﻿E. 
  MUTATIONS 
  

   LECTURE 
  XVI 
  

  

  THE 
  ORIGIN 
  OF 
  THE 
  PELORIC 
  TOAD-FLAX 
  

  

  I 
  have 
  tried 
  to 
  show 
  previously 
  that 
  species, 
  in 
  

   the 
  ordinary 
  sense 
  of 
  the 
  word, 
  consist 
  of 
  dis- 
  

   tinct 
  groups 
  of 
  units. 
  In 
  systematic 
  works 
  

   these 
  groups 
  are 
  all 
  designated 
  by 
  the 
  name 
  of 
  

   varieties, 
  but 
  it 
  is 
  usually 
  granted 
  that 
  the 
  

   units 
  of 
  the 
  system 
  are 
  not 
  always 
  of 
  the 
  same 
  

   value. 
  Hence 
  we 
  have 
  distinguished 
  between 
  

   elementary 
  species 
  and 
  varieties 
  proper. 
  The 
  

   first 
  are 
  combined 
  into 
  species 
  whose 
  common 
  

   original 
  type 
  is 
  now 
  lost 
  or 
  unknown, 
  and 
  from 
  

   their 
  characters 
  is 
  derived 
  an 
  hypothetical 
  im- 
  

   age 
  of 
  what 
  the 
  common 
  ancestor 
  is 
  supposed 
  

   to 
  have 
  been. 
  The 
  varieties 
  proper 
  are 
  derived 
  

   in 
  most 
  cases 
  from 
  still 
  existing 
  types, 
  and 
  

   therefore 
  are 
  subjoined 
  to 
  them. 
  A 
  closer 
  in- 
  

   vestigation 
  has 
  shown 
  that 
  this 
  derivation 
  is 
  

   ordinarily 
  produced 
  by 
  the 
  loss 
  of 
  some 
  definite 
  

   attribute, 
  or 
  by 
  the 
  re-acquisition 
  of 
  an 
  appar- 
  

  

  459 
  

  

  