﻿GENETIC 
  PROGRESS 
  — 
  EAST. 
  287 
  

  

  Logically 
  it 
  followed 
  from 
  the 
  theory 
  of 
  genetic 
  continuity 
  by 
  cell 
  

   division 
  that 
  a 
  material 
  substance 
  passed 
  from 
  cell 
  to 
  cell 
  is 
  the 
  basis 
  

   of 
  all 
  heredity. 
  Naturally, 
  then, 
  the 
  mechanics 
  of 
  cell 
  division 
  was 
  

   the 
  subject 
  of 
  intense 
  investigation. 
  The 
  result 
  was 
  the 
  discovery 
  

   that 
  in 
  building 
  up 
  the 
  tissues 
  of 
  the 
  individual 
  organism, 
  in 
  the 
  

   preparation 
  of 
  the 
  reproductive 
  cells 
  for 
  their 
  special 
  work, 
  and 
  in 
  

   the 
  behavior 
  of 
  these 
  cells 
  in 
  carrying 
  out 
  that 
  work 
  there 
  was 
  an 
  

   essential 
  similarity 
  of 
  the 
  two 
  processes 
  in 
  both 
  animals 
  and 
  plants. 
  

  

  As 
  these 
  studies 
  progressed 
  it 
  became 
  apparent 
  that 
  the 
  cell 
  nucleus 
  

   was 
  the 
  controlling 
  agent 
  of 
  inheritance, 
  and 
  that 
  within 
  the 
  nucleus 
  

   the 
  chromosomes 
  played 
  the 
  star 
  role. 
  This 
  hypothesis, 
  put 
  forth 
  as 
  

   a 
  speculation 
  by 
  Haeckel 
  in 
  1866, 
  within 
  15 
  years 
  gained 
  the 
  sup- 
  

   port 
  of 
  such 
  eminent 
  investigators 
  as 
  Hertwig, 
  Strasburger, 
  and 
  

   Van 
  Beneden, 
  largely 
  because 
  of 
  the 
  similar 
  elaborate 
  preparations 
  

   within 
  the 
  nucleus 
  of 
  egg 
  and 
  of 
  sperm 
  during 
  maturation 
  and 
  of 
  

   their 
  apparently 
  identical 
  contribution 
  of 
  nuclear 
  material 
  in 
  bi- 
  

   parental 
  inheritance. 
  Numerous 
  investigations 
  on 
  artificial 
  fertiliza- 
  

   tion 
  were 
  made 
  by 
  adherents 
  and 
  opponents 
  of 
  this 
  view; 
  but 
  owing 
  

   to 
  the 
  experimental 
  difficulties 
  involved, 
  they 
  were 
  not 
  conclusive. 
  

   Polemic 
  dissertations 
  on 
  the 
  part 
  played 
  by 
  nucleus 
  and 
  cytoplasm 
  

   followed 
  that 
  were 
  reminiscent 
  of 
  discussions 
  in 
  the 
  realm 
  of 
  religion 
  

   or 
  of 
  politics. 
  Gradually 
  the 
  proponents 
  of 
  the 
  view 
  gained 
  more 
  

   and 
  more 
  copverts, 
  not 
  because 
  they 
  were 
  able 
  to 
  demonstrate 
  a 
  mo- 
  

   nopoly 
  of 
  directive 
  action 
  by 
  the 
  nucleus 
  in 
  development 
  and 
  hered- 
  

   ity, 
  not 
  because 
  they 
  could 
  prove 
  that 
  the 
  intricate 
  organization 
  of 
  so 
  

   many 
  unfertilized 
  eggs 
  was 
  controlled 
  by 
  nuclear 
  behavior, 
  for 
  such 
  

   was 
  not 
  the 
  case; 
  it 
  came 
  through 
  small 
  increments 
  to 
  cytological 
  

   knowledge 
  which 
  gradually 
  wove 
  a 
  mesh 
  so 
  fine 
  that 
  there 
  was 
  no 
  

   loophole 
  of 
  escape 
  from 
  the 
  conclusion. 
  Belief 
  in 
  the 
  importance 
  

   of 
  the 
  chromosomes 
  grew, 
  as 
  in 
  the 
  case 
  of 
  organic 
  evolution, 
  not 
  

   because 
  of 
  direct 
  proof, 
  but 
  because 
  of 
  circumstantial 
  evidence. 
  

   Without 
  going 
  into 
  an 
  extended 
  argument 
  on 
  the 
  subject, 
  one 
  may 
  

   recall 
  the 
  constancy 
  of 
  chromosome 
  number 
  in 
  each 
  species, 
  their 
  

   individuality 
  in 
  size 
  and 
  shape, 
  the 
  exactitude 
  of 
  their 
  division 
  

   during 
  growth, 
  and 
  their 
  peculiar 
  behavior 
  at 
  the 
  maturation 
  of 
  the 
  

   germ 
  cells. 
  

  

  NINETEENTH 
  CENTURY 
  THEORIES 
  OF 
  HEREDITY. 
  

  

  These 
  facts, 
  together 
  with 
  numerous 
  minor 
  discoveries, 
  were 
  the 
  

   basis 
  of 
  nineteenth 
  century 
  theories 
  of 
  heredity. 
  But 
  besides 
  the 
  

   efforts 
  of 
  the 
  practical 
  breeders 
  and 
  of 
  the 
  morphologists, 
  a 
  serious 
  

   attempt 
  was 
  made 
  by 
  Francis 
  Galton 
  and 
  Karl 
  Pearson 
  to 
  put 
  

   genetic 
  studies 
  on 
  a 
  firm 
  groundwork 
  of 
  quantitative 
  experiment. 
  

   Essentially 
  their 
  method 
  was 
  to 
  measure 
  the 
  degree 
  of 
  association 
  

  

  