SUBPHYLUM  SPOROZOA
Class  Telosporidia

All  the  members  of  this  class  are  parasitic,  but  only
a  few  have  been  observed  in  man,  and  only  one  genus,
Plasmodium^  is  of  much  importance  in  human  pathology.
Propagation  is  by  means  of  spores,  and  sporulation  ends
the  life  of  the  individual.  In  some  species  there  is  an
alternation  of  generations,  in  one  of  which  sexual  proc-
esses appear.  In  such  cases  the  male  individual  may
be  provided  with  flagella.  Otherwise,  there  are  no
special  organs  of  locomotion.
1.  Genus  Coccidium. — (i)  Coccidium  cuniculi. — This
is  a  very  common  parasite  of  the  rabbit  and  has  been
much  studied;  but  extremely  few  authentic  cases  of
infection  in  man  have  been  reported.  The  parasite,
which  when  fully  developed  is  ovoid  in  shape  and  meas-
ures about  30  to  50  fi  in  length  and  has  a  shell-like
integument,  develops  within  the  epithelial  cells  of  the
bile-passages.  Upon  reaching  adult  size  it  divides  into
a  number  of  spores  or  merozoites  which  enter  other
epithelial  cells  and  repeat  the  cycle.  A  sexual  cycle
outside  the  body,  which  suggests  that  of  the  malarial
parasite,  but  does  not  require  an  insect  host,  also  occurs.
382  ANIMAL  PARASITES

Infection  takes  place  from  ingestion  of  the  resulting
sporozoites.
2.  Genus  Plasmodium. — This  genus  includes  the  ma-
larial parasites  which  have  already  been  described
(see  p.  296).
3.  Qenus  Babesia. — The  proper  position  of  this  genus
is  uncertain.  It  is  placed  among  the  flagellates  by  some.
The  chief  member  is  Babesia  bigeminuniy  the  cause  of
Texas  fever  in  cattle.  It  is  a  minute,  pear-shaped  or-
ganism, lying  in  pairs  within  the  red  blood-corpuscles.
