We  cannot  as  yet  judge  with  certainty  as  to  how  far  the  entire
idants  pass  unchanged  as  regards  their  constituent  ids  from  the
germ-cells  of  one  generation  into  those  of  the  next.  The  phenom-
ena of  the  reduction  in  the  germ-cells  which  have  recently  been
made  known  to  us  in  the  case  of  various  Arthropods  by  the  re-


250  THE  GERM-PLASM

searches  of  Henking,  vom  Rath,  and  Hacker,  indicate  that  even
the  idants  may  become  changed  during  the  process.  If  we  sup-
pose that  in  the  mother  germ-cell,  when  it  is  preparing  for  the
first  reducing  division,  the  ids  become  arranged  in  their  original
order  so  as  to  form  a  long  thread  which  doubles  back  on  itself,  ,
and  thus  gives  rise  to  a  ring,  the  latter  would  become  trans-
versely divided  in  certain  places.  If  the  transverse  divisions
could  take  place  at  different  points,  it  would  be  possible  either
for  the  old  idants  to  be  accurately  restored,  or  for  the  new  ones
to  differ  from  them  to  a  greater  or  lesser  extent.
This  assumption  is  not,  however,  essential  for  a  theory  of
amphigonic  heredity,  and  we  may  here  disregard  it,  although  it
will  doubtless  be  found  to  apply  to  some  extent,  as  was  indicated
above  with  regard  to  such  a  slow  and  slight  change  of  the  idants
due  to  the  disarrangement  in  the  combinations  of  ids  contained
in  them.  It  must  be  left  to  future  researches  to  follow  out  this
process  in  detail,  and  to  show  whether  the  differences  in  the
combination  of  ids  is  merely  due  to  the  halving  and  rearrange-
ment of  the  idants,  or  whether  regular,  or  at  any  rate  frequent,
changes  in  the  composition  of  the  idants  out  of  ids  also  occur.
