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  ANNUAL 
  REPORT 
  SMITHSONIAN 
  INSTITUTION, 
  1922. 
  

  

  between 
  parents 
  and 
  offspring 
  for 
  any 
  particular 
  character. 
  It 
  was 
  

   wholly 
  a 
  group 
  method, 
  and 
  by 
  its 
  very 
  nature 
  precluded 
  both 
  the 
  

   analysis 
  of 
  individual 
  cases 
  and 
  the 
  utilization 
  of 
  biological 
  facts 
  

   among 
  the 
  premises. 
  Its 
  chief 
  generalization, 
  the 
  law 
  of 
  ancestral 
  

   heredity, 
  wherein 
  the 
  correlation 
  of 
  characters 
  among 
  blood 
  rela- 
  

   tives 
  was 
  interpreted 
  as 
  showing 
  the 
  inheritance 
  of 
  an 
  individual 
  to 
  

   be 
  made 
  up 
  of 
  a 
  series 
  of 
  contributions, 
  one-half 
  from 
  the 
  parents, 
  

   one-fourth 
  from 
  the 
  grandparents, 
  and 
  so 
  on, 
  has 
  been 
  shown 
  to 
  be 
  

   erroneous. 
  Having 
  proved 
  no 
  stimulant 
  to 
  productive 
  investigation, 
  

   its 
  discussion 
  has 
  passed 
  from 
  the 
  genetic 
  literature 
  of 
  to-day; 
  but 
  

   the 
  mathematical 
  procedure 
  evolved 
  by 
  the 
  Galtonian 
  school 
  has 
  

   proved 
  to 
  be 
  extremely 
  helpful. 
  

  

  The 
  earlier 
  genetic 
  theories 
  of 
  the 
  period 
  under 
  consideration 
  

   necessarily 
  were 
  highly 
  speculative 
  because 
  of 
  the 
  paucity 
  of 
  known 
  

   facts; 
  but 
  the 
  fundamental 
  postulate 
  of 
  each, 
  active 
  ultra- 
  

   microscopic 
  living 
  units, 
  has 
  been 
  retained 
  in 
  the 
  genetic 
  theory 
  of 
  

   to-day. 
  

  

  Darwin's 
  provisional 
  hypothesis 
  of 
  pangenesis 
  (1868), 
  for 
  ex- 
  

   ample, 
  assumed 
  that 
  such 
  particles, 
  the 
  gemmules, 
  were 
  given 
  off 
  

   at 
  all 
  times 
  by 
  every 
  cell, 
  and 
  passed 
  to 
  all 
  parts 
  of 
  the 
  body 
  in- 
  

   cluding 
  the 
  germ 
  cells. 
  He 
  thus 
  accounted 
  vaguely 
  for 
  the 
  in- 
  

   heritance 
  of 
  acquired 
  characters 
  and 
  for 
  regeneration 
  of 
  parts, 
  as 
  

   well 
  as 
  for 
  ordinary 
  heredity. 
  

  

  Among 
  several 
  contemporary 
  modifications 
  of 
  this 
  type 
  of 
  theory 
  

   was 
  that 
  of 
  De 
  Vries 
  (1889), 
  who 
  assumed 
  that 
  the 
  corpuscles, 
  

   which 
  he 
  called 
  pangens, 
  represented 
  potential 
  elementary 
  body 
  

   characters 
  rather 
  than 
  cell 
  qualities, 
  and 
  that 
  the 
  universe 
  of 
  their 
  

   activity 
  was 
  the 
  cell 
  rather 
  than 
  the 
  body. 
  

  

  It 
  is 
  clear, 
  even 
  with 
  only 
  a 
  glimpse 
  of 
  such 
  theories, 
  that 
  they 
  

   could 
  satisfy 
  none 
  but 
  the 
  philosophically 
  inclined. 
  They 
  did 
  little 
  

   or 
  nothing 
  toward 
  stimulating 
  work 
  designed 
  to 
  test 
  the 
  points 
  

   involved. 
  

  

  A 
  different 
  fate 
  met 
  the 
  speculations 
  of 
  Nageli 
  (1884). 
  Here 
  was 
  

   postulated 
  two 
  types 
  of 
  protoplasm 
  built 
  up 
  of 
  physiological 
  units, 
  

   the 
  micellae 
  : 
  The 
  one 
  was 
  nutritive 
  in 
  its 
  functions, 
  and 
  required 
  no 
  

   particular 
  architecture; 
  the 
  other, 
  the 
  idioplasm, 
  a 
  structure 
  of 
  

   elaborate 
  constitution, 
  was 
  built 
  of 
  units 
  which 
  represented 
  the 
  

   potential 
  elementary 
  characters 
  of 
  the 
  organism. 
  

  

  WEISMANN'S 
  THEORY. 
  

  

  Utilizing 
  this 
  conception, 
  Weismann 
  (1892) 
  evolved 
  a 
  theory 
  

   which 
  more 
  nearly 
  fulfilled 
  the 
  requirements 
  of 
  an 
  experimental 
  

   working 
  hypothesis 
  than 
  any 
  of 
  those 
  previously 
  outlined. 
  The 
  

  

  