AmjJaOnuy'if90.arm'}  Protoplasm  arid  its  History.  49 
protoplasm  interchangeably,  the  latter  term  is  generally  restricted  to  morpho- 
logical and  physiological  conceptions,  the  former  keeps  its  wide  chemical 
significance.  The  chemical  studies  of  protoplasm  by  Rodewald,  Keinke,  Loew, 
Bokorny,  and  microscopically  by  Schwarz,  compel  us  to  recognize  in  proto- 
plasm a  substance  of  bewildering  complexity  of  composition  and  constitution. 
Moreover,  you  all  know  how  wide  this  field  of  research  has  suddenly  become 
by  the  discovery  that  different  microbes  (which  are,  essentially,  minutest 
masses  of  protoplasm)  not  only  give  rise  to  such  diverse  products,  among  others 
the  ptomaines,  but  present  such  diverse  chemical  reactions.  Protoplasm  is  no 
longer  regarded  by  any  one  in  any  sense  as  a  comparatively  simple  substance. 
The  third  thesis,  namely,  protoplasm  has  no  demonstrable  structure,  has 
been  modified  in  a  striking  manner  as  a  result  of  improved  appliances  for  re- 
search. By  better  methods  of  staining,  and  by  the  use  of  homogeneous  i  n- 
mersion  objectives,  the  apparently  structureless  mass  is  seen  to  be  made  up  of 
parts  which  are  easily  distinguishable.  There  has  been,  and  in  fact  is  now,  a 
suspicion  that  some  of  these  appearances,  under  the  influence  of  staining  agents 
are  post-mortem  changes  and.  do  not  belong  to  protoplasm  in  a  living  state. 
But  it  seems  to  be  beyond  reasonable  doubt  that  protoplasm  is  marvellously 
complex  in  its  morphological  and  physical  as  well  as  its  chemical  constitution. 
Fourth,  we  are  to  glance  at  the  accepted  statement  that  the  protoplasmic 
body  or  protoplast  of  one  cell  is  cut  off  by  the  cell  wall  from  all  connection  with 
the  contiguous  cells.  It  has  been  shown  by  Gardiner  and  others  that  there 
are  intercommunicating  threads  of  protoplasm  of  extreme  fineness  between 
adjoining  cells,  and  these  living  threads  maintain  connections,  sometimes  direct, 
sometimes  indirect  between  one  protoplasmic  mass  and  another.  This  has 
been  shown  to  be  so  widely  true  in  the  case  of  plants  investigated  that  the  gen- 
eralization has  been  ventured  on,  that  all  the  protoplasm  throughout  the  plant  is 
continuous. 
The  fifth  thesis  has  been  completely  controverted.  Instead  of  believing,  as 
formerly,  that  all  the  granules  within  the  cell  arise  de  novo  from  the  protoplasm 
in  which  they  are  imbedded,  we  are  now  forced  to  regard  all  of  them  as  springing 
from  pre-existent  bodies  of  the  same  character.  Hofmeister,  in  1867,  stated 
distinctly  that  the  nucleus  arises  from  homogeneous  protoplasm,  and  that  in  all 
cell-division  the  nucleus  must  first  disappear,  two  new  ones  arising  in  its  place. 
The  nucleus  occupied  a  secondary  place  as  a  derivative  organ,  and  the  chloro- 
phyll granules  were  believed  by  him  and  his  contemporaries  to  be  new  forma- 
tions from  homogeneous  protoplasm  under  certain  conditions  of  light,  tempera- 
ture and  food.  Researches  show  that  the  nucleus  in  all  cases  hitherto  exam- 
ined springs  from  a  pre-existent  nucleus  by  a  process  of  division. 
The  extraordinary  manner  in  which  the  nucleus,  both  in  common  cell- 
division  and  in  reproductive  blending,  carries  ancestral  characters  and  controls 
the  distribution  of  nutritive  materials  is  as  yet  the  greatest  mystery  in  vegetable 
life. 
Formerly  it  was  held  that  the  other  granules  imbedded  in  the  protoplasmic 
body  known  as  chlorophyll  granules,  sprang  by  a  process  of  differentiation  from 
the  shapeless  mass  in  each  exposed  cell.  Researches  have  shown  beyond  any 
reasonable  doubt  that  these  chlorophyl  granules  always  arise  by  a  process  of 
division  from  pre-existent  granules.  It  is  known  that  at  the  growing  points, 
where  leaves  are  developed,  the  cells  contain  granules  of  about  the  consistence 
