﻿632 
  Mutations 
  

  

  upon 
  the 
  systematic 
  affinity 
  between 
  the 
  deriva- 
  

   tive 
  species 
  and 
  its 
  nearest 
  probable 
  allies. 
  

   Such 
  reversions 
  are 
  now 
  to 
  be 
  examined 
  at 
  some 
  

   length 
  and 
  may 
  be 
  adequately 
  treated 
  under 
  the 
  

   head 
  of 
  systematic 
  atavism. 
  To 
  this 
  form 
  of 
  

   atavism 
  pertain, 
  on 
  the 
  basis 
  of 
  our 
  definition, 
  

   those 
  phenomena 
  by 
  which 
  species 
  assume 
  one 
  

   or 
  more 
  characters 
  of 
  allies, 
  from 
  which 
  they 
  

   are 
  understood 
  to 
  have 
  descended 
  by 
  the 
  loss 
  of 
  

   the 
  character 
  under 
  discussion. 
  The 
  phenom- 
  

   ena 
  themselves 
  consist 
  in 
  the 
  production 
  of 
  

   anomalies 
  and 
  varieties, 
  and 
  as 
  the 
  genetic 
  

   relation 
  of 
  the 
  latter 
  is 
  often 
  hardly 
  beyond 
  

   doubt, 
  the 
  anomalies 
  seem 
  to 
  afford 
  the 
  best 
  in- 
  

   stances 
  for 
  the 
  study 
  of 
  systematic 
  atavism. 
  

   This 
  study 
  has 
  for 
  its 
  chief 
  aim 
  the 
  demonstra- 
  

   tion 
  of 
  the 
  presence 
  of 
  the 
  latent 
  characters, 
  and 
  

   to 
  show 
  that 
  they 
  return 
  to 
  activity 
  suddenly 
  

   and 
  not 
  by 
  a 
  slow 
  and 
  gradual 
  recovery 
  of 
  the 
  

   former 
  features. 
  It 
  supports 
  the 
  assertion 
  

   that 
  the 
  visible 
  elementary 
  characters 
  are 
  es- 
  

   sentially 
  an 
  external 
  display 
  of 
  qualities 
  carried 
  

   by 
  the 
  bearers 
  of 
  heredity, 
  and 
  that 
  these 
  

   bearers 
  are 
  separate 
  entities, 
  which 
  may 
  be 
  

   mingled 
  together, 
  but 
  are 
  not 
  fused 
  into 
  a 
  

   chaotic 
  primitive 
  life-substance. 
  Systematic 
  

   atavism 
  by 
  this 
  means 
  leads 
  us 
  to 
  a 
  closer 
  ex- 
  

   amination 
  of 
  the 
  internal 
  and 
  concealed 
  causes, 
  

   which 
  rule 
  the 
  affinities 
  and 
  divergencies 
  of 
  

  

  