﻿LECTURE 
  XV 
  

  

  DOUBLE 
  ADAPTATIONS 
  

  

  The 
  chief 
  object 
  of 
  all 
  experimentation 
  is 
  to 
  

   obtain 
  explanations 
  of 
  natural 
  phenomena. 
  

   Experiments 
  are 
  a 
  repetition 
  of 
  things 
  occur- 
  

   ring 
  in 
  nature 
  with 
  the 
  conditions 
  so 
  guarded 
  

   and 
  so 
  closely 
  followed 
  that 
  it 
  is 
  possible 
  to 
  

   make 
  a 
  clear 
  analysis 
  of 
  facts 
  and 
  their 
  

   causes, 
  it 
  being 
  rightfully 
  assumed 
  that 
  the 
  laws 
  

   are 
  the 
  same 
  in 
  both 
  cases. 
  

  

  Experiments 
  on 
  heredity 
  and 
  the 
  experience 
  

   of 
  the 
  breeder 
  find 
  their 
  analogy 
  in 
  the 
  succes- 
  

   sion 
  of 
  generations 
  in 
  the 
  wild 
  state. 
  The 
  sta- 
  

   bility 
  of 
  elementary 
  species 
  and 
  of 
  retrograde 
  

   varieties 
  is 
  quite 
  the 
  same 
  under 
  both 
  condi- 
  

   tions. 
  Progression 
  and 
  retrogression 
  are 
  nar- 
  

   rowly 
  linked 
  everywhere, 
  and 
  the 
  same 
  laws 
  

   govern 
  the 
  abundance 
  of 
  forms 
  in 
  cultivated 
  

   and 
  in 
  wild 
  plants. 
  

  

  Elementary 
  species 
  and 
  retrograde 
  varieties 
  

   are 
  easily 
  recognizable. 
  Ever-sporting 
  varie- 
  

   ties 
  on 
  the 
  contrary 
  are 
  far 
  less 
  obvious, 
  and 
  

   in 
  many 
  cases 
  their 
  hereditary 
  relations 
  have 
  

  

  430 
  

  

  