﻿LECTURE 
  XXIII 
  

  

  TAXONOMIC 
  ANOMALIES 
  

  

  The 
  theory 
  of 
  descent 
  is 
  founded 
  mainly 
  

   on 
  comparative 
  studies, 
  which 
  have 
  the 
  ad- 
  

   vantage 
  of 
  affording 
  a 
  broad 
  base 
  and 
  the 
  

   convincing 
  effect 
  of 
  concurrent 
  evidence 
  

   brought 
  together 
  from 
  widely 
  different 
  sources. 
  

   The 
  theory 
  of 
  mutation 
  on 
  the 
  other 
  hand 
  rests 
  

   directly 
  upon 
  experimental 
  investigations, 
  and 
  

   facts 
  concerning 
  the 
  actual 
  descent 
  of 
  one 
  form 
  

   from 
  another 
  are 
  as 
  yet 
  exceedingly 
  rare. 
  It 
  is 
  

   always 
  difficult 
  to 
  estimate 
  the 
  validity 
  of 
  con- 
  

   clusions 
  drawn 
  from 
  isolated 
  instances 
  selected 
  

   from 
  the 
  whole 
  range 
  of 
  contingent 
  phenomena, 
  

   and 
  this 
  is 
  especially 
  true 
  of 
  the 
  present 
  case. 
  

   Systematic 
  and 
  physiologic 
  facts 
  seem 
  to 
  indi- 
  

   cate 
  the 
  existence 
  of 
  universal 
  laws, 
  and 
  it 
  is 
  not 
  

   probable 
  that 
  the 
  process 
  of 
  production 
  of 
  new 
  

   species 
  would 
  be 
  different 
  in 
  the 
  various 
  parts 
  

   of 
  the 
  animal 
  and 
  vegetable 
  kingdoms. 
  More- 
  

   over 
  the 
  principle 
  of 
  unit-characters, 
  the 
  pre- 
  

   eminent 
  significance 
  of 
  which 
  has 
  come 
  to 
  be 
  

   more 
  fully 
  recognized 
  of 
  late, 
  is 
  in 
  full 
  harmony 
  

  

  658 
  

  

  