﻿568 
  Mutations 
  

  

  great 
  is 
  the 
  chance 
  for 
  a 
  single 
  individual 
  to 
  be 
  

   destroyed 
  in 
  the 
  struggle 
  for 
  life? 
  Hundreds 
  

   of 
  thousands 
  of 
  seeds 
  are 
  produced 
  by 
  la- 
  

   marckiana 
  annually 
  in 
  the 
  field, 
  and 
  only 
  

   some 
  slow 
  increase 
  of 
  the 
  number 
  of 
  specimens 
  

   can 
  be 
  observed. 
  Many 
  seeds 
  do 
  not 
  find 
  the 
  

   proper 
  circumstances 
  for 
  germination, 
  or 
  the 
  

   young 
  seedlings 
  are 
  destroyed 
  by 
  lack 
  of 
  water, 
  

   of 
  air, 
  or 
  of 
  space. 
  Thousands 
  of 
  them 
  are 
  so 
  

   crowded 
  when 
  becoming 
  rosettes 
  that 
  only 
  a 
  few 
  

   succeed 
  in 
  producing 
  stems. 
  Any 
  weakness 
  

   would 
  have 
  destroyed 
  them. 
  As 
  a 
  matter 
  of 
  

   fact 
  they 
  are 
  much 
  oftener 
  produced 
  in 
  the 
  seed 
  

   than 
  seen 
  in 
  the 
  field 
  with 
  the 
  usual 
  unfavorable 
  

   conditions 
  ; 
  the 
  careful 
  sowing 
  of 
  collected 
  seeds 
  

   has 
  given 
  proof 
  of 
  this 
  fact 
  many 
  times. 
  

  

  The 
  experimental 
  proof 
  of 
  this 
  frequency 
  in 
  

   the 
  origin 
  of 
  new 
  types,*seems 
  to 
  overcome 
  many 
  

   difficulties 
  offered 
  bv 
  the 
  current 
  theories 
  on 
  the 
  

  

  / 
  

  

  probable 
  origin 
  of 
  species 
  at 
  large. 
  

  

  VI. 
  The 
  relation 
  "between 
  mutability 
  and 
  fluc- 
  

   tuating 
  variability 
  has 
  always 
  been 
  one 
  of 
  the 
  

   chief 
  difficulties 
  of 
  the 
  followers 
  of 
  Darwin. 
  The 
  

   majority 
  assumed 
  that 
  species 
  arise 
  by 
  the 
  slow 
  

   accumulation 
  of 
  slight 
  fluctuating 
  deviations, 
  

   and 
  the 
  mutations 
  were 
  only 
  to 
  be 
  considered 
  as 
  

   extreme 
  fluctuations, 
  obtained, 
  in 
  the 
  main, 
  by 
  a 
  

   continuous 
  selection 
  of 
  small 
  differences 
  in 
  a 
  

   constant 
  direction. 
  

  

  