﻿690 
  Mutations 
  

  

  microscopical 
  investigations 
  as 
  well 
  as 
  extended 
  

   pedigree-cultures. 
  The 
  cooperation 
  of 
  many 
  

   workers 
  is 
  required 
  to 
  cover 
  the 
  field. 
  Some- 
  

   where 
  no 
  doubt 
  the 
  desired 
  principle 
  lies 
  hid- 
  

   den, 
  but 
  until 
  it 
  is 
  discovered, 
  all 
  methods 
  must 
  

   be 
  tried. 
  

  

  With 
  this 
  conception 
  as 
  the 
  best 
  starting- 
  

   point 
  for 
  further 
  investigation, 
  we 
  may 
  now 
  

   make 
  a 
  brief 
  survey 
  of 
  the 
  other 
  phase 
  of 
  the 
  

   problem. 
  We 
  shall 
  try 
  to 
  connect 
  our 
  observa- 
  

   tions 
  on 
  the 
  evening-primroses 
  with 
  the 
  theory 
  

   of 
  descent 
  at 
  large. 
  

  

  We 
  start 
  with 
  two 
  main 
  facts. 
  One 
  is 
  the 
  

   mutability 
  of 
  Lamarck's 
  primrose, 
  and 
  the 
  sec- 
  

   ond 
  is 
  the 
  immutable 
  condition 
  of 
  quite 
  a 
  num- 
  

   ber 
  of 
  other 
  species. 
  Among 
  them 
  are 
  some 
  

   of 
  its 
  near 
  allies, 
  the 
  common 
  and 
  the 
  small- 
  

   flowered 
  evening-primrose, 
  or 
  Oenothera 
  bien- 
  

   nis 
  and 
  0. 
  muricata. 
  

  

  From 
  these 
  facts, 
  a 
  very 
  important 
  question 
  

   arises 
  in 
  connection 
  with 
  the 
  theory 
  of 
  descent. 
  

   Is 
  the 
  mutability 
  of 
  our 
  evening-primroses 
  tem- 
  

   porary, 
  or 
  is 
  it 
  a 
  permanent 
  condition! 
  A 
  dis- 
  

   cussion 
  of 
  this 
  problem 
  will 
  give 
  us 
  the 
  means 
  of 
  

   reaching 
  a 
  definite 
  idea 
  as 
  to 
  the 
  scope 
  of 
  our 
  

   inquiries. 
  

  

  Let 
  us 
  consider 
  the 
  present 
  first. 
  If 
  mutabil- 
  

   ity 
  is 
  a 
  permanent 
  condition, 
  it 
  has 
  of 
  course 
  no 
  

   beginning, 
  and 
  moreover 
  is 
  not 
  due 
  to 
  the 
  

  

  