In  all  of  them  the  determinants  are  as  similar  as  the  retention
of  the  specific  character  renders  necessary :  that  is  to  say,  all
the  determinants  of  the  same  ontogenetic  stage  are  homologous,
though  at  the  same  time  they  are  never  all  homodynamous,
but  differ  in  many  respects  owing  to  slight  individual  devia-
tions. Hence  different  ids  may  contain  different  variations
of  any  particular  homologous  determinant.  In  the  following
examples,  each  homologous  determinant  is  indicated  by  a  letter,
and  variants  of  a  determinant  are  distinguished  by  dashes  after
each  letter.  Thus  id  i.  of  the  germ-plasm  might,  for  instance,
contain  the  determinants  a,  b,  c,  d,  e, n ;  id  ii.,  the  deter-
minants a,  b',  c,  d',  e, n'  ;    id  iii.,  a',  b'^  c',  d'",  e', n,

and  so  on.  The  total  effect  of  the  idants  is  decided  by  the
struggle  of  the  ids;  the  laws  which  regulate  this  struggle
cannot  at  present  be  determined  more  precisely,  and  until  we
know  more  about  them,  we  may  suppose  that  those  variants


THE  PHENOMENA  OF   REVERSION  3O9

which  are  present  in  the  largest  numbers  always  have  the  best
prospect  of  controlling  the  cell  entirely,  or  at  any  rate  chiefly ;
their  effect  must  be  cumulative,  and  a  small  minority  of  homo-
dynamous  determinants  will  not  be  able  to  take  effect  against  a
large  majority  of  some  other  variant.  The  control  of  the  cell
therefore  results  from  this  struggle  of  the  determinants,  which
must  naturally  not  be  conceived  to  take  place  in  such  a  manner
that  the  group  of  paternal  ids  struggles  with  the  maternal  group,
but  so  that  ^1  the  active  determinants  which  are  contained  in
the  idioplasm  migrate  into  the  cell  body  and  there  strive  to
obtain  the  control.  If  the  parents  of  the  organism  in  question
are  closely  related,  the  same  homodynamous  detenninants  may
very  possibly  be  contained  in  the  idants  of  both  parents,  and
the  forces  of  these  will  then  combine  just  as  would  be  the  case
if  they  had  been  contained  in  one  idant  of  the  father  or  mother.
