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  ANNUAL 
  REPORT 
  SMITHSONIAN 
  INSTITUTION, 
  1929 
  

  

  Suppose 
  you 
  prod 
  the 
  works 
  of 
  a 
  watch 
  at 
  random 
  — 
  bring 
  about 
  some 
  

   alterations 
  in 
  ignorance 
  of 
  the 
  effect 
  it 
  may 
  have? 
  Are 
  you 
  likely 
  

   to 
  make 
  it 
  a 
  better-running 
  watch? 
  A 
  change, 
  purely 
  accidental 
  in 
  

   this 
  sense, 
  wrought 
  in 
  any 
  complicated 
  organization, 
  is 
  more 
  likely 
  

   to 
  injure 
  or 
  wreck 
  than 
  to 
  improve 
  that 
  organization 
  for 
  the 
  specific 
  

   function 
  (in 
  the 
  case 
  of 
  life, 
  multiplication) 
  which 
  it 
  subserves. 
  But, 
  

   unless 
  the 
  organization 
  has 
  reached 
  its 
  absolute 
  maximum 
  of 
  efficiency 
  

   already, 
  there 
  will 
  still 
  remain 
  some 
  changes, 
  and 
  therefore 
  some 
  

   random 
  changes, 
  that 
  will 
  help. 
  And 
  so, 
  occasionally, 
  when 
  your 
  

   watch 
  has 
  stopped 
  or 
  is 
  running 
  poorly, 
  you 
  may 
  knook 
  it, 
  prod 
  it, 
  

   or 
  drop 
  it, 
  and 
  find 
  that, 
  by 
  the 
  lucky 
  replacement 
  of 
  a 
  cog, 
  or 
  the 
  

   displacement 
  of 
  a 
  sand 
  grain, 
  it 
  starts 
  up 
  merrily 
  again. 
  We 
  shall 
  

   return 
  to 
  this 
  topic 
  later. 
  Meanwliile, 
  we 
  stand 
  on 
  our 
  data: 
  Despite 
  

   the 
  staggering 
  complexity 
  of 
  adaptation 
  in 
  living 
  things, 
  the 
  vast 
  

   majority 
  of 
  mutations 
  are, 
  as 
  is 
  to 
  be 
  expected, 
  antiadaptive. 
  

  

  It 
  will 
  not 
  suffice, 
  however, 
  simply 
  to 
  call 
  the 
  changes 
  "accidental." 
  

   An 
  accident 
  is 
  something 
  whose 
  cause 
  was 
  independent 
  of 
  something 
  

   you 
  are 
  interested 
  in, 
  but 
  every 
  accident 
  has 
  its 
  cause 
  just 
  the 
  same. 
  

   And 
  so 
  we 
  return 
  again 
  to 
  our 
  perennial 
  question 
  : 
  What 
  is 
  the 
  cause 
  

   of 
  mutations? 
  Evidently, 
  we 
  may 
  now 
  say, 
  not 
  any 
  outer 
  or 
  inner 
  

   tendency 
  toward 
  perfection 
  of 
  the 
  life 
  force, 
  but 
  that 
  does 
  not 
  help 
  

   us 
  very 
  much, 
  scientifically. 
  The 
  mutations 
  whose 
  origination 
  has 
  

   been 
  known 
  to 
  geneticists 
  have 
  been 
  on 
  the 
  whole 
  very 
  scattered 
  and 
  

   sporadic, 
  so 
  that 
  little 
  of 
  definite 
  information 
  could 
  be 
  obtained 
  by 
  

   collecting 
  these 
  observations 
  concerning 
  the 
  conditions 
  which 
  may 
  

   have 
  been 
  contributary 
  to 
  their 
  occurrence. 
  The 
  trouble 
  was 
  that 
  

   mutations 
  having 
  a 
  conspicuous 
  visible 
  effect 
  are 
  so 
  very 
  rare 
  anyway 
  

   that 
  one 
  does 
  not 
  find 
  enough 
  in 
  any 
  one 
  experiment 
  to 
  count. 
  How- 
  

   ever, 
  the 
  very 
  negativeness 
  of 
  this 
  result, 
  and 
  the 
  varied 
  character 
  of 
  

   the 
  mutations 
  as 
  they 
  did 
  occur, 
  suggested 
  that 
  their 
  occurrence 
  had 
  

   little 
  or 
  no 
  relation 
  to 
  the 
  ordinary 
  variables 
  of 
  the 
  environment. 
  

  

  Altenburg 
  and 
  I, 
  in 
  the 
  work 
  previously 
  alluded 
  to, 
  undertook 
  a 
  

   more 
  systematic 
  test 
  of 
  the 
  possible 
  effectiveness 
  of 
  temperature, 
  

   by 
  using 
  a 
  technique 
  by 
  which 
  we 
  could 
  count 
  the 
  occurrence 
  of 
  

   lethal 
  mutations, 
  since 
  we 
  found 
  these 
  arose 
  so 
  much 
  oftener 
  as 
  to 
  be 
  

   countable. 
  We 
  obtained 
  results 
  indicating, 
  though 
  not 
  proving, 
  that 
  

   a 
  rise 
  in 
  temperature 
  causes 
  a 
  slight 
  increase 
  in 
  mutation 
  frequency, 
  

   just 
  as 
  it 
  hastens 
  chemical 
  reactions. 
  Though 
  we 
  now 
  suspect 
  that 
  the 
  

   difference 
  may 
  really 
  have 
  been 
  due 
  to 
  a 
  slight 
  difi^erence 
  in 
  the 
  amount 
  

   of 
  radiation 
  occurring 
  in 
  the 
  two 
  groups 
  of 
  cultures, 
  warmer 
  and 
  cooler 
  

   respectively, 
  later 
  evidence 
  seemed 
  to 
  substantiate 
  it. 
  At 
  best, 
  the 
  

   result 
  scarcely 
  goes 
  far 
  enough 
  to 
  afford 
  a 
  workable 
  handle 
  for 
  the 
  

   study 
  of 
  the 
  phenomenon, 
  since 
  the 
  numbers 
  obtained 
  even 
  here 
  are 
  

   so 
  trifling 
  in 
  response 
  to 
  the 
  great 
  expenditure 
  of 
  technical 
  effort 
  nec- 
  

   essary. 
  In 
  addition 
  to 
  this 
  work, 
  efforts 
  have 
  been 
  by 
  no 
  means 
  

  

  