﻿354 
  ANNUAL 
  REPORT 
  SMITHSONIAN 
  INSTITUTION, 
  192 
  9 
  

  

  several 
  times 
  stronger 
  than 
  used 
  here. 
  The 
  treated 
  flies 
  were 
  then 
  

   bred 
  to 
  untreated 
  mates, 
  and 
  at 
  the 
  same 
  time 
  numerous 
  control 
  

   matings 
  of 
  the 
  same 
  genetic 
  tj^pe 
  were 
  carried 
  on 
  for 
  comparison, 
  

   consisting 
  of 
  untreated 
  males 
  crossed 
  by 
  untreated 
  females. 
  Thou- 
  

   sands 
  of 
  cultures 
  were 
  used 
  in 
  this 
  and 
  subsequent 
  experiments, 
  in 
  

   order, 
  if 
  possible, 
  to 
  settle 
  the 
  matter 
  beyond 
  any 
  doubt. 
  

  

  The 
  results 
  in 
  these 
  experiments 
  were 
  startling 
  and 
  unequivocal. 
  

   To 
  the 
  toiling 
  pilgrim 
  after 
  plodding 
  through 
  the 
  long 
  and 
  weary 
  

   deserts 
  of 
  changelessness, 
  here 
  indeed 
  was 
  the 
  promised 
  land 
  of 
  

   mutations. 
  All 
  types 
  of 
  mutations, 
  large 
  and 
  small, 
  ugly 
  and 
  beauti- 
  

   ful, 
  burst 
  upon 
  the 
  gaze. 
  Flies 
  with 
  bulging 
  eyes 
  or 
  with 
  flat 
  or 
  

   dented 
  eyes, 
  flies 
  with 
  white, 
  purple, 
  yellow, 
  or 
  brown 
  eyes, 
  or 
  with 
  

   no 
  eyes 
  at 
  all; 
  flies 
  with 
  curly 
  hair, 
  with 
  ruffled 
  hair, 
  with 
  parted 
  hair, 
  

   with 
  fine 
  and 
  with 
  coarse 
  hair, 
  and 
  bald 
  flies; 
  flies 
  with 
  swollen 
  

   antennge, 
  or 
  extra 
  antennae, 
  or 
  legs 
  in 
  place 
  of 
  antennae; 
  flies 
  with 
  

   broad 
  wings, 
  with 
  narrow 
  wings, 
  with 
  upturned 
  wings, 
  with 
  down- 
  

   turned 
  wings, 
  with 
  outstreched 
  wings, 
  with 
  truncated 
  wings, 
  with 
  

   split 
  wings, 
  with 
  spotted 
  wings, 
  with 
  bloated 
  wings, 
  and 
  with 
  vir- 
  

   tually 
  no 
  wings 
  at 
  all. 
  Big 
  flies 
  and 
  little 
  ones, 
  dark 
  ones 
  and 
  light 
  

   ones, 
  active 
  and 
  sluggish 
  ones, 
  fertile 
  and 
  sterile 
  ones, 
  long-lived 
  and 
  

   short-lived 
  ones. 
  Flies 
  that 
  preferred 
  to 
  stay 
  on 
  the 
  ground, 
  flies 
  

   that 
  did 
  not 
  care 
  about 
  the 
  light, 
  flies 
  that 
  had 
  a 
  mixture 
  of 
  sex 
  

   characters, 
  flies 
  that 
  were 
  especially 
  sensitive 
  to 
  warm 
  weather. 
  

   They 
  were 
  a 
  motley 
  throng. 
  What 
  had 
  happened? 
  The 
  roots 
  of 
  life 
  — 
  

   the 
  genes 
  — 
  had 
  indeed 
  been 
  struck, 
  and 
  had 
  yielded. 
  

  

  It 
  must 
  not 
  be 
  supposed 
  that 
  all 
  the 
  above 
  types 
  appeared 
  congre- 
  

   gated 
  together 
  in 
  one 
  family. 
  The 
  vast 
  majority 
  of 
  the 
  offspring 
  that 
  

   hatched 
  still 
  appeared 
  quite 
  normal, 
  and 
  it 
  was 
  only 
  by 
  raking 
  through 
  

   our 
  thousands 
  of 
  cultures 
  that 
  all 
  these 
  types 
  were 
  found. 
  But 
  what 
  

   a 
  difference 
  from 
  the 
  normal 
  frequency 
  of 
  mutation, 
  which 
  is 
  so 
  pain- 
  

   fully 
  low! 
  By 
  checking 
  up 
  with 
  the 
  small 
  numbers 
  of 
  mutants 
  found 
  

   in 
  the 
  numerous 
  untreated 
  or 
  control 
  cultures, 
  which 
  were 
  bred 
  in 
  

   parallel, 
  it 
  was 
  found 
  that 
  the 
  heaviest 
  treatment 
  had 
  increased 
  the 
  

   frequency 
  of 
  mutation 
  about 
  150 
  times; 
  that 
  is, 
  an 
  increase 
  of 
  15,000 
  

   per 
  cent. 
  t 
  

  

  SIMILARITY 
  OF 
  THE 
  X 
  RAY 
  TO 
  THE 
  NATURAL 
  MUTATIONS 
  

  

  These 
  mutations 
  were 
  obviously 
  of 
  the 
  same 
  general 
  nature 
  as 
  the 
  

   spontaneous 
  mutations 
  that 
  occur 
  without 
  X-ray 
  treatment. 
  This 
  

   was 
  shown 
  by 
  the 
  fact 
  that 
  in 
  many 
  cases 
  changes 
  had 
  been 
  produced 
  

   which 
  were 
  undoubtedly 
  identical 
  with 
  spontaneous 
  variations 
  which 
  

   had 
  been 
  found 
  in 
  the 
  previous 
  history 
  of 
  the 
  Drosojphila 
  work 
  ; 
  the 
  

   effects 
  in 
  these 
  cases 
  appeared 
  identical 
  in 
  every 
  particular 
  and 
  the 
  

   method 
  of 
  inheritance, 
  the 
  position 
  of 
  the 
  gene 
  concerned 
  in 
  the 
  

   chromosome 
  was 
  found 
  to 
  be 
  the 
  same. 
  In 
  fact, 
  in 
  the 
  chromo- 
  

  

  