﻿Periodic 
  Mutations 
  709 
  

  

  the 
  group 
  called 
  Oenothera, 
  with 
  a 
  large 
  num- 
  

   ber 
  of 
  species 
  of 
  the 
  same 
  general 
  type 
  as 
  the 
  

   Onagra-foims. 
  Still 
  farther 
  downward 
  comes 
  

   the 
  old 
  genus 
  Oenothera 
  itself, 
  with 
  numerous 
  

   subgenera 
  diverging 
  in 
  sundry 
  characters 
  and 
  

   directions. 
  

  

  Proceeding 
  still 
  farther 
  we 
  might 
  easily 
  con- 
  

   struct 
  a 
  main 
  stem 
  with 
  numerous 
  succeeding 
  

   fans 
  of 
  lateral 
  branches, 
  and 
  thus 
  reach, 
  from 
  

   our 
  new 
  empirical 
  point 
  of 
  view, 
  the 
  theoretical 
  

   conclusion 
  already 
  formulated. 
  

  

  Paleontologic 
  facts 
  readily 
  agree 
  with 
  this 
  

   conception. 
  The 
  swarms 
  of 
  species 
  and 
  va- 
  

   rieties 
  are 
  found 
  to 
  succeed 
  one 
  another 
  like 
  so 
  

   many 
  stories. 
  The 
  same 
  images 
  are 
  repeated, 
  

   and 
  the 
  single 
  stories 
  seem 
  to 
  be 
  connected 
  by 
  

   the 
  main 
  stems, 
  which 
  in 
  each 
  tier 
  produce 
  the 
  

   whole 
  number 
  of 
  allied 
  forms. 
  Only 
  a 
  few 
  pre- 
  

   vailing 
  lines 
  are 
  prolonged 
  through 
  numerous 
  

   geologic 
  periods 
  ; 
  the 
  vast 
  majority 
  of 
  the 
  lat- 
  

   eral 
  branches 
  are 
  limited 
  each 
  to 
  its 
  own 
  storey. 
  

   It 
  is 
  simply 
  the 
  extension 
  of 
  the 
  pedigree 
  of 
  

   the 
  evening-primroses 
  backward 
  through 
  ages, 
  

   with 
  the 
  same 
  construction 
  and 
  the 
  same 
  lead- 
  

   ing 
  features. 
  There 
  can 
  be 
  no 
  doubt 
  that 
  we 
  

   are 
  quite 
  justified 
  in 
  assuming 
  that 
  evolution 
  

   has 
  followed 
  the 
  same 
  general 
  laws 
  through 
  the 
  

   whole 
  duration 
  of 
  life 
  on 
  earth. 
  Only 
  a 
  mo- 
  

   ment 
  of 
  their 
  lifetime 
  is 
  disclosed 
  to 
  us, 
  but 
  it 
  

  

  