Trichomastix,  260,  271 
Trichomonas,  17,  36,  56,  258,  260.  271 

-  eberthi,  8  (Fig.  5),  36 

—  hominis,  272 

—  vaginalis,  272 
Trichonympha,  276 

-  hertwigi,  276 
Trichonymphida,  463 
TrichonymphidcB,  89,  276,  454 
Trichophrya,  461 
Trichophryidw,  461 
Tricharhynchus,  446 
Trichosphcorium,  51,  216,  229 

—  sicboldi,  73  (Fig.  34),  182  (Fig.  81) 
Trima slit/amoeba,  268 

Tripylaria,  251,  256 
Tritoblast,  426 
Trizoio,  349 
Trophic  phase,  324 
Trophochromatin,  71 
Trophochromidia,  150 


Trophonuclons,  78,  85,  286,  288 
Trophozoito,  324 
Tropical  malaria,  358 
Trypanomonad,  282,  298,  299 
Trypanomorpha ,  308 
Trypanophis  grobbeni,  309 
Trypanoplasma,  56,  78,  87,  260,  271,  281, 
287,  308,309,  321,  322 

-  abramidis,  310  (Fig.  134) 

-  borreli,  312 

-  conger  i,  312 

-  dendrocceli,  309 

-  gnjllotalpcB,  309,  310 

-  cjurneyorum,  78  (Fig.  36) 

-  helicis,  309,  311,  312 

-  intestinalis,  312 

-  keysselitzi,  310  (Fig.  134) 

-  ranee,  319 

-  vaginalis,  309 

Trypanosoma,  270,  280,   283,  308,   320, 
321 

-  balbianii,  467 

-  blanchardi,  25 

-  brucii,  19,  25,  26,  27  (Fig.   12),  285, 

291,  296,  305,  306, 308 

-  cazalboui,  304 

-  cruzi,  285,  295,  296 

-  cuniculi,  25,  26  (Fig.  11) 

-  dimorphon,  304 

-  drosophilce,  315  (Fig.  137) 

-  duttoni,  25,  26  (Fig.  11) 

-  elyomis,  25,  26  (Fig.  11) 

-  eguinum,  285,  305 

-  equiperdum,  22,  26,  285 

-  evansi,  26,  27  (Fig.  12),  285 

-  gambiense,  19,  26,  27   (Fig.  12),  285, 

291,  296,  297, 303, 304, 305, 306 

-  granulosum,  288,  297,  298  (Fig.  129) 

-  grayi,  304 

-  hippicum,  285 

-  inopinatum,  290 

-  lewisi,   19,  25,  26  (Fig.  11),  28,  263, 

286,  291,  292,  293  (Fig.  127),  297, 
299,  300  (Fig.  130),  301  (Fig.  131), 
305,  306,  308 

-  longocaudensc,  294 

-  mega,  284  (Fig.  125) 

-  microti,  25,  26  (Fig.  11) 

-  nanum,  27  (Fig.  12) 

-  noctucB,  59   (Fig.   30),   137,   144,   158, 

283,  297,  305,  306,  308,  391 

-  pecaudi,  304 

-  perccB  (myonomos),  58  (Fig.  28) 

—  rabinowitschi,  25 

-  raice,  291,  303 

-  remaki,  9  (Fig.  6) 

-  rhodesiense,  26,  286 

—  rotatorium,  59  (Fig.  30),  283,  297,  307 

—  sanguinis,  283 

—  vittatcc,  303 

-  vivax,  27  (Fig.  12),  287,  291,  304 
Trypanosomes,  syngamy,  136 
Trypanosomidce,  268,  270 
Trypanotoxin,  20 
Trypanozoon,  308 

Ultramicroscopic  stages,  306 

Unciform  individuals,  455 

Undulating  membrane,  55,  260,  286,  287. 

443 

Undulina  ranarum,  283 
Unicellular,  1,  3 


INDEX 


517 


UrceolarincB,  440 
Urheemonagellat,  468 
Urnula,  457,  460 

—  epistylidis,  457  (Fig.  191),  460 
Urnulidce,  460 

Urospora  lagidis  gametes,  174  (Fig.  79) 
U rosporidium,  424 
Urostyla,  440 

Vaccinia,  470 
Vacuole,  43 
Vaginicola,  440 
Vamvyretta,  218 

—  lateritia,  219  (Fig.  86) 
Variola,  470 

Vegetative  chroniatin,  71 
Vermiform  individuals,  455 
Vestibule,  433 

Volutin,  68,  195,  289 
Folvocidce,  267,  275 
Volvox,  3,  131,  206,  267,  276 
Vorticella,  440,  441,  445,  446 


Vorticella  inicrostoma,  1 7 'j  (Fis.  78) 

-  monilata,  446 
Vorticellidrx,  440 
VorticellinoB,  440 

Waanerella,  48,  51,  92,  I'-'i).  246,  246,  248 

-  borealis,  93  (Fig.  48).  247  (Fig.  102) 
Wrong  hosts,  291 

Xenophya,  34,  238 
Xenophyophora,  218,  237 

Yaws,  467 
Yellow  cells,  252 

Zoochlorelkc,  15,  252 
Zoomyxa,  243 
Zoospore,  169,  262 
Zoosporidcs,  218 
Zoothamnium,  440 
Zooxanthellap,  15,  252 
Zygote,  125 


THE   END 


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