﻿Multiplication 
  of 
  Extremes 
  743 
  

  

  of 
  the 
  results 
  of 
  the 
  choice 
  of 
  extremes, 
  which 
  it 
  

   may 
  be 
  easily 
  seen 
  is 
  a 
  matter 
  of 
  the 
  greatest 
  

   practical 
  importance. 
  This 
  choice 
  is 
  generally 
  

   designated 
  as 
  selection, 
  but 
  as 
  with 
  most 
  of 
  the 
  

   terms 
  in 
  the 
  domain 
  of 
  variability, 
  the 
  word 
  

   selection 
  has 
  come 
  to 
  have 
  more 
  than 
  one 
  mean- 
  

   ing. 
  Facts 
  have 
  accumulated 
  enormously 
  since 
  

   the 
  time 
  of 
  Darwin, 
  a 
  more 
  thorough 
  knowl- 
  

   edge 
  has 
  brought 
  about 
  distinctions, 
  and 
  di- 
  

   visions 
  at 
  a 
  rapidly 
  increasing 
  rate, 
  with 
  which 
  

   terminology 
  has 
  not 
  kept 
  pace. 
  Selection 
  in- 
  

   cludes 
  all 
  kinds 
  of 
  choice. 
  Darwin 
  distin- 
  

   guished 
  between 
  natural 
  and 
  artificial 
  selection, 
  

   but 
  proper 
  subdivisions 
  of 
  these 
  conceptions 
  are 
  

   needed. 
  

  

  In 
  the 
  fourth 
  lecture 
  we 
  dealt 
  with 
  this 
  same 
  

   question, 
  and 
  saw 
  that 
  selection 
  must, 
  in 
  the 
  first 
  

   place, 
  make 
  a 
  choice 
  between 
  the 
  elementary 
  

   species 
  of 
  the 
  same 
  systematic 
  form. 
  This 
  

   selection 
  of 
  species 
  or 
  species-selection 
  was 
  the 
  

   work 
  of 
  Le 
  Couteur 
  and 
  Patrick 
  Shirreff, 
  and 
  is 
  

   now 
  in 
  general 
  use 
  in 
  practice 
  where 
  it 
  has 
  re- 
  

   ceived 
  the 
  name 
  of 
  variety-testing. 
  This 
  clear 
  

   and 
  unequivocal 
  term 
  however, 
  can 
  hardly 
  be 
  

   included 
  under 
  the 
  head 
  of 
  natural 
  selection. 
  

   The 
  poetic 
  terminology 
  of 
  selection 
  by 
  nature 
  

   has 
  already 
  brought 
  about 
  many 
  difficulties 
  that 
  

   should 
  be 
  avoided 
  in 
  the 
  future. 
  On 
  the 
  other 
  

   hand, 
  the 
  designation 
  of 
  the 
  process 
  as 
  a 
  natural 
  

  

  