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  viii 
  ) 
  

  

  great 
  seasonal 
  dimorphism, 
  and 
  to 
  a 
  variable 
  single 
  brooded 
  

   species, 
  must 
  be 
  of 
  wide 
  general 
  application 
  ; 
  how 
  general, 
  

   could 
  only 
  be 
  ascertained 
  by 
  the 
  co-operation 
  of 
  many 
  

   observers; 
  and 
  he 
  ventured 
  to 
  hope 
  that 
  entomologists 
  would, 
  

   as 
  opportunity 
  offered, 
  turn 
  their 
  attention 
  to 
  the 
  subject, 
  and 
  

   report 
  the 
  results 
  in 
  the 
  publications 
  devoted 
  to 
  this 
  branch 
  of 
  

   natural 
  history. 
  He 
  thought 
  almost 
  any 
  variable 
  species, 
  

   especially 
  where 
  the 
  variations 
  were 
  associated 
  with 
  climate 
  

   or 
  season, 
  would 
  be 
  worth 
  trying. 
  The 
  means 
  by 
  which 
  tem- 
  

   perature 
  operated 
  was 
  a 
  question 
  of 
  difficulty 
  which 
  such 
  

   experiments 
  and 
  observations 
  might 
  throw 
  light 
  on. 
  Mr. 
  

   Merrifield 
  said 
  he 
  thought 
  it 
  had 
  been 
  shown 
  that 
  general 
  

   retardation 
  was 
  not 
  a 
  satisfactory 
  explanation, 
  for 
  a 
  pupa 
  of 
  

   18 
  weeks, 
  which 
  for 
  the 
  last 
  8 
  or 
  10 
  days 
  was 
  exposed 
  to 
  80°, 
  

   thus 
  being 
  19 
  to 
  20 
  weeks 
  in 
  pupa, 
  produced 
  a 
  lighter-coloured 
  

   moth 
  than 
  one 
  of 
  only 
  2 
  or 
  3 
  weeks 
  that 
  was 
  exposed 
  for 
  18 
  

   or 
  20 
  days 
  to 
  60°, 
  and 
  was 
  thus 
  about 
  5 
  or 
  6 
  weeks 
  in 
  the 
  pupal 
  

   condition. 
  It 
  was 
  of 
  course 
  exceedmgly 
  difficult 
  in 
  ordinary 
  

   cases 
  to 
  distinguish 
  between 
  cold 
  and 
  retardation 
  as 
  a 
  cause, 
  

   because 
  the 
  former 
  produced 
  the 
  latter, 
  and 
  for 
  practical 
  pur- 
  

   poses 
  it 
  did 
  not 
  matter 
  ; 
  but 
  theoretically 
  it 
  was 
  important. 
  

   Prof. 
  Weismann's 
  theory, 
  founded 
  on 
  the 
  proposition 
  that 
  in 
  

   seasonally 
  dimorphic 
  species 
  the 
  ancestral 
  form 
  could 
  not 
  be 
  

   made 
  to 
  assume 
  the 
  characters 
  of 
  the 
  form 
  of 
  later 
  origin, 
  but 
  

   that 
  the 
  latter 
  could 
  be 
  made 
  to 
  assume 
  those 
  of 
  the 
  former, 
  

   did 
  not 
  here 
  fully 
  meet 
  the 
  case 
  so 
  far 
  as 
  the 
  striking 
  character- 
  

   istic 
  of 
  colour 
  was 
  concerned, 
  for 
  it 
  had 
  been 
  shown 
  that 
  

   either 
  the 
  spring 
  or 
  the 
  summer 
  emergence 
  was 
  ready 
  to 
  

   assume 
  the 
  colouring 
  proper 
  to 
  the 
  other 
  when 
  the 
  appropriate 
  

   temperature 
  stimulus 
  was 
  applied. 
  

  

  Mr. 
  Elwes 
  said 
  that 
  in 
  his 
  experience 
  in 
  many 
  parts 
  of 
  the 
  

   Palaearctic 
  region, 
  in 
  Japan, 
  in 
  the 
  Taunus 
  Mountains, 
  on 
  the 
  

   north-eastern 
  shores 
  of 
  the 
  Mediterranean, 
  in 
  the 
  Canary 
  

   Islands, 
  and 
  elsewhere, 
  where 
  there 
  was 
  a 
  combination 
  of 
  

   heat 
  and 
  moisture, 
  all 
  the 
  commoner 
  species 
  of 
  Lepidoptera 
  

   occurring 
  in 
  these 
  countries 
  and 
  districts 
  attained 
  a 
  larger 
  

   size 
  and 
  a 
  greater 
  brilliancy 
  of 
  colouring 
  than 
  in 
  colder 
  and 
  

   drier 
  regions 
  ; 
  and 
  he 
  referred 
  to 
  such 
  species, 
  amongst 
  

   others, 
  as 
  Pieris 
  hrassiccc 
  and 
  Argi/nnis 
  paphia. 
  The 
  discussion 
  

   was 
  continued 
  by 
  Mr. 
  Jacoby, 
  Mr. 
  Fenn, 
  and 
  others. 
  

  

  