1051 
syncj'tium  in  fig.  14  was  sitiiated  iminediatelj  beneath  the  ependyma, 
and  that  in  fig.  15  in  the  dorsal  horn  of  the  spinal  cord  in  a 
yonng  white  moiise  ten  days  old.  Figures  Ib,  2a,  3a,  96,  10,  14, 
15,  16,  17,  18,  19,  20,  and  21  are  pietiires  of  different  stages  of 
young  nerve  cells  engaged  in  amitotic  division.  These  figures  are 
all  drawn  froin  appearances  in  the  spinal  cord  of  a white  nionse, 
the  two  first  from  an  aniinal  24  days  old  and  the  others  from  10 
days  old  animals.  In  the  material  from  toads  and  dogs  that  was 
investigated,  similar  appearances  to  those  in  the  white  mouse  have 
been  fonnd  to  about  the  same  extent.  Fig.  96  shows  one  stage  of 
direct  cell  division  which  in  my  opinion  is  very  rare;  I myself 
have  only  fonnd  this  single  case.  Fig.  20  shows  the  most  advanced 
incision  nsnally  seen.  Transitional  stages  between  this  and  complete 
division  of  the  nuclei  occur  exceedingly  seldom.  1 obtained  a parti- 
cularly  welcome  opportunity  through  Professor  Boekk’s  great  kindness 
during  my  visit  to  Holland  last  summer  — of  observing  in  eelem- 
bryos  that  it  really  is  a tact  that  the  appearance  of  amitoses  is 
very  rare  in  cases  where  the  danghter-niiclei  show  only  very  narrow 
communicating  bridges  between  each  other.  It  is,  as  we  know, 
generally  recognized  that  the  nuclei  in  the  myogene  tissue  increase 
by  direct  division  during  a later  stage  of  its  ditïerentiation  into 
muscular  tibres.  Eel-embryos  are  particularly  suitable  tbr  the  study 
of  this  development  (Godlewski  E.  ^).  Boeke’s  very  tine  preparations 
of  these  embryos  showed  in  this  region  numerous  nuclei  engaged  in 
amitotic  division.  It  is  worthy  of  note  that  here  too,  among  this 
mass  of  nuclei  in  amitotic  division,  no  stage  could  be  discovered 
in  which  the  nucleus  showed  a far  advanced  incision  — and  con- 
sequently  a very  small  communicating  bridge  between  the  two 
daughter-nuclei.  — Accordingly,  after  studying  this  material,  I was 
inclined  to  assurne  that  the  last  part  of  the  process  of  division  took 
place  rapidly,  without  any  narrow  drawn-out  communicating  bridge 
between  the  daughter  nuclei  being  formed.  With  this  in  view,  it  is 
not  strange  that  I looked  upon  the  appearances  that  form  the  basis 
of  fig.  21  with  a certain  amount  of  surprise  and  doubt.  Does  this 
figiire  really  show  stages  of  amitotic  cell  division  or  are  they  only 
artifical  Products?  The  preparations  were  well  fixed  and  as  a matter 
of  fact  do  not  support  the  idea  of  there  being  artificial  products. 
The  nucleoli  show  a particularly  great  generative  tendency.  If  we 
h Godlewski,  E.  Ueber  Kernvermehrung  in  den  quergestreiften  Muskelfasern 
der  Wirbeltiere,  Buil.  intern,  de  1’ Academie  des  Scien.  de  Cracorie,  1900. 
*)  Godlewski,  E.  Die  Entwicklung  des  Skelet-  und  Herzmuskelgewebes  der 
Saugethiere.  Arch.  f.  mier.  Anat.  B.  60,  1902. 
68 
Verslagen  der  Afdeeling  Natuurk.  Dl.  XXVll.  A«.  1918/19. 
